JP4035031B2 - Steering device with variable steering angle ratio - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering angle ratio variable type steering apparatus in which a ratio between a rotation angle of a steering wheel of a vehicle and a cutting angle of a front tire is changed according to a driving state of the vehicle.
[0002]
[Prior art]
The steering wheel rotation angle (steering angle) and tire turning angle (steering angle) to improve steering response at large steering angles at medium and low vehicle speeds and to improve steering stability at high vehicle speeds. ), That is, the steering angle ratio is changed in accordance with the driving state of the vehicle (changes in the steering angle and vehicle speed). No. 38622).
[0003]
The technology described in the above publication outputs a target tire turning angle by multiplying the steering wheel rotation angle by a coefficient that changes according to the rotation angle of the steering wheel and the vehicle speed, and the rotation angle of the steering wheel is in a steady state. Although the tire turning angle can be controlled, it cannot sufficiently cope with the transient state of steering wheel steering.
[0004]
On the other hand, an auxiliary steering device is controlled in consideration of the rotational angular velocity (steering angular velocity) of the steering wheel, and the control amount for the auxiliary steering device is changed depending on whether it is steered quickly or slowly. Angular control devices are also known (see, for example, Japanese Patent Publication No. 2722882). However, according to this technique, it cannot cope with the yaw rate gain changing according to the vehicle speed.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 4-38622 [Patent Document 2]
Patent Publication No. 2722811 [0006]
[Problems to be solved by the invention]
The present invention has been devised to improve such disadvantages of the prior art, that is, the inability to sufficiently cope with the transient state of steering wheel steering and the inability to cope with the change in yaw rate gain according to the vehicle speed. Its main purpose is to provide a steering angle ratio variable type steering device that changes a ratio of a rotation angle of a steering wheel of a vehicle and a front tire turning angle in accordance with a driving state of the vehicle. The behavior is to be able to be precisely controlled.
[0007]
[Means for Solving the Problems]
To achieve the above objects, in the present invention, variable steering ratio steering formed by the ratio between the rotation angle and the sharpness of the front wheel angle of a steering wheel of the vehicle is varied in accordance with the operating condition of the vehicle The target value of the front tire for controlling the angle of the front tire corresponding to the operation amount of the steering wheel according to the driving state of the vehicle is set to the value corresponding to the rotational angle of the steering wheel and the value of the steering wheel. The value is determined based on the sum of the value corresponding to the rotational angular velocity, and the value corresponding to the rotational angular velocity of the steering wheel is decreased as the vehicle speed increases and is shifted from the positive region to the negative region with the predetermined vehicle speed value as a boundary. To do.
[0008]
In this way, the steering angle ratio changes in a direction where the tire turning angle increases as the steer wheel is operated more quickly in the low vehicle speed range, and in the high vehicle speed range, the steering angle ratio with respect to steering of the steering wheel changes. The rudder angle ratio changes so that the responsiveness is lowered.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 1 is a schematic diagram of a basic configuration of a vehicle steering system to which the present invention is applied. The steering device S converts the rotational force applied to the steering wheel 1 into the axial force of the rack shaft 3 via the rack and pinion mechanism 2, and thereby steers the left and right front tires 4. And the assist mechanism (electric power steering device) 6 for assisting the rotational force of the steering wheel 1 by adding the rotational force of the electric motor to the axial force of the rack shaft, and the main steering mechanism 5 and the assist mechanism 6 as a whole. On the other hand, it comprises a slide mechanism 7 that is movably supported to the left and right, and a sub-steer mechanism 8 that moves both the main steering mechanism 5 and the assist mechanism 6 to the left and right with an electric axial force generator.
[0011]
The assist mechanism 6 is for generating an auxiliary torque to be added to the driver's steering wheel operating force according to a predetermined steering condition set in advance, and is not different from a known so-called power steering device. Then, detailed explanation is omitted.
[0012]
According to this steering device S, the driver steers the steering wheel 1 to turn the front tire 4 via the assist mechanism 6, and the main steering mechanism 5 and the axial force generated by the auxiliary steering mechanism 8. By moving the entire assist mechanism 6 to the left and right, the front tire 4 is steered separately from the steering of the steering wheel 1. Then, the rotation angle, that is, the steering angle θ of the steering wheel 1 given by the driver, the traveling speed of the vehicle, that is, the vehicle speed V, and the displacement amount of the auxiliary steering mechanism 8 are detected, and based on these signals, the total tire wear The angle δ is controlled.
