JPH0999851A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the response delay of the pressure rise of a power cylinder when a handle is quickly steered by setting the bevel depth of the underlap valve of the first control valve section shallower than the bevel depth of the underlap valve of the second control valve section within two control valve sections constituting a control valve and connected in parallel with each other. SOLUTION: The bevel depth D1 of the underlap valve of the first control valve section 23 is set small, and the bevel depth D2 of the underlap valve of the second control valve section 24 is set large for the depths in the radial direction of the bevels 21A, 21C formed at the edge sections of the underlap valves of the first and second control valve sections 23, 24 constituting variable throttles V1-V4, V7, V8. A larger quantity of the hydraulic fluid is distributed to the second control valve section 24 connected to a power cylinder by the valve action caused by handle steering. Even when a handle is quickly steered, the feeding capability of the hydraulic liquid to the fluid chamber of the power cylinder is improved, and the response delay of the pressure rise of the power cylinder can be prevented.

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 apparatus used in automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Laid-Open No. 6-127401 discloses a power steering apparatus for preventing the rise of the differential pressure of a power cylinder in the vicinity of neutral to enhance the feeling of neutral rigidity.
There is one described in the publication. The publication described in this publication is provided with two control valve sections connected to a control valve in parallel with each other, one control valve section is configured by a center open type variable throttle, and the other control valve section is a center closed type. It consists of a variable diaphragm and a center open type variable diaphragm.
A power cylinder is connected to the other control valve section.

Therefore, in the vicinity of the neutral position of the steering, a differential pressure is not generated between the oil chambers of the power cylinder due to the center closed type variable throttle, and when the center closed type variable throttle is steered until opening, both power cylinders are opened. A differential pressure is generated in the oil chamber. In this type of power steering device, the hydraulic oil supplied from the pump is passed through only the center open type variable throttle of one control valve unit until the center closed type variable throttle of the other control valve unit starts to open. After the center closed type variable throttle starts to open, the hydraulic oil supplied from the pump is shunted to the two control valve sections, and the center opening type variable throttle throttle opening opens both power cylinders. It is designed to increase the differential pressure in the oil chamber.

[0004]

In the power steering apparatus having the above structure, when the steering wheel is steered suddenly,
There may be a slight response delay in the pressure rise of the power cylinder. This is because the hydraulic oil supplied from the pump is divided into the two control valve portions as described above, so the flow rate of the hydraulic oil supplied to the power cylinder is halved, and therefore the pressure increase due to the sudden steering is increased in the power cylinder. It is considered that this is caused by consumption of the flow rate by the action of supplying the pressure oil to the high pressure side oil chamber or consumption of the flow rate by the action of expanding the hose in the supply line.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the power steering apparatus according to claim 1 is provided in the flow passages respectively connected to the pump and the reservoir. And a first control valve portion for controlling the hydraulic fluid supplied from the pump according to steering of the steering wheel by the variable throttle, and a variable valve provided in the flow passages respectively connected to both the oil chamber of the pump and the power cylinder and the reservoir. A variable control valve that includes a second control valve section that is provided in parallel with a second control valve section that restricts the hydraulic oil that is supplied from the pump to the power cylinder according to the steering of the steering wheel by the throttle and that constitutes the first control valve section. The throttle is constituted by an underlap valve that becomes an underlap at neutral, and one of the variable throttles constituting the second control valve section, which is on the pump side or the reservoir side, is turned on at neutral. The variable throttle is constituted by an overlap valve which is a barlap, and the other variable throttle is an underlap valve which is an underlap when neutral, and the chamfer depth of the underlap valve of the first control valve unit is It is shallower than the chamfer depth of the underlap valve of the second control valve section.

In the power steering apparatus according to a second aspect of the present invention, the variable throttles provided in the flow passages respectively connected to the pump and the reservoir control the hydraulic oil supplied from the pump according to the steering of the steering wheel. A control valve portion of the control valve, and variable throttles provided in the flow passages respectively connected to the oil chamber and the reservoir of the pump and the power cylinder, for throttle control of hydraulic oil supplied from the pump to the power cylinder in response to steering of the steering wheel. A control valve having two control valve portions arranged in parallel is provided, and each variable throttle constituting the first control valve portion is configured by an underlap valve that becomes an underlap at neutral,
Of the variable throttles constituting the second control valve section, one of the variable throttles on the pump side and the reservoir side is constituted by an overlap valve that overlaps at neutral, and the other variable throttle at neutral. The underlap valve is an underlap valve, and the chamfer width of the underlap valve of the first control valve portion is smaller than the chamfer width of the underlap valve of the second control valve portion.

