JPH01115773A - Rear wheel steering device for four-wheel steering car - Google Patents

Abstract

PURPOSE:To eliminate a working space for a motor and to reduce the size of a whole device, by a method wherein, in a rear wheel steering ratio varying mechanism, an electric motor to swing and displace a lever on the rear wheel side according to a running condition is secured on the same axis as the rotary axis of a rotary body and on the car body side. CONSTITUTION:A rear wheel steering ratio varying mechanism 1 located in a transmission rod system 5 to transmit the steering motion of a front wheel 10 to the rear wheel 14 side is provided with a rotary body 3 supported to a bracket 2 in a manner to be rotatable on a vertical axis Z. An arm 4 a tip 4a of which is pivotally mounted to a rod 5a on the front wheel side is extended sideways (in a direction Y) from the body 3, a lever 7 is rotatably supported on an axis X crossing the axis Z at right angles, and and its tip 7a is pivotally mounted to a rod 5b on the rear wheel side. An electric motor 6 is situated in order to rotate the lever 7 on the axis X, but in this case, the motor 6 is placed on the same axis as an axis Z, and its output shaft is coupled to a rotation transmission system, running to the lever 7 side, through an electromagnetic clutch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a rear wheel steering device for a four-wheel steered vehicle, which allows the front wheels and the rear wheels to be steered in conjunction with the front wheels by a steering operation.

(Conventional technology) In recent years, by steering the rear wheels according to the amount of steering (turning amount) of the front wheels, it has been possible to improve the turning ability when driving at low speeds, as well as improve driving stability when driving at medium and high speeds. Four-wheel steering vehicles that can be used as vehicles are attracting attention.

For example, when driving at low speeds, the front wheels are steered with a large steering angle, but if the front and rear wheels are steered in opposite phases (reverse direction steering), the turning radius of the vehicle will be minimized and the turning (small turning) performance will be reduced. On the other hand, when driving at high speeds, the vehicle is often steered with a small steering angle, but in this case, the front and rear wheels are steered in the same phase (same direction steering) or the rear wheels are steered at a zero angle. This is preferable in order to improve the running stability of the vehicle.

As such rear wheel steering devices for four-wheel steering vehicles, various configurations have been proposed, for example, Japanese Patent Laid-Open No. 81
As shown in Publication No. 1830133, etc., by skillfully combining a plurality of levers on three axes and adjusting and controlling the mutual relationship of these levers with an electric motor, the steering operation of the front wheels by steering operation, that is, the steering angle The rear wheel steering ratio variable mechanism that controls the rear wheel steering ratio is located in the middle of the steering force transmission port 7-door system that mechanically transmits the front wheel steering operation to the rear wheels by movement in the longitudinal direction of the vehicle body. Devices with such a configuration are known.

According to such a conventional configuration, the electric motor is
By simply controlling the drive with a controller that inputs vehicle speed signals, etc., the rear wheels can be steered by steering the front wheels by freely adjusting the required steering ratio to be in the same phase or in opposite phases. Moreover, it had advantages such as excellent structural and operational reliability.

[Problem that the invention seeks to solve]

However, although the above-mentioned conventional device can be expected to produce some effects, it has had several problems both in terms of its structure and functionality. That is, in the conventional device described above, there is a main body that is rotatably supported on the vehicle body side about a substantially vertical axis (Z axis), and a main body that extends to the negative side (Y axis) of the main body and is supported from the front wheel side. An arm connected to the transmission rod and an arm extending perpendicularly to the main body axis in the vehicle body longitudinal direction (
The rotation of the front wheels is controlled by an electric motor installed on the main body so as to face the X-axis, and a lever that is fixed at a position where the motor shaft intersects with the Z-axis and whose tip is connected to a transmission rod to the rear wheels. It constitutes a rear wheel steering ratio variable mechanism that controls the rear wheel steering ratio according to the steering operation, and the rotation of the lever by the electric motor changes the connection point of the rear wheel side transmission rod to the lever with respect to the Z axis. It was configured to change the left-right position and control the rear wheel steering ratio.

