JP2003072568A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device which allows a driver to recognize abnormality occurrence in the device immediately. SOLUTION: This device has a structure in which a pair of poppet valves 41, 42 are arranged on the same axis line in the operating direction; when one valve element 41a on the poppet valve 41 side is locked in a state of closing a valve port 40a, tip ends of stopper members 52a, 52b of both valve elements 41a and 42a are contacted with each other and as a result, the operation of the other poppet valve 42 is regulated, which brings about a state of disabling to close the valve port 40b, that is, making it impossible to obtain steering assist efforts.

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, and more particularly to a system for generating a steering assist force by a hydraulic power cylinder.

[0002]

2. Description of the Related Art A conventional power steering device of this type is known, for example, from Japanese Patent Application Laid-Open No. 57-201767.

As shown in FIG. 7, this conventional power steering apparatus drives the reversible oil pump 102 by rotating the electric motor 101 in the normal direction or in the reverse direction, and applies the hydraulic pressure pressurized by the reversible oil pump 102. The steering assist force is generated by selectively supplying the oil to the respective oil chambers 105a and 105b of the power cylinder 105 via the oil passages 103 and 104. Orifices 106 and 107 are provided in the middle of the oil passages 103 and 104, respectively.
A bypass passage 108 that connects the oil passages 103 and 104 is connected between the oil passage 107 and the oil chambers 105a and 105b, and the bypass valve 10 is connected to the bypass passage 108.
9 is installed. Then, the bypass valve 109
Has a valve body 110 in which a large diameter portion 110b is continuously provided on both sides of a small diameter portion 110a in a valve body 111, and springs 11 having the same spring constant are provided on both sides of the valve body 110.
2a and 112b are respectively compressed, and the valve chambers 113a and 113b formed on both sides of the valve body 110 are
Through the pilot passages 114a and 114b, the oil passages 103 and 104 between the reversible oil pump 102 and the orifices 106 and 107 are communicated with each other.

That is, during steering assist, the reversible oil pump 102 rotates and is selectively supplied to either of the oil chambers 105a and 105b of the power cylinder 105. At that time, due to the existence of the orifices 106 and 107, A pressure difference occurs near the discharge port of the reversible oil pump 102,
This pressure difference acts on both valve chambers 113a and 113b via the pilot passages 114a and 114b, so that the valve element 110 of the bypass valve 109 blocks the bypass passage 108.

[0005]

However, the conventional power steering apparatus has the following problems. That is, in the conventional power steering device, as described above, the bypass passage 108
Since only one bypass valve 109 is used to open and close, the bypass valve 109 may be locked in a normally closed state when contamination or the like is mixed in the bypass valve 109. Moreover, since steering assistance is performed even in this state, it may be delayed to find an abnormality in the device. When the reversible oil pump 102 is locked in this state, the power cylinder 10
The communication of hydraulic pressure in the hydraulic chambers 105a and 105b is restricted, and the steering force of the driver is forced more than necessary.

In order to solve the above problems, a method of using a pair of poppet valves instead of one bypass valve 109 can be considered. In the case of a poppet valve, even if contamination or the like is caught between the bypass passage 108 and the valve body of the poppet valve that shuts off the bypass passage 108 and the operation is locked, the bypass passage 108 becomes an open circuit. Therefore, even if the reversible oil pump 102 is locked in this state, the hydraulic pressures in the hydraulic chambers 105a and 105b of the power cylinder 105 are maintained, and manual steering is possible. Further, since steering assist is not performed in a state where the bypass passage 108 is an open circuit due to the lock of the poppet valve, there is an effect that an abnormality of the device can be detected early. However, when contamination or the like is sandwiched between the valve body of the poppet valve and the valve hole accommodating the valve body, the bypass valve may be locked in a normally closed state. Furthermore, when the pair of poppet valves are provided independently of each other, the poppet valves on the unlocked side can be opened and closed, so that steering assistance for both right steering and left steering is performed. Therefore, there is a problem that it may be delayed to detect the abnormality of the device.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a power steering device which enables a driver to immediately recognize the occurrence of an abnormality in the device.

