JP2536203B2 - Front and rear wheel steering vehicle rear wheel steering control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering control device for a front and rear wheel steering vehicle, which steer-controls rear wheels according to a yaw rate generated in a vehicle body.

[Prior Art] Conventionally, an apparatus of this type is provided with a yaw rate detecting means for detecting a yaw rate generated in a vehicle body as disclosed in, for example, Japanese Patent Laid-Open No. 63-207772, and when a vehicle is traveling at high speed,
The rear wheels are steered so as to increase in accordance with the increase in the detected yaw rate in the direction in which the yaw rate is suppressed (in the same phase as the steering of the front wheels when steering the front wheels), thereby improving the running stability of the vehicle at high speeds. ing.

[Problems to be Solved by the Invention] However, in the above-described conventional device, since the rear wheels are steered and controlled regardless of the steering speed of the front wheels, there are the following problems. That is, when the vehicle makes a steady circular turn, the detected yaw rate is large to a certain extent, so the rear wheels are steered to a certain degree in the same phase (direction to suppress the yaw rate) with respect to the front wheels, and the vehicle tends to face the turning tangent side. This makes it difficult for a person to see the turning exit and becomes a negative factor in the turning performance of the vehicle. Further, when the front wheels are steered steeply in order to change the lane of the vehicle or avoid obstacles, the in-phase steering amount of the rear wheels does not become so large, and the running stability of the vehicle is sufficient. It may not be considered. Further, in the case of such a lane change, it is preferable that the rear wheels are steered sufficiently with respect to the front wheels so that the traveling direction of the vehicle is changed linearly rather than turning.

In order to solve such a problem of the conventional device, the present applicant has proposed that in the previous application (Japanese Patent Application No. 1-301571 “Rear wheel steering device for front and rear wheel steering vehicle”), the steering speed of the front wheels is small. By multiplying the detected yaw rate by a coefficient that has a small value when the steering speed is large and a large value when the steering speed is large,
A device that tends to decrease the steering amount of the rear wheels in the in-phase direction with respect to the front wheels when the front wheel steering speed is low, and to increase the steering amount in the in-phase direction when the front wheel steering speed is high. Proposed.

The proposed device solves the above problems, but it has been found that the following new problems occur. That is, when the front wheels are steered in order to change the lane of the vehicle or avoid the obstacles, the front wheels are reversed to the neutral side immediately after that. In such a case, the steering speed temporarily becomes zero when the steering direction of the front wheels is reversed, and only at that time, the steering amount of the rear wheels in the in-phase direction suddenly changes. Further, this phenomenon occurs even when the vehicle is traveling on a rough road surface because the front wheels are alternately steered by the reaction force from the road surface. Such a sudden change in the steering amount of the rear wheels
This is not preferable in terms of running stability of the vehicle and is a problem to be solved.

It is an object of the present invention to provide a rear wheel steering control device for a front and rear wheel steering vehicle that simultaneously solves the problems of the conventional device and the proposed device.

[Means for Solving the Problems] In order to achieve the above object, the structural features of the present invention are, as shown in FIG. 1, a yaw rate detecting means 1 for detecting a yaw rate generated in a vehicle body, and a front wheel FW. Steering speed detecting means 2 for detecting the steering speed of the vehicle, coefficient determining means 3 for determining a coefficient that increases with an increase in the steering speed based on the detected steering speed, and a rear wheel in a direction to suppress the yaw rate. Control amount determining means 4 for determining a control amount for steering control, which is proportional to the determined coefficient and increases as the detected yaw rate increases.
And a steering control means 5 for steering control of the rear wheels RW according to the determined control amount, which is a rear wheel steering control device for a front and rear wheel steering vehicle, the reverse steering detection means detecting a reverse steering state of the front wheels. 6 and the coefficient correction means 7 for correcting the change of the coefficient determined by the coefficient determination means 3 when the reverse steering detection means 6 detects the reverse steering state of the front wheels.

