JPH0979132A - Hydraulic pump - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve self-priming property of a pump and to cope with high speed rotation. SOLUTION: In a hydraulic pump including a main pump and a pilot pump, surplus oil from a relief valve 6 that regulates the discharge pressure of the pilot pump is discharged to an internal chamber 1a of a pump case 1 of the main pump. The suction port 7 of the pump is provided with a guide hole 9 for ejecting excess oil inside the pump case toward the downstream of the suction port 7. As a result, surplus oil is jetted out along the streamline of the suction port 7 to accelerate without disturbing the flow of hydraulic oil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the self-priming property of a hydraulic pump.

[0002]

2. Description of the Related Art As a hydraulic pump generally used for a small construction machine or the like, there is a hydraulic pump provided with a main pump and a pilot pump for operating a valve. Then, in order to omit the hydraulic piping, a low-pressure relief valve for setting the pressure of the pilot pump is provided in a part of the case of the main pump, and the relief excess oil is blown out into the pump case of the main pump. By doing so, not only the piping can be omitted, but also the relief blowing noise can be reduced.

[0003]

By the way, since excess oil from the pilot pump discharged into the internal chamber of the pump case is released from the relief valve, the internal pressure of the case rises when there is no drain pipe connected to the tank in the pump case. To prevent this, the pump case and the suction port of the main pump communicate with each other through an oil passage. However, in this case, when the excess oil from the pump case inner chamber flows into the suction port, the flow of the suction port may be disturbed, which causes a problem that the suction performance is deteriorated.

In order to prevent the deterioration of the suction performance, there is a method of mounting a boost pump for increasing the suction pressure.
In this case, the structure becomes complicated, which leads to increase in size and cost.

The present invention solves such a problem, and an object of the present invention is to improve the self-priming property of the pump and to cope with high speed rotation.

[0006]

A first aspect of the present invention includes a main pump and a pilot pump, and discharges excess oil from a relief valve that regulates the discharge pressure of the pilot pump into the pump case of the main pump. In the hydraulic pump described above, the suction port of the main pump is provided with a guide hole for ejecting excess oil inside the pump case toward the downstream of the suction port.

[0007]

In the first aspect of the invention, the surplus oil of the pilot pump is discharged to the inside of the pump case of the main pump, and the inside of the pump case is along the streamline toward the downstream side of the suction port with respect to the suction port. To drain excess oil. Therefore, the flow in the suction port is accelerated without being disturbed,
Suction performance is improved, pump self-priming is enhanced, and high speed rotation can be supported.

[0008]

1 to 4, reference numeral 1 denotes a pump case, and 2 denotes a port block connected to the pump case 1. Cylinder block 1 of pump case 1
2 are arranged, and by the rotation of the cylinder block 12, a plurality of pistons 13 arranged on the concentric circles of the cylinder block 12 expand and contract while slidingly contacting the swash plate 14, and accordingly, from the suction hole 4 of the port block 2. The suctioned hydraulic oil is discharged through the discharge holes 5a and 5b to the discharge ports 8a and 8b.
And discharges into the main pump.

In this example, the pistons 13 arranged in the cylinder block 12 are arranged in an inner and outer double circle state,
The working oil sucked from the common suction hole 4 is discharged to the inner and outer discharge holes 5a and 5b.

Spindle 1 for rotating cylinder block 12
A trochoid pump 15 as a pilot pump driven by 6 is provided, and a low pressure relief valve 6 is provided inside the port block 2 in order to maintain the pressure of the discharged oil at a predetermined value. The relief valve 6 opens when the pressure in the pilot pump discharge passage exceeds a specified value, and at this time, part of the hydraulic oil is released from the relief passage 6
The passage is configured to be discharged to the internal chamber 1a of the pump case 1 via a.

