JPH04123981A - Rear-wheel steering system for vehicle - Google Patents

Abstract

PURPOSE:To improve the extent of steering stability at time of running at high speed by supporting a rear axle housing for a truck or the like pivotally on a top part of a V-shaped upper radius rod in a car width central part, and suspending each spot of both ends on an undercarriage frame with each air spring. CONSTITUTION:Each spring support member 20 is attached to upper sides in and around both ends in the car width direction of a rear axle housing 16, while air springs 24 interposed between the spring support member 20 and a side rail 12 of an undercarriage frame 10 are installed in front and in the rear of the said housing 16 as holding it in between. In addition, a top part of a V-shaped upper radius rod 26 installed along a center line in the longitudinal direction of a car body is pivotally attached to the upper side of a differential casing 30 installed in the rear axle housing 16, and both leg ends of the rod 26 is pivotally attached to the side rail 12 of the undercarriage frame 10 likewise. Then, the rear axle housing 16 is made free of steerage and rotation by a hydraulic cylinder unit 48 via a lower radius rod 38.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device for a vehicle, particularly a truck.

(Prior Art) In recent years, various four-wheel steering systems and devices have been proposed in which rear wheels are steered in conjunction with front wheel steering in order to improve steering stability during high-speed driving.

However, conventional four-wheel steering systems have all been applied to vehicles in which the front and rear wheels are independently suspended, mostly passenger cars, and vehicles in which the rear wheels are supported within a rigid axle tube or rear axle housing, especially vehicles. A four-wheel steering device for a truck or the like in which double tires are used for the rear wheels has not yet been proposed.

(Problem to be Solved by the Invention) The present invention provides a novel and useful rear wheel that can improve steering stability during high-speed driving in a trunk or the like where the rear wheel is supported by both end portions in the width direction of a rear axle housing. The object of the present invention is to provide a steering device.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a chassis frame, a rear axle housing song that supports rear wheels at both ends in the vehicle width direction, and a space between the rear axle housing and the chassis frame. An interposed air suspension ring is disposed along the center line in the longitudinal direction of the vehicle body, and its apex is pivotally connected to the center portion of the rear axle housing in the vehicle width direction, and the free ends of both legs are respectively pivotally connected to the chassis frame. A pair of left and right lower radius rods, which are arranged approximately symmetrically on both sides of the center line in the longitudinal direction of the vehicle body and whose respective ends are pivotally connected to the rear axle housing; are connected to the other end of the
A pair of rear wheel steering actuators are provided, which actuate when the vehicle is steered while running at high speed, drive the left and right lower radius rods in opposite directions, and rotate the rear axle housing around a pivot point at the apex of the upper radius rod. This invention proposes a rear wheel steering device for a vehicle characterized by the following features.

(Function) According to the present invention, the rear axle 1 housing has its center portion in the vehicle width direction pivotally supported by the apex portion of the 7-shaped three-way radius rod, and the rear axle 1 housing has its central portion in the vehicle width direction supported by air springs at both ends in the vehicle width direction. Since it is suspended on the frame, it can rotate around the apex pivot point of the upper radius rod, in other words, it becomes possible to steer the rear wheels. The steering rotation of the rear axle housing is controlled by a pair of rear wheel steering actuators that actuate a pair of left and right lower radius rods whose respective ends are pivotally connected to the rear axle housing in opposite directions.

(Example) Examples of the present invention will be specifically described below with reference to the accompanying drawings. Reference numeral 10 in the figure is a chassis frame of a vehicle such as a truck, which includes a pair of left and right sight rails 12 extending in the longitudinal direction of the vehicle body, and a plurality of sight rails 12 extending in the vehicle width direction and having both ends fixed to the left and right sight rails 12. The cross member 14 is made up of two cross members 14.

] 6 is a rear axle housing that supports a double tire 18 at the center portion in the vehicle width direction, and 20 is a knot-shaped rear axle housing that is attached to the upper surface of the rear axle housing near both ends in the vehicle width direction by fasteners such as U-bolts 22. A spring support member 24 is disposed at the front and rear of the rear axle housing 16 to sandwich the end of the rear axle housing 16.
0 and the sight rail 12 of the chassis frame 10, which is a well-known air spring.

