JPH06127399A - Power steering - Google Patents

Abstract

PURPOSE:To prevent the rise of cylinder differential pressure around the neutral of a steering wheel so as to improve rigidity around the neutral, and reduce the discharge flow of a pump at the neutral time of the steering wheel so as to save energy. CONSTITUTION:The rotation of a motor 20 for driving a pump 10 is controlled according to a signal from a steering detecting means for detecting the steering of a steering wheel. Each variable throttle of a first control part 17 formed of a first bridge circuit C1 is formed of a center open valve. Out of the respective variable throttles of a second control part 18 formed of a second bridge circuit C2, the variable throttle on the pump 10 side is formed of a center closed valve, and the varible throttle on the reservoir 11 side is formed of a center open valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric / hydraulic power steering device used in automobiles and the like.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 7, an electric / hydraulic power steering system includes a pump 1 driven by a motor M, a reservoir 2, and a power cylinder 3 for power assisting steering operation. Variable diaphragms 4A-4D,
4E to 4H, and a control valve 5 composed of two bridge circuits C1 and C2. The control valve 5 operates in accordance with the rotating operation of the steering wheel 6, and the pump 1
The working oil discharged from the power cylinder 3 is supplied to one oil chamber of the power cylinder 3, and the working oil is discharged from the other oil chamber of the power cylinder 3 to the reservoir 2. Although the power cylinder 3 is connected to each of the bridge circuits C1 and C2 in the figure, the power cylinder 3 is a single one.

[0003]

In the power steering apparatus of this type, as shown by the broken line in FIG. 6, the differential pressure of the power cylinder 3 is increased near the neutral position of the steering wheel (the steering wheel rotation angle θ1 or less). Although it is desired to set the cylinder output to 0 to make the cylinder output manual, when the steering wheel 6 is rotationally operated, the opening areas of the variable throttles 4A to 4H of the control valve 5 are increased / decreased. Even near the neutral position, the differential pressure of the power cylinder 3 gradually increases, and the differential pressure of the power cylinder 3 becomes ΔP1 at the steering wheel rotation angle θ1.

For this reason, the point at which the assist is started becomes unclear, and even in the actual vehicle, there is a problem that the steering feeling in the vicinity of neutral is ambiguous and does not give a firm feeling.

[0005]

The present invention has been made in view of the above-mentioned conventional problems, and it is connected to a pump rotatably driven by a motor and a reservoir, respectively.
A first bridge circuit in which a variable throttle is provided in each of the two flow paths, and a first control unit that throttle-controls the hydraulic oil supplied from the pump according to steering of the steering wheel; and both oil chambers of the pump and the power cylinder. And a reservoir, each of which has a second bridge circuit in which variable throttles are provided in four flow passages, respectively, and a second control unit for throttle-controlling the hydraulic oil supplied from the pump to the power cylinder in response to steering of the steering wheel. A steering control means for detecting steering of the steering wheel, and a motor control device for controlling the rotation speed of the motor in response to a signal from the steering detection means. The variable throttle on the pump side among the variable throttles of the second control unit is constituted by the center close valve, and the variable throttle on the reservoir side is constituted by the open valve. One in which was constituted by printer open valve.

[0006]

With the above construction, the variable throttle on the pump side of the second bridge circuit is maintained in the closed state in the vicinity of the neutral position where the relative rotation angle between the valve shaft and the valve body is small, and both oil chambers of the power cylinder are closed. Since it is connected to the variable throttle reservoir, it is possible to prevent the differential pressure between both oil chambers of the power cylinder from rising near the neutral position, which results in manual steering.

