Variable volume control piston pump

Abstract

A stopper 23 is disposed at the rear of a direction of oscillation of a swash plate 7 caused by a spring 21. The maximum inclination angle of the swash plate 7 can be regulated by the stopper 23. The stopper 23 of a piston pump 1 is accommodated in a cylinder portion 29 formed in a housing 3. A hydraulic circuit 27 is connected to the cylinder portion 29 and a constant hydraulic pressure is applied to the cylinder portion 29. The stopper 23 receives a force in a direction in which the stopper 23 is pushed out from the cylinder portion 29 by the hydraulic pressure. Consequently, the stopper 23 is always maintained pressed against and in contact with the swash plate 7 with a constant pressing force.

Description

Technical Field

[0001] The present invention relates to a constant horsepower control-type variable volume control piston pump.Background Art

[0002] For example, constant horsepower control-type variable volume control piston pumps are widely used to effectively utilize engine output in hydraulic pumps such as for construction equipment. A variable volume piston pump performs constant horsepower control by balancing the moment due to spring load with the moment due to discharge pressure, so that when the discharge pressure increases, the swash plate inclines, and the discharge flow rate decreases.

[0003] As such a variable volume-type piston pump, for example, a constant horsepower control piston pump is proposed in which the oscillation center of a swash plate and the central axis of oscillation thereof are disposed separated from the central axis of the resultant force that presses the swash plate in the axial direction during the operation of a piston (Patent Literature 1). In Patent Literature 1, when one end of the swash plate pushes a spring to reduce the inclination angle of the swash plate, the length of a resultant force lever arm from the piston relative to the oscillation center is reduced. Thus, more ideal constant horsepower control properties can be obtained.

[0004] Patent Document 2 discloses a pump capacity control device causing no state of separating the tip of a control cylinder from a swash plate, and reducing noise even when rear end pressure of the control cylinder of a load sensitive control device 20 is 0 in the pump capacity control device having a constant torque control device 10 and the load sensitive control device 20, and taking preference of constant torque control. The control cylinder 31 has a small hollow piston 33 for pushing the swash plate in the direction for pushing a spring 11 of a constant torque control mechanism 10 by abutting to the swash plate 1, a hollow piston 34 fitting to the outer periphery of the small hollow piston 33 by mutually adjusting an opening part, and the hollow control cylinder 31 fitting to the outer periphery of the hollow piston 34, and having an oil passage 32 for introducing differential pressure of a throttle valve 49 to a bottom part of the hollow piston 31. A small spring 35 is arranged between the small hollow piston 33 and the hollow piston 34, and a drain oil passage 36 for always communicating with a pump drain is arranged in a bottom part of the small hollow piston 32 for abutting to the swash plate 1.

[0005] Patent Document 3 discloses a variable displacement swash plate type piston pump includes first and second housing members fastened to each other by fastening members, a rotary shaft, a swash plate. A section of the inner circumferential surface of the first housing member has a recess. A bulging portion is arranged in a section of the outer circumferential wall of the first housing member. A section of the outer circumferential wall of the second housing member has a closing portion that closes the opening of the recess. The fastening members include first and second fastening members arranged at positions that are on the opposite sides of the recess, inside the width of the swash plate in a direction along the inclination axis of the swash plate, and closer to the rotary shaft than the distal ends of the bulging portion and the closing portion in the bulging direction.

[0006] Patent document 4 discloses another known variable displacement swash plate type piston pump.Citation List Patent Literature

[0007] Patent Document 1: Japanese Unexamined Utility Model Application Publication No. H4-6775 Patent Document 2: JP 3 816786 B2 Patent Document 3: US 2019 / 353150 A1 Patent Document 4: JP H07 158558 A Summary of Invention Technical Problem

[0008] FIGS. 5 and 6 illustrate a conventional piston pump 100, where FIG. 5 shows a swash plate 107 at its maximum angle in a state of maximum discharge volume, and FIG. 6 shows an inclination angle of the swash plate 107 reduced due to oscillation of the swash plate 107.

[0009] A shaft 105 and a cylinder barrel 109 are rotatable about the shaft 105 as their axis. A plurality of cylinders 111 are disposed in the cylinder barrel 109, with each cylinder 111 being provided with a piston 113. An end portion of each piston 113 abuts the swash plate 107 via a shoe 117. The shoe 117 is slidable along the surface of the swash plate 107.

