JPH0911925A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the feeling of rigidity in the straight traveling, and to improve the straight line stability by connecting an accumulator to an oil passage between a control valve and a pump, providing a valve mechanism on the oil passage between the accumulator and the control valve, and pressing the valve member against a shaft by the hydraulic force accumulated in the accumulator during the straight traveling. SOLUTION: In a straight steering position, a valve member 51 of each valve mechanism 50 is pressed in the direction toward the outer circumference of an input shaft 2 by the elastic force of a spring 52 and the hydraulic force accumulated in an accumulator 46, a tip is pressed against a cam surface 53, and a seal ring 56 on the outer circumference is pressed against a valve seat 54b. An oil passage between the accumulator 46 and a control valve 23 is closed. When the steering is made, and first and second valves 24, 25 are relatively turned, the valve member 51 is displaced outwardly in the radial direction and separated away from the valve seat 54b, and the oil passage between the accumulator 46 and the control valve 23 is opened, and the pressure oil reaches a recessed member for feeding the pressure oil of the control valve 23 to generate the necessary assist steering force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system for generating a steering assist force by pressure oil supplied from a pump driven by an electric actuator.

[0002]

2. Description of the Related Art A steering assist force generating hydraulic actuator, a pump driven by an electric actuator, and a control valve provided in an oil passage between the hydraulic actuator and the pump are provided. 2. Description of the Related Art A power steering device that can apply a steering assist force by acting on an actuator has been conventionally used.

By driving the electric actuator only during steering and stopping it during non-steering, energy saving and noise reduction during non-steering are achieved.

However, when the electric actuator is stopped during non-steering, the electric power is supplied by the pump until the amount of pressure oil supplied by the pump reaches the amount necessary to apply a predetermined steering assist force in the initial stage of turning. There is a problem that a delay is generated according to the rising time constant of the actuator and the steering feeling is deteriorated.

Therefore, an accumulator capable of accumulating the hydraulic pressure generated by the pump is connected to the oil passage between the control valve and the pump, and the control valve is closed when the vehicle goes straight and is opened when the vehicle is turned. It has been proposed that the hydraulic pressure initially stored in the accumulator be applied to the hydraulic actuator to compensate for the shortage of pressure oil supplied by the pump at the beginning of steering (see Japanese Patent Laid-Open No. 61-85272).

[0006]

In the above-mentioned conventional power steering system, the control valve arranged between the pump and the hydraulic actuator is simply a three-position switching type on-off valve, and the pump, accumulator and hydraulic actuator are connected to each other. The space between them can be closed when going straight, and can be opened when turning, depending on the turning direction.

However, in an actual power steering device, the control valve arranged between the pump and the hydraulic actuator is controlled by changing the opening degree of the throttle portion provided in the oil passage between the hydraulic actuator and the pump in the steering direction. Not only that, but the one that changes according to the steering torque is used. Therefore, the mere three-position switching type open / close valve in the related art cannot generate the steering assist force according to the steering torque.

Therefore, a control valve capable of changing the opening degree of a throttle portion provided in an oil passage between the hydraulic actuator and the pump in accordance with not only the steering direction but also the steering torque advances straight through the throttle portion. Sometimes it may close completely. For example, as the control valve, as shown in a comparative example of FIG. 8, a tubular first valve member 101 and a second valve member 102 that is inserted into the first valve member 101 and relatively rotates in accordance with a steering torque. And recesses 103 and 104 along the axial direction are formed at an inner circumference of the first valve member 101 and an outer circumference of the second valve member 102 at intervals in the circumferential direction. An inner peripheral surface 10 of the first valve member 101 is used by using a rotary hydraulic control valve in which the throttle portion is between the edge of the first valve member 103 on the axial direction and the edge of the second valve member side recess 104 on the axial direction.
It is conceivable that the throttle portion is closed when going straight by bringing 1a into contact with the outer peripheral surface 102a of the second valve member 102. However, the inner peripheral surface 10 of the first valve member 101
If 1a and the outer peripheral surface 102a of the second valve member 102 are brought into contact with each other, the frictional resistance at the time of turning increases, and the steering feeling deteriorates. Also, both valve members 101,
Since 102 is relatively rotated, it is difficult to completely close it, and the hydraulic pressure of the accumulator drops in a short time.