The reverse steering detecting means 6 may be configured to detect the reverse steering state of the front wheels by the abrupt change in the detected steering speed in the decreasing direction.

[Operation and Effect of the Invention] In the present invention configured as described above, the yaw rate detecting means 1, the steering speed detecting means 2, the coefficient determining means 3, and the control amount determining means 4 are used to detect the yaw rate and the detected steering speed. The control amount is determined, and the steering control means 5 steers the rear wheel RW according to the determined control amount. In such a case, the coefficient determining means 3 determines a coefficient that increases as the steering speed of the front wheels FW increases, and the control amount determining means 4 is a control amount for steering the rear wheels in the direction of suppressing the yaw rate. Since the control amount that is proportional to the determined coefficient and increases as the detected yaw rate increases is determined, when the front wheels FW are steered, the rear wheels RW
Is steered in-phase with the front wheel FW to reduce the yaw rate generated in the vehicle body, and the steering amount is
When the steering speed is low, it tends to decrease, and when the steering speed is high, it tends to increase.

As a result, according to the present invention, as in the case of the above-mentioned proposed device, when the vehicle makes a steady circular turn, the vehicle tends to turn inward, making it easier for the driver to see the turning outlet and ensuring the turning performance of the vehicle. Is planned. Further, when the front wheels RW are steered in order to change the lane of the vehicle or avoid obstacles, the in-phase steering amount of the rear wheels RW becomes large and the running stability of the vehicle is improved. In addition, the traveling direction of the vehicle can be linearly changed.

On the other hand, in this rear wheel steering control device, when the front wheels FW are reversely steered, the reverse steering detection means 6 detects this and the coefficient correction means 7 changes the coefficient determined by the coefficient determination means 3. Since the correction is performed so as to suppress, the steering amount of the rear wheels RW in the in-phase direction does not suddenly decrease even in the same case.

As a result, in order to change the lane of the vehicle or avoid it from an obstacle, the front wheel FW is returned to the neutral state immediately after it is steered steeply, or the front wheel FW is run on a rough road surface.
The steering amount in the in-phase direction of the rear wheel RW does not decrease sharply even if the steering speed is temporarily and suddenly decreased due to the left and right being alternately steered. Since the control is maintained, the running stability of the vehicle can be kept good even in such a case.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 schematically shows the entire front and rear wheel steering vehicle. This front and rear wheel steering vehicle uses a front wheel steering device A that steers left and right front wheels FW1 and FW2, a rear wheel steering device B that steers left and right rear wheels RW1 and RW2, and a left and right rear wheels RW1 and RW2 mechanically by the front wheel steering device B. In addition to various controls, an electric control device C for electrically controlling is provided.

The front wheel steering device A is axially displaced and the left and right front wheels FW1, FW2
It has a rack bar 11 for steering. The rack bar 11 is supported in the steering gear box 12 so as to be displaceable in the axial direction and is connected to the lower end of the steering shaft 13 in the box 12, and a steering handle 14 provided at the upper end of the steering shaft 13. The shaft is displaced in the axial direction according to the rotation of the. The left and right front wheels FW1, FW2 are attached to both ends of the rack bar 11 via the left and right tie rods 15a, 15b and the left and right knuckle arms 16a, 16b.
Are steerably connected, and the front wheels FW1 and FW2 are steered in accordance with the axial displacement of the rack bar 11. A control valve (not shown) consisting of a four-way valve is incorporated in the steering gear box 12,
The valve supplies the hydraulic oil from the shunt valve 18 connected to the hydraulic pump 17 to the power cylinder 21 according to the steering torque acting on the steering shaft 13, and discharges the hydraulic oil from the cylinder 21 to the reservoir 22. . The power cylinder 21 drives the rack bar 11 in the axial direction according to the supply and discharge of hydraulic oil to assist the steering of the left and right front wheels FW1 and FW2.

