JP2021099048A - Piston pump - Google Patents

Abstract

To provide a piston pump that avoids excessive pressure rise by releasing a pressure in a pump when a pressure on a pump discharging side becomes high, and can be decreased in size and simplify a fluid pressure circuit without any difficulty.SOLUTION: An elastically deformable moving control piece 17 is interposed between a cylinder block 20 and a rotary shaft 10 stored in a housing 50. When a pressure of working fluid sent out is excessively high, the moving control piece 17 is deformed by force applied from the working fluid through the cylinder block 20 to permit movement to a rotary shaft axis direction of the cylinder block 20. Since the cylinder block 20 is isolated from a valve plate portion 54 of the housing 50, a discharge port 54b of the valve plate portion 54 is communicated with a suction port 54a to obtain a state that the high pressure of the working fluid in the discharge port 54b releases to the suction port 54a. Even if actuation of a pump is continued, the pressure of the working fluid can be prevented from excessively rising by the pump alone, and a fluid pressure circuit can be simplified.SELECTED DRAWING: Figure 5

Description

The present invention relates to a swash plate type axial piston pump, and more particularly to a piston pump having a structure suitable for miniaturization of the pump and simplification of a fluid pressure circuit.

In the swash plate type axial piston pump, a reciprocating piston is provided in each cylinder of the cylinder block that rotates integrally with the rotating shaft, and the piston is stroked according to the degree of inclination of the sloping plate as the rotating shaft rotates. The end face of the cylinder block is slidably contacted with the valve plate provided on the casing, and the suction port and the discharge port provided on the valve plate are provided with the cylinder port leading to each cylinder on the end face of the cylinder block. The cylinder is connected to the low-pressure side or high-pressure side conduit of the working fluid of the fluid pressure circuit through these cylinder ports and the suction port or the discharge port so as to communicate with each other at a timing suitable for the reciprocating motion. It had a mechanism that enabled the suction or discharge of the working fluid based on the reciprocating motion.
As an example of such a conventional piston pump, there is one disclosed in Utility Model Registration No. 2553032.

Utility Model Registration No. 2553032

In the conventional swash plate type axial piston pump, as shown in the patent document, the piston and the cylinder block are integrally rotated together with the rotating shaft, so that the piston reciprocates and operates from the suction passage (entrance). It has a mechanism to operate as a pump in which oil is pumped to the discharge passage (outlet), and is usually used in a hydraulic circuit in combination with an additional device such as a relief valve or a direction switching valve.

The fields of application of such piston pumps are expanding year by year, and space saving and cost reduction can be achieved by downsizing the pump and simplifying the entire fluid pressure circuit including the pump in a form that suits various situations in which it is used. It has become strongly sought after.

In order to simplify the fluid pressure circuit and reduce the cost, it is easy to think of directly connecting the actuator and the pump that operate with fluid pressure, and many proposals have been made in the past, but the following problems occur. there were.

In a fluid pressure circuit using a conventional piston pump, when it is directly connected to an actuator without using an additional device such as a relief valve or a direction switching valve for simplification, for example, the actuator such as a fluid pressure cylinder ends the operating range. When the flow of the working fluid is stagnant, such as when the pressure reaches the limit, the working fluid pressure on the pump discharge side rises due to the pump that continues to operate. However, since there is no mechanism such as a relief valve to release the pressure in the fluid pressure circuit, the pressure of the working fluid sent by the pump can become excessively high beyond the permissible value of the pump or circuit, so the fluid pressure circuit or the pump itself. May cause damage.

In addition, if the pump is miniaturized in such a case, it is expected that the mechanical strength of the pump will be reduced by the miniaturization, the allowable range for the pressure of the working fluid will be reduced, and the pump will be more easily damaged. ..

From this point of view, in the case of a conventional piston pump, it is difficult to save space in the entire fluid pressure circuit by introducing a simple fluid pressure circuit that does not use an additional device such as a relief valve or by downsizing the pump. There is a problem that there is a limit to space saving and cost reduction of the fluid pressure circuit including the pump.

The present invention has been made to solve the above problems, and when the pressure on the discharge side of the pump becomes higher than the limit, the pressure is released in the pump to avoid an excessive pressure rise and the adverse effects associated therewith. It is an object of the present invention to provide a piston pump that can be reasonably miniaturized and the applied fluid pressure circuit can be simplified.

The piston pump according to the disclosure of the present invention has a rotating shaft, a cylinder block having a plurality of cylinders arranged around the rotating shaft substantially parallel to the axis of the rotating shaft and rotationally symmetrical, and each cylinder of the cylinder block. A piston that is reciprocally inserted and arranged so that one end protrudes from the cylinder, a swash plate that is arranged so as to face one end of each piston and is in contact with one end of each piston, and one of the rotating shafts. In an axial type piston pump including a rotating shaft and a housing that rotatably supports the cylinder block while accommodating a portion, a cylinder block, a piston, and a swash plate portion, the cylinder block is a one end portion of the piston. A plurality of cylinder ports communicating with each cylinder are provided at the end opposite to the protruding side, and in the axial direction of the rotating shaft, between a part of the rotating shaft and a part of the cylinder block. A substantially arc-shaped suction port and discharge that can rotate integrally with the rotating shaft with an elastically deformable movement control piece interposed therebetween, and the housing can intermittently communicate with each cylinder port of the cylinder block. It has a valve plate portion provided with each port, and supports the end surface of the valve plate portion while sliding the end of the cylinder block, and discharges the low-pressure side pipeline of the external fluid pressure circuit to the suction port. When the high-pressure side pipeline of the fluid pressure circuit is connected to the port and the pressure of the fluid sent from the discharge port to the high-pressure side conduit as a pump becomes excessively high, it is based on the pressure applied from the fluid to the cylinder block. The movement control piece is elastically deformed by a force in the axial direction of the rotating shaft, allowing the cylinder block to move relative to the rotating shaft in the axial direction, and separating the cylinder block from the valve plate portion of the housing. is there.