Reference numeral 26 denotes an upper radius rod which is disposed along the center line in the longitudinal direction of the vehicle body and has an angular shape in plan view, and the apex of the radius rod is connected to a pole joint device 28 (or a rubber push-type joint device with the same effect). The rod is pivotally connected to the upper side of the differential casing 30 provided in the central part of the rear axle nozzle housing 16, and the free ends of both legs of the rod are each connected to a pole joint device 32 (or a rubber buttress type joint device with the same effect). ) is pivotally connected to the sight rail 12 (or cross member 14) of the chassis frame 10.

In particular, as clearly shown in FIG. 2, a bracket 34 of 1 Jy is attached to the lower surface of the rear axle housing 16 near both ends in the vehicle width direction together with the spring support member 20.
l? The bracket 3 is fixed together with the bolt 22.
One end of a pair of left and right lower radius rods 38 is pivotally connected to the lower radius rod 4 via a pole joint device 36 (or a rubber bush type joint device having the same effect). The other end of each lower radius rod 38 is pivotally connected via a pin 46 to the lower end of an actuating rod 44 which is pivotally supported by a pin 42 to a bracket 40 fixed to the web or side wall of the sight rail 12. Furthermore, a piston shaft 50 of a hydraulic cylinder device 48 forming a pair of left and right rear wheel steering actuators is pivotally connected to the upper end of the operating lever 44 by a pin 52, and a cylinder 54 of the hydraulic cylinder device It is pivoted to the web or sidewall of the sight rail 12.

The specific structure of the Dalenoyoint devices 28, 32 and 36 is illustrated in FIGS. 4 and 5. first, fourth
In the figure, reference numeral 58 indicates one member that causes relative rotational displacement, ie, the upper radius rod 26 or the lower radius rod 38, and 60 indicates the other member, ie, the rear axle housing 16 or the bracket 34. A shaft 64 having a spherical member 62 is supported on the other member 60, and a pole seat 66 that abuts the spherical member 62 is supported on the one member 58. With this configuration, one member 58 can freely rotate relative to the other member 60 within a plane perpendicular to the axis of the shaft 64 and within a plane including the coaxial line.

Further, in the pole joint device shown in FIG. 5, a housing 2 is formed on one member 58, that is, the upper radius rod 26 or the lower radius rod 38, for accommodating the ball head 70 of the pole stud 68. 7
Pole seats 74 and 76 that abut the ball head 70 within 2
In addition, the pole stud 68 is fixed to the other member 60, that is, the rear axle housing 16 or the bracket 34. With this configuration as well, one member 58 can freely rotate relative to the other member 60 within a plane perpendicular to the axis of the pole stud 68 and within a plane including the coaxial line.

Further, FIG. 6 shows a rubber bush type joint device which is functionally almost the same as the pole joint device described above. A rubber bushing 78 is baked and fixed to the end of one member 58 similar to that shown in FIG. 4, and a spherical member 62 is simultaneously baked and fixed to the inner periphery of the rubber bushing 78. A shaft 64 supported by the other member 60 similar to the above is inserted into the spherical member 62 . Also in this configuration, relative rotation is allowed between the one member 58 and the other member 60 in a plane perpendicular to the axis of the shaft 64 and in a plane including the axis.

Next, in order to prevent the rear axle how song 16 from rising excessively with respect to the chassis frame 10 while the vehicle is running on a rough road, causing a direct collision between the two and damaging the air spring 24, a first As shown by reference numeral 80 in the figure, a bump rubber is disposed on the sight rail 12 of the chassis frame 10 and located above the spring support member 20. The bump rubber 80 can also be disposed inside the rubber diaphragm 82 of the air gel ring 24, as schematically shown in FIG.

