Liquid discharge head

The present application claims priority from Japanese Patent Application No. 2019-011947 filed on Jan. 28, 2019, the disclosure of which is incorporated herein by reference in its entirety.

The present disclosure relates to a liquid discharge head which discharges a liquid from a nozzle.

As an example of a liquid discharge head which discharges a liquid from a nozzle, there is a publicly known recording head which discharges an ink from nozzles. In this publicly known recording head, a first pressure chamber row and a second pressure chamber row, each of which is formed by a plurality of pressure chambers aligned in one direction, are arranged side by side in a direction orthogonal to the one direction. The plurality of pressure chambers forming the first pressure chamber row are connected to a first common channel, and the plurality of pressure chambers forming the second pressure chamber row are connected to a second common channel. Further, each of the pressure chambers is connected to a nozzle via a nozzle channel. Furthermore, a plurality of nozzle channels corresponding to the first pressure chamber row and a plurality of nozzle channels corresponding to the second pressure chamber row are connected individually to one another, respectively, via a plurality of return channels.

In the above-described recording head, the ink flows from the first common channel to the plurality of pressure chambers constructing the first pressure chamber row. Further, the ink flows out from the plurality of pressure chambers constructing the first pressure chamber row to the plurality of pressure chambers constructing the second pressure chamber row, via the nozzle channels and the return channels, respectively. Furthermore, the ink flows out from the plurality of pressure chambers constructing the second pressure chamber row to the second common channel. With this, the ink inside the recording head is circulated.

Here, in the above-described recording head, since the plurality of return channels are provided individually with respect to the plurality of pressure chambers, respectively, each of the return channels has a small cross-sectional area in a cross section orthogonal to the length direction thereof. Namely, each of the return channels has a large channel resistance. Accordingly, there is such a fear that the ink might not be flowed from the pressure chambers constructing the first pressure chamber row to the pressure chambers constructing the second pressure chamber row, respectively, sufficiently or at any sufficient amount. Further, in a case that the channel resistance in the return channels are large, there is such a fear that the ink might flow backward from the return channels and might be leaked from the nozzles, respectively.

An object of the present disclosure is to provide a liquid discharge head capable of allowing the liquid to flow sufficiently among the individual channels.

According to an aspect of the present disclosure, there is provided a liquid discharging head including: a first individual channel row including a plurality of first individual channels which are aligned in a first direction and in which a plurality of first nozzles are opened, respectively; a second individual channel row including a plurality of second individual channels which are aligned in the first direction and in which a plurality of second nozzles are opened, respectively; a first common channel extending in the first direction, connected to the plurality of first individual channels, and having a first connecting part connectable to a liquid supply source; a second common channel extending in the first direction, connected to the plurality of second individual channels, and having a second connecting part connectable to the liquid supply source; and a connecting channel arranged side by side with respect to the first and second individual channel rows in a second direction orthogonal to the first direction, and connecting the plurality of first individual channels and the plurality of second individual channels to one another. The connecting channel includes: a common connecting channel which does not have a connecting part with respect to the liquid supply source and which is communicated with the plurality of first individual channels and the plurality of second individual channels; a plurality of first individual connecting channels which correspond to the plurality of first individual channels, respectively, and each of which connects one of the plurality of first individual channels to the common connecting channel; and a plurality of second individual connecting channels which correspond to the plurality of second individual channels, respectively, and each of which connects one of the plurality of second individual channels to the common connecting channel.

FIG. 1 is a schematic view depicting the configuration of a printer 1 .

FIG. 2 is a plan view of a head unit 11 .

FIG. 3 is a cross-sectional taken along a line III-III in FIG. 2 .

FIG. 4 is a plan view of a head unit 100 .

FIG. 5 is a cross-sectional taken along a line V-V in FIG. 4 .

FIG. 6 is a cross-sectional taken along a line VI-VI in FIG. 4 .

FIG. 7 is a cross-sectional view of a head unit 200 , corresponding to FIG. 3 .

FIG. 8 is a plan view of a head unit 210 , corresponding to FIG. 2 .

FIG. 9 is a cross-sectional view of the head unit 210 , corresponding to FIG. 3 .

FIG. 10 is a cross-sectional view of a head unit 220 , corresponding to FIG. 3 .

FIG. 11 is a plan view of a head unit 230 , corresponding to FIG. 2 .

FIG. 12 is a plan view of a head unit 240 , corresponding to FIG. 2 .

FIG. 13 is a plan view of a head unit 250 , corresponding to FIG. 2 .

FIG. 14 is a plan view of a head unit 260 , corresponding to FIG. 2 .

First Embodiment

In the following, a first embodiment of the present disclosure will be explained.

<Overall Configuration of Printer 1 >

As depicted in FIG. 1 , a printer 1 according to the first embodiment is provided with four ink-jet heads 2 , a platen 3 and conveying rollers 4 and 5 .

The four ink-jet heads 2 are arranged side by side in a conveyance direction (corresponding to a “second direction” of the present disclosure) which is horizontal and in which a recording paper sheet P is conveyed by the conveying rollers 4 and 5 as will be described later on. Each of the four ink-jet heads 2 is provided with four head units 11 (corresponding to a “liquid discharge head” of the present disclosure), and a holding member 12 . Each of the head units 11 discharges or jets an ink from a plurality of nozzles 10 formed in a lower surface thereof. Here, from the plurality of nozzles 10 in the four ink-jet heads 2 , black, yellow, cyan and magenta inks are discharged in this order from the upstream side in the conveyance direction.

Further, in each of the head units 11 , the plurality of nozzles 10 are aligned in a width direction of the paper (corresponding to a “first direction” of the present disclosure) which is horizontal and orthogonal to the conveyance direction to thereby form a nozzle row 9 . Furthermore, each of the head units 11 has two nozzle rows 9 arranged side by side in the conveyance direction. Moreover, between the two nozzle rows 9 , the positions of the nozzles 10 in the width direction are shifted by half a spacing distance (interval) between the nozzles 10 in each of the nozzle rows 9 . Note that the following explanation will be made, with the right side and the left side in the width direction being defined as depicted in FIG. 1 .

Further, each of the ink-jet heads 2 has four head units 11 . In each of the ink-jet heads 2 , two head units 11 among the four head units 11 are arranged side by side in the width direction at a spacing distance (interval) therebetween. Further, in each of the ink-jet heads 2 , remaining two head units 11 among the four head units 11 are also arranged side by side in the width direction at a spacing distance therebetween. Furthermore, among the four head units 11 , the two head units 11 arranged side by side in the width direction and the remaining two head units 11 arranged side by side in the width direction are arranged side by side in the conveyance direction at an interval therebetween. Moreover, two head units 11 arranged on the upstream side in the conveyance direction and two head units 11 arranged on the downstream side in the conveyance direction are arranged so that the positions in the width direction thereof are shifted. Further, a part of the nozzles 10 in each of the two head units 11 arranged on the upstream side in the conveyance direction overlaps with a part of the nozzles 10 in one of the two head units 11 arranged on the downstream side in the conveyance direction. With this, the plurality of nozzles 10 of the four head units 11 are arranged in the width direction over the entire length of the recording paper sheet P. Namely, each of the ink-jet heads 2 is a so-called line head extending in the width direction over the entire length of the recording paper sheet P.

The holding member 12 is a plate-like member which has a rectangular shape and of which longitudinal direction is the width direction; the four head units 11 are fixed to the holding member 12 . Further, the holding member 12 is formed with four through holes 12 a having a rectangular shape and corresponding to the four head units 11 , respectively. The plurality of nozzles 10 in the four head units 11 are exposed to the lower side (the side of the recording paper sheet P) via the four through holes 12 a corresponding thereto respectively.

The platen 3 is arranged at a location below the four the ink-jet heads 2 , and faces (is opposite to) the plurality of nozzles 10 of the four head units 2 . The platen 3 supports the recording paper sheet P from therebelow. The conveying roller 4 is arranged on the upstream side in the conveyance direction of the four ink-jet heads 2 and the platen 3 . The conveying roller 5 is arranged on the downstream side in the conveyance direction of the four ink-jet heads 2 and the platen 3 . The conveying rollers 4 and 5 convey the recording paper sheet P in the conveyance direction.

Further, in the printer 1 , recording is performed with respect to the recording paper P by discharging (jetting) the inks onto the recording paper sheet P from the plurality of nozzles 10 of the four head units 11 of the respective four ink-jet heads 2 , while conveying the recording paper sheet P in the conveyance direction by the conveying rollers 4 and 5 .

<Head Unit 11 >

Next, the head units 11 will be explained in detail. As depicted in FIGS. 2 and 3 , each of the head units 11 is provided with plates 21 to 23 , a vibration plate 25 , a plurality of piezoelectric elements 26 and a protective member 27 .

The plates 21 to 23 are stacked on top of one another in this order from a lower position in an up-down direction (corresponding to a “third direction” of the present disclosure). The plate 21 is formed, for example, of a synthetic resin such as polyimide, etc. Each of the plates 22 and 23 is formed, for example, of silicon (Si). A stacked body of the plates 21 to 23 is formed with a plurality of nozzles 10 , a plurality of pressure chambers 30 , a plurality of descenders 31 , a plurality of throttle portions 32 , and a connecting channel 33 .

The plurality of nozzles 10 are formed in the plate 21 . The plurality of nozzles 10 form the above-described two nozzle rows 9 . Note that in the first embodiment, nozzles 10 , among the plurality of nozzles 10 , which construct a nozzle row 9 located on the downstream side in the conveyance direction (hereinafter also referred to a “nozzle row 9 A” in some cases) among the two nozzle rows 9 correspond to “first nozzles” of the present disclosure; and nozzles 10 , among the plurality of nozzles 10 , which construct a nozzle row 9 located on the upstream side in the conveyance direction (hereinafter also referred to a “nozzle row 9 B” in some cases) among the two nozzle rows 9 correspond “second nozzles” of the present disclosure.

The plurality of pressure chambers 30 correspond to the plurality of nozzles 10 , respectively. The plurality of pressure chambers 30 are formed in the plate 23 . Each of the plurality of pressure chambers 30 has a shape projected in the up-down direction which is a rectangle and of which longitudinal direction is the conveyance direction.

Further, each of the plurality of nozzles 10 overlaps, in the up-down direction, with an end part on one side in the conveyance direction of one of the plurality of pressure chambers 30 . To provide more detailed explanation, each of the nozzles 10 constructing the nozzle row 9 A overlaps, in the up-down direction, with an end part on the upstream side in the conveyance direction of one of the plurality of pressure chambers 30 corresponding thereto. Further, each of the nozzles 10 constructing the nozzle row 9 B overlaps, in the up-down direction, with an end part on the downstream side in the conveyance direction of one of the plurality of pressure chambers 30 corresponding thereto. With this, in the plate 23 , the plurality of pressure chambers 30 are aligned in the width direction to thereby form two pieces of a pressure chamber row 8 which are arranged side by side in the conveyance direction. Further, in the first embodiment, pressure chambers 30 , among the plurality of pressure chambers 30 , constructing a pressure chamber row 8 on the downstream side in the conveyance direction (hereinafter also referred to as a “pressure chamber row 8 A” in some cases) among the two pressure chamber rows 8 correspond to “first pressure chambers” of the present disclosure; and pressure chambers 30 , among the plurality of pressure chambers 30 , constructing a pressure chamber row 8 on the upstream side in the conveyance direction (hereinafter also referred to as a “pressure chamber row 8 B” in some cases) among the two pressure chamber rows 8 correspond to “second pressure chambers” of the present disclosure.

