Hydraulic pumps and construction machinery

Abstract

To provide a hydraulic pump which can suppress the abrasion of a rotating shaft member and a pressing member, and can suppress size enlargement while reducing a manufacturing cost of the pressing member, and a construction machine.SOLUTION: This hydraulic pump comprises a casing, a rotating shaft member 3, a cylinder block, a plurality of pistons, a swash plate, a plurality of shoes, a shoe holding member and a pressing member 27. The hydraulic pump also has an internal peripheral face 91a fit to an external peripheral face 3c between the cylinder block of the rotating shaft member 3 and the swash plate, and presses the shoe holding member toward the sash plate. In a pressing position of the pressing member 27 which presses the shoe holding member, a contact area between the external peripheral face 3c and the internal peripheral face 91a at the swash plate side from a center C3 of the internal peripheral face 91a in an axial direction is larger than a contact area between the external peripheral face 3c and the internal peripheral face 91a at the cylinder block side from the center C3 of the internal peripheral face 91a in the axial direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

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

[0003] A swash plate is provided at the end of each piston opposite to the end where the cylinder chamber is formed, and is supported so that its inclination angle can be changed relative to the casing. The axis of rotation of the inclination angle of the swash plate is perpendicular to the axis of rotation of the cylinder block. A shoe is attached to the end of each piston facing the swash plate so as to be able to slide relative to the swash plate. Each shoe is held integrally by a shoe holding member. The shoe holding member is pressed toward the swash plate by a pressing member fitted to the outer circumferential surface of the rotating shaft member.

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

[0005] Here, the outer peripheral surface of the rotating shaft member may be splined so that the rotating shaft member and the cylinder block rotate together. The rotating shaft member and the cylinder block are splined together by fitting the cylinder block into the splined portion. This fixes the cylinder block to the rotating shaft member so that it cannot rotate. If the spline is to be formed over the entire portion of the rotating shaft member where the cylinder block is fitted, it will extend toward the swash plate side beyond the portion where the cylinder block is fitted for convenience of processing. A pressing member is disposed at the portion where the spline extends. For this reason, the inner peripheral surface of the pressing member may also be splined to spline the rotating shaft member and the pressing member. This configuration can increase the contact area between the outer peripheral surface of the rotating shaft member and the inner peripheral surface of the pressing member. As a result, the surface pressure when the rotating shaft member and the pressing member come into contact is reduced, and wear of the rotating shaft member and the pressing member can be suppressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-56736 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the inner peripheral surface of the pressing member is splined as in the above-mentioned conventional technology, the manufacturing cost of the pressing member may increase. For this reason, it is possible to make the inner peripheral surface of the pressing member flat without splining it. If the inner peripheral surface of the pressing member is flat, the contact area between the outer peripheral surface of the rotating shaft member and the inner peripheral surface of the pressing member will be reduced because the outer peripheral surface of the rotating shaft member is splined. As a result, the contact pressure between the rotating shaft member and the pressing member will be large, and the wear of the rotating shaft member and the pressing member may increase. In particular, the portion of the inner peripheral surface of the pressing member closer to the swash plate is inclined with respect to the axial direction as the swash plate is inclined, and is strongly pressed against the rotating shaft member. For this reason, the portion of the inner peripheral surface of the pressing member closer to the swash plate is easily worn.

[0008] For example, it is possible to offset the position of the pressing member to a portion of the rotating shaft member where the splines are not formed. By configuring in this way, it is possible to increase the contact area between the outer circumferential surface of the rotating shaft member and the inner circumferential surface of the pressing member. However, if this is configured, the axial length of the rotating shaft member needs to be increased by the amount of the offset of the pressing member, which may result in an increase in the size of the hydraulic pump.

[0009] The present invention provides a hydraulic pump and a construction machine that can reduce the manufacturing costs of the pressing member, suppress wear on the rotating shaft member and the pressing member, and suppress an increase in size. [Means for solving the problem]

[0013] The present invention one The hydraulic pump according to the embodiment has a first rotation axis of a cylinder block that rotates around the cylinder block; pistons that are movably provided in each of a plurality of cylinder holes formed in the cylinder block; a swash plate that is supported so that the inclination angle is changeable about a second axis of rotation that intersects with the first axis of rotation and that restricts the movement of the pistons; shoes that are provided between the pistons and the swash plate; shoe holding members that hold the shoes; a pressing member that presses the shoe holding member toward the swash plate; a rotating shaft member having an outer circumferential surface into which an inner circumferential surface of the pressing member is fitted and which has a constant diameter over an entire area where the pressing member is located in a direction parallel to the first rotation axis; The first rotation axis To the line Spline groove formed along and recessed inward from the outer circumferential surface in the radial direction of the rotating shaft member. The spline groove is formed continuously with the spline groove on the swash plate side. and a cut-out groove, the cut-out groove being The groove width narrows as it moves away from the spline groove, and at the pressing position where the shoe holding member is pressed, at least a part between the tip position on the opposite side to the spline groove and the base end position on the spline groove side is the The above At a position facing the inner circumferential surface in the radial direction R .

