JP3096139B2 - Vehicle rear wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering device for controlling turning of a rear wheel using a vehicle speed, a steering angle, and a yaw rate as parameters, and more particularly, to a steering operation when a rapid deceleration operation during turning is detected. Improving safety. Here, the steering ratio θ _S is
The ratio of the front wheel steering angle theta _F for the steering angle theta _R of the rear wheels (= θ _R /
θ _F ).

[0002]

2. Description of the Related Art In general, a rear wheel steering device of a vehicle is designed to steer rear wheels so as to have a predetermined rear wheel steering angle corresponding to a front wheel steering angle. Conventionally, proportional control is performed according to a predetermined steering ratio set according to the vehicle speed or the like. This is a so-called vehicle speed sensitive rear wheel steering device.

In such a rear-wheel steering system, in order to secure the directional stability of the vehicle, the steering ratio is controlled so as to be positive, that is, in the same phase in a middle to high speed range of the vehicle speed. However, since this control is based on the proportional control as described above, the rear wheels are turned to the same phase at the same time as the start of steering, so that sufficient turning performance cannot be obtained. There was a point.

To solve this problem, for example, Japanese Patent Application Laid-Open No. 57-44568 and Japanese Patent Application Laid-Open No.
No. 5 proposes a phase inversion type rear wheel steering device. This means that the yaw rate of the vehicle can be detected, the rear wheels are steered to the opposite phase to the front wheels immediately after the front wheel steering is started, and then steered to the same phase according to the occurrence of the yaw rate. This is called "phase inversion control by yaw rate feedback", and it is possible to achieve both turning performance and directional stability.

[0005] As described above, in the phase inversion control based on the yaw rate feedback, it is extremely important to perform a control operation in which the steering ratio switches from the opposite phase to the same phase in a short time immediately after the start of the front wheel steering. Therefore, in a phase inversion type steering device, it is going to be proposed to employ a high-speed electric motor in order to switch the steering ratio from the opposite phase to the same phase in a short time.

[0006]

As described above, the yaw rate feedback control is a very effective technique for maintaining the attitude of the vehicle when yaw occurs by combining a high-speed electric motor. In a conventional yaw rate feedback control type rear-wheel steering device that does not use a high-speed motor, when sudden braking is applied, the vehicle speed decreases and the steering ratio changes to the opposite phase, so-called "scooping" phenomenon It is pointed out that this occurs. This “scooping” phenomenon becomes remarkable when sudden braking is performed during turning.

Conventionally, the "scooping" at the time of this sudden braking
In order to mitigate the phenomenon, the steering ratio was fixed or decreased slowly. This is because a conventional electric motor having a high rotation speed was not required, and even if the steering ratio was slowly reduced, no serious problem occurred. Originally, the yaw rate feedback control was developed to improve the obstacle avoidance ability and the stability during turning, but the low-speed motor was designed to prevent the `` slipping phenomenon '' during sudden deceleration. Using or controlling the turning ratio to a low rate of change negates the advantage of yaw rate feedback control.

However, when a high-speed electric motor is used as an actuator for controlling the steering ratio, this scooping phenomenon cannot be ignored during sudden braking. Therefore, when it is necessary to truly avoid the phenomenon of "scooping" while securing the advantages of yaw rate feedback control by using a high-speed electric motor (for example, during rapid deceleration braking during turning), the yaw rate feedback control Those that can suppress the effect are preferred.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and has as its object to propose a rear wheel steering device for a vehicle which can ensure a high degree of stability during turning braking. Is what you do.

