JPH07329811A - Vehicle speed sensitive type power steering device - Google Patents

Abstract

PURPOSE:To provide a vehicle speed sensitive type power steering device of a low cost with which effective pressure acting on a power cylinder is variably controlled in accordance with vehicle speed or the like and assist force can be variably controlled. CONSTITUTION:A passage selector valve CV for selectively connecting a pump P and a tank T to a left and a right chambers CL, CR of a power cylinder P/C is provided. The passage selector valve CV is provided with a left and a right pairs of first and second variable restrictors 1R, 1L, 2L, 2R which are opened/closed for feeding pressure oil to the left and the right chambers CL, CR by steering. Passages 14, 15 are provided from the first and the second variable restrictors 1R, 1L, 2L, 2R to the cylinder right and left chambers CL, CR. The passage between the second variable restrictors 2L, 2R and the tank T is provided with a pair of left and right third variable restrictors 21, 22 which in response to operation side cylinder pressure restrict a return side passage area. Further, a vehicle speed sensitive type variable restrictor 23 is provided between the third variable restrictors 21, 22 and the tank T.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the power assist force (steering assist force: boosting ratio) according to vehicle traveling information such as vehicle speed to enable various vehicle traveling conditions and steering operation (steering). The present invention relates to a vehicle speed-sensitive power steering device capable of performing appropriate steering force control according to the magnitude of the load at the time.

[0002]

2. Description of the Related Art In a power steering system that obtains a power assisting force for reducing a steering wheel operating force (steering force) of an automobile, it is desirable to control the steering force according to the traveling speed (vehicle speed) of the vehicle. Be done. That is, steering force control that enables a light steering operation when the vehicle is stopped or running at low speed, and gives the steering wheel a feeling of response and rigidity when running at high speeds and ensures steering stability when going straight Is needed.

For this reason, a flow control type power steering device using a flow control valve is known as a vehicle speed sensitive power steering device. That is, in this type of device, in a pump that is rotationally driven by an engine of an automobile, in addition to a flow rate control valve function that feeds by limiting the pressure oil flow rate to a fixed amount, by reducing the supply flow rate at high speed, The generated pressure is reduced, the power assist force in the power cylinder is reduced, and as a result, the steering force is controlled to be heavier.

However, in such a flow rate control type device, since the flow rate is adjusted according to the flow rate of the feed from the pump, the control range of the steering force is relatively narrow, and the required steering force control can be performed. I couldn't say that.
Further, such a flow rate control type device cannot avoid the problem of poor followability when a sudden steering operation is performed during high-speed traveling.

Further, as a vehicle speed sensitive power steering device, a vehicle speed response is provided by a reaction force piston for selectively restraining or turning the steering input and output shafts according to the magnitude of reaction force hydraulic pressure. A type using a hydraulic reaction force device is also known. That is, when the vehicle is stopped or traveling at low speed, the reaction force hydraulic pressure is minimized to enable a light steering operation, and at the time of high speed traveling, the reaction force hydraulic pressure is increased to give the steering wheel a sense of rigidity, which improves stability when traveling straight. Steering force control that can be ensured is performed.
Various structures have been proposed including 1-105273 and JP-A-61-232466.

However, even in such a hydraulic reaction force control type device, for its operation, a reaction force pressure control valve for obtaining a hydraulic reaction force according to the vehicle speed, and a reaction force between the input and output shafts are provided. It is necessary to provide a piston and a reaction force receiving part facing this,
The number of parts is large, the structure is likely to be complicated, and the cost is high, which is a disadvantage. Further, in such a conventional device, the friction at the hydraulic reaction force device portion is large, which often causes a problem in operation performance.

Therefore, as a vehicle speed sensitive type power steering device of this type, a new system is demanded which is low in cost and can secure a steering force control range in practice. In order to meet such a request, Japanese Patent Laid-Open No. 2-1
As disclosed in Japanese Patent No. 75467, in addition to a vehicle speed responsive variable throttle valve controlled by a vehicle speed, the opening is controlled to be small when the relative angular displacement between the input and output shafts is large. A steering angle responsive variable throttle is added, and the variable throttle valve and the variable throttle connect the supply passage from the pump to the flow passage switching valve and the return passage to the tank from the flow passage switching valve. By controlling the partial flow rate to the bypass passage, the supply flow rate to the power cylinder during steering can be secured.

