JPH07217531A - Variable displacement hydraulic device - Google Patents

Abstract

PURPOSE:To smooth sliding motion between a control cylinder and a cylinder guide so as to enable long-term operation. CONSTITUTION:A variable displacement piston pump has a bias cylinder and a control cylinder 10 for controlling the inclined rotation angle of a yoke for holding a cam plate to change displacement, and a bias cylinder guide and a control cylinder guide 11 for supporting the respective cylinders slidably. A spiral groove 16 with one end 16a opened into the cylinder and with the other end 16b closed is formed at either one of the respective sliding faces between the respective cylinders and cylinder guides. An operating fluid in the cylinder is led into each sliding clearance through the groove 16 so as to reduce contact face pressure during high pressure operation and to prevent seizure during low pressure operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement hydraulic device used as a power transmission mechanism for industrial machines and vehicles.

[0002]

2. Description of the Related Art Conventionally, a swash plate type, a swash shaft type or a radial type piston pump, a piston motor, a vane pump or a vane motor, etc. have been known as this type of variable displacement type hydraulic device.

FIG. 5 is a longitudinal sectional view showing an example of a commonly used swash plate type variable displacement piston pump.
A cylinder block 2 which is a rotating member is rotatably incorporated in the inside of a main body 1 of the apparatus, and a rotation transmission shaft 3 is provided on a central axis A which is a main shaft of the cylinder block 2.
And the rotational force from a drive motor (not shown) is transmitted to the cylinder block 2 via the rotation transmission shaft 3. A plurality of cylinders 2a are provided on the circle one pitch from the center of the cylinder block 2 in parallel with the center axis A and at equal intervals. Each of the cylinders 2a is a piston member which is a movable member that reciprocates. 4 is slidably inserted.

A swash plate 5 is provided inside the main body 1 of the apparatus, which constitutes a capacity varying means with an arbitrary inclination with respect to the center axis A of the cylinder block 2. One end of each piston member 4 is provided with a swash plate 5. The formed spherical portion 4 a is swung freely by a piston shoe 7 connected by an annular shoe plate 6 and slidably contacts the swash plate 5.

A cradle type yoke 8 for integrally holding the swash plate 5 has its swing shaft 8a slidably slidably contacting a bearing 9 formed integrally with the main body 1 of the apparatus, and the central axis A of the cylinder block 2 It swings around a rotation center line X (the rotation center line of the swing shaft 8a) which is orthogonal to.

A control cylinder 10 is fixed to the upper part of the apparatus main body 1, and a control cylinder guide 11 is fixed to the apparatus main body 1.
The control cylinder 10 is slidably mounted on one end of the control cylinder 10, and one end of the control cylinder 10 is pressed against the upper end of the yoke 8. A bias cylinder 12, which is another control cylinder, is slidably mounted on a fixed bias cylinder guide 13 at the bottom of the apparatus body 1. One end of the bias cylinder 12 is urged by a spring 14 at the lower end of the yoke 8. Being crimped by. The control cylinder 10 and the control cylinder guide 11 and the bias cylinder 12 and the bias cylinder guide 13 constitute hydraulic cylinders for controlling the inclination of the swash plate 5, respectively.

Further, a valve plate 15 is provided on the end surface of the apparatus body 1.
Is fixed. This valve plate 15 is used for the cylinder block 2
Is in sliding contact with the end surface of the cylinder block 2 and forms a seal portion for the fluid to be supplied to the cylinder portion 2a together with the bearing of the cylinder block 2. The valve plate 15 has a suction side kidney port which is a fluid supply hole and a discharge side kidney port (which is not shown) which is a fluid discharge hole on a pitch circle facing the cylinder portion 2a. In FIG. 5, reference numeral 20 is a control valve that controls the pressure of the hydraulic fluid introduced into the control cylinder 10.