It is an object of the present invention to provide a power steering device which can solve the above problems.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a hydraulic actuator for generating steering assist force, a pump driven by an electric actuator that can be stopped when the steering is not turned, and an oil between the hydraulic actuator and the pump. A power steering device that includes a control valve that changes an opening degree of a throttle portion provided on a road according to a steering direction and a steering torque, and can apply a steering assist force by causing a hydraulic pressure generated by the pump to act on a hydraulic actuator. In the above, an oil passage between the control valve and the pump is connected to an accumulator capable of accumulating the hydraulic pressure generated by the pump, and a valve mechanism is provided in the oil passage between the accumulator and the control valve. The mechanism includes a cam surface formed on the outer circumference of a shaft that rotates in response to steering, and a valve member that contacts the cam surface and is displaced in response to steering. It has an oil passage between the accumulator and the control valves, the displacement of the valve member, characterized in that it is opened when turning while being closed during straight.

It is preferable that the valve member can be pressed against the outer circumference of the shaft by the hydraulic pressure stored in the accumulator when the vehicle goes straight ahead.

The control valve includes a tubular first valve member,
A second valve member which is inserted into the first valve member and rotates relative to the steering valve according to a steering torque, and a concave portion along the axial direction is formed around the inner circumference of the first valve member and the outer circumference of the second valve member. The first valve member side concave portion is formed between the first valve member side concave portion along the axial direction and the second valve member side concave portion along the axial direction. It is preferable that the shaft is integrated with either one of the second valve member and the second valve member, and the valve seat of the valve member is formed with the other.

The means for detecting the hydraulic pressure stored in the accumulator and the pump are driven during steering and when the hydraulic pressure stored in the accumulator is less than a set pressure.
It is preferable to provide a means for stopping when the hydraulic pressure stored in the accumulator is equal to or higher than the set pressure during non-steering.

A check valve is provided between each oil chamber for generating steering assist force of the hydraulic actuator and a tank under atmospheric pressure so as to allow the flow of oil from the tank to each oil chamber. Is preferred.

[0015]

According to the above-described structure, by stopping the electric actuator when the steering wheel is not steered, it is possible to save energy and reduce noise when the steering wheel is not steered. Also,
An accumulator capable of accumulating the hydraulic pressure generated by the pump is connected to the oil passage between the control valve and the pump, and the oil passage between the accumulator and the control valve is closed when going straight and opened when turning. The hydraulic pressure stored in the accumulator is applied to the hydraulic actuator at the beginning of the rudder to compensate for the shortage of pressure oil supplied by the pump at the beginning of the rudder to prevent deterioration of the steering feel. The control valve controls the opening degree of the throttle portion provided in the oil passage between the hydraulic actuator and the pump,
Since it can be changed according to the steering direction and the steering torque, it is possible to generate a steering assist force according to the steering torque. Between the accumulator and the control valve is opened and closed by a valve member that is displaced by abutting on a cam surface formed on the outer circumference of a shaft that rotates in response to steering,
The opening / closing does not hinder the operation of the control valve, and the steering feeling does not deteriorate.

The valve member is pressed against the shaft that rotates in response to the steering by the hydraulic pressure stored in the accumulator when the vehicle is traveling straight, so that the feeling of rigidity when traveling straight can be improved and the stability of traveling straight can be improved.

The control valve is of a rotary type having a first valve member and a second valve member which rotate relative to each other in accordance with a steering torque, and the shaft is integrated with either one of the valve members and the other. By forming the valve seat of the valve member, the valve member abutting on the cam surface formed on the shaft of the valve member can be displaced according to the steering by the relative rotation of the valve members. This eliminates the need for a dedicated mechanism for displacing the valve member in response to steering,
The configuration can be simplified.

By driving the pump during steering and when the hydraulic pressure stored in the accumulator is less than the set pressure, and stopping during non-steering and when the hydraulic pressure stored in the accumulator is at or above the set pressure, The hydraulic pressure required for the accumulator can be stored while saving energy.

