JPH10100634A - Vehicle stability control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure higher stability by controlling engine output and brakes of respective wheels, and cooperatively controlling damping force of a shock absorber. SOLUTION: An oversteer or understeer tendency of a vehicle judged by a control part 6 of a controller C is transmitted to a controller 9. When the fact of an oversteer tendency is transmitted, the controller 9 relatively heightens front wheel side damping force more than rear wheel side damping force by controlling a shock absorber 10. To the contrary, when the fact of an understeer tendency is transmitted, the controller 9 can relatively heighten the rear wheel side damping force more than the front wheel side damping force by controlling the shock absorber 10. Therefore, sufficient responsiveness of stability control is obtained, and swinging such as rolling is restrained, and high stability can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle stability control device for ensuring the stability of a vehicle during a turn.

[0002]

2. Description of the Related Art Normally, a vehicle turns stably in accordance with a steering operation, but tends to oversteer or understeer depending on unexpected conditions such as road surface conditions, vehicle speed, emergency avoidance, and external factors. Sometimes. As a vehicle stability control device for suppressing such oversteer or understeer tendency, for example, there is one shown in FIG. In this vehicle stability control device, first, the steering angle, the vehicle speed, the yaw rate, and the lateral acceleration are detected by the sensors 1 to 4 and input to the controller C. Then, in the controller C, the signal processing unit 5 performs signal processing on these input signals, and then the control unit 6 determines the traveling state of the vehicle.

For example, when the slip angle of the vehicle body is large and the slip angular velocity is also large, it can be said that the vehicle body tends to oversteer. On the other hand, if the actual yaw rate is smaller than the target yaw rate to be generated, it can be said that the vehicle tends to understeer. When it is determined that the vehicle has an oversteer or understeer tendency, the controller C suppresses the oversteer or understeer tendency as follows.

When the controller C determines that the tendency to oversteer is large, the controller C outputs a signal to the brake actuator 7 to apply a brake to the front wheel on the outside of the turn.
Then, a yawing moment is generated outward of the vehicle to suppress an oversteer tendency. On the other hand, when it is determined that the understeer tendency is large, the controller C outputs a signal to the throttle actuator 8 to control the engine output, and outputs a signal to the brake actuator 7 to apply a brake to the rear wheel. . Then, the braking force of the rear wheel inside the turning is made larger than the braking force of the rear wheel outside the turning, and an inward yawing moment of the vehicle is generated to suppress the understeer tendency.

[0005]

However, in the above-mentioned conventional vehicle stability control device, especially when the vehicle is understeer, the engine output must be controlled to secure the lateral force of the front wheels. In some cases, sufficient responsiveness cannot be obtained. Further, when the engine output and the braking of each wheel are controlled, the frictional force of the tire fluctuates, and the vehicle is more likely to shake such as rolling and pitching. If the damping force of the shock absorber is increased in advance so as to suppress this shaking, the riding comfort during normal running will be degraded. SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle stability control device capable of ensuring higher stability by controlling engine output and braking of each wheel and by cooperatively controlling a damping force of a shock absorber. That is.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a yaw moment is generated by judging an oversteer or understeer tendency from the running state of a vehicle and controlling the engine output and brakes of each wheel.
It is assumed that the vehicle stability control device is configured to suppress the oversteer or understeer tendency. In addition to providing a controller for controlling the shock absorber, this controller controls the shock absorber when the vehicle is over-steering, so that the front wheel side damping force is relatively higher than the rear wheel side damping force, Also, when the vehicle tends to understeer,
It is characterized in that the shock absorber is controlled so that the damping force on the rear wheel side is made relatively higher than the damping force on the front wheel side. The second invention is characterized in that, in the first invention, the damping force characteristic is controlled by changing the size of the orifice of the shock absorber.