[0010]

Means for Solving the Problems and

According to the present invention, there is provided a rear-wheel steering device for a vehicle, comprising: a rear-wheel steering device that performs rear-wheel steering control using a vehicle speed, a steering angle, and a yaw rate as parameters; Actuator means for driving to steer the rear wheel, means for detecting turning of the vehicle, means for detecting sudden deceleration, and restricting the drive gain of the actuator means to be low when sudden deceleration is detected. Regulating means, when the sudden deceleration during the turn
The regulation of the driving gain in, larger than the regulation in time of rapid deceleration of traveling straight. Further, the rear wheel steering device of the vehicle of the present invention is a rear wheel steering device that performs steering control of the rear wheels using the vehicle speed, the steering angle, and the yaw rate as parameters.
Actuator means for driving a rear wheel having a variable drive gain to steer, means for detecting turning of the vehicle, means for detecting rapid deceleration, and said actuator means when sudden deceleration is detected during turning. And a restricting means for restricting the drive gain to a low value. The restricting means increases the control amount of the drive gain as the steering angle increases.

Normally, the drive gain is set higher. If sudden braking is applied during turning, the drive gain of the actuator means is suppressed to a low level, thereby preventing a sudden change in the rear wheel steering angle.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, an embodiment in which a rear wheel steering device of the present invention is applied to a rear wheel steering device that performs a so-called "four-wheel steering device" and performs a so-called "yaw rate feedback control" will be described. It will be described in detail. The rear wheel steering device of this embodiment has the following features. 1: as a mechanical mechanism, in order to change the steering ratio theta _S in accordance with the vehicle speed, employing a high-speed step motor to the steering ratio changing mechanism. This high-speed step motor can control the rotation speed by changing the gain. 2: When a sudden deceleration operation occurs during turning, 2-1: Decrease the gain so that the rotation speed of the electric motor decreases.

2-2: The degree to which the gain is reduced, that is, the degree to which the rotational speed of the motor is reduced, is set to be larger than during the rapid deceleration during straight traveling. While traveling straight, the effect of the yaw rate feedback control is exerted to maximize the avoidance performance. 2-3: The greater the steering angle of the steering wheel, that is, the steeper the turning, the greater the degree of decrease in the rotation speed of the motor.

2-4: Once the gain regulation control is started, the control is continued for a predetermined time so that the motor gain regulation control is not intermittent even if the deceleration operation is performed intermittently. I decided to. FIG. 1 illustrates a configuration of a four-wheel steering system according to an embodiment. As shown, the rear wheel steering device 10 is mechanically connected via a transmission shaft 52 to a front wheel steering mechanism 14 that steers the front wheels 12, and interlocks with front wheel steering by the front wheel steering mechanism 14. , a wheel steering mechanism 18 after the turning to be the target steering angle TGshita _R of a predetermined rear wheel in accordance with the front wheel steering angle theta _S inputted to the rear wheel 16 from the front wheel steering mechanism 14, the rear wheel steering mechanism 18
Provided within a steering-angle-ratio adjusting mechanism 20 for setting and changing the steering angle ratio theta _S, expressed as a ratio of rear wheel steering angle theta _R for the front wheel steering angle theta _F, the steering-angle-ratio adjusting mechanism 20 And a control unit 22 for controlling. The control unit 22 includes a vehicle speed V from the vehicle speed sensor 24 and a front wheel steering angle sensor 26.
(Provided on the steering shaft), the front wheel steering angle θ _F , the steering ratio θ _S from the steering ratio sensor 28, and the yaw rate か ら from the yaw rate sensor 25 are input.

As will be described later, in the present steering system, the rear wheels are steered by hydraulic force. The source of the hydraulic pressure is the pump 29 in FIG. The pump 29 sends the oil retained in the oil tank 19 to the hydraulic release circuit 31 via the pipe 90. The release circuit 31 is a circuit for releasing the hydraulic pressure in the steering device 18 so that the rear wheel is forcibly brought to the neutral position when a failure occurs. Also, 91
Is a return pipe from the steering mechanism 18.