According to such a conventional structure, the lever connected to the rear wheel side is fixed on the motor output shaft at the intersection of the X-axis and the Z-axis, and passes on the Z-axis in the i-right direction. In order to rotate the lever, it is necessary to pivotally support the main body on the vehicle body at both ends on the Z-axis, avoiding the rotation range of the lever. The problem was that the length was restricted and a large rear wheel steering ratio could not be achieved. This is because the length of this lever is one of the factors that determines the rear wheel steering ratio due to the lever ratio with the length of the arm mentioned above, and by increasing the length of this lever and rotating it, it is possible to steer from the Z axis. It is easy to understand that the rear wheel steering ratio can be increased to the extent that the distance between the two wheels can be secured.

In addition, in order to increase the rear wheel steering ratio, if the length is increased, it is necessary to increase the distance between the shaft supports at both ends of the main body so that they do not interfere with this lever, and the device There was also the problem that the entire structure became larger, especially in the Z-axis direction.

For this reason, as a result of various research and development conducted by the present inventors regarding the above-mentioned rear wheel steering ratio variable mechanism, if a configuration as shown schematically in FIG. It has been discovered that by increasing the length, the rear wheel steering ratio can be increased, and the entire device can be made smaller.

To explain this simply, the variable rear wheel steering ratio mechanism, which is indicated by reference numeral 1 as a whole, has a U-shaped bracket 2 on the vehicle body side (not shown).
A rotating body 3, which is a rotating shaft member rotatably supported on an axis Z-Z in the vertical direction of the vehicle body via a rotating body 3;
an input arm 4 that extends sideways (in the Y direction) from the input arm 4 and whose tip 4a is connected to a front wheel side rod 5a for transmitting steering force via a pole joint or the like; A stepping motor that is integrally provided on the side of the rotating body 3 and has an output shaft 6a extending on the axis x-x in the longitudinal direction of the vehicle body so as to pass through the intersection 0 with the main body axis Z-Z and to be orthogonal to the main body axis Z-Z. an electric motor 6, and a tip 7 rotatably supported on the rotary body 3 side and extending laterally of the body 3.
A is comprised of a rear wheel side rod 5b for transmitting steering force and a lever 7 connected via a pole joint or the like.

Note that 8a, 8b; 9 are the brackets 2 of the rotating main body 3.
This is a bearing provided at the shaft support of the motor output shaft 6a within the rotating body 3.

In this example, the lever 7 is connected to the motor output shaft 6.
At the same time, the connection point between the tip 7a and the rear wheel side rod 5b is located at a position apart from the intersection point 0 with the main body axis Z-Z at The lever tip 7a is formed by being displaced by a curved portion or the like so that it is located on an extension line of Lever 7 and movable body 3 connected to the side
The length of the lever 7 is appropriately selected to increase the lever ratio compared to the conventional device, allowing for a larger rear wheel steering ratio, and the distance between the shaft supports at both ends of the movable body 3 is reduced. This allows the space to be narrowed and the overall size to be reduced.

However, in such a device configuration, since the motor 6 attached to the rotating body 3 so as to protrude from the side makes a large turn in response to the steering operation of the front wheels, depending on the weight of the motor 6, there may be an adverse effect due to inertia. This extends to the rotating operation of the rotating body 3, which not only poses a problem in obtaining an appropriate steering operation for the rear wheels, but also increases the size of the entire device due to the need to secure the turning space. In order to protect the turning movement of the motor 6 from the outside, it is necessary to attach a cover or the like, which tends to complicate the structure of the cover.
There are various problems in practical application, such as the troublesome handling of external connection cords, etc., and further improvements are required in consideration of these problems.

