Fluid machine and construction machine

Abstract

The present application relates to fluid machines and construction machines. A main pump of one aspect of the present application includes: a piston; a cylinder (4) that forms a cylinder chamber (17) that houses the piston, and that forms a communication hole (18) that communicates the inside and outside of the cylinder chamber (17); a main housing (2) that houses the cylinder (4), and that forms an ejection path (123); a valve plate (19) that is disposed between the cylinder (4) and the main housing (2), and that forms an ejection port (19b) that communicates the communication hole (18) and the ejection path (123); a plurality of bushings (61, 62) that are arranged in the ejection path (123) along the axial direction of the piston, the plurality of bushings (61, 62) being disposed so as to be relatively displaceable; and a coil spring (63) that is disposed in the ejection path (123), and that urges the plurality of bushings (61, 62) toward the valve plate (19).

Description

Technical Field

[0001] This invention relates to fluid machinery and construction machinery. Background Technology

[0002] As a type of fluid machinery, there exists, for example, a so-called swashplate type hydraulic piston pump (hereinafter referred to as a hydraulic pump) mounted on construction machinery such as hydraulic excavators. This hydraulic pump, for example, includes: a shaft rotatably supported within a pump housing; a cylinder fixed to the outer circumferential surface of the shaft; and multiple pistons. Multiple cylinder chambers are formed within the cylinder body. Each of these cylinder chambers houses a piston in a manner that allows it to slide freely along the axial direction (hereinafter referred to as the axial direction) of the shaft.

[0003] The hydraulic pump includes: a swashplate disposed on a first end side along the axial direction of the cylinder body; and a valve plate disposed on a second end side opposite to the first end. The swashplate restricts the sliding movement of the pistons within the cylinder chamber by means of ends of each piston that can move on the surface of the swashplate. The swashplate changes the volume of the space formed by the cylinder chamber and the pistons according to its inclination angle relative to the pump housing. On the valve plate, an intake port and an outlet port for the flow of working oil are formed at positions corresponding to the multiple cylinder chambers of the cylinder body. The intake port communicates with the intake path of the pump housing. The outlet port communicates with the discharge path of the pump housing.

[0004] Based on this structure, if the cylinder block rotates around its axis, each cylinder chamber rotates around the axis and alternately connects with the valve plate's intake and exhaust ports. When a cylinder chamber is connected to the intake port, the piston slides within the cylinder chamber to increase its volume. This draws working oil from outside the pump casing into the cylinder chamber via the intake path and intake port. When a cylinder chamber is connected to the exhaust port, the piston slides within the cylinder chamber to decrease its volume. This ejects working oil from the cylinder chamber out of the pump casing via the exhaust port and exhaust path.

[0005] Here, a technique is disclosed in which a spring and a bushing are provided in each of the injection paths of the pump housing (for example, see Patent Document 1). The elastic force of the spring is transmitted to the valve plate via the bushing, applying a pushing force towards the cylinder side to the valve plate, thereby improving the sealing between the cylinder and the valve plate. As a result, leakage of working oil from between the cylinder and the valve plate can be suppressed.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2014-98327 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] However, during the operation of the hydraulic pump, the hydraulic pressure on the piston on the side that sprays working oil from the cylinder chamber differs from the hydraulic pressure on the piston on the side that draws working oil from the cylinder chamber. As a result, the piston's pushing force on the swashplate, generated by the reaction force of the hydraulic pressure, is also unbalanced throughout the circumference. Due to this imbalance, the cylinder block may tilt relative to the shaft. Consequently, the valve plate may also tilt relative to the shaft.

[0011] Here, by simply pushing a bushing, as described in the prior art, against the valve plate, the bushing may not fully follow the tilt of the valve plate, creating a gap between the valve plate and the bushing. Working oil may leak from this gap, leading to a decrease in the performance of the hydraulic pump.

[0012] This invention provides a fluid machine and construction machine capable of suppressing performance degradation.

[0013] Solution for solving the problem

[0014] A fluid machine according to one embodiment of the present invention comprises: a piston; a cylinder having a chamber for housing the piston and a communication hole for communicating between the inside and outside of the chamber; a housing for housing the cylinder and having a discharge path; a valve plate disposed between the cylinder and the housing, the valve plate having a discharge outlet for communicating between the communication hole and the discharge path; a plurality of bushings arranged axially along the piston within the discharge path, the bushings being disposed in a manner capable of relative displacement; and an elastic member within the housing disposed within the discharge path, the elastic member within the housing pushing the plurality of bushings toward the valve plate.

[0015] By configuring it in this way, even if the valve plate tilts along with the cylinder block, the bushing located closest to the valve plate can reliably follow the tilt of the valve plate by tilting each bushing individually, bit by bit. Therefore, it is possible to prevent gaps from forming between the valve plate and the bushing, and to suppress leakage of working oil from between them. Consequently, it is possible to suppress the degradation of the fluid machinery's performance.

[0016] In the above structure, the fluid machinery may also have two bushings.

[0017] In the above structure, the multiple bushings can also be separated from each other.

[0018] In the above structure, the multiple bushings may also be an assembly formed by interconnecting each other.

[0019] In the above structure, the plurality of bushings may also be configured such that their axial end faces are in face-to-face contact with each other.

[0020] In the above structure, at least one of the two contacting bushings may have a curved protrusion protruding from the axial end face toward the axial end face of the other bushing.

[0021] In the above structure, a curved protrusion that bulges outwardly is formed on the end face of one bushing, and a plane whose diameter gradually increases as it moves toward the end face of the other bushing is formed on the end face of the other bushing.

[0022] In the above structure, the curved protrusion may also be formed on the end face of one bushing and the end face of the other bushing.

[0023] In the above structure, a curved protrusion that bulges outwardly is formed on the end face of one bushing, and a curved surface that gradually increases in diameter as it moves toward the end face of the other bushing is formed on the end face of the other bushing.

[0024] In the above structure, the curved protrusion and the curved surface may also have an arc-shaped cross section along the axial direction.

[0025] In the above structure, the radius of curvature of the curved protrusion may also be smaller than the radius of curvature of the curved surface.

[0026] In the above structure, one of the plurality of bushings may be softer than the others.

[0027] In the above structure, the bushing that is softer than the other bushings may be positioned closest to the valve plate.

[0028] In the above structure, the bushing located closest to the valve plate among the multiple bushings can also be integrated with the valve plate.

[0029] In the above structure, the fluid machinery may also have a small elastic member disposed between the valve plate and the housing, which pushes the valve plate toward the cylinder side, and a recess is formed in the valve plate to accommodate the small elastic member.

[0030] Another fluid machine according to the present invention comprises: a piston; a cylinder having a chamber for housing the piston and a communicating hole for communicating between the inside and outside of the chamber; a housing housing the cylinder having a discharge path; a valve plate disposed between the cylinder and the housing, the valve plate having a discharge outlet communicating between the communicating hole and the discharge path; a plurality of bushings arranged axially along the piston within the discharge path, the bushings being disposed in a manner capable of relative displacement; and an elastic member disposed within the housing at the discharge path. Within the exit path, the elastic member inside the housing pushes the bushing toward the valve plate. One of the two bushings in contact has a curved protrusion that protrudes from the axial end face toward the axial end face of the other bushing, and the radially outer side of the curved protrusion becomes a convex shape. A curved surface with a gradually increasing diameter as it moves toward the end face of the first bushing is formed on the end face of the other bushing. The cross-sections of the curved protrusion and the curved surface are formed in an arc shape, and the radius of curvature of the curved protrusion is smaller than the radius of curvature of the curved surface.

[0031] By configuring it in this way, even if the valve plate tilts along with the cylinder block, the bushing located closest to the valve plate can reliably follow the tilt of the valve plate by tilting each bushing individually, bit by bit. Therefore, it is possible to prevent gaps from forming between the valve plate and the bushing, and to suppress leakage of working oil from between them. Consequently, it is possible to suppress the degradation of the fluid machinery's performance.

[0032] It can accommodate the curved protrusion within the curved surface, ensuring reliable contact between the curved protrusion and the curved surface. It allows one bushing to smoothly tilt relative to another, thus further improving the bushing's following performance relative to the valve plate.

[0033] Another fluid machine according to the present invention comprises: a piston; a cylinder having a chamber for receiving the piston and a communicating hole for communicating between the inside and outside of the chamber; a housing for receiving the cylinder and having a discharge path; a valve plate disposed between the cylinder and the housing, the valve plate having a discharge outlet for communicating between the communicating hole and the discharge path; and a small elastic member disposed between the valve plate and the housing, the small elastic member pushing the valve plate toward the cylinder side, and a recess for receiving the small elastic member being formed in the valve plate.

