JPH0327428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a four-wheel steering system for a vehicle, which controls the steering of both the front wheels and the rear wheels through steering operation.

(Prior Art) Conventionally, as a four-wheel steering system for this type of vehicle, the steering ratio of the rear wheels to the front wheels is adjusted according to the vehicle speed, as disclosed in, for example, Japanese Unexamined Patent Publication No. 57-11173. Automatically controls and steers the rear wheels in the opposite direction (opposite phase) to the steering direction of the front wheels in the low vehicle speed range below the set speed, thereby reducing the minimum turning radius of the vehicle to enable tight turns, parking, etc. At medium to high vehicle speeds higher than the set speed above, the rear wheels are steered in the same direction (same phase) as the front wheels, thereby reducing the phase delay between the rear wheels and the front wheels. , vehicles that are capable of stably performing lane changes and gentle turns are known.

(Problems to be Solved by the Invention) Vehicles are required to have a function that not only facilitates parking in a garage as described above, but also facilitates parallel parking of the vehicle. In order to satisfy this requirement, the rear wheels must be steered in the same phase as the front wheels at a relatively large steering angle ratio (rear wheel steering angle/front wheel steering angle) in the low vehicle speed range, so that the vehicle can move diagonally. It is necessary to make it easy to move in this direction.

However, in the above-mentioned conventional system, the speed range for in-phase steering of the rear wheels is limited to medium and high vehicle speeds, so in order to satisfy the above requirements, it is necessary to steer the rear wheels in opposite phase in the low speed range and at medium and high vehicle speeds. In addition to the normal rear wheel steering angle characteristic that has the same phase in the area, a rear wheel steering angle characteristic that is different from the normal rear wheel steering angle characteristic is added to facilitate parallel parking of the vehicle, etc. It may be possible to select this by operating a manual switch or the like.

However, in this case, the above-mentioned unusual rear wheel steering angle characteristic is for a special purpose such as parallel parking. is selected, the rear wheels are largely controlled to be in the same phase as the front wheels, and the vehicle is started diagonally forward from parallel parking. Due to the relatively large steering angle to the phase side,
When the vehicle speed enters a medium-high speed range, the turning radius becomes large when the vehicle turns, which hinders normal driving, so it is desirable to improve this in terms of steering stability and safety during driving.

The present invention has been made in view of the above points, and its purpose is to select a rear wheel steering angle characteristic different from the normal one as described above, and after starting, when the vehicle speed becomes equal to or higher than the set vehicle speed, the purpose of the present invention is to By forcibly canceling the selection of the unusual rear wheel steering angle characteristic at this point, the normal rear wheel steering angle characteristic can be automatically restored and normal driving can be performed with good maneuverability and safety. The purpose is to do so.

In that case, the normal rear wheel steering angle characteristics are limited to characteristics that allow the vehicle to run more favorably during normal driving.

(Means for Solving the Problems) In other words, the specific solution of the present invention is a four-wheel steering system for a vehicle that includes a steering system that steers front wheels and a rear wheel steering system that steers rear wheels. Assuming that. A vehicle speed detection means for detecting vehicle speed, a characteristic switching command means for instructing switching of selection of a rear wheel steering angle characteristic with respect to a front wheel steering angle, and a characteristic switching command means for instructing switching of selection of a rear wheel steering angle characteristic with respect to a front wheel steering angle, and a rear wheel steering angle characteristic with respect to a front wheel steering angle changes in accordance with the vehicle speed. At the same time, the characteristics of the rear wheel steering angle with respect to the front wheel steering angle are controlled to be in the same phase at least in the high speed range, and the characteristics are set such that the characteristics of the rear wheel steering angle with respect to the front wheel steering angle are A first control characteristic that is set such that the rate of increase in the wheel turning angle is smaller than the rate of increase in a region where the front wheel turning angle is small, and a second control characteristic that is different from the first control characteristic. a controller is provided, the controller selects the first or second control characteristic in response to a characteristic switching command from the characteristic switching command means, and controls the rear wheel steering device based on the selected control characteristic. . Furthermore, after the characteristic for controlling the rear wheel steering device is selected as the second control characteristic, when the vehicle speed becomes equal to or higher than the set vehicle speed, the second control characteristic is selected.
The controller is configured to include a canceling section for forcibly canceling the selection of the control characteristic.