As described above, according to the disclosure of the present invention, the cylinder block housed in the housing is via a movement control piece that can be elastically deformed between a part of the cylinder block and a part of the rotating shaft in the axial direction of the rotating shaft. When the pressure of the working fluid that is installed and sent out as a pump is excessively high, the movement control piece is elastically deformed by the force applied from the working fluid via the cylinder block, and the rotation axis direction of the cylinder block with respect to the rotation axis. The moved cylinder block is separated from the valve plate portion of the housing, and a gap is created between the valve plate portion and the cylinder block. The discharge port and the suction port can be communicated with each other, and the high pressure of the working fluid in the discharge port leading to the high pressure side pipeline can be obtained to escape to the suction port leading to the low pressure side pipeline, and the operation of the pump continues. However, it is possible to prevent the pressure of the working fluid on the discharge side of the pump or the fluid pressure circuit from rising excessively by the pump alone, and the fluid pressure circuit is not provided with a safety device or the like corresponding to the pressure rise of the working fluid. A circuit configuration can be adopted, and the cost of the fluid pressure circuit can be reduced. In addition, even if the pump is miniaturized so as to reduce the mechanical strength, adverse effects such as damage due to excessive pressure of the working fluid can be avoided, and the pump can be miniaturized and the fluid pressure circuit can be simplified to save the pump. Space can be realized.

Further, the piston pump according to the disclosure of the present invention includes a cylinder block having a rotating shaft, a plurality of cylinders arranged around the rotating shaft substantially parallel to the axis of the rotating shaft and rotationally symmetric, and the cylinder block. A piston that is reciprocally inserted into each cylinder and projects one end from the cylinder, a swash plate that is arranged so as to face one end of each piston and is in contact with one end of each piston, and the rotation shaft. In an axial type piston pump including a rotating shaft and a housing that rotatably supports the cylinder block while accommodating a part of the piston block, a piston, and a swash plate portion, the cylinder block is one end portion of the piston. A plurality of cylinder ports communicating with each cylinder are provided at the end opposite to the protruding side of the piston, and the housing can be rotated integrally with the rotating shaft so that the housing can be attached to each cylinder port of the cylinder block. It has a valve plate portion provided with a substantially arc-shaped suction port and a discharge port that can be intermittently communicated with each other, and supports the end face of the valve plate portion while sliding the end portion of the cylinder block, and externally to the suction port. The low-pressure side pipeline of the fluid pressure circuit is connected to the discharge port, and the high-pressure side pipeline of the fluid pressure circuit is connected to the discharge port. With at least an elastically deformable movement control piece interposed between the part of the piston, the fluid is rotatably supported by the housing and is delivered from the discharge port to the high-pressure side conduit as a pump. When the pressure becomes excessively high, the movement control piece is elastically deformed by the axial force of the rotating shaft based on the pressure applied from the fluid to the cylinder block, and at least in the axial direction of the rotating shaft with respect to the cylinder block and the housing of the rotating shaft. It allows relative movement and separates the cylinder block from the valve plate of the housing.

As described above, according to the disclosure of the present invention, an elastically deformable movement control piece is interposed between a part of the rotating shaft housed in the housing and a part of the housing in the axial direction of the rotating shaft, and serves as a pump. When the pressure of the working fluid to be sent is excessively high, the movement control piece is elastically deformed by the force applied from the working fluid via the cylinder block and the rotating shaft, allowing the relative movement of the rotating shaft with respect to the housing in the axial direction. However, the cylinder block that moves integrally with the rotating shaft is separated from the valve plate portion of the housing, and a gap is created between the valve plate portion and the cylinder block. The discharge port and the suction port can be communicated with each other, and the high pressure of the working fluid in the discharge port leading to the high pressure side pipeline can be obtained to escape to the suction port leading to the low pressure side pipeline, and the operation of the pump continues. However, it is possible to prevent the pressure of the working fluid on the discharge side of the pump or the fluid pressure circuit from rising excessively by the pump alone, and the fluid pressure circuit is not provided with a safety device or the like corresponding to the pressure rise of the working fluid. A circuit configuration can be adopted, and the cost of the fluid pressure circuit can be reduced. In addition, even if the pump is miniaturized so as to reduce the mechanical strength, adverse effects such as damage due to excessive pressure of the working fluid can be avoided, and the pump can be miniaturized and the fluid pressure circuit can be simplified to save the pump. Space can be realized.

Further, the piston pump according to the disclosure of the present invention is formed in a bellows tubular shape with one end closed as needed, and the other end that opens between the piston and the cylinder port in each cylinder of the cylinder block. A stretchable liner portion is provided with the portion side facing the cylinder port side, and the liner portion is preliminarily contracted in the axial direction of the rotation axis with elastic deformation, and the other end of the piston and the cylinder of the cylinder block. It is interposed between the port and the peripheral portion, and urges the piston to the side protruding from the cylinder by an elastic restoring force.

As described above, according to the disclosure of the present invention, an extendable bellows tubular liner portion is provided in each cylinder of the cylinder block, and this liner portion is interposed between the other end of the piston and the peripheral portion of the cylinder port of the cylinder block. The liner portion also expands and contracts with the reciprocating movement of the piston, and the internal volume thereof is changed in the same manner as the cylinder. Through the open end of the liner part facing the cylinder port side, the liner part mainly flows in and out of the liner part, and the liner part takes the role of separating the internal space of the piston cylinder from the outside, and the piston and the cylinder It is not necessary to strictly control the gap between the pistons, and even if there is a gap between the piston and the cylinder, it is difficult for the working fluid to leak from this gap. There is no problem even if the accuracy of the gap cannot be maintained, and space saving can be realized by downsizing the pump.

