JP2001151136A - Vehicle steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle steering device capable of appropriately varying a transmission ratio by means of a small power source without making a driver feel that a steering wheel is strolling when the transmission ratio is heightened, and allowing its designs and specifications to be varied easily. SOLUTION: The vehicle steering device has a steering gear box 3 for converting the rotational movements of the steering wheel and a steering shaft into the linear movements of movable members 30 and 40 in the cross direction of the vehicle, a pair of tie rods 41 connected at their front ends to the knuckle arms 12a of the pair of right and left wheels W, and a pair of joint members 42 for connecting the rear ends of the pair of tie rods 41 to both ends of the movable members 30 and 40 along the cross direction of the vehicle. The height of each joint member 42 is freely variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ratio (actual steering angle) of a rotation operation angle (steering angle) of a steering wheel and an angle (actual steering angle) at which the direction of a wheel is actually changed based on the operation of the steering wheel. Transmission ratio) according to the running conditions of the vehicle.

[0002] The actual steering angle referred to in the present specification means the angle at which the wheel is actually steered, including the effect of the change in the toe of the wheel due to roll steer. Therefore, the transmission ratio referred to in this specification means the ratio between the steering angle and the actual steering angle in consideration of the change in the toe of the wheel due to the roll steering, and the gear ratio of the steering gear box (the steering gear). Ratio) is a different concept.

[0003]

2. Description of the Related Art As is well known, it is desired that the direction of wheels is not largely changed by a slight rotation operation of a steering wheel when a vehicle is running at high speed. Conversely, when the vehicle is running at a low speed, the steering wheel can be largely steered by a small rotation operation amount of the steering wheel, and the rotation operation amount of the steering wheel when turning or entering the garage can be reduced. It is desired.

[0004] In order to meet such a demand, there is a steering apparatus which can change the transmission ratio by using a differential gear mechanism (for example, Japanese Patent Application Laid-Open No. Sho 61-122071). . That is, as shown in FIG. 8, for example, this conventional device is configured as a rack and pinion type steering device having a pinion shaft 90 and a rack bar 91, and a steering wheel and a steering shaft (not shown) Is transmitted to the pinion shaft 90 and then converted into a straight-ahead operation of the rack bar 91 by the rack and pinion mechanism. A tie rod 93 is connected to each of both ends of the rack bar 91 via a rack end / ball joint 92. When the tie rod 93 moves in the vehicle width direction, the tie rod 93 and a knuckle arm (not shown) are provided. The direction of a wheel (not shown) connected via the interface changes. A differential gear mechanism (not shown) for changing the transmission rate of the force from the pinion shaft 90 to the rack bar 91 is provided in a region indicated by reference numeral Na in FIG. The steering gear ratio can be changed.

[0005]

However, the above-described conventional means has the following problems.

First, when the steering gear ratio is increased, the steering force is correspondingly reduced. Therefore, when the vehicle is traveling straight at high speed with a large steering gear ratio, the driver may be given a feeling of wobbling of the steering wheel, and a sense of psychological stability may not be obtained.

Second, it is necessary to change the steering gear ratio against the steering reaction force. Therefore, as a power source for changing the steering gear ratio, a large power source with high output has been required.

Third, in order to change the range in which the transmission ratio can be variably controlled and the specific numerical value of the transmission ratio, for example, by changing the entire differential gear mechanism, the width of the change in the steering gear ratio and the specific value can be changed. It is necessary to change the numerical value. Therefore, it was not easy to change the design specifications.

The present invention has been conceived under such circumstances, and does not give a driver the feeling that the steering wheel fluctuates when the transmission ratio is increased. It is an object of the present invention to provide a vehicle steering system capable of appropriately changing a transmission ratio depending on a source and easily changing a design specification.

[0010]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

A vehicle steering apparatus provided by the present invention includes a steering gear box for converting a rotation operation of a steering wheel and a steering shaft into a linear movement of a movable member in a vehicle width direction, and knuckle arms of a pair of left and right wheels. A vehicle steering system comprising: a pair of tie rods each having a distal end connected thereto; and a pair of joint members connecting each base end of the pair of tie rods to both ends in the vehicle width direction of the movable member. Wherein the height of each joint member is changeable.