(Function) With the above configuration, in the present invention, when the vehicle is normally traveling at high speed, the controller selects the first control characteristic and controls the steering of the rear wheels based on the first control characteristic. As a result, when attempting to change lanes while driving at high speeds, the driver manipulates the steering wheel a little, so the front wheel steering angle is adjusted to a small value, but the rear wheels are also slightly adjusted relative to the front wheel steering angle. Since the rate of increase in the angle is large and the rear wheel steering angle is controlled relatively largely to the same phase side, the acceleration in the lateral direction of the vehicle body becomes large and a quick lane change is performed. Furthermore, when the driver consciously adjusts the front wheel steering angle to change the direction of the vehicle during high-speed driving, the ratio of increase in the rear wheel steering angle to the front wheel steering angle is small, and the front wheels are Since the wheels are steered by a large amount relative to the wheels, the turning performance of the vehicle is improved, and the vehicle changes its direction in accordance with the driver's intention with good responsiveness.

On the other hand, when starting a vehicle from parallel parking, for example, the driver commands switching of the selection of rear wheel steering angle characteristics using characteristic switching command means such as a manual switch, and in response to this, the controller The second control characteristic is selected, and the steering control of the rear wheels is performed based on the selected second control characteristic. As a result, the rear wheels are steered in the same phase as the front wheels when starting, and the vehicle can easily start from parallel parking.

After the vehicle has started, when the vehicle speed becomes equal to or higher than the set vehicle speed, the vehicle in this situation has almost escaped the parallel parking state and is about to transition to normal driving, and the controller uses the release unit to perform the above-mentioned The selection of the second control characteristic is forcibly canceled and the controller selects the first control characteristic. As a result, the steering angle of the rear wheels changes from the same phase side to the zero phase side, and the steering angle on the same phase side becomes smaller, so that when the vehicle is running normally after that, when the vehicle turns, the turning radius will be This means that the vehicle can be driven normally with good maneuverability and safely.

(Effects of the Invention) As explained above, according to the four-wheel steering system for a vehicle of the present invention, the rear wheel steering angle characteristics when the vehicle is running at high speed can be adjusted in a small region and a large region of the front wheel steering angle. By specifying the increase rate of the steering angle toward the same phase side, it is possible to easily and safely change lanes or change the direction of the vehicle during high-speed driving, while also creating a special rear wheel steering characteristic that is different from the rear wheel steering characteristics for normal driving. By setting the rear wheel steering angle characteristic, for example, when starting from parallel parking, you can select this special rear wheel steering angle characteristic to make it easier to maneuver the vehicle at that time, and also to complete the maneuvering. When the vehicle speed is higher than the set vehicle speed, the rear wheel steering angle characteristics are forcibly returned to the normal steering angle characteristics, thereby improving steering stability and safety during normal vehicle driving. It is.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows the overall configuration of a four-wheel steering system for a vehicle, which is a first embodiment of the present invention, in which 1 indicates left and right front wheels 2.
A steering device for steering a and 2b,
The steering device 1 includes a steering wheel 3, a rack and pinion mechanism 4, and left and right tie rods 5, 5.
and left and right knuckle arms 6, 6.

Reference numeral 7 denotes a rear wheel steering device for steering left and right rear wheels 8a, 8b.
and a hydraulic actuator 11 having a rod 11a extending in the lateral direction of the vehicle body and connected via tie rods 10,10. The hydraulic actuator 11 includes a left-turn hydraulic chamber 11c and a right-turn hydraulic chamber 11d, which are partitioned in the lateral direction of the vehicle body by a piston 11b fixed to a rod 11a, and each hydraulic chamber 11c, 11d is provided with a return spring 11e, 11f, respectively. has been reduced. Also,
The rear wheel steering device 7 includes a hydraulic pump 14 driven by an electric motor 12 that sucks oil in an oil reservoir 13 and supplies it to the hydraulic actuator 11, and a switching valve 15 that switches the direction of pressure oil supply from the hydraulic pump 14.
It is equipped with The switching valve 15 is connected to the hydraulic pump 1
4 to left-hand rotation hydraulic chamber 1 of hydraulic actuator 11
Left rotation position 15a that allows pressure oil supply to 1c and oil return from right rotation hydraulic chamber 11d to oil reservoir 13
, a clockwise rotation position 15b that allows oil flow in the opposite direction, and a blocking position 15c that blocks both pressurized oil supply and oil return.When in the left rotation position 15a, the hydraulic actuator 11 is rotated to the left. By moving the rod 11a downward in the figure via the piston 11b by supplying pressure oil to the hydraulic chamber 11c, the left and right rear wheels 8a, 8b are steered to the left (counterclockwise in the figure), while the right When in the rotation position 15b, the rod 11a is moved in the opposite direction to the above by supplying pressure oil to the right turning hydraulic chamber 11d, and the left and right rear wheels 8a, 8b are steered to the right (clockwise in the figure). Furthermore, when positioned at the blocking position 15e, the oil flow is blocked and the movement of the rod 11a is stopped, thereby maintaining the left and right rear wheels 8a, 8b at the current steering angle.

