JPH065951Y2 - Rear-wheel steering system for four-wheel steering vehicle - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an improvement of a rear wheel steering device in a four-wheel steering vehicle in which a front wheel and a rear wheel can be steered in conjunction with a steering operation.

[Conventional technology]

In recent years, by turning the rear wheels in accordance with the steering amount (turning amount) of the front wheels and the vehicle speed, etc., the maneuverability at low speed running is improved and the running stability at mid and high speed running is improved. The four-wheeled steered car that gets is attracting attention. For example, when driving at low speed, the front wheels are steered with a large steering angle. At this time, if the front and rear wheels are steered in the opposite phase (reverse steering), the turning radius of the vehicle is minimized and the turning (small turning) performance is improved. improves. On the other hand, when traveling at high speed, steering is often performed with a small steering angle. At this time, the steering direction of the front and rear wheels may be the same phase (steering in the same direction) or the steering angle of the rear wheels may be zero. It is preferable in order to improve the running stability of the vehicle.

As a rear-wheel steering device for such a four-wheel steering vehicle, various structures have been proposed in the past.
As shown in Japanese Laid-Open Patent Publication No. 63063, a main body rotatably supported on the vehicle body side about a substantially vertical axis (Z axis), and one side (Y axis) extending to the front wheel side. Fixed to a position where the arm connected to the transmission rod from the main body, the electric motor provided in the main body so as to be orthogonal to the main body axis line and oriented in the vehicle longitudinal direction (X axis), and the motor shaft intersecting the Z axis. And a lever whose front end is connected to a transmission rod to the rear wheel side constitutes a rear wheel steering ratio variable mechanism for controlling the steering operation of the front wheel, that is, the steering ratio of the rear wheel with respect to the steering angle. It is known that the wheel turning ratio variable mechanism is provided in the middle of a turning force transmission rod system for mechanically transmitting the turning operation of the front wheels to the rear wheels by the movement in the longitudinal direction of the vehicle body.

Further, according to such a conventional configuration, the electric motor is driven by the controller to which a vehicle speed signal or the like is input to rotate the lever, and the left side of the connecting point of the rear wheel side transmission rod with respect to the Z axis to the lever, By changing the right position,
The rear wheel steering ratio is appropriately controlled, and the rear wheel side can be steered by freely adjusting the front wheel side by the necessary steering ratio to the same phase or the opposite phase by the steering operation of the front wheel side. Excellent in terms of reliability in operation and operation.

[Problems to be solved by the invention]

By the way, according to the rear wheel turning ratio variable mechanism described above, an electric motor is used to rotate the lever, and the motor is controlled by a controller or the like according to the vehicle speed or the like. When a failure such as the above occurs or a malfunction of the controller occurs, it is impossible to control the swing angle of the lever, which is a problem in ensuring maneuverability and traveling stability. Then, as a fail-safe when a failure occurs in such an electric control system, all the electric control signals are turned off signals and a fail-safe mechanism such as a spring is used as a part of the steering link mechanism in the rear wheel steering system. In order to maintain maneuverability and traveling stability, the rear wheel steering system is maintained in a neutral state, that is, the rear wheel is steered, and only the front wheels are steered.

However, it is difficult to always maintain the entire rear wheel steering system in a neutral state by an appropriate external force applied to the rear wheel steering system only with such a fail-safe mechanism such as a spring. It may be possible to attach it to a steering link mechanism or the like, but there were various problems in attaching such a lock mechanism.
That is, in this type of rear wheel steering device, it is unavoidable that the rear wheels are greatly affected by the reaction force from the ground contact surface during traveling, and the influence of such reaction force is caused by the steering link mechanism or the like. As described above, the rear wheel steering system is more prominent on the output side. Therefore, it is necessary for the above-mentioned lock mechanism to have a mechanical structure having sufficient strength to withstand this reaction force. It is necessary to improve the reliability of strength including.

