JP2005146861A - Hydraulic pump - Google Patents

Abstract

To provide a hydraulic pump capable of reducing the load as necessary to suppress the heat generation of a drive source and to reduce the size and weight of a unit including the drive source.
A housing, an input shaft 2 rotatably supported in the housing 1, a cylinder block 7 that rotates integrally with the input shaft 2, and a plurality of pistons formed in the cylinder block 7. In a hydraulic pump (hydraulic pump) P comprising a plurality of pistons slidably housed in each of the housing holes, and a suction port and a discharge port selectively communicating with the piston housing holes, the plurality of pistons The housing holes 9 and 10 and the plurality of pistons 11 and 12 are arranged in two rows on the inner and outer circumferences of the cylinder block 7 to constitute the first pump and the second pump, and the plurality of pistons of the first pump A switching valve 32 is provided between the housing hole 9 and the plurality of piston housing holes 10 of the second pump for communicating or blocking the piston housing holes 9 and 10.
[Selection] Figure 2

Description

  The present invention relates to a piston pump type hydraulic pump that compresses and discharges liquid by reciprocating movement of a plurality of pistons in a cylinder block.

  This type of hydraulic pump is used, for example, as a driving source for a hydraulic actuator for an aircraft, and its basic configuration will be described with reference to FIG. 14 (see, for example, Patent Document 1).

  14 is a cross-sectional view of a conventional hydraulic pump P. The illustrated hydraulic pump P includes a housing 101, an input shaft 102 rotatably supported in the housing 101, and the input shaft 102. A cylinder block 107 that rotates integrally, a plurality of pistons 111 slidably accommodated in each of a plurality of piston accommodation holes 109 formed in the cylinder block 107, and the piston accommodation holes 109 are selectively communicated with each other. Pressure port sucked from the suction port 122 by reciprocating the piston 111 along the swash plate 113 in the piston housing hole 109 by the rotation of the input shaft 102. The pressure is increased and discharged to the discharge port 123.

Japanese Patent Laid-Open No. 2003-139045

  By the way, when the hydraulic pump is operated for a long time in a low rotation high torque state, there is a problem that the electric motor that drives the hydraulic pump generates heat. In order to avoid this problem, it is necessary to increase the size of the electric motor. However, the increase in the size of the electric motor restricts the application target of the hydraulic pump, and particularly aircraft that are required to be small and light. Not suitable for use.

  The present invention has been made in view of the above problems, and the object of the present invention is to reduce the load as necessary to suppress the heat generation of the drive source and to reduce the size and weight of the unit including the drive source. It is to provide a hydraulic pump that can be used.

  In order to achieve the above object, an invention according to claim 1 is formed in a housing, an input shaft rotatably supported in the housing, a cylinder block rotating integrally with the input shaft, and the cylinder block. A plurality of pistons slidably housed in each of the plurality of piston housing holes, a suction port and a discharge port selectively communicating with the piston housing hole, and the piston is moved by rotation of the input shaft. In the hydraulic pump that boosts the pressure liquid sucked from the suction port and discharges it to the discharge port by reciprocating in the piston storage hole, the plurality of piston storage holes and the plurality of pistons are connected to the cylinder block. The first pump and the second pump are arranged in two rows on the inner and outer circumferences, and the plurality of piston housing holes and the second pump of the first pump Between the plurality of the piston housing hole of, characterized in that both the piston housing hole provided switching valve for communicating or blocking.

  According to a second aspect of the present invention, in the first aspect of the present invention, a first port communicating with the plurality of piston housing holes of the first pump and a second port communicating with the plurality of piston housing holes of the second pump. The switching valve is provided in a port plate formed by forming the first port and the second port by the switching valve, and the first port and the second port are communicated or blocked.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the suction port and the discharge port are respectively connected to the suction port and the discharge port of the hydraulic cylinder, and the pressure liquid from the suction port and the discharge port is alternately switched. The hydraulic cylinder is reciprocally driven by switching to and sucking and discharging into the hydraulic cylinder.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the temperature detecting means for detecting the temperature of the driving source for rotationally driving the input shaft, and the temperature detected by the temperature detecting means. Is provided with control means for driving the switching valve to shut off the plurality of piston housing holes of the first pump and the plurality of piston housing holes of the second pump when the pressure exceeds a set value.

