JP2001122141A - Vehicular steering gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular steering gear capable of sufficiently stabilizing vehicular behavior even when a coefficient of friction between wheels and a road surface changes. SOLUTION: A movement of a steering actuator 2 controlled in accordance with an operation of an operation member 1 is transmitted to the wheels 4 so that a steering angle changes in accordance with this movement. In a stat where a coefficient of friction between only a front inner wheel 4 and the road surface is the same or more as a preset reference value, shifted from a state where a coefficient of friction between all the wheels 4 and the road surface is below the preset reference value by an operation of the operation member 1 to right or left, a steering angle variation is increased, compared to the stave where the coefficient of friction between all the wheels 4 and the road surface is below a preset reference value, by control of the steering actuator 2 in accordance with an operation of the operation member 1 to an opposite direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle capable of transmitting a movement of a steering actuator driven in accordance with an operation of an operation member such as a steering wheel to wheels so that a steering angle changes in accordance with the movement. The present invention relates to a steering device.

[0002]

2. Description of the Related Art When a vehicle spins due to excessive speed at the time of a course change such as a lane change or a driver's driving error, the vehicle cannot be steered according to the driver's intention. In order to prevent such a spin, a system for controlling the posture of a vehicle by controlling a braking force or a driving force has been developed.

[0003]

However, the conventional vehicle attitude control system does not cope with the case where the friction coefficient between the wheels and the road surface changes, and sometimes the vehicle behavior cannot be sufficiently stabilized. is there.

[0004] It is an object of the present invention to provide a vehicle steering system that can solve the above-mentioned problems.

[0005]

According to a first feature of the present invention, there is provided an operating member, a steering actuator, and control means capable of controlling the steering actuator in accordance with the operation of the operating member. Means for transmitting the movement of the steering actuator to the front wheels for steering of the vehicle such that the steering angle changes in accordance with the movement; means for determining the coefficient of friction between each wheel of the vehicle and the road surface; By operating the operation member to one of the left and right, from the state where the friction coefficient between all the wheels and the road surface is less than a predetermined reference value, the friction coefficient between only the front inner wheel and the road surface is equal to or more than the reference value. Means for judging whether or not the state has shifted to the state, and means for judging whether or not the operation member has been operated to the other side, the friction coefficient between all wheels and the road surface is less than the reference value From the state, In the state where the friction coefficient between the road surface and the friction coefficient has shifted to the state equal to or more than the reference value, the operation members of the left and right sides of the operating member are different from the state where the friction coefficients between all wheels and the road surface are less than the reference value. The point is that the steering angle change amount by the control of the steering actuator according to the operation is increased.
When the operating member is operated to the left or right while all the wheels of the traveling vehicle are on a road surface having a small friction coefficient, the traveling direction changes and the vehicle attitude changes. When there is a road surface having a large friction coefficient in the traveling direction after this posture change, the state shifts from a state in which all wheels are on a road surface with a small friction coefficient to a state in which only the front inner wheel is on a road surface with a large friction coefficient.
When the vehicle attitude changes due to an increase in the moment to spin the vehicle due to this transition, the driver changes the steering angle in a direction to cancel the attitude change in order to prevent the vehicle from spinning. Operation member is turned back to the left and right sides as described above. According to the first aspect of the present invention, the steering angle change amount by controlling the steering actuator in accordance with the operation of the operation member on the left or right side for preventing the vehicle from being in the spin state is determined for all the traveling vehicles. Can be increased as compared to a case where the operating member is operated in a state where the wheel of the vehicle is on a road surface having a small friction coefficient. Thus, when the vehicle shifts from a road surface having a small coefficient of friction to a road surface having a large friction coefficient due to operation of the operation member to one of the right and left sides, the driver may turn the operation member to the other side to quickly spin the vehicle. Change the steering angle in the direction to cancel the moment
The vehicle can be reliably prevented from being in a spin state.