[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 (not shown) and a reservoir 11.
A power cylinder 12 for power assisting the steering operation, and a rotary control valve 14 that operates in response to the rotation of a steering wheel (not shown) to throttle the hydraulic oil supplied from the pump to the power cylinder. ing.

A metering orifice 17 is provided in the discharge passage 16 of the pump 10, and a bypass valve 18 which responds to the 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 a developed view in FIG. 2, the control valve 14 is connected to a handle 13 and integrally rotates with a valve shaft 21. A valve body 22 connected to a steering linkage that is power assisted by the cylinder 12, a torsion bar (not shown) that connects the valve body 22 and the valve shaft 21 so as to be rotatable relative to each other, and a valve housing (not shown) that houses them. Etc.

The valve shaft 21 and the valve body 2
Two types of control valve portions 23 and 24 for restricting and controlling the hydraulic oil are alternately formed between the two portions at intervals of 90 degrees in the circumferential direction. The first control valve unit 23 has a variable throttle V1 in the flow passages connected to the pump 10 and the reservoir 11, respectively.
It is composed of a first bridge circuit provided with V2, V3, and V4. As shown in A of FIG. 3, the valve control unit forming the variable throttles V1, V2, V3, and V4 is configured as an underlap valve in which the underlap angle in the neutral state is set to θ1.

The second control valve section 24 is connected in parallel with the first control valve section 23, and the pump 10 and the power cylinder 1 are connected.
The second bridge circuit is provided with variable throttles V5, V6, V7, and V8 in the flow paths connected to the two oil chambers 12A and 12B and the reservoir 11, respectively. Of these variable throttles, variable throttles V5, V connected to the pump 10 side
As shown in FIG. 3B, the valve control section 6 is configured as an overlap valve in which the overlap angle at neutral is set to θ1 which is the same as the above. Also,
As shown in C of FIG. 3, the valve control unit that forms the variable throttles V7 and V8 connected to the reservoir 11 side is configured as an underlap valve in which the underlap angle at neutral is set to θ1 which is the same amount as the above. ing.

As shown in FIG. 3, the underlap valve of the first control valve portion 23 and the edge portions of the overlap valve and the underlap valve of the second control valve portion 24 on the valve shaft 21 side are respectively shown in FIG. To chamfer 21
A, 21B, and 21C are formed. As a result,
As shown in, even if it is an underlap valve, the valve is not closed even if it exceeds the underlap angle, and similarly, even if it is an overlap valve, the valve is not completely closed at neutral, The chamfer 21C maintains a small aperture opening.

Chamfers 21A, 21 formed on the respective edge portions of the underlap valves of the first and second control valve portions 23, 24 constituting the variable throttles V1 to V4, V7, V8.
The chamfering width in the rotational direction of C is set to the same L0, but the depths D1 and D2 in the radial direction are made different from each other so that the second control valve portion 24 becomes larger. That is, the chamfering depth D1 of the underlap valve of the first control valve portion 23 is set small, and the chamfering depth D2 of the underlap valve of the second control valve portion 24 is set large, as shown in FIG.
As shown in FIG. 5, even when the aperture areas of the variable apertures V1 to V4 are considerably limited by the chamfer 21A having a small depth, the variable apertures V7 and V8 have a sufficiently large aperture area due to the chamfer 21C having a large depth. It is in a secured state.

In the embodiment configured as described above, the hydraulic fluid 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 valve portions 23, 24. In the neutral state of steering, since the throttle areas of the variable throttles V5 and V6 on the overlap valve side of the second control valve portion 24 are limited, most of the hydraulic oil discharged from the pump 10 is controlled by the first control. Variable throttles V1 and V of the valve unit 23
It is discharged to the reservoir 11 through 2, V3 and V4.

When the handle is rotated and the valve shaft 21 rotates slightly relative to the valve body 22 in the right direction in FIG. 2, the opening of one of the variable throttles V2 and V3 of the first control valve portion 23 is opened. The area is enlarged, and the aperture areas of the other variable diaphragms V1 and V4 are reduced. As a result, the pressure of the pump 10 is slightly increased, but the throttle areas of the variable throttles V5 and V6 of the second control valve portion 24 are sufficiently smaller than the throttle areas of V7 and V8 opening to the reservoir 11 side. Therefore, the pressure difference between the two oil chambers of the power cylinder is kept substantially zero.