By providing a check valve that allows the flow of oil from the tank under atmospheric pressure to the respective oil chambers for generating the steering assist force of the hydraulic actuator, the oil chamber becomes negative pressure due to sudden turning or the like. Can be prevented by supplying oil from the tank, and the steering feeling can be prevented from deteriorating.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The rack and pinion type power steering device 1 shown in FIG. 1 comprises an input shaft 2 connected to a steering wheel H, and an output shaft 4 connected to the input shaft 2 via a torsion bar 3.
The torsion bar 3 is connected to the input shaft 2 via a pin 5, and the output shaft 4 is connected via a serration 6.
It is connected to. A pinion 7 is formed on the output shaft 4, and a steering wheel (not shown) is connected to each end of a rack 8 that meshes with the pinion 7. The input shaft 2 is supported by the valve housing 10a via a bearing 9 and is supported by the output shaft 4 via a bush 11. The output shaft 4 is a bearing 12,
It is supported by the rack housing 10 b via 13.
As a result, the rotation of the input shaft 2 due to the steering of the steering wheel H is performed by the pinion 7 via the torsion bar 3.
The rotation of the pinion 7 causes the rack 8 to move in the axial direction. The wheels are steered by the movement of the rack 8. Oil seals 14 and 15 are provided between the input / output shafts 2 and 4 and the valve housing 10a. Further, a support yoke 16 for supporting the rack 8 is provided, and the support yoke 16 has a spring 17
It is pressed against the rack 8 by the elasticity of.

A hydraulic cylinder 18 is provided as a hydraulic actuator for generating a steering assist force. The hydraulic cylinder 18 includes a cylinder tube composed of a rack housing 10b and a piston 2 which is integrated with the rack 8.
0, and has a right steering assist force generating oil chamber 21 and a left steering assist force generating oil chamber 22 partitioned by the piston 20. The oil chambers 21 and 22 have oil passages 60 and 6 respectively.
1 is connected to a tank 41 under atmospheric pressure, and each oil passage 6
Check valves 62 and 63 that allow the flow of oil from the tank 41 to the oil chambers 21 and 22 are provided in the tanks 0 and 61.

The oil chambers 21 and 22 are connected to a rotary hydraulic control valve 23. The control valve 23 is
A tubular first valve member 24, and the first valve member 24
And a second valve member 25 that is rotatably inserted into the second valve member 25. The first valve member 24 has a tubular body portion 2
4a and annular portions 24b, 24c which are axially separated by being press-fitted into the inner circumferences of both ends of the main body portion 24a. The first valve member 24 is connected to the valve housing 10.
It is rotatably inserted into a through a seal member, is rotatably attached to the output shaft 4 through a pin 26, and its axial movement is restricted by a retaining ring 26 attached to the input shaft 2. The second valve member 25
Are integrally formed on the outer circumference of the input shaft 2. As a result, the first valve member 24 and the second valve member 25 cause the torsion bar 3 depending on the steering torque and the steering direction.
Relative rotation due to the twist of.

As shown in FIG. 2, both annular portions 24b, 24
Between c and the inner circumference of the first valve member 24 and the second
A plurality of recesses along the axial direction are formed on the outer circumference of the valve member 25 at equal intervals in the circumferential direction. The first valve member-side concave portion is composed of four right steering concave portions 27 and four left steering concave portions 28 located at equal intervals in the circumferential direction. The second valve member-side recesses are four pressure oil supply recesses 29 and four pressure oil discharge recesses 3 located at equal intervals in the circumferential direction.
0. The right steering recesses 27 and the left steering recesses 28 are alternately arranged in the circumferential direction, and the pressure oil supply recesses 29 and the pressure oil discharge recesses 30 are alternately arranged in the circumferential direction.

Each of the right steering recesses 27 is formed by the first valve member 2
First flow path 31 and valve housing 1 formed in 4
From the first port 32 formed on the hydraulic cylinder 1
8 to the right steering assist force generating oil chamber 21.

Each of the left steering recesses 28 is formed by the first valve member 2
2 and the second flow path 33 formed in the valve housing 1
From the second port 34 formed in the hydraulic cylinder 1
8 to the left steering assist force generating oil chamber 22.

One annular portion 24 of each pressure oil supply recess 29
As shown in FIG. 1, one end on the b side has a second valve member 25.
Is connected to an extension recess 57 formed on the outer periphery of the. Each of the extension recesses 57 extends from the inlet port 36 formed in the valve housing 10a to the pump 37 via a valve mechanism 50 described later.
Lead to.

