Fluid machinery and construction machinery

Abstract

To provide a fluid machine and a construction machine capable of suppressing the degradation of their performances.SOLUTION: A main pump in the embodiment includes a cylinder block 4 having a cylinder chamber 17 storing a piston and also having a communication hole 18 communicating the inside with the outside of the cylinder chamber 17, a main casing 2 storing the cylinder block 4 and having a discharge path 123, a valve plate 19 arranged between the cylinder block 4 and the main casing 2 and having a discharge port 19b for communicating the communication hole 18 with the discharge path 123, a plurality of bushes 61, 62 arranged in the discharge path 123 side by side along the axial direction of the piston and provided in a relatively displaceable manner, and a coil spring 63 provided in the discharge path 123 for pushing the plurality of bushes 61, 62 against the valve plate 19.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a fluid machine and a construction machine. [Background technology]

[0002] An example of fluid machinery is a so-called swash plate type hydraulic piston pump (hereinafter simply referred to as hydraulic pump) that is mounted on construction machinery such as hydraulic excavators. This type of hydraulic pump includes, for example, a shaft rotatably supported within a pump casing, a cylinder block fixed to the outer circumferential surface of the shaft, and multiple pistons. Multiple cylinder chambers are formed in the cylinder block. Each piston is housed in the cylinder chamber so that it can slide freely along the axial direction of the shaft (hereinafter simply referred to as the axial direction).

[0003] The hydraulic pump also includes a swash plate disposed at a first axial end of the cylinder block, and a valve plate disposed at a second axial end opposite the first end. The swash plate restricts the sliding movement of the pistons within the cylinder chambers via the ends of the pistons, which are movable on the surface of the swash plate. The swash plate changes the spatial volume formed by the cylinder chambers and the pistons depending on the inclination angle relative to the pump casing. The valve plate has suction ports and discharge ports through which hydraulic oil flows, at positions corresponding to the multiple cylinder chambers of the cylinder block. The suction ports are connected to the suction passage of the pump casing. The discharge ports are connected to the discharge passage of the pump casing.

[0004] With this configuration, when the cylinder block rotates around the axis of the shaft, each cylinder chamber rotates around the shaft, alternately communicating with the suction port and discharge port of the valve plate. When the cylinder chamber communicates with the suction port, the piston slides within the cylinder chamber to increase the spatial volume within the cylinder chamber. This allows hydraulic oil to be drawn into the cylinder chamber from outside the pump casing via the suction passage and suction port. On the other hand, when the cylinder chamber communicates with the discharge port, the piston slides within the cylinder chamber to reduce the spatial volume within the cylinder chamber. This allows hydraulic oil to be discharged from the cylinder chamber to outside the pump casing via the discharge port and discharge passage.

[0005] A technique has been disclosed in which one spring and one bush are provided in the discharge passage of the pump casing (see, for example, Patent Document 1). This technique transmits the elastic force of the spring to the valve plate via the bush, applying a pressing force to the valve plate toward the cylinder block, thereby improving the adhesion between the cylinder block and the valve plate. As a result, it is possible to prevent hydraulic oil from leaking from between the cylinder block and the valve plate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-98327 Summary of the Invention [Problem to be solved by the invention]

[0007] During hydraulic pump operation, the hydraulic force acting on the piston discharging hydraulic oil in the cylinder chamber differs from the hydraulic force acting on the piston suctioning hydraulic oil in the cylinder chamber. As a result, the force pressing the piston against the swash plate, which is generated by the reaction force of the hydraulic force, becomes unbalanced all around. This imbalance can cause the cylinder block to tilt relative to the shaft. This can also cause the valve plate to tilt relative to the shaft.

[0008] However, if only one bush is pressed against the valve plate as in the above-mentioned conventional technology, the bush cannot follow the inclination of the valve plate, and a gap may occur between the valve plate and the bush, which may allow hydraulic oil to leak out and reduce the performance of the hydraulic pump.

[0009] The present invention provides a fluid machine and a construction machine that can suppress a decrease in performance. [Means for solving the problem]

[0010] A fluid machine according to one aspect of the present invention comprises a cylinder block having a cylinder chamber in which a piston is housed and a communication hole that connects the inside and outside of the cylinder chamber; a casing in which the cylinder block is housed and which has a discharge passage; a valve plate disposed between the cylinder block and the casing and having a discharge port that connects the communication hole with the discharge passage; a plurality of bushes arranged in a row along the axial direction of the piston within the discharge passage so as to be relatively displaceable; and an elastic member within the casing that is disposed within the discharge passage and presses the plurality of bushes against the valve plate.

[0011] With this configuration, even if the valve plate tilts in response to the tilt of the cylinder block, each of the bushings tilts slightly, ensuring that the bushing closest to the valve plate follows the tilt of the valve plate. This prevents gaps from forming between the valve plate and the bushings, preventing hydraulic oil from leaking from between the valve plate and the bushings. This in turn prevents a decrease in the performance of the fluid machine.

[0012] The above configuration may include two bushings.

[0013] In the above configuration, the plurality of bushes may be separable from one another.

[0014] In the above configuration, the plurality of bushes may be an assembly in which the bushes are connected to one another.

[0015] In the above configuration, the axial end faces of the bushes may be in surface contact with each other.

[0016] In the above configuration, the axial end face of at least one of the two contacting bushes may have a curved convex portion that protrudes toward the axial end face of the other bush.

[0017] In the above configuration, the one end face of the bush may have the curved convex portion that is convex radially outward, and the other end face of the bush may have a flat surface whose diameter gradually increases toward the one end face.

[0018] In the above configuration, the one end surface and the other end surface of the bush may have the curved convex portion.

[0019] In the above configuration, the one end face of the bushing may have the curved convex portion that is convex radially outward, and the other end face of the bushing may have a curved surface whose diameter gradually increases toward the one end face.

[0020] In the above configuration, the curved convex portion and the curved surface may be formed so that a cross section along the axial direction is arc-shaped.

[0021] In the aforementioned configuration, the radius of curvature of the curved convex portion may be smaller than the radius of curvature of the curved surface.

[0022] In the above configuration, one of the plurality of bushings may be softer than the other bushings.

[0023] In the above configuration, the bushing arranged closest to the valve plate among the plurality of bushings may be softer than the other bushings.

[0024] In the above configuration, the bushing arranged closest to the valve plate among the plurality of bushings may be integrated with the valve plate.

[0025] In the above configuration, a small elastic member may be provided between the valve plate and the casing to press the valve plate toward the cylinder block, and a recess may be provided in the valve plate to receive the small elastic member.

[0026] a casing that houses the cylinder block and has a discharge passage; a valve plate that is disposed between the cylinder block and the casing and has a discharge port that connects the discharge passage with the discharge port; a bushing whose end face that abuts against the valve plate tilts in accordance with the tilt of the valve plate; and an elastic member within the casing that is disposed within the discharge passage and presses the bushing against the valve plate, wherein the axial end face of one of the two contacting bushings has a curved convex portion that protrudes toward the axial end face of the other bushing and is convex radially outward, and the other end face of the bushing has a curved surface whose diameter gradually increases toward the one end face, the curved convex portion and the curved surface are formed in an arc-shaped cross section, and the radius of curvature of the curved convex portion is smaller than the radius of curvature of the curved surface.

[0027] With this configuration, even if the valve plate tilts in response to the tilt of the cylinder block, each of the bushings tilts slightly, ensuring that the bushing closest to the valve plate follows the tilt of the valve plate. This prevents gaps from forming between the valve plate and the bushings, preventing hydraulic oil from leaking from between the valve plate and the bushings. This in turn prevents a decrease in the performance of the fluid machine. In addition, the curved convex portion can be contained within the curved surface, ensuring reliable contact of the curved convex portion with the curved surface.Furthermore, one bushing can be smoothly tilted relative to the other, further improving the bushing's ability to follow the valve plate.

