JPH0639100Y2 - Axial piston pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a swash plate type axial piston pump driven by an engine such as a hydraulic power source for general industry or construction machinery, especially for construction machinery.

(Prior Art) The conventional swash plate type axial piston pump is used when it is used in a construction machine, etc. due to cavitation due to suction failure at high speed or low temperature, which causes noise and discharge failure. Had a problem of poor workability.

Therefore, in order to improve the inhalation performance, as disclosed in JP-A-49-77203 and JP-A-49-89903,
It is known that the cylinder barrel itself functions as a centrifugal pump to apply a preload to the suction side, and that the preload pump is integrally or separately attached to an axial piston pump.

Further, as described in Japanese Utility Model Laid-Open No. 57-89876, which improves the suction performance without separately providing a pump or the like, a nozzle blade row is formed in the suction port hole portion of the valve plate, and a suitable It is known that the suction performance is improved by increasing the suction angle to reduce the suction resistance.

On the other hand, although it does not improve the suction performance, a high pressure oil is supplied to the piston cylinder from the side opposite to the valve plate side of the cylinder barrel, that is, from the swash plate.
Some are described in Japanese Patent No. 181. This one is
Vibrations caused by the difference between the closing pressure and the discharge pressure when the suction stroke is completed and communication with the high pressure port in the discharge stroke is started are passed through a small hole formed near the opening of the high pressure port on the sliding surface of the swash plate to the outside. Therefore, the high pressure fluid is intermittently supplied to the cylinder chamber to reduce the pressure.

(Problems to be solved by the invention) However, JP-A-49-77203 and JP-A-49-89903
If a centrifugal pump is provided on the cylinder barrel itself or an external preload pump is attached as in Japanese Patent Laid-Open Publication No. 2004-242242, extra energy is required due to the action of the centrifugal pump or the preload pump, and the efficiency of the entire system deteriorates.
Further, in the case where the entire system is pressurized by an external pump, there are problems that the system becomes complicated and that the member strength of the pump low pressure region is insufficient.

The nozzle blade row as disclosed in Japanese Utility Model Laid-Open No. 57-89876 has a complicated structure, and the suction performance changes depending on the rotation speed.

On the other hand, even if the small hole formed in the sliding surface of the swash plate of JP-A-57-119181 is opened on the suction stroke side, the communication hole provided in the piston and the shoe is small, so there is no self-sufficiency performance. Further, the pressure oil to be supplied is intermittent, and it is not possible to continuously and smoothly supply the hydraulic oil along the suction stroke, so that the suction performance cannot be improved. Further, there is a problem that the structure is still complicated.

The object of the present invention has been made in view of the above problems of the conventional technology, and it is possible to improve the suction performance by a simple and inexpensive structure with high system efficiency and energy saving, enable high speed rotation, and reduce the temperature. An object of the present invention is to provide a swash plate type axial piston pump that does not hinder starting at the time.

(Means for Solving Problems) Therefore, the present invention solves the above-described problems of the conventional products by providing the axial piston pump described in the claims of utility model.

(Example) Next, the Example of this invention is described with reference to drawings.
FIG. 1 is a sectional structural view of an axial piston pump of an embodiment of the present invention, and FIG. 2 is a perspective view of a swash plate 4 of the embodiment of FIG. In the pump, a plurality of cylinder chambers 8 are provided in a cylinder barrel 5 rotatably supported in a housing 1 together with a shaft 3, and a plurality of pistons 6 axially slidably inserted therein, and a plurality of pistons 6 are provided. It includes a valve plate 9 having an intake port 10 and a discharge port 11 which can be opened in each cylinder chamber 8 on one end side, and a swash plate 4 slidingly contacting a head 18 on the other end side of each piston 6 via a shoe 7. . The other end 18 of each piston and the shoe 7 are provided with a self-suction passage 19 communicating with each cylinder chamber 8. The self-inhalation passage 19 is formed as large as possible in terms of strength so as to promote self-inhalation. For example, the piston diameter is about φ16, and the diameter of the self-intake passage 19 is φ4 to φ5. A cocoon-shaped suction port 15 is provided on the sliding contact surface of the swash plate 4 with the shoe 7.
It is provided at a position corresponding to the suction port 10 of the valve plate 9 in the circumferential direction. The cocoon-shaped suction port 15 communicates with the self-suction passage 19 of the shoe 7 at the suction stroke position, and the cocoon-shaped suction port 15 and the communication passage 16 opening into the housing 1 are provided in the swash plate 4. There is. A suction port 17 is provided in the housing 1 and communicates with the inside of the housing.

