JPH08301132A - Flow rate controller in power steering device - Google Patents

Abstract

PURPOSE: To reduce a flow rate of hydraulic oil fed to a control valve in a low load time by arranging inside a flow rate regulating valve a load pressure responding valve which communicates a spring chamber of the flow rate regulating valve with a low pressure side when a load is low, and which shuts off the communication between the spring chamber and the low pressure side responding to the load pressure increased by means of steering operation. CONSTITUTION: Hydraulic oil fed to a supply passage 17 from a pump is fed from a feeding port 20 to a control valve 14 via a metering orifice 21. After passing the metering orifice 21, the hydraulic oil is introduced to a spring chamber 23 and introduced from the spring chamber 23 to a control chamber 32 via a control orifice 33 so as to work as hydraulic thrust pressing a load pressure responding valve 30, and then, discharged from a bypass passage 18 via a variable throttle 35. In this process, a difference between hydraulic thrust working on both ends of the load pressure responding valve 30 is small in a neutral condition of steering, so that the spring chamber 23 is opened to a low pressure side via the variable throttle 35, and then, the hydraulic oil is refluxed to an intake side of a pump 10 from the bypass passage 18, and as a result, an energy loss in the pump 10 is reduced.

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 in a power steering device used in an automobile or the like, and particularly to reduce energy consumption by reducing the flow rate supplied from a pump to a control valve when the load is low. The present invention relates to a flow rate control device in a power steering device that achieves the above.

[0002]

2. Description of the Related Art A flow rate control device in a power steering system in which energy is saved by reducing the flow rate supplied from a pump to a control valve at a low load when a handle is not operated is disclosed, for example, in Japanese Patent Laid-Open No. 6-8840. It is known as described in the publication. In such a flow rate control device, a load pressure sensitive valve whose throttle opening is changed according to the load pressure is provided between the spring chamber and the low pressure side of the flow rate adjusting valve, and when the load is low,
Energy saving is achieved by opening the spring chamber of the flow rate adjusting valve to the low pressure side via the load pressure sensitive valve to reduce the flow rate supplied to the control valve.

[0003]

However, in this type of flow rate control device, a low load is provided in the housing of the pump in addition to the storage hole for storing the flow rate adjusting valve for controlling the flow rate supplied to the control valve. Occasionally, it is necessary to provide a storage hole for storing the load pressure sensitive valve that reduces the flow rate. Therefore, in order to save energy, the pump housing must be separately designed and manufactured, and there is a problem that it is not compatible with conventional pump housings.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, in which variable throttles are provided in the flow passages respectively connected to both the oil chambers of the pump and the power cylinder and the reservoir. Power provided with a control valve and a flow rate adjusting valve for controlling the flow rate to be supplied to the control valve to a predetermined flow rate by opening and closing the bypass passage according to the differential pressure across the metering orifice provided in the discharge passage of the pump In the steering device, a variable throttle that connects the spring chamber of the flow rate adjusting valve to the low pressure side at low load and shuts off the communication between the spring chamber and the low pressure side in response to the load pressure increased by the steering operation. The load pressure sensitive valve provided is provided, and the load pressure sensitive valve is incorporated in the flow rate adjusting valve.

[0005]

With the above-described structure, since the load pressure is low in the neutral steering state, the variable throttle of the load pressure sensitive valve is opened, and the spring chamber side of the flow rate control valve is released to the low pressure side via this variable throttle. As a result, the hydraulic pressure discharged from the pump is returned to the suction side of the pump. Therefore, the supply flow rate of the hydraulic oil supplied to the control valve is reduced, and energy loss can be reduced.

If the load pressure is increased by steering operation in that state, the load pressure sensitive valve is actuated to reduce the variable throttle, and finally it is closed. As a result, the supply flow rate of the hydraulic oil supplied to the control valve is increased to the maximum supply flow rate, which contributes to the assist action.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a hydraulic power steering apparatus. The power steering apparatus mainly includes a pump 10 driven by an automobile engine, a reservoir 11, and a power cylinder 12 for power assisting steering operation. The rotary control valve 14 is operated by the rotation of the steering wheel 13 and throttle-controls the hydraulic oil supplied from the pump 10 to the power cylinder 12.

As shown in FIG. 2, a valve housing hole 16 is formed in the pump housing 15 of the pump 10, and a supply passage 17 communicating with a discharge port of the pump 10 and a suction port of the pump 10 are formed in the valve housing hole 16. A bypass passage 18 that communicates with the valve storage hole 16 is opened in the axial direction of the valve storage hole 16. A union 19 is liquid-tightly screwed to one end of the valve accommodating hole 15, and an outlet 20 communicating with the inlet port of the control valve 14 is opened in the union 19. A metering orifice 21 is formed in the union 19,
The supply passage 17 and the outlet 20 are communicated with each other through the metering orifice 21.