The rear wheel steering device B is axially displaced and the left and right rear wheels RW1, RW2
, The left and right rear wheels RW1, via left and right tie rods 32a, 32b and left and right knuckle arms 33a, 33b, at both ends thereof, as in the case of the front wheel steering device A. RW2 is steerably connected. The relay rod 31 is biased to a neutral position by a spring 34, and is driven in an axial direction by a power cylinder 35.

The power cylinder 35, together with the spool valve 38 and the lever 41, constitutes a hydraulic pressure copying mechanism. The spool valve 38 is a valve sleeve that is axially displaceable with respect to the vehicle body.
38a and a valve spool 38b housed in the sleeve 38a so as to be slidable in the axial direction. The flow dividing valve 18 is provided in accordance with relative displacement between the valve sleeve 38a and the valve spool 38b.
To control the supply of hydraulic oil to one oil chamber of the power cylinder 35 and the discharge of hydraulic oil from the other oil chamber to the reservoir 22. A drive rod 43 biased to a neutral position by a spring 42 is connected to the valve sleeve 38a, and the rod 43 is in contact with a cam plate 44. Cam plate
A pair of cables 45 and 46 are wound around the outer peripheral side surface of 44, and the cables 45 and 46 are fixed to the cam plate 44 at their rear ends. These cables 45,4
Reference numeral 6 is for rotating the cam plate 44 in conjunction with the steering of the left and right front wheels FW1 and FW2. The cam plate 44 is extended to the front of the vehicle, and its front ends are fixed to both ends of the rack bar 11 of the front wheel steering device A. Has been done. Then, when the left and right front wheels FW1, FW2 are steered and the rack bar 11 is displaced left and right, the cables 45, 4
6 rotates the cam plate 44, and this rotation causes the drive rod 43 to be displaced in the axial direction, but when the cam plate 44 is in a small rotation range from the neutral position, the drive rod 43
Is kept in a neutral position. The valve spool 38b of the spool valve 38 is connected to one end of a connecting rod 47, and the other end of the connecting rod 47 engages with the intermediate portion of the lever 41 so as to be tiltable and slidable in the axial direction of the lever 41. .

The lower end of the lever 41 is engaged with the relay rod 31 so as to be tiltable and slidable in the direction perpendicular to the rod 31. lever
The upper end of 41 is rotatably connected to the wheel 48 at a position eccentric from the center of rotation on the upper surface of the wheel 48. The wheel 48 meshes with the worm 51 on the outer circumference thereof, and rotates around the rotation center according to the rotation of the worm 51. The worm 51 is connected to a rotating shaft of an electric motor 52 composed of a step motor so as to rotate integrally therewith.

The electric control device C includes a front wheel steering angle sensor 61 and a vehicle speed sensor 6
2. A yaw rate sensor 63, a rear wheel steering angle sensor 64 and a microcomputer 65 are provided.

The front wheel steering angle sensor 61 is mounted on the outer periphery of the steering shaft 13 and detects the rotation angle of the coaxial 13 so that the left and right front wheels FW are detected.
1, and outputs a detection signal representing the steering angle θf of FW2. The vehicle speed sensor 62 outputs a detection signal indicating the vehicle speed V by detecting the rotation speed of the output shaft of a transmission (not shown). The yaw rate sensor 63 is fixed to the vehicle body and detects the rotational speed of the vehicle body about the vertical axis of the center of gravity, thereby outputting a detection signal representing the yaw rate ωy acting on the vehicle body. The rear wheel steering angle sensor 64 detects the rotation angle of the electric motor 52, and the left and right rear wheels RW1, which are steered according to the rotation of the motor 52, are steered.
A detection signal indicating the steering angle θr of RW2 is output. The front wheel steering angle θf and the rear wheel steering angle θr are determined by the left and right front wheels FW1 and FW.
2 and the left and right rear wheels RW1 and RW2 each show a positive value when steering to the right, and show a negative value when steering each wheel to the left. The yaw rate ωy shows a positive value when the vehicle body rotates clockwise and a negative value when the vehicle body rotates counterclockwise.

