Housing assembly for use in fan unit and fan unit including the same

This is a Continuation-In-Part application of co-pending U.S. patent application Ser. No. 10/908,582 filed on May 18, 2005, pending, which in turn claims priority from Japanese Patent Application No. 2004-147661 filed on May 18, 2004 and Japanese Patent Application No. 2005-135624 filed on May 9, 2005, both of which are hereby incorporated by reference in their entirety.

1. Field of the Invention

The present invention relates to a fan unit including a housing assembly which has a plurality of housings connected to or engaged with each other, and to the housing assembly of the fan unit.

2. Description of the Related Art

In order to improve the high capacity of an air flow and a static pressure generated by a fan without increasing the impeller diameter, a fan unit called “a double fan” is widely used in which a plurality of axial fans are arranged along the rotational axis thereof. Also, another type of fan unit is used which uses centrifugal fans connected in series with a direction in which the air is blown so as to provide a high static pressure.

In an exemplary known fan unit having a plurality of fan impellers, two or more impellers are encased in a single housing or each impeller is encased in each housing, and the housings are connected with each adjoining housing in an axial direction substantially parallel to the rotational axes thereof. Generally, a high development cost is required to design a new fan unit including the design of its housing. Therefore, one way for achieving a cost reduction is to connect or engage a plurality of existing axial fans or centrifugal fans, which meets the performance requested for the new fan unit.

There are two major ways to connect or engage two or more adjoining housings. One way is that flanges of the housings are fixedly coupled to each other by screws, and the other is that elastic hooks formed on one housing are engaged with recesses of the other housing.

In the case where the fans are fixedly connected by screws, however, a special tool such as a screwdriver or wrench may be required. This increases the number of steps for connecting the fans as well as the number of parts of the fan unit, thereby the cost for producing the fan unit may increase because of the complex structure of the fan unit. In connecting the adjoining fans by elastic hooks, on the other hand, since the elastic hooks can be formed at the same time as the housing is formed by a molding process, the cost for the housing with such elastic hooks does not necessarily increase. Also, the elastic hooks can be engaged very simply without increasing the number of steps for engaging the housings.

However, when the connection by elastic hooks is performed, there are two requirements competing with each other. One requirement is to provide a sufficient elasticity for elastic deformation which may be required for engaging the two adjoining fans, and the other requirement is to provide a sufficient engaging force. Specifically, in the case where the elasticity of the elastic hooks is increased to achieve an easier engaging step, the engaging force decreases and an insufficient engaging force may occur. On the other hand, in the case where the elasticity of the elastic hooks is decreased, the engaging force increases but the engaging step becomes difficult because the elastic hooks may be damaged or the housing may be warped.

That is, it is difficult to provide the elastic hooks with an appropriate level of elasticity in the case of using elastic hooks, even though the use of elastic hooks appears to be simple.

According to preferred embodiments of the present invention, a housing assembly for use in a fan unit is provided. The housing assembly includes an upper housing and a lower housing which are coaxially coupled to each other to define a substantially cylindrical space for accommodating at least a plurality of blades therein. The upper housing has a lower end surface and a lower engaging portion adjacent thereto. The lower housing has an upper end surface and an upper engaging portion adjacent thereto.

The lower and upper engaging portions are arranged to engage with each other to couple the upper and lower housings to each other by rotating one of the upper and lower housings about a center axis of the upper and lower housings relative to the other in a first direction (Rd) with the lower end surface of the upper housing in axial contact with the upper end surface of the lower housing.

When the lower and upper engaging portions are in engagement, one of the lower and upper engaging portions presses the other in both axial directions to cause elastic axial deformation of the other, and one of the lower and upper engaging portions presses the other toward both the first direction and a second direction opposite thereto to cause elastic circumferential deformation of the other.

Other features, elements, steps, advantages and characteristics of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.

FIGS. 1A , 1 B, and 1 C are perspective views of a fan unit according to a first preferred embodiment of the present invention.

FIGS. 2A and 2B are enlarged views of the coupling structure of the fan unit according to the first preferred embodiment of the present invention.

FIGS. 3A , 3 B, and 3 C are top views of the fan unit according to the first preferred embodiment of the present invention.

FIGS. 4A and 4B are perspective views of a fan unit according to a second preferred embodiment of the present invention.

FIGS. 5A and 5B are perspective views of another exemplary coupling structure of the fan unit according to the first preferred embodiment of the present invention.

FIG. 6 is a perspective view of a fan unit according to a third preferred embodiment of the present invention.

FIG. 7A is a perspective view of an upper axial fan of the fan unit according to the third preferred embodiment of the present invention.

FIG. 7B is a perspective view of a lower axial fan of the fan unit according to the third preferred embodiment of the present invention.

FIG. 7C is a perspective view of the fan unit according to the third preferred embodiment of the present invention, during coupling of the upper and lower axial fans to each other.

FIG. 8 is an enlarged view of a coupling structure of the fan unit according to the third preferred embodiment of the present invention.

FIG. 9 is an enlarged view of a coupling structure of a fan unit according to a fourth preferred embodiment of the present invention.

FIG. 10 is an enlarged view of a coupling structure of a fan unit according to a fifth preferred embodiment of the present invention.

FIG. 11 is an enlarged view of a coupling structure of a fan unit according to a sixth preferred embodiment of the present invention.

Referring to FIGS. 1A through 11 , preferred embodiments of the present invention will be described. In the following description, each of the four directions is indicated as viewed on the drawings unless otherwise specified, and not specifically limited in embodying the preferred embodiments of the present invention. Also, the uppercase suffixes A through J attached to the reference numerals in the description and drawings designate the components of axial fans 10 A through 10 J, respectively. The components carrying no uppercase suffix designate common or independent parts having similar functions.

First Preferred Embodiment

FIGS. 1A , 1 B, and 1 C are perspective views of a fan unit according to a first preferred embodiment of the present invention. Specifically, FIG. 1C shows the fan unit 1 of the present preferred embodiment assembled by coupling two axial fans 10 A, 10 B, and FIGS. 1A and 1B show the states before being coupled. FIGS. 2A and 2B are enlarged views of the coupling structure of the fan unit of the present preferred embodiment. FIGS. 3A , 3 B, and 3 C are top views of the fan unit of the present preferred embodiment.

Configuration of the Fan Unit

Referring to FIGS. 1A , 1 B, and 1 C, the fan unit 1 includes two axial fans 10 A and 10 B coupled to each other in series in an axial direction substantially parallel to their rotational axes.

The axial fans 10 A, 10 B each include a substantially cylindrical peripheral wall 21 and an impeller 2 having a plurality of blades 22 regularly arranged on the outer peripheral surface of the peripheral wall 21 .

The axial fans 10 A, 10 B each include a housing 4 with a cylindrical portion 41 having a cylindrical inner side surface larger in diameter than the radial outer edge of the blades 22 and concentric with the rotational axis of the impeller 2 .

Further, an electric motor (not shown) arranged to rotate the impeller 2 relative to the housing 4 is mounted on the housing 4 . The electric motor is preferably a DC brushless motor including a shaft fixed at the rotational center of the impeller 2 , a bearing arranged to support the shaft so that the shaft can rotate, a bearing holder supporting the bearing on the housing 4 , a stator including a plurality of coil windings fixed on the outer periphery of the bearing holder, and a rotor magnet fitted on the inner side surface of the peripheral wall 21 of the impeller 2 .

The axial fans 10 A, 10 B can be used independently of each other. In the present preferred embodiment, the lower axial fan 10 A arranged on the axially lower side is combined with the upper axial fan 10 B arranged on the axially upper side.

Housing of the Axial Fans

The ends of the cylindrical portion 41 of the axial fan 10 A are open in the axial direction, and a plurality of flanges 42 A are arranged radially outward of at least the end of the cylindrical portion 41 in opposed relation to the flanges 42 B of the axial fan 10 B. The flanges 42 A are preferably arranged at four locations at 90° intervals around the center axis of the cylindrical portion 41 , for example. The edges of the flanges 42 A preferably define angles of 90° so that the flanges 42 A as a whole substantially assume the shape of a square or substantially a square. The axial fans 10 A and 10 B, when arranged serially along the axis, have the flanges 42 A and 42 B aligned with each other in the axial direction.

