JP2000087845A - Piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cavitation by reducing speed energy of a jet stream flowing into a cylinder port from a notch even in the case of changing an operating condition. SOLUTION: In a valve plate 5 having a suction port 5A and a delivery port 5B relating to a cylinder of a rotatable cylinder block, a notch 5C extended from an end part of the delivery port 5B to a side of the suction port 5A is provided in a slide surface 5D of the valve plate 5 in the vicinity of the bottom dead center of a piston, and a circular arc-shaped groove part 5E along a circular arc formed with an end part of a cylinder port 7A is provided in an end part positioned on the side of the suction port 5A of the notch 5C of the valve plate 5, relating to the cylinder port 7A which can communicate with any of the suction port and the delivery port 5B of the valve plate 5, in an end surface of the cylinder block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston pump provided in a hydraulic shovel or the like, and more particularly to a piston pump having a notch on a sliding surface of a valve plate extending from an end of a discharge port to a suction port. .

[0002]

2. Description of the Related Art A conventional piston pump of this type is disclosed in Japanese Utility Model Laid-Open No. 4-62367. FIG.
FIG. 6 is a cross-sectional view showing the conventional piston pump.
FIG. 6 is a diagram illustrating an arrangement relationship between two notches formed on a valve plate provided in the conventional piston pump shown in FIG. 5 and a cylinder port.

In FIG. 5, reference numeral 21 denotes a casing which forms the outer shell of a piston / pump. The casing 21 comprises a cylindrical casing body 23 and a rear casing 22 which closes the open end of the casing body 23. Made up of Reference numeral 25 denotes a rotating shaft inserted through the casing 21;
Reference numeral 4 denotes a cylinder block that rotates integrally with the rotation shaft 25. A plurality of cylinders 26 are formed around the axis in the cylinder block 24, and each of these cylinders 26 has a piston 27 for sucking and discharging hydraulic oil.
Is stored. Reference numeral 29 denotes a swash plate capable of changing a displacement volume.

Reference numeral 31 denotes a valve plate fixed to the inner surface of the rear casing 22. The valve plate 31 is always in communication with an inflow passage 33 provided in the rear casing 22 and has an eyebrow-shaped suction port 32a. A discharge port 32b formed in an eyebrow shape is always in communication with the inflow passage 34 provided in the rear casing 22. The end face of the cylinder block 24 which is in sliding contact with the valve plate 31 communicates with each of the corresponding ones of the cylinders 26 described above, and any one of the suction port 32a and the discharge port 32b of the valve plate 31 is rotated as the cylinder block 24 rotates. A cylinder port 30 capable of selectively communicating with the crab is formed.

As shown in FIG. 6, a discharge port 32 is provided on a sliding surface of the valve plate 31 on which the cylinder block 24 slides.
A first notch 40 and a second notch 41 are formed extending from the end of b to the side of the suction port 32a.

In this prior art, a rotating shaft 25 is rotated at a predetermined number of rotations to integrally form a cylinder block 24.
Is rotated, the predetermined high-pressure hydraulic oil of the discharge port 32b of the valve plate 31 moves the first notch 40 and the second notch 41 of the valve plate 31 as shown by arrows B and C in FIG. Through the cylinder port 30 as a jet. At this time, the jet indicated by the arrow B and the jet indicated by the arrow C collide in the cylinder port 30, and the collision reduces the velocity energy of the jet and suppresses the collision of the high-speed jet with the inner wall of the cylinder 26. It is supposed to be. This allows
The generation of cavitation is suppressed, the generation of noise is suppressed, and the generation of erosion (crushing) on the inner wall of the cylinder 26 is prevented.

[0007]

However, in the above-mentioned prior art, the rotation speed of the rotary shaft 25 changes during the operation of the piston / pump, or the pressure of the hydraulic oil changes greatly as compared with before. Then, the jets flowing out of each of the first notch 40 and the second notch 41 may not collide. For piston pumps provided in construction machines such as hydraulic excavators, the number of revolutions or the pressure of hydraulic oil may change significantly during the operation of the piston pump, depending on the type of work. Can occur frequently.

