JPH09170567A - Piston type hydraulic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abrasion and seizure of a cylinder block and a piston while minimizing leakage of working oil. SOLUTION: An eccentric groove 1 positioned at a point separated farthest from a central shaft A of a cylinder block 10, positioned between a base end part of a piston at a bottom dead center and an opening part of a cylinder bore 11 and formed as a part of an eccentric hole 2 smaller in diameter than the cylinder bore 11 and decentered from a central shaft C of the cylinder bore 11 is furnished on an inner peripheral surface 11a of the cylinder bore 11 on a swash plate type piston type hydraulic device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a swash plate type piston hydraulic device having improved wear resistance and seizure resistance.

[0002]

2. Description of the Related Art Conventionally, swash plate type piston type hydraulic devices have been widely used as piston pumps and piston motors as power transmission mechanisms for industrial machines and vehicles.

Such a piston pump is specifically as shown in FIG. 3, in which a cylinder block 10 rotatably incorporated in the main body of the device (not shown) is arranged on the same pitch circle on its main shaft. A plurality of cylinder bores 11 are provided in parallel with a certain rotation center axis A.
With the rotation of the cylinder block 10 that is interlocked with the rotation of a drive shaft (not shown) provided coaxially with the cylinder bore 1
The pistons 12 inserted into the base 1 from the base end portion 12b reciprocate to suck and discharge the fluid.

In such a swash plate type piston pump,
The reciprocating motion of the pistons 12 is performed by revolving each piston 12 while slidingly contacting the swash plate 30 through the piston shoe 31 to which the spherical portion 12a at the tip thereof is attached. The swash plate can be rotated as shown by the arrow in the figure to change the inclination angle, and the discharge amount of the pump can be adjusted.

Since each piston 12 makes a stroke motion during the half revolution in the suction direction during the revolution, and in the discharge direction during the remaining half revolution, the cylinder block 1 of the main body of the apparatus.
A valve plate 40 having a not-shown kidney port for fluid supply and fluid discharge is fixedly mounted on a pitch circle corresponding to the cylinder bore 11 of the cylinder block 10 at an end surface slidingly contacting 0, and one surface 40a thereof is fixed to the cylinder block. By making sliding contact with the end surface 10a of 10, it is possible to obtain a continuous pumping action. The structure of the piston motor is almost the same as that of the piston pump, and the operating principle is reversed.

By the way, in such a piston type hydraulic device, as shown in FIG. 4, when the piston 12 comes out of the cylinder bore 11 due to the pressure of the fluid, the pressure P of the fluid in the cylinder bore 11 is applied to the piston 12. The exerted force F = A × P is the shoe pressing force F _S = F perpendicular to the swash plate 30.
Along with / cosθ, it has a radial component force F _R = Ftanθ perpendicular to the piston 12. The piston cross-sectional area is A and the swash plate inclination angle is θ.

Accordingly, the cylinder block 10, a radial force component F _R acting on the piston 12, the contact reaction force R ₁ from the maximum load point 16 at the opening 15 of the cylinder block 10, the base end portion 12b of the piston 12 And the cylinder block 10 is supported by the contact reaction force R ₂ from the contact point 17, and particularly at the maximum load point 16, the maximum load R ₁ =
F _R + R ₂ is working. Further, the maximum load R ₁ becomes larger as the piston 12 comes out of the cylinder bore 11, and becomes the maximum value when the piston 12 comes out most. The maximum load point 1 of the cylinder block 10
6 is a position in the opening 15 of the cylinder bore 11 that is most distant from the central axis A of the cylinder block 10 in the outer peripheral direction.

Since the vertical component force F _R acts between the cylinder block 10 and the piston 12 in this way, the maximum load of the sliding contact surface between the cylinder block 10 and the piston 12, especially the opening 15 of the cylinder block 10. In the vicinity of point 16, problems such as seizure were likely to occur. Therefore, for example, Japanese Patent Application Laid-Open No. 7-217545 and Japanese Patent Application Laid-Open No. 3-189.
In the '375 publication, the inner peripheral surface 1 of the cylinder bore 11 is
A piston type hydraulic device has been proposed in which escape grooves 5, 6 and the like are formed on 1a.

Of these, the former relief groove 5 is formed as a concentric groove having a diameter larger than the diameter of the cylinder bore 11 over the entire inner peripheral surface 11a of the cylinder bore 11, as shown in FIG. The fluid introduced into 5 improves the lubricity of the sliding surface between the cylinder block 10 and the piston 12.

