Hydraulic pump

Abstract

The invention provides a hydraulic pump. This hydraulic pump is provided with: a housing; a shaft supported in the housing so as to be rotatable about an axis; a cylinder that is fitted to the outer peripheral surface of the shaft, rotates integrally with the shaft, and has a cylinder chamber; and a valve plate disposed along the axis so as to overlap the cylinder body, the valve plate having a suction passage and a discharge passage that communicate with the cylinder chamber, the valve plate having a communication path, the communication path being formed on a surface of the valve plate adjacent to the cylinder body, the surface defining the suction passage, and the valve plate being disposed along the axis so as to overlap the cylinder body. The communication path communicates with at least a part of the suction path.

Description

[0001] This application is a divisional application of the application with the application date of August 21, 2020, application number 202010850901.5, and invention title "Hydraulic Pump and Construction Machinery". Technical Field

[0002] The present invention relates to a hydraulic pump and a construction machine. Background Art

[0003] As a hydraulic pump, there is a swash plate type variable displacement hydraulic pump for supplying working oil to various hydraulic actuators mounted on construction machines such as hydraulic excavators. Such a hydraulic pump has a rotating shaft rotatably supported in a housing. A cylinder block is fitted and fixed to the outer peripheral surface of the rotating shaft. The rotating shaft and the cylinder block rotate integrally. A plurality of cylinder holes (cylinder chambers) are provided in the cylinder block. A plunger is inserted into each cylinder hole. And, the cylinder chamber is constituted by the cylinder hole and the plunger.

[0004] In the plunger, a swash plate rotatably supported relative to the housing is provided at an end on the side opposite to the end (the end facing the cylinder chamber) on the side where the cylinder chamber is formed. The rotation axis of the swash plate is orthogonal to the rotation axis of the cylinder block. A slipper capable of moving relative to the swash plate is mounted at an end of each plunger on the swash plate side (the end of each plunger facing the swash plate). Each slipper is integrally held by a slipper holding member. The slipper holding member is pressed toward the swash plate by a pressing member fitted to the outer peripheral surface of the rotating shaft.

[0005] Based on such a structure, the plunger slides along the swash plate, and the displacement in the cylinder hole is restricted by the swash plate. If the plunger slides along the swash plate, the plunger slides and moves in the cylinder hole. By using the resulting change in the volume of the cylinder chamber, working oil is ejected at a predetermined flow rate. If the tilt angle of the swash plate changes, the sliding movement amount of the plunger in the cylinder hole changes, and thus, the ejection amount of the hydraulic pump changes.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 2014-66189 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] For example, construction machines downsize the cooling device (oil cooler) according to model changes, and seek a good thermal balance for hydraulic equipment. In particular, the body size of mini excavators is small, and it is difficult to configure a large cooling device.

[0011] On the other hand, in a conventional hydraulic pump, a rotating cylinder block and a valve plate fixed within a housing are adjacent to each other with working oil therebetween. Due to the friction between the surfaces of the cylinder block and the valve plate that are adjacent to each other with the working oil therebetween, the working oil generates heat and becomes high in temperature. A part of the working oil that has become high in temperature due to heat leakage stays in the housing through the gap between the cylinder block and the valve plate. Therefore, it is considered difficult to appropriately maintain the thermal balance of the hydraulic pump.

[0012] Alternatively, a structure is conceived in which the high-temperature working oil that has leaked and stayed in the housing through the gap between the cylinder block and the valve plate returns to the suction side or the tank via a guiding path. However, even with these structures, the high-temperature working oil stays in the housing. Therefore, it is difficult to appropriately maintain the thermal balance of the hydraulic pump.

[0013] The present invention provides a hydraulic pump and a construction machine that can appropriately maintain thermal balance by suppressing an increase in the temperature of the hydraulic pump.

[0014] Solutions for Solving the Problems

[0015] A hydraulic pump according to one aspect of the present invention includes: a housing; a shaft rotatably supported within the housing 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 cylinder chambers; and a valve plate disposed along the axis so as to overlap the cylinder block, the valve plate having a suction passage and a discharge passage communicating with the cylinder chambers, the valve plate having a communication path formed on a surface of the valve plate adjacent to the cylinder block and for defining the suction passage, the communication path communicating with at least a part of the suction passage.

[0016] A hydraulic pump according to another aspect of the present invention includes: a housing; a shaft rotatably supported within the housing about an axis; a valve plate having a suction passage and a discharge passage; and a cylinder block fitted to an outer peripheral surface of the shaft and rotating integrally with the shaft, and disposed along the axis on the valve plate, the cylinder block having cylinder chambers communicating with the suction passage and the discharge passage, the cylinder block having a communication path formed on a surface of the cylinder block adjacent to the valve plate and for defining the suction passage, the communication path communicating with at least a part of the suction passage.

[0017] With the above configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with working oil therebetween. The working oil generates heat and becomes high in temperature due to the friction between the surfaces of the cylinder block and the valve plate that are adjacent to each other. The high-temperature working oil can be sucked into the suction port via a groove. Therefore, the high-temperature working oil sucked into the suction port does not stay inside the housing, but can be discharged from the discharge port to the discharge passage via the cylinder chambers. Accordingly, it is possible to appropriately maintain the thermal balance by suppressing an increase in the temperature of the hydraulic pump.

[0018] In the above structure, it is also possible that the communication path opens at a portion other than the portion for the partition formation in the adjacent surfaces of the cylinder block and the valve plate.

[0019] By configuring in this way, it is possible to smoothly suck the working oil that has become hot due to the friction between the adjacent surfaces of the rotating cylinder block and the fixed valve plate with the working oil in between and has become high temperature from the external space (the outside except for the surface forming the suction portion of the partition) to the suction port.

[0020] In the above structure, it is also possible that the communication path includes either an inner ring recess or an outer ring recess. The inner ring recess is formed on the surface of the valve plate adjacent to the cylinder block and is located on the inner side in the radial direction of the shaft with respect to the suction passage and the discharge passage. The outer ring recess is formed on the surface of the valve plate adjacent to the cylinder block and is located on the outer side in the radial direction of the shaft with respect to the suction passage and the discharge passage.

[0021] By configuring in this way, it is possible to smoothly suck the working oil that has become high temperature in the inner ring recess to the suction port via the groove. Thus, it is possible to suck the working oil that has become high temperature near the rotating shaft from the suction port and discharge it from the discharge port to the discharge passage, thereby being able to suppress the temperature rise of the hydraulic pump.

[0022] It is possible to smoothly suck the working oil that has become high temperature in the outer ring recess to the suction port via the groove. Thus, it is possible to suck the working oil that has become high temperature between the cylinder block and the valve plate from the suction port and discharge it from the discharge port to the discharge passage. Therefore, it is possible to suppress the temperature rise of the hydraulic pump.

[0023] In the above structure, it is also possible that the communication path is located near the discharge passage.

[0024] By configuring in this way, it is possible to well guide the high-temperature working oil leaking from the discharge port to the discharge passage to the groove. Thus, it is possible to smoothly suck the high-temperature working oil leaking from the discharge port to the discharge passage to the suction port via the groove.

