JPH0585389A - Flow rate control device of working fluid for power steering - Google Patents

Abstract

PURPOSE:To be capable of acquiring a characteristic for decreasing a flow rate in response to a vehicle speed increase, and making energy saving of a pump when high speed traveling is performed, and also to prevent inferior pump suction caused by decrease in pump oil temperature and abnormal sound generation caused by surge pressure by controlling flow rate in response to a pump rotating speed. CONSTITUTION:A plunger 10 is coaxially and integrally provided on a spool valve 8 for controlling at a constant flow rate, a flow rate of a supplying passage 5 which is increased in proportion to a rotating speed of a pump 7 by means of a differential pressure in a throttle passage 9, while suction force for operating the plunger 10 by means of a solenoid 20 is changed, and an area of a by-pass passage 6 for refluxing fluid from the supplying passage 5 to pump 7 is increased so as to decrease a control flow rate of a power steering device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering working fluid flow rate control device capable of controlling the flow rate of a pressure fluid supplied to a power steering apparatus of an automobile in accordance with the rotational speed of a pump and the vehicle speed. Is.

[0002]

2. Description of the Related Art Conventionally, a rotation speed sensitive type flow rate control device for controlling the flow rate of a pressure fluid supplied to a power steering apparatus according to the rotation speed of a pump is known from Japanese Patent Laid-Open No. 56-104186, and A vehicle speed sensitive flow rate control device for controlling according to the vehicle speed is known from Japanese Examined Patent Publication No. S54-4135.

[0003]

In any of the above flow rate control devices, the pressure fluid supplied to the power steering device in order to secure steering stability by increasing the steering force at high rotation or high speed of the pump. In order to reduce the flow rate, the technical idea is to reduce the area of the throttle passage to increase the differential pressure between the supply passage of the pressure fluid discharged from the pump and the throttle passage to increase the bypass amount. In this case, since the upstream side of the throttle passage has a high pressure, the work of the pump is not reduced so much, and there is a problem that the energy is not saved.

Further, since the viscosity of oil increases in cold weather, there is a problem that abnormal noise is generated due to poor suction of the pump or generation of surge pressure when the engine is started.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art. Its characteristic constitution is that the pressure fluid discharged from a pump is passed through a throttle passage from a supply passage. Control flow rate to the power steering device,
In a flow control device for a power steering working fluid that recirculates an excess flow to the suction side of a pump by adjusting the opening of a bypass passage, the flow rate of the supply passage that increases in proportion to the rotational speed of the pump is reduced by the throttle. A spool valve that controls a constant flow rate by balancing the differential pressure of the passage and the spring force, a plunger integrally provided coaxially with the spool valve, and a solenoid that applies a suction force in a direction opposite to the spring force to the plunger are provided. The controller includes a controller that applies a current to the solenoid so that the suction force increases as the vehicle speed increases or when the pump oil temperature is low.

[0006]

With the above structure, the flow rate that increases in proportion to the rotational speed of the pump is controlled to a constant flow rate by the differential pressure in the throttle passage, and the suction force acting on the plunger is changed by the solenoid according to the vehicle speed. The load on the pump is reduced by controlling the flow rate to decrease as the vehicle speed increases. Also, when starting the engine at low temperature, increase the suction force to increase the bypass amount and circulate oil in the pump,
Raise the oil temperature early.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a pump housing, a valve housing hole 2 is penetrated through the pump housing 1, a union 3 is screwed to one end of the valve housing hole 2, and a stopper 4 is fitted to the other end. Has been done. A throttle passage 9 communicating with the valve housing hole 2 is opened in the union 3, and a pressure fluid outlet 3a connected to the power steering apparatus is opened. A supply passage 5 communicating with the discharge side of the pump 7 in the valve storage hole 2.
The bypass passage 6 communicating with the suction side is opened in the axial direction with a space therebetween.

A spool valve 8 for closing the communication passage between the supply passage 5 and the bypass passage 6 and adjusting the opening is slidably fitted in the valve housing hole 2. A groove 8a is provided at one end of the spool valve 8 so that the throttle passage 9 opens into the supply passage 5. A magnetic plunger 10 is coaxially fixed to the other end of the spool valve 8 by press fitting or the like. A spring 11 is interposed between the plunger 10 and the stopper 4, and the spring 11 presses and urges the spool valve 8 in a direction to close the communication path between the supply passage 5 and the bypass passage 6. .. The plunger 10 and the spool valve 8 may be integrally formed of a magnetic material.

