Hydraulic pump and cooling method for hydraulic pump

Abstract

To provide a hydraulic pump that can be efficiently cooled, and to provide a method for cooling a hydraulic pump.SOLUTION: A hydraulic pump includes: a shaft member rotating in a direction about a central axis; a bearing for supporting the shaft member so as to be rotatable; a bearing chamber for holding the bearing: a plate including a suction port and a discharge port from which a working fluid is sucked and discharged with the rotation of the shaft member; and a circulation mechanism for circulating the working fluid, which flows through a low pressure side port of the suction port and the discharge port, through the bearing chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a hydraulic pump and a method for cooling the hydraulic pump. [Background technology]

[0002] 2. Description of the Related Art A hydraulic pump that drives a working fluid is known to have a configuration including a shaft member and a bearing, such as an axial piston pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-520171 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described hydraulic pump, when a sliding bearing is used as the bearing, heat is generated due to friction between the shaft member and the bearing, and therefore efficient cooling is required.

[0005] The present disclosure has been made in view of the above, and has an object to provide a hydraulic pump that can be cooled efficiently and a cooling method for the hydraulic pump. [Means for solving the problem]

[0006] The hydraulic pump according to the present disclosure includes a shaft member that rotates around a central axis, a bearing that rotatably supports the shaft member, a bearing chamber that holds the bearing, and a plate having an intake port and a discharge port through which working fluid is drawn in and discharged as the shaft member rotates, and a circulation mechanism that circulates the working fluid flowing through the low-pressure port of the intake port and the discharge port into the bearing chamber.

[0007] The cooling method for a hydraulic pump according to the present disclosure is a cooling method for a hydraulic pump that includes a shaft member that rotates in a direction around a central axis, a bearing that rotatably supports the shaft member, a bearing chamber that holds the bearing, and a plate having an intake port and a discharge port through which working fluid is drawn in and discharged as the shaft member rotates, wherein the working fluid flowing through the lower-pressure port of the intake port or the discharge port is circulated into the bearing chamber, and the working fluid that has circulated into the bearing chamber is discharged to the outside as drain. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a hydraulic pump that can be cooled efficiently and a cooling method for the hydraulic pump. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a hydraulic pump according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of an operating state of the hydraulic pump. [Figure 3] FIG. 3 is a diagram illustrating an example of a hydraulic pump according to the second embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a selection mechanism. [Figure 5] FIG. 5 is a diagram showing another example of the selection mechanism. [Figure 6] FIG. 6 is a diagram showing another example of the selection mechanism. [Figure 7] FIG. 7 is a diagram illustrating an example of a hydraulic pump according to the third embodiment. [Figure 8] FIG. 8 is a diagram showing an example of a selection mechanism. [Figure 9] FIG. 9 is a diagram illustrating an example of a hydraulic pump according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a hydraulic pump and a cooling method for a hydraulic pump according to the present disclosure will be described with reference to the drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0011] [First embodiment] Fig. 1 is a diagram showing an example of a hydraulic pump 100 according to a first embodiment. The hydraulic pump 100 shown in Fig. 1 is a swash plate type axial piston pump, and uses, for example, hydraulic oil as a working fluid Q. The hydraulic pump 100 includes a shaft member 10, a bearing 20, a cylinder barrel 30, a piston 40, a cam 50, and a housing 60.

[0012] The shaft member 10 is, for example, cylindrical, and one end is connected to a drive device such as a motor (not shown). The shaft member 10 rotates around the central axis AX by the driving force from the drive device. The shaft member 10 is provided, for example, with one end protruding from the housing 60. Hereinafter, the side of the shaft member 10 in the axial direction of the central axis AX that protrudes from the housing 60 will be referred to as the front side, and the side opposite to the front side will be referred to as the rear side (or end side).

[0013] The bearing 20 rotatably supports the shaft member 10. The bearing 20 has a front bearing 21 and a rear bearing 22. The front bearing 21 is disposed on one side of the shaft member 10 in the axial direction of the central axis AX. A rolling bearing, for example, is used as the front bearing 21. The rear bearing 22 is disposed on the other side of the shaft member 10 in the axial direction of the central axis AX. A sliding bearing, for example, is used as the rear bearing 22.

[0014] The cylinder barrel 30 is disposed inside the housing 60 and fixed to the shaft member 10 by, for example, a key or a spline. The cylinder barrel 30 rotates integrally with the shaft member 10 in a direction around the central axis AX.