The plurality of descenders 31 correspond to the plurality of nozzles 10 , respectively, and are formed in the plate 22 . Each of the plurality of descenders 31 extends in the up-down direction and connects one of the plurality of nozzles 10 and one of the plurality of pressure chambers 30 corresponding thereto. Note that in the first embodiment, descenders 31 , among the plurality of descenders 31 , corresponding to the nozzle row 9 A and the pressure chamber row 8 A correspond to “first descenders” of the present disclosure; and descenders 31 , among the plurality of descenders 31 , corresponding to the nozzle row 9 B and the pressure chamber row 8 B correspond to “second descenders” of the present disclosure.

The plurality of throttle portions 32 correspond to the plurality of pressure chambers 30 , respectively, and are formed in the plate 23 . Each of the plurality of throttle portions 32 extends in the conveyance direction, and a part on one side of each of the throttle portions 32 is connected to an end, of one of the pressure chambers 30 , on a side opposite to the nozzle 10 . Further, each of the plurality of throttle portions 32 has a length in the width direction which is shorter than that of one of the plurality of pressure chambers 30 . Accordingly, each of the plurality of throttle portions 32 has a channel resistance greater than that of one of the plurality of pressure chamber 30 .

Further, a certain nozzle 10 among the plurality of nozzles 10 , and one of the plurality of pressure chambers 30 , one of the plurality of descenders 31 and one of the plurality of throttle portions 32 which correspond to the certain nozzle 10 form an individual channel 20 . Furthermore, in the head unit 11 , two individual channel rows 7 , each of which is formed of a plurality of pieces of the individual channel 20 aligned in the width direction, are arranged side by side in the conveyance direction. Note that in the following description, an individual channel row 7 located on the downstream side in the conveyance direction (hereinafter also referred to an “individual channel row 7 A” in some cases) among the two individual channel rows 7 correspond to a “first individual channel row” of the present disclosure; an individual channel row 7 located on the upstream side in the conveyance direction (hereinafter also referred to an “individual channel row 7 B” in some cases) among the two individual channel rows 7 correspond to a “second individual channel row” of the present disclosure. Further, individual channels 20 , among the plurality of individual channels 20 , constructing the individual channel row 7 A (hereinafter also referred to “individual channels 20 A” in some cases) correspond to “first individual channels” of the present disclosure; and individual channels 20 , among the plurality of individual channels 20 , constructing the individual channel row 7 B (hereinafter also referred to “individual channels 20 B” in some cases) correspond to “second individual channels” of the present disclosure.

The connecting channel 33 has one common connecting channel 41 , a plurality of individual connecting channels 42 (corresponding to “first individual connecting channels” of the present disclosure), and a plurality of individual connecting channels 43 (corresponding to “second individual connecting channels” of the present disclosure). The common connecting channel 41 is formed in a lower end part of the plate 22 , and is located between the plurality of individual connecting channels 20 A and the plurality of individual connecting channels 20 B in the conveyance direction. Further, the common connecting channel 41 extends in the width direction along the entire lengths of the individual channel rows 7 A and 7 B. Note that the common connecting channel 41 does not have any connecting part with respect to an ink tank 50 (to be described later on), unlike manifolds 36 and 37 (to be described later on).

The plurality of individual connecting channels 42 correspond to the plurality of individual channels 20 A, respectively, and are formed in the lower end part of the plate 22 . Each of the individual connecting channels 42 extends in the conveyance direction and connects a lower end part of each of the descenders 31 of the individual channels 20 A with the common connecting channel 41 .

The plurality of individual connecting channels 43 correspond to the plurality of individual channels 20 B, respectively, and are formed in the lower end part of the plate 22 . Each of the individual connecting channels 43 extends in the conveyance direction and connects a lower end part of each of the descenders 31 of the individual channels 20 B with the common connecting channel 41 .

Further, the common connecting channel 41 , the plurality of individual connecting channels 42 and the plurality of individual connecting channels 43 are formed at parts, of the plate 22 , which are located at a same height, and have length in the up-down direction which are same with one another. With this, a ceiling surface 41 a of the common connecting channel 41 , a ceiling surface 42 of each of the plurality of individual connecting channels 42 and a ceiling surface 43 a of each of the plurality of individual connecting channels 43 are located on a same plane which is parallel to the width direction and the conveyance direction.

Further, in the conveyance direction, a length Lb 1 of each of the plurality of individual connecting channels 42 and a length Lb 2 of each of the plurality of individual connecting channels 43 are made to be shorter than a length L 3 of the common connecting channel 41 . Furthermore, the length L 3 in the conveyance direction of the common connecting channel 41 is made to be longer than a length Lc 1 in the width direction of each of the plurality of individual connecting channels 42 and a length Lc 2 in the width direction of each of the plurality of individual connecting channels 43 .

Here, provided that, a length La 1 is a length in the up-down direction between the center in the up-down direction of a connecting part of each of the plurality of descenders 31 with respect to one of the plurality of first individual connecting channels 42 , and one of the plurality of nozzles 10 ; and a length La 2 is a length in the up-down direction between the center in the up-down direction of a connecting part of each of the plurality of descenders 31 with respect to one of the plurality of first individual connecting channels 43 , and one of the plurality of nozzles 10 . Further, V is velocity of propagation of pressure wave in a liquid in a case that a piezoelectric element 26 is driven as will be described later on; and T is a period of the pressure wave. In this case, a relationship |La 1 −Lb 1 |=n 1 ×V×T holds, and a relationship |La 2 −Lb 2 =n 2 ×V×T holds. In these relationships, n 1 and n 2 are each a natural number.

The vibration plate 25 is arranged on the upper surface of the plate 23 , and covers the plurality of pressure chambers 30 . The vibration plate 25 is formed, for example, of silicon dioxide (SiO 2 ) or silicon nitride (SiN). The vibration plate 25 is formed, for example, by oxidizing or nitriding an upper end part of the plate 23 .

A plurality of piezoelectric elements 26 correspond to the plurality of pressure chambers 30 , respectively. Each of the plurality of piezoelectric elements 26 is arranged in a part, of the upper surface of the vibration plate 25 , overlapping in the up-down direction with one of the plurality of pressure chambers 30 corresponding thereto. Here, each of the plurality of piezoelectric elements 26 is formed of: a piezoelectric body formed of a piezoelectric material containing, as a main component thereof, lead zirconate titanate which is a mixed crystal of lead titanate and lead zirconate; and electrodes sandwiching the piezoelectric body therebetween in the up-down direction. Further, in a case that any difference in the potential is generated in the electrodes sandwiching the piezoelectric body therebetween so that an electric field is generated in the piezoelectric body, thereby deforming the piezoelectric body piezoelectrically. This deforms each of the piezoelectric elements 26 and a part of the vibration plate 25 which overlaps, in the up-down direction, with a certain pressure chamber 30 among the plurality of the pressure chambers 30 corresponding to each of the piezoelectric elements 26 thereby changing the volume of the certain pressure chamber 30 and thus causing the pressure in the ink inside the certain pressure chamber 30 to vary or change. As a result, ink is jetted or discharged from a certain nozzle 10 included in the nozzles 10 and corresponding to the certain pressure chamber 30 . Note, however, that the construction per se of the piezoelectric element 26 is similar to that of a conventional piezoelectric element, and thus any further detailed explanation therefor will be omitted.

The protective member 27 is formed, for example, of silicon (Si), and is arranged on the upper surface, of the vibration plate 25 , on which the plurality of piezoelectric elements 26 are arranged. Two recessed parts 27 a corresponding to the two pressure chamber rows 7 , respectively, are formed in the lower surface of the protective member 27 . Each of the two recessed parts 27 a extends in the width direction; the plurality of piezoelectric elements 26 corresponding to the respective individual channel rows 7 are accommodated in the inside of the recessed parts 27 a corresponding to the pressure chamber rows 7 , respectively.

Further, the head unit 11 has a first manifold 36 (corresponding to a “first common channel” of the present disclosure) and a second manifold 37 (corresponding to a “second common channel” of the present disclosure). The first manifold 36 extends, in the up-down direction in a lower part of the protecting member 27 , the plate 23 and the vibration plate 25 . Further, the first manifold 36 is located on the downstream side in the conveyance direction of the plurality of individual channels 20 A, and extends in the width direction along the entire length of the individual channel row 7 A. Furthermore, ends on the downstream side in the conveyance direction of the plurality of throttle portions 32 of the plurality of individual channels 20 A are connected to the first manifold 36 .

The second manifold 37 extends, in the up-down direction in the lower part of the protecting member 27 , the plate 23 and the vibration plate 25 . Further, the second manifold 37 is located on the upstream side in the conveyance direction of the plurality of individual channels 20 B, and extends in the width direction along the entire length of the individual channel row 7 B. Furthermore, ends on the upstream side in the conveyance direction of the plurality of throttle portions 32 of the plurality of individual channels 20 B are connected to the second manifold 37 .

Moreover, a supply channel 38 is formed in an upper part of the protecting member 27 , at a location overlapping, in the up-down direction, with a central part in the width direction of the first manifold 36 . A lower end of the supply channel 38 is connected to the first manifold 36 . Further, an upper end of the supply channel 38 is connected to an ink tank 50 (corresponding to a “liquid supply source” of the present disclosure) via a non-depicted channel. Furthermore, a pump 51 is provided on a channel between the supply channel 38 and the ink tank 50 . The pump 51 feds the ink from the ink tank 50 toward the supply channel 38 . Note that in the first embodiment, a connecting part of the first manifold 36 at which the first manifold 36 is connected to the supply channel 38 corresponds to a “first connecting part” of the present disclosure.

Moreover, a discharge channel 39 is formed in the upper part of the protecting member 27 , at a location overlapping, in the up-down direction, with a central part in the width direction of the second manifold 37 . A lower end of the discharge channel 39 is connected to the second manifold 37 . Further, an upper end of the discharge channel 39 is connected to the ink tank 50 via a non-depicted channel. Furthermore, a pump 52 is provided on a channel between the discharge channel 39 and the ink tank 50 . The pump 52 feds the ink from the discharge channel 39 toward the ink tank 50 . Note that in the first embodiment, a connecting part of the second manifold 37 at which the second manifold 37 is connected to the discharge channel 39 corresponds to a “second connecting part” of the present disclosure.

