JPH0516553U - Rear wheel steering system - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To improve the durability of rear axles by facilitating direction changes and garage entry in a narrow site and reducing wear of rear tires. A rear axle housing 18 supporting a rear wheel 20 at both ends, a rear axle housing 18 disposed along a longitudinal centerline of a vehicle body, and its apex pivotally attached to a central portion of the rear axle housing 68, and free ends of both legs of a chassis. An upper radius rod 66 pivotally mounted on the frame 69, and a pair of left and right lower radius rods 72l, 72r pivotally mounted on the rear axle housing at one end of each of which is arranged substantially symmetrically on both sides of the longitudinal center line of the vehicle body. An actuator device 58 for driving the left and right lower radius rods in mutually opposite directions in response to the steering steering of the vehicle and rotating the rear axle housing around the pivot point of the upper radius rod, when the vehicle speed is below the set speed. In addition, the rear axle housing should be steered in the opposite direction to the steered wheels by the rear wheel steering angle set according to the steered steering angle. Is configured.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rear wheel steering device suitable for use in a vehicle, particularly a heavy-duty truck, bus, or other rear two-axle vehicle.

[0002]

[Prior Art]

 Conventionally, in heavy-duty trucks, buses, etc., a rear two-axle vehicle having rear front wheels and rear rear wheels has been widely adopted. The configuration of a typical rear wheel suspension system of this type of rear two-axle vehicle will be described with reference to the side view of FIG. 3. In the figure, reference numeral 10 is a pair of left and right side rails 12 extending in the vehicle longitudinal direction and a vehicle width direction. An undercarriage frame that extends and has both ends fixed to the side rails 12 and a plurality of cross members (not shown), and 14 usually supports rear front wheels 16 of a double tire at both ends in the vehicle width direction. A front rear axle housing, 18 is located at the rear of the front rear axle housing 14 and has rear rear axle housings that normally support rear rear wheels 20 of a double tire at both ends in the vehicle width direction, and 22 is below the undercarriage frame 10. A stacked leaf spring device for suspension of a rear axle, the central portion of which is pivotally supported by a projecting trunnion base 24, wherein a slant is provided on a lower surface of a front end portion of the stacked leaf spring device 22. The front rear axle housing 14 is contacted with both ends of the front rear axle housing 14 in the vehicle width direction through a seat 26, and the rear rear axle housing 18 is mounted on the lower surface of the rear end portion of the leaf spring device 22 via a slide seat 28. The vicinity of both ends in the width direction is in contact. The front rear axle housing 14 has its front end pivotally attached to the same rear axle housing and its rear end pivotally attached to the chassis frame 10 and the trunnion base 24 to form an upper parallel rod 30 and a lower radial rod. The displacement of the front-rear direction is restricted by 32, and the rear rear axle housings 18 are similarly pivotally attached at their front ends to the undercarriage frame 10 and the trunnion base 24 and at their rear ends to the rear rear axle housing 18. The displacement in the front-rear direction is restricted by the upper radius rod 34 and the lower radius rod 36 that form a substantially horizontal link mechanism.

When the above-mentioned rear two-axle truck or bus changes direction in a narrow site to enter a garage, or when making a left turn or a right turn on a narrow road, the front and rear rear axles are used. The rear front wheel 16 and the rear rear wheel 20 supported on both ends of the housings 14 and 18 are fixed in a direction substantially parallel to the longitudinal center line of the vehicle body and are not steered, so that the turning radius becomes large. There was a problem that advanced driving technology and a great amount of time were required to change the direction, and there was a problem that tire wear increased due to large slip of the rear front wheels 16 and the rear rear wheels 20 during turning.

