JP3120707B2 - Variable steering angle ratio steering system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable steering angle ratio steering apparatus for a vehicle, and more particularly to a variable steering angle ratio steering apparatus for a vehicle 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, a steering angle ratio variable steering device for a vehicle which can change a steering gear ratio in accordance with a vehicle speed is known, and an example thereof is disclosed in JP-A-6-227422. It is indicated in the gazette.

[0003] In this vehicle steering angle ratio variable steering apparatus, the axial displacement is made variable while the maximum steering angle of the steered wheels is kept constant, that is, the rotation angle of the rotating member is kept constant.
The maximum steering angle of the steering wheel can be made variable.

Specifically, a large steering angle can be obtained at a large steering angle by increasing the axial displacement of the rotating member, and a large steering angle can be obtained at a small steering angle by decreasing the axial displacement of the rotating member. 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 in the high-speed range T1 is reduced, 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 increases, so that sharp steering characteristics can be realized.

[0005]

However, this vehicle steering angle ratio variable steering system aims at achieving both sharp handling at medium and low speeds and stability at high speeds, but the steering angle ratio does not increase the turning of the vehicle. The characteristics do not take into account the exercise state. Therefore, when the vehicle turns, the changing speed (yaw angular speed) of the vehicle rotation angle (yaw angle) about a vertical line passing through the vehicle center of gravity with respect to the steering angle of the steering wheel.
However, it depends on the vehicle speed. Therefore, it is necessary for the driver to empirically predict the yaw angular velocity and operate the steering wheel, which causes a problem that the steering operation becomes complicated.

In view of the above facts, the present invention can change the steering gear ratio according to the running condition of the vehicle, etc.
It is another object of the present invention to provide a vehicle steering angle ratio variable steering device capable of improving steering operability during turning.

[0007]

According to a first aspect of the present invention, there is provided a vehicle steering angle ratio variable steering apparatus which calculates a steering gear ratio in accordance with a vehicle speed and turns a wheel based on the steering gear ratio. In a vehicle steering angle ratio variable steering device,
In a region below a predetermined vehicle speed, the steering gear ratio is a steering gear ratio at which the yaw angular velocity is constant with respect to the vehicle speed,
A steering gear ratio calculating means for setting the steering gear ratio to a steering gear ratio at which the lateral acceleration is constant with respect to the vehicle speed in a region equal to or higher than the predetermined vehicle speed is provided.

Accordingly, in the vehicle steering angle ratio variable steering apparatus according to the first aspect of the present invention, in a low-to-medium speed range below a predetermined vehicle speed,
Since the steering gear ratio is a steering gear ratio at which the yaw angular speed is constant with respect to the vehicle speed, when the vehicle turns, the yaw angular speed with respect to the vehicle speed is constant. On the other hand, in a high-speed region equal to or higher than the predetermined vehicle speed, the steering gear ratio is a steering gear ratio at which the lateral acceleration is constant with respect to the vehicle speed. Therefore, when the vehicle turns, the lateral acceleration with respect to the vehicle speed is constant.

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

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

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vehicle steering angle ratio variable steering apparatus according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, in a vehicular steering angle ratio variable steering apparatus 10 of the present embodiment, a steering wheel 1
A variable steering gear ratio mechanism 16 is connected to a rotation shaft 14 linked to the second shaft 2. An output shaft 18 protrudes from the variable steering gear ratio mechanism 16, and a pinion 20 connected to the output shaft 18 meshes with a rack shaft 22 connected to steering wheels (not shown).

Accordingly, the rotation of the steering wheel 12 is transmitted to the pinion 20 via the variable steering gear ratio mechanism 16, and the rack shaft 22 is moved in the axial direction (the direction of the arrow W in FIG. 1), whereby the steering wheel is turned. Is to be steered.

The variable steering gear ratio mechanism 16 is connected to a control circuit 24 as steering gear ratio calculation means. The variable steering gear ratio mechanism 16 has a conventionally known structure, and changes the gear ratio of the variable steering gear ratio mechanism 16 based on a gear ratio command signal output from the control circuit 24. . Further, the control circuit 24 is connected to a speedometer 26, and receives a vehicle speed signal.

The control circuit 24 includes a microcomputer, and performs the following control based on a program stored in a built-in storage device in advance.

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

When the vehicle turns, the speed of change (yaw angle speed) of the vehicle rotation angle (yaw angle) about a vertical line passing through the center of gravity of the vehicle changes depending on the magnitude of the vehicle speed.
FIG. 2 shows the steering gear ratio at which the yaw angular velocity becomes constant.
Is indicated by an imaginary line S.

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

In the range M2 where the vehicle speed is from low to medium speed.
When the vehicle speed is between V1 and 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, a region M3 where the vehicle speed is high (the vehicle speed is V
2 or more), the steering gear ratio is set to the steering gear ratio Q at which the lateral G is constant with respect to the vehicle speed.

At the boundary between the regions, the steering gear ratio changes smoothly so that the driver does not feel a sense of 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 variable steering gear ratio 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 quickly obtained, the steering wheel can be steered to the maximum steering angle of the steered wheels with a small steering amount (the steering amount of the steering wheel can be reduced), and the garage can be easily entered.

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

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

[0025]

According to the first aspect of the present invention, there is provided a vehicle steering angle ratio variable steering apparatus which calculates a steering gear ratio in accordance with a vehicle speed and turns a wheel 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 equal to or lower than a predetermined vehicle speed, and the steering gear ratio is set to a constant lateral acceleration with respect to the vehicle speed in a region equal to or higher than the predetermined vehicle speed. With the configuration including the steering gear ratio calculating means for setting the steering gear ratio to a certain value, the steering gear ratio can be changed according to the running state of the vehicle and the like, and the steering operability during turning can be improved. Has excellent effects.

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

[Brief description of the 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 one 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]

 Reference Signs List 10 Steering angle ratio variable steering device for vehicle 12 Steering wheel 14 Rotating shaft 16 Steering gear ratio variable mechanism 18 Output shaft 22 Rack 24 Control circuit 26 Speedometer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-58323 (JP, A) JP-A-5-124533 (JP, A) JP-A-63-240476 (JP, A) JP-A-61- 193969 (JP, A) JP-A-61-122076 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/02

Claims (2)

(57) [Claims] 1. A variable steering angle ratio steering apparatus for a vehicle, which calculates a steering gear ratio according to a vehicle speed and turns a wheel based on the steering gear ratio, wherein the steering gear ratio is set to a vehicle speed in a region below a predetermined vehicle speed. The steering gear ratio at which the yaw angular velocity is constant
A variable steering angle ratio steering apparatus for a vehicle, comprising: a steering gear ratio calculating means for setting a steering gear ratio to a steering gear ratio at 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 vehicle steering angle ratio variable steering apparatus according to claim 1, wherein said steering gear ratio calculating means minimizes a steering gear ratio in an extremely low speed region.