In the embodiment, the pump suction port 17 is provided separately from the suction port 12 that communicates with the suction port 10. However, the pump suction port 17 is connected to the pump suction port 17 by communicating the suction port 12 with the inside of the housing 1 through a passage (not shown). The suction port 12 may be shared.

Regarding the operation, when the shaft 3 is rotated by a prime mover (not shown), the plurality of pistons 6 inserted into the cylinder chamber 8 of the cylinder barrel 5 and the other end head 18 of the piston 6
Shoe 7 that can be fitted and rocked by forming a spherical joint with
Rotates and reciprocates along the swash plate 4, and in the pump discharge stroke, pressure oil is pushed out from the cylinder chamber 8 by the piston, and pressure oil is discharged from the discharge port 13 through the valve plate 9 and the discharge port 11. It

In the pump suction stroke, the working oil flows into the cylinder chamber 8 of the cylinder barrel 5 through the suction port 12 provided in the housing 1 and the cocoon-shaped suction port 10 of the valve plate 9.

Further, in the pump suction stroke, the communication passage 16 of the swash plate 4 from the suction port 17 provided in the housing 1 through the housing 1, the cocoon-shaped suction port 15 provided in the swash plate, the shoe 7, and the piston head 18 are self-suctioned. The hydraulic oil is also sucked into the cylinder chamber 8 through the passage 19.

As described above, in the pump discharge process, the valve plate 9
In the pump suction stroke, the hydraulic oil is sucked from both the suction port 10 of the valve plate 9 and the cocoon-shaped suction port 15 provided on the swash plate through the self-suction passage 19. To do.

As a result of conducting an experiment on the hydraulic pump with a piston diameter of φ16 described above, the suction flow rate from the swash plate side passes through the shoe and piston, but is 1/4 to 1/5 of the flow area on the valve plate side. The maximum speed is 2000
A pump of about rpm can rotate at high speed up to about 2500 rpm.

(Effect of device) Inhalation performance is proportional to the area of the inhalation flow path. Further, in the present invention, the suction performance is improved not only by the valve plate side but also by the swash plate side, so that the suction performance is improved by the increase in the flow passage area. Therefore, cavitation due to suction failure at high speed rotation or at low temperature is eliminated, noise is reduced, discharge failure is eliminated, and workability in construction machines is improved. Further, the self-suction passage provided on the other end of the shoe and the piston is made as large as possible, and the cocoon-shaped suction port of the swash plate is provided along the suction stroke, which enables smoother self-suction. Suitable for higher speed rotation. Since it does not require a preload pump or auxiliary equipment, it has a simple and inexpensive structure and saves energy. Moreover, since the entire system is not pressurized, it is not necessary to increase the strength of the members in the pump low pressure region. Further, since there is no change in the suction performance due to the rotation speed as in the nozzle blade row, the suction performance can be improved in a wider pump rotation speed range.

[Brief description of drawings]

FIG. 1 is a sectional structural view of an axial piston pump which is an embodiment of the present invention, and FIG. 2 is a perspective view of the swash plate shown in FIG. 1 ... Housing, 3 ... Shaft, 4 ... Swash plate, 5 ... Cylinder barrel, 6 ... Piston, 7 ... Shoe, 8 ... Cylinder chamber, 9 ... Valve plate, 10 ... Suction port, 11 …… Discharge port, 15 …… Coconoid suction port, 16 …… Communication passage, 17 …… Pump suction port, 18 …… Piston other end of head, 19 …… Self-suction passage.

Claims (1)

[Scope of utility model registration request] 1. A plurality of pistons that are axially slidably fitted in a plurality of cylinder chambers of a cylinder barrel that is rotatably supported in a housing together with a shaft, and the cylinders on one end side of each piston. In a swash plate type axial piston pump including a valve plate having a cocoon-shaped suction port and a discharge port opening to the chamber, and a swash plate slidable via the other end head of each piston and a shoe,
The other end of each piston and the shoe have a self-intake passage communicating with each cylinder chamber, and the swash plate has an opening at a sliding contact surface between the shoe and the swash plate and has a valve plate of the valve plate. The cocoon-shaped suction port is provided at a position substantially corresponding to the cocoon-shaped suction port in the circumferential direction, and the cocoon-shaped suction port and a communication passage open to the inside of the housing are provided, and the inside of the housing and the pump suction portion are communicated with each other. An axial piston pump having a suction port provided in the housing.