JPH075255Y2 - Axial piston pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an axial piston pump.

[Prior Art] Hydraulic circuits are often used in construction machines, industrial vehicles, machine tools, and the like because they have excellent controllability and can generate large power. There is an axial piston pump as a hydraulic pump as a drive source of a hydraulic circuit. As shown in FIG. 6, a swash plate type axial piston pump, which is a type of axial piston pump, is a cylinder block that rotates integrally with the drive shaft 31.
A plurality of cylinder bores 33 and a cylinder port 33a communicating with the cylinder bore 33 are formed in the cylinder 32, and the piston 3
4 are housed so that they can reciprocate. The drive shaft 31 is loosely inserted in the center of the swash plate 35, and the piston 34 is inserted through the shoe 36 into the swash plate.
It is kept in contact with 35. A valve plate 37 is fixedly arranged at one end of the cylinder block 32 so as to be slidable with respect to the end surface of the cylinder block 32.
As shown in the figure, arc-shaped suction port 38a and discharge port 3
8b is formed. When the cylinder block 32 is rotated in the direction of the arrow in FIG. 6 (clockwise in FIG. 7), the piston 34 is reciprocated, and the piston 34 moves to the left in FIG. 6 in a state corresponding to the suction port 38a. The hydraulic oil is sucked into the cylinder bore 33 from the suction port 38a when moving, and the hydraulic oil is discharged from the discharge port 38b when the piston 34 moves to the right in a state corresponding to the discharge port 38b. There is. Further, the discharge port 38b is divided into a plurality of sections.

[Problems to be Solved by the Invention] In order for the axial piston pump to operate smoothly and efficiently, the rotating cylinder block 32 and the stationary valve plate 37 are always in contact with each other at an appropriate surface pressure, and It is necessary that there is a suitable oil film in between. Therefore, considerable flatness is required for the end surface of the cylinder block 32 and the sliding contact surface of the valve plate 37. However, conventionally, when the axial piston pump is operated for a long period of time, the hydraulic oil is contaminated by the metal powder and dust generated by the wear of the drive unit existing in the hydraulic circuit (contamination), and as a result, the cylinder block 32 of the valve plate 37 is affected. A considerable amount of wear occurs on the sliding contact surface with.
The degree of wear is not uniform over the entire surface, and a portion of the seal portion of the valve plate 37, that is, a peripheral portion of the suction port 38a and the discharge port 38b that does not correspond to the movement locus of the cylinder port 33a (portion indicated by A in FIG. 7). Of the discharge port 38b (the portion shown by B in FIG. 7) and the position corresponding to the top and bottom dead center of the piston 34, that is, the portion between the suction port 38a and the discharge port 38b (see FIG. 7). There is little wear of the part indicated by C). Therefore, in the conventional axial piston pump, the flatness of the sliding contact surface of the valve plate 37 with the cylinder block 32 decreases with the long-term operation.
There is a problem that the amount of hydraulic oil that leaks from between 32 increases and the volumetric efficiency decreases.

The present invention has been made in view of the above problems,
An object of the invention is to provide an axial piston pump capable of preventing local wear of a valve plate and suppressing a decrease in volumetric efficiency even after long-term operation.

[Means for Solving the Problems] In order to achieve the above-mentioned object, in the present invention, the valve plate is non-rotatably fixedly arranged in sliding contact with the end face of the cylinder block that rotates integrally with the drive shaft. Corresponding to the locus of movement of the cylinder port on the sliding contact surface with the cylinder block, a concave portion is provided on the sliding contact surface located between the suction port and the discharge port, and the concave portion and the suction port are adjacent to each other, and the concave portion and the discharge are adjacent to each other. The distance between the ports is set to be equal to or smaller than the diameter of the cylinder port, and the circumferential width of the recess is set to be equal to or smaller than the distance between the cylinder ports.

[Operation] In the axial piston pump of the present invention, due to the presence of the recess formed between the suction port and the discharge port of the valve plate,
The area of the sliding contact surface near the top-bottom dead center is made uniform with the portions corresponding to the suction port and the discharge port. When the cylinder port passes between the suction port and the discharge port of the valve plate as the cylinder block rotates, the suction port and the recess, and the discharge port and the recess or the recesses communicate with each other through the cylinder port. Hydraulic oil slightly leaks to the sliding contact portion between the cylinder block and the valve plate through the recess, and the amount of wear of the sliding portion near the recess due to contaminants in the hydraulic oil causes And the entire sliding contact surface of the valve plate with the cylinder block is evenly worn, and the flatness of the sliding contact surface is kept high even after long-term operation.
Further, since the width of the recess in the circumferential direction is equal to or less than the distance between the cylinder ports, the cylinder port during the discharging process and the cylinder port during the suction stroke are not communicated with each other via the recess.