[Means for solving problems]

In order to meet such demands, the rear wheel steering device for a four-wheel steering vehicle according to the present invention has a variable rear wheel steering ratio mechanism that controls the steering ratio of the rear wheels according to the steering operation of the front wheels. A rotating body rotatably supported by a shaft, an input arm that extends laterally from this body and whose tip is connected to a front wheel rod for transmitting steering force, and an intersection point between these bodies and the arm. a lever that is rotatably supported on an axis perpendicular to the axis of the main body and whose tip extending to the side of the main body is connected to a rear wheel side rod for transmitting steering force; It consists of an electric motor that rotates and displaces the motor, and this electric motor is
A rotation transmission system that is arranged coaxially with the main body axis at one end of the main body, the motor main body is fixed to the vehicle body side, and the motor output shaft is connected to the lever side provided in the main body with a clutch mechanism interposed. It is connected to.

[Effect]

According to the present invention, the rotation body is rotated on an axis perpendicular to the body by an electric motor equipped with a clutch mechanism disposed coaxially with a rotation body that is oscillated and rotated by an arm in accordance with the steering operation of the front wheels. A movably supported lever is controlled to rotate as appropriate depending on various driving conditions such as vehicle speed and steering angle, rear wheel steering angle, etc.
By displacing the position of the connection point with the rear wheel side rod from the axis of the main body in the left-right direction, the connection point of this lever with the rear wheel side rod can be changed to the rotation vJ! of the rotating body! It rotates with the 2+ action, transmits the amount of steering controlled to the required rear wheel steering ratio to the rear wheels via the rear wheel side rod, and performs appropriate and reliable steering control of the rear wheels. Furthermore, in the event of a failure of the motor or the like, the clutch mechanism can disconnect the rotation transmission system to the lever side and ensure two-wheel steering with only the front wheels.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

WIJ Figures 1 to 5 show an embodiment of the rear wheel steering device for a four-wheel steering vehicle according to the present invention, and in these figures, the same or corresponding parts as in Figure 6 described above are designated by the same numbers. Detailed explanation will be omitted.

First, the general structure of the entire steering system of a four-wheel steering vehicle will be briefly explained using FIG. This is a front wheel side steering device for steering in accordance with the steering operation of the steering handle 12, and in this embodiment, an integral type hydraulic power steering device is exemplified. In the figure, reference numerals 11a and llb are a pitman arm and a drive link drawn out from the steering body, and the steering link system 1 supports the front wheels 10 by these.
The structure is such that steering force can be transmitted to the third side. Further, in the figure, reference numerals 11c and 11d denote an oil pump and an oil tank that serve as a pressure oil supply source in the power steering device.

14.14 is a pair of left and right rear wheels (only one is shown)
These rear wheels 14 are also movably supported by a steering link system 15 having the same configuration as the front wheels 10 side described above, and together with this steering link system 15, a rear wheel steering ratio is controlled, which constitutes a rear wheel steering device 16. Linkage type power steering device 1 that generates variable mechanism 1 and steering assist force
7, the required rotation according to the amount of steering of the front wheels 10,
The configuration is such that the wheels are steered in the same phase or in opposite phase depending on the amount of steering.

A steering link mechanism 1 for these front wheels 10 and rear wheels 14 is provided.
Between 3.15 and 15, a part of the steering force transmission system to the front wheel IO side (
In this embodiment, a front wheel rod 5a and a rear wheel rod 5b are provided as a steering force transmission rod system 5 extending in the longitudinal direction of the vehicle body from the front wheel side lower mandrel 12. The structure is such that steering force is transmitted from the front wheel side to the rear wheel side by the movement in the longitudinal direction of the vehicle body. In addition, 18a.

18b is a transmission rod for transmitting the longitudinal movement of the rear wheel rod 5b to the linkage type hydraulic power steering device fi17, and the front rod 18a is equipped with a centering spring mechanism 1 which functions as a fail-safe, which will be described later.
9 is attached.

Further, the linkage type power steering device 17 described above has a well-known configuration, and one end thereof is fixed to the vehicle body side (not shown), and the other end is connected to the steering link mechanism 15 on the rear wheel side. From the wheel side rod 5b side to the transmission rod 18a
, 18b, etc., the steering assist force generated by the power cylinder can be transmitted to the rear wheels 14 in accordance with the rear wheel steering ratio. In addition, 17a and 17 in the figure
b is an oil pump and an oil tank provided on the vehicle body side and serving as a pressure oil supply source.

