JPH0424270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fully hydraulic power steering system for use in vehicles such as forklift trucks and without a steering gear or mechanical link. (Prior Art) As a conventional fully hydraulic power steering device, for example, a device as shown in FIG. 10 is known. (Refer to "Nissan Technique No. 19" published by Nissan Motor Co., Ltd., December 1988; pages 170 to 171) This conventional device 100 includes a steering unit 102 (valve mechanism) operated by a steering wheel 101, and a steering wheel 103. The vehicle was equipped with a steering cylinder 104 for steering the engine, and hydraulic lines 105 and 106 for connecting the steering unit 102 and the steering cylinder 104. In addition, what is shown by 107 in the figure is a steering pump, 108 is a hydraulic oil tank, 109 is a vehicle body, and 11
0 is a steering chain, 111 is a fixed wheel, and 112 is a handle spoke. Therefore, by rotating the steering wheel 101 in the steering direction, an amount of pressure oil sent from the steering pump 107 that is proportional to the steering wheel rotation angle is transferred from the steering unit 102 to the steering cylinder 104 according to the arrow in the figure. The cylinder tube 142 moves according to the amount of oil fed, and the steering wheel 103 is rotated by an angle corresponding to the rotation angle of the handle 101. (Problems to be Solved by the Invention) However, in such a conventional fully hydraulic power steering device, the steering unit 102 and the steering cylinder 104 are connected only through hydraulic lines 105 and 106, and the steering Because it did not have gears or mechanical links, the steering cylinder 1 could be damaged due to oil leaks inside the steering unit 102.
A discrepancy occurred between the amount of oil sent to the steering wheel 104 and the rotation angle of the steering wheel 101, which could potentially change the relative directional position of the steering wheel spokes 112 and the steered wheel 103. In particular, if the steering wheel 101 is deviated from the neutral position even though the steering wheel 103 is in the straight-ahead neutral position, even if the operator tries to turn the steering wheel 101 by relying on the position of the steering wheel 101, the steering wheel 103 is actually in the straight-ahead neutral position. There was an incident where I ended up running. In order to solve such problems, the present applicant has filed Japanese Patent Application No. 60-045777 (Japanese Unexamined Patent Publication No. 61
-205557) (filed on March 8, 1985) as the prior art. In this prior art, when steering with the steering wheel, if there is an error in the stroke of the steering cylinder relative to the rotation angle of the steering wheel, the control unit calculates the difference between the actual cylinder stroke and the target cylinder stroke. When the difference exceeds a predetermined value, a control signal is output to the actuator of the hydraulic oil spilling means so that the difference disappears, causing the handle to idle due to the hydraulic oil spill, and automatically correcting the handle position. The content was that it could be done. However, in this prior art, the actuator always switches to the hydraulic oil outflow side due to oil leakage from the hydraulic line, oil leakage from the piston seal part of the steering cylinder, or shot in the actuator drive circuit system of the control means. Even in the event of a failure, such as when the cylinder is left stranded, a difference will occur in the cylinder stroke with respect to the rotation angle of the handle, and a control signal will be output to the actuator of the hydraulic oil spill means. In this way, if the hydraulic oil spilling means is activated at the time of a failure in which the handle position should not be corrected due to the hydraulic oil spilling by the hydraulic oil spilling means,
There was a problem in that the cylinder stroke did not increase even though the steering wheel was being rotated a lot, making it impossible to obtain the normal steering angle, resulting in a strange feeling when operating the steering wheel. (Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention employs the following solving means. did. The solution of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. In a fully hydraulic power steering device comprising hydraulic lines 4 and 5 to be connected, a drain oil line 9 is connected to the hydraulic line 4, and the drain oil line 9 is configured to switch between a communicating portion 7a and a blocking portion 7b. A hydraulic oil spilling means 7 having an actuator 6 is provided to input a handle rotation angle signal θ and a cylinder stroke signal s, and when the correspondence relationship between both input signals θ and s indicates a normal state, the hydraulic oil spills out. By switching the means 7 to the communication portion 7a, a control signal c for correcting the position of the handle 1 is output to the actuator 6, and when the correspondence relationship between the input signals θ and s indicates a failure state, the hydraulic oil is It is characterized in that it is provided with a control signal 8 that outputs a control stop signal d to the actuator 6 to switch the outflow means 7 to the cutoff part 7b. (Function) Therefore, in the fully hydraulic power steering device of the present invention, by using the solution as described above,
