JPH0460867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-wheel steering system for a vehicle.

Steering in four-wheeled vehicles has conventionally been performed by steering only the front wheels, and this has been considered a matter of course. However, if only the front wheels are steered, the rear wheels may skid, and there is a limit to the turning radius (small turns cannot be made), so in recent years research has been conducted on four-wheel steering systems that steer the rear wheels as well as the front wheels. has been done.

Specifically, when the steering angle of the steering wheel, that is, the steering angle of the front wheels, is relatively small, the rear wheels are steered in the same direction as the front wheels, and when the steering angle of the front wheels becomes relatively large, the rear wheels are steered. By steering in the opposite direction to the front wheels, lateral force is applied to the front and rear wheels at the same time when the front wheels are steered at a small angle at high speeds (because lateral force is not applied only to the rear wheels) There is no lag, allowing smooth lane changes without yawing, for example, and when driving at very low speeds with a large steering angle of the front wheels, it has the advantage of making it possible to park in a garage using a narrow space.

Several conventional technologies have been developed to enable four-wheel steering as described above, but those that use electricity and hydraulics to control the steering of the rear wheels have high costs and reliability problems. Also, although the system in which the front and rear wheels are mechanically connected is highly reliable, it has a problem in that the structure is complicated and impractical in order to perform advanced control.

The present invention solves the above-mentioned problems of the prior art, and aims to provide a four-wheel steering system that has a simple structure, is capable of relatively sophisticated control of the rear wheels, and is highly reliable.

More specifically, a steering device that steers the front wheels and a rear wheel steering device that steers the rear wheels are connected via a rear wheel steering control device that mechanically controls the steering of the rear wheels. The input shaft rotates in conjunction with the operation of the device, and the output shaft rotates in accordance with the output of the rear wheel steering control device, and the rear wheel steering control device is disposed in the middle. two rotating members that face each other and engage with the input shaft via biasing means having torsional elasticity, an output shaft that engages with these members, and the two rotating members between the input and output shafts. A dead zone setting means is provided separately from the input shaft, and includes a dead zone setting means for transmitting only a predetermined rotation angle range of the input shaft to the output shaft, and a reversing means for reversing the rotation direction of the input shaft and transmitting it to the output shaft. When the steering angle is within a predetermined value, the rear wheels are steered in the same direction as the front wheels, and when the steering angle of the front wheels exceeds the predetermined value, the rear wheels are steered in the opposite direction to the front wheels. A configuration of a four-wheel steering device for steering is disclosed.

Embodiments of the present invention will be described below with reference to the drawings, but first, the control relationship between front and rear wheel steering, which is the basis of the present invention, will be described with reference to FIG.

Figure 1 shows the steering angle θ _H of the front wheels 16 (see Figure 2).
This shows the relationship between the steering angle θ _R of the rear wheels 24 (see Figure 2), and when the solid line L is in the quadrant, the front wheels and rear wheels are in the same phase (in the direction of zero steering angle). When in the quadrant, the front and rear wheels are in opposite phases (the front and rear wheels are steered in opposite directions relative to the direction of zero steering angle). Indicates that the vehicle is being steered.

Specifically, when the steered angle θ _H of the front wheels 16 is relatively small, the rear wheels 24 are steered in the same direction as the front wheels, and the steered angle θ _R is proportional to the steered angle θ _H of the front wheels. However, when the steering angle θ _H of the front wheels exceeds the predetermined value θ ₂ , the rear wheels begin to be steered in a direction opposite to the steering direction of the front wheels. However, when the front wheels 16 are steered by an angle θ ₂ , the rear wheels 24 are also steered by an angle θ ₃ in the same direction, so the front wheels are steered by an angle θ ₁ and this steering angle θ ₃ is The rear wheels are in phase with the front wheels until it recovers and reaches zero.

Furthermore, if the front wheels are further steered beyond the angle θ ₁ , the rear wheels will continue to be steered in the opposite direction to the front wheels, and the rear wheels that were being steered in the opposite direction to the front wheels will now be in the opposite phase to the front wheels. It will become.

Next, an explanation will be given based on drawings showing examples.

FIG. 2 is a plan view showing an outline of a four-wheel steering system for a vehicle, and as is well known, the steering wheel 1
0, the piston rod 12 moves leftward or rightward (downward or upward in FIG. 2) with respect to the power cylinder 14, thereby steering the front wheel 16 leftward or rightward. A rack 18 is integrated into the piston rod 12,
A pinion 22 fixed to one end of a rotating shaft (input shaft) 20 meshes with this rack 18.