FIG. 6 is an explanatory view showing the operating principle of this type of swash plate type variable displacement piston pump. The hydraulic fluid having a pressure controlled by the control valve 20 is supplied to the oil passage 11a formed in the control cylinder guide 11 to press the control cylinder 10 against the upper portion of the yoke 8 integrated with the swash plate 5. . The pump discharge pressure acts on the oil passage 13a formed in the bias cylinder guide 13 to press the bias cylinder 12 together with the spring 14 against the lower portion of the yoke 8. In this way, the yoke 8 swings by guiding the pressurized liquid to the control cylinder 10, and the tilting angle of the yoke 8 determined by the balance with the moment of the bias cylinder 12 determines the discharge flow rate of the pump.

The control cylinder 10 and the control cylinder guide 11, the bias cylinder 12 and the bias cylinder guide 13 each have a sliding surface which constitutes a bearing surface and a sealing surface, both of which have wear resistance and wear resistance.
Seizure resistance is required. For this reason, it has been customary to use low-carbon steel that has undergone a surface treatment such as carburizing.Furthermore, an annular groove is formed on either one of these sliding contact surfaces in the radial direction of each cylinder. In addition to maintaining the hydraulic equilibrium of the above, it has been attempted to prevent running out of oil on each sliding contact surface.

The above is the structure of the swash plate type variable displacement piston pump. In the swash shaft type piston pump, the cylinder block and the rotation transmission shaft are connected by a universal link so that the relative angle is variable, and the end of the rotation transmission shaft is connected. The piston guide plate provided in the section and the piston are connected by a piston rod, and the piston reciprocates by the inclination of the cylinder block and the rotation transmission shaft.The inclination of the yoke that holds the cylinder block is controlled by the control cylinder and the bias cylinder. The points controlled by and are similar to those of the swash plate type.

Further, in radial type piston pumps and vane pumps, pistons and vanes radially slidably mounted in a bore of a rotor which is rotated by being driven by a main shaft are mounted on an outer eccentric cam ring by centrifugal force and hydraulic pressure. The fluid is returned by being pressed and rotated from the inside, and the return capacity can be changed by changing the amount of eccentricity.

The structure of the piston motor and the vane motor is almost the same as that of the piston pump and the vane pump, and the operating principle is opposite. That is, the piston or vane is reciprocated by the pressure of the working fluid supplied into the bore of the rotary member, and the motion is converted into the rotation of the rotary member.

[0013]

However, generally, in such a variable displacement type hydraulic device, for example, in the swash plate type variable displacement piston pump as shown in FIG. 5, the control cylinder 10 and the bias cylinder 12 are provided. External force acts in a direction orthogonal to the sliding direction, and the cylinders are always in slidable contact with the cylinder guides 11 and 13, respectively.
FIG. 7 is an explanatory view showing an external force acting on a control cylinder 10 of this type of piston pump. The control cylinder 10 is a reaction force F perpendicular to a plate surface of a swash plate 5 held by a yoke 8.
Is receiving.

The direction of this reaction force F is the control cylinder guide 1
As it intersects with the Y axis direction of 1, the control cylinder 10
A component force F1 parallel to the axis Y and a component force F2 in a direction orthogonal thereto are generated at one end of the. As a result, the control cylinder 1
0 is tilted counterclockwise with respect to the control cylinder guide 11 and is in a one-side contact state, and the control cylinder 10 receives the reaction forces F3 and F4 from the control cylinder guide 11, and the gaps between the two become uneven.

As a result, the side where the opening of the control cylinder 10 contacts the control cylinder guide 11 (lower side in FIG. 7) is closed, and the opposite side (upper side) is opened, and the oil passage 11 is opened.
The hydraulic fluid introduced into the control cylinder 10 through a is leaked to the gap between the control cylinder guide 11 and the pressure difference between the internal pressure and the external pressure.