By forming the flanges 42 A and 42 B of the axial fans 10 A and 10 B in the same shape as shown in FIGS. 3A , 3 B, and 3 C, the fan unit 1 can have the same planar shape as the axial fans 10 A and 10 B.

Before combining the axial fans 10 A and 10 B, the rotational axis of the impeller is displaced by an angle φ from the center axis of the impeller. Also, the angle is zero in the case where the axial fan 10 A is rotated with the contour thereof into alignment with that of the axial fan 10 B, i.e., in the case where the axial fans 10 A and 10 B share the same planar shape.

Flanges

Referring to FIGS. 2A and 2B , the surface of the flanges 42 A of the axial fan 10 A, which is in contact with the flanges 42 B of the axial fan 10 B, defines a flat housing portion 43 A substantially perpendicular to the rotational axis of the impeller 2 . Similarly, the surface of the flanges 42 B of the axial fan 10 B, which is in contact with the flanges 42 A of the axial fan 10 A, defines a flat housing proton 43 B substantially perpendicular to the rotational axis of the impeller 2 . The flat housing portion 43 A of the axial fan 10 A and the flat housing portion 43 B of the axial fan 10 B are in slidable contact with each other, and function as housing engaging portions.

Each flange 42 A has a protrusion 44 A functioning as a housing stopper on the flat housing portion 43 A thereof in opposed relation to the flat housing portion 43 B. The protrusion 44 A is provided with a radial recess 46 A functioning as a housing engaging portion. Also, each flange 42 B is provided with a notch 45 B cut into the flat housing portion 43 B which functions as a stopper corresponding to the protrusion 44 A. Further, the notch 45 B is provided with a radial protrusion 47 B providing a housing engaging portion and has a shape so as to closely engage the radial recess 46 A.

The protrusion 44 A and the notch 45 B are shaped so as to complement each other. Once the flat housing portion 43 A and the flat housing portion 43 B are rotationally slid to reduce the angle φ around the rotational axis of the impeller to zero, the radial protrusions 47 B are fitted, under light pressure, into the radial recesses 46 A located at four points, respectively, so that each notch 45 B and the corresponding protrusion 44 A are fitted closely with each other.

More specifically, each protrusion 44 A is provided with the radial recess 46 A along a peripheral direction around the rotational axis. In the radial recess 46 A, the protrusion 44 A is cut into one-half of the height of the protrusion 44 A from the flat housing portion 43 A, and the peripheral and inner ends thereof are open. The protrusion 44 A has the same height as the thickness of the flange 42 B. Each notch 45 B is has the same shape as the protrusion 44 A. Further, the radial protrusion 47 B in the shape corresponding to the radial recess 46 A is arranged around the rotational axis within the notch 45 B. The radial protrusion 47 B preferably is about one-half as thick as the flange 42 B, and preferably has substantially the same radial thickness as the radial recess 46 A. The height and the radial thickness of the radial recess 46 A are equal to or slightly smaller than the height and the radial thickness, respectively, of the radial protrusion 47 B.

The engagement between the radial recess 46 A and the radial protrusion 47 B defining the engaging portions restricts the axial movement of the axial fans 10 A and 10 B. Also, the friction generated by the contact between the protrusion 44 A including the radial recess 46 A and the notch 45 B including the radial protrusion 47 B restricts the peripheral movement of the axial fans 10 A and 10 B. Further, the flat surface 44 Aa providing lower a flat stopper surface extending at substantially right angles to the peripheral direction of the protrusion 44 A and to the flat housing portion 43 A comes into contact with the flat surface 45 Ba providing an upper flat stopper surface formed at substantially right angles to the peripheral direction of the notch 45 B and to the flat housing portion 43 B, so that the axial fans 10 A and 10 B are peripherally set in position.

The steps of fitting the axial fans 10 A and 10 B are described below.

First, as shown in FIGS. 1A and 3A , the flat housing portion 43 A of each flange 42 A of the axial fan 10 A and the corresponding flat housing portion 43 B of the flange 42 B of the axial fan 10 B are brought into contact with each other. Next, the axial fan 10 B is rotated in a counterclockwise direction, as taken in the plan view of FIG. 3A , around the rotational axis of the impeller with respect to the axial fan 10 A. As a result of this process, the radial protrusion 47 B is fitted in the corresponding radial recess 46 A. Finally, the axial fan 10 B is rotationally slid until the flat surface 44 Aa and the flat surface 45 Ba come into contact with each other. As a result of this process, as shown in FIGS. 1C and 3C , the flanges 42 A and 42 B come into alignment with each other thereby to complete the fan unit 1 .

The axial fans 10 A and 10 B are peripherally set in position by the contact between the flat surface 44 Aa of the protrusion 44 A and the flat surface 45 Ba of the notch 45 B and the resulting restriction of rotation of the axial fan 10 A with respect to the axial fan 10 B.

Incidentally, the radial protrusion 47 B may be arranged on the protrusion 44 A. In such a case, however, the radial recess 46 A is arranged in the notch 45 B.

In the present preferred embodiment, even after assembling the axial fan 10 A on the axial fan 10 B, the assembly can be disassembled by being rotationally slid in the opposite direction (clockwise) to the fitting direction. In other words, the axial fans 10 A, 10 B can be used independently of each other. As a result, the axial fans 10 A, 10 B each can be used as a standard axial fan, and without any design change, assembled into and used in the fan unit 1 .

Also, as shown in FIGS. 5A and 5B , an axial protrusion 47 a defining a tapered step may be provided on each radial protrusion 47 B for engagement with an axial recess 46 a defining a tapered accommodation portion within the radial recess 46 A. This structure is conveniently used in the case where the axial fans 10 A and 10 B, once engaged with each other, are not required to be disassembled.

The axial fans 10 A and 10 B, if not required to be disassembled after mutual engagement and thus to be coupled more strongly, may also be fixed with adhesive. The use of an adhesive increases the fastening force and can eliminate the vibrations between the housings at the same time.

To fix the axial fans 10 A and 10 B with even more strength, welding, screwing, pressure bonding, fitting with a separate material may be used instead of the adhesive.

Also, the axial fan 10 A and the axial fan 10 B may have different characteristics such as air capacity, static pressure, axial thickness, diameter of the impeller 2 or the rotational speed of the impeller 2 .

Further, the fan unit 1 may be configured to have three or more axial fans 10 arranged in the axial direction, for example. In the case where a plurality of axial fans 10 make up the fan unit 1 , the fixing structure according to the present preferred embodiment further enhances the ease of connecting the axial fans 10 .

Further, the protrusion 44 A on the flange 42 A of one axial fan 10 A in the axial direction and the provision of the notch 45 B on the flange 42 B of the other axial fan 10 B makes it possible to couple the axial fans 10 A, 10 B using a single type of housing 4 . Thus, mass production is made possible with reduced production costs.

Also, the axial fans 10 A, 10 B of the present preferred embodiment are better arranged in such a manner that the impellers 2 of axially adjacent axial fans 10 A, 10 B are rotated in opposite directions while blowing air in the same axial direction. By doing so, both the static pressure and the air capacity of the fan unit 1 are improved.

As described above, in the fan unit 1 of the present preferred embodiment, the flat housing portions 43 A and 43 B of the axial fans 10 A and 10 B are rotated in sliding contact with each other, and therefore the axial fans 10 A and 10 B can be coupled to each other with a simple operation. In addition, the axial fans 10 A and 10 B are coupled completely with each other by the engagement between the protrusion 44 A and the notch 45 B and the friction between the flat housing portions 43 A, 43 B in contact with each other. Thus, the stress acting on the protrusion 44 A and the notch 45 B is distributed and an excessive load is prevented from being imposed on the flanges 42 A, 42 B. As a result, the housing 4 is protected from damage or warping. Also, because the protrusion 44 A and the notch 45 B engage each other without being displaced outward or forming a gap, as shown in FIG. 2B , there are no air leaks from between the housings 4 to deteriorate the blowing characteristics.

Second Preferred Embodiment

FIGS. 4A and 4B are perspective views of a fan unit according to a second preferred embodiment of the present invention.