[0004]

[Problems to be solved by the device]

 The present invention has been made in view of the above circumstances, and improves the turning performance of the above-described rear two-axle vehicle, which normally has rear wheels of double tires supported at both ends in the vehicle width direction of a rigid rear axle housing, at low speed running, It is an object of the present invention to provide a rear wheel steering device that can easily change the direction of a narrow site, enter a garage, and turn left or right on a narrow road.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention has a rear axle housing suspended on a chassis frame and supporting rear wheels at both ends in the vehicle width direction, and a top portion of the rear axle housing arranged along the longitudinal center line of the vehicle body. The upper ends of the radius rods, which are V-shaped in plan view, are pivotally attached to the central portion in the vehicle width direction, and the free ends of both legs are also pivotally attached to the chassis frame. A pair of left and right lower radius rods, each of which is attached to the rear axle housing, is connected to the other ends of the left and right lower radius rods, and the left and right lower radius rods are opposite to each other in response to steering steering of the vehicle. The actuator unit for driving the rear axle housing around the apex pivot point of the upper radius rod. The vehicle device is configured to steer the rear axle housing in the opposite direction to the steered wheels by the rear wheel steering angle set according to the steered steering angle when the vehicle speed is equal to or lower than the set speed. It proposes a rear wheel steering system of a vehicle characterized by:

[0006]

【Example】

 Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. (It should be noted that substantially the same members and parts as those of the conventional rear wheel suspension system shown in FIG. 3 are denoted by the same reference numerals, and duplicate description will be omitted.) First, the schematic configuration diagram of FIG. In the figure, reference numeral 38 denotes a front axle that supports front wheels 40 as steering wheels at both ends in the vehicle width direction, and reference numeral 42 steers the front wheels 40 via a normal steering linkage including a drag link, a knuckle arm, a tie rod, and the like. Steering gear 44, a steering wheel for driving the steering gear 42 via a steering shaft 46, a steering wheel steering angle sensor 48 for detecting a rotation angle of the steering shaft 46, and a portion 50 in the drawing. Is mounted on the undercarriage frame 10 indicated by the alternate long and short dash line through an appropriate mounting device, and 52 is the stearin. An oil pump for supplying hydraulic oil as a working medium to the booster in the gear 42, an oil tank 54 for storing the hydraulic oil of the oil pump 52, and a control 56 connected to the discharge side of the oil pump 52. The valve 58 is an actuator for steering the rear wheels, which comprises a hydraulic response device controlled by the control valve 56.

The control valve 56 is driven in the left-right direction in the drawing by an electromagnetic or hydraulic valve actuator 60, and the valve actuator 60 is operated by a controller 62 to command the valve spool 56 ′ of the control valve 56. It is selectively driven to any one of the left movement position, the neutral position and the right movement position. Further, the controller 62 is operated by closing the manual switch 64 that is closed when the driver wants to steer the rear wheels.

In the drawing, the rear rear axle housing 18 and the rear rear wheel 20 of the rear two-axle are shown, and the front rear axle housing 14 and the rear front wheel 16 are omitted in order to avoid excessive congestion in the drawing. Both rear axle housings are suspended on the chassis frame 10 via a leaf spring device 22 similar to that shown in FIG. In this embodiment, the rear rear axle housing 18 is steered, and the front rear axle housing 14, which is not shown, is not steered.

The upper radius rod 66 of the rear rear axle housing 18 has a V-shaped planar shape and is arranged along the vehicle longitudinal direction center line OO, and its V-shaped apex is connected via the ball joint 68 to the rear axle. Both legs of the housing 18 are pivotally attached to the upper side of the central portion in the vehicle width direction, and both leg ends extending forward of the vehicle body are pivotally attached to the chassis frame 10 by ball joints 69. On the other hand, a pair of left and right lower radius rods 72l and 72r pivotally attached to the rear ends of the rear rear axle housings 18 below the both ends in the vehicle width direction via ball joints 70 extend in the front-rear direction, and the above-mentioned center is provided. They are arranged symmetrically with respect to the line OO. The lower radius rods 72l and 72r are connected to a pair of L-shaped levers 76l and 76r whose front ends are rotatably supported on the side rails 12 of the chassis frame via a pivot 74 via a ball joint 78. It is pivotally attached. The left and right levers 76l and 76r are connected to each other by a tie rod 80, and when one lever 76l rotates, the other lever 76r simultaneously rotates at the same angle. The piston shaft 82 of the actuator 58 is pivotally attached to the front extension portion 76l 'of one lever 76l, and the rotation angle of the lever 76l, that is, the rear wheel steering angle is detected via the connecting link 84 at the extension portion. The wheel steering angle sensor 86 is connected. The controller 62 provides the steering wheel steering angle signal θ f from the steering wheel steering angle sensor 48, the rear wheel steering angle θr of the rear wheel steering angle sensor 86, and the transmission 88 of the transmission 88 connected to the engine 50. A vehicle speed signal V of a vehicle speed sensor 90 that detects the vehicle speed from the rotation speed of the output shaft is supplied, and a drive output is supplied to the valve actuator 60 based on these signals.

