Hydraulic pump and construction machinery

Abstract

The present invention provides a hydraulic pump and a construction machine. 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 cylinder chambers; and a valve plate arranged 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 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.

Description

Technical Field

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

[0002] 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 machinery such as hydraulic excavators. This hydraulic pump has a rotating shaft rotatably supported in a housing. A cylinder body is embedded and fixed on the outer peripheral surface of the rotating shaft. The rotating shaft and the cylinder body rotate integrally. A plurality of cylinder holes (cylinder chambers) are provided in the cylinder body. A plunger is inserted into each cylinder hole. And the cylinder chamber is composed of the cylinder hole and the plunger.

[0003] A swash plate supported to be rotatable relative to the housing is provided at the end of the plunger on the side opposite to the end on the side where the cylinder chamber is formed (the end facing the cylinder chamber). The rotation axis of the swash plate is orthogonal to the rotation axis of the cylinder body. A slipper that can move relative to the swash plate is installed at the 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 on the outer peripheral surface of the rotating shaft.

[0004] Based on such a structure, the plunger slides along the inclined plate, and the displacement in the cylinder hole is limited by the inclined plate. If the plunger slides along the inclined plate, the plunger slides in the cylinder hole. The change in the volume of the cylinder chamber caused by this is used to spray the working oil at a predetermined flow rate. If the inclination angle of the inclined plate changes, the sliding movement of the plunger in the cylinder hole changes, and therefore the discharge amount of the hydraulic pump changes.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-66189 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] For example, the cooling device (oil cooler) of construction machinery is miniaturized according to the model change, and a good thermal balance is sought for hydraulic equipment. In particular, the body size of mini excavators is small, making it difficult to configure a large cooling device.

[0010] On the other hand, the rotating cylinder of the conventional hydraulic pump and the valve plate fixed in the housing are adjacent to each other through the working oil. Due to the friction between the surfaces of the cylinder and the valve plate adjacent to each other through the working oil, the working oil is heated and becomes high temperature. A part of the heated and high-temperature working oil leaks from the gap between the cylinder and the valve plate into the housing and is retained. Therefore, it is considered difficult to properly maintain the thermal balance of the hydraulic pump.

[0011] Alternatively, a structure is conceivable in which the high-temperature working oil that has leaked from the gap between the cylinder body and the valve plate into the housing and retained is returned to the suction side or to the tank via a guide path. However, even if these structures are adopted, the high-temperature working oil will be retained in the housing. As a result, it is difficult to properly maintain the thermal balance of the hydraulic pump.

[0012] The present invention provides a hydraulic pump and a construction machine capable of appropriately maintaining thermal balance by suppressing a temperature increase of the hydraulic pump.

[0013] Solutions for solving problems

[0014] A hydraulic pump according to one technical solution of the present invention comprises: a housing; a shaft supported in the housing in a manner rotatable around an axis; a cylinder body engaged with the outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder body having a cylinder chamber; and a valve plate arranged along the axis in a manner overlapping with the cylinder body, having a suction passage and a discharge passage communicating with the cylinder chamber, the valve plate having a communicating path, the communicating path being formed on a surface of the valve plate adjacent to the cylinder body and being a surface for dividing and forming the suction passage, the communicating path being connected to at least a portion of the suction passage.

[0015] A hydraulic pump according to another technical solution of the present invention comprises: a housing; a shaft supported in the housing in a manner rotatable around an axis; a valve plate having a suction passage and a discharge passage; and a cylinder body, which is engaged with the outer peripheral surface of the shaft and rotates integrally with the shaft, and is arranged on the valve plate along the axis, the cylinder body having a cylinder chamber connected to the suction passage and the discharge passage, the cylinder body having a connecting path, the connecting path being formed on a surface of the cylinder body adjacent to the valve plate and being a surface for dividing and forming the suction passage, and the connecting path being connected to at least a portion of the suction passage.

[0016] By configuring as described above, the rotating cylinder body and the fixed valve plate are adjacent to each other with the working oil interposed therebetween. The working oil generates heat and becomes high temperature due to the friction between the adjacent surfaces of the cylinder body and the valve plate. The high-temperature working oil can be sucked into the suction port through the groove. Therefore, the high-temperature working oil sucked into the suction port will not be retained inside the housing, but can be ejected from the ejection port to the ejection passage through the cylinder chamber. Thus, the heat balance can be properly maintained by suppressing the increase in the temperature of the hydraulic pump.

[0017] In the above configuration, the communication path may be open in a portion other than that used for the partitioning formation, among adjacent surfaces of the cylinder and the valve plate.

[0018] With this structure, the working oil which is heated to a high temperature by friction between the surfaces adjacent to each other through the working oil between the rotating cylinder block and the fixed valve plate can be smoothly sucked into the suction port from the external space (the outside except the surface defining the suction portion).

[0019] In the above structure, it may also be that the connecting path includes either an inner ring pit or an outer ring pit, the inner ring pit is formed on the surface of the valve plate adjacent to the cylinder body, and is located on the radial inner side of the axis relative to the suction passage and the discharge passage, and the outer ring pit is formed on the surface of the valve plate adjacent to the cylinder body, and is located on the radial outer side of the axis relative to the suction passage and the discharge passage.

[0020] With this structure, the hot working oil in the inner ring pit can be smoothly sucked into the suction port through the groove. Thus, the hot working oil near the rotating shaft can be sucked from the suction port and ejected from the ejection port to the ejection passage, thereby suppressing the temperature rise of the hydraulic pump.

[0021] The high-temperature working oil in the outer ring pit can be smoothly sucked into the suction port through the groove. As a result, the high-temperature working oil between the cylinder block and the valve plate can be sucked from the suction port and ejected from the ejection port to the ejection passage. Therefore, the temperature rise of the hydraulic pump can be suppressed.

[0022] In the above configuration, the communication path may be located near the discharge passage.

[0023] By configuring in this way, the high-temperature working oil leaking from the discharge port to the discharge passage can be guided to the groove well. Thus, the high-temperature working oil leaking from the discharge port to the discharge passage can be smoothly sucked into the suction port through the groove.

[0024] Since the hydraulic oil in the discharge port is not directly guided to the groove, it is also possible to prevent the discharge flow rate of the hydraulic pump from being deteriorated.

[0025] A hydraulic pump according to another technical solution of the present invention comprises: a housing; a shaft supported in the housing in a manner rotatable around an axis; a cylinder body engaged with an outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder body having a cylinder chamber and a first communicating path formed on a first demarcated surface of the cylinder body; and a valve plate arranged along the axis in a manner overlapping with the first demarcated surface of the cylinder body, having a suction passage and a discharge passage communicating with the cylinder chamber, the valve plate having a second communicating path, the second communicating path being formed on the second demarcated surface of the valve plate at a position opposite to the first communicating path in the axial direction, communicating with at least a portion of the suction passage together with the first communicating path, the second demarcated surface being adjacent to the first demarcated surface and dividing and forming the suction passage.

