JPH0130671B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel steering system for a vehicle that changes the steering ratio and phase of rear wheels relative to front wheels.

[Prior art and problems to be solved by the invention] In JP-A-55-91457 proposed by the present applicant,
2. Description of the Related Art A four-wheel steering system for a vehicle that changes the steering ratio of the rear wheels relative to the front wheels is well known.

The present invention relates to this type of four-wheel steering device,
The objective is to have the rear wheel steering mechanism, which steers the rear wheels, follow the rotation taken from the front wheel steering mechanism, which steers the front wheels in conjunction with the steering operation of the steered wheels, while incorporating a new mechanism. An object of the present invention is to provide a four-wheel steering system for a vehicle that can be used to change the steering ratio and phase of the rear wheels relative to the front wheels.

[Means for Solving the Problems] In order to achieve the above problems, the present invention includes a front wheel steering mechanism 8 that steers the front wheels 6, 6 in conjunction with the steering operation of the steered wheels 1, and rear wheels 36, 36. a rear wheel steering mechanism 38 that steers the front wheels; a rotation shaft 12 that is linked to the front wheel steering mechanism 8 and transmits the front wheel steering direction and amount; and a rotation axis ( yoke member 1 that engages with a rotating member 16 that rotates around (X-X line)
7, a support member 22 that swingably supported the yoke member 17, and an axis (Z
- an actuator 26 that changes the inclination angle of the support member 22 by tilting around the support member 22;
By tilting the yoke member 17 back and forth with respect to the rotation shaft 12, the rotation of the rotation shaft 12 is converted into eccentric rotation of the yoke member 17, so that the rear wheels 36, The present invention is characterized in that a four-wheel steering system for a vehicle is configured to variably control 36 steering ratios and phases.

Specifically, the inclination angle of the support member 22 is changed from the actuator 26 via the worm gears 28 and 29. Further, the displacement of the rotational eccentric position of the yoke member 17 is input to the rear wheel steering mechanism 38.

[Operation] First, the front wheel steering direction and the amount of steering are transmitted by the rotation shaft 12 interlocked with the front wheel steering mechanism 8.

Then, the support member 22 is moved by the actuator 26.
is tilted around an axis (ZZ line) perpendicular to the swing axis (YY line) of the yoke member 17, and as a result, the yoke member 17 having the swing axis (YY line) is tilted around the pivot axis 12. By tilting back and forth against the rotation axis 1
The rotation of 2 is the rotation axis of the rotation member 16 (X-X line)
This is converted into an eccentric rotation of the yoke member 17 through the rotation around the rear wheels 36, 6 relative to the front wheels 6, 6.
The steering ratio and phase of 36 are variable.

In this way, while making the rear wheel steering mechanism 38 follow the rotation taken out from the front wheel steering mechanism 8, changes in the inclination angle of the support member 22 and rotation around the rotation axis (X-X line) of the rotation member 16 are controlled. Due to the eccentric rotation of the yoke member 17 due to the movement, the rear wheels 36,
36 steering ratios and phases can be changed.

Furthermore, the four-wheel steering mechanism as a whole is a mechanism in which the front wheel steering direction and steering amount are transmitted by rotation through the rotation shaft 12, and the inclination angle of the yoke member 17 is changed via the support member 22, so the mechanism itself is made smaller. can. In addition, since the mechanical part that changes the steering ratio and phase does not have a sliding part that moves in the axial direction, the steering rigidity is high.

In particular, since the tilt angle of the support member 22 is changed around the axis (Z-Z line) perpendicular to the swing axis (Y-Y line) of the yoke member 17, the rotation function and the tilt function affect each other. Rotation and tilt can be changed independently. Therefore, there is no need for a correction mechanism that eliminates mutual influence, and the configuration can be made compact.

Further, in the embodiment, the inclination angle of the support member 22 is changed from the actuator 26 to the worm gear 2.
The presence of these worm gears 28 and 29 prevents the actuator (motor) 26 from being turned by an external force, that is, the steering ratio does not change due to an external force.

[Example] Examples will be described below based on the accompanying drawings.

In FIG. 1, a steering shaft 2 of a steering wheel 1 is meshed with a rack shaft 4 in a steering gear box 3 via a pinion, and knuckle arms 7, 7 supporting left and right front wheels 6, 6 are attached to both ends of the rack shaft 4. The front wheels 6, 6 are connected via tie rods 5, 5, and the front wheels 6, 6 are steered in the steering direction of the steered wheels 1 by the front wheel steering mechanism 8, and the steered wheels are steered by a power assisting means (not shown) attached to the steering gear box 3. The steering force of 1 is reduced.