In addition, by urging the piston to the side that protrudes from the cylinder with the liner portion that has been contracted in the axial direction of the rotating shaft in advance, the state of contact with the swash plate portion of one end of the piston can be maintained reasonably, and the piston can be made smoother. It can be reciprocated to ensure and smoothly deliver the working fluid.

Further, in the piston pump according to the disclosure of the present invention, if necessary, the liner portion is provided with a convex portion protruding from a closed one end portion, and the piston is provided with a concave portion at the other end portion. In the cylinder, the convex portion of the liner portion and the concave portion of the piston engage with each other.

As described above, according to the disclosure of the present invention, the convex portion provided at the closed end portion of the liner portion is engaged with the concave portion formed at the other end portion of the piston, and one end of the liner portion is engaged in the cylinder. By making the other end of the piston and the other end of the piston less likely to shift from each other, the expansion and contraction deformation of the liner can be reliably followed by the reciprocating movement of the piston, and the inflow and outflow state of the working fluid according to the movement of the piston can be obtained. In addition to being able to smoothly deliver the working fluid, avoid a situation in which one end of the liner is laterally displaced with respect to the other end of the piston, and the displaced liner is in a state of being biased toward the inner peripheral surface of the cylinder. It is possible to prevent deterioration and damage due to uneven wear of the liner portion.

It is a perspective view of the piston pump which concerns on 1st Embodiment of this invention. It is the schematic explanatory drawing of the fluid pressure circuit to which the piston pump which concerns on 1st Embodiment of this invention is applied. It is a top view of the piston pump which concerns on 1st Embodiment of this invention. FIG. 3 is a schematic cross-sectional view taken along the line AA of FIG. FIG. 3 is a schematic cross-sectional view taken along the line BB of FIG. It is explanatory drawing of the mechanism inside the housing in the piston pump which concerns on 1st Embodiment of this invention. It is a disassembled state explanatory drawing of the internal mechanism in the piston pump which concerns on 1st Embodiment of this invention. It is a separation state explanatory view of the liner part and the piston in the piston pump which concerns on 1st Embodiment of this invention. It is explanatory drawing of the separation state of the cylinder block and the valve plate part in the piston pump which concerns on 1st Embodiment of this invention. It is explanatory drawing of the communication state of the discharge port and the suction port in the piston pump which concerns on 1st Embodiment of this invention. It is the schematic sectional drawing of the piston pump which concerns on 2nd Embodiment of this invention. It is explanatory drawing of the separation state of a cylinder block and a valve plate part in the piston pump which concerns on 2nd Embodiment of this invention. It is the schematic sectional drawing of the piston pump which concerns on other embodiment of this invention. It is explanatory drawing of the separation state of the cylinder block and the valve plate part in the piston pump which concerns on other embodiment of this invention.

(First Embodiment of the present invention)
Hereinafter, the piston pump according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 10. In this embodiment, an example of a small piston pump connected to a predetermined fluid pressure circuit to deliver a working fluid will be described.

In each of the above figures, the piston pump 1 according to the present embodiment includes a rotary shaft 10 that is rotationally driven by an electric motor 60 that is a drive source, and a cylinder block 20 having a plurality of cylinders 21 arranged around the rotary shaft 10. A piston 30 inserted into each cylinder 21 of the cylinder block 20, a swash plate portion 51 in contact with one end of each piston 30, a housing 50 that rotatably supports the rotating shaft 10 and the cylinder block 20, and a housing 50. It is configured to include a bellows tubular liner portion 40 arranged in each cylinder 21 of the cylinder block 20.

Regarding the basic mechanism for delivering the working fluid in the piston pump 1 according to the present embodiment, as in the case of the known swash plate type axial piston pump, each piston 30 is swashed as the rotating shaft 10 rotates. Each cylinder 21 is sequentially subjected to a low pressure of the fluid pressure circuit 80 via a suction port 54a and a discharge port 54b provided in the valve plate portion 54 on the housing 50 side while reciprocating with a stroke according to the degree of inclination of the 51. It communicates with the side pipeline 81 or the high-pressure side pipeline 82, and continuously sucks or discharges the working fluid based on the reciprocating motion of each piston 30, and detailed description thereof will be omitted.

The rotating shaft 10 is formed as a shaft-shaped body made of metal or resin, and the shaft intermediate portion is rotatably supported by the housing 50 by the bearing portion 11. The rotating shaft 10 has one end located outside the housing 50 rotatably connected to the output shaft of the motor 60 via a predetermined connecting member, while the other end located inside the housing 50. The portions are integrally rotatably connected to the cylinder block 20.

In addition, the diameter-expanded portion 12 projecting in the middle of the rotating shaft 15 in a brim shape is in contact with and supported by the axial end of the rotating shaft 15 in the bearing portion 11, so that the rotating shaft 15 is supported in the axial direction. It is a mechanism that is supported so as not to cause unnecessary movements.

The cylinder block 20 is provided with a plurality of circular cross-sectional holes for generating the cylinder 21 around the central axis of the resin columnar body, and is provided with a hole for connecting the other end of the rotating shaft 10 at the center. (See FIGS. 4, 5, and 7). The cylinder 21 in the cylinder block 20 is arranged around the rotating shaft 10 so as to be parallel to the axis of the rotating shaft 10 and rotationally symmetric with the cylinder block 20 connected to the rotating shaft 10.