  According to the first or second aspect of the present invention, since the two-stage switching pump is constituted by the first and second pumps, the load can be reduced by half as necessary, and the heat generation of the drive source can be suppressed. And a unit including a hydraulic pump can be reduced in size and weight.

  According to the third aspect of the present invention, for example, by rotating the drive source forward and backward, the pressure liquid from the suction port and the discharge port is alternately switched and sucked into and discharged from the hydraulic cylinder, whereby the hydraulic cylinder Can be driven reciprocally.

  According to the fourth aspect of the present invention, when the temperature detected by the temperature detecting means exceeds the set value, the switching valve is driven to drive the plurality of piston housing holes of the first pump and the plurality of piston housing holes of the second pump. Therefore, the load of the drive source is halved, the temperature of the drive source is suppressed to a set value or less, and the unit including the drive source and the hydraulic pump can be reduced in size and weight.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
1 is a perspective view in which a part of a hydraulic pump according to the present invention is broken, FIG. 2 is a sectional view of the hydraulic pump, FIG. 3 is a sectional view of a switching valve portion of the hydraulic pump, and FIG. FIG. 5 is a sectional view taken along line BB in FIG. 4, FIG. 6 is a side view of the cylinder block, FIG. 7 is a view in the direction C of FIG. FIG. 9 is a front view of the valve plate, and FIGS. 10 and 11 are hydraulic circuit diagrams of the hydraulic pump.

  The hydraulic pump P according to the present embodiment is a swash plate type hydraulic pump, and an input shaft 2 is rotatably supported in a two-part housing 1. A port plate 4 is attached with a disc-shaped valve plate 3 interposed therebetween.

  As shown in FIGS. 2 and 4, both ends of the input shaft 2 are rotatably supported by a ball bearing 5 provided in the housing 1 and a needle bearing 6 provided in the port plate 4. The cylinder block 7 is spline-fitted to a part thereof. Accordingly, the cylinder block 7 rotates integrally with the input shaft 2 while being in sliding contact with the valve plate 3 in the housing 1. As shown in FIGS. 10 and 11, an electric motor (M) 8 as a drive source is connected to an end portion of the input shaft 2 that extends outward from the housing 1.

  By the way, as shown in FIGS. 2 and 8, the cylinder block 7 has seven piston housing holes 9 and 10 formed in two rows on the inner and outer circumferences. Pistons 11 and 12 are slidably accommodated in the holes 9 and 10, respectively. And the piston accommodation hole 9 arrange | positioned inside and the piston 11 accommodated in this comprise the 1st pump P1 (refer FIG.10 and FIG.11), and are accommodated in the piston accommodation hole 10 arrange | positioned outside and this. The piston 12 constitutes a second pump P2 (see FIGS. 10 and 11).

  As shown in FIGS. 2 and 4, a shoe plate 13 as a swash plate is rotatably supported in the housing 1 by a ball bearing 14 and accommodated in the housing 1. The inclined surface 13 a is inclined with respect to a surface orthogonal to the axis of the input shaft 2. The inclined surfaces 13a of the shoe plate 13 are in contact with the end portions of the pistons 11 and 12, respectively.

  That is, the end portion of each piston 11, 12 extending outward from the cylinder block 7 is engaged with a disc-like retainer plate 15, and the inner peripheral portion of the retainer plate 15 is connected to the pressing member 16. It is tiltably held by spherical contact. The pressing member 16 is fitted and held on the outer periphery of the input shaft 2 so as to be slidable in the axial direction, and is urged in the direction of the shoe plate 13 by a spring 17 which is compressed between the pressing member 16 and the input shaft 2. Has been.

  Therefore, the retainer plate 15 fitted and held by the pressing member 16 is also urged in the direction of the shoe plate 13, and the pistons 11 and 12 engaged therewith are also urged in the same direction. The plate 13 is always brought into contact with the inclined surface 13a. Note that the tilt angle of the inclined surface 13a of the shoe plate 13 can be adjusted by rotating the shoe plate 13 by a mechanism (not shown).

  By the way, as shown in FIGS. 7 and 8, the cylinder block 7 has seven oil holes 18 and 19 each having an elongated shape communicating with the piston housing holes 9 and 10, respectively, on the inner and outer circumferences. Are formed in two rows.

  On the other hand, as shown in FIG. 9, on the inner and outer circumferences corresponding to the positions where the oil holes 18 and 19 of the valve plate 3 are formed, two arc-shaped oil holes 20 and 21 are respectively provided. When the cylinder block 7 rotates together with the input shaft 2 as will be described later, the oil holes 18 and 19 formed in the cylinder block 7 communicate with the oil holes 20 and 21, respectively.

