Hydraulic pump and construction machine

Abstract

To provide a hydraulic pump and a construction machine capable of preferably maintaining a heat balance by suppressing a temperature rise of the hydraulic pump.SOLUTION: A hydraulic pump is equipped with a casing, a rotary shaft, a cylinder block, a plurality of pistons, a valve plate 19, and a swash plate. The valve plate has a suction port 64 and a discharge port 66 that are disposed along a center axis C1 so as to overlap with the cylinder block and communicated to a cylinder hole. A groove portion 65 is provided on an end surface 19a adjacent to the cylinder block. The groove portion 65 is communicated to an inside part 64a opposite to an inside ring recessed portion 62, of the suction port 64.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Hydraulic pumps include swash plate type variable displacement hydraulic pumps for supplying hydraulic oil to various hydraulic actuators mounted on construction machines such as hydraulic excavators. This type of hydraulic pump has a rotating shaft that is rotatably supported within a casing. A cylinder block is fitted and fixed to the outer circumferential surface of the rotating shaft. The rotating shaft and the cylinder block rotate as a unit. The cylinder block is provided with a plurality of cylinder holes (cylinder chambers). A piston is inserted into each cylinder hole. The cylinder holes and the pistons form a cylinder chamber.

[0003] The pistons are provided with a swash plate, which is supported rotatably relative to the casing, at the end opposite the end where the cylinder chamber is formed. The rotation axis of the swash plate is perpendicular to the rotation axis of the cylinder block. Shoes that are movable relative to the swash plate are attached to the end of each piston on the swash plate side. Each shoe is held integrally by a shoe holding member. The shoe holding member is pressed toward the swash plate by a pressing member that is fitted to the outer circumferential surface of the rotating shaft.

[0004] With this configuration, the piston slides along the swash plate, and the swash plate restricts the piston's displacement within the cylinder bore. As the piston slides along the swash plate, the piston slides within the cylinder bore. This causes a change in the volume of the cylinder chamber, which is used to discharge hydraulic oil at a specified flow rate. When the inclination angle of the swash plate changes, the amount of sliding movement of the piston within the cylinder bore changes, and so the discharge volume of the hydraulic pump changes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-66189 A Summary of the Invention [Problem to be solved by the invention]

[0006] Here, for example, in construction machinery, the cooling device (oil cooler) is made smaller with each model change, and good heat balance is required for hydraulic equipment. Mini excavators in particular have a small machine size, making it difficult to install a large cooling device. On the other hand, in conventional hydraulic pumps, the rotating cylinder block and the valve plate fixed inside the casing are adjacent to each other with hydraulic oil interposed between them, and friction between the adjacent surfaces causes the hydraulic oil to heat up and reach a high temperature. It is considered that some of the hydraulic oil that has become hot due to the heat generated leaks out from the gap between the cylinder block and the valve plate into the casing and accumulates there, making it difficult to maintain an optimal heat balance in the hydraulic pump. Alternatively, a configuration may be considered in which the high-temperature hydraulic oil that has leaked and accumulated in the casing from the gap between the cylinder block and the valve plate is returned to the suction side via a guide path or to the tank. However, even if these configurations are adopted, it is difficult to maintain an optimal heat balance in the hydraulic pump due to the high-temperature hydraulic oil remaining in the casing.

[0007] The present invention provides a hydraulic pump and a construction machine that can maintain a favorable heat balance by suppressing an increase in the temperature of the hydraulic pump. [Means for solving the problem]

[0008] A hydraulic pump according to one embodiment of the present invention comprises a casing, a shaft supported in the casing so as to be rotatable about an axis, a cylinder block fitted to an outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber, and a valve plate arranged along the axis so as to overlap the cylinder block, the valve plate having an intake passage and a discharge passage communicating with the cylinder chamber, and a valve plate formed on a surface adjacent to the cylinder block and on a surface defining the intake passage, the valve plate having a connecting passage communicating with at least a part of the intake passage.

[0009] A hydraulic pump according to another aspect of the present invention comprises a casing, a shaft supported in the casing so as to be rotatable about an axis, a valve plate having an suction passage and a discharge passage, and a cylinder block fitted to the outer peripheral surface of the shaft and rotating integrally with the shaft, arranged on the valve plate along the axis, having a cylinder chamber communicating with the suction passage and the discharge passage, and having a connecting passage formed on a surface adjacent to the valve plate and on a surface defining the suction passage, the connecting passage communicating with at least a part of the suction passage.

[0010] With the above configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil between them, and the hydraulic oil that heats up due to friction between the adjacent surfaces and becomes hot can be drawn into the suction port through the groove. Therefore, the high-temperature hydraulic oil drawn into the suction port can be discharged from the discharge port through the cylinder chamber without being retained inside the casing. This makes it possible to maintain a good heat balance by suppressing the temperature rise of the hydraulic pump.

[0011] In the aforementioned configuration, the communication passage may open to a surface between the cylinder block and the valve plate that is adjacent to each other, other than the surface that defines the cylinder block.

[0012] With this configuration, the friction between the adjacent surfaces of the rotating cylinder block and the fixed valve plate via the hydraulic oil allows the hydraulic oil, which heats up and becomes hot, to be smoothly sucked into the suction port from the external space (the outside other than the surface that defines the suction section).

[0013] In the above configuration, the communicating passage may include either an inner ring recess formed on a surface of the valve plate adjacent to the cylinder block and located radially inward of the shaft with respect to the suction passage and the discharge passage, or an outer ring recess formed on a surface of the valve plate adjacent to the cylinder block and located radially outward of the shaft with respect to the suction passage and the discharge passage.

[0014] With this configuration, the high-temperature hydraulic oil in the inner ring recess can be smoothly drawn into the suction port through the groove, allowing the high-temperature hydraulic oil near the rotating shaft to be drawn in through the suction port and discharged from the discharge port, preventing the temperature of the hydraulic pump from rising. In addition, the high-temperature hydraulic oil in the recess of the outer ring can be smoothly drawn into the suction port through the groove, allowing the hydraulic oil that becomes hot between the cylinder block and the valve plate to be drawn in through the suction port and discharged from the discharge port, preventing the temperature of the hydraulic pump from rising.

[0015] In the aforementioned configuration, the communication passage may be located in the vicinity of the discharge passage.

[0016] With this configuration, the high-temperature hydraulic oil leaking from the discharge port can be effectively guided to the groove, so that the high-temperature hydraulic oil leaking from the discharge port can be smoothly sucked into the suction port via the groove. In addition, since the hydraulic oil at the discharge port is not directly led to the groove, a deterioration in the discharge flow rate of the hydraulic pump can be prevented.