In the present invention, the transmission ratio is suitably changed by effectively utilizing the phenomenon that the toe change of the wheels occurs when the vehicle turns and the wheels bounce or rebound relative to the vehicle body. You can do it.
That is, when the suspension and the steering device of the independent suspension system such as the MacPherson strut system and the double wishbone system are combined with each other, when the vehicle turns and the wheels bounce or rebound, the tie rods move upward or downward accordingly. As a result, it is known that a phenomenon occurs in which the wheel is steered in the toe-in direction or the toe-out direction. In the present invention, the movement trajectory of the tip of the tie rod when the above-mentioned phenomenon occurs can be adjusted by changing the height of each joint member, whereby the wheel rolls in the toe-in or toe-out direction. The actual steering angle can be adjusted by adjusting the amount of steering. For example, in the present invention, when each of the joint members is lowered, the amount of turning when the wheels bounce and are turned in the toe-out direction is smaller than when each of the joint members is not lowered. It is possible to increase the actual steering angle of the wheel between the case where the height of each joint member is high and the case where the height is low, and the transmission ratio can be changed by changing the height of each joint member. Can be variously changed. As a result, the following effects can be obtained in the present invention.

First, in the present invention, unlike the prior art, since the steering gear ratio itself is not changed, the steering reaction force at the time of high-speed running is made equal to the steering reaction force at the time of medium / low speed running. It is possible to Therefore, it is possible to prevent the driver from having a feeling that the steering wheel fluctuates when traveling straight at high speed, and to obtain a sense of psychological stability.

Second, in order to change the transmission ratio in the present invention, it is sufficient to move each of the above joint members in the vehicle height direction, and the moving direction is determined by the steering reaction force acting on each part of the steering device. It does not match the direction of action. Therefore, the movement of each of the joint members can be performed with a force smaller than the steering reaction force, and the drive source for changing the transmission ratio can be smaller and lighter than the conventional one. .

Third, in the present invention, the relative relationship between the steering angle and the actual steering angle is changed to various variations by changing the height of each joint member and the timing of changing the height. can do. Therefore, changes in design specifications such as the range in which the transmission ratio can be variably controlled and specific numerical values of the transmission ratio can be made easier than before.

In a preferred embodiment of the present invention, the movable member includes a rack bar extending in a vehicle width direction;
A pair of arms attached to the rack bar and rotatable in the vehicle height direction, and the joint members are supported by the arms.

According to such a configuration, by rotating the pair of arms, it is possible to appropriately change the height of each of the joint members. Of course, when the rack bar is displaced in the vehicle width direction, the joint members are also displaced in the vehicle width direction, so that the steering operation of the wheels can be appropriately performed.

Other features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIGS. 1 to 4 show an example of a vehicle steering system according to the present invention. In the drawings after FIG. 1, an arrow Fr indicates the front of the vehicle, an arrow Up indicates an upper portion in the vehicle height direction, and an arrow w indicates the vehicle width direction.

As best shown in FIG. 3, the steering apparatus A of the present embodiment is used in combination with a suspension S of an independent suspension system. As the suspension S, for example, a conventionally known strut type is used, and one end of each of a pair of left and right wheels (front wheels) W is connected to a body frame 13 via a swing fulcrum 11.
Arm 10 swingable in the vehicle height direction connected to the lower arm 10
Supported by A shock absorber 14 with a coil spring is provided between the knuckle 12 of each wheel W and the vehicle body above it.

As best seen in FIG. 1, the steering system A
Is a steering gear box 3, a pair of arms 40,
A pair of tie rods 41, a pair of ball joints 42,
A toe control bar 43, a first pulley 44, a second pulley 45, and a motor M are generally provided.