[0025] Since the working oil at the discharge port is not directly guided to the groove, it is also possible to prevent the deterioration of the discharge flow rate of the hydraulic pump.

[0026] Another technical solution of the hydraulic pump of the present invention includes: a housing; a shaft rotatably supported in the housing 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 path formed in a first defined surface of the cylinder block; and a valve plate disposed along the axis so as to overlap the first defined surface of the cylinder block, having a suction passage and a discharge passage communicating with the cylinder chamber, the valve plate having a second communication path formed at a position on a second defined surface of the valve plate opposite to the first communication path in the axial direction, communicating with at least a part of the suction passage together with the first communication path, the second defined surface being adjacent to the first defined surface and defining the suction passage.

[0027] With such a configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil therebetween. The hydraulic oil is heated due to the friction between the adjacent surfaces of the cylinder block and the valve plate and becomes high temperature. The high-temperature hydraulic oil can be sucked into the suction port via a groove. Therefore, the high-temperature hydraulic oil sucked into the suction port does not stay inside the housing, but can be discharged from the discharge port to the discharge passage via the cylinder chamber. Thus, the thermal balance can be properly maintained by suppressing the rise in the temperature of the hydraulic pump.

[0028] Another technical solution of the hydraulic pump of the present invention includes: a housing; a shaft rotatably supported in the housing 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 valve plate disposed along the axis so as to overlap the cylinder block, having a suction passage and a discharge passage communicating with the cylinder chamber, and having an inner annular pit, an outer annular pit, and a communication path, the inner annular pit, the outer annular pit, and the communication path being formed on a surface of the valve plate adjacent to the cylinder block and for defining the suction passage, the inner annular pit being located radially inside the shaft with respect to the suction passage and the discharge passage, the outer annular pit being located radially outside the shaft with respect to the suction passage and the discharge passage, and the communication path communicating with at least a part of the suction passage, the inner annular pit, and the outer annular pit.

[0029] With such a configuration, the rotating cylinder block and the fixed valve plate are adjacent to each other with hydraulic oil therebetween. The hydraulic oil is heated due to the friction between the adjacent surfaces of the cylinder block and the valve plate and becomes high temperature. The high-temperature hydraulic oil can be sucked into the suction port from the inner annular pit and the outer annular pit via a groove. Therefore, the high-temperature hydraulic oil sucked into the suction port does not stay inside the housing, but can be discharged from the discharge port to the discharge passage via the cylinder chamber. Thus, the thermal balance can be properly maintained by suppressing the rise in the temperature of the hydraulic pump.

[0030] Another technical solution of the present invention provides a construction machine having a vehicle body equipped with the above hydraulic pump.

[0031] With such a configuration, a construction machine can be provided, which is equipped with a hydraulic pump capable of suppressing the temperature rise of the hydraulic pump to appropriately maintain thermal balance.

[0032] Effects of the Invention

[0033] The above hydraulic pump and construction machine can appropriately maintain thermal balance by suppressing the temperature rise of the hydraulic pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic configuration diagram of a construction machine according to an embodiment of the present invention.

[0035] Figure 2 It is a cross-sectional view of a hydraulic pump according to an embodiment of the present invention.

[0036] Figure 3 It is an enlarged cross-sectional view showing Figure 2 section III.

[0037] Figure 4 It is a top view of a valve plate according to an embodiment of the present invention.

[0038] Figure 5 It is a cross-sectional view of a valve plate showing a first modification of an embodiment of the present invention.

[0039] Figure 6 It is a top view of a valve plate showing a first modification of an embodiment of the present invention.

[0040] Figure 7 It is a cross-sectional view of a valve plate showing a second modification of an embodiment of the present invention.

[0041] Figure 8 It is a top view of a valve plate showing a second modification of an embodiment of the present invention.

[0042] Figure 9 It is a cross-sectional view along line IV-IV of a valve plate showing a third modification of an embodiment of the present invention Figure 10 section.

[0043] Figure 10 It is a top view of a valve plate showing a third modification of an embodiment of the present invention.

[0044] Explanation of Reference Signs

[0045] 1. Hydraulic pump; 2. Housing; 3. Shaft; 3c. Outer peripheral surface; 4. Cylinder block; 4b. End face of the cylinder block (the face adjacent to the valve plate, the first defined face); 5. Swash plate; 19, 80, 90, 95. Valve plate; 19a, 80a, 90a, 95a. End face (the face adjacent to the cylinder block, the second defined face); 21. Plunger; 55. Cylinder bore (cylinder chamber); 62. Inner ring recess (inner ring pit); 63. Outer ring recess (outer ring pit); 64. Suction port (suction passage); 64a. Inner part (at least a part of the suction passage); 64b. Outer part (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 part (communication path); 65a, 82a, 97a. Opening; 66. Discharge port (discharge passage); 68, 84, 92, 98. Gap; 97b. Tip part; 100. Construction machine; 101. Rotating body (vehicle body); 102. Traveling body (vehicle body); 121. First through hole; 122. Second through hole; C1. Central axis (axis). Detailed implementation mode

[0046] Next, the implementation mode of the present invention will be described based on the drawings.

[0047] <Construction machine>

[0048] Figure 1 is a schematic structural diagram of a construction machine 100.

[0049] As Figure 1 shown, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 includes a rotating body (equivalent to the vehicle body in the claims) 101 and a traveling body (equivalent to the vehicle body in the claims) 102. The rotating body 101 is provided on the traveling body 102 in a rotatable manner. A hydraulic pump 1 is mounted on the rotating body 101.

[0050] The rotating body 101 includes: a cab 103 on which an operator can ride; a boom 104, one end of which is swingably connected to the cab 103; an arm 105, one end of which is swingably connected to the other end (tip) of the boom 104 on the side opposite to the cab 103; and a bucket 106, which is swingably connected to the other end (tip) of the arm 105 on the side opposite to the boom 104. The 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 the working oil ejected from the hydraulic pump 1.

[0051] <Hydraulic pump>

[0052] Figure 2 is a cross-sectional view of the hydraulic pump 1.

[0053] As shown Figure 2 in FIG. 1, the hydraulic pump 1 is a so-called swash plate type variable displacement hydraulic pump. The hydraulic pump 1 includes: a housing 2; a shaft 3 rotatably supported inside the housing 2; a cylinder block 4 housed inside the housing 2 and fixed to the shaft 3; a swash plate 5 housed inside the housing 2 so that its tilt angle can be changed and controlling the discharge amount of the working oil discharged from the hydraulic pump 1; and a first biasing portion 6 and a second biasing portion 7 for controlling the tilt angle of the swash plate 5.

[0054] In Figure 2 FIG. 1, for ease of understanding of the description, the scales of the respective components are appropriately changed. In the following description, the direction parallel to the central axis C1 of the shaft 3 (corresponding to the axis in the claims) is simply referred to as the axial direction, the rotation direction of the shaft 3 is simply referred to as the circumferential direction, and the radial direction of the shaft 3 is simply referred to as the radial direction.