Configuration of the Fan Unit

The fan unit 1 B of the present preferred embodiment includes an axial fan 110 A having a similar structure as the axial fan 10 A of the first preferred embodiment and a stationary vane 111 C having fixed blades 123 which are combined serially in the direction of the rotational axis. The stationary vane 111 C includes the plurality of fixed blades 123 regularly arranged on the circumference and a housing 104 C having a cylindrical portion 141 C for fixing the outer peripheral ends of the fixed blades 123 on a cylindrical inner side surface 141 a.

With this configuration, the static pressure characteristics of the axial fan 110 A can be improved. In addition, the use of a plurality of the axial fans 110 A in combination can further improve the performance of the fan unit 1 B.

Housing

The housing 104 C of the stationary vane 111 C, like the housing 104 A of the axial fan 110 A, has a plurality of flanges 142 C. The flanges 142 C each have a similar shape to the flanges 142 A of the axial fan 110 A. In this way, the stationary vane 111 C and the axial fan 110 A are arranged serially along the axial direction in such a manner that the flanges 142 A and 142 C align with each other.

Flanges

The surface of the flanges 142 C of the stationary vane 111 C which is in contact with the flanges 142 A of the axial fan 110 A defines a flat housing portion 143 C substantially perpendicular to the rotational axis. By doing so, the flat housing portions 143 A and 143 C are slidably in contact with each other.

The flanges 142 C of the stationary vane 111 C each have a notch 145 C. The protrusion 144 A and the notch 145 C are so shaped as to complement each other. The protrusion 144 A is provided with a radial recess 146 C along the periphery around the rotational axis. Also, the notch 145 C is provided with a radial protrusion 147 A around the rotational axis in the shape corresponding to the radial recess 146 C. As an alternative, the protrusion 144 A may be provided with the radial protrusion 147 A and the notch 145 C with the radial recess 146 C.

The flat housing portion 143 C provided on each flange 142 C of the stationary vane 111 C and the flat housing portion 143 A provided on each flange 142 A of the axial fan 110 A are brought into contact with each other and rotated around the rotational axis. Then, the radial protrusion 147 A is inserted into the radial recess 146 C.

As an alternative, the notch 145 C may be provided on each flange 142 C of the stationary vane 111 C and the protrusion 147 A on each flange 142 A of the axial fan 110 A. As another alternative, the notch 145 C may be provided on each flange 142 C of the stationary vane 111 C, and the protrusion 144 A may be provided on the corresponding flange 142 C along the rotational axis.

In the present preferred embodiment, the fan unit 1 B may include at least one axial fan 110 A and at least one stationary vane 111 C. In this case, the protrusion 144 A and the notch 145 C may be provided on each component made up of an assembly of several stationary vanes 111 C and axial fans 110 A. By doing so, the assembly time can be reduced. Also, in the case where the fan unit 1 B includes a number of stationary vanes 111 C and axial fans 110 A, the use of the coupling structure according to the present preferred embodiment and the resulting ease of coupling further enhances the ease of connecting the axial fans.

The axial fans 110 A are preferably arranged in such a manner so as to discharge the air in the same direction along the rotational axis of the impeller. The insertion of the stationary vane 111 C between two axial fans 110 A improves the characteristics of both air capacity and static pressure. Also, the static pressure characteristic is preferably improved by arranging the impellers of the adjacent axial fans, with or without the stationary blade therebetween, to rotate in opposite directions as viewed from the axially upper side.

Third Preferred Embodiment

FIG. 6 is a perspective view of a fan unit 1 C of the third preferred embodiment, which includes coupling axial fans 10 C and 10 D to each other. FIGS. 7A , 7 B, and 7 C are perspective views of the axial fans 10 C and 10 D before being coupled. FIG. 8 is an enlarged view of an essential portion of the fan unit 1 C of the present preferred embodiment, i.e., the structure coupling the axial fans 10 C and 10 D. In FIGS. 6 through 8 , like reference signs designate the same or similar components as in FIGS. 1A to 3C .

Referring to FIG. 6 , the fan unit 1 C includes axial fans 10 C and 10 D coaxially arranged with each other. In the present preferred embodiment, the axial fan 10 C is arranged above the axial fan 10 D, as shown in FIG. 6 . The axial fans 10 C and 10 D are coupled in series in the axial direction.

The axial fans 10 C and 10 D are basically the same as the axial fans 10 A and 10 B of the first preferred embodiment but are different at least in the coupling structure. In the following description, the differences between the fan unit 1 C of the present preferred embodiment and the fan unit 1 A of the first preferred embodiment are mainly described.

The axial fan 10 C includes a substantially cylindrical peripheral wall 21 and an impeller 2 having a plurality of blades 22 regularly arranged on the outer side surface of the peripheral wall 21 . The axial fan 10 C also includes a housing 4 C that has an inner radius larger than a distance between an outermost portion of each blade 22 and the center of the housing 4 C. The inner side surface 41 C of the housing 4 C, which is substantially cylindrical in the present preferred embodiment, is substantially concentric with the center axis J 1 of the impeller 2 serving as the rotational axis of the impeller 2 . That is, the housing 4 C defines a substantially cylindrical space therein.

The axial fan 10 C can be used independently of the axial fan 10 D. However, in the present preferred embodiment, the axial fan 10 C is used in combination with another axial fan 10 D arranged below the axial fan 10 C to define the fan unit 1 C. The configuration of the axial fan 10 D is the same as the axial fan 10 C except for its housing. Therefore, the corresponding components of both axial fans 10 C and 10 D are labeled with similar reference signs with different suffixes (corresponding to the suffix of the axial fan) and the detailed description thereof is omitted.

The housing 4 C has a cylindrical portion arranged about the center axis J 1 and is open at both axial ends thereof. A plurality of flanges 42 C- 1 and 42 C- 2 are provided at upper and lower ends of the housing 4 C, respectively. The flanges 42 C- 1 and 42 C- 2 project radially outwards and are preferably arranged about the center axis J 1 at four positions at 90° intervals, for example, as shown in FIG. 6 . The edges of the flanges 42 C- 1 and 42 C- 2 are formed at substantially 90° so that the flanges 42 C- 1 and 42 C- 2 as a whole substantially assume the shape of a square or substantially a square when viewed along the center axis J 1 .

Each flange 42 C- 1 has an attachment hole 421 C- 1 penetrating therethrough along the center axis J 1 . An attachment member such as a screw can be inserted into each attachment hole 421 C- 1 when the fan unit 1 C is attached to another device, e.g., a casing of an electronic device. Similarly, each flange 42 C- 2 which is provided at the lower end surface of the axial fan 10 C to axially oppose the axial fan 10 D has an attachment hole 421 C- 2 for allowing an attachment member to be inserted therethrough. The attachment hole 421 C- 1 and the attachment hole 421 C- 2 associated therewith are aligned with each other in the axial direction when the axial fans 10 C and 10 D are completely coupled to each other, so that a single screw can be inserted into the attachment hole 421 C- 1 and the associated attachment hole 421 C- 2 .

The axial fan 10 D has a housing 4 D which is substantially the same as the housing 4 C except for the coupling structure that will be described below. Therefore, the detailed description of the housing 4 D is omitted here. Please note that attachment holes 421 D- 1 and 421 D- 2 of the housing 4 D are also aligned with each other and with the attachment holes 421 C- 1 and 421 C- 2 of the housing 4 C when the axial fans 10 C and 10 D are completely coupled to each other.

The housings 4 C and 4 D of the axial fans 10 C and 10 D together define a housing assembly. The housings 4 C and 4 D have opposing surfaces 43 C and 43 D, respectively, which axially oppose each other when the housings 4 C and 4 D are coupled to each other. More specifically, the surface 43 C is the lower end surface of the axial fan 10 C, and the surface 43 D is the upper end surface of the axial fan 10 D, in which surfaces 43 C and 43 D are substantially perpendicular to the center axis J 1 .

The coupling of the axial fans 10 C and 10 D is carried out in the following manner. First, the axial fans 10 C and 10 D are arranged coaxially with each other so that the lower end surface 43 C of the housing 4 C is in contact with the upper end surface 43 D of the housing 4 D, as shown in FIG. 7C . Then, the axial fan 10 D is rotated about the center axis J 1 relative to the axial fan 10 C in a predetermined direction Rd (a counterclockwise direction in the example of FIG. 7C ). As a result, the axial fans 10 C and 10 D are coupled to each other, as shown in FIG. 6 . In a state where the axial fans 10 C and 10 D are completely coupled, four attachment holes 421 C- 1 , 421 C- 2 , 421 D- 1 , and 421 D- 2 at each corner are aligned with one another in the axial direction.

