JPH06206568A - Steering device for vehicle - Google Patents

Abstract

PURPOSE:To perform elaborate rear wheel steering control matched with direction stability and turnability even under a particular environment by correcting a rear wheel steer controlling target value to a side of improving the direction stability of a vehicle when it is running under an environment such as the vicinity of an outlet of a tunnel where the direction stability is easily decreased. CONSTITUTION:An on/off signal is input to a control unit 24 from a light switch for switching a side marker lamp lighted and put out. When an on-signal is input from the light switch in running of a vehicle, after setting a flag, a constant of a yaw rate correction term is correction increased, for instance, to 1.2 times at normal time. Thereafter, even when the on-signal is not input from the light switch, a correction increase is continued before the lapse of predetermined time. On the other hand, when the flag is reset in the case of not inputting the on-signal from the light switch, it is off from the origin, and the flag is left as reset to perform no increase correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system, and more particularly to a rear wheel steering control target value based on a predetermined detection signal relating to a running state quantity of the vehicle (for example, vehicle speed, front wheel steering angle, yaw rate, etc.). The present invention relates to a vehicle steering system configured to determine.

[0002]

2. Description of the Related Art Conventionally, a steering device for a vehicle configured to steer the rear wheels in accordance with the turning of the front wheels has conventionally been designed to steer the rear wheels in accordance with the front wheel steering angle or in accordance with the vehicle speed. It is known that a steering wheel is used.
As disclosed in Japanese Patent No. 108079, the rear wheel is steered in consideration of the front wheel steering angle change rate and the yaw rate as the traveling state amount of the other vehicles, so that the turning performance and the directional stability during traveling of the vehicle are improved. It is also known to harmonize and improve sex.

In the above steering device, the target value for rear wheel steering control is determined by adding and subtracting the signal calculation values obtained from the detection signals of the vehicle speed, the front wheel steering angle, the front wheel steering angle change rate, and the yaw rate, respectively. It is configured to steer the rear wheels according to the value.

[0004]

Thus, if the rear wheel steering control target value is determined on the basis of the predetermined detection signal relating to the running state quantity of the vehicle, the rear wheel steering in accordance with this target value is determined. As a result, it is possible to improve the harmony of the turning performance and the directional stability of the vehicle during normal traveling, but the above control may be insufficient depending on the traveling environment of the vehicle. For example, a vehicle may be suddenly exposed to a strong crosswind immediately after exiting a tunnel or a cut-through, but such a disturbance naturally reduces the directional stability of the vehicle.

On the other hand, if the target value for the rear wheel steering control is determined in consideration of the above-mentioned disturbance, it is possible to suppress the deterioration of the directional stability of the vehicle.
If this is done uniformly, the target value for rear-wheel steering control will be determined with emphasis on the directional stability of the vehicle even in a driving environment where there is no risk of the above-mentioned disturbance, so the turning of the vehicle will occur. There is a problem that sex is hindered.

The present invention has been made in view of the above circumstances, and has a grain of wood in which directional stability and turning ability of the vehicle are harmonized not only during normal traveling but also under special traveling environment. An object of the present invention is to provide a vehicle steering system capable of performing fine rear wheel steering control.

[0007]

SUMMARY OF THE INVENTION A vehicle steering system according to the present invention provides a rear wheel steering control target value for stabilizing the directional stability of a vehicle when the vehicle is traveling in an environment in which its directional stability is likely to deteriorate. The above-mentioned object is achieved by making a correction to improve the property.

That is, as described in claim 1, in a steering apparatus for a vehicle, comprising a target value determining means for determining a rear wheel steering control target value based on a predetermined detection signal relating to a running state amount of the vehicle, A traveling environment determining means for determining whether or not the traveling environment of the vehicle is an environment in which the directional stability of the vehicle is likely to be lowered is provided, and the target value determining means is configured so that the vehicle is controlled by the traveling environment determining means. When it is determined that the vehicle is traveling in an environment that tends to reduce the directional stability, the rear wheel steering control target value is configured to be corrected to a side that improves the directional stability of the vehicle. It is characterized by that.

The "rear wheel steering control target value" is not particularly limited as long as it is a target value used for the rear wheel steering control. For example, the rear wheel steering angle, the steering ratio (that is, the front wheel steering). The ratio of the rear wheel steering angle to the corner) can be adopted.