[0034] By configuring it in this way, even if the valve plate tilts along with the cylinder block, the bushing located closest to the valve plate can reliably follow the tilt of the valve plate by tilting each bushing individually, bit by bit. Therefore, it is possible to prevent gaps from forming between the valve plate and the bushing, and to suppress leakage of working oil from between them. Consequently, it is possible to suppress the degradation of the fluid machinery's performance.

[0035] By utilizing small elastic components, the pushing force that compresses the valve plate against the cylinder can be increased. Therefore, the sealing between the cylinder and the valve plate can be improved. This result can suppress leakage of working oil between the cylinder and the valve plate, further improving the performance of the fluid machinery.

[0036] Another technical solution of the present invention provides a construction machine comprising: a vehicle body; and a fluid machine for drawing in and ejecting a fluid that serves as a driving source for the vehicle body, the fluid machine comprising: a piston; a cylinder having a cylinder chamber for housing the piston and having a connecting hole for communicating between the inside and outside of the cylinder chamber; a housing for housing the cylinder and having an ejection path; a valve plate disposed between the cylinder and the housing, the valve plate having an ejection outlet for communicating between the connecting hole and the ejection path; and a plurality of bushings arranged along the axial direction of the piston within the ejection path, the plurality of bushings being capable of relative displacement. The device includes a housing with an elastic member disposed within the ejection path, which pushes the bushing toward the valve plate. One of the two bushings in contact has a curved protrusion that protrudes from the axial end face toward the axial end face of the other bushing, and the radially outer side of the curved protrusion is raised. A curved surface with a gradually increasing diameter toward the end face of the other bushing is formed. The cross-sections of the curved protrusion and the curved surface are arc-shaped, and the radius of curvature of the curved protrusion is smaller than the radius of curvature of the curved surface.

[0037] By constructing it in this way, it is possible to suppress the degradation of the performance of construction machinery.

[0038] The effects of the invention

[0039] The aforementioned fluid machinery and construction machinery can suppress performance degradation. Attached Figure Description

[0040] Figure 1 This is a schematic structural diagram of the construction machinery in an embodiment of the present invention.

[0041] Figure 2 This is a structural diagram showing a portion of the pump unit in an embodiment of the present invention, cut across.

[0042] Figure 3This is a top view of the valve plate in the first embodiment of the present invention, viewed from the first side.

[0043] Figure 4 This is a top view of the valve plate in the first embodiment of the present invention, viewed from the second side.

[0044] Figure 5 It is along Figure 4 A cross-sectional view along line AA.

[0045] Figure 6 yes Figure 2 Enlarged view of part B.

[0046] Figure 7 yes Figure 6 Enlarged view of part C.

[0047] Figure 8 This is an enlarged cross-sectional view of the main parts of the two bushings in the first variation of the first embodiment of the present invention.

[0048] Figure 9 This is a cross-sectional view of two bushings in a second variation of the first embodiment of the present invention.

[0049] Figure 10 This is a cross-sectional view of two bushings in the third variation of the first embodiment of the present invention.

[0050] Figure 11 This is a top view of the valve plate in the second embodiment of the present invention, viewed from the second side.

[0051] Figure 12 This is a partially enlarged cross-sectional view of the valve plate and the bottom wall of the housing body in the second embodiment of the present invention.

[0052] Explanation of reference numerals in the attached figures

[0053] 1. Main pump (fluid machinery); 2. Main housing (casing); 4. Cylinder block; 9. Housing body (casing); 17. Cylinder chamber; 18. Connecting hole; 19, 219. Valve plate; 19b. Injection outlet; 21. Piston; 60. Pushing unit; 61. First bushing (shroud); 61b. Arc surface (bent protrusion); 62. Second bushing (shroud); 62a. Inclined surface (plane); 62b. Arc surface (bent surface); 63. Helical spring (elastic component inside the housing); 81. Small spring (small elastic component); 82. First spring receiving recess (recess); 123. Injection path; 128. Third connecting path (injection path); R1, R2. Radius of curvature. Detailed Implementation

[0054] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0055] <Construction Machinery>

[0056] Figure 1 This is a rough structural diagram of construction machinery 100.

[0057] like Figure 1 As shown, the construction machinery 100 is, for example, a hydraulic excavator. The construction machinery 100 includes a rotating body (an example of the vehicle body in the claims) 101 and a traveling body (an example of the vehicle body in the claims) 102 disposed at the lower part of the rotating body 101. The rotating body 101 rotates above the traveling body 102. The rotating body 101 includes a pump unit (an example of the fluid machinery in the claims) 110.

[0058] The gyropod 101 includes: a cab 103 for supporting an operator riding in the gyropod 101; a boom 104, one end of which is connected to the cab 103; a stick 105, one end of which is connected to the other end of the boom 104; and a bucket 106, which is connected to the other end of the stick 105. The boom 104 swings relative to the cab 103. The stick 105 swings relative to the boom 104. The bucket 106 swings relative to the stick 105.

[0059] Pump unit 110 is located inside cab 103. The working oil supplied from pump unit 110 becomes the driving source for cab 103, boom 104, stick 105 and bucket 106.

[0060] <Pump Unit>

[0061] Figure 2 This is a structural diagram showing a section of the pump unit 110.

[0062] Pump unit 110 is a so-called hydraulic pump. Pump unit 110 draws in and ejects working oil. For example... Figure 2 As shown, the pump unit 110 includes a main pump 1 (an example of the fluid machinery in the claims) which serves as a fluid machine and a gear pump 111 disposed on one side of the main pump 1. Figure 2 The main pump 1 is represented only by a cross section along the axial direction.

[0063] [First Implementation]

[0064] <Main Pump>

[0065] The main pump 1 is a so-called swashplate variable capacity hydraulic pump. The main structure of the main pump 1 is as follows: a main housing (an example of the housing in the claims) 2; a shaft 3, which is supported on the main housing 2 in a manner that allows it to rotate freely about the central axis CL relative to the main housing 2; a cylinder 4, which is housed in the main housing 2 and fixed to the shaft 3; a swashplate 5, which is housed in the main housing 2 and is configured to tilt freely relative to the main housing 2; a piston 21, which is disposed in the cylinder 4; a valve plate 19, which is disposed between the main housing 2 and the cylinder 4; and a pusher unit 60, which is disposed in the main housing 2 and pushes the valve plate 19 toward the cylinder 4.

[0066] exist Figure 2 To make the explanation easier to understand, the scale of each component has been appropriately changed. In the following explanation, the direction parallel to the central axis CL of shaft 3 is called the axial direction, the direction of rotation of shaft 3 is called the circumferential direction, and the radial direction of shaft 3 is simply referred to as the radial direction.

[0067] The main housing 2 comprises: a box-shaped housing body (an example of the housing in the claims) 9 having an opening 9a; and a front flange 10 that blocks the opening 9a of the housing body 9.

[0068] The housing body 9 has a bottom wall 119 provided on the side opposite to the opening 9a. The bottom wall 119 is a wall portion of the housing body 9 located on the central axis CL of the shaft 3. A cylinder 4 is disposed on the inner surface 119a side of the bottom wall 119. A gear pump 111 is mounted on the outer surface 119b of the bottom wall 119.

[0069] A rotating shaft through hole 121 for the shaft 3 to pass through is formed in the bottom wall 119 in such a way that it extends through the thickness of the bottom wall 119. In the rotating shaft through hole 121, a bearing 11 is provided at a position near the inner surface 119a of the bottom wall 119 to support one end of the shaft 3 so that it can rotate freely.

[0070] On the bottom wall 119, a first suction path 122 and a discharge path (an example of the discharge path in the claim) 123 are formed on both radially sides of the rotating shaft through hole 121. The first suction path 122 forms an opening 122a on the first side 119c of the bottom wall 119. The opening 122a of the first suction path 122 communicates with a can (not shown). The first suction path 122 extends within the bottom wall 119 in such a manner that the opening area gradually decreases from the first side 119c toward the rotating shaft through hole 121.

[0071] A first connecting path 124 is formed at the end of the first suction path 122 on the side of the through hole 121 on the rotation axis, which connects the first suction path 122 with the inner surface 119a of the bottom wall 119. The first connecting path 124 connects the first suction path 122 with the suction port 19a of the valve plate 19, which will be described later.

[0072] The end of the first suction path 122 on the side of the rotating shaft through hole 121 is not connected to the rotating shaft through hole 121. A second connecting path 125 is formed at the end of the first suction path 122 on the side of the rotating shaft through hole 121, connecting the first suction path 122 and the outer surface 119b of the bottom wall 119. The second connecting path 125 connects the first suction path 122 to the second suction path 144 of the gear pump 111, which will be described later.

[0073] An O-ring groove 118 is formed on the outer surface 119b of the bottom wall 119 in such a way that it surrounds the through hole 121 of the rotating shaft and the second communication path 125. An O-ring 117 is installed in the O-ring groove 118. The O-ring 117 ensures a seal between the main housing 2 and the gear housing 141 of the gear pump 111 (described later).