[0014] With this configuration, the contact area between the swash plate side of the inner peripheral surface of the pressing member and the outer peripheral surface of the rotating shaft member can be made larger than the contact area between the cylinder block side of the inner peripheral surface of the pressing member and the outer peripheral surface of the rotating shaft member by utilizing the cut-out grooves. Therefore, even if the rotating shaft member is splined, it is possible to reduce the manufacturing cost of the pressing member while suppressing wear of the rotating shaft member and the pressing member, and also to suppress an increase in the size of the hydraulic pump.

[0015] In the above configuration, when the pressing member is in the pressing position, the tip position of the cut-out groove may be closer to the swash plate than the inner circumferential surface of the pressing member, and the base end position of the cut-out groove may be opposite to the inner circumferential surface of the pressing member in the radial direction of the rotating shaft member.

[0016] With this configuration, wear of the rotating shaft member and the pressing member can be more reliably suppressed without increasing the axial length of the rotating shaft member.

[0017] In the above configuration, when the pressing member is in the pressing position, the tip position of the cut-out groove may be a position facing the inner circumferential surface of the pressing member in the radial direction of the rotating shaft member, and the base end position of the cut-out groove may be on the cylinder block side relative to the inner circumferential surface of the pressing member.

[0018] With this configuration, wear of the rotating shaft member and the pressing member can be more reliably suppressed without increasing the axial length of the rotating shaft member.

[0019] In the above configuration, the inner circumferential surface of the pressing member is provided with a pair of inner circumferential surfaces, at least at an end portion of the inner circumferential surface on the swash plate side and an end portion of the inner circumferential surface on the cylinder block side. In the direction parallel to the first rotation axis The chamfered portion may be formed so as to become more spaced from the outer circumferential surface as it moves away from the center.

[0020] By forming the chamfered portion on the inner peripheral surface of the pressing member in this manner, even if the pressing member is tilted due to the tilt of the swash plate, the outer peripheral surface of the rotating shaft member and the inner peripheral surface of the pressing member can be in contact with each other as much as possible. This reduces the surface pressure when the rotating shaft member and the pressing member come into contact with each other, thereby suppressing wear of the rotating shaft member and the pressing member.

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

[0022] By configuring it in this manner, it is possible to provide a construction machine that can reduce the manufacturing costs of the pressing member, suppress wear on the rotating shaft member and the pressing member, and also suppress an increase in size. Effect of the Invention

[0023] The above-described hydraulic pump and construction machine can reduce the manufacturing cost of the pressing member, suppress wear on the rotating shaft member and the pressing member, and also suppress an increase in size. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram of a construction machine according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of a hydraulic pump according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view taken along an axial direction of a pressing member according to an embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a pressing portion of the pressing member and a part of the rotating shaft member according to the embodiment of the present invention. [Diagram 5] FIG. 4 is a partially enlarged perspective view of a second spline of the rotating shaft member according to the embodiment of the present invention. [Figure 6] 5A to 5C are explanatory views of the operation of a second spline of the rotating shaft member and a pressing member according to the embodiment of the present invention. [Figure 7] FIG. 11 is a cross-sectional view taken along an axial direction of a pressing member in a first modified example of the embodiment of the present invention. [Figure 8] FIG. 11 is a cross-sectional view taken along the axial direction of a pressing member in a second modified example of the embodiment of the present invention. [Figure 9] FIG. 13 is a cross-sectional view taken along the axial direction of a pressing member in a third modified example of the embodiment of the present invention. [Figure 10] FIG. 13 is a cross-sectional view taken along the axial direction of a pressing member in a fourth modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0027] The rotating body 101 includes a cab 103 on which an operator can ride, a boom 104 having one end swingably connected to the cab 103, an arm 105 having one end swingably connected to the other end (tip) of the boom 104 opposite the cab 103, and a bucket 106 swingably connected to the other end (tip) of the arm 105 opposite the boom 104. A hydraulic pump 1 is provided in the cab 103. The cab 103, the boom 104, the arm 105, and the bucket 106 are driven by hydraulic oil supplied 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 rotating shaft member 3 rotatably supported relative to the casing 2, a cylinder block 4 housed within the casing 2 and fixed to the rotating shaft member 3, a swash plate 5 housed within the casing 2 so that its inclination angle can be changed and which controls the amount of hydraulic oil discharged from the hydraulic pump 1, and a first biasing unit 6 and a second biasing unit 7 which control the inclination angle of the swash plate 5. In addition, the scale of each member is appropriately changed in Fig. 2 for ease of understanding. In the following description, the direction parallel to the central axis C1 (corresponding to the first rotation axis in the claims) of the rotating shaft member 3 is referred to as the axial direction, the rotation direction of the rotating shaft member 3 is referred to as the circumferential direction, and the radial direction of the rotating shaft member 3 is simply referred to as the radial direction.

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

[0030] Furthermore, a supply port and a discharge port (not shown) are formed in the casing body 9. The supply port is connected to a tank (not shown). The discharge port is connected to a cab 103, a boom 104, an arm 105, and a bucket 106 via a control valve (not shown) or the like.

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

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

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

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

[0035] A recess 20 is formed between the axial center of the through hole 16 and the end 4a so as to surround the periphery of the rotary shaft member 3. A through hole 25 is formed in a part of the inner peripheral surface between the axial center of the through hole 16 and the swash plate 5 side, penetrating the cylinder block 4 in the axial direction. A spring 23 and retainers 24a, 24b, which will be described later, are housed in the recess 20. A connecting member 26, which will be described later, is housed in the through hole 25 so as to be axially movable.

