JPS59213567A - Flow controller for power steering system - Google Patents

Abstract

PURPOSE:In a flow controller where fluid is delivered from a pump through an orifice to a power steering system, to maintain the flow characteristic constant by preparing two orifices and constructing one of them with shape memory alloy which will enlarge opening under low temperature. CONSTITUTION:A spool valve 22 is inserted slidably into a containing hole 11 made through the pump housing 10 and contacted through a spring 26 against a control spool 23 inserted into a hole in an union 21. The control spool 23 is energized by a spring 27 placed between an orifice forming member 24 fitted over the outer end section of union inner hole to contact against the step 21b at the inner end. In such a flow controller, the orifice forming member 24 is formed with first orifice 24a in the center while a plurality of second orifices 24b in the circumference. A doughnut-shaped control member 35 made of shape memory alloy is secured to the orifice 24b to control such that the opening will be enlarged under low temperature.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to a flow rate system in which pressurized fluid discharged from a pump is sent to a power steering device through an orifice, and surplus flow is returned to the suction side through a bypass passage. The present invention relates to a control device, and particularly to a flow rate control device for a power steering device that reduces the flow rate sent to the power steering device as the pump rotation speed increases.

<Prior art> Conventionally, as a flow rate control device having the above function, a pressure difference is generated before and after the control throttle based on an increase in the discharge flow rate due to an increase in the pump rotation speed, and the control spool is displaced by this pressure difference to 1. The opening area of one side of the second orifice is variably controlled, and the pump rotation speed N is adjusted as shown in Fig. 1A.
There is one in which the discharge flow rate Q is lowered when the number of revolutions reaches a certain value.

However, according to such conventional devices, the pressure difference before and after the control fall throttle increases due to the increase in the viscosity of the pressure fluid at low temperatures, and as a result, the control spool is displaced and the first
There was a problem in that the orifice was closed, making it impossible to obtain the required flow characteristics as shown in FIG. 1B.

<Object of the Invention> The present invention has been made in order to solve these conventional problems.1. The purpose is to ensure that the flow rate characteristics do not change regardless of changes in the viscosity of the pressure fluid at low times.

<Structure of the Invention> The present invention has been made to achieve the above-mentioned object, and includes a shape memo 1 in which the shape of the second orifice is memorized so that the opening degree of the second orifice increases when the temperature is low and decreases the opening degree when the temperature is normal. , relates to a flow control device for a power steering device, characterized in that it is constructed of a-alloy.

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

In FIG. 2, 10 is a pump housing, and a storage hole 11 is provided through the pump housing 10 through M, and a union 21 is screwed into one end of this storage hole 11 in a fluid-tight manner. Also, a stopper 25 is provided at the other end of the storage hole 11.
are fitted in a liquid-tight manner.

The spool valve 22 is slidably inserted between the union 21 and the stopper 25 in the storage hole 11.
A first valve chamber 32 and a second valve chamber 33 are formed inside. Further, the spool valve 22 is biased by a spring 26 interposed in the second valve chamber 33 and elastically abuts on a control spool 23 (described later), so that the spool valve 22 is connected to the supply passage 12 and the bypass passage 13 provided in the pump housing 10. communication is cut off. Note that the bypass passage 13 communicates with the suction chamber of the fluid pump.

The control spool 23 is slidably inserted into the inner hole of the union 21, and the control spool 23 is slidably inserted into the inner hole of the union 21. The control spool 23 is biased "ζ" and elastically abuts against the inner end step 21b of the inner hole of the union 21. A communication hole 23 that communicates with the vacant room 34
a is formed, and this communication hole 23a is each orifice 24a of an orifice forming member 24, which will be described later.

24b, the first valve chamber 32 and the outlet port 21a of the union 21 are communicated with each other. Further, a pressure introduction hole 21C provided in the union 21 is opened at the end surface of the stepped portion 23b of the control spool 23. This pressure introduction hole 21C communicates with the supply passage 12, and causes the control spool 23 to slide against the spring 27 when the supply pressure exceeds a predetermined pressure.

The orifice forming member 24 includes each orifice 24 described later.
; together with 1 and 24b, the control nozzle 24c is ω, 7e-ζ
This control nozzle 24C is connected to each orifice 24. a,
A communication hole 21d is provided on the downstream side of the union 21 and the pump housing 24b.

14 and communicates with the second valve chamber 33. As a result, a part of the fluid on the downstream side of each orifice 24a, 24b is guided into the second valve chamber 33, pressures before and after each orifice 24a, 24b act on both ends of the spool valve 22, and each orifice 24a, The spool valve 22 moves in the axial direction in accordance with the differential pressure before and after 24b, and adjusts the opening degree of the bypass passage 13 to maintain the differential pressure constant.

In the orifice forming member 24, a first orifice 24a is formed approximately at the center thereof, and a second orifice 24b consisting of a plurality of small hole groups is formed at the outer periphery of the first orifice 24a. ing. These first.
The second orifices 24a, 24b are normally arranged in the first valve chamber 3.
2 and the outlet 21a are communicated with each other, and the movement of the control spool 23 closes the first orifice 24a and controls its opening degree.

A control member 35 having a cut tongue is fixed in the two orifices 24a, 24b. The control member 35 made of this shape memory alloy is connected to the orifice 24.
Each shape is memorized according to the temperature of the pressure fluid passing through b. For example, when the temperature of the pressure fluid is room temperature, the tongue on the inner circumference becomes a straight line as shown in Fig. 3. 2
The degree of opening of the orifice 24b is made small, and when the temperature is low, the tongue piece bends inward as shown in FIG. 4 to increase the degree of opening of the orifice 24b.

