JPH1086832A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increase of a differential pressure of a power cylinder in the vicinity of the neutral position of a steering wheel so as to improve neutral rigidity of the steering wheel. SOLUTION: A power steering device is provided with a first control unit, in which variable throttles V1-V4 are respectively provided in a flow path connected to a pump 10 and to a reservoir 11, and a second control unit, which is connected to the first control unit in parallel and is provided with variable throttles V5-V8 in a flow path respectively connected to both hydraulic chambers for the pump 10 and the power cylinder 12 and to the reservoir 11. Among the variable throttles V5-V8 in the second control unit, the variable throttles V7, V8 on the reservoir 11 side are constructed of center close valves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering device used for automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, a power steering apparatus for preventing a rise in a differential pressure of a power cylinder near a neutral position and increasing a neutral rigidity includes a pump 5 as shown in FIG.
0, a reservoir 51, a power cylinder 52 for power-assisting the steering operation, and a rotary type for controlling the hydraulic oil supplied from the pump 50 to the power cylinder 52 by operating according to the rotation of a steering wheel (not shown). And a control valve 53.
However, a first control unit composed of center-open type variable throttles V1 to V4 shown in FIG. 3 and a center closed variable throttle V7 and V8 shown in FIG.
The semi-center closed type variable aperture V5, V shown in FIG.
6 and a second control unit.

Here, the opening area of each of the variable diaphragms V1 to V8 changes as shown in FIG. 6 according to the relative rotation angle (valve rotation angle) between the valve shaft 61 and the valve body 62. In the above configuration, in the neutral state of steering, since the center-closed variable throttles V7 and V8 of the second control unit are closed, no hydraulic oil is supplied to the power cylinder 52 and both power cylinders 52 The oil chambers 52A and 52B are connected to the reservoir 51 via semi-center open type variable throttles V5 and V6, and are maintained in a low pressure state. Therefore, the hydraulic oil discharged from the pump 50 is discharged to the reservoir 51 through the variable throttles V1 to V4 of the first control unit.

When a steering wheel (not shown) is rotated and the valve shaft 61 is slightly rotated rightward in FIG. 8 with respect to the valve body 62, one of the variable throttles V2 and V3 of the first control unit is rotated. The opening area is enlarged, and the opening areas of the other variable diaphragms V1, V4 are reduced. As a result, the pressure of the pump 50 gradually increases, but the closed state of the variable throttles V7 and V8 of the second control unit is maintained up to the valve rotation angle θ1. The differential pressure between 52A and 52B is maintained at zero. Therefore, in a neutral dead zone where the valve rotation angle is equal to or less than θ1, an increase in the differential pressure between the two oil chambers 52A and 52B of the power cylinder 52 can be prevented, and near neutral, manual steering is performed, thereby increasing the neutral rigidity.

When the valve rotation angle exceeds θ1, one of the variable throttles V8 on the pump 50 side of the second controller starts to open, and at this time, one of the variable throttles V6 on the reservoir 51 side is in a contracted state. , One oil chamber 5 of the power cylinder 52
2B rises and both oil chambers 52 of the power cylinder 52
A, 52B causes a differential pressure to assist the steering of the steering wheel.

[0006]

In the above configuration,
When the handle is returned, the control valve 53 returns to the neutral position, and the oil chambers 52A, 52B of the power cylinder 52 are returned from the pump 50.
Since the flow path therebetween is closed by the center-closed variable throttles V7 and V8, the oil is supplied to the low-pressure oil chamber 52A from the pump 50 via the center-opened variable throttles V2 and V4 and the semi-center-opened variable throttle V5. However, there is a problem that the return of the steering wheel is deteriorated because the supply is delayed due to the restriction resistance of each variable restriction in the flow path.

[0007]

In order to solve the above-mentioned problems, a power steering apparatus according to the present invention includes a first control unit having a variable throttle provided in a flow path connected to a pump and a reservoir, respectively. A second control unit connected in parallel to the first control unit and provided with a variable throttle in a flow path connected to each of the oil chambers and the reservoir of the pump and the power cylinder; The variable aperture on the reservoir side of each variable aperture is constituted by a center close valve.

With the above configuration, the flow path to the reservoir is closed by the center-closed variable throttle of the second control unit within the range of the small steering angle of the steering wheel.
The two oil chambers of the power cylinder are kept at the same pressure, the rise in the differential pressure is suppressed, and the neutral rigidity of the handle is increased.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a hydraulic power steering device. This power steering device mainly includes a pump 10 driven by an automobile engine, a reservoir 11, and a power cylinder 1 for power assisting steering operation.
2 and a rotary control valve 14 which operates in response to the rotation of the steering wheel 13 to throttle and control the hydraulic oil supplied from the pump to the power cylinder.

A metering orifice 17 is provided in the discharge passage 16 of the pump 10, and a bypass valve 18 responsive to a differential pressure across the metering orifice 17 is provided.
The bypass valve 18 opens and closes a bypass passage 19 communicating with the reservoir 11 so as to maintain the differential pressure across the measuring orifice 17 constant, and controls the flow rate supplied to the control valve 14 to a constant value. The bypass valve 18 is urged by a spring 20 in a direction to close the bypass passage 19.

As shown in FIG. 2, the control valve 14 is connected to the steering wheel 13 and rotates integrally with the valve shaft 21. The control valve 14 is disposed coaxially around the valve shaft 21. Power cylinder 12
A valve body 22 connected to a steering cage which is power assisted by the motor, a torsion bar (not shown) for connecting the valve body 22 and the valve shaft 21 so as to be relatively rotatable, and a valve housing (not shown) for accommodating these. It is configured.

