JPH0419271A - Front wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To steer front wheels by means of an actuator even during failure in operation of a control means by providing a switching means to switch control of operation of the actuator to control of an auxiliary control means during detection of failure in operation of a failure in operation detecting means. CONSTITUTION:When failure in operation occurs to a control unit 15, front wheels 4 and 4 on both sides are not steered along with operation of a handle 8, and a second shaft 10b is not rotated following rotation of a first shaft 10a to which the handle 8 is coupled. In which case, an abnormality detecting means 29 serving as a failure in operation detecting means to detect failure in operation of the control unit 15 based on rotation displacement of the two shafts 10a and 10b and a backup valve mechanism 30 to steer the front wheels 4 and 4 on both sides by means of a hydraulic cylinder 7 along with operation of the handle 8 during detection of failure in operation by means of an abnormality detecting valve mechanism 29 are provided between the first and second shafts 10a and 10b.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a front wheel steering system for a vehicle! In particular, it includes an operation state detection means for detecting the operation state of the steering wheel, an actuator for steering the front wheels, and an actuator for steering the front wheels in accordance with the operation state of the steering wheel detected by the operation state detection means. The present invention relates to a front wheel steering device for a vehicle, including a control means for controlling the operation of the actuator.

(Prior Art) In recent years, front wheel steering devices have been developed that detect the rotation angle of a steering wheel and steer the left and right front wheels using actuators in accordance with the detected rotation angle. According to JP-A-64-1663, the above-mentioned system is equipped with a steering angle sensor for detecting the steering angle of a steering wheel, a hydraulic actuator for steering the front wheels, and a control means for controlling the operation of the hydraulic actuator. By controlling the operation of the hydraulic actuator by the control means based on the steering angle of the steering wheel detected by the steering angle sensor, the left and right front wheels are steered in accordance with the operation state of the steering wheel.

(Problems to be Solved by the Invention) By the way, as described above, there is a front wheel steering device configured to control the operation of the actuator by the control means and steer the left and right front wheels in accordance with the operation state of the steering wheel. In the above, if the control means fails, it becomes impossible to steer the front wheels by the actuator.

Accordingly, the present invention has the control means control the operation of an actuator that steers the front wheels based on the operation state of the steering wheel detected by the operation state detection means, so that the left and right It is an object of the present invention to provide a front wheel steering device for a vehicle configured to steer the front wheels so that the front wheels can be steered by an actuator even when the control means is in failure.

(Means for Solving the Problems) In order to solve the above problems, the present invention is characterized by the following configuration.

First, the invention according to the first claim of the present application (hereinafter referred to as the first invention) includes an operation state detection means for detecting the operation state of the steering wheel, an actuator for steering the front wheels, and an operation state detection means for detecting the operation state of the steering wheel. A front wheel steering system for a vehicle, comprising: a control means for controlling the operation of the actuator so as to steer the front wheels in accordance with an operating state of a steering wheel; The present invention is characterized in that it includes a failure detection means for detecting a failure of the control means, and a switching means for switching the actuation control of the actuator to control by the sub-control means when the failure detection means detects the failure.

By the way, in the front wheel steering device configured to steer the left and right front wheels by controlling the operation of the actuator by the control means as described above, it is possible to steer the front wheels even when the control means fails. In addition, by dividing the steering shaft into the steering wheel side and the front wheel side, and connecting the two so that they can rotate relative to each other, the actuator is controlled by the control means based on the rotation angle of the shaft on the steering wheel side in normal conditions. controls the operation of the steering wheel to steer the left and right front wheels in accordance with the rotation angle of the steering wheel, and in the event of a failure of the control means, the shaft divided into the steering wheel side and the front wheel side is directly connected mechanically. It has been proposed that the relative rotation of the two shafts be restricted so that the two shafts can be rotated integrally with the operation of the steering wheel to steer the left and right front wheels. Therefore, the invention according to claim 2N of the present application (hereinafter referred to as the second invention) includes an operation state detection means for detecting the operation state of the steering wheel, an actuator for steering the front wheels, and the operation state detection means for detecting the operation state of the steering wheel. a first shaft on the steering wheel side and a second shaft on the front wheel side;
a steering shaft divided into two shafts; a dead zone joint that connects the first shaft and the second shaft such that they can rotate relative to each other within a predetermined range; a sub-control means independent of the control means; failure detection means for detecting failure of the control means when the amount of relative rotation between the second shafts exceeds the allowable limit by the dead band joint; and sub-control means for controlling the operation of the actuator when the failure detection means detects the failure; The present invention is characterized in that it is provided with a switching means for switching to control by.

