Fluid pressure valve

This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2018-098339 (filed on May 22, 2018), the contents of which are hereby incorporated by reference in their entirety.

The present disclosure relates to a fluid pressure valve. In particular, the present disclosure relates to a fluid pressure valve used in a fluid pressure servo mechanism.

A fluid pressure servo mechanism is used to control positions and attitudes of various objects such as flight control surfaces of an airplane. The fluid pressure servo mechanism includes a fluid pressure actuator for driving an object to be controlled and a fluid pressure valve for controlling the flow of a working fluid to the fluid pressure actuator. The fluid pressure actuator has a pair of fluid pressure chambers partitioned by a piston. The fluid pressure actuator is operated by supplying the working fluid to one of the pair of fluid pressure chambers while discharging the working fluid from the other fluid pressure chamber according to the position of the valve element of the fluid pressure valve.

Examples of conventional fluid pressure valves are disclosed in Japanese Patent Application Publication No. Hei 6-144385 and Japanese Patent Application Publication No. 2016-068889. As described in these publications, conventional fluid pressure valves include a hollow housing and a valve element for blocking a flow path between two ports in the housing. The flow path between the two ports is defined by a ring-shaped valve seat support fitted in the housing and a valve seat fitted in the valve seat support. In the valve closing position, the valve element closes the opening of the valve seat to block the communication between the two ports, while in the valve opening position, the valve element separates from the valve seat to communicate between the two ports.

In conventional fluid pressure valves, a flow path between the ports is defined by a valve seat support and a valve seat provided inside the housing. Therefore, the conventional fluid pressure valves suffer from a problem that the radial dimension thereof is larger with the thickness of a member for defining the flow path. In many cases, the member for defining the flow path has a large thickness because it needs to have structural strength to withstand the fluid pressure acting thereon from the working fluid. Further, the conventional fluid pressure valves have seal members for preventing leakage of the working fluid, the seal members provided between the valve seat support and the housing and between the valve seat support and the valve seat. These seal members also cause the increase in the radial dimension of the fluid pressure valve.

As described above, in conventional fluid pressure valves, it is difficult to reduce the radial dimension of the housing because the flow path between the two ports is defined by the valve seat support and the valve seat.

An object of the present disclosure is to relieve or overcome at least a part of the above problem. In particular, an object of the present disclosure is to provide a fluid pressure valve having a housing with a small radial dimension. Other objects of the disclosure will be apparent with reference to the entire description in this specification.

A fluid pressure valve according to an embodiment of the present invention comprises a housing including a housing member, the housing member being formed integrally so as to have a first port, a second port, and a flow path connecting between the first port and the second port.

In this fluid pressure valve, the flow path connecting between the first port and the second port is defined by the housing formed integrally, and therefore, there is no need of providing a member (e.g., the valve seat support) separate from the housing to define the flow path. In addition, since the flow path connecting between the first port and the second port is defined by the housing formed integrally, there is no need of providing a seal member to prevent leakage of the working fluid. Thus, in the embodiment described above, the housing of the fluid pressure valve can have a small radial dimension.

In the fluid pressure valve according to an embodiment of the present invention, the housing comprises: a first housing part extending in an axial direction of the housing; and a second housing part disposed adjacent to the first housing part in the axial direction and having a smaller outer diameter than the first housing part, and the first housing part includes the first port, the second port, and the flow path.

In this fluid pressure valve, the housing has a small outer diameter at the second housing part that does not include the flow path connecting between the first port and the second port. Thus, the housing can have a small radial dimension at the second housing part.

The fluid pressure valve according to an embodiment of the present invention further comprises a valve element for opening and closing the flow path, In an embodiment of the present invention, the housing includes a valve seat opposed to the valve element in an axial direction of the housing, and the valve element is movable in the axial direction of the housing and configured to contact with the valve seat in a closed position so as to block the flow path.

In this fluid pressure valve, the flow path can be closed without use of a separate valve seat, because the valve element contacts with the valve seat formed in the housing.

In the fluid pressure valve according to an embodiment of the present invention, the valve element has a larger diameter than the valve seat.

In this fluid pressure valve, the flow path between the first port and the second port can be closed without use of a separate valve seat, because the valve element contacts with the valve seat formed in the housing.

In the fluid pressure valve according to an embodiment of the present invention, the housing includes a projection for directing a flow of a working fluid

In this fluid pressure valve, the flow of the working fluid can be directed with the projection provided on the valve seat. Thus, the flow of the working fluid can be optimized.

In the fluid pressure valve according to an embodiment of the present invention, the valve element includes a projection for directing a flow of a working fluid, the projection being disposed on an end surface of the valve element opposed to the valve seat.

In this fluid pressure valve, the flow of the working fluid can be directed with the projection provided on the valve element. Thus, the flow of the working fluid can be optimized.

In the fluid pressure valve according to an embodiment of the present invention, the flow path includes a circling flow path extending in a circumferential direction of the housing, and a section of the circling flow path has a smaller dimension in a radial direction of the housing than in the axial direction of the same.

In this fluid pressure valve, the circling flow path of the flow path can have a smaller dimension in the radial direction of the housing. Thus, the housing can have a smaller radial dimension.

In the fluid pressure valve according to an embodiment of the present invention, the circling flow path is connected with the first port, and a sectional area of the circling flow path at a first position distal from the first port is larger than that at a second position more proximal to the first port than the first position.

In this fluid pressure valve, the working fluid flowing in via the first port can be easily guided to a position distal from the first port. Therefore, when the valve element is opened, the flow of the working fluid flowing in via the first port can be uniformed.

