JP2569933B2 - Vehicle rear wheel steering system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rear wheel steering device for a vehicle, particularly a truck.

2. Description of the Related Art Conventionally, high-speed traveling is performed in a vehicle in which a rear wheel is supported by a rigid axle tube or a rear axle housing, particularly in a truck, a bus, or the like in which the rear wheel is suspended from a chassis frame via an air suspension device. A rear-wheel steering device in which the rear wheels are steered in conjunction with the steering of the front wheels for the main purpose of improving the steering stability at the time is already disclosed in Japanese Patent Application Laid-Open No. 62-80170.

The above-mentioned proposed rear wheel steering device includes a rear shaft suspended on an underframe via an air spring at both ends in the vehicle width direction.
Through the left and right lower radius rods or torque rods,
While being connected to the chassis frame, two portions of the rear axle at the center in the vehicle width direction are connected to the chassis frame via left and right upper radius rods or torque rods arranged in a V-shape, and further, the left and right lower portions are connected. Hydraulic cylinders are provided on the radius rods respectively, and one hydraulic cylinder is extended and the other hydraulic cylinder is contracted,
It is configured to steer by turning the rear shaft.

However, in the rear wheel steering device proposed above, a hydraulic cylinder is provided inside a lower radius rod having an extremely low ground height to expand and contract the radius rod, so that the hydraulic cylinders respectively connected to the piston side chambers of each hydraulic cylinder are provided. There is a problem that the hose is easily damaged by a flying stone or an obstacle on the ground, and the hydraulic system is very likely to fail. Further, since the hydraulic cylinder must be provided in the lower radius rod having a small outer diameter, it is difficult to secure the required strength as a radius rod in the hollow cylinder portion and the shaft of the piston fitted in the cylinder portion. In addition, since the ground clearance is low, it is difficult to protect the sliding surface exposed to muddy water and the like, and there is a disadvantage that the durability is lacking. In addition, in order to suppress displacement of the rear shaft in the vehicle width direction, the upper radius rod or torque rod arranged in a V-shape is connected to the rear shaft at two places at the center portion of the rear shaft,
There is a danger that running stability may be impaired because the center of the rear shaft during steering is not constant and the steering performance changes during steering during high-speed running.

(Problems to be Solved by the Invention) The present invention can improve steering stability during high-speed running on a truck or the like in which rear wheels are supported at both ends in the vehicle width direction of a rear axle housing, and are used for rear wheel steering. It is an object of the present invention to provide a rear wheel steering device which is less likely to damage an actuator and its attached parts and has excellent durability and reliability.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a chassis frame,
A rear axle housing supporting rear wheels at both ends in the vehicle width direction; an air spring interposed between the rear axle housing and the chassis frame; An upper radius rod having a V-shaped planar shape pivotally attached to the center portion of the housing in the vehicle width direction and having both legs free ends pivotally attached to the chassis frame, respectively, and is substantially symmetrical on both sides of a longitudinal centerline of the vehicle body. And a pair of left and right lower radius rods each having one end pivotally connected to the rear axle housing, an operating lever pivotally supported by the chassis frame with its lower end connected to the other end of the lower radius rod, and the same operation. The upper and lower radial slots are connected to the upper ends of the levers, respectively, and operate during steering during high-speed running of the vehicle. And a pair of rear wheel steering actuators for driving the rear axle housing around an apex of the upper radius rod to drive the rear axle housing in the opposite direction. Things.

(Operation) According to the present invention, the rear axle housing is pivotally supported at the central portion in the vehicle width direction by the apex portion of the V-shaped upper radius rod, and is suspended around the vehicle frame by air springs near both ends in the vehicle width direction. Therefore, the upper axle rod can be pivoted around the apex pivot point of the upper radius rod, in other words, the rear axle housing is fixed around the apex pivot point of the upper radius rod during rear wheel steering. Since the vehicle turns, excellent running stability can be ensured. The steering wheel of the rear axle housing is connected to a pair of left and right lower radius rods each having one end pivotally connected to the rear axle housing via a pair of left and right operating levers pivotally supported by a chassis frame having a sufficient ground clearance. Controlled by a pair of rear-wheel steering actuators that operate in opposite directions, the steering actuator and its accessories (eg, hydraulic hoses) can be safely protected from flying stones, muddy water, and obstacles on the ground. .