[0010] The swash plate 107 is capable of oscillating about an oscillation center 119 with a direction perpendicular to an axial direction of the shaft 105 (direction perpendicular to the paper surface) as the axis of rotation. That is, the angle of the swash plate 107 is variable relative to the shaft 105. A tip end of a spring holder 122 fitted to a spring 121 is in contact with one end portion of the swash plate 107, and the swash plate 107 is pressed by the spring 121. That is, a moment Ms due to a pressing force from the spring 121 is applied to the swash plate 107.

[0011] Rotation of the shaft 105 causes the cylinder barrel 109 to rotate, so that the piston 113 moves along the swash plate 107. Since the swash plate 107 is inclined when this happens, the pistons 113 reciprocate relative to the cylinders 111 according to the distance between the swash plate 107 and the cylinder barrel 109. This causes the suction and discharge of oil in conjunction with the reciprocating motion of the pistons 113.

[0012] Here, the swash plate 107 receives a resultant force from all the pistons 113. A moment Mp due to a pressing force from all the pistons 113 is thus applied to the swash plate 107. That is, the swash plate 107 is held at an angle where the moment Ms due to the spring 121 mentioned above and the moment Mp due to the pistons 113 are balanced.

[0013] FIG. 7A is an enlarged view of the vicinity of a stopper 123 in FIG. 5. As described above, in the state where Ms>Mp, the swash plate 107 oscillates in an anticlockwise direction in FIGS. 5 and 6 due to the pressing force of the spring 121 and is maintained in contact with the stopper 123. That is, the stopper 123 is fixed to a housing and regulates the maximum inclination angle of the swash plate 107. When Mp gradually increases from this state and surpasses Ms, the swash plate 107 starts to oscillate. FIG. 7B illustrates a state immediately after the swash plate 107 has started to oscillate and is separated from the stopper 123.

[0014] Here, the inner pressure of the plurality of cylinders 111 repeats being a suction pressure and a discharge pressure during a single rotation of the shaft 105, so that the piston resultant force that acts on the swash plate 107 varies and vibrations that cause the swash plate 107 to oscillate are generated. These vibrations can generate so-called knocking sounds caused by the contact and separation between the stopper 123 and the swash plate 107 in the vicinity of a cut point where the swash plate starts to oscillate from its maximum inclination angle. That is, when the difference between Mp and Ms is small, a slight gap may be formed between the swash plate 107 and the stopper 123 (portion X in the figure), so that the states illustrated in FIGS. 7A and 7B are repeated due to the pulsations, thereby generating the so-called knocking sounds.

[0015] The present invention has been made in view of such problem, and aims to provide a variable volume control piston pump with low noise.Solution to Problem

[0016] To achieve the aim above, the present invention provides a variable volume control piston pump as defined by claim 1.

[0017] It is desired that the pressing means is a hydraulic piston, and the hydraulic piston is pressed against the swash plate with a constant force.

[0018] A spring may be disposed at a back portion of the hydraulic piston, and the spring may press the hydraulic piston in a pressing direction of the hydraulic piston.

[0019] The stopper may be disposed in a position facing the spring across the swash plate.

[0020] The stopper may be disposed on a side opposite the spring across the support portion.

[0021] According to a first invention, the pressing means capable of pressing the stopper against the swash plate is disposed behind the stopper, and when the angle of the swash plate changes, the stopper follows the swash plate and is maintained pressed against the swash plate with a constant force. Thus, the stopper does not separate from the swash plate and the generation of knocking sounds can be suppressed.

[0022] In particular, if the pressing means is a hydraulic piston, the stopper can always be pressed against the swash plate with a constant force relative to a stroke length of the hydraulic piston. Thus, the stopper can be reliably pressed against the swash plate regardless of the inclination angle of the swash plate.

[0023] Additionally, disposing the spring at the back portion of the hydraulic piston and pressing the hydraulic piston with the spring in the pressing direction of the hydraulic piston makes it possible to smoothly push out the hydraulic piston immediately after the start of oscillation of the swash plate. That is, immediately after the swash plate starts to oscillate from the state of maximum discharge volume, the initial movement of the piston may be unstable due to friction between the hydraulic piston and the cylinder, etc. However, such delay in the movement of the hydraulic piston can be suppressed, and the piston can be more reliably pressed against the swash plate.

