JP2000053005A - Vehicle steering system - Google Patents

Abstract

(57) [Abstract] [Problem] To increase the sense of neutral rigidity of the steered wheels,
To improve the straight running stability during high-speed running. SOLUTION: A steering shaft 2 not mechanically connected to a steering mechanism for changing the direction of wheels, and a pair of coil springs 41 for urging the steered wheels connected thereto to return to a steering neutral point. , 41, and the coil spring 4
A predetermined elastic restoring force is preloaded left and right when the steered wheels are at the steering neutral point, so that the coil springs 4 until the steering torque reaches the preloaded elastic restoring force.
Thus, the deflection of the steering wheels can be restrained to improve the neutral rigidity of the steered wheels.

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 in which a steering shaft connected to a steered wheel is not mechanically connected to a steering mechanism for changing the direction of the wheel.

[0002]

2. Description of the Related Art A vehicle steering system includes a link type in which a steering shaft connected to steered wheels is mechanically connected to a steering mechanism, and a steering system in which the steering shaft is mechanically connected to the steering mechanism. There is no linkless type.

The latter linkless type is disclosed in, for example,
As described in JP-A-153379, the steering shaft is separated from the steering mechanism, a steering motor as a steering actuator is provided in the middle of the steering mechanism, and the control unit includes a steering wheel. By driving and controlling the actuator according to the deviation between the actual steering angle and the target steering angle,
The steering wheel is adjusted to the target steering angle. Further, the steering shaft is provided with a pair of compression coil springs disposed apart in the axial direction to bias the steered wheels toward the steering neutral point, and the vibration of the steered wheels caused by the compression coil springs is caused by the viscous resistance of the fluid. An attenuating damper is provided.

[0004]

However, in the conventional linkless steering apparatus configured as described above, the elastic body that positions the steered wheels at the neutral steering point has a linear elastic restoring force with respect to the steering angle. Because of the gradual increase (broken line in FIG. 6), there is a problem that the steered wheels do not have a sense of neutral rigidity and the straight running stability is impaired during high-speed running.

[0005] Further, since a pair of compression coil springs are arranged around the axis of the steering shaft so as to be separated from each other in the axial direction, the length of the steering shaft becomes longer and the whole device becomes larger. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in a linkless vehicle steering system, a predetermined elastic body for urging the steered wheels to return to a steering neutral point. By preloading the elastic restoring force, the neutral stiffness of the steered wheels can be increased, the straight running stability during high-speed running can be improved, and the gear meshes with a small diameter gear that works with the steering shaft. A projection is provided on the large-diameter gear that is decelerated and rotated, and a pair of coil springs for sandwiching the projection from both sides is used to preload the elastic restoring force, whereby the steered wheels are rotated by 360 degrees or more. Even in such a case, it is an object of the present invention to provide a vehicle steering device capable of reducing the size of a pair of coil springs.

[0007]

According to a first aspect of the present invention, there is provided a vehicle steering system which is connected to a steering shaft supported by a stationary member without being mechanically connected to a steering mechanism for changing the direction of wheels. In a vehicle steering system provided with an elastic body for urging a steered wheel to return to a steering neutral point, a predetermined elastic restoring force is pre-pressed to the left and right when the steered wheel is at the steering neutral point. It is characterized by having.

In the first invention, when the steering angle increases from the steering neutral point, the bending of the elastic body is restricted until the steering torque reaches the elastic restoring force pre-pressed by the elastic body,
Neutral rigidity can be improved. Further, when the steering torque exceeds the preloaded elastic restoring force, the elastic body starts to bend, so that a predetermined steering reaction force can be applied to the steered wheels.

A vehicle steering system according to a second aspect of the present invention is a small-diameter gear interlocked with the steering shaft, a large-diameter gear meshed with the small-diameter gear, and extending radially outward from the large-diameter gear or a member interlocked with the large-diameter gear. A projection, and the elastic body using a pair of coil springs for sandwiching the projection from both sides of the large-diameter gear or the member in the rotation direction, wherein the elastic restoring force is preloaded. .