Furthermore, 16 is a controller for controlling the operation of the rear wheel steering device 7, and the controller 16
A front wheel steering angle sensor 17 for detecting the steering angle of the front wheels 2a, 2b, a vehicle speed sensor 18 as a vehicle speed detecting means for detecting the vehicle speed, and a rear wheel for detecting the amount of left and right movement of the rod 11a of the hydraulic actuator 11. Detection signals from the wheel steering sensor 19 are input to the controller 16, and the switching valve 15 is input to the controller 16.
An excitation coil 15e that attracts and moves the spool 15d is connected. Further, inside the controller 16, there is a characteristic of the movement amount SA of the rod 11a of the hydraulic actuator 11 with respect to the front wheel steering angle θF as shown in FIG. The characteristics are input and stored in advance in two types of modes. As shown by the solid line in the figure, multiple types of these characteristics are set using vehicle speed as a parameter, and in the speed range below _V0 , the rear wheels are in opposite phase to the front wheels, and the vehicle speed is
This is an automatic control mode as a first control characteristic that is set to be in the same phase in the speed range higher than V ₀ so that the vehicle can run well in the entire range from low vehicle speeds to high vehicle speeds, and functions as a normal driving mode. In addition, as shown by the dashed line in the figure, the other characteristic is different from the above-mentioned first control characteristic, and is a second control characteristic that is specially set to correspond to low-speed driving ranges such as when parallel parking the vehicle. This is a fixed mode, and this fixed mode has a characteristic that as the front wheel steered angle θF increases, the rear wheel steered angle θR also increases in the same phase. When the fixed mode is selected by operating a manual switch 20, which will be described later, the front wheel steering angle sensor 1
When the automatic control mode is selected, the target movement amount of the rod 11a of the hydraulic actuator 11 (target rear wheel rotation The steering angle) is calculated based on the selected automatic control mode or fixed mode, and this is compared with the actual movement amount of the rod 11a from the rear wheel steering sensor 19, and the rear wheel steering device is adjusted in a direction to reduce the difference. In order to move the rod 11a of the hydraulic actuator 11 of No. 7, the excitation coil 15e of the switching valve 15 is energized or de-energized to position the switching valve 15 at an appropriate position.

As can be seen from the figure, in the automatic control mode shown in Figure 2, the characteristics in the speed range where the vehicle speed is higher than V ₀ are in phase with the front wheels as described above, and in the range where the front wheel steering angle θF is large. The rate of increase of the rear wheel steered angle θR with respect to the front wheel steered angle θF is set to be smaller than the increase rate in a region where the front wheel steered angle θF is small.

In FIG. 1, reference numeral 20 indicates the rear wheel steering angle characteristic relative to the front wheel steering angle shown in FIG. switch, the manual switch 20
As shown in FIG. 3A, when the switch is turned on, it generates an "H" level fixed mode selection command signal. In addition, 21 is the controller 1
6 is a determination means for detecting when the vehicle speed becomes equal to or higher than a set vehicle speed after the fixed mode is selected, and the establishing means 21 includes a vehicle speed sensor 22 that detects the vehicle speed.
The vehicle speed signal from the vehicle speed sensor 22 is compared with a reference value corresponding to the set vehicle speed set by the reference value setter 23, and when the vehicle speed exceeds the set vehicle speed, the third
The comparator 24 generates an "H" level detection signal as shown in FIG.