When the two jets flowing out of the first notch 40 and the second notch 41 do not collide, a high-speed jet collides with the inner wall of the cylinder 26. In this state, cavitation is generated as described above, and noise is generated accordingly, and erosion is generated on the inner wall of the cylinder block 26. In other words, this conventional technique is not necessarily suitable for application to construction machines such as hydraulic excavators as described above.

The present invention has been made in view of the above-mentioned situation in the prior art, and has as its object the advantage of notching regardless of a change in operating conditions such as a change in rotational speed during operation or a change in pressure of hydraulic oil. An object of the present invention is to provide a piston pump capable of reducing velocity energy of a jet flowing into a cylinder port.

[0010]

In order to achieve this object, an invention according to claim 1 of the present invention has a plurality of cylinders, a rotatable cylinder block, and a cylinder block which is housed in each of the cylinders and operates. A plurality of pistons for performing suction and discharge of oil, and a valve plate having an end port of the cylinder block slidably contacted and having a suction port for sucking the hydraulic oil and a discharge port for discharging the hydraulic oil; A notch extending from the end of the discharge port to the suction port side is provided on a sliding surface of the valve plate near the bottom dead center where the end surface of the cylinder block slides, and slides on the valve plate of the cylinder block. The end face communicates with each of the corresponding ones of the cylinders, and any one of the suction port and the discharge port of the valve plate is rotated with the rotation of the cylinder block. A piston pump having a plurality of cylinder ports which can be selectively communicated with an end of the notch of the valve plate located on the suction port side along an arc forming an end of the cylinder port. It is configured to have a groove.

According to the first aspect of the present invention, the jet flow guided from the end of the notch to the arc-shaped groove is dispersed according to the shape of the arc-shaped groove, thereby reducing the velocity energy of the jet. With the rotation of the cylinder block, the hydraulic oil dispersed as described above flows from the respective portions forming the arc-shaped grooves into the cylinder port from the end formed in the arc of the cylinder port. That is, the large velocity energy of the hydraulic oil flowing out of the discharge port is
It can be reduced by the arc-shaped groove at the end of the notch, and can flow into the cylinder port in that state.

According to a second aspect of the present invention, in the first aspect of the present invention, the diameter of the inner periphery of the arc-shaped groove is changed to the diameter of the arc forming the end of the cylinder port. , And the end of the notch is connected to a substantially central portion of the outer periphery of the arc-shaped groove.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a piston / pump according to the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the piston pump of the present invention, FIG. 2 is a front view showing a valve plate provided in the embodiment shown in FIG. 1, and FIG. 3 is an embodiment shown in FIG. It is a figure explaining the relative operation of the valve plate provided and the sliding surface of a cylinder block.

In FIG. 1, reference numeral 1 denotes a casing forming an outer shell of a piston pump provided in a hydraulic shovel or the like. The casing 1 includes a cylindrical casing main body 2 having a closed portion 2A at one end in the axial direction, and a rear casing 3 that closes an open end of the casing main body 2. A rotating shaft 4 is inserted in the casing 1 in the axial direction thereof, and the rotating shaft 4 is rotatably supported between the closing portion 2A side and the rear casing 3 side.
A cylinder block 6 is spline-coupled to the rotating shaft 4, and the cylinder block 6 rotates integrally with the rotating shaft 4. A plurality of cylinders 7 are formed around the axis in the cylinder block 6, and each of the cylinders 7 accommodates a piston 8 for sucking and discharging hydraulic oil.

A valve plate 5 is fixed to the inner surface of the rear casing 3 described above, and the valve plate 5 has a sliding surface 5D which is in sliding contact with an end surface 6A of the cylinder block 6. Further, the valve plate 5 is formed with a suction port 5A and a discharge port 5B which are always in communication with a pair of inflow / outflow passages (not shown) provided in the rear casing 3 and have eyebrows as shown in FIG. Discharge port 5B of valve plate 5 corresponding to the bottom dead center side of piston 8
Is formed with a notch 5C extending toward the suction port 5A.

An end surface 6A of the cylinder block 6 which is in sliding contact with the sliding surface 5D of the valve plate 5 communicates with a corresponding one of the cylinders 7 described above.
Cylinder port 7 that can selectively communicate with either suction port 5A or discharge port 5B of valve plate 5 with rotation of
A is formed.