In the fluid pressure valve according to an embodiment of the present invention, the housing is configured such that a sectional shape of the circling flow path is at least partially formed of a curved line.

In this fluid pressure valve, when the valve is opened, the working fluid passes along the curved surface and flows out of the circling flow path. Therefore, the pressure loss of the working fluid can be reduced. As a result, the housing can have a small size.

A fluid pressure servo mechanism according to an embodiment of the present invention comprises: a fluid pressure actuator having a pair of fluid pressure chambers; and a fluid pressure valve having a housing and communicating with at least one of the pair of fluid pressure chambers via a connecting flow path. In this fluid pressure servo mechanism, at least part of the connecting flow path extends along an outer surface of the housing.

In this fluid pressure servo mechanism, it is possible to reduce the length of the connecting flow path that connects between the fluid pressure actuator and the fluid pressure valve. For example, a port formed in the fluid pressure actuator and a port formed in the fluid pressure valve can be arranged adjacent to each other so as to reduce the length of the connecting flow path connecting between the ports.

According to the embodiments of the present invention, the fluid pressure valve can have a housing with a small radial dimension.

FIG. 1 schematically shows a servo mechanism including a fluid pressure valve according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a manifold provided with the fluid pressure valve according to the embodiment of the present invention.

FIG. 3 is a sectional view schematically showing a section of the fluid pressure valve according to the embodiment of the present invention cut along the line A-A in FIG. 2 .

FIG. 4 is a sectional view schematically showing a section of the fluid pressure valve according to the embodiment of the present invention cut along the line B-B in FIG. 3 .

FIG. 5 is an enlarged sectional view of the fluid pressure valve of FIG. 3 for describing a flow path between ports. In FIG. 5 , the flow path between the ports is opened.

FIG. 6 is a sectional view schematically showing a part of a housing of the fluid pressure valve.

FIG. 7 is an enlarged sectional view showing a part of the fluid pressure valve of FIG. 3 in an enlarged scale. In FIG. 7 , the flow path between the ports is closed by a valve element.

FIG. 8 is an enlarged sectional view showing a part of the fluid pressure valve of FIG. 3 in an enlarged scale. In FIG. 8 , the flow path between the ports is opened by the valve element.

FIG. 9 is a sectional view of a fluid pressure valve according to another embodiment of the present invention.

FIG. 10 is a sectional view of a fluid pressure valve according to still another embodiment of the present invention.

FIG. 11 is a schematic perspective view of a valve element included in a fluid pressure valve according to yet another embodiment of the present invention.

Various embodiments of the invention will be described hereinafter with reference to the accompanying drawings. In the figures, elements common to different views are denoted by the same reference signs. It should be noted that the drawings do not necessarily appear to an accurate scale, for convenience of description.

The present invention may be applied to a fluid pressure valve having at least two ports. With reference to FIG. 1 , a description is given of a servo mechanism including a fluid pressure valve according to an embodiment of the present invention.

FIG. 1 shows a fluid pressure servo mechanism 1 including a fluid pressure valve 5 according to an embodiment of the present invention. The fluid pressure servo mechanism 1 serves as a flight control surface driving mechanism for driving a flight control surface 1 A of an airplane by operating an actuator 8 . The fluid pressure servo mechanism 1 is an example of a servo mechanism including a fluid pressure valve according to the present invention. The fluid pressure valve according to the present invention may also be used in various servo mechanisms other than the flight control surface driving mechanism.

The fluid pressure servo mechanism 1 includes the actuator 8 for driving the flight control surface 1 A, a fluid pressure source 2 for supplying a working fluid to the actuator 8 , a reservoir 3 for storing the working fluid discharged from the actuator 8 , a control valve 4 , and the fluid pressure valve 5 .

Examples of the flight control surface 1 A include primary control surfaces such as an aileron, a rudder, and an elevator and secondary control surfaces such as a flap and a spoiler.

In the embodiment shown, the actuator 8 may be a hydraulic actuator operated with a pressure oil. In addition, the actuator 8 may also be a hydraulic actuator operated with a working liquid other than a pressure oil, a pneumatic actuator operated with a compressed air, and any hydropneumatic actuator operated with other working fluids. It is also possible that the fluid pressure servo mechanism 1 includes a plurality of actuators.

The actuator 8 is partitioned into a first fluid pressure chamber 8 a and a second fluid pressure chamber 8 b by a piston 8 c provided in a hollow cylinder 13 . The cylinder 13 of the actuator 8 is open at one end in the longitudinal direction and is closed at the other. The piston 8 c is connected with a piston rod 8 d. The piston rod 8 d is partially projected out of the cylinder 13 .

The control valve 4 may be a solenoid valve. The control valve 4 is disposed between the actuator 8 , and the fluid pressure source 2 and the reservoir 3 and controls supply of the working fluid from the fluid pressure source 2 to the first fluid pressure chamber 8 a and the second fluid pressure chamber 8 b and discharge of the working fluid from the first fluid pressure chamber 8 a and the second fluid pressure chamber 8 b to the reservoir 3 . The control valve 4 is connected to the fluid pressure source 2 via a flow path 12 a, to the reservoir 3 via a flow path 12 b, and to the first fluid pressure chamber 8 a of the actuator 8 via a flow path 11 d. The control valve 4 includes an electromagnetic coil and a movable core and is configured to excite the electromagnetic coil based on a control signal input from a controller 10 and displace the movable core by the magnetic flux generated from the excited electromagnetic coil, thereby to switch the flow path of pressure oil communicating with the fluid pressure chambers 8 a, 8 b. More specifically, the control valve 4 can switch between a first communication position 4 X, a second communication position 4 Y, and a blocking position 4 Z. In the first communication position 4 X, the control valve 4 supplies the oil to the first fluid pressure chamber 8 a and discharges the oil from the second fluid pressure chamber 8 b; in the second communication position 4 Y, the control valve 4 discharges the oil from the first fluid pressure chamber 8 a and supplies the oil to the second fluid pressure chamber 8 b; and in the blocking position 4 Z, the control valve 4 blocks the supply of the oil to the fluid pressure chambers 8 a, 8 b and the discharge of the oil from the fluid pressure chambers 8 a, 8 b.