The control of the turning ratio variable mechanism 20 by the control unit 22 is performed in the middle vehicle speed range or the high vehicle speed range.
When the front wheel 12 is steered from the steering angle zero, a negative start immediately after turning ratio theta _S of the front wheel steering, then the so-called "phase inversion to be performed so as to positively the said transfer steering ratio theta _S Control "is performed. FIG. 2 is a perspective view showing the rear wheel steering mechanism 18, and FIG.
Next, the turning ratio variable mechanism 20 in the rear wheel turning mechanism 18 is shown in detail in the direction V-V in FIG.

As shown in FIG. 2, the rear wheel steering mechanism 18 includes:
The variable steering ratio mechanism 20, hydraulic switching valve 32, rear wheel steering rod 34, displacement transmission mechanism 36, and hydraulic power cylinder 38 are provided. The turning ratio variable mechanism 20 includes an output rod 40, a bevel gear 42, a swing shaft member 44,
A pendulum arm 46 and a connecting rod 48 are provided, and these members are accommodated in a case 50 as shown in FIG.

The output rod 40 is supported slidably casing 50 in the axial L ₃ direction, its axis by stroke displacement to the axis L direction, the rear wheel steering rod 34 through the displacement transmitting mechanism 36 In the direction (vehicle width direction), whereby the rear wheels connected to both ends of the rear wheel steering rod 34 are steered. The bevel gear 42 is supported by the case 50 so as to be rotatable about an axis L ₁ coaxial with the axis L ₃ of the output rod 40. Then, the pinion 52a of the rear end of the transfer shaft 52 to the bevel gear 42 meshing is adapted to rotate about the axis L ₁ along with the rotation by the steering of the steering wheel 30. That is, the front wheel steering angle θ _F is input from the front wheel steering mechanism 14 to the rear wheel steering mechanism 18 via the transmission shaft 52.

The oscillating shaft member 44 has an axis L _{2 that} can take a position (position shown) coaxial with the axis L ₃ of the output rod 40.
And is fixed to the swing gear 54. The oscillating gear 54 meshes with a worm 58 that is rotated by driving of a servomotor 56 controlled by the control unit 22, and rotates around an axis perpendicular to the paper plane intersecting with the axis L ₂ , thereby oscillating. The shaft member 44 is also rotated at the same time. That is, as will be apparent from the detailed description later, the servo motor 56 can variably set the steering ratio depending on the rotational angle position.

The pendulum arm 46, be coupled to swingably rocking shaft member 44 about the axis L ₂ of the pivot shaft member 44, the axis L ₄ of該振Ko arm 46, the pivot shaft member 44
The connection position to the swing shaft member 44 is determined so as to pass through the intersection of the rotation axis of the swing shaft member 44 and the axis L ₂ of the swing shaft member 44.
Connecting rod 48 has an axis L ₅ parallel to the axis L ₃ of the output rod 40 is connected to the output rod 40, bevel gear 42 and the pendulum arm 46. Connected to the output rod 40 it is done by screwing one end of the connecting rod 48 fixed to the lever 40a to the end portion of the output rod 40, connected to the bevel gear 42, from the axis L ₁ of the bevel gear 42 This is achieved by inserting the other end of the connecting rod 48 into an insertion hole 42a formed in the bevel gear 42 at a point of the distance γ,
The pendulum arm 46 is inserted into an insertion hole 60a of a ball joint member 60 provided at an end of the connection rod 48 so as to be rotatable in all directions.
Therefore, the connecting rod 48 is fixed with respect to the output rod 40, but the axis L _{5 with} respect to the bevel gear 42.
Is slidable in the direction (i.e. the axis L ₃ direction), the axis L ₃ in the state of the axis L ₄ direction (for pendulum arm 46
(In the direction perpendicular to the direction). The axis L ₄ of the pendulum arm 46 is changed to the axis L ₄ by the rotation of the swing shaft member 44.
Inclination with respect to the orthogonal direction of, but the pendulum arm 46 in the inclined direction so that the slide comprises a sliding component orthogonal the direction of the axis L ₃ in this case, and the rotation of the ball joint member 60 since挾角change in the axis L ₄ and the axis which L ₅ is absorbed by the action, component in the orthogonal direction of the axis L ₃ of the force transmitted from the pendulum arm 46 to the connecting rod 48 it is absorbed in the connection point, Relative movement in this direction becomes possible.