(Function) In both the first and second inventions, there is provided a sub-control means independent of the control means, a failure detection means for detecting a failure of the control means, and an actuator that steers the front wheels when the failure detection means detects a failure. and switching means for switching the operation control of the actuator to control by the sub-control means, so that when the control means fails, the sub-control means will control the operation of the actuator, so that when the control means fails, the actuator is controlled by the sub-control means. Even in this case, the left and right front wheels are steered by the actuator as the steering wheel is operated.

In particular, according to the second invention, the failure detection means includes the first and second
Since the control means is configured to detect a failure when the amount of relative rotation between the shafts exceeds the allowable limit by the dead band joint, there is no need to take any special measures when configuring the failure detection means. It can be configured simply.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an overall system diagram of a front wheel steering device for a vehicle according to the present invention, and the steering device 1 includes tie rods 2 at both ends.
, 2 and the left and right front wheels 4 via the knuckle arms 3, 3.
．． 4 is connected to the left and right cylinder chambers 7 by a piston 6 integrally provided with the steering rod 5.
a, 7b are formed to steer the front wheels 4, 4, a first shaft 10a having a handle 8 attached to one end, and a rack and pinion mechanism 9 connected to the front wheels 4, 4 side. The steering shaft 10 is divided into a second shaft 10b, and an oil pump 11 is connected to the left and right cylinder chambers 7a and 7b of the hydraulic cylinder 7.
a hydraulic control valve 12 for supplying and discharging hydraulic oil from the hydraulic cylinder 7; a pilot valve 14 provided in the middle of a pair of supply and discharge passages 13a and 13b connecting the hydraulic control valve 12 and the hydraulic cylinder 7; It has a control unit 15 that steers the left and right front wheels 4.4 by controlling the operation of the hydraulic control valve 12.

Second, the control unit 15 receives a signal from a steering angle sensor 16 that detects the operating state of the handle 8, that is, the rotation angle of the first shaft 10a to which the handle 8 is attached, and a signal from the vicinity of the hydraulic cylinder 7. A signal from a potentiometer 17, which is disposed at the front wheel, detects the amount of steering of the left and right front wheels 4.4 based on the displacement of the steering rod 5 in the vehicle width direction, and a brake switch 18, which detects the state of depression of the brake. , a signal from a yaw rate sensor 19 that detects the yaw rate acting on the vehicle body, and a signal from the G sensor 20 that detects the lateral G acting on the vehicle body.
A signal from the wiper switch 21 that detects the operating state of the wiper is inputted, and based on these input signals, the control unit 15 sends a signal to the hydraulic control valve 12 to control its operation. A control signal is output.

Further, as shown in FIG. 2.3, the first shaft 10
The end of the second shaft 10b is externally fitted onto the tip of the second shaft 10b, so that both the shafts 10a, 10b are connected to be relatively rotatable, and the two shafts 10a, 1
A dead zone joint 22 is provided to restrict the relative rotation range of 0b. This dead zone joint 22 is connected to the above-mentioned shaft 10.
a, and an engagement hole 22c formed in the second shaft 10b to restrict the rotation range of the engagement piece 22b. The piece 22b is rotatable within the opening range of the engagement hole 22C, so that the first and second shafts 10
a and 10b are connected to be relatively rotatable within a predetermined range.