The fluid pressure valve 5 is connected to the control valve 4 via a flow path 11 a, to the second fluid pressure chamber 8 b of the actuator 8 via a flow path 11 b, and to the reservoir 3 via a flow path 11 e. The fluid pressure valve 5 includes a check valve 6 and a relief valve 7 . The check valve 6 can switch between a communication position 6 X and a blocking position 6 Y. In the communication position 6 X, the check valve 6 communicates between the second fluid pressure chamber 8 b and the control valve 4 ; and in the blocking position 6 Y, the check valve 6 blocks the communication between the second fluid pressure chamber 8 b and the control valve 4 . When the fluid pressure (pilot pressure) is supplied from the fluid pressure source 2 via the flow path 11 c, the check valve 6 is set to the communication position 6 X. The relief valve 7 is configured to discharge the working fluid to the reservoir 3 when the fluid pressure in the second fluid pressure chamber 8 b of the actuator 8 is equal to or higher than a prescribed value. The check valve 6 is provided with an auxiliary flow path 11 f for taking out the pilot pressure from a closed flow path formed in the check valve 6 when set at the blocking position 6 Y.

The actuator 8 may include a position sensor 9 for sensing the position of the piston 8 c. The position sensor 9 may be a linear variable differential transformer (LVDT).

The controller 10 includes a processor for performing various arithmetic operations, a memory for storing various programs and various data, and a device interface connected to the position sensor 9 and other devices. The controller 10 outputs control pulses to the control valve 4 to switch the control valve 4 . The controller 10 identifies the position of the piston 8 c based on the sensing signal from the position sensor 9 and performs feedback control based on the identified position of the piston 8 c so as to set the flight control surface 1 A to a target position in accordance with the flight conditions of the airplane.

A description is given of the operation of the fluid pressure servo mechanism 1 . The fluid pressure from the fluid pressure source 2 is supplied to the fluid pressure valve 5 as the pilot pressure, and thus the fluid pressure valve 5 takes the communication position 6 X.

When the control valve 4 is set to the first communication position 4 X based on the control signal from the controller 10 , the working fluid in the fluid pressure source 2 is supplied to the first fluid pressure chamber 8 a via the control valve 4 , and the working fluid in the second fluid pressure chamber 8 b is discharged to the reservoir 3 via the fluid pressure valve 5 and the control valve 4 . This operation causes expansion of the first fluid pressure chamber 8 a and contraction of the second fluid pressure chamber 8 b, and therefore, the flight control surface 1 A moves upward

When the control valve 4 is set to the second communication position 4 Y based on the control signal from the controller 10 , the oil in the fluid pressure source 2 is supplied to the second fluid pressure chamber 8 b via the control valve 4 and the fluid pressure valve 5 , and the oil in the first fluid pressure chamber 8 a is discharged to the reservoir 3 via the control valve 4 . This operation causes expansion of the second fluid pressure chamber 8 b and contraction of the first fluid pressure chamber 8 a, and therefore, the flight control surface 1 A moves downward.

Next, with reference to FIG. 2 , a description is given of a manifold including the fluid pressure valve 5 and the actuator 8 . FIG. 2 is a perspective view schematically showing a manifold 20 including the fluid pressure valve 5 and the actuator 8 . The manifold 20 also includes various fluid pressure devices other than the fluid pressure valve 5 and the actuator 8 .

As shown, the manifold 20 includes a housing 51 that forms a shell of the fluid pressure valve 5 , the cylinder 13 of the actuator 8 , a joint 4 a to which the control valve 4 is connected, and the flow paths 11 a to 11 f, 12 a, 12 b. The flow paths 11 d, 12 a, 12 b, provided behind the cylinder 13 , are not shown in FIG. 2 . The control valve 4 is mounted, or bolted for example, to the manifold 20 via the joint 4 a. In addition to the control valve 4 , various members may be mounted to the manifold 20 so as to cooperate with the actuator 8 and/or the fluid pressure valve 5 .

The manifold 20 may be configured such that the entirety, the main part, or a part thereof is integrated. For example, the housing 51 of the fluid pressure valve 5 may be integrated with the cylinder 13 of the actuator 8 .

A part or the entirety of each of the flow paths 11 a to 11 f, 12 a, 12 b may extend along the outer surface of the cylinder 13 of the actuator 8 . In the embodiment shown, the flow path 11 a extends from the joint 4 a to the housing 51 of the fluid pressure valve 5 along the outer surface of the cylinder 13 , and the flow path 11 b extends along the cylinder 13 from a port (not shown) formed in the cylinder 13 and communicating with the second fluid pressure chamber 8 b, to the fluid pressure valve 5 .

In an embodiment of the present invention, the manifold 20 is formed of various metal materials or various resin materials by additive manufacturing. Metal materials for the manifold 20 include titanium, aluminum, nickel, cobalt, chromium, stainless steels, and other metal materials suitable for additive manufacturing. Resin materials for the manifold 20 include polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyether imide (PEI), polyphenylene sulfide (PPS), polysulfone (PSU), polyamide (PA), polyphthalamide (PPA), and other resin materials suitable for additive manufacturing.

