JPH03276871A - Four-wheel steering system for automobile - Google Patents

Abstract

PURPOSE:To facilitate careful rear-wheel steering control even if there is no supply of hydraulic pressure by connecting respective power steering units for both front and rear wheels mechanically via a rear-wheel steering route provided with a regulating mechanism and a hydraulic mechanism. CONSTITUTION:A front-wheel power steering system 1 comprises a front-wheel steering control valve 7, and a driving cylinder 2 is connected to a hydraulic supply source 8 via this front-wheel steering control valve 7. In addition, an interval between a steering wheel shaft 15 and the driving cylinder 2 is mechanically connected together by a front-wheel steering route 16 via the front-wheel steering control valve 7. On the other hand, a rear-wheel power steering system 66 is provided with a drive cylinder unit 67 and a rear-wheel steering control valve 68, and an interval between both these power steering systems 1 and 66 is connected together via a rear-wheel side steering route 73 in which a rear-wheel side hydraulic mechanism 74 is installed, and the input shaft 75 is connected to a regulating mechanism 77 via a rotation transfer shaft 76, and another rotation transfer shaft 78 extends toward the front-wheel power steering system 1 from this mechanism 77.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a four-wheel steering system for a motor vehicle that steers not only the front wheels but also the rear wheels by operating a steering wheel.

(Prior Art) In recent years, automobile bodies have become increasingly larger, and therefore their turning radius has also tended to increase.

Therefore, instead of steering only the front wheels by operating the steering wheel, by steering both the front wheels and the rear wheels, you can not only reduce the turning radius and improve the turning performance of the vehicle, but also improve steering stability. It will also be possible to improve the

Furthermore, in order to improve the turning performance and steering stability of the vehicle by steering the rear wheels, the rear wheels must be steered in the same phase or in opposite phase to the steering of the front wheels, as necessary. Therefore, the rear wheels are driven by double-acting double-acting drive cylinders. Further, the operation of this drive cylinder is controlled by a rear wheel steering control valve. That is,
The rear wheel steering control valve is composed of, for example, an electromagnetic directional control valve, and is inserted into a hydraulic circuit connecting between the drive cylinder and the pressure fluid supply source. And the rear wheel steering control valve is
It is electrically connected to a controller, and this controller is configured to output a control signal for switching the rear wheel steering control valve in consideration of the front wheel steering angle, vehicle speed, etc.

(Problems to be Solved by the Invention) By the way, in the above-mentioned conventional rear wheel steering system, the drive cylinder is operated by its own hydraulic circuit, so for example, this hydraulic circuit may be damaged. If the controller malfunctions or becomes inoperable, steering control of the rear wheels will become impossible. Furthermore, if the supply of pressure fluid to the drive cylinders is controlled only by the rear wheel steering control valve, it is not possible to precisely control the drive cylinders, that is, the rear wheels, for front wheel steering, which is the intended purpose. It is difficult to achieve good turning performance and steering stability of an automobile.

This invention was made based on the above-mentioned circumstances, and
The purpose of this is to be able to reliably steer the rear wheels in conjunction with front wheel steering, and also to be able to finely control the steering of not only the front wheels but also the rear wheels, thereby improving the turning performance and steering stability of the vehicle. An object of the present invention is to provide a four-wheel steering system for a vehicle that can be improved.

(Means for Solving the Problems) A four-wheel steering system for a vehicle according to the present invention includes a front-wheel power steering unit that is driven by operation of a steering handle to vary a front-wheel steering angle, and a front-wheel power steering unit that is driven by operation of a steering handle. A front wheel side hydraulic mechanism is inserted into the front wheel steering path that mechanically connects the front wheel steering path, and controls the phase of the front wheel steering angle in response to front wheel steering by operating the steering wheel, and a front wheel power steering unit that controls the front wheel steering angle. mechanically coupled via a pathway;
A rear wheel power steering unit that is driven in response to the front wheel power steering unit to vary the rear wheel steering angle, and a rear wheel power steering unit that is inserted in the rear wheel steering path and that is driven by the front wheel power steering unit to change the rear wheel steering angle. The adjustment mechanism adjusts the amount of operation transmitted to the power steering unit, and the rear wheel steering is inserted in the rear wheel steering path and is performed in response to the front wheel power steering unit.
It is inserted into a hydraulic circuit that connects a rear wheel side hydraulic mechanism that controls the phase of the rear wheel steering angle, the front wheel side and rear wheel side hydraulic pressure mechanisms, and a pressure fluid supply source. It is configured to include a phase control valve that controls the supply of pressure fluid to the side hydraulic mechanism, and a controller that controls the operation of this phase control valve.