On the other hand, in the inner chamber 1a of the pump case 1,
The cylinder block 12 and the like are arranged,
A guide hole 9 for guiding the excess oil is formed in a suction port 7 that communicates with the suction hole 4 formed in the port block 2 from the internal chamber 1a. The guide hole 9 is provided in the plug 10 and ejects excess oil toward the downstream of the suction port 7 along the streamline. The plug 10 is formed in a cylindrical shape, and the base end side is fixed by the nut 11 in the internal chamber 1a, and the guide hole 9 is formed in the axial center of the plug 10. It bends at a right angle toward it, and excess oil is blown out along the streamline of the hydraulic oil flowing through the suction port 7.

With the above-mentioned structure, the operation will be described.

When the piston 13 reciprocates due to the rotation of the cylinder block 12 driven by the main shaft 16, the working oil sucked from the suction hole 4 via the suction port 7 becomes
It is discharged from the discharge holes 5a and 5b to the discharge ports 8a and 8b.

On the other hand, the relief valve 6 whose discharge pressure from the trochoid pump 15 as a pilot pump is low
When the pressure set by is exceeded, the relief valve 6 is opened and a part of the hydraulic oil is discharged to the internal chamber 1a of the pump case 1.

The hydraulic oil discharged into the internal chamber 1a flows into the low-pressure suction port 7 through the guide hole 9 of the plug 10 after contributing to the lubrication of the internal chamber 1a. Since the surplus oil is jetted downstream along the streamline of the hydraulic oil flowing through, the flow in the suction port 7 is accelerated without being disturbed, and the pump suction performance from the suction hole 4 is improved. As a result, the self-priming property of the pump is enhanced, and it is possible to support higher speed rotation.

Next, another embodiment will be described. In FIG. 5, the shape of the plug 10 is different, and the portion exposed to the suction port 7 is thin so that it is parallel to the streamline from upstream to downstream. It is formed in the flat section 15 having a thickness.

In this way, the flow resistance at the suction port 7 of the plug 10 is reduced by that much, and the suction performance can be improved.

Further, in the embodiment shown in FIG. 6, the portion exposed to the suction port 7 of the plug 10 is made smaller than the diameter of the base portion to form the small diameter portion 16.

Even in this case, since the small diameter portion 16 is only exposed to the suction port 7, the flow resistance becomes small,
The suction performance can be improved.

In the embodiment shown in FIG. 7, instead of providing the plug 10, a guide hole 9 is provided in a part of the wall portion 17 of the suction port 7 so as to be parallel to the streamline of the hydraulic oil flowing through the suction port 7. Is formed, the guide hole 9 is communicated with the internal chamber 1a of the pump case 1, and the surplus oil is jetted out along the streamline. Reference numeral 18 is a blind plug for closing the base end of the processed hole.

In this way, the excess oil is jetted toward the downstream side along the inner wall of the suction port 7, and the pump suction performance can be improved.

The axis of the guide hole 9 may be parallel to the streamline of the suction port 7 as described above, or may be formed so as to obliquely intersect toward the downstream side.

Further, at this time, at the same time, the surplus oil can be jetted from the substantially tangential direction of the inner peripheral surface so as to swirl along the inner peripheral surface of the suction port 7.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an entire pump showing an embodiment of the present invention.

FIG. 2 is a sectional view mainly showing the port block.

FIG. 3 is a plan view of the same.

FIG. 4 is a side view of the same.

FIG. 5 is a perspective view of a plug showing another embodiment.

FIG. 6 is a perspective view of a plug showing still another embodiment.

FIG. 7 is a sectional view of a suction port showing still another embodiment.

[Explanation of symbols]

 1 Pump Case 2 Port Block 4 Suction Hole 5a Discharge Hole 5b Discharge Hole 6 Relief Valve 7 Suction Port 8a Discharge Port 8b Discharge Port 9 Guide Hole 9a Outlet 10 Plug 12 Cylinder Block 13 Piston 15 Trochoid Pump

Claims (1)

[Claims] 1. A hydraulic pump comprising a main pump and a pilot pump, wherein surplus oil from a relief valve that regulates the discharge pressure of the pilot pump is discharged into the pump case of the main pump. The hydraulic pump is characterized in that a guide hole for ejecting excess oil inside the pump case toward the downstream of the suction port is provided.