A typical example of the above-mentioned "environment in which the directional stability of the vehicle is likely to be deteriorated" is an environment in which the vehicle is traveling near a tunnel exit or a cutout exit, which is susceptible to cross winds, but is of course limited to this. Not a thing. For example, considering that it is difficult to judge the surroundings when driving at night as compared to when driving at daytime, the environment in which driving is performed at night can be included as the “environment that tends to reduce the directional stability of the vehicle”. .

The above-mentioned "correction of the target value for rear wheel steering control" is
Of course, the rear wheel steering control target value itself may be corrected, but the above-mentioned "determination of the rear wheel steering control target value" is obtained from a plurality of detection signals related to the vehicle running state amount. When a plurality of calculated signal values are added or subtracted, the target value for rear wheel steering control is corrected by a correction that increases the contribution rate to the determination of the target value for rear wheel steering control of a predetermined signal calculated value. May be As the "predetermined signal calculation value" here, for example, a signal calculation value obtained from a vehicle speed signal or a yaw rate signal can be adopted.

[0012]

When the vehicle is subjected to a disturbance such as a strong crosswind, the directional stability of the vehicle is deteriorated. However, in the present invention, the directional stability of the vehicle such as in the vicinity of a tunnel or an opening of a vehicle is stabilized. When driving in an environment that tends to reduce the vehicle stability, it is configured to correct the rear wheel steering control target value to the side that improves the directional stability of the vehicle. Can be suppressed. Further, in a traveling environment in which there is no possibility of being affected by the disturbance, the correction is not performed, so it is possible to prevent the turning ability of the vehicle from being unduly disturbed.

Therefore, according to the present invention, it is possible to perform a fine-grained rear wheel steering control in which the directional stability and the turning performance of the vehicle are harmonized not only during normal traveling but also under a special vehicle traveling environment. it can.

Further, as described in claim 5, when the vehicle width light is turned on, the rear wheel steering control target value is corrected to the side for improving the directional stability of the vehicle, and after the vehicle width light is turned off. If the above correction is canceled when a predetermined time has elapsed, the correction will be performed while the vehicle is traveling in the tunnel and near the exit of the tunnel.
It is possible to suppress the decrease in directional stability when driving near the tunnel exit with a simple method, and while turning of the vehicle inside the tunnel is not required so much, directional stability of the vehicle can be improved as much as possible for safety. It is possible to improve the directional stability of the vehicle under the desired traveling environment.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a vehicle steering system according to the present invention.

As shown in the figure, a vehicle steering system 10 according to this embodiment includes a front wheel steering mechanism 14 for steering front wheels 12.
The front wheel steering mechanism 14 is mechanically connected to the front wheel steering mechanism 14 via a transmission shaft 16. The front wheel steering angle is input to the rear wheels 18 from the front wheel steering mechanism 14 in conjunction with the front wheel steering by the front wheel steering mechanism 14. A rear-wheel steering mechanism 20 that steers to a predetermined target rear-wheel steering angle TGθ _R (which will be described later) according to θ _F , and a front-wheel steering angle θ provided in the rear-wheel steering mechanism 20. _A steering ratio variable mechanism 22 for setting and changing a steering ratio θ _S represented as a ratio of a rear wheel steering angle θ _{R to F} and a control unit 24 for controlling the steering ratio variable mechanism 22 are provided. And the control unit 24
The vehicle speed V from the vehicle speed sensor 26, the yaw rate ψ ′ from the yaw rate sensor 28, the steering ratio θ _S from the steering ratio sensor 30, and the front wheel steering angle θ _F from the front wheel steering angle sensor 32 (provided on the steering shaft). A signal is input. The configuration of the rear wheel steering mechanism 20 is publicly known from the above publication (Japanese Patent Laid-Open No. 4-108079), and thus detailed description thereof will be omitted.

[0018] The control unit 24 is obtained from each of the detection signals of the vehicle speed V, the yaw rate [psi _F2 'and front wheel steering angle theta _F, front wheel steering angle change rate theta obtained by further differentiating the front wheel steering angle theta _F' A target steering ratio TGθ _S (rear wheel steering control target value) for the steering ratio variable mechanism 22 is determined by adding / subtracting the signal calculation value, and this target steering ratio TGθ _{S is} further determined.
However, when it exceeds the predetermined allowable range set according to the vehicle speed, the target turning ratio TGθ _S is corrected to a value within the allowable range. Then, using the corrected target turning ratio TGθ _S1 , the target rear wheel steering angle TGθ _R is calculated by the following equation: TGθ _R = θ _F · TGθ _S1 .