On the other hand, the rear wheel 24 is a rotating shaft (output shaft) as is well known.
30, the piston rod 26 is moved leftward or rightward with respect to the power cylinder 28, thereby being steered leftward or rightward.

The rotating shafts 20 and 30 are connected by a rear wheel steering control device 50, which will be described in detail later.

Moreover, the power cylinder 14 on the front wheel 16 side and the power cylinder 28 on the rear wheel side each have hydraulic tanks 3.
The pressure oil in the hydraulic pump 2 is sucked up by the hydraulic pump 34, divided into two directions by the flow divider 36, and is collected into the hydraulic tank 34 after operating the steering device 15 and the rear wheel steering device 25. It's becoming like that. Power cylinder 14, 2
The amount of pressurized oil supplied to each of the rotors 8 and 8 is controlled by valves that open and close in response to the amount of steering of the handle wheel 10 and the amount of rotation of the rotary shaft 30, respectively.

Next, regarding the rear wheel steering control device 50, FIG.
This will be explained based on FIG.

In FIG. 3, the input shaft 20 and output shaft 30 are rotatably supported below a box-shaped housing 52, and the free end of the input shaft 20 is fitted into a fitting portion 54 of the output shaft 30. A gear 56 and a flange member 58 are fixed to the input shaft 20 near one side wall of the housing 52. The gear 56 meshes with an idle gear 62 fixed to a rotating shaft 60, and this idle gear 62 meshes with a gear 66 on a rotating shaft 64 rotatably mounted above the housing 52. . Further, the flange member 58 and the flange portion 68 formed continuously on the output shaft 30 are connected to the cylindrical member 70.
The flange member 5
8. The output shaft 30, which includes the cylindrical member 70 and the flange portion 68, rotates integrally.
The cylindrical member 70 has two ribs 7 on the outer peripheral surface of the intermediate portion.
2, 74 are formed, and as shown in FIGS. 4 and 5, each rib 72, 74 has a cylindrical member 70.
Bolts 76 and 78 are screwed together in opposing directions in a direction perpendicular to the radial direction.

A pair of rotating members 80 and 90 are rotatably attached within the space defined by the flange member 58, the cylindrical member 70, and the flange portion 68. One rotating member 80 consists of a fitting part 82 fitted to the input shaft 20, a flange part 84, and a cylindrical part 86 extending in the axial direction from a part near the outer periphery of the flange part 84. It has a protrusion 85 on the top. The other rotating member 90 has a fitting part 92 fitted to the input shaft 20 and a flange part 9.
4, and a cylindrical portion 96 extending in the axial direction from a portion near the inner circumference of the flange portion 94.
4 has a protrusion 95 on its outer periphery. Moreover, as is clear from FIGS. 4 and 5, each fitting portion 82,
Bolts 88 and 98 are screwed into each of the pins 92 in opposite directions, and the pin 1 inserted onto the input shaft 20
02 and 104. and,
Both flange parts 84, 94 and both cylindrical parts 86, 96
A torsion spring 106 is located within the space defined by
is disposed, and its both ends are locked to the outer cylindrical portion 86 and the inner cylindrical portion 96, respectively. This spring 106 rotates the rotating member 80 in the clockwise direction and rotates the rotating member 9
0 in the left rotation direction with a predetermined set load, which causes the protrusions 85, 95 and pins 76, 78 to
is in contact.

A gear 108 is provided at the fitting portion 54 of the output shaft 30.
is fixedly installed, and this gear 108 is connected to the rotating shaft 6.
A gear 11 fixedly mounted on a rotating shaft 110 rotatably attached to a housing 52 opposite to the gear 11
3, and constitutes a reversing means for reversing the direction of the input shaft and transmitting the same to the output shaft.

As shown in FIG. 6, the inner ends of the rotating shafts 64 and 110 have a pair of protrusions 112 and 114 spaced apart in the diametrical direction, and constitute a dead zone setting means that does not transmit the rotation of the input shaft to the output shaft. However, after the protrusions come into contact with each other, the rotation of the rotating shaft 20 becomes the same as that of the rotating shaft 3.
0.

Next, the operation of this embodiment will be explained.