Each of these sensors 61 to 64 is connected to the interface 65f of the microcomputer 65. The microcomputer 65 includes a ROM 65b and a CPU 65 that are commonly connected to the bus 65a.
c, RAM 65d, timer circuit 65e and interface 65f. The ROM 65b stores the programs corresponding to the flowcharts of FIGS. 3 and 4, and the steering angle ratio coefficient.
K ₁ , the steering speed coefficient K ₂ and the yaw rate coefficient K ₃ are stored as a steering angle ratio coefficient table, a steering speed coefficient table and a yaw rate coefficient table, respectively. The steering angle ratio coefficient K ₁ changes according to the vehicle speed V, and as shown in the graph of FIG. 5, shows a negative value in the low vehicle speed region and the medium speed region. Since the steering speed coefficient K ₂ changes according to the steering speed f, as shown in FIG. 6, it shows a small positive value in a region where the absolute value | f | of the same speed f is small, and the absolute value | It shows a large positive value in a large f | area. The yaw rate coefficient K ₃ also changes according to the vehicle speed V, and as shown in the graph of FIG. 7, shows a value that increases as the vehicle speed V increases from a medium range to a large range of the vehicle speed V.

The CPU 65c executes the above program, RAM6
Reference numeral 5d is for temporarily storing variables required for executing the program, and the timer circuit 65e is for measuring elapsed time and outputting the measured time value TIM. As described above, the interface 65f inputs each detection signal from each sensor 61 to 64 and outputs a rotation control signal to the electric motor 52.

Next, the operation of the embodiment configured as described above will be described.

When the ignition switch (not shown) is closed, the CPU 65c starts execution of the program in step 70 of FIG. 3, and in step 71 initialization processing such as clearing various data in the RAM 65b and the timer circuit 65e. After executing, the processing after step 72 is repeatedly executed. In step 72, the measured time value TIM is read from the timer circuit 65e, and the same time value TIM is compared with a predetermined value T ₀ set in advance. In this case, if the measured time value TIM is less than the predetermined value T ₀ , the process of step 72 is repeatedly executed based on the determination of “NO” in step 72. On the other hand, during the repeating process of step 72, the timer circuit 65e sequentially increases the measured time value TIM with the passage of time, and when the same time value TIM becomes equal to or larger than the predetermined value T ₀ , it is determined as “YES” in step 72. In step 73, the timer circuit 6
The measured time value TIM of 5e is cleared to "0", and the program proceeds to step 74 and thereafter. In such a case, the timer circuit 65e acts so as to start increasing the measured time value TIM sequentially from "0" again, so that the CPU 65c executes the processing of steps 74 to 80 at each time represented by the predetermined value T ₀ ,
In other cases, the process of step 72 is repeatedly executed.

In step 74, the respective detection signals from the front wheel steering angle sensor 61, the vehicle speed sensor 62, the yaw rate sensor 63, and the rear wheel steering angle sensor 64 are respectively taken in, and the front wheel steering angle θ
f, vehicle speed V, yaw rate ωy, and rear wheel steering angle θr are stored in the RAM 65d as data. In such a case, regarding the front wheel steering angle θf, the fetched data is stored in the RAM 65d as new data representing the current front wheel steering angle θf, and is also stored in the RAM 65d from before because of the differentiating process described later. The data representing the previous front wheel steering angle θf stored in the RAM is updated and stored in the RAM 65d as past data.

After the processing in step 74, in step 75, the front wheel steering angle θf is differentiated based on the new data and the past data concerning the front wheel steering angle θf, and the differentiated value is stored in the RAM 65d as the front wheel steering speed f. . In the differential calculation in such a case, the process of step 72 is always performed at the time represented by the predetermined value T ₀ by the process of step 72. Therefore, the old and new data relating to the front wheel steering angle θf can be obtained. The difference may be divided by the predetermined value T ₀ .

Next, in step 76, the steering angle ratio coefficient table in the ROM 65b is referred to derive the steering angle ratio coefficient K ₁ corresponding to the vehicle speed V, and in step 77 the steering speed coefficient K ₂ is derived.