According to the second aspect of the present invention, the number of steered wheels is 360.
Even when rotating more than degrees, the rotation angle of the projection can be reduced, so that the pair of coil springs can be reduced in size and the members provided with these coil springs can be reduced in size. Since it can be disposed radially outward of the large-diameter gear, the axial length of the steering shaft is smaller than that of the conventional example in which a pair of compression coil springs are arranged at a distance in the axial direction around the axis of the steering shaft. Can be shortened, and the overall size can be reduced as compared with the conventional example.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a sectional view of a steering shaft portion of a vehicle steering system according to the present invention, and FIG. 3 is a schematic diagram of the steering system.

The vehicle steering system includes a steering mechanism 1 for causing a pair of steering wheels A, A disposed on the left and right sides of a vehicle body (not shown) to perform a steering operation, and mechanically controlling the steering mechanism 1. A rotatable steering shaft 2 disposed separately, and the steering shaft 2
A steering wheel 3 connected to the upper end of the steering wheel, an elastic body 4 for urging the steering wheel 3 to the neutral steering point, and a steering limit angle setting for setting a left-right steering limit angle with respect to the neutral steering point of the steering wheel 3 Means 5 and a steering control unit 6 using a microprocessor
And a steering motor 7 disposed in the middle of the steering mechanism 1. The operation of the steering control unit 6 in accordance with the steering of the steered wheels 3 drives the steering motor 7 to control the steering mechanism 1. It is configured to operate.

As is well known, the steering mechanism 1 includes both ends of a steering shaft 11 that extends in the left-right direction of the vehicle body and slides in the axial direction, and knuckle arms 12 that support the wheels A, A. 12
Are connected by separate tie rods 13, 13, and the knuckle arms 12, 12 are pushed and pulled via the tie rods 13, 13 by sliding the steering shaft 11 in both directions.
A is to steer A left and right, and this steering is
The rotation of the steering motor 7 formed coaxially in the middle of the first motor 1 is converted into sliding of the steering shaft 11 by an appropriate motion conversion mechanism.

The rotation of the steering shaft 11 around the shaft is restricted by rotation restricting means (not shown) interposed between the steering shaft 11 and the steering shaft housing 14.
The rotation of the steering motor 7 is converted into sliding in the axial direction of the steering shaft 11, and the steering (steering for steering) according to the rotation of the steering motor 7 is performed. The steering of the wheels A, A) is performed. The steering shaft housing 14 is provided with a rotation angle sensor 15 for detecting the rotation angle of the steering motor 7, and outputs a signal indicating the rotation position of the output shaft of the steering motor 7 to the steering control unit 6. Has been given to.

An operation command from the steering control unit 6 is given to the steering motor 7 via a drive circuit (not shown), and the steering motor 7 is driven in accordance with the operation command. is there. The amount of operation of the steering mechanism 1 in response to this drive is detected by a tie rod displacement sensor 16 that detects the displacement of the connection between the steering shaft 11 and the tie rod 13 on one side. The signal indicating the steering angle is provided to the steering control unit 6.

Also, the tie rods 13 on both sides have
A tie rod axial force sensor 17, 17 for detecting an axial force (tensile force or compressive force) acting in these axial directions is additionally provided, and the detection results are obtained by the steering wheels A, The steering control unit 6 is provided as a signal indicating the road surface reaction force applied to A.

A steering angle sensor (not shown) for detecting the rotation angle of the steering shaft 2 is provided between the steering shaft 2 and the steering shaft housing 8 on which the steering shaft 2 is supported, and the steering of the steered wheels 3 is performed. The signal indicating the angle is given to the steering control unit 6.

A reaction motor (DC motor) 9 is attached to the outside of the steering shaft housing 8 in such a manner that the steering shaft 2 and the axis are orthogonal to each other as shown in FIG.