The union 21 has a substantially cylindrical shape, and its inner end is loosely fitted into the storage hole 11, and a control aperture 31 is formed between the outer periphery of the inner end and the inner periphery of the storage hole 11. 3
1, the supply passage 12 and the first valve chamber 32 are communicated with each other. When the discharge flow rate of the working fluid supplied to the supply passage 12 increases, the control throttle 31 is formed into a vacant space that passes through the supply passage 12 and the first valve chamber 32 on both the upstream and downstream sides due to the flow resistance. 34, and the control spool 23 is axially displaced in accordance with this pressure difference.

In the flow control device configured in this manner, when the fluid pump is driven by the vehicle engine, working fluid is supplied from the discharge chamber of the fluid pump to the supply passage 12. The supplied working fluid passes through the control throttle 31 and enters the first valve chamber 32.
is supplied from the first valve chamber 32 to the communication hole 23a and each orifice 24a.

241) and is fed to the power steering device from the outlet jla of the union 21.

When the rotational speed of the fluid pump is low, the discharge flow rate of the working fluid is small, so the spool valve 22 closes the bypass passage 13 and directs all of the working fluid to each orifice 24.
The spool valve 22 is supplied to the power steering device via the orifice 24.a and 24b.When the discharge flow rate of the working fluid increases as the rotational speed of the fluid pump increases, the spool valve 22 is supplied to the power steering device through the orifice 24.a and 24b. a, 2'4
The bypass passage 13 is opened by sliding to keep the difference 1F between before and after b constant, and the surplus flow of the working fluid is returned to the suction chamber of the fluid pump through the bypass passage 13. As a result, the working fluid supplied to the power steering device is supplied to each orifice 24a.
, 24b is maintained at the predetermined amount Q1 shown in FIG.

Furthermore, when the rotational speed of the fluid pump further increases as the vehicle starts to run at high speed, and the discharge flow rate of the working fluid supplied to the supply passage 12 increases, fluid resistance in the control throttle 31 causes the inside of the supply passage 12 to increase. The fluid pressure increases, and a difference and pressure are generated between the supply passage 12 and the first valve chamber 32, and
The pressure in the supply passage 12 acts as a pushing force that causes the control spool 23 to slide against the spring 27 through the pressure introduction hole 21c. Therefore, when the pressure in the supply passage 12 increases in response to an increase in the discharge flow rate of the working fluid until it overcomes the force of the spring 27, the control spool 23G gradually slides against the spring 27, and finally 1st orifice 2
4a is completely closed, the flow rate of the working fluid supplied to the power steering device is maintained at the flow rate Q2 determined by the second orifice 24b.

By operating the control spool 23 in this manner, when the vehicle is traveling at low speed, the flow rate supplied to the power steering device is increased to lighten the steering wheel steering, and as the vehicle shifts to high speed traveling, the power steering device is increased. By gradually reducing the flow rate supplied to the vehicle, it is possible to gradually make steering operation heavier and provide high-speed stability without causing discomfort to the driver.

By the way, when the pressure fluid is at room temperature, normal flow characteristics can be obtained as described above, but when the pressure fluid is at a low temperature, the viscosity of the fluid is low.
The throttling resistance of the control orifice 31 becomes large and a pressure difference is generated before and after the control orifice 310, and as a result, the control spool 23 slides and the first orifice 24a is closed.
As shown in Figure 2, it becomes impossible to secure the necessary flow rate.
However, in the present invention, since the control member 35 that sets the opening degree of the second orifice 24b is formed of a shape memory alloy, the opening area is small when the pressure fluid is at room temperature, as shown in FIG. A certain control member 35
As shown in the figure, the opening area has changed to a larger shape.

Therefore, the control spool 23 moves and the first orifice 2
4a closes and the flow rate decreases, the second orifice 2
4b becomes larger to compensate for the decrease in flow rate in the first orifice 24a, there is no decrease in flow rate as a whole, and accurate flow control becomes possible.

<Effects of the Invention> As described above, the flow rate control device for a power steering device of the present invention increases the throttle opening of the second orifice when the temperature is low.
Since it is constructed from a shape memory alloy that memorizes each shape that reduces the throttle opening at room temperature, it has the advantage of not changing its flow characteristics regardless of changes in the viscosity of the pressure fluid at low temperatures. have

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a graph showing the flow rate characteristics with respect to the pump rotation speed, FIG. 2 is a sectional view showing the flow rate control device of the present invention, and FIGS. 3 and 4 are the same. FIG. 3 is a partially enlarged cross-sectional view showing the main parts of the flow rate control device. 12... Supply passage, 13... Bypass passage, 22.
...Spool valve, 23...Control spool, 24a...
・First orifice, 24b...Second orifice, 31
... Control aperture, 35... Control member. 1 patented person Toyota Machinery Co., Ltd.

Claims (1)

[Claims] (1) The first one from the supply passage leading to the pump. The flow rate adjusting spool valve adjusts the opening degree of the bypass passage so that the pressure fluid sent to the power steering device via the second orifice and a part of the pressure fluid are returned to the suction side of the pump as surplus flow; A control spool is provided in the supply passage and displaces according to the pressure difference before and after the control throttle to control the opening degree of the first orifice, and the control spool is configured to increase the throttle opening degree of the second orifice when the temperature is low and to restrict the opening degree at room temperature. 1. A flow control device for a power steering device, characterized in that each shape that reduces the opening degree is made of a shape memory alloy.