The piston 30 is inserted into each cylinder 21 of the cylinder block 20 with one end protruding from the cylinder 21 (see FIGS. 4, 5, and 6).
The cylinder block 20 is provided with a plurality of cylinder ports 22 which are through holes communicating with each cylinder 21 at an end portion of the piston 30 opposite to the protruding side (see FIG. 6).

In addition, the cylinder block 20 is connected to the rotating shaft 10 by inserting the other end of the rotating shaft 10 into a hole in the center portion so that the cylinder block 20 can rotate integrally with the rotating shaft 10, for example, a known spline shaft. It is a mechanism that allows relative movement of the rotating shaft 10 in the axial direction by using a coupling method with a spline hole. Further, a movement control piece 17 made of an elastically deformable elastic material is disposed between the bottom of the hole at the center of the cylinder block 20 and the other end of the rotating shaft 10, and the axial direction of the rotating shaft 10 The movement control piece 17 is interposed between the other end of the rotating shaft 10 and the central portion of the cylinder block 20 (see FIGS. 4 and 5).

The piston 30 is formed as a resin columnar body, and is inserted and arranged in each cylinder 21 of the cylinder block 20 so as to be reciprocating. The piston 30 is in a state in which a metal or resin sphere 31 for facilitating contact with another object is rotatably embedded in one end thereof, and the one end is projected from the cylinder 21. ing. Further, a recess 32 having a predetermined depth is provided at the other end of the piston 30 (see FIGS. 4, 5, and 8).
A liner portion 40 is arranged in the cylinder 21 between the other end of the piston 30 and the cylinder port 22 of the cylinder block 20.

The housing 50 has a substantially box-shaped container shape, and can rotate the rotating shaft 10 and the cylinder block 20 while accommodating a part of the rotating shaft 10, a cylinder block 20, a piston 30, and a swash plate portion 51 inside. It supports.

Inside the housing 50, the swash plate portion 51, which is a ring-shaped flat surface inclined in a predetermined direction with respect to the axial direction of the rotating shaft 10, faces one end of each piston 30 and is integrated with the housing 50. It is a configuration in which it is arranged (see FIGS. 4 and 6). The swash plate portion 51 is located at a portion separated from the cylinder block 20 and comes into contact with the sphere 31 at one end of each piston 30.

Further, the housing 50 is provided with a substantially arc-shaped suction port 54a and a discharge port 54b that can intermittently communicate with each cylinder port 22 of the cylinder block 20 inside the side opposite to the side with the swash plate portion 51. It has a valve plate portion 54 (see FIGS. 3, 4, and 5). The housing 50 rotatably supports the cylinder block 20 while sliding the end portion of the cylinder block 20 against the end surface of the valve plate portion 54. The end face of the valve plate portion 54 is a spherical surface known to be superior in terms of performance stability as compared with the case of a flat surface, and the end portion of the cylinder block 20 that is in sliding contact with the spherical surface portion is also the valve plate portion 54. It has a spherical shape corresponding to the side.

In addition, the housing 50 is provided with a tubular inlet portion 52 communicating with the suction port 54a in an outwardly protruding state, and a tubular outlet portion 53 communicating with the discharge port 54b is also provided in an outwardly protruding state. (See FIGS. 1 and 3). Then, the low-pressure side pipeline 81 of the external fluid pressure circuit 80 is connected to the inlet portion 52, and the high-pressure side pipeline 82 of the fluid pressure circuit 80 is connected to the outlet portion 53 (see FIG. 2). ..

The liner portion 40 is formed in a bellows tubular shape with one end closed, and can be expanded and contracted in the longitudinal direction of the pipe, and is opened between the piston 30 and the cylinder port 22 in each cylinder 21 of the cylinder block 20. The other end side is arranged toward the cylinder port 22 side (see FIGS. 4 and 5).

The liner portion 40 is interposed between the other end of the piston 30 and the peripheral portion of the cylinder port 22 of the cylinder block 20 with elastic deformation that is contracted in the axial direction of the rotating shaft 10 in advance, and restores the original shape. The mechanism is such that the piston 30 is urged to the side protruding from the cylinder 21 by the elastic force.
By urging the piston 30 by the liner portion 40, it is possible to maintain a state in which one end of the piston 30 is in contact with the swash plate portion 51.

Further, the liner portion 40 is provided with a convex portion 41 protruding from a closed one end portion by a predetermined length, and the convex portion 41 and the concave portion 32 at the other end of the piston 30 engage with each other in the cylinder 21 (FIG. 4, FIG. (See FIGS. 5 and 8).

A flexible wedge-shaped cross-sectional lip portion is provided on the opening edge of the other end of the liner portion 40 so as to be in close contact with the peripheral portion of the cylinder port 22 of the cylinder block 20 to improve the sealing property. May be good.

Next, the operating state of the piston pump according to the present embodiment will be described. As a premise, the piston pump 1 operates by obtaining a driving force from an electric motor 60 which is a driving source, and a high-pressure side pipe of a fluid pressure circuit 80 in which a working fluid of a predetermined pressure is directly connected to an actuator 70 such as a fluid pressure cylinder as a pressure source. It is assumed that the working fluid that has exited the actuator 70 can be continuously sent out toward the road 82 and can be continuously received through the low pressure side pipeline 81 of the fluid pressure circuit 80.

When the electric motor 60, which is a drive source, operates, the rotary shaft 10 and the cylinder block 20 connected to the output shaft rotate. One end of the piston 30 protruding from the cylinder 21 of the cylinder block 20 is pressed against the swash plate 51 by the elastic force of the liner 40 in the cylinder 21.