The reaction force motor 9 has a worm 30 connected to an output end thereof inside the steering shaft housing 8 and a worm wheel 3 fitted to an outer periphery of an intermediate portion of the steering shaft 2.
1 and applies a rotational force to the steering shaft 2 via the worm 30 and the worm wheel 31 to apply a reaction force to the steering wheel 3 fixed to one end of the steering shaft 2 in a direction opposite to the operation direction. It is made to do.

The reaction force is applied to the steered wheels 3 by the reaction motor 9 by simulating the road surface reaction force actually applied to the steering wheels A, A to the steered wheels 3 in accordance with the steering. The operation command from the steering control unit 6 is given to the reaction force motor 9 via a drive circuit (not shown), and the reaction motor 9 is driven in accordance with the operation command.

Therefore, it is necessary to apply a steering torque against the reaction force generated by the reaction motor 9 to the rotation operation of the steering wheel 3, and the steering torque applied to the steering wheel 3 in this manner is controlled by the steering shaft. The rotation position of the steered wheels 3 is detected by the torque sensor 32 provided between the intermediate portion of the steering wheel 2 and the inner periphery of the steering shaft housing 8, including the operation direction.

As described above, the steering control unit 6 includes the steering mechanism 1
Is provided as an input from the rotation angle sensor 15, the tie rod displacement sensor 16, and the tie rod axial force sensors 17, 17, and the operation state of the steered wheels 3 is indicated by the torque. It is provided as inputs from a sensor 32 and a steering angle sensor. In addition to these, on the input side of the steering control unit 6, an output of a vehicle speed sensor 33 for detecting a running speed of the vehicle, a yaw rate for detecting a yaw rate of the vehicle The output of the sensor 34, the output of the lateral acceleration sensor 35 for detecting the lateral acceleration of the vehicle, and the output of the longitudinal acceleration sensor 36 for detecting the longitudinal acceleration of the vehicle are provided.

The vehicle speed sensor 33 may be, for example, a rotational speed sensor that detects the rotational speed of the front wheel or the rear wheel corresponding to the vehicle speed. Further, the yaw rate sensor 34 and the lateral acceleration sensor 35 are both for knowing the turning state of the vehicle, and when one of them fails, the other is used for fail-safe use. Normally, the output of the yaw rate sensor 34 is used as a signal indicating the turning state.

On the other hand, the output of the steering control unit 6 is sent to the steering motor 7 for causing the steering mechanism 1 to perform a steering operation and the reaction force motor 9 for applying a reaction force to the steered wheels 3 as described above. The steering motor 7 and the reaction motor 9 are provided via respective drive circuits, and are individually driven in response to operation commands from the steering control unit 6.

The steering shaft 2, which is mechanically separated from the steering mechanism 1 that performs the above-described steering operation, is arranged via a steering shaft housing 8 as schematically shown in FIG. It is supported by an appropriate part.

The steering shaft 2 has a first steering shaft 21 having one end directly connected to the steering wheel 3 and a solid second steering shaft 22 connected to the other end of the first steering shaft 21 by a dowel pin 2a.
(A torsion bar), a cylindrical third steering shaft 23 fitted to the outer periphery of one end of the second steering shaft 22 and having one end coupled by the dowel pin 2a, and the third steering shaft 23 and the second steering shaft. The second steering shaft 2 is inserted around the other end of the shaft 22 and
2 and a cylindrical fourth steering shaft 24 connected by a dowel pin 2b. The steering shaft 2 is rotatable with respect to the steering shaft housing 8 via bearings.

The steering limit angle setting means 5 for setting the steering limit angle of the steered wheel 3 is provided between the outer periphery of the other end of the fourth steering shaft 24 and the steering shaft housing 8. A worm shaft 38 having a worm (small diameter gear) 37 is connected to the other end of the fourth steering shaft 24.