[0017] A hydraulic pump according to another aspect of the present invention comprises a casing, a shaft supported in the casing so as to be rotatable about an axis, a cylinder block fitted to an outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber and a first communicating passage formed in a first demarcated surface, and a valve plate arranged along the axis so as to overlap the first demarcated surface of the cylinder block, the valve plate having an intake passage and a discharge passage communicating with the cylinder chamber, the valve plate being adjacent to the first demarcated surface and formed at a position opposite in the axial direction to the first communicating passage in a second demarcated surface that defines the intake passage, the valve plate having a second communicating passage that, together with the first communicating passage, communicates with at least a part of the intake passage.

[0018] With this configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil between them, and the hydraulic oil that heats up due to friction between the adjacent surfaces and becomes hot can be drawn into the suction port through the groove. Therefore, the high-temperature hydraulic oil drawn into the suction port can be discharged from the discharge port through the cylinder chamber without being retained inside the casing. This makes it possible to maintain an optimal heat balance by suppressing the temperature rise of the hydraulic pump.

[0019] A hydraulic pump according to another aspect of the present invention comprises a casing, a shaft supported in the casing so as to be rotatable about an axis, a cylinder block fitted to an outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber, and a valve plate arranged along the axis so as to overlap the cylinder block, the valve plate having an intake passage and a discharge passage communicating with the cylinder chamber, the valve plate being formed on a surface adjacent to the cylinder block and defining the intake passage, the valve plate having an inner ring recess located radially inward of the shaft with respect to the intake passage and the discharge passage, an outer ring recess located radially outward of the shaft with respect to the intake passage and the discharge passage, and a connecting passage communicating with at least a portion of the intake passage and either the inner ring recess or the outer ring recess.

[0020] With this configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil between them, and the hydraulic oil that heats up due to friction between the adjacent surfaces and becomes hot can be drawn into the intake port through the inner ring recess and the outer ring recess and the groove. Therefore, the hot hydraulic oil drawn into the intake port can be discharged from the discharge port through the cylinder chamber without being retained inside the casing. This makes it possible to maintain an optimal heat balance by suppressing the temperature rise of the hydraulic pump.

[0021] A construction machine according to another aspect of the present invention includes a vehicle body on which the above-mentioned hydraulic pump is mounted.

[0022] By configuring in this manner, it is possible to provide a construction machine equipped with a hydraulic pump that can suppress an increase in the temperature of the hydraulic pump and maintain a favorable heat balance. Effect of the Invention

[0023] The above-described hydraulic pump and construction machine are able to maintain a favorable heat balance by suppressing an increase in the temperature of the hydraulic pump. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram of a construction machine according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of a hydraulic pump according to an embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion III in FIG. 2 . [Figure 4] FIG. 4 is a plan view of a valve plate according to an embodiment of the present invention. [Diagram 5] FIG. 4 is a cross-sectional view showing a valve plate in a first modified example of the embodiment of the present invention. [Figure 6] FIG. 4 is a plan view of a valve plate in a first modified example of the embodiment of the present invention. [Figure 7] FIG. 11 is a cross-sectional view showing a valve plate in a second modified example of the embodiment of the present invention. [Figure 8] FIG. 11 is a plan view of a valve plate in a second modified example of the embodiment of the present invention. [Figure 9] 11 is a cross-sectional view taken along line IV-IV in FIG. 10 of a valve plate according to a third modified example of the embodiment of the present invention. [Figure 10] FIG. 13 is a plan view of a valve plate in a third modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Next, an embodiment of the present invention will be described with reference to the drawings.

[0026] <Construction machinery> FIG. 1 is a schematic configuration diagram of a construction machine 100. As shown in Fig. 1, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 includes a revolving body (corresponding to the vehicle body in the claims) 101 and a running body (corresponding to the vehicle body in the claims) 102. The revolving body 101 is provided on the running body 102 so as to be capable of revolving. A hydraulic pump 1 is mounted on the revolving body 101.

[0027] The rotating body 101 includes a cab 103 on which an operator can ride, a boom 104 having one end swingably connected to the cab 103, an arm 105 having one end swingably connected to the other end (tip) of the boom 104 opposite the cab 103, and a bucket 106 swingably connected to the other end (tip) of the arm 105 opposite the boom 104. A hydraulic pump 1 is provided in the cab 103. The cab 103, the boom 104, the arm 105, and the bucket 106 are driven by hydraulic oil discharged from the hydraulic pump 1.

[0028] <Hydraulic pump> FIG. 2 is a cross-sectional view of the hydraulic pump 1. 2, the hydraulic pump 1 is a so-called swash plate type variable displacement hydraulic pump. The hydraulic pump 1 includes a casing 2, a shaft 3 rotatably supported inside the casing 2, a cylinder block 4 housed inside the casing 2 and fixed to the shaft 3, a swash plate 5 housed inside the casing 2 so that its inclination angle can be changed and which controls the amount of hydraulic oil discharged from the hydraulic pump 1, and a first biasing unit 6 and a second biasing unit 7 which control the inclination angle of the swash plate 5. In addition, the scale of each component is appropriately changed in Fig. 2 for ease of understanding. In the following description, the direction parallel to the central axis C1 of the shaft 3 (corresponding to the axis in the claims) is referred to as the axial direction, the rotation direction of the shaft 3 is referred to as the circumferential direction, and the radial direction of the shaft 3 is simply referred to as the radial direction.

[0029] The casing 2 includes a box-shaped casing body 9 having an opening 9a, and a front flange 10 that closes the opening 9a of the casing body 9. The casing body 9 is provided with a bearing 11 at a bottom 9b opposite to the opening 9a, which rotatably supports one end of the shaft 3. A first guide portion 49 is provided on the inner surface of a side surface 9c of the casing body 9, which guides a biasing rod 46 of the second biasing portion 7, which will be described later. A mounting recess 48 is formed at the bottom 9b of the casing body 9, which leads to the first guide portion 49. A biasing pin unit 50 of the second biasing portion 7, which will be described later, is attached to the mounting recess 48.

[0030] Furthermore, a suction passage 71 (see FIG. 3) and a discharge passage 72 (see FIG. 3) are formed in the casing body 9. The suction passage 71 is connected to a tank (not shown). The discharge passage 72 is connected to a cab 103, a boom 104, an arm 105, and a bucket 106 via a control valve (not shown) and the like.

[0031] A swash plate support portion 30 is formed on the inner surface 10a of the front flange 10 on the casing body 9 side. The swash plate support portion 30 supports the swash plate 5 so that the inclination angle can be changed. The swash plate support portion 30 is formed with a semicircular recess 30a when viewed from the radial direction. The swash plate 5 is supported by this recess 30a. In addition, a male-threaded stopper 40 is provided on the radially outer side of the front flange 10. The stopper 40 supports a part of the swash plate 5 and regulates the inclination angle of the swash plate 5. By turning the stopper 40 with respect to the front flange 10, the amount of protrusion of the stopper 40 from the inner surface 10a of the front flange 10 changes. This regulates the inclination angle of the swash plate 5.