A second feature of the present invention is that an operating member, a steering actuator, control means capable of controlling the steering actuator in accordance with an operation of the operating member, and a movement of the steering actuator To the front wheels for steering of the vehicle such that the steering angle changes in accordance with the movement of the vehicle, means for detecting the coefficient of friction between each wheel of the vehicle and the road surface, all the wheels and the road surface Means for determining whether the coefficient of friction between the vehicle and the vehicle is less than a predetermined reference value, means for detecting a variable correlated with a change in posture due to a change in the traveling direction of the vehicle, Means for storing a predetermined relationship with the steering angle change amount in the direction of canceling, the coefficient of friction between all the wheels and the road surface is less than the reference value, and the absolute value of the variable amount is predetermined. When exceeding the set value , Regardless of the operation of the operation member, in that it comprises a means for controlling the steering actuator to produce a change in the steering angle determined from said stored relationship and its variables. When steering is performed to the left or right while all wheels of the traveling vehicle are on a road surface having a small friction coefficient, the traveling direction changes and the vehicle attitude changes.
When there is a road surface having a large friction coefficient in the traveling direction after this posture change, the state shifts from a state in which all wheels are on a road surface with a small friction coefficient to a state in which only the front inner wheel is on a road surface with a large friction coefficient. When the vehicle attitude changes due to an increase in the moment of spinning the vehicle due to this shift, the normal driver steers the vehicle in a direction to cancel the attitude change in order to prevent the vehicle from spinning. The operation member is turned back to the other side so that the angle changes.
However, an inexperienced driver or the like cannot properly operate the operation member to cancel the change in the posture. On the other hand, according to the second feature of the present invention, when all wheels are on a road surface having a small coefficient of friction and the absolute value of a variable correlating to a change in the vehicle attitude exceeds a set value, driving is performed. The steering actuator is controlled so as to generate a change in the steering angle in a direction to cancel the change in the vehicle attitude regardless of the operation of the operation member by the user. Thus, in a state where all the wheels are on a road surface having a small friction coefficient, a change in the vehicle attitude can be suppressed in advance before shifting from that state to a state where only the front inner wheel is on a road surface having a large friction coefficient. This prevents the vehicle from spinning when shifting to a state where only the front inner wheel is on a road surface having a large friction coefficient. It is preferable to detect the yaw rate of the vehicle as a variable correlated with the change in the attitude of the vehicle. Since the attitude of the vehicle changes due to the yaw motion when the traveling direction changes, a yaw moment acts on the vehicle. Therefore, by determining the amount of change in the steering angle in a direction to cancel the change in the attitude of the vehicle according to the yaw rate of the vehicle, the change in the attitude of the vehicle can be reliably suppressed.

In the present invention, means for storing a predetermined relationship among the friction coefficient, the vehicle speed, and the rotation speed of each wheel,
It is preferable to include means for detecting the vehicle speed, means for detecting the rotational speed of each wheel, and means for calculating the friction coefficient from the stored relationship, the detected vehicle speed and the wheel rotational speed. Since the rotational speed of each wheel increases as the friction coefficient between each wheel and the road surface decreases and as the vehicle speed increases, the relationship between the friction coefficient, the vehicle speed, and the rotational speed of each wheel increases. By pre-determining and storing,
The friction coefficient can be obtained by detecting the vehicle speed and the wheel rotation speed. Accordingly, the determination whether the friction coefficient between all the wheels and the road surface is less than the reference value and the determination whether only the friction coefficient between the front inner wheel and the road surface are equal to or more than the reference value are accurately performed. It can be carried out.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. The vehicle steering system shown in FIG.
The movement of the steering actuator 2 driven in response to the rotation operation of the operation member 1 simulating a steering wheel changes the steering angle according to the movement without mechanically connecting the operation member 1 to the wheels 4. To the front left and right wheels 4 for steering.

The steering actuator 2 can be constituted by an electric motor such as a known brushless motor. The steering gear 3 has a motion conversion mechanism that converts the rotational motion of the output shaft of the steering actuator 2 into a linear motion of the steering rod 7. The movement of the steering rod 7 is transmitted to the wheel 4 via the tie rod 8 and the knuckle arm 9, and the toe angle of the wheel 4 changes. As the steering gear 3, a known gear can be used, and the configuration is not limited as long as the movement of the steering actuator 2 can be transmitted to the wheels 4 so that the steering angle changes. In a state where the steering actuator 2 is not driven, the wheel alignment is set so that the wheels 4 can return to the straight steering position by the self-aligning torque. The rear left and right wheels may also transmit the movement of the steering actuator for steering.

