JPH0958508A - Variable steering angle ratio steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the steering gear ratio according to a traveling condition or the like of a vehicle, and improve steering operability at the time of turning. SOLUTION: Rotation of a steering wheel 12 is transmitted to a pinion 20 through a steering gear ratio variable mechanism 16, and a rack shaft 22 moves, and a steered wheel is steered. The steering gear ratio variable mechanism 16 is connected to a control circuit 24 connected to a speedometer 26. The control circuit 24 minimizes the steering gear ratio in an area where car speed is up to low speed, and sets the steering gear ratio in which yaw angular velocity becomes constant to the car speed in an area where the car speed is up to medium speed from low speed, and sets the steering gear ratio in which lateral acceleration becomes constant to the car speed in an area where the car speed is high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering angle ratio variable steering device, and more particularly to a vehicle steering angle ratio variable steering device capable of changing a steering gear ratio according to a vehicle speed or the like.

[0002]

2. Description of the Related Art Conventionally, in a vehicle such as an automobile, there has been known a vehicle steering angle ratio variable steering device capable of changing a steering gear ratio according to a vehicle speed, and one example thereof is Japanese Patent Laid-Open No. 6-227422. It is shown in the official gazette.

In this vehicle steering angle ratio variable steering apparatus, the axial displacement amount is variable while the maximum steering angle of the steered wheels is constant, that is, the rotation angle of the rotating member is constant.
The maximum steering angle of the steering wheel can be made variable.

Specifically, if the amount of axial displacement of the rotating member is increased, a large steering angle is obtained at a large steering angle, and if the amount of axial displacement of the rotating member is decreased, a large steering angle is obtained at a small steering angle. Is obtained. By controlling the change in the steering gear ratio at this time, as shown in FIG. 3, the rack stroke (steering angle ratio) with respect to the steering angle of the steering wheel becomes small in the high speed range T1, so that stable steering characteristics can be realized.
In the low speed range T2, the rack stroke (steering angle ratio) with respect to the steering angle of the steering wheel becomes large, so that sharp steering characteristics can be realized.

[0005]

However, this steering gear ratio variable steering system for a vehicle aims to achieve both sharp handling at medium and low speeds and stability at high speeds. The characteristics do not take into consideration the movement state. Therefore, when the vehicle turns, the changing speed (yaw angular speed) of the vehicle rotation angle (yaw angle) around the vertical line passing through the center of gravity of the vehicle with respect to the steering angle of the steering wheel.
However, it depends on the size of the vehicle. Therefore, the driver must empirically predict the yaw angular velocity to operate the steering wheel, which makes the steering operation complicated.

In consideration of the above facts, the present invention can change the steering gear ratio according to the running condition of the vehicle,
Further, it is an object of the present invention to obtain a steering angle ratio variable steering device for a vehicle that can improve steering operability during turning.

[0007]

According to a first aspect of the present invention, there is provided a variable steering angle ratio steering device for a vehicle which calculates a steering gear ratio according to a vehicle speed and steers wheels based on the steering gear ratio. In the vehicle steering angle ratio variable steering device,
In the region below the predetermined vehicle speed, the steering gear ratio is set to the steering gear ratio at which the yaw angular velocity is constant with respect to the vehicle speed,
In a region where the vehicle speed is equal to or higher than a predetermined vehicle speed, a steering gear ratio calculation means is provided for making the steering gear ratio a steering gear ratio at which the lateral acceleration is constant with respect to the vehicle speed.

Therefore, in the vehicle steering angle ratio variable steering system according to the present invention as set forth in claim 1, in the low and medium speed range below a predetermined vehicle speed,
Since the steering gear ratio is a steering gear ratio in which the yaw angular velocity is constant with respect to the vehicle speed, when the vehicle turns, the yaw angular velocity with respect to the vehicle speed is constant. On the other hand, in a high speed range equal to or higher than the predetermined vehicle speed, the steering gear ratio becomes a steering gear ratio in which the lateral acceleration becomes constant with respect to the vehicle speed. Therefore, when the vehicle turns, the lateral acceleration with respect to the vehicle speed becomes constant.

According to a second aspect of the present invention, in the vehicle steering angle ratio variable steering device according to the first aspect, the steering gear ratio calculating means minimizes the steering gear ratio in an extremely low speed region. .

Therefore, in the vehicle steering angle ratio variable steering apparatus according to the second aspect of the present invention, the steering gear ratio is minimized and the required steering angle can be quickly obtained in the extremely low speed range.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a variable steering angle ratio steering device for a vehicle according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, in the vehicle steering angle ratio variable steering system 10 of this embodiment, the steering wheel 1 is used.
A steering gear ratio variable mechanism 16 is connected to a rotary shaft 14 that interlocks with the gear 2. An output shaft 18 projects from the steering gear ratio variable mechanism 16, and a pinion 20 connected to the output shaft 18 meshes with a rack shaft 22 connected to a steering wheel (not shown).

Therefore, the rotation of the steering wheel 12 is transmitted to the pinion 20 through the steering gear ratio variable mechanism 16 and the rack shaft 22 moves in the axial direction (direction of arrow W in FIG. 1), whereby the steering wheel is rotated. Is steered.