The target turning ratio TGθ _S is expressed by the following equation: TGθ _S = -G ₁ · f ₁ (V) · θ _{S · ST} + G ₂ · K
₂ (θ _F2 ) ・ J ₂ (｜ θ ′ _F2 ｜) ・ f ₂ (V) ・ θ
_{S · YAW -G 3 · K 3} (θ F2) · f 3 (V) · θ S · STD + G
It is set at ₄ · f ₄ (V).

In the above equation, the first term on the right side is the steering angle correction term,
The second term is a yaw rate correction term, the third term is a steering angle change rate correction term, and the fourth term is a vehicle speed response term which is a base when performing rear wheel steering control according to the vehicle speed. By setting the target steering ratio TGθ _S in this manner, when the front wheels are steered from the straight traveling state based on the vehicle speed-sensitive rear wheel steering control, the rear wheels face the front wheels in the initial stage of the steering. The steering is controlled to the opposite phase side to improve the turning ability, and then the yaw rate is generated and the rear wheels are steered to the same phase side where the direction is the same as that of the front wheels to achieve directional stability. Inversion control) can be performed.

In the above equation, G ₁ , G ₂ , G ₃ , and G ₄ are constants, and the other variables are the vehicle speed V, the yaw rate ψ ′, and the front wheel steering angle θ _F, as shown in FIG. Based on this, it is calculated as follows.

First, variables f ₁ (V) and f of each term on the right side
₂ (V), f ₃ (V), and f ₄ (V) are vehicle speed sensitive gains, and map m10, m5, m13,
Each is calculated by m1. Of the above maps, maps m10 and m13 are variables f
_{The characteristics are such that 1} (V) and f ₃ (V) are 0 in the low vehicle speed and high vehicle speed regions, and have positive constant values in the medium vehicle speed region. Further, the map m5 of the above maps has a characteristic that the variable f ₂ (V) is set to 0 in the low vehicle speed region and to a constant positive value in the medium vehicle speed and high vehicle speed regions, respectively.
Furthermore, the remaining map m1 changes the variable f ₄ (V) from a negative large value in the low vehicle speed region, to a positive value in the medium vehicle speed region as the vehicle speed increases, and in the high vehicle speed region a large positive value. It is a characteristic to be a value.

Next, the variable θ _{S · ST} of the first term on the right side is a steering angle correction value, and after offsetting the front wheel steering angle θ _F by map m8 to θ _F1 , this is changed by map m11. A hysteresis is added to θ _F1 to obtain θ _F2 , and the absolute value thereof is calculated from | θ _F2 | to be calculated by a map m9. Adding the offset in the map m8 is
This is to prevent unnecessary control from being performed by providing a dead zone in the minute rudder angle region.
The reason for adding the hysteresis at 1 is to prevent hunting from occurring in the control. In the map m9, when the variable θ _{S · ST} is 0 in the small steering angle region, a value proportional to the steering angle in the medium steering angle region, a positive constant value in the large steering angle region, and a larger steering angle region. Has a characteristic of being 0 when an abnormality occurs.

Next, the variable θ _{S · YAW} of the second term on the right side is a yaw rate correction value, and after the yaw rate ψ ′ is offset by the map m2 to ψ ′ ₁ , the map m3 is obtained.
The ψ from 'hysteresis was ψ added to _{1' 2,} and calculates the map m4 by. The reason for adding the offset and hysteresis is the same as in the case of the variable θ _{S · ST} . The map m4 has the characteristic that the variable θ _{S · YAW} is set to a value proportional to ψ ′ ₂ in the small yaw rate region, a positive constant value in the medium yaw rate region, and 0 in the large yaw rate region when an abnormality occurs. .

The variable K ₂ (θ _F2 ) of the second term on the right side is
It is the steering angle sensitive gain, and θ _F2 obtained in the map m11
From the map m6. The map m6 has a characteristic that the variable K ₂ (θ _F2 ) is a value substantially proportional to θ _F2 in the small front wheel steering angle region, and a value that the increase rate decreases as the front wheel steering angle increases.