[0021] Thus, the connection between the connecting rod 48 and the pendulum arm 46 in the steering-angle-ratio adjusting mechanism 20, so have been made so as to be moved relative to each other in the direction perpendicular to the axis L _3, pendulum arm 46 The locus of the connection point between the pendulum arm 46 and the connection rod 48 when is rotated is the axis L ₃
Is a circular locus or an elliptical locus on the outer peripheral surface of a cylinder having a radius γ centered at.

FIG. 4 shows that the axis L ₂ of the swinging shaft member 8 is inclined by θ with respect to the axis L ₃ of the output rod 40 (ie, the axis L ₄ of the pendulum arm 46 is perpendicular to the axis L ₃ ). FIG. 6 is a diagram showing how the output rod 40 is displaced when the output rod 40 is tilted θ. As apparent from the figure, even pendulum arm 46 swings to the left or right direction, the displacement of the connecting point between the connecting rod 48 and the pendulum arm 46 being equal the swing amount, respectively the axis L ₃ direction S, and the output rod 40 and coupling rod 48 is respectively also the axis L ₃ direction displacement of the output rod 4 from being fixedly connected S.

As described above, the output rod 40 shown in FIG.
Are equal to each other if the swing amount of the pendulum arm 46 is equal. However, the displacement amount S itself is the same as the steering amount of the steering wheel, and the rotation amount of the bevel gear 42 accompanying this is the same. However, it changes depending on the magnitude of θ. Accordingly, the steering ratio θ _S is determined by the servo motor 5
6 can be set and changed by setting and changing the magnitude of the inclination θ of the swing shaft 46 by the operation control of 6.
Further, the swing shaft member 44 can be tilted not only counterclockwise but also clockwise as described above. At this time, the moving direction of the output rod 40 with respect to the rotation of the bevel gear 42 is opposite to the above case. Become. As a result, it is possible to steer the steering wheel or steer the rear wheels in the same or opposite phases with respect to the front wheels.

The turning ratio θ _S set and changed by the turning ratio variable mechanism 20 is determined by the turning ratio sensor 28 attached to the turning shaft member 44 as shown in FIG. 44 is detected based on the inclination θ. Next, portions other than the variable steering ratio mechanism 20 in the rear wheel steering mechanism 18 will be described.

First, the hydraulic switching valve 32 is provided with a valve housing 62 and a housing 6 inside the housing 62.
It consists displaceably housed spool 64. an axis parallel L ₆ direction to the axis L ₃ of the output rod 40 with respect to 2. The spool 52 is displaced by the output rod 40 and the rear wheel steering rod 34 via the displacement transmission mechanism 36. Supply of hydraulic pressure to the hydraulic power cylinder 38 is controlled by the displacement of the spool 64. That is, when the spool 64 is displaced rightward from a neutral position with respect to the illustrated valve housing 62, hydraulic pressure is supplied to the right oil chamber 66 of the hydraulic power cylinder 38, When displaced to the left, the oil chamber is supplied to the left oil chamber 68 of the hydraulic power cylinder 38.

The rear wheel steering rod 34 is connected to the chamber rod 4
0 extending in the axial L ₃ parallel to the vehicle width direction, and tie rods (not shown) displaced in that direction, which steers the rear wheels coupled to the right and left ends through the knuckle arms, the displacement hydraulic This is performed by the hydraulic pressure of the power cylinder 38. The rear wheel steering rod 34 is provided with a centering spring 70. If the hydraulic system of the hydraulic power cylinder 38 is lost due to damage or failure of the hydraulic system of the hydraulic switching valve 32 or the hydraulic power cylinder 38, or damage or failure of the mechanical system of the rear wheel steering device 10, the hydraulic system When the system is released to the drain and the hydraulic pressure in the hydraulic power cylinder 38 is lost, the rear wheel steering rod 34 is positioned by the centering spring 70 at a neutral position, that is, at a position where the rear wheel is not steered and is in a straight running state. In addition, it is configured to achieve a so-called fail-safe.