[0007]

1 to 3 show a vehicle stability control apparatus according to a first embodiment of the present invention. In the vehicle stability control device of the first embodiment, the engine output and the braking of each wheel are controlled in accordance with the running state of the vehicle, and the tendency of the vehicle to oversteer or understeer is suppressed, as in the conventional example. ing. However, since this control has already been described, a detailed description thereof will be omitted here. At this time, as described below,
The damping force of the shock absorber 10 on each wheel side is also controlled.

The controller 9 is informed of the tendency of the vehicle to oversteer or understeer determined by the controller 6 of the controller C. When the vehicle is informed that the vehicle is over-steering, the controller 9 controls the shock absorber 10 to increase the front-wheel-side damping force relatively to the rear-wheel-side damping force. On the other hand, when the controller 9 is informed that the vehicle is understeer, the controller 9 controls the shock absorber 10 to relatively increase the damping force on the rear wheel side relative to the damping force on the front wheel side.

Hereinafter, the relationship between the steering characteristic of the vehicle and the damping force characteristic of the shock absorber 10 will be described.
First, the relationship between the steering characteristics of the vehicle and the cornering power will be described. Although a detailed description thereof is omitted, a static margin SM is an amount indicating the static direction stability and instability of the vehicle. _{. S.M = (K 2 L 2} -K 1 L 1) / {(K 1 + K 2) × L} K 1: left and right front wheels total cornering power K _2: left and right rear wheels total cornering power L: wheelbase L ₁ : Distance from front wheel of center of gravity internally dividing wheelbase L ₂ : Distance from rear wheel of center of gravity internally dividing wheelbase

[0010] Then, S. M. = 0, i.e., if _{K 2 L 2 -K 1 L 1} = 0, the vehicle is in a neutral steering state no change in turning radius regardless of the vehicle speed. In contrast, S. M. <0, i.e., when _{K 2 L 2 -K 1 L 1} <0, the vehicle is said to be in over-steering tendency of turning radius becomes smaller. Moreover, S. M.> 0, i.e., when _{K 2 L 2 -K 1 L 1} > 0, the vehicle is said to be in the understeer tendency of turning radius increases.

From this, when the vehicle has a tendency to oversteer or understeer, that is, K ₂ L ₂
When −K ₁ L ₁ <0 or K ₂ L ₂ −K ₁ L ₁ > 0, if it is brought close to K ₂ L ₂ −K ₁ L ₁ = 0, oversteer or understeer is obtained. It can be seen that the tendency can be suppressed. Here, it is known that the cornering power K has a relationship shown in FIG.

As shown in FIG. 2, for example, if a load movement of ΔW occurs on the left and right wheels on which the load W acts, the cornering powers are K _H and K _L , respectively. The sum of these cornering power K _H, K _L is a 2K _M. In contrast, when there is no load movement ΔW, the sum of the cornering powers of the left and right wheels is 2K. Therefore, the decrease in the cornering power due to the load movement ΔW is equivalent to exactly 2 (K−K _M ).

By the way, when the vehicle body rolls, the right and left load movements of ΔW ₁ and ΔW ₂ occur on the front and rear wheels, respectively. Therefore, as described above, when the vehicle body rolls, the cornering power of the front and rear wheels becomes the load movement ΔW ₁ ,
It will decrease according to the magnitude of ΔW ₂ . here,
It has already been described that when there is a relationship of K ₂ L ₂ −K ₁ L ₁ <0, there is a tendency to oversteer. Therefore, in order to suppress this oversteer tendency, the relationship is expressed as K ₂ L ₂ −
K ₁ L ₁ = as close to 0, the cornering power K ₂ of the rear wheel, it is understood that it Shiteyare relatively larger than the front wheel cornering power K _1. Then, the cornering power K ₂ of the rear wheel to relatively larger than the front wheel cornering power K ₁ is front wheel load movement ΔW
₁ may be made relatively larger than the load movement ΔW ₂ of the rear wheels.