[Embodiment] An embodiment embodying the present invention will be described below with reference to FIGS. As shown in FIG. 2, a drive shaft 3 is rotatably supported via a bearing 4 between the casing 1 and the end cover 2. A cylinder block 7 is supported on the spline portion 5 of the drive shaft 3 so as to rotate integrally with the drive shaft 3 in a state where the rear end of the valve plate 6 fixed to the end cover 2 is in sliding contact with the valve plate 6. A support member 8 is supported on the spline portion 5 on the front end side of the cylinder block 7 so as to be axially slidable and integrally rotatable. A plurality of cylinder bores 9 are formed in the cylinder block 7 so as to extend parallel to the drive shaft 3 and the centers thereof are located on the same circumference with the drive shaft 3 as the center. A piston 10 is reciprocally housed in the cylinder bore 9. A shoe retainer 12 that engages with a shoe 11 provided at the tip of the piston 10 is supported on the spherical surface portion 8a of the support member 8. Housing 13 provided at the center of the cylinder block 7
A stopper ring 14 is fixed near the valve plate 6 on one end, and a locking ring 15 loosely fitted to the drive shaft 3 is accommodated near the other end, and is locked between the locking ring 14 and the locking ring 15. Support member 8 for ring 15
A spring 16 for biasing the side is interposed. A plurality of pins 17 penetrate the cylinder block 7, and one end of the pins 17 is in contact with the end surface of the support member 8 and the other end is in contact with the locking ring 16 in the accommodating portion 13. . That is, the pressing force of the spring 16 is transmitted to the support member 8 through the pin 17, and the shoe 11 is slidably contacted with the swash plate 18a by the shoe retainer 12 supported by the spherical surface portion 8a of the support member 8.
It is designed to be pressed by. The shoe retainer 12 separates the shoe 11 from the sliding contact portion 18a when the shoe 11 receives a force in a direction in which the shoe 11 is separated from the sliding contact portion 18a due to the line resistance on the suction side of the hydraulic oil in the suction stroke of the piston 10. Play a role in suppressing

The valve plate 6 has a cylinder port 19 when the piston 10 moves from the suction side (in FIG. 2, the piston 10 moves from the upper part to the lower part).
1 and a position corresponding to the rotation locus of the cylinder port 19 when the piston 10 moves from the discharge side (the piston 10 moves from the lower side to the upper side in FIG. 2) as shown in FIG. Circular suction port 20 and discharge port
21 are formed respectively. 2 intake ports,
The discharge port 21 is divided into three. Further, the end cover 2 is formed with a suction passage and a discharge passage (both not shown) communicating with the suction port 20 and the discharge port 21, respectively.

The sliding contact surface of the valve plate 6 with the cylinder block 7 is formed with a stepped portion 6a at the outer peripheral edge thereof which is lowered by one step to increase the surface pressure of the contact surface between the cylinder block 7 and the valve plate 6 and Leakage of hydraulic oil from the machine is suppressed. Further, as shown in FIG. 1, one recess 22 is formed between each suction port 20 and each discharge port 21. The recess 22 is formed such that the radial width W of the valve plate 6 is equal to the widths of the suction port 20 and the discharge port 21, and the distance a between the adjacent suction port 20 and discharge port 21 is the major axis b of the cylinder port 19.
It is formed to have the following length. That is, the cylinder port 19 is the suction port 20 and the recess 22 or the discharge port 21.
The suction port 20 and the recess 22 or the discharge port 21 and the recess 22 can communicate with each other via the cylinder port 19 when passing through a corresponding position between the recess 22 and the recess 22. Also, the recess
The circumferential width c of 22 is formed so as to be equal to or less than the distance d between the cylinder ports 19. That is, the cylinder port
19 is the suction port 20 and the recess 22 or the discharge port 21 and the recess
The cylinder port during the discharge stroke and the cylinder port during the suction stroke cannot communicate with each other through the concave portion 22 when passing through a position corresponding to that between the cylinder port 22 and the cylinder 22.

The swash plate 18 is rotatably arranged with respect to the casing 1 about a support shaft (not shown) arranged perpendicular to the plane of FIG. Is urged by the urging rod 23 provided in the direction in which the inclination angle α increases, and by the movement of the operating body 25 provided on the opposite side of the urging rod 23 and operated via the control valve 24. The inclination angle α is changed as necessary to change the discharge amount (suction amount).

Next, the operation of the device configured as described above will be described. When the axial piston pump is operated, the cylinder block 7 rotates integrally with the rotation of the drive shaft 3. Since the piston 10 is constantly pressed against the sliding portion 18a of the swash plate 18 via the shoe 11, the piston 10 reciprocates in the cylinder bore 9 as the cylinder block 7 rotates, and the drive shaft 3
Revolve around. When the cylinder bore 9 moves to a position corresponding to the suction port 20, the piston 10 is rotationally moved from the upper part to the lower part in FIG. 2, and the working oil is sucked into the cylinder bore 9 through the suction port 20. Further, when the piston 10 moves past the bottom dead center and moves to the position corresponding to the discharge port 21, the piston 10 is rotationally moved from the lower part to the upper part in FIG. 2, and the hydraulic oil sucked into the cylinder bore 9 is discharged. It is discharged from the discharge passage via the port 21. The stroke of the piston 10 is defined by the inclination angle α of the swash plate 18, and the inclination angle α
The larger the value of, the larger the amount of suction and the amount of discharge.