As shown in detail in FIG. 4, the process of step 77 is started at step 90, and at step 91, the old steering speed coefficient K _20LD is set at the previous step 77 (step 9).
0 to 95), the steering speed coefficient K ₂ calculated by the processing is set, and then in step 92, the steering speed coefficient table in the ROM 65b is referred to and the absolute value of the front wheel steering speed f | f |
The steering speed coefficient K ₂ corresponding to is derived. Next, at step 93, the steering speed coefficient K ₂ derived this time is subtracted from the old steering speed coefficient K _20LD, and the subtraction result K _20LD
Whether -K ₂ is preset larger than a predetermined value C is determined. This determination is to determine whether or not the steering speed coefficient K ₂ has drastically decreased. The absolute value of the front wheel steering speed f |
If f | does not decrease sharply and the steering speed coefficient K ₂ does not decrease rapidly, “NO” in step 93, that is,
_{Based on} the determination that K _20LD −K ₂ <C, the processing for determining the steering speed coefficient K ₂ ends in step 95. On the other hand, in order to change the lane of the vehicle or avoid it from obstacles, the left and right front wheels FW1 and FW2 are steered immediately after being steered, or the front wheels FW1 and FW2 alternate left and right while traveling on a rough road surface. The steering angle θf of the left and right front wheels FW1, FW2 changes as shown in FIG. 8 (A), and the front wheel steering speed f changes as shown in FIG. 8 (B). When the steering speed coefficient K ₂ derived in the step 92 changes as shown in FIG. 8 (C), “YES” in step 93, that is, K _20LD , due to the rapid decrease of the coefficient K _2. −K ₂ ≧
It is determined that the steering speed coefficient K is C, and in step 94 the steering speed coefficient K ₂ is a small predetermined value ΔC from the old steering speed coefficient K _20LD.
Is set to a small value K _20LD −ΔC, and step 9
At 5, the process of determining the steering speed coefficient K ₂ ends. As a result, only the steep change in the steering speed coefficient K ₂ is suppressed.

After the processing in step 77 for determining the steering speed coefficient K ₂ , the yaw rate coefficient K ₃ corresponding to the vehicle speed V is referred to in step 78 by referring to the yaw rate coefficient table in the ROM 65b.
Is derived.

Next, in step 79, the derived steering angle ratio coefficient K ₁ ,
The target rear wheel steering angle θr * is calculated by executing the following arithmetic expression based on the steering speed coefficient K ₂ and the yaw rate coefficient K _3, and the detected front wheel steering angle θf and yaw rate ωy.

θr * = K ₁ · θf + K ₂ · K ₃ · ωy In step 80, the difference θr * −θr between the target rear wheel steering angle θr * and the detected rear wheel steering angle θr is calculated, and the difference is calculated. A control signal indicating the corresponding rotation amount of the electric motor 52 is output to the interface 65f. The interface 65f, based on the control signal, the electric motor 5
2 is rotated by a rotation amount corresponding to the difference θr * −θr, and the steering angles of the left and right rear wheels RW1 and RW2 are changed to the target rear wheel steering angle θ.
Set to r *.

The steering control of the left and right rear wheels RW1, RW2 will be described in detail. The rotation of the electric motor 52 causes the worm 51 to rotate.
The rotating plate 48 rotates via the. In this case, the upper end of the lever 41 is eccentrically mounted on the rotary plate 48 so as to be eccentric from the rotation center of the rotary plate 48, so that the upper end of the lever 41 can rotate in the left-right direction in FIG. 2 depending on the rotation amount of the electric motor. Is displaced to. Due to this displacement, the valve spool 38b assembled in the middle of the lever 41 is also displaced in the same direction, and a relative displacement is generated between the valve sleeve 38a and the valve spool 38b.
In such a case, the spool valve 38 cooperates with the relay rod 31 and the lever 41 to control the supply / discharge of hydraulic oil to / from the power cylinder 35 so as to eliminate the relative displacement between the valve sleeve 38a and the valve spool 38b. Then, the relay rod 31 is displaced in the left-right direction by an amount corresponding to the displacement amount of the upper end portion of the lever 41, so that the left and right rear wheels RW1, RW2 are steered to the target rear-wheel steering angle θr *.