[0026] With such a structure, the rotating cylinder body and the fixed valve plate are adjacent to each other with the working oil interposed therebetween. The working oil generates heat and becomes high temperature due to the friction between the adjacent surfaces of the cylinder body and the valve plate. The high-temperature working oil can be sucked into the suction port through the groove. Therefore, the high-temperature working oil sucked into the suction port will not be retained inside the housing, but can be ejected from the ejection port to the ejection passage through the cylinder chamber. Thus, the heat balance can be properly maintained by suppressing the increase in the temperature of the hydraulic pump.

[0027] A hydraulic pump according to another embodiment of the present invention comprises: a housing; a shaft supported in the housing in a manner rotatable about an axis; a cylinder body fitted with an outer peripheral surface of the shaft and rotating integrally with the shaft, the cylinder body having a cylinder chamber; and a valve plate arranged along the axis in a manner overlapping with the cylinder body, having a suction passage and a discharge passage communicating with the cylinder chamber, and having an inner ring recess, an outer ring recess, and a communication path, wherein the inner ring recess, the outer ring recess, and the communication path are formed on a surface of the valve plate adjacent to the cylinder body and for dividing and forming the suction passage, the inner ring recess is located on the inner side of the shaft in the radial direction relative to the suction passage and the discharge passage, the outer ring recess is located on the outer side of the shaft in the radial direction relative to the suction passage and the discharge passage, and the communication path is communicated with at least a portion of the suction passage, the inner ring recess, and any one of the inner ring recess and the outer ring recess.

[0028] With such a structure, the rotating cylinder body and the fixed valve plate are adjacent to each other with the working oil interposed therebetween. The working oil generates heat and becomes high temperature due to the friction between the adjacent surfaces of the cylinder body and the valve plate. The high-temperature working oil can be sucked into the suction port from the inner ring pit and the outer ring pit via the groove. Therefore, the high-temperature working oil sucked into the suction port will not be retained inside the housing, but can be ejected from the ejection port to the ejection passage via the cylinder chamber. Thus, the thermal balance can be properly maintained by suppressing the increase in the temperature of the hydraulic pump.

[0029] A construction machine according to another aspect of the present invention includes a vehicle body on which the above-mentioned hydraulic pump is mounted.

[0030] With such a configuration, it is possible to provide a construction machine including a hydraulic pump capable of suppressing a rise in the temperature of the hydraulic pump and maintaining an appropriate thermal balance.

[0031] Effects of the Invention

[0032] The above-described hydraulic pump and construction machine can appropriately maintain thermal balance by suppressing a rise in the temperature of the hydraulic pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic configuration diagram of a construction machine according to an embodiment of the present invention.

[0034] Figure 2 It is a cross-sectional view of a hydraulic pump according to an embodiment of the present invention.

[0035] Figure 3 It is magnified Figure 2 A cross-sectional view of part III.

[0036] Figure 4 It is a top view of the valve plate according to the embodiment of the present invention.

[0037] Figure 5 It is a cross-sectional view showing a valve plate according to a first modified example of the embodiment of the present invention.

[0038] Figure 6 It is a top view of a valve plate according to a first modified example of the embodiment of the present invention.

[0039] Figure 7 It is a cross-sectional view of a valve plate showing a second modified example of the embodiment of the present invention.

[0040] Figure 8 It is a top view of a valve plate according to a second modified example of the embodiment of the present invention.

[0041] Fig. 9 The valve plate of the third modified example of the embodiment of the present invention is along Fig.10 A cross-sectional view taken along line IV-IV.

[0042] Fig.10 It is a top view of a valve plate according to a third modified example of the embodiment of the present invention.

[0043] Description of Reference Numerals

[0044] 1. Hydraulic pump; 2. Housing; 3. Shaft; 3c. Outer peripheral surface; 4. Cylinder; 4b. End surface of cylinder (surface adjacent to the surface of valve plate, first demarcated surface); 5. Inclined plate; 19, 80, 90, 95. Valve plate; 19a, 80a, 90a, 95a. End surface (surface adjacent to the surface of cylinder, second demarcated surface); 21. Plunger; 55. Cylinder hole (cylinder chamber); 62. Inner ring recess (inner ring pit); 63. Outer ring recess (outer ring pit); 64. Suction port (suction passage); 64a. Inner portion (at least a portion of the suction passage); 6 4b, outer portion (at least a portion of the suction passage); 64c, at least a portion of the suction port (at least a portion of the suction passage); 65, 65b, 82, 82b, 97, 97c, groove portion (communication path); 65a, 82a, 97a, opening portion; 66, discharge port (discharge passage); 68, 84, 92, 98, gap; 97b, top end portion; 100, construction machinery; 101, rotating body (body); 102, traveling body (body); 121, first through hole; 122, second through hole; C1, center axis (axis). DETAILED DESCRIPTION

[0045] Next, embodiments of the present invention will be described based on the drawings.

[0046] <Construction machinery>

[0047] Figure 1 It is a schematic structural diagram of the construction machine 100.

[0048] like Figure 1 As shown, the construction machine 100 is, for example, a hydraulic excavator. The construction machine 100 includes a revolving body (equivalent to the vehicle body in the claims) 101 and a traveling body (equivalent to the vehicle body in the claims) 102. The revolving body 101 is rotatably provided on the traveling body 102. The revolving body 101 is equipped with a hydraulic pump 1.

[0049] The revolving body 101 includes: a cab 103 in which an operator can sit; a boom 104, one end of which is connected to the cab 103 in a swingable manner; an arm 105, one end of which is connected to the other end (top end) of the boom 104 on the opposite side of the cab 103 in a swingable manner; and a bucket 106, which is connected to the other end (top end) of the arm 105 on the opposite side of the boom 104 in a swingable manner. 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 ejected from the hydraulic pump 1.

[0050] <Hydraulic pump>

[0051] Figure 2 It is a cross-sectional view of the hydraulic pump 1 .

[0052] like Figure 2 As shown, 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 4 housed inside the housing 2 and fixed to the shaft 3; a swash plate 5 housed in the housing 2 in a manner capable of changing its inclination angle and controlling the discharge amount of the working oil discharged from the hydraulic pump 1; and a first force applying portion 6 and a second force applying portion 7 that control the inclination angle of the swash plate 5.

