JPS59220456A - Flow volume control device for motor steering device - Google Patents

Abstract

PURPOSE:To keep the same supply of a pressure fluid to a motor steering device even at a time of low temperature by opening and closing an orifice regardless of a change of viscosity of the pressure fluid at the low temperature, using a coil soring made of shape-memory alloys to make to obtain the same flow volume characteristics with the normal time flow volume characteristics of the pressure fluid. CONSTITUTION:When a pressure fluid is in a low temperature, a big differential pressure works between a supply route 12 and the first valve chamber 32 comparing to the normal temperature in a control spool 23 as the viscosity of the fluid is big. A spring 27 bigger by the amount of differential pressure between the normal temperature and the low temperature is used and the first orifice 24a is closed by the control spool 23 when a rotation number of the pump gose up sufficiently. When the fluid is in the normal temperature, a coil spring 28 made of shape-memory alloys is made to have a repulsive power to decrease the repulsive power of the spring 27 and the first orifice 24a is made to close with the control spool 23 by the same rotation number of the pump at the time of low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a flow control device for a power steering device.

<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 this pressure difference causes the control spool to be moved by the repulsive force of a spring. The opening area of the orifice is variably controlled by displacing the orifice against the pressure, and the discharge flow rate Q is decreased when the pump rotation speed N reaches a certain rotation speed as shown in FIG. Some are designed to give stability to steering wheel operation.

However, according to such conventional devices, the viscosity of the pressure fluid is high at low temperatures, so the differential pressure across the control throttle increases, and as a result, the control spool displaces and throttles the orifice before the pump rotation speed increases sufficiently. As a result, the flow rate characteristic becomes as shown in FIG. 1B. For this reason, when the pressure fluid is at a low temperature, there are blind spots where the pressure fluid supplied to the power steering device is insufficient.

<Purpose of the Invention> The present invention was made to solve such problems in the prior art, and its purpose is to improve the flow rate of pressure fluid at room temperature regardless of the viscosity change of pressure fluid at low temperature. so that flow characteristics similar to the characteristics can be obtained,
The purpose is to prevent the pressure fluid supplied to the power steering device from going down even at low temperatures.

<Structure of the Invention> The present invention has been made to achieve the above object, and includes a spring that applies a repelling force to the control spool, and a spring that deforms so that its free length becomes shorter when the pressure fluid is at a low temperature. A flow rate for a power steering device, characterized in that the coil spring is made of a shape memory alloy and has a shape in which the free length becomes longer in order to reduce the repulsive force exerted on the control spool by the spring at room temperature. Regarding a control device.

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

In FIG. 2, reference numeral 10 denotes a pump housing, and a storage hole 11 is provided through the pump housing 10, and a union 21 is screwed into one end of the storage hole 1 in a fluid-tight manner. Further, a stopper 25 is fitted to the other end of the storage hole 11 in a liquid-tight manner.

A spool valve 22 is slidably inserted into the storage hole 11,
A first valve chamber 32 and a second valve chamber 33 are formed within the storage hole 11 . Further, the spool valve 22 is biased by a spring 26 interposed in the second valve chamber 33, and the movement of the spool valve 22 causes the supply passage 12 and the bypass passage 13 provided in the pump housing 10 to communicate or shut off. ing. Note that the supply passage 12 communicates with a discharge chamber of the fluid pump, and the bypass passage 13 communicates with a suction chamber of the fluid pump.

In the inner hole of the union 21, a control spool 23 slides between an orifice forming member 24 fitted on the outer end side of the inner hole of the union 21 and a stepped portion 21b on the inner end side of the inner hole of the union 21. It can be inserted easily. This control spool 23 is formed with a communication hole 23a that communicates with the first valve chamber 32. 21a.

Note that the outlet 21a of the union 21 is connected to a power steering device.

The orifice forming member 24 is equipped with a control nozzle 24C, and the control nozzle 24C is connected to each orifice 24.
The downstream sides of a and 24b are communicated with the second valve chamber 33 through communication holes 21d and 14 provided in the union 21 and the pump housing 10. This allows each orifice 2
A portion of the downstream fluid 4a, 24b is guided into the second valve chamber 33, and each orifice 24a, 24b is provided at both ends of the spool valve 22.
4b acts before and after each orifice 24a.

The spool valve 22 moves in the axial direction as a result of the differential pressure mill before and after the bypass passage 1 to maintain the differential pressure constant.
Adjust the opening degree of 3.

5- Further, a pressure introduction hole 21C is opened in the union 21, which communicates the supply passage 12 with the inner end side step portion 21b of the union 21. A spring 27 made of an iron-based material is interposed between the control spool 23 and the orifice forming member 24 to provide repulsive force to the orifice forming member 24, and a shape memory alloy made of Ni-Ti is interposed between the union 21 and the control spool 23. A coil spring 28 manufactured by Manufacturer Co., Ltd. is inserted. This coil spring 28 has a shape in which the free length of the pressure fluid becomes long when the pressure fluid is at room temperature (above 0° C.), and applies a repulsive force to the control spool 23 in the opposite direction to that of the spring 27. When the temperature is low, the repellency is lost and the spring 2
7 deforms so that the free length becomes shorter. As a result, when the pressure fluid is at a low temperature, the repulsive force of the spring 27 acts on the control spool 23, and when the pressure fluid is at room temperature, the repulsive force of the coil spring 28 is subtracted from the repulsive force of the spring 27 on the control spool 23. A pressing force is applied.

