JPH0587061A - Flow-rate control device - Google Patents

Abstract

PURPOSE:To secure the smooth operation of a flow-rate control spool valve and reduce the manufacturing cost. CONSTITUTION:A cylindrical space 4a is formed within a pump housing 4 so that a cylindrical sleeve 6 is coupled in the space, and a spool valve is slidably inserted into the cylindrical sleeve. Bypass openings 61 are formed in the radial direction at symmetrical positions on the circumferential wall of the cylindrical sleeve in order to bypass a part of fluid which is discharged while being released due to the movement of the spool valve, to a fluid inlet path 45, and each fluid inflow path 46 from a reservoir is opened respectively at the outlet sections of these bypass openings. Since the bypass openings formed on the symmetrical positions at both sides are released by the spool valve, pressure at both the sides of the valve is balanced when the valve is released. This configuration thereby causes no lateral force to act on the spool valve, and the valve is thereby smoothly operated. Since a space for the spool valve to slide, is formed within the cylindrical sleeve coupled in the inside of the housing, processing excellent in accuracy can be performed at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate control device, and more particularly to a structural improvement of a flow rate control device provided with a spool valve for adjusting a pump discharge amount to a constant value.

[0002]

2. Description of the Related Art A vane pump in which a plurality of vanes are provided on the outer periphery of a rotary rotor, and a fluid is sucked into a pump chamber defined by these vanes and compressed and discharged has high pump efficiency and can be miniaturized. , Is widely used as a pump for automobiles. Of these, when used as a hydraulic pump for power steering, etc., the pump is provided with a flow rate control device for making the amount of oil supplied to the steering gear box constant, and an example thereof is shown in FIG.

In the figure, the discharge port 42 from the pump chamber is shown.
The fluid discharged to the pump is discharged to the outside of the pump from a fluid discharge passage 43 provided with an orifice 44 on the way through a passage in the pump housing 4 as indicated by an arrow in the figure. The fluid discharge path 4
A cylindrical space 4a formed at the top of the housing 4 coaxially with 3
A spool valve 5 for flow rate control is movably arranged inside, and a pressure (discharge pressure) downstream of the orifice 44 is introduced behind the spool valve 5 by a pressure guide path (not shown). The spring-biased spool valve 5 is moved to the left in the drawing by the differential pressure before and after the orifice 44 generated according to the amount of discharged fluid, opening the bypass opening 48, and a part of the discharged fluid is indicated by the arrow in the drawing. Is bypassed to the fluid suction passage 45 on the outer periphery of the cam ring 3 to maintain the pump discharge amount constant. The bypass flow becomes a jet flow, and the fluid from the reservoir outside the pump is entrained from the fluid inflow path 46 that opens in the middle to efficiently supply the fluid to the suction port.

[0004]

By the way, in the above-mentioned conventional structure, when the bypass opening 48 is opened, the land 51 of the spool valve 5 has a negative pressure on the side facing the bypass jet flow and a negative pressure on the opposite side. Since a large positive pressure of the discharged fluid is applied, as shown by the arrow in the figure, a lateral force acts on the entire spool valve 5 to cause friction with the inner wall of the housing during valve operation, resulting in wear or, in extreme cases, sticking. There was a problem.

In order to solve this, for example, in Japanese Patent Laid-Open No. 61-228167, a groove for allowing a part of the discharge fluid to flow is formed in the inner wall of the housing facing the bypass opening to form a spool valve land. Attempts have been made to balance the pressure on both sides of the spool valve, which can reduce the lateral force acting on the spool valve.
Depending on the application, it is not enough.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a flow control device which eliminates the lateral force acting on the spool valve to enable smooth operation and is easy to manufacture.

[0007]

The structure of the present invention will be described. A cylindrical space 4a is formed in a housing 4 and the space 4 is formed.
The tubular sleeve 6 is fitted into the inside of a and the tubular sleeve 6
A spool valve 5 is slidably inserted therein, and the cylinder sleeve 6 is opened at a radially symmetrical position of the peripheral wall by the movement of the spool valve 5 to return a part of the discharge fluid to the pump portion. The openings 61 are formed respectively, and the fluid inflow passages 46 extending from the reservoir are opened at the outlets of the bypass openings 61.

[0008]

In the flow rate control device having the above construction, the spool valve 5 is moved to maintain the discharge amount constant and the bypass opening 6 is moved.
1 is opened, but this bypass opening 61 is used for the spool valve 5
Since both sides are symmetrically formed, the pressures on both sides of the valve at the time of opening the opening become negative pressures by the bypass flow and both are balanced. Therefore, lateral force does not act on the spool valve 5, and smooth valve operation without wear or sticking is realized.

A space in which the spool valve 5 slides is formed in a cylindrical sleeve 6 fitted in a cylindrical space 4a of the housing 4, and a bypass opening 61 is also formed in the cylindrical sleeve 6.
Therefore, it is possible to perform highly accurate processing at a low cost as compared with the case where the housing 4 is directly machined. In particular, when an aluminum housing is used to reduce the weight of the pump, another metal that can be easily processed can be used for the tubular sleeve, which is advantageous.

[0010]

[Embodiment 1] In FIG. 1, a rotating circular rotor 1 is provided in a pump housing 4, and a plurality of vanes 2 equidistantly provided on the outer periphery of the rotor divide an elliptical inner peripheral space of a cam ring 3 into a pump chamber. It is P. The volume of the pump chamber P periodically expands and contracts with the rotation of the rotor 1 (arrow in the figure), and fluid is sucked into the left and right suction ports 41 into the pump chamber P whose volume gradually increases, and the volume gradually decreases. The fluid is compressed and discharged from the pump chamber P to the upper and lower discharge ports 42.