Furthermore, a rotary take-off shaft 9 that meshes with the rack shaft 4 via a pinion is installed in the steering gear box 3 and protrudes rearward, and a long rotary shaft 12 is connected to the rotary take-off shaft 9 via a universal joint 11. A second
An input shaft 14 shown in the figures to FIG. 4 is connected.

An output shaft 16 serving as a rotating member is connected to the input shaft 14 via a pin joint 15, and the output shaft 16 is rotatably fitted into a yoke member 17.
The front part of the yoke member 17 has upper and lower bifurcated parts 18, 18.
The bifurcated portions 18 and 18 are pivotally connected to the upper and lower sides of the support member 22, which has a hollow rectangular shape in front view, by means of vertical support shafts 19, 19, so that the yoke member 17 supports the support member 22 in the upper and lower directions. Axis 19, 19
It is supported so that it can swing freely from side to side.

The support member 22 is a housing 24 fixed to the vehicle body.
A horizontal support shaft 23 protrudes outward from the left and right,
23, and as a result, the support member 22 is supported with respect to the housing 24 so as to be tiltable in the front-rear direction around the left and right support shafts 23, 23.

In this way, the steering ratio changing mechanism 25 is constructed, and furthermore, a motor 26 serving as an actuator is fixedly installed on one outer surface of the housing 24.
A drive shaft 27 protruding downward from the support member 22 and one support shaft 23 of the support member 22 are connected via worm gears 28 and 29. That is, the worm 28 is attached to the drive shaft 27.
A pinion 29 that meshes with the worm 28 is fixed to the support shaft 23.

Further, as shown in FIG. 4, a rear wheel steering control device 31 using an on-vehicle computer, a vehicle speed detecting means 32 for detecting vehicle speed, and a position detecting means 33 for detecting the inclination state of the support member 22 are provided. The control device 31 includes a vehicle speed detection stage 32 and a position detection means 3.
After receiving the signal from motor 3, the appropriate control signal is sent to motor 2.
6 to control its drive.

As shown in FIG. 1, knuckle arms 37, 37 that support the left and right rear wheels 36, 36 are connected to the rear of the yoke member 17 via tie rods 35, 35, and the rear wheels 36, 36 are controlled by the rear wheel steering mechanism 38.
36 is steered as described later in accordance with the operation of the steering ratio changing mechanism 25 by the rear wheel steering control device 31.

The above four-wheel steering system, especially the rear wheels 36, 36
The function of the steering ratio changing mechanism 25 will be explained based on FIG. 5.

First, when the output shaft 16 is located concentrically with the input shaft 14 as shown in FIG.
The input shaft 14 is rotated by the rotation of the rotation shaft 12 that is linked to the front wheel steering mechanism 8 and transmits the front wheel steering direction and amount.
Even if the output shaft 16 rotates via the yoke member 1
Since the tie rod 7 does not rotate around the YY line which is the axis of the support shaft 19, the tie rod 35 does not move in the left-right direction. Therefore, only the front wheels 6, 6 are steered, and the rear wheels 36, 36 are not steered at all.

When the vehicle speed changes from this state, the rear wheel steering control device 31 activates the vehicle speed detection means 32 and the position detection means 33.
The motor 26 receives a signal from the motor 26, makes a judgment, and sends an appropriate control signal corresponding to the vehicle speed to the motor 26 to control its drive. The rotation of the drive shaft 27 due to the drive of the motor 26 is transmitted to the support shaft 23 of the support member 22 via the worm gears 28 and 29, and the rotation of the support shaft 23 causes the support member 22 to rotate along the axis of the support shaft 23, which is Z-
It rotates around the Z line and tilts forward and backward.

That is, if the vehicle speed decreases from the state shown in Figure 5a,
For example, as shown in Figure b, due to the inclination of the support member 22, the output shaft 16 together with the yoke member 17 is inclined downward by an angle α with respect to the 17, this is converted into a rotation around the Y'-Y' line in which the support shaft 19 is tilted backward by an angle α.

Here, the rotation angle φ of the yoke member 17 around the Y'-Y' line with respect to the inclination angle α and the rotation angle θ of the input shaft 12.
The relationship between the rotation angles θ and φ is expressed as tanφ=sinα tanθ, that is, by changing the inclination angle α, the relationship between the rotation angles θ and φ becomes variable.