Moreover, in a case that the pumps 51 and 52 are driven, the ink inside the ink tank 50 is allowed to flow into the first manifold 36 via the supply channel 38 . The ink inside the first manifold 36 flows from the plurality of throttle portions 32 into the plurality of individual channels 20 A, respectively. The ink inside the plurality of individual channels 20 A flows, via the plurality of individual connecting channels 42 , respectively, into the common connecting channel 41 , and further flows into the plurality of individual channels 20 B via the plurality of individual connecting channels 43 , respectively. The ink inside the plurality of individual channels 20 B flows from the plurality of throttle portions 32 , respectively, into the second manifold 37 . The ink inside the second manifold 37 is discharged from the discharge channel 39 , and returns to the ink tank 50 . With this, the ink is circulated between the head unit 11 and the ink tank 50 . Note that it is allowable that only one of the pumps 51 and 52 is provided. In such a case also, it is possible to circulate the ink in a similar manner as described above.

<Effects of First Embodiment>

In the first embodiment, the common connecting channel 41 , which is common to the plurality of individual connecting channels 42 corresponding to the plurality of individual channels 20 A, respectively, and the plurality of individual connecting channel 43 corresponding to the plurality of individual channels 20 B, respectively, is provided between the plurality of individual connecting channels 42 and the plurality of individual connecting channels 43 . With this, the channel resistance of the connecting channel 33 connecting the plurality of individual channels 20 A and the plurality of individual channels 20 B is made to be small, thereby making it possible to cause the ink to flow sufficiently between the plurality of individual channels 20 A and the plurality of individual channels 20 B via the connecting channel 33 . Further, since the channel resistance of the connecting channel 33 is small, the ink flows easily into the connecting channel 33 , while avoiding such a situation that the ink leaks from the nozzles 10 .

Further, in the first embodiment, each of the individual connecting channels 42 is connected to one of the descenders 31 of the individual channels 20 A, and each of the individual connecting channels 43 is connected to one of the descenders 31 of the individual channels 20 B. With this, it is possible to flow the ink sufficiently between the descenders 31 of the plurality of individual channels 20 A and the descenders 31 of the plurality of individual channels 20 B, via the connecting channel 33 .

Furthermore, in the first embodiment, the plurality of individual connecting channels 42 are connected to the lower end parts of the descenders 31 of the individual channels 20 A, respectively, and the plurality of individual connecting channels 43 are connected to the lower end parts of the descenders 31 of the individual channels 20 B, respectively. Moreover, the positions and length in the up-down direction are all same in (among) the common connecting channel 41 and the plurality of individual connecting channels 42 and the plurality of individual connecting channels 43 ; the common connecting channel 41 has no parts which are located below the plurality of individual connecting channels 42 and the plurality of individual connecting channels 43 . With this, it is possible allow each of the plurality of individual connecting channels 42 and the plurality of individual connecting channels 43 to be connected to a part, in the descender 31 , which is located closely to the nozzle 10 in the up-down direction as much as possible. As a result, it is possible to discharge any air bubble, inflowing into the descender 31 of each of the individual channels 20 A from the nozzle of each of the individual channel 20 A, effectively to the second manifold 37 via the connecting channel 33 and one of the individual channels 20 B. Further, in a case that ink is circulated between the head unit 11 and the ink tank 50 , the ink is allowed to flow in the part, of the descender 31 , which is close to the nozzle 10 , thereby making it possible to suppress any drying of the ink inside the nozzle 10 .

Further, in the first embodiment, the relationship |La 1 −Lb 1 =n 1 ×V×T holds, and the relationship |La 2 −Lb 2 |=n 2 ×V×T holds. With this, a pressure wave propagating in the inside of the descender 31 from the pressure chamber 30 toward the nozzle 10 , and a pressure wave propagating from the descender 31 toward the individual connecting channel 42 , 43 and reflected off the connecting part at which the individual connecting channel 42 , 43 is connected to the common connecting channel 41 and returning back to the descender 31 do not become to be inverse phases to each other, do not cancel each other out and are not attenuated. With this, it is possible to avoid such a situation that the ink cannot be normally discharged from the nozzle 10 .

Furthermore, in the first embodiment, the ceiling surface 41 a of the common connecting channel 41 and the ceiling surface 42 a of each of the plurality of individual connecting channels 42 and the ceiling surface 43 a of each of the plurality of individual connecting channels 43 are located on the same horizontal plane. Accordingly, any air bubble inside the connecting channel 33 flows smoothly along the ceiling surfaces 41 a to 43 a between the common connecting channel 41 and the individual connecting channels 42 and 43 . With this, it is possible to avoid such a situation that the air bubble remains or accumulates in the inside of the connecting channel 33 .

Moreover, in the first embodiment, with respect to such a configuration that the individual channel row 7 A and the individual channel row 7 B are arranged in the conveyance direction at the interval therebetween, it is possible to arrange the connecting channel 33 , which includes the common connecting channel 41 which extends in the width direction along the entire length of the individual channel rows 7 A and 7 B and of which volume is allowed to be large, between the individual channel rows 7 A and 7 B in the conveyance direction.

Further, in the first embodiment, the length L 3 in the conveyance direction of the common connecting channel 41 is made to be longer than the length Lc 1 in the width direction of each of the plurality of individual connecting channels 42 and the length Lc 2 in the width direction of each of the plurality of individual connecting channels 43 . With this, it is possible to make the volume of the common connecting channel 41 to be large, and to make the channel resistance in the connecting channel 33 as a whole to be small.

Furthermore, in the first embodiment, the length Lb 1 in the conveyance direction of each of the plurality of individual connecting channels 42 and the length Lb 2 in the conveyance direction of each of the plurality of individual connecting channels 43 are made to be shorter than the length L 3 in the conveyance direction of the common connecting channel 41 . With this, in the conveyance direction, the lengths of the individual channels 42 and 43 of which channel resistance is large is made to be short, and the length of the common connecting channel 41 of which channel resistance is small is made to be long, thereby making it possible to make the channel resistance of the connecting channel 33 as a whole to be small as much as possible.

Second Embodiment

Next, a second embodiment of the present disclosure will be explained. The second embodiment has such a configuration wherein the head unit 11 in the first embodiment is replaced by a head unit 100 .

<Head Unit 100 >

As depicted in FIGS. 4 to 6 , the head units 100 is provided with a plurality of plates 111 to 113 , a vibration plate 115 , a plurality of piezoelectric elements 116 and a protective member 117 .

The plurality of plates 111 to 113 are stacked on top of one another in this order from a lower position in the up-down direction. The plate 111 is formed, for example, of a synthetic resin material such as polyimide, etc. Each of the plates 112 and 113 is formed, for example, of silicon (Si). A stacked body of the plates 111 to 113 is formed with a plurality of nozzles 100 , a plurality of pressure chambers 130 , a plurality of descenders 131 , a plurality of throttles 132 , and two connecting channels 133 a and 133 b.

The plurality of nozzles 110 are formed in the plate 111 . Further, the plate 111 has four nozzle rows 109 ( 109 A, 109 B, 109 C and 109 D) each of which is formed by aligning nozzles 110 , among the plurality of nozzles 110 , in the width direction.

The nozzle row 109 B is arranged on the left side in the width direction of the nozzle row 109 A, and nozzles 110 , among the plurality of nozzles 110 , which construct the nozzle row 109 A and nozzles 110 , among the plurality of nozzles 110 , which construct the nozzle row 109 B are aligned in the width direction to form a row. Note, however, that a spacing distance (gap) J between a leftmost nozzle 110 located on the leftmost side among the nozzles 110 constructing the nozzle row 109 A and a rightmost nozzle 110 located on the rightmost side among the nozzles 110 constructing the nozzle row 109 B is m times (m is an integer of not less than 2 (two), in FIG. 4 , m=2) a spacing distance K between the nozzles 110 in each of the nozzle rows 109 A and 109 B.

The nozzle rows 109 C and 109 D are arranged on the downstream side in the conveyance direction of the nozzle rows 109 A and 109 B. The nozzle row 109 D is arranged on the left side in the width direction of the nozzle row 109 C; and nozzles 110 , among the plurality of nozzles 110 , constructing the nozzle row 109 C and nozzles 110 , among the plurality of nozzles 110 , constructing the nozzle row 109 D are aligned in the width direction to form a row. Note, however, that a spacing distance (gap) J between a leftmost nozzle 110 located on the leftmost side among the nozzles 110 constructing the nozzle row 109 C and a rightmost nozzle 110 located on the rightmost side among the nozzles 110 constructing the nozzle row 109 D is m times (m is an integer of not less than 2 (two), in FIG. 4 , m=2) a spacing distance K between the nozzles 110 in each of the nozzle rows 109 C and 109 D.

Further, the nozzles 110 constructing the nozzle rows 109 C and 109 D are shifted relative to the nozzles 110 constructing the nozzle rows 109 A and 109 B, only by a length which is half the spacing distance K among the nozzles 110 in each of the nozzle rows 109 A to 109 D. Further, the number of the nozzles 110 constructing the nozzle row 109 C is greater than the number of the nozzles 110 constructing the nozzle row 109 A; and the number of the nozzles 110 constructing the nozzle row 109 D is smaller than the number of the nozzles 110 constructing the nozzle row 109 B.

With this, a position in the width direction of an area 105 A between the nozzle row 109 A (“individual channel row 107 A” which will be described later on) and the nozzle row 109 B (“individual channel row 107 B” which will be described later on) is different from a position in the width direction of an area 105 B between the nozzle row 109 C (“individual channel row 107 C” which will be described later on) and the nozzle row 109 D (“individual channel row 107 D” which will be described later on). Further, the nozzles 110 constructing the nozzle row 109 C is located at a position in the width direction between the nozzle row 109 A and the nozzle row 109 B. Furthermore, the nozzles 110 constructing the nozzle row 109 B is located at a position in the width direction between the nozzle row 109 C and the nozzle row 109 D.

Note that in the second embodiment, the nozzles 110 which construct the nozzle rows 109 A and 109 C correspond to “first nozzles” of the present disclosure; and the nozzles 110 which construct the nozzle rows 109 B and 109 D correspond to “second nozzles” of the present disclosure.

The plurality of pressure chambers 130 correspond to the plurality of nozzles 110 , respectively. The plurality of pressure chambers 130 are formed in the plate 113 . Each of the plurality of pressure chambers 130 has a shape similar to the shape of the pressure chamber 30 . Further, similarly to the first embodiment, each of the plurality of nozzles 110 overlaps, in the up-down direction, with an end part on one side in the conveyance direction of one of the plurality of pressure chambers 130 . With this, in the plate 113 , the plurality of pressure chambers 130 are aligned in the width direction to thereby form four pieces of a pressure chamber row 108 (pressure chamber rows 108 A, 108 B, 108 C and 108 D). Note that in the second embodiment, pressure chambers 130 , among the plurality of pressure chambers 130 , constructing the pressure chamber rows 109 A and 108 C correspond to “first pressure chambers” of the present disclosure; and pressure chambers 130 , among the plurality of pressure chambers 130 , constructing the pressure chamber rows 108 B and 108 D correspond to “second pressure chambers” of the present disclosure.