When steering of the steering wheel is detected, the rotation speed of the motor that drives the pump is increased by the motor control device, and the pump discharge flow rate is increased to the level required for power assist. This pump discharge flow rate is supplied to the variable throttle power cylinder of the bridge circuit which is opened by steering the steering wheel, and power assists the steering wheel steering.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an electric / hydraulic power steering apparatus. This power steering apparatus is a pump (hydraulic power supply source) driven by a motor 20 whose rotation is controlled as described later.
10, a reservoir 11, a power cylinder 12 for power assisting steering operation, and a rotary control valve 14 that operates according to the rotation of a steering wheel 13 to throttle the hydraulic oil supplied from the pump 10 to the power cylinder 12. Is equipped with.

As shown in FIG. 2, the control valve 14 is connected to a steering wheel 13 and integrally rotates with a valve shaft 15, and the power valve 12 is coaxially arranged on the outer circumference of the valve shaft 15. A valve body 16 connected to a steering linkage that is power assisted by a valve body, a torsion bar (not shown) that connects the valve shaft 15 and the valve body 16 in a relatively rotatable manner, and a valve housing (not shown) that houses them. Has been done. And, between the valve shaft 15 and the valve body 16, the hydraulic oil is throttle-controlled 2
The first control unit 17 and the second control unit 18 of the type are alternately formed at intervals of 90 degrees in the circumferential direction.

The first control unit 17 has four flow paths L1, L2 and L connected to the pump 10 and the reservoir 11, respectively.
The first bridge circuit C1 has variable diaphragms V1, V2, V3 and V4 provided at L3 and L4. These variable throttles V1, V2, V3 and V4 are configured as semi-center open valves as shown in FIG. The opening areas of the variable diaphragms V1, V2, V3, V4 change as shown in the diagram A of FIG. 6 according to the relative rotation angle (valve rotation angle) between the valve shaft 15 and the valve body 16.

The second control section 18 includes the bridge circuit C1.
Is connected in parallel to each of the four oil passages 12A, 12B of the pump 10 and the power cylinder 12 and the reservoir 11, and the variable throttle V is connected to the four flow paths L5, L6, L7, L8.
Second bridge circuit C2 provided with V5, V6, V7 and V8
It is composed by. Among these variable throttles, the variable throttles V5 and V6 connected to the pump 10 side are configured as center close valves as shown in FIG.
The variable throttles V7 and V8 connected to the first side are configured as center open valves as shown in FIG. The opening areas of the variable diaphragms V5 and V6 change according to the valve rotation angle as shown in B of FIG.
The opening area of No. changes according to the valve rotation angle as shown in C of FIG.

Reference numeral 21 is a pressure switch for detecting the pressure in the discharge passage of the pump 10, and 22 is a vehicle speed sensor for detecting the vehicle speed. The pressure switch 21 and the vehicle speed sensor 22.
Signal is input to the electronic control unit 23. The electronic control unit 23 calculates a motor rotation speed signal based on these signals, and outputs this motor rotation speed signal to the motor control unit 24 which controls the rotation of the motor 20. That is, the electronic control unit 23 controls the motor control unit 24 so as to increase the motor rotation speed when the pressure in the discharge passage increases due to steering of the steering wheel and to decrease the motor rotation speed when the vehicle speed increases.

In the present embodiment constructed as described above, the hydraulic oil discharged from the pump 10 is variable throttles V1, V of the bridge circuit C1 in the neutral steering state.
The pressure in the discharge passage of the pump 10 is low and no signal is output from the pressure switch 21 because the pressure is discharged to the reservoir 11 without receiving a large resistance via 2, V3 and V4. Therefore, the motor 20 that drives the pump 10 is driven at a low speed, and the pump discharge flow rate is suppressed to save energy. In the vicinity of neutral steering, since the variable throttles V5 and V6 of the bridge circuit C2 are closed, hydraulic oil is not supplied to the power cylinder 12, and both oil chambers 12A and 12B of the power cylinder 12 are variable throttles. V7, V8
It is connected to the reservoir 11 via and is kept in a low pressure (0) state.