[0074] Based on this structure, the working oil is drawn into the first suction path 122 from the tank not shown. The working oil drawn into the first suction path 122 flows into the first connecting path 124 and the second connecting path 125.

[0075] The ejection path 123 has an opening 123a on the second side 119d, located on the side opposite to the first side 119c, through the through hole 121 of the rotation axis in the bottom wall 119. The opening 123a is connected to the cab 103, boom 104, stick 105, and bucket 106 by means of a control valve (not shown). The ejection path 123 extends from the second side 119d toward the through hole 121 of the rotation axis within the bottom wall 119.

[0076] The end of the ejection path 123 on the side of the rotation shaft through hole 121 is not connected to the rotation shaft through hole 121. A third connecting path (an example of the ejection path in the claim) 128 is formed at the end of the ejection path 123 on the side of the rotation shaft through hole 121, connecting the ejection path 123 to the inner surface 119a of the bottom wall 119. The third connecting path 128 connects the ejection path 123 to the ejection outlet 19b of the valve plate 19, which will be described later.

[0077] A through hole 13 is formed in the front flange 10 for the shaft 3 to pass through. A bearing 14 is provided in the through hole 13 to support the other end of the shaft 3 so that it can rotate freely. An oil seal 15 is provided in the through hole 13 on the side opposite to the housing body 9 (outer side of the front flange 10) than the bearing 14. The oil seal 15 prevents working oil from flowing out from the inside and prevents foreign objects from entering between the shaft 3 and the front flange 10.

[0078] Two mounting plates 137 are integrally formed with the front flange 10. The two mounting plates 137 are arranged on both sides radially apart from the shaft 3. The mounting plates 137 extend radially outward. The two mounting plates 137 are used to fix the main pump 1 to a drive source such as an engine provided with the rotary body 101.

[0079] Shaft 3 is formed in a stepped shape. Shaft 3 is integrally formed from shaft body 131, first bearing portion 132, transmission shaft 133, second bearing portion 134 and connecting shaft 135 arranged on the same axis. The first bearing portion 132 extends from shaft body 131 toward one end of shaft 3 (the bottom wall 119 side of main housing 2). The transmission shaft 133 extends from the first bearing portion 132 toward the side opposite to shaft body 131. The second bearing portion 134 extends from shaft body 131 toward the other end of shaft 3 (the front flange 10 side). The connecting shaft 135 extends from the second bearing portion 134 toward the side opposite to shaft body 131.

[0080] The shaft body 131 is disposed within the main housing 2. A first spline 131a is formed on the shaft body 131. A cylinder 4 is fitted into the first spline 131a. A pressing member 27 is fitted into the outer peripheral surface of the shaft body 131 near the second bearing portion 134. The pressing member 27 is used to press the slipper retaining member 29, which will be described later.

[0081] The diameter of the first bearing portion 132 is smaller than the diameter of the shaft body 131. The first bearing portion 132 is rotatably supported by the bearing 11 on the bottom wall 119.

[0082] The transmission shaft 133 transmits the rotational force of the shaft 3 to the gear pump 111. The shaft diameter of the transmission shaft 133 is smaller than the shaft diameter of the first bearing portion 132. The transmission shaft 133 protrudes towards the gear pump 111 via the bearing 11. The transmission shaft 133 is disposed within the rotating shaft through hole 121 of the bottom wall 119. A cylindrical coupling 136 is fitted onto the outer circumferential surface of the transmission shaft 133. The coupling 136 rotates integrally with the transmission shaft 133. The end of the coupling 136 opposite to the first bearing portion 132 protrudes outward from the bottom wall 119 via the rotating shaft through hole 121. This protruding portion is connected to the gear pump 111.

[0083] The shaft diameter of the second bearing section 134 is larger than that of the first bearing section 132. The second bearing section 134 is rotatably supported on the bearing 14 of the front flange 10.

[0084] The connecting shaft 135 is connected to a power source such as an engine (not shown). The shaft diameter of the connecting shaft 135 is smaller than the shaft diameter of the second bearing portion 134. The front end of the connecting shaft 135 on the side opposite to the second bearing portion 134 protrudes outward from the front flange 10 via a bearing 14. A second spline 135a is formed at the front end of the connecting shaft 135. The power source such as the engine (not shown) and the shaft 3 are connected by this second spline 135a.

[0085] The cylinder body 4, fixed to the shaft 3, is cylindrical. A through hole 16 is formed in the radial center of the cylinder body 4 for the shaft 3 to be inserted or pressed in. A spline 16a is formed on the inner wall surface of the through hole 16. This spline 16a is engaged with the first spline 131a of the shaft body 131. The shaft 3 and the cylinder body 4 rotate integrally by means of each spline 16a, 131a.

[0086] A recess 20 is formed around the shaft 3 between the axial center of the through hole 16 and the end 4a on the side of the bottom wall 119. A through hole 25, extending axially through the cylinder 4, is partially formed on the inner wall surface between the axial center of the through hole 16 and the side of the front flange 10. The spring 23 and seat rings 24a and 24b, described later, are housed in the recess 20. The connecting member 26, described later, is housed in the through hole 25 in a manner that allows for free axial movement.

[0087] A plurality of cylinder chambers 17 are formed in the cylinder body 4 surrounding the shaft 3. The plurality of cylinder chambers 17 are arranged at equal intervals along a predetermined pitch circle concentric with the central axis CL. The cylinder chamber 17 is a recess that is open on the front flange 10 side and closed on the bottom wall 119 side. At the end 4a of the cylinder body 4, a communication hole (an example of a cylinder body communication hole in the claims) 18 is formed at a position corresponding to each cylinder chamber 17, allowing each cylinder chamber 17 to communicate with the outside of the cylinder body 4.

[0088] Each cylinder chamber 17 houses a piston 21 that can slide freely along the axial direction. Thus, the piston 21 rotates around the central axis CL as the shaft 3 and cylinder 4 rotate.

[0089] A cavity is formed inside the piston 21 to store the working oil in the cylinder chamber 17. The sliding movement of the piston 21 is related to the intake and ejection of the working oil relative to the cylinder chamber 17.

[0090] That is, when piston 21 is pulled out of cylinder chamber 17, the volume of space inside cylinder chamber 17 increases, and working oil is drawn into cylinder chamber 17 through connecting hole 18 (drawing process). From the moment piston 21 is pulled out of cylinder chamber 17 to its maximum bottom dead center, piston 21 changes to the action of entering cylinder chamber 17. As piston 21 enters cylinder chamber 17, the volume of space inside cylinder chamber 17 decreases, and working oil is ejected from cylinder chamber 17 through connecting hole 18 (ejection process). From the moment piston 21 enters cylinder chamber 17 to its maximum top dead center, the action of piston 21 changes back to bottom dead center.

[0091] A spherical protrusion 28 is integrally formed at the end of the piston 21 near the front flange 10. A plurality of slippers 22 are mounted on the protrusion 28. The slippers 22 are used to correlate the sliding movement of the piston 21 with the tilting of the ramp 5. A spherical recess 22a is formed on the side of the slipper 22 that receives the protrusion 28, corresponding to the shape of the protrusion 28. The protrusion 28 of the piston 21 is embedded in the inner wall surface of the recess 22a. The slipper 22 is connected to the protrusion 28 of the piston 21 in a manner that allows it to rotate relative to the protrusion 28 of the piston 21.

[0092] The spring 23 housed in the recess 20 of the cylinder body 4 is, for example, a coil spring. The spring 23 is compressed between the two bearings 24a and 24b housed in the recess 20. Due to the elastic force, the spring 23 generates a pushing force in the direction of extension. The pushing force of the spring 23 is transmitted to the connecting member 26 via one of the bearings 24a and 24b. The pushing force of the spring 23 is transmitted to the pushing member 27, which is fitted with the outer peripheral surface of the shaft body 131, via the connecting member 26.

[0093] A ramp 5 is disposed on the inner surface 10a of the front flange 10 on the side of the housing body 9. The ramp 5 restricts the axial displacement of each piston 21 by being inclined relative to the front flange 10. A through hole 32 for the shaft 3 to pass through is formed at the radial center of the ramp 5. The ramp 5 has a flat sliding surface 5a formed on the side of the cylinder 4. A plurality of slippers 22 move on this sliding surface 5a.

[0094] Each slipper 22 is integrated using a slipper retaining member 29. A pushing member 27 contacts the slipper retaining member 29 and pushes it towards the inclined plate 5. The slipper 22 moves in a manner that follows the sliding surface 5a of the inclined plate 5. As a result, the piston 21, rotating around the central axis CL, slides relative to the cylinder chamber 17. That is, the amount of sliding movement of the piston 21 is controlled by the inclined plate 5. In other words, the amount of sliding movement of the piston 21 is determined by the tilt angle of the inclined plate 5. Further, the inclined plate 5 controls the amount of working oil injected from the main pump 1. The tilt angle of the inclined plate 5 is controlled by an actuator (not shown). Details of these actuators will be described later.