[0053] exist Figure 2 In order to make the description easier to understand, the scales of the components are appropriately changed. In the following description, the direction parallel to the central axis line C1 of the shaft 3 (equivalent to the axis line in the claims) is referred to as the axial direction, the rotation direction of the shaft 3 is referred to as the circumferential direction, and the radial direction of the shaft 3 is referred to as the radial direction.

[0054] The housing 2 includes a box-shaped housing body 9 having an opening 9 a and a front flange 10 that closes the opening 9 a of the housing body 9 .

[0055] A bearing 11 that rotatably supports one end of the shaft 3 is provided at the bottom 9b on the side opposite to the opening 9a of the housing body 9. A first guide portion 49 that guides a later-described force application rod 46 of the second force application portion 7 is provided on the inner surface side of the side surface 9c of the housing body 9. A mounting recess 48 that communicates with the first guide portion 49 is formed at the bottom 9b of the housing body 9. A later-described force application pin unit 50 of the second force application portion 7 is mounted in the mounting recess 48.

[0056] Furthermore, a suction passage 71 is formed in the housing body 9 (see Figure 3 ) and the ejection passage 72 (refer to Figure 3 The suction passage 71 is connected to a tank (not shown). The discharge passage 72 is connected to the cab 103, the boom 104, the arm 105, and the bucket 106 via a control valve (not shown).

[0057] A swash plate support portion 30 is formed protrudingly on the inner surface 10a of the flange 10 on the housing body 9 side (the inner surface 10a facing the housing body 9). The swash plate support portion 30 supports the swash plate 5 so that the inclination angle can be changed. A recessed 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 recessed portion 30a.

[0058] An externally threaded stopper 40 is provided at a radially outer portion of the front flange 10. The stopper 40 supports a portion of the swash plate 5 to limit the inclination angle of the swash plate 5. By rotating the stopper 40 relative to the front flange 10, the amount of the stopper 40 protruding relative to the inner surface 10a side of the front flange 10 changes. As a result, the inclination angle of the swash plate 5 is limited.

[0059] The front flange 10 is provided with a through hole 13 through which the shaft 3 can pass. The through hole 13 is provided with a bearing 14 that supports the other end side of the shaft 3 so that it can rotate freely. An oil seal 15 is provided at a position on the side of the through hole 13 that is opposite to the housing body 9 (outside the front flange 10) from 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 oil from flowing out from the inside. The oil seal 15 prevents foreign matter from entering between the front flange 10 and the shaft 3.

[0060] 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 via the first spline 3a. A second spline 3b is formed at a portion of the outer peripheral surface 3c of the shaft 3 that is closer to the bottom 9b side of the housing body 9 than the swash plate 5, that is, at the axial center of the shaft 3. The cylinder block 4 is fitted into a portion of the outer peripheral surface 3c of the shaft 3 that corresponds to the second spline 3b.

[0061] The first splines 3 a and the second splines 3 b are formed by, for example, cutting the outer peripheral surface 3 c of the shaft 3 using a dedicated tool (a cutter or the like) not shown.

[0062] The cylinder body 4 is formed in a cylindrical shape. A through hole 16 is formed in the radial center of the cylinder body 4, into which the shaft 3 can be inserted or pressed. 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 body 4 rotate integrally.

[0063] A recessed portion 20 is formed between the axial center and the end portion 4a of the through hole 16 so as to surround the shaft 3. A through hole 25 is formed partially on the inner peripheral surface between the axial center and the side of the swash plate 5 of the through hole 16 so as to penetrate the cylinder body 4 in the axial direction. A spring 23 and collars 24a and 24b described later are accommodated in the recessed portion 20. A connecting member 26 described later is accommodated in the through hole 25 so as to be movable in the axial direction.

[0064] A plurality of cylinder holes 17 are formed in the cylinder block 4 so as to surround the shaft 3. The cylinder holes 17 are arranged at equal intervals along the circumferential direction. The cylinder holes 17 are formed along the axial direction, and the cylinder holes 17 are open on the inclined plate 5 side. A communication hole 18 is formed at a position corresponding to each cylinder hole 17 at the end 4a of the cylinder block 4 on the side opposite to the front flange 10, which connects these cylinder holes 17 and the outside of the cylinder block 4.

[0065] Figure 3 It is magnified Figure 2 A cross-sectional view of part III. Figure 4 It is a top view of the valve plate 19.

[0066] like Figure 2 , Figure 3 , Figure 4 As shown, a disc-shaped valve plate 19 is provided at the end 4a of the cylinder body 4 in a manner overlapping with the end surface 4b of the end 4a along the central axis C1 of the shaft 3 (equivalent to the surface adjacent to the surface of the valve plate, the first demarcated surface in the claims). The valve plate 19 is fixed to the housing body 9. Even when the cylinder body 4 rotates together with the shaft 3, the valve plate 19 is stationary relative to the housing 2 (housing body 9).

[0067] The valve plate 19 is formed with an insertion hole 61 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 in a circular shape. The valve plate 19 has: an inner ring recess (equivalent to the inner ring pit in the claims) 62, which is arranged radially inward 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 radially outward of the inner ring recess 62; a suction port (equivalent to the suction passage in the claims) 64; a groove (equivalent to the communication path in the claims) 65; and a discharge port (equivalent to the discharge passage in the claims) 66. The end surface 4b of the cylinder body 4 overlaps with the end surface 19a of the valve plate 19 that is opposite to the end surface 4b of the cylinder body 4 (equivalent to the surface adjacent to the surface of the cylinder body in the claims, the second demarcated surface) 19a. As a result, the suction port 64 and the discharge port 66 are divided and formed. The suction port 64 and the discharge port 66 refer to the entire passage constituting these suction ports 64 and the discharge port 66, rather than just the ends of the passage.

[0068] The inner ring recess 62 is formed in a substantially annular shape when viewed from the axial direction. The inner ring recess 62 opens at the end surface 19a of the valve plate 19. The inner ring recess 62 is formed in an annular shape along the insertion hole 61 at a position closer to the inside in the radial direction. The inner ring recess 62 is located on the inner side of the shaft 3 in the radial direction relative to the suction port 64 and the discharge port 66.

[0069] The outer ring recess 63 is formed in a substantially annular shape when viewed from the axial direction. The outer ring recess 63 opens at the end face 19a of the valve plate 19 that is opposite to the end face 4b of the cylinder body 4. The outer ring recess 63 is formed in an annular shape along the outer peripheral surface 19b of the valve plate 19 at a position close to the outside in the radial direction. The outer ring recess 63 is located on the outside of the shaft 3 in the radial direction relative to the suction port 64 and the discharge port 66.