Since the swash plate portion 51 is tilted with respect to the axial direction of the rotary shaft 10, the piston 30 that rotates around the axis of the rotary shaft 10 together with the cylinder block 20 has one end of the piston 30 moving along the swash plate portion 51. As it rotates, the piston 30 reciprocates with respect to the cylinder block 20 in the axial direction of the rotating shaft 10. The piston 30 reciprocates once in one rotation with respect to the swash plate portion 51.

In the rotation of the cylinder block 20 and the piston 30, one end of the piston 30 is guided away from the cylinder block 20 on the swash plate portion 51 in contact, and when the piston 30 advances from the cylinder 21, the cylinder 21 The internal volume of the liner portion 40 is expanded, and the liner portion 40 inside the liner portion 40 is also stretched and deformed to expand the internal volume thereof. At this time, the cylinder port 22 of the cylinder 21 whose internal volume is expanded leads to the space portion inside the liner portion 40 which is also expanded, while facing the suction port 54a of the valve plate portion 54 in the housing 50. It is in a state of communicating with. As a result, the working fluid flows from the low pressure side pipeline 81 of the fluid pressure circuit 80 into the cylinder 21, that is, inside the liner portion 40 through the suction port 54a of the valve plate portion 54 in the housing 50 and the cylinder port 22 of the cylinder block 20. It is sucked into the space and flows in.

On the other hand, due to the change in the relative positional relationship with the swash plate portion 51 due to the rotation, one end of the piston 30 is guided on the swash plate portion 51 in contact with the swash plate portion 51 in a direction approaching the cylinder block 20 from the cylinder 21 of the piston 30. The amount of advancement of the cylinder 21 is reduced, that is, when the piston 30 is retracted toward the cylinder 21, the internal volume of the cylinder 21 is reduced. In this case, the liner portion 40 inside the cylinder 21 is also contracted and deformed to reduce its internal volume. At this time, the cylinder port 22 of the cylinder 21 whose internal volume is reduced communicates with the space portion inside the liner portion 40 which is also reduced, while facing the discharge port 54b of the valve plate portion 54 in the housing 50. Is in a state of doing.

As a result, the working fluid is extruded from the inside of the cylinder 21, that is, the space inside the liner portion 40, and is discharged through the cylinder port 22 of the cylinder block 20 and the discharge port 54b of the valve plate portion 54 in the housing 50. It is sent from the outlet portion 53 of the above to the high pressure side pipeline 82 of the fluid pressure circuit 80.

The high-pressure working fluid delivered to the high-pressure side pipeline 82 reaches the actuator 70 and activates the actuator 70. Then, the working fluid having a lower pressure from the actuator 70 flows toward the piston pump 1 through the low-pressure side pipeline 81 and flows into the inlet portion 52 of the housing 50.

In the conventional swash plate type axial piston pump, when the cylinder block or piston is miniaturized in order to miniaturize the pump, the precision of machining generally deteriorates relatively with the miniaturization, and the finishing machining is also realistic. Therefore, the accuracy of the gap between the piston and the cylinder cannot be ensured, and the leakage of fluid between the piston and the cylinder cannot be avoided. In this respect, it is difficult to realize miniaturization.

On the other hand, in the piston pump of the present embodiment, by using the liner portion 40, the fluid entering and exiting the cylinder 21 through the cylinder port 22 is in a state of mainly flowing in and out of the liner portion 40, and the fluid reciprocates in the piston 30. It is sucked into the liner portion 40 that deforms according to the movement and discharged from the liner portion 40, and even if there is a gap between the piston 30 and the cylinder 21, the fluid does not go there and leaks. This can be avoided and the miniaturization of the pump can be realized without any trouble.

When the actuator 70 connected to the piston pump 1 by the fluid pressure circuit 80 and operated by the fluid pressure from the piston pump 1 is a fluid pressure cylinder, the actuator 70 reaches the end of the operating range such as the maximum position or the minimum position of the stroke. However, if the piston pump 1 continues to operate as it is, the pressure of the working fluid sent to the high-pressure side pipeline 82 increases on the pump side, while the fluid pressure does not decrease due to the operation due to some trouble. ..

However, in the piston pump 1 of the present embodiment, when the pressure of the working fluid at the discharge port 54b becomes excessively high, that is, when the pressure exceeds a preset upper limit pressure, the cylinder receives the high pressure of the working fluid. The block 20 elastically deforms the movement control piece 17 and the liner portion 40 in a contracting direction, moves relative to the rotating shaft 10 in the axial direction thereof, and separates from the valve plate portion 54, and separates the valve plate portion 54 from the cylinder block. A gap through which the fluid can flow is created between the 20 and the 20 (see FIGS. 9 and 10).

With this gap, the discharge port 54b and the suction port 54a can communicate with each other, and it is possible to obtain a state in which the pressure of the high-pressure side pipe 82 escapes to the low-pressure side pipe 81. As a result, even if the rotating shaft 10 and the cylinder block 20 continue to rotate and the piston 30 reciprocates, and the inflow and outflow of the working fluid through the cylinder port 22 continues, the pressure of the fluid pressure circuit 80 further increases. It will not rise.