[0095] <Valve Plate>

[0096] The valve plate 19 is disposed between the end face 4b of the end 4a of the cylinder body 4 and the inner surface 119a of the bottom wall 119 of the housing body 9. The valve plate 19 is formed in the shape of a circular plate. The valve plate 19 is disposed on the bottom wall 119 of the housing body 9 in a manner that prevents it from rotating. That is, although the valve plate 19 does not rotate relative to the bottom wall 119 of the housing body 9, it is possible for it to separate from the inner surface 119a of the bottom wall 119.

[0097] Even when the cylinder 4 and shaft 3 rotate around the central axis CL, the valve plate 19 remains stationary relative to the main housing 2 (housing body 9). The cylinder 4 is supported by the hydrostatic pressure of the oil film of working oil formed between the valve plate 19 and the end face 4b of the cylinder 4.

[0098] Figure 3 This is a top view viewed from the first side 41a of the valve plate 19, which is near the cylinder 4. Figure 4 This is a top view viewed from the second side 41b of the valve plate 19, which is near the bottom wall 119. Figure 5 It is along Figure 4 A cross-sectional view along line AA.

[0099] like Figures 3-5 As shown, a through hole 42 for the shaft 3 to pass through is formed at the radial center of the valve plate 19, extending through the thickness of the valve plate 19. An inner recess 43, which is annular in shape when viewed from the axial direction, is formed on the first surface 41a of the valve plate 19, surrounding the through hole 42 and communicating with it. An outer recess 44, which is annular along the outer periphery, is formed on the first surface 41a of the valve plate 19.

[0100] The valve plate 19 is formed with an intake port 19a that communicates with each of the communication holes 18 of the cylinder 4 in a manner that extends through the thickness of the valve plate 19. The shape of the intake port 19a is, for example, an arc within a specified angle range around the central axis CL, and is formed into an elongated oval shape.

[0101] Each cylinder chamber 17 is connected to the first communication path 124 formed in the housing body 9 via the intake port 19a of the valve plate 19 and the communication hole 18 of the cylinder body 4.

[0102] An outlet 19b is formed between the second surface 41b of the valve plate 19 and the center of the valve plate 19 in the thickness direction. The outlet 19b is formed to be circular in axial view. The outlet 19b is disposed on the side opposite to the circumferential center of the suction port 19a through the through hole 42.

[0103] Between the first surface 41a of the valve plate 19 and the center of the valve plate 19 in the thickness direction, a long recess 45 is formed on the side opposite to the suction port 19a, separated by the through hole 42, which communicates with the nozzle 19b.

[0104] The elongated recess 45 communicates with the nozzle 19b, and therefore, the elongated recess 45 is a part of the nozzle 19b. The elongated recess 45 is, for example, an arc within a predetermined angle range around the central axis CL, and is formed into an elongated oval shape. The elongated recess 45 and the suction port 19a are disposed on the same segment circle.

[0105] Each cylinder chamber 17 is connected to the third communication path 128 formed in the housing body 9 via the nozzle 19b of the valve plate 19, the elongated recess 45 and the communication hole 18 of the cylinder body 4.

[0106] On the first surface 41a of the valve plate 19, a pair of switching lands 47a and 47b (bottom dead center switching land 47a and top dead center switching land 47b) are formed between the two ends of the intake port 19a in the longitudinal direction and the two ends of the elongated recess 45 in the longitudinal direction. In other words, the intake port 19a and the elongated recess 45 are formed on both sides separated by a pair of switching lands 47a and 47b. The pair of switching lands 47a and 47b are on the same plane as the first surface 41a. When the cylinder body 4 rotates, the connecting hole 18 of the cylinder body 4 is switched to communicate with the intake port 19a or with the elongated recess 45 by means of the pair of switching lands 47a and 47b.

[0107] In the following description, the switching land 47a, which corresponds to the part of the piston 21 whose movement changes from bottom dead center to top dead center, is called the bottom dead center switching land 47a. The switching land 47b, which corresponds to the part of the piston 21 whose movement changes from top dead center to bottom dead center, is called the top dead center switching land 47b.

[0108] A piston receiving recess 49 is formed between the second surface 41b of the valve plate 19 and the center of the valve plate 19 in the thickness direction, at positions corresponding to both ends of the elongated recess 45 in the length direction. The piston receiving recess 49 is circular in shape when viewed axially. The diameter of the piston receiving recess 49 is larger than the diameter of the nozzle 19b. The piston receiving recess 49 is connected to both ends of the elongated recess 45 in the length direction.

[0109] A circular, plate-shaped push piston 46 is housed in the piston receiving recess 49. The central axis Co of the push piston 46 is along the axial direction. The diameter of the push piston 46 is approximately the same as or slightly smaller than the diameter of the piston receiving recess 49.

[0110] like Figure 3As shown, a notch 50 is formed on the first surface 41a of the valve plate 19, extending from the end of the long recess 45 near the lower dead center switching land 47a towards the lower dead center switching land 47a (the long-distance end of the intake port 19a). The notch 50 is formed such that, viewed axially, it tapers towards the long-distance end of the long recess 45 towards the long-distance end of the intake port 19a. The notch 50 is also formed such that its depth gradually decreases towards the long-distance end of the long recess 45 towards the long-distance end of the intake port 19a.

[0111] <Push Unit>

[0112] Figure 6 yes Figure 2 Enlarged view of part B.

[0113] like Figure 2 , Figure 6 As shown, a pushing unit 60 is provided in the third communication path 128 on the bottom wall 119 of the housing body 9. The pushing unit 60 pushes the valve plate 19 toward the cylinder 4, mainly to suppress the leakage of working oil between the valve plate 19 and the bottom wall 119 of the housing body 9. The pushing unit 60 includes: two bushings 61 and 62 (first bushing 61 and second bushing 62, an example of bushings in the claims), which are disposed on the valve plate 19 side of the third communication path 128; and a helical spring (an example of an elastic member in the housing in the claims) 63, which is disposed on the side opposite to the valve plate 19 across each bushing 61 and 62.

[0114] Figure 7 yes Figure 6 Enlarged view of part C.

[0115] like Figure 6 , Figure 7 As shown, two bushings 61 and 62 are arranged along the axial direction. The two bushings 61 and 62 are separated from each other and can be offset relative to each other. The first bushing 61, located on the valve plate 19 side, is formed in an annular shape. The cross-sectional shape of the first bushing 61 along the axial direction is quadrilateral. The valve plate 19 side of the first bushing 61 is a flat surface (an example of the end face in the claim) 61a. This flat surface 61a contacts the second surface 41b of the valve plate 19.

[0116] On the side of the first bushing 61 opposite to the flat surface 61a in the axial direction, an arcuate surface (an example of the curved protrusion in the claim) 61b is formed between the inner and outer peripheries. The arcuate surface 61b is formed in an arcuate cross-section along the axial direction in such a way that its outer diameter gradually decreases as it moves toward the second bushing 62. The arcuate surface 61b is formed in such a way that it becomes a convex shape on the radially outer side.

[0117] The mechanical strength (hardness) of the first bushing 61 is lower than that of the valve plate 19. In other words, the first bushing 61 is softer than the valve plate 19.

[0118] Of the two bushings 61 and 62, the second bushing 62, which is disposed on the side opposite to the valve plate 19 and separated from the first bushing 61, is formed into a cylindrical shape. The mechanical strength (hardness) of the second bushing 62 is higher than that of the first bushing 61. In other words, the first bushing 61 is softer than the second bushing 62.

[0119] The axial length of the second bushing 62 is sufficiently long relative to the axial length (thickness) of the first bushing 61. The inner diameter of the second bushing 62 is approximately the same as the inner diameter of the first bushing 61. The outer diameter of the second bushing 62 is slightly larger than the outer diameter of the first bushing 61. An inclined surface (an example of a plane in the claims) 62a is formed circumferentially on the end face of the second bushing 62 on the side closer to the first bushing 61. The inclined surface 62a is formed such that the inner diameter of the second bushing 62 gradually increases towards the side closer to the first bushing 61. The arcuate surface 61b of the first bushing 61 abuts against this inclined surface 62a. The abutment between the arcuate surface 61b and the inclined surface 62a brings the first bushing 61 into surface contact with the second bushing 62.