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

[0037] A disk-shaped valve plate 19 is provided at the end 4a of the cylinder block 4 so as to overlap with the end face of the end 4a. The valve plate 19 is fixed to the casing body 9. Even when the cylinder block 4 rotates together with the rotating shaft member 3, the valve plate 19 is stationary with respect to the casing 2 (casing body 9).

[0038] Supply and discharge ports (not shown) communicating with each of the communication holes 18 in the cylinder block 4 are formed through the valve plate 19 in the thickness direction of the valve plate 19. Each cylinder bore 17 is communicated with a supply port and a discharge port (not shown) formed in the casing body 9 via these supply and discharge ports of the valve plate 19 and the communication holes 18 in the cylinder block 4. Because the valve plate 19 is fixed to the casing body 9, the cylinder bore 17 is switched between a state in which hydraulic oil is supplied from the supply port via the valve plate 19 and a state in which hydraulic oil is discharged to the discharge port, depending on the rotation state of the cylinder block 4.

[0039] A piston 21 is housed in each cylinder bore 17 so as to be slidable along the axial direction. By housing the piston 21 in the cylinder bore 17, the piston 21 revolves around the central axis C1 of the rotating shaft member 3 as the rotating shaft member 3 and the cylinder block 4 rotate. A spherical protrusion 28 is integrally formed on the end of the piston 21 on the swash plate 5 side. The inside of the piston 21 is hollow. This cavity is filled with the hydraulic oil in the cylinder bore 17. Therefore, the reciprocating motion of the piston 21 is linked to the supply and discharge of the hydraulic oil to the cylinder bore 17. In other words, when the piston 21 is pulled out of the cylinder bore 17, the hydraulic oil is supplied into the cylinder bore 17 from a supply port. When the piston 21 enters the cylinder bore 17, the hydraulic oil is discharged from the cylinder bore 17 to a discharge port.

[0040] The spring 23 housed in the recess 20 of the cylinder block 4 is, for example, a coil spring. The spring 23 is compressed between two retainers 24a, 24b housed in the recess 20. Therefore, the spring 23 generates a biasing force in a direction in which it expands due to its elastic force. The biasing force of the spring 23 is transmitted to the connecting member 26 via one of the two retainers 24a, 24b. A pressing member 27 is fitted to the outer circumferential surface 3c of the rotating shaft member 3 on the front flange 10 side of the connecting member 26, that is, between the cylinder block 4 and the swash plate 5.

[0041] FIG. 3 is a cross-sectional view of the pressing member 27 taken along the axial direction. 2 and 3, the pressing member 27 is formed in a substantially cylindrical shape. The pressing member 27 is formed by integrally molding a pressing portion 91 on the swash plate 5 side and a leg portion 92 extending from the pressing portion 91 toward the cylinder block 4 side.

[0042] The inner peripheral surface 91a of the pressing portion 91 is formed flat and parallel to the axial direction with no irregularities as seen in the cross section of Fig. 3. This inner peripheral surface 91a is fitted into the outer peripheral surface 3c of the rotating shaft member 3. The outer peripheral surface 91b of the pressing portion 91 is formed in a fan-shaped shape such that the outer diameter gradually increases toward the leg portion 92. The leg portion 92 is formed so that the inner diameter of the inner peripheral surface 92a of the leg portion 92 is larger than the inner diameter of the inner peripheral surface 91a of the pressing portion 91. The connecting member 26 abuts against an end surface 92b of the leg portion 92 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. In the pressing member 27, an outer peripheral surface 91b of a pressing portion 91 abuts against a shoe holding member 29 described below, and presses the shoe holding member 29 toward the swash plate 5.

[0043] A shoe 22 is attached to a protrusion 28 of each piston 21 housed in each cylinder bore 17 of the cylinder block 4. A spherical recess 22a is formed on the surface of the shoe 22 that receives the protrusion 28 so as to correspond to the shape of the protrusion 28. The protrusion 28 of the piston 21 is fitted into this recess 22a. In this way, the shoe 22 is rotatably connected to the protrusion 28 of the piston 21. Each shoe 22 is integrally held by a shoe holding member 29. This shoe holding member 29 is pressed toward the swash plate 5 by a pressing member 27. Furthermore, each shoe 22 is pressed toward the swash plate 5 by the pressing member 27 via the shoe holding member 29.

[0044] The swash plate 5 has a role of restricting the displacement of each piston 21 in the axial direction by rotating and tilting. The swash plate 5 has a swash plate body 31 that is annular when viewed from the cylinder block 4 side. An insertion hole 32 that penetrates in the axial direction is formed in the radial center of the swash plate body 31. The rotating shaft member 3 is inserted into 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 slidably pressed against this sliding surface 31a.

[0045] Two support protrusions 33, 34 are disposed on the rear side of the sliding surface 31a of the swash plate body 31 so as to face each other in the radial direction with the insertion hole 32 as the center. The two support protrusions 33, 34 are for supporting the swash plate 5 on the front flange 10 so that the inclination angle can be changed. Each support protrusion 33, 34 is formed in a semicircular shape when viewed from the radial direction and has an arcuate surface 33a, 34a. Each support protrusion 33, 34 is formed to protrude from the swash plate body 31 so that the arcuate surfaces 33a, 34a face the front flange 10 side.