On the other hand, when K ₂ L ₂ −K ₁ L ₁ > 0, there is a tendency to understeer. Therefore, in order to suppress the understeer tendency, the relationship as close to the _{K 2 L 2 -K 1 L 1} = 0, than cornering power K ₂ of the rear wheels to the front wheels of the cornering power K ₁ relatively It can be seen that it should be made larger. Then, to relatively greater than the cornering power K ₂ of the rear wheels to the front wheels of the cornering power K ₁ is a load movement [Delta] W ₂ of the rear wheel, it Shiteyare relatively larger than the load movement [Delta] W ₁ of the front wheel .

Next, the relationship between the load movement ΔW and the damping force of the shock absorber 10 will be described. Assuming that the roll stiffness of the front and rear wheel suspension devices is m ₁ and m ₂ , the rolling moment due to the inertial force is μWh, and the moment due to gravity caused by the inclination of the vehicle body is Whφ, (m ₁ + m ₂ ) φ = μWh + Whφ μ : Centripetal acceleration coefficient W: vehicle weight h: distance between center point of vehicle weight and roll axis φ: roll angle.

Assuming that the load movement on the front and rear wheels is ΔW ₁ and ΔW ₂ , respectively, m ₁ φ = ΔW ₁ d ₁ − from the balance of the moment around the roll in a plane perpendicular to the front and rear direction at the front and rear wheel positions. _{μWl 2 h 1 / l m 2} φ = ΔW 2 d 2 -μWl 1 h 2 / l d 1, d 2: tread h ₁ between the front and rear wheels, h _2: roll center height l ₁ from the ground of the front and rear wheels, l ₂ : It is understood that the distance l = l ₁ + l ₂ must be established between the front and rear wheel axles and the vehicle center of gravity in the horizontal plane.

From these equations, the load shift ΔW ₁ ,
When ΔW ₂ is obtained, ΔW ₁ = μW / d ₁ × [h / ｛1+ (m ₂ / m ₁ ) − (Wh / m
₁ )} + h ₁ × l ₂ / l] ΔW ₂ = μW / d ₂ × [h / ｛1+ (m ₁ / m ₂ ) − (Wh / m
₂ )} + h ₂ × l ₁ / l]. As can be seen, the roll stiffness m ₁ , m ₂ of the front and rear wheels is such that the larger the ratio m ₁ / m ₂ , the larger the load transfer ΔW ₁ for the front wheels and the smaller the load transfer ΔW ₂ for the rear wheels. . Conversely, if it is less, the smaller the load movement [Delta] W ₁ is a front wheel, it can be seen that load movement [Delta] W ₂ becomes larger than the rear wheel.

As described above, by controlling the ratio of roll stiffness m ₁ / m ₂ on the front and rear wheels, the load movements ΔW ₁ and ΔW ₂ at the front and rear wheels can be changed. If the load movements ΔW ₁ and ΔW ₂ at the front and rear wheels change, K ₂ L ₂ −K
₁ Cornering power K ₁ , K ₂ so that L ₁ = 0
Can be changed, and the oversteer or understeer mechanism of the vehicle can be suppressed.

For example, when the vehicle tends to oversteer, by controlling the shock absorber 10 to make the front wheel side damping force relatively higher than the rear wheel side damping force, the roll rigidity ratio m _{1 is obtained.} / M ₂ can be increased. Therefore, the load movement ΔW _{1 of the} front wheel is changed to the load movement ΔW _{2 of the} rear wheel.
May also be relatively larger than the cornering power K ₂ of the rear wheels, it can be relatively larger than the front wheel cornering power K _1. Then, if the cornering power K ₂ of the rear wheel relatively larger than the front wheel cornering power K _1, the relationship between _{K 2 L 2 -K 1 L 1} <0, K 2 L 2 -K 1 L 1 = 0 can be approached, and the tendency to oversteer can be suppressed.

