Fluid machinery and construction machinery

Abstract

To provide a fluid machine and a construction machine capable of suppressing the machining cost of a valve plate and of achieving sufficient effects of preventing the corrosion of a cylinder chamber.SOLUTION: A main pump in the embodiment includes a cylinder block, a piston slidably stored in the cylinder chamber, a casing storing the cylinder block, and a valve plate 19 arranged between the cylinder block and the casing, the valve plate 19 having a suction port, a discharge port formed on the opposite side to the suction port across a pair of changeover lands formed on a first face 41a, a piston storage recessed part 49 storing a pressing piston, and a valve plate communication hole 51 communicating the piston storage recessed part 49 with the changeover land.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. Pistons are housed in these cylinder chambers so that they 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 port communicates with an suction passage in the pump casing. The discharge port communicates with a discharge passage in the pump casing. A switching land facing the second end of the cylinder block is formed between the suction port and the discharge port on the end face of the valve plate facing the cylinder block.

[0004] With this configuration, when the cylinder block rotates around the axis of the shaft, each cylinder chamber rotates around the shaft and alternately connects to the suction port and the discharge port via the switching land of the valve plate. When the cylinder chamber connects to the suction port, the piston slides within the cylinder chamber to increase the volume of the interior space within the cylinder chamber. This causes hydraulic oil to be drawn into the cylinder chamber from outside the pump casing via the suction passage and the suction port (suction stroke). On the other hand, when the cylinder chamber connects to the discharge port, the piston slides within the cylinder chamber to reduce the volume of the interior space within the cylinder chamber. This causes hydraulic oil to be discharged from the cylinder chamber to outside the pump casing via the discharge port and the discharge passage (discharge stroke).

[0005] Here, when the cylinder chamber connects to the discharge port, the cylinder chamber suddenly opens through the discharge port, which can cause a pressure difference that can result in hydraulic oil being sprayed back into the cylinder chamber. In such a case, the high-speed fluid (hydraulic oil) collides with the inner wall surface of the cylinder chamber, causing cavitation erosion (hereinafter referred to as corrosion). For this reason, a technique for forming a hole that connects the discharge port of the valve plate to the switching land of the valve plate has been disclosed (see, for example, Patent Document 1). Another technique for forming a notch in the switching land of the valve plate, located at the bottom dead center where the valve switches from the suction stroke to the discharge stroke, has also been disclosed (see, for example, Patent Document 2). Both techniques attempt to suppress sudden pressure changes in the cylinder chamber by introducing the pressure of the fluid on the discharge port side into the cylinder chamber. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 57-171086 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-174690 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned Patent Document 1, it is difficult to easily process the holes, which may increase the cost of processing the valve plate. Furthermore, in the above-mentioned Patent Document 2, the pressure of the discharge port is bypassed to the cylinder chamber immediately near the discharge port, which may make it difficult to obtain the effect of preventing corrosion.

[0008] The present invention provides a fluid machine and a construction machine that can reduce the processing costs of the valve plate and can obtain a sufficient corrosion prevention effect for the cylinder chamber. [Means for solving the problem]

[0009] a piston slidably housed in the cylinder chamber and configured to compress the cylinder chamber during a discharge stroke and expand the cylinder chamber during a suction stroke; a casing housing the cylinder block and having an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; and a pressing member configured to press the valve plate toward the cylinder block. The valve plate has an intake port communicating the block communication hole with the intake passage, a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, and communicating the block communication hole with the discharge passage, a pressing member accommodating recess formed on a second surface opposite the first surface at a position avoiding the suction passage and the discharge passage, and configured to accommodate the pressing member, and a valve plate communication hole communicating the pressing member accommodating recess with the switching land.

[0010] By forming the valve plate communication hole using the pressing member receiving recess in this way, the pressure at the discharge port can be bypassed to the switching land side via the valve plate communication hole, which prevents sudden pressure changes in the cylinder chamber, thereby reducing the processing cost of the valve plate and providing sufficient corrosion protection for the cylinder chamber.

[0011] In the above configuration, the valve plate may have a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is at the bottom dead center position where the piston switches from the suction stroke to the discharge stroke, and the valve plate communicating hole may be positioned at a position spaced from the tip of the notch on the opposite side from the discharge port toward the suction port.

[0012] In the above configuration, the valve plate may have a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at the bottom dead center position where the piston switches from the suction stroke to the discharge stroke, and the valve plate communicating hole may be located at the tip of the notch on the opposite side from the discharge port.