The worm shaft 38 is rotatably supported by the steering shaft housing 8 via a pair of bearings, and a worm wheel (large-diameter gear) 39 meshing with the worm 37 is provided via a bearing. The rotation of the fourth steering shaft 24 is reduced and transmitted to the worm wheel 39 while being rotatably supported by the steering shaft housing 8.

At one end of the shaft of the worm wheel 39, there is provided a plate-like projection 40 extending radially outward of the shaft. Elastic bodies 4, 4 for biasing to the steering neutral point are provided on the steering shaft housing 8. In addition, the projection 40 may be provided on the wheel portion of the worm wheel 39 or a member interlocked with the worm wheel 39, in addition to being provided on the shaft portion.

The elastic members 4 and 4 use a pair of coil springs for sandwiching the projections 40 from both sides in the rotation direction of the worm wheel 39. The elastic restoring force of these coil springs 41 and 41 in the axial length direction is used. By acting on both side surfaces of the projection 40, the steering wheel 3 is urged to return to the steering neutral point.

Each of the coil springs 41 is preloaded with a predetermined elastic restoring force in the axial direction, and the steering torque of the steered wheels 3 reaches the preloaded elastic restoring force as shown by the solid line in FIG. During this period, when the deflection of the coil springs 41 is restricted, one of the coil springs 41 starts to bend when the steering torque exceeds the preloaded elastic restoring force.

The coil springs 41, 41 sandwich the projection 40 via spring receivers 42, 42 at one ends of which are received in the axial direction. Further, the coil springs 41 are provided on the steering shaft housing 8 supporting the coil springs 41, 41.
Screw bodies 43, 43 for pressing the other end portions in the axial length direction
Are screwed, and the elastic restoring force of the coil springs 41, 41, which is preloaded, can be adjusted by rotating the screw bodies 43, 43. In addition, screw body 4
The screw bodies 43, 43 are fixed by tightening the lock nuts 44, 44 at the positions adjusted to a predetermined elastic restoring force by screwing the lock nuts 44, 44 with the lock nuts 43, 43, and the pre-loaded elastic restoring force. Can be held.

The steering limit angle setting means 5 enables the steering limit angle of the steered wheels 3 to be set beyond 180 degrees from the neutral steering point, and is deviated from the fourth steering shaft 24 with respect to the axis. A first projection 51 provided, a second projection 52 provided on the steering shaft housing 8 and projecting in the axial length direction of the fourth steering shaft 24, and a fourth steering shaft between the first and second projections 51, 52. 24 is provided so as to be rotatable around, and protrudes outward from one end in the axial direction and is capable of engaging with the first projection 51. A rotating ring 55 having a fourth protrusion 54 that can engage with the second protrusion 52 is provided.

When the steered wheels 3 are steered from the steering neutral point to the left or right, the steering shaft 2 at the steering neutral point is moved to the first protrusion 5.
1 rotates with respect to the rotating ring 55 until the first projection 51 engages with the third projection 53 of the rotating ring 55, and the first projection 51
When engaged with the projection 53, the rotating ring 55 moves the fourth steering shaft 24.
And the fourth projection 54 of the rotary ring 55 engages with the second projection 52 of the steering shaft housing 8 to prevent further rotation. Thus, the rotating ring 5
By providing 5, the steering limit angle can be 180 degrees or more and less than 360 degrees.

The vehicle steering system configured as described above has the following features.
Since the pair of coil springs 41, 41 for urging the steered wheels 3 to return to the steering neutral point is provided, when the steering angle from the steering neutral point to the left or right increases, the steering torque is reduced by the coil spring 41. Until the prestressed elastic restoring force (a in FIG. 6) of the coil springs 41, 41 is reached, the bending of each of the coil springs 41, 41 in the axial direction is restrained, and the sense of neutral rigidity can be improved.