As described above, in the piston pump according to the present embodiment, the cylinder block 20 housed in the housing 50 is elastic between the central portion of the cylinder block 20 and the other end of the rotating shaft 10 in the axial direction of the rotating shaft 10. When the pressure of the working fluid sent out as a pump is excessively high with the deformable movement control piece 17 interposed therebetween, the movement control piece 17 is elastically deformed by the force applied from the working fluid via the cylinder block 20. Allows the cylinder block 20 to move relative to the rotary shaft 10 in the direction of the rotary axis axis, and the moved cylinder block 20 is separated from the valve plate portion 54 of the housing 50 and is separated between the valve plate portion 54 and the cylinder block 20. Since a gap is formed in the valve plate portion 54, the discharge port 54b and the suction port 54a of the valve plate portion 54 can communicate with each other, and the high pressure of the working fluid in the discharge port 54b leading to the high pressure side pipeline 82 is increased. It is possible to obtain a state of escape to the suction port 54a leading to the low pressure side pipeline 81, and even if the operation of the pump continues, the pressure of the working fluid in the discharge side of the pump and the fluid pressure circuit 80 rises excessively. Since it can be stopped independently, it is possible to adopt a simple circuit configuration in which the fluid pressure circuit 80 is not provided with a safety device or the like corresponding to an increase in the pressure of the working fluid, and the cost of the fluid pressure circuit 80 can be reduced. In addition, even if the pump is miniaturized so as to reduce the mechanical strength, adverse effects such as damage due to excessive pressure of the working fluid can be avoided, and the pump can be miniaturized and the fluid pressure circuit can be simplified to save the pump. Space can be realized.

(Second Embodiment of the present invention)
The piston pump according to the second embodiment of the present invention will be described with reference to FIGS. 11 and 12. Also in this embodiment, an example of a small piston pump connected to a predetermined fluid pressure circuit and delivering a working fluid will be described.

In each of the drawings, the piston pump 1 according to the present embodiment includes a rotating shaft 15, a cylinder block 20, a piston 30, a swash plate portion 51, a housing 55, and a liner portion 40, as in the first embodiment. On the other hand, the difference is that the rotating shaft 15 is elastically deformable between a part of the rotating shaft 15 and a part of the housing 55 in the axial direction of the rotating shaft 15. It has a structure that is rotatably supported by the housing 55 with the housing 55 interposed therebetween.

The basic mechanism for delivering the working fluid in the piston pump 1 according to the present embodiment is the same as that of the known swash plate type axial piston pump, and detailed description thereof will be omitted. Further, in the piston pump 1 according to the present embodiment, the cylinder block 20, the piston 30, the swash plate portion 51 and the valve plate portion 54 of the housing 55, and the liner portion 40 have the same configurations as those of the first embodiment. A detailed description thereof will be omitted.

Similar to the first embodiment, the rotating shaft 15 is formed as a shaft-shaped body made of metal or resin, and the shaft intermediate portion is rotatably supported by the bearing portion 11 on the housing 55 to the outside of the housing 55. One end located is connected to the output shaft of the motor 60, and the other end located inside the housing 55 is connected to the cylinder block 20.

On the other hand, unlike the rotary shaft 10 in the first embodiment, the rotary shaft 15 is connected to the cylinder block 20 by inserting the other end of the rotary shaft 15 into a hole in the center of the cylinder block 20. , No inclusions are interposed between the other end of the rotating shaft 15 and the bottom of the hole of the cylinder block 20, and the cylinder block 20 is not allowed to move relative to the rotating shaft 15 in the axial direction and rotates. It is in a state of being integrally fixed with the other end of the shaft 15.

In addition, the diameter-expanded portion 12 protruding in the middle of the rotating shaft 15 in a brim shape is in contact with and supported by the axial end of the rotating shaft 15 in the bearing portion 11, as in the first embodiment. The rotating shaft 15 is supported so as not to cause unnecessary movement in the axial direction thereof.

Similar to the first embodiment, the housing 55 has a substantially box-shaped container shape, and has a rotating shaft while accommodating a part of the rotating shaft 15, a cylinder block 20, a piston 30, and a swash plate portion 51 inside. The configuration is such that the 15 and the cylinder block 20 are rotatably supported, but the difference is that the bearing portion 11 that supports the rotating shaft 15 can be moved within a predetermined range with respect to the housing 55 in the axial direction of the rotating shaft 15. A spring-shaped movement control piece 18 that can be elastically deformed is arranged along the peripheral portion of the shaft hole 56 that penetrates the rotating shaft 15 at one end of the housing 55. There is (see FIG. 11).
That is, the bearing portion 11 and the movement control piece 18 are interposed between the enlarged diameter portion 12 of the rotating shaft 15 and the peripheral portion of the shaft hole 56 at one end of the housing 55.

In this way, in the axial direction of the rotating shaft 15, not only the bearing portion 11 but also the elastically deformable movement control piece 18 is interposed between the enlarged diameter portion 12 of the rotating shaft 15 and the peripheral portion of the shaft hole 56 of the housing 55. As a result, the rotary shaft 15 is rotatably supported by the housing 55, and when the movement control piece 18 is elastically deformed in the axial direction of the rotary shaft 15, the rotary shaft 15 is rotatably supported. The bearing portion 11 is movable with respect to the housing 55 in the axial direction of the rotating shaft 15 by the amount of deformation of the movement control piece 18 (see FIG. 12).

Since the rotating shaft 15 is integrated with the cylinder block 20 at other ends, the cylinder block 20 also moves when the rotating shaft 15 moves in the axial direction with elastic deformation of the movement control piece 18. It moves integrally in the axial direction. Conversely, a force in the axial direction of the rotating shaft 15 is applied to the cylinder block 20, and this force is transmitted to the movement control piece 18 via the rotating shaft 15 and the bearing portion 11, and when this is elastically deformed, the cylinder block 20 Is in a state of moving together with the rotating shaft 15 in the axial direction of the rotating shaft 15 with respect to the housing 55.