The operating member 1 is connected to a rotating shaft 10 rotatably supported by the vehicle body. A reaction force actuator 19 for applying a torque to the rotating shaft 10 is provided to apply a steering reaction force required for steering the operation member 1. The reaction force actuator 19 can be constituted by an electric motor such as a brushless motor having an output shaft integrated with the rotating shaft 10.

An elastic member 30 is provided for giving elasticity in a direction for returning the operating member 1 to the straight steering position. The elastic member 30 can be constituted by, for example, a spring that gives elasticity to the rotating shaft 10. When the reaction force actuator 19 does not apply torque to the rotating shaft 10, the operating member 1 returns to the straight steering position due to its elasticity.

An angle sensor 11 for detecting an operation angle δh corresponding to the rotation angle of the rotary shaft 10 as an operation input value of the operation member 1 is provided. A torque sensor 12 for detecting a torque transmitted by the rotary shaft 10 as an operation torque T of the operation member 1 is provided. A steering angle sensor 13 for detecting the steering angle δ of the wheel 4 is provided. In the present embodiment, the steering angle sensor 13 is constituted by a potentiometer for detecting the operation amount of the steering rod 7 corresponding to the steering angle δ. Speed sensor 14 for detecting vehicle speed v
Is provided. A wheel speed sensor 15 for detecting each rotation speed of each wheel 4 is provided.

The steering actuator 2, the angle sensor 11, the torque sensor 12, the steering angle sensor 13, the speed sensor 14, and the wheel speed sensor 15 are connected to a control device 20 constituted by a computer.

The control procedure by the control device 20 will be described with reference to the flowchart of FIG. First, detection data of the vehicle speed v, the steering angle δ, the operation angle δh, the operation torque T, and the wheel rotation speed by each sensor are read (step 10).
1).

Next, as the operation reaction force, the target steering torque T^* 
The reaction force actuator 19 is controlled so that
(Step 102). In the present embodiment, the target steering
Luc T ^* Is a function K1 of the operation angle δh, and the function K1
Are predetermined and stored in the control device 20. This function
Target steering angle determined according to the detected operation angle δh based on K1
Luc T^* The deviation obtained by subtracting the detected operating torque T from
Thus, the reaction force actuator 19 is controlled. An example
For example, as the operation angle δh increases, the target steering torque T^* But
The function K1 is determined to be smaller.

Next, it is determined whether or not the coefficient of friction between all the wheels 4 and the road surface is less than a preset reference value (step 103). The control device 20 stores a predetermined relationship between the friction coefficient between each of the wheels 4 of the vehicle and the road surface, the vehicle speed, and the rotation speed of each wheel, and stores the stored relationship and the speed sensor 14. From the vehicle speed v detected by the above and the wheel rotation speed detected by the wheel speed sensor 15, the friction coefficient is obtained. When the friction coefficient is equal to or more than the reference value, the state where all the wheels 4 are on the low μ road surface having a small friction coefficient is shifted to the state where only the front inner wheel is on the high μ road surface having a large friction coefficient. In doing so, it may be determined so that the vehicle is not likely to be in a spin state. Note that the reference value may be a function of a variable representing a vehicle running state such as the vehicle speed v and the steering angle δ. For example, the reference value may be reduced as the vehicle speed v and the steering angle δ increase.