(Examples) Examples of the present invention will be specifically described below with reference to the accompanying drawings. In the drawing, reference numeral 10 denotes a chassis frame of a vehicle such as a truck, and a pair of left and right side rails extending in a vehicle front-rear direction.
12 and the left and right side rails extending in the vehicle width direction
And a plurality of cross members 14 fixedly attached to the same. 16 is a rear axle housing supporting a double tire 18 at both ends in the vehicle width direction, 20 is a hat-type spring support member mounted on a top surface near both ends in the vehicle width direction of the rear axle housing by a fixing tool such as a U bolt 22, Reference numeral 24 denotes an air spring, which is disposed in front and rear of the rear axle housing 16 across the end of the rear axle housing 16 and is interposed between the spring support member 20 and the side rail 12 of the chassis frame 10.

26 is an upper radius rod which is disposed along the center line in the front-rear direction of the vehicle body and has a V-shaped planar shape, and the apex of the radius rod has a ball joint device 28 (or a rubber bush type joint device having the same effect). The rear axle housing 16 is pivotally mounted on the upper side of a differential casing 30 provided at a central portion of the rear axle housing 16, and the free ends of both legs of the rod are respectively connected to a ball joint device 32 (or a rubber bush type joint device having the same effect). ) Through the side rails 12 (or cross members 14) of the chassis frame 10
Is pivoted to.

In particular, as shown in FIG. 2, a bracket 34 and a spring support member 20 are attached to a U-bolt 22 on the lower surface near both ends in the vehicle width direction of the rear axle housing 16.
One end of a pair of left and right lower radius rods 38 is pivotally connected to the bracket 34 via a ball joint device 36 (or a rubber bush type joint device having the same effect). The other end of each lower radius rod 38
A lower end of an operating lever 44 pivotally supported by a pin 42 on a bracket 40 fixed to a web or a side wall of the side rail 12 is pivotally connected via a pin 46, respectively. Further, a piston shaft 50 of a hydraulic cylinder device 48 forming a pair of left and right rear wheel steering actuators is pinned on the upper end of the operating lever 44.
The cylinder 54 of the hydraulic cylinder device is pivotally connected to a web or a side wall of the side rail 12 by a pin 56.

The specific configuration of the ball joint devices 28, 32 and 36 is illustrated in FIGS. 4 and 5. First, in FIG. 4, reference numeral 58 denotes one of the members that cause relative rotational displacement, that is, the upper radius rod 26 or the lower radius rod 38.
60 is the other member, namely the rear axle housing 16
Or the bracket 34. The other member 60 supports a shaft 64 having a spherical member 62, and the one member 58 supports a ball seat 66 that contacts the spherical member 62.
With this configuration, one member 58 can freely rotate with respect to the other member 60 in a plane orthogonal to the axis of the shaft 64 and in a plane including the coaxial line.

The ball joint device shown in FIG.
A housing 72 for accommodating the ball head 70 of the ball stud 68 is formed on one member 58, that is, the upper radius rod 26 or the lower radius rod 38, and the ball head 70 is housed in the housing 72.
And the ball studs 68 are fixed to the other member 60, that is, the rear axle housing 16 or the bracket 34. Even with this configuration, one member 58 can freely rotate relative to the other member 60 in a plane orthogonal to the axis of the ball stud 68 and in a plane including the coaxial line.