[0024] Such pressing means may be disposed in a position facing the spring across the swash plate, or may be disposed on a side opposite the spring across the support portion of the swash plate. In both cases, the stopper can regulate the maximum inclination angle of the swash plate and suppress the generation of knocking sounds during the oscillation of the swash plate.Advantageous Effects of Invention

[0025] The present invention is capable of providing a variable volume control piston pump with low noise.Brief Description of Drawings

[0026] FIG. 1 illustrates a piston pump 1 in a state of maximum discharge volume. FIG. 2 illustrates the piston pump 1 in a state in which the swash plate 7 has oscillated. FIG. 3A is an enlarged view of the vicinity of a stopper 23 in the state of maximum discharge volume. FIG. 3B is an enlarged view of the vicinity of the stopper 23 in the state in which the swash plate 7 has oscillated. FIG. 4 illustrates a piston pump 1a in the state of maximum discharge volume. FIG. 5 illustrates a piston pump 100 in the state of maximum discharge volume. FIG. 6 illustrates the piston pump 100 in the state in which a swash plate 107 has oscillated. FIG. 7A is an enlarged view of the vicinity of a stopper 123 in the state of maximum discharge volume. FIG. 7B is an enlarged view of the vicinity of the stopper 123 in a state in which the swash plate 7 has started to oscillate. Description of Embodiments

[0027] A piston pump according to embodiments of the present invention will be described below. FIG. 1 illustrates a piston pump 1 in a state of maximum discharge volume, and FIG. 2 illustrates the piston pump 1 in a state in which a swash plate 7 has oscillated. The piston pump of this embodiment is a constant horsepower variable volume control-type piston pump.

[0028] The piston pump 1 is composed mainly of a shaft 5, the swash plate 7, a cylinder barrel 9, a valve plate 15, a spring 21, etc. The shaft 5, the swash plate 7, the cylinder barrel 9, the valve plate 15, the spring 21, etc., are accommodated inside a housing 3.

[0029] The shaft 5 is rotatably attached to the housing 3. The cylinder barrel 9 is connected to the shaft 5. That is, the cylinder barrel 9 is rotatable together with the shaft 5 about the shaft 5 as its axis. A plurality of cylinders 11 are disposed in the cylinder barrel 9 at predetermined intervals in a circumferential direction about the shaft 5. A piston 13 that is capable of reciprocating in an axial direction of the shaft 5 is disposed in each of the cylinders 11.

[0030] An end portion of each piston 13 abuts the swash plate 7 via a shoe 17. The shoe 17 is slidable along the surface of the swash plate 7. That is, the end portion of the piston 13 moves in the circumferential direction about the shaft 5 along the surface of the swash plate 7.

[0031] The swash plate 7 is capable of oscillating about a support portion (an oscillation center 19) with a direction perpendicular to the axial direction of the shaft 5 (direction perpendicular to the paper surface) as the axis of rotation. That is, the angle of the swash plate 7 is variable relative to the shaft 5. It should be noted that unlike the cylinder barrel 9, the swash plate 7 does not rotate about the shaft 5 as its axis of rotation.

[0032] The swash plate 7 is provided with an arm portion at one end portion (upper side in the figure). At the arm portion, a tip end of the spring 21 is in contact with the swash plate 7 via a spring holder 22, and the swash plate 7 is pressed by the spring 21 so that an inclination angle relative to the shaft 5 increases. That is, the moment Ms (see FIG. 5) due to the pressing force from the spring 21 is applied to the swash plate 7 relative to the oscillation center 19. The swash plate 7 inclines in an anticlockwise direction in the figure starting from the oscillation center 19 by the moment Ms due to the force from the spring 21.

[0033] A stopper 23 is disposed at the rear of a direction of oscillation of the swash plate 7 caused by the spring 21. That is, the stopper 23 is disposed in a position facing the spring 21 across the swash plate 7. In the state illustrated in FIG. 1, the swash plate 7 is at its maximum inclination angle, where further oscillation of the swash plate 7 is regulated by the stopper 23. That is, the maximum inclination angle of the swash plate 7 can be regulated by the stopper 23. The function of the stopper 23 will be described in detail further below.

[0034] As described above, the rotation of the shaft 5 causes the cylinder barrel 9 to rotate together with the shaft 5. The cylinders 11 and the pistons 13 provided in the cylinder barrel 9 thus move about the shaft 5. Additionally, as described above, the end portions of the pistons 13 are movable along the surface of the swash plate 7.

