JP2004168166A - Rudder angle ratio variable-type steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly control the vehicle behavior in a transient state by a rudder angle ratio variable-type steering device for changing a ratio of a rotating angle of a steering wheel of a vehicle and a tire turning angle in accordance with a vehicle driving condition. <P>SOLUTION: This steering angle ratio variable-type steering device wherein the ratio of the rotating angle of the steering wheel of the vehicle and the tire turning angle is changed in accordance with the vehicle driving condition, determines a steering angle ratio on the basis of the sum of a proportional depending on the rotating angle of the steering wheel and a differential depending on a rotating angle speed of the steering wheel, and the differential is transferred from a positive zone to a negative zone in accordance with increase and decrease in car speed. Whereby in a low speed zone, the steering angle ratio is changed in such manner that the faster the steering wheel is operated, the more the tire turning angle is increased, and in a high speed zone, the steering angle ratio is changed to lower the response of the tire turning angle to the steering of the steering wheel. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable steering angle ratio steering apparatus for changing a ratio between a rotation angle of a steering wheel of a vehicle and a turning angle of a tire according to a driving state of the vehicle.
[0002]
[Prior art]
In order to improve steering responsiveness at large steering angles at medium and low vehicle speeds, and to enhance steering stability at high vehicle speeds, the steering wheel rotation angle (steering angle) and tire turning angle (steering angle) ), That is, the steering angle ratio is changed according to the driving state of the vehicle (changes in the steering angle and the vehicle speed). 38622).
[0003]
The technique described in the above publication is to output a target tire turning angle by multiplying the rotation angle of the steering wheel by a coefficient that changes according to the rotation angle and the vehicle speed of the steering wheel, and output the target tire turning angle in a steady state. Can be controlled, but cannot sufficiently cope with the transient state of steering wheel steering.
[0004]
On the other hand, the auxiliary steering device is controlled in consideration of the rotational angular speed (steering angular speed) of the steering wheel, and the control amount for the auxiliary steering device is changed between when the steering is performed quickly and when the steering is performed slowly. Angle control devices are also known (see, for example, Patent Publication No. 2722881). However, according to this technique, it is not possible to cope with a change in the yaw rate gain according to the vehicle speed.
[0005]
[Patent Document 1]
Japanese Patent Publication No. Hei 4-38622 [Patent Document 2]
Patent Publication No. 2722881 [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 point that the transient state of the steering wheel steering cannot be sufficiently coped with and the point that the yaw rate gain cannot be changed in accordance with the vehicle speed. Its main purpose is to provide a variable steering angle ratio type steering device for changing the ratio between the turning angle of the steering wheel of the vehicle and the tire turning angle in accordance with the driving condition of the vehicle. Controllable.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, in the present invention, a variable steering angle ratio type steering device for changing the ratio between the rotation angle of the steering wheel of the vehicle and the turning angle of the tire according to the driving state of the vehicle, The steering angle ratio shall be determined based on the sum of the proportional term depending on the rotation angle of the steering wheel and the differential term depending on the rotational angular velocity of the steering wheel. Shift to the negative region.
[0008]
In this way, in a low vehicle speed range, the steer link wheel is operated more quickly, the steering angle ratio changes in a direction in which the tire turning angle increases, and in a high vehicle speed range, the steering angle ratio with respect to the steering wheel steering is changed. The steering angle ratio changes so that the response becomes low.
[0009]
BEST MODE FOR CARRYING OUT 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 a rotational force applied to the steering wheel 1 into an axial force of a rack shaft 3 via a rack-and-pinion mechanism 2, and uses the main steering mechanism 5 to steer the left and right front tires 4. And an assist mechanism (electric power steering device) 6 that adds the rotational force of the electric motor to the axial force of the rack shaft to assist the rotational force of the steering wheel 1, and the entire main steering mechanism 5 and the assist mechanism 6 on the vehicle body. It comprises a slide mechanism 7 that supports the main steering mechanism 5 and the assist mechanism 6 to move left and right together 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. A detailed description will be omitted.
[0012]
According to the steering device S, when the driver steers the steering wheel 1, the front tire 4 is turned via the assist mechanism 6, and the main steering mechanism 5 and the main steering mechanism 5 are driven by the axial force generated by the auxiliary steering mechanism 8. By moving the entire assist mechanism 6 right and left, the front tire 4 is steered separately from the steering of the steering wheel 1. Then, the rotation angle of the steering wheel 1, that is, the steering angle θ, the running speed of the vehicle, that is, the vehicle speed V, and the displacement amount of the sub-steering mechanism 8, which are given by the driver, are detected. 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. Thus, 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 [delta], the steering angle θ value that determines the basic ratio 11 based only on (rotation angle of the steering wheel 1 by the driver gave), i.e. the value only by the action of the main steering mechanism 5 [delta] _N, 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]
Where θ is the steering angle, k ₀ is a coefficient that varies according to the steering angle θ and the vehicle speed V at that time (see FIG. 3), and k ₁ is a coefficient that varies 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 at that time and the steering angular velocity d [theta] / dt, by changing the k ₀ corresponding to the steering angle θ and the vehicle speed V, the improvement of the yaw rate gain of the low vehicle speed region And a decrease in yaw rate gain in a high vehicle speed range can be achieved (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 a positive region to a negative region at the boundary. In other words, in the low vehicle speed range, the quicker the operation of the steer link wheel, the more the tire turning angle increases, that is, the steering gear ratio tends to be quick, and the yaw rate gain characteristics provide high responsive agile maneuverability. At high vehicle speeds, the steer link wheel tends to be turned back when operated quickly, the response of the tire turning angle to steering wheel steering does not become too sensitive, and the yaw rate gain characteristics have a damping convergence. The maneuverability with a high sense of stability can be obtained.
[0021]
From the above, when traveling under the same conditions, high responsiveness is obtained in the low vehicle speed range as compared with the conventional vehicle. Therefore, as shown in FIG. (The peak value of the steering angle is reduced), and in a high vehicle speed range, the damping effect is increased as compared with the conventional vehicle, so that the convergence time of the yaw rate is reduced as shown in FIG. 7 ( Yaw rate flattens early).
[0022]
【The invention's effect】
As described in detail above, according to the present invention, the linear sensation of the steady yaw rate gain change with respect to the vehicle speed is improved, and the quick sensation in the low vehicle speed range and the high vehi In addition, a great effect can be achieved in addition to achieving a sense of stability at a higher level.
[Brief description of the drawings]
1 is a schematic configuration diagram of a variable steering angle ratio type steering device to which the present invention is applied; FIG. 2 is a control block diagram of the present invention; FIG. 3 is a setting map of a proportional term coefficient; FIG. FIG. 5 is a graph showing the relationship between yaw rate gain and vehicle speed. FIG. 6 is a graph showing steering angle change. FIG. 7 is a graph showing yaw rate change.
Reference Signs List 1 steering wheel 5 main steering mechanism 8 auxiliary steering mechanism 11 basic ratio 12 function generator

Claims (1)

A steering angle ratio variable steering device for changing a ratio between a rotation angle of a steering wheel of a vehicle and a turning angle of a tire according to a driving state of the vehicle,
The steering angle ratio is determined based on the sum of a proportional term that depends on the rotation angle of the steering wheel and a differential term that depends on the rotation angular velocity of the steering wheel,
The variable steering angle ratio type steering apparatus according to claim 1, wherein the differential term shifts from a positive region to a negative region in accordance with an increase in vehicle speed.

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