[0046] The arcuate surfaces 33a, 34a of the support protrusions 33, 34 are slidably abutted against the recessed portion 30a of the swash plate support portion 30 formed to protrude from the front flange 10. The arcuate surfaces 33a, 34a slide against the recessed portion 30a, thereby rotating the swash plate 5 relative to the front flange 10. That is, the rotation axis C2 (corresponding to the second rotation axis in the claims) of the swash plate 5 is perpendicular to the central axis C1 of the rotating shaft member 3 and is located at the arc center of the recessed portion 30a and the arcuate surfaces 33a, 34a (see FIG. 2). In other words, the rotation axis C2 is along the radial direction. The swash plate 5 rotates about the rotation axis C2.

[0047] A first biased portion 37 and a second biased portion 38 are integrally formed on a radial side portion of the swash plate body 31, and are opposed to each other in the radial direction with the insertion hole 32 as the center. The opposing direction of the first biased portion 37 and the second biased portion 38 is perpendicular to the opposing direction of the two support protrusions 33, 34. The first biased portion 37 and the second biased portion 38 extend radially outward from the swash plate body 31. A surface 38a of the second biased portion 38 on the front flange 10 side abuts against a stopper 40 provided on the front flange 10.

[0048] A connecting recess 39 is formed on the radial outer side (tip side) of the first biased portion 37 on the surface opposite to the protruding direction of each of the support protrusions 33, 34 (the surface on the cylinder block 4 side). The first biased portion 6 is connected to the connecting recess 39. The connecting recess 39 is formed in a circular shape when viewed in the axial direction. An abutment surface 41 is formed on almost the entire surface of the second urged portion 38 on the side opposite to the protruding direction of the support protrusions 33, 34 (the surface on the cylinder block 4 side). The abutment surface 41 is formed by cutting the second urged portion 38 flat. The second urged portion 7 abuts against the abutment surface 41.

[0049] The swash plate 5 configured in this manner rotates relative to the front flange 10, so that the first biased portion 37 and the second biased portion 38 tilt toward or away from the front flange 10. In other words, the tilt angle of the swash plate 5 can be regarded as the tilt angle of the swash plate 5 with respect to a plane perpendicular to the rotating shaft member 3. Here, the inclination angle of the swash plate 5 refers to the angle between the sliding surface 31a and a plane perpendicular to the rotating shaft member 3. In other words, the smaller this angle is, the smaller the inclination angle of the swash plate 5 is.

[0050] The first biasing portion 6 biases the swash plate 5 in a direction that increases the inclination angle of the swash plate 5. The first biasing portion 6 includes a first retainer 42 disposed on the bottom 9b side of the casing body 9, a second retainer 43 disposed on the swash plate 5 side, and a first spring 44 and a second spring 45 disposed between the first retainer 42 and the second retainer 43. A spherical connecting protrusion 43a is formed on the second retainer 43 facing the swash plate 5. The connecting protrusion 43a comes into contact with the connecting recess 39 of the swash plate 5, whereby the second retainer 43 is rotatably connected to the swash plate 5.

[0051] The first spring 44 is compressed between the first retainer 42 and the second retainer 43. Therefore, the first spring 44 generates a biasing force in a direction in which the first spring 44 expands due to its elastic force. The second spring 45 is disposed inside the first spring 44. Therefore, the outer diameter of the second spring 45 is smaller than the outer diameter of the first spring 44. The second spring 45 is fixed to the second retainer 43.

[0052] When the inclination angle of the swash plate 5 is large (see FIG. 2), the second spring 45 is separated from the first retainer 42. As a result, when the inclination angle of the swash plate 5 is large, only the biasing force of the first spring 44 acts on the swash plate 5. In contrast, when the inclination angle of the swash plate 5 decreases, the second spring 45 comes into contact with the first retainer 42 at a certain inclination angle. When the inclination angle of the swash plate 5 decreases further, the second spring 45 is also compressed between the first retainer 42 and the second retainer 43. As a result, the biasing forces of both the first spring 44 and the second spring 45 act on the swash plate 5.

[0053] In this way, the first biasing portion 6 can change the biasing force in a stepwise manner according to the inclination angle of the swash plate 5. The second spring 45 is not limited to being fixed to the second retainer 43, and may be fixed to the first retainer 42. Also, the second spring 45 may not be fixed to either the first retainer 42 or the second retainer 43, and may be movable between the first retainer 42 and the second retainer 43.

[0054] The second biasing portion 7 applies a biasing force to the swash plate 5 in a direction opposite to the biasing force applied to the swash plate 5 by the first biasing portion 6. In particular, the second biasing portion 7 biases the swash plate 5 in a direction to decrease the inclination angle of the swash plate 5, against the biasing force applied by the first biasing portion 6 in a direction to increase the inclination angle of the swash plate 5. The second urging section 7 includes a urging rod 46 and a urging pin unit 50. The urging pin unit 50 mainly includes a unit case 51 and a plurality of urging pins 52, 53. Although only two of the plurality of urging pins 52, 53 are shown in Fig. 2, for example, four of the plurality of urging pins 52, 53 are provided.