[0035] Since the swash plate 7 is inclined when this happens, the pistons 13 reciprocate relative to the cylinders 11 according to the distance between the swash plate 7 and the cylinder barrel 9. For example, in FIG. 1, the piston 13 illustrated above the shaft 5 is in a fully extended state from the cylinder 11, and the piston 13 illustrated below the shaft 5 is in a fully retracted state in the cylinder 11.

[0036] A hole is formed in a predetermined position of the valve plate 15. Thus, when the piston 13 transitions from the retracted state to the extended state, oil is sucked into the cylinder 11 via the hole in the valve plate 15. Additionally, when the piston 13 transitions from the extended state to the retracted state, oil is discharged via the hole in the valve plate 15. That is, as illustrated in FIG. 1, when the inclination angle of the swash plate 7 is at its maximum, the discharge volume of the oil is at its highest, and as illustrated in FIG. 2, when the inclination angle of the swash plate 7 decreases, the discharge volume of the oil decreases.

[0037] Here, as described above, the swash plate 7 receives the resultant force from all the pistons 13. That is, the moment Mp (see FIG. 5) due to the pressing force from all the pistons 13 is applied to the swash plate 7. Thus, in a state in which Ms>Mp, the swash plate 7 inclines in a direction in which the inclination angle increases (anticlockwise direction in the figure), and in a state in which Ms<Mp, the swash plate 7 inclines in a direction in which the inclination angle decreases (clockwise direction in the figure) against the moment Ms by the spring 21. As the inclination angle of the swash plate 7 decreases, the pressing force of the spring 21 increases, so that the swash plate 7 is held at an angle where Ms and Mp are balanced. That is, when hydraulic pressure increases, the piston pump 1 reduces the discharge volume to perform constant horsepower control.

[0038] The function of the stopper 23 of the piston pump 1 will next be described in detail. FIG. 3A is an enlarged view of the vicinity of the stopper 23 in FIG. 1. FIG. 3B is an enlarged view of the vicinity of the stopper 23 in FIG. 2, and illustrates a state in which the swash plate 7 has oscillated from the state shown in FIG. 3A in the direction in which the inclination angle of the swash plate 7 decreases.

[0039] The stopper 23 of the piston pump 1 is accommodated in a cylinder portion 29 formed in the housing 3. A hydraulic circuit 27 is connected to the cylinder portion 29 and a constant hydraulic pressure (P in the figure) is applied to the cylinder portion 29. It should be noted that the flow paths and various valves that form the hydraulic circuit 27 may be disposed outside the housing 3 or may be accommodated inside the housing 3.

[0040] The stopper 23 receives a force in a direction in which the stopper 23 is pushed out from the cylinder portion 29 by the hydraulic pressure. The stopper 23 can thus press the swash plate 7 with a constant force. That is, the stopper 23 is a hydraulic piston and functions as a pressing means for pressing the stopper 23 against the swash plate 7 with a predetermined force.

[0041] Here, as described above, the inclination angle of the swash plate 7 is maintained in a state in which the moment Ms on the swash plate 7 due to the pressing force of the spring 21 is balanced with the reverse moment Mp on the swash plate 7 due to the resultant force of the pistons 13. Thus, a spring force of the spring 21 is set in advance taking into account a pressing force of the stopper 23.

[0042] As described above, the pressing force of the stopper 23 is sufficiently smaller than the pressing force of the spring 21, and when the moment Ms due to the spring 21 is greater than the moment Mp due to the hydraulic pressure from the pistons 13, the stopper 23 is retracted into the cylinder portion 29 to the limit of retraction by the pressing force of the spring 21 via the swash plate 7, as illustrated in FIG. 1.

[0043] Here, the fully retracted state of the stopper 23 in the cylinder portion 29 means that the stopper 23 cannot move backward any further. The stopper 23 thus has the function of regulating the maximum inclination angle of the swash plate 7.

[0044] In contrast, when Mp is greater than Ms, the swash plate 7 oscillates in the direction in which the inclination angle decreases. A pressing force is applied to the stopper 23 from behind when this happens, so that the stopper 23 follows the swash plate 7 and is maintained in contact with the swash plate 7. Additionally, a stroke length of the stopper 23 is set to be greater than or equal to a displacement amount in an oscillating range of the swash plate 7 (maximum displacement amount of the spring 21). That is, the stopper 23 has a movable range that can follow the total oscillating range of the swash plate 7 set for the piston pump 1 (i.e., the range from the state illustrated in FIG. 1 to the state in which the spring 21 is most compressed in the range of use).