(Function) According to the four-wheel steering device described above, since the front wheel power steering unit and the rear wheel power steering unit are mechanically connected via the rear wheel steering path,
The rear wheel power steering unit can be driven via the front wheel power steering unit by operating the steering wheel even if no pressure fluid is supplied.

That is, the rear wheels can also be steered by operating the steering wheel.

In addition, since the rear wheel steering path is equipped with an adjustment mechanism,
With this adjustment mechanism, the amount of operation to be transmitted from the front wheel power steering unit to the rear wheel power steering unit can be adjusted, and the characteristics of rear wheel steering with respect to front wheel steering can be arbitrarily set. From this, it is possible to use a rear wheel power steering unit having the same structure as the front wheel power steering unit.

Furthermore, since front wheel and rear wheel hydraulic pressure mechanisms are inserted in the front wheel steering path and the rear wheel steering path, respectively, the supply of pressure fluid to these front wheel and rear wheel hydraulic pressure mechanisms can be controlled in phase. If controlled by a valve, in addition to operating the steering wheel,
This means that not only the front wheels but also the rear wheels can be steered more precisely.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

Referring to FIG. 1, a four-wheel steering system is schematically shown, which includes a front-wheel power steering unit, i.e., a front-wheel power steering device l. This front wheel power steering device 1 has a drive cylinder 2, and the drive cylinder 2 is composed of a double-rod double-acting hydraulic cylinder. Both piston rods 3 of the drive cylinder 2 are connected to a front wheel 5 via a tie rod 4 and a knuckle (not shown), respectively. In FIG. 1, only one side of the connection between the drive cylinder 2 and the front wheel 5 is shown.

The front wheel power steering device 1 includes a front wheel steering control valve 7 , and the drive cylinder 2 is connected to a pressure fluid supply source 8 via the front wheel steering control valve 7 . This pressure fluid supply source 8 has a tandem-type hydraulic pump unit 8 driven by an automobile engine 9, and a pressure fluid supply pipe 10 extending from one pump 8a of this hydraulic pump unit 8 is It is connected to one port of the front wheel steering control valve 7. Here, the front wheel steering control valve 7 has, for example, 4 points, 3
Therefore, in the pressure fluid supply line 10, the portion downstream of the front wheel steering control valve 7 is a branch supply extending from the two ports of the front wheel steering control valve 7. Conduit 10a.

10b. These branch supply pipes 10a.

10b are connected to both pressure chambers of the drive cylinder 2, respectively. Further, a pressure fluid return line 11 extends from the remaining port of the front wheel steering control valve 7, and this return line 11 is connected to a pressure liquid reservoir 12. Also,
A pressure fluid suction line 13 extends from the reservoir 12 and is connected to the hydraulic pump unit 8 .

As is well known, the front wheel steering control valve 7 is switched by operating the steering wheel 14 of the automobile. are mechanically connected by a front wheel steering path 16 via a front wheel steering control valve 7.

In this regard, referring to FIGS. 2 and 3, a portion of the front wheel steering path 16 including the front wheel steering control valve 7 is specifically shown. This front wheel steering path 16 is provided with a gear casing 17, which, as seen in FIG. 2, consists of an upper casing 18 and a lower casing 19.

The upper casing 18 has a cylindrical shape with an enlarged diameter at its upper portion, and its upper end is closed by an end plate 20.

An input shaft 21 is disposed concentrically within the upper casing 18. The input shaft 21 is made of a hollow shaft, and its upper end passes through the end plate 20 in a liquid-tight manner and rotatably, and is inserted into the upper casing 18.
extends outside.

That is, a bearing 22 and a seal 23 are arranged between the end plate 20 and the input shaft 21.