[0055] The unit case 51 is attached so as to be fitted into the attachment recess 48 of the casing body 9. A plurality of second guide portions 54 for guiding the plurality of 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 penetrating the unit case 51 in the axial direction. A cylinder hole 55 communicating with one of the plurality of second guide portions 54 is provided on the unit case 51 on the side opposite the swash plate 5. The cylinder hole 55 opens on the side opposite the second guide portions 54 of the unit case 51. The opening of the cylinder hole 55 is closed by a cap member 57.

[0056] A cylindrical biasing piston 56 is disposed within the cylinder bore 55 so as to be slidable 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 axially slidable. 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.

[0057] The second guide portion 54 receives, for example, a signal pressure due to hydraulic oil discharged from the hydraulic pump 1, a signal pressure from another hydraulic pump driven by the same drive source, or a signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same drive source. The cylinder hole 55 receives, for example, a signal pressure generated by a control valve. Each of the biasing pins 52, 53 biases the biasing rod 46 toward the swash plate 5 in response to the signal pressure corresponding to each of the biasing pins 52, 53.

[0058] The biasing rod 46 is disposed between the contact surface 41 of the swash plate 5 and each of the biasing pins 52, 53. The biasing rod 46 is formed in a cylindrical shape so as to be elongated in the axial direction, and is guided by a first guide portion 49 of the casing body 9 so as to be axially movable. A spherical surface 46a is formed on the end of the urging rod 46 on the contact surface 41 side. Therefore, even if the angle between the swash plate 5 (contact surface 41) and the urging rod 46 changes due to a change in the inclination angle of the swash plate 5, the urging force against the swash plate 5 can be appropriately transmitted from the spherical surface 46a to the contact surface 41.

[0059] (Positional relationship between the second spline of the rotating shaft member and the pressing member) Fig. 4 is an enlarged cross-sectional view of the pressing portion 91 of the pressing member 27 and a portion of the rotating shaft member 3 into which the pressing portion 91 is fitted. Fig. 4 corresponds to portion A in Fig. 2. Fig. 5 is a partially enlarged perspective view of the second spline 3b formed on the outer circumferential surface 3c of the rotating shaft member 3. As shown in Figures 2, 4 and 5, the second spline 3b is composed of a spline groove 93 formed over the entire area where the cylinder block 4 is fitted, and a cut-out groove 94 formed contiguous to the spline groove 93 on the swash plate 5 side of the spline groove 93.

[0060] The spline grooves 93 are formed at equal intervals in the circumferential direction. The spline grooves 93 are formed to have a constant groove depth. The spline grooves 93 extend toward the swash plate 5 side beyond the portion of the rotating shaft member 3 where the cylinder block 4 is fitted. The cut-up grooves 94 are formed on the swash plate 5 side of each spline groove 93. The cut-up grooves 94 are formed so that the groove depth gradually becomes shallower as the groove moves away from the spline grooves 93, that is, toward the swash plate 5 side. Also, the cut-up grooves 94 are formed so that the groove width gradually becomes narrower toward the swash plate 5 side when viewed in the radial direction. The shape of the cut-out groove 94 is determined by the diameter of a spline forming tool (such as a cutter) not shown, etc. In the following description, the end of the cut-out groove 94 on the swash plate 5 side is referred to as the tip of the cut-out groove 94, and the starting position of the cut-out groove 94, that is, the end of the cut-out groove 94 closest to the spline groove 93, is referred to as the base end of the cut-out groove 94.

[0061] Here, in a pressing position where the outer peripheral surface 91b of the pressing portion 91 abuts against the shoe retaining member 29 and the pressing member 27 presses the shoe retaining member 29 toward the swash plate 5 (hereinafter simply referred to as the pressing position of the pressing member 27), a tip position P1 of the cut-out groove 94 is closer to the swash plate 5 than the inner peripheral surface 91a of the pressing portion 91. Also, in the pressing position of the pressing member 27, a base end position P2 of the cut-out groove 94 is opposite to the inner peripheral surface 91a of the pressing portion 91 in the radial direction.

[0062] As described above, the cut-up groove 94 is tapered so that the groove width gradually narrows toward the swash plate 5 side as viewed from the radial direction (see FIG. 5). Therefore, at the pressing position of the pressing member 27, the contact area between the outer circumferential surface 3c of the rotating shaft member 3 and the inner circumferential surface 91a of the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner circumferential surface 91a of the pressing portion 91 (hereinafter referred to as the axial center C3 of the inner circumferential surface 91a) is larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner circumferential surface 91a. The axial center C3 of the inner circumferential surface 91a corresponds to the center in the first rotation axis direction of the inner circumferential surface in the claims.

[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 supply of hydraulic oil to the cylinder bore 17). More specifically, first, the rotating shaft member 3 is rotated by power from a power source such as an engine, thereby rotating the cylinder block 4 integrally with the rotating shaft member 3. As the cylinder block 4 rotates, the piston 21 revolves around the central axis C1 of the rotating shaft member 3.

