JPH044473B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a piston device for a swash plate type piston pump/motor.

[Background of the invention]

FIG. 4 is a sectional view showing an example of a conventional swash plate type piston pump/motor.

In FIG. 4, reference numeral 1 denotes a cylinder block, which is spline-coupled to a drive shaft (not shown) and rotates in synchronization with the rotation of the drive shaft. cylinder block 1
A plurality of cylinders 2 are bored at equal intervals in the axial direction, and a piston 3 is inserted into each cylinder 2 so as to be able to reciprocate. The tip 3a of the piston 3 has a spherical shape, and is engaged with the shoe 4, so that the piston 3 is swingably supported by the shoe 4. 5 is a swash plate, and the swash plate 5 is connected to the cylinder block 1.
They face each other at a predetermined angle.
The shoe 4 is in contact with the surface thereof.

A swash plate type piston pump configured like this
In the motor, when the cylinder block 1 rotates, the shoe 4 engaged with the tip 3a of the piston 3
slides on the swash plate 5. Since the swash plate 5 is inclined with respect to the axis of the cylinder block 1, the piston 3 moves back and forth within the cylinder 2 while the cylinder block 1 is rotating, and operates as a pump or a motor. At this time, high pressure is generated in the cylinder 2, so the piston 3 is pressed against the swash plate 5 via the shoe 4, and the piston 3 is forced into the cylinder 2 as shown in the figure.
The force F _P due to internal pressure, the axial force F _A from the swash plate 5 via the shoe 4, the radial force F _R generated according to the tilt of the swash plate 5, and the force F _R are balanced. The force generated between piston 3 and cylinder 2 due to
F ₁ and F ₂ act. Of these forces,
F ₁ and F ₂ change according to the stroke amount of the piston 3, and the position where the piston 3 is farthest from the cylinder 2, that is, the top dead center of the stroke where the distance from the open end of the cylinder 2 to the shoe 4 is the longest The maximum value is reached at .

By the way, a slight gap is provided between the piston 3 and the cylinder 2 in order for the piston 3 to reciprocate within the cylinder 2.
As shown in the figure, the portion transmitting the aforementioned force _F1 is a local contact portion between the opening 2a of the cylinder 2 and the outer circumferential surface of the piston 3, resulting in a very high contact surface pressure. This also applies to the contact portion between the rear end portion 3b of the piston 3 and the inner circumferential wall of the cylinder 2, which transmits the force _F2 .

If the piston 3 reciprocates inside the cylinder 2 under high contact surface pressure, it may cause seizing or abnormal wear, shortening the life of the pump/motor or making it impossible to use it at high pressure. This causes various problems such as not being able to provide a large tilting angle. Note that this problem arises because F ₁ =F _R +F ₂ , that is, F ₁ >F ₂ , as is clear from the balance of forces shown in FIG _.
The opening 2a of the cylinder 2 and the piston 3 on which
This is most likely to occur at the contact area with the outer peripheral surface of the

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide a swash plate type piston pump/motor which can have a long life and increase energy density by preventing local contact between a piston and a cylinder.

[Summary of the invention]

In order to achieve this object, the present invention is characterized in that a spherical bearing is interposed between the piston and the cylinder.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 shows a swash plate type piston pump according to the present invention.
4 is a sectional view of essential parts of a first embodiment of a piston device for a motor, 6 is a spherical bearing, and parts corresponding to those in FIG. 4 are given the same reference numerals.

In FIG. 1, the spherical bearing 6 is composed of an inner ring 6a and an outer ring 6b, of which the outer ring 6b
is fixed in a recess 2b formed in the cylinder opening 2a of the cylinder block 1 by means such as press fitting. On the other hand, the piston 3 is slidably inserted into a hole 6c bored in the center of the inner ring 6a, and the inner ring 6a is aligned with the spherical part between the outer ring 6b and the outer circumference of the piston 3. The inner ring 6a contacts with a surface pressure distributed over the width A of the inner ring 6a. Therefore, in the transmission part of the force F ₁ , which is the most severe condition, it is possible to eliminate the sliding due to the high contact surface pressure that conventionally occurs, thereby reducing the life of the pump and motor such as seizure and abnormal wear. It is possible to eliminate problems that adversely affect the pump and motor, and it is also possible to use the pump motor at a higher pressure and a larger tilt angle than in the past. Note that the effects in this embodiment are as follows:
Since this is the same as the conventional example described above, its explanation will be omitted.