If the coefficient of friction between all the wheels 4 and the road surface is less than the reference value in step 103, the low μ flag is turned on (step 104), and then the steering angle is set to the target value δ.
^The steering actuator 2 is controlled so that it can be set to ^* (step 105). In the present embodiment, the target steering angle δ ^* is a function K2 of the operation angle δh that is the operation input value.
The function K2 is predetermined and stored in the control device 20. The steering actuator 2 is controlled such that a deviation obtained by subtracting the detected steering angle δ from the target steering angle δ ^* determined according to the detected operation angle δh based on this function K2 becomes zero. The steering actuator 2 has an operation angle δh
The operation member 1 is not limited to being controlled only according to
What is necessary is just to be able to control according to the operation of. For example, the detected operation torque T is used as the operation input value instead of the detected operation angle δh,
The target steering angle δ ^* may be determined as a function of the operating torque T, and the target steering angle δ ^* may be determined from the detected operating torque T. Further, the target steering angle δ ^* may be a function of, for example, the vehicle speed v as well as the operation angle δh, and the target steering angle δ ^* may be changed not only by the operation angle δh but also by the vehicle speed v. Further, in order to prevent the vehicle behavior from becoming unstable when controlling the steering actuator 2 in accordance with the operation of the operation member 1 to change the steering angle δ, for example, the vehicle behavior may become unstable. In some cases, a vehicle behavior stabilizing system that controls the attitude of the vehicle by controlling the braking force or the driving force may be used together.

Next, it is determined whether or not to end the control, for example, based on the on / off of a key switch for starting the engine of the vehicle (step 106). If not, the process returns to step 101.

If the friction coefficients between all the wheels 4 and the road surface are not less than the reference value in step 103, it is determined whether or not the low μ flag is on (step 107). At 105, the steering actuator 2 is controlled.

If the low μ flag is on in step 107, it is determined whether or not the spin flag is on (step 108). If the spin flag is not on, it is determined whether the friction coefficient between the front inner wheel and the road surface is equal to or greater than the reference value and the friction coefficient between the remaining wheels and the road surface is less than the reference value. (Step 109). That is,
When all the wheels 4 of the traveling vehicle 100 are on the road surface U1 having a small coefficient of friction as shown by the solid line in FIG. 4 and the operating member 1 is operated to the left or right, the traveling direction changes as shown by the dashed line and The vehicle attitude changes. When there is a road surface U2 having a large friction coefficient in the traveling direction after the change, from a state where all the wheels 4 are on a road surface having a small friction coefficient, to a state where only the front inner wheel 4 is on a road surface U2 having a large friction coefficient. Transition. Therefore, by operating the operation member 1 to the left or right, the friction coefficient between all the wheels 4 and the road surface is changed from a state where the friction coefficient is less than a predetermined reference value to the friction coefficient between only the front inner wheel 4 and the road surface. It is determined whether the state has shifted to the reference value or more. In the present embodiment, the operation direction of the operation member 1 is detected by the torque sensor 12, but the detection means is not particularly limited.

In step 109, when only the front inner wheel 4 is on the road surface U2 having a large friction coefficient, the moment for spinning the vehicle increases. In this case, the spin flag is turned on (step 110), and then step At 105, the steering actuator 2 is controlled.

If the spin flag is on in step 108, it is determined whether the operating member 1 has been operated to the left or right (step 111). That is, the operation member 1
Is operated on one of the left and right sides to shift from a state in which all the wheels 4 are on the road surface U1 with a small friction coefficient to a state in which only the front inner wheel 4 is on a road surface U2 with a large friction coefficient, and try to spin the vehicle. When the moment to be increased increases, as shown by a two-dot chain line in FIG. 4, it is determined whether or not the driver has turned the operating member 1 to the left or right to prevent the vehicle from spinning.

If the turning operation has not been performed in step 111, the steering actuator 2 is controlled in step 105.

When the turning operation is performed in step 111, the steering actuator 2 is controlled so that the steering angle can be set to the target value δ ^* (step 1).
12). In step 112, ^* the target steering angle [delta] is N times the target steering angle [delta] ^* in step 105 (N
> 1), the ratio of the steering angle to the operation amount of the operation member 1 becomes larger than in step 105. That is, in the state where the friction coefficient between all the wheels 4 and the road surface is less than the reference value, and the friction coefficient between only the front inner wheel 4 and the road surface is greater than the reference value, Compared with the state where the friction coefficient between the wheel 4 and the road surface is less than the reference value, the steering angle change amount by the control of the steering actuator 2 in accordance with the turning operation of the operating member 1 to the other side is increased. Thereafter, at step 106, it is determined whether or not to end the control.