A bypass valve 22 for adjusting the flow rate is slidably fitted in the valve storage hole 16, and a spring chamber 23 is formed at one end of the bypass valve 22. The spring chamber 23 is provided with a spring 24 that biases the bypass valve 22 in a direction that normally closes the bypass passage 18. The spring chamber 23 is a communication passage 25 formed in the pump housing 15.
Through the metering orifice 21. As a result, the differential pressure across the metering orifice 21 is introduced to both ends of the bypass valve 22, and the bypass valve 22 adjusts the opening of the bypass passage 18 so as to maintain the differential pressure across the metering orifice 21 constant. There is. With the metering orifice 21, the bypass valve 22 and the spring 24 described above, the flow rate adjusting valve 26
Is composed.

The bypass valve 22 includes the spring chamber 2
The accommodation hole 27 opening to the 3 side is opened.
An escape passage 28, which is in constant communication with the bypass passage 18, is opened at the bottom of the. A load pressure sensitive valve 30 is slidably inserted in the accommodation hole 27 in a slidable manner. One end of the load pressure sensitive valve 30 is exposed to the spring chamber 23, and the other end of the load pressure sensitive valve 30 opens and closes the relief passage 28. The protrusion 31 is formed. The control projection 31 and the escape passage 28 constitute a variable throttle 35. As a result, the pressure receiving areas A1 and A2 at both ends of the load pressure sensitive valve 30 have the same control protrusion 31
Is larger on the one end side exposed to the spring chamber 23, and the pressure receiving areas on both ends are different.

The load pressure sensitive valve 30 and the bypass valve 2
A control chamber 32 is formed between the control chamber 32 and the control chamber 32, and the control chamber 32 communicates with the spring chamber 23 via a control orifice 33 formed in the bypass valve 22. The control room 32
A spring 34 is inserted into the load pressure sensitive valve 30 by the biasing force of the spring 34, and the control projection 31 of the load pressure sensitive valve 30 is normally held at the sliding end position where the passage 28 is opened to fully open the variable throttle 35. There is.

The pressure P1 before passing through the control orifice 33 acts on the pressure receiving area A1 at one end of the load pressure sensitive valve 30, and the pressure receiving area A2 at the other end after passing through the control orifice 33. The pressure P2 acts. That is, the thrust force F1 that presses the load pressure sensitive valve 30 toward the control chamber 32 side (in the left direction in the figure) is F1 = P1 × A1, and the supply chamber 24
The thrust F2 that pushes to the side (left in the figure) is F2 = P2
XA2 + Fs. Here, Fs represents the spring force of the spring 34.

As shown in FIG. 1, the control valve 14 has four flow paths L1 and L2, which are connected to the oil chambers of the pump 10 and the power cylinder 12 and the reservoir 11, respectively.
Center-open type variable diaphragms V1, V2 on L3, L4,
It has a configuration in which V3 and V4 are provided. Reference numeral 40 in FIG. 1 denotes a relief valve. The relief valve 40 operates when the pressure in the spring chamber 23 of the bypass valve 22 becomes equal to or higher than a set pressure, and the relief passage opened to the protrusion 31. The relief valve 40 is built in the load pressure sensitive valve 30. The relief valve 40 is installed in the bypass passage 18 via the relief passage 41 and the relief passage 28.

Next, the operation will be described based on the above-mentioned configuration. When the pump 10 is driven by the automobile engine,
The hydraulic oil is discharged from the discharge port of the pump 10 into the supply passage 17. The hydraulic oil discharged to the supply passage 17 is supplied from the delivery port 20 to the control valve 14 via the metering orifice 21. Also, the hydraulic oil is metering orifice 2
After passing 1, the spring chamber 23 is introduced into the spring chamber 23, and is further introduced into the control chamber 32 from the spring chamber 23 through the control orifice 33 to act as a hydraulic thrust force for pressing the load pressure sensitive valve 30 to the right in FIG. At the same time, it is discharged from the bypass passage 18 via the variable throttle 35.