[0055] The housing 2 includes: a box-shaped housing body 9 having an opening 9a; and a front flange 10 closing the opening 9a of the housing body 9.

[0056] A bearing 11 rotatably supporting one end of the shaft 3 is provided at the bottom 9b of the housing body 9 on the side opposite to the opening 9a. A first guide portion 49 for guiding a biasing rod 46 (described later) of the second biasing portion 7 is provided on the inner surface side of the side surface 9c of the housing body 9. An installation recess 48 communicating with the first guide portion 49 is formed in the bottom 9b of the housing body 9. A biasing pin unit 50 (described later) of the second biasing portion 7 is installed in the installation recess 48.

[0057] Moreover, a suction passage 71 (see Figure 3 ) and a discharge passage 72 (see Figure 3 ) are formed in the housing body 9. The suction passage 71 is connected to a tank (not shown). The discharge passage 72 is connected to a cab 103, an arm 104, a boom 105, and a bucket 106 via a control valve (not shown) or the like.

[0058] A swash plate support portion 30 is formed to project on the inner surface 10a (the inner surface 10a facing the housing body 9) of the flange 10 on the side of the housing body 9. The swash plate support portion 30 supports the swash plate 5 so that its tilt angle can be changed. A concave portion 30a having a semicircular shape when viewed from the radial direction is formed in the swash plate support portion 30. The swash plate 5 is supported by the concave portion 30a.

[0059] An externally threaded stopper 40 is provided at a portion of the front flange 10 on the radially outer side. The stopper 40 supports a part of the swash plate 5 and restricts the tilt angle of the swash plate 5. By rotating the stopper 40 relative to the front flange 10, the protruding amount of the stopper 40 protruding toward the inner surface 10a side of the front flange 10 changes. Thereby, the tilt angle of the swash plate 5 is restricted.

[0060] A through hole 13 through which the shaft 3 can pass is formed in the front flange 10. A bearing 14 that rotatably supports the other end side of the shaft 3 is provided in the through hole 13. An oil seal 15 is provided at a position in the through hole 13 on the side opposite to the housing main body 9 (outside of the front flange 10) with respect to the bearing 14. The other end of the shaft 3 passes through the bearing 14 and the oil seal 15 and protrudes to the outside of the front flange 10. The oil seal 15 prevents the outflow of oil from the inside. The oil seal 15 prevents foreign matters and the like from entering between the front flange 10 and the shaft 3.

[0061] A first spline 3a is formed at 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 by means of the first spline 3a. A second spline 3b is formed at the axial center of the shaft 3, that is, at a portion of the outer peripheral surface 3c of the shaft 3 on the bottom 9b side of the housing main body 9 with respect to the swash plate 5. A cylinder block 4 is fitted at a position on the outer peripheral surface 3c of the shaft 3 corresponding to the second spline 3b.

[0062] The first spline 3a and the second spline 3b are formed by performing cutting on the outer peripheral surface 3c of the shaft 3, for example, using a dedicated tool (such as a cutting tool) (not shown).

[0063] The cylinder block 4 is formed in a cylindrical shape. A through hole 16 through which the shaft 3 can be inserted or pressed is formed at the radial center of the cylinder block 4. A spline 16a is also formed in the through hole 16. The spline 16a is spline-coupled with the second spline 3b of the shaft 3. Thus, the shaft 3 and the cylinder block 4 rotate integrally.

[0064] A recess 20 is formed in the through hole 16 from the axial center to the end 4a so as to surround the shaft 3. A through hole 25 that axially penetrates the cylinder block 4 is formed in a part of the inner peripheral surface of the through hole 16 from the axial center to the swash plate 5 side. A spring 23 and snap rings 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.

[0065] A plurality of cylinder bores 17 are formed in the cylinder block 4 so as to surround the shaft 3. The cylinder bores 17 are arranged at equal intervals in the circumferential direction. The cylinder bores 17 are formed axially, and the swash plate 5 side of the cylinder bores 17 is open. Communication holes 18 that connect the cylinder bores 17 and the outside of the cylinder block 4 are formed at positions corresponding to the respective cylinder bores 17 at the end 4a of the cylinder block 4 on the side opposite to the front flange 10.

[0066] Figure 3 Is an enlarged view showing Figure 2 A cross-sectional view of part III. Figure 4 Is a top view of the valve plate 19.

[0067] As Figure 2 ,Figure 3 , Figure 4 As shown in Figure 4 , at the end 4a of the cylinder block 4, a disc-shaped valve plate 19 is provided in a manner overlapping the end face 4b of the end 4a along the central axis C1 of the shaft 3 (the face adjacent to the valve plate surface and the first defined surface in the claims). The valve plate 19 is fixed to the housing main body 9. Even when the cylinder block 4 rotates together with the shaft 3, the valve plate 19 remains stationary relative to the housing 2 (housing main body 9).

[0068] The valve plate 19 has an insertion hole 61 formed in the center for the shaft 3 to pass through along the central axis C1, and the outer shape of the valve plate 19 is formed as a circle. The valve plate 19 has: an inner ring recess (equivalent to the inner ring pit in the claims) 62, which is arranged on the radially inner side along the outer edge of the insertion hole 61; an outer ring recess (equivalent to the outer ring pit in the claims) 63, which is arranged at a position radially outside the inner ring recess 62; a suction port (equivalent to the suction passage in the claims) 64; a groove portion (equivalent to the communication path in the claims) 65; and a discharge port (equivalent to the discharge passage in the claims) 66. The end face 4b of the cylinder block 4 overlaps the end face 19a of the valve plate 19 opposite to the end face 4b of the cylinder block 4 (the face adjacent to the cylinder block surface and the second defined surface in the claims). Thus, the suction port 64 and the discharge port 66 are partitioned and formed. The suction port 64 and the discharge port 66 refer to the entire passages constituting these suction port 64 and discharge port 66, rather than just the ends of the passages.

[0069] The inner ring recess 62 is formed in a substantially circular ring shape when viewed axially. The inner ring recess 62 opens on the end face 19a of the valve plate 19. The inner ring recess 62 is formed in a ring shape along the insertion hole 61 at a position radially inward. The inner ring recess 62 is located radially inside the shaft 3 relative to the suction port 64 and the discharge port 66.

[0070] The outer ring recess 63 is formed in a substantially circular ring shape when viewed axially. The outer ring recess 63 opens on the end face 19a of the valve plate 19 opposite to the end face 4b of the cylinder block 4. The outer ring recess 63 is formed in a ring shape along the outer peripheral surface 19b of the valve plate 19 at a position radially outward. The outer ring recess 63 is located radially outside the shaft 3 relative to the suction port 64 and the discharge port 66.