[0013] In the above configuration, the pressing member may be a small disc-shaped piston.

[0014] According to another aspect of the present invention, there is provided a fluid machine comprising: a cylinder block having a cylinder chamber and a block communication hole that communicates the inside and outside of the cylinder chamber; a piston that is slidably housed in the cylinder chamber and performs a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has a suction passage and a discharge passage; a valve plate that is arranged between the cylinder block and the casing; and a pressing member that presses the valve plate toward the cylinder block, wherein the valve plate has a suction port that communicates the block communication hole with the suction passage and a piston that is slidably housed in the cylinder chamber and performs a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a discharge port formed on the opposite side of the suction port across a pair of switching lands formed on a first surface on the side opposite the first surface, the discharge port communicating between the block communication hole and the discharge passage; a pressing member accommodating recess formed on a second surface opposite the first surface at a position avoiding the suction passage and the discharge passage, the pressing member accommodating recess being configured to accommodate the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at the bottom dead center position where the piston switches from the suction stroke to the discharge stroke; and a valve plate communication hole located at a position away from the tip of the notch on the opposite side of the discharge port toward the suction port, the valve plate communication hole communicating between the pressing member accommodating recess and the switching land.

[0015] With this configuration, the valve plate communication hole is formed by utilizing the pressing member accommodating recess, and the pressure at the discharge port is transmitted through this valve plate communication hole. under This allows the valve plate to be bypassed to the dead center switching land side, preventing back injection of fluid into the cylinder chamber during the discharge stroke, thereby reducing the processing cost of the valve plate and providing sufficient corrosion protection for the cylinder chamber.

[0016] According to another aspect of the present invention, there is provided a fluid machine comprising: a cylinder block having a cylinder chamber and a block communication hole that communicates the inside and outside of the cylinder chamber; a piston that is slidably housed in the cylinder chamber and performs a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has a suction passage and a discharge passage; a valve plate that is arranged between the cylinder block and the casing; and a pressing member that presses the valve plate toward the cylinder block, wherein the valve plate has a suction port that communicates the block communication hole with the suction passage, and The piston has a discharge port formed on the opposite side of the intake port, across a pair of switching lands formed on a first surface on the cylinder block side, and communicating the block communication hole with the discharge path; a pressing member accommodating recess formed on a second surface opposite the first surface at a position avoiding the intake port and the discharge port, and accommodating the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at the bottom dead center position where the piston switches from the intake stroke to the discharge stroke; and a valve plate communication hole located at the tip of the notch on the opposite side of the discharge port, and communicating the pressing member accommodating recess with the switching land.

[0017] Here, the switching land is formed by polishing the valve plate during the finish processing of the valve plate. In this case, by forming a valve plate communication hole at the tip of the notch, it is possible to prevent the distance between the notch and the valve plate communication hole from changing due to the polishing stock removal. In other words, although the tip position of the notch changes due to the polishing stock removal, by forming a valve plate communication hole at the tip of the notch, it is possible to prevent the distance between the notch and the valve plate communication hole from changing. Therefore, the effect of the valve plate communication hole can be stabilized regardless of the polishing stock removal.

[0018] 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 an actuator provided on the vehicle body, the fluid machine comprising: a cylinder block having a cylinder chamber and a block communication hole that communicates the inside and outside of the cylinder chamber; a piston that is slidably housed in the cylinder chamber and performs a discharge process that compresses the cylinder chamber and a suction process that expands the cylinder chamber; a casing that houses the cylinder block and has a suction passage and a discharge passage; a valve plate that is arranged between the cylinder block and the casing; and a pressing member that presses the valve plate against the cylinder block side. a discharge port formed on the opposite side of the suction port across a pair of switching lands formed on a first surface of the cylinder block side, the discharge port communicating the block communication hole with the discharge path; a pressing member accommodating recess formed on a second surface opposite the first surface at a position avoiding the suction port and the discharge port, and accommodating the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at the bottom dead center position where the piston switches from the suction stroke to the discharge stroke; and a valve plate communication hole located at a position away from the tip of the notch on the opposite side of the discharge port toward the suction port, the valve plate communication hole communicating the pressing member accommodating recess and the switching land.

[0019] By configuring it in this way, it is possible to provide a construction machine that can reduce the processing costs of the valve plate and obtain sufficient corrosion prevention effects for the cylinder chamber.