[0070] 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 through the thickness direction of the valve plate 19 in a manner that communicates with each communication hole 18 of the cylinder block 4. The suction port 64 communicates with each cylinder hole 17 via each communication hole 18 of the cylinder block 4.

[0071] A groove portion 65 is formed on the end surface 19a of the valve plate 19. The groove portion 65 is connected to at least a portion 64a of the suction port 64 (specifically, substantially the entire inner portion opposite to the inner ring recess 62). The groove portion 65 is connected to the inner ring recess 62. In other words, the groove portion 65 has an opening portion 65a that opens to the inner ring recess 62. In further other words, the groove portion 65 has an opening portion 65a on the outside (inner ring recess 62) of the end surface 19a except for the portion that divides and forms the suction port 64 and the discharge port 66. The inner portion 64a of the suction port 64 opposite to the inner ring recess 62 is connected to the inner ring recess 62 via the groove portion 65 (opening portion 65a).

[0072] The valve plate 19 is provided with a discharge port 66 between the inner annular recess 62 and the outer annular recess 63 in the radial direction and on the other side (the side opposite to the suction port 64) in the circumferential direction. The discharge port 66 includes a first discharge port 66a on the inner side in the radial direction and a second discharge port 66b on the outer side in the radial direction. The first discharge port 66a and the second discharge port 66b are formed in a curved shape along the inner annular recess 62 and the outer annular 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 in a manner to communicate with the communication holes 18 of the cylinder body 4. The discharge ports 66a and 66b are communicated with the cylinder holes 17 via the communication holes 18 of the cylinder body 4.

[0073] Each cylinder hole 17 communicates with a suction passage 71 formed in the housing body 9 via a suction port 64 of the valve plate 19 and a communication hole 18 of the cylinder block 4. Each cylinder hole 17 communicates with a discharge passage 72 formed in the housing body 9 via a discharge port 66 of the valve plate 19 and a communication hole 18 of the cylinder block 4.

[0074] The valve plate 19 is fixed to the housing body 9. In this state, the cylinder block 4 is rotated together with the shaft 3. The cylinder hole 17 is connected to 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 switches to a state in which the working oil is sucked from the suction passage 71 through the suction port 64 of the valve plate 19 and a state in which the working oil is discharged to the discharge passage 72 through the discharge port 66 of the valve plate 19 according to the rotation state of the cylinder block 4.

[0075] A plunger 21 is accommodated in each cylinder hole 17 so as to be movable in the axial direction. 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 4 rotate.

[0076] A spherical convex portion 28 is integrally formed at the end of the plunger 21 on the swash plate 5 side. The interior of the plunger 21 is formed as a cavity. The cavity is filled with the working oil in the cylinder hole 17. Therefore, the reciprocating motion of the plunger 21 is associated with the suction and discharge of the working oil relative to the cylinder hole 17. That is, when the plunger 21 is pulled out of the cylinder hole 17, the working oil is sucked into the interior of the cylinder hole 17 from the suction passage 71 and the suction port 64. When the plunger 21 enters the interior of the cylinder hole 17, the working oil is discharged from the interior of the cylinder hole 17 to the discharge port 66 and the discharge passage 72.

[0077] like Figure 2 As shown, the spring 23 accommodated in the recess 20 of the cylinder body 4 is, for example, a coil spring. The spring 23 is compressed between the two collars 24a and 24b accommodated in the recess 20. Therefore, the spring 23 generates a force in the direction of extension due to its elastic force. The force of the spring 23 is transmitted to the connecting member 26 via one collar 24b of the two collars 24a and 24b. In the portion closer to the front flange 10 side than the connecting member 26 (between the cylinder body 4 and the inclined plate 5), the pressing member 27 is fitted to the outer peripheral surface 3c of the shaft 3.

[0078] The pressing member 27 is formed in a substantially cylindrical shape. The connecting member 26 contacts the end surface of the pressing member 27 on the side opposite to the front flange 10. The force of the spring 23 applied to the connecting member 26 is transmitted to the pressing member 27. The pressing member 27 contacts the shoe holding member 29 to be described later, and presses the shoe holding member 29 toward the swash plate 5 side (the direction of the swash plate 5).

[0079] Shoes 22 are mounted on the convex portions 28 of the plungers 21 housed in the cylinder holes 17 of the cylinder block 4. Spherical recesses 22a are formed on the surface of the shoe 22 on one side of the side that accommodates the convex portion 28 in a manner corresponding to the shape of the convex portion 28. That is, a recess 22a for accommodating the convex portion 28 is formed on one surface of the shoe 22. The shape of the recess 22a is a spherical shape corresponding to the shape of the convex portion 28. The convex portion 28 of the plunger 21 is fitted into the recess 22a. Thus, the shoe 22 is connected to the convex portion 28 of the plunger 21 so as to be rotatable.

[0080] Each shoe 22 is integrally held by a shoe holding member 29. The shoe holding member 29 is pressed toward the swash plate 5 by the pressing member 27. Each shoe 22 is pressed toward the swash plate 5 by the pressing member 27 via the shoe holding member 29.

[0081] The swash plate 5 has the following function: it rotates and tilts, thereby limiting 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 cylinder body 4 side. A through hole 32 that penetrates in the axial direction is formed in the radial center of the swash plate body 31. The shaft 3 penetrates (penetrates) the through hole 32. A flat sliding surface 31a is formed on the cylinder body 4 side of the swash plate body 31. Each shoe 22 is pressed against the sliding surface 31a in a movable manner.

[0082] The two supporting protrusions 33 and 34 are arranged on the back side of the sliding surface 31a of the inclined plate body 31. The two supporting protrusions 33 and 34 are arranged opposite to each other in the radial direction of the front and back of the paper with the through hole 32 as the center. The two supporting protrusions 33 and 34 support the inclined plate 5 on the front flange 10 in a manner that the inclination angle can be changed. Each supporting protrusion 33 and 34 is formed in a semicircular shape when viewed from the radial direction. The supporting protrusion 33 has an arc surface 33a. The supporting protrusion 34 has an arc surface 34a. These arc surfaces 33a and 34a face the front flange 10 side. Each supporting protrusion 33 and 34 is formed to protrude from the inclined plate body 31.

[0083] The arcuate surfaces 33a and 34a of the supporting protrusions 33 and 34 are movably in contact with the recessed portion 30a of the swash plate supporting portion 30 formed to protrude from the front flange 10. The arcuate surfaces 33a and 34a slide on the recessed portion 30a. As a result, the swash plate 5 rotates relative to the front flange 10.