The pressure oil discharge recesses 30 are formed in the second valve member 25 by a first discharge passage 38, a passage 47 between the input shaft 2 and the inner and outer circumferences of the torsion bar 3, and the input shaft 2 shown in FIG. It communicates with the tank 41 through the formed second discharge passage 39 and the discharge port 40 formed in the valve housing 10a.

As a result, the oil chambers 21 and 22 of the hydraulic cylinder 18 are connected to the pump 37 via the intervalve oil passage 42 formed between the inner and outer circumferences of the first valve member 24 and the second valve member 25. To be done. In the intervalve oil passage 42, the first
Between the valve member side concave portion and the second valve member side concave portion, there are throttle portions A, B, C and D whose opening degrees are changed by relative rotation of both valve members 24 and 25. Each throttle part A, B, C, D
The degree of opening of the hydraulic cylinder changes according to the steering direction and the steering torque, so that the hydraulic pressure acting on the hydraulic cylinder 18 is controlled.

FIG. 2 shows the relative positions of the valve members 24 and 25 in the straight steering position where steering is not performed. In this state, the pressure oil supply recesses 29 and the pressure oil discharge recesses are shown. The apertures of the narrowed portions A, B, C, and D between 30 and 30 are constant. Therefore, even if the pressure oil is supplied to the pressure oil supply recesses 29, the steering assist force is not generated, so that it is not necessary to supply the pressure oil to the pressure oil supply recesses 29.

When the steering wheel is steered rightward from the straight-ahead steering position, the torsion bar 3 is twisted according to the steering torque to rotate the valve members 24 and 25 relative to each other, whereby the right steering recesses 27 and the pressure oil supply recesses 29 are formed. Between the left steering recesses 28 and the pressure oil discharge recesses 30, and the left steering recesses 28 and the pressure oil supply recesses 30. The opening degree of the throttle portion C between the recess portion 29 and the opening portion of the throttle portion D between each right steering recess portion 27 and each pressure oil discharge recess portion 30 becomes small. As a result, pressure oil corresponding to the steering torque is supplied from the pump 37 to the right steering assist force generating oil chamber 21, and the left steering assist force generating oil chamber 22 is supplied from the left steering assist force generating oil chamber 22.
The oil is returned to 1, and the steering assist force to the right of the vehicle acts on the rack 8.

When the vehicle is steered to the left from the straight-ahead steering position, the openings of the throttles A, B, C and D change in the opposite manner to the case of steering to the right, so that the steering assist force to the left of the vehicle is increased. It acts on the rack 8.

As shown in FIG. 1, an accumulator 46 capable of accumulating the hydraulic pressure generated by the pump 37 is connected to the oil passage between the control valve 23 and the pump 37. The check valve 4 is provided in the oil passage between the accumulator 46 and the pump 37.
7 is provided to prevent backflow of pressure oil from the accumulator 46 to the pump 37.

A valve mechanism 50 is provided in the oil passage between the accumulator 46 and the control valve 23. As shown in FIGS. 3 and 4, the valve mechanism 50 has four cam surfaces 53 formed on the outer periphery of the input shaft 2 at equal intervals in the circumferential direction.
And four valve members 51 facing each cam surface 53.

Each cam surface 53 has a concave spherical shape and is continuous with the above-mentioned extended concave portion 57.

Each valve member 51 is radially movably inserted into a through hole 54 that radially extends through the annular portion 24b of the first valve member 24, and the tip end protruding from the through hole 54 is the cam surface 53. Abut. The outer circumference of the tip of each valve member 51 is a conical surface 51a whose diameter decreases toward the cam surface 53, and a seal ring 56 is attached to the outer circumference of the conical surface 51a and receives the valve member 51 via the seal ring 56. A valve seat 54b is formed on the inner circumference of the through hole 54. A tubular member 55 is screwed into each through hole 54, and a spring 52 that applies an elastic force that presses the valve member 51 against the valve seat 54b is interposed between the tubular member 55 and the valve member 51. Also,
The valve housing 10a so as to connect the through holes 54 to each other.
Inner peripheral groove 10a 'and inner peripheral groove 2 of the annular portion 24b.
4b 'is formed, and the inlet port 36 is connected to the circumferential groove 10a' on the inner circumference of the valve housing 10a.

