JPH08338357A - Variable displacement type piston pump - Google Patents

Abstract

PURPOSE: To obtain a variable displacement type piston pump of a minimum capacity starting type which can prevent a sudden increase of inclination of a swash plate. CONSTITUTION: A control piston 15 presses a swash plate 8 in the direction of the maximum inclination by the hydraulic force of an operating oil fed to a control chamber 14. And a restoration spring 16 energizes the swash plate 8 in the direction of the minimum inclination. By the force relation between the hydraulic force fed to the control chamber 14α of a control cylinder 14, and the spring force of the restoration spring 16, the inclination of the swash plate 8 is determined. And the control chamber 14α and a discharge passage 13 are connected through a pressure leading passage 30, and a throttle is placed on the pressure leading passage 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement piston pump whose discharge capacity is changed by adjusting the tilt angle of a swash plate.

[0002]

2. Description of the Related Art For example, as a variable displacement piston pump (hereinafter, simply referred to as a pump) used as a hydraulic pressure generation source of a hydraulic circuit, there is one disclosed in Japanese Utility Model Laid-Open No. 49-16806. That is, in the pump of this publication, the cylinder block is rotated integrally with the rotary shaft. The piston is housed in the cylinder bore of the cylinder block, and is biased by the pressing spring housed in the cylinder bore in a direction projecting from the bore. The swash plate receives one end of the piston and defines the piston stroke by the inclination with respect to the rotation axis direction. The tilt angle of the swash plate, that is, the discharge capacity of the pump, is the force of the return spring that biases the swash plate in the maximum tilt direction and the force of the control piston that pushes the swash plate in the minimum tilt direction against the return spring. It is adjusted according to the relationship.

In the pump having the above structure, the return spring urges the swash plate in the maximum inclination direction, and when the pump is stopped, the opposing force of the control cylinder is lost, and the swash plate is in the maximum inclination state by the return spring. Will be stationary. Therefore,
At the time of next operation, the pump will be started with the maximum inclination angle, that is, the maximum capacity, and there is a problem that the starting torque becomes extremely large. In addition, since the control hydraulic pressure of the control cylinder cannot be obtained in the non-cargo handling state, the minimum capacity operation cannot be performed. Therefore, a disconnecting device for cutting off the input to the pump is required.

In order to solve the above problems, for example, the pump disclosed in Japanese Patent Laid-Open No. 6-257558 by the present applicant is effective. The return spring in the pump is
The swash plate is biased in the minimum tilt direction, and the control piston pushes the swash plate in the maximum tilt direction against the spring force. Therefore, the swash plate is held at the minimum inclination angle by the return spring when the cargo is not loaded, and the pump can be operated with the minimum capacity, so that the disconnecting device becomes unnecessary.

[0005]

By the way, in the pump disclosed in Japanese Unexamined Patent Publication No. 6-257558, the pressure spring is
It is housed in a spring housing chamber formed between the cylinder block and the rotating shaft. The shoes are connected to one end of each piston, and each shoe is moored by a retainer. Then, the spring force of the pressing spring acts on the retainer via a spring receiver, a pivot, etc., so that each shoe is pressed against the swash plate.

However, the above-mentioned pump has a complicated structure due to a retainer, a pivot, etc., resulting in a high cost. In addition, a space for accommodating the pressing spring is required between the cylinder block and the rotary shaft, which causes a problem of increasing the size of the cylinder block and the size of the pump.

Therefore, in the minimum capacity starting type pump disclosed in Japanese Unexamined Patent Publication No. 6-257558, the actual opening of the Japanese Utility Model Publication No. 49-168
It is conceivable that the technique disclosed in Japanese Patent Laid-Open No. 06-2006, that is, the pressing spring is housed in each cylinder bore to directly urge each piston in the swash plate direction. This eliminates the need for a retainer for mooring the shoe, a pivot, and the like, and allows the pump to be configured easily and inexpensively. In this case, even if the spring is housed in each cylinder bore, the cost can be reduced as compared with a retainer, a pivot, or the like. Further, since it is not necessary to secure a space for accommodating the pressing spring in the cylinder block, there is an advantage that the cylinder block can be made compact and the entire pump can be downsized.