The hydraulic power cylinder 38 is for displacing the rear wheel steering rod 34 in the vehicle width direction by an oil compression force, and a piston 72 is directly fixed to the rear wheel steering rod 34. Left and right oil chambers 68, 6
6 are provided.
The seal members 74 and 76 are fixed to a housing 78 of the hydraulic power cylinder 38 and are slidable with the rear wheel steering rod 34.

The displacement transmission mechanism 36 includes an output rod 34
, The spool 64 and the rear wheel steering rod 34 are engaged with each other, the displacement of the output rod 40 causes the spool 64 to be displaced in a predetermined direction, and the rear wheel steering rod generated by the displacement of the spool 64. 3
4 is configured to be operated in a direction to displace the spool 64 in a direction opposite to the above direction.

That is, the displacement transmitting mechanism 36 is constituted by a cross lever composed of a vertical lever and a horizontal lever.
One end A of the vertical lever is connected to the output rod 40, the other end B is connected to the rear wheel steering rod 34, one end of the horizontal lever is connected to the case of the rear wheel steering device 10 which is fixed in an oblique body, and the other end D is connected to the spool 64.
Is engaged. The engagement ends A, B, and D are respectively provided with an output rod 40, a rear wheel steering rod 34, and a spool 64.
Are engaged with each other so as to be axially immovable and movably and rotatably in other directions, and the engagement end C is rotatably and non-movably engaged by a ball joint. ing.

[0030] By the output rod 40 strokes displaced in the axial L ₃ directions, allowed displace the rear wheel steering rod 34 through the displacement transmitting mechanism 36 in the axial direction, thereby, the both ends of the rear-wheel steering rod 34 Although the rear wheel (not shown) connected to the steering unit is steered, the operation principle of the steering amount transmission is not directly related to the present invention, and this is described in Japanese Patent Application Laid-Open No. 1-273772. Since it is described in detail, its detailed description is omitted.

As described in detail above, the rear wheel according to the present embodiment
The steering device 10 is mechanically connected to the front wheel steering mechanism 14.
Variable steering ratio mechanism 20 provided in rear wheel steering mechanism 18
Control of phase inversion by controlling
When the front wheel 12 is at zero steering angle, the rear wheel 14 is
Thus, the steering angle can be reliably maintained at zero. Next, the real
The control procedure according to the embodiment will be described with reference to two methods.
You. The control shown in these two methods is the control unit.
Target turning ratio TGθ by knit 22 _SSettings and motor
56 is a control of the control gain.First method The first method will be described with reference to FIG. This second
The first method is that the brake switch 70 is on and the car
Speed V decreases rapidly (−ΔV> −ΔV₀V₀Is fixed
Number), the steering angle is a predetermined value (θ_F0)
Is: (Brake ON) * (− ΔV> −ΔV₀) * (Θ_F≧ θ_F0) ....... If (1) is true, the following control is performed. That is,
In step S10, the target turning ratio TGθ_SAnd calculate it
Output to the data 56. However, as shown in step S12
The steering angle is a predetermined value θ_F0If it is more than
The current flowing through the motor 56 is limited.

FIG. 6 shows the operation at this time. When the sudden braking starts at time t ₀ , if the steering angle of the steering wheel is equal to or larger than θ _F0 , the target turning ratio TGθ _S decreases according to the vehicle speed as shown in FIG. 6, but the current flowing to the motor is limited. Therefore, the actual steering ratio θ _S falls later than the actual steering ratio θ _S (detected by the sensor 28). As a result, when the vehicle is suddenly braked during turning, the turning ratio is delayed from oscillating in the opposite phase, so that a sudden change in the behavior of the vehicle is prevented.