Further, while driving on a rough road, the rear axle housing 16 may be displaced excessively downward relative to the chassis frame 1o, and the heavy rear wheel and the rear axle housing 16 may be suspended from the chassis frame, causing the Airsgerinda 24 to To prevent damage, a hanging stop device as shown in FIG. 7 is provided. In the figure, reference numeral 84 denotes a stopper bracket fixed to the inner surface of the web of the sight rail 12, and 86 denotes a stopper bracket whose lower end is connected to the
? - A stomper rod 90 is connected to the rear axle housing 16 via a joint device 88 similar to a rubber bush pivot device or an equivalent rubber bushing pivot device.

With this configuration, if the rear axle housing 16 descends excessively with respect to the chassis frame 10, the stopper rod 8
By the head 92 of the stopper rubber 9 coming into contact with the top plate of the stopper rubber 9, further downward displacement of the rear axle housing 16 is prevented.

In FIG. 1, the reference numeral 94 is a normal shock absorber interposed between the chassis frame 10 and the rear axle housing 16.

Finally, FIG. 8 is a conceptual diagram of a device for controlling the operation of the rear wheel steering actuator 48.

In the figure, reference numeral 96 is an optical pulse non-contact type steering angle sensor that is installed on the steering shaft 98 to detect the steering angle, 10o is a vehicle speed sensor, 1o2 is a yaw rate sensor,
104 is the steering angle signal of the steering angle sensor 96 and the vehicle speed sensor 1
A controller 108 is a hydraulic pump that controls a control valve 106 that receives a vehicle speed signal of 00 and a turning signal of a yaw rate sensor 102 and operates a rear wheel steering actuator 48.

When the vehicle is traveling at high speed, when the steering wheel 110 is operated and the front wheels 112 are steered, a steering angle signal from the steering angle sensor 96, a vehicle speed signal from the vehicle speed sensor 100, and a turning signal from the yaw rate sensor 102 are received. The controller [04] issues a drive signal to the control valve 106, and the control valve is operated. The high pressure hydraulic oil discharged from the hydraulic pump 0108 by the operation of the control valve 106 is supplied to the pair of rear wheel steering actuators 48 .
The actuators operate in opposite directions, that is, when one actuator extends, the other actuator contracts.

When steering the rear wheels for the purpose of improving steering stability when the vehicle is running at high speed, the rear wheels 18 are usually steered by a small steering angle, for example, about 1 to 5 degrees, in the same direction as the front wheels 112. be done. However, in connection with the steering of the front wheels 112, the rear wheels 18 are first steered by a slight angle in the opposite direction to the steering direction of the front wheels 112, and after an instant, the rear wheels 18 are steered by a slight angle in the same direction as the steering direction of the front wheels 112. It is also possible to employ an angularly steered rear wheel steering system.

In the above configuration, the cylinder 54 of the hydraulic cylinder device 48 forming the rear wheel steering actuator has a built-in stopper that limits the extension and contraction of the piston shaft 50.
The rear axle housing 16, that is, the rear wheel 18, is provided so that it can be correctly steered by a preset slight steering angle of 1 to 5 degrees, for example, 1 degree, when the hydraulic cylinder device 48 is inactive. locking by actuation of neutral springs or hydraulically (such as 1 in both chambers of the piston)
The piston shaft 50 is fixed at the neutral position, and the rear axle housing 16, that is, the rear wheel 18, is maintained in a straight-ahead state with zero steering angle.

When the front wheels 112 are steered while the vehicle is running at high speed, the υ control valve 106 is activated by a command from the controller 104 as described above.
is activated, and the pair of rear wheel steering actuators 48 are activated in opposite directions. Piston shaft 5 of each actuator
The actuating levers 44, each of which has one end connected to the actuating lever 44, rotate in opposite directions. A lower radius rod 38 connected to the other ends of -4 and 4 is driven toward the rear of the vehicle body. As a result, the rear axle housing 16 has a steering angle set around the apex of the upper radius rod 26 forming a figure 7 shape.
It will be rotated and steered in either the left or right direction,
Steering stability during high speed steering is improved in a manner well known in the art. The rotation of the steering stop of the rear axle housing 16 is extremely smooth because the suspension spring is an air sill ring 24, and its rubber diaphragm 82 is freely deflected in the horizontal direction.