The plurality of descenders 131 correspond to the plurality of nozzles 110 , respectively, and are formed in the plate 112 . Each of the plurality of descenders 131 extends in the up-down direction and connects one of the plurality of nozzles 110 and one of the plurality of pressure chambers 130 corresponding thereto. Note that in the second embodiment, descenders 131 , among the plurality of descenders 131 , corresponding to the nozzle rows 109 A and 109 C correspond to “first descenders” of the present disclosure; and descenders 131 , among the plurality of descenders 131 , corresponding to the nozzle rows 109 B and 109 D correspond to “second descenders” of the present disclosure.

The plurality of throttles 132 correspond to the plurality of pressure chambers 130 , respectively, and are formed in the plate 113 . Each of the plurality of throttles 132 extends in the conveyance direction, and a part on one side in the conveyance direction of each of the plurality of throttles 132 is connected to an end, of one of the pressure chambers 130 , on a side opposite to the nozzle 110 .

Further, a certain nozzle 110 among the plurality of nozzles 110 , and one of the plurality of pressure chambers 130 , one of the plurality of descenders 131 , and one of the plurality of throttles 132 which correspond to the certain nozzle 110 form an individual channel 120 . Furthermore, the head unit 100 has four individual channel rows 107 ( 107 A, 107 B, 107 C and 107 D) each of which is formed by aligning a plurality of pieces of the individual channel 120 in the width direction. Note that in the following description, the plurality of individual channels 102 constructing the individual channel rows 107 A, 107 B, 107 C and 107 D are also referred to as “individual channels 120 A, 120 B, 120 C and 120 D”, respectively. In the second embodiment, the individual channel rows 107 A and 107 C correspond to a “first individual channel row” of the present disclosure; and the individual channel rows 107 B and 107 D correspond to a “second individual channel row” of the present disclosure. Furthermore, the individual channels 120 A and 102 C correspond to “first individual channels” of the present disclosure; and individual channels 120 B and 120 D correspond to “second individual channels” of the present disclosure.

Moreover, in the following explanation, a row in which the individual channel row 107 A and the individual channel row 107 B are combined and in which a plurality of pieces of the individual channel 120 are aligned (arranged side by side) in the width direction are collectively referred to as a synthetized individual channel row 106 A, in some cases. Further, a row in which the individual channel row 107 C and the individual channel row 107 D are combined and in which a plurality of pieces of the individual channel 120 are aligned (arranged side by side) in the width direction is collectively referred to as a synthetized individual channel row 106 B, in some cases. Note that, in the second embodiment, the synthetized individual channel rows 106 A and 106 B each correspond to an “individual channel row” of the present disclosure.

The connecting channel 133 a is provided with respect to the synthetized individual channel row 106 A (individual channel rows 107 A, 107 C). The connecting channel 133 a has one common connecting channel 141 a , a plurality of individual connecting channels 142 a , and a plurality of individual connecting channels 143 a . The common connecting channel 141 a is formed in a lower end part of the plate 112 , and is located between the synthetized individual channel rows 106 A and 106 B in the conveyance direction. Further, the common connecting channel 141 a extends in the width direction along the entire length of the synthetized individual channel row 106 A. Furthermore, the common connecting channel 141 a has a length in the conveyance direction which is constant regardless of a position in the width direction, and thus has a cross-sectional area, of a cross section orthogonal to the width direction, which is constant. With this, the common connecting channel 141 a has channel resistance per unit length which is constant regardless of the position in the width direction. Note that the common connecting channel 141 a does not have any connecting part with respect to the ink tank 150 , unlike manifolds 136 a and 137 a which will be described later on.

The plurality of individual connecting channels 142 a correspond to the plurality of individual channels 120 A, respectively, and are formed in the lower end part of the plate 122 . Each of the individual connecting channels 142 a extends in the conveyance direction and connects a lower end part of one of the descenders 131 of the individual channels 120 A with the common connecting channel 141 a . Further, in the plurality of individual connecting channels 142 a , a length Lc 11 in the width direction of a certain individual connecting channel 142 a among the individual connecting channels 142 a becomes shorter as the certain individual connecting channel 142 a is located more closely to the left side in the width direction (to the side of the individual channel row 107 B), thereby making a cross-sectional area, of a cross section orthogonal to the conveyance direction, of the certain individual connecting channel 142 a among the plurality of individual connecting channels 142 a to be smaller as the certain individual connecting channel 142 a is located more closely to the left side in the width direction (to the side of the individual connecting channel row 107 B). With this, in the plurality of individual connecting channels 142 a , the channel resistance of the certain individual connecting channel 142 a among the plurality of individual connecting channel 142 a becomes greater as the certain individual connecting channel 142 a is located, in the width direction, more closely to the left side (to the side of the individual connecting channel row 107 B).

The plurality of individual connecting channels 143 a correspond to the plurality of individual channels 120 B, respectively, and are formed in the lower end part of the plate 122 . Each of the individual connecting channels 143 a extends in the conveyance direction and connects a lower end part of one of the descenders 131 of the individual channels 120 B with the common connecting channel 141 a . Further, in the plurality of individual connecting channels 143 a , a length Lc 21 in the width direction of a certain individual connecting channel 143 a among the individual connecting channels 143 a becomes shorter as the certain individual connecting channel 143 a is located more closely to the right side in the width direction (to the side of the individual channel row 107 A), thereby making a cross-sectional area, of a cross section orthogonal to the conveyance direction, of the certain individual connecting channel 143 a among the plurality of individual connecting channels 143 a to be smaller as the certain individual connecting channel 143 a is located more closely to the right side in the width direction (to the side of the individual channel row 107 A). With this, in the plurality of individual connecting channels 143 a , the channel resistance of the certain individual connecting channel 143 a among the plurality of individual connecting channel 143 a becomes greater as the certain individual connecting channel 143 a is located, in the width direction, more closely to the right side (toward the individual connecting channel row 107 A).

The connecting channel 133 b is provided with respect to the synthetized individual channel row 106 B (individual channel rows 107 C, 107 D). The connecting channel 133 b has one common connecting channel 141 b , a plurality of individual connecting channels 142 b , and a plurality of individual connecting channels 143 b . The common connecting channel 141 b is formed in the lower end part of the plate 112 , and is located between the common connecting channel 141 a and the synthetized individual channel row 106 B in the conveyance direction. Further, the common connecting channel 141 b extends in the width direction along the entire length of the synthetized individual channel row 106 B. Furthermore, the common connecting channel 141 b has a length in the conveyance direction which is constant regardless of a position in the width direction, and thus has a cross-sectional area, of a cross section orthogonal to the width direction, which is constant. With this, the common connecting channel 141 b has channel resistance per unit length which is constant regardless of the position in the width direction. Note that the common connecting channel 141 b does not have any connecting part with respect to the ink tank 150 , unlike the manifolds 136 a and 137 a which will be described later on.

The plurality of individual connecting channels 142 b correspond to the plurality of individual channels 120 C, respectively, and are formed in the lower end part of the plate 122 . Each of the individual connecting channels 142 b extends in the conveyance direction and connects a lower end part of one of the descenders 131 of the individual channels 120 C with the common connecting channel 141 b . Further, in the plurality of individual connecting channels 142 b , a length Lcl 2 in the width direction of a certain individual connecting channel 142 b among the individual connecting channels 142 b becomes shorter as the certain individual connecting channel 142 b is located more closely to the left side in the width direction (to the side of the individual channel row 107 D), thereby making a cross-sectional area, of a cross section orthogonal to the conveyance direction, of the certain individual connecting channel 142 b among the plurality of individual connecting channels 142 b to be smaller as the certain individual connecting channel 142 b is located more closely to the left side in the width direction (to the side of the individual channel row 107 D). With this, in the plurality of individual connecting channels 142 b , the channel resistance of the certain individual connecting channel 142 b among the plurality of individual connecting channel 142 b becomes greater as the certain individual connecting channel 142 b is located, in the width direction, more closely to the left side (toward the individual connecting channel row 107 D).

The plurality of individual connecting channels 143 b correspond to the plurality of individual channels 120 D, respectively, and are formed in the lower end part of the plate 122 . Each of the individual connecting channels 143 b extends in the conveyance direction and connects a lower end part of one of the descenders 131 of the individual channels 120 D with the common connecting channel 141 b . Further, in the plurality of individual connecting channels 143 b , a length Lc 22 in the width direction of a certain individual connecting channel 143 b among the individual connecting channels 143 b becomes shorter as the certain individual connecting channel 143 b is located more closely to the right side in the width direction (to the side of the individual channel row 107 C), thereby making a cross-sectional area, of the cross section orthogonal to the conveyance direction, of the certain individual connecting channel 143 b among the plurality of individual connecting channels 143 b to be smaller as the certain individual connecting channel 143 b is located more closely to the right side in the width direction (to the side of the individual channel row 107 C). With this, in the plurality of individual connecting channels 143 b , the channel resistance of the certain individual connecting channel 143 b among the plurality of individual connecting channel 143 b becomes greater as the certain individual connecting channel 143 b is located, in the width direction, more closely to the right side (toward the individual connecting channel row 107 C).

The vibration plate 115 is similar to the vibration plate 25 , is arranged on the upper surface of the plate 113 , and covers the plurality of pressure chambers 130 . The plurality of piezoelectric elements 116 correspond to the plurality of pressure chambers 130 , respectively. The plurality of piezoelectric elements 116 are similar to the plurality of piezoelectric elements 26 ; each of the plurality of piezoelectric elements 116 is arranged in a part, of the upper surface of the vibration plate 115 , overlapping in the up-down direction with one of the plurality of pressure chambers 130 corresponding thereto.

The protective member 117 is arranged on the upper surface, of the vibration plate 115 , on which the plurality of piezoelectric elements 116 are arranged. Two recessed parts 117 a corresponding to the synthetized individual channel rows 106 A and 106 B, respectively, are formed in the lower surface of the protective member 117 . Each of the two recessed parts 117 a extends in the width direction; the piezoelectric elements 116 corresponding to the respective synthetized individual channel rows 106 A and 106 B are accommodated in the inside of the recessed parts 117 a corresponding to the synthetized individual channel rows 106 A and 106 B, respectively.

Further, the head unit 100 has two first manifolds 136 a , 136 b (corresponding to a “first common channel” of the present disclosure) and two second manifolds 137 a , 137 b (corresponding to a “second common channel” of the present disclosure).

The first manifold 136 a extends, in the up-down direction in a lower part of the protecting member 117 , the plate 113 and the vibration plate 115 . Further, the first manifold 136 a is located on the upstream side in the conveyance direction of the individual channel row 107 A, and extends in the width direction along the entire length of the individual channel row 107 A. Furthermore, ends on the upstream side in the conveyance direction of the plurality of throttles 132 of the plurality of individual channels 120 A are connected to the first manifold 136 a.