In the control means 8, the handle rotation angle signal θ and the cylinder stroke signal s are inputted, and when the correspondence relationship between the two input signals θ and s indicates a normal state, the hydraulic oil outflow means 7 is switched to the communication portion 7a. As a result, a control signal c for correcting the position of the handle 1 is output to the actuator 6. Therefore, if there is an error in the cylinder stroke with respect to the handle rotation angle, the hydraulic lines 4 and 5
The hydraulic oil flows out from one side through the drain oil line 9 → the communication part 7a of the hydraulic oil outflow means 7 → the other side of the hydraulic lines 4 and 5 → the steering unit 2,
By causing the handle 1 to rotate idly due to this leakage of hydraulic oil, the handle position is automatically corrected. On the other hand, in the control means 8, the handle rotation angle signal θ and the cylinder stroke signal s are input, and when the correspondence relationship between the two input signals θ and s indicates a failure state, the hydraulic oil spill means 7 is connected to the cutoff portion 7b. A control stop signal d for switching is output to the actuator 6. Therefore, when a failure occurs in the control system of the device, the drain oil line 9 is shut off by the shutoff part 7b of the hydraulic oil outflow means 7, and the hydraulic lines 4 and 5 are disconnected from the drain oil line 9 and the hydraulic oil. The state is similar to that of a normal fully hydraulic power steering device in which the outflow means 7 is not provided, and although steering wheel position correction control is not performed, normal steering operation is guaranteed. (Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.
In describing the embodiment, a fully hydraulic power steering system for a three-wheeled forklift truck will be taken as an example. First, the configuration of the embodiment shown in FIGS. 2 to 6 will be explained. 10 is a handle, and this handle 10 has handle spokes 11 for improved operability.
is provided. Reference numeral 12 denotes a steering unit, which is directly operated by the handle 10. This steering unit 12 is a valve mechanism, and out of pressure oil sent from a steering pump 13, which will be described later, oil is proportional to the rotation angle of the steering wheel. It has the function of sending the amount to the steering cylinder 14. 14 is a steering cylinder, which is connected to the vehicle body 1;
5, a cylinder tube 17 that is a movable member, and a piston 18 that reciprocates within the cylinder tube 17.
It is equipped with. A steering wheel 19 is connected to the cylinder tube 17 by a steering chain 20, 20, and is steered by movement of the cylinder tube 17. 21 and 22 are hydraulic lines, which connect the steering unit 12 and the steering cylinder 14.
This hydraulic line 21, 2
2, one line serves as a feed line for feeding pressurized hydraulic oil from the steering pump 13 during steering, and the other line serves as a return line for returning oil to the hydraulic oil tank 23. Note that pressurized oil is sent to the steering cylinder 14 through the hollow part of the cylinder rod 16, and oil is also returned through the hollow part. Drain oil lines 24 and 25 are connected to the hydraulic lines 21 and 22, and electromagnetic switching valves 26 and 27 are provided in the middle of the drain oil lines 24 and 25. ，
27, when one side is open, the hydraulic line 21,
The handle position is corrected by causing the oil to flow out into one of the hydraulic oil tanks 23 of 22. Said electromagnetic switching valves 26, 27 (hydraulic oil outflow means)
As shown in FIG. 3, the one-way valve parts 33, 34
Solenoids (actuators 31, 32 and springs 37, 38) that switch between the drain oil lines 24, 25 and the orifices 39, 40 ( A specific example of the electromagnetic switching valve 26 will be explained with reference to FIG. Orifice 39, one-way valve port 4
3, valve frame 44, port frame 45, input port 4
6, an output port 47, and a guide 48.
A hydraulic line 21 is connected to the input port 46.
The drain oil line 24 on the side is connected to the output port 47, and the drain oil line 24 on the hydraulic oil tank 23 side is connected to the output port 47. Therefore, when the solenoid 31 is de-energized, the movable spool 4 is biased by the spring 37.