At this time, particularly in the control cylinder, the hydraulic fluid flowing through the narrow sliding gap between the control cylinder 10 and the control cylinder guide 11 suddenly expands and the pressure drops in the opening-side clearance. When the internal pressure is high, a sharp pressure odor is produced. On the other hand, the hydraulic fluid having a higher pressure than the opening side is introduced into the sliding gap on the closing side.

FIG. 8 is an explanatory view showing a pressure distribution state of the hydraulic fluid in the control cylinder when the annular groove is not formed on the sliding contact surface between the control cylinder 10 and the control cylinder guide 11. As can be seen from FIG. 8, when the annular groove is not formed on the sliding contact surface between the control cylinder 10 and the control cylinder guide 11, the opening S side of the control cylinder 10 and the control cylinder guide 11 contact the side S. It can be expected that the effect of pressing downward is to reduce the contact pressure.

Therefore, when the pressure in the control cylinder becomes particularly high, the frictional resistance with the control cylinder guide becomes smaller if the annular groove is not provided in the sliding contact portion, but the operation in the control cylinder becomes smaller. When the fluid pressure becomes extremely low, the working fluid does not flow into the sliding gap between the control cylinder and the control cylinder guide, and they become solid contact with each other. Depending on the situation, there was a problem that it burned and was destroyed.

This problem also applies to the sliding contact portion between the bias cylinder 12 and the bias cylinder guide 13. The present invention has been made in view of the above points, and it is an object of the present invention to smoothly slide a displacement control cylinder and a cylinder guide to enable long-term operation.

[0020]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention achieves the above-mentioned object by a rotating member that rotates in synchronism with the rotation of a main shaft, and a volume change caused by reciprocating movement in the rotating member. A variable displacement liquid having a movable member for performing repatriation, a capacity varying means for varying the volume of revolving capacity of the main shaft per revolution to change the recirculation capacity, and a hydraulic cylinder for controlling the capacity varying means. In the pressure device, there is provided a variable displacement hydraulic device in which a spiral groove is formed on one of the sliding contact surfaces of the fixed side and the movable side of the hydraulic cylinder.

Further, in the above variable displacement type hydraulic device, it is more preferable that a plurality of spiral grooves are formed at equal intervals in the phase direction. One end of the spiral groove is opened inside the hydraulic cylinder and the other end is opened. It is preferably closed.

[0022]

With the variable displacement hydraulic device according to the present invention configured as described above, the spiral groove formed on one of the sliding contact surfaces of the fixed side and the movable side of the hydraulic cylinder is
Unlike the annular groove, the effect of creating a hydraulic equilibrium state is low, and the pressure distribution is almost the same as when using a grooveless cylinder, reducing the solid contact surface pressure when the pressure inside the cylinder is high. Has an effect on. Then, even when the pressure of the hydraulic fluid in the cylinder is relatively low, the hydraulic fluid can be guided to the sliding gap between the cylinder and the cylinder guide through the above-mentioned spiral groove, and smooth operation becomes possible. .

By forming a plurality of spiral grooves, hydraulic imbalance other than external force acting in the sliding direction of the movable side of the hydraulic cylinder can be prevented. Furthermore, if one end of the spiral groove is opened inside the hydraulic cylinder and the other end is closed, the sliding gap between the cylinder and the cylinder guide is positively affected even when the pressure of the hydraulic fluid in the hydraulic cylinder is low. The hydraulic fluid can be effectively guided, and the sliding resistance can be further reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a perspective view showing a control cylinder portion of a swash plate type variable displacement piston pump according to a first embodiment of the present invention, and other configurations are the same as those in FIG.

In the first embodiment, a spiral groove 16 is formed on the outer peripheral surface of the control cylinder guide 11 on the fixed side of the control hydraulic cylinder, and one end 16a of the groove 16 is formed inside the control cylinder 10 on the movable side. The other end 16b is closed.

