JPH0968155A - Piston type liquid pressure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wearing resistance and seizure resistance when a device is operated at a high pressure, by positioning a load force point in a radial direction, acting in a cylinder block, in the vicinity of the center in an axial direction of a spline part. SOLUTION: An internal diametric spline part 2d in a neck part internal peripheral surface of a cylinder block 2 is fitted to an external diametric spline part 3a of a shaft 3, and a spherical washer 10 of spherical external shape is slidably mounted in a cylindrical neck part peripheral surface to be energized leftward. In this way, a piston shoe 7 is brought into press contact with a swash plate 5 through a shoe plate 6. A point of application of load force P in a radial direction acting in the cylinder block 2 from a piston 4 is positioned in the vicinity of the center in an axial direction of the internal diametric spline part 2d. An escape 16, gradually enlarged in both sides in the axial direction with a corresponding point Q on the periphery serving as the vertex, is provided so as to prevent the cylinder block 2 from tilting even when the shaft 3 is deflected by a load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swash plate type piston pump that reciprocates a piston according to a tilt angle of a swash plate by rotation of a cylinder block to suck and discharge a fluid, and a piston that reciprocates a fluid pressure. The present invention relates to a swash plate type piston type hydraulic device such as a swash plate type piston motor which moves and reciprocates the piston into rotation of a cylinder block.

[0002]

2. Description of the Related Art This type of piston type hydraulic device has been widely used as a power transmission mechanism for industrial machines and vehicles. FIG. 3 is a vertical cross-sectional view showing an example of a conventionally used swash plate type variable displacement piston pump.

A cylinder block 2 is rotatably incorporated in the main body 1 of the apparatus. A shaft 3 serving as a rotary shaft is provided on a central axis C of the cylinder block 2 so as to spline-connect the two, and a drive (not shown) is provided. The rotational force from the motor is transmitted to the cylinder block 2 via the shaft 3. A plurality of cylinder bores 2a are provided on the same pitch circle from the center of the cylinder block 2 in parallel with the center axis C and at equal intervals, and reciprocating pistons 4 are slidably inserted into these cylinder bores 2a. is there.

Further, inside the apparatus main body 1, a swash plate 5 which constitutes a capacity varying means with an arbitrary tilt angle with respect to the central axis C of the cylinder block 2 can be tilted by a bearing (not shown). It is provided. A spherical portion 4a formed at one end of each piston 4 is rotatably mounted on a piston shoe 7 connected by an annular shoe plate 6 and is pressed by a spring 9 through a pin 8 toward the swash plate 5 outer circumference. The helical washer 10 having a spherical surface presses the piston shoe 7 against the swash plate 5 via the shoe plate 6, so that the piston 4 is moved along the swash plate 5. The inner diameter spline portion 10a formed on the inner peripheral surface of the helical washer 10 is slidably fitted to the outer diameter spline portion 3a formed on the outer peripheral surface of the shaft 3.

A control cylinder 11 is slidably mounted on an upper part of the apparatus body 1 to a control cylinder guide 12 fixed to a valve plate 15 which is integral with the apparatus body 1. One end of the control cylinder 11 is a swash plate 5. Pressed onto the upper end. A bias piston 13, which is another control member, is provided in the lower portion of the apparatus main body 1 so as to be in pressure contact with the swash plate 5 by the biasing force of a spring 14, and the swash plate 5 is provided by the bias piston 13 and the control cylinder 11. Control the inclination of.

Further, a wafer plate 15a fixed to the valve plate 15 is provided on the end surface of the apparatus main body 1, and this wafer plate 15a is in sliding contact with the end surface of the cylinder block 2 so as to prevent the fluid supplied to the cylinder bore 2a. It forms a seal. The wafer plate 15a is provided with 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 bore 2a.

In the swash plate type variable displacement piston pump having such a structure, one end of each piston 4 revolves along the swash plate 5 via the piston shoe 7 to cause a stroke motion. At this time, in the discharge process, the piston 4 is pressed in the direction of the swash plate 5 by its discharge pressure, and in the suction process, the helical force is pressed in the direction of the swash plate 5 by the biasing force of the spring 9 via the pin 8. The shoe plate 6 slidingly contacting the washer 10 on the inner peripheral surface presses the piston shoe 7 against the swash plate 5, thereby allowing the piston 4 to follow the swash plate 5.