[0008]

In order to achieve the above-mentioned object, a power steering apparatus according to claim 1 of the present invention comprises a steering shaft linked to a steering mechanism and a hydraulic pressure for assisting the steering force of the steering mechanism. A power cylinder, a reversible pump having a pair of discharge ports for supplying hydraulic pressure to both hydraulic chambers of the hydraulic power cylinder via a first communication passage and a second communication passage, and An electric motor driven in reverse rotation,
Steering direction detecting means for detecting the rotation direction of the steering shaft,
Steering force detecting means for detecting the steering force acting on the steering shaft, and the electric motor based on the steering force signal detected by the steering force detecting means and the rotation direction signal of the steering shaft detected by the steering direction detecting means. An electric motor control means for outputting a drive signal, a bypass passage for bypassing between the hydraulic chambers of the hydraulic power cylinder or between the first and second communicating passages, and a bypass passage interposed in the middle of the bypass passage, A pair of poppet valves for opening and closing the bypass passage based on hydraulic signals from the first communication passage and the second communication passage; and a biasing means for biasing the pair of poppet valves in a direction of opening the bypass passage. , And the two poppet valves are arranged in the same axial direction in the operating direction, and at least one of the poppet valves has an axially opposite surface abutting the other. Therefore, when one of the poppet valves operates in the direction to close the bypass passage, the other poppet valve is provided with a restricting means for restricting the operating range between them so as not to close the bypass passage. The means.

A power steering apparatus according to a second aspect is the power steering apparatus according to the first aspect,
By providing the regulating means on both poppet valves respectively, both poppet valves are formed in the same shape.

A power steering device according to a third aspect is the power steering device according to the first or second aspect, wherein differential pressure generating means is provided in the middle of the first communication passage and the second communication passage, respectively. The poppet valve is configured to open and close the bypass passages based on the hydraulic signals of the first communication passage and the second communication passage upstream of the differential pressure generating means.

A power steering device according to a fourth aspect is the power steering device according to any one of the first to third aspects, wherein the steering force acting on the steering shaft detected by the steering force detecting means is a predetermined value or more. In some cases, the means provided with an abnormality determination means for determining the abnormality of the device.

[0012]

In the power steering apparatus according to the first aspect of the present invention, since it is configured as described above, when one of the poppet valves is locked in a state of operating in the direction of closing the bypass passage, the shaft of the regulating means is locked. By contacting the other facing poppet valve with the normal poppet valve, the operating range of the normal poppet valve is regulated so as not to close the bypass passage. Therefore, in the steering direction in which the steering assist force is generated by closing the normal poppet valve side, the steering assist force cannot be obtained, which is known as a change in the steering feeling. You will be able to recognize immediately.

In the power steering apparatus according to the second aspect, as described above, the restricting means is provided on both poppet valves, so that both poppet valves are formed in the same shape. The cost can be reduced.

As described above, the power steering apparatus according to the third aspect includes differential pressure generating means in the middle of the first communication passage and the second communication passage, and the pair of poppet valves generate the differential pressure. Since the bypass passages are opened and closed based on the hydraulic signals of the first communication passage and the second communication passage upstream of the means, the discharge fluid pressure is directly received to operate. Because you can
The operation response of the poppet valve will be good.

As described above, in the power steering apparatus according to the present invention, when the steering force acting on the steering shaft detected by the steering force detecting means is equal to or more than a predetermined value, an abnormality of the apparatus is judged. In addition to being known as a change in the steering feeling, a means equipped with a judgment means
The light or sound enables the driver to surely recognize the occurrence of the abnormality in the device.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment of the Invention) First, the configuration of the first embodiment of the present invention will be described with reference to FIG.