By forming such a spiral groove 16 in the control cylinder guide 11, the hydraulic fluid having the control pressure introduced into the control cylinder 10 through the oil passage 11a is supplied to the control cylinder guide 11. And is guided to the sliding contact surface with the control cylinder guide 11. As a result, as shown in FIG. 2, the end of the control cylinder 10 is moved to the control cylinder guide 1
The pressure on the side of the point S that contacts 1 is increased, and the pressure distribution becomes close to that in the case of the grooveless piston shown in FIG. 8, and the contact surface pressure reducing effect on the side of the point S can be obtained.

Further, the control cylinder 1 passes through this groove 16.
Even if the hydraulic fluid pressure is extremely low, the hydraulic fluid guided to the sliding contact surface between 0 and the control cylinder guide 11 can positively guide the hydraulic fluid to the sliding gap between the two, so that smooth operation can be achieved. It will be possible.

In the above-described first embodiment, the external force F1 shown in FIG. 7 depends on the positional relationship between the cut and the cut of the spiral groove 16 formed in the control cylinder guide 11.
There may be some hydraulic imbalance in the direction of.

FIG. 3 is a perspective view showing a control cylinder portion of a second embodiment of the present invention which solves the above problems. In the second embodiment, a plurality of (two in the figure) spiral grooves 17 are arranged on the outer peripheral surface of the control cylinder guide 11 at equal intervals in the phase direction.
A and 17B are formed. In this way, a plurality of grooves 17
By forming A and 17B, it becomes possible to prevent hydraulic imbalance other than the external force of the control cylinder 10 acting in the axial direction of the control cylinder guide 11.

Further, the ends 16a, 17a, 17 of the spiral grooves 16, 17A, 17B of the first and second embodiments are formed.
b is opened in the control cylinder 10 and the other ends 16b, 17
When c and 17d are closed, the control cylinder 1
The pressure at the point S (see FIG. 2) on the closing side of 0 is further increased, and the contact surface pressure with the control cylinder guide 11 can be further reduced.

According to these first and second embodiments, the spiral groove 1 formed on the outer peripheral surface of the control cylinder guide 11 is described.
Since 6, 17A and 17B can be machined by the same machine tool (lathe etc.) as the machining of the outer diameter of the control cylinder guide 11, the extra cost required for the groove machining is almost unnecessary and can be supplied at a low cost. it can.

Next, FIG. 4 is a perspective view showing the inside of the control cylinder according to the third embodiment of the present invention, which is cut away.
In the third embodiment, a spiral groove 18 is formed on the inner peripheral surface of the control cylinder 10 in a sliding contact surface with the control cylinder guide 11, and the hydraulic fluid inside the control cylinder 10 is controlled through the groove 18. It is guided to the sliding gap between the cylinder 10 and the control cylinder guide 11.

By forming such a spiral groove 18 on the inner peripheral surface of the control cylinder 10, the formation range of the groove 18 can be formed over the entire length of the inner peripheral surface of the control cylinder 10 in the longitudinal direction. Therefore, the stroke of the control cylinder 10 can be increased. Also in the third embodiment, the hydraulic fluid in the control cylinder 10 is guided to the sliding gap with the control cylinder guide 11 through the groove 18, and the pressure distribution is almost the same as that in FIG. 2 of the first embodiment. Therefore, the contact surface pressure reducing effect can be obtained, and at the same time, smooth operation of the control cylinder 10 at low pressure can be achieved.

Further, in the above-described third embodiment, if a plurality of spiral grooves are formed on the inner peripheral surface of the control cylinder 10 at equal intervals in the phase direction, the control cylinder guide may be formed as in the second embodiment. Control cylinder 10 acting in the axial direction of 11
It is possible to prevent hydraulic imbalance other than the external force.

When one end of these spiral grooves is opened on the far side of the control cylinder 10 and the other end is closed on the front side thereof, the pressure at the point S (FIG. 2) on the close side of the control cylinder 10 is reduced. It can be further raised to further reduce the contact surface pressure with the control cylinder guide 11.

