JPH092295A - Steering gear for vehicle - Google Patents

Abstract

PURPOSE: To judge inclined degree of a wheel only by looking at an angle of a steering wheel by setting a pitch of rack teeth so that the maximum rota tion angle of the steering wheel generating a maximum steering angle to a wheel is within one rotation on a single side in a rack and pinion steering gear. CONSTITUTION: In a front wheel steering gear, in a normal area of steering at the time of traveling at medium-high speed, a stroke of a rack shaft 5 to a steering quantity of a steering wheel 1 is made small compared with the time of a large steering angle, that is, a relatively large gear ratio area is provided, while the stroke of the rack shaft 5 is made large in a large steering angle range of the steering wheel 1 so as to be suited to perform large steering in low speed travel. Rack teeth 5a are formed at variable pitch in order to make the whole rotation angle of the steering wheel 1 small. That is, the pitch of the rack teeth 5a is made larger as it goes away from neutral so that a pinion 4 reaches the terminal end of the rack teeth 5a when it is rotated almost one round, thus affording a maximum steering angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system having a rack and pinion mechanism, and more particularly to a rack steering system.
The present invention relates to a variable gear ratio steering device in which a gear ratio of an AND / pinion mechanism changes according to a steering angle.

[0002]

2. Description of the Related Art In a steering device having a rack and pinion mechanism, a steering shaft connected to a steering wheel is connected to a universal joint, and a rotary motion of a pinion connected to the steering shaft is connected to a straight line of a rack. It is converted into a motion, and further converted into a steering motion of a wheel through a tie rod and a knuckle arm.

[0003]

By the way, in the conventional general rack-and-pinion mechanism, the maximum turning angle is 1.5 rotations on one side of the steering wheel (540 rpm) with the pitch of the pinion and the rack teeth being constant. As can be obtained by
That is, the steering characteristic is generally set to about 1.5 rotations (540 °). Therefore, visually check the wheels before riding,
After that, if the steering wheel is visually inspected, the direction in which the wheel is turned with respect to the position of the steering wheel 1 can be intuitively understood to some extent, but the turning angle θ of the tire is often unknown. For example, in the case of FIG. 3A, the actual turning angle β ° of the steering wheel 1 and the steering angle of the steering wheel which is intuitively determined substantially match. However, in the case of FIG. 3B, the actual handle 1
The steering angle is 360 ° + β, but it is difficult to judge whether the steering angle of the steering wheel 1 is β ° or 360 + β °. In some cases, it is possible to make a mistake in the judgment and assume that the tire is in a straight state by turning the steering wheel back by β ° when starting. Then, the driver noticed this when the vehicle was trying to move in an unexpected direction and had to make a sharp steering wheel correction, which was uncomfortable.

In addition, the operation of the steering wheel that rotates 540 ° on one side as described above has a low responsiveness and is not suitable for traveling that requires agile steering.
As shown in (1), it is necessary to cross the hands gripping the steering wheel near 180 ° and 450 ° and further hold the handle, which makes it difficult to delicately steer the vehicle at that portion, and maneuverability deteriorates. It suffices to make the steering characteristic smaller than 1.5 revolutions, but this time, the responsiveness in the vicinity of the center (steering angle 0 °) is too high, and in some cases there is a concern that high-speed stability may be reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and its main purpose is to prevent the wheel turning angle when the vehicle is stopped without impairing stability at high speed and maneuverability at low speed. It is an object of the present invention to provide a vehicle steering system in which it is easy to intuitively recognize from the apparent steering angle of the steering wheel and the cost increase for that is minimized.