[0033] Even if sudden braking is performed, it is less than steering angle theta _F0, times in order to give priority to the head of the focus to avoid performance, control gain of the motor as compared with the case of the above steering angle theta _F0 Do not lower. Further, once the conditions of steps S2, S4, and S6 are satisfied, the control for reducing the control gain of the motor 56 is continued for a predetermined time. This is because the sudden braking operation is often performed in several steps, and limiting the motor gain every time the brake is turned on means that the control oscillates and the stability of the vehicle is rather reduced. This is because it is inhibited.

The "normal control" in step S8
Means that the target turning ratio TGθ _S and the target rear wheel steering angle θ _RT are as follows: θ _RT = k ₁ · V · θ _F + k ₂ · V · ψ (2) Set to. The second approach the second approach, the conditions of (1) in the first approach
When the steering angle is less than the steering angle θ _F0 , the TG θ S is not updated in the first method in step S10, but the TG θ S is fixed, and the control gain of the motor is limited. This is to prevent the "slipping" phenomenon more reliably than the technique.

That is, in FIG. 7, in steps S20, S22, and S24, the satisfaction of the above condition (1) is monitored. Under the condition (1) above,
In step S24, the steering wheel angle is less than the predetermined value (θ _F0 ).
Then, in step S26, it is determined that this control is being executed.
The flag F to be stored is turned on, and at step S27
Reset the timer TM. Also, in step S28,
The turning ratio TGθS is fixed, and the motor is set in step S30.
The control for suppressing the control gain of 56 is continued. Thus,
When the vehicle is suddenly decelerating, the steering wheel angle is less than the specified value (θ _F0 )
If the target steering ratio is fixed,
The vehicle position is stabilized because the inbound is restricted. On the other hand
Once the above condition (1) is satisfied,
In step S34, the flag F is turned on.
Is determined.

When the flag F is turned on, even if one of the above conditions (1) becomes unsatisfied, the flag F is set. Therefore, the flow proceeds to step S36, where the target rotation is performed according to the equation (2). to calculate the rudder ratio TGθ _S. Then, in step S38, the control gain of the motor is suppressed. The control of step S36 and step S38 is the same as the operation of step S10 and step S12 in the first method. Then, in step S40, the timer TM starts counting up.

When the control from the start of counting by the timer TM in steps S36 to S38 to the time-out is compared with that in steps S28 to S30, the former has a fixed steering ratio, whereas the latter has a fixed steering ratio. Is changed according to the vehicle speed V at that time according to the equation (2). That is, since the latter performs the steering ratio control according to the generation of the iodine, the turning property is improved. this is,
The fact that at least one of the conditions (1) is not satisfied is based on the reason that the turning performance may be slightly more important than the maneuverability.

As described above, according to this embodiment,
The following effects can be obtained. 1: Since the high-speed stepping motor is used in the variable steering ratio mechanism, the advantage of the yaw rate feedback control of agile turning is promoted during normal running. 2: The abrupt shift of the steering ratio to the opposite phase when sudden braking occurs during turning due to the adoption of the high-speed motor is as follows: 2-1: By reducing the rotation speed of the electric motor, and 2-2: By fixing the steering ratio, the degree to which the gain is reduced, that is, the moe is prevented, so that stable steering performance can be secured even in the case of sudden braking during turning. 3: The degree of decrease in the rotation speed is greater in the case of sudden braking during turning than in the case of sudden deceleration while traveling straight, so that during straight traveling, the effect of yaw rate feedback control is exerted, thereby avoiding performance. Can be maximized. 4: The greater the steering angle of the steering wheel, that is, the steeper the turn, the greater the degree of decrease in the rotation speed of the motor. 5: Once the regulation control is started, by continuing for a predetermined time, the regulation control of the motor gain does not become intermittent even if the deceleration operation is performed intermittently.