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

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

[0066] Here, when the inclination angle of the swash plate 5 (sliding surface 31a) changes, the stroke (sliding distance) of the reciprocating motion of the pistons 21 changes. That is, the greater the inclination angle of the swash plate 5, the greater the amount of hydraulic oil supplied to and discharged from the cylinder bores 17 accompanying the reciprocating motion of each piston 21. In contrast, the smaller the inclination angle of the swash plate 5, the smaller the amount of hydraulic oil supplied to and discharged from the cylinder bores 17 accompanying 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 rotating shaft member 3. Therefore, the amount of hydraulic oil discharged from each cylinder bore 17 also becomes zero.

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

[0068] Next, the rotational operation of the swash plate 5 will be described. The first biasing portion 6 biases the swash plate 5 in a direction that increases the inclination angle of the swash plate 5. The second biasing portion 7 biases the swash plate 5 in a direction that decreases the inclination angle of the swash plate 5. The swash plate 5 tilts and stops at a position where the magnitude of the moment around the rotation axis C2 of the swash plate 5 caused by the biasing force of the first biasing portion 6 (counterclockwise moment in FIG. 2, hereinafter simply referred to as counterclockwise moment) is equal to the magnitude of the moment around the rotation axis C2 of the swash plate 5 caused by the second biasing portion 7 (clockwise moment in FIG. 2, hereinafter simply referred to as clockwise moment).

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

[0070] When the clockwise moment by the second biasing portion 7 is changed, the biasing force of the biasing rod 46 on the swash plate 5 is changed. That is, for example, a signal pressure due to the hydraulic oil discharged from the hydraulic pump 1, a signal pressure from another hydraulic pump driven by the same drive source, or a signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same drive source is input to the second guide portion 54 of the second biasing portion 7. For example, a signal pressure generated by a control valve is input to the cylinder hole 55. The biasing pins 52 and 53 bias the biasing rod 46 according to the magnitude of these signal pressures. As a result, the biasing force of the biasing rod 46 on the swash plate 5 changes.

[0071] (Action between the second spline of the rotating shaft member and the pressing member) Next, the function of the second spline 3b of the rotating shaft member 3 and the pressing member 27 will be described with reference to FIG. 6 is a diagram illustrating the action of the second spline 3b of the rotating shaft member 3 and the pressing member 27. Fig. 6 corresponds to part B in Fig. 2. 6, for example, when the swash plate 5 is tilted (tilted counterclockwise in FIG. 6), a clockwise force F acts on the pressing member 27 pressing the shoe holding member 29. As a result, the pressing member 27 is tilted, and the swash plate 5 side of the pressing portion 91 of the pressing member 27 (see portion S1 in FIG. 6) is strongly pressed against the outer circumferential surface 3c of the rotating shaft member 3 below the central axis C1 of the rotating shaft member 3 in FIG.

[0072] Here, in the pressing position of the pressing member 27, the tip position P1 of the cut-up groove 94 in the second spline 3b is closer to the swash plate 5 than the inner peripheral surface 91a of the pressing portion 91. In addition, in the pressing position of the pressing member 27, the base end position P2 of the cut-up groove 94 in the second spline 3b is a position radially opposed to the inner peripheral surface 91a of the pressing portion 91. Therefore, in the pressing position of the pressing member 27, the contact area between the rotating shaft member 3 and the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner peripheral surface 91a is larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner peripheral surface 91a. Since the surface pressure of the pressing portion 91 having a large contact area is reduced by that amount, the wear of the rotating shaft member 3 and the pressing portion 91 is suppressed even when the pressing portion 91 is strongly pressed against the outer peripheral surface 3c of the rotating shaft member 3.

[0073] Incidentally, when a clockwise force F is applied to the pressing member 27, the cylinder block 4 side of the pressing portion 91 (see the portion S2 in FIG. 6) is strongly pressed against the outer circumferential surface 3c of the rotating shaft member 3 above the central axis C1 of the rotating shaft member 3 in FIG. 6, in contrast to the portion below the central axis C1. Here, the cylinder block 4 side of the pressing portion 91 (the portion S2 in FIG. 6) is farther from the bearing 14 on which the rotating shaft member 3 is rotatably supported than the swash plate 5 side of the pressing portion 91 (the portion S1 in FIG. 6). The amount of deflection of the rotating shaft member 3 increases as the position moves away from the bearings 14 and 11 on which it is supported. Therefore, the cylinder block 4 side of the pressing portion 91 is not strongly pressed against the outer circumferential surface 3c of the rotating shaft member 3, as compared with the swash plate 5 side of the pressing portion 91. Therefore, at the pressing position of the pressing member 27, even if the contact area between the rotating shaft member 3 and the pressing portion 91 from the axial center C3 of the inner surface 91a to the cylinder block 4 side is smaller than the contact area between the rotating shaft member 3 and the pressing portion 91 from the axial center C3 of the inner surface 91a to the swash plate 5 side, wear of the rotating shaft member 3 and the pressing portion 91 is not accelerated.