[0028] A fluid machine according to another aspect of the present invention comprises a cylinder block having a cylinder chamber in which a piston is accommodated and having a communication hole connecting the inside and outside of the cylinder chamber; a casing in which the cylinder block is accommodated and having a discharge passage; a valve plate arranged between the cylinder block and the casing and having a discharge port connecting the communication hole with the discharge passage; and a small elastic member arranged between the valve plate and the casing and pressing the valve plate toward the cylinder block, wherein the valve plate is provided with a recess to receive the small elastic member.

[0029] With this configuration, even if the valve plate tilts in response to the tilt of the cylinder block, each of the bushings tilts slightly, ensuring that the bushing closest to the valve plate follows the tilt of the valve plate. This prevents gaps from forming between the valve plate and the bushings, preventing hydraulic oil from leaking from between the valve plate and the bushings. This in turn prevents a decrease in the performance of the fluid machine. In addition, the small elastic member can increase the pressing force of the valve plate against the cylinder block, thereby improving the degree of contact between the cylinder block and the valve plate. As a result, it is possible to prevent hydraulic oil from leaking out from between the cylinder block and the valve plate, further improving the performance of the fluid machine.

[0030] A construction machine according to another aspect of the present invention comprises a vehicle body and a fluid machine that sucks in and discharges a fluid that serves as a drive source for the vehicle body, the fluid machine comprising a cylinder block having a cylinder chamber in which a piston is housed and having a communication hole that connects the inside and outside of the cylinder chamber, a casing that houses the cylinder block and has a discharge passage, a valve plate that is disposed between the cylinder block and the casing and has a discharge port that connects the communication hole with the discharge passage, and a valve plate whose end face that abuts against the valve plate is inclined in accordance with the inclination of the valve plate. and a casing internal elastic member that is provided within the discharge passage and presses the bush toward the valve plate, wherein the axial end face of one of the two contacting bushes has a curved convex portion that protrudes toward the axial end face of the other and is convex radially outward, and the other end face of the bush has a curved surface whose diameter gradually increases toward the one end face, the curved convex portion and the curved surface are formed in an arc-shaped cross section, and the radius of curvature of the curved convex portion is smaller than the radius of curvature of the curved surface.

[0031] By configuring it in this way, it is possible to suppress a decrease in the performance of the construction machine. [Effects of the Invention]

[0032] The above-described fluid machinery and construction machinery can suppress performance degradation. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a schematic configuration diagram of a construction machine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a partially cutaway view of a pump unit according to an embodiment of the present invention. [Figure 3] FIG. 2 is a plan view of the valve plate according to the first embodiment of the present invention, viewed from the first surface side. [Figure 4] FIG. 3 is a plan view of the valve plate according to the first embodiment of the present invention, viewed from the second surface side. [Figure 5] 4. FIG. 5 is a cross-sectional view taken along line AA in FIG. [Figure 6] Enlarged view of part B in Figure 2. [Figure 7] Enlarged view of part C in Figure 6. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a main portion of two bushes in a first modified example of the first embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view of two bushes in a second modified example of the first embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view of two bushes in a third modified example of the first embodiment of the present invention. [Figure 11] FIG. 10 is a plan view of a valve plate according to a second embodiment of the present invention, viewed from the second surface side. [Figure 12] FIG. 10 is an enlarged cross-sectional view of a portion of a valve plate and a bottom wall of a casing body in a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] Next, an embodiment of the present invention will be described with reference to the drawings.

[0035] <Construction machinery> FIG. 1 is a schematic diagram of a construction machine 100. As shown in FIG. As shown in Fig. 1, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 comprises a revolving body (an example of a vehicle body in the claims) 101 and a running body (an example of a vehicle body in the claims) 102 provided below the revolving body 101. The revolving body 101 revolves above the running body 102. The revolving body 101 comprises a pump unit 110 (an example of a fluid machine in the claims).

[0036] The rotating unit 101 includes a cab 103 that supports an operator riding on the rotating unit 101, a boom 104 having one end connected to the cab 103, an arm 105 having one end connected to the other end of the boom 104, and a bucket 106 connected to the other end of the arm 105. The boom 104 swings relative to the cab 103. The arm 105 swings relative to the boom 104. The bucket 106 swings relative to the arm 105. The pump unit 110 is provided in the cab 103. The hydraulic oil supplied from the pump unit 110 serves as a drive source for the cab 103, the boom 104, the arm 105, and the bucket 106.

[0037] <Pump unit> FIG. 2 is a structural diagram showing the pump unit 110 with a part cut away. The pump unit 110 is a so-called hydraulic pump that sucks in and discharges hydraulic oil. As shown in Fig. 2, the pump unit 110 includes a main pump 1 (an example of the fluid machine in the claims) as a fluid machine, and a gear pump 111 provided on one side of the main pump 1. Note that Fig. 2 shows only the main pump 1 in cross section along the axial direction.

[0038] [First embodiment] <Main pump> The main pump 1 is a so-called swash plate type variable displacement hydraulic pump. The main pump 1 mainly comprises a main casing (an example of a casing in the claims) 2, a shaft 3 supported on the main casing 2 so as to be rotatable about a central axis CL, a cylinder block 4 housed in the main casing 2 and fixed to the shaft 3, a swash plate 5 housed in the main casing 2 so as to be tiltable with respect to the main casing 2, pistons 21 provided in the cylinder block 4, a valve plate 19 disposed between the main casing 2 and the cylinder block 4, and a pressing unit 60 provided on the main casing 2 for pressing the valve plate 19 against the cylinder block 4. In order to make the explanation easier to understand, the scale of each component has been appropriately changed in Fig. 2. In the following explanation, the direction parallel to the central axis CL of the shaft 3 will be referred to as the axial direction, the rotation direction of the shaft 3 will be referred to as the circumferential direction, and the radial direction of the shaft 3 will be simply referred to as the radial direction.

[0039] The main casing 2 includes a box-shaped casing body 9 (an example of the casing in the claims) having an opening 9a, and a front flange 10 that closes the opening 9a of the casing body 9. The casing body 9 has a bottom wall 119 provided on the opposite side to the opening 9a. The bottom wall 119 is a wall portion of the casing body 9 located on the central axis CL of the shaft 3. The cylinder block 4 is disposed on the side of an inner surface 119a of the bottom wall 119. The gear pump 111 is attached to an outer surface 119b of the bottom wall 119.

[0040] A rotary shaft insertion hole 121, through which the shaft 3 is inserted, is formed in the bottom wall 119 so as to penetrate in the thickness direction of the bottom wall 119. A bearing 11 is provided in the rotary shaft insertion hole 121 near an inner surface 119a of the bottom wall 119, to rotatably support one end of the shaft 3.

[0041] A first suction passage 122 and a discharge passage (an example of the discharge passage in the claims) 123 are formed in the bottom wall 119 on both radial sides of the rotary shaft insertion hole 121. The first suction passage 122 forms an opening 122a in a first side surface 119c of the bottom wall 119. The opening 122a of the first suction passage 122 communicates with a tank (not shown). The first suction passage 122 extends into the bottom wall 119 such that the opening area gradually decreases from the first side surface 119c toward the rotary shaft insertion hole 121.

[0042] A first communication passage 124 is formed at the end of the first suction passage 122 on the rotary shaft insertion hole 121 side, and connects the first suction passage 122 to an inner surface 119a of the bottom wall 119. The first communication passage 124 connects the first suction passage 122 to a suction port 19a of the valve plate 19, which will be described later. The end of the first suction passage 122 on the rotating shaft insertion hole 121 side does not communicate with this rotating shaft insertion hole 121. A second communication passage 125 that communicates the first suction passage 122 with an outer surface 119b of the bottom wall 119 is formed at the end of the first suction passage 122 on the rotating shaft insertion hole 121 side. The second communication passage 125 communicates the first suction passage 122 with a second suction passage 144 of the gear pump 111, which will be described later.

[0043] An O-ring groove 118 is formed on the outer surface 119b of the bottom wall 119 so as to surround the periphery of the rotary shaft insertion hole 121 and the second communication passage 125. An O-ring 117 is fitted in this O-ring groove 118. The O-ring 117 ensures sealing between the main casing 2 and a gear casing 141 (described later) of the gear pump 111.

