Hydraulic pumps and construction machinery

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 used to supply hydraulic oil to various hydraulic actuators mounted on construction machinery 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 has multiple cylinder holes (cylinder chambers). A piston is inserted into each cylinder hole. The cylinder holes and pistons together form a cylinder chamber.

[0003] The pistons are provided with a swash plate at the end opposite the end where the cylinder chambers are formed, which is rotatably supported relative to the casing. The rotation axis of the swash plate is perpendicular to the rotation axis of the cylinder block. Shoes are attached to the end of each piston facing the swash plate, allowing them to move relative to the swash plate. Each shoe is integrally held by a shoe holder. The shoe holder is pressed toward the swash plate by a pressing member fitted to the outer circumferential surface of the rotary shaft.

[0004] With this configuration, the piston slides along the swash plate, which restricts its displacement within the cylinder bore. As the piston slides along the swash plate, it slides within the cylinder bore. This changes the volume of the cylinder chamber, which is used to discharge hydraulic oil at a predetermined flow rate. As the tilt angle of the swash plate changes, the amount of sliding movement of the piston within the cylinder bore changes, which in turn changes the discharge volume of the hydraulic pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-66189 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, for example, in construction machinery, the cooling devices (oil coolers) are made smaller with each model change, and good heat balance is required for hydraulic equipment. Mini excavators in particular have small machine sizes, making it difficult to install large cooling devices. 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 sandwiched between them, and friction between the adjacent surfaces causes the hydraulic oil to heat up and reach a high temperature.Some of the heated hydraulic oil leaks out of the gap between the cylinder block and the valve plate and accumulates inside the casing, making it difficult to maintain an optimal heat balance in the hydraulic pump. Alternatively, a configuration could be considered in which high-temperature hydraulic oil that leaks from the gap between the cylinder block and the valve plate and accumulates inside the casing is returned to the suction side via a guide path or to the tank. However, even with these configurations, it is difficult to maintain an optimal heat balance in the hydraulic pump due to the high-temperature hydraulic oil remaining inside 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 aspect of the present invention comprises a casing, a shaft supported within the casing so as to be rotatable about its axis, a cylinder block fitted to the 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 the valve plate having a connecting passage formed on a surface adjacent to the cylinder block and defining the intake passage, the connecting passage communicating with at least a portion of the intake passage.

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

[0010] With the above-described configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil interposed between them, and the hydraulic oil, which heats up due to friction between the adjacent surfaces and reaches a high temperature, can be drawn into the intake port through the groove. This allows the high-temperature hydraulic oil drawn into the intake port to be discharged from the discharge port via the cylinder chamber without accumulating inside the casing. This suppresses the temperature rise of the hydraulic pump and maintains an optimal heat balance.

[0011] In the above configuration, the communication passage may open to a surface other than the defining surface among the adjacent surfaces of the cylinder block and the valve plate.

[0012] By configuring it in this way, the friction between the adjacent surfaces of the rotating cylinder block and the fixed valve plate through the hydraulic oil allows the hydraulic oil, which heats up and becomes hot, to be smoothly sucked into the intake port from the external space (outside the surface other than the surface defining the intake 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] This configuration allows the high-temperature hydraulic oil in the inner ring recess to 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 through 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 high-temperature hydraulic oil 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 above configuration, the communication passage may be located near the discharge passage.

[0016] This configuration allows high-temperature hydraulic oil leaking from the discharge port to be efficiently guided into the groove, allowing the high-temperature hydraulic oil leaking from the discharge port to be smoothly drawn into the suction port via the groove. Furthermore, since the hydraulic oil at the discharge port is not directly led to the groove, it is possible to prevent the discharge flow rate of the hydraulic pump from being reduced.

[0017] A hydraulic pump according to another aspect of the present invention comprises a casing, a shaft supported within the casing so as to be rotatable about an axis, a cylinder block fitted to the outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder block having a cylinder chamber and a first communication 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 communication passage in a second demarcated surface that defines the intake passage, the valve plate having a second communication passage that communicates with at least a part of the intake passage together with the first communication 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, which heats up due to friction between the adjacent surfaces and reaches a high temperature, can be drawn into the intake port through the groove. This allows the high-temperature hydraulic oil drawn into the intake port to be discharged from the discharge port via the cylinder chamber without accumulating inside the casing. This suppresses the temperature rise of the hydraulic pump and maintains an optimal heat balance.