The relief groove 6 of the latter is, as shown in FIG. 6, the central axis A of the cylinder block 10 and the cylinder bore 1.
1 is at a position where the plane passing through the central axis of the cylinder 1 intersects with the cylinder bore 11, one end is slightly inside the cylinder bore 11 from the front end, and the other end is at bottom dead center (the piston 12 is the most dislocated from the cylinder bore 11). ) Is provided at a position deeper than the rear end of the piston 12 arranged in (4), and the fluid introduced into the escape groove 6 makes the sliding of the piston 12 smooth.

[0011]

However, the relief groove 5 shown in FIG. 5 is formed over the entire circumference of the inner peripheral surface 11a of the cylinder bore 11, and the relief groove 6 shown in FIG.
Is a fluid that extends farther than the position of the base end portion 12b of the piston 12 at the bottom dead center, so that an unnecessarily large amount of hydraulic fluid is introduced into these grooves, and the opening portion of the cylinder bore 11 is in each case. There was a problem with the sealing property of No. 15.

The relief groove 5 shown in FIG.
Is formed over the entire inner peripheral surface 11a of
Further, since the relief groove 6 of FIG. 6 is formed to a depth of the cylinder bore 11 with a constant width, machining of these relief grooves 5 and 6 in the cylinder bore 11 is not easy, and the manufacturing efficiency is improved. Had lowered.

In view of the above problems, the present invention provides a piston type hydraulic device capable of preventing wear and seizure of a cylinder block and a piston while minimizing leakage of hydraulic oil. To aim.

[0014]

According to the present invention, there is provided a cylinder block which rotates in association with rotation of a main shaft, and a plurality of cylinder bores which are provided on the same pitch circle from the center axis of the cylinder block in parallel with the main shaft. A piston slidably inserted in each of the cylinder bores; a swash plate slidably contacting one end of each of the pistons to reciprocate the piston in the cylinder bore as the cylinder block rotates; In a piston type hydraulic device provided with a valve plate having a supply hole and a discharge hole of a fluid for slidingly contacting an end surface of the cylinder bore, a point farthest from a central axis of the cylinder block on an inner peripheral surface of the cylinder bore. Located between the base end of the piston and the opening of the cylinder bore at the bottom dead center. A small diameter, and having an eccentric groove formed as a part of the eccentric hole which is eccentric from the central axis of the cylinder bore.

[0015]

In the present invention, when the piston slides in the cylinder bore, the hydraulic oil is introduced into the eccentric groove formed on the inner peripheral surface of the cylinder bore immediately adjacent to the maximum load point of the cylinder block. In particular, the lubricity between the cylinder block and the piston is improved near the maximum load point where wear and seizure are likely to occur. Further, at this time, since only the minimum necessary eccentric groove is provided, the leakage of the hydraulic oil from the opening of the cylinder bore can be suppressed to the minimum. Furthermore, since the eccentric groove is formed as a part of the eccentric hole with respect to the cylinder bore, the eccentric groove can be easily cut by using a proper tool.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In the present invention, in FIG. 3, the eccentric groove 1 as shown in FIGS. 1 and 2 is formed on the inner peripheral surface of the cylinder bore 11. The eccentric groove 1 is formed in a shape along the outer peripheral surface of the cylindrical eccentric hole 2 shown by imaginary lines in FIGS.

The central axis B of the eccentric hole 2 is outside the central axis C of the radiation connecting the central axis A of the cylinder block 10 and the central axis C of the cylinder bore 11 by χ from the central axis C. It is eccentric. As a result, the eccentric groove 1 is
The inner wall of the cylinder bore 11 is formed on the circumference farthest from the central axis A of the cylinder block 10.

Further, the eccentric groove 1 is formed in the cylinder bore 11 of the piston 12 shown in FIG. 4 in the axial direction of the cylinder bore 11.
Arrangement that maximizes the amount of escape L ₁ (piston 12
(Bottom dead center) of the piston 12 and the opening 15 of the cylinder bore 11 are located within a range of a distance L ₂ .

With such an arrangement, the eccentric groove 1 is formed as shown in FIG.
It will be provided immediately adjacent to the maximum load point 16 shown in FIG.

Further, in the processing for forming the eccentric groove 1 having a shape along a part of the outer peripheral surface of the eccentric hole 2, for example, a center boring machine or the like is used to decenter the center axis C of the cylinder bore 11 by a predetermined amount χ. This can be easily performed by making a hole at a position with a predetermined diameter.