Focusing on one piston 4, a stroke is made in the suction direction during the half revolution during the revolution, and in the discharge direction during the remaining half revolution. Therefore, if the wafer plate 15a having the semi-arc shaped kidney port is fixed to the valve plate 15, a continuous pumping action can be obtained. The structure of the piston motor is also
It is almost the same as the above piston pump, but the operating principle is reversed.

[0009]

However, in such a conventional piston type hydraulic device, the shaft 3
The inner diameter spline portion 10 formed on the inner peripheral surface of the helical washer 10 on the outer diameter spline portion 3a formed on the outer peripheral surface of the
Since the helical washer 10 is held by fitting a, the swash plate 5 is tilted in the piston type hydraulic device in which the tilt center A of the swash plate 5 is offset from the center point B of the piston 4. In doing so, the ball center point B of the piston 4 moves, and along with that, the helical washer 10 also needs to move in the axial direction.

Normally, the outer and inner diameter spline portions 3a,
A certain amount of play is provided between the 10a due to the processing precision of the spline teeth and restrictions on the assemblability, and the helical washer 10 is constantly subjected to the twisting force from the sliding surface with the shoe plate 6, A large friction is generated when the helical washer 10 moves in the axial direction, and an extremely large frictional force is generated especially when the swash plate 5 is tilted at a high speed.

As a result, the pressing load set by the spring 9 changes, and when the pressing load decreases, the piston shoe 7 floats up from the swash plate 5 during the suction process, causing the piston shoe 7 to come into partial contact with the swash plate 5. This may cause abnormal wear of the piston shoe 7 and the swash plate 5, and if the pressing load increases, the helical washer 1
0 and the sliding surface of the shoe plate 6 may cause seizure or abnormal wear.

In order to solve such a problem, conventionally, an expensive gun metal material having good seizure resistance is used as the material of the helical washer 10, and the helical washer 10 is used.
Of the helical washer 10 by increasing the dimension of the shoe plate 6 or by extending the inner surface of the shoe plate 6 so that the sliding surface position of the shoe plate 6 with the helical washer 10 is extended.
The seizure was prevented by reducing the contact angle with the contact surface and lowering the surface pressure of the sliding part. However, with such a method, it is impossible to avoid an increase in cost due to the use of an expensive material such as a gunmetal system and an increase in the size of the pump by increasing the size.

In the conventional piston type hydraulic device, the piston 4 is attached to the outer diameter spline portion 3a of the shaft 3.
The shaft 3 is bent by the radial force generated from the piston 4 when operating at a high pressure by providing reliefs called crownings that gradually expand on both sides in the axial direction around the point corresponding to the ball center point B of In some cases, however, the end surface of the cylinder block 2 can be kept parallel to the wafer plate 15a due to the clearance provided in the outer diameter spline portion.

However, in the crowned shaft 3, there is too much play with the inner diameter spline portion 10a of the helical washer 10 that fits into the outer diameter spline portion 3a, and the size of the helical washer 10 is restricted. For this reason, it is not possible to adopt a helical washer method, and a shoe plate that is in sliding contact with a retainer fixed to the swash plate via a spacer is a method called a normal hanging type in which the piston shoe is along the swash plate. Was used. This method has a problem that the number of parts is increased and the assembling property is poor and the cost is increased as compared with the helical washer method. The present invention has been made in view of the above points, and an object of the present invention is to provide a piston-type hydraulic device having excellent wear resistance and seizure resistance at high pressure at low cost.