Next, the coupling of the axial fans 10 C and 10 D is described in more detail, referring to the coupling structure provided in the housings 4 C and 4 D.

Referring to FIG. 7A , the housing 4 C of the upper axial fan 10 C is provided with a lower engaging portion 47 C adjacent to the lower end surface 43 C. The lower engaging portion 47 C is arranged to extend along the outer side surface of the cylindrical portion of the housing 4 C so as not to project beyond the outer periphery of the flange 42 C- 2 . In the present preferred embodiment, one end of the lower engaging portion 47 C is connected to one flange 42 C- 2 , as shown in FIG. 7A . The lower engaging portion 47 C has a protrusion 471 C which protrudes from the outer side surface of the cylindrical portion of the housing 4 C away from the center axis J 1 . The lower engaging portion 47 C also has a first lower locking portion 472 C and a second lower locking portion 473 C on the upper end surface of the protrusion 471 C. In the present preferred embodiment, the upper end surface of the protrusion 471 C is substantially flat and substantially perpendicular to the center axis J 1 , except for a region where the first and second lower locking portions 472 C and 473 C are provided. The outer side surface 4711 C of the protrusion 471 C defines a portion of a cylindrical plane centered about the center axis J 1 . The axial thickness of the protrusion 471 C is preferably thinner than that of the flange 42 C- 2 . The lower end surface of the protrusion 471 C is in the same plane as the lower end surface 43 C of the housing 4 C.

The first lower locking portion 472 C provided on the upper end surface of the protrusion 471 C includes a contact surface 4721 C and a sloping surface 4722 C. The sloping surface 4722 C which is an upper end surface of the first lower locking portion 472 C slopes upward from the upper end surface of the protrusion 471 C in the counterclockwise direction in FIG. 7A . An angle of the sloping surface 4722 C with respect to the upper end surface of the protrusion 471 C can be any angle as long as a sufficient locking performance is achieved. Please note that, in a case of manufacturing the housing by a molding process, a draft angle is also taken into consideration.

The second lower locking portion 473 C provided on the upper end surface of the protrusion 471 C axially extends upward from the upper end surface of the protrusion 471 C along the outer side surface of the cylindrical portion of the housing 4 C. The second lower locking portion 473 C also has a contact surface 4731 C on the opposite side to the first lower locking portion 472 C. In the example of FIG. 7A , the contact surface 4731 C is an upstream side surface in the counterclockwise direction.

Referring to FIG. 7B , the coupling structure of the housing 4 D of the lower axial fan 10 D is described. The housing 4 D is provided with an upper engaging portion 48 D adjacent to the upper end surface 43 D of the housing 4 D. In the present preferred embodiment, the upper engaging portion 48 D projects upward in the axial direction from the upper end surface of the flange 42 D- 1 , as shown in FIG. 7B . The upper engaging portion 48 D has a base portion 481 D projecting axially upward. The inner side surface 4811 D of the base portion 481 D, i.e., the radially inner surface thereof, defines a portion of a cylindrical plane centered about the center axis J 1 . In the present preferred embodiment, the inner side surface 4811 D has approximately the same radius as the outer side surface 4711 C of the protrusion 471 C of the housing 4 C (see FIG. 7A ).

At the axially upper end of the base portion 481 D are provided a first upper locking portion 482 D and a second upper locking portion 483 D both of which project radially inward from the upper end of the base portion 481 D. In the present preferred embodiment, the second upper locking portion 483 D is arranged on the upstream side of the first upper locking portion 482 D in the counterclockwise direction in FIG. 7B , for example.

The first and second upper locking portions 482 D and 483 D have contact surfaces 4821 D and 4831 D, respectively, which oppose each other in the circumferential direction of the cylindrical portion of the housing 4 D. Each of the inner side surfaces 4822 D and 4832 D of the first and second upper locking portions 482 D and 483 D define a portion of a cylindrical plane centered about the center axis J 1 . However, the inner side surfaces 4822 D and 4832 D have a different radius. In the present preferred embodiment, the radius of the inner side surface 4822 D is larger than that of the inner side surface 4832 D which is approximately the same as the radius of the outer side surface of the cylindrical portion of the housing 4 C.

The axial dimension of the space between each of the lower ends of the first and second upper locking portions 482 D and 483 D and the upper end surface 43 D of the housing 4 D is approximately the same as or slightly smaller than the axial dimension of the protrusion 471 C of the housing 4 C of the upper axial fan 10 C. In the present preferred embodiment, the axial dimension of the space between each of the first and second upper locking portions 482 D and 483 D and the upper end surface 43 D is smaller than the axial thickness of the protrusion 471 C.

The steps for coupling the axial fans 10 C and 10 D to each other are now described.

First, as shown in FIG. 7C , the axial fans 10 C and 10 D are arranged coaxially with each other so that the lower end surface 43 C of the housing 4 C and the upper end surface 43 D of the housing 4 D are in axial contact with each other. Please note that the upper engaging portion 48 D of the housing 4 D is arranged on the upstream side of the lower engaging portion 47 C of the housing 4 C in the counterclockwise direction in FIG. 7C .

Then, the housing 4 D is rotated about the center axis J 1 relative to the housing 4 C in the direction Rd, i.e., the counterclockwise direction in FIG. 7C . As a result, the upper engaging portion 48 D engages with the lower engaging portion 47 C, and the flanges 42 C- 1 , 42 C- 2 , 42 D- 1 , and 42 D- 2 at each corner are aligned with one another in the axial direction. In this manner, the fan unit 1 C is completely coupled.

FIG. 8 shows the details of the upper and lower engaging portions 48 D and 47 C.

When the housing 4 D is rotated relative to the housing 4 C, the upper end surface 43 D of the housing 4 D slides on the lower end surface 43 C of the housing 4 C. When the upper engaging portion 48 D reaches the lower engaging portion 47 C, the protrusion 471 C of the lower engaging portion 47 C enters into the space between the lower end surface of the first upper locking portion 482 D and the upper end surface of the flange 42 D- 1 , i.e., the upper end surface 43 D of the housing 4 D. In this space, the axial movement of the protrusion 471 C is restricted by the first upper locking portion 482 D and the flange 42 D- 1 . In addition, the radial movement of the base portion 481 D of the housing 4 D and the protrusion 471 C of the housing 4 C is also restricted because the inner side surface 4811 D of the base portion 481 D and the outer side surface 4711 C of the protrusion 471 C come into contact with each other in the radial direction. The outer side surface 4711 C of the protrusion 471 C also guides the upper engaging portion 48 D so that the upper engaging portion 48 D moves along the direction Rd.

As the housing 4 D is rotated further, the first upper locking portion 482 D passes outside the second lower locking portion 473 C of the housing 4 C. Since the inner side surface 4822 D of the first upper locking portion 482 D has a radius larger than that of the outer side surface of the second lower locking portion 473 C in the present preferred embodiment, the first upper locking portion 482 D does not come into contact with the second lower locking portion 473 C.

When the housing 4 D is rotated further, the lower end surface of the first upper locking portion 482 D reaches the sloping surface 4722 C of the second upper locking portion 472 C. Therefore, with the rotation of the housing 4 D, the first upper locking portion 482 D is elastically deformed upward in the axial direction by the sloping surface 4722 C.

When the housing 4 D is further rotated, the protrusion 471 C enters into the space between the lower end surface of the second upper locking portion 483 D and the flange 42 D- 1 (i.e., the upper end surface 43 D of the housing 4 D). In this space, the axial movement of the protrusion 471 C is restricted by the second upper locking portion 483 D and the flange 42 D- 1 . Then, as the housing 4 D is rotated further, the contact surface 4831 D of the second upper locking portion 483 D comes into contact with the contact surface 4731 C of the second lower locking portion 473 C in the direction Rd. At this time, the first upper locking portion 482 D is located on the upper surface of the sloping surface 4722 C of the first lower locking portion 472 C.

When the housing 4 D is further rotated while the contact surface 4831 D of the second upper locking portion 483 D is in contact with the contact surface 4731 C of the second lower locking portion 473 C, the first upper locking portion 482 D moves forward of the sloping surface 4722 C of the second lower locking portion 472 C in the direction Rd with the second upper locking portion 483 D elastically deformed. As a result, the upward deformation of the first upper locking portion 482 D is released, and the lower end surface of the first upper locking portion 482 D comes into contact with the upper end surface of the protrusion 471 C.