With such a construction, the divided flow rate to the tank side can be controlled by the vehicle speed responsive variable throttle valve whose opening is controlled according to the vehicle speed. Further, the steering angle responsive variable throttle provided in the bypass passage decreases in opening degree when the steering wheel operation amount increases. Regardless of the opening of the throttle valve, the flow through the bypass passage can be restricted, and as a result, the supply flow rate to the power cylinder can be secured.

Therefore, in such a conventional device, even when the opening of the vehicle-speed-responsive variable throttle valve is large, such as when traveling at medium and high speeds, the opening of the steering-angle-responsive variable throttle is interlocked with the steering wheel operation. Since it can be made smaller, the flow rate discharged from the bypass passage is reduced to secure the supply flow rate to the power cylinder, solving the problem of responsiveness deterioration due to insufficient flow rate as in the past, and steering force control according to running conditions Can be optimized.

In other words, in this conventional example, in the above-mentioned conventional apparatus, the flow rate supplied to the power cylinder is extremely reduced when the vehicle is traveling at medium and high speeds, thereby increasing the speed of the steering wheel operation and the amount of steering wheel operation. When the throttle opening is controlled by the size of the steering angle, that is, when the relative displacement angle between the input and output shafts is large, the opening becomes small. It has been attempted to solve the problem by adding a variable throttle configured so as to secure the supply flow rate to the power cylinder side when the load increases.

[0011]

However, according to the conventional vehicle speed-sensitive power steering apparatus improved as described above, the working pressure on the positive pressure side (high pressure side) in the flow path switching valve and the power cylinder is increased. It is only controlled, and there is still room for improvement.

That is, according to the above-mentioned conventional device, a variable speed control type variable throttle valve that responds to the vehicle speed and a steering angle are provided in a passage that bypasses the supply passage on the upstream side of the flow path switching valve and the return passage on the downstream side. It is a structure in which a steering angle responsive variable diaphragm that interlocks is separately provided, and the number of parts is large, the structure is complicated, and the cost is high. It is hoped that some measures will be taken.

Particularly, in this type of vehicle speed sensitive power steering device, responsiveness and followability at the time of steering at high speed traveling can be ensured, and the steering and steering can be sharpened at the time of traveling. Some consideration should be given so that there is little influence of friction such as reaction force mechanism parts, etc., and that the problem of fluid noise associated with cavitation, etc. due to rapid flow of fluid pressure during sudden steering can be suppressed. Is desired.

The present invention has been made in view of the above circumstances, and improves a fluid pressure circuit structure from a pump or a tank to a power cylinder via a flow path switching valve, and is variable in response to a vehicle speed or the like. By combining the throttle, the effective pressure acting on the power cylinder can be variably controlled to the required state by the vehicle speed and the load fluctuation such as the increase of the steering angle during steering, and the assist force can be variably and reliably controlled. It is an object of the present invention to provide an inexpensive vehicle speed-sensitive power steering device that can reduce the amount of fluid noise.

[0015]

SUMMARY OF THE INVENTION A vehicle speed sensitive power steering system according to the present invention is a power system in which a pump side and a tank side are selectively connected via a flow path switching valve which is controlled to switch according to a steering operation. Passage between the left and right passages to the left and right chambers of the cylinder between the tank and the pair of left and right second variable throttles, which are opened and closed by steering, and the return passage in response to the cylinder pressure on the operating side. A pair of left and right third variable throttles for reducing the area is provided, and a vehicle speed responsive variable throttle is provided between the third variable throttle and the tank.

Further, the vehicle speed sensitive power steering device according to the present invention comprises a pair of left and right third variable valves provided in the left and right passages between the tank and the second variable throttle forming the flow path switching valve. A throttle is provided in the middle of the left and right output side passages from the flow passage switching valve to the cylinder left and right chambers, and a vehicle speed responsive variable throttle is provided in the return passage from the flow passage switching valve to the tank. is there.

[0017]

According to the present invention, when not steering, the pair of third variable throttles provided in the left and right passages of the power cylinder left and right chambers and forming a pair of left and right are controlled by the pressure balance in each passage.
Each passage is kept open and the return flow of fluid pressure is maintained as desired.

Further, during steering, the third variable throttle in the middle of the return passage operates so as to limit the flow of the fluid pressure on the return side by the fluid pressure (cylinder pressure) in the passage on the operating side. , Which limits the return of fluid pressure from the return chamber of the power cylinder.