Of the sliding contact surface of the valve plate 6 with respect to the cylinder block 7, a portion corresponding to the movement locus of the cylinder port 19, that is, a partition portion of the suction port 20, a partition portion of the discharge port 21, and between the suction port 20 and the discharge port 21. The part is not always in sliding contact with the end surface of the cylinder block 7, but the cylinder port
19 and the end surface of the cylinder block 7 are alternately slidably contacted. Therefore, the abrasion is less likely to proceed as compared with the outer and inner peripheral portions of the suction port 20 and the discharge port 21 which are always in sliding contact with the end surface of the cylinder block 7. In the present invention, the recess 22 is formed in the portion of the sliding contact surface of the valve plate 6 which is less likely to wear, and the substantial area of the sliding contact surface is made uniform around the suction port 20 and the discharge port 21.

On the other hand, if you run the axial piston pump for a long time,
When the operating oil is contaminated by the metal powder or dust generated by the abrasion of the drive portion existing in the hydraulic circuit, and the contaminated operating oil enters the sliding contact surface between the valve plate 6 and the cylinder block 7, the abrasion of the portion is caused. It will progress faster. Since the recess 22 is formed between the suction port 20 and the discharge port 21, the discharge port 21 and the recess 22 are separated from each other when the cylinder port 19 passes through the position corresponding to between the discharge port 21 and the recess 22. The recess 22 and the suction port 20 are communicated with each other when passing through a position corresponding to between the recess 22 and the suction port 20. As a result, hydraulic oil leaks around the recess 22 and the contaminated hydraulic oil enters the sliding contact surface between the valve plate 6 and the cylinder block 7 to accelerate the wear of the relevant portion, thereby reducing the suction port 20 and The amount of wear of the peripheral portion of the discharge port 21 approaches, and the wear of the sliding contact surface of the valve plate 6 progresses uniformly as a whole. Therefore, the flatness of the sliding contact surface of the valve plate 6 is maintained even after long-time operation, and the decrease in volume efficiency is suppressed as compared with the case where the recess 22 is not provided.

A partition is formed in the discharge port 21, and the suction port
When there is no partition part in 20, the wear of the partition part is less than that in the other parts, and therefore the amount of wear is unbalanced between the discharge port 21 side and the suction port 20 side. However, in this embodiment, since the intake port 20 is also provided with a partition, the wear of both of them progresses in a balanced state, and the flatness of the sliding contact surface of the valve plate 6 is maintained even after long-term operation. To help. Further, when the intake port 20 is also provided with a partition portion, the deformation of the valve plate 6 during heat treatment, processing, etc. during manufacturing is reduced, and the flatness of the sliding contact surface is easily obtained.

The present invention is not limited to the above embodiment,
For example, instead of forming the recess 22 into an elliptical shape, both ports 20, 2
A circular shape having a diameter equal to the width of 1 may be formed, or a plurality of recesses 22 having a diameter smaller than the width of both ports 20 and 21 may be provided as shown in FIG. Also in this case, when the cylinder port 19 moves to a position corresponding to the recess 22, the peripheral edge of the recess 22 is uniformly worn with other parts by the same action as described above. Further, it may be applied to a fixed displacement type axial piston pump instead of a variable displacement type axial piston pump, or to a slant shaft type axial piston pump as shown in FIG. 5 other than the swash plate type axial piston pump. .

[Advantages of the Invention] As described in detail above, according to the present invention, local wear of the valve plate is prevented, and wear of the sliding contact surface progresses uniformly,
The flatness of the sliding contact surface is maintained even after long-term operation,
It has an excellent effect that it is possible to suppress the decrease in volumetric efficiency due to the contamination of hydraulic oil, which is the most problematic problem with axial piston pumps.

[Brief description of drawings]

FIGS. 1 to 3 show an embodiment embodying the present invention. FIG. 1 is a diagram of a valve plate viewed from the line II in FIG. 2, and FIG. 2 is a swash plate type axial piston pump. FIG. 3 is a longitudinal sectional view, FIG. 3 is a view of an end surface of a cylinder block, FIG. 4 is a front view of a valve plate of a modified example, FIG. 5 is a schematic view of a main portion of an oblique shaft type axial piston pump, and FIG. FIG. 7 is a schematic diagram showing the relationship between the suction port and the discharge port of the valve plate and the cylinder port. Drive shaft 3, valve plate 6, cylinder block 7, piston 10,
Cylinder port 19, suction port 20, discharge port 21, recess
twenty two.

Claims (1)

[Scope of utility model registration request] 1. A valve plate (6) is non-rotatably fixed in a state of slidingly contacting an end surface of a cylinder block (7) which rotates integrally with a drive shaft (3), and the cylinder block of the valve plate (6). The recess (22) is provided on the sliding contact surface located between the suction port (20) and the discharge port (21) corresponding to the movement locus of the cylinder port (19) on the sliding contact surface with (7). ,
The intervals between the recess (22) and the suction port (20), and between the recess (22) and the discharge port (21) that are adjacent to each other are each less than or equal to the diameter of the cylinder port (19), and the circumferential width of the recess is the cylinder port (19). Axial piston pump designed to be less than the distance.