Subsequently, the second upper locking portion 483 D which is elastically deformed pulls the first upper locking portion 482 D toward the opposite direction to the direction Rd. At this time, the contact surface 4821 D of the first upper locking portion 482 D comes into contact with the contact surface 4721 C of the first lower locking portion 472 C. In the present preferred embodiment, the distance between the contact surface 4821 D of the first upper locking portion 482 D and the contact surface 4831 D of the second lower locking portion 483 D in the direction Rd is smaller than the distance between the contact surface 4721 C of the first lower locking portion 472 C and the contact surface 4731 C of the second upper locking portion 473 C in the direction Rd. Therefore, the first and second upper locking portions 482 D and 483 D are pressed toward the direction Rd and the direction opposite thereto by the first and second lower locking portions 472 C and 473 C. Therefore, further rotation of the housing 4 D relative to the housing 4 C about the center axis J 1 is prevented. Also, the coupling of the housings 4 C and 4 D has no play.

In addition, the protrusion 471 C is axially sandwiched between a portion of the upper engaging portion 48 D and the upper end surface of the housing 4 D while being pressed from both axial sides (i.e., in two axial directions) to cause elastic axial deformation of the protrusion 471 C. Therefore, the axial movement of the housings 4 C and 4 D is also prevented.

The aforementioned coupling structure is also preferably provided at the other three corners of the housings 4 C and 4 D, for example. Accordingly, it is possible to reduce possibilities that the engaging portions may be broken by a force applied substantially perpendicularly to the center axis J 1 .

In the present preferred embodiment, the engaging portion is preferably integral with the corresponding housing and preferably formed by injection molding using a single resin or plastic. This can minimize the increase in the manufacturing cost because the housing can be mass-produced by using a molding die.

Fourth Preferred Embodiment

FIG. 9 is an enlarged view of the coupling structure of a fan unit according to a fourth preferred embodiment of the present invention.

Except for the coupling structure, the fan unit of the present preferred embodiment preferably is substantially the same as that of the third preferred embodiment. Therefore, the coupling structure is mainly described in the following description. Please note the corresponding components of the fan units of the present preferred embodiment and the third preferred embodiment are labeled with reference signs with different suffixes. The suffixes correspond to the suffixes of the axial fans.

Referring to FIG. 9 , a housing 4 E of an upper axial fan 10 E is provided with a lower engaging portion 47 E adjacent to the upper end surface thereof. The lower engaging portion 47 E extends in the circumferential direction of the outer side surface of the cylindrical portion of the housing 4 E, as shown in FIG. 9 . The lower engaging portion 47 E has a protrusion 471 E which protrudes from the outer side surface of the cylindrical portion of the housing 4 E away from the center axis J 1 . The lower engaging portion 47 E also has a first lower locking portion 472 E and a second lower locking portion 473 E on the upper end surface of the protrusion 471 E. The upper end surface of the protrusion 471 E is substantially flat and substantially perpendicular to the center axis J 1 , except for a region where the first and second lower locking portions 472 E and 473 E are provided. The outer side surface 4711 E of the lower engaging portion 471 E defines a portion of a cylindrical plane centered about the center axis J 1 . The axial thickness of the protrusion 471 E is preferably less than that of the flange 42 E. The lower surface of the protrusion 471 E is in the same plane as the lower end surface 43 E of the housing 4 E. As shown in FIG. 9 , the protrusion 471 E extends in the circumferential direction of the cylindrical portion of the housing 4 E so as not to project beyond the outer edge of the flange 42 E, and is connected to the flange 42 E at one end thereof, i.e., the end closer to the first lower locking portion 472 E than to the second lower locking portion 473 E. Please note that the flange 42 E has substantially the same configuration as the flanges of the axial fans of the third preferred embodiment. Also, attachment holes 421 E, 421 F are provided in the flanges 42 E, 42 F, respectively.

The first lower locking portion 472 E on the upper end surface of the protrusion 471 E includes a contact surface 4721 E and a sloping surface 4722 E, as shown in FIG. 9 . The sloping surface 4722 E slopes upward in the clockwise direction to the contact surface 4721 E in FIG. 9 . An angle of the contact surface 4721 E with respect to the upper end surface of the can be any angle, as long as a sufficient locking performance can be achieved. Please note that, in a case of manufacturing the housing by a molding process, a draft angle is also taken into consideration.

The second lower locking portion 473 E provided on the upper end surface of the protrusion 471 E is arranged to the left of the first lower locking portion 472 E in the example of FIG. 9 , so as to be continuous with the first lower locking portion 472 E. More specifically, the upper surface of the second lower locking portion 473 E is continuous with the sloping surface 4722 E of the first lower locking portion 472 E. That is, the height of the upper end surface of the second lower locking portion 473 E from the upper surface of the protrusion 471 E is substantially the same as the minimum height of the sloping surface 4722 E of the first lower locking portion 472 E from the upper surface of the protrusion 471 E. Please note that the minimum height of the sloping surface 4722 E is the height thereof at the end of the sloping surface 4722 E connected to the second lower locking portion 473 E in the present preferred embodiment. The second lower locking portion 473 E has a contact surface 4731 E at the opposite end to the first lower locking portion 472 E. Similarly with the angle of the contact surface 4721 E, an angle of the contact surface 4731 E with respect to the upper end surface of the protrusion 471 E can be any angle as long as a sufficient locking performance can be achieved. Also, a draft angle is taken into consideration when the housing 4 E is manufactured by a molding process.

A housing 4 F of the lower axial fan 10 F is provided with an upper engaging portion 48 F adjacent to the upper end surface thereof. The upper engaging portion 48 F projects upward in the axial direction from the upper end surface of the flange 42 F, as shown in FIG. 9 . The upper engaging portion 48 F has a base portion 481 F projecting axially upward. The inner side surface 4811 F of the base portion 481 F, i.e., the radially inner surface thereof defines a portion of a cylindrical plane centered about the center axis J 1 . In the present preferred embodiment, the inner side surface 4811 F preferably has approximately the same radius as the outer side surface 4711 E of the protrusion 471 E of the housing 4 E.

At the axially upper end of the base portion 481 F are provided a first upper locking portion 482 F and a second upper locking portion 483 F, both of which project radially inward from the upper end of the base portion 481 F. In the present preferred embodiment, the first upper locking portion 482 F is arranged on the downstream side of the second upper locking portion 483 F in the counterclockwise direction in FIG. 9 , which corresponds to the direction of rotation of the housing 4 F described later, for example.

The first upper locking portion 482 F and the second upper locking portion 483 F have contact surfaces 4821 F and 4831 F, respectively, which oppose each other. Each of the inner side surfaces 4822 F and 4832 F of the first and second upper locking portions 482 F and 483 F define a portion of a cylindrical plane centered about the center axis J 1 . The inner side surfaces 4822 F and 4832 F have substantially the same radius as each other. Also, the inner side surfaces 4822 F and 4832 F have approximately the same radius as the outer side surface of the housing 4 E of the upper axial fan 10 E.

The axial dimension of the space between the lower end surface of the first upper locking portion 482 F and the upper end surface 43 F of the housing 4 F, i.e., the height of the lower end surface of the first upper locking portion 482 F from the upper end surface 43 F is approximately the same as or slightly smaller than the total axial thickness of the protrusion 471 E of the housing 4 E and the axial thickness of the second lower locking portion 473 E. Moreover, the axial dimension of the space between the lower end surface of the second upper locking portion 483 F and the upper end surface 43 F is approximately the same as or slightly smaller than the axial thickness of the protrusion 471 E of the housing 4 E.

The coupling of the axial fans 10 E and 10 F to each other is now described.

First, the axial fans 10 E and 10 F are arranged coaxially with each other so that the lower end surface 43 E of the housing 4 E and the upper end surface 43 F of the housing 4 F are in axial contact with each other, as shown in FIG. 9 . In this step, the housing 4 F is shifted relative to the housing 4 E with the upper engaging portion 48 F arranged on the upstream side of the lower engaging portion 47 E in the counterclockwise direction in FIG. 9 .