[0071] The suction port 64 is located between the inner ring recess 62 and the outer ring recess 63 of the valve plate 19 in the radial direction and is formed on one side in the circumferential direction. The suction port 64 is formed in a curved shape along the inner ring recess 62 and the outer ring recess 63. The suction port 64 is formed to penetrate in the thickness direction of the valve plate 19 in a manner communicating with the respective communication holes 18 of the cylinder block 4. The suction port 64 communicates with the respective cylinder holes 17 via the respective communication holes 18 of the cylinder block 4.

[0072] A groove portion 65 is formed on the end face 19a of the valve plate 19. The groove portion 65 communicates with at least a part of the suction port 64 (specifically, substantially the whole of the inner part opposite to the inner ring recess 62) 64a. The groove portion 65 communicates with the inner ring recess 62. In other words, the groove portion 65 has an opening portion 65a that opens into the inner ring recess 62. Further in other words, the groove portion 65 has the opening portion 65a on the outer part (inner ring recess 62) of the end face 19a except for the parts that demarcate and form the suction port 64 and the discharge port 66. The inner part 64a of the suction port 64 that is opposite to the inner ring recess 62 communicates with the inner ring recess 62 via the groove portion 65 (opening portion 65a).

[0073] In the valve plate 19, a discharge port 66 is formed in the radial direction between the inner ring recess 62 and the outer ring recess 63 and on the other side in the circumferential direction (the side opposite to the suction port 64). 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. The first discharge port 66a and the second discharge port 66b are formed to penetrate in the thickness direction of the valve plate 19 so as to communicate with the respective communication holes 18 of the cylinder block 4. The respective discharge ports 66a, 66b communicate with the respective cylinder holes 17 via the respective communication holes 18 of the cylinder block 4.

[0074] Between each cylinder hole 17 and the suction passage 71 formed in the housing main body 9, they communicate via the suction port 64 of the valve plate 19 and the communication hole 18 of the cylinder block 4. Between each cylinder hole 17 and the discharge passage 72 formed in the housing main body 9, they communicate via the discharge port 66 of the valve plate 19 and the communication hole 18 of the cylinder block 4.

[0075] The valve plate 19 is fixed to the housing main body 9. In this state, the cylinder block 4 is rotated together with the shaft 3. The cylinder hole 17 communicates with the suction port 64 and the discharge port 66 of the valve plate 19 according to the rotation state of the cylinder block 4. Thus, the cylinder hole 17 is switched to a state of sucking working oil from the suction passage 71 via the suction port 64 of the valve plate 19 and a state of discharging working oil to the discharge passage 72 via the discharge port 66 of the valve plate 19 according to the rotation state of the cylinder block 4.

[0076] In each cylinder hole 17, a plunger 21 that is movable axially is accommodated. The plunger 21 is accommodated in the cylinder hole 17. Thus, the plunger 21 revolves around the central axis C1 of the shaft 3 as the shaft 3 and the cylinder block 4 rotate.

[0077] A spherical convex portion 28 is integrally formed at the end of the plunger 21 on the swash plate 5 side. The inside of the plunger 21 is formed as a cavity. This cavity is filled with working oil in the cylinder bore 17. Therefore, the reciprocating motion of the plunger 21 is associated with the suction and ejection of the working oil relative to the cylinder bore 17. That is, when the plunger 21 is pulled out from the cylinder bore 17, the working oil is sucked into the inside of the cylinder bore 17 from the suction passage 71 and the suction port 64. When the plunger 21 enters the inside of the cylinder bore 17, the working oil is ejected from the inside of the cylinder bore 17 to the ejection port 66 and the ejection passage 72.

[0078] As Figure 2 shown, the spring 23 housed in the recess 20 of the cylinder block 4 is, for example, a helical spring. The spring 23 is compressed between two snap rings 24a, 24b housed in the recess 20. Therefore, the spring 23 generates a force in the direction of elongation due to its elastic force. The force of the spring 23 is transmitted to the connecting member 26 by one of the two snap rings 24a, 24b, i.e., the snap ring 24b. In the portion closer to the front flange 10 than the connecting member 26 (between the cylinder block 4 and the swash plate 5), the pressing member 27 is fitted onto the outer peripheral surface 3c of the shaft 3.

[0079] The pressing member 27 is formed in a substantially cylindrical shape. The connecting member 26 abuts against the end surface of the pressing member 27 on the side opposite to the front flange 10. The 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 later-described slipper holding member 29 and presses the slipper holding member 29 toward the swash plate 5 side (in the direction of the swash plate 5).

[0080] In each plunger 21 in each cylinder bore 17 housed in the cylinder block 4, a slipper 22 is mounted on the convex portion 28 of these plungers 21. A spherical concave portion 22a is formed on the surface of the slipper 22 on the side for housing the convex portion 28 in a shape corresponding to the shape of the convex portion 28. That is, a concave portion 22a for housing the convex portion 28 is formed on one surface of the slipper 22. The shape of the concave portion 22a is spherical corresponding to the shape of the convex portion 28. The convex portion 28 of the plunger 21 is fitted into this concave portion 22a. Thus, the slipper 22 is connected to be rotatable relative to the convex portion 28 of the plunger 21.

[0081] Each slipper 22 is integrally held by a slipper holding member 29. This slipper holding member 29 is pressed toward the swash plate 5 side by the pressing member 27. By means of the slipper holding member 29, each slipper 22 is pressed toward the swash plate 5 side by the pressing member 27.

[0082] The swash plate 5 has the following functions: it rotates and tilts, thereby restricting the displacement of each plunger 21 in the axial direction. The swash plate 5 has a swash plate body 31 that is annular when viewed from the side of the cylinder block 4. A through hole 32 that penetrates in the axial direction is formed at the radial center of the swash plate body 31. The shaft 3 penetrates (passes through) the through hole 32. A flat sliding surface 31a is formed on the side of the swash plate body 31 facing the cylinder block 4. Each slipper 22 is pressed against the sliding surface 31a in a movable manner.

[0083] Two support protrusions 33, 34 are arranged on the back side of the sliding surface 31a of the swash plate body 31. The two support protrusions 33, 34 are arranged opposite to each other in the front-back direction of the paper surface in the radial direction with the through hole 32 as the center. The two support protrusions 33, 34 support the swash plate 5 in a manner that the tilt angle can be changed with respect to the front flange 10. Each support protrusion 33, 34 is formed in a semicircular shape when viewed from the radial direction. The support protrusion 33 has an arc surface 33a. The support protrusion 34 has an arc surface 34a. These arc surfaces 33a, 34a face the side of the front flange 10. Each support protrusion 33, 34 is formed to protrude from the swash plate body 31.

[0084] The arc surfaces 33a, 34a of each support protrusion 33, 34 are movably abutted against the concave portion 30a of the swash plate support portion 30 formed to protrude on the front flange 10. The arc surfaces 33a, 34a slide at the concave portion 30a. Thereby, the swash plate 5 rotates with respect to the front flange 10.