[0020] 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 an actuator provided on the vehicle body, the fluid machine comprising: a cylinder block having a cylinder chamber and a block communication hole that communicates the inside and outside of the cylinder chamber; a piston that is slidably housed in the cylinder chamber and performs a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has a suction passage and a discharge passage; a valve plate that is arranged between the cylinder block and the casing; and a pressing member that presses the valve plate toward the cylinder block side, the valve plate having a front end that is connected to the front end of the cylinder block. a discharge port formed on the opposite side of the suction port across a pair of switching lands formed on a first surface of the cylinder block side, the discharge port communicating with the block communication hole and the discharge path; a pressing member accommodating recess formed on a second surface opposite the first surface at a position avoiding the suction port and the discharge port, the pressing member accommodating recess; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at the bottom dead center position where the piston switches from the suction stroke to the discharge stroke; and a valve plate communication hole located at the tip of the notch on the opposite side of the discharge port, the pressing member accommodating recess and the switching land communicating with each other.

[0021] By configuring in this manner, it is possible to provide a construction machine that can stabilize the effect of the valve plate through-hole regardless of the grinding amount. [Effects of the Invention]

[0022] The above-described fluid machinery and construction machinery can reduce the processing costs of the valve plate and can obtain a sufficient corrosion prevention effect for the cylinder chamber. [Brief explanation of the drawings]

[0023] [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 a first surface side of a valve plate in the first embodiment of the present invention. [Figure 4] FIG. 3 is a plan view of the second surface side of the valve plate in the first embodiment of the present invention. [Figure 5] Cross-sectional view taken along line AA in Figure 4. [Figure 6] FIG. 4 is a cross-sectional view taken along line BB in FIG. 3. [Figure 7] FIG. 6 is a cross-sectional view of a main part of a valve plate according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Next, an embodiment of the present invention will be described with reference to the drawings.

[0025] <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).

[0026] 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.

[0027] <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 a cross section along the axial direction. In Fig. 2, the scale of each component has been appropriately changed to make the explanation easier to understand.

[0028] <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 by the main casing 2 so as to be rotatable about a central axis C, 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 relative 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 piston (an example of a pressing member in the claims) 46 provided on the valve plate 19. 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 C 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.

[0029] 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 C of the shaft 3. The cylinder block 4 is disposed on the inner surface 119a side of the bottom wall 119. The gear pump 111 is attached to the outer surface 119b of the bottom wall 119.

[0030] 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.

[0031] A first suction passage (an example of the suction passage in the claims) 122 and a discharge passage 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 128 is formed at the end of the discharge passage 123 on the rotary shaft insertion hole 121 side, connecting the discharge passage 123 to an inner surface 119a of the bottom wall 119. The third communication passage 128 connects the discharge passage 123 to a discharge port 19b of the valve plate 19, which will be described later.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 C. 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.

[0046] A piston 21 is housed in each cylinder chamber 17 so as to be slidable along the axial direction. As a result, the piston 21 rotates around the central axis C 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] Each shoe 22 is integrated by a shoe holding member 29. The pressing member 27 contacts the shoe holding member 29 and presses the shoe holding 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 C, 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.

[0052] [First embodiment] <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 C. 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.

[0053] 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.

[0054] 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 C, 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 .

[0055] 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.

[0056] 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 the shape of an arc within a predetermined angular range around the central axis C and in the shape of an ellipse. 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 .

[0057] 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.

[0058] 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.

[0059] Between the second surface 41b of the valve plate 19 and the center in the thickness direction of the valve plate 19, piston accommodating recesses 49 (an example of the pressing member accommodating recesses in the claims) are formed at positions corresponding to both longitudinal ends of the long recess 45. The positions at which these piston accommodating recesses 49 are formed also avoid the first suction passage 122 and the discharge passage 123 formed in the casing body 9. These avoided positions mean positions that do not communicate with the first suction passage 122 and the discharge passage 123. In other words, the piston accommodating recesses 49 are formed at positions that do not communicate with the first suction passage 122 and the discharge passage 123.

[0060] 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 ends of the elongated recess 45 in the longitudinal direction.

[0061] 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.

[0062] FIG. 6 is a cross-sectional view taken along line BB in FIG. 3, 4, and 6, 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 the ends facing the bottom dead center switching land 47a, 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.