[0084] A first force-applied portion 37 and a second force-applied portion 38 are integrally formed on the radial side of the swash plate body 31, and are radially opposed to each other with the through hole 32 as the center. The direction in which the first force-applied portion 37 and the second force-applied portion 38 are opposed to each other is orthogonal to the direction in which the two supporting protrusions 33 and 34 are opposed to each other. The first force-applied portion 37 and the second force-applied portion 38 extend radially outward from the swash plate body 31. A surface 38a of the second force-applied portion 38 on the side of the front flange 10 abuts against a stopper 40 provided to the front flange 10.

[0085] A connecting recess 39 is formed on the radially outer side (top end side) of the first biased portion 37 on the surface (surface on the cylinder 4 side) on the side opposite to the protruding direction of each supporting protrusion 33, 34. The first biasing portion 6 is connected to the connecting recess 39. The connecting recess 39 is formed in a circular shape when viewed from the axial direction.

[0086] The second biased portion 38 has an abutment surface 41 formed on the substantially entire surface (the surface on the cylinder 4 side) on the side opposite to the protruding direction of each supporting protrusion 33, 34. The abutment surface 41 is formed by flatly cutting the second biased portion 38. The second biasing portion 7 abuts against the abutment surface 41.

[0087] The swash plate 5 configured in this manner rotates relative to the front flange 10 . As a result, the first biased portion 37 and the second biased portion 38 are inclined so as to approach or move away from the front flange 10 .

[0088] The inclination angle of the swash plate 5 is an angle formed by the sliding surface 31a and a plane perpendicular to the shaft 3. That is, the smaller the angle is, the smaller the inclination angle of the swash plate 5 is.

[0089] The first urging portion 6 urges the swash plate 5 in a direction in which the inclination angle of the swash plate 5 increases. The first urging portion 6 includes a first collar 42 disposed on the bottom 9b side of the housing body 9, a second collar 43 disposed on the swash plate 5 side, and a first spring 44 and a second spring 45 disposed between the first collar 42 and the second collar 43.

[0090] A spherical connection protrusion 43a is formed to protrude from the swash plate 5 side of the second collar 43. The second collar 43 is rotatably connected to the swash plate 5 by the contact between the connection protrusion 43a and the connection recess 39 of the swash plate 5.

[0091] The first spring 44 is compressed between the first collar 42 and the second collar 43. Therefore, the first spring 44 generates a biasing force in a direction in which the first spring 44 is extended due to its elastic force.

[0092] The second spring 45 is arranged 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 collar 43.

[0093] The second spring 45 is in a state where the inclined plate 5 has a large inclination angle ( Figure 2 Thus, when the inclined plate 5 has a large inclination angle, only the biasing force of the first spring 44 acts on the inclined plate 5.

[0094] On the other hand, if the inclination angle of the swash plate 5 decreases, the second spring 45 contacts the first collar 42 at a certain inclination angle. If the inclination angle of the swash plate 5 further decreases, the second spring 45 is also compressed between the first collar 42 and the second collar 43. Thus, the urging forces of the first spring 44 and the second spring 45 act on the swash plate 5.

[0095] In this way, the first force applying portion 6 can change its force in stages according to the inclination angle of the swash plate 5. The second spring 45 is not limited to being fixed to the second collar 43, and the second spring 45 may also be fixed to the first collar 42. The second spring 45 may also be not fixed to either the first collar 42 or the second collar 43, but may move between the first collar 42 and the second collar 43.

[0096] The second force applying portion 7 applies a force in the direction opposite to the force applied by the first force applying portion 6 to the swash plate 5. In particular, the second force applying portion 7 overcomes the force applied by the first force applying portion 6 in the direction of increasing the inclination angle of the swash plate 5 and applies a force to the swash plate 5 in the direction of decreasing the inclination angle of the swash plate 5.

[0097] The second urging portion 7 includes an urging rod 46 and an urging pin unit 50. The urging pin unit 50 mainly includes a unit case 51 and a plurality of urging pins 52 and 53. Figure 2 In the figure, only two of the plurality of force applying pins 52 and 53 are shown, but, for example, four of the plurality of force applying pins 52 and 53 are provided.

[0098] The unit housing 51 is installed in a manner of being embedded in the mounting recess 48 of the housing body 9. A plurality of second guide portions 54 for guiding a plurality of force-applying pins 52 and 53 are provided on the side of the unit housing 51 close to the swash plate 5. The second guide portion 54 is a hole that penetrates the unit housing 51 in the axial direction. A cylinder hole 55 (equivalent to the cylinder chamber in the claims) that communicates with one of the plurality of second guide 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 guide portion 54. The opening of the cylinder hole 55 is blocked by a cover member 57.

[0099] A cylindrical urging plunger 56 is disposed in the cylinder hole 55 so as to be movable in the axial direction relative to the cylinder hole 55 .

[0100] Each of the urging pins 52 and 53 is accommodated in the second guide portion 54 so as to be movable in the axial direction. One urging pin 52 among the plurality of urging pins 52 and 53 is formed longer than the other urging pins 53. Such one urging pin 52 is accommodated in the second guide portion 54 communicated with the cylinder hole 55. The end of the one urging pin 52 on the side opposite to the swash plate 5 protrudes toward the cylinder hole 55.

[0101] For example, a signal pressure based on the hydraulic oil discharged from the hydraulic pump 1, a signal pressure from another hydraulic pump driven by the same driving source, a signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same driving source, etc. is input to the second guide portion 54. A signal pressure generated by, for example, a control valve is input to the cylinder hole 55. Each of the urging pins 52 and 53 urges the urging rod 46 toward the swash plate 5 according to the signal pressure corresponding to each of the urging pins 52 and 53.

[0102] The urging rod 46 is disposed between the contact surface 41 of the swash plate 5 and the urging pins 52 and 53. The urging rod 46 is formed in a cylindrical shape so as to be elongated in the axial direction. The urging rod 46 is guided by the first guide portion 49 of the housing body 9 so as to be movable in the axial direction.

[0103] The spherical surface 46a is formed at 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 the change in the inclination angle of the swash plate 5, the force acting on the swash plate 5 can be properly transmitted from the spherical surface 46a to the contact surface 41.

[0104] <Operation of the hydraulic pump>

[0105] Next, the operation of the hydraulic pump 1 will be described.

[0106] The hydraulic pump 1 outputs a driving force based on the discharge of the hydraulic oil from the cylinder bore 17 (and the suction of the hydraulic oil into the cylinder bore 17 ).

[0107] More specifically, first, the shaft 3 is rotated by power from a power source such as an engine, so that the cylinder 4 rotates integrally with the shaft 3. As the cylinder 4 rotates, the plunger 21 revolves around the central axis C1 of the shaft 3.