The electric steering control by the various sensors 61 to 64 and the microcomputer 65 has a small front wheel steering angle θf and a small rotation amount even if the cam plate 44 rotates. This is a case where 38a is almost at the reference position and mechanical control via the cables 45 and 46 does not affect the steering control of the left and right rear wheels RW1 and RW2.

In this way, the left and right rear wheels RW1, RW2 are electrically steered, and as a result, the steering angle ratio coefficient K ₁ shows a negative value in the low vehicle speed and medium vehicle speed regions, and the steering control will be described later. In addition, since the steering of the vehicle is affected in a region where the front wheel steering angle θf is small, the steering control improves the initial turning property of the vehicle when the left and right front wheels FW1 and FW2 are steered during low-speed to medium-speed traveling. . Further, since the yaw rate coefficient K ₃ shows a positive value at medium speed and high speed regions, the by the steering control, the steering of the front left and right wheels FW1, FW2 from medium speed to high speed running, generated in the vehicle body due like crosswinds As a result, the yaw rate is suppressed, and the running stability of the vehicle at medium speed and high speed is improved.

And, this is the yaw rate control term K ₃ · .omega.y is further multiplied by the steering speed factor K _2, the coefficient K ₂ indicates a small value when the front wheel steering speed f is small, and a large value when the speed f is greater Is set so that
When the left and right front wheels FW1, FW2 are steered slowly or when the steering is stopped, the control term for steering the left and right rear wheels RW1, RW2 in the direction to suppress the yaw rate (in-phase direction)
K ₂ · K ₃ · ωy tends to be small, and when the left and right front wheels FW 1, FW 2 are steered steeply, the control terms K ₂ · K ₃
・ Ωy tends to increase. This reduces the amount of in-phase steering of the left and right rear wheels RW1, RW2 when the vehicle is in a steady circular turn, so that the vehicle tends to turn inward, making it easier for the driver to see the turning exit and ensuring the turning performance of the vehicle. Is planned. In addition, in order to change the lane of the vehicle and avoid obstacles, the left and right front wheels FW1, FW
When 2 is steered steeply, the in-phase steering amount of the left and right rear wheels RW1, RW2 increases, so that the running stability of the vehicle is improved and the traveling direction of the vehicle can be linearly changed. become.

Further, in the determination of the steering speed coefficient K ₂ , if the same coefficient K _2, that is, the front wheel steering speed f is largely changed in the direction of decreasing by the processing of steps 93 and 94, the steering speed coefficient K ₂ Is modified to suppress changes in the.
As a result, the steering speed coefficient K ₂ that changes as shown by the broken line in FIG. 9 changes without the correction as shown by the solid line in FIG. 9 in order to change the lane of the vehicle or avoid the obstacle. , The front wheel FW is turned immediately after it is steered steeply, or the left and right front wheels FW1, FW2 are steered alternately left and right due to the road surface reaction force while traveling on a rough road surface, and the steering speed temporarily and suddenly decreases. Also, the control term K _{2 for} the left and right rear wheels RW1, RW2
・ K ₃ · ωy does not decrease sharply and the steering control in the in-phase direction on the safe side is maintained.
The running safety of the vehicle is kept good.