The second manifold 137 a extends, in the up-down direction in the lower part of the protecting member 117 , the plate 113 and the vibration plate 115 . Further, the second manifold 137 a is located on the upstream side in the conveyance direction of the individual channel row 107 B, and extends in the width direction along the entire length of the individual channel row 107 B. Furthermore, ends on the upstream side in the conveyance direction of the plurality of throttles 132 of the plurality of individual channels 120 B are connected to the second manifold 137 a.

Further, a connecting channel 135 a extending in the width direction and connecting the first manifold 136 a and the second manifold 137 a is arranged in parts, of the plate 113 and the vibration plate 115 , respectively, which are arranged between the first and second manifolds 136 a and 137 a in the width direction. The connecting channel 135 a has a length in the conveyance direction which is shorter than those of the first and second manifolds 136 a and 137 a , and thus has a small cross-sectional area of a cross section orthogonal to the width direction. With this, the connecting channel 135 a has channel resistance per unit length which is greater than that of each of the first and second manifolds 136 a and 137 a.

The first manifold 136 b extends, in the up-down direction in the lower part of the protecting member 117 , the plate 113 and the vibration plate 115 . Further, the first manifold 136 b is located on the downstream side in the conveyance direction of the individual channel row 107 C, and extends in the width direction along the entire length of the individual channel row 107 C. Furthermore, ends on the downstream side in the conveyance direction of the plurality of throttles 132 of the plurality of individual channels 120 C are connected to the first manifold 136 b.

The second manifold 137 b extends, in the up-down direction in the lower part of the protecting member 117 , the plate 113 and the vibration plate 115 . Further, the second manifold 137 b is located on the downstream side in the conveyance direction of the individual channel row 107 D, and extends in the width direction along the entire length of the individual channel row 107 D. Furthermore, ends on the downstream side in the conveyance direction of the plurality of throttles 132 of the plurality of individual channels 120 D are connected to the second manifold 137 b.

Further, a connecting channel 135 b extending in the width direction and connecting the first manifold 136 b and the second manifold 137 b is arranged in parts, of the plate 113 and the vibration plate 115 , respectively, which are arranged between the first and second manifolds 136 b and 137 b in the width direction. The connecting channel 135 b has a length in the conveyance direction which is shorter than those of the first and second manifolds 136 b and 137 b , and thus has a small cross-sectional area of a cross section orthogonal to the width direction. With this, the connecting channel 135 b has channel resistance per unit length which is greater than that of each of the first and second manifolds 136 b and 137 b.

Furthermore, as depicted in FIGS. 4 and 5 , a supply channel 138 a which is connected to the first manifold 136 a is formed in an upper part of the protecting member 117 , at a location overlapping, in the up-down direction, with a right end part in the width direction of the first manifold 136 a . Further, the supply channel 138 a is connected to an ink tank 150 (corresponding to a “liquid supply source” of the present disclosure) via a non-depicted channel which is provided with a pump 151 a at an intermediate part thereof. The pump 151 a feds the ink from the ink tank 150 toward the supply channel 138 a.

Furthermore, a supply channel 138 b which is connected to the first manifold 136 b is formed in the upper part of the protecting member 117 , at a location overlapping, in the up-down direction, with a right end part in the width direction of the first manifold 136 b . Further, the supply channel 138 b is connected to the ink tank 150 via a non-depicted channel which is provided with a pump 151 b at an intermediate part thereof. The pump 151 b feds the ink from the ink tank 150 toward the supply channel 138 b.

Note that in the second embodiment, connecting parts of the first manifolds 136 a and 136 b at which the first manifolds 136 a and 136 b are connected to the supply channels 138 a and 138 b , respectively, correspond to a “first connecting part” of the present disclosure.

Further, as depicted in FIGS. 4 and 6 , a discharge channel 139 a is formed in the upper part of the protecting member 117 , at a location overlapping, in the up-down direction, with a left end part in the width direction of the second manifold 137 a . The discharge channel 139 a is connected to the second manifold 137 a at an lower end part of the discharge channel 139 a . Further, an upper end part of the discharge channel 139 a is connected to the ink tank 150 via a non-depicted channel. A pump 152 a is provided in a channel between the discharge channel 139 a and the ink tank 150 . The pump 152 a feds the ink from the discharge channel 139 a toward the ink tank 150 .

Furthermore, a discharge channel 139 b is formed in the upper part of the protecting member 117 , at a location overlapping, in the up-down direction, with a left end part in the width direction of the second manifold 137 b . The discharge channel 139 b is connected to the second manifold 137 b at an lower end part of the discharge channel 139 b . Further, an upper end part of the discharge channel 139 b is connected to the ink tank 150 via a non-depicted channel. A pump 152 b is provided on in a channel between the discharge channel 139 b and the ink tank 150 . The pump 152 b feds the ink from the discharge channel 139 b toward the ink tank 150 .

Note that in the second embodiment, connecting parts of the second manifolds 137 a and 137 b at which the second manifolds 137 a and 137 b are connected to the discharge channels 139 a and 139 b , respectively, correspond to a “second connecting part” of the present disclosure.

Further, in a case that the pumps 151 a , 151 b , 152 a and 152 b are driven, the ink inside the ink tank 150 is allowed to flow into the first manifolds 136 a and 136 b via the supply channels 138 a and 138 b , respectively. The ink inside the first manifolds 136 a and 136 b flows mainly from the plurality of throttles 132 into the plurality of individual channels 120 A and 120 C, respectively. Further, a part of the ink inside the first manifolds 136 a and 136 b flows into the second manifolds 137 a and 137 b via the connecting channels 135 a and 135 b , respectively.

The ink inside the plurality of individual channels 120 A and the plurality of individual channels 120 C flows, via the plurality of individual connecting channels 142 a and the plurality of individual connecting channels 142 b , into the common connecting channels 141 a and 141 b , respectively, and further flows into the plurality of individual channels 120 B and the plurality of individual channels 120 D via the plurality of individual connecting channels 143 a and the plurality of individual connecting channels 143 b , respectively. The ink inside the plurality of individual channels 120 B and the plurality of individual channels 120 D flows from the plurality of throttles 132 and into the second manifolds 137 a and 137 b , respectively. The ink inside the second manifolds 137 a and 137 b is discharged from the discharge channels 139 a and 139 b , respectively, and returns to the ink tank 150 . With this, the ink is circulated between the head unit 100 and the ink tank 150 .

Note that in the second embodiment, it is allowable that the supply channels 138 a and 138 b and the discharge channels 139 a and 139 b are connected to the one tank 150 . The present disclosure, however, is not limited to this configuration. It is allowable that an ink tank connected to the supply channel 138 a and the discharge channel 139 a is provided separately from an ink tank connected to the supply channel 138 b and the discharge channel 139 b . Alternatively, it is allowable that only one of the pumps 151 a and 152 a is provided, or that only one of the pumps 151 b and 152 b is provided. In such a case also, it is possible to circulate the ink in a similar manner as described above.

<Effects>

In the second embodiment, the common connecting channel 141 a , which is common to the plurality of individual connecting channels 142 a provided individually with respect to the plurality of individual channels 120 A, respectively, and the plurality of individual connecting channel 143 a provided individually with respect to the plurality of individual channels 120 C, respectively, is provided between the plurality of individual connecting channels 142 a and the plurality of individual connecting channels 143 a . With this, the channel resistance of the connecting channel 133 a connecting the plurality of individual channels 120 A and the plurality of individual channels 120 C is made to be small, thereby making it possible to cause the ink to flow sufficiently between the plurality of individual channels 120 A and the plurality of individual channels 120 C via the connecting channel 133 a . Further, since the channel resistance of the connecting channel 133 a is small, the ink flows easily from the connecting channel 133 a into the descenders 131 of the individual channels 120 A, while avoiding such a situation that the ink leaks from the nozzles 110 .

Similarly, the common connecting channel 141 b , which is common to the plurality of individual connecting channels 142 b provided individually with respect to the plurality of individual channels 120 B, respectively, and the plurality of individual connecting channel 143 b provided individually with respect to the plurality of individual channels 120 D, respectively, is provided between the plurality of individual connecting channels 142 b and the plurality of individual connecting channels 143 b . With this, the channel resistance of the connecting channel 133 b connecting the plurality of individual channels 120 B and the plurality of individual channels 120 D is made to be small, thereby making it possible to cause the ink to flow sufficiently between the plurality of individual channels 120 B and the plurality of individual channels 120 D via the connecting channel 133 b . Further, since the channel resistance of the connecting channel 133 b is small, the ink flows easily from the connecting channel 133 b into the descenders 131 of the individual channels 120 B, while avoiding such a situation that the ink leaks from the nozzles 110 .

Further, in the second embodiment, with respect to such a configuration that the individual channel row 107 A and the individual channel row 107 B are arranged side by side in the width direction so as to form one synthetized individual channel row 106 A, the connecting channel 133 a which includes the common connecting channel 141 a which extends in the width direction and of which volume is relatively large can be arranged along the entire length of the synthetized individual channel row 106 A. Similarly, with respect to such a configuration that the individual channel row 107 C and the individual channel row 107 D are arranged side by side in the width direction so as to form one synthetized individual channel row 106 B, the connecting channel 133 b which includes the common connecting channel 141 b which extends in the width direction and of which volume is relatively large can be arranged along the entire length of the synthetized individual channel row 106 B.

Here, there is considered such a case that, unlike the second embodiment, the channel resistance is uniform in all the individual connecting channels 142 a , that the channel resistance is uniform in all the individual connecting channels 143 a , and that the channel resistance per unit length is constant in the common connecting channel 141 a regardless of the position in the width direction. In such a case, when the ink flows between the plurality of individual channels 120 A and the plurality of individual channel 120 B via the connecting channel 133 a , the ink is less likely to easily flow to an individual channel 120 A which is included in the plurality of individual channels 120 A and which is located on the right side, far from the individual channel row 107 B, and to an individual channel 120 B which is included in the plurality of individual channels 120 B and which is located on the left side, far from the individual channel row 107 A.

Further, there is considered such a case that, unlike the second embodiment, the channel resistance is uniform in all the individual connecting channels 142 b ; that the channel resistance is uniform in all the individual connecting channels 143 b ; and that the channel resistance per unit length is constant in the common connecting channel 141 b regardless of the position in the width direction. In such a case, when the ink flows between the plurality of individual channels 120 C and the plurality of individual channel 120 D via the connecting channel 133 b , the ink is less likely to easily flow to an individual channel 120 C which is included in the plurality of individual channels 120 C and which is located on the right side, far from the individual channel row 107 D, and to an individual channel 120 D which is included in the plurality of individual channels 120 D and which is located on the left side, far from the individual channel row 107 C.