The present invention can be variously modified without departing from the spirit thereof. For example, in the above embodiment, the control gain has a stepped shape, but may have a linear characteristic.

[0040]

As described above, according to the first aspect of the present invention, the drive gain is made variable in the rear wheel steering device which performs rear wheel turning control using the vehicle speed, the steering angle and the yaw rate as parameters. Actuator means for driving the rear wheels to turn, means for detecting turning of the vehicle, means for detecting sudden deceleration, and regulating means for regulating the drive gain of the actuator means low when sudden deceleration is detected The restricting means makes the regulation of the drive gain at the time of sudden deceleration during turning larger than the regulation at the time of sudden deceleration while traveling straight.

As a result, normally, when the drive gain is set to a high value and sudden braking is applied during turning, the drive gain of the actuator is suppressed to a low level, so that the fluctuation of the rear wheel steering angle is prevented from becoming sharp. Is done. In addition, since the regulation of the drive gain at the time of sudden deceleration during turning is greater than the regulation at the time of sudden deceleration during straight traveling, avoidance performance during straight traveling is ensured.

According to the second aspect of the present invention, the drive gain is regulated such that the greater the steering angle, the greater the regulation amount. And the maneuverability increases. In particular, according to the third aspect of the invention, when turning and sudden braking are performed during the phase inversion control of the steering ratio, the steering ratio is prevented from shifting to the opposite phase,
Steerability is ensured.

In particular, according to the invention of claim 4, when sudden braking during turning is detected, the regulation of the gain by the regulating means is continued for a predetermined time, so that the regulation of the gain by the regulating means oscillates. Is prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a four-wheel steering system according to a preferred embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a main part of the rear wheel steering device according to the embodiment illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a configuration of a main part of the variable steering ratio mechanism according to the embodiment illustrated in FIG. 1;

FIG. 4 is a view for explaining the operating principle of the variable steering ratio mechanism of FIG. 3;

FIG. 5 is a flowchart showing a control procedure of the embodiment.

FIG. 6 is a timing chart illustrating an operation according to the gender of FIG. 5;

FIG. 7 is a flowchart illustrating a control procedure according to another embodiment.

[Explanation of symbols]

 Reference Signs List 18 rear wheel turning mechanism, 20 turning ratio variable mechanism, 22 control unit, 25 yaw rate sensor 24 vehicle speed sensor 31 hydraulic release circuit, 56 step motor, 83 open / close valve, 70 brake switch

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI B62D 137: 00 (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 6/00 B62D 7/14

Claims (4)

(57) [Claims] 1. A rear-wheel steering device that performs rear-wheel steering control using a vehicle speed, a steering angle, and a yaw rate as parameters. Means for detecting turning, means for detecting rapid deceleration, and restricting means for restricting the drive gain of the actuator means to a low value when sudden deceleration is detected ; the regulation of the driving gain during rapid deceleration, rear wheel steering apparatus for a vehicle, which comprises greater than regulations during rapid deceleration in straight. 2. A rear-wheel steering device that performs steering control of a rear wheel by using a vehicle speed, a steering angle, and a yaw rate as parameters, comprising: actuator means for driving a rear wheel having a variable drive gain to steer; Means for detecting turning, means for detecting rapid deceleration, and restricting means for restricting the drive gain of the actuator means to a low value when sudden deceleration is detected during turning, wherein the restricting means comprises: A rear wheel steering device for a vehicle, wherein the regulation amount of the gain is increased as the steering angle increases. 3. The steering control of the rear wheels, wherein the order of the steering ratio
3. The method according to claim 1, wherein phase inversion control is performed.
A rear wheel steering device for a vehicle according to claim 1. 4. A rapid braking during turning by the detecting means.
When detected, the regulation of the gain by the regulation means is prescribed.
The method according to claim 1, wherein the time is continued.
Rear wheel steering system for vehicles.