[0032] Further, the front flange 10 is formed with a through hole 13 through which the shaft 3 can be inserted. A bearing 14 that rotatably supports the other end of the shaft 3 is provided in this through hole 13. Further, an oil seal 15 is provided in the through hole 13 on the opposite side of the bearing 14 to the casing body 9 (outside the front flange 10). The other end of the shaft 3 protrudes to the outside of the front flange 10 via the bearing 14 and the oil seal 15. The oil seal 15 prevents oil from leaking from the inside and prevents foreign matter from entering between the front flange 10 and the shaft 3.

[0033] A first spline 3a is formed on the other end of the shaft 3 that protrudes through the oil seal 15. A power source such as an engine (not shown) is connected to the shaft 3 via this first spline 3a. A second spline 3b is formed on the outer circumferential surface 3c of the shaft 3 closer to the bottom 9b of the casing body 9 than the swash plate 5, that is, in the axial center of the shaft 3. A cylinder block 4 is fitted onto the outer circumferential surface 3c of the shaft 3 at a location corresponding to the second spline 3b. The first spline 3a and the second spline 3b are formed, for example, by cutting the outer circumferential surface 3c of the shaft 3 with a dedicated tool (such as a cutter) not shown.

[0034] The cylinder block 4 is formed in a cylindrical shape. A through hole 16 into which the shaft 3 can be inserted or press-fitted is formed in the radial center of the cylinder block 4. A spline 16a is also formed in the through hole 16. The spline 16a and a second spline 3b of the shaft 3 are spline-coupled. This allows the shaft 3 and the cylinder block 4 to rotate integrally.

[0035] A recess 20 is formed between the axial center of the through hole 16 and the end 4a so as to surround the periphery of the shaft 3. A through hole 25 that axially penetrates the cylinder block 4 is formed in a part of the inner peripheral surface between the axial center of the through hole 16 and the swash plate 5 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.

[0036] A plurality of cylinder holes 17 are formed in the cylinder block 4 so as to surround the shaft 3. The cylinder holes 17 are arranged at equal intervals in the circumferential direction. The cylinder holes 17 are also formed in the axial direction and are open on the swash plate 5 side. Communication holes 18 are formed in the end portion 4a of the cylinder block 4 opposite the front flange 10 at positions corresponding to the respective cylinder holes 17, connecting the cylinder holes 17 to the outside of the cylinder block 4.

[0037] Fig. 3 is an enlarged cross-sectional view of part III in Fig. 2. Fig. 4 is a plan view of the valve plate 19. 2, 3 and 4, a disk-shaped valve plate 19 is provided at an end 4a of the cylinder block 4 so as to overlap an end face 4b (a face adjacent to the face of the valve plate in the claims, corresponding to a first defined face) of the end 4a along the central axis C1 of the shaft 3. The valve plate 19 is fixed to the casing body 9. Even when the cylinder block 4 rotates together with the shaft 3, the valve plate 19 is stationary with respect to the casing 2 (casing body 9).

[0038] The valve plate 19 has an insertion hole 61 in the center through which the shaft 3 penetrates along the central axis C1, and has a circular outer shape. The valve plate 19 has an inner ring recess (corresponding to the inner ring recess in the claims) 62 arranged radially inward, an outer ring recess (corresponding to the outer ring recess in the claims) 63 arranged radially outward, an intake port (corresponding to the intake passage in the claims) 64, a groove portion (corresponding to the communication passage in the claims) 65, and an exhaust port (corresponding to the exhaust passage in the claims) 66. The intake port 64 and the exhaust port 66 are defined by overlapping the end face 4b of the cylinder block 4 and the end face 19a of the valve plate 19 facing the end face 4b of the cylinder block 4 (the face adjacent to the face of the cylinder block in the claims, corresponding to the second demarcated face). The intake port 64 and the exhaust port 66 refer to the entire passages constituting the intake port 64 and the exhaust port 66, and do not refer to only the ends of the passages.

[0039] The inner ring recess 62 is formed in a substantially circular ring shape when viewed in the axial direction. The inner ring recess 62 opens to the end face 19a of the valve plate 19. The inner ring recess 62 is formed in a ring shape on the radially inner side along the insertion hole 61, and is located on the radially inner side of the shaft 3 with respect to the suction port 64 and the discharge port 66. The outer ring recess 63 is formed in a substantially circular ring shape when viewed in the axial direction. The outer ring recess 63 opens to an end face 19a of the valve plate 19 that faces the end face 4b of the cylinder block 4. The outer ring recess 63 is formed in a ring shape on the radially outer side along the outer circumferential surface 19b of the valve plate 19, and is located on the radially outer side of the shaft 3 with respect to the suction port 64 and the discharge port 66.

[0040] The suction port 64 is formed radially between the inner ring recess 62 and the outer ring recess 63 of the valve plate 19 and on one side in the circumferential direction. The suction port 64 is curved along the inner ring recess 62 and the outer ring recess 63, and penetrates the valve plate 19 in the thickness direction so as to communicate with each of the communication holes 18 of the cylinder block 4. The suction port 64 communicates with each of the cylinder bores 17 via each of the communication holes 18 of the cylinder block 4.

[0041] Furthermore, a groove 65 is formed in the end face 19a of the valve plate 19. The groove 65 communicates with at least a part 64a of the suction port 64 (specifically, almost the entire inner portion facing the inner ring recess 62) and with the inner ring recess 62. In other words, the groove 65 has an opening 65a that opens into the inner ring recess 62. In other words, the groove 65 has an opening 65a on the outside (inner ring recess 62) other than the end face 19a that defines the suction port 64 and the discharge port 66. The inner portion 64a of the suction port 64 that faces the inner ring recess 62 communicates with the inner ring recess 62 via the groove 65 (opening 65a).

[0042] Further, a discharge port 66 is formed in the valve plate 19 on the other circumferential side, i.e., the opposite side of the suction port 64, between the inner ring recess 62 and the outer ring recess 63 in the radial direction. The discharge port 66 has a first discharge port 66a on the radially inner side and a second discharge port 66b on the radially outer side. The first discharge port 66a and the second discharge port 66b are formed in a curved shape along the inner ring recess 62 and the outer ring recess 63, and are formed penetrating the valve plate 19 in the thickness direction so as to communicate with each communication hole 18 of the cylinder block 4. Each discharge port 66a, 66b communicates with each cylinder bore 17 via each communication hole 18 of the cylinder block 4.

[0043] Each cylinder bore 17 communicates with a suction passage 71 formed in the casing body 9 via a suction port 64 of the valve plate 19 and a communication hole 18 of the cylinder block 4. Each cylinder bore 17 communicates with a discharge passage 72 formed in the casing body 9 via a discharge port 66 of the valve plate 19 and a communication hole 18 of the cylinder block 4.