In the rear wheel steering device 16 having such a configuration, the transmission rod system 5 is provided in the middle of the transmission rod system 5 that transmits the steering operation of the front wheels 10 by the steering operation to the rear wheels 14 by movement in the longitudinal direction of the vehicle body. As is clear from FIGS. 1 to 3, the rear wheel steering ratio variable mechanism 1, which controls the steering ratio in consideration of vehicle speed, etc., is installed on the vehicle body side (not shown) via a bracket 2 that controls the vertical and vertical steering ratios of the vehicle body. A rotating body 3 which is a rotating shaft member rotatably supported on an axis Z-Z in the direction, and a tip 4a extending sideways (Y-Y direction) integrally from this body 3.
The arm 4 is connected to the front wheel rod 5a for transmitting steering force via a ball joint, etc., and the axis x passes through the intersection 0 of the rotating body 3 and the arm 4 and is orthogonal to the body axis Z-Z. - The tip 7a rotatably supported on the main body 3 and extending laterally is the rear wheel side rod 5b for transmitting steering force.
a lever 7 connected to the
It is composed of an electric motor 6 that rotates and displaces on x.

Now, according to the present invention, the above-mentioned rear wheel steering ratio variable mechanism 1
In this case, the electric motor 6 is arranged coaxially with the main body axis Z-Z at one end of the main body 3, and the motor main body movement including the stator is fixed to the vehicle body side (bracket 2 side), and the motor output It is characterized in that the shaft 6a is connected to the rotation transmission system 20 that reaches the lever 7 side provided in the main body 3 with an electromagnetic clutch 30 interposed therebetween as a clutch mechanism. Furthermore, in this embodiment, the lever 7 is provided at a position spaced apart from the intersection point 0 on the axis x-x orthogonal to the main body axis Z-Z, and at the connection point between the lever tip 7a and the rear wheel loft 5b. is positioned on an extension of the main body axis Z-Z when the rear wheels 14 are not steered.

To explain this in detail, 1. According to the present invention, the electric motor 6, which was rotating together with the rotating body 3 that is oscillated and rotated by the arm 4 in response to the steering operation of the front wheels 10, is moved coaxially with the main body 2 (
2-2) By fixing the motor 6 to the bracket 2, which is the fixed side, no turning space is required for the motor 6, and the entire device can be made smaller compared to the conventional structure. Furthermore, since the motor 6 is located on the same axis Z-Z as the main body 3 and does not rotate,
The structure is simple and easy to assemble, and it can be used with simple protective covers (
There are advantages such as that it is only necessary to provide a device (not shown) as necessary. In particular, in such a motor-fixed device, the motor 6 is pulled out and fixed to the electromagnetic clutch 30 described above and a deceleration screw described later.

Here, the problem with adopting such a configuration is that the main body 3 rotates when the front wheel steering operation is transmitted to the arm 4, and the main body 3 and the motor output shaft 6a rotate.
A positional shift occurs in the rotational direction between the two, which causes a problem when rotating and displacing the lever 7 supported on the main body 3 side. However, such a positional shift in the rotational direction can be easily resolved by detecting the positional relationship between the main body 3 and the lever 7 and controlling the drive of the motor 6 using a value calculated based on the detected positional relationship.