1, the one-way valve port 43 is closed, and a so-called one-way valve is inserted that only allows flow from the output port 47 to the input port 46 via the orifice 39 (toward the one-way valve part 33 side). switching state), and when the solenoid 31 is energized,
By pulling up the movable spool 41 against the spring 37, the input port 46 and the output port 47 are brought into communication via the orifice 39 (switched state to the drain section 35 side). 28 is a control unit which inputs the handle rotation angle signal θ from the handle rotation angle sensor 29 and the cylinder stroke signal s from the cylinder position sensor 30, and receives these input signals θ,
Arithmetic processing is performed based on s, and control signals a and b are output to the solenoids 31 and 32 of the electromagnetic on-off valves 26 and 27, and both input signals θ,
When the relationship between the handle rotation speed Vh based on s and the cylinder stroke speed Vs indicates a fault condition,
A control stop signal d is output in place of the control signals a and b. Further, when the control unit 28 outputs the control stop signal d, the warning lamp 60
Further, based on the cylinder stroke speed Vs, an angle display signal f is output to the steering angle display means 61. Specific examples of the steering wheel rotation angle sensor 29 are shown in FIGS. 5 and 6. To explain with a diagram, in terms of the structure, a worm 51 is fixed to a steering shaft 50, and a worm wheel 53 that meshes with the worm 51 is fixed to a shaft 54 of a steering wheel rotation angle sensor 29 having a potentiometer structure. The rotation angle sensor 29 is attached to the steering column 55. Therefore, when the steering shaft 50 is rotated during steering, the rotation decelerated by the worm 51 and the worm wheel 53 is input to the shaft 54, and the degree of rotation of the shaft 54 is detected as an electrical signal by the steering wheel rotation angle sensor 29. By converting to , the steering wheel rotation angle is measured. Further, the control unit 28 has a third
As shown in the figure, an A-D conversion circuit 281, an A-D
Conversion circuit 282, RAM (random access.
memory) 283, ROM (read-only memory) 284, clock circuit 285, CPU (central processing unit) 286, control signal generation circuit 287, control stop signal generation circuit 28
8. Consists of a lighting signal generation circuit 289 and an angle display signal generation circuit 290. The A-D conversion circuit 281 converts the steering wheel rotation angle signal θ input as an electrical signal into the CPU 28.
This circuit converts the signal into a digital signal that can be processed in step 6. The A-D conversion circuit 282 sends a cylinder stroke signal s (an analog signal based on a current value) from the cylinder position sensor 30 using a variable resistor to the CPU.
This circuit converts the signal into a digital signal that can be processed using H.286. The RAM 283 is a readable and writable memory, and is a circuit that temporarily stores the handle rotation angle signal θ and the cylinder stroke signal s, which are digital signals, until the calculation processing time comes. The ROM 284 is a read-only memory, and information that serves as the basis for arithmetic expressions and comparison judgments is stored in advance in this RAM 284. This ROM 284 contains the reference value Vh of the handle rotation speed Vh, the normal limit value Vs of the cylinder stroke speed Vs corresponding to the handle rotation speed Vh, the handle rotation angle θ and the cylinder stroke x which are control target values for handle position correction. , the allowable error Δn between the target cylinder stroke xn and the actual cylinder stroke xm, etc. are stored in the form of a table or the like. The control target value is the ratio of the cylinder stroke x to the handle rotation angle θ, as shown in graph A in FIG. 7, and the ideal control value (shown in graph B).
is set smaller than the ratio of both θ and x. The clock circuit 285 is a circuit that sets the calculation processing time of the CPU 286. The CPU 286 is called a central processing unit, and reads out signals written in the RAM 283 and ROM 284, performs arithmetic processing according to a predetermined procedure, and operates each signal generation circuit 287, 28.
8,290 is a circuit that outputs the result signal. The control signal generation circuit 287 includes the CPU 286
Based on the result signal from the solenoids 31, 32
This is a circuit that outputs control signals a and b for the ON-
It is an OFF electrical signal, and solenoids 31 and 32
When an ON signal is output to one side, the solenoid switching valve 2
One of 6 and 27 is switched to the drain section side, and the hydraulic oil is drained for the signal output time. The control stop signal generation circuit 288
Based on the result signal from 86, solenoids 31,
A circuit that outputs a control stop signal d to 32,
This control stop signal d is generated by the solenoids 31 and 32.
If ON, turn it OFF; if OFF, leave it as is.
This is a signal that maintains the OFF state. The lighting signal generation circuit 289 includes a CPU 286.