[0044] With this configuration, hydraulic oil is drawn from a tank (not shown) into the first suction passage 122. The hydraulic oil drawn into the first suction passage 122 flows into the first communication passage 124 and the second communication passage 125.

[0045] The discharge passage 123 has an opening 123a formed in a second side surface 119d located on the opposite side of the rotary shaft insertion hole 121 from the first side surface 119c of the bottom wall 119. The opening 123a is connected to the cab 103, the boom 104, the arm 105, and the bucket 106 via a control valve or the like (not shown). The discharge passage 123 extends from the second side surface 119d toward the rotary shaft insertion hole 121 inside the bottom wall 119.

[0046] The end of the discharge passage 123 on the rotary shaft insertion hole 121 side does not communicate with the rotary shaft insertion hole 121. A third communication passage (an example of the discharge passage in the claims) 128 is formed at the end of the discharge passage 123 on the rotary shaft insertion hole 121 side, connecting the discharge passage 123 with an inner surface 119a of the bottom wall 119. The third communication passage 128 connects the discharge passage 123 with a discharge port 19b of the valve plate 19, which will be described later.

[0047] The front flange 10 is formed with a through hole 13 through which the shaft 3 is inserted. A bearing 14 is provided in the through hole 13 to rotatably support the other end of the shaft 3. An oil seal 15 is also provided in the through hole 13 on the opposite side of the bearing 14 from the casing main body 9 (outside the front flange 10). The oil seal 15 prevents the leakage of hydraulic oil from the inside and prevents the intrusion of foreign matter between the shaft 3 and the front flange 10.

[0048] Two mounting plates 137 are integrally formed with the front flange 10. The two mounting plates 137 are arranged on both radial sides of 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 on the rotating body 101.

[0049] The shaft 3 is formed in a stepped shape. The shaft 3 is integrally formed with a coaxially arranged shaft body 131, a first bearing portion 132 extending from the shaft body 131 to one end side of the shaft 3 (toward the bottom wall 119 of the main casing 2), a transmission shaft 133 extending from the first bearing portion 132 on the opposite side of the shaft body 131, a second bearing portion 134 extending from the shaft body 131 to the other end side of the shaft 3 (toward the front flange 10), and a connecting shaft 135 extending from the second bearing portion 134 on the opposite side of the shaft body 131.

[0050] The shaft body 131 is disposed inside the main casing 2. A first spline 131a is formed on the shaft body 131. The cylinder block 4 is fitted onto this first spline 131a. A pressing member 27 is fitted onto the outer circumferential surface of the shaft body 131, near the second bearing portion 134. The pressing member 27 presses a shoe holding member 29, which will be described later. The shaft diameter of the first bearing portion 132 is smaller than the shaft diameter of the shaft main body 131. The first bearing portion 132 is rotatably supported by the bearing 11 of the bottom wall 119.

[0051] 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 toward the gear pump 111 via the bearing 11. The transmission shaft 133 is disposed in the rotary shaft insertion 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 the first bearing portion 132 protrudes outside the bottom wall 119 via the rotary shaft insertion hole 121. This protruding portion is connected to the gear pump 111.

[0052] The shaft diameter of the second bearing portion 134 is larger than the shaft diameter of the first bearing portion 132. The second bearing portion 134 is rotatably supported by the bearing 14 of the front flange 10. 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 tip of the connecting shaft 135 opposite the second bearing portion 134 protrudes outside the front flange 10 via the bearing 14. A second spline 135a is formed at the tip of the connecting shaft 135. The power source such as an engine (not shown) is connected to the shaft 3 via this second spline 135a.

[0053] The cylinder block 4 fixed to the shaft 3 is formed in a cylindrical shape. A through-hole 16 into which the shaft 3 is inserted or press-fitted is formed in the radial center of the cylinder block 4. A spline 16a is formed on the inner wall surface of the through-hole 16. This spline 16a is coupled to a first spline 131a of a shaft main body 131. The shaft 3 and the cylinder block 4 rotate together via the splines 16a and 131a.

[0054] A recess 20 is formed to surround the periphery of the shaft 3 from the axial center of the through hole 16 to the end 4a on the bottom wall 119 side. A through hole 25 that axially penetrates the cylinder block 4 is formed in part of the inner wall surface from the axial center of the through hole 16 to the front flange 10 side. A spring 23 and retainers 24a, 24b, which will be described later, are housed in the recess 20. A connecting member 26, which will be described later, is housed in the through hole 25 so as to be axially movable.

[0055] A plurality of cylinder chambers 17 are formed in the cylinder block 4 so as to surround the periphery of the shaft 3. The plurality of cylinder chambers 17 are arranged at equal intervals in the circumferential direction on a predetermined pitch circle concentric with the central axis CL. Each cylinder chamber 17 is a recess that is open on the front flange 10 side and closed on the bottom wall 119 side. Communication holes (an example of block communication holes in the claims) 18 that connect each cylinder chamber 17 to the outside of the cylinder block 4 are formed in the end 4a of the cylinder block 4 at positions corresponding to each cylinder chamber 17.

[0056] A piston 21 is housed in each cylinder chamber 17 so as to be slidable along the axial direction, causing the piston 21 to rotate around the central axis CL as the shaft 3 and the cylinder block 4 rotate. A cavity is formed inside the piston 21 to store the hydraulic oil in the cylinder chamber 17. The sliding movement of the piston 21 is linked to the intake and discharge of hydraulic oil into the cylinder chamber 17.

[0057] That is, when the piston 21 is pulled out from the cylinder chamber 17, the spatial volume within the cylinder chamber 17 increases, and hydraulic oil is sucked into the cylinder chamber 17 through the communicating hole 18 (suction stroke). From bottom dead center, where the piston 21 is pulled out to the furthest extent from the cylinder chamber 17, the piston 21 moves forward into the cylinder chamber 17. When the piston 21 moves forward into the cylinder chamber 17, the spatial volume within the cylinder chamber 17 decreases, and hydraulic oil is discharged from the cylinder chamber 17 through the communicating hole 18 (discharge stroke). Then, the movement of the piston 21 changes again from top dead center, where the piston 21 is furthest forward into the cylinder chamber 17, to bottom dead center.

[0058] A spherical protrusion 28 is integrally formed on the end of the piston 21 on the front flange 10 side. A plurality of shoes 22 are attached to the protrusion 28. The shoes 22 are used to correlate the sliding movement of the piston 21 with the inclination of the swash plate 5. A spherical recess 22a is formed on the surface of the shoe 22 that receives the protrusion 28 so as to correspond to the shape of the protrusion 28. The protrusion 28 of the piston 21 is fitted into the inner wall surface of the recess 22a. The shoes 22 are rotatably connected to the protrusion 28 of the piston 21.

[0059] The spring 23 housed in the recess 20 of the cylinder block 4 is, for example, a coil spring. The spring 23 is compressed between two retainers 24a, 24b housed in the recess 20. The spring 23 generates a pressing force in the direction of extension due to its elastic force. The pressing force of the spring 23 is transmitted to a connecting member 26 via one of the two retainers 24a, 24b, retainer 24b. The pressing force of the spring 23 is transmitted via the connecting member 26 to a pressing member 27 fitted onto the outer peripheral surface of the shaft main body 131.

[0060] The swash plate 5 is mounted on the inner surface 10a of the front flange 10 on the casing body 9 side. The swash plate 5 is tilted relative to the front flange 10 to restrict the axial displacement of each piston 21. An insertion hole 32 for inserting the shaft 3 is formed in the radial center of the swash plate 5. The swash plate 5 has a flat sliding surface 5a formed on the cylinder block 4 side. A plurality of shoes 22 move on this sliding surface 5a.

[0061] Each shoe 22 is integrated by a shoe retaining member 29. The pressing member 27 contacts the shoe retaining member 29 and presses the shoe retaining member 29 toward the swash plate 5. The shoes 22 move to follow the sliding surface 5a of the swash plate 5. This causes the pistons 21, which revolve around the central axis CL, to slide relative to the cylinder chamber 17. That is, the sliding distance of the pistons 21 is controlled by the swash plate 5. In other words, the sliding distance of the pistons 21 is determined by the inclination angle of the swash plate 5. In other words, the swash plate 5 controls the amount of hydraulic oil discharged from the main pump 1. The inclination angle of the swash plate 5 is controlled by an actuator (not shown). These details will be described later.