[0120] On the end face of the second bushing 62 opposite to the first bushing 61, a spring receiving recess 64 is formed in the radial center. One end of a coil spring 63 is received in this spring receiving recess 64. The coil spring 63 is housed within the third connecting path 128 in a slightly compressed state. Therefore, each bushing 61, 62 is pushed towards the valve plate 19 by the elastic force of the coil spring 63. The elastic force of the coil spring 63 is also transmitted to the valve plate 19 via the second bushing 62 and the first bushing 61. Consequently, the valve plate 19 is pushed towards the cylinder body 4 by the pushing unit 60.

[0121] The third connecting path 128 is formed in a manner corresponding to the shape of the pressing unit 60. That is, the third connecting path 128 has a bushing storage portion 65 and a spring storage portion 66 that are connected to each other.

[0122] The bushing receiving portion 65 houses the two bushings 61 and 62 of the pressing unit 60. The bushing receiving portion 65 is circular in shape when viewed axially. The inner diameter of the bushing receiving portion 65 is approximately the same as or slightly larger than the outer diameter of the second bushing 62. That is, the outer circumferential surface of the second bushing 62 fits into the inner circumferential surface of the bushing receiving portion 65. The outer diameter of the first bushing 61 is smaller than the outer diameter of the second bushing 62. Therefore, a gap is formed between the inner circumferential surface of the bushing receiving portion 65 and the outer circumferential surface of the first bushing 61.

[0123] The axial length of the bushing storage portion 65 is slightly longer than the axial length of the portion that overlaps the first bushing 61 and the second bushing 62.

[0124] The spring receiving portion 66 is formed in a circular shape when viewed from the axial direction. The inner diameter of the spring receiving portion 66 is smaller than the inner diameter of the bushing receiving portion 65 by means of a step. More specifically, the inner diameter of the spring receiving portion 66 is approximately the same as the outer diameter of the spring receiving recess 64 formed in the second bushing 62. At one end of the spring receiving portion 66 on the side opposite to the bushing receiving portion 65, a flat base surface 66a is formed along the inner circumferential surface of the spring receiving portion 66. The other end of the helical spring 63 abuts against this base surface 66a. An ejection path 123 is formed in a manner that communicates with one end and the side of the bushing receiving portion 65, which is formed in this way.

[0125] <Gear Pump>

[0126] like Figure 2 As shown, a gear pump 111 installed on one side of the main pump 1 functions as an auxiliary pump. The gear pump 111 includes a gear housing 141 and a drive gear and a driven gear (not shown).

[0127] A cuboid gear housing 141 is disposed on the outer surface 119b of the bottom wall 119 of the main housing 2. A second intake path 144 is formed on the first wall surface 141a of the gear housing 141 that overlaps with the main housing 2, communicating with the second communication path 125 of the main housing 2. The second intake path 144 connects the inside and outside of the first wall surface 141a of the gear housing 141.

[0128] On the first wall surface 141a of the gear housing 141, a coupling through hole 149 is formed at a position corresponding to the rotating shaft through hole 121 of the main housing 2. The end of the coupling 136 on the side of the gear pump 111 protrudes into the gear housing 141 through the coupling through hole 149.

[0129] A third ejection path (not shown) is formed on a second wall surface 141b of the gear housing 141, which is orthogonal to the first wall surface 141a and faces the same direction as the second side surface 119d of the main housing 2. An opening of the third ejection path is formed on the second wall surface 141b.

[0130] A drive gear and a driven gear (not shown) are rotatably supported within a gear housing 141 and mesh with each other. The drive gear is connected to a coupling 136 protruding from the main housing 2 via a coupling through-hole 149. The rotational force of the shaft 3 in the main pump 1 is transmitted to the drive gear via the coupling 136. The driven gear meshes with the drive gear, therefore, the driven gear rotates synchronously with the drive gear.

[0131] <Pump Unit Operation>

[0132] Next, the operation of pump unit 110 will be explained.

[0133] First, the operation of main pump 1 will be explained.

[0134] The main pump 1 outputs driving force based on the ejection of working oil from cylinder chamber 17 and the intake of working oil into cylinder chamber 17.

[0135] More specifically, as the shaft 3 rotates due to the power from a power source such as an engine, the cylinder block 4 rotates integrally with the shaft 3. As the cylinder block 4 rotates, the piston 21 rotates around the central axis CL of the shaft 3.

[0136] Due to the pushing force of the spring 23, regardless of the tilt angle of the inclined plate 5, each slipper 22 mounted on the protrusion 28 of each piston 21 appropriately follows and presses against the sliding surface 5a of the inclined plate 5. The protrusion 28 of the piston 21 is formed in a spherical shape, and the recess 22a of the slipper 22 into which the protrusion 28 is inserted is also formed in a spherical shape. The pushing member 27 applies a pushing pressure towards the inclined plate 5 to each slipper 22 by means of the slipper retaining member 29. Even if the tilt angle of the inclined plate 5 changes, each slipper 22 follows the tilt of the inclined plate 5 and appropriately follows and presses against the sliding surface 5a.

[0137] As the cylinder 4 rotates, if the piston 21 rotates around the central axis CL of the shaft 3, then each slipper 22 also moves while rotating around the central axis CL of the shaft 3 on the sliding surface 5a of the inclined plate 5. Thus, each piston 21 reciprocates by sliding along the axial direction within each cylinder chamber 17.

[0138] When piston 21 changes from top dead center to bottom dead center, cylinder chamber 17 (connecting hole 18) housing piston 21 passes through the long recess 45 of valve plate 19 via top dead center switching portion 47b and intake port 19a. At this time, working oil is drawn into cylinder chamber 17 from the first intake path 122 of main housing 2 via the first connecting path 124, intake port 19a and connecting hole 18 (intake process).

[0139] As piston 21 rotates from bottom dead center to top dead center, cylinder chamber 17 (connecting hole 18) housing piston 21 passes through the intake port 19a of valve plate 19 via bottom dead center switching section 47a and elongated recess 45. At this time, working oil is ejected from cylinder chamber 17 via connecting hole 18, elongated recess 45, ejector port 19b, third connecting path 128, and ejection path 123 (ejection process).

[0140] If the tilt angle of the inclined plate 5 (sliding surface 5a) changes, the stroke (distance traveled) of the reciprocating motion of the piston 21 changes. The larger the tilt angle of the inclined plate 5, the greater the intake and discharge of working oil relative to the cylinder chamber 17 caused by the reciprocating motion of each piston 21. The smaller the tilt angle of the inclined plate 5, the smaller the intake and discharge of working oil relative to the cylinder chamber 17 caused by the reciprocating motion of each piston 21. When the tilt angle of the inclined plate 5 is zero, even if the piston 21 rotates around the central axis CL of the shaft 3, each piston 21 does not reciprocate. When the tilt angle of the inclined plate 5 is zero, the discharge of working oil from each cylinder chamber 17 is also zero.

[0141] During the spraying process, the working oil sprayed from the cylinder chamber 17 to the elongated recess 45 is sprayed not only to the spray outlet 19b but also to the piston receiving recess 49. A push piston 46 is housed in the piston receiving recess 49. Therefore, due to the pressure of the working oil, the push piston 46 is pushed towards the inner surface 119a of the bottom wall 119 in the main housing 2. The reaction force generated by the push piston 46 being pushed against the inner surface 119a of the bottom wall 119 creates a pushing force that pushes the valve plate 19 towards the end face 4b of the cylinder body 4.

[0142] The working oil sprayed from the cylinder chamber 17 forms an oil film between the part of the valve plate 19 second surface 41b except for the through hole 42, the intake port 19a, the spray port 19b and the piston receiving recess 49 and the inner surface 119a of the bottom wall 119.

[0143] The pushing force is generated by the pistons 21 housed in the cylinder chambers 17 of the cylinder body 4 pushing the cylinder body 4 towards the valve plate 19. The pushing force, as the force of the valve plate 19 towards the cylinder body 4, includes the reaction force of the working oil acting on the cylinder chamber 17 to push the piston 46 and the force towards the cylinder body 4 generated by the pushing unit 60.

[0144] The working oil sprayed from the cylinder chamber 17 forms an oil film between the first surface 41a of the valve plate 19 (excluding the through hole 42, intake port 19a, elongated recess 45, inner recess 43, and outer recess 44) and the end face 4b of the cylinder body 4. The reaction force of this oil film becomes a repulsive force that pulls the valve plate 19 away from the end face 4b of the cylinder body 4. In addition, the repulsive force is also supported by hydraulic pressure acting on the end face 4b of the cylinder body 4 from the intake port 19a and the spray port 19b of the valve plate 19. By balancing these pushing forces with the repulsive force, the positional relationship between the cylinder body 4 and the valve plate 19 is properly ensured.

[0145] However, the balance between the pushing force and the recoil force may be disrupted, causing the cylinder block 4 to tilt relative to the shaft 3. Consequently, the valve plate 19 may also tilt relative to the shaft 3. If the valve plate 19 tilts, the first bushing 61 will tilt in tandem with it.