Based on the result signal from the control stop signal generation circuit 288 (the same result signal to the control stop signal generation circuit 288),
This is a circuit that outputs a lighting signal e for 0. The angle display signal generation circuit 290
Based on the result signal from 86, the steering angle display means 6
This is a circuit that outputs an angle display signal f with respect to 1. Next, the operation of the embodiment will be explained. First, the control unit 28 shown in FIG.
The control inspection operation will be described using a flowchart showing the flow of the operation in the CPU 286. In step 150, the handle rotation angle sensor 2
The handle rotation angle signal θ from 9 and the cylinder stroke signal s from the cylinder position sensor 30 are read. Note that this signal reading is temporarily stored in the RAM 283 and read from the RAM 283 to the CPU 286. In step 151, the handle rotation speed Vh and cylinder stroke speed Vs are calculated based on the signals θ and s read in step 150. Note that this calculation is performed by differentiation with respect to time t. Vh=dθ/dt Vs=ds/dt In step 152, the cylinder stroke amount S due to steering is calculated based on the cylinder stroke speed Vs calculated in step 151. Note that this calculation is performed by integrating over time t. S=∫ ^t Vs In step 153, a result signal corresponding to the cylinder stroke amount S calculated in step 152 is output to the angle display signal generation circuit 290. The steering angle is displayed based on this result signal,
The operator can use this as a guide for operating the handle. In step 154, the absolute value |Vh| of the handle rotation speed Vh calculated in step 151 is determined as the reference value.
It is determined whether or not it is equal to or higher than Vh. Then, if it is below the reference value Vh , step 150
Return to the next step 155 if it is higher than the reference value Vh .
Or proceed to step 156. In other words, in an example in which a failure is determined based on the speed ratio, if the handle rotation speed Vh is too small, there is a high possibility that it will result in a judgment error to use it as a judgment criterion, and the sensor may malfunction. This is because many cases are caused by malfunctions or malfunctions. In step 155, the normal limit value Vs of the cylinder stroke speed Vs with respect to the handle rotation speed Vh is determined.
The table is retrieved from the ROM 284. In addition, the normal limit value Vs is the handle rotation speed Vh when there is no failure such as oil leakage and normal operation.
Measure the cylinder stroke speed Vs for
This is a value set after confirming the error range by taking into account error factors such as steering resistance and road surface conditions. In step 157, the absolute value |Vs| of the actual cylinder stroke speed Vs is compared with the normal limit value Vs from step 155, and if the relationship |Vs|≧ Vs is established, it is determined that the cylinder stroke speed is normal. The handle position correction is controlled according to the flowchart shown in FIG. 9, and if the relationship |Vs|< Vs , it is determined that there is a failure and the process proceeds to step 158. Furthermore, in step 156 and step 159,
Operations similar to steps 155 and 157 are performed. In step 158, it is determined whether or not the solenoids 31 and 32 are ON when a failure is determined in step 157 or step 159. If the solenoids 31 and 32 are OFF, the handle position is corrected while maintaining that state. The control operation is not performed and the process returns to step 150, and the solenoid 31,
32 is ON, the control stop signal generation circuit 28
A result signal for turning off the solenoids 31 and 32 is output to the control section 8 (steps 160 and 161), and a result signal for turning on the warning lamp 60 is output to the lighting signal generation circuit 289. In this way, when the correspondence relationship between the steering wheel rotation speed Vh and the cylinder stroke speed Vs indicates a failure state, the operation of the hydraulic oil spill means is stopped by the control stop signal d, and the hydraulic oil spill causes abnormality in steering operation. (For example, no matter how much you turn the steering wheel 10, the steering wheel 1
(e.g., when the movement of the steering wheel 9 is small), the operation of the steering wheel may be delayed somewhat compared to normal conditions, or the steering wheel 10 may have to be turned more, but the steering wheel can remain in a steerable state for a while. I can do it. Furthermore, in the event of this failure, the warning lamp 6
0 lights up, any of the mechanical system of the device,
Alternatively, it can be known that a failure has occurred in the control system, and it can be used as a guide for when to inspect or replace parts. In the past, to ensure safety, parts were replaced during periodic inspections, and even parts that worked normally were replaced without being used until the end of their service life. Next, the control unit 28 shown in FIG.