On one side, the input shaft 21 has a protruding end protruding from the upper casing 18 that is mechanically coupled, for example, through serrations, to a portion of the front wheel steering path 16 on the steering handle 14 side, and on the other side, the protruding end protruding from the upper casing 18 It is mechanically connected to the front wheel steering control valve 7 housed within 18 .

Here, the input shaft 21 and the front wheel steering control valve 7 are not simply mechanically connected, but are mechanically connected via a front wheel side hydraulic mechanism 23 inserted in the front wheel steering path 16. There is. Therefore, first, the front wheel side hydraulic mechanism 24 will be explained here.

The front wheel side hydraulic mechanism 24 includes a control cylinder 25 that surrounds the input shaft 21 located inside the upper casing 18, and the control cylinder 25 is rotatably supported by the upper casing 18 via a bearing 26. ing. On the other hand, a small diameter ring 26 and a large diameter ring 27 are sequentially arranged between the outer peripheral surface of the control cylinder 25 and the inner peripheral surface of the upper casing 18. Here, the small diameter ring 26 is fixed to the outer peripheral surface of the control cylinder 25, and the large diameter ring 27 is
It is fixed to the inner peripheral surface of the upper casing 18. Therefore, the control cylinder 25 is controlled by either the small diameter ring 26 or the large diameter ring 2.
It is rotatable while being in sliding contact with 7.

As is clear from FIG. 3, inside the control cylinder 25,
A through hole 28 is formed through which the input shaft 21 is inserted, and a pair of axial grooves 29 that are connected to the through hole 28 are further formed in the control cylinder 25 . These axial grooves 29 form the end plate 20 of the control cylinder 25.
It extends in the axial direction of the input shaft 21 from the side end surface, and is positioned at a distance in the diametrical direction of the input shaft 21 .

On the other hand, a pair of drive claws 30 that enter into the axial groove 29 are integrally formed on the input shaft 21 . These driving claws 3
0 has a plate shape, is positioned within the axial groove 29 with play in the circumferential direction of the input shaft 21, and extends along the axial groove 29 as is clear from FIG. .

Furthermore, in the control cylinder 25, two sets of cylinder holes 31 are formed respectively for each axial groove 29, that is, for each drive claw 30, opposing each other with the drive claw 30 in between. The holes 31 are spaced apart in the axial direction of the axial groove 29 . The paired cylinder holes 31 have one end open to the corresponding axial groove 29 and the other end open to the outer circumferential surface of the control cylinder 25 . The other ends of the cylinder holes 31, which are adjacent to each other in the axial direction of the axial hole 29 and are in different sets, are connected to the control cylinder 25.
They communicate with each other via four notched grooves 32 formed on the outer circumferential surface of the two.

A plunger 33 is fitted into each cylinder hole 31, and one end of each plunger 33 on the drive claw 30 side is
It has a hemispherical shape.

A pair of circumferential grooves 34a and 34b are formed on the circumferential surface of the large-diameter ring 27, respectively.

Here, one circumferential groove 34a is connected to a port 35a formed in the upper casing 18, and the other circumferential groove 34b is connected to a port 35b also formed in the upper casing 18.

Furthermore, a pair of circumferential grooves 37a, 3 are formed on the outer peripheral surface of the small diameter ring 26, corresponding to the circumferential grooves 34a, 34b of the large diameter ring 27.
7b are formed respectively. In the large diameter ring 27, communication holes 38 are formed at equal intervals in the circumferential direction to communicate between the circumferential groove 34a and the circumferential groove 37a.
4b and the circumferential groove 37b are also formed at equal intervals in the circumferential direction. The small diameter ring 26 has the notch groove 3 of the control cylinder 25 described above.
2, two communication holes 40 are formed to communicate between the two notch grooves 32 and the circumferential groove 37a, which are diagonally located in FIG. 3. In addition, the small diameter ring 26 includes
Furthermore, two communication holes 41 are also formed to allow communication between the remaining two diagonally located notch grooves 32 and the circumferential groove 37b, respectively.

As shown in FIG.
Connected via 3.

This phase control valve 42 consists of an electromagnetic direction switching valve with 4 points, whereas the relief valve 43 has 3 points.
Consists of an electromagnetic directional valve with one and two positions. Therefore, the pressure liquid supply line 44 extending from the pump 8b is
The part downstream of the IJ-F valve 43 is a branch supply pipe 44.
a, 44b, and then the corresponding one 35a via the phase control valve 42.