The fluid is supplied to each suction port 41 (arrows in the figure) by the left and right fluid suction passages 45 formed between the outer circumference of the cam ring 3 and the inner circumference of the pump housing 4.
A cylindrical space 4a having one closed end is formed in the top of the pump housing 4 in parallel with the rotation axis of the rotor 1 (FIG. 2).
A cylindrical sleeve 6 is driven and fixed in the space 4a. Circular bypass openings 61 are formed in the sleeve 6 at left and right symmetrical positions (FIGS. 1 and 3), and the fluid suction passages 45 communicate with the openings 61.

Inside the sleeve 6, a coil spring 5 is provided on the back side.
The spool valve 5 is biased by 2 so as to be horizontally slidable, and the opening area of the bypass opening 61 is changed according to the movement amount of the spool valve 5.

A cylindrical plug member 47 having an orifice 44 formed in the inner periphery is screwed into the opening of the cylindrical space 4a, and the inner space is a fluid for delivering the fluid discharged from the discharge port 42. It is the discharge path 43.

Fluid inflow path 4 leading to a reservoir outside the pump
6 (FIG. 1) has one end opening at the top surface of the pump housing 4,
The other end branches left and right along the outer circumference of the sleeve 6 and communicates with the fluid suction passage 45 at the outlet of the bypass opening 61 in the forward direction on the side where negative pressure is generated by the bypass flow.

The fluid discharged from the discharge port 42 is discharged to the outside of the pump through the fluid discharge passage 43, but the fluid pressure immediately after the orifice 44 is the coil spring 52 due to the pressure guide passage (not shown).
It is introduced behind the spool valve 5 provided with. Then, when the fluid discharge amount increases, the spool valve 5 moves to the left in FIG. 3 due to the differential pressure generated before and after the orifice 44, the bypass opening 61 opens, and a part of the discharged fluid partially flows into the fluid suction passage 4.
By-passing to 5 (arrow in the figure), the fluid discharge amount is maintained constant.

At the time of this fluid bypass, the bypass opening 61 opened by the spool valve 5 has its land 51.
Since they are located symmetrically with respect to each other, the negative pressure of the bypass jet flow acts evenly on the spool valve 5 from both sides, and no lateral force perpendicular to the axis is received. Therefore, the spool valve 5 operates smoothly without causing wear or sticking.

The bypass flow jetted from each bypass opening 61 entrains the fluid that has passed through the fluid inflow passage 46 (FIG. 1) and efficiently sends it to the fluid suction passage 45 without causing cavitation or the like. This improves pump efficiency.

Since the moving space of the spool valve 5 is formed in the sleeve 6 driven into the pump housing 4, and the bypass opening 61 is also provided in the peripheral wall of the sleeve 6,
It is not necessary to increase the processing accuracy of the pump housing 4 itself that is molded, and the manufacturing cost can be reduced.

[0019]

Second Embodiment The present invention can be applied to an apparatus of the type in which a spool valve 5 is provided so as to be orthogonal to the pump axis as shown in FIGS. In this case, the bypass openings 61 are formed in the upper and lower peripheral walls of the sleeve 6, and the fluid inflow passages 46 and the fluid suction passages 45 are connected to each other at the outlets of the openings 61.

According to this structure, in addition to the effects of the above-described embodiment, as shown by the arrows in FIG. 4, the bypass jets from the upper and lower sides, which are entrained with the fluid in the respective fluid inflow passages 46, are applied to the cam ring 3.
When the cam ring 3 merges with each other at the apex of the outer periphery of the cam ring 3, uneven flow in one circumferential direction of the cam ring 3 is eliminated, and the fluid is evenly diverted to the left and right fluid suction passages 45 to improve pump efficiency.

[0021]

As described above, according to the flow rate control device of the present invention, since the lateral force generated by the bypass jet flow does not act on the fluid control valve, smooth operation without wear or sticking is realized, and the cylinder Since the sleeve is provided with the spool valve sliding portion and the bypass opening having the processing accuracy and the pump housing does not need the passage having the accuracy, the manufacturing cost can be reduced.

[Brief description of drawings]

1 is a cross-sectional view of a pump provided with a flow rate control device showing an embodiment of the present invention, and is a cross-sectional view taken along line I-I of FIG.

FIG. 2 is a vertical sectional view of a pump.

FIG. 3 is a sectional view taken along line III-III in FIG.

4 is a cross-sectional view of a pump provided with a flow rate control device showing another embodiment of the present invention, which is a cross-sectional view taken along line IV-IV of FIG.

FIG. 5 is a vertical sectional view of a pump.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a vertical cross-sectional view of a main part of a pump provided with a flow rate control device showing a conventional example.

[Explanation of symbols]

 1 rotor 2 vane 3 cam ring 4 pump housing 4a tubular space 41 suction port 42 discharge port 43 fluid discharge passage 44 orifice 45 fluid suction passage 46 fluid inflow passage 5 spool valve 6 cylinder sleeve 61 bypass opening

Claims (1)

[Claims] 1. A cylindrical space is formed in a housing, a cylindrical sleeve is fitted in the space, a spool valve is slidably inserted in the cylindrical sleeve, and a peripheral wall is formed in the cylindrical sleeve. At the symmetric positions in the radial direction of the bypass valve, bypass openings that are opened by the movement of the spool valve and return a part of the discharge fluid to the pump section are formed respectively, and at the outlet sections of these bypass openings,
A flow rate control device characterized in that each fluid inflow path extending from the reservoir is opened.