[0146] A gap is formed between the inner circumferential surface of the bushing housing 65 and the outer circumferential surface of the first bushing 61. Even if the first bushing 61 is tilted within the bushing housing 65, the inner circumferential surface of the bushing housing 65 and the outer circumferential surface of the first bushing 61 will not interfere. Moreover, the axial length (thickness) of the first bushing 61 is sufficiently short relative to the axial length of the second bushing 62. Therefore, even if the first bushing 61 is tilted, the radial deviation of the first bushing 61 is small, thus reliably preventing interference between the inner circumferential surface of the bushing housing 65 and the outer circumferential surface of the first bushing 61.

[0147] The second bushing 62, which is separate from the first bushing 61, fits into the inner circumferential surface of the bushing storage portion 65, so the second bushing 62 will not tilt.

[0148] The axial length of the bushing housing 65 is slightly longer than the axial length of the overlap between the first bushing 61 and the second bushing 62. Therefore, even if the second bushing 62 slides due to the tilt of the first bushing 61, causing slight compression and deformation of the coil spring 63, it is possible to prevent the second bushing 62 from abutting against the stepped surface 65a between the bushing housing 65 and the spring housing 66. In other words, sliding movement of the second bushing 62 within the bushing housing 65 is permitted.

[0149] For the first bushing 61 and the second bushing 62, the arcuate surface 61b of the first bushing 61 contacts the inclined surface 62a of the second bushing 62. Due to the arcuate surface 61b, the first bushing 61 smoothly tilts relative to the second bushing 62. Due to the arcuate surface 61b, even when the first bushing 61 is tilted, only the contact position between the arcuate surface 61b and the inclined surface 62a shifts, reliably maintaining the contact between the arcuate surface 61b and the inclined surface 62a. The posture of the second bushing 62 does not change, therefore, the elastic force of the helical spring 63 is reliably applied to the second bushing 62, and the tightness between the arcuate surface 61b and the inclined surface 62a is also reliably maintained. Therefore, leakage of working oil from the valve plate 19 between the first bushing 61 and the second bushing 62 is suppressed. As a result, leakage of working oil from the valve plate 19 between the valve plate 19 and the bottom wall 119 of the housing body 9 is also suppressed.

[0150] Next, the operation of gear pump 111 will be explained.

[0151] The drive gear of gear pump 111 is connected to the shaft 3 of main pump 1 via coupling 136, so the drive gear rotates integrally with shaft 3. The driven gear meshing with the drive gear also rotates synchronously with the drive gear. The working oil flowing in the first suction path 122 is drawn into the second suction path 144 via the second connecting path 125 of the main housing 2. The working oil flows between the gears and the inner surface of the gear housing 141 and into the third discharge path (not shown). The working oil is discharged through the opening of the third discharge path.

[0152] Thus, in the first embodiment described above, the main pump 1 houses a pressing unit 60 in the third communication path 128. The pressing unit 60 includes two bushings 61 and 62, which are separable from each other; and a coil spring 63 that pushes the two bushings 61 and 62 toward the valve plate 19. Therefore, even when the valve plate 19 is tilted relative to the shaft 3, the first bushing 61 of the two bushings 61 and 62 can reliably follow the tilt of the valve plate 19. By using two bushings 61 and 62, compared to the case where the two bushings 61 and 62 are integrated, the radial deviation when one bushing (the first bushing 61) is tilted can be reduced. That is, only the first bushing 61 is tilted, thus preventing interference between the outer peripheral surface of the first bushing 61 and the inner peripheral surface of the bushing housing portion 65. This result prevents gaps from forming between the valve plate 19 and the bushings 61, 62, and suppresses leakage of working oil between the valve plate 19 and the bushings 61, 62. Therefore, it can suppress the deterioration of the performance of the main pump 1.

[0153] With just two bushings 61 and 62, the valve plate 19 can be tilted, preventing working oil from leaking between the valve plate 19 and the bushings 61 and 62. Therefore, it is possible to prevent an increase in the number of components in the main pump 1 as a whole and to provide a high-performance main pump 1.

[0154] The two bushings 61 and 62 are separable from each other, thus allowing for easy replacement of each bushing 61 and 62. Therefore, a main pump 1 with excellent maintainability can be provided.

[0155] By forming an arcuate surface 61b on the first bushing 61 and an inclined surface 62a on the second bushing 62, even if the first bushing 61 is tilted relative to the shaft 3, the first bushing 61 and the second bushing 62 can maintain a gapless ground contact. Therefore, the tightness of the fit between the first bushing 61 and the second bushing 62 can be improved with a simple construction. The surface pressure applied to each bushing 61, 62 can be reduced, thus extending the product life of each bushing 61, 62. The first bushing 61 can be smoothly tilted relative to the second bushing 62, thus improving the follow-through of the tilt of the first bushing 61 relative to the valve plate 19.

[0156] The mechanical strength (hardness) of the second bushing 62 is higher than that of the first bushing 61. Thus, by changing the mechanical strength (hardness) of the two bushings 61 and 62, it is possible to designate only one bushing to wear actively. In other words, the first bushing 61 can be made to wear more easily. Therefore, only the first bushing 61 needs to be replaced during maintenance, reducing the overall maintenance cost of bushings 61 and 62.

[0157] By making the first bushing 61, which is located on the side of the valve plate 19, softer (with weaker mechanical strength), wear on the valve plate 19 in contact with the first bushing 61 can be suppressed. The manufacturing cost of the valve plate 19 is higher than that of the first bushing 61. Therefore, by actively causing wear on the first bushing 61, the replacement frequency of the valve plate 19 can be reduced, thereby lowering the maintenance cost of the main pump 1.

[0158] In the first embodiment described above, the case where the pressing unit 60 is equipped with a helical spring 63 that pushes the two bushings 61, 62 toward the valve plate 19 has been described. However, it is not limited to this, and various elastic members that can push the two bushings 61, 62 toward the valve plate 19 can be used. For example, rubber or the like can be used instead of the helical spring 63.

[0159] In the first embodiment described above, the case where the two bushings 61 and 62 constituting the pressing unit 60 are arranged in a separable manner was explained. The case where the first bushing 61 has an arcuate surface 61b and the second bushing 62 has an inclined surface 62a was explained. The case where the first bushing 61 and the second bushing 62 come into surface contact through the contact of these arcuate surfaces 61b and inclined surfaces 62a was explained. However, this is not limited to these cases; the arcuate surface 61b and the inclined surface 62a can also be formed in the opposite manner. That is, the first bushing 61 can be formed with an inclined surface such that its outer diameter gradually decreases towards the second bushing 62. The second bushing 62 can also be formed with an arcuate surface such that its inner diameter gradually increases towards the first bushing 61. The first bushing 61 and the second bushing 62 can also be configured as follows.

[0160] [First Variation]

[0161] Figure 8 This is an enlarged cross-sectional view of the main parts of the two bushings 61 and 62 in the first variation of the first embodiment. Figure 8 With the aforementioned Figure 7 Correspondingly, in the following description, the same reference numerals are used for the same forms as in the first embodiment described above, and the descriptions are omitted (the same applies to the following variations and the second embodiment).

[0162] like Figure 8 As shown, the inclined surface 62a of the second bushing 62 can also be replaced by an arcuate surface (an example of a curved surface in the claims) 62b formed on the second bushing 62. The arcuate surface 62b is formed in an arcuate cross-section along the axial direction in such a way that its inner diameter gradually increases as it moves toward the first bushing 61. The arcuate surface 62b is formed in such a way that it becomes concave on the radially inward side. The radius of curvature R2 of the arcuate surface 62b of the second bushing 62 is larger than the radius of curvature R1 of the arcuate surface 61b of the first bushing 61.

[0163] Therefore, according to the first modification described above, the two bushings 61 and 62 can be made to contact more smoothly. As a result, the surface pressure applied to each bushing 61 and 62 can be reduced, and the product life of each bushing 61 and 62 can be extended. The first bushing 61 can be tilted more reliably relative to the second bushing 62 more easily.

[0164] The radius of curvature R2 of the arc surface 62b of the second bushing 62 is larger than the radius of curvature R1 of the arc surface 61b of the first bushing 61. Therefore, the arc surface 61b of the first bushing 61 can be accommodated within the arc surface 62b of the second bushing 62. The arc surfaces 61b and 62b are in contact with each other, thus allowing the first bushing 61 to smoothly tilt relative to the second bushing 62. Therefore, the following performance of the first bushing 61 relative to the valve plate 19 can be further improved.

[0165] [Second Variation]

[0166] Figure 9 This is a cross-sectional view of the two bushings 61 and 62 in the second variation of the first embodiment.

[0167] like Figure 9 As shown, the difference between the first and second modifications described above is as follows: in the first modification, the two bushings 61 and 62 are provided in a separable manner, while in the second modification, the two bushings 61 and 62 are integrated.