By the way, in the pump of the minimum capacity starting type, when the extension operation of the control piston, that is, the tilting of the swash plate in the direction of the maximum tilt is rapidly performed, the piston is mainly caused by its own inertial force. In some cases, the shoe cannot rise to the tilt of the swash plate and the shoe rises above the swash plate. Therefore, in the pump combining the techniques of the above two publications, since the retainer for mooring each shoe is deleted, the shoe raised with respect to the swash plate interferes with the adjacent shoe and is damaged. There were problems such as.

In order to prevent this, it is conceivable to increase the spring force of the pressing spring to increase the biasing force of the piston in the swash plate direction. However, with this method, the sliding contact resistance of the shoe with respect to the swash plate becomes large, resulting in excessive power loss and seizure of both.

The present invention has been made in view of the problems existing in the above-mentioned prior art, and an object thereof is to provide a variable displacement piston pump capable of preventing a sudden increase in the inclination angle of a swash plate. To do.

[0011]

In order to achieve the above object, according to the invention of claim 1, a housing provided with a suction passage and a discharge passage and a rotary shaft supported by the housing are integrally rotatably fitted. A cylinder block, a cylinder bore formed in the cylinder block and alternately communicating with the suction passage and the discharge passage as the rotary shaft rotates, a piston housed in the cylinder bore, and one end of the piston. Between the swash plate and the housing, a swash plate that receives the connected shoes and defines a piston stroke according to the tilt angle, a pressing spring that is housed in the cylinder bore and biases the piston in the swash plate direction, And a control piston that is provided in the housing and that pushes the swash plate in the maximum tilt direction. And trawl cylinder, a variable displacement piston pump having a pressure guide passage for connecting the discharge passage and the control chamber of the control cylinder, and a diaphragm interposed on Doshirube passage.

According to the second aspect of the invention, the pressure guiding passage is formed in the housing by punching. In the invention of claim 3, the throttle is configured by forming a part of the pressure guiding path as a fine hole.

In the invention of claim 4, a capacity control valve for connecting the discharge passage and the control chamber in response to a pressure increase in the pressure guiding path is interposed on the pressure guiding path, and the throttle has a capacity. It is interposed between the control valve and the control chamber.

According to a fifth aspect of the present invention, the capacity control valve is integrally provided with the housing.

[0015]

According to the first aspect of the invention having the above-mentioned structure, each piston is pressed against the swash plate through the shoe by the pressing spring housed in each cylinder bore. When the cylinder block is rotated integrally with the rotary shaft, the piston is reciprocated in the stroke defined by the swash plate. Therefore, the hydraulic oil sucked into the cylinder bore through the suction passage is discharged by the pump action by connecting the cylinder bore to the discharge passage.

By adopting the construction in which the pressing spring is housed in each cylinder bore as described above, the spring force of the pressing spring can directly act on each piston,
The retainer for mooring the shoes of each piston and the pivot for applying the spring force of the pressing spring to the retainer, which have been conventionally required, are unnecessary. Further, it is not necessary to secure a space for accommodating the pressing spring between the cylinder block and the rotary shaft, and the cylinder block can be made compact to downsize the entire pump.

A throttle is provided in the middle of the pressure guiding path. Therefore, even if the pressure in the discharge passage is rapidly increased, the hydraulic oil flowing into the control chamber via the pressure guiding passage is throttled by the throttle, so that the control piston extends slowly. As a result, it is possible to prevent a sudden increase in the tilt angle of the swash plate, and the piston can easily follow the tilting of the swash plate. Therefore, it is possible to prevent damage to the shoe due to lifting of the shoe. Further, since the pressing spring does not have to have a strong spring force, wear of the shoe and the swash plate due to sliding contact with each other and power loss can be reduced.