[0015] The cylinder barrel 30 has a plurality of cylinders 31. The plurality of cylinders 31 are arranged at predetermined intervals around the central axis AX. For example, the inner wall of each cylinder 31 is formed into a cylindrical shape, and the cylinders 31 are arranged parallel to the axial direction of the central axis AX. A cylinder port 32 is provided on an end face of each cylinder 31. The cylinder port 32 is connected to the suction port P1 or the discharge port P2.

[0016] A piston 40 is provided in each cylinder 31. The piston 40 is capable of reciprocating in the axial direction of the central axis AX while in contact with the inner wall of the cylinder 31. A head 41 of the piston 40 protrudes from the inside of the cylinder 31 toward the cam 50. The head 41 is supported by the cam 50.

[0017] The cam 50 is provided so as not to rotate around the central axis AX. The cam 50 has a support surface 51 that slidably supports the head 41 of the piston 40. With this configuration, when the cylinder barrel 30 rotates around the central axis AX, the cam 50 causes the head 41 of the piston 40 to slide around the central axis AX, allowing the head 41 to move back and forth inside the cylinder 31 in the axial direction of the central axis AX.

[0018] The housing 60 has a casing 61, a front plate 62, and an end plate 63. The casing 61 is arranged circumferentially on the side of the hydraulic pump 100. Working fluid Q leaking from the cylinder 31 and the like flows through a casing interior 61a surrounded by the casing 61. The casing interior 61a is maintained at a predetermined drain pressure. The casing 61 is provided with a drain discharge portion 69 that discharges the working fluid Q flowing through the casing interior 61a as drain.

[0019] The front plate 62 is disposed at one end of the hydraulic pump 100 on one side of the central axis AX.

[0020] The end plate 63 is disposed at the other end of the central axis AX of the hydraulic pump 100. The end plate 63 has a suction port P1, a discharge port P2, a bearing chamber 64, a drain connection passage 65, and a flow mechanism 70.

[0021] The suction port P1 is a port through which the working fluid Q is drawn in from the outside. The discharge port P2 is a port through which the working fluid Q is discharged to the outside. The suction port P1 is designed to be at low pressure when the hydraulic pump 100 is operating. For example, the suction port P1 can be designed to have a large-diameter flow path to reduce suction resistance. The discharge port P2 is designed to be at high pressure when the hydraulic pump 100 is operating. For example, the discharge port P2 can be designed to have a small-diameter flow path to reduce the pressure-receiving area in order to ensure durability even when high pressure is reached.

[0022] The bearing chamber 64 holds the rear bearing 22. The drain connection passage 65 connects the bearing chamber 64 with the casing interior 61a. The bearing chamber 64 is maintained at a predetermined drain pressure.

[0023] The flow mechanism 70 allows the working fluid Q flowing through the lower-pressure port of the suction port P1 or the discharge port P2, i.e., the suction port P1 in this embodiment, to flow to the bearing chamber 64. The flow mechanism 70 has a first flow path 71. The first flow path 71 connects the suction port P1 and the bearing chamber 64.

[0024] Next, the operation of the hydraulic pump 100 will be described. Fig. 2 is a diagram showing an example of an operating state of the hydraulic pump 100. As shown in Fig. 2, in the hydraulic pump 100, when the shaft member 10 is rotated by, for example, an external motor, the cylinder barrel 30 rotates in conjunction with the rotation of the shaft member 10. When the cylinder barrel 30 rotates, the head 41 of the piston 40 slides in a direction around the central axis AX. This causes the piston 40 to reciprocate inside the cylinder 31 in the axial direction of the central axis AX.

[0025] While the piston 40 moves from the bottom dead center to the top dead center, the cylinder 31 is connected to the suction port P1 via the cylinder port 32. In this case, working fluid Q is drawn into the cylinder 31 as the piston 40 moves. As the working fluid Q is drawn in, the pressure in the suction port P1 becomes low.

[0026] Furthermore, while the piston 40 moves from the top dead center to the bottom dead center, the cylinder 31 is connected to the discharge port P2 via the cylinder port 32. In this case, working fluid Q is discharged from the cylinder 31 to the discharge port P2 as the piston 40 moves. As the working fluid Q is discharged, the pressure in the discharge port P2 becomes high.