  Further, the port plate 4 is formed with a first port 22 and a second port 23 respectively communicating with the oil holes 20 and 21 formed in the valve plate 3, and the first port 22 communicating with the first pump P1 is formed. As shown in FIG. 5, ports 24 formed in a right angle direction communicate with the ports 22, respectively. These ports 24 are connected to a hydraulic cylinder 25 as an actuator shown in FIGS. 10 and 11. .

  Here, the oil holes 18 and 20, the first port 22 and the port 24 communicating with the piston housing hole 9 of the first pump P1 form oil passages a and b in the hydraulic circuit shown in FIGS. Yes. Further, the oil holes 19 and 21 and the second port 23 communicating with the piston housing hole 10 of the second pump P2 form oil passages c and d in the hydraulic circuit shown in FIGS.

  As shown in FIGS. 10 and 11, the hydraulic cylinder 25 is configured such that a piston 27 is slidably fitted into the cylinder 26, and rods 28 and 29 are integrally formed from both sides of the piston 27. It is extended. In the cylinder 26, oil chambers S1 and S2 defined by a piston 27 are formed. The oil passage b is connected to one oil chamber S1 through an oil hole 26a, and the other oil chamber S2 is formed. Is connected to the oil passage a through an oil hole 26b.

  10 and 11, the oil passage a and the oil passage b are connected by an oil passage e, and an oil passage f connected to the oil tank 30 is connected in the middle of the oil passage e. On both sides of the oil passage e across the oil passage f, check valves 31 that allow the oil to flow in the direction of the hydraulic cylinder 25 are provided.

  2 and 3, the port plate 4 includes an oil passage a on the first pump P1 side, an oil passage c on the second pump P2 side, an oil passage b on the first pump P side, and a second passage. An electromagnetic solenoid type switching valve 32 is provided for communicating and blocking the oil passage d on the pump P2 side. The switching valve 32 includes a rod-shaped spool 34 slidably fitted in a circular hole 33 formed in the port plate 4, and the spool 34 is moved in one direction (an oil passage a, an oil passage c, and an oil passage b). And a spring 35 for energizing the oil passage d) and an electromagnetic coil 36 excited by energization.

  Here, oil grooves g, h, i, j are respectively formed in the spool 34 of the switching valve 32, and the oil groove g and the oil groove j are communicated with each other by an oil passage 37.

  10 and 11, a control means 38 such as a microcomputer is electrically connected to the electromagnetic coil 36 of the switching valve 32, and the temperature of the electric motor 8 is controlled in the control means 38. A temperature sensor 39 for detection is electrically connected.

  Next, the operation of the hydraulic pump P having the above configuration will be described based on FIG. 2, FIG. 3, FIG. 10, and FIG.

  When the input shaft 2 is rotationally driven by the electric motor 8, the cylinder block 7 rotates together with the input shaft 2 while being in sliding contact with the valve plate 3 in the housing 1. Then, a plurality of pistons 11 constituting the first pump P1 housed in the piston housing hole 9 of the cylinder block 7 and a plurality of second pumps P2 housed in the piston housing hole 10 arranged on the outside thereof. The piston 12 reciprocates in the piston housing holes 9 and 10 along the inclined surface 13a of the shoe plate 13 to perform a pumping action.

  On the other hand, the temperature of the electric motor 8 as a drive source is detected by the temperature sensor 39, and the signal is transmitted to the control means 38. The control means 38 detects that the detected temperature of the electric motor 8 is below a set value. In some cases, the electromagnetic coil 36 of the switching valve 32 is energized. Then, the spool 34 is slid against the urging force of the spring 35 by the electromagnetic force generated in the electromagnetic coil 36, and the first pump P1 side is caused by the oil groove h of the spool 34 as shown in FIGS. The oil passage a and the oil passage c on the second pump P2 side are communicated with each other, and the oil passage b on the first pump P1 side and the oil passage d on the second pump P2 side are communicated by the oil groove j of the spool 34. The hydraulic cylinder 25 is driven by oil discharged from the first and second pumps P1 and P2, respectively.