[0015]

In order to achieve the above object, the present invention is a cylinder block which is connected to a rotation transmission shaft and rotates around a central axis, and is slidably inserted into a cylinder bore of the cylinder block. A piston with a piston shoe fitted loosely on one end, a swash plate that slidably contacts the piston shoe, a helical washer biased in the direction that presses the piston shoe against the swash plate, and one end surface of the cylinder block that slides into the cylinder block. A piston type hydraulic device having a valve plate having a fluid supply hole and a fluid discharge hole, wherein an inner diameter spline portion formed on an inner peripheral surface of a neck portion projecting from the other end surface of the cylinder block; An outer diameter spline portion formed on the outer peripheral surface of the rotation transmission shaft and slidably fitted to the inner diameter spline portion of the cylinder block;
And a cylindrical portion that is formed on the outer peripheral surface of the neck portion of the cylinder block and on which the inner peripheral surface of the helical washer is slidably fitted, and the load force point in the radial direction that acts on the cylinder block from the piston The present invention provides a piston type hydraulic device which is located near the center of the inner diameter spline portion of the cylinder block in the axial direction.

In the piston type hydraulic device described above, it is preferable that the outer diameter spline portion of the rotation transmission shaft is provided with a relief that gradually expands to both sides in the axial direction with the load application point as the apex.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. Parts corresponding to FIG. 3 are designated by the same reference numerals. FIG. 1 is an enlarged sectional view showing an embodiment of the present invention, and FIG. 2 is a vertical sectional view showing a structure of a swash plate type piston pump embodying the present invention.

First, of the configuration of the swash plate type piston pump embodying the present invention, the points different from those of FIG. 3 will be mainly described with reference to FIG. In the drawing of the cylinder block 2, a small diameter cylindrical neck portion 2b and a large diameter cylindrical neck portion 2c are projected on the left end side, and an inner diameter spline portion 2d is formed on the inner peripheral surface of these cylindrical neck portions 2b, 2c. This inner diameter spline part 2d
Outer diameter spline portion 3a formed on the outer peripheral surface of the shaft 3
To fit.

Small diameter cylindrical neck 2 of cylinder block 2
On the outer peripheral surface of b, the inner peripheral surface of the helical washer 10 having a spherical outer shape and an inner peripheral surface formed into a cylindrical inner surface is slidably loosely fitted and disposed inside the cylinder block 2. The outer peripheral surface of the helical washer 10 is brought into sliding contact with the inner peripheral surface of the shoe plate 6 via the pin 8 by the biasing force of the spring 9.
By pressing the piston shoe 7 against the swash plate 5, the piston 4 reciprocates to form a pump mechanism.

The inner diameter spline portion 2d formed on the inner peripheral surface of the neck portion of the cylinder block 2 is, as shown in detail in FIG. 1, centered on the load force point P in the radial direction which acts on the cylinder block 2 from the piston 4. This inner diameter spline part 2 is set so that it can cover both sides in the axial direction.
The outer diameter spline portion 3a of the shaft 3 that can be fitted into d is gradually expanded on both sides in the axial direction with the point Q of the outer peripheral surface corresponding to the load force point P as the apex, in both the tooth length direction and the tooth width direction. Forming a relief 16 called crowning.

The size of the relief 16 is such that when the shaft 3 bends due to a radial load acting on the shaft 3 from the piston 4 via the cylinder block 2, the fitting portions of the inner and outer diameter spline portions 2d and 3a. It is specified that the load is always applied with the above point Q as the apex, but depending on the size of the load, a flat surface with a width of several millimeters may be provided at the apex in order to reduce the concentration of the load on the apex. It does not matter even if it is provided. Incidentally, the amount of bending of the shaft 3 can be calculated from the magnitude of the load applied to the shaft 3. The other configuration is shown in FIG.
Is the same as

In the swash plate type piston pump having such a structure, even if the shaft 3 bends at the time of high pressure operation, the inner and outer diameter spline portions 2d and 3a have points Q with the point Q corresponding to the load force point P in the radial direction as the apex. Since the cylinder block 2 is fitted in such a manner that the cylinder block 2 can be swung freely, there is no risk of generating a moment to incline the cylinder block 2, and the end face of the cylinder block 2 and the wafer plate 15a are kept parallel to each other, so that both can be operated even during high-speed operation. It is possible to maintain good sealing property.

In the above embodiment, the case where the present invention is applied to the swash plate radial pump for high pressure operation has been described. However, in the swash plate radial pump for medium and low pressure,
Although it is not necessary to provide the escape 16 on the shaft 3, it is possible to improve wear resistance and seizure resistance at low cost by configuring the helical washer 10 as described above. Further, although the case where the present invention is applied to the swash plate type piston pump has been described in the above embodiment, the present invention is not limited to this, and can be applied to a swash plate type piston motor without any trouble.