[0062] <Valve plate> The valve plate 19 is disposed between the end face 4b of the end 4a of the cylinder block 4 and the inner surface 119a of the bottom wall 119 of the casing body 9. The valve plate 19 is formed in a disk shape. The valve plate 19 is non-rotatably attached to the bottom wall 119 of the casing body 9. That is, although the valve plate 19 does not rotate relative to the bottom wall 119 of the casing body 9, it may move away from the inner surface 119a of the bottom wall 119. The valve plate 19 remains stationary relative to the main casing 2 (casing body 9) even when the cylinder block 4 and shaft 3 rotate around the central axis CL. The cylinder block 4 is supported by the static pressure of the oil film of hydraulic oil formed between the valve plate 19 and the end face 4b of the cylinder block 4.

[0063] Fig. 3 is a plan view of the valve plate 19 as seen from the first surface 41a side on the cylinder block 4 side. Fig. 4 is a plan view of the valve plate 19 as seen from the second surface 41b side on the bottom wall 119 side. Fig. 5 is a cross-sectional view taken along line AA in Fig. 4. 3 to 5, a through hole 42 for inserting the shaft 3 is formed in the radial center of the valve plate 19, penetrating the valve plate 19 in the thickness direction. An inner recess 43 that is annular when viewed from the axial direction is formed in the first surface 41a of the valve plate 19 so as to surround the periphery of the through hole 42 and to communicate with the through hole 42. In addition, an outer recess 44 that is annular is formed in the first surface 41a of the valve plate 19 along the outer periphery.

[0064] Intake ports 19a, which communicate with the respective communication holes 18 of the cylinder block 4, are formed through the valve plate 19 in the thickness direction of the valve plate 19. The outer shape of the intake port 19a is, for example, an arc shape within a predetermined angle range around the central axis CL, and is also formed into an elliptical shape. Each cylinder chamber 17 communicates with a first communication passage 124 formed in the casing body 9 via an intake port 19 a of the valve plate 19 and a communication hole 18 in the cylinder block 4 .

[0065] Discharge port 19b is formed between second surface 41b of valve plate 19 and the center in the thickness direction of valve plate 19. Discharge port 19b is formed in a circular shape when viewed in the axial direction. Discharge port 19b is located on the opposite side of the circumferential center of suction port 19a, with through hole 42 in between. A long recess 45 communicating with the discharge port 19b is formed between the first surface 41a of the valve plate 19 and the center of the valve plate 19 in the thickness direction, on the opposite side of the through hole 42 from the suction port 19a.

[0066] The long recess 45 communicates with the discharge port 19b and is therefore part of the discharge port 19b. The long recess 45 is formed, for example, in an arc shape within a predetermined angular range around the central axis CL and in an elliptical shape. The long recess 45 and the suction port 19a are arranged on the same pitch circle. Each cylinder chamber 17 communicates with a third communication passage 128 formed in the casing body 9 via the discharge port 19 b of the valve plate 19 , the elongated recess 45 , and the communication hole 18 of the cylinder block 4 .

[0067] A pair of switching lands 47a, 47b (bottom dead center switching land 47a and top dead center switching land 47b) is formed on the first surface 41a of the valve plate 19 between both longitudinal ends of the suction port 19a and both longitudinal ends of the elongated recess 45. In other words, the suction port 19a and the elongated recess 45 are formed on both sides of the pair of switching lands 47a, 47b. The pair of switching lands 47a, 47b are flush with the first surface 41a. When the cylinder block 4 is rotated, the communication hole 18 of the cylinder block 4 switches between communicating with the suction port 19a and communicating with the elongated recess 45 via the pair of switching lands 47a, 47b.

[0068] In the following description, of the pair of switching lands 47a, 47b, the switching land 47a corresponding to the position where the movement of the piston 21 transitions from bottom dead center to top dead center will be referred to as bottom dead center switching land 47a. Also, of the pair of switching lands 47a, 47b, the switching land 47b corresponding to the position where the movement of the piston 21 transitions from top dead center to bottom dead center will be referred to as top dead center switching land 47b.

[0069] Piston accommodating recesses 49 are 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 longitudinal ends of the long recess 45. The piston accommodating recess 49 is formed in a circular shape when viewed in the axial direction. The diameter of the piston accommodating recess 49 is larger than the diameter of the discharge port 19b. The piston accommodating recess 49 communicates with both longitudinal ends of the long recess 45.

[0070] A disk-shaped pressing piston 46 is housed in the piston housing recess 49. The central axis Co of the pressing piston 46 is along the axial direction. The diameter of the pressing piston 46 is approximately the same as or slightly smaller than the diameter of the piston housing recess 49.

[0071] 3, a notch 50 is formed in the first surface 41a of the valve plate 19. The notch 50 extends from one of the longitudinal ends of the long recess 45, one of which is located on the bottom dead center switching land 47a side, toward the bottom dead center switching land 47a (the longitudinal end of the suction port 19a). The notch 50 is tapered from the longitudinal end of the long recess 45 toward the longitudinal end of the suction port 19a when viewed in the axial direction. The notch 50 is also formed so that the depth of the notch gradually decreases from the longitudinal end of the long recess 45 toward the longitudinal end of the suction port 19a.

[0072] <Pressing unit> FIG. 6 is an enlarged view of part B in FIG. 2 and 6, a pressing unit 60 is provided in the third communication passage 128 in the bottom wall 119 of the casing main body 9. The pressing unit 60 presses the valve plate 19 toward the cylinder block 4, and its main purpose is to prevent hydraulic oil from leaking from between the valve plate 19 and the bottom wall 119 of the casing main body 9. The pressing unit 60 includes two bushings 61, 62 (a first bushing 61 and a second bushing 62; examples of the bushes in the claims) arranged on the valve plate 19 side of the third communication passage 128, and a coil spring 63 (an example of the internal casing elastic member in the claims) arranged on the opposite side of the valve plate 19 with the bushings 61, 62 in between.

[0073] FIG. 7 is an enlarged view of part C in FIG. As shown in Figures 6 and 7, two bushes 61, 62 are arranged side by side in the axial direction. The two bushes 61, 62 are provided so as to be separable from each other and can be displaced relative to each other. Of the two bushes 61, 62, the first bush 61 arranged on the valve plate 19 side is formed in a ring shape. The first bush 61 has a cross section along the axial direction that is rectangular. The valve plate 19 side of the first bush 61 has a flat surface 61a (an example of an end surface in the claims). This flat surface 61a comes into contact with the second surface 41b of the valve plate 19.

[0074] An arcuate surface (an example of a curved convex portion in the claims) 61b is formed on the axially opposite side of the flat surface 61a of the first bushing 61, from the inner peripheral edge to the outer peripheral edge. The arcuate surface 61b has an arcuate cross section along the axial direction so that the outer diameter gradually decreases toward the second bushing 62. The arcuate surface 61b is also formed so that the radially outward side is convex. Furthermore, the mechanical strength (hardness) of the first bushing 61 is lower than the mechanical strength (hardness) of the valve plate 19. In other words, the first bushing 61 is softer than the valve plate 19.

[0075] Of the two bushes 61, 62, the second bush 62, which is disposed on the opposite side of the first bush 61 from the valve plate 19, is formed in a cylindrical shape. The mechanical strength (hardness) of the second bush 62 is higher than the mechanical strength (hardness) of the first bush 61. In other words, the first bush 61 is softer than the second bush 62.

[0076] The axial length of the second bushing 62 is sufficiently longer than the axial length (thickness) of the first bushing 61. The inner diameter of the second bushing 62 is substantially 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 flat surface in the claims) 62a is formed around the entire periphery of the end face of the second bushing 62 on the first bushing 61 side. The inclined surface 62a is formed so that the diameter of the inner diameter of the second bushing 62 gradually increases as it approaches the first bushing 61 side. An arcuate surface 61b of the first bushing 61 abuts against this inclined surface 62a. The arcuate surface 61b abuts against the inclined surface 62a, so that the first bushing 61 and the second bushing 62 are in surface contact with each other.