FIG. 1 is an overall schematic configuration diagram showing a power steering device according to a first embodiment of the invention. As shown in FIG. 1, a steering shaft 22 to which a steering wheel 21 as a steering input means is connected. The rack and pinion 24 provided on the output shaft 23 at the lower end of the steering shaft 22 and the steering wheel 2 provided on the lower end side of the output shaft 23.
A torque sensor 26 for detecting the steering rotation torque of 1;
A hydraulic cylinder 27 connected to the rack and a hydraulic circuit 28 for supplying and discharging hydraulic pressure to and from the hydraulic cylinder 27 are provided.

In the hydraulic cylinder 27, a piston rod 30 connected to the rack penetrates through a cylindrical cylinder portion 29 extending in the width direction of the vehicle body, and the piston rod 30 has an internal cylindrical cylinder portion 29. A piston 31 that slides on is fixed. A left and right first hydraulic chamber 32 and a second hydraulic chamber 33 are separated by a piston 31 in the tubular cylinder portion 29. 25a and 25b are
The left and right front wheels are connected to both ends of the piston rod 30 via links.

The hydraulic circuit 28 has a pair of first and second communication passages 3 each having one end connected to the hydraulic chambers 32 and 33.
4, 35 and one reversible pump 37 connected to the other ends of both the communication passages 34, 35 and capable of rotating in the forward and reverse directions by a pump motor 36; It is composed of an opening mechanism 38 that opens both the hydraulic chambers 32 and 33 under conditions, and a reservoir 39 that is arranged upstream of the reversible pump 37 and that stores hydraulic oil inside.

The opening mechanism 38 includes both communication passages 34 and 35.
A bypass passage 40 which is connected between the bypass passage 40 and the reversible pump 37, and poppet valves 41 and 42 which are opening / closing valves provided in the middle of the bypass passage 40 to communicate or block the bypass passage 40, and Communication passages 34, 3
5 is provided to generate a differential pressure, and each poppet valve 4
It is provided with a pair of pressure control valves 43 and 44 which are differential pressure generating means for opening and closing the valves 1 and 42.

The pressure control valves 4 are provided between the first and second communication passages 34 and 35 and the bypass passage 40.
3 and 44 are connected to communication passages 45 and 46, and the communication passages 45 and 46 are allowed to flow only hydraulic oil from the hydraulic chambers 32 and 33 toward the reversible pump 37. Check valves 47 and 48 are provided respectively.

The central portion of the bypass passage 40 is connected to the reservoir 39 via a third communication passage 49.

Each of the poppet valves 41 and 42 has a pair of cylindrical valve holes 41b and 42b arranged substantially in series in the middle of the bypass passage 40 and the valve holes 41b and 42b. A substantially cylindrical valve body 41a, 4
2a is provided slidably. Further, each valve hole 4
In the pressure receiving chambers 41c and 42c provided on the rear end side of 1b and 42b, tension springs 50 and 51, which are biasing means, are housed, respectively.
Are valve openings 40 provided in the middle of the bypass passage 40.
the valve bodies 41a, 4 in the direction of opening a, 40b respectively.
By biasing 2a, the bypass passage 40 is maintained in a communicating state. The third communication passage 49 is connected to the bypass passage 40 between the poppet valves 41 and 42.

Further, the valve bodies 41a and 42a are connected to the front end portions of the valve holes 41b and 42b facing each other from the center side end portions 40c and 40d of the bypass passage 40 to the valve holes 41b and 42b. The differential pressure between the hydraulic pressure acting on the front end portion and the hydraulic pressure acting on the rear end portions of the valve holes 41b, 42b from the introduction passages 53, 54, which will be described later, causes relative sliding in the opening / closing direction. In addition, each valve body 41a, 42
a is a stopper member 52a, 5a, 5a, 5b, 5b, 5c, 5d, 5c, 5d, 5d, 5c, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d, 5d.
2b are respectively formed so as to project.