Further, the variable J ₂ (│θ ') of the second term on the right side
_F2 |) is the steering angle change rate sensitive gain, and is the map m1.
The absolute value was obtained by differentiating θ _F2 obtained in 1 | θ ′ _F2 |
Is calculated from the map m7. In the map m7, the variable J ₂ (| θ ′ _F2 |) is changed to | θ ′ _F2 |
Is small, that is, a small value in the small front wheel steering angle change rate area, a large value in the middle front wheel steering angle change rate area, and a value that is even smaller in the large front wheel steering angle change rate area than in the small front wheel steering angle change rate area. Has become.

Next, the variable θ _{S · STD} of the third term on the right side is a steering angle change rate correction value, and is calculated by the map m12 from the value θ ′ _F2 obtained by differentiating the θ _F2 obtained by the map m11. It has become. In the map m12, the variable θ _{S · STD} is
The value in the small front wheel steering angle change rate region in proportion to the theta _'F2, positive constant value in the middle front wheel steering angle change rate region, a large front wheel steering angle change rate region has the characteristic to 0 as an abnormality has occurred .

The variable K ₃ (θ _F2 ) of the third term on the right side is
It is the steering angle sensitive gain, and θ _F2 obtained in the map m11
Is calculated from the map m14. The map m14 has a characteristic in which the variable K ₃ (θ _F2 ) is a value that is substantially proportional to θ _F2 in the small front wheel steering angle region, and a value that the increase rate decreases as the front wheel steering angle increases.

The target turning ratio TGθ _S is determined by adding / subtracting the signal operation value obtained by multiplying the above constants and variables for each term on the right side of the above equation. This addition / subtraction value indicates an abnormal value. Then, since the target turning ratio TGθ _S also becomes an abnormal value, the target turning ratio TGθ _S becomes
When the allowable range set in accordance with the vehicle speed V (the shaded area in the map m15) is exceeded, the target turning ratio TGθ _S is either the upper limit value or the lower limit value within the allowable range (the curve indicated by the broken line in the map m15). ) To be corrected. The curve indicated by the solid line in the map m15 is the variable f ₄ (v) shown in the map m1.

As shown in FIG. 1, an ON / OFF signal is further input to the control unit 24 from a light switch 34 for switching ON / OFF of a side lamp.

Next, the operation of this embodiment will be described.

The rear wheel steering control by the control unit 24 is performed as shown in the flow chart of FIG.

First, when an ON signal is input from the light switch 34 while the vehicle is traveling (step S1), the vehicle enters the tunnel (or becomes a night-time traveling state,
Alternatively, after the flag F is set as having entered into the fog (step S2), the constant G ₂ of the yaw rate correction term is corrected to be 1.2 times the normal value (step S3). After that, even if the ON signal is not input from the light switch 34 (steps S1 and S4), the increase correction is continued until a predetermined time elapses (step S5), and the flag F is reset after the predetermined time elapses. The increase correction is canceled (steps S6 and S7).

On the other hand, when the ON signal is not input from the light switch 34 (step S1) and the flag F is reset (step S4), it is determined that the light switch 34 is originally OFF and the flag F is set to OFF. The above-mentioned increase correction is not performed as it is in the reset state (step S
6, S7).

With such control, the following operational effects can be obtained.

That is, the output of the yaw rate correction term is a parameter that is added in addition and subtraction for determining the target turning ratio TGθ _S , and is used to improve the directional stability of the vehicle, but in the present embodiment, Since the constant G ₂ of the yaw rate correction term is increased and corrected when the side light is turned on, and the correction is canceled when a predetermined time has elapsed after the side light is turned off, the vehicle passes through the tunnel. At that time, the above correction is performed while the vehicle is traveling in the tunnel and near the exit of the tunnel,
The directional stability of the vehicle can be improved.

That is, the turning of the vehicle is not required so much in the tunnel, but in the driving environment where it is desired to improve the directional stability of the vehicle for safety, it is possible to improve the directional stability of the vehicle. In a driving environment near the exit of the tunnel, where the vehicle is likely to suffer a disturbance such as a strong crosswind and its directional stability is likely to be degraded, it is possible to suppress the degradation of the directional stability of the vehicle. Moreover, such an effect can be obtained by a simple control method using the on / off operation of the light switch 34.

Further, even when the vehicle is not passing through a tunnel, the vehicle is in a traveling environment in which it is desired to improve the directional stability of the vehicle as much as possible for safety, such as when the vehicle is traveling at night or when entering a fog. Sometimes the light switch 34
The above-described increase correction is performed by the on / off operation of (1) at least until such a vehicle traveling environment is exited, so that the directional stability of the vehicle can be improved.