As shown in FIG. 1, a swash plate 10 for changing the applied volume is provided in the casing 1 at a position facing the valve plate 5. The cylinder block 6
A spring 11 is arranged between the rotary shaft 4 and the rotating shaft 4. The spring force of the spring 11 is applied to the cylinder block 6, whereby the cylinder block 6 is pressed against the valve plate 5. The spring force of the spring 11 is applied to the retainer 14 via the rod 12 and the bush 13, whereby the shoe 8A rotatably connected to the piston 8 is pressed against the swash plate 10.

A notch 5C formed at the end of the discharge port 5B located near the bottom dead center of the piston 8 of the valve plate 5
At the end located on the suction port 5A side, an arc-shaped groove 5E is formed along the arc forming the end 7B of the cylinder port 7A as shown in FIGS. This arc-shaped groove 5
The size of the inner circumference 5F of E is set to be equal to the diameter of the arc forming the end 7B of the cylinder port 7A, for example.

In the present embodiment having such a configuration,
When the cylinder block 6 rotates together with the rotation shaft 4, the piston 8 reciprocates a stroke according to the inclination angle of the swash plate 10. Further, each cylinder port 7A of the cylinder block 6 is sequentially connected to a suction port 5A and a discharge port 5B of the valve plate 5. As a result, the hydraulic oil is supplied to the rear casing 3
Of the valve plate 5 through an inflow passage (not shown)
A is sucked into the cylinder 7 from A, and then the hydraulic oil in the cylinder 7 is discharged through a discharge port 5B of the valve plate 5 to an outflow passage (not shown) of the rear casing 3.

The state when each of the cylinder ports 7A of the above-described cylinder block 6 is switched from the suction port 5A of the valve plate 5 to the discharge port 5B will be described with reference to FIG.

The notch 5C formed at the end of the discharge port 5B of the valve plate 5 has an arc-shaped groove 5E formed at the end of the notch 5C which faces the suction port 5A. Is supplied via At this time, notch 5C
The jet flow guided from the end portion to the arc-shaped groove portion 5E is dispersed according to the shape of the arc-shaped groove portion 5E, whereby the velocity energy of the jet is reduced. When the cylinder port 7A is brought into communication with the arc-shaped groove portion 5E with the rotation of the cylinder block 6, the hydraulic oil dispersed as described above is moved from the respective portions forming the arc-shaped groove portion 5E to the arrows 5K in FIG. As shown by, the cylinder port 7A flows into the cylinder port 7A through an arc-shaped end. At this time, the arc of the end portion 7B of the cylinder port 7A and the inner periphery 5F of the arc-shaped groove 5E coincide with each other so that the arc-shaped groove 5E is formed.
Communicates with the cylinder port 7A, so that the notch 5C
Jet from the dominant dominant. However, since the hydraulic oil is basically dispersed according to the shape of the arc-shaped groove 5E as described above, the large velocity energy of the hydraulic oil is reduced in the arc-shaped groove 5E as described above, and this velocity energy is reduced. It is possible to make the operating oil thus caused flow into the cylinder port 7A.

According to this embodiment, the cylinder block 6
With the rotation of the hydraulic pump, the hydraulic oil whose speed energy has been reduced as described above is supplied from the arc-shaped groove portion 5E to the cylinder port 7A, so that the piston pump such as the rotational speed of the cylinder block 6 and the pressure change of the hydraulic oil are changed. Irrespective of a change in the operating conditions during the operation of the cylinder block, the occurrence of cavitation can be prevented, the occurrence of noise can be prevented, and the occurrence of erosion on the inner wall of the cylinder block 6 can be prevented. Therefore, the present invention is suitable for application to construction machines such as a hydraulic shovel in which operating conditions frequently change during operation.

FIG. 4 is a diagram showing a main part of another embodiment of the present invention. In the other embodiment shown in FIG. 4, the diameter of the inner circumference 5F of the arc-shaped groove 5E is set slightly smaller than the diameter of the arc forming the end 7B of the cylinder port 7A, and the notch 5C is formed. Are connected to the substantially central portion of the outer periphery of the arc-shaped groove 5E. Other configurations are the same as those of the embodiment shown in FIGS.