Therefore, when the handle 8 connected to one end of the first shaft 10a is operated, a signal from the steering angle sensor 16 indicating the rotation angle of the first shaft 10a is input to the control unit 15, and the signal is input to the control unit 15. The operation of the hydraulic control valve 12 is controlled by the control unit 15 based on the signals from the brake switch 18, the wiper switch 21, and the sensors 19 and 20, thereby controlling the left and right sides of the hydraulic cylinder 7. Hydraulic oil is supplied to and discharged from the cylinder chambers 7a and 7b, so that the left and right front wheels 4° 4 are steered by the hydraulic cylinder 7 in response to the operating state of the handle 8. .

As shown in FIG. 2, a sleeve 24 that engages with a spline 23a formed on the outer periphery of the shaft end is fitted onto the shaft end of the second shaft 10b. 1. The sleeve 24 is placed at a predetermined position on the shaft 10a.
A spline 23b is formed which engages with the spline 23b. The sleeve 24 is urged in a predetermined direction by a coil spring 26 interposed between the sleeve 24 and a bracket 25 fixed to the outer circumference of the second shaft 10b. Further, a lock lever 27 whose distal end engages with the sleeve 24 to restrict movement of the sleeve 24 is rotatably supported on the bracket 25.
An electromagnet 28 is provided for disengaging the lever 27 from the sleeve 24. When the electromagnet 28 is energized, the tip of the lock lever 27 separates from the sleeve 24, thereby causing the lock lever 27 to disengage from the sleeve 24. The sleeve 24 is biased by the coil spring 26 to slide in the axial direction, and the sleeve 24 is attached to the spline 23a formed on the second shaft 10b and the first shaft 10a.
, 23b, thereby causing the first and second shafts 1
0a and 10b are mechanically directly connected and rotated together by operating the handle 8.

By the way, if a failure occurs in the control unit 15, the left and right front wheels 4 may
．． 4 is not steered, and the second shaft 10b is not rotated following the rotation of the first shaft 10a to which the handle 8 is connected. Therefore, as shown in FIG. 2, the above-mentioned 1. Between the second shafts 10a and 10b, there is provided an abnormality detection valve mechanism 29 as a failure detection means for detecting failure of the control unit 15 based on the rotational displacement of both shafts 10a and 10b, and the abnormality detection valve mechanism 29. A backup valve mechanism 30 is provided that steers the left and right front wheels 4.4 by the hydraulic cylinder 7 in response to the operation of the handle 8 when a failure is detected.

Next, the configurations of the abnormality detection valve mechanism 29 and the backup mechanism 30 will be explained in more detail based on FIG. A first boat 31 into which hydraulic pressure is introduced from the first boat 31, second and third boats 32 and 33 formed on the left and right sides of the first boat 31 and supplying hydraulic pressure to the backup valve mechanism 30 side,
It is formed on the outer periphery of the shaft 10a, and when the control unit 15 malfunctions, the first
Boat 31 and second boat 32, or the second boat 31
and a communication groove 34 that communicates with the third boat 33.

On the other hand, the backup valve mechanism 30
0b and connected to the second boat 32 in the abnormality detection valve mechanism 29 via the first supply passage 35a, and the third boat in the abnormality detection valve mechanism 29 as well. 33 through the second supply passage 35b, the third and fourth boats 38 and 39
, the fifth and sixth boats 40.41 formed between the first and second boats 36 and 37, the communication groove 42 located between these fifth and sixth boats 40.41, and the third , 4th port 38. 7th and 8th bow formed between 38) 4
3.44 and these 7. A communication groove 45 located between the eighth boats 43 and 44, a pair of communication grooves 46 and 47 formed on the outer circumference of the first shaft 10a, and a drain boat 48 formed between these communication grooves 47 and 48. and a drain passage 49 in which one end of the drain boat 48 is open.
It is composed of. The fifth and eighth boats 40.44 are connected to the pilot valve 14 via the first supply and discharge passage 50a, and the sixth and seventh ports 41.4
3 is connected to the pilot valve 14 via the second supply/discharge passage 50b.
The pilot valve 14 is connected to the pilot pressure from the first and second supply passages 35a and 35b.