According to the second aspect of the present invention, the pressure guiding passage can be formed by making a hole in the housing, and the number of parts for constructing the pressure guiding passage can be reduced as compared with the case where a pipe or the like is externally attached to the pump. It can be reduced.

According to the third aspect of the present invention, a part of the pressure guiding path is a pore and the same portion is a diaphragm. Therefore, it is not necessary to make the entire pressure guiding path into fine pores that are difficult to process, and the processing becomes easy.

According to the fourth aspect of the present invention, the displacement control valve is operated in response to the pressure increase in the pressure guide passage, and the discharge passage and the control chamber are connected. Therefore, the control piston is extended by the hydraulic pressure introduced into the control chamber, the swash plate is pushed in the maximum tilt direction, and the discharge capacity of the pump is increased.

Here, the throttle is interposed between the capacity control valve and the control chamber, and the hydraulic pressure introduced into the capacity control valve is not restricted. Therefore, the displacement control valve operates without delay with respect to the pressure increase in the discharge passage.

According to the invention of claim 5, the displacement control valve is provided integrally with the housing. So, for example,
Since the housing also serves as the casing of the valve,
The number of parts can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a hydraulic system including a variable displacement piston pump (hereinafter, simply referred to as a pump) of the present embodiment. First, the pump will be described. The front housing 1 is the center housing 2
Is joined and fixed to the front end of the rear housing 3 and the rear housing 3 is joined and fixed to the rear end of the center housing 2. A closed space formed by the housings 1 to 3 forms a crank chamber 4. The rotary shaft 5 is supported in the crank chamber 4 between the front housing 1 and the rear housing 3. The rotary shaft 5 is connected at its protruding end portion from the front housing 1 to a power take-out device (not shown) so that it can be directly rotated by the engine.

The cylinder block 6 includes the crank chamber 4
In the inside, it is spline-fitted to the rotary shaft 5 so as to be integrally rotatable. A plurality of cylinder bores 6α are formed around the rotary shaft 5 in the cylinder block 6, and pistons 7 are housed in the respective cylinder bores 6α. The swash plate 8 is supported by the front housing 1 in the crank chamber 4 via a support shaft 8α and can swing back and forth in the direction of the rotation axis 5. The pressing spring 9 is arranged in each cylinder bore 6α, and each piston 7 is connected to the swash plate 8a.
The cylinder block 6 is biased toward the rear housing 3 while being biased toward the rear housing 3. Therefore, the piston 7
Is pressed against the swash plate 8 with the shoe 10 connected to one end thereof via spherical joints 7α and 10α, and the cylinder block 6 is attached to the valve plate 11 fixed to the inner end wall surface of the rear housing 3. It has been pressed.

By rotating the cylinder block 6 integrally with the rotary shaft 5, each piston 7 is reciprocated in a stroke defined by the tilt angle of the swash plate 8, and the cylinder bore 6α is moved by the valve plate 11. Are alternately communicated with the suction port 11α and the discharge port 11β which are formed in a circular arc shape. As a result, the hydraulic oil is sucked into the cylinder bore 6α from the suction port 11α, and the hydraulic oil in the cylinder bore 6α is pumped to the discharge port 1α.
It is discharged from 1β. The suction passage 12 and the discharge passage 13 are formed in the rear housing 3 and communicate with the suction port 11α and the discharge port 11β, respectively.

The control cylinder 14 is cantilevered on the rear housing 3, and a control piston 15 is accommodated in the control cylinder 14. The control piston 15 pushes the swash plate 8 in the maximum tilt direction by the hydraulic pressure of the hydraulic oil supplied to the control chamber 14α of the control cylinder 14. A return spring 16 as a biasing means is interposed between the swash plate 8 and the front housing 1 and biases the swash plate 8 in the minimum tilt angle direction. Then, the control cylinder 14
The inclination angle of the swash plate 8 is determined by the force relationship between the hydraulic pressure supplied to the control chamber 14α and the spring force of the return spring 16 via the swash plate 8. Since the control chamber 14α in the control cylinder 14 is at atmospheric pressure when the engine is stopped, the swash plate 8 is at the minimum tilt position (about 0.1 to 4 °) due to the spring force of the return spring 16. That is, the minimum ejection volume position close to zero volume is maintained.