Additive manufacturing methods applicable to the present invention include direct metal laser melting (DMLM), direct metal laser sintering (DMLS), selective laser sintering (SLS), selective laser melting (SLM), electron beam melting (EBM), fusion deposition modeling (FDM), stereolithography, hot melt lamination, powder fixation, and other additive manufacturing methods known to those skilled in the art, or processes including these methods combined together.

The above description of the manifold 20 is for illustration purpose, and the modes described explicitly in this specification do not limit the shape, production, method, arrangement, and other features of the manifold 20 . For example, in the embodiment shown, the actuator 8 and the fluid pressure valve 5 are arranged so as to be longitudinally in parallel to each other. It is also possible that the actuator 8 and the fluid pressure valve 5 are not longitudinally in parallel to each other.

Installation of the components of the fluid pressure servo mechanism 1 to the manifold 20 makes it possible to reduce the length of the flow path 11 b that connects between the fluid pressure actuator 8 and the fluid pressure valve 5 . For example, a port (not shown) formed in the fluid pressure actuator 8 and a port (a first port 61 a described later) formed in the fluid pressure valve Scan be arranged adjacent to each other so as to reduce the length of the flow path 11 b.

Next, with reference to FIGS. 3 and 4 , a further description is given of the fluid pressure valve 5 according to the embodiment of the present invention. FIG. 3 is a sectional view schematically showing a section of the fluid pressure valve 5 of FIG. 2 cut along the line A-A, and FIG. 4 is a sectional view schematically showing a section of the fluid pressure valve 5 cut along the line B-B in FIG. 3 .

As shown in these drawings, the fluid pressure valve 5 is provided with the housing 51 that serves as a casing. The housing 51 has a cylindrical shape that extends along the central axis C. The housing 51 includes an inner space that extends through the housing 51 along the central axis C.

In this specification, the direction along the central axis C may be referred to as the longitudinal direction of the housing 51 , and the directions orthogonally intersecting the central axis C may be referred to as the radial directions of the housing 51 .

The housing 51 includes includes a housing member 151 . The housing member 151 includes a housing member 51 a , a housing member 51 b , a housing member 51 c , and a housing member 51 d , and these housing members are arranged in the direction from the end in the second direction W 2 to the end in the first direction W 1 along the central axis C. The housing members each extend in the direction of the central axis C. The housing member 51 c has a larger outer diameter than the housing member 51 b and the housing member 51 d adjacent to the housing member 51 c . In one embodiment, the housing member 51 c may be referred to as first housing part and the housing member 51 d may be referred to as second housing part.

The entirety of the housing 51 may be formed integrally, or a part of the components of the housing 51 may be formed integrally. The housing 51 may be formed of a plurality of unit members formed separately and joined together by bolt fastening, welding, or other joining methods. In the embodiment of the present invention, the entirety of the housing member 51 c included in the housing 51 is formed integrally. When it is described herein that a housing or a housing member is “formed integrally” the housing or the housing member is a unitary member, not a composite member that can be divided into a plurality of parts. There is no junction surface between a plurality of parts in the housing or the housing member formed integrally. Accordingly, when the entirety of the housing 51 is formed integrally, the housing 51 is a unitary member, and when the entirety of the housing member 51 c is formed integrally, the housing member 51 c is a unitary member. The housing 51 may be produced by integrally forming each of the housing member 51 a, the housing member 51 b, the housing member 51 c, and the housing member 51 d and joining these four integrally formed housing members to adjacent ones.

The housing 51 has a plurality of ports formed therein that communicate between the inner space and the outside thereof. In the embodiment shown, there are formed a first port 61 a that communicates with the second fluid pressure chamber 8 b, a second port 61 b that communicates with the control valve 4 , and a third port 61 c that communicates with the fluid pressure source 2 . In addition to the ports shown, the housing 51 has a discharge port that communicates with the reservoir 3 and an auxiliary oil passage port that communicates with an auxiliary oil passage 11 f, and these ports are omitted in FIG. 4 . The discharge port that communicates with the reservoir 3 is disposed, for example, between the second port 61 b and the third port 61 c. The auxiliary oil passage port that communicates with the auxiliary oil passage 11 f is formed, for example, on the first direction W 1 side of the third port 61 c.

The housing 51 contains, in the inner space thereof, a cap 52 , a valve element 53 , a rod 55 , a slider 57 , a plunger 58 , a plug 59 , and other components of the fluid pressure valve 5 .

The cap 52 is mounted on an end of the housing 51 on the second direction W 2 side. The cap 52 blocks an opening in the end of the housing 51 on the second direction W 2 side. In the embodiment shown, the cap 52 includes a cap base 52 a, and a cap sleeve 52 b that extends from the cap base 52 a in the first direction W 1 and has a cylindrical shape. The cap base 52 a has an external thread formed in the outer peripheral surface thereof. The external thread is threadedly engaged with an internal thread formed in an inner peripheral surface of the housing member 51 a, and the cap sleeve 52 b is fitted on the inner side of the housing member 51 b, such that the cap 52 is mounted on the housing 51 . The cap base 52 a has a first recess 52 c formed therein in the direction of the central axis C, and the cap sleeve 52 b has a second recess 52 d having a larger diameter than the first recess 52 c.

The valve element 53 includes a valve element head 53 a and a valve element base 53 b extending from the valve element head 53 a in the second direction W 2 . The valve element 53 is disposed such that a distal end of the valve element base 53 b is received in the first recess 52 c and the second recess 52 d of the cap 52 . The valve element head 53 a has a cylindrical shape and is fitted on the inner side of the housing member 51 c. In the embodiment shown, an end surface 53 c of the valve element head 53 a facing toward the first direction W 1 is a flat plane perpendicular to the central axis C. The valve element 53 is slidable along the central axis C.