[0044] Here, the valve plate 19 is fixed to the casing body 9. In this state, by rotating the cylinder block 4 together with the shaft 3, the cylinder bore 17 communicates with the suction port 64 and the discharge port 66 of the valve plate 19 depending on the rotation state of the cylinder block 4. As a result, the cylinder bore 17 is switched between a state in which hydraulic oil is sucked from the suction passage 71 via the suction port 64 of the valve plate 19 and a state in which hydraulic oil is discharged to the discharge passage 72 via the discharge port 66 of the valve plate 19 depending on the rotation state of the cylinder block 4.

[0045] A piston 21 is housed in each cylinder bore 17 so as to be movable axially. By housing the piston 21 in the cylinder bore 17, the piston 21 revolves around the central axis C1 of the shaft 3 as the shaft 3 and the cylinder block 4 rotate. A spherical protrusion 28 is integrally formed on the end of the piston 21 on the swash plate 5 side. The inside of the piston 21 is hollow. This cavity is filled with the hydraulic oil in the cylinder bore 17. Therefore, the reciprocating motion of the piston 21 is linked to the suction and discharge of the hydraulic oil into the cylinder bore 17. That is, when the piston 21 is pulled out of the cylinder bore 17, the hydraulic oil is sucked into the inside of the cylinder bore 17 through the suction passage 71 and the suction port 64. When the piston 21 enters the inside of the cylinder bore 17, the hydraulic oil is discharged from the inside of the cylinder bore 17 to the discharge port 66 and the discharge passage 72.

[0046] As shown in Fig. 2, 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. Therefore, the spring 23 generates a biasing force in a direction in which it expands due to its elastic force. The biasing force of the spring 23 is transmitted to the connecting member 26 via one of the two retainers 24a, 24b, the retainer 24b. A pressing member 27 is fitted to the outer circumferential surface 3c of the shaft 3 on the front flange 10 side of the connecting member 26, that is, between the cylinder block 4 and the swash plate 5.

[0047] The pressing member 27 is formed in a substantially cylindrical shape. The connecting member 26 abuts against the end face of the pressing member 27 on the connecting member 26 side. The biasing force of the spring 23 received by the connecting member 26 is transmitted to the pressing member 27. The pressing member 27 abuts against a shoe holding member 29 described later, and presses the shoe holding member 29 toward the swash plate 5.

[0048] A shoe 22 is attached to a protrusion 28 of each piston 21 housed in each cylinder bore 17 of the cylinder block 4. 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 this recess 22a. In this way, the shoe 22 is rotatably connected to the protrusion 28 of the piston 21. Each shoe 22 is integrally held by a shoe holding member 29. This shoe holding member 29 is pressed toward the swash plate 5 by a pressing member 27. Furthermore, each shoe 22 is pressed toward the swash plate 5 by the pressing member 27 via the shoe holding member 29.

[0049] The swash plate 5 has a role of restricting the displacement of each piston 21 in the axial direction by rotating and tilting. The swash plate 5 has a swash plate body 31 that is annular when viewed from the cylinder block 4 side. An insertion hole 32 that penetrates in the axial direction is formed in the radial center of the swash plate body 31. The shaft 3 is inserted (passes through) the insertion hole 32. A flat sliding surface 31a is formed on the cylinder block 4 side of the swash plate body 31. Each shoe 22 is movably pressed against this sliding surface 31a.

[0050] Two support protrusions 33, 34 are disposed on the rear side of the sliding surface 31a of the swash plate body 31, facing each other in the radial direction of the drawing with the insertion hole 32 as the center. The two support protrusions 33, 34 are for supporting the swash plate 5 on the front flange 10 so that the inclination angle can be changed. Each support protrusion 33, 34 is formed in a semicircular shape when viewed from the radial direction, and has arcuate surfaces 33a, 34a. Each support protrusion 33, 34 is formed to protrude from the swash plate body 31 so that the arcuate surfaces 33a, 34a face the front flange 10 side.

[0051] The arcuate surfaces 33a, 34a of the support protrusions 33, 34 are movably abutted against the recessed portion 30a of the swash plate support portion 30 formed to protrude from the front flange 10. The arcuate surfaces 33a, 34a slide on the recessed portion 30a, whereby the swash plate 5 rotates relative to the front flange 10. A first biased portion 37 and a second biased portion 38 are integrally formed on a radial side portion of the swash plate body 31, and are opposed to each other in the radial direction with the insertion hole 32 as the center. The opposing direction of the first biased portion 37 and the second biased portion 38 is perpendicular to the opposing direction of the two support protrusions 33, 34. The first biased portion 37 and the second biased portion 38 extend radially outward from the swash plate body 31. A surface 38a of the second biased portion 38 on the front flange 10 side abuts against a stopper 40 provided on the front flange 10.

[0052] A connecting recess 39 is formed on the radial outer side (tip side) of the first biased portion 37 on the surface opposite to the protruding direction of each of the support protrusions 33, 34 (the surface on the cylinder block 4 side). The first biased portion 6 is connected to the connecting recess 39. The connecting recess 39 is formed in a circular shape when viewed in the axial direction. An abutment surface 41 is formed on almost the entire surface of the second urged portion 38 on the side opposite to the protruding direction of the support protrusions 33, 34 (the surface on the cylinder block 4 side). The abutment surface 41 is formed by cutting the second urged portion 38 flat. The second urged portion 7 abuts against the abutment surface 41.

[0053] The swash plate 5 configured in this manner rotates relative to the front flange 10 , and thereby tilts so that the first biased portion 37 and the second biased portion 38 approach or move away from the front flange 10 . Here, the inclination angle of the swash plate 5 refers to the angle between the sliding surface 31a and a plane perpendicular to the shaft 3. In other words, the smaller this angle is, the smaller the inclination angle of the swash plate 5 is.

[0054] The first biasing portion 6 biases the swash plate 5 in a direction that increases the inclination angle of the swash plate 5. The first biasing portion 6 includes a first retainer 42 disposed on the bottom 9b side of the casing body 9, a second retainer 43 disposed on the swash plate 5 side, and a first spring 44 and a second spring 45 disposed between the first retainer 42 and the second retainer 43. A spherical connecting protrusion 43a is formed on the second retainer 43 facing the swash plate 5. The connecting protrusion 43a comes into contact with the connecting recess 39 of the swash plate 5, whereby the second retainer 43 is rotatably connected to the swash plate 5.

[0055] The first spring 44 is compressed between the first retainer 42 and the second retainer 43. Therefore, the first spring 44 generates a biasing force in a direction in which the first spring 44 expands due to its elastic force. The second spring 45 is disposed inside the first spring 44. Therefore, the outer diameter of the second spring 45 is smaller than the outer diameter of the first spring 44. The second spring 45 is fixed to the second retainer 43.