[0027] In this way, by operating the hydraulic pump 100, the suction port P1 becomes the low-pressure side and the discharge port P2 becomes the high-pressure side. In other words, the suction port P1 becomes the low-pressure side port. In this embodiment, the working fluid Q flows from the suction port P1 to the bearing chamber 64 through the first flow path 71 provided in the end plate 63. The shaft member 10 and the rear bearing 22 are cooled by the working fluid Q flowing from the suction port P1 to the bearing chamber 64.

[0028] When the working fluid Q that has entered through the suction port P1 is discharged from the discharge port P2, the temperature of the fluid rises due to compression by the piston 40, resistance to passage through the flow path, and the like. Therefore, the working fluid Q present in the suction port P1 is at a lower pressure and temperature than the working fluid Q flowing through the discharge port P2. This allows the working fluid Q to flow from the suction port P1 to the bearing chamber 64 at an appropriate flow rate, thereby efficiently cooling the shaft member 10 and the rear bearing 22. The working fluid Q that flows into the bearing chamber 64 flows through the drain connection flow path 65 into the casing interior 61a and is discharged to the outside as drain from the drain discharge portion 69.

[0029] As described above, the hydraulic pump 100 according to this embodiment includes the shaft member 10 that rotates around the central axis AX, the rear bearing 20 that rotatably supports the shaft member 10, the bearing chamber 64 that holds the rear bearing 20, the end plate 63 that has the suction port P1 and the discharge port P2 through which the working fluid is sucked in and discharged as the shaft member 10 rotates, and the circulation mechanism 70 that circulates the working fluid Q that flows through the lower-pressure port of the suction port P1 or the discharge port P2 to the bearing chamber 64.

[0030] Therefore, the shaft member 10 and the rear bearing 22 are cooled by the working fluid Q that flows from the suction port P1 to the bearing chamber 64. The temperature of the working fluid Q that flows through the suction port P1 is lower than that of the working fluid Q that flows through the discharge port P2 because the working fluid Q does not pass through the cylinder 31. Therefore, by circulating the working fluid Q from the suction port P1 to the bearing chamber 64, the shaft member 10 and the rear bearing 22 can be efficiently cooled, and therefore the hydraulic pump 100 can be efficiently cooled.

[0031] In the hydraulic pump 100 according to this embodiment, the flow mechanism 70 has a first flow path 71 that connects the suction port P1 and the bearing chamber 64. Therefore, the working fluid Q can be reliably circulated from the suction port P1 to the bearing chamber 64 via the first flow path 71.

[0032] The hydraulic pump 100 according to this embodiment further includes a plurality of cylinders 31 arranged in a direction circumferential to the central axis AX, each having a cylinder 31 port 32 through which the working fluid Q is drawn in and discharged, and which move in a direction circumferential to the axis as the shaft member 10 rotates, and a piston 40 provided in each of the cylinders 31, which reciprocates in conjunction with the movement of the cylinder 31 in the direction circumferential to the axis. Therefore, in the hydraulic pump 100, which is an axial piston pump including a plurality of cylinders 31 and pistons 40, the shaft member 10 and the rear bearing 22 can be efficiently cooled.

[0033] A cooling method for a hydraulic pump 100 according to this embodiment is a cooling method for a hydraulic pump including: a shaft member 10 that rotates in a direction around a central axis AX; a rear bearing 22 that rotatably supports the shaft member 10; a plurality of cylinders 31 that are arranged in a direction around the central axis AX and have cylinder 31 ports 32 through which a working fluid Q is taken in and discharged, and that move in a direction around the axis as the shaft member 10 rotates; a piston 40 that is provided in each of the cylinders 31 and moves back and forth in conjunction with the movement of the cylinder 31 in the direction around the axis; a bearing chamber 64 that holds the rear bearing 22; and an end plate 63 that has an intake port P1 and a discharge port P2 that are arranged so as to be connectable to the rotating cylinder 31 ports 32, wherein the working fluid Q flowing through the lower-pressure port of the intake port P1 or the discharge port P2 is circulated through the bearing chamber 64, and the working fluid Q that has circulated through the bearing chamber 64 is discharged to the outside as drain. Therefore, by circulating the working fluid Q from the suction port P1 to the bearing chamber 64, it is possible to efficiently cool the shaft member 10 and the rear bearing 22, and therefore to efficiently cool the hydraulic pump 100. In addition, the working fluid Q flowing in the bearing chamber 64 flows into the casing interior 61a via the drain connection passage 65 and is discharged to the outside as drain.