The valve element 53 is configured and arranged so as to block a flow path between the first port 61 a and the second port 61 b when the valve element 53 is in a closed position along the central axis C. FIG. 4 shows the valve element 53 in the closed position.

The cap sleeve 52 b of the cap 52 is provided with a press spring 54 . The press spring 54 is disposed between a bottom surface of the second recess 52 d of the cap 52 and the valve element head 53 a and configured to bias the valve element head 53 a in the first direction W 1 .

The slider 57 is disposed in the housing 51 between the second port 61 b and the third port 61 c so as to be slidable with respect to the housing 51 in the direction of the central axis C. The slider 57 has a cup-like shape that is open toward the cap 52 (the second direction W 2 ). The rod 55 is provided in the slider 57 . The rod 55 includes a rod base 55 a having a disk-like shape and a rod body 55 b extending from the rod base 55 a toward the cap 52 (the second direction W 2 ). The rod 55 is mounted on the slider 57 via the rod base 55 a. The distal end (the end on the second direction W 2 side) of the rod body 55 b is in contact with the valve element 53 . Between the rod base 55 a and an inner wall of the housing 51 , there is provided a press spring 56 . The press spring 56 biases the rod base 55 a toward the plug 59 (the first direction W 1 ). The slider 57 is movable along the central axis C toward the second direction W 2 by a pilot pressure supplied via the third port 61 c. As the slider 57 moves in the second direction W 2 , the rod 55 also moves in the second direction W 2 . This causes the rod body 55 b to press the valve element 53 in the second direction W 2 , and thus the valve element 53 also moves in the second direction W 2 . As a result, the flow path between the first port 61 a and the second port 61 b is opened. In this way, the pilot pressure supplied to the fluid pressure cylinder 5 opens the flow path between the first port 61 a and the second port 61 b.

The plug 59 is mounted on an end of the housing 51 on the first direction W 1 side and blocks an opening in an end of the housing 51 on the first direction W 1 side.

The plug 59 has a recess that is open toward the slider 57 (the second direction W 2 ), and the plunger 58 is disposed in this recess. Between the plunger 58 and the recess of the plug 59 , there is formed an inner space 60 c. The plug 59 has a cutout formed therein (not shown), and the inner space 60 c communicates with the auxiliary oil passage 11 f via the cutout and a port (not shown). The plunger 58 is disposed such that an end surface thereof on the second direction W 2 side contacts with the slider 57 .

As shown, the housing member 51 c of the housing 51 has a first circling flow path 62 and a second circling flow path 68 formed therein. The first circling flow path 62 extends circumferentially around the central axis C, and the second circling flow path 68 is disposed at a distance from the first circling flow path 62 toward the first direction W 1 along the central axis C. The first circling flow path 62 is connected with the first port 61 a. The second circling flow path 68 is connected with the second port 61 b.

Next, with additional reference to FIG. 5 , a further description will be given of a flow path that connects between the first port 61 a and the second port 61 b in the housing 51 . FIG. 5 is an enlarged sectional view showing a part of the housing member 51 c of the fluid pressure valve 5 in an enlarged scale.

As shown, the first circling flow path 62 has a substantially rectangular section. The first circling flow path 62 is defined by a first wall 62 a , a second wall 62 b , a third wall 62 c , and a fourth wall 62 d . In one embodiment, the first wall 62 a , the second wall 62 b , the third wall 62 c , and the fourth wall 62 d of the first circling flow path 62 may be referred to as sectional shape of the first circling flow path 62 . The first wall 62 a extends in the direction of the central axis C and has a communication hole connected with the first port 61 a ; the second wall 62 b extends from the first wall 62 a in a substantially radial direction; the third wall 62 c is disposed radially inside the first wall 62 a a so as to be opposed to the first wall 62 a ; and the fourth wall 62 d is disposed on the first direction W 1 side of the second wall 62 b in the direction of the central axis C so as to be opposed to the second wall 62 b . The third wall 62 c has a cutout formed therein to allow the working fluid to flow radially inward. In the embodiment of the present invention; the first circling flow path 62 is formed such that the dimension L 1 of the section thereof in the radial direction (the distance L 1 between the first wall 62 a and the third wall 62 c ) is smaller than the dimension L 2 of the same in the direction of the central axis C (the distance L 2 between the second wall 62 b and the fourth wall 62 d ).

As with the first circling flow path 62 , the second circling flow path 68 is formed such that the section thereof has a substantially rectangular shape. The second circling flow path 68 is defined by a first wall 68 a, a second wall 68 b, a third wall 68 c, and a fourth wall 68 d. The first wall 68 a extends in the direction of the central axis C and has a communication hole connected with the second port 61 b; the second wall 68 b extends from the first wall 68 a in a substantially radial direction; the third wall 68 c is disposed radially inside the first wall 68 a so as to be opposed to the first wall 68 a; and the fourth wall 68 d is disposed on the first direction W 1 side of the second wall 68 b in the direction of the central axis C so as to be opposed to the second wall 68 b. The third wall 68 c has a cutout formed therein to allow the working fluid to flow radially inward. In the embodiment of the present invention, the second circling flow path 68 is formed such that the dimension L 3 of the section thereof in the radial direction (the distance L 3 between the first wall 68 a and the third wall 68 c ) is smaller than the dimension L 4 of the same in the direction of the central axis C (the distance L 4 between the second wall 68 b and the fourth wall 68 d ).