[0056] When the inclination angle of the swash plate 5 is large (as shown in FIG. 2), the second spring 45 is separated from the first retainer 42. As a result, when the inclination angle of the swash plate 5 is large, only the biasing force of the first spring 44 acts on the swash plate 5. In contrast, when the inclination angle of the swash plate 5 decreases, the second spring 45 comes into contact with the first retainer 42 at a certain inclination angle. When the inclination angle of the swash plate 5 decreases further, the second spring 45 is also compressed between the first retainer 42 and the second retainer 43. As a result, the biasing forces of both the first spring 44 and the second spring 45 act on the swash plate 5.

[0057] In this way, the first biasing portion 6 can change the biasing force in a stepwise manner according to the inclination angle of the swash plate 5. The second spring 45 is not limited to being fixed to the second retainer 43, and may be fixed to the first retainer 42. Also, the second spring 45 may not be fixed to either the first retainer 42 or the second retainer 43, and may be movable between the first retainer 42 and the second retainer 43.

[0058] The second biasing portion 7 applies a biasing force to the swash plate 5 in a direction opposite to the biasing force applied to the swash plate 5 by the first biasing portion 6. In particular, the second biasing portion 7 biases the swash plate 5 in a direction to decrease the inclination angle of the swash plate 5 against the biasing force applied by the first biasing portion 6 in a direction to increase the inclination angle of the swash plate 5. The second biasing portion 7 includes a biasing rod 46 and a biasing pin unit 50. The biasing pin unit 50 mainly includes a unit case 51 and a plurality of biasing pins 52, 53. Although only two of the plurality of biasing pins 52, 53 are shown in FIG. 2, the plurality of biasing pins 52, 53 may be provided in a number of, for example, four.

[0059] The unit case 51 is attached so as to be fitted into the attachment recess 48 of the casing body 9. A plurality of second guide portions 54 for guiding the plurality of urging pins 52, 53 are provided on the unit case 51 on the side facing the swash plate 5. The second guide portions 54 are holes penetrating the unit case 51 in the axial direction. A cylinder hole (corresponding to a cylinder chamber in the claims) 55 communicating with one of the plurality of second guide portions 54 is provided on the side of the unit case 51 opposite to the swash plate 5. The cylinder hole 55 opens on the side of the unit case 51 opposite to the second guide portions 54. The opening of the cylinder hole 55 is closed by a cap member 57.

[0060] A cylindrical biasing piston 56 is disposed within the cylinder bore 55 so as to be movable axially relative to the cylinder bore 55 . The biasing pins 52, 53 are housed in the second guide portion 54 so as to be movable in the axial direction. One of the biasing pins 52, 53 is formed longer than the other biasing pin 53. Such one biasing pin 52 is housed in the second guide portion 54 which communicates with the cylinder bore 55. An end of the one biasing pin 52 opposite to the swash plate 5 protrudes into the cylinder bore 55.

[0061] The second guide portion 54 receives, for example, a signal pressure due to hydraulic oil discharged from the hydraulic pump 1, a signal pressure from another hydraulic pump driven by the same drive source, or a signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same drive source. The cylinder hole 55 receives, for example, a signal pressure generated by a control valve. Each of the biasing pins 52, 53 biases the biasing rod 46 toward the swash plate 5 in response to the signal pressure corresponding to each of the biasing pins 52, 53.

[0062] The biasing rod 46 is disposed between the contact surface 41 of the swash plate 5 and each of the biasing pins 52, 53. The biasing rod 46 is formed in a cylindrical shape so as to be elongated in the axial direction, and is guided by a first guide portion 49 of the casing body 9 so as to be axially movable. A spherical surface 46a is formed on the end of the urging rod 46 on the contact surface 41 side. Therefore, even if the angle between the swash plate 5 (contact surface 41) and the urging rod 46 changes due to a change in the inclination angle of the swash plate 5, the urging force against the swash plate 5 can be appropriately transmitted from the spherical surface 46a to the contact surface 41.

[0063] <Hydraulic pump operation> Next, the operation of the hydraulic pump 1 will be described. The hydraulic pump 1 outputs a driving force based on the discharge of hydraulic oil from the cylinder bore 17 (and the suction of hydraulic oil into the cylinder bore 17). More specifically, first, the shaft 3 is rotated by power from a power source such as an engine, thereby rotating the cylinder block 4 integrally with the shaft 3. As the cylinder block 4 rotates, the piston 21 revolves around the central axis C1 of the shaft 3.

[0064] Each shoe 22 attached to the protrusion 28 of each piston 21 is pressed against the sliding surface 31a of the swash plate 5 by the biasing force of the spring 23 in a suitable manner regardless of the inclination angle of the swash plate 5. The protrusion 28 of the piston 21 is formed in a spherical shape, and the recess 22a of the shoe 22 into which the protrusion 28 is fitted is also formed in a spherical shape. Each shoe 22 is pressed against the swash plate 5 by the pressing member 27 via the shoe holding member 29. Therefore, even if the inclination angle of the swash plate 5 changes, each shoe 22 is pressed against the sliding surface 31a in a suitable manner in accordance with the inclination of the swash plate 5.

[0065] When the pistons 21 revolve around the central axis C1 of the shaft 3 as the cylinder block 4 rotates, each shoe 22 also slides on the sliding surface 31a of the swash plate 5 while revolving around the central axis C1 of the shaft 3. This causes each piston 21 to move axially within each cylinder bore 17, causing each piston 21 to reciprocate. In this manner, the swash plate 5 restricts the displacement of each piston 21 in the axial direction. In response to the reciprocating motion of the pistons 21, hydraulic oil is discharged from some of the cylinder bores 17 and sucked into the other cylinder bores 17, thereby realizing a hydraulic pump.

[0066] Here, when the inclination angle of the swash plate 5 (sliding surface 31a) changes, the stroke (sliding distance) of the reciprocating motion of the pistons 21 changes. That is, the greater the inclination angle of the swash plate 5, the greater the amount of hydraulic oil sucked into and discharged from the cylinder bores 17 due to the reciprocating motion of each piston 21. In contrast, the smaller the inclination angle of the swash plate 5, the smaller the amount of hydraulic oil sucked into and discharged from the cylinder bores 17 due to the reciprocating motion of each piston 21. When the inclination angle of the swash plate 5 is 0 degrees, each piston 21 does not reciprocate even when it revolves around the central axis C1 of the shaft 3. Therefore, the amount of hydraulic oil discharged from each cylinder bore 17 also becomes zero.

[0067] In addition, a male-threaded stopper 40 is provided on the radially outer side of the front flange 10. Therefore, when the inclination angle of the swash plate 5 is reduced, the swash plate 5 comes into contact with the stopper 40. The stopper 40 can be moved forward and backward with respect to the swash plate 5 by rotating it. Therefore, the minimum inclination angle of the swash plate 5 can be appropriately adjusted by moving the stopper 40 forward and backward with respect to the swash plate 5.