In the above first to third embodiments, the case where the present invention is applied to the control cylinder 10 has been described, but the bias cylinder 12 which is another control cylinder having the same structure as the control cylinder 10 is described. By forming a spiral groove in the same manner on the side as well, severe wear that occurs on the sliding surface between the bias cylinder 12 and the bias cylinder guide 13 during high pressure operation and seizure due to oil film breakage that occurs during low speed operation can be avoided. Can be prevented.

Further, in each of the above embodiments, the fixed side of the control cylinder and the bias cylinder for controlling the tilt angle of the swash plate is slidably inserted in the shaft-shaped member, and the movable side is slidably inserted in the shaft-shaped member. Although a cylindrical member is used, the fixed side is a cylindrical member,
It is also possible to make the movable side an axial member.

Further, the present invention is not limited to the swash plate type piston pump and the piston motor, and may also be applied to the swash plate type piston pump, the piston motor, the radial type piston pump, the piston motor, the vane pump, the vane motor and the like. The number of hydraulic cylinders for control is not limited to two, and may be one or three or more.

[0039]

As described above, in the variable displacement hydraulic device according to the present invention, the spiral groove is formed on one of the sliding contact surfaces of the fixed side and the movable side of the control hydraulic cylinder. Therefore, it is possible to reduce the surface pressure of frictional sliding that occurs during high-pressure operation, and at the same time, to actively introduce the hydraulic fluid to the above-mentioned sliding contact surface during low-pressure operation, and to prevent burning due to oil film shortage. It is possible to prevent sticking.

Further, by forming a plurality of spiral grooves, it is possible to prevent the occurrence of hydraulic imbalance other than the external force that should originally act on the movable portion of the hydraulic cylinder. Furthermore, by opening one end of the spiral groove inside the hydraulic cylinder and closing the other end, the hydraulic fluid is actively guided to the sliding gap even when the hydraulic fluid pressure inside the cylinder is extremely low. It is possible to operate smoothly.

[Brief description of drawings]

FIG. 1 is a perspective view showing a control cylinder portion of a first embodiment of the present invention.

FIG. 2 is an explanatory view showing a pressure distribution state of the hydraulic fluid which similarly acts on the control cylinder.

FIG. 3 is a perspective view showing a control cylinder portion of a second embodiment of the present invention.

FIG. 4 is a perspective view showing a control cylinder portion of a third embodiment of the present invention by cutting out the control cylinder.

FIG. 5 is a vertical sectional view showing an example of a swash plate type piston pump.

FIG. 6 is an explanatory view showing the operating principle of this type of swash plate type piston pump.

FIG. 7 is an explanatory diagram showing a force that similarly acts on the control cylinder.

FIG. 8 is an explanatory diagram showing a pressure distribution state of the hydraulic fluid that similarly acts on the control cylinder.

[Explanation of symbols]

 1: Device body 2: Cylinder block 4: Piston member 5: Swash plate 8: Yoke 10: Control cylinder 11: Control cylinder guide 12: Bias cylinder 13: Bias cylinder guide 16, 17A, 17B, 18: Spiral groove

Claims (3)

[Claims] 1. A rotary member that rotates in synchronization with the rotation of a main shaft, a movable member that sends back a fluid by a volume change caused by reciprocating motion in the rotary member, and a rotary member per one rotation of the main shaft. In a variable displacement type hydraulic device having a capacity varying means for varying a volume change amount to change a return capacity thereof and a hydraulic cylinder for controlling the capacity varying means, a fixed side and a movable side of the hydraulic cylinder are provided. A variable displacement hydraulic device, wherein a spiral groove is formed on either one of the sliding contact surfaces. 2. A variable displacement type hydraulic device according to claim 1, wherein a plurality of spiral grooves are formed in equal distribution in the phase direction. 3. The spiral groove has one end opened inside the hydraulic cylinder and the other end closed.
Alternatively, the variable displacement hydraulic device according to item 2.