In particular, the lock mechanism provided in the above-described steering link mechanism needs to be able to reliably lock against the above-mentioned external force, and as a power source for driving such a lock mechanism, a considerably large machine can be used. It is necessary and practically a problem, not only complicating the structure of the entire rear wheel steering device, but also causing problems such as an increase in size and weight of the entire device and further increase in cost. It is hoped that some measures will be taken to clear the points.

Further, it should be noted in providing such a lock mechanism that the entire rear wheel steering device can always return to the neutral position when the locking operation is performed during the rear wheel steering operation. Consideration may be given to these points, and these points must be taken into consideration.

[Means for solving problems]

In order to meet such a demand, the rear wheel steering device of the four-wheel steering vehicle according to the present invention rotates with respect to a rotation main body rotated by an arm to which a front wheel side rod for transmitting a steering force is connected. A lever in a rear wheel steering ratio variable mechanism in which a rear wheel rod for transmitting a steering force is connected to a tip end that is rotatably supported and extends laterally of the main body, and is selectively rotationally controlled by an electric motor. An engaging pin and an actuator for driving the engaging pin, which are selectively moved forward and backward with respect to a side surface portion parallel to the rotation direction of the lever, are provided on the main body side, and the tip of the lever is rotated relative to the side surface portion of the lever. An engaging groove is formed in which the engaging pin is engaged in a neutral state located on the axis, and both side surfaces in the direction of rotation of the lever side surface portion reaching the engaging groove and both side edge portions of the lever and the engaging pin. From the lever Is obtained so as to form cam shapes, as guided by the engaging groove when the protruded been.

[Action]

According to the present invention, a lever that is rotatably supported on an axis line orthogonal to the axis of a rotating body that is oscillated according to the turning operation of the front wheels is driven by an electric motor to control the vehicle speed and the steering angle. Rotation is controlled according to various running conditions such as the rear wheel turning angle, etc., and the position of the connection point with the rear wheel rod is displaced in the left and right direction from the axis of the main body, so that the lever The connection point rotates along with the rotation of the main body, and the steering amount controlled to the required rear wheel steering ratio is transmitted to the rear wheel side via the rear wheel side rod to ensure an appropriate and reliable rear wheel. The steering control of the wheels can be performed, and when the electric motor or its controller is out of order, the lever can be appropriately and surely held in the neutral state by the engagement pin by the actuator or in the neutral state. To restore the rear wheels to the steered state properly and surely. It is capable of.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

1 to 6 show an embodiment of a rear wheel steering system for a four-wheel steering vehicle according to the present invention. In these figures, first,
The schematic configuration of the entire steering system of a four-wheel steering vehicle will be briefly described with reference to FIG. 6. Reference numerals 1 and 1 are a pair of left and right front wheels (only one is shown), and 2 is a steering wheel for these front wheels 1. A front wheel side steering device for steering according to the steering operation of the steering wheel 3. In this embodiment, an oil pump 2a is used for the tank 2.
The case of an integral type hydraulic power steering apparatus in which a required steering assist force is generated by a flow path switching valve and a power cylinder (not shown) by feeding pressure oil from b is illustrated. In addition, reference numeral 2c in the drawing denotes a steering body, which is configured to be able to transmit a steering force to a steering link system 4 side supporting the front wheels 1 via a pitman arm 2d and a drag link 2e.

5 and 5 are a pair of left and right rear wheels (only one is shown),
These rear wheels 5 are also rotatably supported by a steering link system 6 having a configuration similar to that of the front wheels 1 described above, and the rear wheel steering ratio variable that constitutes a rear wheel steering device 10 together with the steering link system 6 is variable. The mechanism 11 and the linkage type power steering device 7 for generating steering assist force are configured to steer the same phase or the opposite phase with a required steering amount corresponding to the steering amount of the front wheel 1.