[0068] Next, the rotational operation of the swash plate 5 will be described. The first biasing portion 6 biases the swash plate 5 in a direction that increases the inclination angle of the swash plate 5. The second biasing portion 7 biases the swash plate 5 in a direction that decreases the inclination angle of the swash plate 5. The swash plate 5 tilts and stops at a position where the magnitude of the moment around the rotation axis of the swash plate 5 caused by the biasing force of the first biasing portion 6 (counterclockwise moment in FIG. 2) and the magnitude of the moment around the rotation axis of the swash plate 5 caused by the second biasing portion 7 (clockwise moment in FIG. 2) are equal. Hereinafter, the counterclockwise moment in Figure 2 will be simply referred to as the counterclockwise moment, and the clockwise moment in Figure 2 will be simply referred to as the clockwise moment.

[0069] In other words, when the clockwise moment by the second biasing portion 7 is increased, the inclination angle of the swash plate 5 is decreased. The first spring 44 and the second spring 45 of the first biasing portion 6 are compressed accordingly, and the counterclockwise moment by the first biasing portion 6 is also increased. As a result, the clockwise moment by the second biasing portion 7 and the counterclockwise moment by the first biasing portion 6 become equal, and the swash plate 5 stops at a predetermined inclination.

[0070] On the other hand, when the clockwise moment by the second biasing portion 7 is reduced, the biasing forces of the first spring 44 and the second spring 45 of the first biasing portion 6 prevail, and the inclination angle of the swash plate 5 increases. When the first spring 44 and the second spring 45 are expanded accordingly, the biasing force by the first biasing portion 6 decreases. As a result, the clockwise moment by the second biasing portion 7 and the counterclockwise moment by the first biasing portion 6 become equal, and the swash plate 5 stops at a predetermined inclination.

[0071] When the clockwise moment by the second biasing portion 7 is changed, the biasing force of the biasing rod 46 on the swash plate 5 is changed. That is, for example, a signal pressure due to the hydraulic oil discharged from the hydraulic pump 1, a signal pressure from another hydraulic pump driven by the same drive source, or a signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same drive source is input to the second guide portion 54 of the second biasing portion 7. For example, a signal pressure generated by a control valve is input to the cylinder hole 55. The biasing pins 52 and 53 bias the biasing rod 46 according to the magnitude of these signal pressures. As a result, the biasing force of the biasing rod 46 on the swash plate 5 changes.

[0072] Next, an operation for maintaining a suitable heat balance in the hydraulic pump 1 will be described with reference to FIGS. 2, 3, and 4, by rotating the cylinder block 4 together with the shaft 3, the cylinder bores 17 and the communication holes 18 revolve around the central axis C1 of the shaft 3. In this state, the valve plate 19 is fixed to the casing body 9. Therefore, depending on the rotation state of the cylinder block 4, the cylinder bores 17 communicate with the suction port 64 and the discharge port 66 of the valve plate 19 via the communication holes 18.

[0073] As a result, the cylinder bore 17 is switched between a suction state in which hydraulic oil is sucked in and a discharge state in which hydraulic oil is discharged, depending on the rotation state of the cylinder block 4. Specifically, in the suction state, the cylinder bore 17 sucks hydraulic oil from the suction passage 71 through the suction port 64 of the valve plate 19 and into the inside of the cylinder bore 17 from the communication hole 18 (see arrow A in FIG. 3). In addition, in the discharge state, the cylinder bore 17 discharges hydraulic oil from inside the cylinder bore 17 through the communication hole 18 and from the discharge port 66 of the valve plate 19 to the discharge passage 72 (see arrow B in FIG. 3).

[0074] Here, an oil film of hydraulic oil is formed between the adjacent end faces 4b, 19a of the cylinder block 4 and the valve plate 19. This oil film heats up and becomes hot due to friction between the adjacent end faces 4b, 19a. A part of the hydraulic oil that has been heated and has become hot leaks out from between the adjacent end faces 4b, 19a into the inner ring recess 62 and the outer ring recess 63.

[0075] The inner ring recess 62 communicates with an inner portion 64a of the suction port 64 that faces the inner ring recess 62 via a groove 65 (opening 65a). Therefore, the hydraulic oil that has been heated by friction between the adjacent end faces 4b, 19a can be smoothly drawn from the inner ring recess 62 through the groove 65 (opening 65a) into the suction port 64 (see arrow C in FIG. 3). The high-temperature hydraulic oil drawn into the suction port 64 from the groove 65 can be smoothly drawn into the inside of the cylinder bore 17 through the communication hole 18 (see arrow D in FIG. 3). High-temperature hydraulic oil sucked into the inside of the cylinder bore 17 can be smoothly discharged from the discharge port 66 of the valve plate 19 through the communication hole 18 to the discharge passage 72 while the cylinder bore 17 is in a discharged state (see arrow B in FIG. 3).

[0076] As a result, high-temperature hydraulic oil that has flowed out (leaked) from gaps (places where an oil film is formed; hereinafter, gaps have the same meaning) 68 between adjacent end faces 4b, 19a into the inner ring recess 62 can be smoothly discharged from the discharge port 66 via each cylinder hole 17 without being retained inside the casing 2. This makes it possible to provide a hydraulic pump 1 that can maintain a favorable heat balance by suppressing an increase in the temperature of the hydraulic pump 1.

[0077] Returning to Fig. 1, the hydraulic pump 1 is mounted on a revolving body 101 of the construction machine 100. By configuring it in this way, it is possible to provide a construction machine 100 equipped with a hydraulic pump 1 that can suppress an increase in temperature of the hydraulic pump 1 and maintain a favorable heat balance.

[0078] In the above embodiment, the groove 65 is formed in the end face 19a of the valve plate 19 out of the adjacent end faces 4b, 19a of the cylinder block 4 and the valve plate 19. The inner ring recess 62 is connected to the suction port 64 through this groove 65 (opening 65a). However, this is not limited to this, and a groove 65b (see two-dot chain line in FIG. 3) may be formed in the end face 4b of the cylinder block 4, and the inner ring recess 62 may be connected to the suction port 64 through this groove.

[0079] In the above embodiment, the groove 65 is formed in almost the entire inner portion 64a of the suction port 64 facing the inner ring recess 62. The inner portion 64a of the suction port 64 communicates with the inner ring recess 62 via the groove 65 (opening 65a). However, the present invention is not limited to this, and it is sufficient that the groove 65 is formed in a part of the inner portion 64a of the suction port 64 and the suction port 64 and the inner ring recess 62 communicate with each other via the groove 65. In addition, the groove 65 may be replaced by a through hole penetrating the valve plate 19 in the thickness direction.