The stopper members 52a and 52b are connected to the bypass passage 40 and the bypass passage 40 and the reservoir 39 by contacting one of the valve bodies 41a and 42a with one of the valve openings 40a and 40b of the bypass passage 40. In the state where the space between the third communication passage 49 and the communicating third communication passage 49 is closed, the tip surfaces of the stopper members 52a and 52b contact each other so that the other of the valve openings 40a and 40b is not at least closed. In the first embodiment of the present invention, the valve openings 40a and 40b are not closed at the same time by the tip end surfaces of the cylindrical stopper members 52a and 52b contacting each other. Is configured. In addition, each valve body 41a, 42a
Seal rings 41d and 42d are attached to the outer peripheral portion of the. The valve bodies 41a and 42a are formed in the same shape including the stopper members 52a and 52b.

Further, the pressure receiving chambers 41c and 42c are
The pair of introduction passages 53 and 54 are connected to the reversible pump 36 substantially immediately downstream thereof so that the oil pressure directly downstream thereof is directly supplied.

The pressure control valves 43 and 44 have a pair of ball valve bodies 43a and 44a for opening and closing the open ends of the first and second passages 34 and 35 on the reversible pump side. Return springs 43b and 44b for urging the valve bodies 43a and 44a in a closing direction with a predetermined load are provided, and a differential pressure is generated by the urging force.

The reservoir 39 is adapted to supply and replenish the hydraulic oil stored therein to the reversible pump 37 via the supply passage 55, and at the same time, the reversible pump 37.
The leaked hydraulic oil is collected from each of the components.

The motor pump 36 is configured to be controlled in forward and reverse rotation by a control current output from a controller (electric motor control means) 56 equipped with a microcomputer. This controller 56 is controlled by the torque sensor 26. The control current is output by calculation based on the information signal such as the steering input torque.

Next, the operation and effect of the first embodiment of the present invention will be described. (B) Normal operation of both poppet valves First, when the driver rotates the steering wheel 21 to the left as shown by the arrow in the figure while driving the vehicle in a normal manner, as shown in FIG. For example, the reversible pump 37 is driven in the normal direction as the pump motor 36 is controlled in the normal direction by the control signal from the controller 56. A part of the hydraulic oil discharged into the first communication passage 34 by such a pump action flows into the pressure receiving chamber 41c from the introduction passage, and this is higher than the hydraulic pressure of the hydraulic oil that has passed through the pressure control valve 43. Therefore, due to this pressure difference, the poppet valve 4
The first valve body 41a resists the spring force of the tension spring 50 and is pressed rightward as shown in the figure, so that the valve body 41a closes the valve opening 40a. On the other hand, the valve body 42a is maintained in a state where the valve opening 40b is opened by the spring force of the tension spring 51.

As a result, the hydraulic oil discharged from the reversible pump 37 causes the ball valve body 43a of the pressure control valve 43.
Is supplied to the hydraulic chamber 32 while pushing open against the spring force of the return spring 43b. At the same time, the hydraulic oil discharged from the hydraulic chamber 33 into the second communication passage 35 by the suction action of the reversible pump 37 once flows into the bypass passage 40 and then to the communication passage 46 from here as indicated by the arrow. Then, the check valve 48 is opened here, and the second communication passage 35 is again opened.
Is sucked into the reversible pump 37.

Therefore, the hydraulic pressure is relatively supplied to or discharged from each of the hydraulic chambers 32 and 33 to give an assisting force to the counterclockwise steering force of the steering wheel 21 by the driver. The load can be reduced and the operability of the steering wheel 21 can be improved.

In the state where the left-handed steering state is maintained, the power supply to the pump motor 36 is cut off and the hydraulic circuit 28 is closed, whereby the hydraulic chamber 3 is closed.
The state in which hydraulic pressure is applied inside 2 is maintained.

On the other hand, when the steering wheel 21 is turned back from the left rotation steering state to the original state and the driver further steers the steering wheel 21 to the right as shown by the arrow in FIG. Reverse the reversible pump 37 via the motor 36,
As a result, contrary to the above, the hydraulic oil is discharged to the second communication passage 35, and similarly to the above, the hydraulic pressure is relatively supplied to or discharged from the hydraulic chambers 32 and 33, and the steering by the driver is performed. The assisting force is applied to the right-hand steering force of the wheel 21, which reduces the load of the right-hand steering and improves the operability of the steering wheel 21.

(B) When the reversible pump is locked The reversible pump 37 is locked and becomes inoperative due to, for example, an electrical failure of the pump motor 36 or a mechanical failure of the reversible pump 37. In this case, since the hydraulic pressure from the reversible pump 37 does not act from the introduction passages 53 and 54 into the pressure receiving chambers 41c and 42c, the valve bodies 41a and 42a of the poppet valves 41 and 42 are different from those shown in FIG. As shown, the valve forces 40a and 41a are kept open by the spring forces of the tension springs 50 and 51, whereby the bypass passage 40 is brought into communication. Therefore, although the steering assist force is lost due to the locking of the reversible pump 37, the steering wheel 2 operated by the driver is removed.
It will be in a state where you can secure 1 mane steer.

(C) When the poppet valve is locked When one of the valve bodies 41a and 42a of the poppet valves 41 and 42 is locked with one of the valve openings 40a and 40b closed, for example, as shown in FIG. As shown in FIG. 4, when the valve body 41a on the poppet valve 41 side is locked with the valve opening 40a closed, when the steering wheel 21 is turned counterclockwise, the valve opening 40a is closed from the beginning. Therefore, the same operation as in the case of the normal operation of both poppet valves in (a) above is performed, and an assist force is applied to the left-handed steering force of the steering wheel 21.

However, as shown by the arrow in FIG. 4, during the clockwise rotation steering, the valve body 41a on the poppet valve 41 side.
However, since it is locked with the valve port 40a closed,
When the front end surfaces of the stopper members 52a and 52b of the two valve bodies 41a and 42a come into contact with each other, the other valve opening 40b cannot be closed. Therefore, the reversible pump 37
The hydraulic oil discharged from the second communication passage 35 side passes through the valve opening 40b of the bypass passage 40 and is discharged to the reservoir 39 via the third communication passage 49. Therefore, since the steering assist force is not obtained, it is known as a change in the steering feeling, and thus the driver can immediately recognize the occurrence of the abnormality in the device.

Further, since the valve bodies 41a and 42a are formed in the same shape including the stopper members 52a and 52b, the cost can be reduced by sharing the parts. Also, since both valve bodies 41a, 42a are not always connected by the stopper members 52a, 52b, both poppet valves 41, 42 operate independently of each other in the normal state of the device. For this reason, the sliding friction and the tension spring 50,
The biasing forces of 51 only act individually. Therefore, the respective operations are smooth, and the operation responsiveness of the poppet valves 41 and 42 can be improved.

The first communication passage 34 and the second communication passage 3
5, pressure control valves 43 and 44 are provided respectively, and the pair of poppet valves 41 and 42 are based on the hydraulic signals of the first communication passage 34 and the second communication passage 35 upstream of the pressure control valves 43 and 44. By configuring the bypass passages 40 to be opened and closed respectively, it is possible to directly receive and actuate the discharge liquid pressure from the reversible pump 37, thereby enhancing the operation responsiveness of the poppet valves 41 and 42. Will be able to.

Next, another embodiment of the present invention will be described. In the description of the other embodiments of the present invention, the same components as those of the first embodiment of the present invention will not be illustrated and described, or will be denoted by the same reference numerals and the description thereof will be omitted, Only the points will be described.