As described above, according to the present embodiment, the fine-grained rear wheel steering control that balances the directional stability and the turning performance of the vehicle not only during normal traveling but also under a special vehicle traveling environment is performed. It can be carried out.

If the target is only when passing through the tunnel, the illumination in the tunnel may be detected instead of the on / off operation of the light switch 34.

In the present embodiment, the traveling environment that tends to reduce the directional stability of the vehicle is the environment where the vehicle is traveling near the exit of the tunnel. However, in addition to this, traveling that tends to reduce the directional stability of the vehicle. As an environment, there is an environment where the vehicle is running near the cut-out exit, but in this case, if it is determined that the vehicle is running near the cut-out exit using, for example, an illuminance sensor, Similar to the example
It is possible to suppress a decrease in directional stability of the vehicle.

In the vehicle steering system according to the above embodiment, the front wheel steering mechanism 14 and the rear wheel steering mechanism 20 have the transmission shaft 16.
The steering ratio (target steering ratio TGθ _S ) is adopted as the target value for rear wheel steering control, and the correction value TGθ _S1 of the target steering ratio TGθ _S and the front wheel steering are used. from the angle θ _F, TGθ the arithmetic expression _R = _{θ F} · _{TGθ S1,} is configured so as to calculate a target rear wheel steering angle TGθ _R, front steering angle target rear-wheel steering angle TGθ _R θ _F It is needless to say that the same operation and effect as in the present embodiment can be obtained by using the above control method even in a vehicle steering system configured to perform direct calculation independently of the above.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a vehicle steering system according to the invention.

FIG. 2 is a control block diagram showing the operation of the above embodiment.

FIG. 3 is a flow chart showing the operation of the above embodiment.

[Explanation of symbols]

10 Steering Device 14 Front Wheel Steering Mechanism 20 Rear Wheel Steering Mechanism 22 Steering Ratio Variable Mechanism 24 Control Unit (Target Value Determining Means, Running Environment Determining Means) 26 Vehicle Speed Sensor 28 Yaw Rate Sensor 30 Steering Ratio Sensor 32 Front Wheel Steering Angle Sensor 34 Light switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B62D 137: 00 (72) Inventor Tetsuya Tachihata 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation (72) Inventor Kiyoshi Sakamoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (6)

[Claims] 1. A steering system for a vehicle, comprising: a target value determining means for determining a rear wheel steering control target value based on a predetermined detection signal relating to a running state quantity of the vehicle, wherein the traveling environment of the vehicle is the direction of the vehicle. Driving environment determining means for determining whether or not the environment is likely to reduce stability is provided, and the target value determining means is configured to reduce the directional stability of the vehicle by the traveling environment determining means. When it is determined that the vehicle is traveling, the rear wheel steering control target value is configured to be corrected to a side that improves directional stability of the vehicle. . 2. The vehicle steering system according to claim 1, wherein the "environment in which the directional stability of the vehicle is likely to be deteriorated" is an environment in which the vehicle is traveling near a tunnel exit. 3. The “environment in which the directional stability of the vehicle is likely to be deteriorated” is an environment in which the vehicle is running near a cut-out exit.
The steering apparatus for a vehicle according to claim 1, wherein: 4. The steering apparatus for a vehicle according to claim 1, wherein the “environment in which the directional stability of the vehicle is easily deteriorated” is an environment in which the vehicle is traveling at night. 5. A steering apparatus for a vehicle, comprising: a target value determining means for determining a rear wheel steering control target value based on a predetermined detection signal relating to a running state quantity of the vehicle, wherein the target value determining means is a vehicle width. It is configured to correct the rear wheel steering control target value to a side that improves the directional stability of the vehicle when the light is turned on, and to cancel the correction when a predetermined time elapses after the sideways light is turned off. ing,
A vehicle steering system characterized by the above. 6. The “predetermined detection signal” includes a plurality of detection signals including a yaw rate detection signal, and the “determination of a rear wheel steering control target value” includes a plurality of detection signals obtained from the plurality of detection signals. It is performed by adding and subtracting a signal calculation value, and the "correction" is a correction for increasing the contribution rate of the signal calculation value obtained from the yaw rate detection signal to the rear wheel steering control target value determination. Claims 1 to 1 characterized
5. The vehicle steering system according to any one of 5 above.