The output signal from the manual switch 20 and the output signal from the determining means 21 are output to a switch circuit 25. The switch circuit 25
receives the output signal of the manual switch 20 and the inverted signal of the output signal of the determining means 21.
AND circuit 25a and the manual switch 2
an edge trigger type flip-flop circuit 25c that is set upon receiving a fixed mode selection command signal of 0 and reset upon receiving a signal obtained by inverting the selection signal or a detection signal from the determination means 21 via an OR circuit 25b; The above first AND circuit 2
A second AND circuit 25 receives an output signal as shown in FIG. 3C from the flip-flop circuit 25a and an output signal as shown in FIG. 3D from the flip-flop circuit 25c.
It consists of d. As shown in FIG. 3E, the output signal of the second AND circuit 25d becomes "H" level when the manual switch 20 is turned on (see A in the same figure), and thereafter, the determination means 21 generates a determination signal. (see part a of the same figure), the pulse signal is forcibly reset to the "L" level, and thereafter remains at the "L" level regardless of whether the judgment signal is generated (see part a of the same figure). It's summery. Then, the output signal of the switch circuit 25 (second AND circuit 25d
output signal) is output to the controller 16, and when the output signal is at the "H" level, the controller 16 selects the fixed mode, while at the "L" level, the controller 16 selects the fixed mode.
The automatic control mode is selected when the level is reached.

Therefore, with the above configuration, the fixed mode is selected by turning on the manual switch 20, and then the determining means 21 determines when the vehicle speed has increased above the set vehicle speed, and when that determination signal is generated, the determination signal is Based on this, a canceling unit 43 is configured to forcibly cancel the selection of the fixed mode of the controller 16.

The controller 16 controls the hydraulic pump 14 so that the operating speed of the hydraulic actuator 11 becomes slower as the actual amount of movement of the rod 11a of the hydraulic actuator 11 approaches the target amount of movement.
The electric motor 12 is drive-controlled so that the rate of increase in oil pressure from the hydraulic actuator 11 to the hydraulic actuator 11 gradually decreases. Further, 26 is an in-vehicle battery.

Next, the operation of the above embodiment will be explained. First, in the normal case when the manual switch 20 is not turned on, the output of the second AND circuit 25d of the switch circuit 25 is at the "L" level, so the controller 16 selects the automatic control mode shown in FIG. The rear wheels are steered based on the automatic control mode. As a result, when changing lanes at high speeds, the front wheel steering angle θF is adjusted to a relatively small value by the driver, but the automatic control mode selected above does not operate in the region where the front wheel steering angle θF is small. The increase rate of the rear wheel steering angle θR is large, and the rear wheel steering angle θR is controlled relatively largely to the same phase side, so the lateral acceleration of the vehicle body can be obtained sensitively and with good response, allowing for quick lane changes. At the same time, when the driver significantly adjusts the front wheel steering angle θF to consciously change the direction of the vehicle while driving at high speed, the automatic control mode rear wheel rotation is performed in the region where the front wheel steering angle θF is large. Since the increase rate of the steering angle θR is small, the front wheel steering angle θF is largely steered relative to the rear wheel steering angle θR, which improves the turning performance of the vehicle and the vehicle's direction. will change quickly.

On the other hand, for example, when starting the vehicle diagonally forward from a parallel parking state, the manual switch 20 is activated.
It is operated ON. Therefore, the second AND circuit 25d of the switch circuit 25 goes to the "H" level as shown in FIG. 3E, and the controller 16 selects the fixed mode among the characteristics shown in FIG. When the steering wheel 3 is steered in the traveling direction, the controller 16 controls the hydraulic actuator 11 according to the actual front wheel steering angle (for example, θFO) based on the fixed mode.
The target movement amount (for example, SAO) of the rod 11a is calculated. Therefore, when the operation of the switching valve 15 is controlled by the controller 16, the horizontal movement amount of the rod 11a of the hydraulic actuator 11 becomes the target movement amount SAO, and the rear wheels 8a and 8b are moved to the target movement amount SAO. The vehicle will be steered to a corresponding in-phase steering angle (for example, θRO). As a result, the vehicle easily starts and moves diagonally forward by steering the front wheels 2a, 2b and the rear wheels 8a, 8b in the same direction.