Furthermore, in these cases, the pressure drop gradient in the ink in the common connecting channels 133 a and 133 b becomes great. In the connecting channels 133 a and 133 b , paths in which the ink flows in the individual channels 120 A and 120 B of the individual channel rows 107 A and 107 B on the upstream side in the conveyance direction, respectively, and paths in which the ink flows in the individual channels 120 C and 120 D of the individual channel rows 107 CB and 107 D on the downstream side in the conveyance direction, respectively are long. Therefore, in a case that the above-described pressure drop gradient is great, there is such a fear that the meniscus of the ink is destroyed in the nozzles 110 of the individual channels 120 A to 120 D.

In the second embodiment, the channel resistance per unit length is constant in the common connecting channel 141 a regardless of the position in the width direction. In contrast, the channel resistance of a certain individual channel 120 A among the plurality of individual channels 120 A becomes greater as the certain individual channel 120 A is located, in the width direction, more closely to the individual connecting channel row 107 B; and the channel resistance of a certain individual channel 120 B among the plurality of individual channels 120 B becomes greater as the certain individual channel 120 B is located, in the width direction, more closely to the individual connecting channel row 107 A. With this, as a certain individual channel 120 A among the plurality of individual channels 120 A is located, in the width direction, more remotely from the individual connecting channel row 107 B, the ink flows more easily from the certain individual channel 120 A into the common connecting channel 141 a ; and as the certain individual channel 120 B among the plurality of individual channels 120 B is located, in the width direction, more remotely to the individual connecting channel row 107 A, the ink flows more easily into the certain individual channel 120 B from the common connecting channel 141 a . As a result, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 A and 120 B.

Furthermore, in the second embodiment, the channel resistance per unit length is constant in the common connecting channel 141 b regardless of the position in the width direction. In contrast, the channel resistance of a certain individual channel 120 C among the plurality of individual channels 120 C becomes greater as the certain individual channel 120 C is located, in the width direction, more closely to the individual connecting channel row 107 D; and the channel resistance of a certain individual channel 120 D among the plurality of individual channels 120 D becomes greater as the certain individual channel 120 D is located, in the width direction, more closely to the individual connecting channel row 107 C. With this, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 C and 120 D, in a similar manner as that described above regarding the plurality of individual channels 120 A and 120 B.

Moreover, in a case that the connecting channels 133 a and 133 b are configured as described above, it is possible make the pressure drop gradient of the ink to be small in the connecting channels 133 a and 133 b . With this, it is possible to prevent the meniscus of the ink from being destroyed in the nozzles 110 of the individual channels 120 A and 120 B on the upstream side in the conveyance direction in the individual channel rows 107 A and 107 B, respectively, and to prevent the meniscus of the ink from being destroyed in the nozzles 110 of the individual channels 120 C and 120 D on the downstream side in the conveyance direction in the individual channel rows 107 C and 107 D, respectively.

Further, in the second embodiment, the channel resistance per unit length is constant in each of the common connecting channels 141 a and 141 b regardless of the position in the width direction, as described above. With this, it is possible to make the configuration of each of the common connecting channels 141 a and 141 b to be simple.

Furthermore, in the second embodiment, the spacing distance J between a leftmost nozzle 110 of the individual channel 120 A located on the leftmost side in the width direction among the plurality of individual channels 120 A and a rightmost nozzle 110 of the individual channel 120 A located on the rightmost side in the width direction among the plurality of individual channels 120 B is greater than the spacing distance K between the nozzles 110 in each of the plurality of individual channels 120 A and the plurality of individual channels 120 B, as described above. Similarly, the spacing distance J between a leftmost nozzle 110 of the individual channel 120 C located on the leftmost side in the width direction among the plurality of individual channels 120 C and a rightmost nozzle 110 of the individual channel 120 D located on the rightmost side in the width direction among the plurality of individual channels 120 D is greater than the spacing distance K between the nozzles 110 in each of the plurality of individual channels 120 C and the plurality of individual channels 120 D, as described above.

With respect to this configuration, the second embodiment makes the position in the width direction of the area 105 A between the individual channel row 107 A and the individual channel row 107 B in the synthetized individual channel row 106 A to be different from the position in the width direction of the area 105 B between the individual channel row 107 C and the individual channel row 107 D in the synthetized individual channel row 106 B. With this, the nozzles 110 of the individual channels 120 C are arranged at the position in the width direction of the area 105 A in which the nozzles 110 of the individual channels 120 A and the nozzles 110 of the individual channels 120 B are not arranged; and the nozzles 110 of the individual channels 120 B are located at the position of the area 105 B in which the nozzles 110 of the individual channels 120 C and the nozzles 110 of the individual channels 120 D are not arranged. As a result, the nozzles 110 can be arranged, at any position in the width direction, with a density which is not less than that in each of the nozzle rows 109 A to 110 D.

Note that in such a case, unlike the second embodiment, that the area 105 A and the area 105 B overlap with each other in the conveyance direction and that an image is recorded by the printer on a recording paper sheet P, then any dots are not formed in a part, of the recording paper sheet P, corresponding to the areas 105 A and 105 B, and a white streak is formed in the recorded image. Even though the lengths in the width direction of the areas 105 A and 105 B are short, the white streak is conspicuous even if the length in the width direction of the white streak is short.

In the case of the second embodiment, in an area in which the individual channel row 107 A and the individual channel row 107 C overlap with each other in the conveyance direction, the nozzles 110 of the individual channel row 107 A and the nozzles 110 of the individual channel rows 107 C are arranged in the width direction alternately at a spacing distance K/2 which is half the spacing distance K between the nozzles 110 in each of the individual channel rows 107 A and 107 B. Similarly, in an area in which the individual channel row 107 B and the individual channel row 107 D overlap with each other in the conveyance direction, the nozzles 110 of the individual channel row 107 B and the nozzles 110 of the individual channel rows 107 D are arranged in the width direction alternately at a spacing distance K/2 which is half the spacing distance K between the nozzles 110 in each of the individual channel rows 107 C and 107 D.

With respect to this configuration, in the conveyance direction, in the area between the individual channel rows 107 A and 107 C, only the nozzles 110 of the individual channel 107 C are arranged side by side in the width direction at the spacing distance K. Similarly, in the conveyance direction, in the area between the individual channel row 107 B and 107 D, only the nozzles 110 of the individual channel 107 B are arranged side by side in the width direction at the spacing distance K.

Accordingly, in a case that an image is recorded by the printer on a recording paper sheet P, in a part (image part), of the recorded image, corresponding to the area in which the individual channel row 107 A and the individual channel row 107 C overlap with each other in the conveyance direction and in an image part of the recorded image corresponding the area in which the individual channel row 107 B and the individual channel row 107 D overlap with each other in the conveyance direction, the dots are arranged side by side in the width direction at the spacing distance K/2. In contrast, in an image part, of the recorded image, corresponding to the area between individual channel row 107 A and the individual channel row 107 B and in an image part, of the recorded image, corresponding to the area between individual channel row 107 C and the individual channel row 107 D, the dots are arranged side by side in the width direction at the spacing distance K. Namely, in the recorded image, the parts in which the spacing distance between the dots in the width direction are different are present.

However, the length in the width direction of the image part corresponding to the area between the individual channel row 107 A and the individual channel row 107 B, and the length in the width direction of the image part corresponding to the area between the individual channel row 107 C and the individual channel row 107 D are short. Therefore, the influence, caused by the above-described difference in the spacing distance between the dots, on the image quality of the recorded image is small.

Further, in the second embodiment, the first manifold 136 a and the second manifold 137 a which are arranged side by side in the width direction are connected to each other via the connecting channel 135 a . With this, the ink is allowed to flow between the first manifold 136 a and the second manifold 137 a via the connecting channel 135 a , thereby making it possible to prevent the ink from stagnating at a left end part of the first manifold 136 a and a right end part of the second manifold 137 a . On the other hand, since the channel resistance per unit length of the connecting channel 135 a is greater than the channel resistance per unit length of each of the first and second manifolds 136 a and 137 a , it is possible to avoid such a situation that the ink flows too much from the first manifold 136 a to the second manifold 137 a via the connecting channel 135 a and that the ink does not flow sufficiently to the individual channels 120 A and 120 B.

Furthermore, in the second embodiment, the first manifold 136 b and the second manifold 137 b which are arranged side by side in the width direction are connected to each other via the connecting channel 135 b . With this, it is possible to prevent the ink from stagnating at a left end part of the first manifold 136 b and a right end part of the second manifold 137 b , in a similar manner as that described above regarding the first manifold 136 a and the second manifold 137 a . On the other hand, it is possible to avoid such a situation that the ink flows too much from the first manifold 136 b to the second manifold 137 b via the connecting channel 135 b and that the ink does not flow sufficiently to the individual channels 120 C and 120 D.

[Modifications]

In the foregoing, the first and second embodiments of the present disclosure have been explained. The present disclosure, however, is not limited to or restricted by the above-described first and second embodiments; a variety of kinds of changes are possible, within the range described in the claims.

In each of the first and second embodiments, the common connecting channel and the plurality of individual connecting channels have the positions in the up-down direction and the lengths in the up-down direction which are same with one another. Further, the ceiling surface of the common connecting channel and the ceiling surfaces of the plurality of individual connecting channels are located on a same plane which is parallel to the width direction and the conveyance direction. The present disclosure, however, is not limited to or restricted by this configuration. For example, it is allowable that the ceiling surface of the common connecting channel and the ceiling surfaces of the plurality of individual connecting channels have positions in the up-down direction which are different from each other.

Alternatively, in a first modification as depicted in FIG. 7 , for example, a plate 201 is arranged between a plate 21 and a plate 22 in a head unit 200 . Further, in a connecting channel 202 of the head unit 200 , a common connecting channel 203 extends in a lower part of the plate 22 and the plate 201 , and extends downwardly up to a location below a plurality of individual connecting channels 42 and a plurality of individual connecting channels 43 . Further, in the case of the first modification, the common connecting channel 203 is allowed to have a volume greater than that of the common connecting channel 41 in the first embodiment.

Furthermore, also in the second embodiment, it is allowable that another plate is arranged between the plate 111 and the plate 112 , and that a common connecting channel is configured to extend up to a location below the plurality of individual connecting channels 142 a , 142 b , 143 a and 143 b.

Moreover, in the first and second embodiments, although the individual connecting channels are connected to the lower end parts of the descenders, respectively, the present disclosure is not limited to this configuration. The individual connecting channels may be connected to parts, of the descenders, which are different from the lower end parts thereof, respectively.

Further, the individual connecting channels are not limited to being connected to the descenders, respectively. For example, in a head unit 210 of a second modification, a connecting channel 211 has a common connecting channel 212 , a plurality of individual connecting channels 213 and a plurality of individual connecting channel 214 , as depicted in FIGS. 8 and 9 .

The common connecting channel 212 is formed in an upper part of the plate 23 , and at a location which is positioned between the plurality of individual connecting channels 7 A and the plurality of individual connecting channels 7 B in the conveyance direction. Further, the common connecting channel 212 extends in the width direction along the entire lengths of the individual channel rows 7 A and 7 B.