Here, the control unit 15 under normal conditions
The steering control operation of the front wheels 4, 4 will be explained based on the flow chart shown in FIG. 5. First, in step Sl, the control unit 15 inputs the steering wheel steering angle θh1 detected by the steering angle sensor 16. Then, in step S2, it is determined whether or not it is the correction control timing based on the difference between the steering wheel steering angle θh1 and the target steering angle θh2 for actually steering the left and right front wheels 4.4. When there is a difference between the steering wheel steering angle θhl and the target steering angle θh2 and it is determined that it is correction control timing, the hydraulic cylinder 7 is driven in step S3 to steer the front wheels 4°4 in a predetermined direction. let Then,
In step S4, the value obtained by adding the correction amount by the hydraulic cylinder 7 to the steering wheel steering angle θh1 is the target steering angle θh2.
If YES, the operation of the hydraulic cylinder 7 is stopped in step S. If the determination is NO, the hydraulic cylinder 7 is continuously driven, step S6 is executed, and it is determined whether the steering control operation of the front wheels 4, 4 by the hydraulic cylinder 7 has timed out. In the case of time-up, this control operation is immediately stopped in step S7, and if the time-up is not time-up, in step S8, the difference between the steering wheel steering angle θh1 and the target steering angle θh2 and the dead band joint 22 are adjusted to a predetermined rotation range. compared with the allowable relative rotation limit θho between the first and second shafts 10a and 10b that are relatively rotatably connected,
When the difference between the steering wheel steering angle θh1 and the target steering angle θh2 reaches the relative rotation permissible limit θhO, step S7 is executed to stop the control operation, and the difference between the steering wheel steering angle θhl and the target steering angle θh2 is If the difference is within the relative rotation tolerance range θho, correction control by the hydraulic cylinder 7 is subsequently performed.

Next, based on FIGS. 6 to 13, the control operation for determining the target steering angle θh2 corresponding to the steering wheel steering angle θh1 according to the driving state by the control unit 15 will be explained. As shown in FIG. unit 1
5 calculates the steering speed from the displacement acceleration θh1 of the steering wheel 8 obtained based on the signal from the steering angle sensor 16 in step S10', and then, in step 81', the brake is depressed in response to the signal from the brake switch 18. Determine whether the Then, when the brake is depressed, the correction amount A corresponding to the steering speed when the brake is depressed is calculated from the map showing the relationship between the steering speed and the corresponding correction amount A shown in FIG. , step S1. At ', the target steering angle θh2 is set to the value obtained by adding the correction amount AI to the target steering angle θh2 in normal conditions. Further, when it is determined in step 881' that the brake is not depressed, in step S14', a correction amount A2 corresponding to the steering speed when the brake is not depressed is calculated from the map shown in FIG. In step 815', the target steering angle θh in normal conditions is
The target steering angle θh2 is set to the value obtained by adding the correction amount A2 to the correction amount A2. In this way, the target θh2 is set in correspondence with the steering angular speed and the brake depression state, so that when the steering speed is high and the brake is depressed, and prompt correction is required, the target steering angle By setting θh2 large, correction control can be performed quickly.

Further, FIG. 8 shows a control operation for setting the target steering angle θh2 according to the yaw rate acting on the vehicle body, and the control unit 15 sets the target steering angle θh1-0 in step S20'.
When it is determined as YES, that is, the handle 8
When it is determined that the vehicle is hardly being steered, in step 821', the yaw rate acting on the vehicle body is calculated based on the signal from the yaw rate sensor 19, and then in step 822', the yaw rate shown in FIG. 9 and the corresponding correction amount are calculated. A correction amount B corresponding to the yaw rate calculated in step S21' is calculated from a map showing the relationship with B. Then, the target steering angle θh2 is set to a value obtained by subtracting the correction amount B from the target steering angle θh2 in normal times. In this way, when the yaw rate is acting, the target steering angle θh2 is adjusted so as to cancel out the influence of the yaw rate.
will be set.