(Embodiment 2 of the invention) In Embodiment 2 of the present invention, as shown in the enlarged view of the essential portion of FIG.
This is a modified example in which only one of the valve bodies 41a (or 42a) of the first and the second 42 is formed so as to project.

(Third Embodiment of the Invention) In the third embodiment of the present invention, when the steering force acting on the steering shaft 22 detected by the torque sensor (steering force detecting means) is a predetermined value or more, An example is shown in which an abnormality determining means for determining an abnormality of the device is provided, and a lamp or a warning sound is used to notify the driver of the occurrence of the abnormality of the device when the abnormality is determined. Therefore, in addition to the abnormality of the device being known as a change in the steering feeling, the driver can be surely made aware of the occurrence of the abnormality of the device by the light or sound.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to the embodiments of the present invention, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention.

For example, in the embodiment of the invention, the bypass flow passage 40 is connected between the first and second communication passages 34, 35, but is directly connected between the hydraulic chambers 32, 33 of the hydraulic cylinder 27. You may do it.

In the embodiment of the invention, the pressure control valve is used as the differential pressure generating means, but an orifice may be used. Further, in the embodiment of the invention, the tension springs 50 and 51 are used as the biasing means, but a pressing spring may be used. When using the pressure spring, for example, as shown in FIG.
A similar function can be achieved by mounting only one compression spring 57 between a and 42a.

Further, for example, when the valve body 41a on the side of one poppet valve 41 is locked with the valve port 40a closed, the valve port 40b of the other poppet valve 42.
The degree of opening is arbitrary, and in addition to the case where the steering assist force is not obtained at all in the fully opened state, the steering assist force can be weakened by setting it to a slightly narrowed degree. .

[0047]

As described above, the present invention claims 1.
In the power steering device described above, as described above, a bypass passage that bypasses between the hydraulic chambers of the hydraulic power cylinder or between the first and second communication passages is interposed in the middle of the bypass passage. A pair of poppet valves for opening and closing the bypass passage based on hydraulic signals from the first communication passage and the second communication passage, and a biasing means for urging the pair of poppet valves in a direction of opening the bypass passage. And both of the poppet valves are arranged in the same axial direction in the operating direction thereof, and at least one of the poppet valves has an axially opposed surface in contact with the other poppet valve. When the poppet valve is operating in the direction to close the bypass passage, the other poppet valve is in the operating range so that it does not close the bypass passage. By providing the regulation means for regulating, when one of the poppet valves is locked with the bypass passage closed and an abnormal state occurs, the steering assist force is generated by closing the normal poppet valve side. In the steering direction, since the steering assist force cannot be obtained, it is known as a change in the steering feeling, and thus the driver can immediately recognize the occurrence of the abnormality in the device.

A power steering apparatus according to a second aspect is the power steering apparatus according to the first aspect,
Since the poppet valves are formed in the same shape by providing the regulating means on both poppet valves respectively, the cost can be reduced by sharing the parts.

A power steering device according to a third aspect is the power steering device according to the first or second aspect, wherein differential pressure generating means is provided in the middle of the first communication passage and the second communication passage, respectively. The poppet valve is configured to open and close the bypass passages on the basis of the hydraulic signals of the first communication passage and the second communication passage upstream of the differential pressure generating means, respectively. Since the pressure can be directly received and actuated, the actuation response of the poppet valve can be enhanced.

A power steering device according to a fourth aspect is the power steering device according to any one of the first to third aspects, wherein the steering force acting on the steering shaft detected by the steering force detecting means is a predetermined value or more. In some cases, by adopting a means equipped with an abnormality determining means for determining an abnormality of the device, in addition to being known as a change in steering feeling, it is possible to ensure that the driver will not experience an abnormality in the device due to light or sound. You will be able to recognize.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire power steering device according to a first embodiment of the invention.

FIG. 2 is an operation explanatory diagram showing a state of the power steering device according to the first embodiment of the present invention during left steering.