Therefore, in the vicinity of the neutral position where the valve rotation angle is θ1 or less, the variable throttles V1 to V4, V7 and V8 of the underlap valves of the first and second control valve portions 23 and 24.
Despite the change in the throttle area, the oil chambers 12A and 12B of the power cylinder 12 are maintained at substantially the same pressure, and the neutral rigidity is enhanced. When the valve rotation angle exceeds θ1, one variable throttle V6 on the pump 10 side of the second control valve portion 24 starts to open, and at this time, one variable throttle V8 on the reservoir side is in a contracted state, so the power cylinder The pressure in one of the oil chambers 12B of the power cylinder 12 rises, and the other oil chamber 12A is opened to the reservoir 11 via the variable throttle V5 in the expanded state. Therefore, the differential pressure between the oil chambers 12A and 12B of the power cylinder 12 is increased. Occurs,
Assist steering steering. Therefore, the TM-P characteristic showing the relationship of the differential pressure (P) of the power cylinder 12 with respect to the manual torque (TM) is as shown in FIG.

By the way, when the valve rotation angle reaches θ1,
The throttle area of the variable throttles V1 to V4 formed by the underlap valve of the first control valve portion 23 having a small chamfer depth is extremely small, whereas the second control valve portion having a large chamfer depth is extremely small. The aperture areas of the variable throttles V7 and V8 formed by the 24 underlap valves are still sufficiently secured,
The ratios of these diaphragm areas are variable diaphragms V1 to V4, V7,
It is maintained until V8 is completely closed.

Therefore, the flow rate of the hydraulic oil flowing through the first control valve portion 23 is such that the hydraulic oil supplied from the pump 10 does not reach the valve rotation angle θ1 at which the overlap valve starts to open as shown in FIG. 6A. Almost all the amount. However, when the valve rotation angle exceeds θ1, the flow rate of the hydraulic oil flowing through the first control valve portion 23 sharply decreases in accordance with the opening of the chamfer 21A having a small chamfer depth. On the other hand, the flow rate of the hydraulic oil flowing through the second control valve section 24 is 2
By the action of 1C, as shown in B of the same figure, the flow rate increases in inverse proportion to the flow rate of the hydraulic oil flowing through the first control valve portion 23.

Therefore, since a large amount of hydraulic oil is distributed to the second control valve portion 24 connected to the power cylinder 12 by steering the steering wheel, even if the steering wheel is steered steeply, the oil chamber of the power cylinder 12 is It is possible to improve the ability to supply hydraulic oil to the engine and prevent a decrease in assist. Further, FIG. 7 shows another embodiment of the present invention, in which chamfer depths of chamfers 21A1 and 21C1 formed at the valve edge portions of the underlap valves of the first and second control valve portions 23 and 24 are shown. The chamfer widths L1 and L2 are made different so that the second control valve portion 24 becomes larger, instead of making the same (D0). In this embodiment also, when the steering wheel is steered. Since the variable throttle of the first control valve portion 23 is limited and a large amount of hydraulic oil flows to the second control valve portion 24,
The same effect as that of the above-described embodiment can be expected.

Further, the first and second control valve portions 23, 2
The chamfer formed on each valve edge portion of the underlap valve No. 4 can also be different in both depth and width. FIG. 8 shows still another embodiment of the present invention.
Of the variable throttles V5 to V8 of the control valve unit 24 of the pump 1
The valve control unit forming the variable throttles V5 and V6 connected to the 0 side is an underlap valve, and the valve control unit forming the variable throttles V7 and V8 connected to the reservoir 11 side is an overlap valve.

Also in this embodiment, the same operation as that of the above-mentioned embodiment can be expected, and in addition to that, the handle return can be improved. That is, since the valve shaft 21 and the valve body 22 return to the neutral position when the handle is returned, the variable throttles V7, V
The communication with the reservoir 11 is blocked by 8 and the variable throttles V5 and V6 are provided in one oil chamber 12B of the power cylinder 12.
The hydraulic oil is smoothly supplied from the other oil chamber 12A via the valve, and the handle return characteristic is improved as compared with the above-described embodiment.