[0168] More specifically, a protrusion 71 protruding toward the inner circumferential surface of the second bushing 62 is integrally formed on the end face of the first bushing 61 on the side adjacent to the second bushing 62. The outer diameter of the protrusion 71 is slightly smaller than the inner diameter of the second bushing 62. A neck 72 is formed on the protrusion 71 at a position slightly closer to the front end than the front end of the protrusion 71. The neck 72 is formed in a U-shaped cross-sectional shape along the axial direction. The minimum outer diameter of the neck 72 is smaller than the outer diameter of the front end of the protrusion 71.

[0169] In the second bushing 62, an inner flange portion 73 protruding radially inward is integrally formed at the end (base end) of the arcuate surface 62b opposite to that of the first bushing 61. The surface 73a of the inner flange portion 73 on the side facing the first bushing 61 is formed into an arcuate cross-section along the axial direction in a manner that smoothly connects with the arcuate surface 62b. At the radially inward end of the inner flange portion 73, a rounded corner portion 73b is formed in a manner that corresponds to the shape of the neck 72 of the protrusion 71 of the first bushing 61. Such an inner flange portion 73 is housed within the neck 72. Thus, they are engaged with each other in a state that allows the first bushing 61 to tilt relative to the second bushing 62 and restricts the movement of the first bushing 61 relative to the second bushing 62.

[0170] Thus, in the second variation described above, the two bushings 61 and 62 are integrated and can be displaced relative to each other. In other words, the two bushings 61 and 62 are an assembly that can be displaced relative to each other. Therefore, the two bushings 61 and 62 can be easily assembled within the third connecting path 128. Consequently, a main pump 1 with excellent assemblability can be provided.

[0171] [3rd Variation]

[0172] Figure 10 This is a cross-sectional view of the two bushings 61 and 62 in the third variation of the first embodiment.

[0173] like Figure 10 As shown, the difference between the second and third modifications is as follows: in the second modification, the bushings 61 and 62 engage with the outer peripheral surface of the first bushing 61 and the inner peripheral surface of the second bushing 62, while in the third modification, the bushings 61 and 62 engage with the inner peripheral surface of the first bushing 61 and the outer peripheral surface of the second bushing 62.

[0174] More specifically, an arcuate surface 61c is formed on the inner circumferential surface of the first bushing 61 on the side closer to the second bushing 62. The arcuate surface 61c is formed in an arc shape such that its inner diameter gradually increases towards the second bushing 62. The arcuate surface 61c is formed such that its radially inward side is concave.

[0175] A first protrusion 74 protruding toward the second bushing 62 is integrally formed on the end face of the first bushing 61 on the side near the second bushing 62. The outer diameter of the first protrusion 74 is the same as the outer diameter of the first bushing 61. A first recess 75 is formed around the entire circumference of the first protrusion 74, slightly closer to the front end than the front end of the first protrusion 74. The first recess 75 is formed in a U-shaped cross-section along the axial direction. The maximum inner diameter of the first recess 75 is larger than the inner diameter of the front end of the first protrusion 74. A rounded corner 74a is formed on the radially inner side of the first protrusion 74.

[0176] A second protrusion 76 is integrally formed on the end face of the second bushing 62 on the side near the first bushing 61, protruding toward the inner peripheral surface of the first protrusion 74. An arcuate surface 76a is formed on the outer peripheral surface of the second protrusion 76, corresponding to the arcuate surface 61c of the first protrusion 74. The arcuate surface 76a is formed in an arc shape such that its outer diameter gradually decreases as it moves toward the first bushing 61. The arcuate surface 76a is formed to bulge radially outward. The radius of curvature R4 of the arcuate surface 76a is smaller than the radius of curvature R3 of the arcuate surface 61c of the first bushing 61. The arcuate surface 76a of the second protrusion 76 contacts the arcuate surface 61c of the first bushing 61.

[0177] At the base end of the second protrusion 76 on the side opposite to the front end, a second recess 77 is formed around the entire circumference of its outer peripheral surface. The second recess 77 is formed in a U-shape in cross-section along the axial direction. The first protrusion 74 is housed within the second recess 77. Thus, they engage with each other in a state that allows the first bushing 61 to tilt relative to the second bushing 62 and restricts the movement of the first bushing 61 relative to the second bushing 62.

[0178] Therefore, according to the third modification described above, the same effect as the second modification described above can be achieved.

[0179] [Other variations]

[0180] In the first embodiment and the first to third modifications described above, the case where the pressing unit 60 has two bushings 61 and 62 was explained. However, it is not limited to this, and the pressing unit 60 may also have two or more bushings.

[0181] The case where the first bushing 61 has arcuate surfaces 61b and 61c, and the second bushing 62 has arcuate surfaces 62b and 76a, has been described. However, it is not limited to this; curved surfaces can also be used instead of arcuate surfaces 61b, 61c, 62b, and 76a. A curved surface refers to a shape whose cross-sectional shape along the axial direction is curved rather than arcuate.

[0182] Both the first bushing 61 and the second bushing 62 can also have convex arc surfaces. Even in this case, the same effect as the first embodiment described above can be achieved.

[0183] In the first embodiment and the first to third modifications described above, the first bushing 61 and the valve plate 19 were described as separate units. However, this is not a limitation; the valve plate 19 and the first bushing 61 can also be integrated. When the push unit 60 has two or more bushings, it is sufficient to integrate the bushing located closest to the valve plate 19 with the valve plate 19. By configuring it in this way, the number of components in the main pump 1 can be reduced. Therefore, the overall manufacturing cost of the main pump 1 can be reduced.

[0184] [Second Implementation]

[0185] Next, based on Figure 11 , Figure 12 The second embodiment of the present invention will be described.

[0186] Figure 11 This is a top view of the valve plate 219 in the second embodiment, viewed from the second surface 241b side of the bottom wall 119 side of the housing body 9. Figure 11 With the aforementioned Figure 4 Correspondingly. Figure 12 It is a magnified partial cross-sectional view of the valve plate 219 and the bottom wall 119 of the housing body 9.

[0187] like Figure 11 , Figure 12 As shown, the difference between the second embodiment and the first embodiment lies in the following aspects: In the valve plate 219 of the second embodiment, a spring receiving recess (an example of a recess in the claim) 82 is formed on the second surface 241b to receive a small spring (an example of a small elastic member in the claim) 81, whereas in the valve plate 19 of the first embodiment, the spring receiving recess 82 is not formed.

[0188] The small spring 81 is used to push the valve plate 19 toward the cylinder 4.

[0189] Two first spring receiving recesses 82 are formed on the second surface 241b of the valve plate 219. The two first spring receiving recesses 82 are positioned between the two ends of the intake port 19a along its length and the piston receiving recess 49. The diameter of the first spring receiving recess 82 is smaller than the diameter of the piston receiving recess 49. However, this is not a limitation; the diameter of the first spring receiving recess 82 can be any size that allows it to be formed on the second surface 241b of the valve plate 219.

[0190] The depth of the first spring receiving recess 82 is approximately half the thickness of the valve plate 219. However, it is not limited to this, as long as the depth of the first spring receiving recess 82 is sufficient to ensure the mechanical strength of the valve plate 219.

[0191] On the bottom wall 119 of the housing body 9, a second spring receiving recess 83 is formed on the inner surface 119a at a position corresponding to the first spring receiving recess 82. The shape of the second spring receiving recess 83 corresponds to the shape of the first spring receiving recess 82. That is, the diameter and depth of the second spring receiving recess 83 are approximately the same as the diameter and depth of the first spring receiving recess 82.

[0192] The second surface 241b of the valve plate 219 overlaps with the inner surface 119a of the bottom wall 119, thereby forming a spring storage portion 84 between the bottom wall 119 and the valve plate 219 using the spring storage recesses 82 and 83. The small spring 81 is stored in the spring storage portion 84 in a slightly compressed state. As a result, the elastic force of the small spring 81 pushes against the valve plate 219.

[0193] Therefore, according to the second embodiment described above, the pushing force that pushes the valve plate 219 against the cylinder 4 can be increased by using the small spring 81. This improves the sealing between the cylinder 4 and the valve plate 219. As a result, leakage of working oil between the cylinder 4 and the valve plate 219 can be suppressed, further improving the performance of the main pump 1.

[0194] By forming a first spring receiving recess 82 in the valve plate 219, the axial length of the main pump 1 can be suppressed, and the free length of the small spring 81 can be made as long as possible. Therefore, the elastic force of the small spring 81 can be increased, and the tightness between the cylinder 4 and the valve plate 219 can be improved more reliably. Consequently, the performance of the main pump 1 can be improved more reliably.

