JPH0525708B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a power steering device that sends pressurized fluid discharged from a pump to a power steering device via a throttle passage, and returns surplus flow to the suction side through a bypass passage. The present invention relates to a flow rate control device for steering working fluid, and particularly to a flow rate control device that reduces the flow rate sent to a power steering device as the pump rotational speed increases.

<Prior art> When an automobile is running at high speed, it is desirable to increase the steering reaction force felt by the driver, and as the pump rotation speed increases, the control flow rate to the power steering device is decreased. A sensitive pump was developed. This is, for example, the special public service of 1973
As described in the publication, an adjustment rod consisting of a small diameter part and a large diameter part is fixed to one end of the flow rate adjustment valve, and the throttle passage is made variable according to the displacement of the flow rate adjustment valve due to an increase in the pump rotation speed. control to reduce the control flow rate to the power steering device.

However, with known pump devices, if the viscosity of the hydraulic oil is constant, the expected flow rate drop characteristic can be obtained, but since the viscosity of the hydraulic oil changes with temperature, when the viscosity is high (at low temperature), The flow rate passing through the throttle passage decreases, and as the flow rate decreases, the flow rate regulating valve is displaced in a direction that opens the bypass passage further, resulting in a further decrease in the flow rate. As a result, the flow rate characteristics become as shown in the diagram A in FIG. 4, and there is a problem that the required flow rate cannot be secured.

<Object of the Invention> An object of the invention is to ensure a flow rate to the power steering device even at low temperatures.

<Structure of the Invention> In order to achieve the above-mentioned object, the present invention stores a cylindrical control spool in a union so as to be movable relative to a flow rate adjustment spool valve, and forms a throttle passage in this control spool. The first and second restriction holes are formed, and a spring is provided that presses the control spool in the direction of contacting the spool valve, and the pressing force of the spring causes the control spool to bypass when the control spool is in contact with the spool valve. The first restriction hole is opened on the outer peripheral surface of the control spool so that when the passage is opened wide, the first restriction hole is closed by the inner periphery of the union, and when the viscosity of the hydraulic oil is normal, the control spool is closed. The control spool is brought into contact with the spool valve by the pressing force of the spring, and when the viscosity of the hydraulic oil is high and the pressure difference between the first and second restriction holes becomes larger than the pressing force of the spring, the control spool is brought into contact with the spool valve. The first restricting holes are spaced further apart from each other so that the first restricting holes are not blocked, thereby ensuring a flow rate.

<Examples> Examples of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 10 denotes a pump housing. A valve housing hole 11 is passed through the pump housing 10, and a pressure fluid outlet 12 is provided at one end of the valve housing hole 11 leading to a normally open type control valve of a power steering device. The union 13 formed with is screwed on,
A stopper 14 is fitted to the other end. Valve storage hole 1
1, a supply passage 15 and a bypass passage 16 are opened spaced apart in the axial direction, and the supply passage 15 communicates with a discharge chamber of the pump, and the bypass passage 16 communicates with a suction chamber of the pump.

A spool valve 1 for adjusting the flow rate is provided in the valve storage hole 11 in order to close the communication path between the supply passage 15 and the bypass passage 16 and to adjust the opening degree of the communication passage.
A first valve chamber 18 and a second valve chamber 19 are formed on both sides of the spool valve 17. The second valve chamber 19 is provided with a spring 20 that presses the spool valve 17 toward the first valve chamber 18 , and the repulsive force of the spring 20 normally holds the spool valve 17 in a position where it contacts the union 13 . However, communication between the supply passage 15 that opens into the first valve chamber 18 and the bypass passage 16 is cut off.

The union 13 has a cylindrical control spool 21.
is slidably fitted therein, and first and second restriction holes 23, 24 are formed in this control spool 21.
The outlet port 12 and the first valve chamber 18 are communicated with each other through the first and second restriction holes 23 and 24. Here, the first restriction hole 23 is connected to the control spool 21.
The aperture opening can be changed by sliding the
It is opened in the fitting surface (outer peripheral surface) with the union 13. A spring 25 that presses the control spool 21 toward the first valve chamber 18 is incorporated in the union 13, and the repulsive force of the spring 25 normally holds the control spool 21 in a position where it contacts the spool valve 17. There is. When the spool valve 17 slides, the control spool 21 slides due to the repulsive force of the spring 25, and the first restriction hole 23 is variably controlled by the union 13. That is, while the pump rotation speed is low and the amount of displacement of the spool valve 17 is small, the first restriction hole 23 is not yet throttled by the union 13, and the flow rate passing area is smaller than that of the first and second restriction holes 2.
3 and 24, but when the pump rotation speed increases and the spool valve 17 is largely displaced, the first restriction hole 23 is gradually restricted by the union 13 and finally closed, and the power steering It is designed to reduce the flow rate to the extraction device.

One end of a communication hole 37 is opened in the second valve chamber 19, and the other end of this communication hole 37 is opened in the second valve chamber 19.
The fluid that has passed through the restriction holes 23 and 24 is led to the second valve chamber 19 through the communication hole 37 . As a result, the restriction holes 23 and 2 are provided on both end faces of the spool valve 17.
Since the pressure before the passage of the restriction hole 2 and the pressure after the passage of the restriction hole 2 act, the spool valve 17 is moved in the axial direction according to the pressure drop in the restriction hole 23 and 24.
The opening degree of the bypass passage 16 is adjusted in order to maintain the pressure drop at a constant value at 3 and 24.