[0077] A spring receiving recess 64 is formed in most of the radial center of the end face of the second bushing 62 opposite the first bushing 61. One end of a coil spring 63 is housed in this spring receiving recess 64. The coil spring 63 is housed in the third communication passage 128 in a slightly compressed and deformed state. Therefore, the elastic force of the coil spring 63 presses the bushings 61, 62 toward the valve plate 19. 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, and as a result, the valve plate 19 is pressed toward the cylinder block 4 by the pressing unit 60.

[0078] Here, the third communication passage 128 is formed to correspond to the shape of the pressing unit 60. That is, the third communication passage 128 has a bushing accommodating portion 65 and a spring accommodating portion 66 that are connected to and communicate with each other.

[0079] The bushing storage section 65 stores the two bushings 61, 62 of the pressing unit 60. The bushing storage section 65 is formed in a circular shape when viewed in the axial direction. The inner diameter of the bushing storage section 65 is approximately the same as or slightly larger than the outer diameter of the second bushing 62. In other words, the outer peripheral surface of the second bushing 62 is fitted onto the inner peripheral surface of the bushing storage section 65. Because the outer diameter of the first bushing 61 is smaller than the outer diameter of the second bushing 62, a gap is formed between the inner peripheral surface of the bushing storage section 65 and the outer peripheral surface of the first bushing 61. The axial length of the bushing storage portion 65 is slightly longer than the axial length of the first bushing 61 and the second bushing 62 stacked together.

[0080] The spring accommodating portion 66 is formed in a circular shape when viewed in the axial direction. The inner diameter of the spring accommodating portion 66 is smaller than the inner diameter of the bushing accommodating portion 65 via a step. More specifically, the inner diameter of the spring accommodating portion 66 is approximately the same as the outer diameter of the spring receiving recess 64 formed in the second bushing 62. A flat seating surface 66a is formed along the inner circumferential surface of the spring accommodating portion 66 at one end of the spring accommodating portion 66 opposite the bushing accommodating portion 65. The other end of the coil spring 63 abuts against this seating surface 66a. A discharge passage 123 is formed to communicate with one end and side of the bushing accommodating portion 65 formed in this manner.

[0081] <Gear pump> 2, a gear pump 111 provided on one side of the main pump 1 functions as an additional pump. The gear pump 111 includes a gear casing 141, and a drive gear and a driven gear (not shown). The rectangular parallelepiped gear casing 141 is disposed on the outer surface 119b of the bottom wall 119 of the main casing 2. A second suction passage 144 communicating with the second communication passage 125 of the main casing 2 is formed in a first wall surface 141a of the gear casing 141 that overlaps with the main casing 2. The second suction passage 144 connects the inside and outside of the first wall surface 141a of the gear casing 141.

[0082] A coupling insertion hole 149 is formed in a first wall surface 141a of the gear casing 141 at a position corresponding to the rotary shaft insertion hole 121 of the main casing 2. The end of the coupling 136 on the gear pump 111 side protrudes into the gear casing 141 through the coupling insertion hole 149. A third discharge passage (not shown) is formed in a second wall surface 141b of the gear casing 141 that is perpendicular to the first wall surface 141a and faces the same direction as the second side surface 119d of the main casing 2. An opening of the third discharge passage is formed in the second wall surface 141b.

[0083] A drive gear and a driven gear (not shown) are rotatably supported within a gear casing 141 and mesh with each other. The drive gear is connected to a coupling 136 that protrudes from the main casing 2 through a coupling insertion 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 and therefore rotates in synchronization with the drive gear.

[0084] <Pump unit operation> Next, the operation of the pump unit 110 will be described. First, the operation of the main pump 1 will be described. The main pump 1 outputs a driving force based on the discharge of hydraulic oil from the cylinder chamber 17 and the suction of hydraulic oil into the cylinder chamber 17 . More specifically, as the shaft 3 rotates due to 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 pistons 21 rotate around the central axis CL of the shaft 3.

[0085] The shoes 22 attached to the protrusions 28 of the pistons 21 are pressed against the sliding surfaces 5a of the swash plate 5 by the pressing force of the springs 23, regardless of the inclination angle of the swash plate 5. The protrusions 28 of the pistons 21 are spherical, and the recesses 22a of the shoes 22 into which the protrusions 28 fit are also spherical. The pressing members 27 apply pressure to the shoes 22 toward the swash plate 5 via the shoe retaining members 29. Even if the inclination angle of the swash plate 5 changes, the shoes 22 are pressed against the sliding surfaces 5a in accordance with the inclination of the swash plate 5.

[0086] As the cylinder block 4 rotates, the pistons 21 rotate around the central axis CL of the shaft 3, and each shoe 22 also moves on the sliding surface 5a of the swash plate 5 while rotating around the central axis CL of the shaft 3. As a result, each piston 21 slides axially within each cylinder chamber 17, performing reciprocating motion.

[0087] When the piston 21 moves from the top dead center to the bottom dead center, the cylinder chamber 17 (communication hole 18) housing the piston 21 passes above the suction port 19a from the long recess 45 of the valve plate 19, via the top dead center switching land 47b. At this time, hydraulic oil is sucked into the cylinder chamber 17 from the first suction passage 122 of the main casing 2, through the first communication passage 124, the suction port 19a, and the communication hole 18 (suction process).

[0088] On the other hand, when the piston 21 moves from the bottom dead center to the top dead center, the cylinder chamber 17 (communication hole 18) containing the piston 21 passes over the elongated recess 45 from the intake port 19a of the valve plate 19 via the bottom dead center switching land 47a. At this time, the hydraulic oil is discharged from the cylinder chamber 17 via the communication hole 18, the elongated recess 45, the discharge port 19b, the third communication passage 128, and the discharge path 123 (discharge process).

[0089] Note that, when the inclination angle of the swash plate 5 (sliding surface 5a) changes, the stroke (travel distance) of the reciprocating movement of the pistons 21 changes. The greater the inclination angle of the swash plate 5, the greater the amount of hydraulic oil drawn into and discharged from the cylinder chamber 17 due to the reciprocating movement of each piston 21. The smaller the inclination angle of the swash plate 5, the smaller the amount of hydraulic oil drawn into and discharged from the cylinder chamber 17 due to the reciprocating movement of each piston 21. When the inclination angle of the swash plate 5 is zero, each piston 21 does not reciprocate even when the piston 21 rotates around the central axis CL of the shaft 3. When the inclination angle of the swash plate 5 is zero, the amount of hydraulic oil discharged from each cylinder chamber 17 also becomes zero.

[0090] During the discharge stroke, the hydraulic oil discharged from the cylinder chamber 17 to the elongated recess 45 is also discharged to the piston accommodating recess 49 in addition to the discharge port 19b. Since the pressing piston 46 is accommodated in the piston accommodating recess 49, the pressure of the hydraulic oil presses the pressing piston 46 toward the inner surface 119a of the bottom wall 119 of the main casing 2. A pressing force that presses the valve plate 19 against the end face 4b of the cylinder block 4 is generated by the reaction force caused by the pressing piston 46 being pressed against the inner surface 119a of the bottom wall 119.

[0091] In addition, the hydraulic oil discharged from the cylinder chamber 17 forms an oil film between the second surface 41b of the valve plate 19 and the inner surface 119a of the bottom wall 119, excluding the through hole 42, the intake port 19a, the discharge port 19b, and the piston accommodating recess 49. The pressing force is generated by the pistons 21 housed in each cylinder chamber 17 of the cylinder block 4 pressing the cylinder block 4 against the valve plate 19. The pressing force also includes a reaction force of the hydraulic oil acting on the cylinder chambers 17 pressing the pressing pistons 46, and a force acting toward the cylinder block 4 by the pressing unit 60, as forces that move the valve plate 19 toward the cylinder block 4.