[0108] Each of the shoes 22 attached to the convex portion 28 of each plunger 21 appropriately follows the sliding surface 31a of the swash plate 5 and is pressed against the sliding surface 31a of the swash plate 5 due to the urging force of the spring 23 regardless of the inclination angle of the swash plate 5. The convex portion 28 of the plunger 21 is formed in a spherical shape, and the concave portion 22a of the shoe 22 into which the convex portion 28 is inserted is also formed in a spherical shape. Each of the shoes 22 is pressed toward the swash plate 5 side by the pressing member 27 via the shoe holding member 29. Therefore, even if the inclination angle of the swash plate 5 changes, each of the shoes 22 follows the inclination of the swash plate 5 and appropriately follows the sliding surface 31a and is pressed against the sliding surface 31a.

[0109] When the plunger 21 revolves around the central axis C1 of the shaft 3 as the cylinder body 4 rotates, each shoe 22 also slides on the sliding surface 31a of the swash plate 5 while revolving around the central axis C1 of the shaft 3. As a result, each plunger 21 moves in the axial direction in each cylinder hole 17, and each plunger 21 reciprocates. In this way, the swash plate 5 restricts the displacement of each plunger 21 in the axial direction. According to the reciprocating action of the plunger 21, the working oil is ejected from a part of the cylinder holes 17, and the working oil is sucked into the other cylinder holes 17, thereby realizing a hydraulic pump.

[0110] 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 the ejection amount of the working oil relative to the cylinder hole 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 the ejection amount of the working oil relative to the cylinder hole 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 hole 17 is also zero.

[0111] An externally 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 contacts the stopper 40. The stopper 40 can be moved forward and backward relative to the swash plate 5 by rotating. Therefore, 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.

[0112] Next, the rotation operation of the swash plate 5 will be described.

[0113] The swash plate 5 is urged by the first force applying portion 6 in a direction in which the inclination angle of the swash plate 5 increases. The swash plate 5 is urged by the second force applying portion 7 in a direction in which the inclination angle of the swash plate 5 decreases. The swash plate 5 is subjected to a torque (in Figure 2 The magnitude of the torque (in which the torque is counterclockwise) and the torque (in which the torque is counterclockwise) generated by the second force applying portion 7 about the rotation axis of the swash plate 5 are Figure 2 The torque is clockwise in the middle and stops at a position where the torque is equal to the original torque.

[0114] Below, we will Figure 2 The counterclockwise torque in is referred to as counterclockwise torque. Figure 2 The clockwise torque in is referred to as clockwise torque.

[0115] That is, if the clockwise torque generated by the second force applying part 7 is increased, the inclination angle of the swash plate 5 becomes smaller. Accordingly, the first spring 44 and the second spring 45 of the first force applying part 6 are compressed, and the counterclockwise torque generated by the first force applying part 6 also becomes larger. As a result, the clockwise torque generated by the second force applying part 7 is equal to the counterclockwise torque generated by the first force applying part 6, and the swash plate 5 stops at a predetermined inclination.

[0116] On the other hand, if the clockwise torque generated by the second force applying part 7 is reduced, the force of the first spring 44 and the second spring 45 of the first force applying part 6 is greater than the clockwise torque generated by the second force applying part 7, and the inclination angle of the swash plate 5 increases. In conjunction with this, if the first spring 44 and the second spring 45 are extended, the force generated by the first force applying part 6 becomes smaller. As a result, the clockwise torque generated by the second force applying part 7 is equal to the counterclockwise torque generated by the first force applying part 6, and the swash plate 5 stops at a predetermined inclination. "Predetermined inclination" means that the acute angle formed by the sliding surface 31a formed on the swash plate body 31 of the swash plate 5 relative to the plane 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 obtain the effect of the present invention, it may be an angle other than the above-mentioned angle range.

[0117] When the clockwise torque generated by the second force applying part 7 is changed, the force applied by the force applying rod 46 to the swash plate 5 is changed. That is, for example, the signal pressure based on the hydraulic oil ejected from the hydraulic pump 1, the signal pressure from another hydraulic pump driven by the same driving source, the signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same driving source, etc. is input to the second guide part 54 of the second force applying part 7. The signal pressure generated by, for example, a control valve is input to the cylinder hole 55. According to the magnitude of these signal pressures, each force applying pin 52, 53 applies force to the force applying rod 46. As a result, the force applied by the force applying rod 46 to the swash plate 5 is changed.

[0118] Next, based on Figure 2 , Figure 3 , Figure 4 The operation of appropriately maintaining the thermal balance of the hydraulic pump 1 will be described.

[0119] like Figure 2 , Figure 3 , Figure 4 As shown, the cylinder body 4 is rotated together with the shaft 3. As a result, each cylinder hole 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 body 9. Therefore, according to the rotation state of the cylinder body 4, each cylinder hole 17 is connected to the suction port 64 and the discharge port 66 of the valve plate 19 via each communication hole 18.

[0120] Thus, the cylinder hole 17 switches between a suction state for sucking the hydraulic oil and a discharge state for discharging the hydraulic oil according to the rotation state of the cylinder block 4. Specifically, in the suction state, the cylinder hole 17 sucks the hydraulic oil of the suction passage 71 from the communication hole 18 into the cylinder hole 17 through the suction port 64 of the valve plate 19 (see Figure 3 The cylinder hole 17 ejects the hydraulic oil in the cylinder hole 17 from the ejection port 66 of the valve plate 19 to the ejection passage 72 through the communication hole 18 in the ejection state (see arrow A in FIG. 1 ). Figure 3 Arrow B).

[0121] An oil film made of working oil is formed between the cylinder body 4 and the adjacent end faces 4b and 19a of the valve plate 19. The oil film generates heat and reaches a high temperature due to the friction between the adjacent end faces 4b and 19a. A part of the working oil that generates heat and reaches a high temperature leaks from between the adjacent end faces 4b and 19a to the inner annular concave portion 62 and the outer annular concave portion 63.

[0122] The inner ring recess 62 is connected to the inner portion 64a of the suction port 64, which is opposite to the inner ring recess 62, via the groove 65 (opening 65a). Therefore, the working oil heated to a high temperature by the friction between the adjacent end surfaces 4b and 19a can be smoothly sucked from the inner ring recess 62 to the suction port 64 via the groove 65 (opening 65a) (see FIG. Figure 3 The high-temperature hydraulic oil sucked from the groove 65 to the suction port 64 can be smoothly sucked into the cylinder bore 17 through the communication hole 18 (see arrow C in FIG. 1 ). Figure 3 The arrow D in the figure).

[0123] In the discharge state of the cylinder bore 17, the high-temperature hydraulic oil sucked into the cylinder bore 17 can be smoothly discharged from the discharge port 66 of the valve plate 19 to the discharge passage 72 via the communication hole 18 (see Figure 3 Arrow B).