As a result, when the pressure of the working fluid sent from the discharge port 54b to the high-pressure side pipeline 82 as a pump becomes high to some extent, the axial force of the rotating shaft 15 based on the pressure applied from the working fluid to the cylinder block 20 becomes the rotating shaft 15. By pressing the movement control piece 18 via the bearing portion 11 or the bearing portion 11, the movement control piece 18 is elastically deformed, and the rotation shaft 15 is allowed to move in the axial direction with respect to the housing 55 of the cylinder block 20 and the rotation shaft 15. , The cylinder block 20 is separated from the valve plate portion 54 of the housing 55.

Next, the internal state when the delivery pressure of the working fluid in the piston pump according to the present embodiment rises abnormally will be described. The normal operating state of the piston pump according to the present embodiment is the same as that of the first embodiment, and detailed description thereof will be omitted.

When the actuator 70 connected to the piston pump 1 of the present embodiment by the fluid pressure circuit 80 and operated by the fluid pressure from the piston pump 1 is a fluid pressure cylinder, the actuator 70 operates such as the maximum position and the minimum position of the stroke. When the end of the range is reached or due to some trouble, the fluid pressure does not drop due to operation, while the piston pump 1 operates as it is and continues to send the working fluid, the high pressure side pipeline on this pump side. The pressure of the working fluid delivered to 82 increases.

However, in the piston pump 1, when the pressure of the working fluid at the discharge port 54b becomes excessively high, that is, when the pressure exceeds a preset upper limit pressure, the cylinder block 20 that receives the high pressure of the working fluid becomes the cylinder block 20. The liner portion 40 is elastically deformed in the direction of being compressed in the axial direction of the rotating shaft 15, and the movement control piece 18 is elastically deformed in the direction of being compressed via the rotating shaft 15 and the bearing portion 11, while the rotating shaft is elastically deformed with respect to the housing 55. It moves together with the rotating shaft 15 and the bearing portion 11 in the axial direction of 15. This movement separates the cylinder block 20 from the valve plate portion 54, and creates a gap through which fluid can flow between the valve plate portion 54 and the cylinder block 20 (see FIG. 12).

With this gap, the discharge port 54b and the suction port 54a can communicate with each other, and it is possible to obtain a state in which the pressure of the high-pressure side pipe 82 escapes to the low-pressure side pipe 81. As a result, even if the rotating shaft 15 and the cylinder block 20 continue to rotate and the piston 30 reciprocates, and the inflow and outflow of the working fluid in the piston pump 1 continues, the pressure in the fluid pressure circuit 80 rises further. There is nothing to do.

As described above, in the piston pump according to the present embodiment, the movement control piece 18 that can be elastically deformed between a part of the rotating shaft 15 housed in the housing 55 and a part of the housing 55 in the axial direction of the rotating shaft 15. When the pressure of the working fluid sent out as a pump is excessively high, the movement control piece 18 is elastically deformed by the force applied from the working fluid via the cylinder block 20 and the rotating shaft 15 to the housing 55. The cylinder block 20 that allows relative movement of the rotating shaft 15 in the axial direction and moves integrally with the rotating shaft 15 is separated from the valve plate portion 54 of the housing 55 and is separated between the valve plate portion 54 and the cylinder block 20. Since a gap is formed in the valve plate portion 54, the discharge port 54b and the suction port 54a of the valve plate portion 54 can communicate with each other, and the high pressure of the working fluid in the discharge port 54b leading to the high pressure side pipeline 82 is increased. It is possible to obtain a state of escape to the suction port 54a leading to the low pressure side pipeline 81, and even if the operation of the pump continues, the pressure of the working fluid in the discharge side of the pump and the fluid pressure circuit 80 rises excessively. Since it can be stopped independently, it is possible to adopt a simple circuit configuration in which the fluid pressure circuit 80 is not provided with a safety device or the like corresponding to an increase in the pressure of the working fluid, and the cost of the fluid pressure circuit 80 can be reduced. Further, even if the pump is miniaturized so as to reduce the mechanical strength, adverse effects such as breakage due to excessive pressure of the working fluid can be avoided, and the pump is miniaturized and the fluid pressure circuit 80 is simplified. Space saving can be realized.

In the piston pump according to each of the above embodiments, the swash plate portion 51 is integrated with the housings 50 and 55 to fix the inclination angle, and the swash plate portion 51 has a simple structure to reduce the size and reduction of the pump. Although the configuration gives priority to cost reduction, it is not limited to this, and the swash plate portion, which is also used in known swash plate type axial piston pumps, is separated from the housing to make the inclination angle variable, and the swash plate portion is inclined. The amount of working fluid delivered by the pump may be adjusted by setting the angle.

Further, in the piston pump according to each of the above-described embodiments, O-rings, springs, etc. separate from the rotating shafts 10 and 15 are provided as the movement control pieces 17 and 18, and the pressure of the working fluid delivered as the pump is within an appropriate range. The cylinder block 20 is not allowed to move in the direction of the axis of rotation, and the discharge port 54b and the suction port 54a are maintained in an isolated state. On the other hand, when the pressure of the working fluid is excessively high, the working fluid is transferred to the cylinder. The movement control pieces 17 and 18 are elastically deformed by the force applied via the block 20 and the like so that the cylinder block 20 moves away from the valve plate portion 54 with respect to the housings 50 and 55, so that the valve plate portion 54 and the cylinder A gap is created between the block 20 and the block 20, and the high pressure of the working fluid in the discharge port 54b is released to the suction port 54a through the gap. However, the present invention is not limited to this, and if it plays a role of controlling the movement of the cylinder block based on the pressure applied from the working fluid like the movement control piece, the rotation shaft is integrated with the rotation shaft from the beginning. The elastic material portion forming a part of the above may be provided at a predetermined portion facing the cylinder block or the housing in the axial direction of the rotating shaft.