Thereafter, when the vehicle speed becomes equal to or higher than the set vehicle speed, that is, when the vehicle attempts to exit the parallel parking state and shift to normal driving, a determination signal is generated from the determination means 21, and accordingly, the second When the output signal of the AND circuit 25d becomes "L" level, the selection of the fixed mode of the controller 16 is forcibly canceled by the cancellation section 43. As a result, the controller automatically switches the straight steering angle characteristic of the recreational wheel to the automatic control mode shown in FIG. (for example
SA′O) is calculated. As a result, by controlling the operation of the switching valve 15 by the controller 16, the rear wheels 8a and 8b are controlled to be steered to the same phase steering angle (for example, θR'O) in the normal driving mode based on the automatic control mode. The steering angle on the same phase side based on the fixed mode is
The steering angle is smaller than SAO. Therefore, after selecting fixed mode, if the vehicle speed exceeds the set vehicle speed,
By controlling the steering angle of the rear wheels 8a and 8b based on the automatic control mode as the normal driving mode, the vehicle can travel safely and with good maneuverability, such as not increasing the turning radius even during subsequent turns. become.

Furthermore, if the manual switch 20 is turned off after the vehicle has started until the vehicle speed reaches the set vehicle speed, the output signal of the second AND circuit 25d goes to the "L" level, as shown by the broken line in FIG. Therefore, the fixed mode selection of the controller 16 is immediately canceled accordingly, so that the rear wheels 8a, 8b
The steering will be controlled based on the automatic control mode.

FIG. 4 shows a second embodiment of the present invention, and shows the first embodiment of the invention.
In this embodiment, the rear wheel steering device 7 is configured with a hydraulically controlled device, but instead is configured with a link mechanism that is linked to the steering device 1 (note that the same parts as in the first embodiment are the same). ), and the explanation thereof will be omitted).

That is, in FIG. 4, a first I-shaped link 28 disposed in the longitudinal direction of the vehicle body is connected to the rack 4a of the rack and pinion mechanism 4 via an L-shaped link 27, and the rack 4a of the rack 4a is connected in the lateral direction of the vehicle body. By rotating the L-shaped link 27 about its fulcrum 27a in accordance with the movement, the I-shaped link 28 is moved in the longitudinal direction of the vehicle body. Further, one end 29a of a variable lever ratio link 29 disposed in the lateral direction of the vehicle body is connected to the rear end portion of the I-shaped link 28. The variable lever ratio link 29 is provided with a movable fulcrum 30 that is slidable along the variable link 29, and one end 2 of the variable lever ratio link 29 is positioned at the movable fulcrum 30 as a fulcrum.
9a is moved in the longitudinal direction of the vehicle body in accordance with the movement of the first I-shaped link 28. Further, a second I-shaped link 31 disposed in the longitudinal direction of the vehicle body is provided at the center portion 29b of the variable lever ratio link 29.
A rod 33 in the lateral direction of the vehicle body is connected to the rear end of the I-shaped link 31 via an L-shaped link 32, and is connected to tie rods 10, 10 of the left and right rear wheels 8a, 8b. By moving the I-shaped link 31 in the longitudinal direction of the vehicle body, the L-shaped link 32 is rotated about its fulcrum 32a, thereby moving the rod 33 in the lateral direction of the vehicle body, thereby steering the left and right rear wheels 8a, 8b. I try to do that. The above constitutes the rear wheel steering device 7'.

The movable fulcrum 30 of the variable lever ratio link 29 is connected to a threaded member 36 that threads onto a threaded rod 35 in the lateral direction of the vehicle body which is rotationally driven by an electric motor 34. stick 3
By moving the threaded member 36 in the lateral direction of the vehicle body by the rotation of 5, the movable fulcrum 30 is slid in the lateral direction of the vehicle body along the variable lever ratio link 29, and the movable fulcrum 30 is moved to the central portion 29b as shown in the figure. When positioned further to the right, the center portion 29b of the variable link 29 moves in the same direction as the one end 29a of the variable link 29 interlocking with the first I-shaped link 28, so that the second I-shaped link 31 as the first I
Move the rear wheel 8 in the same direction as the shaped link 28.
a, 8b are steered in the same phase as the front wheels 2a, 2b, while the movable fulcrum 30 is steered at one end 29a of the variable link 29.
and the central portion 29b, the central portion 29b moves in the opposite direction to the end 29a, thereby moving the second I-shaped link 31 in the opposite direction to the first I-shaped link 28, When the rear wheels 8a, 8b are steered in a phase opposite to that of the front wheels 2a, 2b, and the movable fulcrum 30 is positioned to coincide with the center portion 29b, the second I-shape is set regardless of the movement of the one end 33a in the longitudinal direction of the vehicle body. By stopping the movement of the link 31, the rear wheels 8 are rotated independently of the steering of the front wheels 2a and 2b.
The steering angles of wheels a and 8b are set to zero, that is, the rear wheels 8a and 8
b is steered in a direction parallel to the longitudinal direction of the vehicle body.