When the engine 50 of the vehicle is started and driving is started, the controller 62 starts the operation according to the flowchart of FIG. Since the manual changeover switch 64 is opened during normal traveling, the program proceeds to NO in step S ₁ , and the controller 62 does not supply the left or right drive output to the valve actuator 60. At this time, even if the steering wheel 44 is operated to steer the front wheels 40, the valve actuator 60 holds the valve spool 56 ′ of the control valve 56 at the neutral position, so that the two chambers of the pistons of the actuator 58 are closed. The spool 56 'is closed by the lands, and the piston shaft 82 of the actuator is fixed in the neutral position. Since the piston shaft 82 is in the neutral position, the levers 76l and 76r are held in the neutral position, respectively, and the rear rear axle housing 18 is fixed to the neutral position via the lower radius rods 72l and 72r. During normal traveling, in order to more reliably hold the rear rear axle housing 18 in the neutral position and ensure traveling stability, either one of the levers 76l or 76r is automatically opened by opening the manual changeover switch 64. A lock device (not shown) that locks the chassis frame 10 and unlocks the one lever by closing the changeover switch 64 can be additionally provided.

When the driver wants to steer the rear wheels and closes the changeover switch 64 when changing the direction or entering the garage in a narrow freight dump, the program proceeds to step S._TwoAnd the vehicle speed V is the set vehicle speed V₁It is checked whether or not the speed is lower (usually set to a low speed of about 20 to 30 km / h). If the vehicle speed V is the set vehicle speed V₁When the speed is higher, the process proceeds to NO and the rear wheel steering is not performed as in the above. Vehicle speed V is set vehicle speed V₁If lower, the program will step S_ThreeThen, the steering steering angle θf and the rear wheel steering angle θr of the front wheels 40 are read, and then step S_Four  At, the required rear wheel steering angle K 1 as a function of the steering steering angle θf and the rear wheel steering angle θr is calculated. When the steering steering angle θf is the maximum steering angle, the required rear wheel steering angle K is in the opposite phase of the steering steering angle θf (that is, when θf is left steering, it is right steering) and the normal maximum steering angle K is obtained. The angle is set to about 5 °, and when the steering angle θf is less than or equal to the maximum steering angle, the required rear wheel steering angle K is set to an intermediate value smaller than the maximum steering angle, for example, 5 °. Step S₅In Step S, unless the required rear wheel steering angle K = 0 is checked and the rear wheel steering is not completed,₆At either K> 0 (YES) or K <0 (NO), the controller 62 moves the valve spool 56 'of the control valve 56 to the right with respect to the valve actuator 60 (step S).₇ ) Or left movement (step S₈) Will be done. When the actuator 58 is actuated by the right or left movement of the valve spool 56 ', the rear wheels 20 are steered to the opposite phase as described later, and the steering angle θr becomes the required steering angle K = It becomes 0 and the drive output supplied from the controller 62 to the valve actuator 60 disappears.