A cargo handling switching valve 21, which also functions as a capacity control valve for controlling the discharge capacity of the pump, is arranged in the suction passage 12 and the discharge passage 13. Further, the lifting cylinder 22 serving as a cargo handling actuator has a suction pipe line 23 and a discharge pipe line 2 with respect to the suction passage 12 and the discharge passage 13.
4 are connected. In addition, in FIG.
Is a relief valve for releasing the pressure to the tank T and protecting the circuit when the pressure in the circuit becomes excessive.

Next, the cargo handling switching valve 21 will be described. As shown in FIGS. 1 to 4 (FIGS. 2 to 4 are cross-sectional views from a direction different from FIG. 1), the first and second valve chambers 1
3α and 13β are provided in the rear housing 3 in the middle of the discharge passage 13. The first valve chamber 13α and the valve chamber 12α of the suction passage 12 are connected by a first communication passage 25. Further, the first valve chamber 13α and the second valve chamber 13β are communicated with each other by a second communication passage 26.
Then, the spool 27 is operated by the operation lever 28,
A neutral (non-loading) position (FIG. 2) that opens the first communication passage 25 and closes the second communication passage 26, the first communication passage 25, and the second communication passage 25.
Select the first cargo handling (up) position (FIG. 3) that closes the communication passage 26 together, or the second cargo handling (down) position (FIG. 4) that opens the first communication passage 25 and the second communication passage 26. It is arranged by switching.

The check valve 29 is interposed in the discharge passage 13 located between the first valve chamber 13α and the second valve chamber 13β. The check valve 29 allows the flow of hydraulic oil from the first valve chamber 13α to the second valve chamber 13β side above a certain pressure (spring force), and blocks the flow in the opposite direction. There is.

As shown in FIGS. 1 and 5, the control chamber 14α of the control cylinder 14 has a pressure guide passage 30.
Through the discharge passage 13 on the upstream side of the first valve chamber 13α. In the present embodiment, a part of the pressure guiding passage 30 is formed as a fine hole, and the same portion forms the throttle 30α.

Next, the operation of the hydraulic system having the above construction will be described. When the engine is stopped, the cargo handling switching valve 21
Has been switched to the non-loading position (FIG. 2). In this state, the first communication passage 25 is opened and the second communication passage 26 is closed, and the pressure in the control chamber 14α is the tank pressure. Therefore, the swash plate 8 is held at the minimum tilt angle position by the return spring 16.

When the engine is started in this state, the rotary shaft 5 is rotated via the power take-out device. Therefore, the pump is started in the minimum capacity state. At this time, as described above, the first communication passage 25 allows the first valve chamber 13α of the discharge passage 13 to be released.
Since the valve chamber 12α of the suction passage 12 is communicated with
The pressure in the pressure guiding passage 30 is never increased. Therefore,
Since the pump continues to operate in the minimum capacity state, it is not necessary to interpose a disconnecting device or the like with the power take-off device.

From this state, when the cargo handling switching valve 21 is switched from the non-cargo handling position to the first cargo handling position (FIGS. 2 to 3), both the first communication passage 25 and the second communication passage 26 are closed. Become. Therefore, the discharge port 11β of the pump
A small amount of hydraulic oil is sent from the discharge passage 13 to the discharge passage 13.
At this time, due to the spring load of the check valve 29 provided in the middle of the discharge passage 13, the pressure inside the discharge passage 13 upstream of the valve 29 is increased. As a result, hydraulic oil is supplied from the pressure guiding passage 30 to the control chamber 14α of the control cylinder 14, and the control piston 15 is extended. Therefore, the swash plate 8 pushed by the control piston 15 is tilted in the maximum tilt direction, the discharge capacity of the pump is increased, and the discharge pressure is increased. As a result, the check valve 29 of the discharge passage 13 is opened, high-pressure hydraulic oil is supplied from the discharge conduit 24 to the working chamber 22α of the elevating cylinder 22, and the piston rod 22γ rises.

