JPS586069B2 - Yuatsu pump motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic pump motor that can improve sliding performance between a spherical surface of a piston and a ball, and between a piston and a cylinder.

As shown in Fig. 1, a conventional radial piston type hydraulic pump motor incorporates a piston 3 equipped with a ball 2 that rolls on a corrugated cam surface 1 into a rotor 4, and rotates the rotor 4 by supplying high-pressure oil. It is used as a hydraulic motor, and also as a hydraulic pump that supplies high pressure oil by rotating the rotor 4.

However, in the above-mentioned hydraulic pump motor, the ball 2 generates a reaction force F due to the slope of the wavy cam surface 1, so the sliding surfaces between the spherical part of the piston 3 and the ball 2 and between the piston 3 and the cylinder are strong. Pressed.

Therefore, in order to enable the above-mentioned hydraulic pump motor to be used even under high load conditions, an oil film is formed between the spherical part of the piston 3 and the ball 2, and between the piston 3 and the cylinder, and at the same time the direction is sequentially varied. It is necessary to apply high pressure oil to the gap section facing the side pressure.

If high-pressure oil is not sufficiently supplied to these gaps, large frictional forces will occur between the balls and the spherical surfaces of the pistons, and on the sliding surfaces between the pistons and cylinders. This causes galling on the sliding surface.

When such a galling phenomenon occurs, the spherical surface of the cylinder or piston is damaged, and this damage further induces the galling phenomenon, ultimately leading to destruction of the hydraulic pump motor.

Based on these circumstances, in order to improve the galling phenomenon described above, the applicant has already proposed a means for supplying lubricating oil to sliding surfaces as shown in Japanese Utility Model Publication No. 47-34888.

However, this known technology supplies high-pressure oil to the gap between the ball and the dividing spherical surface of the piston, and to the oil groove provided in the dividing spherical surface and the gap between the large diameter part of the piston and the cylinder hole. As a result, the high-pressure oil is not retained on the partitioned spherical surface of the piston, and it becomes difficult to keep the ball floating on the spherical surface of the piston, since the small oil hole provided in the piston communicates with the small oil hole.

As a result, the load capacity for holding the ball on the spherical portion cannot be maintained as desired.

In addition, since a plurality of partitioned spherical surfaces are formed in the spherical part by the notched grooves, when the piston rotates within the cylinder, the direction of reaction force applied to the ball matches the notched grooves of the spherical part, so that the spherical part is insufficient load capacity.

Furthermore, the distribution area of high-pressure oil on the spherical portion is restricted and reduced.

Furthermore, it has the disadvantage that the manufacturing process of the spherical part is complicated.

In view of the above points, it is an object of the present invention to provide a hydraulic pump motor that is easy to manufacture and process and can be used with high performance even under high load conditions.

The present invention will be explained below with reference to the illustrated embodiments.

2 and 3 are diagrams showing the piston portion of the hydraulic pump motor of the present invention. In these figures, the same reference numerals as in FIG. This cylinder 5 has a small diameter part 5a near the center of the rotor 4 and a large diameter part 5b outside thereof.

The piston 3 is slidably fitted into the cylinder 5, an oil seal 6 is provided in the small diameter portion 3a, and a spherical surface 7 on which the ball 2 is mounted is provided in the large diameter portion 3b. is formed.

8 is an oil chamber of the piston 3, 9 is an oil passage communicating with the oil chamber 8,
The oil passage 9 sequentially communicates with an oil supply passage and an oil discharge passage as the rotor 4 rotates.

A truncated cone-shaped oil groove 10 is provided in the center of the spherical surface 7 of the piston 3, and an oil groove 10 in the shape of a truncated cone is provided on the outer peripheral surface of the large diameter portion 3b of the piston 3, as shown in FIG. Four oil grooves 11 are provided at equal intervals in a plane perpendicular to this.

These oil grooves 10, 11 are formed into thin oil holes 12, 13, .
It communicates with the oil chamber 8 of the piston 3 by.

Restrictions 14 are provided on the oil chamber 8 side of the piston 3 in the small oil holes 12 and 13, respectively.

This throttle 14 has the property that there is a large pressure loss when pressure oil is flowing through the small oil holes 12 and 13, and no pressure loss occurs when there is no flow of pressure oil. Oil groove 1 of spherical surface 7 corresponding to ball 2 pressed by
It serves to apply high pressure oil to the oil groove 11 in the large diameter portion 3b of the piston 3 that is in contact with the piston 3 and the cylinder 5.

Next, a case where the hydraulic pump motor of the present invention is used as a hydraulic motor will be explained.

As shown in FIG. 2, when the ball 2 is located on the slope N of the wavy cam surface 1 and descends from the peak M, the piston 3 and the ball 2 are subjected to a reaction force F due to the slope N of the wavy cam surface 1.
receive.

The ball 2 and the large diameter portion 3b of the piston 3 are pressed rightward by a component FX of the reaction force F in a direction perpendicular to the piston axis.

As a result, a narrow gap Ga is created on the right side between the ball 2 and the spherical surface 7 of the piston 3, and a narrow oil hole 1 is formed in this gap Ga.
2. The flow rate of pressurized oil supplied through the oil groove 10 becomes smaller.