In step 109, when only the front inner wheel 4 is not on the road surface U2 having a large friction coefficient, the other wheels 4 are also on the road surface U2 having a large friction coefficient. In this case, the low μ flag and the spin flag are released (step 11).
3) Then, in step 105, the steering actuator 2 is controlled.

According to the first embodiment, by operating the operating member 1 to the left or right, from a state where all the wheels 4 are on the road surface U1 having a small friction coefficient, only the front inner wheel 4 is changed to a road surface having a large friction coefficient. By shifting to the state at U2, when the moment for spinning the vehicle increases, the steering according to the turning operation of the operation member 1 to the other side to the left or right for preventing the vehicle from spinning. The change amount of the steering angle by the control of the actuator 2 can be increased as compared with the case where the operation member 1 is turned back while all the wheels 4 of the traveling vehicle are on the road surface U1 having a small friction coefficient. Thereby, when the vehicle shifts from the road surface U1 having a small coefficient of friction to the road surface U2 having a large friction coefficient by the operation of the operation member 1 to one of the right and left sides, the driver quickly switches the operation member 1 to the other side, so that the vehicle is quickly operated. By changing the steering angle in a direction to cancel the moment for spinning the vehicle, it is possible to reliably prevent the vehicle from spinning.

A second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and differences will be described. In the vehicle steering system according to the second embodiment shown in FIG. 5, a yaw rate sensor 16 that detects a yaw rate γ of the vehicle as a variable correlated with a posture change due to a change in the traveling direction of the vehicle is connected to the control device 20. The predetermined relationship between the yaw rate γ and the amount of change in the steering angle in the direction to cancel the change in attitude is determined by the control device 2.
0 is stored. The sign of the yaw rate γ is reversed when the traveling direction of the vehicle changes to one of the left and right sides and when it changes to the other side.

The control procedure of the control device 20 according to the second embodiment will be described with reference to the flowchart of FIG.
First, the vehicle speed v, yaw rate γ, steering angle δ,
The detection data of the operation angle δh, the operation torque T, and the wheel rotation speed are read (step 201).

Next, the target steering torque T ^{* is used} as the operation reaction force ^.
The reaction force actuator 19 is controlled so that the force can be applied (step 202). The setting of the target steering torque T ^* and the control of the reaction force actuator 19 are the same as in the first embodiment.

Next, it is determined whether or not the coefficient of friction between all the wheels 4 and the road surface is smaller than a preset reference value (step 203). The detection of the friction coefficient and the setting and determination of the reference value are the same as in the first embodiment.

If the coefficient of friction between all the wheels 4 and the road surface is not less than the reference value in step 203, the steering actuator 2 is controlled so that the steering angle can be set to the target value δ ^* (step 204). ). The target steering angle δ
The setting of ^* and the control of the steering actuator 2 are the same as in the first embodiment.

Next, it is determined whether or not to end the control, for example, based on the on / off of a key switch for starting the engine of the vehicle (step 205). If not, the process returns to step 201.

If the coefficient of friction between all the wheels 4 and the road surface is smaller than the reference value in step 203, it is determined whether or not the absolute value of the detected yaw rate γ exceeds a predetermined set value α (step 203). Step 206). The set value α
Even if the coefficient of friction between all the wheels 4 and the road surface is less than the reference value, and the friction coefficient between only the front inner wheel 4 and the road surface is higher than the reference value, the vehicle If the absolute value of the yaw rate γ is equal to or smaller than the set value α, the vehicle behavior is set so as not to be unstable, and may be zero.

In step 206, the detected yaw rate γ
Is smaller than or equal to the set value α, the steering actuator 2 is controlled in step 204.