Therefore, in FIG. 5b, the yoke member 17
When rotated around the Y'--Y' line, the tie rod 35 is moved in the left-right direction, and for example, the rear wheels 36, 36 are steered in the opposite direction to the front wheels 6, 6.

When the vehicle speed increases from the state shown in FIG. As a result, the rotation of the input shaft 14 is converted to rotation around the Y″-Y″ line in which the support shaft 19 is tilted forward by the angle α by the yoke member 17, and this time, the front wheel 6 , 6 are steered in the same direction as the rear wheels 36, 36.

[Effects of the Invention] As described above, according to the present invention, the direction and amount of steering of the front wheels are transmitted by the rotation shaft interlocked with the front wheel steering mechanism, and the actuator moves the support member along the swing axis of the yoke member. By tilting the yoke member, which has a swing axis, back and forth with respect to the rotation axis, the rotation of the rotation axis can be changed to the rotation of the rotation member around the rotation axis. By converting the rotation into eccentric rotation of the yoke member through the yoke member, the steering ratio and phase of the rear wheels relative to the front wheels can be variably controlled.
While the rear wheel steering mechanism follows the rotation extracted from the front wheel steering mechanism, the front wheel is rotated by eccentric rotation of the yoke member due to changes in the inclination angle of the support member and rotation of the rotation member around the rotation axis. It is possible to change the steering ratio and phase of the rear wheels.

Furthermore, the four-wheel steering mechanism as a whole is a mechanism in which the direction and amount of steering of the front wheels are transmitted through the rotation shaft, and the inclination angle of the yoke member is changed via the support member, so the mechanism itself can be made smaller. Even in the mechanism section that changes the steering ratio, the steering rigidity is high because there is no sliding section that moves in the axial direction.

In particular, since the tilt angle of the support member is changed around the axis perpendicular to the swing axis of the yoke member, the rotation function and the tilt function do not affect each other, and the rotation and tilt can be changed independently. Therefore, there is no need for a correction mechanism for eliminating mutual influence, and the structure can be made compact.

In addition, in the embodiment, the inclination angle of the support member is changed from the actuator through the worm gear, and due to the presence of this worm gear, the actuator (motor) is not turned by external force, that is, the actuator (motor) is not turned by external force. The ratio remains unchanged.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view of a four-wheel steering device according to the present invention, Fig. 2 is a perspective view of a housing portion that houses a steering ratio changing mechanism, Fig. 3 is a sectional view taken along the line of Fig. 2, and Fig. 4 is a perspective view of the main parts including the steering ratio changing mechanism,
Figures 5a to 5c are perspective views showing the operating principle of the steering ratio changing mechanism. In addition, in the drawing, 1 is a steering wheel, 3 is a steering gear box, 4 is a rack shaft, 6 is a front wheel, 8 is a front wheel steering mechanism, 9 is a rotating shaft, 12 is a rotating shaft, 13 is a universal joint, 14 is an input shaft, 15 is a pin joint, 16 is a rotating member, 17 is a yoke member, 19 is a support shaft, 22 is a support member, 23 is a support shaft, 24 is a housing, 25 is a steering ratio changing mechanism, and 26 is an actuator. , 28 and 29 are worm gears, 31 is a rear wheel steering control device, 32 is a vehicle speed detection means, 33 is a position detection means, 36 is a rear wheel, and 38 is a rear wheel steering mechanism.

Claims (1)

[Scope of Claims] 1. A front wheel steering mechanism that steers the front wheels in conjunction with the steering operation of the steered wheels; a rear wheel steering mechanism that steers the rear wheels; and a front wheel steering mechanism that steers the front wheels in conjunction with the front wheel steering mechanism. a rotation shaft that transmits the steering direction and the amount of steering; a yoke member that is connected to the rotation shaft and engages with a rotation member that rotates around the rotation axis; and a yoke member that swingably supports the yoke member. a support member; and an actuator that changes the inclination angle of the support member by tilting the support member around an axis perpendicular to a swing axis of the yoke member, the actuator tilting the support member with respect to the rotation axis. The fourth aspect of the vehicle is characterized in that the steering ratio and phase of the rear wheels relative to the front wheels are variably controlled by converting rotation of the rotation shaft into eccentric rotation of the yoke member by tilting the rotation shaft forward and backward. Wheel steering device. 2. The four-wheel steering system for a vehicle according to claim 1, wherein the change in the inclination angle of the support member is performed from the actuator via a worm gear. 3. The four-wheel steering system for a vehicle according to claim 1, characterized in that a displacement of the rotational eccentric position of the yoke member is input to the rear wheel steering mechanism.