  That is, as described above, when the piston 11 of the first pump P1 and the piston 12 of the second pump P2 reciprocate in the cylinder block 7, the oil in the oil chamber S1 of the hydraulic cylinder 25 is changed to the first and second pumps P1, 1. The pistons 11 and 12 in the suction stroke of P2 are sucked into the piston housing holes 9 and 10 of the first and second pumps P1 and P2 through the oil passages b and d by the suction action.

  The oil sucked into the piston housing holes 9 and 10 is compressed and pressurized as the pistons 11 and 12 move to the discharge stroke, and the oil discharged from the second pump P2 passes through the oil passage c. The oil that has been discharged from the first pump P <b> 1 to the oil passage a is joined, and the joined oil is supplied to the oil chamber S <b> 2 of the hydraulic cylinder 25. Accordingly, in the hydraulic cylinder 25, the piston 27 and the rods 28 and 29 are moved in the direction of the arrow x in FIG. 10 to operate a mechanism (not shown). At this time, if the amount of oil supplied to the oil chamber S2 of the hydraulic cylinder 25 is insufficient, the oil in the oil tank 30 is supplied from the oil passage f to the oil chamber S2 via the check valve 21 and the oil passage a. Is done.

  Next, when the electric motor 8 is reversed and the input shaft 2 and the cylinder block 7 are also reversed, the suction and the discharge are reversed, and the piston 27 and the rods 28 and 29 of the hydraulic cylinder 25 are driven in the opposite directions.

  That is, when the pistons 11 and 12 of the first and second pumps P1 and P2 reciprocate in the cylinder block 7, the oil in the oil chamber S2 of the hydraulic cylinder 25 is sucked by the first and second pumps P1 and P2. The pistons 11 and 12 are sucked into the piston housing holes 9 of the first pump P1 through the oil passage a by the suction action of the pistons 11 and 12 and sucked into the piston housing holes 10 of the second pump P2 through the oil passage c. .

  The oil sucked into the piston housing holes 9 and 10 is compressed and pressurized as the pistons 11 and 12 move to the discharge stroke, and the oil discharged from the second pump P2 passes through the oil passage d. The oil that has been discharged from the first pump P <b> 1 to the oil passage b joins, and the joined oil is supplied to the oil chamber S <b> 1 of the hydraulic cylinder 25. Accordingly, in the hydraulic cylinder 25, the piston 27 and the rods 28 and 29 are moved in the direction of the arrow y in FIG. 10 to operate a mechanism (not shown). In this embodiment, the electric motor 8 is reversely rotated to change the oil discharge direction of the pumps P1 and P2. However, the shoe plate 13 is rotated by a mechanism (not shown) and the inclination direction is shown in FIG. The oil discharge direction of each pump P1, P2 can also be changed by reversing the direction shown.

  By the way, in the high load state where the first and second pumps P1 and P2 are simultaneously operated as described above, the electric motor 8 is operated in a low rotation high torque state. However, in this high load state, the electric motor 8 is operated for a long time. As a result, there arises a problem that the electric motor 8 generates heat.

  Therefore, in the present embodiment, when the temperature of the electric motor 8 detected by the temperature sensor 39 exceeds the set value, the control means 38 cuts off the energization to the electromagnetic coil 36 of the switching valve 32 and turns the switching valve 32 on. As shown in FIGS. 2 and 11, the oil path a on the first pump P1 side and the oil path c on the second pump P2 side are shut off, and the oil path b on the first pump P1 side and the second pump P2 are switched. The oil path d on the side is shut off, and the hydraulic cylinder 25 is driven only by the oil discharged from the first pump P1.

  That is, when the energization of the switching valve 32 to the electromagnetic coil 36 is interrupted, the spool 34 of the switching valve 32 is moved as shown in FIGS. 2 and 11 by the urging force of the spring 35, and the oil on the first pump P1 side is moved. The path a and the oil path c on the second pump P2 side are blocked, and the oil path b on the first pump P1 side and the oil path d on the second pump P2 side are blocked. Further, the oil passages c and d of the second pump P2 are communicated with each other by an oil passage 37.

  Therefore, in this state, in the second pump, the oil only circulates through the oil passages c and d, and the second pump P2 is not involved in driving the hydraulic cylinder 25. On the other hand, in the first pump P1, the oil in the oil chamber S1 of the hydraulic cylinder 25 is sucked into the piston housing holes 9 of the cylinder block 7 through the oil passage b by the suction action of the piston 11 in the suction stroke. .