When the rotation of the steering wheel 20 and the steering shaft 21 shown in FIG. 3 is transmitted to the pinion shaft 31, the steering gear box 3 converts the rotation into a straight-ahead movement of the rack bar 30 in the vehicle width direction. The basic structure is the same as that of the conventional rack and pinion system. The case 31 of the steering gear box 3
It is fixedly attached to the body frame 13 via a plurality of brackets 32.

The pair of arms 40 are attached to both ends (longitudinal ends) of the rack bar 30 in the vehicle width direction. More specifically, as best seen in FIG. 2, each arm 40 has a small-diameter portion 33 at the longitudinal end of the rack bar 30 penetrating therethrough, and a nut screwed into the small-diameter portion 33. Each arm 40 is attached to each small-diameter portion 33 by fastening 50. However, each arm 40 is mounted so as to be rotatable around the small diameter portion 33 of the rack bar 30 in the vehicle height direction, and a thrust bearing 51 for smooth rotation is provided on one side thereof. ing.

As shown in FIG. 1, each of the tie rods 41 has a knuckle arm 12a at the tip end of the wheel W.
And a ball joint (tie rod end / ball joint) 49. As the tie rod 41 is displaced in the vehicle width direction, the direction of the wheel W is changed. However, the base end of each tie rod 41 is attached to each arm 40 via each ball joint 42. Each ball joint 42 corresponds to a so-called rack-end ball joint. When each arm 40 rotates in the vehicle height direction as indicated by an arrow N1 in the figure, the height is changed accordingly. It has become.

The toe control bar 43 extends in the vehicle width direction and connects the pair of arms 40 to each other.
First and second pulleys 44 and 45 and motor M
Is a pair of arms 4 via a toe control bar 43.
A drive mechanism for rotating 0 in the vehicle height direction is configured. The second pulley 45 is fitted around the case 31 of the steering gear box 3 and is rotatable around the case 31. The second pulley 45 has a structure in which a plurality of divided members are connected to each other using bolts so that the case 31 can be sandwiched from both sides thereof, so that the outside of the case 31 can be easily fitted. I have. The first pulley 44 is rotatable in both forward and reverse directions by a motor M.
The first and second pulleys 44 and 45 are connected to each other via a wire 52 so that the rotational force of the fourth pulley 45 is transmitted to the second pulley 45. However, the second pulley 45
Has a toe control bar 43 penetrating therethrough. Therefore, in the steering device A, by driving the motor M, the toe control bar 43 and the pair of arms 40 can be rotated around the axis of the rack bar 30 in the vehicle height direction. Accordingly, the height of each ball joint 42 can be freely changed. That is, in the steering device A, as shown in FIG. 3, each ball joint 42 can be raised, or as shown in FIG. 4, each ball joint 42 can be lowered.

Next, the operation of the steering device A having the above configuration will be described.

The steering apparatus A of the present embodiment makes use of the roll steering phenomenon in which the direction of the wheel changes when the vehicle rolls and the wheel bounces or rebounds. Is controlled. In order to understand the operation of the steering device A according to the present embodiment, it is necessary to understand the principle of such a roll steer, and the contents will be described first with reference to FIGS.

FIG. 6 schematically shows a vehicle in which a strut type suspension and a steering device are combined. In the figure, reference numeral 85 is a steering gear box. When the vehicle turns, as shown in the figure, the outer-wheel-side wheels Wa bounce relative to the vehicle body, and the inner-wheel-side wheels Wb rebound relative to the vehicle body. When the wheel Wa bounces, as shown in FIG. 7A, the lower arm 80 rotates upward around the swing fulcrum 81 and the tie rod 82
Also rotates upward about the ball joint 83 (rack end ball joint). However, since the rotation radius and the rotation trajectories L1 and L2 of the respective tip portions of these members are different, for example, the tip portion 82a of the tie rod 82 is inward in the vehicle width direction relative to the tip portion 80a of the lower arm 80. May be displaced. For this reason, FIG.
As shown in (5), the knuckle arm 84 to which the distal end portion 82a of the tie rod 82 is connected is pulled inward in the vehicle width direction, causing an alignment change in which the wheel Wa is steered in the toe-out direction by a predetermined angle θ. When the phenomenon of turning the wheel Wa in the toe-out direction is caused when the wheel Wa is to be steered in the toe-in direction, it is possible to reduce the actual steering angle of the wheel Wa,
The present invention uses such a principle to control the actual steering angle of the wheel. Wheel W on the rebound side shown in FIG.
In the case of b, contrary to the above, roll steering in which the wheel Wb is steered in the toe-in direction occurs.