On the other hand, the steering wheel 14 is largely turned, and the left and right front wheels FW
When the steering angle θf of 1, FW2 becomes large, the rotation angle of the cam plate 44 which is rotationally driven via the cables 45, 46 becomes large due to the axial displacement of the rack bar 11, and the drive rod 43
Starts to move in the axial direction. Due to this displacement, the valve sleeve 38a is displaced in the same direction and a relative displacement is caused between the valve sleeve 38a and the valve spool 38b, and the spool valve 38, the power cylinder 35, the relay rod 31
And the hydraulic imitation of lever 41 causes the left and right rear wheels RW1, RW2
Is steering controlled. In this steering control, due to the cam shape of the cam plate 44, the left and right rear wheels RW1, RW2 are
Since it is set to steer in reverse phase with respect to W1 and FW2, the mechanical anti-phase steering control by such cables 45, 46, cam plate 44 etc. improves the small turning performance of the vehicle at low speed running To do. In this case as well, the above-described electric steering control is also operating, but since the control amount is smaller than this mechanical steering control, in this case, the mechanical steering control has priority. .

In the above embodiment, the arithmetic expression θr * = K ₁ · θ
The target rear wheel steering angle θr * is calculated based on f + K ₂ · K ₃ · ωy, and the left and right rear wheels RW1 and RW2 are electrically steered to the same target rear wheel steering angle θr *. If the initial turning property during traveling is not a problem, the control term K ₁ · θf relating to the initial turning property is deleted, and the arithmetic expression θr * = K ₂ ·
The target rear wheel steering angle θr * may be calculated based on K ₃ · ωy, and the left and right rear wheels RW1 and RW2 may be electrically steered to the target rear wheel steering angle θr *.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims corresponding to the configuration of the present invention described in the claims, and FIG. 2 is an overall schematic view of a front and rear wheel steering vehicle showing an embodiment of the present invention, FIGS. 3 and 4 FIG. 7 is a flow chart of a program executed by the microcomputer of FIG. 2, FIG. 5 is a change characteristic graph of the steering angle ratio coefficient K ₁ , FIG. 6 is a change characteristic graph of the steering speed coefficient K ₂ , and FIG.
The figure shows the change characteristic graph of the yaw rate coefficient K ₃ , Fig. 8 (A)
Is the front wheel steering angle θ during the steering wheel switching operation
FIG. 8B is a graph showing the time change of f, and FIG. 8B is a graph showing the time change of the front wheel steering speed f during the same operation.
FIG. 9C is a graph showing the change over time of the steering speed coefficient K ₂ before correction during the same operation, and FIG. 9 is a graph showing the state change of the steering speed coefficient K ₂ before and after correction. Explanation of symbols A ... front wheel steering device, B ... rear wheel steering device, C ... electric control device, FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 61 ...
Front wheel steering angle sensor, 62 …… Vehicle speed sensor, 63 …… Yaw rate sensor, 64 …… Rear wheel steering angle sensor, 65 …… Microcomputer.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication B62D 137: 00 B62D 137: 00 (72) Inventor Hideo Inoue 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Hiroaki Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Shin Koike 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Mizuho Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Masa Ishikawa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Hideki Kusunoki 1 Toyota Town, Toyota City, Aichi Prefecture Within Toyota Motor Corporation (56) References Japanese Unexamined Patent Publication No. 172071 (JP, A)

Claims (2)

(57) [Claims] 1. A yaw rate detecting means for detecting a yaw rate generated in a vehicle body, a steering speed detecting means for detecting a steering speed of front wheels, and a coefficient which increases based on the detected steering speed as the steering speed increases. And a control amount for steering control of the rear wheels in the direction of suppressing the yaw rate, the control amount being proportional to the determined coefficient and increasing as the detected yaw rate increases. A rear-wheel steering control device for a front-rear wheel steering vehicle, comprising: a control amount determining means; and a steering control means for steering-controlling rear wheels according to the determined control amount, the reverse steering detecting a reverse steering state of a front wheel. A detecting means and a coefficient which is corrected when the reverse steering state of the front wheels is detected by the reverse steering detecting means so as to suppress a change in the coefficient determined by the coefficient determining means. Wheel steering control device after the front and rear wheel steering vehicle, characterized in that a positive means. 2. A rear wheel steering system for a front and rear wheel steering vehicle, wherein the reverse steering detecting means according to claim 1 detects a reverse steering state of front wheels based on a sudden change in the detected steering speed in a decreasing direction. Control device.