[0085] On the radial side portion of the swash plate body 31, a first force-applied portion 37 and a second force-applied portion 38 that are opposite to each other in the radial direction with the through hole 32 as the center are integrally formed. The direction in which the first force-applied portion 37 and the second force-applied portion 38 are opposite to each other is orthogonal to the direction in which the two support protrusions 33, 34 are opposite to each other. The first force-applied portion 37 and the second force-applied portion 38 extend from the swash plate body 31 toward the outside in the radial direction. The surface 38a of the second force-applied portion 38 on the side closer to the front flange 10 abuts against the stopper 40 provided on the front flange 10.

[0086] On the outside in the radial direction (the tip side) of the first force-applied portion 37, a connecting concave portion 39 is formed on the surface (the side closer to the cylinder block 4) on the side opposite to the protruding direction of each support protrusion 33, 34. The first force-applying portion 6 is connected to the connecting concave portion 39. The connecting concave portion 39 is formed in a circular shape when viewed from the axial direction.

[0087] An abutting surface 41 is formed on substantially the entire surface of the second force-applied portion 38 on the side opposite to the protruding direction of each support protrusion 33, 34 (the side closer to the cylinder block 4). The abutting surface 41 is formed by flatly cutting the second force-applied portion 38. The second force-applying portion 7 abuts against the abutting surface 41.

[0088] The swash plate 5 configured in this way rotates relative to the front flange 10. As a result, the first force-applied portion 37 and the second force-applied portion 38 are inclined so as to approach and separate from the front flange 10.

[0089] The inclination angle of the swash plate 5 refers to the angle formed by the sliding surface 31a and the surface orthogonal to the shaft 3. That is to say, the smaller this angle is, the smaller the inclination angle of the swash plate 5 is.

[0090] The first biasing portion 6 biases the swash plate 5 in the direction in which the inclination angle of the swash plate 5 becomes larger. The first biasing portion 6 includes: a first snap ring 42 disposed on the bottom 9b side of the housing main body 9; a second snap ring 43 disposed on the swash plate 5 side; and a first spring 44 and a second spring 45 disposed between the first snap ring 42 and the second snap ring 43.

[0091] A spherical connecting convex portion 43a is formed to protrude on the swash plate 5 side of the second snap ring 43. By the connecting convex portion 43a abutting against the connecting concave portion 39 of the swash plate 5, the second snap ring 43 is connected to be rotatable relative to the swash plate 5.

[0092] The first spring 44 is compressed between the first snap ring 42 and the second snap ring 43. Therefore, due to its elastic force, the first spring 44 generates a force in the direction in which the first spring 44 extends.

[0093] 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 snap ring 43.

[0094] The second spring 45 is separated from the first snap ring 42 in a state where the inclination angle of the swash plate 5 is large ( Figure 2 the state shown). Thus, when the inclination angle of the swash plate 5 is large, only the force of the first spring 44 acts on the swash plate 5.

[0095] In contrast, if the inclination angle of the swash plate 5 becomes smaller, then at a certain inclination angle, the second spring 45 comes into contact with the first snap ring 42. If the inclination angle of the swash plate 5 becomes even smaller, then the second spring 45 is also compressed between the first snap ring 42 and the second snap ring 43. Thus, the forces of both the first spring 44 and the second spring 45 act on the swash plate 5.

[0096] In this way, the first biasing portion 6 can change its acting force step by step according to the inclination angle of the swash plate 5. The second spring 45 is not limited to being fixed to the second snap ring 43, and the second spring 45 can also be fixed to the first snap ring 42. The second spring 45 can also be not fixed to either the first snap ring 42 or the second snap ring 43, but move between the first snap ring 42 and the second snap ring 43.

[0097] The second biasing portion 7 applies a biasing force to the swash plate 5 in a direction opposite to the biasing force of the first biasing portion 6 on the swash plate 5. In particular, the second biasing portion 7 biases the swash plate 5 in a direction in which the tilt angle of the swash plate 5 decreases, overcoming the biasing force of the first biasing portion 6 that causes the tilt angle of the swash plate 5 to increase.

[0098] 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 housing 51 and a plurality of biasing pins 52, 53. In Figure 2 , only two of the plurality of biasing pins 52, 53 are shown, but for example, four biasing pins 52, 53 are provided.

[0099] The unit housing 51 is mounted in the mounting recess 48 of the housing body 9 in an inserted manner. A plurality of second guiding portions 54 for guiding the plurality of biasing pins 52, 53 are provided on the side of the unit housing 51 closer to the swash plate 5. The second guiding portions 54 are holes that penetrate the unit housing 51 along the axial direction. A cylinder hole 55 (corresponding to the cylinder chamber in the claims) that communicates with one of the plurality of second guiding portions 54 is provided on the side of the unit housing 51 opposite to the swash plate 5. The cylinder hole 55 opens on the side of the unit housing 51 opposite to the second guiding portion 54. The opening of the cylinder hole 55 is blocked by a cover member 57.

[0100] A cylindrical biasing plunger 56 is disposed in the cylinder hole 55 so as to be axially movable relative to the cylinder hole 55.

[0101] Each of the biasing pins 52, 53 is received in the second guiding portion 54 so as to be axially movable. One of the plurality of biasing pins 52, 53, i.e., the biasing pin 52, is formed longer than the other biasing pin 53. Such a biasing pin 52 is received in the second guiding portion 54 that communicates with the cylinder hole 55. The end of the biasing pin 52 on the side opposite to the swash plate 5 protrudes into the cylinder hole 55.

[0102] For example, it is input to the second guiding portion 54 based on the signal pressure of the working oil ejected from the hydraulic pump 1, the signal pressure of other hydraulic pumps driven by the same drive source, the signal pressure corresponding to the operation of external devices such as an air conditioner driven by the same drive source, etc. The signal pressure generated by, for example, a control valve is input to the cylinder hole 55. Each of the biasing pins 52, 53 biases the biasing rod 46 toward the swash plate 5 according to the signal pressure corresponding to each of the biasing pins 52, 53.

[0103] The biasing rod 46 is disposed between the abutting 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 axially elongated. The biasing rod 46 is guided by the first guiding portion 49 of the housing body 9 so as to be axially movable.

[0104] A spherical surface 46a is formed at the end of the pressing rod 46 on the side of the abutting surface 41. Therefore, even if the angle formed by the inclined plate 5 (abutting surface 41) and the pressing rod 46 changes due to the change in the inclination angle of the inclined plate 5, the acting force on the inclined plate 5 can be properly transmitted from the spherical surface 46a to the abutting surface 41.

[0105] <Operation of the hydraulic pump>

[0106] Next, the operation of the hydraulic pump 1 will be described.

[0107] The hydraulic pump 1 outputs a driving force based on the ejection of the working oil from the cylinder bore 17 (and the suction of the working oil into the cylinder bore 17).

[0108] More specifically, first, the shaft 3 is rotated by the power from a power source such as an engine, so that the cylinder block 4 rotates integrally with the shaft 3. As the cylinder block 4 rotates, the plunger 21 revolves around the central axis C1 of the shaft 3.