With this plunger 10, the plunger 1
Front chamber 13 in the valve housing hole 2 in front of 0, and plunger 1
A rear chamber 14 is defined in the valve housing hole 2 at the rear of 0. The plunger 10 is a cylindrical body, and an axial groove passage 15 that communicates the front chamber 13 and the rear chamber 14 is provided on the outer periphery of the plunger 10.
Are formed.

The front chamber 13 is pressured via a control nozzle 16 bored in the union 3 downstream of the throttle passage 9 and a communication hole 17 bored in the pump housing 1 communicating with the control nozzle 16. The rear chamber 14 is communicated with the fluid outlet 3a, and is communicated with the bypass passage 6 through a passage hole 18 bored in the spool valve 8 and a check valve 12 and an orifice 19 provided in the cylinder of the plunger 10. is doing.

Reference numeral 20 denotes a solenoid, which is fixed to the pump housing 1 on the opposite side of the union 3 via a non-magnetic material 25. The solenoid 20 is composed of a coil 22 wound around a bobbin 21 made of a non-magnetic material around a yoke 23 made of a magnetic material, and a magnetic material cover 24 covering the coil 22, and the plunger 10 forms a solenoid valve. is doing.

A vehicle speed detection signal is input to the solenoid 20, and the solenoid 20 is electrically connected to the controller 26 so that the applied current i increases and the attraction force F of the plunger 10 increases as the vehicle speed increases. Further, when the oil temperature detection signal of the pump 7 is input and the oil temperature becomes lower than a certain temperature, the applied current i becomes the maximum value.

Next, the operation of the device of the present invention having the above structure will be described. When the pump 7 is rotationally driven by the automobile engine, the working fluid is sucked into the pump chamber from the suction side and the pressure fluid is discharged from the discharge side. The discharged pressure fluid is supplied to the valve accommodating hole 2 of the throttle passage 9 via the supply passage 5 and is sent to the power steering device from the pressure fluid outlet 3a via the throttle passage 9.

While the vehicle speed is 0 or low and the pump speed is low, the current i applied to the solenoid 20 is 0 and the pump discharge amount is small, so that the spool valve 8 is set by the set load of the spring 11 as shown in FIG. The bypass passage 6 is closed, and the entire pump discharge flow amount is sent to the power steering device through the throttle passage 9.

The discharge flow rate increases as the pump rotation speed increases, and the pressure on the upstream side of the throttle passage 9 increases in accordance with the discharge flow rate. At this time, the pressure on the downstream side of the throttle passage 9 passes from the control nozzle 16 through the communication hole 17 to the plunger 1
0 enters the front chamber 1 and is introduced into the rear chamber 14 through the groove passage 15. Further, as shown in FIG. 2, the spool valve 8 moves against the pressing force of the spring 11 due to the differential pressure before and after the throttle passage 9 to open the bypass passage 6 and bypass the excess flow to the bypass passage 6 to pump the pump 7. Return to the inhalation side. As a result, the pressure fluid sent to the power steering apparatus is maintained at a predetermined amount by the throttle passage 9.

Thus, even if the solenoid 20 does not operate, the control flow rate to the power steering apparatus is controlled to a constant flow rate regardless of the rotation speed of the pump 7. Further, the check valve 12 opens when the pressure in the rear chamber 14 becomes equal to or higher than the set pressure, and has the action of letting the high-pressure oil escape to the bypass passage 6.