[0019] A hydraulic pump according to another aspect of the present invention comprises a casing, a shaft supported within the casing so as to be rotatable about its axis, a cylinder block fitted to the 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 valve plate having a communicating 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, which heats up due to friction between the adjacent surfaces and reaches a high temperature, can be drawn into the intake port from the inner ring recess and the outer ring recess through the groove. This allows the high-temperature hydraulic oil drawn into the intake port to be discharged from the discharge port via the cylinder chamber without accumulating inside the casing. This suppresses temperature increases in the hydraulic pump and maintains an optimal heat balance.

[0021] A construction machine according to another aspect of the present invention includes a vehicle body on which the above-described 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. [Effects of the Invention]

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

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

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

[0026] <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 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 able to revolve. 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 inside 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 tilt 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 tilt angle of the swash plate 5. 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 C1 of the shaft 3 (corresponding to the axis in the claims) 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 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. A bearing 11 that rotatably supports one end of the shaft 3 is provided on a bottom 9b of the casing body 9 opposite the opening 9a. A first guide portion 49 that guides a biasing rod 46 (described later) of the second biasing portion 7 is provided on the inner side of a side surface 9c of the casing body 9. A mounting recess 48 that communicates with the first guide portion 49 is formed on the bottom 9b of the casing body 9. A biasing pin unit 50 (described later) of the second biasing portion 7 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, facing the casing body 9. The swash plate support portion 30 supports the swash plate 5 so that the inclination angle of the swash plate 5 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. The front flange 10 is provided with a male-threaded stopper 40 on its radially outer side. The stopper 40 supports a portion of the swash plate 5 and regulates the inclination angle of the swash plate 5. By rotating the stopper 40 relative to the front flange 10, the amount by which the stopper 40 protrudes from the inner surface 10a of the front flange 10 changes, thereby regulating the inclination angle of the swash plate 5.

[0032] The front flange 10 is also 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. 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 other end of the shaft 3 protrudes outside 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, i.e., at 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 (cutter or the like) not shown.

[0034] The cylinder block 4 is formed in a cylindrical shape. A through-hole 16 is formed in the radial center of the cylinder block 4, into which the shaft 3 can be inserted or press-fitted. A spline 16a is also formed in the through-hole 16. This 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 in the through hole 16 from the axial center to the end 4a so as to surround the periphery of the shaft 3. Furthermore, a through hole 25 is formed in part of the inner circumferential surface of the through hole 16 from the axial center to the swash plate 5 side, penetrating the cylinder block 4 in the axial direction. A spring 23 and retainers 24a and 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] The cylinder block 4 is formed with a plurality of cylinder holes 17 surrounding the shaft 3. The cylinder holes 17 are arranged at equal intervals along the circumferential direction. The cylinder holes 17 are also formed along the axial direction and open on the swash plate 5 side. Communication holes 18 are formed in the end 4a of the cylinder block 4 opposite the front flange 10 at positions corresponding to the 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 disc-shaped valve plate 19 is provided at an end 4a of the cylinder block 4 so as to overlap an end face 4b of the end 4a (the face adjacent to the face of the valve plate in the claims, which corresponds to the first demarcated face) along the central axis C1 of the shaft 3. The valve plate 19 is fixed to the casing main body 9. Even when the cylinder block 4 rotates together with the shaft 3, the valve plate 19 remains stationary relative to the casing 2 (casing main body 9).