[0109] Each slipper 22 mounted on the convex portion 28 of each plunger 21 is properly pressed against the sliding surface 31a of the swash plate 5 following the sliding surface 31a of the swash plate 5 regardless of the inclination angle of the swash plate 5 due to the acting force of the spring 23. The convex portion 28 of the plunger 21 is formed in a spherical shape, and the concave portion 22a of the slipper 22 into which the convex portion 28 is inserted is also formed in a spherical shape. Each slipper 22 is pressed toward the swash plate 5 by the pressing member 27 via the slipper holding member 29. Therefore, even if the inclination angle of the swash plate 5 changes, each slipper 22 follows the inclination of the swash plate 5 and is properly pressed against the sliding surface 31a following the sliding surface 31a.

[0110] If, as the cylinder block 4 rotates, the plunger 21 revolves around the central axis C1 of the shaft 3, each slipper 22 also slides on the sliding surface 31a of the swash plate 5 while revolving around the central axis C1 of the shaft 3. As a result, each plunger 21 moves axially within each cylinder bore 17, and each plunger 21 performs a reciprocating motion. In this way, the swash plate 5 restricts the displacement of each plunger 21 in the axial direction. According to the reciprocating motion of the plunger 21, the working oil is ejected from a part of the cylinder bores 17, and the working oil is sucked into the other cylinder bores 17, realizing the hydraulic pump.

[0111] If the inclination angle of the swash plate 5 (sliding surface 31a) changes, the stroke (sliding distance) of the reciprocating motion of the plunger 21 changes. That is, the larger the inclination angle of the swash plate 5, the larger the suction amount and ejection amount of the working oil relative to the cylinder bore 17 accompanying the reciprocating motion of each plunger 21. In contrast, the smaller the inclination angle of the swash plate 5, the smaller the suction amount and ejection amount of the working oil relative to the cylinder bore 17 accompanying the reciprocating motion of each plunger 21. When the inclination angle of the swash plate 5 is 0 degrees, even if the plunger 21 revolves around the central axis C1 of the shaft 3, each plunger 21 does not reciprocate. Therefore, the ejection amount of the working oil from each cylinder bore 17 is also zero.

[0112] An external-threaded stopper 40 is provided at a radially outer portion of the front flange 10. Therefore, if the inclination angle of the swash plate 5 is reduced, the swash plate 5 abuts against the stopper 40. The stopper 40 can move forward and backward relative to the swash plate 5 by rotation. Thus, by moving the stopper 40 forward and backward relative to the swash plate 5, the minimum inclination angle of the swash plate 5 can be appropriately adjusted.

[0113] Next, the rotation operation of the swash plate 5 will be described.

[0114] The swash plate 5 is urged by the first urging portion 6 in the direction in which the inclination angle of the swash plate 5 increases. The swash plate 5 is urged by the second urging portion 7 in the direction in which the inclination angle of the swash plate 5 decreases. The swash plate 5 tilts and stops at a position where the magnitude of the torque about the rotation axis of the swash plate 5 generated by the acting force of the first urging portion 6 (the torque is counterclockwise in Figure 2 is equal to the magnitude of the torque about the rotation axis of the swash plate 5 generated by the second urging portion 7 (the torque is clockwise in Figure 2 ).

[0115] Hereinafter, the counterclockwise torque in Figure 2 will be simply referred to as the counterclockwise torque. The clockwise torque in Figure 2 will be simply referred to as the clockwise torque.

[0116] That is, if the clockwise torque generated by the second urging portion 7 is increased, the inclination angle of the swash plate 5 becomes smaller. Correspondingly, the first spring 44 and the second spring 45 of the first urging portion 6 are compressed and the counterclockwise torque generated by the first urging portion 6 also becomes larger. Thereby, the clockwise torque generated by the second urging portion 7 is equal to the counterclockwise torque generated by the first urging portion 6, and the swash plate 5 stops at a predetermined inclination.

[0117] On the other hand, if the clockwise torque generated by the second biasing portion 7 is reduced, the acting forces of the first spring 44 and the second spring 45 of the first biasing portion 6 are greater than the clockwise torque generated by the second biasing portion 7, and the inclination angle of the swash plate 5 becomes larger. Along with this, if the first spring 44 and the second spring 45 are stretched, the acting force generated by the first biasing portion 6 becomes smaller. As a result, the clockwise torque generated by the second biasing portion 7 is equal to the counterclockwise torque generated by the first biasing portion 6, and the swash plate 5 stops at a predetermined inclination. The "predetermined inclination" means that the acute angle formed by the sliding surface 31a formed by the swash plate main body 31 of the swash plate 5 with respect to the surface orthogonal to the central axis C1 of the shaft 3 is in the range of 0 degrees to 20 degrees. The numerical value of the "predetermined inclination" is not limited to this numerical range. As long as it is an angle that can achieve the effects of the present invention, it may also be an angle other than the above-mentioned angle range.

[0118] When changing the clockwise torque generated by the second biasing portion 7, the acting force of the biasing rod 46 on the swash plate 5 is changed. That is, for example, it is input to the second guiding portion 54 of the second biasing portion 7 based on the signal pressure of the working oil ejected from the hydraulic pump 1, the signal pressure from other hydraulic pumps driven by the same drive source, the signal pressure corresponding to the operation of external devices such as an air conditioner driven by the same drive source, etc. The signal pressure generated by, for example, a control valve is input to the cylinder bore 55. According to the magnitudes of these signal pressures, the respective biasing pins 52 and 53 bias the biasing rod 46. As a result, the acting force of the biasing rod 46 on the swash plate 5 is changed.

[0119] Next, based on Figure 2 、 Figure 3 、 Figure 4 the operation of properly maintaining the thermal balance of the hydraulic pump 1 will be described.

[0120] As Figure 2 、 Figure 3 、 Figure 4 shown, the cylinder block 4 is rotated together with the shaft 3. As a result, each cylinder bore 17 and each communication hole 18 revolve around the central axis C1 of the shaft 3. In this state, the valve plate 19 is fixed to the housing main body 9. Therefore, according to the rotation state of the cylinder block 4, each cylinder bore 17 communicates with the suction port 64 and the discharge port 66 of the valve plate 19 via each communication hole 18.

[0121] As a result, the cylinder bore 17 is switched between an inhalation state of inhaling the working oil and an ejection state of ejecting the working oil according to the rotation state of the cylinder block 4. Specifically, the cylinder bore 17 inhales the working oil in the inhalation passage 71 from the communication hole 18 into the inside of the cylinder bore 17 via the suction port 64 of the valve plate 19 in the inhalation state (refer to the arrow A in Figure 3 ). The cylinder bore 17 ejects the working oil inside the cylinder bore 17 from the discharge port 66 of the valve plate 19 to the discharge passage 72 via the communication hole 18 in the ejection state (refer toFigure 3 the arrow B in

[0122] An oil film formed by working oil is formed between the end faces 4b and 19a of the cylinder block 4 adjacent to the valve plate 19. This oil film heats up due to the friction between the adjacent end faces 4b and 19a and becomes high temperature. A part of the working oil that has become high temperature due to heating leaks from between the adjacent end faces 4b and 19a into the inner ring recess 62 and the outer ring recess 63.