[0063] The valve plate 19 has a valve plate communication hole 51 formed in a bottom surface 49a of the piston accommodating recess 49 located on the bottom dead center changeover land 47a side, which connects the bottom surface 49a and the bottom dead center changeover land 47a. The valve plate communication hole 51 is a very small hole. The valve plate communication hole 51 extends in the axial direction. The valve plate communication hole 51 is located slightly away from the tip of the notch 50 and slightly closer to the longitudinal end of the intake port 19a. The valve plate communication hole 51 communicates with each communication hole 18 of the cylinder block 4.

[0064] <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.

[0065] 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.

[0066] 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.

[0067] <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 C of the shaft 3.

[0068] 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.

[0069] As the cylinder block 4 rotates, the pistons 21 rotate around the central axis C 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 C of the shaft 3. As a result, each piston 21 slides axially within each cylinder chamber 17, performing reciprocating motion.

[0070] 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).

[0071] 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).

[0072] Furthermore, 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 C 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.

[0073] 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.

[0074] 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 chamber 17 pressing the pressing piston 46 as a force moving the valve plate 19 toward the cylinder block 4.

[0075] 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.

[0076] However, when the cylinder chamber 17 (communication hole 18) passes through the bottom dead center switching land 47a and communicates with the elongated recess 45 (discharge port 19b), the cylinder chamber 17 is suddenly opened via the elongated recess 45 (discharge port 19b), which may result in a pressure difference causing back-spray of hydraulic oil into the cylinder chamber 17. The notch 50 formed in the first surface 41a of the valve plate 19 functions to mitigate sudden pressure fluctuations in the cylinder chamber 17.

[0077] In addition, in the valve plate 19 of the first embodiment, a valve plate communication hole 51 is formed in the bottom surface 49a of the piston accommodating recess 49, connecting the bottom surface 49a to the bottom dead center switching land 47a. Therefore, just before the cylinder chamber 17 (communication hole 18) and the elongated recess 45 (discharge port 19b) communicate with each other, the cylinder chamber 17 (communication hole 18) and the valve plate communication hole 51 communicate with each other. As a result, the pressure of the hydraulic oil in the piston accommodating recess 49 (discharge port 19b) (hereinafter referred to as the hydraulic oil discharge pressure) is introduced into the cylinder chamber 17, slightly increasing the pressure in the cylinder chamber 17. This prevents the hydraulic oil from being reversely injected into the cylinder chamber 17 at the timing when the cylinder chamber 17 (communication hole 18) and the elongated recess 45 (discharge port 19b) communicate with each other.

[0078] 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.

[0079] As described above, the valve plate 19 in the first embodiment has a valve plate communication hole 51 formed on the bottom surface 49a of the piston accommodating recess 49, which communicates the bottom surface 49a with the bottom dead center switching land 47a. Therefore, just before the hydraulic oil passes through the bottom dead center switching land 47a and communicates with the cylinder chamber 17 (communication hole 18) and the elongated recess 45 (discharge port 19b), the discharge pressure of the hydraulic oil can be introduced into the cylinder chamber 17 via the valve plate communication hole 51. As a result, back-spray of the hydraulic oil into the cylinder chamber 17 can be prevented at the timing when the cylinder chamber 17 (communication hole 18) and the elongated recess 45 (discharge port 19b) communicate with each other. Therefore, corrosion of the cylinder chamber 17 due to back-spray of the hydraulic oil into the cylinder chamber 17 can be reliably suppressed.

[0080] Furthermore, by forming the valve plate communication hole 51 using the piston accommodating recess 49 that generates a pressing force on the valve plate 19 against the cylinder block 4, the pressure of the hydraulic oil from the discharge port 19b can be easily introduced into this valve plate communication hole 51. This makes it possible to reduce the processing costs of the valve plate 19. The valve plate communication hole 51 is disposed slightly away from the tip of the notch 50 toward the longitudinal end of the suction port 19a. Therefore, the discharge pressure of the hydraulic oil can be reliably introduced into the cylinder chamber 17 just before the hydraulic oil passes through the bottom dead center switching land 47a and communicates with the cylinder chamber 17 (communication hole 18) and the elongated recess 45 (discharge port 19b).

[0081] A disk-shaped pressing piston 46 is housed in a piston housing recess 49 formed in the valve plate 19. By applying the discharge pressure of the hydraulic oil to this pressing piston 46, a pressing force toward the cylinder block 4 can be easily applied to the valve plate 19.