Then, the housing 4 F is rotated about the center axis J 1 relative to the housing 4 E in the direction Rd. In the present preferred embodiment, the direction Rd is the counterclockwise direction. As a result, the lower engaging portion 47 E engages with the upper engaging portion 48 F, thereby completing the fan unit.

In this relative rotation, the lower end surface 43 E of the housing 4 E slides on the upper end surface 43 F of the housing 4 F. When the upper engaging portion 48 F reaches the lower engaging portion 47 E, the protrusion 471 E of the lower engaging portion 47 E enters the space between the lower end surface of the first upper locking portion 482 F and the upper end surface of the flange 42 F, i.e., the upper end surface 43 F of the housing 4 F. At the same time, the inner side surface 4811 F of the base portion 481 F of the upper engaging portion 48 F and the outer side surface 4711 E of the protrusion 471 E of the lower engaging portion 471 E come into contact with each other in the radial direction. Thus, the radial movement of the base portion 481 F and the protrusion 471 E is also restricted. The outer side surface 4711 E of the protrusion 471 E guides the upper engaging portion 48 F in the direction Rd.

When the housing 4 F is rotated further, the first upper locking portion 482 F passes over the second lower locking portion 473 E.

Then, the lower end surface of the first upper locking portion 482 F reaches the upper surface of the sloping surface 4722 E of the second upper locking portion 473 E. Therefore, with the rotation of the housing 4 F, the first upper locking portion 482 F is elastically deformed upward in the axial direction by the sloping surface 4722 E.

As the housing 4 F is rotated further, the protrusion 471 E enters into the space between the lower end surface of the second upper locking portion 483 F and the flange 42 F, i.e., the upper end surface 43 F of the housing 4 F. In this space, the axial movement of the protrusion 471 E is restricted by the second upper locking portion 483 F and the flange 42 F. Then, as the housing 4 F is rotated further, the contact surface 4831 F of the second upper locking portion 483 F comes into contact with the contact surface 4731 E of the second lower locking portion 473 E. At this time, the first upper locking portion 482 F is located on the upper surface (sloping surface) 4722 E of the first lower locking portion 472 E.

When the housing 4 F is rotated further while the contact surface 4831 F of the second upper locking portion 483 F is in contact with the contact surface 4731 E of the second lower locking portion 473 E, the first upper locking portion 482 F is forced to move forward of the sloping surface 4722 E of the second upper locking portion 472 E in the direction Rd with the second upper locking portion 483 F elastically deformed. As a result, the upward deformation of the first upper locking portion 482 F is released, and the lower end surface of the first upper locking portion 482 F comes into contact with the upper end surface of the protrusion 471 E.

Subsequently, the second upper locking portion 483 F which is elastically deformed pulls the first upper locking portion 482 F toward the opposite direction to the direction Rd. At this time, the contact surface 4821 F of the first upper locking portion 482 F comes into contact with the contact surface 4721 E of the first lower locking portion 472 E in the direction Rd. The distance between the contact surface 4821 F of the first upper locking portion 482 F and the contact surface 4831 F of the second upper locking portion 483 F in the direction Rd is smaller than the distance between the contact surface 4721 E of the first lower locking portion 472 E and the contact surface 4731 E of the second lower locking portion 473 E in the direction Rd in the present preferred embodiment. Therefore, the first and second upper locking portions 482 F and 483 F are pressed toward the direction Rd and the direction opposite thereto by the first and second upper locking portions 472 E and 473 E. Therefore, further rotation of the housing 4 F relative to the housing 4 E about the center axis J 1 is prevented. Also, the coupling of the housings 4 E and 4 F has no play.

In addition, the protrusion 471 E is axially sandwiched between a portion of the upper engaging portion 48 F and the upper end surface of the housing 4 F while being pressed from both axial sides (i.e., in two axial directions) to cause elastic axial deformation of the protrusion 471 E. Therefore, the axial movement of the housings 4 C and 4 D is also prevented.

Fifth Preferred Embodiment

FIG. 10 is an enlarged view of the coupling structure of a fan unit according to a fifth preferred embodiment of the present invention.

Except for the coupling structure, the fan unit of the present preferred embodiment is substantially the same as that of the third preferred embodiment. Therefore, the coupling structure is mainly described in the following description. Please note the corresponding components of the fan units of the present preferred embodiment and the third preferred embodiment are labeled with reference signs with different suffixes. The suffixes correspond to the suffixes of the axial fans.

Referring to FIG. 10 , a housing 4 G of an upper axial fan 10 G is provided with a lower engaging portion 47 G adjacent to the lower end surface thereof. The lower engaging portion 47 G extends in the circumferential direction of the cylindrical portion of the housing 4 G, as shown in FIG. 10 . The lower engaging portion 47 G has a protrusion 471 G which protrudes from the outer side surface of the cylindrical portion of the housing 4 G away from the center axis J 1 . The lower engaging portion 47 G also has a first lower locking portion 472 G and a second lower locking portion 473 G on the upper end surface of the protrusion 471 G. The upper end surface of the protrusion 471 G is substantially flat and substantially perpendicular to the center axis J 1 except for a region where the first and second lower locking portions 472 G and 473 G are provided in the present preferred embodiment. The outer side surface 4711 G forms a portion of a cylindrical plane centered about the center axis J 1 . The axial thickness of the protrusion 471 G is preferably thinner than that of the flange 42 G. The lower end surface of the protrusion 471 G is in the same plane as the lower end surface of the housing 4 G. The protrusion 471 G extends in the circumferential direction of the cylindrical portion of the housing 4 G so as not to project beyond the outer edge of the flange 42 G, and is connected to the flange 42 G at one end which is closer to the first lower locking portion 4721 G than to the second lower locking portion 4731 G. Also, attachment holes 421 G, 421 H are provided in the flanges 42 G, 42 H, respectively

The first lower locking portion 472 G provided on the upper end surface of the protrusion 471 G projects from the protrusion 471 G upward in the axial direction along the outer side surface of the cylindrical portion of the housing 4 G. The first lower locking portion 472 G is configured by a contact surface 4721 G and a sloping surface 4722 G as an outer side surface. The sloping surface 4722 G slopes such that it extends away from the outer side surface of the cylindrical portion of the housing 4 G as it extends in the clockwise direction in FIG. 10 . The contact surface 4721 G is arranged at the upstream end of the sloping surface 4722 G in the clockwise direction. An angle of the contact surface 4721 G can be any angle as long as a sufficient locking performance can be achieved. In a case of manufacturing the housing 4 G by molding, a draft angle is also taken into consideration when the angle of the contact surface 4721 G is set.

The second lower locking portion 473 G provided on the upper end surface of the protrusion 471 G projects from the protrusion 471 G upward in the axial direction along the outer side surface of the cylindrical portion of the housing 4 G. The second lower locking portion 473 G is arranged on the upstream side of the first lower locking portion 472 G in the counterclockwise direction which is the direction of rotation of the housing 4 H described later. The outer side surface of the second lower locking portion 473 G is continuous with the sloping surface 4722 G of the first lower locking portion 472 G. In other words, the distance of the outer side surface of the second lower locking portion 473 G from the center axis J 1 is substantially the same as the minimum distance of the sloping surface 4722 G of the first lower locking portion 472 G from the center axis J 1 . The second lower locking portion 473 G has a contact surface 4731 G at the opposite end to the first lower locking portion 472 G.

A housing 4 H of a lower axial fan 10 H is provided with an upper engaging portion 48 H adjacent to the upper end surface thereof. The upper engaging portion 48 H protrudes upward in the axial direction from the upper surface of the flange 42 H, as shown in FIG. 10 . The upper engaging portion 48 H has a base portion 481 H projecting axially upward. The inner side surface 4811 H of the base portion 481 H, i.e., the radially inner surface thereof forms a portion of a cylindrical plane centered about the center axis J 1 . In the present preferred embodiment, the inner side surface 4811 H preferably has approximately the same radius as the outer side surface 4711 G of the protrusion 471 G of the housing 4 G.

At the axially upper end of the base portion 481 H are provided a first upper locking portion 482 H and a second upper locking portion 483 H both of which project radially inward from the upper end of the base portion 481 H. In the present preferred embodiment, the first upper locking portion 482 H is arranged on the downstream side of the second upper locking portion 483 H in the counterclockwise direction in FIG. 10 , for example.