The steering gear ratio variable mechanism 16 is connected to a control circuit 24 as a steering gear ratio calculation means. The steering gear ratio variable mechanism 16 has a conventionally well-known structure and changes the gear ratio of the steering gear ratio variable mechanism 16 based on a gear ratio command signal output from the control circuit 24. . The control circuit 24 is also connected to a speedometer 26 so that a vehicle speed signal can be input.

The control circuit 24 is constituted by including a microcomputer, and the following control is performed based on a program stored in advance in a built-in storage device.

That is, based on the vehicle speed signal input from the speedometer 26, as shown in FIG. 2, in the region M1 where the vehicle speed is low (when the vehicle speed is 0 to V1), as shown by the solid line K. , It is designed to minimize the steering gear ratio.

When the vehicle turns, the rate of change (yaw angle) of the vehicle rotation angle (yaw angle) around the vertical line passing through the center of gravity of the vehicle changes depending on the magnitude of the vehicle speed.
The steering gear ratio at which the yaw angular velocity is constant is shown in FIG.
Is indicated by an imaginary line S.

On the other hand, when the vehicle turns, lateral acceleration (lateral G) acts on the vehicle, and the steering gear ratio at which the lateral G is constant is shown by a broken line Q in FIG.

Further, the region M2 where the vehicle speed is from low speed to medium speed
When the vehicle speed is V1 to V2, the steering gear ratio is set to the steering gear ratio S at which the yaw angular speed is constant with respect to the vehicle speed.

Further, the region where the vehicle speed is high M3 (the vehicle speed is V
2), the steering gear ratio is set to the steering gear ratio Q in which the lateral G is constant with respect to the vehicle speed.

The steering gear ratio is smoothly changed at the boundary of each area so that the driver does not feel discontinuity.

Next, the operation of the present embodiment will be described. In the vehicle steering angle ratio variable steering device 10 of the present embodiment, the control circuit 2
Reference numeral 4 changes the gear ratio of the steering gear ratio variable mechanism 16 based on the vehicle speed signal input from the speedometer 26. At this time, in the region M1 where the vehicle speed is low, the steering gear ratio is minimized as shown by the solid line K in FIG. Therefore, the required actual steering angle can be obtained quickly, the steering wheel can be steered to the maximum steering angle with a small steering amount of the steering wheel (the steering amount of the steering wheel can be reduced), and the garage can be easily put in.

Further, the region M2 where the vehicle speed is from low speed to medium speed
Then, the steering gear ratio S is set so that the yaw angular velocity is constant with respect to the vehicle speed. Therefore, the yaw angular velocity during turning of the vehicle does not change depending on the vehicle speed, and the steering stability can be secured.

Further, in the region M3 where the vehicle speed is high, the steering gear ratio Q is set so that the lateral G is constant with respect to the vehicle speed. Therefore, the lateral G when turning the vehicle does not change depending on the vehicle speed, the driver's fatigue can be reduced, and the steering angle change of the steered wheels with respect to the steering amount of the steering wheel becomes small, so that the steering stability is improved. Can be secured.

[0025]

According to the vehicle steering angle ratio variable steering system of the present invention, the steering gear ratio is calculated according to the vehicle speed and the wheels are steered based on the steering gear ratio. In the variable ratio steering device, the steering gear ratio is set to a steering gear ratio at which the yaw angular velocity is constant with respect to the vehicle speed in a region below a predetermined vehicle speed, and the lateral acceleration is constant to the vehicle speed in a region above a predetermined vehicle speed. Since the steering gear ratio calculating means for changing the steering gear ratio is provided, the steering gear ratio can be changed according to the traveling state of the vehicle and the steering operability during turning can be improved. Has excellent effect.

According to a second aspect of the present invention, in the vehicle steering angle ratio variable steering device according to the first aspect, the steering gear ratio calculating means minimizes the steering gear ratio in the extremely low speed region, so that in the extremely low speed region. The required effect is that the required steering angle can be quickly obtained and the operability is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a vehicle steering angle ratio variable steering device according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a vehicle speed and a steering gear ratio of the vehicle steering angle ratio variable steering device according to the embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a vehicle speed and a steering angle ratio of a vehicle steering angle ratio variable steering device according to a conventional embodiment.

[Explanation of symbols]

 10 Vehicle Steering Angle Ratio Variable Steering Device 12 Steering Wheel 14 Rotating Shaft 16 Steering Gear Ratio Variable Mechanism 18 Output Shaft 22 Rack 24 Control Circuit 26 Speedometer

Claims (2)

[Claims] 1. A variable steering angle ratio steering device for a vehicle, which calculates a steering gear ratio according to a vehicle speed and steers wheels according to the steering gear ratio, wherein the steering gear ratio is set to a vehicle speed in a region below a predetermined vehicle speed. On the other hand, the steering gear ratio with which the yaw angular velocity is constant,
A steering gear ratio variable steering device for a vehicle, comprising: steering gear ratio calculation means for making a steering gear ratio a steering gear ratio in which a lateral acceleration is constant with respect to a vehicle speed in a region equal to or higher than a predetermined vehicle speed. 2. The variable steering angle ratio steering apparatus for a vehicle according to claim 1, wherein the steering gear ratio calculation means minimizes the steering gear ratio in an extremely low speed range.