When the vehicle is traveling at a low speed, the vehicle speed responsive variable throttle provided in the return passage of the power cylinder is in an open state, so that the amount of fluid pressure supplied to the working side chamber of the power cylinder is also equal to that of the return side. The amount of return from the chamber to the tank also increases. When the steering force is small and the fluid pressure in the operating-side cylinder chamber is large, the return-side cylinder chamber is restricted in its return to the tank by the action of the third variable throttle, resulting in an increase in back pressure. Therefore, the generation of fluid noise can be reduced.

On the other hand, when traveling at high speed, the return passage in the power cylinder is closed by the vehicle speed responsive variable throttle, and the amount of fluid pressure supplied to the working cylinder chamber is also the tank from the return chamber. The amount of return to is also small. And
When the steering force is small and the fluid pressure to the operating side cylinder chamber is small, the control by the third variable throttle on the return side is also small, but the fluid pressure in the return side cylinder chamber is less than the pressure on the return side by the tank. Is a high intermediate pressure and the back pressure will increase. As a result, the escape of the fluid pressure from the return side chamber in the power cylinder is limited, so it becomes so-called back pressure control, and the effective pressure in the power cylinder is controlled to be relatively low. The assisting force is reduced, and the steering operation can be given a sense of response to improve steering stability.

[0021]

1 and 2 show an embodiment of a vehicle speed-sensitive power steering apparatus according to the present invention. In these drawings, first, in a vehicle speed-sensitive power steering apparatus generally designated by reference numeral 10 The outline of the hydraulic circuit will be described with reference to FIG. 1. This hydraulic circuit is a flow path switching valve in which pressure oil fed from a main pump P that is a hydraulic source is switched and controlled by a steering operation by a steering handle. The CV is configured to be fed to the left and right chambers CL and CR of the power cylinder (indicated by P / C in the drawing), which is an apparatus actuator, and to be recirculated to the tank T.

Reference numeral 11 in the drawing denotes a supply passage extending from the pump P to the hydraulic bridge circuit of the flow passage switching valve CV, and 12, 13
Is the left and right passages that form a bridge circuit in this flow path switching valve CV, 14 and 15 are the left of the power cylinder P / C,
The left to the right chamber, the left and right output passages from the right passages 12 and 13, and 16 from the bridge circuit of the flow passage switching valve CV to the tank T.
It is a return passage leading to.

As is well known, in the left and right passages 12 and 13 forming the hydraulic bridge circuit of the above-mentioned flow path switching valve CV, the first variable throttles 1R and 1L and the second variable throttles 2L and 2R are known. Are provided facing each other. Then, from the left and right passages 12 and 13 between the first and second variable diaphragms 1R and 2L; 1L and 2R, the left and right output passages 14,
15 is pulled out, power cylinder left, right chamber CL, CR
The hydraulic pressure is appropriately supplied to or recirculated to.

Such a power steering device 10
Is the pressure oil from the pump P at the flow path switching valve CV,
By switching the passages 12 and 13 to the left and right chambers CR and CL of the power cylinder P / C in accordance with the steering direction and steering angle of the steering wheel, one of the chambers CR and CL is controlled.
It is well known that the power assisting force for assisting the steering force can be obtained by supplying the power to the tank T through the passage 14 or 15 and connecting the other chamber to the tank T through the passage 15 or 14 in the same manner. Therefore, detailed description thereof is omitted here.

According to the present invention, as is apparent from FIGS. 1 and 2, the power cylinder left to which the pump P and the tank T are selectively connected via the bridge circuit of the flow path switching valve CV described above. , The left and right passage 1 to the right ventricle CL, CR
2, 14; 13, 15 are respectively provided with a pair of left and right third variable throttles 21 and 22 which are control members for controlling the flow of pressure oil, and a pair of left and right third variable throttles are provided. Connect the diaphragms 21 and 22 to the mating connecting passages 13 and 15 respectively.
Alternatively, the third variable throttle 2 which is configured to operate in response to the hydraulic pressure in 12 and 14 (that is, the cylinder pressure on the operating side) to reduce the passage area on the return side, and which forms a pair of left and right sides.
A vehicle speed responsive variable throttle 23 is provided in a part of the return passage 16 that goes through the tanks 1 and 22 to the tank T side.

In FIG. 1, 21a and 22a are on the left,
This is a pilot pressure passage for controlling the opening and closing of the variable throttle portion by the third pair of right and left variable throttles 21 and 22 according to the size of the pressure oil in the mating passage.