Further, according to the present invention, the output shaft 6a of the motor 6 fixedly provided on the bracket 2 is connected to the rotation transmission system 20 extending to the lever 7 on the side of the main body 3 via the electromagnetic clutch 30, This can be effective in ensuring operational reliability of the device i16 and improving running stability. That is, in the rear wheel steering ratio variable mechanism l described above, if the electric motor 6 becomes locked for some reason, for example, a part of the magnet breaks and falls off and gets caught between it and the armature, the The entire wheel steering device 16 will lock, and in the worst case, the front wheels 10. This may lead to problems such as the rear wheels 14 becoming unable to be steered, and a fail-safe mechanism that can eliminate such problems is required. Therefore, according to the present invention,
An electromagnetic clutch 30 is interposed in connecting the output shaft 6a of the electric motor 6 to the lever 7,
By operating this electromagnetic clutch 30 in the disengagement direction when the above-mentioned motor lock etc. occurs, the lever 7, main body 3, etc. are maintained in a rotatable state, thereby controlling the operation of the rear wheel steering device 16. This ensures reliability as well as driving stability. Here, the above-mentioned control of the electromagnetic clutch 30 includes, for example, normally energizing the clutch 30 to keep it in a connected state, but when a motor lock occurs or an abnormal current occurs, the controller etc. cuts off the energization and clutches the clutch 30 in a connected state. Note that it is better to use a method such as setting 30 in a disconnected state.

As such an electromagnetic clutch 30, it is preferable to appropriately adopt one having a conventionally well-known configuration, and a detailed explanation thereof will be omitted.

Further, according to the present invention, the above-mentioned main body 3 and motor 6
The lever 7, which is rotated at the same time, is controlled to rotate as appropriate by the motor 6 according to various driving conditions such as vehicle speed and steering angle, and the rear wheel turning angle, so that the position of the connection point with the rear wheel side rod 5b is adjusted to the main body axis. By displacing the lever 7 in the left-right direction from Z-Z, the connection point (7a) with the rear wheel side rod 5b of the lever 7 rotates with the rotational movement of the rotating body 3, and the desired rear wheel rotation is achieved. There is also an advantage that the steering amount controlled by the steering ratio can be transmitted to the rear wheels 14 side via the rear wheel side loader 5b, and appropriate and reliable steering control of the rear wheels can be performed. According to such a configuration,
While the mechanism as the rear wheel steering ratio variable mechanism l can be properly and sufficiently secured, there is no need to consider problems such as interference between the lever 7 connected to the rear wheel side and the movable body 3, and the length of the lever 7 can be appropriately selected, it is possible to increase the lever ratio compared to the conventional device, and to increase the rear wheel steering ratio, and it is also possible to downsize the entire device including the main body 3.

Here, to briefly explain the operation of the variable rear wheel steering ratio mechanism 1 having the above-described configuration, first, as shown in FIG.
When the lever tip 7a (connection point with the rear wheel side) is located on the axis Z-Z, the rear wheels 14 are not steered, regardless of the steering operation on the front wheel 10 side accompanying the steering operation. maintained in condition. This is easily understood because even if the rotating body 3 is rotated by the arm 4 due to the steering operation of the front wheel 10, the lever tip 7a only rotates on the axis Z-Z.

Further, the electric motor 6 is driven according to various driving conditions such as vehicle speed and steering angle, rear wheel turning angle, etc., and the electromagnetic clutch 30
When the lever tip 7a is rotated in the left-right direction by the rotation transmission system 20 via the rotation transmission system 20, the lever tip 7a is rotated along the axis Z-
Rotating around this axis Z-Z according to the amount of displacement from above Z, the rear wheel rod 5b moves in the longitudinal direction of the vehicle body and steers the rear wheel 14 with an appropriate steering ratio. It is possible to do so. In this case, the rear wheels are steered in the same or opposite phase to the front wheels depending on the direction in which the lever 7 is tilted, and the steering characteristics can be freely selected by controlling the motor 6 as necessary. It is.

Further, in this embodiment, details of the rear wheel steering ratio variable mechanism 1 described above are as follows. That is, the main body 3 is
As is clear from FIG. 1, etc., the small diameter portion 3a of the bracket 2 is rotatably supported by the split bushing 21, and the motor is positioned on the same axis Z-Z at the distal end side. 6 is the connecting cylinder 4 on the bracket 2 side
0 with bolts, etc. In addition, the above-mentioned split bushing 21 is divided into two cylindrical parts 21a, 21.
a, and annular plate portions 21b, 21b disposed on both ends thereof and also divided into two.