[0092] Furthermore, the hydraulic oil discharged from the cylinder chamber 17 forms an oil film between the end face 4b of the cylinder block 4 and the first surface 41a of the valve plate 19, excluding the through-hole 42, the suction port 19a, the elongated recess 45, the inner recess 43, and the outer recess 44. The reaction force of this oil film acts as a separation force that pulls the valve plate 19 away from the end face 4b of the cylinder block 4. Other separation forces include hydraulic pressure acting on the end face 4b of the cylinder block 4 from the suction port 19a and the discharge port 19b of the valve plate 19. The balance between these pressing forces and separation forces maintains the proper positional relationship between the cylinder block 4 and the valve plate 19.

[0093] However, there is a possibility that the balance between the pressing force and the separating force will be lost, causing the cylinder block 4 to tilt relative to the shaft 3. Following this, there is a possibility that the valve plate 19 will also tilt relative to the shaft 3. If the valve plate 19 tilts, the first bushing 61 will also tilt accordingly. Here, a gap is formed between the inner peripheral surface of the bushing accommodating portion 65 and the outer peripheral surface of the first bushing 61. Even if the first bushing 61 tilts inside the bushing accommodating portion 65, the inner peripheral surface of the bushing accommodating portion 65 and the outer peripheral surface of the first bushing 61 will not interfere with each other. Moreover, the axial length (thickness) of the first bushing 61 is sufficiently short compared to the axial length of the second bushing 62. Therefore, even if the first bushing 61 tilts, the amount of radial displacement of the first bushing 61 is small, so interference between the inner peripheral surface of the bushing accommodating portion 65 and the outer peripheral surface of the first bushing 61 is reliably prevented.

[0094] On the other hand, the second bushing 62, which is separated from the first bushing 61, is fitted into the inner peripheral surface of the bushing storage portion 65, and therefore the second bushing 62 does not tilt. Furthermore, the axial length of the bushing storage portion 65 is slightly longer than the axial length of the overlapping first bushing 61 and second bushing 62. Therefore, even if the second bushing 62 slides so that the coil spring 63 is compressed and deformed slightly due to tilting of the first bushing 61, the second bushing 62 can be prevented from hitting the step surface 65a between the bushing storage portion 65 and the spring storage portion 66. In other words, the second bushing 62 is allowed to slide within the bushing storage portion 65.

[0095] Here, the first bushing 61 and the second bushing 62 are in contact with each other such that the arcuate surface 61b of the first bushing 61 contacts the inclined surface 62a of the second bushing 62. The arcuate surface 61b allows the first bushing 61 to tilt smoothly relative to the second bushing 62. Even if the first bushing 61 tilts, the arcuate surface 61b only displaces the contact position between the arcuate surface 61b and the inclined surface 62a, ensuring that the contact between the arcuate surface 61b and the inclined surface 62a is maintained. Because the position of the second bushing 62 remains unchanged, the elastic force of the coil spring 63 is reliably applied to the second bushing 62, ensuring that the degree of contact between the arcuate surface 61b and the inclined surface 62a is maintained. This prevents hydraulic oil from leaking between the valve plate 19 and the first bushing 61 or the second bushing 62. As a result, hydraulic oil is prevented from leaking between the valve plate 19 and the bottom wall 119 of the casing body 9.

[0096] Next, the operation of the gear pump 111 will be described. The drive gear of the gear pump 111 is connected to the shaft 3 of the main pump 1 via a coupling 136, and therefore rotates integrally with the shaft 3. The driven gear meshed with the drive gear also rotates synchronously with the drive gear. Hydraulic oil flowing through the first suction passage 122 via the second communication passage 125 of the main casing 2 is sucked into the second suction passage 144. The hydraulic oil flows between each gear and the inner surface of the gear casing 141 to the third discharge passage (not shown). The hydraulic oil is discharged through the opening of the third discharge passage.

[0097] As described above, in the main pump 1 according to the first embodiment, the pressing unit 60 is housed in the third communication passage 128. The pressing unit 60 includes two bushings 61, 62 that are separable from each other and a coil spring 63 that presses the two bushings 61, 62 toward the valve plate 19. Therefore, even if the valve plate 19 tilts relative to the shaft 3, the first bushing 61 of the two bushings 61, 62 can reliably follow the tilt of the valve plate 19. Furthermore, by using two bushings 61, 62, the amount of radial displacement when one bushing (the first bushing 61) tilts can be reduced compared to when the two bushings 61, 62 are integral. In other words, because only the first bushing 61 tilts, interference between the outer circumferential surface of the first bushing 61 and the inner circumferential surface of the bushing storage portion 65 can be prevented. As a result, it is possible to prevent gaps from being generated between the valve plate 19 and each of the bushes 61, 62, and to prevent the hydraulic oil from leaking out from between the valve plate 19 and the bushes 61, 62. Therefore, it is possible to prevent a decrease in the performance of the main pump 1.

[0098] Moreover, the two bushes 61, 62 alone can follow the inclination of the valve plate 19, and leakage of hydraulic oil from between the valve plate 19 and the bushes 61, 62 can be prevented, so that a high-performance main pump 1 can be provided while suppressing an increase in the number of parts in the main pump 1 as a whole. Furthermore, since the two bushes 61, 62 are separable from each other, it is possible to easily replace each of the bushes 61, 62. This makes it possible to provide a main pump 1 that is easy to maintain.

[0099] Furthermore, by forming the arc surface 61b on the first bushing 61 and the inclined surface 62a on the second bushing 62, the first bushing 61 and the second bushing 62 can be in surface contact with each other without any gaps even if the first bushing 61 is tilted relative to the shaft 3. This makes it possible to increase the degree of contact between the first bushing 61 and the second bushing 62 with a simple structure. Furthermore, since the surface pressure acting between the bushings 61 and 62 can be reduced, the product life of the bushings 61 and 62 can be extended. Furthermore, since the first bushing 61 can be smoothly tilted relative to the second bushing 62, the ability of the first bushing 61 to follow the tilt of the valve plate 19 can be improved.

[0100] Furthermore, the mechanical strength (hardness) of the second bushing 62 is greater than that of the first bushing 61. In this way, by changing the mechanical strength (hardness) of the two bushings 61, 62, it is possible to reduce the number of bushes that actively wear down to one. In other words, it is possible to make the first bushing 61 more susceptible to wear. Therefore, during maintenance, only the first bushing 61 needs to be replaced, and the maintenance costs for the bushings 61, 62 as a whole can be reduced.

[0101] Furthermore, by making the first bush 61, which is disposed on the valve plate 19 side of the two bushes 61, 62, soft (by weakening its mechanical strength), it is possible to suppress wear of the valve plate 19 which comes into contact with the first bush 61. Since the manufacturing cost of the valve plate 19 is higher than the manufacturing cost of the first bush 61, by actively causing wear of the first bush 61 out of the valve plate 19 and the first bush 61, it is possible to reduce the frequency of replacing the valve plate 19 and reduce the maintenance cost of the main pump 1.

[0102] In the first embodiment described above, the pressing unit 60 is described as including the coil spring 63 that presses the two bushings 61, 62 against the valve plate 19. However, this is not limited to this, and various elastic members that can press the two bushings 61, 62 against the valve plate 19 can be used. For example, rubber or the like can be used instead of the coil spring 63.

[0103] In the first embodiment described above, the two bushes 61 and 62 constituting the pressing unit 60 are separable from each other. Furthermore, the first bush 61 of the two bushes 61 and 62 has an arcuate surface 61b, and the second bush 62 has an inclined surface 62a. The arcuate surface 61b and the inclined surface 62a are abutted against each other, resulting in surface contact between the first bush 61 and the second bush 62. However, this is not limiting, and the arcuate surface 61b and the inclined surface 62a may be reversed. That is, the first bush 61 may have an inclined surface such that the outer diameter gradually decreases toward the second bush 62. The second bush 62 may have an arcuate surface such that the inner diameter of the second bush 62 gradually increases toward the first bush 61. The first bush 61 and the second bush 62 may also be configured as follows.