A control throttle 31 is formed between the open inner end of the union 21 and the inner periphery of the storage hole 116, and the supply passage 12 and the first valve chamber 32 are communicated through the control throttle 31. It has become. This control throttle 31 is connected to the supply passage 1
When the discharge flow rate of the pressure fluid supplied to the valve chamber 2 increases, a pressure difference occurs between the supply passage 12 and the first valve chamber 32 due to the flow resistance, and the control spool 23 moves against the spring 27 in response to this pressure difference. It is designed to be displaced in the axial direction. When the pressure difference between the supply passage 12 and the first valve chamber 32 is large, the first orifice 24a of the orifice forming member 24 is closed by the control spool 23, and the second orifice 24a is closed by the control spool 23.
The distribution channel is narrowed down to only b.

In the flow control device configured as described above, when the fluid pump is driven by the vehicle engine, pressure fluid is supplied from the discharge chamber of the fluid pump to the supply passage 12, and when the rotational speed of the fluid pump is low, the pressure fluid is supplied to the supply passage 12. Since the discharge flow rate is small, the spool valve 22 closes the bypass passage 13 and supplies the entire amount of pressure fluid to the power steering device via each orifice 24a, 24b. However, as the rotational speed of the fluid pump increases, When the discharge flow rate of pressure fluid increases, spool valve 2
2 slides to keep the differential pressure before and after the orifices 24a, 24b constant, thereby opening the bypass passage 13 and allowing the surplus flow of pressure fluid to flow back through the bypass passage 13 to the suction chamber of the fluid pump. As a result, the pressure fluid delivered to the power steering system is determined by each orifice 24a, 24b.

In addition, as the vehicle moves to high-speed running, the fluid pressure in the fluid cylinder increases, creating a pressure difference between the supply passage 12 and the first valve chamber 32, and the pressure in the supply passage 12 decreases to the pressure introduction hole 21c.
acts as a pressing force to cause the control spool 23 to slide against the spring 27 through the spring 27. Therefore, when the pressure in the supply passage 12 increases until it overcomes the biasing force of the spring 27 as the discharge flow rate of the pressure fluid increases, the control spool 2
3 gradually slides against the spring 27, and finally the first orifice 24a is completely closed.
4b. By the way, when the pressure fluid is at a low temperature, the viscosity of the fluid is high, so a large pressure difference acts on the control spool 23 between the supply passage 12 and the first valve chamber 32 compared to when the fluid is at room temperature. By using the spring 27 which is larger than the differential pressure at the time, the first orifice 24a is closed by the control spool 23 after the rotational speed of the pump has sufficiently increased.

When the fluid is at room temperature, the coil spring 28 is made to have a repulsive force, and the coil spring 28 reduces the repulsive force of the spring 27, so that the first orifice 24a is rotated at the same number of revolutions of the pump as when the fluid is at a low temperature. Control spool 23 causes it to close.

<Effects of the Invention> As described above, in the present invention, the spring that applies repulsive force to the control spool deforms so that the free length of the pressure fluid becomes short = 9- when the pressure fluid is at a low temperature. The coil spring is made of a shape memory alloy that memorizes a shape with a long free length to cancel out the repulsive force exerted on the control spool by the spring at room temperature. This has the advantage that a flow rate characteristic similar to that at room temperature can be obtained, and a predetermined flow rate can be obtained even when the pressure fluid supplied to the power steering device is at a low temperature.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a graph showing flow rate characteristics with respect to pump rotation speed, and FIG. 2 is a sectional view showing a flow rate control device of the present invention. 12... Supply passage, 13... Bypass passage, 22.
... Spool valve, 23 ... Control spool, 24a, 2
4b...orifice, 27...spring, 28.
...Coil spring, 31...Control aperture. Patent applicant Toyota Machinery Co., Ltd. 10-

Claims (1)

[Claims] +11 Pressure fluid sent to the power steering device from the supply passage leading to the pump via the orifice, and a flow rate adjustment that adjusts the opening degree of the bypass passage so that a portion of the pressure fluid flows back to the suction side of the pump as surplus flow. a control spool provided in the supply passage that controls the opening degree of the orifice by elastically deforming a spring in response to a pressure difference before and after the control throttle, and displacing the orifice in a direction to throttle the orifice; It is made of a shape memory alloy that memorizes a shape that is deformed so that the free length is shortened by the spring at low temperatures, and that the free length is lengthened at room temperature to displace the control spool in a direction to narrow the orifice against the spring. A flow control device for a power steering device, characterized in that it is equipped with a coil spring.