3 and 4 show the state in the straight steering position. In this state, each valve member 51 is pushed in the direction toward the outer circumference of the input shaft 2 by the elasticity of the spring 52 and the hydraulic pressure stored in the accumulator 46, the tip is pressed against the cam surface 53, and the seal ring 56 on the outer circumference is pushed. Is pressed against the valve seat 54b. As a result, the accumulator 46
The oil passage between the control valve 23 and the control valve 23 is closed.

FIG. 5 shows that the first valve member 24 has been steered.
And the second valve member 25 are relatively rotated. The relative rotation causes the cam surface 53 and the valve member 51 to move relative to each other, and the valve member 51 is displaced radially outward. Due to this displacement, the seal ring 56 on the outer periphery of the valve member 51 and the valve seat 54b are separated from each other. As a result, the oil passage between the accumulator 46 and the control valve 23 is opened, and as shown by the arrow in the figure,
The pressure oil from the accumulator 46 and the pump 37 flows from the inlet port 36 to the circumferential groove 10 as shown in FIG.
a through the through hole 54, through the through hole 54 between the outer periphery of the valve member 51 and the valve seat 54b, and through the circumferential groove 24b 'to the cam surface 53, and from the cam surface 53 to the above-mentioned extended recess. The pressure oil supply concave portion 29 of the control valve 23 is reached via 57. A variable throttle is provided between the outer periphery of the valve member 51 and the valve seat 54b, but the opening degree of the steering assist force is required by controlling the opening degree of the throttle portions A, B, C and D by the control valve 23. Is set so that sufficient pressure oil can be supplied to generate. This constitutes the hydraulic circuit shown in FIG.

As shown in FIG. 6, the pump 37 is driven by an electric motor (electric actuator) 43, and the electric motor 43 is controlled by a controller 44. The control device 44 is connected to a steering detection device 45 that detects whether or not the steering wheel H is steered. The steering detection device 45 can be configured by, for example, a sensor for detecting the rotation angle of the input shaft 2. Further, the control device 44 is connected to a pressure sensor 48 that detects the hydraulic pressure stored in the accumulator 46. The control device 4
4, the pump 37 is driven during steering and when the hydraulic pressure stored in the accumulator 46 is less than the set pressure (for example, 30 kg / cm ² ). Further, the control device 44 stops the pump 37 when the steering wheel is not steered and the hydraulic pressure stored in the accumulator 46 is equal to or higher than the set pressure.

FIG. 7 shows the relationship between the elapsed time from the start of driving of the pump 37 and the total value of the discharge flow rates of the pump 37 and the accumulator 46, and the shaded area in the figure shows the discharge flow rate of the accumulator 46. From this, it can be confirmed that the shortage of the discharge flow rate of the pump 37 can be compensated by the accumulator 46 at the beginning of driving the pump 37.

According to the above-described embodiment, by stopping the motor 43 during non-steering, energy saving and noise reduction during non-steering can be achieved. In addition, by connecting the accumulator 46 to the oil passage between the control valve 23 and the pump 37, and closing the oil passage between the accumulator 46 and the control valve 23 by the valve mechanism 50 when going straight and opening when turning. At the beginning of steering, the hydraulic cylinder 18 was replaced by the accumulator 4
The hydraulic pressure stored in 6 is applied to the pump 37 at the beginning of steering.
It is possible to compensate for the shortage of the pressure oil supply amount due to and prevent the steering feeling from deteriorating. The control valve 23 has a throttle portion A,
Since the opening degrees of B, C, and D can be changed according to the steering direction and the steering torque, it is possible to generate the steering assist force according to the steering torque. The accumulator 46
Between the control valve 23 and the control valve 23 is opened and closed by a valve member 51 which is displaced by coming into contact with a cam surface 53 formed on the outer periphery of the input shaft 2 which rotates in response to steering. The operation of 23 is not hindered and the steering feeling is not deteriorated.

The valve member 51 is pressed against the input shaft 2 by the hydraulic pressure stored in the accumulator 46 when going straight, so that the feeling of rigidity when going straight can be improved and the straight running stability can be improved.