Furthermore, FIG. 10 shows a control operation for setting the target steering angle θh2 according to the lateral G acting on the vehicle body. First, in step Sho', the lateral G acting on the vehicle body is determined by the signal from the G sensor 20. In step S31', the first
The correction amount C is calculated from a map showing the relationship between the lateral G and the corresponding correction amount C shown in FIG. Next, step S32
', the correction amount C is added to the target steering angle θh2 in normal conditions.
The target steering angle θh2 is set to the value obtained by adding . In this manner, when lateral G is acting, the target steering angle θh2 is set in consideration of the influence of this lateral G.

Furthermore, FIG. 12 shows a control operation for setting the target steering angle θh2 according to changes in road surface conditions.
0'', the signal from the wiper switch 21 is input, and in step 841', the correction weight is calculated from the map showing the relationship between the wiper operating state shown in FIG. 13, that is, the road surface friction coefficient and the corresponding correction weight. Then step S4□
'The target steering angle θh2 is set to a value obtained by subtracting the correction scale from the target steering angle θh2 in normal conditions. In this way, when the wiper is activated, that is, when the road surface friction resistance is low, the target θh2 is
will be set.

Next, the steering operation of the front wheels 4, 4 when the control unit 15 is out of order will be explained. When the control unit 15 is out of order, the front wheels 4, 4 are not steered in accordance with the operation of the steering wheel 8. The handle 8
The second shaft 10b connected to the front wheels 4, 4 does not rotate following the rotation of the first shaft 10a connected to the front wheels 4, 4. That is, when the handle 8 is operated in the direction of arrow A as shown in FIG. 4(II) from the neutral state shown in FIG. 4(I), only the first shaft 10a rotates in the direction of arrow A, The first in the abnormality detection valve mechanism 29
The boat 31 and the second boat 32 communicate with each other via the communication groove 34, so that the hydraulic pressure introduced into the communication groove 34 from the first boat 31 is transferred from the second boat 32 via the first supply passage 35a. It will be supplied to the first and second boats 36 and 37 in the backup valve mechanism 30.

Further, the pilot pressure from the first supply passage 35a acts on the pilot valve 14, and the pilot pressure from the first supply passage 35a acts on the pilot valve 14.
will be switched. In this case, the first and second boats 36 in the backup valve mechanism 30
．． The hydraulic pressure supplied to the hydraulic cylinder 7 passes through the communication groove 42 from the communication grooves 46 and 47 and is drained via the drain boat 48 and the drain passage 49, and the hydraulic pressure is supplied to the hydraulic cylinder 7 via the pilot valve 14. is never supplied.

As shown in FIG. 4 (I[[), as the handle 8 is operated, the first shaft 10a is further rotated in the direction of arrow A, so that the
The hydraulic pressure supplied from the boat 32 to the first boat 36 of the backup valve mechanism 30 via the first supply passage 35a is supplied from the fifth boat 40 to the pilot valve 14 via the first supply/discharge passage 50a. , hydraulic pressure is supplied to the hydraulic cylinder 7, and the piston 6 integrally provided on the steering rod 5 moves in a predetermined direction in response to the operation of the handle 8 in the direction of the arrow A, whereby the left and right front wheels 4 .4 will be steered.

Furthermore, when the handle 8 is operated in the opposite direction of arrow A,
Hydraulic pressure is supplied from the third boat 33 of the abnormality detection valve mechanism 29 to the backup valve mechanism 30 via the second supply passage 35b, and as a result, similarly to the above,
The pilot valve 14 is switched and hydraulic pressure is supplied to the hydraulic cylinder 7 via the pilot valve 14, and as the handle 8 is operated in the opposite direction of arrow A, the left and right front wheels 4, 4 are moved in a predetermined direction. It will be steered to.

In this way, even when the control unit 15 is out of order, the left and right front wheels 4, 4 can be steered by the hydraulic cylinder 7 in conjunction with the operation of the handle 8.

Further, FIG. 14 shows a second embodiment of a front wheel steering system for a vehicle, and this steering system 51 has tie rods 52, 52 and knuckle arms 53, 53 at both ends, similar to the first embodiment. A steering rod 55 to which the left and right front wheels 54,54 are connected via a piston 56 integrally provided with the steering rod 55 provides left and right cylinder chambers 57a,
57b is formed to steer the front wheels 54.54, a first shaft 60a having a handle 58 attached to one end, and a rack and nion mechanism 59 connected to the front wheels 54.54 side. Second shaft 60b
a steering shaft 60 divided into two parts; a hydraulic control valve 62 for supplying and discharging hydraulic oil from the oil pump 61 to the left and right cylinder chambers 57a and 57b of the hydraulic cylinder 57; It has a control unit 65 that steers the left and right front wheels 54 and 54 by controlling the operation.