The first and second upper locking portions 482 H and 483 H have contact surfaces 4821 H and 4831 H, respectively, which oppose each other. Each of the inner side surfaces 4822 H and 4832 H of the first and second upper locking portions 482 H and 483 H forms a portion of a cylindrical plane centered about the center axis J 1 . However, the inner side surfaces 4822 H and 4832 H are different from each other in their radius. In the present preferred embodiment, the radius of the inner side surface 4822 H is larger than that of the inner side surface 4832 H that is approximately the same as the radius of the outer side surface of the cylindrical portion of the housing 4 G.

The axial dimension of the space between each of the first and second upper locking portions 482 H and 483 H and the upper end surface 43 H of the housing 4 H is approximately the same as or slightly smaller than the axial thickness of the protrusion 471 G of the housing 4 G.

The coupling of the axial fans 10 G and 10 H to each other is now described.

First, the axial fans 10 G and 10 H are arranged coaxially with each other so that the lower end surface of the housing 4 G and the upper end surface 422 H of the housing 4 H are in axial contact with each other, as shown in FIG. 10 . In this step, the housing 4 H is shifted relative to the housing 4 G with the upper engaging portion 48 H arranged on the upstream side of the lower engaging portion 47 G in the counterclockwise direction in FIG. 10 in which the housing 4 H is to be rotated.

Then, the housing 4 H is rotated about the center axis J 1 relative to the housing 4 G in the direction Rd. In the present preferred embodiment, the direction Rd is the counterclockwise direction in FIG. 10 . As a result, the lower engaging portion 47 G engages with the upper engaging portion 48 H, thereby completing the fan unit of the present preferred embodiment.

During the relative rotation, the lower end surface of the housing 4 G slides on the upper end surface of the housing 4 H. When the upper engaging portion 48 H reaches the lower engaging portion 47 G, the protrusion 471 G of the housing 4 G enters the space between the lower end surface of the first upper locking portion 482 H and the flange 42 H (i.e., the upper end surface 43 H of the housing 4 H). At the same time, the inner side surface 4811 H of the base portion 481 H of the housing 4 H and the outer side surface 4711 G of the protrusion 471 G of the housing 4 G come into contact with each other in the radial direction. Thus, the radial movement of the base portion 481 H and the protrusion 471 G is restricted. The outer side surface 4711 G of the protrusion 471 G guides the upper engaging portion 48 H so that the upper engaging portion 48 H moves along the direction Rd.

When the housing 4 H is rotated further, the first upper locking portion 482 H passes outside the second lower locking portion 473 G in the radial direction.

Then, the lower end surface of the first upper locking portion 482 H reaches the sloping surface 4722 G of the second upper locking portion 472 G, as the housing 4 H is rotated further. While passing by the sloping surface 4722 G, the first upper locking portion 482 H is elastically deformed radially outwards, i.e., in a direction away from the center axis J 1 , by the sloping surface 4722 G.

When the housing 4 H is rotated further, the protrusion 471 G enters into the space between the lower end surface of the second upper locking portion 483 H and the flange 42 H (i.e., the upper end surface 422 H of the housing 4 H). In this space, the axial movement of the protrusion 471 G is restricted by the second upper locking portion 483 H and the flange 42 H so as not to make axial movement. As the housing 4 H is rotated further, the contact surface 4831 H of the second upper locking portion 483 H comes into contact with the contact surface 4731 G of the second lower locking portion 473 G in the direction Rd. At this time, the first upper locking portion 482 H is located radially outside the sloping surface 4722 G of the first lower locking portion 472 G.

When the housing 4 H is further rotated while the contact surface 4831 H of the second upper locking portion 483 H is in contact with the contact surface 4731 G of the second lower locking portion 473 G, the first upper locking portion 482 H is forced to move forward of the outer side surface 4722 G of the second upper locking portion 472 G in the direction Rd with the second upper locking portion 483 H elastically deformed. As a result, the radially outward deformation of the first upper locking portion 482 H is released and the inner side surface 4822 H of the first upper locking portion 482 H comes into contact with the outer side surface of the cylindrical portion of the housing 4 G.

Subsequently, the second upper locking portion 483 H which is elastically deformed pulls the first upper locking portion 482 H toward the opposite direction to the direction Rd. At this time, the contact surface 4821 H of the first upper locking portion 482 H comes into contact with the contact surface 4721 G of the first lower locking portion 472 G in the direction Rd. In the present preferred embodiment, the distance between the contact surface 4821 H of the first upper locking portion 482 H and the contact surface 4831 H of the second upper locking portion 483 H in the direction Rd is smaller than the distance between the contact surface 4721 G of the first lower locking portion 472 G and the contact surface 4731 G of the second lower locking portion 473 G in the rotating direction Rd. Therefore, the first and second upper locking portions 482 H and 483 H are pressed toward the direction Rd and the direction opposite thereto by the first and second lower locking portions 472 G and 473 G. Therefore, further rotation of the housing 4 H relative to the housing 4 G about the center axis J 1 is prevented. Also, the coupling of the housings 4 G and 4 H has no play.

In addition, the protrusion 471 G is axially sandwiched between a portion of the upper engaging portion 48 H and the upper end surface of the housing 4 H while being pressed from both axial sides (i.e., in two axial directions) to cause elastic axial deformation of the protrusion 471 G. Therefore, the axial movement of the housings 4 G and 4 H is also prevented.

Sixth Preferred Embodiment

FIG. 11 is an enlarged view of the coupling structure of a fan unit according to a sixth preferred embodiment of the present invention.

The fan unit of the present preferred embodiment is the same as that of the third preferred embodiment except for the coupling structure. Therefore, the coupling structure is mainly described in the following description. Please note the corresponding components of the fan units of the present preferred embodiment and the third preferred embodiment are labeled with reference signs with different suffixes. The suffixes correspond to the suffixes of the axial fans.

Referring to FIG. 11 , a housing 4 I of an upper axial fan 10 I is provided with a lower engaging portion 47 I adjacent to the lower end surface thereof. The lower engaging portion 47 I extends in the circumferential direction of the outer side surface of the cylindrical portion of the housing 4 I. The lower engaging portion 47 I has a protrusion 471 I which protrudes from the outer side surface of the cylindrical portion of the housing 4 I away from the center axis J 1 . The lower engaging portion 47 I also has a first lower locking portion 472 I and a second lower locking portion 473 I on the outer side surface of the protrusion 471 I. A portion 4711 I of the outer side surface of the protrusion 471 I, which is located on the upstream side of the first and second lower locking portions 472 I and 473 I in the counterclockwise direction, forms a portion of a cylindrical plane centered about the center axis J 1 . Also, a portion 4712 I of the outer side surface of the protrusion 471 I, which is located on the downstream side of the first and second lower locking portions 472 I and 473 I in the counterclockwise direction, forms a portion of a cylindrical plane centered about the center axis J 1 . The radius of the portion 4712 I is larger than that of the portion 4711 I in the present preferred embodiment. The axial thickness of the protrusion 471 I is preferably thinner than that of the flange 42 I. The lower end surface of the protrusion 471 I is in the same plane as the lower end surface of the housing 4 I. The protrusion 471 I extends in the circumferential direction of the cylindrical portion of the housing 4 I so that it does not project beyond the outer edge of the flange 42 I, and is connected to the flange 42 I at the end which is closer to the first lower locking portion 472 I than to the second lower locking portion 473 I, as shown in FIG. 11 . Also, attachment holes 421 I, 421 J are provided in the flanges 42 I, 42 J, respectively

The first lower locking portion 472 I provided on the radially outer surface of the protrusion 471 I projects radially outwards. The first lower locking portion 472 I includes a contact surface 4721 I and a sloping surface 4722 I. The sloping surface 4722 I gradually extends away from the outer side surface of the cylindrical portion of the housing 4 I as it extends in the counterclockwise direction in FIG. 11 . The contact surface 472 I is arranged at the opposite end thereof to the second lower locking portion 473 I, i.e., the downstream end in the counterclockwise direction.