The control operation for steering wheel position correction will be described with reference to a flowchart showing the flow of operations in the CPU 286. In step 200, a handle rotation angle signal θ is read from the RAM 283, indicating the actual handle rotation angle θn when the handle 10 is rotated in one direction. In step 201, based on the handle rotation angle θn read out in step 200, the ROM is
The target cylinder stroke xn is looked up from the target value A stored in 284. For example, in Fig. 7, if the handle rotation angle θn is θ ₁ , the target cylinder stroke xn
becomes x ₁ . In step 202, the actual handle rotation angle θn
A cylinder stroke signal s indicating the actual cylinder stroke xn is read from the RAM 283. For example, in FIG. 7, the actual cylinder stroke xn is assumed to be _x2 . In step 203, the actual cylinder stroke
If xn is a function f(t) of time t, is the slope of this function, that is, the value differentiated with time t, positive?
Depending on whether the value is negative, it is determined whether the steering direction is right or left. Note that this steering direction determination may be made using the steering wheel rotation angle θn or the target cylinder stroke xn. Further, in step 203, if the value differentiated with respect to time t is zero, it means that steering is not being performed, and the process proceeds to step 204, where no result signal is output from the CPU 286. In the case of right steering, the process proceeds from step 203 to step 205. In step 205, the stroke difference δ between the actual cylinder stroke xm and the target cylinder stroke xn is calculated. be done. For example, as shown in FIG. 7, if xm is x ₂ and xn is x ₁ , the stroke difference δ is δ ₁ = x ₂ −
It is obtained by calculating x ₁ . In the next step 206, it is determined whether the stroke difference δ obtained in the step 205 is larger or smaller than a predetermined stroke error δn. If the relationship is δ≦δn, it is assumed that position correction control is not required, and the process proceeds to step 204.
If the relationship is δ>δn, it is assumed that position correction control is required and the process proceeds to step 207. In step 207, the CPU 286 sends the solenoid
2 to output a resultant signal. In other words, when steering to the right, hydraulic oil is sent from the steering unit 12 to the steering cylinder 14 via the hydraulic line 22, contrary to FIG. The valve 27 is switched to the drain part 36 side, and the hydraulic oil is released to the hydraulic oil tank 23 via the drain oil pipe 25 and the electromagnetic on-off valve 27 provided in the hydraulic line 22, and the handle 10 is released without changing the cylinder stroke. The position of the handle 10 is corrected by idling the handle 10 in the steering direction. For example, in FIG. 7, if δ ₁ >δn, only the handle rotation angle θ advances in the direction of arrow E. Also, in the case of left steering, as in the case of right steering, steps 208 and 209 are passed, and then step
Proceeding to either step 204 or step 210, the position of the handle 10 is corrected. The above control operation is repeated at predetermined time intervals to correct the position of the handle 10 in the delay direction. The hydraulic oil drained when correcting the position of the handle 10 due to this hydraulic oil leakage is carried out through the orifice 39,
40, the outflow flow rate is restricted by the orifices 39 and 40, and the pressure within the steering cylinder 14 does not drop suddenly. In other words, draining is performed in the same manner as part of the pressurized oil supplied from one of the hydraulic lines 21 and 22 is diverted to the drain side, and pressure transmission to the inside of the steering cylinder 14 is also cut off. First, even if a self-returning force is applied to the steering cylinder 14 from the steering wheel 19, the position of the steering cylinder 14 can be maintained as it is. In this way, by maintaining the position of the steering cylinder 14, the steering wheel 19 is prevented from rotating in the straight-ahead direction opposite to the steering direction during position correction, thereby eliminating the steering discomfort. This also increases the stability of vehicle behavior during steering. In addition, when correcting the position of the handle 10, if the steering cylinder 14 moves somewhat due to excessive self-returning force being applied from the steering wheel 19, the hydraulic line and cylinder chamber on the side that is not drained will be moved by the amount of movement. The volume expands, and the negative pressure causes bubbles, etc., and it becomes impossible to transmit pressure. However, the one-way valve portion 3 of the electromagnetic switching valves 26 and 27
3 and 34, the hydraulic oil can flow from the hydraulic oil tank 23 side to the hydraulic lines 21 and 22 side through the drain oil line 24, so that drainage is performed due to the pressure difference. Hydraulic oil is supplied to the hydraulic line on the other side, and the above-mentioned bubbles etc. do not occur. Furthermore, in the embodiment, by setting the ratio (x/θ) between the handle rotation angle θ and the cylinder stroke x at the control target value A to be smaller than the ratio at the ideal control value B, the stroke difference is reduced in most cases. Since δ is larger than the predetermined error δn, the position of the steering wheel 10 due to hydraulic oil spillage can be frequently corrected, and the position control is performed in the delayed direction, which is preferable since there is no discomfort in the steering feel. becomes. Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included. For example, in the embodiment, two electromagnetic switching valves are used as the hydraulic oil spilling means, but
Other hydraulic oil spill means may be used, such as those described in US Pat. No. 0,457,777. Further, although an example in which an on-vehicle computer is used as the control means has been shown, an ordinary electric circuit or a combination of an electric circuit and a computer may be used. Further, instead of the cylinder stroke signal, a turning angle signal of a steered wheel may be used as a cylinder stroke equivalent signal. Furthermore, although the steering cylinder is shown as a cylinder that operates linearly, it may also be one that performs rotational or curved movement. Further, in the embodiment, the failure is determined based on the handle rotation speed and the cylinder stroke speed, but the failure may be determined based on either the handle rotation angle or the cylinder stroke. In addition to the warning lamp, warning means in the event of a failure may include emitting a warning sound or operating a brake. Further, an input signal check circuit may be provided to provide a function of deactivating the actuator if the input signal is abnormal. (Effects of the Invention) As explained above, in the fully hydraulic power steering device of the present invention, as described in the claims, the steering wheel rotation angle signal and the cylinder stroke signal are inputted, When the correspondence between the signals indicates a normal state, a control signal is output to the actuator to correct the position of the handle by switching the hydraulic oil outflow means to the communication section, and the correspondence between the two input signals indicates a failure state. When the relationship shown is as shown, a control means is provided that outputs a control stop signal to the actuator to switch the hydraulic oil outflow means to the cutoff part. Therefore, during normal operation, the steering wheel position correction for the steering cylinder position is ensured by the hydraulic oil outflow, but in the event of a failure, the control means outputs a control stop signal to the actuator. By stopping the steering wheel position correction, it is possible to avoid the feeling of discomfort in steering caused by correction control of the steering wheel position due to hydraulic oil leakage, even though the cause is a failure.

[Brief explanation of drawings]

Fig. 1 is a conceptual claim diagram showing a fully hydraulic power steering device of the present invention, Fig. 2 is a plan view showing a three-wheeled forklift truck equipped with the embodiment device, and Fig. 3 is a block diagram of the embodiment device. Fourth
The figure is a sectional view showing a specific example of the electromagnetic switching valve of the embodiment device, FIGS. 5 and 6 are a sectional view and partially cutaway side view showing a specific example of the handle rotation angle sensor of the embodiment device, and FIG. is a graph showing control target values stored in advance in the control unit of the embodiment device;
8 and 9 are flowcharts showing the flow of operations in the CPU of the control unit of the embodiment device, and FIG. 10 is a plan view showing a three-wheeled forklift truck equipped with a conventional fully hydraulic power steering device. It is. DESCRIPTION OF SYMBOLS 1... Handle, 2... Steering unit, 3... Steering cylinder, 4, 5... Hydraulic line, 6... Actuator, 7... Hydraulic oil outflow means, 7a... Communication part, 7b... Blocking part, 8
...Control means, 9...Drain oil line, θ...
Handle rotation angle signal, s... cylinder stroke signal, c... control signal, d... control stop signal.

Claims (1)

[Scope of Claims] 1. An all-hydraulic power steering device comprising a steering unit operated by a handle, a steering cylinder that steers a steering wheel, and a hydraulic line that connects the steering unit and the steering cylinder. , connecting a drain oil line to the hydraulic line;
A hydraulic oil outflow means having an actuator for switching between a communication part and a cutoff part is provided in the drain oil line, a handle rotation angle signal and a cylinder stroke signal are inputted, and the correspondence relationship between the two input signals indicates a normal state. At this time, a control signal is output to the actuator to correct the position of the handle by switching the hydraulic oil outflow means to the communication section, and when the correspondence relationship between the two input signals indicates a failure state, the hydraulic oil outflow means is output to the actuator. A fully hydraulic power steering device comprising a control means for outputting a control stop signal to an actuator to switch the means to a cutoff section.