In a proper state, the steering wheel 13
Is rotated and the valve shaft 16 is moved to the valve body 1.
2 relative to 7 in the leftward direction, the opening area of one of the variable diaphragms V1 and V4 of the bridge circuit C1 is enlarged and the opening area of the other variable diaphragms V2 and V3 is reduced. The pressure gradually rises. Then, when the valve rotation angle becomes θ1, the variable throttle V5 of the bridge circuit C2 starts to open, and when the valve rotation angle becomes θ2, the pressure in the discharge passage of the pump 10 becomes equal to or higher than the predetermined pressure, and the pressure switch 21 is turned on. Becomes The ON signal of the pressure switch 21 causes the electronic control unit 23 to move to the motor 20.
The rotational speed of is increased and the pump 10 discharges the flow rate required for assisting.

In the above embodiment, the steering wheel steering is detected by the pressure switch 21 which detects the load pressure of the pump 10. However, steering steering may detect other relative rotation angles of the valve. It is possible by the method. Further, in the above-described embodiment, the example in which the motor 20 for driving the pump 10 is controlled according to the load pressure and the vehicle speed has been described, but the motor control by the vehicle speed is effective in providing the vehicle speed sensitivity. However, control by vehicle speed is not always essential.

[0016]

As described above, according to the present invention, since the cylinder differential pressure is prevented from increasing near the neutral position and the manual steering is performed near the neutral position, the neutral rigidity can be improved and the steering wheel can be neutralized. In the above configuration, the pump discharge flow rate is reduced and the pump discharge flow rate is increased during steering, which is effective in energy saving.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a power steering apparatus showing an embodiment of the present invention.

FIG. 2 is a development view in which a half circumference portion of a control valve is developed.

FIG. 3 is an enlarged view of part A of FIG.

FIG. 4 is an enlarged view of part B of FIG.

5 is an enlarged view of a C portion of FIG.

FIG. 6 is a graph showing a relationship between a valve rotation angle and an opening area of a variable diaphragm.

FIG. 7 is a graph showing a relationship between a valve rotation angle and a cylinder differential pressure.

FIG. 8 is a diagram showing a conventional power steering apparatus.

[Explanation of Codes] 10 Pump 11 Reservoir 12 Power Cylinder 17 First Control Unit 18 Second Control Unit C1 First Bridge Circuit C2 Second Bridge Circuit V1 to V4 Variable Aperture (Semi-center Open) V5, V6 Variable Aperture ( Center closed) V7, V8 Variable throttle (center open) 20 Motor 21 Pressure switch 22 Vehicle speed sensor 23 Electronic control unit 24 Motor control unit

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[Procedure amendment]

[Submission date] November 9, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B62D 123: 00 (72) Inventor Kenichi Fukumura 1-1-1, Asahimachi, Kariya city, Aichi prefecture Toyota Koki Co., Ltd. In the company

Claims (2)

[Claims] 1. A hydraulic fluid supplied from a pump in response to steering of a steering wheel, which comprises a first bridge circuit in which variable throttles are respectively provided in four flow paths connected to a pump and a reservoir which are rotationally driven by a motor. And a second bridge circuit in which variable throttles are provided in four flow paths connected to both the oil chambers of the pump and the power cylinder and the reservoir, respectively. Second control section for restricting the hydraulic oil supplied from the pump to the power cylinder, steering detecting means for detecting steering of the steering wheel, and controlling the rotation speed of the motor according to a signal from the steering detecting means. And a motor controller for controlling the variable throttles of the first control section, each variable throttle of the first control section being a center open valve, and a pump of the variable throttles of the second control section. A power steering apparatus, characterized in that the variable throttle on the side is constituted by a center close valve and the variable throttle on the reservoir side is constituted by a center open valve. 2. A vehicle speed sensor for detecting a vehicle speed is provided, and the motor control device is controlled so as to decrease the rotation speed of the motor as the vehicle speed increases in accordance with a signal from the vehicle speed sensor. Item 1. The power steering apparatus according to item 1.