Now, FIG. 1 shows a case where the front wheel 40 as a steering wheel is steered to the left as an example in a state where the changeover switch 64 is closed by the driver. The valve actuator 60 is actuated by the drive output of the controller 62 to move the valve spool 56 'of the control valve 56 to the left, and the working pressure oil discharged from the oil pump 52 is supplied to the left chamber of the piston of the actuator 58. The right chamber of the piston communicates with the oil tank 54 via the control valve 56, and the piston and the piston shaft 82 move to the right. The right movement of the piston shaft 82 causes the lever 76l to rotate clockwise around the pivot 74, and the lever 76r to rotate in the same direction and the same angle via the tie rod 80. By the above rotation of the levers 76l and 76r, the lower radius rod 72l is displaced forward of the vehicle body, while the lower radius rod 72r is displaced rearward of the vehicle body. Therefore, the rear rear axle housing 18 is connected to the apex ball joint of the upper radius rod 66. It rotates clockwise around 68, and the rear rear wheel 20 is steered to the right in the opposite direction to the front wheel 40. When a signal indicating the steering angle θr of the rear rear wheels 20 is supplied from the steering angle sensor 86 to the controller 62 and the steering angle θr becomes equal to the required steering angle K described above, the valve spool 56 ′ of the control valve 56 is in the neutral position. Is returned to Oki. When the rear rear axle housing 18 is rotated, both end portions in the vehicle width direction slide smoothly with respect to the leaf spring device 22 via the slide seats 28. As described above, by steering the rear and rear wheels 20 in a slight reverse phase in relation to the steered steering of the front wheels 40, the turning radius of the vehicle can be made sufficiently small and the direction can be changed in a narrow site. It is possible to smoothly and easily put the vehicle in a garage, and to reduce the tire slip of the rear rear wheel 20 to improve its durability.

In the above embodiment, only the rear rear wheel 20 of the rear two-axle is steered and the rear front wheel 16 is not steered. However, if necessary, a structure substantially similar to that described above is used. It is also possible to steer the rear front wheels 16.

[0014]

[Effect of the device]

 As described above, the vehicle rear wheel steering system according to the present invention includes a rear axle housing suspended on a chassis frame and supporting rear wheels at both ends in the vehicle width direction. An upper radius rod whose planar shape is V-shaped with its apex portion pivotally attached to the central portion of the rear axle housing in the vehicle width direction and the free end portions of both legs respectively attached to the chassis frame, and the vehicle longitudinal direction centerline. Of the pair of left and right lower radius rods, which are arranged substantially symmetrically on both sides of the rear axle housing and are pivotally attached to the rear axle housing, and the other ends of the lower radius rods are respectively connected to the left and right sides in response to the steering operation of the vehicle. Actuator device for driving the lower radius rods of the rear axles in opposite directions to rotate the rear axle housing around the top pivot point of the upper radius rods. The actuator device is configured to steer the rear axle housing in the direction opposite to the steering wheel by the rear wheel steering angle set according to the steering angle when the vehicle speed is equal to or lower than the set speed. This is advantageous in practical use because it can change direction and enter a garage quickly and easily in a narrow yard, and can improve the durability of the rear wheel tires.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation mode of the controller in FIG.

FIG. 3 is a side view of a rear wheel suspension device in a conventional rear two-axle vehicle.

[Explanation of symbols]

 10 Chassis frame 14 Front rear axle housing 16 Rear front wheel 18 Rear rear axle housing 20 Rear rear wheel 22 Lap leaf spring device 40 Front wheel (steering wheel) 42 Steering gear 44 Steering wheel 50 Engine 52 Oil pump 56 Control valve 58 Actuator 62 Controller 66 Above Radius rod 72l and 72r Lower radius rod

Claims (1)

[Scope of utility model registration request] 1. A rear axle housing suspended on a chassis frame and supporting rear wheels at both ends in the vehicle width direction, the rear axle housing being disposed along a longitudinal center line of the vehicle body and having its apex at the center portion of the rear axle housing in the vehicle width direction. An upper radius rod having a V-shaped plan shape, in which both free ends of the legs are pivotally attached to the undercarriage frame, respectively, and one end of each of the upper radius rods is arranged substantially symmetrically on both sides of the center line in the vehicle longitudinal direction. The pair of left and right lower radius rods pivotally attached to the rear axle housing and the other ends of the lower radius rods are respectively connected to drive the left and right lower radius rods in opposite directions in response to the steering operation of the vehicle. An actuator device is provided for rotating around the apex pivot point of the upper radius rod, the actuator device comprising: Is less than or equal to a set speed, the rear axle housing is configured to be steered in the opposite direction to the steered wheels by the rear wheel steering angle set according to the steered steering angle. Wheel steering device.