FIG. 3 is an operation explanatory diagram showing a state of the power steering device according to the first embodiment of the invention when steering to the right.

FIG. 4 is an operation explanatory view showing a state when the power steering device according to the first embodiment of the present invention fails.

FIG. 5 is an enlarged view of a main part showing a power steering device according to a second embodiment of the invention.

FIG. 6 is an enlarged view of a main part showing another example of the biasing means.

FIG. 7 is an overall schematic configuration diagram showing a conventional power steering device.

[Explanation of symbols]

21 Steering Wheel 22 Steering Shaft 23 Output Shaft 24 Rack and Pinion 25a Left Front Wheel 25b Right Front Wheel 26 Torque Sensor (Steering Force Detection Means / Steering Direction Detection Means) 27 Hydraulic Cylinder 28 Hydraulic Circuit 29 Cylindrical Cylinder 30 Piston Rod 31 Piston 32 First hydraulic chamber 33 Second hydraulic chamber 34 First communication passage 35 Second communication passage 36 Pump motor 37 Reversible pump 38 Opening mechanism 39 Reservoir 40 Bypass passage 40a Valve opening 40b Valve opening 40c End 40d End 41 Poppet valve 41a Valve body 41b Valve hole 41c Pressure receiving chamber 41d Seal ring 42 Poppet valve 42a Valve body 42b Valve hole 42c Pressure receiving chamber 42d Seal ring 43 Pressure control valve (Differential pressure generating means) 43a Ball valve body 43b Return spring 44 Pressure control valve (Differential pressure) Generating means) 44a Ball valve body 44b Chain spring 45 Communication passage 46 Communication passage 47 Check valve 48 Check valve 49 Third communication passage 50 Extension spring (biasing means) 51 Extension spring (biasing means) 52a Stopper member (regulation means) 52b Stopper member (regulation means) 55 supply path 56 controller (electric motor control means) 57 compression spring (biasing means)

Claims (4)

[Claims] 1. A steering shaft linked to a steering mechanism, a hydraulic power cylinder for assisting the steering force of the steering mechanism, a first communication passage for each hydraulic chamber of the hydraulic power cylinder,
A reversible pump having a pair of discharge ports for supplying hydraulic pressure via a second communication passage, an electric motor for driving the reversible pump in forward and reverse directions, and a steering direction detecting means for detecting a rotation direction of the steering shaft. Steering force detecting means for detecting a steering force acting on the steering shaft, and a steering force signal detected by the steering force detecting means and a rotation direction signal of the steering shaft detected by the steering direction detecting means. An electric motor control means for outputting a drive signal to the electric motor, a bypass passage for bypassing between the hydraulic chambers of the hydraulic power cylinder or between the first and second communicating passages, and an intermediate portion of the bypass passage. And a pair of poppet valves for opening and closing the bypass passage based on the hydraulic signals from the first communication passage and the second communication passage, and energizing the pair of poppet valves in a direction of opening the bypass passage. Urging means, and the two poppet valves are arranged in the same axial direction in the operating direction thereof, and at least one of the poppet valves has an axially opposite surface abutting the other. When one of the poppet valves operates in the direction of closing the bypass passage, the other poppet valve is provided with a restricting means for restricting the operating range between them so as not to close the bypass passage. Power steering device characterized by. 2. The power steering device according to claim 1, wherein both the poppet valves are formed in the same shape by providing the restricting means on each of the poppet valves. 3. A differential pressure generating means is provided in the middle of each of the first communication passage and the second communication passage, and the pair of poppet valves are provided with a first communication passage and a second communication passage upstream of the differential pressure generation means. 3. The power steering device according to claim 1, wherein the power steering device is configured to open and close each of the bypass passages based on a hydraulic signal of the passage. 4. An abnormality determining means for determining an abnormality of the device when the steering force acting on the steering shaft detected by the steering force detecting means is equal to or more than a predetermined value. The power steering device according to any one of 1 to 3.