[0123] The inner ring recess 62 communicates with the inner part 64a of the suction port 64 opposite to the inner ring recess 62 via the groove part 65 (opening part 65a). Therefore, the working oil that has become high temperature due to the friction between the adjacent end faces 4b and 19a can be smoothly sucked from the inner ring recess 62 via the groove part 65 (opening part 65a) into the suction port 64 (refer to Figure 3 the arrow C in Figure 3 The high-temperature working oil sucked into the suction port 64 from the groove part 65 can be smoothly sucked into the inside of the cylinder hole 17 via the communication hole 18 (refer to

[0124] During the ejection state of the cylinder hole 17, the high-temperature working oil sucked into the inside of the cylinder hole 17 can be smoothly ejected from the ejection port 66 of the valve plate 19 into the ejection passage 72 via the communication hole 18 (refer to Figure 3 the arrow B in

[0125] As a result, the high-temperature working oil that flows out (leaks) from the gap (the part where the oil film is formed, hereinafter, the gap has the same meaning) 68 between the adjacent end faces 4b and 19a into the inner ring recess 62 does not stay inside the housing 2, but can be smoothly ejected from the ejection port 66 via each cylinder hole 17. Thus, a hydraulic pump 1 that can appropriately maintain thermal balance by suppressing the temperature rise of the hydraulic pump 1 can be provided.

[0126] Return Figure 1 , the hydraulic pump 1 is mounted on the rotating body 101 of the construction machine 100. With such a configuration, a construction machine 100 equipped with a hydraulic pump 1 that can suppress the temperature rise of the hydraulic pump 1 and appropriately maintain thermal balance can be provided.

[0127] In the above-described embodiment, the case where the groove part 65 is formed in the end face 19a of the valve plate 19 among the adjacent end faces 4b and 19a of the cylinder block 4 and the valve plate 19 has been described. Also, the case where the inner ring recess 62 communicates with the suction port 64 via the groove part 65 (opening part 65a) has been described. However, it is not limited to this, and it may be that a groove part 65b is formed in the end face 4b of the cylinder block 4 (refer to Figure 3 the double-dot chain line in

[0128] In the above-described embodiment, the case where the groove portion 65 is formed substantially over the entire inner portion 64a of the suction port 64 that faces the inner annular recess 62 has been described. Further, the case where the inner portion 64a of the suction port 64 communicates with the inner annular recess 62 via the groove portion 65 (opening portion 65a) has been described. However, the present invention is not limited thereto, and it is sufficient that the groove portion 65 is formed in a part of the inner portion 64a of the suction port 64, and the suction port 64 and the inner annular recess 62 communicate with each other via the groove portion 65. Instead of the groove portion 65, a through-hole that penetrates the valve plate 19 in the thickness direction may be provided.

[0129] [First Modified Example]

[0130] Figure 5 FIG. is a cross-sectional view showing the valve plate 80 of the first modified example. Figure 6 FIG. is a top view of the valve plate 80. Figure 5 , Figure 6 Corresponding to the foregoing Figure 3 , Figure 4 (the same applies to the following Figure 7 , Figure 8 , Figure 9 , Figure 10 as well). The same reference numerals are given to the same configurations as those in the foregoing embodiment, and the description thereof is omitted (the same applies to the following modified examples).

[0131] As shown in Figure 2 , Figure 5 , Figure 6 , a groove portion (corresponding to the communication path in the claims) 82 is formed in an end face (corresponding to the face adjacent to the face of the cylinder block in the claims, the second defining face) 80a of the valve plate 80 that is adjacent to the end face 4b of the cylinder block 4. The groove portion 82 communicates with at least a part of the suction port 64 (specifically, the outer portion 64b that faces the outer annular recess 63), and also communicates with the outer annular recess 63. In other words, the groove portion 82 has an opening portion 82a that opens in the outer annular recess 63. Further in other words, the groove portion 82 has an opening portion 82a in the outer portion (outer annular recess 63) of the end face 80a other than the portions that define the suction port 64 and the discharge port 66. Substantially the entire outer portion 64b of the suction port 64 that faces the outer annular recess 63 communicates with the outer annular recess 63 via the groove portion 82 (opening portion 82a).

[0132] Based on such a structure, it is possible to smoothly suck the working oil that has become hot due to friction between the end face 4b of the adjacent cylinder block 4 and the end face 80a of the valve plate 80 and has become high-temperature from the outer annular recess 63 to the suction port 64 via the groove portion 82 (see Figure 5The arrow E) in it. The high-temperature working oil sucked into the suction port 64 from the groove portion 82 can be smoothly sucked into the inside of the cylinder bore 17 through the communication hole 18 (refer to Figure 5 The arrow F) in it.

[0133] The high-temperature working oil sucked into the inside of the cylinder bore 17 can be smoothly ejected in the ejection state of the cylinder bore 17 in the same manner as in the above-described embodiment.

[0134] Therefore, the high-temperature working oil flowing out (leaking) from the gap 84 between the adjacent end faces 4b and 80a to the outer ring recess 63 does not stay inside the housing 2, but can be smoothly ejected from the ejection port 66 through each cylinder bore 17. Thus, a hydraulic pump 1 that can appropriately maintain the thermal balance by suppressing the temperature rise of the hydraulic pump 1 can be provided.

[0135] In the above-described first modification, the case where the groove portion 82 is formed in the end face 80a of the valve plate 80 among the adjacent end faces 4b and 80a of the cylinder block 4 and the valve plate 80 has been described. Also, the case where the outer ring recess 63 communicates with the suction port 64 through the groove portion 82 has been described. However, it is not limited thereto, and it may be that a groove portion 82b (refer to Figure 5 The double-dot chain line) is formed in the end face 4b of the cylinder block 4, and the outer ring recess 63 communicates with the suction port 64 through the groove portion.

[0136] In the above-described first modification, the case where the groove portion 82 is formed in substantially the entire outer portion 64b of the suction port 64 that faces the outer ring recess 63 has been described. Also, the case where the outer portion 64b of the suction port 64 communicates with the outer ring recess 63 through the groove portion 82 (opening portion 82a) has been described. However, it is not limited thereto, and it is sufficient that the groove portion 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 through the groove portion 82. Instead of the groove portion 82, a through hole penetrating the valve plate 19 in the thickness direction may be provided.

[0137] [Second Modification]

[0138] Figure 7 It is a cross-sectional view showing the valve plate 90 of the second modification. Figure 8 It is a top view of the valve plate 90.

[0139] As Figure 2 , Figure 7 , Figure 8As shown, the second modified example is a combination of the so-called above-described embodiment and the first modified example, and has a shape that penetrates the groove portion 65 of the above-described embodiment and the groove portion 82 of the first modified example in the thickness direction, respectively. That is, a first through-hole 121 that penetrates in the thickness direction of the valve plate 90 is formed in the end surface 90a of the valve plate 90 that is adjacent to the end surface 4b of the cylinder block 4 (corresponding to the surface adjacent to the surface of the cylinder block and the second defining surface in the claims) to replace the groove portion 65 of the above-described embodiment. A second through-hole 122 that penetrates in the thickness direction of the valve plate 90 is formed in the end surface 90a of the valve plate 90 to replace the groove portion 82.