When lowering the lifted piston rod 22γ, the cargo handling switching valve 21 is moved from the first cargo handling position to the second cargo handling position.
A switching operation is performed to the cargo handling position (FIGS. 3 to 4). Then, the first and second communication passages 25 and 26 are opened, and the working chamber 2
The hydraulic oil in 2α is the discharge pipe line 24, the discharge passage 13, the second valve chamber 13β, the second communication passage 26, the first valve chamber 13α, the first communication passage 25, the valve chamber 12α, the suction passage 12, and the suction pipe. Road 23
Through the reservoir tank T, and the piston rod 22γ is lowered.

Further, since the discharge passage 13 and the suction passage 12 are communicated with each other, the pressure in the discharge passage 13 is drastically reduced, and the supply of hydraulic oil from the pressure guiding passage 30 to the control chamber 14α is stopped. It Therefore, the swash plate 8 is returned to the minimum tilt angle position (FIG. 1) by the return spring 16, and the pump shifts to the minimum displacement operation.

On the other hand, when the cargo handling switching valve 21 is switched to the neutral position while the piston rod 22γ is being raised (FIGS. 3 and 2), the closed first communication passage 25 is opened. Therefore, the pump is switched from the maximum capacity operation to the minimum capacity operation. Then, the check valve 29 blocks backflow of the working oil from the working chamber 22α, so that the piston rod 22γ is stopped at a predetermined position.

When the cargo handling switching valve 21 is again switched to the first cargo handling position (FIGS. 2 to 3), the open first communication passage 25 is closed. Therefore, the discharge passage 1
The high pressure on the downstream side of the second valve chamber 13β in No. 3 is rapidly introduced to the upstream side of the first valve chamber 13α. However, since the flow rate of the hydraulic oil introduced into the control chamber 14α via the pressure guiding passage 30 is throttled by the throttle 30α interposed on the pressure guiding passage 30, a rapid pressure increase in the control chamber 14α occurs. It can be suppressed. Therefore, the extension operation of the control piston 15 becomes slow, and a sudden increase in the tilt angle of the swash plate 8 is prevented. Therefore, the discharge capacity of the pump is slowly changed from the minimum capacity to the maximum capacity.

The present embodiment having the above-mentioned structure has the following effects. The discharge passage 1 is formed by the throttle 30α provided on the pressure guide passage 30.
Even when the pressure in 3 is rapidly increased, the extension operation of the control piston 15 can be slowed to prevent a sudden increase in the inclination angle of the swash plate 8. Therefore, the piston 7 can easily follow the tilting of the swash plate 8, the shoe 10 can be prevented from rising, and damage due to interference between the adjacent shoes 10 can be prevented. Further, since it is not necessary to increase the spring force of the pressing spring 9, it is possible to reduce the sliding contact wear and the power loss due to the pressing contact between the shoe 10 and the swash plate 8. A pressing spring 9 for pressing the piston 7 (shoe 10) against the swash plate 8 is housed in each cylinder bore 6α. Therefore, a spring force can be directly applied to each piston 7, and an expensive and complicated retainer, a pivot, or the like is not required, and the cost of the pump can be reduced. Further, since it is not necessary to interpose a pressing spring between the cylinder block 6 and the rotary shaft 5, the cylinder block 6 can be made compact and the entire pump can be made compact. The pressure guiding path 30 is formed by making a hole in the rear housing 3. Therefore, because of the structure of the pressure guiding path 30, the number of parts can be reduced as compared with the case where the pipe or the like is externally attached to the pump. The throttle 30α is configured by forming a part of the pressure guiding path 30 as a fine hole. Therefore, it is not necessary to make the entire pressure guiding passage 30 into a fine hole that is difficult to process, and the processing becomes easy. Since this pump is a minimum capacity start-up type, there is no problem that the starting torque at start-up becomes large. Further, in the non-carrying state, the swash plate 8 is moved by the return spring 16.
Is kept in the minimum tilt position so no disconnection device is needed to shut off the input to the pump. Therefore, the hydraulic system can be configured easily and inexpensively. A capacity control valve (cargo handling switching valve) 21 that controls the discharge capacity of the pump is provided integrally with the housing 3 of the pump. Therefore, for example, the rear housing 3 also serves as the casing of the valve 21, so that the number of parts can be reduced and the cost can be reduced. The cargo handling switching valve 21 has a capacity control function as well as a cargo handling switching function. Therefore, cargo handling switching and capacity control can be performed without separately providing a capacity control valve, and cost reduction can be achieved in a hydraulic system incorporating this pump.