In addition, 40 in the figure is a pressure relief valve incorporated in the spool valve 17, and is composed of a ball valve 41 and a spring 42. When the pressure in the second valve chamber 19 exceeds the set pressure, the pressing force of the spring 42 is applied. In response, the ball valve 41 is opened to allow the fluid in the second valve chamber 19 to escape to the bypass passage 16 through the escape hole 36.

Next, the operation of the flow control device configured as described above will be explained.

When the pump rotor is rotationally driven by the automobile engine, working fluid in the fluid tank is sucked into the pump chamber from the suction chamber, and pressurized fluid is discharged from the pump chamber into the discharge chamber. The pressure fluid discharged into the discharge chamber passes through the restriction holes 23 and 24 and is supplied to the power steering device from the outlet 12, and the fluid returned from the power steering device is collected in the fluid tank and sucked into the pump chamber again. be done.

When the pump rotation speed is low, the pump discharge flow rate is also small, so the spool valve 17 closes the bypass passage 16, and the total pump discharge flow rate is reduced to the limit hole 23, 2.
4 to the power steering device, but as the pump rotation speed increases, the discharge flow rate also increases, and the spool valve 17 is slid to keep the pressure difference before and after the restriction holes 23 and 24 constant, and the bypass is performed. The passageway 16 is gradually opened to bypass excess flow to the bypass passageway 16. Thereby, the pressure fluid sent to the power steering device is maintained at a predetermined amount Q1 determined by the restricting area of the restriction holes 23 and 24 of the control spool 21.

When the pump rotational speed is further increased as the automobile shifts to high-speed running, the spool valve 17 is displaced to open the bypass passage 16 more widely. At this time, if the viscosity of the pressure fluid is normal,
The pressure difference before and after the restriction holes 23 and 24 is caused by the spring 2
5, the control spool 21 is not large enough to displace the control spool 21 against the spool valve 17 due to the pressing force of the spring 25.
and is displaced integrally with the spool valve 17.

Therefore, as described above, as the spool valve 17 is displaced to widen the bypass passage 16, the first restriction hole 23 of the control spool 21 is gradually controlled by the union 13 as shown in FIG. is finally closed, and the pressure fluid sent to the power steering device gradually decreases from the flow rate Q1 as shown in line B in FIG.
It is reduced to a predetermined amount Q2 determined by the aperture area of No. 4. Therefore, when driving at high speed, the driver can enjoy the steering reaction force obtained by reducing the supply flow rate, and high speed stability is improved.

By the way, at low temperatures, the viscosity of the hydraulic oil increases, so the pressure difference between the first valve chamber 18 and the delivery port 12 increases, and as a result, as shown in FIG. 3, the control spool overcomes the repulsive force of the spring 25. 21 toward the delivery port, the first restriction hole 23 is moved even when the spool valve 17 is largely displaced.
is not closed, and the flow rate Q3 is ensured as shown in diagram C in FIG.

<Effects of the Invention> As described above, the present invention accommodates the control spool in which the first and second restriction holes are formed so as to be movable relative to the flow rate adjustment spool valve, and when the viscosity of the hydraulic oil is at normal temperature. The control spool is brought into contact with the spool valve by the pressing force of the spring and is displaced together with the spool valve, thereby closing the first restriction hole of the control spool in response to an increase in the displacement of the spool valve, thereby opening the throttle passage. Since the structure is designed to reduce the flow rate, as the traveling speed of the vehicle increases and the pump rotation speed increases, the flow rate sent to the power steering device can be decreased. This will improve driving stability and reduce horsepower. In addition, at low temperatures when the viscosity of the hydraulic oil is high, the control spool is separated from the spool valve to prevent the first restriction hole from being blocked, making it possible to secure the necessary flow rate even at low temperatures. The operational stability of the extraction device is significantly improved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a cross-sectional view of a flow rate control device, FIGS. 2 and 3 are cross-sectional views showing operating states, and FIG. 4 is a flow rate characteristic with respect to pump rotation speed. It is a line diagram. 10...Pump housing, 12...Outlet port,
13... Union, 15... Supply passage, 16...
Bypass passage, 17... Spool valve for flow rate adjustment,
21...Control spool, 23...First restriction hole, 2
4...Second restriction hole, 25...Spring.

Claims (1)

[Claims] 1 Pressurized fluid discharged from the pump is sent to the power steering device via the throttle passage, and the opening degree of the bypass passage is adjusted by a flow rate adjustment spool valve that responds to the pressure difference between the front and rear of the throttle passage, thereby reducing the surplus flow. is used as a flow rate control device for the power steering working fluid that is returned to the suction side of the pump, and a cylindrical control spool is housed in the union so as to be movable relative to the spool valve, and the control spool is connected to the throttle passage. a spring is provided for pressing the control spool in the direction of contacting the spool valve, and the control spool is brought into contact with the spool valve by the pressing force of the spring. A first restriction hole is opened in the outer circumferential surface of the control spool so that when the control spool opens the bypass passage largely in the state in which the bypass passage is opened, the first restriction hole is closed by the inner circumference of the union. When the viscosity is normal, the control spool is brought into contact with the spool valve by the pressing force of a spring;
When the viscosity of the hydraulic oil is high and the pressure difference across the first and second restriction holes becomes larger than the pressing force of the spring, the control spool is separated from the spool valve to open the first restriction hole. A power steering working fluid flow rate control device configured to prevent blockage.