On the other hand, when the vehicle tends to understeer, the shock absorber 10 is controlled to make the damping force on the rear wheel relatively higher than the damping force on the front wheel.
The roll rigidity ratio m ₁ / m ₂ can be reduced. Therefore, the load movement ΔW _{2 of the} rear wheel is changed by the load movement ΔW of the front wheel.
W ₁ may also be relatively larger than the front wheels of the cornering power K _1, it can be relatively greater than the cornering power K ₂ of the rear wheel. Then, the cornering of the rear wheels of the front wheel cornering power K ₁ power K ₂
If it is relatively larger, the relationship of K ₂ L ₂ −K ₁ L ₁ > 0 can be made closer to K ₂ L ₂ −K ₁ L ₁ = 0, and the understeer tendency can be suppressed.

In the first embodiment, although not specifically shown, the size of the orifice in the shock absorber can be changed in order to control the damping force characteristic of the shock absorber 10. The controller 9 selects the size of the orifice according to the running state of the vehicle, and increases or decreases the damping force.

According to the vehicle stability control apparatus of the first embodiment, in addition to controlling the engine output and the braking of each wheel, the damping force of the shock absorber is coordinately controlled, so that sufficient responsiveness can be obtained. Can be. Also, during normal running, the optimal damping force for normal running of the vehicle can be maintained, so that the riding comfort is not degraded. When turning, the vehicle approaches K ₂ L ₂ −K ₁ L ₁ = 0 in order to suppress the tendency of the vehicle to oversteer or understeer, so that fluctuations in the ground contact of the wheels can be suppressed, and shaking such as rolling and pitching can be suppressed. Control and higher stability can be ensured.

The vehicle stability control device according to the second embodiment shown in FIG. 4 is different from the vehicle stability control device according to the first embodiment only in the signal input to the controller 9. Therefore, in the following, the differences will be mainly described, the same components will be denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 4, the controller 9 includes a controller C
The signal processed by the signal processing unit is directly input. The controller 9 determines the tendency of the vehicle to oversteer or understeer based on the input signal, and controls the damping force characteristic of the shock absorber 10. According to the vehicle stability control device of the second embodiment as described above, more responsiveness can be obtained, and high stability can be secured.

That is, in the first embodiment, the control of the engine output and the brake of each wheel, and the control of the shock absorber 10
The control of the damping force characteristic is performed based on the same judgment in the control unit 6. On the other hand, in the second embodiment, for example, if the controller 9 determines the oversteer or understeer tendency from the processed signal at the initial time, before the oversteer or understeer tendency becomes strong, This can be suppressed. In the first and second embodiments,
Although the controller C and the controller 9 have been described as being separate from each other, they may of course be integrated.

[0025]

According to the first aspect of the present invention, a sufficient responsiveness of the stability control can be obtained by controlling the engine output and the braking of each wheel and by cooperatively controlling the damping force of the shock absorber. In addition, swaying such as rolling and pitching can be suppressed, and higher stability can be ensured. According to the second aspect, in the first aspect, the damping force characteristics can be freely controlled by changing the size of the orifice.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a vehicle stability control device according to a first embodiment.

FIG. 2 is a diagram showing a relationship between a cornering power and a load.

FIG. 3 is a diagram showing a roll state of a vehicle body.

FIG. 4 is a circuit diagram of a vehicle stability control device according to a second embodiment.

FIG. 5 is a circuit diagram of a conventional vehicle stability control device.

[Explanation of symbols]

 1-4 sensor 7 brake actuator 8 throttle actuator 9 controller 10 shock absorber

Claims (2)

[Claims] 1. A configuration for judging an oversteer or understeer tendency from a running state of a vehicle, controlling an engine output and braking of each wheel, generating a yawing moment, and suppressing the oversteer or understeer tendency. In the vehicle stability control device, a controller for controlling the shock absorber is provided, and the controller controls the shock absorber when the vehicle tends to oversteer, so that the front wheel side damping force is reduced to the rear wheel side damping force. And a shock absorber controlled when the vehicle tends to understeer, so that the rear-wheel-side damping force is relatively higher than the front-wheel-side damping force. Stability control device. 2. The vehicle stability control device according to claim 1, wherein the damping force characteristic is controlled by changing the size of the orifice of the shock absorber.