[0038] The valve plate 19 has a circular outer shape and a central insertion hole 61 through which the shaft 3 passes along the central axis C1. The valve plate 19 has an inner ring recess (corresponding to the inner ring recess in the claims) 62 disposed radially inward, an outer ring recess (corresponding to the outer ring recess in the claims) 63 disposed radially outward, an intake port (corresponding to the intake passage in the claims) 64, a groove (corresponding to the communication passage in the claims) 65, and an exhaust port (corresponding to the discharge passage in the claims) 66. The intake port 64 and the discharge port 66 are defined by the overlapping of 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 surface adjacent to the surface of the cylinder block in the claims, corresponding to the second demarcated surface). Note that the intake port 64 and the discharge port 66 refer to the entire passages constituting these intake port 64 and discharge port 66, and not just the ends of these 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 radially inward along the insertion hole 61, and is located radially inward 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 peripheral surface 19b of the valve plate 19, and is located radially outward of the shaft 3 with respect to the intake 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, on one circumferential side. 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 in the cylinder block 4. The suction port 64 communicates with each of the cylinder bores 17 via each of the communication holes 18 in 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 portion 64a of the suction port 64 (specifically, substantially the entire inner portion facing the inner ring recess 62) and also communicates 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 yet other words, the groove 65 has an opening 65a on the outside (in the 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] Furthermore, 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, radially between the inner ring recess 62 and the outer ring recess 63. 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 to penetrate the valve plate 19 in the thickness direction so as to communicate with each of the communication holes 18 in the cylinder block 4. Each of the discharge ports 66a, 66b communicates with each of the cylinder bores 17 via each of the communication holes 18 in 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 in the valve plate 19 and a communication hole 18 in the cylinder block 4. Furthermore, each cylinder bore 17 communicates with a discharge passage 72 formed in the casing body 9 via a discharge port 66 in the valve plate 19 and a communication hole 18 in the cylinder block 4.

[0044] Here, a 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, depending on the rotation state of the cylinder block 4, 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.

[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 facing the swash plate 5. The piston 21 has a hollow interior. This hollow is filled with hydraulic oil in the cylinder bore 17. Therefore, the reciprocating motion of the piston 21 is linked to the suction and discharge of hydraulic oil into the cylinder bore 17. That is, when the piston 21 is pulled out of the cylinder bore 17, hydraulic oil is sucked into the cylinder bore 17 through the suction passage 71 and the suction port 64. When the piston 21 advances into the cylinder bore 17, hydraulic oil is discharged from the cylinder bore 17 to the discharge port 66 and the discharge passage 72.

[0046] As shown in Figure 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. As a result, the spring 23 generates a biasing force in the direction of expansion 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 peripheral surface 3c of the shaft 3 closer to the front flange 10 than the connecting member 26, i.e., 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, corresponding to the shape of the protrusion 28. The protrusion 28 of the piston 21 is fitted into this recess 22a. This allows the shoe 22 to be 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 rotates and tilts to restrict the axial displacement of each piston 21. The swash plate 5 has a ring-shaped swash plate body 31 when viewed from the cylinder block 4 side. An insertion hole 32 is formed in the radial center of the swash plate body 31, penetrating it in the axial direction. 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 arranged on the back side of the sliding surface 31a of the swash plate body 31, facing each other in the radial direction, i.e., the front-to-back direction of the drawing, with the insertion hole 32 as the center. The two support protrusions 33, 34 support the swash plate 5 on the front flange 10 so that the tilt angle can be changed. Each support protrusion 33, 34 is formed in a semicircular shape when viewed in the radial direction and has an arcuate surface 33a, 34a. Each support protrusion 33, 34 is formed to protrude from the swash plate body 31 so that the arcuate surface 33a, 34a faces the front flange 10.

[0051] The arcuate surfaces 33a, 34a of the support protrusions 33, 34 are movably abutted against the recessed portions 30a of the swash plate support portion 30 that protrudes from the front flange 10. The arcuate surfaces 33a, 34a slide along the recessed portions 30a, causing the swash plate 5 to rotate relative to the front flange 10. A first biased portion 37 and a second biased portion 38 are integrally formed on the radial side of the swash plate body 31. The first biased portion 37 and the second biased portion 38 are opposed to each other in the radial direction around the insertion hole 32. 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 facing the front flange 10 abuts against a stopper 40 provided on the front flange 10.

[0052] A connecting recess 39 is formed on the radially 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 opposite to the protruding direction of the support protrusions 33, 34 (the surface facing the cylinder block 4). 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, thereby tilting the first biased portion 37 and the second biased portion 38 so as to move toward or 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 becomes.

[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 portion 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, thereby connecting the second retainer 43 to the swash plate 5 in a freely rotatable manner.