21c and 21c, it is easy to assemble, and the shaft support portion of the main body 3 can be made smaller in the radial direction. In particular, by using such a split bushing 21, it is possible to efficiently utilize dead space, which is a problem when using ball bearings, etc., to achieve downsizing in the radial direction, and to properly control the main body 3 in the thrust and radial directions. It can be pivoted.

Also, the motor output shaft 6a protruding toward the main body 3 side
is connected to the first transmission shaft 22 constituting the rotation transmission system 20 via the electromagnetic clutch 30 and a reduction gear section 23 using a planetary gear mechanism or the like. In addition,
This reduction gear part 23 is not necessarily required, and it goes without saying that the motor output shaft 6a may be directly connected to the first transmission shaft 22 in some cases.

Further, the first transmission shaft 22, which extends inside the small diameter portion 3a along the axis Z-Z, extends inside the main body 3 along the axis Z-Z.
A second transmission shaft 24 that is rotatably supported in the axis x-x direction perpendicular to Z and is coupled to enable rotation transmission through transmission gears 25a and 25b such as bevel gears, and this second transmission shaft 24
By fixing the base end of the lever 7 on top, the lever 7 is configured to be able to swing in response to the rotation of the motor 6. In addition, 1. The second transmission shaft 22°24 is
Of course, it is supported by a bearing or the like so that it can rotate freely within the main body 3.

Further, the above-mentioned motor 6 is energized by the battery 27 via the power controller 26b in response to a signal from the signal controller 26a so that the rotation speed is determined based on various driving conditions of the vehicle, such as vehicle speed and steering angle. In addition to being driven, it is configured to be stopped by feeding back the rear wheel steering ratio. Here, in FIG. 5, 28a is a vehicle speed sensor, 28b is a front wheel side steering angle sensor attached to a steering shaft, etc., and 29 is a front wheel side steering angle sensor attached to a steering shaft, etc., and 29 is an axis line x-x of the rear wheel steering ratio variable mechanism 1. This is a rear wheel steering ratio detection sensor provided on the main body 3 side so as to face the base end. The rear wheel steering ratio detecting sensor 29 is extremely easy to install and can detect the front wheel steering angle and rear wheel steering ratio with high accuracy, and has great advantages. Further, the input signal to the controller 26a described above is not limited to the vehicle speed or the steering angle, but may also be, for example, the lateral force applied to the vehicle body.

Furthermore, according to the rear wheel steering ratio variable mechanism 1 described above, the fifth
As is clear from the figure, the axis of rotation x-x of the lever 7 points in the longitudinal direction of the vehicle body, and even if the vehicle speed changes while driving straight, the motor 6 is driven, and the lever 7 is rotated, the rear wheel The configuration is such that the rear wheels 14 can maintain a straight traveling state without any influence on the sides.

Further, in this embodiment, the input arm 4 for transmitting the steering ratio from the front wheel side is configured as a separate member from the rotating main body 3, as is clear from FIG. It is configured to be detachably attached and fixed using fastening means (4b) such as bolts. And in such a configuration,
When applying to vehicle models with different layouts, etc.

By making it possible to share the components such as the main body 3 except for the arm 4, reducing costs, and making it easier to manufacture the 3 parts of the main body, the 4 part of the arm is made of high-strength material, etc. It has the advantage of ensuring its strength.

By the way, according to the rear wheel steering device 16 having such a configuration, a stopper is required for mechanically locking the amount of steering on the rear wheel 14 side within a predetermined range. The main body 3 of the rear wheel steering ratio variable mechanism 1, which is the input side member of the wheel steering system, has a V-groove that sandwiches the lever 7 provided on the second transmission shaft 24 from both sides, as shown in FIG. It is preferable that the stopper member 31 having the stopper member 31a is detachably provided with a bolt or the like. In this way, the external force from the rear wheel 14 side to the lever 7 can be transmitted to the steering link mechanism 15 or the like on the rear wheel side. Since the force acting on the stopper member 31 is smaller than that of the stopper member 31, it is possible not only to simplify the structure of the collar compared to the conventional one, but also to change the movable range of the lever 7, which changes depending on the vehicle model, and the shape of the main body 3. This is advantageous in increasing the versatility of the device and reducing its cost at the same time.