[0034] [Second embodiment] Next, a hydraulic pump 200 according to a second embodiment will be described. Fig. 3 is a diagram showing an example of the hydraulic pump 200 according to the second embodiment. The hydraulic pump 200 according to the second embodiment has a different flow mechanism configuration from the hydraulic pump 100 according to the first embodiment. The following description will focus on the differences from the first embodiment.

[0035] In the hydraulic pump 200 according to this embodiment, the flow mechanism 170 has a first flow path 71, a second flow path 72, and a selection mechanism 80. The first flow path 71 connects the suction port P1 and the bearing chamber 64. The second flow path 72 connects the discharge port P2 and the bearing chamber 64. The first flow path 71 and the second flow path 72 are provided in the end plate 63. The selection mechanism 80 selects and connects the lower-pressure port of the suction port P1 or the discharge port P2 to the bearing chamber 64.

[0036] The selection mechanism 80 has a first check valve 81 and a second check valve 82. The first check valve 81 is provided in the first flow path 71. The first check valve 81 opens when the differential pressure obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the suction port P1 is equal to or less than a specified value, and closes when this differential pressure exceeds the specified value.

[0037] The second check valve 82 is provided in the second flow path 72. The second check valve 82 opens when the differential pressure obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the discharge port P2 is equal to or less than a specified value, and closes when this differential pressure exceeds the specified value.

[0038] 4 is a diagram showing an example of the selection mechanism 80. In FIG. 4, the first check valve 81 will be used as an example for explanation, but the same explanation can be applied to the second check valve 82. As shown in FIG. 4, the selection mechanism 80 has the first check valve 81, a first wall portion 83, a second wall portion 84, and a spring portion 85.

[0039] The first wall portion 83 is provided on the suction port P1 side and has an opening 83a. The second wall portion 84 has a flat plate portion 84a and a cylindrical portion 84b. One end of the spring portion 85 is supported by the flat plate portion 84a, and the other end is supported by a flange portion 81a (described later) of the first check valve 81.

[0040] The first check valve 81 has a flange portion 81a and a columnar portion 81b. The flange portion 81a is arranged to cover the opening 83a of the first wall portion 83. The flange portion 81a is biased toward the first wall portion 83 by the elastic force of the spring portion 85. The flange portion 81a has a through flow passage 81c. The through flow passage 81c is provided so as to penetrate the flange portion 81a. The columnar portion 81b is inserted into the cylindrical portion 84b. The columnar portion 81b is movable along the longitudinal direction of the cylindrical portion 84b. The columnar portion 81b has a through flow passage 81d. The through flow passage 81d penetrates from the side of the columnar portion 81b to the end face of the columnar portion 81b on the bearing chamber 64 side.

[0041] 4, when the force generated by the pressure difference between the pressure in suction port P1 and the pressure in bearing chamber 64 is smaller than the elastic force of spring portion 85, first check valve 81 is in a state in which flange portion 81a is urged toward first wall portion 83 by the elastic force of spring portion 85. In this state, suction port P1 and bearing chamber 64 are in communication with each other via through-flow paths 81c and 81d. Therefore, working fluid from suction port P1 is supplied to bearing chamber 64.

[0042] 4, when the force generated by the pressure difference between the pressure in suction port P1 and the pressure in bearing chamber 64 is greater than the elastic force of spring portion 85, first check valve 81 is pushed toward bearing chamber 64 by the pressure of the working fluid in suction port P1, and through-flow passage 81d of columnar portion 81b is blocked by cylindrical portion 84b. In this state, suction port P1 and bearing chamber 64 are not connected.

[0043] Fig. 5 is a diagram showing another example of the selection mechanism. In Fig. 5, the first check valve 81A will be used as an example for explanation, but the same explanation can be applied to the second check valve 82. As shown in Fig. 5, the selection mechanism 80A has a first check valve 81A, a cylindrical portion 83A, a plug 84A, and a spring portion 85A.

[0044] The cylindrical portion 83A is connected to the first flow path 71 and extends in one direction. The cylindrical portion 83A has an enlarged diameter portion 83e, a reduced diameter portion 83f, and a stepped portion 83g. A first check valve 81A is housed inside the cylindrical portion 83A. The first check valve 81A has an enlarged diameter portion 81e, a reduced diameter portion 81f, and a stepped portion 81g. The enlarged diameter portion 81e is disposed in the enlarged diameter portion 83e of the cylindrical portion 83A. The reduced diameter portion 81f is disposed in the reduced diameter portion 83f of the cylindrical portion 83A. The stepped portion 81g faces the stepped portion 83g of the cylindrical portion 83A. The plug 84A abuts against the enlarged diameter end of the first check valve 81A. Within the cylindrical portion 83A, the enlarged diameter end of the first check valve 81A is connected to the first flow path 71 via the branch flow path 71a. One end of spring portion 85A is supported by step 81g of first check valve 81A, and the other end is supported by step 83g of cylindrical portion 83A. Spring portion 85A applies elastic force in the direction in which step 81g and step 83g move apart.