[0140] The first through-hole 121 communicates with at least a part of the suction port 64 (specifically, substantially the entire inner portion that faces the inner ring recess 62) 64a and also communicates with the inner ring recess 62. That is, 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 first through-hole 121.

[0141] The second through-hole 122 communicates with at least a part of the suction port 64 (specifically, the outer portion that faces the outer ring recess 63) 64b and also communicates with the outer ring recess 63. That is, substantially the entire outer portion 64b of the suction port 64 that faces the outer ring recess 63 communicates with the outer ring recess 63 via the second through-hole 122.

[0142] Based on such a structure, it is possible to smoothly suck the working oil that has become hot due to the friction between the end surface 4b of the adjacent cylinder block 4 and the end surface 90a of the valve plate 90 and has become high temperature from the inner ring recess 62 to the suction port 64 via the first through-hole 121 (refer to the arrow G in Figure 7 ). And it is possible to smoothly suck the working oil that has become hot due to the friction between the adjacent end surfaces 4b, 90a and has become high temperature from the outer ring recess 63 to the suction port 64 via the second through-hole 122 (refer to the arrow H in Figure 7 ).

[0143] It is possible to smoothly suck the high-temperature working oil sucked into the suction port 64 from the first through-hole 121 and the second through-hole 122 into the inside of the cylinder bore 17 via the communication hole 18 (refer to the arrow I in Figure 7 ). And it is possible to smoothly eject the high-temperature working oil sucked into the inside of the cylinder bore 17 from the ejection port 66 in the ejection state of the cylinder bore 17 in the same manner as in the above-described embodiment.

[0144] Therefore, the high-temperature working oil flowing out (leaking out) from the gap 92 between the adjacent end faces 4b and 90a does not stay inside the housing 2, but can be ejected more smoothly from the ejection port 66 through each cylinder hole 17. Thereby, a hydraulic pump 1 can be provided that can more appropriately maintain the thermal balance by better suppressing the rise in temperature of the hydraulic pump 1.

[0145] In the above-described second modification, the case where the first through-hole 121 and the second through-hole 122 are formed in the end face 90a of the valve plate 90 has been described. Also, the case where the inner ring recess 62 and the outer ring recess 63 communicate with the suction port 64 through the first through-hole 121 and the second through-hole 122 has been described. However, it is not limited thereto, and it may be that the groove portion 65b of the above-described embodiment and the groove portion 82b of the first modification (both are shown by the double-dashed line in Figure 7 are formed in the end face 4b of the cylinder block 4, and the inner ring recess 62 and the outer ring recess 63 communicate with the suction port 64 through the respective groove portions 65b and 82b.

[0146] [Third Modification]

[0147] Figure 9 is a cross-sectional view of the valve plate 95 of the third modification along the Figure 10 IV-IV line. Figure 10 is a top view of the valve plate 95 of the third modification.

[0148] As shown in Figure 2 , Figure 9 , Figure 10 , a groove portion (corresponding to the communication path in the claims) 97 is formed in the 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 and the second delimiting face in the claims). The groove portion 97 communicates with at least a part 64c of the suction port 64. The groove portion 97 has an opening portion 97a opening to the gap 98 between the suction port 64 and the ejection port 66 and a tip portion 97b near the ejection port 66 between the adjacent end faces 4b and 95a of the cylinder block 4 and the valve plate 95.

[0149] Based on such a structure, the working oil that has become hot due to the friction between the end face 4b of the adjacent cylinder block 4 and the end face 95a of the valve plate 95 can be smoothly sucked into the suction port 64 through the gap 98 and the groove portion 97 (refer to the arrow J in Figure 9 ).

[0150] The top end portion 97b of the groove portion 97 is located near the ejection port 66 (specifically, the inner ejection port 66a). Therefore, the high-temperature working oil leaking into the gap 98 can be guided well to the groove portion 97. Thereby, the high-temperature working oil can be sucked more smoothly into the suction port 64 via the groove portion 97 (refer to Figure 9 the arrow J in).

[0151] The high-temperature working oil sucked from the groove portion 97 into the suction port 64 can be smoothly sucked into the interior of the cylinder bore 17 via the communication hole 18 (refer to Figure 9 the arrow K in). And the high-temperature working oil sucked into the interior of the cylinder bore 17 can be smoothly ejected from the ejection port 66 in the ejection state of the cylinder bore 17 in the same manner as in the above-described embodiment.

[0152] Therefore, the high-temperature working oil flowing out (leaking) into the gap 98 does not stay inside the housing 2, but can be ejected more smoothly from the ejection port 66 via each cylinder bore 17. Thereby, a hydraulic pump 1 can be provided that can more appropriately maintain the thermal balance by more effectively suppressing the rise in the temperature of the hydraulic pump 1.

[0153] In the above-described third modification example, the case where the groove portion 97 is formed in the end face 95a of the valve plate 95 in the adjacent end faces 4b, 95a of the cylinder block 4 and the valve plate 95 has been described. And the case where the groove portion 97 communicates with the suction port 64 has been described. However, it is not limited thereto, and it may be that a groove portion 97c is formed in the end face 4b of the cylinder block 4 (refer to Figure 9 the double-dot chain line in), and the groove portion communicates with the suction port 64.

[0154] The present invention is not limited to the above-described embodiments, and includes embodiments obtained by making various modifications to the above-described embodiments without departing from the gist of the present invention.

[0155] For example, in the above-described embodiment, the case where the construction machine 100 is a hydraulic excavator has been described. However, it is not limited thereto, and the above-described hydraulic pump 1 can be used in various construction machines.

Claims

1. A hydraulic pump, wherein, the hydraulic pump includes: a housing; a shaft rotatably supported within the housing 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 cylinder chambers; and a valve plate disposed along the axis so as to overlap the cylinder block, having a suction passage and a discharge passage communicating with the cylinder chambers, the valve plate having a communication path formed in a portion of the surface of the valve plate adjacent to the cylinder block and only for partitioning and forming the suction passage, the communication path includes an inner annular recess and an outer annular recess, the inner annular recess is formed on the surface of the valve plate adjacent to the cylinder block, and is located radially inward of the shaft with respect to the suction passage and the discharge passage, the outer annular recess is formed on the surface of the valve plate adjacent to the cylinder block, and is located radially outward of the shaft with respect to the suction passage and the discharge passage, the suction passage is formed in a curved shape along an outer peripheral surface of the valve plate that is annular when viewed from the axial direction, and is formed to penetrate in the thickness direction of the valve plate, when viewed from the axial direction, the inner annular recess and the outer annular recess extend in a curved shape along the suction passage, either one of the inner annular recess and the outer annular recess communicates with the suction passage, and the other of the inner annular recess and the outer annular recess is separated from the suction passage.

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