In the steering apparatus A of the present embodiment, control is performed to change the height of each ball joint 42 according to, for example, the vehicle speed. When the vehicle speed is high, the ball joints 42 are lowered by operating the motor M, for example, as shown in FIG. In such a state, when the vehicle turns and rolls and the wheel W on the outer wheel side bounces, as shown by the phantom line in FIG. 5, when the height of the ball joint 42 is low, the tip of the tie rod 41 The locus L3 drawn by the ball joint 49 is different from the locus L4 drawn by the ball joint 49 when the height of the ball joint 42 shown by the solid line in the figure is high. That is, the trajectory L3 when the height of the ball joint 42 is low is larger than the trajectory L4 when the height of the ball joint 42 is high when the wheel W bounces upward and the ball joint 49 and the knuckle arm 12
a becomes a trajectory for displacing a more inward in the vehicle width direction.
Therefore, the amount of turning of the wheel W in the toe-out direction when the alignant change as shown in FIGS. 7A and 7B occurs can be increased accordingly.

When the vehicle is turning, the outer wheel W
Is actually steered in the toe-in direction. Therefore, the actual steering angle of the wheel W is a value obtained by subtracting the angle at which the wheel W is steered in the toe-out direction due to the above-described alignment change from the steering angle of the wheel W corresponding to the rotational operation amount of the steering wheel 20. . As described above, at the time of high-speed running, the amount of roll steer in which the wheel W is steered in the toe-out direction can be increased, so that the ratio between the steering angle and the actual steering angle can be increased. Therefore,
The stability of the vehicle during high-speed running can be improved.

The other wheel W located on the inner wheel side and rebounding causes a roll steer to be steered in the toe-in direction opposite to the above-described wheel W on the bounding side. The amount of steering in the toe-in direction can be increased by the lower height of the ball joint 42 according to the same principle as described above. Therefore, for the inner wheels that are steered to toe-out,
The actual steering angle can be reduced, and the stability of the vehicle can be increased.

Next, when the vehicle speed is low, the motor M
Is reversed to move each ball joint 42 to a higher position, contrary to the above. In this way, as can be understood from the contents described with reference to FIG. 5, the amount by which the wheel W is steered in the toe-out direction when the wheel W bounces is determined by the height of each ball joint 42. Is smaller than when the steering angle is low, and the actual steering angle can be increased. Similarly, when the wheel W rebounds, the amount by which the wheel W is steered in the toe-in direction can be reduced, and the actual steering angle can be increased. Therefore, in this case, the transmission ratio can be made smaller than in the case of high-speed running, and the operability of the steering wheel 20 when turning the vehicle at low speed can be improved.

As described above, in the steering device A of the present embodiment, the transmission ratio can be changed without changing the steering gear ratio of the steering device. For this reason,
It is possible to eliminate the feeling of wobbling of the steering wheel 20 that would occur when the steering gear ratio is increased during high-speed running.

The amount of steering in the toe-out direction when the wheel W bounces and the amount of steering in the toe-in direction when the wheel W rebounds are determined by the ball joints 42.
Can be controlled by adjusting the height. Therefore, in the steering device A, for example, the vehicle speed is divided into a plurality of stages such as a low speed region, a medium speed region, and a high speed region, and the height of each ball joint 42 is set to a predetermined height according to the speed region. With such a change, a transmission ratio suitable for those speeds can be obtained. Of course, it is also possible to control the height of each ball joint 42 by considering the roll angle and the yaw rate of the vehicle as parameters other than the vehicle speed. The relationship between the steering angle and the actual steering angle can be easily changed by changing the height of each ball joint 42, the timing of changing the height, and the like. By changing the distance L between the center of rotation of each arm 40 and the center of each ball joint 42, the relationship between the amount of rotation of the drive shaft of the motor M and the amount of displacement of each ball joint 42 in the vehicle height direction is determined. Can also be easily changed. Therefore, in the steering device A, the design specification can be easily changed.