  The oil sucked into each piston housing hole 9 is compressed and pressurized when the piston 11 moves to the discharge stroke, and the oil discharged from the first pump P1 passes through the oil passage a to the oil in the hydraulic cylinder 25. Supplyed to chamber S2. Accordingly, in the hydraulic cylinder 25, the piston 27 and the rods 28 and 29 are moved in the direction of the arrow x in FIG. 11 to operate a mechanism (not shown).

  Next, when the electric motor 8 is reversed and the input shaft 2 and the cylinder block 7 are also reversed, the suction and the discharge are reversed, and the piston 27 and the rods 28 and 29 of the hydraulic cylinder 25 are driven in the opposite directions.

  That is, when the piston 11 of the first pump P1 reciprocates in the cylinder block 7, the oil in the oil chamber S2 of the hydraulic cylinder 25 passes through the oil passage a by the suction action of the piston 11 in the suction stroke of the first pump P1. It is sucked into each piston housing hole 9 of the first pump P1.

  The oil sucked into each piston housing hole 9 is compressed and pressurized when the piston 11 moves to the discharge stroke, and is supplied to the oil chamber S1 of the hydraulic cylinder 25 through the oil passage b. Accordingly, in the hydraulic cylinder 25, the piston 27 and the rods 28 and 29 are moved in the direction of the arrow y in FIG. 11 to operate a mechanism (not shown). Even in this case, in the second pump P2, the oil only circulates through the oil passages c and d, and the second pump P2 is not involved in driving the hydraulic cylinder 25.

  As described above, in the present embodiment, when the temperature of the electric motor 8 detected by the temperature sensor 39 exceeds the set value, the hydraulic cylinder 25 is driven only by the oil discharged from the first pump P1. Therefore, the load of the electric motor 8 is halved, the electric motor 8 rotates at a high speed and its heat generation is suppressed, and the unit including the electric motor 8 and the hydraulic pump P can be reduced in size and weight. The unit can also be used for aircraft.

<Embodiment 2>
Next, a second embodiment of the present invention will be described with reference to FIGS.

  12 and 13 are hydraulic circuit diagrams of the hydraulic pump according to the present embodiment. In these drawings, the same elements as those shown in FIGS. 10 and 11 are denoted by the same reference numerals, and The description about them is omitted.

  In the present embodiment, a case where the hydraulic pump P is used as a one-way pump and the hydraulic motor 40 is driven to rotate in one direction by the hydraulic pump P will be described.

  When the first and second pumps P1, P2 are driven by the electric motor 8, the temperature of the electric motor 8 is detected by the temperature sensor 39, and the signal is transmitted to the control means 38. The control means 38 When the temperature of the electric motor 8 is not more than the set value, the electromagnetic coil 36 of the switching valve 32 is energized to switch the switching valve 32 to the position shown in FIG. Then, the oil path a on the first pump P1 side and the oil path c on the second pump P2 side are communicated with each other, and the oil path b on the first pump P1 side and the oil path d on the second pump P2 side are communicated with each other. The oil in the oil tank 41 is sucked into the first pump P1 through the oil passage b, and sucked into the second pump P2 through the oil passage d to be pressurized. Then, the oil discharged from the second pump P2 to the oil passage c merges with the oil discharged from the first pump P1 to the oil passage a and is supplied to the hydraulic motor 40 to drive the hydraulic motor 40. After being provided, the oil tank 41 is discharged. Thereafter, the same operation is repeated, and the hydraulic motor 40 is continuously rotated in one direction.

  By the way, in the high load state where the first and second pumps P1 and P2 are simultaneously operated as described above, the electric motor 8 is operated in a low rotation high torque state. However, in this high load state, the electric motor 8 is operated for a long time. As a result, there arises a problem that the electric motor 8 generates heat.

  Therefore, also in the present embodiment, when the temperature of the electric motor 8 detected by the temperature sensor 39 exceeds the set value, the control means 38 cuts off the energization to the electromagnetic coil 36 of the switching valve 32 and switches the switching valve 32. As shown in FIG. 13, the oil passage a on the first pump P1 side and the oil passage c on the second pump P2 side are shut off, and the oil passage b on the first pump P1 side and the second pump P2 side The oil passage d is shut off, and the hydraulic motor 40 is driven only by the oil discharged from the first pump P1. In this case, in the second pump P2, the oil only circulates through the oil passages c and d, and the second pump P2 is not involved in driving the hydraulic motor 40.