Then, the steering link mechanisms 4, 6 for the front wheels 1 and the rear wheels 5
In between, a steering force transmission rod system 8 extending in the front-rear direction of the vehicle body from a part of the steering force transmission system to the front wheel 1 side (the pitman arm 2d on the front wheel side in this embodiment) is provided as a front wheel side. A rod 8a and a rear wheel side rod 8b are provided, and the steering force is transmitted from the front wheel side to the rear wheel side by the movement in the vehicle front-rear direction. Reference numerals 9a and 9b are transmission rods for transmitting the back-and-forth movement of the rear wheel side rod 8b to the linkage type hydraulic power steering apparatus 7. The front side rod 9a is provided with a centering spring mechanism 30 described later. Has been done. Further, the linkage type power steering apparatus 7 described above has a well-known configuration, one end thereof is fixed to the vehicle body side (not shown), and the other end side thereof is connected to the rear wheel side rod 8b side. The steering assist force generated in the section is transmitted to the rear wheel 5 side. Here, 7a and 7b in the figure are an oil pump and an oil tank attached to the vehicle body side.

In the rear wheel steering device 10 of the four-wheel steering vehicle having such a configuration, the steering operation is provided in the middle of the transmission rod system 8 that transmits the steering operation of the front wheels 1 by the steering operation to the rear wheels 5 by the movement in the longitudinal direction of the vehicle body. The rear wheel turning ratio variable mechanism 11 for controlling the turning ratio of the rear wheels 5 with respect to the angle in consideration of the vehicle speed and the like is configured as shown in FIGS. 1 to 4.

That is, the rear wheel turning ratio varying mechanism 11 is a turning shaft member that is rotatably supported on the vehicle body side (not shown) via the bracket 12 on the axis ZZ in the vertical direction of the vehicle body. The main body 13 and the front wheel side rod 8 for integrally transmitting the steering force with the front end 14a extending integrally from the main body 13 laterally (Y direction).
arm 14 connected to a via a ball joint or the like
And a tip 15a that is rotatably supported on the axis X-X that passes through the intersection O between the rotation body 13 and the arm 14 and that is orthogonal to the body axis Z-Z and that extends to the side of the body 13. Lever 1 connected to rear wheel side rod 8b for transmitting steering force
5 and an electric motor 16 for rotating and displacing the lever 15 on the axis X-X. Here, as is apparent from FIG. 6, the rear wheel turning ratio varying mechanism 11 may be disposed on the vehicle body with the motor 16 mounting side facing upward.

Further, according to the present embodiment, the lever 15 described above is provided at a position separated from the intersection O on the axis X-X orthogonal to the main body axis Z-Z, and the lever tip 15a and the rear wheel side rod 8b are provided. Is connected to the extension line of the main body axis ZZ when the rear wheel 5 is not steered.
If such a configuration is adopted, the rear wheel steering ratio variable mechanism 11
Function can be properly and sufficiently ensured, on the other hand, consideration of problems such as interference between the lever 15 connected to the rear wheel side and the movable body 13 is unnecessary, and the length of the lever 15 can be appropriately selected. Compared to the device, the lever ratio can be made larger and the rear wheel steering ratio can be made larger.
It is possible to achieve downsizing of the entire device including the device 3 described above.

Further, according to this embodiment, the electric motor 16 is connected to the main body 1
3 is provided coaxially with the main body axis Z-Z at one end side thereof, and its output shaft 16a is connected to the lever 15 by a rotation transmission system 20 provided in the main body. That is,
An electric motor 16 which is rotated together with a rotating body 13 which is rocked and rotated by an arm 14 in accordance with a steering operation of the front wheels 1.
By being configured to rotate on the same axis (Z-Z) as the main body 13, the operating space may be smaller than that of the conventional structure in which the motor 16 is rotated together with the main body 13,
The overall size of the device can be reduced, there is no adverse effect due to inertia, etc., and the motor 16 and the main body 13 are coaxial Z-.
Protective cover 17 as it only rotates on Z
(See FIG. 1 etc.), it is possible to obtain an advantage such as a simple structure.

Further, the lever 15 which is rotated together with the main body 13 and the motor 16 described above is appropriately rotated by the motor 16 according to various traveling conditions such as vehicle speed and steering angle and the rear wheel turning angle, and the rear wheel rod 8b. By displacing the connecting point position with the left and right from the main body axis ZZ, the connecting point (15a) with the rear wheel rod 8b of the lever 15 is accompanied by the turning operation of the turning main body 13. That is, the turning amount controlled to the required rear wheel turning ratio is transmitted to the rear wheel 5 side via the rear wheel side rod 8b, and an appropriate and reliable turning control of the rear wheel can be performed. There are also advantages.