In the steering apparatus A of this embodiment, the height of each ball joint 42 is changed by rotating each arm 40 and the toe control bar 43 in the vehicle height direction. The rotation direction is a direction orthogonal to the direction in which the steering reaction force acts on each tie rod 41 and each rack bar 30 from each wheel W. Therefore, the height of each ball joint 42 can be changed with a force smaller than the steering reaction force, and a small and lightweight motor M can be used.

The specific structure of each part of the vehicle steering system according to the present invention is not limited to the above-described embodiment, and various design changes can be made.

In the above-described embodiment, the case where the tie rod is located behind the wheel and the wheel steers in the toe-out direction when the wheel bounces is described as an example. Depending on the specific structure (for example, a structure in which a tie rod is in front of the wheel), the wheel may steer in the toe-in direction opposite to the above when the wheel bounces. The present invention is
It is also possible to apply to such a suspension. In this case, by changing the height of the joint member (joint member corresponding to the ball joint 42) at the base end of the tie rod, when the wheel bounces, Is adjusted in the toe-in direction, whereby the steering control intended by the present invention can be performed. The present invention is not limited to the strut type suspension, and can be applied to a case where a wishbone type suspension or another type of suspension is used.

In the present invention, the specific means for changing the height of the joint member at the base end of the tie rod is not limited to that of the above embodiment, and various other means may be used. It is possible. Further, in the present invention, a steering gear box of a type different from the rack and pinion type can be used. Further, it goes without saying that the present invention can be configured as a steering device having a power steering function.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing an example of a vehicle steering system according to the present invention.

FIG. 2 is a plan view of a main part of FIG.

FIG. 3 is a front view from the front of the vehicle schematically showing an example of the entire structure of the vehicle steering device according to the present invention.

FIG. 4 is a front view from the front of the vehicle, schematically illustrating an operation state of the entire structure of the vehicle steering device according to the present invention.

FIG. 5 is an operation explanatory view of the present invention.

FIG. 6 is a front view from the front of the vehicle, schematically showing an operation state of wheels for understanding the present invention.

FIG. 7A is a front view of a main part from the front of the vehicle, schematically showing an operation state of wheels for understanding the present invention, and FIG. 7B is a plan view of the main part.

FIG. 8 is a sectional view of a main part showing a conventional example.

[Description of Signs] A Steering device M Motor 3 Steering gear box 30 Rack bar 40 Arm 41 Tie rod 42 Ball joint 43 Toe control bar 44 First pulley 45 Second pulley

Continued on the front page F term (reference) 3D001 AA12 AA43 BA02 BA03 DA04 EA22 EB12 ED02 3D032 CC00 CC08 CC49 DA23 EA01 EB05 EC31 GG01 3D033 JB01 JB19 3D034 BA02 BC02 BC14 BC25 BD02 BD05

Claims (2)

[Claims] 1. A steering gear box for converting a rotation operation of a steering wheel and a steering shaft into a linear movement of a movable member in a vehicle width direction, and a pair of tie rods each having a distal end connected to each knuckle arm of a pair of left and right wheels. And a pair of joint members for connecting each base end of the pair of tie rods to both ends of the movable member in the vehicle width direction, wherein the height of each of the joint members is A steering device for a vehicle, wherein the steering wheel is changeable. 2. The movable member includes a rack bar extending in the vehicle width direction, and a pair of arms attached to the rack bar and rotatable in the vehicle height direction. , Supported by each of the above arms,
The vehicle steering apparatus according to claim 1.