The second lower locking portion 473 I provided on the outer side surface of the protrusion 471 I projects radially outwards. The second lower locking portion 473 I is arranged on the upstream side of the first lower locking portion 472 I in the counterclockwise direction in FIG. 11 corresponding to the direction of rotation of the housing 4 J described later. That is, the second lower locking portion 473 I is arranged on the left of the first lower locking portion 472 I in FIG. 11 . The outer side surface of the second lower locking portion 473 I is continuous with the sloping surface 4722 I of the first lower locking portion 472 I. In other words, the distance of the outer side surface of the second lower locking portion 473 I from the center axis J 1 is substantially the same as the minimum distance of the sloping surface 4722 I of the first lower locking portion 472 I from the center axis J 1 . The second lower locking portion 473 I has a contact surface 4731 I at one end opposite to the first lower locking portion 472 I.

A housing 4 J of the lower axial fan 10 J is provided with an upper engaging portion 48 J adjacent to the upper end surface thereof. The upper engaging portion 48 J projects upward in the axial direction from the upper surface of the flange 42 J, as shown in FIG. 11 . The upper engaging portion 48 J has a base portion 481 J projecting axially upward.

On the inner side surface of the base portion 481 J are formed at a first upper locking portion 482 J and a second upper locking portion 483 J arranged on the upstream side of the first upper locking portion 482 J in the counterclockwise direction in FIG. 11 . Each of the first and second upper locking portions 482 J and 483 J extends over the entire length of the base portion 481 J in the axial direction along the inner side surface of the base portion 481 J. Moreover, the upper end of each of the first and second upper locking portions 482 J and 483 J projects radially inward from the upper end of the base portion 481 J. A portion of the radially inner surface of the first upper locking portion 482 J located below the upper projection thereof, which is hereinafter referred to as an inner side surface 4823 J, forms a portion of a cylindrical plane centered about the center axis J 1 . Similarly, a portion of the radially inner surface of the second upper locking portion 483 J located below the upper projection thereof, which is hereinafter referred to as an inner side surface 4833 J, forms a portion of a cylindrical plane centered about the center axis J 1 . In the present preferred embodiment, the radius of the inner side surface 4823 J preferably is approximately the same as that of the outer side surface 4712 I of the protrusion 471 I, and the radius of the inner side surface 4833 J preferably is approximately the same as that of the outer side surface 4711 I of the protrusion 471 I.

The first and second upper locking portions 482 J and 483 J have contact surfaces 4821 J and 4831 J, respectively, which oppose each other. Each of the inner side surfaces 4822 J and 4832 J of the upper projections of the first and second upper locking portions 482 J and 483 J defines a portion of a cylindrical plane centered about the center axis J 1 . The inner side surfaces 4822 J and 4832 J preferably have approximately the same radius as the outer side surface of the cylindrical portion of the housing 4 I.

The axial dimension of the space between the lower end surface of the upper projection of each of the first and second upper locking portions 482 J and 483 J and the upper end surface 422 J of the housing 4 J is approximately the same as or slightly smaller than the axial thickness of the protrusion 471 I of the housing 4 I in the present preferred embodiment.

The coupling of the axial fans 10 I and 10 J to each other is now described.

First, the axial fans 10 I and 10 J are arranged coaxially with each other so that the lower end surface of the housing 4 I and the upper end surface of the housing 4 J are in axial contact with each other, as shown in FIG. 11 . In this step, the housing 4 J is shifted relative to the housing 4 I with the upper engaging portion 48 J arranged on the upstream side of the lower engaging portion 47 I in the counterclockwise direction in FIG. 11 .

Then, the housing 4 J is rotated about the center axis J 1 relative to the housing 4 I in the direction Rd. In the present preferred embodiment, the direction Rd is the counterclockwise direction in FIG. 11 . As a result, the lower engaging portion 47 I engages with the upper engaging portion 48 J, thereby forming the fan unit of the present preferred embodiment.

During the rotation, when the lower end surface of the housing 4 I slides on the upper end surface of the housing 4 J. The upper engaging portion 48 J reaches the lower engaging portion 47 I, the protrusion 471 I enters the space between the lower end surface of the upper projection of the first upper locking portion 482 J and the flange 42 J, i.e., the upper end surface of the housing 4 J. At the same time, the inner side surface 4823 J of the first upper locking portion 482 J, which is below the upper projection thereof, comes into contact with the outer side surface 4711 I of the protrusion 471 I in the radial direction. Thus, the radial movement of the base portion 481 J and the protrusion 471 I is restricted. The outer side surface 4711 I of the protrusion 471 I guides the upper engaging portion 48 J so that the upper engaging portion 48 J moves along the direction Rd.

When the housing 4 J is rotated further, the first upper locking portion 482 J passes outside the second lower locking portion 473 I in the radial direction.

Then, the inner side surface 4823 J of the first upper locking portion 482 J, which is below the upper projection thereof, reaches the sloping surface 4722 I of the second lower locking portion 472 I. While passing by the sloping surface 4722 I, the first upper locking portion 482 J is elastically deformed radially outwards, i.e., in a direction away from the center axis J 1 by the sloping surface 4722 I.

When the housing 4 J is rotated further, the protrusion 471 I enters into the space between the lower end surface of the upper projection of the second upper locking portion 483 J and the flange 42 J, i.e., the upper end surface of the housing 4 J. In this space, the axial movement of the protrusion 471 I is restricted by the second upper locking portion 483 J and the flange 42 J. As the housing 4 J is rotated further, the contact surface 4831 J of the second upper locking portion 483 J comes into contact with the contact surface 4731 I of the second lower locking portion 473 I in the direction Rd. At this time, the first upper locking portion 482 J is located radially outside the outer side surface 4722 I of the first lower locking portion 472 I.

When the housing 4 J is further rotated while the contact surface 4831 J of the second upper locking portion 483 J is in contact with the contact surface 4731 I of the second lower locking portion 473 I, the first upper locking portion 482 J is forced to move forward of the outer side surface 4722 I of the second lower locking portion 472 I in the direction Rd with the second upper locking portion 483 J elastically deformed. Consequently, the radially outward deformation of the first upper locking portion 482 J is released and the inner end surface of the upper projection of the first upper locking portion 482 J comes into contact with the outer side surface of the cylindrical portion of the housing 4 I.

Subsequently, the second upper locking portion 483 J which is elastically deformed pulls the first upper locking portion 482 J toward the opposite direction to the direction Rd. At this time, the contact surface 4821 J of the first upper locking portion 482 J comes into contact with the contact surface 4721 I of the first lower locking portion 472 I in the direction Rd. The distance between the contact surface 4821 J of the first upper locking portion 482 J and the contact surface 4831 J of the second upper locking portion 483 J in the direction Rd is smaller than the distance between the contact surface 4721 I of the first lower locking portion 472 I and the contact surface 4731 I of the second lower locking portion 473 I in the direction Rd in the present preferred embodiment. Therefore, the first and second upper locking portions 482 J and 483 J are pressed toward the rotating direction Rd and the direction opposite thereto by the first and second upper locking portions 472 I and 473 I. Therefore, further rotation of the housing 4 J relative to the housing 4 I about the center axis J 1 is prevented. Also, the coupling of the housings 4 I and 4 J have no play.

In addition, the protrusion 471 I is axially sandwiched between a portion of the upper engaging portion 48 J and the upper end surface of the housing 4 D while being pressed from both axial sides (i.e., in two axial directions) to cause elastic axial deformation of the protrusion 471 I. Therefore, the axial movement of the housings 4 I and 4 J is also prevented.

In the above description, the preferred embodiments of the present invention are described. However, the present invention is not limited thereto but can be modified in various ways. For example, exemplary combinations of the first upper locking portion, the second upper locking portion, the first lower locking portion, and the second lower locking portion are described in the preferred embodiments. However, the present invention is not limited thereto. Any combination of the upper and lower locking portions can be used in the present invention.

Moreover, only the fan units including two axial fans are described in the aforementioned preferred embodiments. However, the number of the coupled axial fans is not limited two. For example, three or more axial fans can be coupled to one another with any of the aforementioned coupling structures.

The material of the housings, for example, may be any of various resin or plastic or a die-cast aluminum material. Also, the protrusions and the notches may take any arbitrary shape as required.

Further, the cylindrical portions are not required to have a completely cylindrical inner side surface, but may have a venturi-shaped inner side surface with the diameter changing in the direction along the rotational axis of the impeller, or a wide tapered opening.

Also, the rotational axis of the impeller and the center axis of the housing are not required to coincide with each other but may be displaced from each other.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.