[0045] 5, when the force generated by the pressure difference between the pressure in suction port P1 and the pressure in bearing chamber 64 is smaller than the elastic force of spring portion 85A, first check valve 81A is biased toward plug 84A by the elastic force of spring portion 85A. In this state, suction port P1 and bearing chamber 64 are connected via first flow path 71. Therefore, working fluid from suction port P1 is supplied to bearing chamber 64.

[0046] 5, when the force generated by the pressure difference between the pressure in suction port P1 and the pressure in bearing chamber 64 is greater than the elastic force of spring portion 85A, the end face of first check valve 81A on the side of enlarged diameter portion 81e is pushed toward reduced diameter portion 81f by the pressure of the working fluid in suction port P1, causing it to move and close first flow path 71. In this state, suction port P1 and bearing chamber 64 are not connected to each other.

[0047] Depending on the usage of the hydraulic pump 200, the working fluid may be drawn in through the discharge port P2 and discharged from the suction port P1. In this way, when the working fluid Q is caused to flow backward from the normal usage, the discharge port P2 becomes a low-pressure port and the suction port P1 becomes a high-pressure port.

[0048] Therefore, the hydraulic pump 200 can be designed to have small-diameter flow paths that reduce the pressure-receiving area in order to ensure sufficient durability when high pressure (discharge side) is reached for both the suction port P1 and the discharge port P2. In this case, the suction port P1 also has a small diameter, which increases suction resistance. Therefore, to compensate for the suction resistance, a boost pump 90, for example, can be installed in the flow path connected to the suction port P1.

[0049] In such a case, in the hydraulic pump 200 according to the second embodiment, for example, in normal use, that is, when the differential pressure obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the suction port P1 is equal to or less than a specified value and the differential pressure obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the discharge port P2 exceeds a specified value, the first check valve 81 is in an open state and the second check valve 82 is in a closed state. Therefore, the suction port P1, which is the low-pressure port, is connected to the bearing chamber 64.

[0050] Furthermore, in a mode of use that causes the working fluid Q to flow backward, that is, when the pressure difference obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the suction port P1 exceeds a specified value and the pressure difference obtained by subtracting the pressure in the bearing chamber 64 from the pressure in the discharge port P2 is equal to or less than a specified value, the first check valve 81 is closed and the second check valve 82 is open. Therefore, the discharge port P2, which is the low-pressure port, is connected to the bearing chamber 64.

[0051] Fig. 6 shows another example of the selection mechanism. In Fig. 6, the first check valve is used as an example for explanation, but the same explanation can be applied to the second check valve. As shown in Fig. 6, the selection mechanism 80B has a first check valve 81B, a cylindrical portion 93, a wall portion 94, and a spring portion 95.

[0052] The cylindrical portion 93 is disposed within the first flow path 71. The cylindrical portion 93 has an opening 93a that opens to the suction port P1 side. The wall portion 94 is disposed inside the cylindrical portion 93. The wall portion 94 is disposed, for example, at the end on the bearing chamber 64 side so as to close the interior of the cylindrical portion 93. The wall portion 94 has a through flow path 94a and a through hole 94b. The through flow path 94a provides communication between the interior of the cylindrical portion 93 and the bearing chamber 64. A columnar portion 81q of a first check valve 81B, which will be described later, is inserted through the through hole 94b. One end of the spring portion 95 is supported by the wall portion 94, and the other end is supported by a flange portion 81p, which will be described later, of the first check valve 81B.

[0053] The first check valve 81B has a flange portion 81p, a columnar portion 81q, and an expanded diameter portion 81r. The flange portion 81p is arranged to cover an opening 93a of the cylindrical portion 93. The flange portion 81p is biased in a direction away from the opening 93a toward the suction port P1 by the elastic force of a spring portion 95. The columnar portion 81q is arranged to penetrate a through-hole 94b in the cylindrical portion 93 and the wall portion 94. The columnar portion 81q is movable along the longitudinal direction of the cylindrical portion 93. The expanded diameter portion 81r is provided at the end of the columnar portion 81q opposite the flange portion 81p. The expanded diameter portion 81r has a larger diameter than the columnar portion 81q. The expanded diameter portion 81r abuts against the wall portion 94, thereby restricting movement of the first check valve 81B toward the suction port P1.