The control valve 23 is of a rotary type and the input shaft 2 is integrated with the second valve member 25.
By forming the valve seat 54b of the valve member 51 on the valve member 24, the relative rotation of the two valve members 24, 25 causes the valve member 51 abutting against the cam surface 53 formed on the input shaft 2 to be steered. Can be displaced. This eliminates the need for a dedicated mechanism for displacing the valve member 51 in response to steering, thus simplifying the structure.

The pump 37 is driven during steering and when the hydraulic pressure stored in the accumulator 46 is less than the set pressure, and is stopped during non-steering and when the hydraulic pressure stored in the accumulator 46 is above the set pressure. As a result, the required hydraulic pressure can be stored in the accumulator 46 while saving energy.

From the tank 41 under atmospheric pressure to the hydraulic cylinder 1
The check valves 62 and 63 that allow the flow of oil to the steering assist force generating oil chambers 21 and 22 of 8 are provided to prevent the oil chambers 21 and 22 from becoming negative pressure due to rapid turning. The oil can be supplied from the tank 41 to prevent the deterioration of the steering feeling.

The present invention is not limited to the above embodiment. For example, the present invention can be applied to a ball screw type power steering device.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a power steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view of a main part of the valve mechanism according to the embodiment of the present invention.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a sectional view for explaining the operation of the valve mechanism according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of a configuration of a tearing device according to an embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between the elapsed time from the start of driving the pump and the total value of the discharge flow rates of the pump and the accumulator in the embodiment of the present invention.

FIG. 8 is a partial cross-sectional view of a hydraulic control valve of a comparative example.

[Explanation of symbols]

 2 Input Shaft 18 Hydraulic Cylinder (Hydraulic Actuator) 21, 22 Oil Chamber 23 Control Valve 24 First Valve Member 25 Second Valve Member 37 Pump 41 Tank 43 Electric Motor (Electric Actuator) 44 Control Device 46 Accumulator 48 Pressure Sensor 50 Valve Mechanism 51 valve member 53 cam surface 54b valve seat 62, 63 check valve A, B, C, D throttle part

Claims (5)

[Claims] 1. A hydraulic actuator for generating a steering assist force, a pump driven by an electric actuator that can be stopped when the steering is not turned, and an opening of a throttle portion provided in an oil passage between the hydraulic actuator and the pump. In a power steering device that is provided with a control valve that changes the degree according to the steering direction and the steering torque, and can apply a steering assist force by causing the hydraulic pressure generated by the pump to act on a hydraulic actuator. An accumulator capable of accumulating the hydraulic pressure generated by the pump is connected to the oil passage between the two, and a valve mechanism is provided in the oil passage between the accumulator and the control valve, and the valve mechanism rotates according to steering. A cam surface formed on the outer periphery of the shaft, and a valve member that is displaced in response to steering by contacting the cam surface. An oil passage between the over motor and the control valve, the displacement of the valve member, a power steering device to be opened when turning while being closed during straight. 2. The power steering device according to claim 1, wherein the valve member can be pressed against the outer circumference of the shaft by the hydraulic pressure stored in the accumulator when the vehicle goes straight. 3. The control valve has a tubular first valve member and a second valve member that is inserted into the first valve member and relatively rotates in response to a steering torque. The inner periphery of the second valve member and the outer periphery of the second valve member are formed with circumferentially spaced recesses in the circumferential direction, and the edges of the first valve member-side recess along the axial direction and the shaft of the second valve member-side recess. The narrowed portion is between the edge along the direction, the shaft is integrated with one of the first valve member and the second valve member, and the valve seat of the valve member is formed on the other. The power steering device according to 1 or 2. 4. A means for detecting the hydraulic pressure stored in the accumulator, and a pump for driving the pump during steering and when the hydraulic pressure stored in the accumulator is less than a set pressure, and during non-steering. The power steering device according to any one of claims 1 to 3, further comprising means for stopping the hydraulic pressure stored in the accumulator when the hydraulic pressure is equal to or higher than a set pressure. 5. A check valve is provided between each oil pressure chamber for generating steering assist force of the hydraulic actuator and a tank under atmospheric pressure so as to allow an oil flow from the tank to each oil chamber. The power steering device according to any one of claims 1 to 4.