1, -1- of the rear axle housing 16 with respect to the chassis freight JO while the vehicle is moving straight and turning during steering.
The downward movement is performed in such a way that the air suspension ring 24 receives a load, and at this time the rear axle how 1.゛Fugu 16 is I
On the other hand, parallel link movement is performed up and down by the bus rod 26 and the lower radius rod 38. Furthermore, the upper radius rod 26 is connected to the &-leaf joint devices 28 and 32 (
The lower radius rod 38 is pivotally connected to the rear axle housing 16 by a similar ball joint device 36 (or a rubber bush joint device with the same effect) to the rear axle housing 16 and the chassis frame 10. Therefore, even if the rear axle housing 16 tilts from side to side or rolls when traveling on an uneven road or when turning, the displacement is not hindered.

In addition, in the above embodiment, a vehicle with one rear axle is illustrated, but in the case of a vehicle with two rear axles, a rear wheel steering device similar to that described above may be provided on both the rear front axle and the rear axle. It will be done. Unfortunately, in vehicles with two rear axles, one of the rear axles is often configured as a dead axle that does not transmit driving force, but the steering device itself is substantially the same as in the case of the drive wheels illustrated.

(Effects of the Invention) As described above, the rear wheel steering device for a vehicle according to the present invention comprises a chassis frame, a rear axle housing that supports rear wheels at both ends in the vehicle ri direction, the rear axle housing, and the chassis frame described in “2”. Air spring interposed between
A curved planar shape disposed along the center line in the longitudinal direction of the vehicle body, the apex of which is pivotally connected to the central portion of the rear axle housing in the vehicle 11 direction, and the free end portions of both legs are pivotally connected to the vehicle chassis fleno, respectively. a pair of left and right lower radius rods that are arranged approximately symmetrically on both sides of the longitudinal centerline of the vehicle body and have one end of the husband pivotally connected to the rear axle housing, and the other end of the lower radius rod. a pair of rear wheel steering actuators that are connected to each other and actuated during steering when the vehicle is running at high speed to drive the left and right lower radius rods in opposite directions and rotate the rear axle housing around a pivot point at the apex of the upper radius rod; This feature is industrially useful because it can improve the steering stability of a truck or the like equipped with a rigid rear axle tube during high-speed running.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of the present invention, FIG. 2 is a side view of the rear wheel steering device shown in FIG. 1, and FIG. 3 is a side view of the rear wheel steering device shown in FIG. 1. Schematic plan view, Figures 4 and 5
The figure shows ball joint device 28 in the device shown in FIG.
6 is a cross-sectional view of a rubber bush type joint device having approximately the same effect as the ball joint device shown in FIGS. 4 and 5, and FIG. 7 is a cross-sectional view of the rear axle. FIG. 8 is a front view showing a suspension stopper device for the Howsong 16, and is a schematic configuration diagram of an operation control device for the rear wheel steering actuator 48 in FIG. 1. 10... Chassis frame,] 2... Seidrail, 16
... Rear axle housing, 24 ... Air spring, 26 ... "Three-way radius rod, 28. 32 and 36 ... Ball joint device, 38 ... Lower radius rod, 44 ... Operating lever 48 ...・Rear wheel steering actuator. O ~

Claims (1)

[Claims] An undercarriage frame, a rear axle housing that supports the rear wheels at both ends in the vehicle width direction, an air spring interposed between the rear axle housing and the undercarriage frame, and an apex portion thereof arranged along the longitudinal center line of the vehicle body. An upper radius rod having a dogleg shape in plan view, which is pivotally connected to the center portion of the rear axle housing in the vehicle width direction, and whose free ends of both legs are pivotally connected to the chassis frame, respectively, and approximately on both sides of the center line in the longitudinal direction of the vehicle body. A pair of left and right lower radius rods are arranged symmetrically and have one end pivotally connected to the rear axle housing, and are connected to the other end of the lower radius rod, respectively, and are activated when the vehicle is steered at high speed to move the left and right lower radius rods. A rear wheel steering device for a vehicle, comprising a pair of rear wheel steering actuators that drive radius rods in opposite directions and rotate the rear axle housing around the pivot point of the apex portion of the upper radius rod.