[0054] 6, when the force generated by the pressure difference between the pressure in the suction port P1 and the pressure in the bearing chamber 64 is smaller than the elastic force of the spring portion 95, the first check valve 81B is in a state in which the flange portion 81p is urged toward the suction port P1 by the elastic force of the spring portion 95. In this state, the opening 93a of the cylindrical portion 93 is opened. Therefore, the suction port P1 and the bearing chamber 64 are communicated via the opening 93a, the interior of the cylindrical portion 93, and the through-flow passage 94a. Therefore, the working fluid in the suction port P1 is supplied to the bearing chamber 64.

[0055] 6, when the force generated by the pressure difference between the pressure in suction port P1 and the pressure in bearing chamber 64 is greater than the elastic force of spring portion 95, first check valve 81B is pushed toward bearing chamber 64 by the pressure of the working fluid in suction port P1, and opening 93a of cylindrical portion 93 is blocked by flange portion 81p. In this state, suction port P1 and bearing chamber 64 are not connected to each other.

[0056] As described above, in the hydraulic pump 200 according to this embodiment, the flow mechanism 70 includes the first flow path 71, the second flow path 72 that connects the discharge port P2 and the bearing chamber 64, and the selection mechanism 80 that selects and connects the lower-pressure port of the suction port P1 or the discharge port P2 to the bearing chamber 64. Therefore, in addition to the normal usage in which the working fluid is drawn in through the suction port P1 and discharged from the discharge port P2, even in a usage in which the working fluid is drawn in through the discharge port P2 and discharged from the suction port P1, the working fluid Q flowing through the lower-pressure port of the suction port P1 or the discharge port P2 can be circulated to the bearing chamber 64.

[0057] [Third embodiment] Next, a hydraulic pump 300 according to a third embodiment will be described. Fig. 7 is a diagram showing an example of a hydraulic pump 300 according to the third embodiment. The hydraulic pump 300 according to the third embodiment has a different flow mechanism configuration from the hydraulic pumps according to the above embodiments. The following description will focus on the differences from the above embodiments.

[0058] In the hydraulic pump 300 according to this embodiment, the flow mechanism 270 has a third flow path 73, a fourth flow path 74, a fifth flow path 75, and a selection mechanism 280. The third flow path 73 is connected to the suction port P1. The fourth flow path 74 is connected to the discharge port P2. The fifth flow path 75 is connected to the bearing chamber 64. The third flow path 73, the fourth flow path 74, and the fifth flow path 75 are provided in the end plate 63.

[0059] 8 is a diagram schematically illustrating an example of the selection mechanism 280. As shown in FIG. 8, the selection mechanism 280 has a pressure chamber 86 and a spool member 87. The pressure chamber 86 is connected to the third flow path 73, the fourth flow path 74, and the fifth flow path 75. An end 86a of the pressure chamber 86 on the spool 87a side is connected to the branch flow path 76 from the third flow path 73. An end 86b of the pressure chamber 86 on the spool 87b side is connected to the branch flow path 77 from the fourth flow path 74. The pressure chamber 86 has steps 86c and 86d that restrict the movement of the spool member 87.

[0060] The spool 87a moves within the pressure chamber 86 so that the flow paths connected to the low-pressure ports of the third flow path 73 and the fourth flow path 74 are connected to the fifth flow path 75, and so that the flow paths connected to the high-pressure ports are not connected to the fifth flow path 75.

[0061] 8, when the pressure at the discharge port P2 is greater than the pressure at the suction port P1, the pressure at the discharge port P2 pushes the spool 87b from the end 86b of the pressure chamber 86 through the branch passage 77 from the fourth passage 74, and moves the spool member 87 to the stepped portion 86c. In this state, the third passage 73 and the fifth passage 75 are connected to each other, and the fourth passage 74 is blocked by the spool 87b. Therefore, the working fluid at the suction port P1 is supplied to the bearing chamber 64.