[0082] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. Fig. 7 is a cross-sectional view of a main part of a valve plate 219 in the second embodiment. Fig. 7 corresponds to the above-mentioned Fig. 6. Note that the same reference numerals are used to designate the same aspects as in the first embodiment, and the description thereof will be omitted. 7, the difference between the first and second embodiments is that in the valve plate 19 of the first embodiment, the valve plate communication hole 51 is located at a position slightly spaced from the tip of the notch 50, whereas in the valve plate 219 of the second embodiment, the valve plate communication hole 52 is located at the tip of the notch 50. In the second embodiment, the valve plate communication hole 52 communicates with the notch 50 on the first surface 41a side of the valve plate 219.

[0083] Here, the switching lands 47a, 47b of the valve plate 219 are formed by polishing the valve plate 219 during finish machining of the valve plate 219. At this time, by forming the valve plate communication holes 52 at the tips of the notches 50, it is possible to prevent the distance between the notches 50 and the valve plate communication holes 52 from changing due to the polishing stock. In other words, although the tip position of the notch 50 changes due to the polishing stock, by forming the valve plate communication holes 52 at the tips of the notches 50, it is possible to prevent this change in the distance between the notch 50 and the valve plate communication holes 52. In other words, regardless of the polishing stock, the valve plate communication holes 52 always communicate with the notches 50 on the first surface 41a side of the valve plate 219. Therefore, the effect of the valve plate communication holes 52 can be stabilized regardless of the polishing stock.

[0084] The present invention is not limited to the above-described embodiment, but 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.

[0085] In the above-described embodiment, the main pump 1 using hydraulic oil as the fluid machine has been described. However, the present invention is not limited to this, and the configuration of the valve plate 19, 219 described above can be applied to various fluid machines using various fluids other than hydraulic oil. In the above embodiment, the valve plate 19 has been described as having a valve plate communication hole 51 formed in the bottom surface 49a of the piston accommodating recess 49 arranged on the bottom dead center switching land 47a side, which connects the bottom surface 49a and the bottom dead center switching land 47a. However, this is not limited to this, and the valve plate communication hole 51 may be formed in the bottom surface 49a of the piston accommodating recess 49 arranged on the top dead center switching land 47b side, which connects the bottom surface 49a and the top dead center switching land 47b.

[0086] 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.

[0087] In the above embodiment, the piston accommodating recess 49 is formed in the valve plate 19 at positions corresponding to both longitudinal ends of the long recess 45. However, this is not limited thereto, and the piston accommodating recess 49 may be formed in any position that avoids the first suction passage 122 and the discharge passage 123 (a position that does not communicate with the first suction passage 122 and the discharge passage 123). Then, a pressing force toward the cylinder block 4 is generated on the valve plate 19 by the pressure of the hydraulic oil discharged into the piston accommodating recess 49 through the valve plate communication hole 51.

[0088] If the piston accommodating recess 49 communicates with the first suction passage 122 or the discharge passage 123, the hydraulic oil discharged into the piston accommodating recess 49 will leak into the first suction passage 122 or the discharge passage 123. With this configuration, it is difficult to generate a pressing force on the valve plate 19 toward the cylinder block 4 by the pressure of the hydraulic oil discharged into the piston accommodating recess 49.

[0089] In the above embodiment, the valve plate communication hole 51 formed in the valve plate 19 extends along the axial direction. However, this is not limited to this, and the valve plate communication hole 51 may be formed so as to communicate between the piston accommodating recess 49 of the valve plate 19 and the switching lands 47a, 47b.

[0090] 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]

[0091] 1...Main pump (fluid machinery), 2...Main casing (casing), 4...Cylinder block, 17...Cylinder chamber, 18...Communication hole (block communication hole), 19, 219...Valve plate, 19a...Suction port, 19b...Discharge port, 21...Piston, 41a...First surface, 41b...Second surface, 46...Pressing piston (pressing member), 47a...Bottom dead center switching land, 47b...Top dead center switching land, 49...Piston accommodating recess (pressing member accommodating recess), 50...Notch, 51...Valve plate communication hole, 101...Swivel body (vehicle body), 102...Travel body (vehicle body), 122...First suction passage (suction passage), 123...Discharge passage

Claims

1. a cylinder block having a cylinder chamber and a block communication hole that connects the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber and performing a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; a pressing member that presses the valve plate toward the cylinder block, The valve plate is an intake port that connects the block communication hole and the intake path; a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, the discharge port communicating the block communication hole with the discharge passage; a pressing member accommodating recess formed in a second surface opposite to the first surface at a position avoiding the suction passage and the discharge passage, and configured to accommodate the pressing member; a valve plate communication hole that connects the pressing member accommodating recess and the switching land; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed at a position avoiding the valve plate communication hole on the first surface side; Including, The communication recess communicates the discharge port body with the pressing member accommodating recess. Fluid machinery.