The first wall 62 a, the second wall 62 b, the third wall 62 c, and the fourth wall 62 d of the first circling flow path 62 may curve in the axial direction along the central axis C. The first wall 62 a either extends in parallel with the central axis C or curve with a larger radius of curvature in the axial direction along the central axis C than the third wall 62 c. Likewise, the first wall 68 a, the second wall 68 b, the third wall 68 c, and the fourth wall 68 d of the second circling flow path 68 may curve in the axial direction along the central axis C. The first wall 68 a either extends in parallel with the central axis C or curve with a larger radius of curvature in the axial direction along the central axis C than the third wall 68 c.

Between the first circling flow path 62 and the second circling flow path 68 , there is disposed a mount 70 constituting a part of the housing member 51 c. The mount 70 is formed integrally with the housing member 51 c. A part of the mount 70 is positioned between the first circling flow path 62 and the second circling flow path 68 . The mount 70 projects radially inward from the outer side of the housing 51 . In the embodiment shown, the mount 70 extends from the region between the first circling flow path 62 and the second circling flow path 68 to the region radially inside the first circling flow path 62 . The mount 70 includes a slope surface 71 adjacent to the third wall 62 c of the first circling flow path 62 , a seat surface 72 adjacent to the first slope surface 71 , a cylindrical surface 73 adjacent to the seat surface 72 , and a plurality of tubular surfaces 74 extending from the cylindrical surface 73 to the second circling flow path 68 . Each of the slope surface 71 , the seat surface 72 , the cylindrical surface 73 , and the plurality of tubular surfaces 74 constitutes a part of the housing member 51 c.

The slope surface 71 extends in the circumferential direction around the central axis C and in the direction oblique to the central axis C radially inward from the third wall 62 c of the first circling flow path 62 . The slope surface 71 may be curved toward the central axis C. The slope surface 71 and the third wall 62 c of the first circling flow path 62 may be connected with each other via a curved surface

The seat surface 72 extends generally radially inward from the radially inner end of the slope surface 71 . The seat surface 72 has an opening formed near the central axis C. The seat surface 72 is opposed to the end surface 53 c of the valve element 53 . The seat surface 72 has a recess 72 a formed toward the first direction W 1 along the central axis C. The recess 72 a extends circumferentially around the central axis C, with an outer valve seat 72 b provided on the radially outer side of the recess 72 a and an inner valve seat 72 c provided on radially inner side of the recess 72 a. The inner valve seat 72 c has a ring-like shape that extends circumferentially around the central axis C. The inner circumferential surface of the inner valve seat 72 c defines the opening in the seat surface 72 . In this way, the seat surface 72 includes the outer valve seat 72 b, the recess 72 a, and the inner valve seat 72 c arranged in the order from the radially outer side to the radially inner side. The valve element 53 blocks the flow path between the first port 61 a and the second port 61 b when the end surface 53 c of the valve element head 53 a contacts with the inner valve seat 72 c. To establish the blocking of the flow path, the valve element 53 is formed such that the valve element head 53 a has a larger diameter than the inner valve seat 72 c.

The slope surface 71 has four recesses 64 a, 64 b, 64 c, 64 d formed toward the first direction W 1 . These recesses 64 a, 64 b, 64 c, 64 d are arranged circumferentially around the central axis C at substantially regular intervals. Each of the recesses 64 a, 64 b, 64 c, 64 d extends radially from the slope surface 71 to the outer edge of the seat surface 72 . Therefore, each of the recesses 64 a, 64 b, 64 c, 64 d is connected with the recess 72 a. As shown in FIG. 3 , these recesses 64 a, 64 b, 64 c, 64 d divide the outer valve seat 72 b into four parts. Each of the four parts of the outer valve seat 72 b extends by less than 90° in the circumferential direction around the central axis C.

The cylindrical surface 73 has a substantially cylindrical shape that extends along the central axis C from the radially inner end of the seat surface 72 . The cylindrical surface 73 includes a first cylindrical surface 73 a having a large diameter, a second cylindrical surface 73 b having a smaller diameter than the first cylindrical surface 73 a, and a slant surface 73 c connecting between the first cylindrical surface 73 a and the second cylindrical surface 73 b.

The plurality of tubular surfaces 74 each have a tubular shape that extends in the direction oblique to the central axis C radially outward from the end of the cylindrical surface 73 on the first direction W 1 side. The plurality of tubular surfaces may include a desired number of tubular surfaces.

With additional reference to FIG. 6 , a description will be given of the flow path 65 that connects between the first port 61 a and the second port 61 b. FIG. 6 is a sectional view of the housing member 51 c cut along the B-B line in FIG. 3 . For clear representation of the flow path, FIG. 6 omits the valve element 53 , the rod body 55 b, and the press spring 56 .

As shown, the flow path 65 for the working fluid connecting between the first port 61 a and the second port 61 b includes the first circling flow path 62 , a first flow path 65 a, a second flow path 65 b, a third flow path 65 c, and the second circling flow path 68 . As described above, the first circling flow path 62 and the second circling flow path 68 extend circumferentially around the central axis C. The first circling flow path 62 communicates with the first port 61 a, and the second circling flow path 68 communicates with the second port 61 b. The first flow path 65 a extends radially inward from the first circling flow path 62 . At least a part of the first flow path 65 a is defined by the slope surface 71 and the seat surface 72 . The second flow path 65 b is defined by the cylindrical surface 73 . The second flow path 65 b extends from the first flow path 65 a in the first direction W 1 along the central axis C. The third flow path 65 c is defined by the tubular surfaces 74 . The third flow path 65 c connects between the second flow path 65 b and the second circling flow path 68 . The flow path 65 contains the valve element 53 and the rod body 55 b.