The radius of the eccentric hole 2 is equal to that of the cylinder bore 11.
The eccentric hole 2 has a height of the cylinder which is smaller than that of the piston 12 and the base end 12b of the piston 12 and the cylinder bore 1.
When the distance L _{2 from the} first opening 15 is the smallest at the bottom dead center of the piston 12, a material that fits within this distance is selected. Therefore, the eccentric groove 1 may be larger than necessary. Limited.

Next, the operation will be described.

In association with the rotation of the cylinder block 10 about the rotation axis A, the piston 12 is connected to the cylinder bore 11
Slide inside. At this time, as shown in FIG. 4, in the vicinity of the maximum load point 16 of the cylinder block 10, the maximum load R
₁ = F _R + R ₂ works.

By the way, since the eccentric groove 1 is formed immediately adjacent to the maximum load point 16, the hydraulic oil is introduced into the eccentric groove 1, so that the cylinder block 10 and the piston in the vicinity of the maximum load point 16 are guided. Lubricity in sliding with 12 is improved, and wear resistance and seizure resistance of the cylinder block 10 and the piston 12 are significantly improved.

At this time, only the minimum necessary eccentric groove 1 is provided, and no groove is provided on the inner wall of the cylinder bore 11 on the side opposite to the eccentric groove 1. Therefore, excess hydraulic oil is introduced. Therefore, leakage of the hydraulic oil from the opening 15 of the cylinder bore 11 is suppressed to the minimum. That is,
In the present invention, since the eccentric groove 1 for preventing seizure is provided only in the portion where the seizure is most likely to occur, the wear and seizure of the cylinder block 10 and the piston 12 are prevented, and the hydraulic oil from the eccentric groove 1 is prevented. It is possible to maximize the prevention of leakage.

Further, since the eccentric groove 1 is formed as a part of the eccentric hole 2 with respect to the cylinder bore 11, it does not take time and labor unlike the conventional example, and the eccentric groove 1 is easily cut by a boring machine or the like. be able to.

[0028]

According to the present invention, when the piston slides in the cylinder bore, the working oil is introduced into the eccentric groove formed immediately adjacent to the maximum load point of the cylinder block, and the working oil particularly wears. Lubrication between the cylinder block and piston near the maximum load point where seizure is likely to occur is improved, and the wear resistance and seizure resistance of the cylinder block and piston are greatly improved. Since only the minimum required oil is provided, leakage of hydraulic oil from the opening of the cylinder bore is minimized, wear and seizure of the cylinder block and piston are prevented, and hydraulic oil from the eccentric groove is prevented. It is possible to prevent leaks of the eccentricity to the maximum, and since the eccentric groove is formed as a part of the eccentric hole for the cylinder bore, the eccentric groove can be formed by using an appropriate tool. It can be cut into easy.

[Brief description of the drawings]

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

FIG. 2 is a front view of the same.

FIG. 3 is a sectional view showing a swash plate type piston type hydraulic device.

FIG. 4 is an explanatory view showing the action of force in the piston type hydraulic device.

FIG. 5 is a view showing a clearance groove of a conventional example.

FIG. 6 is a view showing another conventional escape groove.

[Explanation of symbols]

 1 Eccentric Groove 2 Eccentric Hole 10 Cylinder Block 11 Cylinder Bore 11a Inner Surface 12 Piston 12b Base End 15 Opening 30 Swash Plate 40 Valve Plate A Center Axis C Center Axis

Claims (1)

[Claims] 1. A cylinder block that rotates in association with rotation of a main shaft, a plurality of cylinder bores provided on the same pitch circle from the center axis of the cylinder block in parallel with the main shaft, and slidable to each of these cylinder bores. Pistons inserted in the cylinder block, a swash plate slidingly contacting one end of these pistons to reciprocate the piston in the cylinder bore as the cylinder block rotates, and a swash plate slidingly contacting one end face of the cylinder block to A piston-type hydraulic device comprising: a valve plate having a fluid supply hole and a fluid discharge hole; and a bottom plate located on the inner peripheral surface of the cylinder bore at a position farthest from the central axis of the cylinder block. Is located between the base end of the piston and the opening of the cylinder bore at a point, has a smaller diameter than the cylinder bore, and is cylindrical. The piston-type hydraulic device characterized by comprising an eccentric groove formed as a part of the eccentric hole which is eccentric from the central axis of the bore.