Figure 2 shows a swash plate type piston pump according to the present invention.
FIG. 7 is a sectional view of a main part of a second embodiment of a piston device for a motor. This embodiment differs from the first embodiment in that, in addition to the spherical bearing 6 described above, another spherical bearing 7 is also provided in the force _F2 transmission section. That is, the inner ring 7a constituting the spherical bearing 7 is fixed to the stepped portion 3c formed on the rear end 3b of the piston 3 by means such as press fitting, and the outer periphery of the outer ring 7b is configured to come into sliding contact with the inner periphery of the cylinder 2. There is.

In one embodiment configured in this way, the force
In addition to the F ₁ transmission section, the high surface pressure section at the force F ₂ transmission section can also be eliminated, so the pump/motor can be operated at a higher pressure and at a larger tilting angle than in the first embodiment. Can be used in

Figure 3 shows a swash plate type piston pump according to the present invention.
FIG. 7 is a sectional view of main parts of a third embodiment of a piston device for a motor. In this embodiment, the recess 2b is formed relatively long in the axial direction of the cylinder 2, and the above-mentioned spherical bearing 6 and another spherical bearing 8 are arranged at a predetermined interval in the recess 2b. be. That is, the outer ring 8b of the spherical bearing 8 is fixed to the inner part of the recess 2b by press-fitting or the like, and the outer ring 6b of the spherical bearing 6 is fixed by press-fitting or the like to the opening side of the recess 2b via the sleeve 9. , 8 inner ring 6
The piston 3 is configured to slide on the inner periphery of the pistons a and 8a. Even in the embodiment configured in this manner, the high surface pressure portion in the transmission portion of the force F ₁ and the force F ₂ can be eliminated, as in the second embodiment described above.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to eliminate local contact between the piston and the cylinder, and therefore, it is possible to eliminate defects that adversely affect the pump motor, such as seizure and abnormal wear, and further, Pumps and motors can be used at high pressures and large tilt angles, making it possible to increase energy density.

[Brief explanation of drawings]

Figure 1 shows a swash plate type piston pump according to the present invention.
Cross-sectional view of main parts showing the piston device of the motor, 2nd
3 and 3 are cross-sectional views of essential parts showing other embodiments of the piston device for a swash plate type piston pump/motor according to the present invention, and FIGS. 4 and 5 show a piston device for a conventional swash plate type piston pump/motor. FIG. 1...Cylinder block, 2...Cylinder, 2
a...opening, 2b...recess, 3...piston,
3c...Step part, 4...Show, 5...Swash plate, 6,
7, 8... Spherical bearing, 6a, 7a, 8a... Inner ring, 6b, 7b, 8b... Outer ring, 9... Sleeve.

Claims (1)

[Scope of Claims] 1. A rotatable cylinder block and a piston slidably inserted into a cylinder of the cylinder block, and as the cylinder block rotates, the piston is guided by a swash plate and the cylinder 1. A piston device for a swash plate type piston pump/motor, characterized in that a spherical bearing is interposed between the piston and the inner wall of the cylinder in the swash plate type piston pump/motor that reciprocates within the cylinder. 2. The swash plate type piston pump/motor according to claim 1, wherein the outer ring of the spherical bearing is supported by the cylinder block, and the inner ring of the spherical bearing is in sliding contact with the outer peripheral wall of the piston. piston device. 3. A piston device for a swash plate type piston pump/motor according to claim 1, characterized in that a plurality of the spherical bearings are provided at predetermined intervals.