The valve shaft 21 and the valve body 2
2, two types of control units 2 for restricting hydraulic oil
3 and 24 are alternately formed at intervals of 90 degrees in the circumferential direction. The first control unit 23 includes four flow paths L1, L2, and L connected to the pump 10 and the reservoir 11, respectively.
3, a first bridge circuit C1 provided with variable diaphragms V1, V2, V3, V4 at L4. As shown in FIG. 3, these variable apertures V1, V2, V3, and V4 are configured as center open valves, and their opening areas vary according to the relative rotation angle (valve rotation angle) between the valve shaft 21 and the valve body 22. It changes as shown in FIG.

The second control unit 24 is connected in parallel to the first bridge circuit C1, and includes a pump 10 and a power cylinder 1
A second bridge circuit C in which four flow paths L5, L6, L7, L8 respectively connected to the two oil chambers 12A, 12B and the reservoir 11 are provided with variable throttles V5, V6, V7, V8.
2. Of these variable throttles, the variable throttles V5 and V6 connected to the pump 10 are configured as semi-center open valves as shown in FIG.
Also, variable apertures V7 and V8 connected to the reservoir 11 side
Are configured as center close valves as shown in FIG. 5, and these variable throttles V5 and V6 and the variable throttle V
7, the opening area of V8 changes as shown in FIG. 6 according to the relative rotation angle (valve rotation angle) between the valve shaft 21 and the valve body 22.

In FIG. 1, reference numeral 30 denotes a pressure fluid supply hose, and reference numeral 31 denotes a relief valve. In the present embodiment configured as described above, the hydraulic oil discharged from the pump 10 is controlled to a constant flow rate by the metering orifice 17 and the bypass valve 18, and the first and second control units 23,
24. In the neutral state of steering, the center-closed variable throttles V7 and V8 of the second control unit 24 are closed, while the center-opened variable throttles V5 and V6 are open. ,
The reference numeral 12B communicates via the center-open type variable throttles V5 and V6 and is kept at the same pressure. Therefore, the hydraulic oil discharged from the pump 10 is equally supplied to the oil chambers 12A and 12B, while the variable throttles V1, V2 and V of the first control unit 23 are controlled.
3, is discharged to the reservoir 11 through V4.

When the steering wheel 13 is rotated and the valve shaft 21 is slightly rotated relative to the valve body 22, for example, rightward in FIG.
The opening area of one of the variable stops V2 and V3 of the control unit 23 is increased, and the opening area of the other of the variable stops V1 and V4 is reduced. As a result, the pressure of the pump 10 gradually increases. However, as shown in FIG.
Since the closed state of V8 is maintained up to the valve rotation angle θ1, the differential pressure between both oil chambers of the power cylinder is 0 until the angle θ1.
Is held.

Therefore, in the neutral dead zone equal to or less than the valve rotation angle θ1, both oil chambers 12A,
An increase in the differential pressure of 2B can be prevented, and manual steering is performed near neutral, thereby increasing neutral rigidity. When the valve rotation angle exceeds θ1, one of the variable throttles V5 on the pump 10 side of the second control unit 24 is in a reduced state, and one of the variable throttles V7 on the reservoir side starts to open.
The hydraulic oil in one of the two oil chambers 12A is discharged to the reservoir 11 through the variable throttle V7. Thereby, the oil chamber 12A
Of the oil chamber 1 of the power cylinder 12
A differential pressure is generated between 2A and 12B to assist steering.

When the handle is returned, the valve shaft 2
1 and the valve body 22 have returned to the neutral position, and the communication with the reservoir 11 has been interrupted by the variable throttles V7 and V8, so that the oil chamber 12B has oil through the center-open type variable throttles V5 and V6. Since the working oil is smoothly supplied from the chamber 12A, the return of the handle is improved. According to the above-described embodiment, near the neutral position of the steering wheel 13 where the valve rotation angle is equal to or less than θ1, even if the pressure of the pump 10 increases due to a change in the aperture of the variable aperture of the first bridge circuit C1. , The second bridge circuit C
The action of the center close valve 2 prevents the pressure difference between the two oil chambers 12A and 12B of the power cylinder 12 from increasing.

[0018] Therefore, in the vicinity of neutral, manual steering is performed to improve steering wheel rigidity, and since the start of assist becomes clear, the steering feeling can be improved. When the handle is returned, the communication between the power cylinder 12 and the reservoir 11 is cut off by the center-closed variable throttles V7 and V8. The oil is smoothly supplied to the other oil chamber via the variable throttles V5 and V6, so that the return of the steering wheel can be improved.

[0019]

As described above, according to the present invention, there is an effect that the handle rigidity near the neutral position can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a power steering device according to an embodiment of the present invention.

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

FIG. 3 is a detailed view of a part A in FIG. 2;

FIG. 4 is a detailed view of a portion B in FIG. 2;

FIG. 5 is a detailed view of a portion C in FIG. 2;

FIG. 6 is a graph showing an opening area of a variable throttle with respect to a valve rotation angle.

FIG. 7 is a graph showing a differential pressure of a power cylinder with respect to a valve rotation angle.

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

[Description of Signs] 10 Pump 11 Reservoir 12 Power cylinder 13 Steering wheel 14 Control valve 23 First control unit 24 Second control unit V1 to V4 Variable throttle (center open) V5 to V6 Variable throttle (semi-center open) V7 to V8 Variable aperture (center closed)

Claims (1)

[Claims] A first control unit having a variable throttle provided in a flow path connected to each of a pump and a reservoir; a first oil pressure chamber connected to the first control unit in parallel with both oil chambers of the pump and the power cylinder; A second control unit having a variable throttle provided in a flow path connected to each of the variable throttles, wherein the variable throttle on the reservoir side among the variable throttles of the second control unit is constituted by a center close valve. Power steering device.