[0006] The present inventors have found that in a normal steering range during medium- and high-speed traveling (for example, in a range of about 150 ° from the neutral side to the left and right), the rack shaft relative to the steering amount of the steering wheel compared to the large steering angle. The stroke of the steering wheel is small, that is, the area where the gear ratio is relatively large is provided, and when performing large steering at low speed traveling, the stroke of the rack shaft is increased in the large steering angle range of the steering wheel to increase the rotation angle of the entire steering wheel. A variable steering angle ratio steering device that is made smaller, in particular, a variable gear ratio mechanism, for example, by using a rack and pinion mechanism, by using a variable steering angle ratio steering device in which the teeth of the rack have a variable pitch We focused on the fact that the steering characteristics can be set to some extent.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the above object is achieved by rolling with a handle via a rack and pinion mechanism in which the pitch of the rack teeth is set to be larger near the ends than at the neutral position. In a vehicle steering system in which a steering wheel is connected, the pitch of the rack teeth is set such that the maximum rotation angle of the steering wheel that generates the maximum steering angle is within one rotation on each side. It is achieved by providing a vehicle steering system. In particular, it is preferable to set the rotation angle of the steering wheel to one rotation on each side, and it is more preferable to provide a power steering device that applies an auxiliary steering force to the steering device.

[0008]

By doing so, it is possible to judge how much the wheel is actually tilted only by looking at the angle of the steering wheel. Moreover, in the vicinity of the neutral position, the same responsiveness as that of the conventional steering device in which the pitch of the rack teeth is constant can be obtained. Further, by setting the maximum rotation angle of the steering wheel to one rotation or less on one side, it is possible to cross the hands gripping the steering wheel until reaching the maximum steering angle, and to carry out another change operation only once, thus improving maneuverability.

FIG. 5 is a graph showing the relationship between the maximum steering angle at which the maximum steering angle can be obtained and the turning performance (relationship between steering angle and yaw angle) of a rack of a rack and pinion mechanism. A variable steering ratio steering device having variable teeth (hereinafter, simply referred to as variable steering ratio steering device in the present specification) is shown by a solid line, and a steering device having a constant rack tooth pitch (hereinafter, referred to as the present specification). In the description, it is referred to as a constant steering angle ratio steering device.)
Is indicated by a broken line. Generally, it is said that a turning performance of about 0.3 is preferable. In order to obtain a turning performance of about 0.3, the steering characteristic is around 540 ° in the constant steering angle ratio steering device, and the steering characteristic is in the variable steering angle ratio steering device. Characteristic is about 300 ° or more. Therefore, if the turning angle of the steering wheel is set to about one rotation on one side, the responsiveness during running becomes substantially the same as the conventional steering characteristic with the turning characteristic of 1.5 rotations without sensitization. By additionally providing the power steering mechanism in such a setting, the load at a large steering angle at a low speed is remarkably reduced, and the steering feeling becomes similar to that of the constant steering angle ratio steering device.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a preferred embodiment of the present invention.

FIG. 1 is a diagram showing a schematic configuration of a rack-and-pinion type steering device having an electric power steering device to which the present invention is applied. A universal joint 3a for the steering shaft 2 that is integrally connected to the steering wheel 1.
A pinion 4 of a rack-and-pinion mechanism is connected via a connecting shaft 3 having 3b, and both ends of a rack shaft 5 that meshes with the pinion 4 and can reciprocate in the vehicle width direction are connected to left and right via tie rods 6. The knuckle arm of the front wheel 7 is connected. As a result, a normal rack-and-pinion steering operation can be performed. Further, in order to reduce the manual steering force of the steering wheel 1, an electric power steering device 8 which applies an auxiliary steering force acts on the rack shaft 5.

A steering torque detector 10 having a built-in torsion bar for detecting the manual steering force acting on the pinion 4 is provided in the steering gear box, and the detection signal is input to the control unit 11. There is. The control section 11 outputs the motor drive signal to the motor 8 in the electric power steering apparatus 12 by using the detection signal as a main signal and controls the motor drive signal.

In the above steering device, in a normal steering range during medium- and high-speed traveling (for example, a range of about 150 ° from the neutral side to the left and right), the rack amount relative to the steering amount of the steering wheel 1 is larger than that at a large steering angle. When the stroke of the shaft 5 is small, that is, a region having a relatively large gear ratio is provided, and when the steering wheel is steered at a low speed, the stroke of the rack shaft 5 is increased within the large steering angle range of the steering wheel 1 to increase the stroke of the steering wheel 1. In order to reduce the entire rotation angle, the rack teeth 5a have a variable pitch as shown in FIGS. 2 (a) and 2 (b). That is, the rack teeth 5a
The pitch is increased as it moves away from the neutral position (the portion where the pinion 4 is shown by the phantom line in the figure) (the portion where the pinion 4 is shown by the solid line in the figure). When the pinion 4 makes about one rotation (360 ° rotation), the rack teeth 5a reach the end and the maximum steering angle is obtained, that is, the steering characteristic is set to about one rotation. Therefore, when the steering wheel 1 is rotated substantially one turn to the left or right, the maximum steering angle is obtained, and the steering angle of the wheel can be easily recognized by the angle of the steering wheel 1 when the vehicle is stopped. Further, as shown in FIG. 5, in the variable steering angle ratio steering device, since the turning characteristic is larger than 300 °, the turning ability becomes about 0.3, and a proper steering feeling can be obtained.