Here, the operation of the rear wheel turning ratio variable mechanism 11 having the above-described configuration will be briefly described. First, as shown in FIG. 6 and the like, the lever tip 15a (the connection point with the rear wheel side) is the axis Z-.
When located on Z, the rear wheels 5 are maintained in the unsteered state regardless of the steering operation on the front wheel 1 side associated with the steering operation.

This is because even if the turning main body 13 is turned by the arm 14 due to the turning operation of the front wheels 1, the lever tip 15a moves along the axis ZZ.
It will be easily understood as it only pivots on.

Further, when the electric motor 16 is driven according to various traveling conditions such as vehicle speed and steering angle and the rear wheel steering angle to rotate the lever tip 15a in the left-right direction, the front wheel 1 is rotated by the steering operation. By the movement of the turning main body 13, the lever tip 15a turns about this axis ZZ according to the amount of displacement from the axis ZZ, whereby the rear wheel side rod 8b moves in the front-back direction of the vehicle body. It is possible to move and steer the rear wheel 5 at an appropriate steering ratio. In this case, the rear wheel side is steered in the same phase or in the opposite phase as the front wheel side depending on the tilting direction of the lever 15, and the steering characteristic can be freely selected by appropriately controlling the motor 16 as necessary. It is a thing.

Further, in the present embodiment, the details of the rear wheel steering ratio varying mechanism 11 described above are as follows. That is, the main body 13
As is apparent from FIG. 1 and the like, the small diameter portion 13a of the bracket 12 is rotatably supported by the split bush 21, and the motor 16 (main body portion including the stator is attached to the flange portion on the tip side thereof. ) Are fixed by bolts or the like, and these are integrally rotatable. The split bush 21 is divided into two cylindrical body portions 21a and 21a and annular plate portions 21b, 21b;
It is composed of c and 21c so that it can be easily assembled, and at the same time, it is possible to achieve downsizing in the radial direction at the shaft supporting portion of the main body 13.

Further, the output shaft 16a of the motor facing the inside of the main body 13 is
It is connected to a first transmission shaft 22 constituting the rotation transmission system 20 via a reduction gear unit 23 utilizing a planetary gear mechanism or the like. Of course, the reduction gear unit 23 can be omitted.

Further, the first transmission shaft 22 extending along the axis Z-Z in the small diameter portion 13a is axially supported in the main body 13 in the axis X-X direction orthogonal to the axis Z-Z. The second
Transmission shaft 24 and transmission gears 25a, 25b by bevel gears or the like
Is connected so that rotation can be transmitted, and by fixing the base end portion of the lever 15 on the second transmission shaft 24, the swing displacement of the lever 15 can be obtained according to the rotation of the motor 16. ing. The first and second transmission shafts 2
The reference numerals 2 and 24 are rotatably supported in the main body 13 by bearings or the like.

Further, the motor 16 is energized and controlled by the battery 27 via the power controller 26b by the signal from the signal controller 26a so that the rotation speed is determined by various traveling conditions of the vehicle, for example, the vehicle speed and the steering angle. It is configured to be driven and stopped by feeding back the rear wheel turning ratio. Reference numeral 28 in FIG. 6 denotes a vehicle speed sensor, and 29a denotes a steering angle of the front wheel 1 by detecting a rotation amount of a motor 16 (a stator portion thereof) attached to an upper end portion of the cover 17 and rotated together with the main body 13. A steering angle sensor 29b for detecting the rear wheel steering ratio is provided on the main body 13 side so as to face the base end portion of the lever 15 on the axis XX on the rear wheel steering ratio variable mechanism 11 side. It is a sensor. The input signal to the controller 26a is not limited to the vehicle speed or the like, and may be, for example, the lateral G applied to the vehicle body.