[0104] [First Modification] Fig. 8 is an enlarged cross-sectional view of the main parts of two bushings 61, 62 in a first modified example of the first embodiment. Fig. 8 corresponds to the above-mentioned Fig. 7. In the following explanation, the same features as those in the above-mentioned first embodiment are given the same reference numerals and explanations thereof will be omitted (the same applies to the following modified example and second embodiment). 8, instead of the inclined surface 62a of the second bushing 62, an arcuate surface (an example of a curved surface in the claims) 62b may be formed on the second bushing 62. The arcuate surface 62b has an arcuate cross section along the axial direction so that the inner diameter gradually increases toward the first bushing 61. The arcuate surface 62b is also formed so that its radially inner side is concave. The radius of curvature R2 of the arcuate surface 62b of the second bushing 62 is greater than the radius of curvature R1 of the arcuate surface 61b of the first bushing 61.

[0105] Therefore, according to the first modified example described above, the two bushes 61, 62 can be brought into contact with each other more smoothly. As a result, the surface pressure acting between the bushes 61, 62 can be reduced, thereby extending the product life of the bushes 61, 62. In addition, the first bush 61 can be more easily and reliably tilted relative to the second bush 62. 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, so that the arcuate surface 61b of the first bushing 61 can be contained within the arcuate surface 62b of the second bushing 62. Furthermore, because the arcuate surfaces 61b, 62b are in contact with each other, the first bushing 61 can be smoothly tilted relative to the second bushing 62. This further improves the ability of the first bushing 61 to follow the valve plate 19.

[0106] [Second Modification] FIG. 9 is a cross-sectional view of two bushings 61 and 62 in a second modified example of the first embodiment. As shown in FIG. 9, the difference between the first and second modified examples described above is that in the first modified example, the two bushings 61, 62 are provided separably from each other, whereas in the second modified example, the two bushings 61, 62 are integrated.

[0107] More specifically, a convex portion 71 that protrudes toward the inner peripheral surface of the second bushing 62 is integrally formed on the end face of the first bushing 61 facing the second bushing 62. The outer diameter of the convex portion 71 is slightly smaller than the inner diameter of the second bushing 62. A constricted portion 72 is formed on the convex portion 71 slightly before the tip of the convex portion 71. The constricted portion 72 is formed so that its cross section along the axial direction is U-shaped. The minimum outer diameter of the constricted portion 72 is smaller than the outer diameter of the tip of the convex portion 71.

[0108] An inner flange portion 73 that protrudes radially inward is integrally formed with the second bushing 62 at the end (base end) of the arcuate surface 62b opposite the first bushing 61. A surface 73a of the inner flange portion 73 facing the first bushing 61 has an arc-shaped cross section along the axial direction so as to smoothly connect with the arcuate surface 62b. A rounded chamfered portion 73b is formed at the radially inner end of the inner flange portion 73 so as to correspond to the shape of the constricted portion 72 of the protrusion 71 of the first bushing 61. Such an inner flange portion 73 is housed within the constricted portion 72. As a result, the first bushing 61 and the second bushing 62 engage with each other while allowing tilting of the first bushing 61 relative to the second bushing 62 and restricting movement of the first bushing 61 relative to the second bushing 62.

[0109] As described above, in the second modified example, the two bushings 61, 62 are integrated and relatively displaceable. In other words, the two bushings 61, 62 are a single assembly that is relatively displaceable. This allows the two bushings 61, 62 to be easily assembled into the third communication passage 128. This makes it possible to provide a main pump 1 that is easy to assemble.

[0110] [Third Modification] FIG. 10 is a cross-sectional view of two bushings 61 and 62 in a third modified example of the first embodiment. As shown in Figure 10, the difference between the second and third modified examples described above is that in the second modified example, the bushes 61 and 62 engage with each other at the outer peripheral surface side of the first bush 61 and the inner peripheral surface side of the second bush 62, whereas in the third modified example, the bushes 61 and 62 engage with each other at the inner peripheral surface side of the first bush 61 and the outer peripheral surface side of the second bush 62.

[0111] More specifically, an arcuate surface 61c is formed on the inner circumferential surface of the first bushing 61 on the side of the second bushing 62. The arcuate surface 61c is formed in an arc shape such that the inner diameter gradually increases toward the second bushing 62. The arcuate surface 61c is also formed so that the radially inner side is concave. A first protrusion 74 protruding toward the second bush 62 is integrally formed on the end face of the first bush 61 on the second bush 62 side. The outer diameter of the first protrusion 74 is the same as the outer diameter of the first bush 61. A first recess 75 is formed around the entire circumference of the first protrusion 74, slightly before the tip of the first protrusion 74. The first recess 75 is formed so that its cross section along the axial direction is U-shaped. The maximum inner diameter of the first recess 75 is larger than the inner diameter of the tip of the first protrusion 74. A rounded chamfer 74a is formed on the radially inner side of the first protrusion 74.

[0112] A second protrusion 76 that protrudes toward the inner peripheral surface of the first protrusion 74 is integrally formed on the end surface of the second bushing 62 facing the first bushing 61. An arcuate surface 76a is formed on the outer peripheral surface of the second protrusion 76 to correspond to the arcuate surface 61c of the first protrusion 74. The arcuate surface 76a is formed in an arc shape such that the outer diameter gradually decreases toward the first bushing 61. The arcuate surface 76a is also formed so that its radially outward surface is convex. 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 comes into contact with the arcuate surface 61c of the first bushing 61.

[0113] A second recess 77 is formed around the entire outer periphery of the base end opposite the tip of the second protrusion 76. The second recess 77 is formed so that its cross section along the axial direction is U-shaped. The first protrusion 74 is housed within this second recess 77. This allows the first bushing 61 to tilt relative to the second bushing 62, but the first bushing 61 engages with the second bushing 62 in a state where movement of the first bushing 61 relative to the second bushing 62 is restricted.

[0114] Therefore, according to the third modified example, it is possible to achieve the same effects as the second modified example.

[0115] [Other variations] In the first embodiment and the first to third modified examples described above, the pressing unit 60 is described as including two bushes 61 and 62. However, this is not limited to this, and the pressing unit 60 may include two or more bushes. In the above description, the first bushing 61 has arcuate surfaces 61b and 61c, and the second bushing 62 has arcuate surfaces 62b and 76a. However, this is not limiting, and the arcuate surfaces 61b, 61c, 62b, and 76a may be replaced with curved surfaces. A curved surface refers to a cross-sectional shape along the axial direction that is not an arc but is curved.

[0116] Furthermore, both the first bushing 61 and the second bushing 62 may have a convex arc surface. Even in this case, the same effects as those of the first embodiment can be achieved.

[0117] In the first embodiment and the first to third modified examples described above, the first bushing 61 is described as being separate from the valve plate 19. However, this is not limited to this, and the valve plate 19 and the first bushing 61 may be integrated together. When the pressing unit 60 includes two or more bushings, the bushing closest to the valve plate 19 may be integrated with the valve plate 19. This configuration reduces the number of parts in the main pump 1. As a result, the manufacturing costs of the main pump 1 as a whole can be reduced.

[0118] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. Fig. 11 is a plan view of the valve plate 219 in the second embodiment, viewed from the second surface 241b side on the bottom wall 119 side of the casing main body 9. Fig. 11 corresponds to the above-mentioned Fig. 4. Fig. 12 is an enlarged cross-sectional view of a portion of the valve plate 219 and the bottom wall 119 of the casing main body 9. As shown in Figures 11 and 12, the difference between the second embodiment and the first embodiment is that the valve plate 219 of the second embodiment has a spring storage recess (an example of a recess in the claims) 82 formed on the second surface 241b to store a small spring (an example of a small elastic member in the claims) 81, whereas the valve plate 19 of the first embodiment does not have a spring storage recess 82 formed therein.

[0119] The small spring 81 is for pressing the valve plate 19 toward the cylinder block 4 . Two first spring accommodating recesses 82 are formed on the second surface 241b of the valve plate 219. The two first spring accommodating recesses 82 are arranged between both longitudinal ends of the suction port 19a and the piston accommodating recess 49. The diameter of the first spring accommodating recess 82 is smaller than the diameter of the piston accommodating recess 49. However, this is not a limitation, and the diameter of the first spring accommodating recess 82 may be any size that allows the first spring accommodating recess 82 to be formed on the second surface 241b of the valve plate 219.