Further, the controller 16 has input and stored in advance the rear wheel turning angle characteristics with respect to the front wheel turning angle, that is, the fulcrum position characteristics of the movable fulcrum 30 with respect to the front wheel turning angle, and the fulcrum position characteristics of the movable fulcrum 30 on the variable lever ratio link 29. Rear wheel steering sensor 1 that detects position
A detection signal 9' is input. Then, the controller 16 compares the target fulcrum position calculated based on the fulcrum position characteristics of the movable fulcrum 30 with the actual fulcrum position from the rear wheel steering sensor 19'.
It is configured to control the operation of the electric motor 34 so as to reduce the difference. The other configurations are the same as those of the first embodiment.

Therefore, in the second embodiment, when the vehicle speed increases to exceed the set speed after starting in the fixed mode, the controller 16 controls the operation of the electric motor 34 based on the automatic control mode by forcibly canceling the fixed mode. Therefore, the movable fulcrum 30 is positioned at the target fulcrum position based on the automatic control mode, thus ensuring the steering stability and running safety of the vehicle as in the first embodiment. Can be done.

In the above explanation, the fixed mode of the rear wheel steering characteristics input and stored in the controller 16 is a characteristic in which the rear wheel steering angle θR increases in the same phase as the front wheels as shown in FIG. For example, in addition to the fixed mode that increases in the same phase as shown by the dashed line in Fig. 5, the mode increases in the opposite phase as shown in the broken line in Fig. 5. It is also possible to set many fixed modes.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is an overall schematic configuration diagram showing the first embodiment; FIG. 2 is a diagram showing rear wheel steering angle characteristics relative to the front wheel steering angle input and stored in the controller; Figures 3A to 3E are diagrams showing respective waveforms of the output of the manual switch, the output of the determination means, and the output of each element of the switch circuit, respectively.
The figure is an overall schematic configuration diagram showing the second embodiment, and FIG. 5 is a diagram showing another example of the rear wheel turning angle characteristic input and stored in the controller. 1... Steering device, 2a, 2b... Front wheels, 7, 7'... Rear wheel steering device, 8a, 8b...
Rear wheel, 11... Hydraulic actuator, 15... Switching valve, 16... Controller, 18... Vehicle speed sensor (vehicle speed detection means), 20... Manual switch (characteristic switching command means), 21... Judgment means, 2
3...Reference value setter, 24...Comparator, 3
5... Lever ratio variable link, 36... Movable fulcrum,
40...Electric motor, 41...Screw rod, 43...Release part.

Claims (1)

[Claims] 1. In a four-wheel steering device for a vehicle that includes a steering device that steers front wheels and a rear wheel steering device that steers rear wheels, a vehicle speed detection means that detects vehicle speed;
a characteristic switching command means for instructing switching of selection of a rear wheel turning angle characteristic with respect to a front wheel turning angle; a plurality of rear wheel turning angle characteristics with respect to a front wheel turning angle are set so as to change according to vehicle speed; In a high speed range, the characteristics of the rear wheel steering angle are controlled to be in the same phase as the front wheel steering angle, and this characteristic is such that the increase rate of the rear wheel steering angle with respect to the front wheel steering angle in a region where the front wheel steering angle is large is higher than the front wheel steering angle. The first value is set to be smaller than the rate of increase in areas with small corners.
and a second control characteristic different from the first control characteristic, and selects the first or second control characteristic in response to a characteristic switching command from the characteristic switching command means, and selects the first or second control characteristic. a controller that controls the rear wheel steering device based on the control characteristics,
The controller includes a canceling unit that forcibly cancels the selection of the second control characteristic when the vehicle speed becomes equal to or higher than the set vehicle speed after the characteristic for controlling the rear wheel steering device is selected as the second control characteristic. A four-wheel steering device for a vehicle characterized by: