JPH0468185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-wheel steering system for a vehicle, and the present invention relates to a four-wheel steering system for a vehicle. This invention relates to a mechanically controlled four-wheel steering device.

Conventionally, four-wheeled vehicles are typically steered by turning only the front wheels using the steering wheel, but steering only the front wheels may cause sideslip in the rear wheels depending on the driving situation, or limit the turning radius. Problems have been pointed out in terms of maneuverability and steering, such as the inability to make small turns due to heavy rotation, and in light of this problem, a four-wheel steering system that steers the rear wheels as well as the front wheels has recently been proposed and researched.

In other words, with a four-wheel steering system, if the rear wheels are steered in the same direction as the front wheels when driving at relatively high speeds, lateral force is applied to the front and rear wheels at the same time, so the phase shift from the steered wheels is There is no lag, and the vehicle's attitude can be maintained almost on the tangent to the turning circle, making it possible to smoothly change lanes when driving at high speeds, for example. Also, if the rear wheels are steered in the opposite direction to the front wheels when driving at very low speeds, the direction of the vehicle can be changed significantly, which is convenient for parallel parking or parking in a garage.

Furthermore, considering that the front wheels are not steered significantly at relatively high speeds, and the front wheels are steered significantly when driving at relatively low speeds, the rear wheels are also steered within the range where the front wheels are steered small. steer in the same direction,
It can be seen that a four-wheel steering system that steers the rear wheels in the opposite direction is required when making a large turn.

In principle, the four-wheel steering system described above can be realized using various methods, but those that use many electrical and hydraulic means have a complicated structure.
They are relatively expensive and also have many problems in terms of maintenance, safety in the event of a breakdown, and other reliability issues.

In view of the above problems, the present invention transmits the operation of a steering device as a control force for controlling the operation of a rear wheel steering device by mechanical means, and uses this control force to actuate the rear wheel steering device. The object of the present invention is to provide a four-wheel steering system for a vehicle that uses a power steering system to amplify steering force and has a simple structure and high reliability.

In order to achieve the above object, the present invention is configured to transmit the force from the steering device that steers the front wheels to the rear wheel steering device as a control force, and at least one of the steering device and the rear wheel steering device is powered. a steering device, and a same-direction steering control force transmission means for transmitting a steering force for steering the rear wheels in the same direction as the front wheels to the rear wheel steering device; a reverse direction steering control force transmission means for transmitting a steering force for steering the vehicle in a direction opposite to that of the front wheels to the rear wheel steering device; when receiving control force only from the same direction steering control force transmission means; transmitting this control force to the rear wheel steering device, and further absorbing the same direction steering control force when receiving a control force that reverses the steering direction of the front wheels from the reverse direction steering control force transmission means; reversible direction transmission means for transmitting only the operation by the reverse direction steering control force to the rear wheel steering device; when the steering angle of the front wheels is within a predetermined angle range, the reverse direction steering control force is inactivated and the reverse direction is carried out; The structure includes a dead zone setting means that does not transmit steering control force.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view of a vehicle equipped with a first embodiment of the present invention. In the figure, the rotation of the steering shaft 2 caused by the steering operation of the steering wheel 1 is converted into linear motion of a rack gear 4, which is a piston rod, by a gear box 3 that houses a motion conversion mechanism (not shown) such as a known rack and pinion mechanism. . The rack gear 4 has a piston portion (not shown), which is fitted inside the power cylinder 5. Both ends of the rack gear 4 are connected to knuckle arms 7, 7 via side rods 6, 6, and the knuckle arms 7, 7 follow the linear movement of the rack gear 4 to the left and right (in the vertical direction in the figure) about the pivot shafts 7a, 7a. It swings left and right, thereby steering the front wheels 8, 8 via a known mechanism.

In the power steering system of this embodiment, supply oil discharged from the hydraulic pump 9 and separated by the flow distribution valve 10 is supplied to the left and right chambers of the power cylinder 5 via the hydraulic pipe 11 and the control valve section 12. As a result, the differential pressure between the left and right chambers of the power cylinder 5 is transmitted to the rack gear 4, which is a piston rod, and the front wheels 8 are power assisted and steered. The reservoir tank 13 has pipes 14 and 15, respectively.
It is connected to the pump 9 and the control valve section 12 via.

A pin 16 is buried at a continuous point between the rack gear 4 and the side rod 6 at the bottom in the figure, and this is located at the L
It engages with the forked portion 17a of the mold link 17. L
A rod member 18, which is an input shaft means that is connected to a power steering device composed of a rack gear 4, a power cylinder 5, etc. and steers the front wheels, and is linearly moved, is connected to the molded link 17 by a pin. Rod member 18
moves in the left-right direction in the figure, that is, in the longitudinal direction of the vehicle, as the L-shaped link 17 swings. The rod member 18 has a cylinder part 19 and a branch part 20, and inside the cylinder part 19, a first translation member 21, a second translation member 2
2, a spring member 23 disposed between them is housed, and two flange parts 24,
An output shaft 26 having a diameter of 25 extends. The first translational member 21 engages with the first shoulder portion 19a of the cylinder portion 19, and receives only a force from the rod member 18 in a first direction, rightward in the figure. The second translational member 22 engages with the second shoulder portion 19b of the cylinder portion 19, and receives only a force from the rod member 18 in a second direction, to the left in the figure. The spring member 23 contacts the first and second translational members 21 and 22 and biases them in the second direction and the first direction with a predetermined set load, respectively. The two flange portions 24 and 25 of the output shaft 26 engage with the first translational member 21 and the second translational member 22, respectively, and receive a force in the second direction from the first translational member 21. A force in a first direction is applied to this, and while receiving a force in the first direction from the second linear motion member 22, a force in a second direction is applied thereto. Since the predetermined set load is set to be larger than the force from the rod member 18, if no other force is applied to the output shaft 26, the horizontal movement of the rod member 18 will continue as it is to the second translation member 22, Via the spring member 23, the first translational member 21, and the flange portion 24, or the first translational member 21, the spring member 23, and the second translational member 2
2. It is transmitted to the output shaft 26 via the flange portion 25 and moves it in the same direction as the rod member 18. In addition, the pin 16, L-shaped link 17, rod member 1
8. The cylinder portion 19 and the output shaft 26 constitute a means for transmitting steering control force in the same direction.

On the other hand, another rod member 28 having a cylinder portion 27 is connected with a pin to the branch portion 20 of the rod member 18, and a piston rod 29 is inserted into this cylinder portion 27.
A piston portion 30 is fitted.

Therefore, the horizontal movement of the rod member 28 is caused by the piston portion 3.
When the piston rod 0 is in contact with either the left or right walls 27a, 27b of the cylinder portion 27, the piston rod 2
9 to move the piston rod 29 in the same direction, but no transmission occurs at positions in between. In addition,
The piston section 30 and the cylinder section 27 constitute dead zone setting means.

This position range in which the wheels do not come into contact corresponds to a range in which the absolute value of the steering angle of the front wheels 8 is equal to or less than a predetermined value.

The piston rod 29 is pin-coupled to a link 31, and the link 31 is swingable about a pivot 31a and has a fork 31b at the other end, which engages with a pin 32 embedded in the output shaft 26. Also, from the rod member 18 to the rod member 28 and the piston rod 29
The force transmitted via the link member 31 is transmitted from the rod member 18 to the first or second translation member 21,
22 and the sum of these forces is greater than the predetermined set load, the direction of which is reversed and transmitted to the output shaft 26.

Therefore, the piston portion 30 of the piston rod 29
hits either of the left and right walls 27a, 27b of the cylinder portion 27, and the rod member 18 passes through this path.
When a reversed force is transmitted to the output shaft 26, the output shaft 26 connects the first translation member 21 via the flange portion 24 or the second translation member 22 via the flange portion 25 into the cylinder portion 19. the rod member 18 while compressing the spring member 23 by moving it relatively.
move in the direction opposite to the movement of. In addition, branch 2
0, the rod member 28, the cylinder portion 27, the piston portion 30, the piston rod 29, and the link 31 constitute a reverse direction steering control force transmission means. In addition, both flange parts 24, 25, both translational members 21,
22 and the spring member 23 constitute a reversible directional transmission means which absorbs the latter force and transmits only the former force when the force from the piston rod 29 and the force from the cylinder portion 19 are opposed to each other.

A rack 33 is formed on the output shaft 26.
This engages pinion 34. Figure 2 shows this part viewed from the side. Output shaft 2
6 rotates the pinion 34, and this rotation is also transmitted through the shaft 35 to control the control valve section 36.

On the other hand, the flow rate distribution valve 10 and the reservoir tank 13
The hydraulic pipes 37 and 38 from the control valve section 36 are connected to the left and right chambers of the power cylinder 39 through the control valve section 36.
Under this control, the differential pressure between the left and right chambers of the power cylinder 39 is transmitted to the piston rod 40, which is moved left and right. In this way, in accordance with the left-right movement of the rack gear 4 on the front wheel side, when the piston portion 30 is in contact with the wall 27a or 27b of the cylinder portion 27, the direction of the piston rod 40 on the rear wheel side is reversed and moves linearly. When it is not on, it moves directly in the same direction. Further, the direct motion of the piston rod 40 is also transmitted to the rear wheels 43, 43 via the side rods 41, 41 and knuckle arms 42, 42, similarly to the front wheels, to steer the wheels.

The operation of the first embodiment configured as above will be explained. Now, if the steering wheel 1 is turned to the right from the neutral position with zero steering angle (position N in FIG. 3), the mechanism in the gearbox 3 and the action of the power cylinder 5 will cause the rack gear 4 to move downward in FIG. It moves to the left and steers the front wheels 8, 8 to the right (this steering angle is shown by the θ _H axis in FIG. 3).

At the same time, the L-shaped link 17 is turned to the left, and the rod member 18 is moved directly in the forward direction of the vehicle.
Due to this movement, force is transmitted to the output shaft 26 via the second shoulder portion 19b, the second translational member 22, the spring member 23, the first translational member 21, and the flange portion 24, which also causes the output shaft to be translated forward. try to make it happen. and,
In the range where the rightward turning angle of the front wheels 8, 8 is _less than the predetermined value θ1, the piston portion 30 of the piston rod 29 has not yet come into contact with the right wall 27b of the cylinder portion 27 of the rod member 28. The movement of the rod member 18 is only transmitted to the rod member 28 and not to the piston rod 29, and is not transmitted to the link 3.
No force is transmitted to the output shaft 26 from the side 1. Therefore, the force transmitted from the piston rod 18 to the output shaft 26 via the spring member 23, etc.
3 is not compressed and the output shaft 26 is moved in the same direction as the rod member 18. As a result, pinion 3
The control valve section 36 is controlled through the rotation of the power cylinder 41, and the piston rod 40 is moved to the left, that is, downward in the figure, due to the differential pressure between the left and right spaces of the power cylinder 41, and the rear wheels 43, 43 are moved in the same direction as the front wheels 8, 8. Turn the steering to the right (this turning angle is θ _R in Figure 3).
(indicated by the axis).

However, when the rightward steering angle of the front wheels 8, ₈ exceeds the predetermined value θ1, the piston portion 30 comes into contact with the right wall 27b of the cylinder portion 27, and the movement of the rod member 18 is reduced. The force is also transmitted to the piston rod 29 via the link 31, and is further transmitted to the output shaft 26 as an inverted force via the link 31.
Then, the spring member 23 is moved to the left via the second shoulder portion 19b and the second linear motion member 22, that is, to the second direction.
A force in the direction is applied, and a force in the right direction, that is, the first direction, is applied via the flange portion 24 of the output shaft 26 and the first translational member 21. Here, since the sum of these two forces is larger than the set load of the spring member 23, and the former of these two forces is smaller than the latter, the second translational member 22 is applied to the second shoulder 19b. Only the first translational member 21 moves away from the first shoulder portion 19a while remaining in contact and compresses the spring member 23. Therefore, while the rod member 18 moves forward, ie, to the left, the output shaft 26 begins to move rearward, ie, to the right, and the control of the control valve section 36 is reversed, so that the steering has been steered to the right. The wheels 43, 43 begin to be steered to the left. In this way, when the front wheels 8, 8 are further steered to the right,
Finally, at the turning angle θ ₂ , the rear wheels 43, 43 pass the neutral position and are turned to the left.

When turning the steering wheel 1 to the left from the neutral position,
This is the same as above except that the operation is reversed.

In this way, when the front wheels 8, 8 are within the predetermined steering angle range (the range of θ ₁ or less left and right) sandwiching the neutral position N, the front wheels 8 and the rear wheels 43 are steered in the same direction, and within this range. When outside, the rear wheel 43 is the front wheel 8
is steered in the opposite direction. As a result, the front and rear wheels 8, 43 are in a state of being steered to the same side with respect to the neutral position within a predetermined range (range of θ ₂ or less in left and right directions) including and outside the predetermined steering angle range, Outside the range (more than θ ₂ left and right), the vehicle is steered to the opposite side of the neutral position.

Next, a second embodiment will be explained. FIG. 4 is a plan view showing an outline of a vehicle equipped with the second embodiment,
Portions common to the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof will be omitted as appropriate.

A rack 44 is integrally attached to the rack gear 4, which is a piston rod, and moves linearly with the rack gear 4 left and right, that is, up and down in FIG.
A pinion 46 fixed to the front end of an input shaft 45 meshes with the rack gear 4, and as the rack gear 4 moves linearly, the input shaft 45 rotates.

On the other hand, the rear wheels 43, 43 are steered by the control valve section 36 being controlled by the rotation of the output shaft 47, whereby the rack gear 40 is moved by the differential pressure between the left and right chambers of the power cylinder 39.

A rear wheel steering control device 50 is connected between the input and output shafts 45 and 47.
The output shaft 47 is controlled in accordance with the operation of the input shaft 45.

Next, the control device 50 will be explained based on FIGS. 5 to 8.

In FIG. 5, the input shaft 45 and output shaft 47 are rotatably supported below a box-shaped housing 52, and the free end of the input shaft 45 is fitted into the fitting portion 54 of the output shaft 47. A gear 56 is fixed to the input shaft 45 near one side wall of the housing 52, and a support flange member 58 is provided so as to be relatively rotatable. 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. . The flange member 58
and a flange portion 68 formed continuously on the output shaft 47 are interconnected by a cylindrical member 70, and the output shaft 47 including the flange member 58, the cylindrical member 70, and the flange portion 68 are integrally connected to each other by a cylindrical member 70. It is supposed to rotate. Two ribs 72, 74 are formed on the outer peripheral surface of the intermediate portion of the cylindrical member 70, and as shown in FIGS. 6 and 7, each rib 72, 74
Bolts 76 and 78 are screwed together in directions perpendicular to the radial direction of the cylindrical member 70 and facing each other.

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 45, 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 45 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.
It has a protrusion 95 on the outer periphery. Figures 6 and 7
As is clear from the figure, bolts 88 and 98 are screwed into the fitting portions 82 and 92 in opposite directions, and a pin 102 and a pin 102 inserted onto the input shaft 45,
104. Both flanges 8
A torsion spring 106 is disposed within a space defined by the cylindrical portions 86 and 94 and the cylindrical portions 86 and 96, and both ends of the torsion spring 106 are locked to the flange portions 84 and 94, respectively. This spring 106 biases the rotating member 80 in the clockwise rotation direction and the rotating member 90 in the clockwise rotation direction with a predetermined set load, so that the protrusions 85, 95 and pins 76, 78 are normally brought into contact with each other. There is. Note that the pair of rotating members 80, 90,
Spring 106, cylindrical member 70 and flange portion 68
This constitutes the same direction steering control force transmission means.

A gear 108 is attached to the fitting portion 54 of the output shaft 47 so as to rotate integrally therewith, and this gear is mounted on a rotating shaft 110 rotatably attached to the housing 52 facing the rotating shaft 64 It is meshed with a fixed gear 113.

As shown in FIG. 8, the inner ends of the rotating shafts 64 and 110 each have a pair of protrusions 112 and 114 spaced apart from each other in the diametrical direction, which constitute a dead zone setting means, and after the protrusions come into contact with each other, The rotation of the input shaft 45 is reversed and transmitted to the output shaft 47 via these shafts 64 and 110. Note that the gears 62, 66 and the shafts 64, 110 constitute a reverse steering control force means.

Next, the operation of this example will be explained.

Further, since the set load of the spring 106 is made to flex when rotational forces are applied in opposite directions from both rotating members, the rotation of the input shaft 45 is absorbed by this deformation, and the rotation of the input shaft 45 is absorbed. Only control forces are transmitted. In addition, both flanges 8
4, 94, both cylindrical parts 86, 96 and spring 106
constitutes a reversible directional transmission means.

If the steering wheel 1 is now turned to the right, the control valve 12 is controlled in accordance with the amount of steering,
The piston rod 4 moves to the left by the action of the pressure oil in the power cylinder 5, steering the front wheels 8, 8 to the right, and the input shaft 45 is rotated to the right through the engagement between the rack 44 and the pinion 46. .

When the input shaft 45 is rotated to the right, the rotating member 90 is rotated to the right through contact between the pin 104 and the bolt 98 shown in FIG. Since the rotational force is set to be larger than the rotational force of the shaft 45, the rotating member 80 does not bend, and the rotating member 80 rotates to the right integrally with the rotating member 90 via the spring 96.

In that case, the cylindrical member 72, i.e., the output shaft 47 is
will rotate to the right.

When the input shaft 45 rotates to the right, the rotating shaft 64 also rotates to the right via the gears 56, 62, and 66, but the front wheel 8
When the steering angle θ _H is smaller than θ ₁ in FIG.
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. Therefore, the output shaft 47 has two rotating members 80,
Only the rotational force via 90 is transmitted.

When the output shaft 47 rotates to the right, the control valve 36 is controlled and the piston rod 4 is
is moved to the left, and the rear wheel 43 is steered to the right.

However, as in the first embodiment, when the steering angle of the front wheels 8, 8 to the right becomes θ ₁ or more, the protrusion 112 of the rotating shaft 64 and the protrusion 114 of the rotating shaft 110 come into contact, and the input The movement of the shaft 45 is caused by these rotational shafts 6.
4, 110, etc., and is further transmitted to gear 11.
2,108 as the force reversed by the output shaft 47.
can be conveyed to. Then, a force in the left rotation direction is applied to the spring 106 via the cylindrical member 70 and the rotating member 80, and a force in the right rotation direction is also applied via the rotation member 90. And these two forces and spring 10
Input shaft 45
rotates to the right together with the rotating member 90, while the output shaft 47 rotates to the left together with the cylindrical member 70 and the rotating member 80 while deflecting the spring 106. In this way, the control of the control valve section 36 is reversed, and the rear wheels 43, 43, which have been steered to the right, begin to be steered to the left. Then, when the front wheels 8, 8 are further steered to the right, the steering angle θ ₂ (the third
(see figure), the rear wheels 43, 43 pass the neutral position and are steered to the left.

When turning the steering wheel 1 to the left from the neutral position,
This is the same as above except that the operation is reversed.

As described above, according to the present invention, a mechanical rear wheel steering control device comprising a biasing means such as a spring member, a rotating member, a linearly moving member, etc. is used to transfer the force from, for example, the power steering device to the rear wheel. Since this is controlled by transmitting the control force to the wheel steering device, there are fewer electrical means and hydraulic means, and complicated wiring and piping are reduced, making it mechanically simple and easy to maintain. is also inexpensive.

Furthermore, since the transmission of the control force that steers the rear wheels is mechanically connected, even in the unlikely event of a malfunction, the movement of the wheels will be regulated to a certain extent, which is superior in terms of safety and reliability. There is.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a vehicle equipped with the first embodiment of the present invention, FIG. 2 is a side view of the rear wheel portion of FIG. 1, and FIG. 3 is a graph for explaining the operation. Fourth
The figure is a plan view of a vehicle equipped with the second embodiment of the present invention, FIG. 5 is a detailed view of the rear wheel steering control device of FIG. 4, and FIGS. -, - and - sectional views of the figure. [Explanation of symbols of main parts] Front wheels...8, Power steering device for steering the front wheels...1 to 15, Rear wheels...
43, Rear wheel steering device...34-42, Rear wheel steering control device...18-32, 50.

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 in accordance with a steering amount; and a power steering device provided in at least one of the steering device and the rear wheel steering device, The rear wheel steering control device includes a same direction steering control force transmitting means for transmitting a same direction steering control force to the rear wheel steering device so as to steer the rear wheels in the same direction as the front wheels; and the same direction steering control force. reverse direction steering control force transmission means for transmitting the same direction steering control force to a rear wheel steering device as a reverse direction steering control force so as to reverse the direction of the rear wheels and steer the rear wheels in a direction opposite to that of the front wheels; reversible direction transmission means that attracts and transmits only the operation of the reverse direction steering control force; when the steering angle of the front wheels is within a predetermined angle range, the operation of the reversible direction transmission means is restricted; 1. A four-wheel steering system for a vehicle, comprising: dead zone setting means for operating only a same-direction steering control force transmission means.