Further, as shown in an enlarged view in FIG. 15, the first shaft 60a and the second shaft 60b can be relatively rotated within a predetermined range by a dead band joint 72 having the same structure as in the first embodiment. is connected to. That is, the engagement piece 72 is fixed to the first shaft 60a by a mounting bolt 72a.
b, and a retaining hole 72c formed in the second shaft 60b to restrict the rotation range of the engagement piece 72b, the dead band joint 72
is configured.

The control unit 65 receives a signal from a steering angle sensor 66 that detects the operating state of the handle 58, that is, the rotation angle of the first shaft 60a to which the handle 58 is attached, and a signal from the vicinity of the hydraulic cylinder 57. A signal from a potentiometer 67 which is disposed at the front wheel and detects the amount of steering of the left and right front wheels 54 and 54 based on the displacement of the steering rod 55 in the vehicle width direction is inputted, and also based on these input signals. The control unit 65 outputs a control signal to the hydraulic control valve 62 to control its operation.

Although not shown, signals from the brake switch, yaw rate sensor, G sensor, and wiper switch are input to the control unit 65 as in the first embodiment.

Further, this steering device 51 includes a watchdog timer 79 having a conventionally well-known configuration as a failure detection means for detecting a failure of the control unit 65, a signal from the steering angle sensor 66, and a signal from the potentiometer. 67
A comparator 80 is provided to which signals from the control unit 65 and the hydraulic control valve 6 are input.
In the middle of the first circuit 81 connected to the movable contact 8
2 is provided. Further, the movable contact 8 is connected to a ground circuit 83 whose one end is connected to the watchdog timer 79 and a second circuit 84 whose one end is connected to the comparator 80.
An electromagnetic relay 85 is configured to switch 2, and when the control unit 65 fails, a watchdog timer 79
The ground circuit 83 is energized from the ground circuit 83, thereby energizing the coil 85a of the electromagnetic relay 85 and switching the movable contact 82, so that the comparator 80 and the hydraulic control valve 62 are connected to the first and second circuits 81. 84. As a result, the steering wheel 58 is
The operation of the hydraulic control valve 62 is feedback-controlled by the comparator 80 so that the left and right front wheels 54, 54 are steered in response to the operation.

According to the above configuration, when the control unit 65 malfunctions, the comparator 80 controls the operation of the hydraulic control valve 62, so that even when the control unit 65 malfunctions, the operation of the handle 58 is still possible. Accordingly, the left and right front wheels 54 are activated by the hydraulic cylinder 57.
54 can be steered.

Further, the failure detection means for detecting failure of the control unit 15 may be configured as follows. That is, as shown in FIG. 15, limit switches 99 and 99 are disposed on both sides of the engagement hole 72c constituting the dead band joint 72, and the rotation state of the first shaft 60a is controlled by the limit switches 99 and 99. By detecting this, a failure of the control unit 65 is detected. That is, when the control unit 65 fails, only the first shaft 60a rotates with the operation of the steering wheel.
The engagement piece 72b fixedly attached to 0a comes into contact with one of the limit switches 99, thereby detecting a failure of the control unit 65. According to this,
When configuring the failure detection means of the control unit 65, it can be simply configured without taking any special measures.

Note that in place of the limit switches 99 and 99, a pressure-sensitive rubber or an optical sensor consisting of a light emitter and a light receiver may be used, or alternatively, the first and second shafts 60a
, 60b, by disposing a potentiometer that detects the rotation difference between the two shafts 60a, 60b, the two shafts 60a detected by the potentiometer.
The configuration may be such that failure of the control unit 15 is detected based on the rotation difference between the rotations 60b and 60b.