In this way, the flow path 65 connecting between the first port 61 a and the second port 61 b is defined by the housing 51 (the housing 51 c in the embodiment shown). Therefore, in the fluid pressure valve 5 , there is no need of providing, in the inner space of the housing 51 , a member separate from the housing 51 (for example, the valve seat support or the valve seat separate from the housing in the conventional art) to define the flow path 65 connecting between the first port 61 a and the second port 61 b. The flow path 65 contains the valve element 53 for opening and closing the flow path 65 and the rod body 55 b for pressing the valve element 53 , and these members serve to open and close the flow path 65 , not to define the flow path 65 . Therefore, the flow path 65 connecting between the first port 61 a and the second port 61 b is defined only by the housing 51 except for the members for opening and closing the flow path 65 .

With reference to FIGS. 7 and 8 , a description will be given of a valve opening motion performed by the valve element 53 of the fluid pressure valve 5 . FIGS. 7 and 8 are enlarged sectional views showing a part around the housing member 51 c of the fluid pressure valve 5 in an enlarged scale. FIG. 7 shows the valve element 53 in the closed position, and FIG. 8 shows the valve element 53 in the opened position.

As shown in FIG. 7 , the valve element 53 in the closed position is situated such that the end surface 53 c thereof is in contact with the four parts of the outer valve seat 72 b and the inner valve seat 72 c.

When, for example, a pilot pressure is supplied from the fluid pressure source 2 via the third port 61 c, the valve element 53 moves from the closed position shown in FIG. 7 to the valve opening position shown in FIG. 8 in the second direction W 2 along the central axis C. In the opened position, the valve element 53 is separated from the outer valve seat 72 b and the inner valve seat 72 c. In this way, the valve element 53 moves from the closed position to the opened position. In addition, the valve element 53 also moves from the closed position to the opened position when the flight control surface 1 A moves with no pilot pressure supplied and when the pressure in the closed oil passage between the valve element 53 and the second fluid pressure chamber 8 b exceeds a prescribed value.

When the valve element 53 moves to the opened position, the working fluid accumulated in the first circling flow path 62 and the working fluid discharged from the second fluid pressure chamber 8 b pass through the first flow path 65 a, the second flow path 65 b, and the third flow path 65 c and flow into the second circling flow path 68 , and then these working fluids flow out of the second circling flow path 68 , pass the second port 61 b, the flow path 11 a, the control valve 4 , and the flow path 12 b, and flow into the reservoir 3 .

In the fluid pressure valve 5 described above, the flow path 65 connecting between the first port 61 a and the second port 61 b is defined by the housing 51 formed integrally (or by the housing member 51 c constituting a part of the housing 51 and formed integrally), and therefore, there is no need of providing a member (e.g., the valve seat support used conventionally) separate from the housing 51 to define the flow path 65 . In addition, since the flow path 65 connecting between the first port 61 a and the second port 61 b is defined by the housing 51 formed integrally (or by the housing member 51 c constituting a part of the housing 51 and formed integrally), there is no need of providing a seal member to prevent leakage of the working fluid. Thus, in the embodiment described above, the housing 51 of the fluid pressure valve 5 can have a small radial dimension.

In the housing 51 of the fluid pressure valve 5 , the housing members (e.g., at least one of the housing member 51 a, the housing member 51 b, and the housing member 51 d ) other than the housing member 51 c including the flow path connecting the first port 61 a and the second port 61 b can have an outer diameter smaller than that of the housing member 51 c. Thus, portions of the housing 51 other than the housing member 51 c can have a smaller radial dimension.

In the fluid pressure valve 5 , the flow path 65 can be closed without use of a separate valve seat, because the valve element 53 contacts with the inner valve seat 72 c formed in the housing 51 .

In the fluid pressure valve 5 , the flow path between the first port 61 a and the second port 61 b can be closed without use of a separate valve seat, because the valve element 53 contacts with the inner valve seat 72 c formed in the housing 51 .

In the fluid pressure valve 5 , the first circling flow path 62 can have a smaller dimension in the radial direction of the housing 51 than in the longitudinal direction of the same. Thus, the housing 51 can have a smaller radial dimension.

In the fluid pressure valve 5 , at least one of the first wall 62 a, the second wall 62 b, the third wall 62 c, and the fourth wall 62 d that define the first circling flow path 62 can be formed so as to be curved in the axial direction along the central axis C. This causes the working fluid to flow into the second flow path 65 b via the curved surface when the valve is opened. Therefore, the pressure loss of the working fluid flowing from the first port 61 a into the second port 61 b can be reduced. As a result, the housing 51 can have a small size.

Next, with reference to FIG. 9 , a description is given of a fluid pressure valve according to another embodiment of the present invention. FIG. 9 is a sectional view of a fluid pressure valve 105 according to another embodiment of the present invention cut along a cutting line corresponding to the A-A line. The fluid pressure valve 105 is different from the fluid pressure valve 5 in that the first circling flow path 62 is provided with a projection for directing the flow of the working fluid.

In the fluid pressure valve 105 as shown, the first circling flow path 62 is provided with a projection 106 . In the embodiment shown, the projection 106 projects from the fourth wall 62 d defining the first circling flow path 62 in the second direction W 2 along the central axis C. The projection 106 is formed integrally with the housing 51 , constituting a part thereof. The projection 106 is disposed, for example, in a virtual line connecting between the first port 61 a and the central axis C (or the second flow path 65 b ).