[0013]
Here, the auxiliary steering mechanism 8 is controlled so as to continuously increase or decrease the tire turning angle δ with respect to the steering angle θ according to the driving state. Thereby, the ratio between the steering angle θ and the tire turning angle δ, that is, the steering angle ratio can be changed according to the driving state.
[0014]
Next, a control algorithm according to the present invention will be described with reference to FIG.
[0015]
The target tire turning angle δ is a value determined by the basic ratio 11 based only on the steering angle θ (the rotation angle of the steering wheel 1 given by the driver), that is, the value δ _N based only on the action of the main steering mechanism 5 and the steering angle. θ and the value determined by the function generator 12 based on the vehicle speed V, the words are determined by adding the value [delta] _C by the action of the auxiliary steering mechanism 8.
[0016]
Here responsive compensation target tire turning angle [delta] _C is calculated by the following equation.
[0017]
δ _C = k ₁ · (dθ / dt) + k ₀ · θ
[0018]
However, θ is a steering angle, k ₀ is a coefficient (see FIG. 3) that changes according to the steering angle θ and the vehicle speed V at that time, and k ₁ is a coefficient that changes according to the vehicle speed V (see FIG. 4). ).
[0019]
According to this, the changes the k ₁ in accordance with the vehicle speed V when the its, by changing the k ₀ corresponding to the steering angle θ and the vehicle speed V, the improvement in the yaw rate gain of the low vehicle speed region, high vehicle speed It is possible to achieve both a reduction in the yaw rate gain in the region (see FIG. 5).
[0020]
Such properties, particularly the change corresponding to the vehicle speed V of the differential coefficient k _1, as shown in FIG. 4, the differential coefficient k ₁ in accordance with the vehicle speed V is substantially linearly decreasing, yet certain speed It is obtained by shifting from the positive region to the negative region at the boundary. In other words, in the low vehicle speed range, the steer wheel is operated more quickly and the tire turning angle increases. At high vehicle speeds, if the steer wheel is operated quickly, it tends to be switched back, the response of the tire turning angle to the steering wheel steering is not sensitive, and the yaw rate gain characteristics are damped. A highly maneuverable and stable maneuverability can be obtained.
[0021]
From the above, when traveling under the same conditions, high responsiveness can be obtained in the low vehicle speed range as compared with the conventional vehicle, so that the corrected steering angle for the vehicle behavior can be reduced as shown in FIG. (The peak value of the steering angle becomes lower), and in the high vehicle speed range, the damping effect is enhanced as compared with the conventional vehicle, so that the convergence time of the yaw rate is shortened as shown in FIG. Yaw rate flattenes early).
[0022]
【The invention's effect】
As described above in detail, according to the present invention, the sense of linearity of the steady yaw gain gain change with respect to the vehicle speed is improved, and the quick feeling and the high vehicle speed range in the low vehicle speed range of the vehicle using the steering angle ratio variable type steering device. It is possible to achieve a great effect in making the sense of stability at a higher level compatible.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a steering angle ratio variable type steering apparatus to which the present invention is applied. FIG. 2 is a control block diagram of the present invention. FIG. 3 is a proportional term coefficient setting map. Coefficient setting map [Fig. 5] Graph showing the relationship between yaw rate gain and vehicle speed [Fig. 6] Graph showing steering angle change [Fig. 7] Graph showing yaw rate change [Explanation of symbols]
1 Steering wheel 5 Main steering mechanism 8 Sub steering mechanism 11 Basic ratio 12 Function generator

Claims (1)

A variable steering ratio steering apparatus comprising as varied according to the ratio between the rotation angle and the sharpness of the front wheel angle of a vehicle steering wheel to the operating state of the vehicle,
The target value of the front tire turning angle for controlling the turning angle of the front tire corresponding to the operation amount of the steering wheel according to the driving state of the vehicle is a value corresponding to the rotation angle of the steering wheel and the steering wheel. It is determined based on the sum of the value corresponding to the rotational angular velocity of the wheel,
A steering angle ratio variable type steering apparatus characterized in that the value corresponding to the rotational angular velocity of the steering wheel decreases as the vehicle speed increases and shifts from a positive region to a negative region with a predetermined vehicle speed value as a boundary. .

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