[0120] The depth of the first spring accommodating recess 82 is approximately half the thickness of the valve plate 219. However, this is not limited to this, and the depth of the first spring accommodating recess 82 may be any depth that ensures the mechanical strength of the valve plate 219. Meanwhile, a second spring accommodating recess 83 is formed in the bottom wall 119 of the casing body 9 at a position on the inner surface 119a corresponding to the first spring accommodating recess 82. The shape of the second spring accommodating recess 83 corresponds to the shape of the first spring accommodating recess 82. In other words, the diameter and depth of the second spring accommodating recess 83 are approximately the same as the diameter and depth of the first spring accommodating recess 82.

[0121] The second surface 241b of the valve plate 219 overlaps the inner surface 119a of the bottom wall 119, and a spring storage section 84 is formed between the bottom wall 119 and the valve plate 219 by the spring storage recesses 82, 83. The small spring 81 is stored in this spring storage section 84 in a slightly compressed state. As a result, the elastic force of the small spring 81 is pressed against the valve plate 219.

[0122] Therefore, according to the second embodiment described above, the small spring 81 can increase the pressing force of the valve plate 219 against the cylinder block 4. This increases the degree of contact between the cylinder block 4 and the valve plate 219. As a result, it is possible to prevent hydraulic oil from leaking from between the cylinder block 4 and the valve plate 219, further improving the performance of the main pump 1.

[0123] Furthermore, by forming the first spring accommodating recess 82 in the valve plate 219, the free length of the small spring 81 can be made as long as possible while preventing the axial length of the main pump 1 from becoming too long. This makes it possible to increase the spring force of the small spring 81 and more reliably increase the degree of contact between the cylinder block 4 and the valve plate 219. This therefore more reliably improves the performance of the main pump 1.

[0124] In the second embodiment described above, the small spring 81 is provided between the valve plate 219 and the bottom wall 119 of the casing body 9. However, this is not limited to this, and various elastic members that can press the valve plate 19 toward the cylinder block 4 can be used. For example, rubber or the like can be used instead of the small spring 81.

[0125] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above embodiment, the construction machine 100 is a hydraulic excavator, but the present invention is not limited to this and various construction machines can be used.

[0126] In the above-described embodiment, the main pump 1 using hydraulic oil as the fluid has been described as the fluid machine. However, the present invention is not limited to this, and the configurations of the above-described embodiments and modifications can be applied to various fluid machines using various fluids other than hydraulic oil. For example, the configurations of the above-described embodiments and modifications can be applied to a hydraulic motor as the fluid machine.

[0127] In the above embodiment, the disk-shaped pressing piston 46 is housed in the piston housing recess 49 formed in the valve plate 19. However, it is sufficient if a pressing force is generated on the valve plate 19 toward the cylinder block 4 by the pressure of the hydraulic oil discharged into the piston housing recess 49. For example, the pressing piston 46 does not have to be provided in the piston housing recess 49. Also, a compression coil spring or the like may be housed in the piston housing recess 49 instead of the pressing piston 46. The elastic force of this compression coil spring may apply a pressing force to the valve plate 19 toward the cylinder block 4.

[0128] Among the embodiments disclosed in this specification, those that are comprised of multiple objects may be integrated, and conversely, those that are comprised of a single object may be separated into multiple objects. Regardless of whether they are integrated, it is sufficient that they are configured to achieve the object of the invention. [Explanation of symbols]

[0129] 1...Main pump (fluid machinery), 2...Main casing (casing), 4...Cylinder block, 9...Casing body (casing), 17...Cylinder chamber, 18...Communicating hole, 19, 219...Valve plate, 19b...Discharge port, 21...Piston, 60...Pressing unit, 61...First bush (bush), 61b...Circular surface (curved convex portion), 62...Second bush (bush), 62a...Inclined surface (flat surface), 62b...Circular surface (curved surface), 63...Coil spring (Casing interior elastic member), 81...Small spring (Small elastic member), 82...First spring storage recess (recess), 123...Discharge passage, 128...Third communication passage (discharge passage), R1, R2...Curvature radius

Claims

1. a cylinder block having a cylinder chamber in which a piston is accommodated and a communication hole that connects the inside and outside of the cylinder chamber; a casing that houses the cylinder block and has a discharge passage; a valve plate disposed between the cylinder block and the casing; a plurality of bushes arranged side by side in the axial direction of the piston in the discharge passage so as to be relatively displaceable; a casing internal elastic member that is provided in the discharge passage and presses the plurality of bushes toward the valve plate; a pressing member that presses the valve plate toward the cylinder block; Equipped with The valve plate is a discharge port that connects the communication hole and the discharge path; a pressing member accommodating recess formed on a second surface opposite to the first surface on the cylinder block side, the pressing member accommodating recess configured to accommodate the pressing member; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed on the first surface side; Including, The communication recess communicates the discharge port main body with the pressing member accommodating recess.

2. The plurality of bushes are separable from one another. The fluid machinery according to claim 1 .

3. The fluid machinery according to claim 1 , wherein the plurality of bushes are connected to each other to form an assembly.

4. The fluid machine according to any one of claims 1 to 3, wherein end faces of the bushes in the axial direction are in line contact with each other.

5. The axial end face of at least one of the two bushings that contact each other has a curved convex portion that protrudes toward the axial end face of the other bushing. The fluid machinery according to claim 4.

6. the one end surface of the bushing has the curved convex portion that is convex on the radially outer side, The other end surface of the bushing has a flat surface whose diameter gradually increases toward the one end surface. The fluid machinery according to claim 5.

7. The fluid machine according to claim 5 , wherein the one end surface and the other end surface of the bushing have the curved convex portion.

8. the one end surface of the bushing has the curved convex portion that is convex on the radially outer side, The other end surface of the bushing has a curved surface whose diameter gradually increases toward the one end surface. The fluid machinery according to claim 5.

9. The fluid machine according to claim 8 , wherein the curved convex portion and the curved surface have a cross section along the axial direction that is formed in an arc shape.

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

11. The fluid machine according to any one of claims 1 to 10, wherein one of the plurality of bushes is softer than the other bushes.

12. Among the plurality of bushes, the bush arranged closest to the valve plate is softer than the other bushes. The fluid machinery according to claim 11.

13. Of the plurality of bushes, the bush arranged closest to the valve plate is integrated with the valve plate. The fluid machinery according to any one of claims 1 to 12.

14. a small elastic member provided between the valve plate and the casing for pressing the valve plate toward the cylinder block; A recess for receiving the small elastic member is provided in the valve plate. The fluid machinery according to any one of claims 1 to 13.

15. The car body and a fluid machine that draws in and discharges fluid that serves as a driving source for the vehicle body, The fluid machine includes: a cylinder block having a cylinder chamber in which a piston is accommodated and a communication hole that connects the inside and outside of the cylinder chamber; a casing that houses the cylinder block and has a discharge passage; a valve plate disposed between the cylinder block and the casing; a bushing having an end surface that abuts against the valve plate inclined in accordance with the inclination of the valve plate; a casing internal elastic member that is provided in the discharge passage and presses the bushing toward the valve plate; a pressing member that presses the valve plate toward the cylinder block; Equipped with In the axial direction of the piston, one end surface of the two bushes that come into contact has a curved convex portion that protrudes toward the other end surface and is convex on the radially outward side, the other end surface of the bushing has a curved surface whose diameter gradually increases toward the one end surface, the curved convex portion and the curved surface are formed to have an arc-shaped cross section, and the radius of curvature of the curved convex portion is smaller than the radius of curvature of the curved surface; The valve plate is a discharge port that connects the communication hole and the discharge path; a pressing member accommodating recess formed on a second surface opposite to the first surface on the cylinder block side, the pressing member accommodating recess configured to accommodate the pressing member; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed on the first surface side; Including, The communication recess communicates the discharge port body with the pressing member accommodating recess. Construction machinery.

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