That is, reference numeral 24 in FIG. 2 denotes a control box portion provided with the above-mentioned pair of left and right third variable apertures 21 and 22, which constitutes a part of the left and right output side passages 14 and 15. Passage parts 14a, 1 leading to the left and right chambers CL, CR of the cylinder
5a. Then, a pair of communication holes 25a, 26 are provided between the passages 14a, 15a arranged in parallel.
a is formed, and the left and right rod bodies 25, 2 are formed inside thereof.
6 is configured to be able to move back and forth against the springs 25b and 26b depending on the size of the pressure oil in the mating passages 15a and 14a. The distal end portions of these rod bodies 25, 26 selectively face the corresponding passage portions 14a, 15a,
The flow of pressure oil flowing through the passage can be regulated.

According to such a configuration, at the time of non-steering,
Cylinder left, left to the right chamber CL, CR, left, right provided in the output side passages 14 and 15 which are connecting passages, a pair of left and right third pair
Body 27, 28 constituting the variable diaphragms 21, 22 of
However, by maintaining the respective passages 14 and 15 in an open state due to the pressure balance in the respective passages 15 and 14, the flow of pressure oil on the return side and further on the working side is maintained in a required state. become.

[0029] This means that the vehicle is stopped, running at low speed,
This is also the case during high-speed traveling, and in particular during high-speed traveling, the variable throttle 23 of the return passage 16 is narrowed and the return side is restricted, so it is possible to give a feeling of response when trying to steer the steering wheel. , It is possible to bring out the sharpness when holding the steering.

During steering, the connection passage 1 on the return side
A pair of third variable throttles 21, 22 in the middle of 2, 14; 13, 15 limit the flow of the pressure oil by facing the return side passages 15a, 14a by the pressure oil in the operating side connection passage. So as to limit the return amount of the fluid pressure from the chamber CR or CL on the return side of the power cylinder P / C.

When the vehicle is traveling at a low speed, the vehicle speed responsive variable throttle 23 provided in the return passage 14 or 15 of the power cylinder P / C is in an open state. Both the supply amount and the return amount from the return side chamber to the tank are large. And the steering force is small,
Since the hydraulic pressure in the operating-side cylinder chamber increases, the return-side cylinder chamber is restricted in its return to the tank T by the action of the third variable throttle 21 or 22, which results in an increase in back pressure. The loss can be reduced and the generation of fluid noise can be reduced.

On the other hand, when traveling at high speed, the power cylinder P
The return passage 14 or 15 at the power cylinder P / C is closed by the vehicle speed responsive variable throttle 23.
Both the amount of pressure oil supplied to the operating chamber and the amount of return from the returning chamber to the tank T are small. When the steering force is small and the hydraulic pressure to the operating side cylinder chamber is small, the control by the third variable throttle 21 or 22 on the returning side is also small, but the hydraulic pressure in the returning side cylinder chamber is returned by the tank T. The back pressure rises because the intermediate pressure is higher than the side pressure. As a result, the escape of the pressure oil from the return side chamber in the power cylinder P / C is limited, so that so-called back pressure control is performed, and the effective pressure in the power cylinder P / C becomes relatively low. The assist force is reduced by this, and the steering operation can be improved by improving the steering stability.

According to this embodiment, the flow path switching valve C
A control box section 24 having a pair of left and right third variable diaphragms 21 and 22 between the V and the power cylinder P / C.
Since the above structure is provided, the required operational effects can be achieved despite the simple structure.

In particular, according to the present invention, with the above-described structure, by reducing the effective pressure when the vehicle is running, it is possible to give a suitable feeling during steering and during steering, and also at the output side during running. You can increase the friction at the time of steering,
The sharpness when holding the steering can be achieved.

Here, in this embodiment, in the vehicle speed sensitive power steering device, the left and right connecting passages 12, 14; 13 for selectively connecting the pump P and the tank T to the left and right chambers CL, CR of the power cylinder. A pair of left and right third variable throttles 21, 2 for controlling the flow of pressure oil in
2, rod bodies 25 and 26 are provided in the middle of the left and right output passages 14 and 15 from the flow path switching valve CV to the left of the power cylinder, the right chambers CL and CR, and the vehicle speed responsive variable throttle 23.
Is provided in the middle of the return passage 16 from the flow path switching valve CV to the tank T, and the configuration is simple and the number of constituent parts may be minimum, so that cost reduction and high reliability can be achieved.