[0062] 8, when the pressure at the suction port P1 is greater than the pressure at the discharge port P2, the pressure at the suction port P1 pushes the spool 87a from the end 86a of the pressure chamber 86 through the branch passage 76 from the third passage 73, and moves the spool member 87 to the stepped portion 86d. In this state, the fourth passage 74 and the fifth passage 75 are connected to each other, and the third passage 73 is blocked by the spool 87a. Therefore, the working fluid at the suction port P1 is supplied to the bearing chamber 64.

[0063] Thus, in the hydraulic pump 300 according to the third embodiment, for example, during normal use, that is, when the pressure at the suction port P1 is lower than the pressure at the discharge port P2, the spool 87a moves within the pressure chamber 86, connecting the third flow path 73 to the fifth flow path 75 and disconnecting the fourth flow path 74 from the fifth flow path 75. Therefore, the suction port P1, which is the low-pressure port, is connected to the bearing chamber 64.

[0064] Furthermore, when the working fluid Q is allowed to flow backward, that is, when the pressure at the suction port P1 is higher than the pressure at the discharge port P2, the spool 87a moves within the pressure chamber 86, connecting the fourth flow path 74 to the fifth flow path 75 and disconnecting the third flow path 73 from the fifth flow path 75. Therefore, the discharge port P2, which is the low-pressure port, is connected to the bearing chamber 64.

[0065] As described above, in the hydraulic pump 300 according to this embodiment, the flow mechanism 270 includes the third flow path 73 connected to the suction port P1, the fourth flow path 74 connected to the discharge port P2, and the fifth flow path 75 connected to the bearing chamber 64. The selection mechanism 280 includes the pressure chamber 86 connected to each of the third flow path 73, the fourth flow path 74, and the fifth flow path 75, and the spool 87a that moves within the pressure chamber 86 so that the flow paths connected to the low-pressure ports of the third flow path 73 and the fourth flow path 74 are connected to the fifth flow path 75 and the flow paths connected to the high-pressure ports are not connected to the fifth flow path 75. Therefore, in addition to the normal usage in which the working fluid is sucked in through the suction port P1 and discharged through the discharge port P2, even in a usage in which the working fluid is sucked in through the discharge port P2 and discharged through the suction port P1, the working fluid Q flowing through the low-pressure port of the suction port P1 and the discharge port P2 can be circulated to the bearing chamber 64.

[0066] [Fourth embodiment] Next, a hydraulic pump 400 according to a fourth embodiment will be described. Fig. 9 is a diagram showing an example of the hydraulic pump 400 according to the fourth embodiment. The hydraulic pump 400 according to the fourth embodiment differs from the hydraulic pump 200 described in the second embodiment in the configuration of the end plates, but other configurations are similar to the hydraulic pump 200 described in the second embodiment. The following description will focus on the differences from the second embodiment.

[0067] In the hydraulic pump 400 according to this embodiment, the end plate 363 has an external communication passage 66 and an end cover (opening / closing portion) 67. The external communication passage 66 extends from the bearing chamber 64 to the rear end, and connects the bearing chamber 64 to the outside. The end cover 67 is detachably attached to the rear end of the end plate 363. The end cover 67 can switch between opening and closing the external communication passage 66. In other words, the end cover 67 closes the external communication passage 66 when attached to the end plate 363, and opens the external communication passage 66 when removed from the end plate 363.

[0068] In the hydraulic pump 400, the working fluid Q in the bearing chamber 64 can be discharged to the outside by removing the end cover 67. In this state, the lower-pressure port of the suction port P1 or the discharge port P2 may be overflowed by, for example, an external boost pump 90. This allows a larger amount of working fluid Q to flow from the first flow path 71 or the second flow path 72 to the bearing chamber 64 than in normal use, thereby preventing clogging of the first flow path 71 and the second flow path 72 and the first check valve 81 and the second check valve 82.

[0069] The technical scope of the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the present invention. For example, in the configuration of the fourth embodiment, a filter may be disposed in at least one of the first flow path 71 closer to the suction port P1 than the first check valve 81 and the second flow path 72 closer to the discharge port P2 than the second check valve 82. This can prevent clogging of the first check valve 81 and the second check valve 82. This filter can be removed and cleaned, for example, when the low-pressure port is overflowed.