[0074] As described above, in the above embodiment, at the pressing position of the pressing member 27, the contact area between the rotating shaft member 3 and the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner circumferential surface 91a is larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner circumferential surface 91a. In other words, the contact area can be increased at a portion of the inner circumferential surface 91a of the pressing portion 91 (pressing member 27) that comes into particularly strong contact with the outer circumferential surface 3c of the rotating shaft member 3. In this way, by increasing the contact area between the rotating shaft member 3 and the pressing portion 91 only at necessary locations, it is possible to reduce the surface pressure between the rotating shaft member 3 and the pressing portion 91 without having to shift (offset) the pressing member 27 toward the swash plate 5 so as to completely avoid the second spline 3b. This makes it possible to reliably suppress wear of the rotating shaft member 3 and the pressing member 27. In addition, even if the inner circumferential surface 91a of the pressing portion 91 is formed flat, it is possible to prevent the axial length of the rotating shaft member 3 from becoming long. This makes it possible to reduce the manufacturing cost of the pressing member 27 while suppressing an increase in the size of the hydraulic pump 1.

[0075] In order to change the contact area between the rotating shaft member 3 and the pressing portion 91 around the axial center C3 of the inner peripheral surface 91a, the tip end position P1 of the cut groove 94 is located closer to the swash plate 5 than the inner peripheral surface 91a of the pressing portion 91 at the pressing position of the pressing member 27. In addition, the base end position P2 of the cut groove 94 is located in a position facing the inner peripheral surface 91a of the pressing portion 91 in the radial direction. In this way, by using the cut groove 94 of the second spline 3b, it is possible to efficiently reduce the manufacturing cost of the pressing member 27 and suppress wear of the rotating shaft member 3 and the pressing member 27 without performing additional processing on the rotating shaft member 3 to shorten the axial length. In addition, it is possible to suppress an increase in size of the hydraulic pump 1.

[0076] In the above embodiment, the case has been described where, in the pressing position of the pressing member 27, the tip end position P1 of the cut-out groove 94 is closer to the swash plate 5 than the inner circumferential surface 91a of the pressing portion 91. Also, in the pressing position of the pressing member 27, the base end position P2 of the cut-out groove 94 is a position radially opposed to the inner circumferential surface 91a of the pressing portion 91. However, this is not limited thereto, and in the pressing position of the pressing member 27, the tip end position P1 of the cut-out groove 94 may be an end of the inner circumferential surface 91a of the pressing portion 91 on the swash plate 5 side. Also, in the pressing position of the pressing member 27, the base end position P2 of the cut-out groove 94 may be closer to the cylinder block 4 than the inner circumferential surface 91a of the pressing portion 91.

[0077] That is, in the pressing position of the pressing member 27, at least one of the tip position P1 and the base position P2 of the cut-out groove 94, P1, P2, may be located radially opposite to the inner circumferential surface 91a of the pressing portion 91. With this configuration, in the pressing position of the pressing member 27, the contact area between the rotating shaft member 3 and the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner circumferential surface 91a is larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner circumferential surface 91a.

[0078] In the above embodiment, the inner circumferential surface 91a of the pressing portion 91 of the pressing member 27 is formed flat. However, this is not limited to this, and the inner circumferential surface 91a of the pressing portion 91 may be formed as in each of the following modified examples.

[0079] (First Modification) Fig. 7 is a cross-sectional view taken along the axial direction of pressing member 27 in the first modified example. Fig. 7 corresponds to Fig. 3 described above (the same applies to Figs. 8 to 10 below). Also, the same reference numerals are used to designate the same aspects as in the above-described embodiment, and descriptions thereof will be omitted (the same applies to the following modified examples). 7, the inner peripheral surface of the pressing portion 91 of the pressing member 27 is a curved surface 291a (corresponding to a chamfered portion in the claims) that is curved when viewed in a cross section along the axial direction. The curved surface 291a is curved so that the axial center protrudes most radially inward. In other words, the curved surface 291a is formed so that it gradually moves away from the outer peripheral surface 3c of the rotating shaft member 3 as it moves away from the axial center.

[0080] With this configuration, even if the pressing member 27 is tilted due to the tilt of the swash plate 5 (see FIG. 6), the outer circumferential surface 3c of the rotating shaft member 3 and the curved surface 291a of the pressing portion 91 can be brought into contact with each other as much as possible. Therefore, in addition to the same effects as those of the above-mentioned embodiment, the surface pressure between the rotating shaft member 3 and the pressing portion 91 can be further reduced, and wear of the rotating shaft member 3 and the pressing member 27 can be more reliably suppressed.

[0081] (Second Modification) FIG. 8 is a cross-sectional view taken along the axial direction of a pressing member 27 in the second modified example. 8, a rounded chamfered portion (corresponding to the chamfered portion in the claims) 391a is formed on the periphery on both axial sides of an inner circumferential surface 91a of the pressing portion 91 of the pressing member 27. By forming the rounded chamfered portion 391a, the inner circumferential surface 91a is gradually spaced apart from the outer circumferential surface 3c of the rotating shaft member 3 at both axial ends of the inner circumferential surface 91a as it approaches both axial ends. Therefore, according to the second modified example, the same effects as those of the first modified example described above are achieved.

[0082] (Third Modification) FIG. 9 is a cross-sectional view taken along the axial direction of a pressing member 27 in the third modified example. 9, the inner peripheral surface of the pressing portion 91 of the pressing member 27 is formed as an inclined surface (corresponding to a chamfered portion in the claims) 491a such that the axial center of the inner peripheral surface protrudes most radially inward when viewed in a cross section along the axial direction. In other words, the inclined surface 491a is formed so as to be gradually spaced apart from the outer peripheral surface 3c of the rotating shaft member 3 as it moves away from the axial center. Therefore, according to the third modified example, the same effects as those of the first modified example described above are achieved.