Now, if the steering wheel 10 is turned to the right, the oil amount control valve in the power cylinder 14 opens in response to the amount of steering, and the piston rod 12 moves to the left (downward in FIG. 2) due to the action of the pressure oil. move and steer the front wheels 16 to the right, and at the same time
8 and the pinion 22, the input shaft 20 is rotated to the right (as shown in FIGS. 4 and 5). Input shaft 20
When the rotation member 90 is rotated to the right, the rotating member 90 is rotated to the right through the contact between the pin 104 and the bolt 98, but the spring 10
6, the set load is applied to the rotating member 90, that is, the input shaft 2.
Since the rotational force is set to be larger than zero rotational force, the rotating member 80 rotates to the right integrally with the rotating member 90 via the spring 106 without bending at all. Then, through the contact between the protrusion 85 and the bolt 76, the cylindrical member 70
In other words, the output shaft 30 rotates to the right.

When the input shaft 20 rotates to the right, the rotating shaft 64 also rotates to the right via the gears 56, 62, and 66, but the front wheel 1
When the steering angle θ _H of the rotating shaft 64 is smaller than the angle θ ₂ , the speed is reduced by the gear ratio of the gears 56 , 62 and 66 , and the projection 112 of the rotating shaft 64 and the rotating shaft 110
Since there is a predetermined distance between the protrusion 114 and the protrusion 114,
The rotation of the rotating shaft 64 is not transmitted to the rotating shaft 110. When the output shaft 30 rotates to the right, the power cylinder 2
The oil control valve 8 opens in response to the amount of rotation, and the piston rod 26 is moved to the left (downward in FIG. 2) by the pressure oil, and the rear wheel 24 is steered to the right.

In this way, when the steering angle θ _H of the front wheels 16 is smaller than the angle θ ₂ , both the front wheels 16 and the rear wheels 24 are steered to the right and are in the same phase, so they can be smoothly driven when driving at high speeds. This will allow you to do things like lane changes.

When the handle wheel 10 continues to turn to the right and the steering angle θ _H of the front wheel 16 becomes larger than the angle θ ₁ , a force in the right turning direction is applied from the input shaft 20 to the rotating member 90 and a force is applied from the output shaft 30 to the rotating member 80 .
A force in the left rotation direction is applied to the spring 106, and the spring 106 is deformed by both forces. That is, input shaft 2
When the rotation amount of 0 exceeds a certain value, gears 56, 6
2 and 66, the protrusion 112 of the rotating shaft 64 and the protrusion 114 of the rotating shaft 110 come into contact with each other, and both rotating shafts 6
4,110 rotates to the right as a unit. As a result, the output shaft 30
The cylindrical member 70 is rotated to the left, and the rotating member 80 is rotated to the left through contact between the protrusion 85 and the bolt 76.

Here, the set load of the spring 106 is such that it does not deflect when a rotational force is applied only from the rotating member 90 side, but it deflects when a rotational force is applied in opposite directions from both rotating members 80 and 90. Therefore, due to this deformation, the rotation of the rotating member 90, that is, the input shaft 20, is absorbed and is not transmitted to the output shaft 30. The gears 56, 62 and 66 and the gears 113, 108 are connected to the output shaft 30 as described above.
The arrangement, number of teeth, radius, etc. are selected so that the rotation member 80 is rotated in the opposite direction to the input shaft 20, and the rotation member 80 is rotated with a force large enough to deflect the spring 106.

Note that when the steering angle θ _H of the front wheels 16 is between the angles θ ₁ and θ ₂ , the front wheels 16 and the rear wheels 24 are steered in opposite directions, but the rear wheels 24 are steered to the left. The front wheels 16 and the rear wheels 24 are in the same phase because the state where the steering angle is zero is being returned from the state where the vehicle was steered by the angle θ ₃ .

Then, the handle wheel 10 is further rotated to the right,
When the steering angle θ _H of the front wheels 16 becomes larger than the angle θ ₁ , the rotating members 90 and 80 and the rotating shafts 64 and 110
etc. continue to operate in the same direction as described above, and the rear wheels 24
is in opposite phase to the front wheel 16. In other words, the front wheels 16 are steered to the right, but the rear wheels 24 are steered to the left,
Furthermore, since the front wheels 16 and the rear wheels 24 are in opposite phases, it is possible to quickly change the direction of the vehicle by utilizing a narrow space when parking the vehicle.