[0055] The first spring 44 is compressed between the first retainer 42 and the second retainer 43. Therefore, the elastic force of the first spring 44 generates a biasing force in a direction in which the first spring 44 expands. 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 spaced apart 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. On the other hand, 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 its biasing force in stages 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, but may be fixed to the first retainer 42. Alternatively, the second spring 45 may be movable between the first retainer 42 and the second retainer 43 without being fixed to either the first retainer 42 or 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 by the first biasing portion 6 to the swash plate 5. 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, resisting the biasing force applied by the first biasing portion 6 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 and 53. Although only two of the biasing pins 52 and 53 are shown in FIG. 2, the number of the biasing pins 52 and 53 may be, for example, four.

[0059] The unit case 51 is mounted to be fitted into the mounting recess 48 of the casing body 9. A plurality of second guide portions 54 that guide the plurality of biasing 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 that penetrate the unit case 51 in the axial direction. A cylinder hole (corresponding to a cylinder chamber in the claims) 55 that communicates with one of the plurality of second guide portions 54 is provided on the side of the unit case 51 opposite the swash plate 5. The cylinder hole 55 opens on the side of the unit case 51 opposite 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 in the cylinder bore 55 so as to be movable in the axial direction relative to the cylinder bore 55 . The second guide portion 54 accommodates the urging pins 52, 53 so as to be movable in the axial direction. One of the urging pins 52, 53 is longer than the other urging pin 53. The one urging pin 52 is accommodated in the second guide portion 54, which communicates with the cylinder bore 55. The end of the one urging 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 bore 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 the biasing pin 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 movably axially. A spherical surface 46a is formed on the end of the biasing rod 46 on the contact surface 41 side. Therefore, even if the angle between the swash plate 5 (contact surface 41) and the biasing rod 46 changes due to a change in the inclination angle of the swash plate 5, the biasing 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, which rotates the cylinder block 4 integrally with the shaft 3. As the cylinder block 4 rotates, the pistons 21 revolve around the central axis C1 of the shaft 3.

[0064] The springs 23 bias the shoes 22 attached to the protrusions 28 of the pistons 21 so that they properly follow and press against the sliding surfaces 31a of the swash plate 5 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 press the shoes 22 toward the swash plate 5 via the shoe retaining members 29. Therefore, even if the inclination angle of the swash plate 5 changes, the shoes 22 follow the inclination of the swash plate 5 and are properly pressed against the sliding surfaces 31a.

[0065] As the cylinder block 4 rotates, the pistons 21 revolve around the central axis C1 of the shaft 3, causing each shoe 22 to slide on the sliding surface 31a of the swash plate 5 while also 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 way, the swash plate 5 restricts the displacement of each piston 21 in the axial direction. As the pistons 21 reciprocate, 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 drawn into and discharged from the cylinder bores 17 due to the reciprocating motion of each piston 21. Conversely, the smaller the inclination angle of the swash plate 5, the smaller the amount of hydraulic oil drawn 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] A male-threaded stopper 40 is provided on the radially outer side of the front flange 10. As a result, 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 rotated to move forward and backward relative to the swash plate 5. Therefore, the minimum inclination angle of the swash plate 5 can be adjusted appropriately by moving the stopper 40 forward and backward relative to the swash plate 5.

[0068] Next, the rotational movement of the swash plate 5 will be described. The swash plate 5 is biased by the first biasing portion 6 in a direction that increases the inclination angle of the swash plate 5. The swash plate 5 is also biased by the second biasing portion 7 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 due to 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 due to 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, increasing the clockwise moment by the second biasing portion 7 reduces the tilt angle of the swash plate 5. This causes the first spring 44 and the second spring 45 of the first biasing portion 6 to be compressed, increasing the counterclockwise moment by the first biasing portion 6. 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 tilt.

[0070] On the other hand, when the clockwise moment by the second biasing portion 7 is reduced, the biasing force of the first spring 44 and the second spring 45 of the first biasing portion 6 prevails, increasing the tilt angle of the swash plate 5. 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 tilt.

[0071] When the clockwise moment applied by the second biasing portion 7 is changed, the biasing force of the biasing rod 46 on the swash plate 5 is changed. For example, the second guide portion 54 of the second biasing portion 7 receives signal pressures such as those generated by hydraulic oil discharged from the hydraulic pump 1, those from other hydraulic pumps driven by the same drive source, and those corresponding to the operation of external devices such as an air conditioner driven by the same drive source. The cylinder bore 55 receives signal pressures generated by, for example, a control valve. The biasing pins 52 and 53 bias the biasing rod 46 in accordance with the magnitude of these signal pressures. This changes the biasing force of the biasing rod 46 on the swash plate 5.