FIG. 3 shows another embodiment of the present invention. In this embodiment, in a rotor 31 and a sleeve 32 which constitute a rotary valve known as a flow path switching valve CV, a third variable valve is provided in a part of its passage. Rod body 2 as diaphragms 21 and 22
5, 26 are power cylinders left on the sleeve 32, left and right output ports (left, right chambers CL, CR).
33, 34 (corresponding to the right output side passage) are selectively faced to close the passage. In the drawings, the same or corresponding parts as those in FIGS. 1 and 2 described above are designated by the same reference numerals, and detailed description thereof will be omitted. Further, although a detailed description of well-known components as a rotary valve is omitted, a plurality of passage grooves are formed in the rotor 31 and the sleeve 32 in the circumferential direction, and the pump P, the tank T, the left and right cylinder chambers are formed in them. Ports to CL and CR are drilled.

With this structure, in the conventionally known flow path switching valve CV using a rotary valve, the rod bodies 25 and 26 as the third variable throttles and their communicating hole portions 25a and 26a are attached. It is sufficient, the number of constituent parts is minimum, and the cost can be reduced.

The area of the passages (output ports) 33, 34 closed by the rods 25, 26 described above may be set as needed, and the output ports are paired as in the above-described embodiment. In some cases, the structure may be attached to only one of them. Further, in the above-described embodiment, the case where the rod bodies 25 and 26 are biased by the springs 25b and 26b is shown, but the movement of the rod bodies 25 and 26 is adjusted by friction such as O-ring to adjust the movement. Modifications such as installation in the state are conceivable.

FIG. 4 shows another embodiment of the present invention, and shows a case where the present invention is applied to the rotary valve CV portion of the steering main body portion in a conventionally known power steering apparatus. Also in this embodiment, the same or corresponding parts as those in the above-mentioned embodiments are designated by the same reference numerals and the description thereof will be omitted. In the figure, 40 is a steering body, 41 is the rotor 31 and sleeve 3.
This is a torsion bar that connects the two shaft members to each other so that they can be rotationally displaced relative to each other. Since other configurations are well known, a detailed description thereof will be omitted.

Needless to say, even with such a structure, the same operational effects as those of the above-described embodiment can be obtained.

That is, according to the present invention, the rotary valve structure as described above is simply improved, and the variable throttle 23 for obtaining the response to the vehicle speed and the like is combined so that the power cylinder P / C can be operated. The pressure control (back pressure control) on the return side is performed, the effective pressure of the power cylinder P / C is controlled, and the power assist force control according to the information such as the vehicle speed is performed in a required state to provide the steering wheel to the driver. It is possible to give a moderate feeling of response. In particular, according to such a configuration, by simply improving the valve structure and adding the vehicle speed sensitive variable throttle 23 to the back pressure control system, the vehicle speed sensitive power can be produced at low cost and with high reliability. You can get steering.

It is needless to say that the present invention is not limited to the structure of the above-described embodiment, and the shape, structure, etc. of each part of the vehicle speed sensitive power steering device 10 can be appropriately modified or changed. For example, in the above-described embodiment, various modifications are conceivable as the structure of each part including the rotary valve type flow path switching valve CV as well known in the art.

[0043]

As described above, according to the vehicle speed sensitive power steering device of the present invention, the pump side and the tank side are selectively connected via the flow path switching valve which is controlled to switch according to the steering operation. Power cylinder left, left to the right chamber, left, right between the pair of left and right second variable throttles that are opened and closed by steering in the right passage and the tank, and return in response to the cylinder pressure on the operating side. Left to narrow the side passage area,
Since the third variable throttle forming the right pair is provided and the vehicle speed responsive variable throttle is provided between the third variable throttle and the tank, despite the simple configuration, various excellent effects listed below are obtained. There is.

That is, according to the present invention, the operating pressure on the reverse pressure side (return side to the tank) of the power cylinder is operated by the passage pressure on the opposite side, and the pair of left and right third variable throttles and By controlling the back pressure with the vehicle speed sensitive variable throttle, it is possible to control so as to reduce the working pressure (effective pressure) of the power cylinder that is generated during steering when the vehicle is traveling, and by making the steering wheel heavier It is possible to give a feeling of response to the helmsman, and it is possible to secure the steering followability particularly when traveling at high speed.

Further, according to the present invention as described above, when the vehicle is traveling, the required assist force can be controlled by increasing the friction on the output side, so that the steering and the steering can be kept sharp.