Moreover, this stopper 31 member, as shown in FIG.
The mounting of the sensor 29, which detects the rear wheel steering ratio by detecting the rotational position of the lever 7, also functions as a base. In the figure, reference numeral 32 denotes an adjustment screw 33 screwed into the shaft 24 in order to adjust and fix the center, angle, etc. of the detection shaft 32a of the sensor 29 fitted into the tip of the second transmission shaft 24.
34 is a locking screw that closes the adjustment hole at the base end of the lever 7 to prevent the adjustment screw 32 from falling off, and 34 is an adjustment hole formed in the stopper member 31 for adjusting these screws 32 and 33. It is. Such a configuration is necessary because the sensor 29 described above must be adjusted in the entire assembled state.

Further, according to the above-mentioned rear wheel steering device LLB, the motor,
In addition to the above-mentioned electromagnetic clutch 30, a fail-safe mechanism that locks the rear wheel steering operation at the neutral position and performs two-wheel steering using only the front wheels in the event of a failure in the electrical system, such as the controller, is required. As such a fail-safe, as shown in FIG. 4, a support is provided to slidably support the front rod 18a of the transmission system that transmits the longitudinal motion of the rear wheel rod 5b to the rear wheel on the axis mX-X. A centering spring mechanism 19 attached to the section is utilized. That is, within a casing 35 to which a bracket 35a fixed to the vehicle body is attached, tin link receivers 36a and 36b are provided oppositely at positions spaced apart from each other by a predetermined distance from the transmission rod 18a, and a centering spring 37 is interposed between them. There is.

The rod 18a operates to bend the spring 37 by means of the receivers 36a and 36b, and normally steers the rear wheels, but in the event of a failure of the motor 6, etc., the spring force causes the rod 18a to be placed in a neutral state. This serves to ensure that the rear wheels are in a neutral state and to maintain the two-wheel steering state of only the front wheels 10. Here, each receiver 36a-.

36b is adapted to be operated following the movement of only one of the rods 18a.

In addition, as the above-mentioned fail-safe mechanism, as shown in FIG.
A locking mechanism is provided which can forcibly maintain the two-wheel steering condition of only the front wheels by engaging the tip of the piston rod 38a into the locking groove 39 on the lever 7 side and maintaining the lever 7 in a neutral condition. It's good to do that.

Note that the present invention is not limited to the structure of the embodiment described above, but
The shape, structure, etc. of each part of the rear wheel steering device 16, including the steering link mechanisms 13, 15, etc. on the rear wheel side, may be modified or changed as appropriate, and various modifications may be considered, such as the implementation described above. Although omitted in the example, a cover for protecting the electric motor 6 fixed coaxially with the rotating body 3 may be fixedly provided on the bracket 2 side, or the location of the motor 6 etc. If such protection is not necessary, the motor body may be provided with a boot that protects only the cord etc. drawn out from the motor 6, and a rotation transmission system that transmits the rotation from the motor 6 to the lever 7 may be used. However, various modifications can be considered. Further, in the above embodiment, the electromagnetic clutch 30 is used as a clutch mechanism to connect the motor output shaft 6a to the rotation transmission system 20 on the lever 7 side. Various clutch mechanisms are conceivable as long as they can be separated.

Further, in the above-described embodiment, in order to obtain rear wheel steering force in the rear wheel steering device 16, the power steering device 17 is used as a steering assisting means in the same way as on the front wheel IO side, for example. Although it can be effective in preventing negative effects on steering operation, which is a problem when steering resistance is large when turning the rear wheels due to the weight of large vehicles, etc., A manual steering mechanism may also be used.

〔Effect of the invention〕

As explained above, according to the rear wheel steering device for a four-wheel steering vehicle according to the present invention, in the variable rear wheel steering ratio mechanism that controls the steering ratio of the rear wheels according to the steering operation of the front wheels, The electric motor is rotated toward the vehicle body to swing and displace the lever on the rear wheel side, which is tiltable with respect to the rotating body rotated by the arm of the main body. The motor is fixed to the vehicle body on the same axis as the dynamic axis, and the motor output shaft is connected to the rotation transmission system provided in the main body and connected to the lever side with a clutch mechanism interposed. Although the structure is simple and inexpensive, it can properly and sufficiently function as a variable rear wheel steering ratio mechanism, while eliminating the need for a space for the motor to operate, making the overall size smaller, and improving ease of assembly. In addition, it eliminates the negative effects of inertia caused by motor turning, which was the case with conventional motors, and enables appropriate and reliable rear wheel steering ratio control. It has various excellent effects, such as eliminating problems such as kinking and improving the reliability of each part. Furthermore, according to the present invention, since the output shaft of the motor is connected to the rotation transmission system to the lever side by a clutch mechanism such as an electromagnetic clutch, in the event of an abnormality such as a motor lock, the rear wheel steering device is freed. This is effective in ensuring operational reliability as a rear wheel steering device and improving running stability, such as by enabling two-wheel steering of only the front wheels.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a variable rear wheel steering ratio mechanism showing an embodiment of a rear wheel steering device for a four-wheel steering vehicle according to the present invention, FIGS. 2 and 3 are a side view and a bottom view thereof, Fig. 4 is a schematic cross-sectional view showing the centering spring mechanism part, Fig. 5 is a schematic perspective view showing the overall steering system configuration of a four-wheel steering vehicle, and Fig. 6 is a schematic diagram of a conventional rear wheel steering ratio variable mechanism. FIG. l... Rear wheel steering ratio variable mechanism, 2... Bracket, 3... Rotating body, 4... Arm, 5a, 5b
... Front wheel side and rear wheel side rods constituting the steering force transmission rod system, 6... Electric motor, 7... Bar, 10... Front wheel, ll-・φ・Front wheel side steering device, 12... Steering handle, 13... Front wheel side steering link mechanism, 14... Rear wheel, 15...
Rear wheel side steering link mechanism, 16... rear wheel steering device,
17...Hydraulic power steering device on the rear wheel side, 18a. 18b...Transmission rod, 19...Center spring mechanism, 20...Rotation transmission system, 22.24...
- First and second transmission shafts, 25a, 25b...transmission gears such as bevel gears, 26a, 26b...controller, 28a...vehicle speed sensor, 28b...
Steering angle sensor, 29... Rear wheel steering ratio detection sensor, 3
0...Electromagnetic clutch (clutch mechanism), 4″0...
...Connected cylinder. Patent applicant Jidosha Kiki Co., Ltd.

Claims (2)

[Claims] (1) A rotating body that is pivotably supported on the vehicle body side, an arm that extends laterally from this body and whose tip is connected to a front wheel rod for transmitting steering force, and these bodies and the arm. a lever that is rotatably supported on an axis that passes through an intersection with the main body axis and that is orthogonal to the main body axis, and whose tip that extends to the side of the main body is connected to a rear wheel side rod for transmitting steering force; A variable rear wheel steering ratio mechanism includes an electric motor that rotationally displaces the lever on the axis, the electric motor is disposed coaxially with the axis of the main body at one end side of the main body, and the motor main body is A rear wheel drive for a four-wheel steering vehicle, characterized in that the motor is fixed to the vehicle body side and the motor output shaft is connected to a rotation transmission system provided in the body and extending to a lever side with a clutch mechanism interposed therebetween. Rudder device. (2) The lever is rotatably provided at a position spaced apart from the intersection on the axis perpendicular to the axis of the rotating body, and
The four-wheel vehicle according to claim 1, wherein the connection point between the tip of the lever and the rear wheel rod is located on an extension of the main body axis when the rear wheels are not steered. Rear wheel steering device for steered vehicles.