Further, according to the rear wheel turning ratio varying mechanism 11 described above, as is apparent from FIG. 6, the rotation axis line XX of the lever 15 is obtained.
Is oriented in the front-rear direction of the vehicle body, and even if the vehicle speed changes in a straight traveling state and the motor 16 is driven to rotate the lever 15, the rear wheel side is not affected and the straight traveling state of the rear wheel 5 is maintained. It is configured so that it can.

By the way, according to the rear wheel steering device 10 having such a configuration, a stopper is required for mechanically locking the steering amount on the rear wheel 5 side within a predetermined range. As shown in FIG. 3 etc., the lever 15 provided on the second transmission shaft 24 is sandwiched between the main body 13 of the rear wheel steering ratio varying mechanism 11 which is the input side member of the rear wheel steering system. Stopper member 31 having V groove 31a
It is advisable to attach and detach with a bolt or the like. With this configuration, since the transmission of the external force from the rear wheel 5 side to the lever 15 is smaller than that of the rear wheel steering link mechanism 6 and the like, the force acting on the stopper member 31 is small and the conventional Not only can the stopper structure be simplified, but the movable range of the lever 15 that changes depending on the vehicle type can be adjusted without changing the shape of the main body 13 or the like, thereby increasing the versatility of the device. This is advantageous in raising the cost and reducing the cost at the same time. Also, this stopper 3
As shown in FIG. 1, one member is a sensor 29 that detects the rear wheel turning ratio by detecting the turning position of the lever 15.
It also functions as a mounting base for b. 32 in the figure
Is an adjusting screw screwed into the shaft 24 in order to adjust and fix the center and angle of the detection shaft 32a of the sensor 29b fitted to the tip of the second transmission shaft 24, and 33 is a dropout of the adjusting screw 32. A locking screw that closes the adjustment hole at the proximal end of the lever 15 to prevent it, and 34 is a screw
It is an adjustment hole formed in the stopper member 31 for adjusting 2, 33. Such a configuration has the above-described sensor 29b.
Is necessary because it has to be adjusted in the overall assembled state.

Further, in the above-mentioned rear wheel steering apparatus 10, a fail-safe mechanism is required that locks the steering operation of the rear wheels at the neutral position to perform two-wheel steering of only the front wheels when a failure occurs in the electric system such as the motor and the controller. According to the present embodiment, as such a fail safe, as shown in FIG. 5, the front rod 9a of the transmission system for transmitting the longitudinal movement of the rear wheel rod 8b to the rear wheel side is used. A centering spring mechanism 30 attached to a support portion slidably supported on the axis XX is used. That is, the spring receiving rings 36a and 36b are provided opposite to each other at a position spaced apart by a predetermined distance from the transmission rod 9a in the casing 35 provided with the brackets 35a and 35a fixed to the vehicle body side, and the centering spring 37 is interposed therebetween. Has been done.
The rod 9a is provided with locking members 38a and 38b that are provided on the outer periphery of the rod 9a at predetermined intervals so that the receiving ring 36 can be received.
By selectively moving a and 36b to the other side, the spring 37 moves so as to bend, and the rear wheel side is normally steered. However, when the motor 16 malfunctions, the spring force causes the rod 9a to become neutral. The rear wheel side is returned to the state, thereby ensuring the neutral state on the rear wheel side and maintaining the two-wheel steering state of only the front wheel 1. Here, the receiving rings 36a and 36b are locked so as to face each other at predetermined intervals on both ends of the casing 35, and are moved to the other side following the movement of only one of the rods 9a. It is like this.