In the above-mentioned embodiment, the neutral rigidity is enhanced near the neutral position by the overlap valve, but the overlap valve may be changed to a center closed valve which completely closes the variable throttle at the neutral position. It should be understood that the overlap valve is not limited to the one shown in the embodiment and includes such a center closed valve.

Further, in the above embodiment, the chamfer depth of the underlap valve of the first control valve portion 23 is made small so as to be different from the chamfer depth of the underlap valve of the second control valve portion 24. However, the chamfering of the underlap valve of the first control valve portion 23 may be eliminated, and the chamfering depth of the underlap valve of the second control valve portion 24 may be made different. In this case, the valve rotation angle is the first control valve unit 2
When the underlap amount of the center open valve of No. 3 is reached, the center open valve of the first control valve unit 23 is closed, and thereafter the hydraulic oil from the pump 10 is supplied only to the second control valve unit 24. become.

[0024]

As described above, according to the present invention, the chamfer depth of the center open valve of the first control valve portion is made shallower than the chamfer depth of the center open valve of the second control valve portion,
Set the chamfer width of the center open valve of the first control valve section to the second
By making the chamfer width smaller than the center open valve of the control valve section of the control valve section, a large amount of hydraulic oil is distributed to the second control valve section connected to the power cylinder by the valve operation by steering the steering wheel, and therefore the handle Even when the steering wheel is suddenly steered, the ability to supply the hydraulic oil to the oil chamber of the power cylinder is improved, and there is an effect that it is possible to prevent a response delay from occurring in the pressure rise of the power cylinder.

[Brief description of 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 portions A, B, and C of FIG.

4 is a diagram showing an operating state of FIG. 3. FIG.

FIG. 5 is a characteristic diagram showing the relationship between the manual torque and the differential pressure of the power cylinder.

FIG. 6 is a graph showing distribution of flow rates to the first and second control valve portions with respect to a valve rotation angle.

FIG. 7 is a detailed view corresponding to FIG. 3 showing another embodiment of the present invention.

FIG. 8 is a detailed view corresponding to FIG. 2 showing still another embodiment of the present invention.

[Explanation of symbols]

 10 Pump 11 Reservoir 12 Power Cylinder 14 Control Valve 21A, 21B, 21C Chamfer 23 First Control Valve Section 24 Second Control Valve Section V1-V8 Variable Throttle

Claims (3)

[Claims] 1. A first control valve section for controlling the amount of hydraulic fluid supplied from a pump in response to steering of a steering wheel by a variable throttle provided in a flow path connected to a pump and a reservoir, the pump and a power cylinder. And a second control valve section for controlling the throttle of the hydraulic oil supplied from the pump to the power cylinder in response to the steering of the steering wheel by the variable throttles provided in the flow passages respectively connected to both the oil chambers and the reservoir. A control valve is provided, and each variable throttle forming the first control valve section is an underlap valve that becomes an underlap at neutral, and the pump side of the variable throttles forming the second control valve section is provided. One of the variable throttles on the reservoir side and the reservoir side is composed of an overlap valve that overlaps at neutral, and the other variable throttle has an underlap at neutral. And a chamfer depth of the underlap valve of the first control valve section is shallower than a chamfer depth of the underlap valve of the second control valve section. Device. 2. A first control valve section for controlling the amount of hydraulic fluid supplied from the pump according to steering of the steering wheel by means of variable throttles provided in the flow passages respectively connected to the pump and the reservoir, the pump and the power cylinder. And a second control valve section for controlling the throttle of the hydraulic oil supplied from the pump to the power cylinder in response to the steering of the steering wheel by the variable throttles provided in the flow passages respectively connected to both the oil chambers and the reservoir. A control valve is provided, and each variable throttle forming the first control valve section is an underlap valve that becomes an underlap at neutral, and the pump side of the variable throttles forming the second control valve section is provided. One of the variable throttles on the reservoir side and the reservoir side is composed of an overlap valve that overlaps at neutral, and the other variable throttle has an underlap at neutral. A power steering system comprising a double lap valve, the chamfer width of the underlap valve of the first control valve section being smaller than the chamfer width of the underlap valve of the second control valve section. apparatus. 3. The underlap amount of the underlap valve of the first control valve portion and the underlap amount of the underlap valve of the second control valve portion are made equal to each other. Power steering device.