Further, according to the vehicle speed sensitive power steering apparatus of the present invention, the third pair of left and right provided in the left and right passages between the second variable throttle forming the flow path switching valve and the tank. The variable throttle of the, from the flow path switching valve to the cylinder left,
Since it is provided in the middle of the left and right output side passages to the right chamber, and the vehicle speed responsive variable throttle is provided in the middle of the return passage from the flow path switching valve to the tank, it has a simple structure, Cost can be reduced by minimizing the number of components
Moreover, high reliability can be exhibited.

That is, during steering, the third variable throttle in the middle of the return side connection passage operates so as to limit the flow of the fluid pressure on the return side by the fluid pressure in the operation side connection passage. Limits the return of fluid pressure from the return chamber of the power cylinder. When the vehicle travels at a low speed, the vehicle speed responsive variable throttle provided in the return passage of the power cylinder is in an open state, so the amount of fluid pressure supplied to the working chamber of the power cylinder is also reduced from the return chamber. The amount of return to the tank also increases. When the steering force is small and the fluid pressure in the operating-side cylinder chamber is large, the return-side cylinder chamber is restricted in its return to the tank by the action of the third variable throttle, resulting in an increase in back pressure. Therefore, the generation of fluid noise can be reduced.

During high speed traveling, the return passage in the power cylinder is closed by the vehicle speed responsive variable throttle, and the amount of fluid pressure supplied to the working chamber of the power cylinder is also from the return chamber. The amount of return to the tank of the
When the steering force is small and the fluid pressure to the working-side cylinder chamber is small, the control by the third variable throttle on the return side is also small, but the fluid pressure in the return-side cylinder chamber is lower than the pressure on the return side by the tank. Is set to a high intermediate pressure and the back pressure rises, and as a result, the escape of fluid pressure from the return side chamber in the power cylinder is limited. The effective pressure is controlled to be relatively low, which reduces the assisting force, which gives a feeling of response to the steering operation and improves the steering stability.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part showing an embodiment of a vehicle speed-sensitive power steering device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment in which the vehicle speed sensitive power steering device shown in FIG. 1 is specifically implemented.

FIG. 3 is a schematic configuration diagram showing another embodiment in which the vehicle speed sensitive power steering device shown in FIG. 1 is implemented in a rotary type flow path switching valve portion.

FIG. 4 is a schematic cross-sectional view when the vehicle speed-sensitive power steering device shown in FIG. 1 is applied to a rotary valve portion of a power steering body.

[Explanation of symbols]

1L, 1R ... First variable aperture, 2L, 2R ... Second variable aperture, 10 ... Vehicle speed sensitive power steering device, 11
... Supply passages, 12, 13 ... Left and right connecting passages constituting fluid pressure bridge circuit, 14, 15 ... Left, right output side passages, 1
6 ... Return passages 21, 22 ... Left and right pair of third variable throttles, 23 ... Vehicle speed responsive variable throttle, 31 ... Rotor, 3
2 ... Sleeve, 33, 34 ... Left, right output port P ... Pump, T ... Tank, CV ... Rotary valve type flow path switching valve,
P / C ... Power cylinder, CR, CL ... Cylinder left, right chamber.

Claims (2)

[Claims] 1. A pump side, a tank side is a power cylinder left, and a flow path switching valve is controlled to be switched according to a steering operation.
The flow path switching valve is configured to be selectively connected to the right chamber, and the flow path switching valve is opened / closed to supply pressure oil to the cylinder left / right chamber with a steering operation. A power steering apparatus having first and second variable throttles and providing left and right output side passages between the first and second variable throttles to the cylinder left and right chambers, wherein the second variable throttle is provided. The left and right passages between the throttle and the tank are provided with a pair of left and right third variable throttles for reducing the passage area on the return side in response to the cylinder pressure on the operating side, and the third variable throttle. A vehicle speed-sensitive power steering device characterized in that a vehicle speed responsive variable throttle is provided between the throttle and the tank. 2. The vehicle speed-sensitive power steering device according to claim 1, wherein a second variable throttle forming a flow path switching valve and a left portion between the tank,
The pair of left and right third variable throttles provided in the right passage is provided in the middle of the left and right output passages from the flow passage switching valve to the cylinder left and the right chamber, and the vehicle speed responsive variable throttle is A vehicle speed-sensitive power steering device, characterized in that the power steering device is provided in the return passage from the flow passage switching valve to the tank.