In addition to this, the attraction force F of the plunger 10 by the solenoid 20 is as shown in FIG.
The shapes and positional relationships of the plunger 10 and the yoke 23 are configured such that the tip position of 0 has the maximum suction force at the XA position and has the minimum suction force at the XC position. The XA position is a position where the spool valve 8 comes into contact with the union 3, and the XC position is a position where the spool valve 8 moves in a normally used maximum load and no load condition. When the vehicle speed increases, the current i applied to the solenoid 20 from the controller 26 gradually increases (for example, when the vehicle speed is 30 km / h, i
= 0.4 A, 90 km / when it is 0.2 A, 60 km / h
It is set to 0.6 A for h and 0.8 A for 120 km / h. Along with this, the suction force F of the plunger 10 gradually increases. However, in FIG. 3, the suction force is maximum at the XA position, X
Although it is minimized at the C position, it becomes X from the XA position.
The suction force may be constant in the range of the C position.

When the plunger 10 is sucked, the spool valve 8 opens the opening area of the bypass passage 6 larger than that when the suction force does not act, and the throttle passage 9 is opened.
The amount of recirculation to the pump 7 is gradually increased without generating a high pressure upstream. As a result, the relationship between the control flow rate to the power steering apparatus and the pump rotation speed is expressed as shown in FIG. 4, and as shown in FIG. 5, the control flow rate to the power steering apparatus changes according to the increase in vehicle speed. As a result, the steering force at the time of high speed traveling is increased and steering stability is ensured.

When the temperature is low (for example, at -20 ° C.), the current i applied to the solenoid 20 is set to 0.8 A, which is the maximum, to increase the suction force, and the opening area of the bypass passage 6 is maximized. Set to open. This allows
Oil whose viscosity increases due to low temperature at engine start, etc., circulates in the pump to raise the oil temperature early and reduce the increasing viscosity to improve pump suction and generate surge pressure. Prevent.

[0020]

As described above, according to the present invention, a plunger is attached to a spool valve for controlling the flow rate of the supply passage, which increases in proportion to the rotational speed of the pump, to a constant flow rate by balancing the differential pressure of the throttle passage and the spring force. A controller that coaxially and integrally installs a solenoid that acts on the plunger with an attraction force in the direction opposite to the spring force, and applies a current to the solenoid to increase the attraction force as the vehicle speed increases or when the pump oil temperature is low. Because of the configuration with, it is possible to obtain a fine pump control flow rate that is proportional to the vehicle speed and the pump speed.
The characteristic that the control flow rate of the power steering device is secured during stationary operation and the control flow rate is reduced during high speed traveling to maintain steering stability.

Further, the differential pressure in the throttle passage is not increased for drooping, but the solenoid is used to attract the plunger in the direction opposite to the spring force so that the area of the bypass passage is increased and the bypass flow rate is adjusted according to the vehicle speed. Therefore, a large pressure is not generated on the upstream side of the throttle passage during high-speed traveling, the load on the pump is reduced, and energy saving of the pump is obtained.

Further, when the engine is started in cold weather, the oil of increased viscosity is circulated in the pump to raise the oil temperature early, thereby preventing generation of abnormal noise due to poor suction of the pump or surge pressure. effective.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the device of the present invention when not in operation.

FIG. 2 is a sectional view of the device of the present invention during operation.

FIG. 3 is a diagram showing the attraction force and stroke diagram of the plunger according to the device of the present invention.

FIG. 4 is a characteristic diagram of drooping by the device of the present invention.

FIG. 5 is a diagram showing a relationship between a flow rate and a vehicle speed by the device of the present invention.

[Explanation of symbols]

 1 Pump Housing 2 Valve Storage Hole 3 Union 5 Supply Passage 6 Bypass Passage 7 Pump 8 Spool Valve 9 Throttling Passage 10 Plunger 11 Spring 20 Solenoid 26 Controller

Claims (1)

[Claims] 1. A control fluid flow of pressure fluid discharged from a pump is supplied from a supply passage to a power steering device via a throttle passage, and a surplus flow is returned to an intake side of the pump by adjusting an opening of a bypass passage. In a flow control device for a power steering working fluid, a spool valve for controlling the flow rate of the supply passage, which increases in proportion to the rotational speed of the pump, to a constant flow rate by balancing the differential pressure of the throttle passage and the spring force. , A plunger integrally provided coaxially with the spool valve and a solenoid for exerting a suction force in the direction opposite to the spring force on the plunger are provided, and the suction force increases as the vehicle speed increases or when the pump oil temperature is low. A flow control device for a power steering working fluid, comprising a controller for applying a current to the solenoid as described above.