The plurality of individual connecting channels 213 correspond to the plurality of individual channels 20 A, respectively, and are formed in the upper part of the plate 23 . The plurality of individual connecting channels 213 are arranged, in the conveyance direction, between the plurality of individual channels 20 A and the common connecting channel 212 , extend in the conveyance direction and connect a plurality of pressure chambers 30 of the plurality of individual channels 20 A to the common connecting channel 212 .

The plurality of individual connecting channels 214 correspond to the plurality of individual channels 20 B, respectively, and are formed in the upper part of the plate 23 . The plurality of individual connecting channels 214 are arranged, in the conveyance direction, between the plurality of individual channels 20 B and the common connecting channel 212 , extend in the conveyance direction and connect a plurality of pressure chambers 30 of the plurality of individual channels 20 B to the common connecting channel 212 .

Further, the common connecting channel 212 and the plurality of individual connecting channels 213 and the plurality of individual connecting channels 214 have the positions in the up-down direction and the lengths in the up-down direction which are same to one another. With this, a ceiling surface 212 a of the common connecting channel 212 , a ceiling surface 213 a of each of the plurality of individual connecting channels 213 and a ceiling surface 214 a of each of the plurality of individual connecting channels 43 are located on a same plane which is parallel to the width direction and the conveyance direction.

Furthermore, in the second modification, the ink inside the plurality of pressure chambers 30 constructing the plurality of individual channels 20 A, respectively, flows to the common connecting channel 212 via the plurality of individual connecting channels 213 , and further flows to the plurality of pressure chambers 30 of the plurality of individual connecting channels 20 B via the plurality of individual connecting channels 214 , respectively. Moreover, in this case, any air bubble flowing into the pressure chamber 30 of a certain individual channel 20 A among the plurality of individual channels 20 A flows into the pressure chamber 30 of the individual channel 20 B which is included in the plurality of individual channels 20 B, and which corresponds to the certain individual channel 20 A, via the individual connecting channel 213 , the common connecting chamber 212 and the individual connecting channel 214 . With this, it is possible to sufficiently discharge the air bubble inside the pressure chamber 30 therefrom.

Further, also in the second embodiment, it is allowable to form connecting channels connecting the pressure chambers 130 of the individual channels 120 A to the pressure chambers 130 of the individual channels 120 B, respectively, at an upper part of the plate 113 , and to form connecting channels connecting the pressure chambers 130 of the individual channels 120 C to the pressure chambers 130 of the individual channels 120 D, respectively, at the upper part of the plate 113 , similarly to the second modification.

Furthermore, each of the individual channels is not limited to being connected to the connecting channel only at one position (location). For example, in a thirdmodification as depicted in FIG. 10 , a head unit 220 has a configuration wherein the connecting channel 33 of the head unit 11 in the first embodiment is replaced by a connecting channel 221 .

The connecting channel 221 has a common connecting channel 222 , and pluralities of individual connecting channels 223 to 226 . The common connecting channel 222 extends in the plates 22 and 23 in the up-down direction. Further, the common connecting channel 222 extends in the width direction along the entire lengths of the individual channel rows 7 A and 7 B.

The plurality of individual connecting channels 223 are similar to the plurality of individual connecting channels 42 of the first embodiment; each of the plurality of individual connecting channels 223 extends in the conveyance direction and connects a lower end part of the descender 31 of one of the individual channels 20 A to a lower end part of the common connecting channel 222 . The plurality of individual connecting channels 224 are similar to the plurality of individual connecting channels 43 of the first embodiment; each of the plurality of individual connecting channels 224 extends in the conveyance direction and connect a lower end part of the descender 31 of one of the individual channels 20 B to the lower end part of the common connecting channel 222 .

The plurality of individual connecting channels 225 are similar to the plurality of individual connecting channels 213 of the second modification; each of the plurality of individual connecting channels 225 extends in the conveyance direction and connects the pressure chamber 30 of one of the individual channels 20 A to an upper end part of the common connecting channel 222 . The plurality of individual connecting channels 226 are similar to the plurality of individual connecting channels 214 of the second modification; each of the plurality of individual connecting channels 226 extends in the conveyance direction and connects the pressure chamber 30 of one of the individual channels 20 B to the upper end part of the common connecting channel 222 .

Further, in the third modification, the ink is allowed to flow between the descenders 31 and the pressure chambers 30 of the plurality of individual channels 20 A and the descenders 31 and the pressure chambers 30 of the plurality of individual channels 20 B, via the connecting channel 221 . Furthermore, in this case, both of any air bubbles accumulated in the pressure chamber(s) 30 and any air bubbles flowing into the nozzle(s) 10 can be discharged efficiently. Moreover, it is possible to suppress any drying of the ink inside the nozzles 10 .

Further, an inner wall surface of the common connecting channel may be configured so as to allow any air bubble(s) inside the common connecting channel to flow out therefrom easily. For example, in a fourth modification as depicted in FIG. 11 , a head unit 230 has a configuration wherein the connecting channel 41 of the head unit 11 is replaced by a connecting channel 231 . In the common connecting channel 231 , a plurality of individual connecting channels 43 are connected to an inner wall surface 231 a on the upstream side in the conveyance direction of the common connecting channel 231 . Furthermore, a plurality of parts, of the inner wall surface 231 a , located between two individual connecting channels 43 which are included in the plurality of individual connecting channels 43 and which are adjacent to each other in the width direction, extend while being inclined with respect to the width direction so that each of the plurality of parts approaches in the width direction further toward the upstream side in the conveyance direction (toward the outside of the common connecting channel 41 in the conveyance direction), as each of the parts approaches more closely in the width direction to the two second individual connecting channels 43 .

In this case, any air bubble reaching the inner wall surface 231 a , of the common connecting channel 231 , in which each of the plurality of individual connecting channels 43 is open, is guided smoothly to each of the plurality of individual connecting channels 43 along the inner wall surface 231 a . With this, it is possible to allow the air bubble to flow smoothly from the common connecting channel 231 to each of the plurality of individual connecting channels 43 .

Alternatively, for example in a fifth modification as depicted in FIG. 12 , a head unit 240 has a configuration wherein the common connecting channel 41 in the head unit 11 is replaced by a common connecting channel 241 . In the common connecting channel 241 , a plurality of individual connecting channels 43 are connected to an inner wall surface 241 a on the upstream side in the conveyance direction of the common connecting channel 241 . Further, in the inner wall surface 241 a , a plurality of parts, of the inner wall surface 241 a , located between two individual connecting channels 43 which are included in the plurality of individual connecting channels 43 and which are adjacent to each other in the width direction, are curved so that each of the plurality of parts projects toward the inner side in the conveyance direction of the common connecting channel 241 .

In this case, any air bubble reaching the inner wall surface 241 a , of the common connecting channel 241 , in which each of the plurality of individual connecting channels 43 is open, is guided smoothly to each of the plurality of individual connecting channels 43 along the inner wall surface 241 a . With this, it is possible to allow the air bubble to flow smoothly from the common connecting channel 241 to each of the plurality of individual connecting channels 43 .

Further, in the second embodiment, it is allowable that a plurality of parts, of an inner wall surface on the upstream side in the conveyance direction of the common connecting channel 141 a , located between two individual connecting channels 143 a which are included in the plurality of individual connecting channels 143 a and which are adjacent to each other in the width direction, and/or a plurality of parts, of an inner wall surface on the downstream side in the conveyance direction of the common connecting channel 141 b , located between two individual connecting channels 143 b which are included in the plurality of individual connecting channels 143 b and which are adjacent to each other in the width direction, is/are configured to be inclined or curved surfaces with respect to the width direction, in a similar manner as in the third and fourth modifications.

Furthermore, in the second embodiment, the common connecting channel 141 a has the channel resistance per unit length which is constant regardless of the position in the width direction; in the plurality of individual connecting channels 142 a , the channel resistance of the certain individual connecting channel 142 a among the plurality of individual connecting channel 142 a becomes greater as the certain individual connecting channel 142 a is located, in the width direction, more closely to the individual connecting channel row 107 B; and in the plurality of individual connecting channels 143 a , the channel resistance of the certain individual connecting channel 143 a among the plurality of individual connecting channel 143 a becomes greater as the certain individual connecting channel 143 a is located, in the width direction, more closely to the individual connecting channel row 107 A, to thereby allow the ink to flow uniformly in the plurality of individual channels 120 A and 120 B. Further, the common connecting channel 141 b has the channel resistance per unit length which is constant regardless of the position in the width direction; in the plurality of individual connecting channels 142 b , the channel resistance of the certain individual connecting channel 142 b among the plurality of individual connecting channel 142 b becomes greater as the certain individual connecting channel 142 b is located, in the width direction, more closely to the individual connecting channel row 107 D; and in the plurality of individual connecting channels 143 b , the channel resistance of the certain individual connecting channel 143 b among the plurality of individual connecting channel 143 b becomes greater as the certain individual connecting channel 143 b is located, in the width direction, more closely to the individual connecting channel row 107 C, to thereby allow the ink to flow uniformly in the plurality of individual channels 120 C and 120 D. The present disclosure, however, is not limited to this configuration.

For example, in a sixth modification as depicted in FIG. 13 , a head unit 250 has a configuration wherein the connecting channels 133 a and 133 b of the head unit 100 in the second embodiment are replaced by connecting channels 251 a and 252 b.

The connecting channel 251 a has a common connecting channel 252 a , a plurality of individual connecting channels 253 a , and a plurality of individual connecting channels 254 a . Although the common connecting channel 252 a extends in the width direction along the entire length of the synthetized individual channel row 106 A (individual channel rows 107 A, 107 B) similarly to the common connecting channel 141 a , the common connecting channel 252 a has such a configuration, unlike the common connecting channel 141 a , that the length in the conveyance direction becomes shorter, as approaching closely toward the central side in the width direction, thereby making the cross-sectional area of a cross section orthogonal to the width direction to be smaller, as approaching closely toward the central side in the width direction. With this, in the common connecting channel 252 a , the channel resistance per unit length becomes greater, as approaching closely toward the central side in the width direction. Further, in the common connecting channel 252 a , the channel resistance per unit length becomes the greatest at a part, in the width direction, which is located between the individual channel row 107 A and the individual channel row 107 B.

The plurality of individual connecting channels 253 a correspond to the plurality of individual channels 120 A, respectively; each of the plurality of individual connecting channels 253 a extends in the conveyance direction, and connects the descender 131 of one of the plurality of individual channels 120 A to the common connecting channel 252 a . Further, the plurality of individual connecting channels 253 a have lengths in the width direction which are all the same. With this, the channel resistances of all the plurality of individual connecting channels 253 a are substantially same to one another.

The plurality of individual connecting channels 254 a correspond to the plurality of individual channels 120 B, respectively; each of the plurality of individual connecting channels 254 a extends in the conveyance direction, and connects the descender 131 of one of the plurality of individual channels 120 B to the common connecting channel 252 a . Further, the plurality of individual connecting channels 254 a have lengths in the width direction which are all the same. With this, the channel resistances of all the plurality of individual connecting channels 254 a are substantially same to one another.