According to the present invention, in the rear wheel steering ratio varying mechanism 11 of the rear wheel steering apparatus 10 having the above-described configuration, the rear wheel steering ratio variable mechanism 11 is rotatably supported by the rotation main body 13 according to traveling conditions such as vehicle speed. As shown in FIG. 1 and the like, with respect to the rear wheel side lever 15 which is oscillatingly displaced, an engaging pin 40a which is selectively moved forward and backward with respect to a side surface portion 15b parallel to the rotation direction and its drive. A fluid pressure cylinder 40 is provided as an actuator for the main body 13 and the lever side surface portion 15 is provided.
An engaging groove 41 into which the engaging pin 40a is engaged is formed in the neutral state in which the lever tip 15a is located on the main body axis ZZ with respect to b, and the lever side surface portion 15b reaching the engaging groove 41 is formed. Both side surfaces 41a, 41b of the rotation direction of the lever, both side edge portions 42a, 42b of the lever, and the engaging pin 40a.
It is characterized in that the tip end portion is formed in a cam shape so as to be guided into the engagement groove 41 when the engagement pin 40a is disengaged from the lever 15 and projected. In this embodiment, the fluid pressure cylinder 40 as the actuator described above is provided with the piston 45 in the cylinder hole 43, which is constantly urged by the spring 44 so that the engagement pin 40a projects toward the lever 15 side. In addition, the engagement pin 40a of the piston 45 is normally attached to the lever 1
In the cylinder hole 43, an appropriate fluid pressure such as air pressure or hydraulic pressure is supplied to the chamber on the side of the engagement pin 40a so as to be separated from the side of No. Engagement pin 40 by cutting off fluid pressure
The case where a is configured to be pushed out by the spring 44 is shown. However, the actuator is not limited to the fluid pressure cylinder, and an electromagnetic solenoid, a stepping motor, or the like may be used as the actuator of the engagement pin 40a as long as this type of movement is possible. Further, what is required as the engagement groove 41 on the lever 15 side with which the engagement pin 40a is engaged is the lever 1
5 is a movement in the rotation direction, and it suffices if the groove wall portions on both sides thereof are accurately formed so as to be engaged with the engagement pin 40a and the movement is restrained. For example, in the longitudinal direction of the lever 15. Is preferably formed into a long groove for reasons such as workability.

That is, according to the rear wheel steering ratio varying mechanism 11 described above,
When the two wheels are steered only by the front wheels during high-speed traveling by using it, or when the electric control system including the motor 16 fails, the centering spring mechanism 30 as a fail safe described above restores and holds the neutral state. As a lock mechanism for ensuring the holding state at the neutral position of the lever 15 (the neutral position where the lever tip 15a is located on the rotation axis ZZ of the main body 13), the actuator using the fluid pressure cylinder 40 described above is used. The driven engagement pin 40a is provided, and the engagement groove 41 with which the engagement pin 40a is engaged is formed on the lever 15 side.

According to such a configuration, when the specification is such that only the front wheels are used for two-wheel steering during high-speed traveling as described above and only small turning performance is ensured during low-speed traveling, or when the electric control system fails, Engagement pin 4 as shown in Figure (a)
0a engages with the engagement groove 41 to bring the rear wheel 5 into the non-steered state, and when the front wheel 1 alone is being steered by the two wheels, the lever 15
Since the movement of the lever can be completely locked, it is excellent in terms of maneuverability and running stability.
Since only a small acting force is applied to the steering wheel mechanism side which is the output side of the rear wheel steering system, the engagement pin 40a
There is an advantage that the structure of the engaging means such as can be simplified.
Further, in such a lock structure, the locking pin 40
The acting force from the rear wheel side that acts on a is small as described above, and it may be a simple actuator (40). In particular, such a locking mechanism can be applied to the fail-safe mechanism by the centering spring 37 described above. It will be easily understood that, when used together, an even better fail-safe effect can be obtained.

Here, using such an engagement pin 40a, the lever 15
The problem with locking and holding is that the lever 15 is rotationally displaced when the engagement pin 40a projects, and the engagement pin 40a is disengaged from the engagement groove 41 without being engaged. There is a point that it will end up. In particular, the above-described engagement pin 40a is engaged only when the lever 15 is correctly positioned in the neutral position and the two are in a completely matched positional relationship. Not being able to obtain a proper locked state, which not only poses a problem in terms of the reliability of the operation of the apparatus, but also causes a problem that the engaging pin 40a is damaged by the returning operation of the lever 15.