For example, as shown in FIGS. 13 and 14, a part of the other end side of the rotating shaft 10 is used as the elastic material portion 10a, and the elastic material portion 10a at the other end of the rotating shaft 10 is provided at the bottom of the hole at the center of the cylinder block 20. When the pressure of the working fluid sent out as a pump is excessively high when they are brought into contact with each other, the elastic material portion of the rotating shaft 10 is subjected to the force applied from the working fluid via the cylinder block 20 as in the first embodiment. The 10a is elastically deformed to allow the cylinder block 20 to move relative to the rotation axis 10 in the direction of the rotation axis axis, and the moved cylinder block 20 is separated from the valve plate portion 54 of the housing 50 to be separated from the valve plate portion 54. A state is obtained in which a gap is formed between the cylinder block 20 and the high pressure of the working fluid in the discharge port 54b to be released to the suction port 54a.

1 Piston pump 10, 15 Rotating shaft 10a Elastic material part 11 Bearing part 12 Diameter expansion part 17, 18 Movement control piece 20 Cylinder block 21 Cylinder 22 Cylinder port 30 Piston 31 Sphere 32 Recession 50, 55 Housing 51 Slanted plate part 52 Inlet part 53 Outlet part 54 Valve plate part 54a Suction port 54b Discharge port 56 Shaft hole 40 Liner part 41 Convex part 60 Electric motor 70 Actuator 80 Fluid pressure circuit 81 Low pressure side pipeline 82 High pressure side pipeline

Claims (4)

A cylinder block having a rotating shaft, a cylinder block having a plurality of cylinders arranged around the rotating shaft substantially parallel to the axis of the rotating shaft and rotationally symmetrical, and a cylinder block reciprocatingly inserted and arranged in each cylinder of the cylinder block. A piston that projects one end from the cylinder, a swash plate that is arranged so as to face one end of each piston and is in contact with one end of each piston, a part of the rotating shaft, a cylinder block, a piston, and a swash plate. In an axial type piston pump, which includes a rotating shaft and a housing that rotatably supports a cylinder block while accommodating a portion inside.
The cylinder block is provided with a plurality of cylinder ports communicating with each cylinder at the end opposite to the protruding side of one end of the piston, and a part of the rotating shaft in the axial direction of the rotating shaft. With a movement control piece that can be elastically deformed between the cylinder block and a part of the cylinder block, it can rotate integrally with the rotating shaft.
The housing has a valve plate portion provided with a substantially arc-shaped suction port and a discharge port that can intermittently communicate with each cylinder port of the cylinder block, and a cylinder block end portion is provided on an end surface of the valve plate portion. It is supported while being slidably contacted, and the low pressure side pipeline of the external fluid pressure circuit is connected to the suction port, and the high pressure side pipeline of the fluid pressure circuit is connected to the discharge port.
When the pressure of the working fluid sent from the discharge port to the high-pressure side pipeline as a pump becomes excessively high, the movement control piece is elastically deformed by the axial force of the rotating shaft based on the pressure applied from the working fluid to the cylinder block. A piston pump characterized by allowing the cylinder block to move relative to the rotating shaft in the axial direction and separating the cylinder block from the valve plate portion of the housing. A cylinder block having a rotating shaft, a cylinder block having a plurality of cylinders arranged around the rotating shaft substantially parallel to the axis of the rotating shaft and rotationally symmetrical, and a cylinder block reciprocatingly inserted and arranged in each cylinder of the cylinder block. A piston that projects one end from the cylinder, a swash plate that is arranged so as to face one end of each piston and is in contact with one end of each piston, a part of the rotating shaft, a cylinder block, a piston, and a swash plate. In an axial type piston pump provided with a rotating shaft and a housing that rotatably supports a cylinder block while accommodating a portion inside.
The cylinder block is provided with a plurality of cylinder ports communicating with each cylinder at the end opposite to the protruding side of one end of the piston, and is made rotatable integrally with the rotating shaft.
The housing has a valve plate portion provided with a substantially arc-shaped suction port and a discharge port that can intermittently communicate with each cylinder port of the cylinder block, and a cylinder block end portion is provided on an end surface of the valve plate portion. The suction port is connected to the low pressure side pipeline of the external fluid pressure circuit, and the discharge port is connected to the high pressure side pipeline of the fluid pressure circuit.
The rotating shaft can rotate in the housing with at least an elastically deformable movement control piece interposed between a part of the rotating shaft and a part of the housing in the axial direction of the rotating shaft. Being supported
When the pressure of the fluid sent from the discharge port to the high-pressure side pipeline as a pump becomes excessively high, the movement control piece is elastically deformed by the axial force of the rotating shaft based on the pressure applied from the fluid to the cylinder block. A piston pump characterized in that at least the cylinder block and the rotating shaft are allowed to move relative to the housing of the rotating shaft in the axial direction, and the cylinder block is separated from the valve plate portion of the housing. In the piston pump according to claim 1 or 2,
It is formed in a bellows tubular shape with one end closed, and can be expanded and contracted so that the other end side that opens between the piston and the cylinder port in each cylinder of the cylinder block is directed toward the cylinder port side. Equipped with a liner part
The side where the liner portion is interposed between the other end of the piston and the peripheral portion of the cylinder port of the cylinder block with elastic deformation that is previously contracted in the axial direction of the rotating shaft, and the piston protrudes from the cylinder by elastic restoring force. A piston pump characterized by urging. In the piston pump according to claim 3,
The liner portion is provided with a convex portion protruding from a closed one end portion.
The piston is provided with a recess at the other end.
A piston pump characterized in that a convex portion of a liner portion and a concave portion of a piston are engaged in the cylinder.

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