  As described above, also in the present embodiment, when the temperature of the electric motor 8 detected by the temperature sensor 39 exceeds the set value, the hydraulic motor 8 is driven only by the oil discharged from the first pump P1. Therefore, the load of the electric motor 8 is halved, the electric motor 8 rotates at a high speed and the heat generation thereof is suppressed, and the unit including the electric motor 8 and the hydraulic pump P can be reduced in size and weight. Can also be used for aircraft.

  In the above embodiment, the hydraulic pump that uses oil as the working fluid has been described. However, the present invention can be similarly applied to a hydraulic pump that uses any other liquid.

  The present invention is not limited to the swash plate type, but can be applied to other piston pump type hydraulic pumps such as a swash shaft type or a rotary swash plate type. It is possible to obtain an effect of suppressing heat generation and reducing the size and weight of the unit including the drive source.

It is the perspective view which fractured | ruptured a part of hydraulic pump which concerns on Embodiment 1 of this invention. It is sectional drawing of the hydraulic pump which concerns on Embodiment 1 of this invention. It is sectional drawing of the switching valve part of the hydraulic pump which concerns on Embodiment 1 of this invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. It is a side view of the cylinder block of the hydraulic pump which concerns on Embodiment 1 of this invention. It is a figure of the arrow C direction of FIG. It is a figure of the arrow D direction of FIG. It is a front view of the valve plate of the hydraulic pump which concerns on Embodiment 1 of this invention. 1 is a hydraulic circuit diagram of a hydraulic pump according to Embodiment 1 of the present invention. 1 is a hydraulic circuit diagram of a hydraulic pump according to Embodiment 1 of the present invention. It is a hydraulic circuit diagram of the hydraulic pump which concerns on Embodiment 2 of this invention. It is a hydraulic circuit diagram of the hydraulic pump which concerns on Embodiment 2 of this invention. It is sectional drawing of the conventional hydraulic pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Input shaft 3 Valve plate 4 Port plate 7 Cylinder block 8 Electric motor (drive source)
9,10 Piston storage hole 11,12 Piston 13 Shoe plate (swash plate)
18-21 Oil hole 22 1st port 23 2nd port 24 Port 25 Hydraulic cylinder (hydraulic pressure cylinder)
26a, 26b Oil hole (suction port, discharge port)
DESCRIPTION OF SYMBOLS 30 Oil tank 31 Check valve 32 Switching valve 34 Spool 35 Spring 36 Electromagnetic coil 37 Oil path 38 Control means 39 Temperature sensor (temperature detection means)
40 Hydraulic motor 41 Oil tank P Hydraulic pump (hydraulic pump)
P1 1st pump P2 2nd pump S1, S2 Oil chamber af Oil path gj Oil groove

Claims (4)

A housing, an input shaft rotatably supported in the housing, a cylinder block that rotates integrally with the input shaft, and a plurality of piston housing holes formed in the cylinder block are slidably housed. A plurality of the pistons, a suction port and a discharge port that selectively communicate with the piston housing hole, and by reciprocating the piston in the piston housing hole by rotation of the input shaft, In the hydraulic pump that raises the pressure of the sucked pressure liquid and discharges it to the discharge port,
The plurality of piston housing holes and the plurality of pistons are arranged in two rows on the inner and outer circumferences of the cylinder block to form a first pump and a second pump, and a plurality of piston housing holes of the first pump; A hydraulic pump characterized in that a switching valve for communicating or blocking both piston housing holes is provided between the plurality of piston housing holes of the second pump.   The switching valve is provided on a port plate formed with a first port communicating with the plurality of piston housing holes of the first pump and a second port communicating with the plurality of piston housing holes of the second pump, The hydraulic pump according to claim 1, wherein the first port and the second port are communicated or blocked by a valve.   By connecting the suction port and the discharge port to the suction port and the discharge port of the hydraulic cylinder, respectively, and switching the pressure liquid from the suction port and the discharge port alternately to suck and discharge into the hydraulic cylinder, the hydraulic cylinder The hydraulic pump according to claim 1, wherein the hydraulic pump is reciprocally driven.   Temperature detecting means for detecting the temperature of a driving source for rotationally driving the input shaft; and when the temperature detected by the temperature detecting means exceeds a set value, the switching valve is driven to accommodate a plurality of pistons of the first pump. The hydraulic pump according to any one of claims 1 to 3, further comprising a control unit configured to block the hole and the plurality of piston housing holes of the second pump.

Images