In this embodiment, the rack-and-pinion mechanism is used, and the variable steering angle ratio steering device in which the teeth of the rack have a variable pitch is used. However, the transmission ratio between the pinion and the steering wheel is It goes without saying that the same effect can be obtained by using other variable steering ratio steering devices such as those that change according to the steering angle, and the setting can be arbitrarily changed.

[0015]

As is apparent from the above description, according to the vehicle steering system of the present invention, the rack and pinion in which the pitch of the rack teeth is set to be larger in the vicinity of the end portion than in the neutral position. In a vehicle steering system in which a steering wheel and a steered wheel are connected via a mechanism, the maximum steering angle of the steering wheel that produces the maximum steering angle is set within one rotation on each side, so that the steering wheel is stopped when the vehicle is stopped. The steering angle of the wheel can be easily recognized by the angle of. In addition, the pitch of the rack teeth becomes narrow near the neutral position, and the stroke of the rack shaft is small with respect to the steering amount of the steering wheel. Vehicle behavior, eg yaw rate,
Sensitivity to lateral acceleration can be suppressed, and maneuverability during high-speed traveling is not reduced. In addition, the operation of crossing the hands gripping the steering wheel until reaching the maximum steering angle and further changing the grip is improved once, and maneuverability is improved. Further, by setting the maximum rotation angle of the handle to be 300 degrees or more on one side, the turning performance becomes about 0.3 which is preferable, and high maneuverability can be obtained. Further, by additionally providing the power steering mechanism in such a setting, the load at a large steering angle at a low speed is remarkably reduced, the steering feeling becomes similar to that of the constant steering angle ratio steering device, and the maneuverability with a high phase is achieved. can get. Moreover, since this can be achieved only by changing the pitch of the rack teeth, the cost increase can be minimized.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a rack-and-pinion type steering device having an electric power steering device to which the present invention is applied.

2 (a) is an enlarged plan view of an essential part of FIG. 1, and FIG. 2 (b) is
Sectional drawing seen about the bb line of (a).

3A and 3B are diagrams showing a relationship between a steering wheel turning angle and a tire turning angle in a conventional constant steering angle ratio steering device.

FIG. 4 is a graph showing a relationship between a steering angle of a steering wheel and maneuverability.

FIG. 5 is a graph showing the relationship between the maximum steering angle at which the maximum steering angle is obtained and the turning performance (relationship between steering angle and yaw angle).

[Explanation of symbols]

 1 steering wheel 2 steering shaft 3 connecting shafts 3a and 3b universal joint 4 pinion shaft 5 rack 5a rack tooth 6 tie rod 7 front wheel 8 electric power steering device 10 steering torque detector 11 control unit

Claims (4)

[Claims] 1. A rack and rack having a pitch of rack teeth set to be larger in the vicinity of an end than in a neutral position.
In a vehicle steering system in which a steering wheel and steered wheels are connected via a pinion mechanism, the rack teeth are set so that the maximum turning angle of the steering wheel that produces the maximum turning angle is within one rotation on one side. A vehicle steering system characterized in that the pitch of the vehicle is set. 2. The maximum rotation angle of the handle is 30 on one side.
The vehicle steering system according to claim 1, wherein the steering system is set to 0 degrees or more. 3. The steering apparatus for a vehicle according to claim 1, wherein the steering wheel has a rotation angle of about one rotation on each side. 4. The vehicle steering system according to claim 1, further comprising a power steering system for applying an auxiliary steering force to the steering system.