In step 206, the detected yaw rate γ
Is greater than the set value α, the steering actuator 2 is controlled so as to generate a change in the steering angle obtained from the yaw rate γ and the stored relationship, regardless of the operation of the operating member 1. That is, the target steering angle δ ^* is a function K4 of the yaw rate γ of the vehicle, and the deviation obtained by subtracting the detected steering angle δ from the target steering angle δ ^* determined based on the detected yaw rate γ based on the function becomes zero. The steering actuator 2 is controlled (step 207). Thereby, when the coefficient of friction between all the wheels 4 and the road surface is less than the reference value and the absolute value of the yaw rate γ exceeds the set value α, regardless of the operation of the operation member 1, The steering actuator 2 is controlled so as to generate a change in the steering angle determined from the yaw rate γ and the stored relationship, that is, to change the steering angle in a direction to cancel the change in the attitude of the vehicle. Thereafter, in step 205, it is determined whether or not to end the control. Others are the same as the first embodiment.

As shown by the solid line in FIG.
When all the wheels 4 of 00 are steered to the left or right in a state where the wheels 4 are on the road surface U1 having a small friction coefficient, the traveling direction changes and the vehicle attitude changes as shown by the dashed line. When there is a road surface U2 having a large friction coefficient in the traveling direction after this posture change, all the wheels 4 are on the road surface U1 having a small friction coefficient.
From the upper state, the state shifts to the state where only the front inner wheel 4 is on the road surface U2 having a large friction coefficient. With this transition, vehicle 1
If the vehicle attitude changes due to an increase in the moment for spinning 00, the vehicle 100 may be a normal driver.
The operation member 1 is turned back to the left or right so that the steering angle changes in a direction to cancel the change in the posture in order to prevent the spinning state. However, immature drivers, etc.
The operation of the operation member 1 for canceling the posture change cannot be performed properly. On the other hand, according to the second embodiment, when all the wheels 4 are on a road surface having a small friction coefficient and the absolute value of the yaw rate γ correlated with the change in the vehicle attitude exceeds the set value α. Operation member 1 by driver
The steering actuator 2 is controlled so as to generate a change in the steering angle in a direction to cancel the change in the vehicle attitude, regardless of the operation of the vehicle. Thereby, as shown by the two-dot chain line in FIG. 7, when all the wheels 4 are on the road surface U1 having a small friction coefficient, the state shifts from that state to the state where only the front inner wheel 4 is on the road surface U2 having a large friction coefficient. Before changing the vehicle, the change in the vehicle attitude can be suppressed in advance. Thereby, the front inner ring 4
The vehicle 100 can be prevented from spinning when shifting to a state where only the friction coefficient is on the road surface U2. Further, according to the second embodiment, the yaw rate γ of the vehicle 100 is detected as a variable correlated with the posture change. Vehicle 10
In the case of 0, since the posture changes due to the yaw motion when the traveling direction changes, the yaw moment acts on the vehicle 100. Therefore, by determining the amount of change in the steering angle in the direction to cancel the change in the attitude of the vehicle 100 according to the yaw rate γ of the vehicle 100, the change in the attitude of the vehicle 100 can be reliably suppressed.

In the first and second embodiments, the rotational speed of each wheel 4 increases as the friction coefficient between each wheel 4 and the road surface decreases and as the vehicle speed v increases. The relationship between the friction coefficient, the vehicle speed v, and the rotation speed of each wheel 4 is predetermined and stored, and the friction coefficient is determined by detecting the vehicle speed v and the wheel rotation speed. Thereby, all the wheels 4
It is possible to accurately determine whether or not the friction coefficient between the vehicle and the road surface is less than the reference value and whether or not only the friction coefficient between the front inner wheel and the road surface is equal to or more than the reference value.

The present invention is not limited to the above embodiments.
For example, the present invention may be applied to a vehicle in which an operation member and wheels are mechanically connected. Further, in the second embodiment, a lateral acceleration other than the yaw rate, for example, a lateral acceleration may be detected as a variable correlated with a posture change due to a change in the traveling direction of the vehicle.

[0039]

According to the present invention, it is possible to provide a vehicle steering system capable of sufficiently stabilizing the vehicle behavior even when the friction coefficient between the wheels and the road surface changes.