On the contrary, a gap Gb larger than the gap Ga is created on the left side between the ball 2 and the spherical surface 7 of the piston 3, and the pressure is supplied to this gap Gb through the thin oil hole 12 and the oil groove 10. Oil flow rate increases.

Therefore, the pressure generated in the gap Gb is smaller than that in the gap Ga.

Therefore, in the gap between the spherical surface 7 of the piston 3 and the ball 2, there is a fifth
Since the oil film pressure distribution as shown in the figure and the differential pressure relationship between the right and left parts of the spherical surface as shown in Figure 6 occur, this oil film pressure difference, that is, the pressure at the hatched part A in Figure 6, acts as a force pushing the ball 2 back to the left, forms an appropriate oil film between the ball 2 and the spherical surface 7, and balances with the component force Fx of the reaction force F.

The ball 2 is also pressed upward by the piston axis direction component Fy of the reaction force F.

When the ball 2 is pressed upward in this way, the piston 3
The gap Gc between the center part of the spherical surface 7 and the ball 2 becomes smaller, and the gap Gc passes through the thin oil hole 12 and through the oil groove 10.
Since the flow rate of pressure oil supplied to the small oil hole 12 is small,
The pressure drop across the throttle 14 becomes smaller.

Therefore, the pressure in the oil groove 10 becomes high, pushing the ball 2 back downward to form an appropriate oil film between the ball 2 and the center of the spherical surface 7, and balancing it with the component force Fy of the reaction force F.

Of the oil film pressure generated between the ball 2 and the spherical surface 7, the oil film pressure at the center of the spherical surface 7 is p, as shown in FIG.
acts especially as a force pushing back the ball 2 in the piston axis direction, and the oil film pressure p on the side surface of the spherical surface 7 also contributes to the balance with the component force Fy of the reaction force F, but it also contributes to the balance with the component force Fx of the reaction force F. It has a strong contribution to balance.

Further, the piston 3 on which the ball 2 is mounted is pushed to the right by a component force Fx of the reaction force F, as shown in FIG.

When the large diameter portion 3b of the piston 3 is pressed to the right toward the cylinder 5 in this way, the large diameter portion 3b of the piston 3 and the cylinder
A narrow clearance Ha is created on the right side between the piston 3 and the left side of the cylinder 5, and a relatively wide clearance Hb is created on the left side between the large diameter portion 3b of the piston 3 and the cylinder 5. Due to the difference in distribution, the piston 3 is pushed back to the left against the reaction force F.

Therefore, an appropriate oil film is formed between the large diameter portion 3b of the piston 3 and the cylinder 5, and the sliding performance between the piston 3 and the cylinder 5 can be improved.

In addition, in the above example, the oil groove provided on the outer peripheral surface of the large diameter portion 3b of the piston 3 is linear, but it may be formed into a groove of various shapes or may be formed into a hole shape. .

As described in detail above, the present invention provides oil grooves that have no communication relationship on the spherical surface of the piston, which is the sliding surface with the balls, and on the outer peripheral surface of the large diameter part of the piston, which is the sliding surface with the cylinder. Since the oil film pressure is distributed in the reaction force acting area of the spherical surface of the piston and the outer circumferential surface of the large diameter portion of the piston, the area where high pressure oil is distributed is not restricted compared to conventional methods, and the area of the piston is It is possible to obtain sufficient load capacity to hold the ball on the spherical surface.

In addition, unlike conventional systems, the present invention does not have a cutout groove in the spherical surface that does not generate oil film pressure, so even if the piston rotates within the cylinder for some reason, the oil film pressure that opposes the direction of the reaction force acting on the ball will be suppressed. Obtainable.

Furthermore, according to the present invention, for the spherical surface of the piston, it is only necessary to provide one oil groove in the center of the spherical surface instead of forming multiple partitioned spherical surfaces as in the past, making the machining work easier than in the past. This method not only has the advantage of being able to reduce manufacturing costs significantly, but also has the effect of significantly reducing production costs.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a conventional radial piston type hydraulic pump motor, FIG. 2 is a diagram showing an embodiment of the piston portion of the hydraulic pump motor of the present invention, and FIG.
Figure 4 is a view taken along the ■-■ line in Figure 2, Figures 5 and 6 are oil films formed between the ball and the spherical surface when subjected to reaction force. FIG. 3 is a diagram showing pressure distribution and differential pressure relationship. 2... Ball, 3... Piston, 3b... Large diameter part of piston 3, 7... Spherical surface, 8... Oil chamber, 10, 11... Oil groove, 12.13... Thin oil hole, 14... ...Aperture.

Claims (1)

[Claims] 1 A ball that rolls on a cam surface is attached to the spherical surface of the large diameter part of the piston, and this piston is installed in a cylinder so as to be able to reciprocate, and the pressure oil in the oil chamber on the small diameter part of the piston is controlled by each having a throttle. and a hydraulic pump motor in which oil is supplied to the gap between the ball and the spherical surface of the piston and the gap between the large diameter part of the piston and the cylinder through small oil holes independently provided in the piston, A plurality of oil grooves that are supplied with pressure oil through small oil holes are provided at equal intervals on the outer peripheral surface of the large diameter part of the piston, and one oil groove that is supplied with pressure oil through the independently provided thin oil holes. A hydraulic pump motor characterized in that a groove is provided at the center of the spherical surface of the piston.