[0083] (Fourth Modification) FIG. 10 is a cross-sectional view taken along the axial direction of a pressing member 27 in the fourth modified example. 10, a chamfered surface portion (corresponding to the chamfered surface portion in the claims) 591a is formed on the periphery on both axial sides of an inner peripheral surface 91a of the pressing portion 91 of the pressing member 27. By forming the chamfered surface portion 591a, the inner peripheral surface 91a is gradually spaced apart from the outer peripheral surface 3c of the rotating shaft member 3 at both axial ends of the inner peripheral surface 91a toward both axial ends. Therefore, according to the fourth modified example, the same effects as those of the first modified example described above are achieved.

[0084] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above embodiment, the construction machine 100 is a hydraulic excavator. However, the present invention is not limited to this, and the above hydraulic pump 1 can be used in various construction machines.

[0085] In the above embodiment, the second spline 3b for fixing the cylinder block 4 is formed on the outer circumferential surface 3c of the rotating shaft member 3. The positional relationship between the second spline 3b and the pressing member 27 is specified, so that the contact area between the rotating shaft member 3 and the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner circumferential surface 91a is larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner circumferential surface 91a. However, this is not limited to this, and it is sufficient that a recess for fixing the cylinder block 4 is formed on the outer circumferential surface 3c of the rotating shaft member 3 instead of the second spline 3b. For example, knurling or the like is also included. Furthermore, at the pressing position of the pressing member 27, the contact area between the rotating shaft member 3 and the pressing portion 91 on the swash plate 5 side from the axial center C3 of the inner surface 91a should be larger than the contact area between the rotating shaft member 3 and the pressing portion 91 on the cylinder block 4 side from the axial center C3 of the inner surface 91a. [Explanation of symbols]

[0086] Reference Signs List 1...hydraulic pump, 2...casing, 3...rotating shaft member, 3b...second spline (spline), 3c...outer peripheral surface, 4...cylinder block, 5...swash plate, 21...piston, 22...shoe, 27...pressing member, 29...shoe retaining member, 55...cylinder hole, 91...pressing portion (pressing member), 91a...inner peripheral surface, 92...leg (pressing member), 93...spline groove, 94...cut groove, 100...construction machine , 101... rotating body (vehicle body), 102... running body (vehicle body), 291a... curved surface (chamfered portion), 391a... rounded chamfered portion (chamfered portion), 491a... inclined surface (chamfered portion), 591a... flat chamfered portion (chamfered portion), C1... central axis (first rotation axis), C2... rotation axis (second rotation axis), C3... axial center of inner circumferential surface (center of inner circumferential surface in the first rotation axis direction), P1... tip position, P2... base end position

Claims

1. a cylinder block that rotates about a first axis of rotation; a piston movably provided in each of a plurality of cylinder bores formed in the cylinder block; a swash plate that is supported so that its inclination angle can be changed around a second axis of rotation that intersects with the first axis of rotation and that restricts movement of the piston; a shoe provided between the piston and the swash plate; A shoe holding member for holding the shoe; a pressing member having a pressing portion that contacts the shoe holding member and presses the shoe holding member toward the swash plate, and a leg portion that extends from the pressing portion toward the cylinder block and has an inner diameter larger than that of the pressing portion; a rotating shaft member having the first rotation axis as a central axis and rotating integrally with the cylinder block, the rotating shaft member has an outer circumferential surface into which an inner circumferential surface of the pressing member is fitted and which has a constant diameter over an entire area where the pressing member is located in a direction parallel to the first rotation axis; a spline groove recessed inward from the outer circumferential surface in a radial direction of the rotating shaft member and formed along the first rotation axis; and a cut-up groove recessed inward from the outer circumferential surface in the radial direction of the rotating shaft member, formed continuously with the spline groove on the swash plate side of the spline groove, and having a groove width narrowing with increasing distance from the spline groove, when the pressing member is in a pressing position where it presses the shoe retaining member, in a plan view from a radial direction of the rotating shaft member, a portion of an inner circumferential surface of the pressing portion that is closer to the swash plate than a center in a direction parallel to the first rotation axis on the one side contacts the outer circumferential surface of the rotating shaft member, while on the other side a portion of the inner circumferential surface of the pressing portion that is closer to the cylinder block than the center contacts the outer circumferential surface, a hydraulic pump in which, when the pressing member is in the pressing position, a tip end position of the cut-out groove on the side opposite the spline groove is closer to the swash plate than the inner circumferential surface of the pressing portion, and a base end position of the cut-out groove on the spline groove side is opposite to the inner circumferential surface of the pressing portion in the radial direction of the rotating shaft member.

2. 2. The hydraulic pump according to claim 1, wherein a chamfer is formed on at least an end portion of the inner circumferential surface of the pressing portion on the swash plate side and an end portion of the inner circumferential surface of the pressing portion on the cylinder block side, the chamfer being spaced apart from the outer circumferential surface as it moves away from the center of the inner circumferential surface of the pressing portion.

3. A hydraulic pump according to claim 1 or 2; A vehicle body on which the hydraulic pump is mounted; Construction machinery equipped with

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