[0124] As a result, the high-temperature hydraulic oil flowing out (leaking out) from the gap (a portion where an oil film is formed; hereinafter, the gap has the same meaning) 68 between the adjacent end surfaces 4b and 19a to the inner ring recess 62 does not remain inside the housing 2, but can be smoothly ejected from the ejection port 66 via each cylinder hole 17. Thus, the hydraulic pump 1 that can appropriately maintain thermal balance by suppressing a rise in the temperature of the hydraulic pump 1 can be provided.

[0125] return Figure 1 The hydraulic pump 1 is mounted on the revolving body 101 of the construction machine 100. With such a configuration, it is possible to provide the construction machine 100 including the hydraulic pump 1 that can suppress the increase in the temperature of the hydraulic pump 1 and maintain a suitable thermal balance.

[0126] In the above-mentioned embodiment, the case where the groove 65 is formed on the end surface 19a of the valve plate 19 among the adjacent end surfaces 4b and 19a of the cylinder body 4 and the valve plate 19 is described. The case where the inner ring recess 62 is connected to the suction port 64 via the groove 65 (opening 65a) is described. However, the present invention is not limited to this. Alternatively, the groove 65b may be formed on the end surface 4b of the cylinder body 4 (see Figure 3 The inner ring recess 62 is connected to the suction port 64 via the groove.

[0127] In the above-mentioned embodiment, the case where the groove 65 is formed in the substantially entire inner portion 64a of the suction port 64 opposite to the inner ring recess 62 is described. In addition, the case where the inner portion 64a of the suction port 64 is connected to the inner ring recess 62 via the groove 65 (opening 65a) is described. However, it is not limited to this, and the groove 65 is formed in a part of the inner portion 64a of the suction port 64, and the suction port 64 and the inner ring recess 62 are connected via the groove 65. It is also possible to provide a through hole that penetrates the valve plate 19 in the thickness direction instead of the groove 65.

[0128] [First Modification]

[0129] Figure 5 It is a cross-sectional view showing a valve plate 80 according to a first modified example. Figure 6 80 is a top view of the valve plate 80 . Figure 5 , Figure 6 With the aforementioned Figure 3 , Figure 4 Corresponding (for the following Figure 7 , Figure 8 , Fig. 9 , Fig.10 The same reference numerals are used for the same configurations as those in the above-mentioned embodiment, and description thereof will be omitted (this also applies to the following modified examples).

[0130] like Figure 2 , Figure 5 , Figure 6 As shown, a groove portion (equivalent to the communication path in the claims) 82 is formed on the end surface 80a of the valve plate 80 adjacent to the end surface 4b of the cylinder body 4 (equivalent to the surface adjacent to the surface of the cylinder body, the second demarcated surface in the claims). The groove portion 82 is connected to at least a portion of the suction port 64 (specifically, the outer portion opposite to the outer ring recess 63) 64b, and is connected to the outer ring recess 63. In other words, the groove portion 82 has an opening portion 82a that opens to the outer ring recess 63. In further other words, the groove portion 82 has an opening portion 82a on the outside (outer ring recess 63) of the end surface 80a except for the portion that divides and forms the suction port 64 and the discharge port 66. The substantially entire outer portion 64b of the suction port 64 opposite to the outer ring recess 63 is connected to the outer ring recess 63 via the groove portion 82 (opening portion 82a).

[0131] Based on such a structure, the working oil heated to a high temperature by the friction between the end surface 4b of the adjacent cylinder block 4 and the end surface 80a of the valve plate 80 can be smoothly sucked from the outer ring recess 63 through the groove 82 to the suction port 64 (see Figure 5The high-temperature hydraulic oil sucked from the groove 82 to the suction port 64 can be smoothly sucked into the cylinder bore 17 through the communication hole 18 (see arrow E in FIG. 1 ). Figure 5 Arrow F in the figure).

[0132] The high-temperature hydraulic oil sucked into the cylinder bore 17 can be smoothly discharged in the discharge state of the cylinder bore 17 similarly to the above-described embodiment.

[0133] Therefore, the high-temperature hydraulic oil flowing out (leaking out) from the gap 84 between the adjacent end surfaces 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 hole 17. Thus, it is possible to provide a hydraulic pump 1 that can appropriately maintain thermal balance by suppressing a rise in the temperature of the hydraulic pump 1.

[0134] In the first modification, the case where the groove 82 is formed on the end face 80a of the valve plate 80, of the adjacent end faces 4b and 80a of the cylinder body 4 and the valve plate 80, is described. The case where the outer ring recess 63 is connected to the suction port 64 via the groove 82 is described. However, the present invention is not limited thereto, and the groove 82b may be formed on the end face 4b of the cylinder body 4 (see Figure 5 The outer ring recess 63 is connected to the suction port 64 via the groove portion.

[0135] In the first modified example described above, a case where the groove 82 is formed in substantially the entire outer portion 64b of the suction port 64 that is opposite to the outer ring recess 63 is described. Also, a case where the outer portion 64b of the suction port 64 is connected to the outer ring recess 63 via the groove 82 (opening 82a) is described. However, this is not limited to this, and the groove 82 may be formed in a portion of the outer portion 64b of the suction port 64, and the suction port 64 and the outer ring recess 63 may be connected via the groove 82. Instead of the groove 82, a through hole may be provided that penetrates the valve plate 19 in the thickness direction.

[0136] [Second Modification]

[0137] Figure 7 It is a cross-sectional view showing a valve plate 90 according to a second modified example. Figure 8 1 is a top view of the valve plate 90 .

[0138] like Figure 2 , Figure 7 , Figure 8As shown, the second modification is a combination of the above-mentioned embodiment and the first modification, and is a shape that penetrates the groove 65 of the above-mentioned embodiment and the groove 82 of the first modification in the thickness direction. That is, the first through hole 121 penetrating in the thickness direction of the valve plate 90 is formed on the end surface 90a of the valve plate 90 adjacent to the end surface 4b of the cylinder body 4 (equivalent to the surface adjacent to the surface of the cylinder body, the second demarcated surface in the claims) instead of the groove 65 of the above-mentioned embodiment. The second through hole 122 penetrating in the thickness direction of the valve plate 90 is formed on the end surface 90a of the valve plate 90 instead of the groove 82.

[0139] The first through hole 121 is communicated with at least a portion (specifically, substantially the entire inner portion opposite to the inner annular recess 62) 64a of the suction port 64, and is communicated with the inner annular recess 62. That is, the inner portion 64a of the suction port 64 opposite to the inner annular recess 62 is communicated with the inner annular recess 62 via the first through hole 121.