[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, when the cylinder block 4 rotates 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 rotational state of the cylinder block 4, the cylinder bores 17 communicate with the suction ports 64 and the discharge ports 66 of the valve plate 19 via the communication holes 18.

[0073] As a result, the cylinder bore 17 is switched between an intake state in which hydraulic oil is drawn in and a discharge state in which hydraulic oil is discharged, depending on the rotation state of the cylinder block 4. Specifically, in the intake state, the cylinder bore 17 draws hydraulic oil from the intake passage 71 through the intake port 64 of the valve plate 19 and into the interior of the cylinder bore 17 through 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 due to friction between the adjacent end faces 4b, 19a, and becomes hot. Some of the heated hydraulic oil 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, high-temperature hydraulic oil that is 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 cylinder bore 17 through the communication hole 18 (see arrow D in FIG. 3). High-temperature hydraulic oil drawn into the cylinder bore 17 can be smoothly discharged from the discharge port 66 of the valve plate 19 to the discharge passage 72 via the communication hole 18 while the cylinder bore 17 is in a discharge state (see arrow B in FIG. 3).

[0076] As a result, high-temperature hydraulic oil that has flowed out (leaked) from gaps (areas 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 bore 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.

[0077] Returning to Fig. 1, the hydraulic pump 1 is mounted on a revolving bed 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 the 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 the 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 that faces the inner ring recess 62. The inner portion 64a of the suction port 64 is connected to the inner ring recess 62 via the groove 65 (opening 65a). However, this 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 that the suction port 64 and the inner ring recess 62 are connected to each other via the groove 65. Furthermore, the groove 65 may be replaced by a through-hole that penetrates the valve plate 19 in the thickness direction.

[0080] [First Modification] Fig. 5 is a cross-sectional view showing valve plate 80 in a first modified example. Fig. 6 is a plan view of 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). Furthermore, 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 Figures 2, 5, and 6, a groove (corresponding to a communicating passage in the claims) 82 is formed in an end face 80a of the valve plate 80 adjacent to 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 defining face). The groove 82 communicates with at least a portion 64b of the intake port 64 (specifically, an outer portion facing the outer ring recess 63) 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 yet another way, the groove 82 has an opening 82a on the outside (outer ring recess 63) other than the end face 80a that defines the intake port 64 and the discharge port 66. Almost the entire outer portion 64b of the intake 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 high-temperature hydraulic oil generated 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 into the suction port 64 (see arrow E in FIG. 5). The high-temperature hydraulic oil drawn into the suction port 64 from the groove 82 can then be smoothly drawn into the cylinder bore 17 through the communication hole 18 (see arrow F in FIG. 5). The high-temperature hydraulic oil drawn into the cylinder bore 17 can be smoothly discharged in the discharge state of the cylinder bore 17, as in 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 bore 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 first modified example described above, 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. 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 first modified example described above, the groove 82 is formed in almost the entire outer portion 64b of the suction port 64 that faces the outer ring recess 63. The outer portion 64b of the suction port 64 is connected to the outer ring recess 63 via the groove 82 (opening 82a). However, this 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 that the suction port 64 and the outer ring recess 63 are connected to each other via this groove 82. Furthermore, the groove 82 may be replaced by a through-hole that penetrates the valve plate 19 in the thickness direction.

[0086] [Second Modification] 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. 2, 7, and 8, the second modified example is a combination of the above-described embodiment and the first modified example, with the groove 65 of the above-described embodiment and the groove 82 of the first modified example each penetrating through the thickness direction. That is, a first through-hole 121 penetrating through the thickness direction of the valve plate 90 is formed in an end face 90a of the valve plate 90 adjacent to the end face 4b of the cylinder block 4 (corresponding to the surface adjacent to the surface of the cylinder block in the claims, the second demarcated surface). In place of the groove 65 of the above-described embodiment, a second through-hole 122 penetrating through the thickness direction of the valve plate 90 is formed in the end face 90a of the valve plate 90 instead of the groove 82.