(Effects of the Invention) As described above, in both the first and second inventions, the sub-control means independent of the control means, the failure detection means for detecting a failure of the control means, and the failure detection means when the failure is detected by the failure detection means. By providing a switching means for switching the operation control of the actuator to control by the sub-control means, when the control means fails, the sub-control means controls the operation of the actuator that steers the front wheels. Even if the control means fails, the front wheels can be steered by the actuator in conjunction with the operation of the steering wheel.

In particular, according to the second invention, the failure detection means includes the first and second
Since the control means is configured to detect a failure when the amount of relative rotation between the shafts exceeds the allowable limit by the dead band joint, there is no need to take any special measures when configuring the failure detection means. It can be configured simply.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall system diagram of a front wheel steering device for a vehicle according to this embodiment, and FIG. 2 is a diagram showing a first shaft and a second shaft that constitute the steering device. FIG. 3 is an enlarged sectional view of the connecting part, FIG. 3 is a sectional view taken along the line ■-■ in FIG. It is. In addition, Fig. 5 is a flowchart showing the front wheel steering control operation by the control unit, Fig. 6 is a flowchart showing the control operation to set a target steering angle according to the steering speed, and Fig. 7 is a flowchart showing the steering speed and steering angle. A map showing the relationship between the yaw rate and the steering angle correction amount; FIG. 8 is a flowchart of a control operation for setting a target steering angle according to the yaw rate; FIG. 9 is a map showing the relationship between the yaw rate and the steering angle correction amount;
Figure 10 is a flowchart showing the control operation for setting the target steering angle according to the lateral G, Figure 11 is a map showing the relationship between the lateral G and the steering angle correction amount, and Figure 12 is the target according to the road surface condition. Flowchart diagram showing the control operation for setting the rudder angle, 1st
Figure 3 is a map showing the relationship between the operating state of the wiper switch and the steering angle correction amount, and Figure 14 is a map showing the relationship between the operating state of the wiper switch and the amount of steering angle correction.
FIG. 15, which is an overall system diagram of the embodiment, is an enlarged sectional view of essential parts showing another embodiment of the insensitive joint and failure detection means in the second embodiment. 1.51...Front wheel steering device, 7,12,57°62.
...Actuator (7,57...Hydraulic cylinder, 1
2.62... Hydraulic control valve), 8.58... Steering wheel (handle), 10.60... Steering shaft, 10a. 60a...first shaft, 10b, 60b...second shaft
Shaft, 15.65... Control means (control unit), 29, 79.99... Failure detection means (29
... Abnormality detection valve mechanism, 79 ... Watchdog timer, 99 ... Limit switch), 30.80.
...Sub-control means (30...backup valve mechanism,
80... comparator), 14.85... switching means (14
...Pilot valve, 85...Electromagnetic relay).

Claims (2)

[Claims] (1) an operation state detection means for detecting the operation state of the steering wheel; an actuator for steering the front wheels;
and a control means for controlling the operation of the actuator so as to steer the front wheels in accordance with the operation state of the steering wheel detected by the operation state detection means, which is independent from the control means. a sub-control means, a failure detection means for detecting a failure of the control means, and a switching means for switching operation control of the actuator to control by the sub-control means when the failure detection means detects a failure. The vehicle's front wheel steering system features a distinctive feature. (2) an operation state detection means for detecting the operation state of the steering wheel; and an actuator for steering the front wheels;
a control means for controlling the operation of the actuator so as to steer the front wheels in accordance with the operation state of the steering wheel detected by the operation state detection means; a first shaft on the steering wheel side and a second shaft on the front wheel side; a steering shaft divided into two shafts; a dead zone joint that connects the first shaft and the second shaft such that they can rotate relative to each other within a predetermined range; a sub-control means independent of the control means; a failure detection means for detecting a failure of the control means when the amount of relative rotation between the second shafts exceeds the allowable limit by the dead band joint; and a sub-control means for controlling the operation of the actuator when the failure detection means detects the failure. 1. A front wheel steering device for a vehicle, characterized in that the front wheel steering device is equipped with a switching means for switching control to control according to the present invention.