[0024]

As described above, in the piston type hydraulic device according to the present invention, the inner peripheral surface of the helical washer is loosely fitted to the cylindrical portion of the outer peripheral surface of the neck portion of the cylinder block, and the outer surface of the rotation transmitting shaft is not provided. Since the radial load force point acting on the cylinder from the piston is located near the axial center of the inner diameter spline part of the inner peripheral surface of the neck fitted to the radial spline part, the neck of the helical washer and cylinder block is located. It is possible to increase the size of the fitting surface of the shoe plate and the holding force against the twisting force received from the shoe plate.

Therefore, even when the helical washer is moved in the axial direction as the swash plate is tilted, the slidability is good, and it is possible to reduce the increase / decrease in the pressing load on the shoe plate. There is no need to increase the load for pushing in the plate direction, and it is not necessary to use expensive materials with good seizure resistance for the helical washer and cylinder block, and wear resistance and seizure resistance are improved with inexpensive materials. Can be made. Further, since it is not necessary to enlarge the helical washer or to project the inner diameter portion of the shoe plate, it is possible to downsize the piston type hydraulic device and further reduce the cost.

In the above apparatus, if the outer diameter spline portion of the rotation transmission shaft is provided with a relief with the load force point as the apex, even if the rotation transmission shaft is bent by the load in the radial direction during high pressure operation, the load Since the inner and outer diameter splines are fitted with the force application point as the apex, the moment to tilt the cylinder block does not occur, the parallelism with the valve plate is maintained, and good sealing performance can be maintained. Become. Furthermore, even if a clearance is provided on the outer diameter spline part of the rotation transmission shaft, there will be space in the helical washer mounting part, so it will be cheaper and easier to assemble instead of the expensive expensive downsizing type. It can be made into a helical washer that allows

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example of a swash plate type piston pump embodying the present invention.

FIG. 3 is a longitudinal sectional view showing an example of a conventional piston type hydraulic device.

[Explanation of symbols]

1: Device body 2: Cylinder block 2a: Cylinder bore 2d: Inner diameter spline part 3: Shaft 3a: Outer diameter spline part 4: Piston 5: Swash plate 6: Shoe plate 7: Piston shoe 10: Spiral washer 15: Valve plate 15a : Wafer plate 16: Escape (crowning)

Claims (2)

[Claims] 1. An apparatus main body, a cylinder block rotatably incorporated in the apparatus main body, and connected to a rotation transmission shaft, and a cylinder block parallel to the center axis on the same pitch circle from the center axis of the cylinder block. A plurality of cylinder bores provided in the cylinder bore, pistons slidably inserted into the cylinder bores and having piston shoes loosely fitted to one end, and the pistons slidingly contact the piston shoes, and the pistons are accommodated in the cylinder bores as the cylinder block rotates. A reciprocating swash plate, a helical washer mounted around the center axis and urged in a direction to press the piston shoe against the swash plate via a shoe plate, and a slidable plate on one end surface of the cylinder block. Piston type hydraulic pressure provided with a valve plate that is in contact with and has a fluid supply hole and a fluid discharge hole to the cylinder bore The device is slidable on an inner diameter spline portion formed on an inner peripheral surface of a neck portion protruding from the other end surface of the cylinder block and an inner diameter spline portion formed on an outer peripheral surface of the rotation transmission shaft. An outer diameter spline portion that fits into the cylinder block, and a cylindrical portion that is formed on the outer peripheral surface of the neck portion of the cylinder block and on which the inner peripheral surface of the helical washer slidably fits, and from the piston to the cylinder block. A piston type hydraulic device characterized in that a radial force applying point acting on is located near the axial center of the inner diameter spline portion of the cylinder block. 2. The piston type hydraulic device according to claim 1, wherein an outer diameter spline portion of the rotation transmission shaft is provided with a relief that gradually expands to both sides in the axial direction with the load force point as an apex. Piston type hydraulic device.