2. the valve plate has a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke, The valve plate communication hole is disposed at a position spaced from the tip of the notch on the opposite side to the discharge port toward the suction port. The fluid machinery according to claim 1 .

3. the valve plate has a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is located at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke, The fluid machine according to claim 1 , wherein the valve plate communication hole is disposed at a tip of the notch on a side opposite to the discharge port.

4. The pressing member is a small disc-shaped piston. The fluid machine according to any one of claims 1 to 3.

5. a cylinder block having a cylinder chamber and a block communication hole that connects the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber and performing a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; a pressing member that presses the valve plate toward the cylinder block, The valve plate is an intake port that connects the block communication hole and the intake path; a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, the discharge port communicating the block communication hole with the discharge passage; a pressing member accommodating recess formed in a second surface opposite to the first surface at a position avoiding the suction port and the discharge port, and configured to accommodate the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke; a valve plate communication hole that is disposed at a position spaced from a tip of the notch on the opposite side from the discharge port toward the suction port and that allows the pressing member accommodating recess and the switching land to communicate with each other; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed at a position avoiding the valve plate communication hole on the first surface side; Including, The communication recess communicates the discharge port body with the pressing member accommodating recess. Fluid machinery.

6. a cylinder block having a cylinder chamber and a block communication hole that connects the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber and performing a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; a pressing member that presses the valve plate toward the cylinder block, The valve plate is an intake port that connects the block communication hole and the intake path; a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, the discharge port communicating the block communication hole with the discharge passage; a pressing member accommodating recess formed in a second surface opposite to the first surface at a position avoiding the suction port and the discharge port, and configured to accommodate the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke; a valve plate communication hole that is disposed at the tip of the notch opposite to the discharge port and that communicates the pressing member accommodating recess and the switching land; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed at a position avoiding the valve plate communication hole on the first surface side; Including, The communication recess communicates the discharge port body with the pressing member accommodating recess. Fluid machinery.

7. 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 and a block communication hole that connects the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber and performing a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; a pressing member that presses the valve plate toward the cylinder block, The valve plate is an intake port that connects the block communication hole and the intake path; a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, the discharge port communicating the block communication hole with the discharge passage; a pressing member accommodating recess formed in a second surface opposite to the first surface at a position avoiding the suction port and the discharge port, and configured to accommodate the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke; a valve plate communication hole that is disposed at a position spaced from a tip of the notch on the opposite side from the discharge port toward the suction port and that allows the pressing member accommodating recess and the switching land to communicate with each other; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed at a position avoiding the valve plate communication hole on the first surface side; Including, The communication recess communicates the discharge port body with the pressing member accommodating recess. Construction machinery.

8. 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 and a block communication hole that connects the inside and outside of the cylinder chamber; a piston slidably housed in the cylinder chamber and performing a discharge process to compress the cylinder chamber and a suction process to expand the cylinder chamber; a casing that houses the cylinder block and has an intake passage and a discharge passage; a valve plate disposed between the cylinder block and the casing; a pressing member that presses the valve plate toward the cylinder block, The valve plate is an intake port that connects the block communication hole and the intake path; a discharge port formed on the opposite side of the intake port across a pair of switching lands formed on a first surface of the cylinder block, the discharge port communicating the block communication hole with the discharge passage; a pressing member accommodating recess formed in a second surface opposite to the first surface at a position avoiding the suction port and the discharge port, and configured to accommodate the pressing member; a notch extending from the discharge port toward a bottom dead center switching land of the pair of switching lands that is at a bottom dead center position where the piston switches from the suction stroke to the discharge stroke; a valve plate communication hole that is disposed at the tip of the notch opposite to the discharge port and that communicates the pressing member accommodating recess and the switching land; and The discharge port is a discharge port body communicating with the discharge path; a communication recess formed at a position avoiding the valve plate communication hole 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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