[0140] The second through hole 122 is communicated with at least a portion (specifically, an outer portion opposite to the outer ring recess 63) 64b of the suction port 64, and is communicated with the outer ring recess 63. That is, substantially the entire outer portion 64b of the suction port 64 opposite to the outer ring recess 63 is communicated with the outer ring recess 63 via the second through hole 122.

[0141] Based on such a structure, the working oil which is heated and becomes high temperature 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 can be smoothly sucked from the inner ring recess 62 through the first through hole 121 to the suction port 64 (see Figure 7 The working oil which has been heated by the friction between the adjacent end faces 4b and 90a and has reached a high temperature can be smoothly sucked from the outer ring recess 63 through the second through hole 122 to the suction port 64 (refer to Figure 7 Arrow H in the figure).

[0142] The high-temperature hydraulic oil sucked into the suction port 64 from the first through hole 121 and the second through hole 122 can be smoothly sucked into the cylinder hole 17 through the communication hole 18 (see Figure 7 The high-temperature hydraulic oil sucked into the cylinder hole 17 can be smoothly ejected from the ejection port 66 in the ejection state of the cylinder hole 17, similarly to the above-mentioned embodiment.

[0143] Therefore, the high-temperature hydraulic oil flowing out (leaking out) from the gap 92 between the adjacent end surfaces 4b and 90a to the inner annular recess 62 and the outer annular recess 63 does not stay inside the housing 2, but can be ejected more smoothly from the ejection port 66 through each cylinder hole 17. Thus, it is possible to provide a hydraulic pump 1 that can more appropriately maintain thermal balance by more effectively suppressing the increase in the temperature of the hydraulic pump 1.

[0144] In the second modified example described above, the case where the first through hole 121 and the second through hole 122 are formed on the end surface 90a of the valve plate 90 is described. The case where the inner ring recess 62 and the outer ring recess 63 are connected to the suction port 64 via the first through hole 121 and the second through hole 122 is described. However, this is not limited to this, and the groove 65b of the above-mentioned embodiment and the groove 82b of the first modified example (both refer to Figure 7 The inner ring recess 62 and the outer ring recess 63 are connected to the suction port 64 via the grooves 65b and 82b.

[0145] [Third Modification]

[0146] Fig. 9 The valve plate 95 of the third modified example is along Fig.10 A cross-sectional view taken along line IV-IV. Fig.10 It is a top view of the valve plate 95 of the third modified example.

[0147] like Figure 2 , Fig. 9 , Fig.10 As shown, a groove portion (equivalent to the communication path in the claims) 97 is formed on the end surface 95a of the valve plate 95 adjacent to the end surface 4b of the cylinder body 4 (equivalent to the surface adjacent to the surface of the cylinder body, the second demarcated surface in the claims). The groove portion 97 is connected to at least a portion 64c of the suction port 64. The groove portion 97 has an opening portion 97a that opens to the gap 98 between the suction port 64 and the outside of the discharge port 66 between the adjacent end surfaces 4b and 95a of the cylinder body 4 and the valve plate 95, and a top end portion 97b located near the discharge port 66.

[0148] With such a structure, the working oil heated to a high temperature by the friction between the end surface 4b of the adjacent cylinder block 4 and the end surface 95a of the valve plate 95 can be smoothly sucked into the suction port 64 through the gap 98 and the groove 97 (see Fig. 9 The arrow in J).

[0149] The top end 97b of the groove 97 is located near the discharge port 66 (specifically, the inner discharge port 66a). Therefore, the high-temperature working oil leaking into the gap 98 can be well guided to the groove 97. As a result, the high-temperature working oil can be more smoothly sucked into the suction port 64 through the groove 97 (see Fig. 9 The arrow J).

[0150] The high-temperature hydraulic oil sucked from the groove portion 97 to the suction port 64 can be smoothly sucked into the cylinder hole 17 through the communication hole 18 (see Fig. 9 The high-temperature hydraulic oil sucked into the cylinder hole 17 can be smoothly ejected from the ejection port 66 in the ejection state of the cylinder hole 17, similarly to the above-mentioned embodiment.

[0151] Therefore, the high-temperature hydraulic oil flowing out (leaking into) the gap 98 does not stay inside the housing 2, but can be more smoothly discharged from the discharge port 66 through each cylinder hole 17. Thus, it is possible to provide a hydraulic pump 1 that can better maintain thermal balance by better suppressing the increase in the temperature of the hydraulic pump 1.

[0152] In the third modification, the case where the groove 97 is formed on the end surface 95a of the valve plate 95 among the adjacent end surfaces 4b and 95a of the cylinder body 4 and the valve plate 95 is described. The case where the groove 97 is connected to the suction port 64 is described. However, the present invention is not limited to this. Alternatively, the groove 97c may be formed on the end surface 4b of the cylinder body 4 (see Fig. 9 The groove portion is connected to the suction port 64.

[0153] The present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment without departing from the gist of the present invention.

[0154] For example, in the above-mentioned embodiment, the case where the construction machine 100 is a hydraulic excavator is described. However, the present invention is not limited to this, and the above-mentioned hydraulic pump 1 can be adopted 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 rotatable integrally with the shaft, the cylinder block having cylinder chambers; and a disk-shaped valve plate disposed along the axis so as to overlap the cylinder block, the cylinder block having a first delimiting surface adjacent to the valve plate, the valve plate having: a second delimiting surface adjacent to the first delimiting surface; an insertion hole located at the center of the valve plate when viewed in a direction along the axis, the shaft passing through the insertion hole in the direction along the axis; a suction passage and a discharge passage disposed at different positions in the circumferential direction of the valve plate and communicating with the cylinder chambers; an inner annular recess located radially inward of the suction passage and the discharge passage and radially outward of the insertion hole, formed in a ring shape along the insertion hole and opening at the second delimiting surface; an outer annular recess located radially outward of the suction passage and the discharge passage, formed in a ring shape along an outer peripheral surface of the valve plate and opening at the second delimiting surface; and a friction end face portion located at the outermost peripheral portion of the second delimiting surface, continuous in the radial direction between an outer peripheral wall of the outer annular recess and the outer peripheral surface of the valve plate, an inner peripheral wall of the inner annular recess having an opening communicating with the insertion hole and continuous with an opening of the inner annular recess at the second delimiting surface, an outer peripheral wall of the inner annular recess having an opening communicating with the suction passage and continuous with an opening of the inner annular recess at the second delimiting surface, an inner peripheral wall of the outer annular recess having an opening communicating with the suction passage and continuous with an opening of the outer annular recess at the second delimiting surface, the friction end face portion being arranged to contact the first delimiting surface in the same plane over the entire circumference in the circumferential direction.

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

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