[0045] Thus, as illustrated in FIG. 3B, even when the inclination angle of the swash plate 7 is at its minimum in the set range, the stopper 23 is maintained pressing the swash plate 7 with a predetermined pressing force. That is, the stopper 23 is always maintained pressed against and in contact with the swash plate 7 with a constant pressing force. Thus, as described above, even if pulsations (vibrations) occur in the swash plate 7 during the repeated suction and discharge of oil by the plurality of the pistons 13, the stopper 23 will follow these vibrations and always be maintained in contact with the swash plate 7. Consequently, the generation of the so-called knocking sounds can be suppressed.

[0046] A pin 31 having a diameter smaller than that of the body of the stopper 23 is provided behind the stopper 23. Additionally, the housing 3 is provided with a hole 33 behind the cylinder portion 29, and the pin 31 is accommodated in the hole 33. Additionally, a disc spring 25 having a diameter greater than that of the hole 33 is disposed at a back portion of the stopper 23 in the cylinder portion 29. The disc spring 25 is capable of pressing the stopper 23 from behind in a direction toward the swash plate 7. A hole is formed in the disc spring 25, and the pin 31 is inserted into the hole in the disc spring 25. Additionally, as described above, in the fully retracted state of the stopper 23 in the cylinder portion 29, the disc spring 25 is compressed.

[0047] In the case in which the stopper 23 is a hydraulic piston, the operation of the stopper 23 may be unstable from the state in which the swash plate 7 is pressed by the spring 21 at its maximum inclination angle to immediately after the start of oscillation of the swash plate 7, as illustrated in FIG. 3A. For example, the moment the swash plate 7 oscillates slightly from the state in which the stopper 23 is fully retracted in the cylinder portion 29 and stopped due to the force from the swash plate 7, the following motion to the oscillation of the swash plate 7 may be momentarily delayed due to the effects of friction, etc., between the stopper 23 and the cylinder portion 29.

[0048] In contrast, the disc spring 25 helps the operation of the stopper 23 immediately after the swash plate 7 starts to move. The stopper 23 can thus stably maintain the pressing state of the swash plate 7 from the start of operation.

[0049] It should be noted that the length of the pin 31 is set to the stroke length of the stopper 23 or more. The pin 31 thus does not fall out of the hole 33 in the movable range of the stopper 23. Consequently, the disc spring 25 does not come off the pin 31, and is always held on the outer circumference of the pin 31 (behind the stopper 23).

[0050] Although in the piston pump 1 illustrated in FIG. 1, etc., the stopper 23 is disposed on the side opposite the spring 21 across the swash plate 7, the placement of the stopper 23 is not limited thereto. FIG. 4 illustrates a piston pump 1a according to another embodiment. It should be noted that in the mechanism of the piston pump 1a, same reference signs as those in FIG. 1, etc., are given to the configurations that exhibit similar functions as those of the piston pump 1, and redundant description will be omitted.

[0051] The piston pump 1a has a substantially similar structure to the piston pump 1, except for the placement of the stopper 23. In the piston pump 1a, the stopper 23 is disposed on a side opposite the spring 21 across the support portion (oscillation center 19) of the swash plate 7. That is, the pressing direction of the spring 21 toward the swash plate 7 is the same as the pressing direction of the stopper 23 toward the swash plate 7 (left direction in the figure).

[0052] In this embodiment, the stopper 23 is also a hydraulic piston, and has a stroke length that is capable of following the oscillating range of the swash plate 7. That is, the stopper 23 follows the oscillation of the swash plate 7 and is always maintained in contact with the swash plate 7. Additionally, since there is a limit of retraction into the cylinder portion 29, the stopper 23 can also exhibit the function as a stopper that regulates further inclination of the swash plate 7.

[0053] In the embodiments as described above, the stopper 23 that regulates the maximum inclination angle of the swash plate 7 is capable of moving by following the oscillation of the swash plate 7. Additionally, since the stroke length of the stopper 23 can cover the oscillating range of the swash plate 7, the tip end of the stopper 23 does not separate from the swash plate 7. Thus, the generation of the so-called knocking sounds caused by the swash plate 7 and the stopper 23 can be suppressed.