[0195] In the second embodiment described above, the case where a small spring 81 is provided between the valve plate 219 and the bottom wall 119 of the housing body 9 has been explained. However, it is not limited to this, and various elastic members that can push the valve plate 19 toward the cylinder 4 can be used. For example, rubber or the like can be used instead of the small spring 81.

[0196] This invention is not limited to the embodiments described above, but includes various modifications to the embodiments described above without departing from the spirit of this invention.

[0197] For example, in the above embodiment, the case where the construction machinery 100 is a hydraulic excavator has been described. However, it is not limited to this, and various types of construction machinery can be used.

[0198] In the above embodiments, the main pump 1, which uses working oil as the fluid, has been described as a fluid machine. However, it is not limited to this; the structures of the above embodiments and modifications can be adopted in various fluid machines that use various fluids other than working oil. For example, the structures of the above embodiments and modifications can be adopted in a hydraulic motor as a fluid machine.

[0199] In the above embodiment, the case where the circular push piston 46 is housed in the piston housing recess 49 formed in the valve plate 19 has been described. However, it is sufficient to use the pressure of the working oil sprayed into the piston housing recess 49 to generate a pushing force toward the cylinder 4 on the valve plate 19. For example, the push piston 46 may not be provided in the piston housing recess 49. Alternatively, a compression coil spring or the like may be housed in the piston housing recess 49 instead of the push piston 46. The elastic force of the compression coil spring may also be used to apply a pushing force toward the cylinder 4 to the valve plate 19.

[0200] In the embodiments disclosed in this specification, a component composed of multiple objects can be integrated into one unit, and conversely, a component composed of a single object can be divided into multiple objects. Whether integrated or not, it can be constructed in a manner that achieves the purpose of the invention.

Claims

1. A fluid machine, wherein the fluid machine is provided with: a piston; a cylinder which forms a cylinder chamber that houses the piston, and which forms a communication hole that communicates the inside and outside of the cylinder chamber; a housing that houses the cylinder, the housing forming an ejection path; a valve plate disposed between the cylinder and the housing; a plurality of bushings arranged in the ejection path along the axial direction of the piston, the plurality of bushings being disposed so as to be relatively displaceable; a housing-internal elastic member disposed in the ejection path, the housing-internal elastic member urging the plurality of bushings toward the valve plate; and a piston-urging member that urges the valve plate toward the end surface of the cylinder, the valve plate has: a first surface on the side of the cylinder; a second surface on the side opposite the first surface; an ejection port that communicates the communication hole and the ejection path; a piston-housing recess formed between the second surface and the thickness-direction center of the valve plate, which houses the piston-urging member; and a long recess formed between the first surface and the thickness-direction center of the valve plate, which communicates with the ejection port, the piston-housing recess and the long recess communicate at both ends in the length direction thereof.

2. The fluid machine according to claim 1, wherein the plurality of bushings are separable from each other.

3. The fluid machine according to claim 1, wherein the plurality of bushings are an assembly that is joined to each other.

4. The fluid machine according to any one of claims 1 to 3, wherein the plurality of bushings are arranged in a state in which the end surfaces in the axial direction thereof are in surface contact with each other.

5. The fluid machine according to claim 4, wherein at least one of the two bushings that are in contact is formed with a curved protrusion that protrudes from the end surface in the axial direction thereof toward the end surface in the axial direction of the other bushing.

6. The fluid machine according to claim 5, wherein the end surface of the one bushing is formed with the curved protrusion that is convex on the radially outer side thereof, the end surface of the other bushing is formed with a flat surface that gradually increases in diameter as it goes toward the end surface of the one bushing.

7. The fluid machine according to claim 5, wherein the end surface of the one bushing and the end surface of the other bushing are formed with the curved protrusion.

8. The fluid machine according to claim 5, wherein the end surface of the one bushing is formed with the curved protrusion that is convex on the radially outer side thereof, the end surface of the other bushing is formed with a curved surface that gradually increases in diameter as it goes toward the end surface of the one bushing.

9. The fluid machine according to claim 8, wherein the curved protrusion and the curved surface are formed in a circular-arc shape in cross section along the axial direction.

10. The fluid machine according to claim 9, wherein the radius of curvature of the curved protrusion is smaller than the radius of curvature of the curved surface.

11. The fluid machine according to any one of claims 1 to 3, wherein one of the plurality of bushings is softer than the other bushings.

12. The fluid machine according to claim 11, wherein ​ ​ The bushing softer than the other bushings is arranged at a position closest to the valve plate side.

13. The fluid machine according to any one of claims 1 to 3, wherein The bushing arranged at a position closest to the valve plate side among the plurality of bushings is integrated with the valve plate.

14. The fluid machine according to any one of claims 1 to 3, wherein The fluid machine is provided with a small elastic member arranged between the valve plate and the case and pushing the valve plate toward the cylinder side, The valve plate is formed with a recess that accommodates the small elastic member.

15. A fluid machine, wherein The fluid machine is provided with: a piston; a cylinder that is formed with a cylinder chamber that accommodates the piston and is formed with a communication hole that communicates the inside and outside of the cylinder chamber; a case that accommodates the cylinder, the case being formed with an ejection path; a valve plate arranged between the cylinder and the case; a plurality of bushings arranged in the ejection path along the axial direction of the piston, the plurality of bushings being arranged so as to be relatively displaceable; a case-internal elastic member arranged in the ejection path, the case-internal elastic member pushing the bushings toward the valve plate; and a push piston that pushes the valve plate toward the end surface of the cylinder, one of the two bushings that are in contact is formed with a curved protrusion that protrudes from the end surface in the axial direction toward the end surface in the axial direction of the other bushing, and the radially outer side of the curved protrusion is convex, the end surface of the other bushing is formed with a curved surface that gradually increases in diameter as it goes toward the end surface of the one bushing, the cross section of the curved protrusion and the curved surface is formed in a circular arc shape, the radius of curvature of the curved protrusion is smaller than the radius of curvature of the curved surface, the valve plate has: a first surface on the side of the cylinder; a second surface on the side opposite the first surface; an ejection port that communicates the communication hole and the ejection path; a piston-accommodating recess formed between the thickness direction center of the valve plate from the second surface and the valve plate, which accommodates the push piston; and a long recess formed between the thickness direction center of the valve plate from the first surface, which communicates with the ejection port, the piston-accommodating recess and the long recess communicate with both ends in the length direction.

16. A fluid machine, wherein The fluid machine is provided with: a piston; a cylinder that is formed with a cylinder chamber that accommodates the piston and is formed with a communication hole that communicates the inside and outside of the cylinder chamber; a case that accommodates the cylinder, the case being formed with an ejection path; a valve plate arranged between the cylinder and the case; a small elastic member arranged between the valve plate and the case, the small elastic member pushing the valve plate toward the cylinder side; and a push piston that pushes the valve plate toward the end surface of the cylinder, the valve plate is formed with a recess that accommodates the small elastic member, the valve plate has: a first surface on the side of the cylinder; a second surface on the side opposite the first surface; an ejection port that communicates the communication hole and the ejection path; ​ a piston housing recess formed between the second face and the thickness direction center of the valve plate, which houses the push piston; and a long recess formed between the first face and the thickness direction center of the valve plate, which communicates with the discharge port, the piston housing recess and the long recess communicate with both ends in the length direction.

17. A construction machine, wherein the construction machine is provided with: a vehicle body; and a fluid machine that sucks in and discharges a fluid that is a driving source of the vehicle body, the fluid machine is provided with: a piston; a cylinder that forms a cylinder chamber that houses the piston, and forms a communication hole that communicates the inside and outside of the cylinder chamber; a housing that houses the cylinder, the housing forming a discharge path; a valve plate that is disposed between the cylinder and the housing; a plurality of bushings that are arranged in the discharge path in the axial direction of the piston, the plurality of bushings being disposed so as to be relatively displaceable; a housing internal elastic member that is provided in the discharge path, the housing internal elastic member pushing the bushings toward the valve plate; and a push piston that pushes the valve plate toward the end face of the cylinder, one of the two bushings that are in contact is formed with a curved protrusion that protrudes from the end face in the axial direction toward the end face in the axial direction of the other bushing, and the radially outer side of the curved protrusion is convex, the end face of the other bushing is formed with a curved surface that gradually increases in diameter as it goes toward the end face of the one bushing, the cross section of the curved protrusion and the curved surface is formed in an arc shape, the radius of curvature of the curved protrusion is smaller than the radius of curvature of the curved surface, the valve plate has: a first face on the side of the cylinder; a second face on the side opposite the first face; a discharge port that communicates the communication hole and the discharge path; a piston housing recess formed between the second face and the thickness direction center of the valve plate, which houses the push piston; and a long recess formed between the first face and the thickness direction center of the valve plate, which communicates with the discharge port, the piston housing recess and the long recess communicate with both ends in the length direction. ​

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