[0039]

[Other Embodiment] Another embodiment of the present invention will be described below with reference to FIG. It should be noted that only the differences from the above embodiment will be described.

In the present embodiment, the minimum inclination angle of the swash plate 8 is set to approximately 0 °, and the control piston 15 is forcibly operated when the pump is started, so that the swash plate 8 is
It is designed to increase the inclination angle of.

That is, the solenoid 35 is attached to the outer wall of the rear housing 3, and the rod 35α of the solenoid 35 is connected to the protruding end of the control piston 15. Then, the solenoid 35 is operated by arbitrarily operating the main switch 36, and the control piston 15 is extended.

Therefore, when the pump is started, by operating the main switch 36, the inclination angle of the swash plate 8 is displaced from the minimum inclination angle to, for example, 2 to 5 degrees regardless of the hydraulic pressure in the pressure guide passage 30. To be done. The capacity control valve 37 is interposed on the pressure guiding passage 30 that connects the discharge conduit 24 and the control chamber 14α, and when the pressure in the pressure guiding passage 30 is above the set pressure in response to the pressure in the pressure guiding passage 30. The spool 37α is moved against the spring force to connect the discharge conduit 24 and the control chamber 14α.

In the present embodiment, the throttle 30α is interposed between the displacement control valve 37 and the control chamber 14α in the pressure guiding passage 30 and throttles the hydraulic oil introduced into the control chamber 14α. , The control piston 15 is prevented from extending rapidly. Therefore, the same effect as that of the above-described embodiment can be obtained.

Further, the throttle 30α is provided between the displacement control valve 37 and the control chamber 14α on the pressure guiding path 30, and the hydraulic oil introduced into the displacement control valve 37 is not throttled by the throttle 30α. Absent. Therefore, the capacity control valve 37 can appropriately respond to the pressure increase in the discharge conduit 24 and can perform an appropriate capacity control operation.

Furthermore, since the solenoid 35 forcibly extends the control piston 15 irrespective of the pressure in the discharge conduit 24 when the pump is started, the tilt angle of the swash plate 8 can be set to approximately 0 °. it can. Therefore,
The power loss during the minimum capacity operation can be reduced as compared with the pumps of the above-described embodiments.

The following embodiments can be carried out without departing from the spirit of the present invention. (1) The cargo handling switching valve 21 should be configured separately from the housings 1 to 3. (2) The cargo handling switching valve 21 and the pump capacity control function of the cargo handling switching valve 21 are configured by separate valves. (3) The pressure guiding path 30 should be a fine hole to have a throttling effect as a whole. (4) The hydraulic oil may be throttled by inserting and arranging a throttle pin in the pressure guide passage 30. In this way, the throttle amount can be simplified by preparing throttle pins having various outer diameters when assembling the pump and selecting the throttle pin according to the dimensional tolerance of the pressure guide passage 30 in each pump. And it can be adjusted appropriately. (5) By arranging the pipe material in the pressure guiding passage 30, the through hole of the pipe material is used as a throttle. (6) A wire slightly smaller than the hole is put in the pressure guide path 30 to form a diaphragm member, and both ends of the wire are bent to prevent the wire from coming off. (7) Instead of the return spring 16, the swing center (8
By decentering α) toward the bottom dead center side with respect to the central axis of the rotary shaft 5, the swash plate 8 is returned to the minimum tilt position by the sum of the spring force of the pressing spring 9.