35b, respectively. A pressure fluid return line 45 is branched from the branch supply line 44 b between the relief valve 43 and the phase control valve 42 , and this return line 45 is connected to the reservoir 12 .

In the state shown in FIG. 1, the relief valve 43 is in the release position and the phase control valve 42 is in the neutral position.

Each of the phase control valve 42 and the relief valve 43 is
It is electrically connected to a controller 46, and the controller 46 is supplied with sensor signals from a steering wheel angle sensor 47 that detects the steering wheel angle of the steering wheel 14 and a vehicle speed sensor 48 that detects the vehicle speed of the automobile. It looks like this.

Continuing the explanation regarding the front wheel steering path 16 with reference to FIG. 2 again, the rotary valve body 49 of the front wheel steering control valve 7 is integrally formed with the aforementioned control cylinder 25. The rotary valve body 49 is composed of a hollow shaft having a diameter smaller than that of the control cylinder 25 and extends on the opposite side from the input shaft 21 . The inner end of the input shaft 21 is connected to the needle bearing 5 with respect to the rotary valve body 49.
Supported through 0.

A two-stage upper and lower torsion bar 52 that extends beyond the rotary valve body 49 is housed within the input shaft 21.
One end of the torsion bar 52 is connected to the protruding end of the input shaft 21 via a pin, and the center portion thereof is connected to an end of the rotary valve body 49 via a connecting pin 53. Therefore, the input shaft 21 is connected to the steering handle 14.
When the rotary valve body 49 is rotated by the operation, the rotary valve body 49 is also rotated. Here, since the rotary valve body 49 and the aforementioned control cylinder 25 are integrated, this control cylinder 2
5 is of course also rotated together with the rotary valve body 49.

A sleeve 54 that cooperates with the rotary valve body 49 and forms the front wheel steering control valve 7 is disposed between the rotary valve body 49 and the small diameter portion of the upper casing 18 .

This sleeve 54 is rotatably arranged relative to the upper casing 18.

The torsion bar 52 extends from the rotary valve body 49 further through the lower casing 19, and a pinion shaft 55 is disposed within the lower casing 19 so as to surround the torsion bar 52. That is, the pinion shaft 55 is constituted by a hollow shaft, and one end thereof, that is, the upper end thereof as seen in FIG. .

Further, the upper end of the pinion shaft 55 is supported by the upper casing 18 via a seal 56, and is supported by the lower casing 19 via a pair of bearings 57. The pinion shaft 55 has a lower end connected to the torsion bar 52 via a pin 58, and an upper end connected to the sleeve 54 of the front wheel steering control valve 7 via a pin 59.

A pinion 60 is integrally formed on the pinion shaft 55, and the pinion 60 is meshed with a rack 61. When viewed in FIG. 2, this rack 61 extends in a direction perpendicular to the plane of the paper so as to penetrate inside the lower casing 19. In the lower casing 19, the rack 61
is slidably guided in its axial direction by a guide 62, and the guide 62 is urged toward the rack 61 by a plug 63 via a pressure spring 64. The rack 61 is formed integrally with one piston rod 3 of the drive cylinder 2 in the front wheel power steering device 1 described above.

In the front wheel steering control valve 7 described above, the rotary valve body 49
The passage system itself within and within the sleeve 54 is known, and the function of the front wheel steering control valve 7 itself is also known.
Description regarding the passage system will be omitted. Further, in relation to the front wheel steering control valve 7, when the above-mentioned torsion bar 52 is viewed from above and below the pin 53, the rigidity of the upper part is sufficiently greater than the rigidity of the lower part.

According to the above-described steering system for the front wheels 5, when the steering handle 14 is operated, the rotation of the steering handle 14 is directed from the handle shaft 15 to the front wheel steering path 16.
That is, as shown in FIG. 2, the signal is transmitted from the input shaft 21 to the rotary valve body 49 of the front wheel steering control valve 7 via the upper part of the torsion bar 52, and from this rotary valve body 49 to the torsion bar 52. through the lower part of the pinion shaft 5
5, that is, the signal is transmitted to the pinion 60. In other words, the pinion 60 is rotated by a rotation angle that corresponds to the amount of operation of the steering handle 14, that is, the steering wheel angle, and in a direction that corresponds to the direction in which the steering handle 14 is operated. The rotation of the pinion 60 is controlled by the rack 61.
is converted into an axial displacement of the piston rod 3 in the drive cylinder 2, and as a result, both front shafts 5 are steered according to the amount and direction of operation of the steering handle 14. .

As described above, when the steering force of the steering handle 14 is transmitted to the pinion 60, the lower part of the torsion bar 52 has lower torsional rigidity than the upper part, so that the torsion is not applied. The lower portion of the bar 52 will be twisted relative to its upper portion. That is, in this case, since the pinion shaft 55 and the sleeve 54 of the front wheel steering control valve 7 are connected to each other via the pin 59, in the front wheel steering control valve 7, the rotary valve body 49 and A relative rotational phase difference is generated between the sleeve 54 and the front wheel steering control valve 7, and based on this rotational phase difference, the switching operation of the front wheel steering control valve 7 is performed as is known in the art. As a result, the pressure fluid from the pump 8a is supplied to one pressure chamber of the drive cylinder 2, and the piston rod 3 of the drive cylinder 2 is moved not only by the operating force of the steering handle 14 but also by the pressure of the pressure fluid. is also displaced in the axial direction, and the operating force of the handle 14 when steering the front wheels 5 can be reduced.

Further, in this embodiment, the front wheel power steering device 1
The front wheel side hydraulic mechanism 23 mentioned above is built in,
Since the front wheel side hydraulic mechanism 23 is connected to the pump 8b via the phase control valve 43, the front wheel 5 is controlled when the front wheel 5 is steered based on the operation of the steering handle 14. The phase of the steering can be controlled.

That is, first, in FIG. 1, it is assumed that the relief valve 43 is switched from the illustrated release position to the operating position, and in this state, by operating the steering handle 14, as shown in FIG. When the input shaft 21 is rotated counterclockwise, the two notch grooves 32 located in front of the drive pawl 30 on the input shaft 21 when viewed in the direction of rotation, in this case, the inside thereof is shown in FIG. In order to increase the pressure in the notched groove 32, which is shown with the symbol A, the phase control valve 42 is
is operated by switching from the neutral position to one switching position.

That is, in this case, the phase control valve 42 is operated to switch so as to supply pressure fluid from the port 35a shown in solid lines in FIG. 3, while discharging pressure fluid from the port 35b shown in broken lines. be done.

In this way, when the pressure in the notch groove 32 marked with the symbol A is increased, each of the plungers 33 in the cylinder hole 31 that is paired with the notch groove 32 is moved in the axial direction from the cylinder hole 31. Since the input shaft 21 is displaced toward the groove 29 side, the input shaft 21 itself is rotated clockwise relative to the control cylinder 25 via the drive pawl 30 . This means that when the upper part of the torsion bar 52 is forcibly twisted, the pinion 60 is forced to rotate against the input shaft 2I, which is the control cylinder 25, that is, the rotary valve body 49 of the front wheel steering control valve 7 and the pinion shaft 55. Therefore, with respect to the steering angle of the front wheels 5 based on the operation of the steering lever 14, the actual steering angle of the front wheels 5 is controlled to be advanced. become.

In addition, when the steering wheel 14 is operated in the opposite direction to the case described above, the phase control valve 42 is switched from its neutral position to the other switching position, so that even in this case, the steering wheel 14 is operated. The steering angle of the front wheels 5 can be advanced and controlled in response to the operation of the handle 14. Note that when the above-mentioned phase control valve 42 is returned to the neutral position, the upper portion of the torsion bar 52 is released from twisting, and the advance angle control of the front wheels 5 is discontinued.

Although the above description concerns the steering system for the front wheels 5, the steering system for the rear wheels 65 is also configured by a similar steering system to that for the front wheels 5, as shown in FIG. be able to. That is, the rear wheel 65
The steering system also includes a rear wheel power steering device 6.
6, this rear wheel power steering device 66
Similar to the front wheel power steering device 1, the front wheel power steering device 1 includes a drive cylinder unit 67 and a rear wheel steering control valve 68. Here, since the drive cylinder 67 and the rear wheel steering control valve 68 have basically the same structure as that of the front wheel power steering device 1, in FIG.
Members having the same functions are designated by the same reference numerals, detailed explanations thereof will be omitted, and only differences will be explained below.

The pressure liquid supply pipe 10 extending from the pump 8a described above includes:
A flow divider valve 70 is inserted, and from this flow divider valve 70,
A rear wheel side pressure fluid supply conduit 71 extends. This rear wheel side pressure liquid supply pipe 71 is branched into branch supply pipes 71a and 71b via a rear wheel steering control valve 68, and these branch supply pipes 71a.

71b are connected to both pressure chambers of the drive cylinder 67, respectively. Further, a pressure fluid return line 72 extends from the rear wheel steering control valve 68, and this return line 72 is connected to the aforementioned return line 45.

The rear wheel power steering device 66 and the front wheel power steering device 1 are mechanically connected via a rear wheel steering path 73. That is, the rear wheel steering path 73
First, a rear wheel hydraulic pressure mechanism 74 is provided, and this rear wheel hydraulic pressure mechanism 74 is connected to the front wheel hydraulic pressure mechanism 23 described above.
It has a similar structure. Therefore, there is a relationship similar to that between the front wheel side hydraulic pressure mechanism 23 and the front wheel steering control valve 7 described above, and the rear wheel side hydraulic pressure mechanism 74 is connected to the rear wheel steering control valve 6.
It is built to work together with 8.

The rear wheel steering path 73, that is, the rear wheel side hydraulic pressure mechanism 74
The input shaft 75 is connected to an adjustment mechanism 77 via a rotation transmission shaft 76.
and from this adjustment mechanism 77,
A rotation transmission shaft 78 extends toward the front wheel power steering device 1 . A pinion 79 is attached to the tip of the rotation transmission shaft 78, whereas a pinion 79 is attached to the other piston rod 3 of the front wheel power steering device l, that is, its drive cylinder, although it is not shown in detail. A rack 80 is formed that meshes with the pinion 79.

The adjustment mechanism 77 described above determines the steering angle function between the steering angle of the front wheels 5 and the steering angle of the rear wheels 65. It is configured. Therefore, the reduction gearbox accommodates reduction gears 81, 82 attached to both ends of the rotation transmission shaft 76, 79, and these reduction gears 81, 82 mesh with each other. Therefore, when the front wheel power steering device 1 is driven and the piston rod 3 of the drive cylinder 2 is displaced in the axial direction, this amount of displacement is converted into rotation of the rotation transmission shaft 78 via the pinion 80, The rotation of this rotation transmission shaft 78 is then reduced by reduction gears 81 and 82 of the reduction gear box.
Rotation transmission shaft 76, that is, input shaft 7 of rear wheel side hydraulic mechanism 74
5 will be transmitted.

In this way, when the input shaft 75 is rotated, the rear wheel power steering device 66 is driven in the same manner as in the front wheel power steering device 1, whereby the rear wheels 65 are controlled by the steering of the front wheels 5. They will be steered in the same phase. Also, at this time, the rear wheel power steering device 6
In case 6, the rear wheel steering control valve 68 is also switched in response to the rotation of the input shaft 75, so the drive cylinder 67 is of course operated by hydraulic pressure.

The rear wheel hydraulic mechanism 74 is connected to the phase control valve 42 described above in the same way as the front wheel hydraulic mechanism 23. However, in the rear wheel hydraulic mechanism 74, , one port 35a is connected via the conduit 83a,
It is connected to a branch supply pipe 44b between the phase control valve 42 and the front wheel side hydraulic mechanism 23, and the other port h35b is connected to the phase control valve 42 and the front wheel side hydraulic mechanism 23 via a pipe 83b. It is connected to a branch supply conduit 44a between the hydraulic mechanism 23 and the hydraulic mechanism 23. Therefore, the rear wheel hydraulic pressure mechanism 74 is operated in the opposite direction to the front wheel hydraulic pressure mechanism 23. Therefore, when the front wheel power steering device 1 is operated and rotational force is transmitted to the input shaft 75 via the rear wheel steering path 73, and at the same time the rear wheel side hydraulic mechanism 74 is operated, this rear wheel When the amount of operation by the side hydraulic mechanism 74 is larger, the control cylinder 25, that is, the pinion 60 of the rear wheel power steering device 66, is rotated in the opposite direction to the direction of rotation transmitted to the input shaft 75. As a result, the rear wheels 65 are steered in a phase opposite to the steering of the front wheels 5.

Note that after this, when the operation of the rear wheel side hydraulic mechanism 74 is stopped, the rear wheels 65 receive the rotational force from the front wheel power steering device l side, so that the rear wheels 65 respond to the steering of the front wheels 5 as described above. They will be steered in the same phase.

The advance angle control of the front wheels 5 and the instantaneous reverse phase control of the rear wheels 65 described above are shown in the area indicated by a broken line in FIG. 4. Such phase advance and reverse phase control of the front wheels 5 and rear wheels 65 can be easily obtained by controlling the switching of the phase control valve 42 by the controller 46, which controls the steering wheel angle sensor 47 and the vehicle speed. Basically, based on the sensor signal from the sensor 48, when the vehicle speed is in the medium to low speed range and the steering wheel angle or steering angular velocity is large, the phase control valve 42 is switched and activated to control the phase advance of the front wheels 5 and Momentary reverse phase control of the rear wheels 65 is performed. Therefore, in this case, both the yaw response and the lateral acceleration response of the vehicle can be improved, and the turning performance and steering stability of the vehicle can also be improved. On the other hand, when the vehicle speed is high, the controller 46 stops the switching operation of the phase control valve 42, thereby improving the running stability of the vehicle.

In this embodiment, the timing of the switching and return operation in the phase control valve 42 is set according to the vehicle speed and the steering wheel angle or the steering angular velocity, so that the phase advance control of the front wheel steering and the rear wheel steering can be performed. Instantaneous reverse phase control can be carried out in fine detail.

In addition, in the case of this embodiment, even if the pressure fluid pipe or the like to the rear wheel power steering device 66 is damaged, the rear wheel power steering device 66 will not be able to connect the front wheel power steering device 1 to the rear wheel steering path 73. Since they are mechanically connected via the
The drive cylinder 67 of the rear wheel power steering device 66 can be mechanically driven to steer the rear wheels 65,
Steering of the rear wheels 65 will not become impossible.

Furthermore, due to the operation of the front wheel side hydraulic pressure mechanism 23 and the rear wheel side hydraulic pressure mechanism 74, even if the upper part of the torsion bar 52 in the steering path is completely damaged, the input shaft 21.76 will not rotate. It is mechanically transmitted to the control cylinder 25 via the drive pawl 30, and from the control cylinder 25 to the pinion shaft 55, that is, the pinion 60 via the rotary valve body 49 and the lower part of the torsion bar 52. Therefore, even in this case, the steering of the front wheels 5 and rear wheels 65 will not become impossible.

This invention is not limited to the one embodiment described above, and various modifications are possible. That is, referring to FIG. 5, there is shown a four-wheel steering system according to another embodiment of the present invention. The four-wheel steering system shown in Fig.
Since most of the configuration is the same as the four-wheel steering system shown in the figure, parts and members having the same functions as those in Figure 1 are given the same reference numerals, and their explanations are omitted. will only explain the differences.

In the four-wheel steering system shown in FIG. 5, the rear wheel hydraulic pressure mechanism 74 is not connected to the phase control valve 42 and is paired with a phase control valve 90 that is separate from the phase control valve 42. ing.

Like the phase control valve 42, the phase control valve 90 is composed of a four-point, three-position directional switching valve, and is electrically connected to the controller 46.

One pipe line 83a of the rear wheel side hydraulic pressure mechanism 74 is connected to a branch supply pipe line 44a between the phase control valve 42 and the relief valve 43 via a phase control valve 90. Further, the other pipe line 83b of the rear wheel side hydraulic mechanism 74 is connected to the return pipe line 72 via a phase control valve 90.

Therefore, as described above, if the phase control valve 90 that is paired with the rear wheel hydraulic pressure mechanism 74 is provided separately in addition to the phase control valve 42, it will be independent of the operation of the front wheel hydraulic pressure mechanism 23. hand,
The operation of the rear wheel hydraulic mechanism 74 can be controlled. As a result, in the embodiment shown in Fig. 1, when the vehicle speed is in the medium to low speed range, the rear wheels are basically only controlled with the characteristics shown by F1 in Fig. 6 in contrast to the front wheel steering. However, in the case of the embodiment shown in FIG. 5, at the same time as the front wheel steering is started,
By performing the switching operation of the phase control valve 90, for example, F2. As shown by F3, it is possible to obtain characteristics similar to those obtained by moving the characteristics of Fl in parallel, and the steering of the rear wheels can be controlled more precisely according to requests.

Further, in the embodiments shown in FIGS. 1 and 5, a reduction gearbox is used as the adjustment mechanism 77, but a cam mechanism may be used instead of this reduction gearbox. That is, for example, in the front wheel power steering device 1, this cam mechanism changes the axial displacement of the piston rod 3 of the drive cylinder 2 to the rear wheel power cylinder device 66.
Any device that converts the rotation of the input shaft 75 into the rotation of the input shaft 75 may be used.

(Effects of the Invention) As explained above, according to the four-wheel steering device for a vehicle of the present invention, the front wheel power steering unit and the rear wheel power steering unit are mechanically connected via the rear wheel steering path. Therefore, even if the hydraulic pressure circuit on the rear wheel power steering unit side fails, the operation of the rear wheel power steering unit, that is, the steering of the rear wheels will not become impossible.

In addition, the front wheel and rear wheel power steering units have
Since the front wheel and rear wheel hydraulic pressure mechanisms are combined, it is possible to advance the front wheels by as much as 4 degrees and to control the rear wheels momentarily in reverse phase relative to the steering wheel angle. Furthermore, it becomes possible to precisely control the steering of the front wheels and rear wheels.

Furthermore, by inserting an adjustment mechanism in the rear wheel steering path, it is possible to use the same unit for the front wheel and rear wheel power steering units, thereby reducing the cost of the four-wheel steering system. It has the following effects.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention.
The figure is a schematic configuration diagram of the four-wheel steering system, FIG. 2 is a sectional view specifically showing a front wheel steering path and a part of the front wheel power steering device, and FIG. 3 is a schematic diagram of the four-wheel steering system. −■
A cross-sectional view taken along the line, FIG. 4 is a graph showing phase advance and instantaneous reverse phase control for the front and rear wheels, and FIG. 5 is a four-wheel steering system showing another embodiment of the present invention. FIG. 6 is a graph showing the steering characteristics of the rear wheels relative to the front wheels. 1... Front wheel power steering device (front wheel power steering unit), 5... Front wheel, 16... Front wheel steering path, 23... Front wheel side hydraulic pressure mechanism, 42.90...
Phase control valve, 65... Rear wheel, 73... Rear wheel steering path, 74... Rear wheel side hydraulic pressure mechanism, 77... Adjustment mechanism.

Claims (1)

[Claims] A front wheel power steering unit that is driven by the operation of the steering wheel to vary the front wheel steering angle, and a front wheel steering path that mechanically connects the steering wheel and the front wheel power steering unit. For front wheel steering, a front wheel side hydraulic mechanism that controls the phase of the front wheel steering angle is mechanically connected to the front wheel power steering unit via the rear wheel steering path, and is driven in response to the front wheel power steering unit. , a rear wheel power steering unit that varies the rear wheel steering angle, and is inserted in the rear wheel steering path, and adjusts the amount of operation transmitted from the front wheel power steering unit to the rear wheel power steering unit by the rear wheel steering path. an adjustment mechanism, a rear wheel side hydraulic mechanism that is inserted in the rear wheel steering path and controls the phase of the rear wheel steering angle for rear wheel steering performed in response to the front wheel power steering unit; A phase control valve that is inserted into a hydraulic circuit that connects a rear wheel hydraulic mechanism and a pressure fluid supply source and controls the supply of pressure fluid to the front wheel and rear wheel hydraulic mechanisms, and this phase control valve. 1. A four-wheel steering device for an automobile, comprising a controller that controls the operation of a valve.