With this configuration, when the cylinder port 27 and the arc-shaped groove 5E come into communication with each other with the rotation of the cylinder block 6, the arc-shape is within a very short time range. Each part of the inner periphery 5F of the groove 5E does not communicate with the end 7B of the cylinder port 7A at the same time. Instead, as shown in FIG. 4, the distal end 5G of the arc-shaped groove 5E first communicates, and then the distal end 5G. The part to be installed communicates. That is, the communication with the cylinder port 2A starts sequentially from the outer portion of the inner periphery 5F of the arc-shaped groove 5E. As a result, the flow indicated by the arrow 16 from the notch 5C can be prevented from becoming dominant, and the hydraulic oil dispersed in the arc-shaped groove 5E is substantially removed from each part of the inner circumference 5F of the arc-shaped groove 5E. The cavitation can be evenly guided to the cylinder port 7A, and the occurrence of cavitation can be more effectively prevented. As a result, the generation of noise and the erosion on the inner wall of the cylinder block 6 can be reliably prevented.

[0025]

As described above, according to the present invention, the end of the notch is not affected by a change in operating conditions such as a change in the rotational speed during operation or a change in the pressure of the hydraulic oil. The jet flow flowing out of the discharge port of the valve plate can be dispersed by the arc-shaped groove portion provided in the valve plate, and the velocity energy of the jet flow flowing into the cylinder port from the notch can be reduced, thereby preventing cavitation. Accordingly, generation of noise can be prevented, and erosion of the wall surface of the cylinder can be prevented. Therefore, the present invention is suitable for application to construction machines such as a hydraulic shovel in which operating conditions frequently change during operation.

According to the second aspect of the present invention,
Since the communication with the cylinder port starts sequentially from the outer part of the inner circumference of the arc-shaped groove, it is possible to prevent the flow from the notch from becoming dominant, and the hydraulic oil is almost evenly distributed from each part of the inner circumference of the arc-shaped groove. The cavitation can be guided to the cylinder port, and the occurrence of cavitation can be better prevented, and accordingly, the generation of noise and the occurrence of erosion on the inner wall of the cylinder block can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a piston pump of the present invention.

FIG. 2 is a front view showing a valve plate provided in the embodiment shown in FIG. 1;

FIG. 3 is a diagram illustrating a relative operation between a valve plate provided in the embodiment shown in FIG. 1 and a sliding surface of a cylinder block.

FIG. 4 is a diagram showing a main part of another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing an example of a conventional piston pump.

6 is a diagram showing a positional relationship between two notches formed on a valve plate provided in the piston pump shown in FIG. 5 and a cylinder port.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 4 Rotating shaft 5 Valve plate 5A Suction port 5B Discharge port 5C Notch 5D Sliding surface 5E Arc-shaped groove 5F Inner diameter 5G Tip 6 Cylinder block 6A End face 7 Cylinder 7A Cylinder port 8 Piston

Claims (2)

[Claims] Claims: 1. A rotatable cylinder block having a plurality of cylinders and housed in each of the cylinders,
A plurality of pistons for sucking and discharging hydraulic oil, and a valve plate having an end surface of the cylinder block slidably contacted and having a suction port for sucking the hydraulic oil and a discharge port for discharging the hydraulic oil, wherein the piston A notch extending from the end of the discharge port to the suction port side is provided on a sliding surface of the valve plate near the bottom dead center where the end surface of the cylinder block slides, and the valve plate slides on the valve plate of the cylinder block. A plurality of cylinder ports that communicate with corresponding ones of the cylinders and that can selectively communicate with one of the suction port and the discharge port of the valve plate with the rotation of the cylinder block are provided on the contacting end face. An end of the cylinder port is formed at an end of the notch of the valve plate located on the suction port side. Piston pump, characterized in that a circular arc-shaped groove portion along the arc. 2. The method according to claim 1, wherein a diameter of an inner circumference of the arc-shaped groove is set smaller than a diameter of an arc forming the end of the cylinder port, and an end of the notch is formed in the arc-shaped groove. 2. The piston / pump according to claim 1, wherein the piston / pump is connected to a substantially central portion of the outer periphery.