The steering torque is controlled by the coil springs 41 and 4.
When the prestressed elastic restoring force exceeds 1, the one of the coil springs 41 starts to bend as shown in FIG. 6B, and thereafter, the steering can be performed against the elastic restoring force of the coil springs 41, 41. Therefore, a predetermined steering reaction force can be applied to the steered wheels 3.

The projections 40 are provided on the worm wheel 39 which is engaged with the worm 37 which rotates in conjunction with the fourth steering shaft 24 and is rotated at a reduced speed.
More than one degree, and the projection 40 at this time can be moved by about 1/10 rotation. Therefore, each of the coil springs 41, 41 can be reduced in size. The steering shaft housing 8 provided with 41 can be downsized.

Further, a projection 40 extending radially outward from a worm wheel (rotating member) 39 which rotates in conjunction with the fourth steering shaft 24 is provided. A pair of coil springs 4
Since the steering shaft housings 1 and 41 are provided on the steering shaft housing 8, the fourth
The axial length of the steering shaft 2 such as the steering shaft 24 can be reduced as compared with the conventional example in which a pair of compression coil springs are arranged around the axis of the steering shaft so as to be separated in the axial direction.

Although the worm 37 is used as the small-diameter gear and the worm wheel 39 is used as the large-diameter gear in the embodiment described above, a pair of other spur gears may be used.

[0040]

According to the steering apparatus for a vehicle according to the first invention, when the steering angle increases from the neutral steering point, until the steering torque reaches the prestressed elastic restoring force of the elastic body, Bending is restrained, and a sense of neutral rigidity can be improved. Further, when the steering torque exceeds the preloaded elastic restoring force, the elastic body starts to bend, so that a predetermined steering reaction force can be applied to the steered wheels.

According to the vehicle steering system of the second aspect,
Even when the steered wheels rotate more than 360 degrees, the rotation angle of the protrusion can be reduced, so that the pair of coil springs can be reduced in size, and the members provided with these coil springs can be reduced in size. Can be arranged radially outward of the large-diameter gear, so that a pair of compression coil springs are arranged around the axis of the steering shaft at a distance from each other in the axial direction. The length of the shaft can be shortened, and the overall size can be reduced as compared with the conventional example.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of a steering shaft portion of a vehicle steering system according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a schematic diagram showing an embodiment of a vehicle steering system according to the present invention.

FIG. 4 is a plan view of the vehicle steering system according to the present invention.

FIG. 5 is a side view of the vehicle steering system according to the present invention.

FIG. 6 is a characteristic diagram of a steering torque with respect to a steering angle of the vehicle steering system according to the present invention.

FIG. 7 is a perspective view of a steering limit angle setting unit of the vehicle steering system according to the present invention.

FIG. 8 is a schematic diagram showing an operation of a steering limit angle setting means of the vehicle steering device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering mechanism 2 Steering shaft 3 Steering wheel 4 Elastic body 8 Steering shaft housing (stationary member) 37 Worm (small diameter gear) 39 Worm wheel (large diameter gear) 40 Projection 41 Coil spring

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroshi Kawaguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3D033 CA02 CA05 CA11 CA13 CA14 CA16 CA17 CA21 CA27

Claims (2)

[Claims] 1. A method for urging a steering wheel connected to a steering shaft supported by a stationary member without returning to a steering mechanism for changing the direction of a wheel to return to a steering neutral point. The vehicle steering system according to claim 1, wherein the elastic body is pre-loaded with a predetermined elastic restoring force to the left and right when the steered wheel is at a steering neutral point. 2. A small-diameter gear interlocking with the steering shaft, a large-diameter gear meshing therewith, a projection extending radially outward from the large-diameter gear or a member interlocking therewith, and the large-diameter gear 2. The vehicle steering system according to claim 1, further comprising: a pair of coil springs for sandwiching the member from both sides in the rotation direction of the member, wherein the elastic restoring force is preloaded.