The working fluid flowing from the first port 61 a into the first circling flow path 62 flows around or over the projection 106 and is directed toward the second flow path 65 b. Thus, the flow of the working fluid from the first port 61 a toward the second flow path 65 b can be more uniformed in the circumferential direction around the central axis C. More specifically, the flow running straight from the first port 61 a toward the second flow path 65 b is checked by the projection 106 , and the flow running from the direction where the projection 106 is absent around the central axis C toward the second flow path 65 b is facilitated. The flow of the working fluid from the first port 61 a toward the second fluid path 65 b is thus uniformed, thereby to prevent the valve element 53 and the rod body 55 b from being tilted with respect to the central axis C due to the fluid pressure of the working fluid.

The number, shape, and arrangement of the projections 106 formed in the fluid pressure valve 105 are not limited to those in the illustrated embodiment. For example, it is possible to provide two or more projections 106 . The projection 106 may also be formed in various positions other than the virtual line connecting between the first port 61 a and the central axis C. The number, shape, and arrangement of the projections 106 may be modified suitably for the purpose of optimizing the flow of the working fluid or other purposes.

Next, with reference to FIG. 10 , a description is given of a fluid pressure valve according to still another embodiment of the present invention. FIG. 10 is a sectional view of a fluid pressure valve 115 according to another embodiment of the present invention cut along a cutting line corresponding to the A-A line. The fluid pressure valve 115 has a first circling flow path 162 in place of the first circling flow path 62 .

As shown, the first circling flow path 162 is formed such that the radial dimension L 5 thereof at a first position P 1 distal from the first port 61 a is larger than the radial dimension L 6 thereof at a second position P 2 proximal to the first port 61 a. As a result, the sectional area of the first circling flow path 162 at the first position P 1 is larger than that at the second position P 2 .

In the embodiment shown in FIG. 10 , the housing member 51 c has a smaller thickness at the first position P 1 than at the second position P 2 . In this way, the housing member 51 c has different thicknesses at the first position P 1 and the second position P 2 that is distant from the first position P 1 in the circumferential direction, such that the sectional area of the flow path in the housing member 51 c can be varied in the circumferential direction. It is also possible to form the first circling flow path 162 in a different manner.

According to the above embodiment, the working fluid flowing from the first port 61 a into the first circling flow path 162 can be easily guided in the first circling flow path 162 to the first position P 1 distal from the first port 61 a. Thus, the flow of the working fluid from the first port 61 a toward the second flow path 65 b can be more uniformed in the circumferential direction around the central axis C. As a result, the valve element 53 and the rod body 55 b can be prevented from being tilted with respect to the central axis C due to the fluid pressure of the working fluid

Next, with reference to FIG. 11 , a description is given of a valve element used in a fluid pressure valve according to yet another embodiment of the present invention. FIG. 11 is a schematic perspective view of a valve element 153 included in a fluid pressure valve according to yet another embodiment of the present invention. The valve element 153 may replace the valve 53 in the fluid pressure valve 5 and other fluid pressure valves to which the present invention is applied.

As shown, the valve element 153 includes a valve element head 153 a and a valve element base 153 b extending from the valve element head 153 a. When the valve element 153 is installed in the fluid pressure valve 5 , a distal end of the valve element base 153 b is received in the first recess 52 c and the second recess 52 d of the cap 52 .

The end surface 153 c of the valve element 153 has four projections 154 a to 154 d formed thereon. The projections 154 a to 154 d project from the end surface 153 c of the valve element 153 . When the valve element 153 is installed in the fluid pressure valve 5 , the projections 154 a to 154 d are disposed in the first circling flow path 62 . The valve element 153 may be installed in the fluid pressure valve 5 such that one of the projections 154 a to 154 d is disposed in the virtual line connecting between the first port 61 a and the central axis C (or the second flow path 65 b ).

The projections 154 a to 154 d, disposed in the first circling flow path 62 , direct the flow of the working fluid flowing in the first circling flow path 62 . For example, one of the projections 154 a to 154 d may be disposed in the virtual line connecting between the first port 61 a and the central axis C (or the second flow path 65 b ) so as to check the flow running straight from the first port 61 a toward the second flow path 65 b. As a result, the rod body 55 b can be prevented from being tilted with respect to the central axis C due to the fluid pressure of the working fluid.

The number, shape, and arrangement of the projections 154 a to 154 d formed on the valve element 153 are not limited to those in the illustrated embodiment. For example, the valve element 153 may have three or less projections formed thereon. The number, shape, and arrangement of the projections formed on the end surface 153 c of the valve element 153 may be modified suitably for the purpose of optimizing the flow of the working fluid or other purposes.

The dimensions, materials, and arrangements of the constituents described in this specification are not limited to those explicitly described for the embodiments, and the constituents can be modified to have any dimensions, materials, and arrangements within the scope of the present invention. The elements other than those explicitly described herein may be added to the described embodiments, and some of the elements described for the embodiments may be omitted.

The fluid pressure servo mechanism 1 shown in FIG. 1 is an example of a fluid pressure servo mechanism to which the present invention is applicable. The fluid pressure servo mechanism 1 can be modified desirably in accordance with its applications based on technical knowledge of those skilled in the art. For example, the fluid pressure servo mechanism 1 may include a fluid pressure device not explicitly described in this specification or the appended drawings. The processing and control performed by the controller 10 may alternatively be performed by a plurality of controllers in a distributed manner.

The specific shapes, arrangements, functions, and materials of the components of the fluid pressure valves 5 , 105 , 115 explicitly described in this specification or the appended drawings are merely for illustration. The shapes, arrangements, functions, and materials of the components of the fluid pressure valves 5 , 105 , 115 can be modified desirably within the purport of the present invention.