[0070] Furthermore, in the above embodiment, an axial piston pump has been described as an example of a hydraulic pump, but the present invention is not limited to this. The above description can be applied to other types of hydraulic pumps as long as they have a shaft member that rotates around the central axis AX and a bearing that rotatably supports the shaft member. [Explanation of symbols]

[0071] Q Working fluid P1 Intake port P2 discharge port AX center axis 10 Shaft member 20 Bearings 21 Front bearing 22 Rear bearing 31 cylinders 32 Cylinder port, port 40 pistons 41 Head 50 Cam 51 Support surface 60 cabinets 61 Casing 61a Inside the casing 62 Front Plate 63,363 End Plate 64 Bearing chamber 65 Drain connection passage 66 External communication path 67 End cover 69 Drain discharge section 70,170,270 Distribution mechanism 71 First Channel 71a, 76, 77 Branch channel 72 Second Channel 73 Third Channel 74 4th Channel 75 5th Channel 80, 80A, 280 selection mechanism 81,81A First check valve 81a, 81p flange 81b,81q Columnar part 81c, 81d, 94a Through-flow passage 81e,83e,81r Expanded diameter part 81f,83f Reduced diameter part 81g,83g,86c,86d Stepped section 82 Second check valve 83 1st wall section 83A, 84b Cylindrical part 83a,93a opening 84 2nd wall section 84A plug 84a Flat plate part 85,85A spring part 86 Pressure Chamber 86a,86b end 87 Spool member 87a, 87b spool 90 Boost Pump 93 Cylindrical part 94 Wall 94b through hole 100,200,300,400 Hydraulic Pump

Claims

1. a shaft member that rotates in a direction around a central axis; a bearing that rotatably supports the shaft member; a plate having a bearing chamber for holding the bearing, and an intake port and an exhaust port through which the working fluid is drawn in and exhausted as the shaft member rotates; a circulation mechanism that circulates the working fluid flowing through the low-pressure port of the suction port and the discharge port to the bearing chamber; Equipped with The distribution mechanism is a first flow passage communicating the suction port and the bearing chamber; a second flow path that communicates the discharge port and the bearing chamber; a selection mechanism that selects and connects the low-pressure port of the suction port and the discharge port to the bearing chamber; have Hydraulic pump.

2. The first flow path and the second flow path are provided in the plate.

2. The hydraulic pump of claim 1.

3. The selection mechanism includes: a first check valve that is provided in the first flow path and that opens when a pressure difference, obtained by subtracting the pressure in the bearing chamber from the pressure in the suction port, is equal to or less than a specified value, and that closes when the pressure difference exceeds the specified value; a second check valve that is provided in the second flow path and that opens when a differential pressure obtained by subtracting the pressure in the bearing chamber from the pressure in the discharge port is equal to or less than a specified value, and that closes when the differential pressure exceeds the specified value; have The hydraulic pump according to claim 1 or 2.

4. The distribution mechanism is a third flow path connected to the suction port; a fourth flow path connected to the discharge port; a fifth flow path connected to the bearing chamber, The selection mechanism includes: pressure chambers connected to the third flow path, the fourth flow path, and the fifth flow path, respectively; a spool that moves within the pressure chamber so that one of the third flow path and the fourth flow path connected to the port on the low pressure side is connected to the fifth flow path, and so that the flow path connected to the port on the high pressure side is not connected to the fifth flow path; have The hydraulic pump according to claim 1 or 2.

5. The plate has an external communication passage that communicates the bearing chamber with the outside, an opening / closing unit that can switch between opening and closing the external communication passage; have The hydraulic pump according to any one of claims 1 to 4.

6. The bearing is a sliding bearing The hydraulic pump according to any one of claims 1 to 5.

7. a plurality of cylinders arranged in a rotational direction of the central axis, each having an opening through which a working fluid is drawn and discharged, and each moving in the rotational direction as the shaft member rotates; a piston provided in each of the cylinders, the piston reciprocating in response to the movement of the cylinder in the direction around the axis; The hydraulic pump according to any one of claims 1 to 6, further comprising:

8. a shaft member that rotates in a direction around a central axis; a bearing that rotatably supports the shaft member; a plate having a bearing chamber for holding the bearing, and an intake port and an exhaust port through which the working fluid is drawn in and exhausted as the shaft member rotates; Equipped with the suction port and the bearing chamber are connected by a first flow path; A cooling method for a hydraulic pump in which the discharge port and the bearing chamber are connected by a second flow path, By selectively connecting the low-pressure port of the suction port and the discharge port to the bearing chamber, the working fluid flowing through the low-pressure port of the suction port and the discharge port is circulated to the bearing chamber, The working fluid that has been circulated in the bearing chamber is discharged to the outside as a drain. Cooling method for hydraulic pumps.

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