Therefore, according to the present invention, the tip end of the engagement pin 40a is formed into a cam shape such as a curved surface that is easy to engage, and both side portions of the engagement groove 41 of the lever 15 are engaged with the engagement pin 40a.
While the pin 40a is pushed toward the actuator side by the engagement with the tip end of the a, the lever 15 is allowed to rotate to the neutral position, and when the pin 15a reaches the neutral position, the pin 15a projects again to engage the engaging groove 41.
It is configured so that it can be guided and engaged therein, which can be easily understood from FIG. 2 (b). By adopting such a configuration, even when the position of the lever 15 is displaced from the engagement pin 40a,
Since a simple and reliable engagement state can be obtained only by the restoration rotation on the lever 15 side, the reliability in the operation of the device can be improved, and the two-wheel steering state of only the front wheels can be surely ensured when necessary. In addition, it is possible to exert an effect in securing traveling stability.

The present invention is not limited to the structure of the embodiment described above,
The shape, structure, etc. of each part of the rear wheel steering device 10, including the steering linkages 4, 6 on the rear wheel side, can be freely modified and changed, and various modified examples can be considered. For example, in the above-described embodiment, the lock mechanism characterizing the present invention has been described in which the engaging pin 40a that is moved forward and backward by the actuator (40) is engaged with the engaging groove 41 on the lever 15 side. However, the present invention is not limited to this, and various modifications are conceivable with respect to the type of actuator, the holding structure of the engagement pin, the engagement groove and the shape of the cams on both sides of the engagement groove. It will be readily understood that any locking arrangement capable of locking is sufficient.

Further, in the above-described embodiment, the cover 17 for protecting the electric motor 16 coaxially connected to the rotating body 13 is fixedly provided on the bracket 12 side. However, the present invention is not limited to this, and when the protection from the position where the motor 16 or the like is disposed is not necessary, boots that protect only the cord or the like drawn from the motor 16 may be provided in the motor main body. Various modifications can be considered as a rotation transmission system that transmits rotation to the lever 15.

Furthermore, in the above-described embodiment, the motor 16 is used to rotate the main body 1.
The case where the motor 16 is attached to the third side and is rotated together with the main body 13 has been described, but the present invention is not limited to this. For example, as shown in FIG.
Is fixed to the fixed-side bracket 12 via a connecting tubular body 50 internally provided, and the motor 16 is drive-controlled by a value calculated from the amount of rotation of the main body 13 in relation to the lever 15. However, it will be easily understood that the same effects as those of the above-described embodiment can be obtained. Further, in such a configuration, since the main body of the motor 16 is in a fixed state, there is no problem that the lead or the like pulled out from the rear end is twisted, which is a great advantage. Here, reference numeral 51 in the drawing is an electromagnetic clutch as a clutch mechanism provided between the motor output shaft 16a and the reduction gear portion 23. When such a clutch 51 is provided, unexpected occurrence such as motor lock occurs. It is effective in preparing for a situation and performing appropriate control of the motor.

Further, in the above-described embodiment, in order to obtain the rear wheel steering force in the rear wheel steering device 10, the case where the power steering device 7 is used as the steering assisting means is shown as in the front wheel 1 side.
For example, it is effective in preventing the adverse effect on the steering operation, which is a problem when the steering resistance is large when steering the rear wheels, such as in a large vehicle, but it is effective in a small vehicle. Alternatively, a manual steering mechanism may be used.

[Effect of device]

As described above, according to the rear wheel steering system of the four-wheel steering vehicle according to the present invention, the turning main body of the rear wheel steering ratio variable mechanism that controls the steering ratio of the rear wheels according to the steering operation of the front wheels. With respect to the lever on the rear wheel side which is rotatably rotatably supported and swingably displaced according to traveling conditions such as vehicle speed, the side surface portion parallel to the rotation direction is selectively advanced and retracted. A pin and an actuator for driving the pin are provided on the main body side, and an engaging groove into which the engaging pin is inserted is provided in a recessed state with respect to a side surface of the lever in a neutral state in which the lever tip is located on the main body axis. A cam that guides both side surfaces of the lever side surface in the turning direction to the mating groove, both side edge portions of the lever, and the engagement pin into the engagement groove when the engagement pin is disengaged from the lever and projected. Since it is formed in a shape, it does not matter even if it is a simple and inexpensive structure. If the electric motor or its controller fails, the lever can be locked and locked in the neutral position, and the steered state of the rear wheels can be maintained easily and appropriately. The effect of external force is smaller than that of a steering link mechanism, which is the output side of the wheel steering system, and there are various practical advantages such as the structure of the lock mechanism and its related members can be simplified. In particular, the lock mechanism that characterizes the present invention can exhibit the effect as a fail-safe mechanism when used in combination with a centering spring mechanism or the like.