In addition, what has been explained above is the handle wheel 10.
is steered to the right, thereby steering the front wheels 16 to the right. However, if the steering wheel 10 is steered to the left and the front wheels 16 are steered to the left, the input The shaft 20 rotates to the left, and the pin 10
2. Bolt 88 and protrusion 95, bolt 78 and related members (rotating members 80, 90, gears 56, 62 and 66, rotating shafts 80, 90, gears 112, 108, etc.) are all opposite to those described above. It will be clear that the desired operation is achieved by rotation in the direction of .

Next, a second embodiment in which the present invention is applied to a four-wheel steering system equipped with manual steering will be described with reference to FIG. 7. A pinion 122 is fixed to the lower end of a handle shaft 120 to which the steering wheel 10 is fixed. pinion 1
22 is engaged with a rack portion 126 formed on a shaft member 124 for steering the front wheels 16. As in the above embodiment, a pinion 22 fixed to the front end of the rotary shaft 20 is engaged with the rack 18 extending from the shaft member 124. Further, a pinion 128 is fixed to the rear end of the rotating shaft (output shaft) 30 which is operatively connected to the rotating shaft (input shaft) 20 via the rear wheel steering control device 50, and rotates the rear wheels 24. Rack portion 132 formed on the steering shaft member 130
The pinion 128 is meshed with.

In this embodiment, the front wheels are moved only by the steering force of the handle wheel 10 instead of the hydraulic driving force.
6. There is no difference from the above embodiment except that the rear wheels 24 are steered, so a detailed explanation will be omitted.

As described above, the rear wheel steering control device in a four-wheel steering system according to the present invention includes two wheels that face each other and engage with the input shaft via a biasing means having torsional elasticity disposed in the middle. a rotating member, an output shaft that engages with these, and a dead zone setting that is provided separately from the two rotating members between the input and output shafts and transmits only a predetermined rotation angle range of the input shaft to the output shaft; and the reversing means for reversing the rotational direction of the input shaft and transmitting it to the output shaft are included in a simple structure as a whole, so it is inexpensive, highly reliable, and relatively sophisticated. A four-wheel steering device capable of rear wheel control can be obtained.

Note that the rear wheel steering control force in the embodiment of the present invention is the force that operates the changeover valve, switch, etc. in the case of power steering, but in the second embodiment, the rear wheel steering control force is the force that actually operates in the case of manual steering. This corresponds to the rear wheel steering force that steers the rear wheels.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the steering control relationship between front wheels and rear wheels, which is the basis of this invention, and Fig. 2 is a diagram showing a four-wheel steering system for a vehicle equipped with power steering, which is the first embodiment of this invention. 3 is a cross-sectional view of an embodiment of the rear wheel steering control device, FIG. 4 and FIG. 5 are a cross-sectional view and a cross-sectional view of FIG. 3, respectively, and FIG. FIG. 7 is a diagram showing an outline of another embodiment. Explanation of symbols of main parts: 10 is a handwheel, 15 is a steering device, 20 is an input shaft, 2
5 is a rear wheel steering device, 30 is an output shaft, 50 is a rear wheel steering control device, 64 is a first rotating shaft, 80 is a first rotating member, 90 is a second rotating member, 106 is a spring member, 110 is the second rotation axis.

Claims (1)

[Scope of Claims] 1. A steering device that steers the front wheels of a vehicle; a rear wheel steering device that steers the rear wheels of the vehicle; and a steering device that is provided between the steering device and the rear wheel steering device and that steers the front wheels of the vehicle. a rear wheel steering control device based on a mechanical configuration that controls the rear wheel steering device according to a steering amount; a first rotational member that engages with the input shaft and transmits only rotation of the input shaft in a first rotational direction; and a second rotational direction opposite to the first rotational direction. a second rotating member that transmits only the rotation of the first rotating member; a biasing means that biases in a first rotational direction; and a biasing means that engages with the first rotational member and receives rotation in a second rotational direction from the first rotational member; The rotation in the first rotational direction is transmitted to the second rotational member, and the rotation in the first rotational direction is transmitted to the second rotational member. an output shaft that transmits rotation in the second rotational direction and operates the rear wheel steering device; and an output shaft that is provided between the input shaft and the output shaft separately from the first and second rotating members, and that is provided between the input shaft and the output shaft to adjust the steering angle of the front wheels. dead zone setting means that does not transmit the rotation of the input shaft to the output shaft in an angular range in which the absolute value of A four-wheel steering device for a vehicle, characterized in that it is equipped with a reversing means for reversing the vehicle.