[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 64b of the suction port 64 (specifically, an outer portion facing the outer ring recess 63), 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 into 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 into the suction port 64 (see arrow H in FIG. 7).

[0089] High-temperature hydraulic oil drawn into the suction port 64 from the first through-hole 121 and the second through-hole 122 can be smoothly drawn into the inside of the cylinder bore 17 via the communication hole 18 (see arrow I in FIG. 7). As in the above embodiment, the high-temperature hydraulic oil drawn 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.

[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 via 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 temperature rise in the hydraulic pump 1 and thereby maintain a more favorable heat balance.

[0091] In the second modified example described above, 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. The groove 65b of the above embodiment or the groove 82b of the first modified example (both 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 communicating 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 the face adjacent to the face of the cylinder block in the claims, the second defined face). The groove 97 communicates with at least a portion 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 and reaches a high temperature due to 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 intake 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, high-temperature hydraulic oil that has leaked into the gap 98 can be effectively 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 drawn into the suction port 64 from the groove portion 97 can be smoothly drawn into the inside of the cylinder bore 17 through the communication hole 18 (see arrow K in FIG. 9). As in the above embodiment, the high-temperature hydraulic oil drawn 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. Therefore, high-temperature hydraulic oil that has flowed out (leaked) into the gap 98 can be more smoothly discharged from the discharge port 66 via each cylinder bore 17 without accumulating inside the casing 2. This makes it possible to provide a hydraulic pump 1 that can more effectively suppress temperature increases in the hydraulic pump 1 and thereby maintain a more optimal heat balance.

[0095] In the third modified example described above, a groove 97 is formed in the end surface 95a of the valve plate 95 between the adjacent end surfaces 4b, 95a of the cylinder block 4 and the valve plate 95. This groove 97 is connected to the suction port 64. However, this is not limiting, and a groove 97c (see the two-dot chain line in FIG. 9) may be formed in the end surface 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 a variety of 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...gap, 97b...tip portion, 100...construction machine, 101...swinging body (vehicle body), 102...traveling body (vehicle body), 121...first through hole, 122...second through hole, C1...central axis (axis)

Claims

1. A casing; a shaft supported within the casing so as to be rotatable about its axis; a cylinder block fitted to an outer peripheral surface of the shaft, rotating integrally with the shaft, and having a cylinder chamber; a disc-shaped valve plate disposed along the axis so as to overlap the cylinder block, the cylinder block has a first defining surface adjacent to the valve plate; The valve plate is a second demarcated surface adjacent to the first demarcated surface; an insertion hole located at the center of the valve plate when viewed from the direction along the axis, and through which the shaft passes in the direction along the axis; an intake passage and a discharge passage, which are disposed at different positions in the circumferential direction of the valve plate and communicate with the cylinder chamber; an inner ring recess located radially inward of the valve plate with respect to the suction passage and the discharge passage and located radially outward of the insertion hole, the inner ring recess formed annularly along the insertion hole, and opening at the second defining surface; an outer ring recess located radially outward of the suction passage and the discharge passage, the outer ring recess being formed annularly along the outer peripheral surface of the valve plate and opening into the second defining surface; a friction end surface portion located at the outermost periphery of the second defining surface and continuing in the radial direction between the outer circumferential wall of the outer ring recess and the outer circumferential surface of the valve plate; and an inner peripheral wall of the inner ring recess has an opening that communicates with the insertion hole and is continuous with an opening of the second defining surface of the inner ring recess; an outer peripheral wall of the inner ring recess has an opening that communicates with the suction passage and is continuous with an opening of the second defining surface of the inner ring recess; an inner peripheral wall of the outer ring recess has an opening that communicates with the suction passage and is continuous with an opening of the second defining surface of the outer ring recess; The friction end surface portion is provided so as to contact the first demarcating surface on the same plane over the entire circumference in the circumferential direction. Hydraulic pump.

2. The outer peripheral surface of the valve plate is The second demarcated surface is connected to the back surface located on the opposite side of the second demarcated surface in the direction along the axis, and the entire outer periphery of the second demarcated surface is connected to the back surface, and the outer periphery of the second demarcated surface is connected to the back surface. The second demarcated surface has the same diameter at each position in the direction along the axis. The hydraulic pump according to claim 1 .

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