[Brief description of drawings]

FIG. 1 is a sectional view of a rear wheel steering ratio variable mechanism showing an embodiment of a rear wheel steering system for a four-wheel steering vehicle according to the present invention, and FIG.
(a) and (b) are operation explanatory views shown in section along the line II-II in FIG. 1, FIGS. 3 and 4 are side views and bottom views, and FIG. 5 shows a centering spring mechanism portion. FIG. 6 is a schematic perspective view showing a steering system configuration of the entire four-wheel steering vehicle, and FIG. 7 is a cross-sectional view of a rear wheel steering ratio varying mechanism showing another embodiment of the present invention. 5 ... rear wheel, 6 ... rear wheel side steering link mechanism, 7 ... rear wheel side hydraulic power steering device, 8 ... steering force transmission rod system,
8a, 8b ... front wheel side and rear wheel side rods, 9a, 9b
...... Transmission rod, 10 ...... Rear wheel steering device, 11 ...... Rear wheel steering ratio variable mechanism, 12 ...... Bracket, 13 ...... Rotation body, 14 ...... Arm, 15 ...... Lever, 16 ...... Electric motor , 17 ... Cover, 20 ... Rotation transmission system, 22, 2
4 ... First and second transmission shafts, 25a, 25b ... Transmission gears such as bevel gears, 26a, 26b ... Controller, 28 ... Vehicle speed sensor, 29a ... Steering angle sensor, 2
9b: rear wheel steering ratio detection sensor, 30: centering spring mechanism, 37: centering spring, 4
0 ... Fluid pressure cylinder (actuator), 40a ...
Engagement pin, 41 ... Engagement groove, 41a, 41b ... Engagement groove both side surfaces, 42a, 42b ... Lever side edge portion, 44 ... Spring.

Claims (3)

[Scope of utility model registration request] 1. A rotating main body which is rotated by an arm to which a front wheel side rod for transmitting a steering force is connected, and a main body rotatably supported on the main body on an axis perpendicular to the rotational axis. A rear wheel steering ratio variable mechanism having a lever, which is selectively rotated by an electric motor and has a lever connected to a rear wheel rod for transmitting a steering force, is provided at a tip extending laterally of the main body. An engaging pin and an actuator for driving the engaging pin, which are selectively moved forward and backward with respect to a side surface portion parallel to the rotation direction of the lever, are provided on the main body side, and the lever tip end of the main body side is provided with respect to the lever side surface portion. An engaging groove into which the engaging pin is engaged is provided in a neutral state on the rotation axis, and both side surfaces of the lever side surface to reach the engaging groove in the direction of rotation and both side edge portions of the lever are provided. The engaging pin and the lever The engaging groove wheel turning device after the four-wheel steering vehicle, characterized in that formed in the cam shaped to be guided in when protruded out from. 2. A lever is rotatably provided at a position separated from its intersection point on an axis orthogonal to the axis of rotation of the main body, and a connection point between the lever tip and a rear wheel side rod is provided at the rear wheel side. The rear wheel steering device for a four-wheel steering vehicle according to claim 1, characterized in that the rear wheel steering device is positioned on an extension of the main body axis line during steering. 3. A utility model registration claim according to claim 1, wherein the driving actuator for moving the engaging pin forward and backward is configured to allow the retracting operation when the engaging pin projects. Alternatively, the four-wheel steering vehicle rear-wheel steering device according to the second aspect.