In the neutral state of the steering, the hydraulic oil supplied to the control valve 14 is controlled by the variable throttle V1 and V2.
3 and V4 are equally discharged to the reservoir 11, and both oil chambers of the power cylinder 12 are maintained in a uniform low pressure state. In this state, since the load pressure (pump pressure) is low, the hydraulic thrust difference acting on both ends of the load pressure sensitive valve 30 is small, and due to the action of the spring 34, F1 (P1 × A1) <F2
The relationship of (P2 × A1 + Fs) is established. Therefore, the load pressure sensitive valve 30 is held at the right end where the variable throttle 35 is fully opened by the urging force of the spring 34, and the spring chamber 23 of the bypass valve 22 is released to the low pressure side via the variable throttle 35. Therefore, the pilot flow rate is leaked from the spring chamber 23 to the low pressure side, and the pressure in the spring chamber 23 is reduced, so that the bypass valve 22 is moved in a direction to open the bypass passage 18 more and more hydraulic oil is discharged from the pump 10. It is bypassed to the bypass passage 18 and is returned to the suction side of the pump 10. Therefore, the supply flow rate of the hydraulic oil supplied to the control valve 14 is reduced to the flow rate Q1 shown in FIG. Thereby, the energy loss of the pump power can be reduced.

From this state, the steering wheel 13
Is rotated, the variable diaphragms V1 and V3 and the variable diaphragms V2 and V3 are rotated in accordance with the rotation direction of the steering wheel 13.
Either one of 4 is enlarged and the other is reduced,
The load pressure rises and a differential pressure is generated in both oil chambers of the power cylinder 12. When this load pressure rises to P1, the difference in the pressure receiving area of the load pressure sensitive valve 30 increases the hydraulic thrust difference acting on both ends of the load pressure sensitive valve 30 to overcome the spring force of the spring 34, and F1 (P1 × A1 )> F2 (P2 × A2 + F
s). As a result, the load pressure sensitive valve 30 moves to the left in FIG. 1 against the spring 34, and the variable throttle 35 is contracted. Furthermore, when the load pressure rises to P2 and the left-right thrust difference increases, the variable throttle 35 is finally closed. Therefore, the pilot flow rate leaked from the spring chamber 23 to the bypass passage 18 via the control orifice 33, the control chamber 32 and the variable throttle 35 becomes zero. As a result, the pressure of the spring chamber 23 of the bypass valve 22 is increased, so that the bypass valve 22 is displaced in the direction of narrowing the bypass passage 18, and the supply flow rate of the hydraulic oil supplied to the control valve 14 is the maximum shown in FIG. It is increased to the supply flow rate Q2 and contributes to the assisting action.

The load pressure sensitive valve 30 in the above-mentioned embodiment can be any valve that can open the spring chamber of the flow rate adjusting valve to the low pressure side to reduce the flow rate of the hydraulic oil supplied to the control valve when the load is low. Good.

[0018]

As described above, according to the present invention, when the load is low, the spring chamber of the flow rate adjusting valve is connected to the low pressure side, and the spring chamber and the low pressure side are operated in response to the load pressure increased by the steering operation. Since the load pressure sensitive valve that shuts off the communication is provided inside the flow rate adjustment valve, it saves energy by reducing the flow rate of hydraulic oil supplied to the control valve at low load without making any changes to the pump housing. Therefore, it is possible to improve the compatibility of the pump housing.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a flow rate control device in a power steering system showing an embodiment of the present invention.

FIG. 2 is a detailed cross-sectional view of a portion B of FIG. 1 showing details of the flow rate control device.

FIG. 3 is a graph showing a supply flow rate characteristic with respect to a load pressure.

[Explanation of symbols]

 10 Pump 11 Reservoir 12 Power Cylinder 15 Pump Housing 17 Supply Passage 18 Bypass Passage 21 Metering Orifice 22 Bypass Valve 23 Spring Chamber 26 Flow Control Valve 30 Load Pressure Sensitive Valve 34 Spring V1-V4 Variable Throttle

Claims (2)

[Claims] 1. A differential pressure across a metering orifice provided in a discharge passage of the pump, and a control valve provided with a variable throttle in each of the flow passages respectively connected to both the oil chamber of the pump and the power cylinder and the reservoir. In a power steering apparatus equipped with a flow rate adjusting valve that opens and closes a bypass passage according to the above, and controls the flow rate to be supplied to the control valve to a predetermined flow rate, the spring chamber of the flow rate adjusting valve is set to a low pressure side at low load A load pressure sensitive valve provided with a variable throttle that communicates with it and responds to a load pressure that increases due to steering operation and shuts off the communication between the spring chamber and the low pressure side, and the load pressure sensitive valve is provided in the flow rate adjusting valve. A flow rate control device in a power steering device characterized by being incorporated. 2. The flow rate control device in a power steering system according to claim 1, wherein both ends of the load pressure sensitive valve have a pressure receiving area difference.