[0080] [First Modification] Fig. 5 is a cross-sectional view showing a valve plate 80 in a first modified example. Fig. 6 is a plan view of the valve plate 80. Figs. 5 and 6 correspond to Figs. 3 and 4 described above (the same applies to Figs. 7, 8, 9, and 10 below). Also, the same reference numerals are used to designate the same aspects as in the above-described embodiment, and descriptions thereof will be omitted (the same applies to the following modified examples).

[0081] As shown in Figs. 2, 5 and 6, a groove (corresponding to a communication passage in the claims) 82 is formed in an end face (corresponding to a face adjacent to the face of the cylinder block in the claims, corresponding to a second defining face) 80a of the valve plate 80 adjacent to the end face 4b of the cylinder block 4. The groove 82 communicates with at least a part of the suction port 64 (specifically, an outer part facing the outer ring recess 63) 64b and also communicates with the outer ring recess 63. In other words, the groove 82 has an opening 82a that opens into the outer ring recess 63. In further words, the groove 82 has an opening 82a on the outside (outer ring recess 63) other than the end face 80a that defines the suction port 64 and the discharge port 66. Almost the entire outer part 64b of the suction port 64 facing the outer ring recess 63 communicates with the outer ring recess 63 via the groove 82 (opening 82a).

[0082] With this configuration, the hydraulic oil that is heated by friction between the end face 4b of the adjacent cylinder block 4 and the end face 80a of the valve plate 80 can be smoothly drawn from the outer ring recess 63 through the groove 82 to the suction port 64 (see arrow E in FIG. 5). The high-temperature hydraulic oil drawn from the groove 82 to the suction port 64 can be smoothly drawn into the inside of the cylinder bore 17 through the communication hole 18 (see arrow F in FIG. 5). The high-temperature hydraulic oil sucked into the inside of the cylinder bore 17 can be discharged smoothly in the discharge state of the cylinder bore 17, similarly to the above embodiment.

[0083] Therefore, high-temperature hydraulic oil that has flowed out (leaked) from the gap 84 between the adjacent end faces 4b, 80a into the outer ring recess 63 can be smoothly discharged from the discharge port 66 via each cylinder hole 17 without accumulating inside the casing 2. This makes it possible to provide a hydraulic pump 1 that can maintain a favorable heat balance by suppressing an increase in the temperature of the hydraulic pump 1.

[0084] In the above-mentioned first modified example, a groove 82 is formed in the end face 80a of the valve plate 80 out of the adjacent end faces 4b, 80a of the cylinder block 4 and the valve plate 80. A case has been described in which the outer ring recess 63 is connected to the suction port 64 via this groove 82. However, this is not limited to this, and a groove 82b (see the two-dot chain line in FIG. 5) may be formed in the end face 4b of the cylinder block 4, and the outer ring recess 63 may be connected to the suction port 64 via the groove.

[0085] In the above-described first modified example, the groove 82 is formed in almost the entire outer portion 64b of the suction port 64 facing the outer ring recess 63. The outer portion 64b of the suction port 64 communicates with the outer ring recess 63 via the groove 82 (opening 82a). However, the present invention is not limited to this, and it is sufficient that the groove 82 is formed in a part of the outer portion 64b of the suction port 64 and the suction port 64 and the outer ring recess 63 communicate with each other via the groove 82. In addition, the groove 82 may be replaced with a through hole penetrating the valve plate 19 in the thickness direction.

[0086] [Second modified example] Fig. 7 is a cross-sectional view showing a valve plate 90 in the second modified example, and Fig. 8 is a plan view of the valve plate 90. As shown in Figures 2, 7 and 8, the second modified example is a combination of the above-mentioned embodiment and the first modified example, and further has a shape in which the groove 65 in the above-mentioned embodiment and the groove 82 in the first modified example are each penetrated in the thickness direction. That is, a first through hole 121 is formed in an end face 90a of the valve plate 90 adjacent to the end face 4b of the cylinder block 4 (a face adjacent to the face of the cylinder block in the claims, corresponding to the second demarcated face) in place of the groove 65 in the above-mentioned embodiment, penetrating the valve plate 90 in the thickness direction. Also, a second through hole 122 is formed in place of the groove 82 in place of the groove 82, penetrating the valve plate 90 in the thickness direction.

[0087] The first through hole 121 communicates with at least a portion 64a of the suction port 64 (specifically, almost the entire inner portion facing the inner ring recess 62) and also communicates with the inner ring recess 62. That is, the inner portion 64a of the suction port 64 facing the inner ring recess 62 communicates with the inner ring recess 62 via the first through hole 121. Further, the second through hole 122 communicates with at least a portion (specifically, an outer portion 64b facing the outer ring recess 63) of the suction port 64, and also communicates with the outer ring recess 63. That is, almost the entire outer portion 64b of the suction port 64 facing the outer ring recess 63 communicates with the outer ring recess 63 via the second through hole 122.

[0088] With this configuration, hydraulic oil that has been heated and reached a high temperature due to friction between the end face 4b of the adjacent cylinder block 4 and the end face 90a of the valve plate 90 can be smoothly drawn from the inner ring recess 62 through the first through hole 121 to the suction port 64 (see arrow G in FIG. 7). Also, hydraulic oil that has been heated and reached a high temperature due to friction between the adjacent end faces 4b, 90a can be smoothly drawn from the outer ring recess 63 through the second through hole 122 to the suction port 64 (see arrow H in FIG. 7).

[0089] The high-temperature hydraulic oil sucked into the suction port 64 from the first through hole 121 and the second through hole 122 can be smoothly sucked into the inside of the cylinder bore 17 through the communication hole 18 (see arrow I in FIG. 7). The high-temperature hydraulic oil sucked into the inside of the cylinder bore 17 can be smoothly discharged from the discharge port 66 in the discharge state of the cylinder bore 17, as in the above embodiment.

[0090] Therefore, high-temperature hydraulic oil that has flowed out (leaked) from the gap 92 between the adjacent end faces 4b, 90a into the inner ring recess 62 and the outer ring recess 63 can be more smoothly discharged from the discharge port 66 through each cylinder bore 17 without being retained inside the casing 2. This makes it possible to provide a hydraulic pump 1 that can more effectively suppress an increase in the temperature of the hydraulic pump 1 and thereby more favorably maintain heat balance.

[0091] In the above-mentioned second modified example, the first through hole 121 and the second through hole 122 are formed in the end face 90a of the valve plate 90. The inner ring recess 62 and the outer ring recess 63 are connected to the suction port 64 via the first through hole 121 and the second through hole 122. However, this is not limited to this, and the groove 65b of the above-mentioned embodiment or the groove 82b of the first modified example (both of which are shown by the two-dot chain line in FIG. 7) may be formed in the end face 4b of the cylinder block 4, and the inner ring recess 62 and the outer ring recess 63 may be connected to the suction port 64 via the grooves 65b, 82b.