The connecting channel 251 b has a common connecting channel 252 b , a plurality of individual connecting channels 253 b , and a plurality of individual connecting channels 254 b . Although the common connecting channel 252 b extends in the width direction along the entire length of the synthetized individual channel row 106 B (individual channel rows 107 C, 107 D) similarly to the common connecting channel 141 b , the common connecting channel 252 b has such a configuration, unlike the common connecting channel 141 b , that the length in the conveyance direction becomes shorter, as approaching closely toward the central side in the width direction, thereby making the cross-sectional area of a cross section orthogonal to the width direction to be smaller, as approaching closely toward the central side in the width direction. With this, in the common connecting channel 252 b , the channel resistance per unit length becomes greater, as approaching closely toward the central side in the width direction. Further, in the common connecting channel 252 b , the channel resistance per unit length becomes the greatest at a part, in the width direction, which is located between the individual channel row 107 C and the individual channel row 107 D.

The plurality of individual connecting channels 253 b correspond to the plurality of individual channels 120 C, respectively; each of the plurality of individual connecting channels 253 b extends in the conveyance direction, and connects the descender 131 of one of the plurality of individual channels 120 C to the common connecting channel 252 b . Further, the plurality of individual connecting channels 253 b have lengths in the width direction which are all the same. With this, the channel resistances of all the plurality of individual connecting channels 253 b are substantially same to one another.

The plurality of individual connecting channels 254 b correspond to the plurality of individual channels 120 D, respectively; each of the plurality of individual connecting channels 254 b extends in the conveyance direction, and connects the descender 131 of one of the plurality of individual channels 120 D to the common connecting channel 252 b . Further, the plurality of individual connecting channels 254 b have lengths in the width direction which are all the same. With this, the channel resistances of all the plurality of individual connecting channels 254 b are substantially same to one another.

In the sixth modification, the channel resistances in all the plurality of individual connecting channels 253 a are all the same, and the channel resistances in all the plurality of individual connecting channels 254 a are all the same. In contrast, in parts, of the common connecting channel 252 a , which are connected to the plurality of individual connecting channels 253 a , respectively, the channel resistance per unit length is greater as a part, among the parts, is located more closely to the individual channel row 107 B in the width direction. Further, in parts, of the common connecting channel 252 a , which are connected to the plurality of individual connecting channels 254 a , respectively, the channel resistance per unit length is greater as a part, among the parts, is located more closely to the individual channel row 107 A in the width direction. With this, as a certain individual channel 120 A among the plurality of individual channels 120 A is located, in the width direction, more remotely from the individual connecting channel row 107 B, the ink flows more easily from the certain individual channel 120 A into the common connecting channel 252 a ; and as the certain individual channel 120 B among the plurality of individual channels 120 B is located, in the width direction, more remotely to the individual connecting channel row 107 A, the ink flows more easily into the certain individual channel 120 B from the common connecting channel 252 a . As a result, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 A and 120 B.

Similarly, the channel resistances in all the plurality of individual connecting channels 253 a are all the same, and the channel resistances in all the plurality of individual connecting channels 254 b are all the same. In contrast, in parts, of the common connecting channel 252 b , which are connected to the plurality of individual connecting channels 253 b , respectively, the channel resistance per unit length is greater as a part, among the parts, is located more closely to the individual channel row 107 D in the width direction. Further, in parts, of the common connecting channel 252 b , which are connected to the plurality of individual connecting channels 254 b , respectively, the channel resistance per unit length is greater as a part, among the parts, is located more closely to the individual channel row 107 C in the width direction. With this, as a certain individual channel 120 C among the plurality of individual channels 120 C is located, in the width direction, more remotely from the individual connecting channel row 107 D, the ink flows more easily from the certain individual channel 120 C into the common connecting channel 252 b ; and as the certain individual channel 120 D among the plurality of individual channels 120 D is located, in the width direction, more remotely to the individual connecting channel row 107 C, the ink flows more easily into the certain individual channel 120 D from the common connecting channel 252 b . As a result, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 C and 120 D.

In a seventh modification as depicted in FIG. 14 , a head unit 260 has a configuration wherein the common connecting channels 252 a and 252 b of the head unit 250 in the sixth embodiment is replaced by common connecting channels 261 a and 261 b . The common connecting channel 261 a has a configuration wherein a length in the conveyance direction which is constant regardless of a position in the width direction at a channel part 262 a at which the common connecting channel 261 a is connected to a plurality of individual channels 170 A, and at a channel part 263 a at which the common connecting channel 261 a is connected to a plurality of individual channels 170 B. On the other hand, the common connecting channel 261 a has a channel part 264 a which is located between the channel parts 262 a and 263 a in the width direction; in the channel part 264 a , a length in the conveyance direction is made to be smaller than those in the channel parts 262 a and 263 a , thereby making a cross-sectional area of a cross section orthogonal to the width direction of the channel part 264 a to be smaller than those of the channel parts 262 a and 263 a . With this, the common connecting channel 261 a has a channel resistance per unit length which is greater in the channel part 264 a , than in each of the channel parts 262 a and 263 a.

The common connecting channel 261 b has a configuration wherein a length in the conveyance direction which is constant regardless of a position in the width direction at a channel part 262 b at which the common connecting channel 261 b is connected to a plurality of individual channels 170 C, and at a channel part 263 b at which the common connecting channel 261 b is connected to a plurality of individual channels 170 D. On the other hand, the common connecting channel 261 b has a channel part 264 b which is located between the channel parts 262 b and 263 b in the width direction; in the channel part 264 b , a length in the conveyance direction is made to be smaller than those in the channel parts 262 b and 263 b , thereby making a cross-sectional area of a cross section orthogonal to the width direction of the channel part 264 b to be smaller than those of the channel parts 262 b and 263 b . With this, the common connecting channel 261 b has a channel resistance per unit length which is greater in the channel part 264 b , than in each of the channel parts 262 b and 263 b.

Further, in the case of the seventh modification, a plurality of parts, in the common connecting channel 261 a , which communicate the individual connecting channels 142 a with the individual connecting channels 143 a each include the channel part 264 a . Furthermore, the channel part 264 a is a part at which the channel resistance per unit length is the greatest in the common connecting channel 261 a . With this, it is possible to reduce the difference to be small in the channel resistance among the plurality of parts which communicate the individual connecting channels 142 a with the individual connecting channels 143 a . As a result, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 A and the plurality of individual channels 120 B.

Similarly, a plurality of parts, in the common connecting channel 261 b , which communicate the individual connecting channels 142 b with the individual connecting channels 143 b each include the channel part 264 b . Further, the channel part 264 b is a part at which the channel resistance per unit length is the greatest in the common connecting channel 261 b . With this, it is possible to reduce the difference to be small in the channel resistance among the plurality of parts which communicate the individual connecting channels 142 b with the individual connecting channels 143 b . As a result, it is possible to allow the ink to flow uniformly in the plurality of individual channels 120 C and the plurality of individual channels 120 D.

Further, in the second embodiment, the connecting channel may be configured to have: common connecting channels 252 a and 252 b which are similar to those in the sixth modification; and a plurality of individual connecting channels 142 a , a plurality of individual connecting channels 142 b , a plurality of individual connecting channels 143 a and a plurality of individual connecting channels 143 b which are similar to those in the second embodiment. Alternatively, in the second embodiment, the connecting channel may be configured to have: common connecting channels 261 a and 262 b which are similar to those in the seventh modification; and a plurality of individual connecting channels 142 a , a plurality of individual connecting channels 142 b , a plurality of individual connecting channels 143 a and a plurality of individual connecting channels 143 b which are similar to those in the second embodiment.

Furthermore, in the second embodiment, although the first manifold 136 a and the second manifold 137 a are connected to each other by the connecting channel 135 a , and the first manifold 136 b and the second manifold 137 b are connected to each other by the connecting channel 135 b , the present disclosure is not limited to this configuration. It is allowable that the connecting channel 135 a is omitted (is not provided), and that the first manifold 136 a and the second manifold 137 a may be separated (isolated) from each other in the width direction. Moreover, it is allowable that the connecting channel 135 b is omitted (is not provided), and that the first manifold 136 b and the second manifold 137 b may be separated (isolated) from each other in the width direction.

Further, in the second embodiment, although the head unit 100 is provided with the two synthetized individual channel rows 106 A and 106 B which are arranged side by side in the conveyance direction, the present disclosure is not limited to this configuration. For example, in the second embodiment, the head unit may be provided with three or more synthetized individual channel rows which are arranged side by side in the conveyance direction.

Furthermore, in the second embodiment, the distance J in the width direction between an individual channel 120 A, which is included in the plurality of individual channel 120 A and which is located most closely to the individual channel row 107 B, and an individual channel 120 B, which is included in the plurality of individual channel 120 B and which is located most closely to the individual channel row 107 A is greater than the distance K in the width direction among the plurality of individual channels 120 A and the distance K in the width direction among the plurality of individual channels 120 B. Moreover, the distance J in the width direction between an individual channel 120 C, which is included in the plurality of individual channel 120 C and which is located most closely to the individual channel row 107 D, and an individual channel 120 D, which is included in the plurality of individual channel 120 D and which is located most closely to the individual channel row 107 C is greater than the distance K in the width direction among the plurality of individual channels 120 C and the distance K in the width direction among the plurality of individual channels 120 D. The present disclosure, however, is not limited to this configuration. For example, in a case that the first manifold and the second manifold can be arranged to be close to each other in the width direction, the above-described distance K and the above-described distance J may be same. Further, in such a case, the head unit may be provided with only one piece of the synthetized individual channel row.

Further, in the first embodiment, the relationship |La 1 −Lb 1 |=n 1 ×V×T holds, and the relationship |La 2 −Lb 2 |=n 2 ×V×T holds. The present disclosure, however, is not limited to this. It is allowable that only one of the two relationships holds. Alternatively, it is allowable that both the two relationships do not hold.

Furthermore, it is allowable that the direction in which the ink is circulated between the head unit and the ink tank is a reverse direction to the above-described direction. For example, in the first embodiment, the directions in which the ink is fed by the pumps 51 and 52 , respectively, may all be reversed. Further, in the second embodiment, the directions in which the ink is fed by the pumps 151 a , 151 b , 152 a and 152 b , respectively, may all be reversed.

Furthermore, the present disclosure is not limited to the configuration wherein the ink is circulated between the head unit and the ink tank. For example, it is allowable that in the first and second embodiments, any pomp is not provided between the head unit and the ink tank. In such a case, accompanying with the discharge of the ink from the nozzles, the ink inside the manifolds flows from the throttles into the individual channels, respectively, and the ink inside the connecting channels flows from descenders into the individual channels, respectively.

Further, although the foregoing explanation has been given about the examples wherein the present disclosure is applied to an ink-jet head (head unit) which discharges the ink from the nozzles, the present disclosure is not limited to this configuration. For example, it is also possible to apply the present disclosure to a liquid discharge head which is configured to discharge, from the nozzle(s), a liquid different from the ink.