[0054] For example, even if the stopper 23 is movable and is capable of following the oscillation of the swash plate 7, if the stroke length is not sufficient, the stopper 23 and the swash plate 7 may separate at certain inclination angles of the swash plate 7, thereby causing knocking sounds. However, in the piston pump according to the embodiments, the stroke length of the stopper 23 can sufficiently cover the oscillating range of the swash plate 7, so that the generation of knocking sounds can always be suppressed regardless of pressure (regardless of the inclination angle of the swash plate 7).

[0055] Additionally, the stopper 23 being a hydraulic piston enables the stopper 23 to always be continuously pressed against the swash plate 7 with a constant force.

[0056] Furthermore, disposing the disc spring 25 at the back portion of the stopper 23 enables the disc spring 25 to help the movement of the stopper 23 at the start of operation to reliably press the stopper 23 against the swash plate 7.

[0057] It should be noted that the placement of the stopper 23 is not limited to the embodiments described above. Additionally, the pressing means for pressing the stopper 23 from behind is not limited, and may involve other methods besides hydraulics. Furthermore, the disc spring 25 is not a necessarily essential element to be disposed behind the stopper 23, and other elastic members are also acceptable instead of the disc spring 25.Examples

[0058] Noise was evaluated using piston pumps having a conventional fixed stopper and a swash plate following-type stopper according to this embodiment. Both cases were evaluated at 50°C, 2600 min -1< , and a pressure at a cut-off point (swash plate oscillation start pressure) of -5 MPa.

[0059] As a result, knocking sounds were generated in the conventional pump, with the maximum noise being 89.6 dB, whereas in the pump according to this embodiment, no knocking sounds were generated, with the maximum noise reduced to 80.9 dB.Reference Signs List

[0060] 1, 1aPiston pump 3Housing 5Shaft 7Swash plate 9Cylinder barrel 11Cylinder 13Piston 15Valve plate 17Shoe 19Oscillation center 21Spring 22Spring holder 23Stopper 25Disc spring 27Hydraulic circuit 29Cylinder portion 31Pin 33Hole 100Piston pump 105Shaft 107Swash plate 109Cylinder barrel 111Cylinder 113Piston 117Shoe 119Oscillation center 121Spring 122Spring holder 123Stopper

Claims

1. A variable volume control piston pump (1), comprising, a housing (3) within which are housed: a cylinder barrel (9) rotatable together with a shaft (5) about an axis of the shaft; a plurality of cylinders (11) disposed in the cylinder barrel (9) at predetermined intervals in a circumferential direction about the shaft (5); a plurality of pistons (13) capable of reciprocating in an axial direction of the shaft (5) relative to a respective cylinder of the cylinders (11); a swash plate (7) capable of oscillating about a support portion to allow an angle to be variable relative to the pistons (13); a spring (21) capable of pressing a portion of the swash plate (7) to increase an inclination angle of the swash plate (7); and a stopper (23) configured to regulate a maximum inclination angle of the swash plate (7), wherein an end portion of the piston (13) is movable along a surface of the swash plate (7), wherein the stopper (23) is a pressing means for pressing against the swash plate (7) with a predetermined force, characterized in that the stopper (23) is configured to be maintained pressed against the swash plate (7) with a constant force in a total oscillating range of the swash plate (7), and a moment to change an inclination angle of the swash plate (7) due to a pressing force of the stopper (23) is smaller than a moment to change an inclination angle of the swash plate (7) due to a pressing force of the spring (21).

2. The variable volume control piston pump (1) according to claim 1, wherein the pressing means is a hydraulic piston (23), and wherein the hydraulic piston (23) is pressed against the swash plate (7) with a constant force.

3. The variable volume control piston pump (1) according to claim 2, wherein a spring (25) is disposed at a back portion of the hydraulic piston (23), and wherein the spring (25) presses the hydraulic piston (23) in a pressing direction of the hydraulic piston (23).

4. The variable volume control piston pump (1) according to claim 1, wherein the stopper (23) is disposed in a position facing the spring (21) across the swash plate (7).

5. The variable volume control piston pump (1) according to claim 1, wherein the stopper (23) is disposed on a side opposite the spring (21) across the support portion.

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