[0092] [Third Modification] Fig. 9 is a cross-sectional view of the valve plate 95 of the third modified example taken along line IV-IV in Fig. 10. Fig. 10 is a plan view of the valve plate 95 of the third modified example. 2, 9 and 10, a groove (corresponding to a communication passage in the claims) 97 is formed in an end face 95a of the valve plate 95 adjacent to the end face 4b of the cylinder block 4 (corresponding to a face adjacent to the face of the cylinder block in the claims, a second defined face). The groove 97 communicates with at least a part 64c of the suction port 64. Furthermore, the groove 97 has an opening 97a between the adjacent end faces 4b, 95a of the cylinder block 4 and the valve plate 95 that opens into a gap 98 outside the suction port 64 and the discharge port 66, and a tip end 97b located near the discharge port 66.

[0093] With this configuration, the hydraulic oil that is heated by friction between the end face 4b of the adjacent cylinder block 4 and the end face 95a of the valve plate 90 can be smoothly sucked into the suction port 64 through the gap 98 and groove portion 97 (see arrow J in Figure 9). Here, the tip end 97b of the groove 97 is located near the discharge port 66 (specifically, the inner discharge port 66a). Therefore, the high-temperature hydraulic oil leaking into the gap 98 can be smoothly guided to the groove 97. This allows the high-temperature hydraulic oil to be more smoothly sucked into the suction port 64 through the groove 97 (see arrow J in FIG. 9).

[0094] The high-temperature hydraulic oil sucked into the suction port 64 from the groove portion 97 can be smoothly sucked into the inside of the cylinder bore 17 through the communication hole 18 (see arrow K in FIG. 9). The high-temperature hydraulic oil sucked into the inside of the cylinder bore 17 can be smoothly discharged from the discharge port 66 in the discharge state of the cylinder bore 17, as in the above embodiment. Therefore, high-temperature hydraulic oil that has flowed out (leaked) into gap 98 can be more smoothly discharged from discharge port 66 through each cylinder hole 17 without accumulating inside casing 2. This makes it possible to provide a hydraulic pump 1 that can more effectively suppress an increase in temperature of hydraulic pump 1 and thereby more favorably maintain heat balance.

[0095] In the above-mentioned third modified example, a groove 97 is formed in the end face 95a of the valve plate 95 between adjacent end faces 4b, 95a of the cylinder block 4 and the valve plate 95. The groove 97 is connected to the suction port 64. However, this is not limited to the above. A groove 97c (see two-dot chain line in FIG. 9) may be formed in the end face 4b of the cylinder block 4 and connected to the suction port 64.

[0096] 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. However, the present invention is not limited to this, and the above hydraulic pump 1 can be used in various construction machines. [Explanation of symbols]

[0097] 1...hydraulic pump, 2...casing, 3...shaft, 3c...outer peripheral surface, 4...cylinder block, 4b...end surface of cylinder block (surface adjacent to the surface of the valve plate, first defining surface), 5...swash plate, 19, 80, 90, 95...valve plate, 19a, 80a, 90a, 95a...end surface (surface adjacent to the surface of the cylinder block, second defining surface), 21...piston, 55...cylinder bore (cylinder chamber), 62...inner ring recess (inner ring recess), 63...outer ring recess (outer ring recess), 64...suction port (suction passage), 64a ...inner portion (at least a part of the suction passage), 64b...outer portion (at least a part of the suction passage), 64c...at least a part of the suction port (at least a part of the suction passage), 65, 65b, 82, 82b, 97, 97c...groove portion (communication passage), 65a, 82a, 97a...opening, 66...discharge port (discharge passage), 68, 84, 92, 98...space, 97b...tip portion, 100...construction machine, 101...swivel body (vehicle body), 102...traveling body (vehicle body), 121...first through hole, 122...second through hole, C1...center axis (axis)

Claims

1. A casing; A shaft supported within the casing so as to be rotatable about an axis; a cylinder block fitted to an outer circumferential surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber; a valve plate disposed along the axis so as to overlap the cylinder block, the valve plate having an intake passage and a discharge passage communicating with the cylinder chamber, the valve plate having a communication passage formed on a surface adjacent to the cylinder block and on a surface defining the intake passage, the communication passage communicating with at least a part of the intake passage; A hydraulic pump comprising:

2. A casing; A shaft supported within the casing so as to be rotatable about an axis; a valve plate having a suction passage and a discharge passage; a cylinder block fitted to an outer circumferential surface of the shaft to rotate integrally with the shaft, disposed on the valve plate along the axis, having a cylinder chamber communicating with the suction passage and the discharge passage, and having a communication passage formed on a surface adjacent to the valve plate and on a surface defining the suction passage, the communication passage communicating with at least a part of the suction passage; A hydraulic pump comprising:

3. The communication passage is open to a surface other than the surface that defines the cylinder block and the valve plate, among the adjacent surfaces of the cylinder block and the valve plate. The hydraulic pump according to claim 1 or 2.

4. The communication passage is an inner ring recess formed on a surface of the valve plate adjacent to the cylinder block and located radially inward of the shaft with respect to the suction passage and the discharge passage; or an outer ring recess formed on a surface of the valve plate adjacent to the cylinder block and located radially outward of the shaft with respect to the suction passage and the discharge passage; Includes either The hydraulic pump according to claim 3.

5. The communication passage is located near the discharge passage. The hydraulic pump according to claim 1 or 2.

6. A casing; A shaft supported within the casing so as to be rotatable about an axis; a cylinder block fitted to an outer circumferential surface of the shaft and rotating integrally with the shaft, having a cylinder chamber and a first communication passage formed in a first defining surface; a valve plate disposed along the axis so as to overlap the first defining surface of the cylinder block, having an intake passage and a discharge passage communicating with the cylinder chamber, adjacent to the first defining surface and formed at a position facing the first communication passage in the axial direction in a second defining surface that defines the intake passage, and having a second communication passage communicating with at least a part of the intake passage together with the first communication passage; A hydraulic pump comprising:

7. A casing; A shaft supported within the casing so as to be rotatable about an axis; a cylinder block fitted to an outer circumferential surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber; a valve plate disposed along the axis so as to overlap the cylinder block, having an intake passage and a discharge passage communicating with the cylinder chamber, the valve plate being formed on a surface adjacent to the cylinder block and defining the intake passage, the valve plate having an inner ring recess positioned radially inward of the shaft with respect to the intake passage and the discharge passage, an outer ring recess positioned radially outward of the shaft with respect to the intake passage and the discharge passage, and a communication passage communicating with at least a portion of the intake passage and either the inner ring recess or the outer ring recess; A hydraulic pump comprising:

8. A construction machine comprising a vehicle body on which the hydraulic pump according to any one of claims 1 to 7 is mounted.

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