[0040]

Disclosure of Other Techniques In each of the above embodiments of the present invention, the friction coefficient between each wheel 4 and the road surface is detected. However, it is necessary to determine the friction coefficient between each wheel 4 and the road surface. If not, a value corresponding to the load of the steering actuator 2, for example, a time integrated value of the load current is obtained, and a value corresponding to the steering angle δ, for example, the operation amount of the steering rod 7, is obtained. Alternatively, the reference value of the integrated value and the steering angle corresponding value may be determined in advance and stored in the control device 20, and the obtained value may be compared with the reference data to estimate the friction coefficient. That is, when the integral value is large and the steering angle corresponding value is small, the friction coefficient is large, and when the integral value is small and the steering angle corresponding value is large, the friction coefficient is small as compared with the stored reference data. The coefficient of friction can be determined from the ratio of the determined value to.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a steering device according to a first embodiment of the present invention;

FIG. 2 is a flowchart showing a control procedure of the steering device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a control procedure of the steering device according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an operation of the steering device according to the first embodiment of the present invention;

FIG. 5 is a configuration explanatory view of a steering device according to a second embodiment of the present invention.

FIG. 6 is a flowchart showing a control procedure of a steering device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating the operation of a steering device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a technique for obtaining a friction coefficient between a wheel and a road surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Operating member 2 Steering actuator 4 Wheel 11 Angle sensor 13 Steering angle sensor 14 Speed sensor 15 Wheel speed sensor 16 Yaw rate sensor 20 Control device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shiro Nakano 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka Inside Koyo Seiko Co., Ltd. No. 8 F-term in Koyo Seiko Co., Ltd. (reference) 3D032 CC05 DA03 DA04 DA15 DA23 DA24 DA33 DA82 DB13 DC34 DD02 EA01 EB04 EB12

Claims (4)

[Claims] An operating member, a steering actuator, control means capable of controlling the steering actuator in accordance with an operation of the operating member, and a movement of the steering actuator. Means for transmitting to the front steering wheel of the vehicle so as to change, means for determining the coefficient of friction between each wheel of the vehicle and the road surface, and all the wheels and the road surface Means for judging whether or not the friction coefficient between the front inner wheel and the road surface has shifted from the state in which the coefficient of friction is less than a predetermined reference value to the state in which the coefficient of friction between the front inner wheel and the road surface is equal to or more than the reference value. Means for determining whether or not the left and right sides have been operated, from the state where the friction coefficient between all wheels and the road surface is less than the reference value, the friction coefficient between only the front inner wheel and the road surface is Move to a state above the reference value In this state, the amount of change in the steering angle due to the control of the steering actuator in accordance with the operation of the operating member to the left or right is increased compared to the state in which the friction coefficients between all the wheels and the road surface are less than the reference value. A vehicle steering system characterized by being performed. 2. An operation member, a steering actuator, control means capable of controlling the steering actuator in accordance with an operation of the operation member, and a steering angle in accordance with the movement of the steering actuator. The means for transmitting to the steering front wheel of the vehicle so as to change, the means for detecting the coefficient of friction between each wheel of the vehicle and the road surface, and the coefficient of friction between all the wheels and the road surface are preset. Means for judging whether or not the reference value is less than the reference value, means for detecting a variable correlated with a posture change due to a change in the traveling direction of the vehicle, the variable, and a steering angle change amount in a direction to cancel the posture change. Means for storing a predetermined relationship between the operating member and the friction member between all the wheels and the road surface is less than the reference value, and when the absolute value of the variable exceeds a predetermined value. Regardless of the operation of Vehicle steering apparatus characterized by comprising a means for controlling the steering actuator to produce a change in the steering angle determined from said stored relationship and its variables. 3. The vehicle steering system according to claim 2, wherein a yaw rate of the vehicle is detected as the variable correlated with a change in the attitude of the vehicle. 4. A means for storing a predetermined relationship between the coefficient of friction, the vehicle speed, and the rotational speed of each wheel, a means for detecting the vehicle speed, a means for detecting each rotational speed of each wheel, and the stored memory. The vehicle steering apparatus according to any one of claims 1 to 3, further comprising: means for calculating the friction coefficient from the detected relationship and the detected vehicle speed and wheel rotation speed.