The technical idea other than the claims that can be understood from the above embodiment will be described. The variable displacement piston pump according to claim 1, wherein the throttle is configured by inserting and arranging a throttle member in the pressure guiding path.

In this way, the adjustment of the diaphragm amount becomes easy and appropriate.

[0049]

According to the invention of claim 1, the pump can be constructed inexpensively and easily and further in a small size by accommodating the pressing spring in the cylinder bore. Then, it is possible to prevent the swash plate from suddenly increasing its inclination angle by the diaphragm, prevent the shoe from rising, and prevent the shoe from being damaged.

According to the invention of claim 2, the number of parts for the pressure guiding path can be reduced. According to the invention of claim 3, the processing of the drawing becomes easy. According to the invention of claim 4, the operation of the displacement control valve is appropriately performed in accordance with the pressure increase in the discharge passage.

According to the invention of claim 5, the number of parts can be reduced and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a hydraulic system including a variable displacement piston pump.

FIG. 2 is a partial cross-sectional view of the cargo handling switching valve, but the cross-sectional direction is different from that in FIG.

FIG. 3 is a partial cross-sectional view of a cargo switching valve.

FIG. 4 is a partial cross-sectional view of a cargo handling switching valve.

FIG. 5 is an enlarged view of a main part of FIG.

FIG. 6 is a diagram showing another embodiment, which is a circuit diagram including a pump.

[Explanation of symbols]

1 ... Front housing, 2 ... Center housing, 3 ...
Rear housing, 5 ... Rotating shaft, 6 ... Cylinder block,
6α ... Cylinder bore, 7 ... Piston, 8 ... Swash plate, 9 ... Pressing spring, 10 ... Shoe, 12 ... Suction passage, 13 ... Discharge passage, 14 ... Control cylinder, 14α ... Control chamber, 1
5 ... Control piston, 16 ... Return spring as biasing means, 30 ... Pressure guide path, 30α ... Throttle.

Front page continuation (72) Minoru Ogura Minoru Ogura 2-chome, Toyota-cho, Kariya city, Aichi Stock company Toyota Industries Corp.

Claims (5)

[Claims] 1. A housing provided with an intake passage and a discharge passage, a cylinder block which is integrally rotatably fitted to a rotation shaft supported by the housing, and the cylinder block which is formed in the cylinder block and rotates with the rotation shaft. The cylinder bore alternately communicating with the suction passage and the discharge passage, the piston housed in the cylinder bore, and the shoe connected to one end of the piston are received, and the piston stroke is defined according to the tilt angle. A swash plate, a pressing spring housed in the cylinder bore for urging the piston in the swash plate direction, and an urging means interposed between the swash plate and the housing for urging the swash plate in the minimum tilt direction. And provided on the housing,
A control cylinder provided with a control piston for pushing the swash plate in the maximum inclination direction, a pressure guiding passage connecting the control chamber of the control cylinder and the discharge passage, and a throttle interposed on the pressure guiding passage. Variable displacement piston pump. 2. The variable displacement piston pump according to claim 1, wherein the pressure guiding passage is formed by being bored in the housing. 3. The variable displacement piston pump according to claim 1, wherein the throttle is formed by forming a part of the pressure guide path as a fine hole. 4. A capacity control valve, which is connected to the discharge passage and the control chamber in response to an increase in pressure in the pressure guiding path, is interposed on the pressure guiding path, and the throttle restricts the capacity control valve and the control chamber. The variable displacement piston pump according to any one of claims 1 to 3, which is interposed between and. 5. The variable displacement piston pump according to claim 4, wherein the displacement control valve is provided integrally with the housing.