Further, FIG. 6 shows a rubber bush type joint device which is functionally substantially the same as the above-mentioned ball joint device. A rubber bush 78 is fixed to the end of one member 58 similar to that shown in FIG. 4 by baking, and a spherical member 62 is simultaneously fixed to the inner periphery of the rubber bush 78 by baking. A shaft 64 supported by the other member 60 is inserted through the spherical member 62. Also in this configuration, relative rotation between 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 is allowed.

Next, in order to prevent the rear axle housing 16 from rising excessively with respect to the chassis frame 10 while the vehicle is traveling on a rough road, to prevent the two from directly colliding and the air spring 24 from being damaged, FIG. As shown by reference numeral 80,
A bump rubber located above the spring support member 20 is provided on the side rail 12 of the chassis frame 10. The bump rubber 80 can be disposed inside a rubber diaphragm 82 of the air spring 24, as schematically shown in FIG.

Also, during traveling on rough roads, the rear axle housing 16 causes excessive displacement downward with respect to the chassis frame 10, and the heavy rear wheels and the rear axle housing 16 are suspended from the chassis frame, and the air spring 24 In order to prevent breakage of the suspension, a suspension stopper device as shown in FIG. 7 is provided. In the drawing, reference numeral 84 denotes a stopper bracket fixed to the inner side surface of the web of the side rail 12, and 86 denotes a rear axle having a lower end thereof through a ball joint device or a joint device 88 similar to the rubber bush pivot device of the same effect. A stopper rod 90 connected to the housing 16 is a stopper rubber.

With this configuration, when the rear axle housing 16 is excessively lowered with respect to the bogie frame 10, the head 92 of the stopper rod 86 abuts against the top plate of the stopper rubber 90, and further lowering displacement of the rear axle housing 16 is prevented. .

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

Finally, FIG. 8 is a conceptual block diagram of a device for controlling the operation of the rear wheel steering actuator 48. In the figure, reference numeral 96 denotes a steering angle sensor of a light pulse non-contact type, for example, which is disposed on a steering shaft 98 and detects a steering angle, 100 denotes a vehicle speed sensor, 102 denotes a yaw rate sensor, and 104 denotes a steering angle signal of the steering angle sensor 96. A controller that receives a vehicle speed signal of a vehicle speed sensor 100 and a turning signal of a yaw rate sensor 102 and controls a control valve 106 that operates a rear wheel steering actuator 48; 1
08 is a hydraulic pump.

When the steering wheel 110 is operated and the front wheels 112 are steered while the vehicle is traveling at high speed, a steering angle sensor is provided.
The controller 104 that receives the 96 steering angle signal, the vehicle speed signal of the vehicle speed sensor 100, and the turning signal of the yaw rate sensor 102 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 108 by the operation of the control valve 106 is supplied to a pair of rear wheel steering actuators 48. When the actuators 48 are moved in opposite directions, that is, when one of the left and right actuators is extended, the other actuator is extended. Act to contract.

When the rear wheels are steered to improve the steering stability during high-speed running of the vehicle, 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 steering direction of the front wheels 112. . However, in connection with the steering of the front wheels 112,
The rear wheel 18 is steered by a slight angle in the direction opposite to the steering direction of the vehicle, and after a short time, the rear wheel 18 is steered by a small angle in the same direction as the steering direction of the front wheel 112. It is also possible.

In the above configuration, the cylinder 54 of the hydraulic cylinder device 48 forming the rear wheel steering actuator has the piston shaft 50
A stopper is provided to limit the extension and contraction strokes of the rear axle housing 16 even if a large disturbance acts on the rear wheel by the stopper. When the device 48 is at rest, the piston shaft 50 is brought into the neutral position by actuation of a built-in neutral spring or by hydraulically locking (acting equal hydraulic pressure on both side chambers of the piston to fix the piston in the neutral position). , And the rear axle housing 16, that is, the rear wheel 18, is held in a straight traveling state with a steering angle of zero.

When the front wheels 112 are steered during high-speed running of the vehicle, the control valve 106 is operated by the command of the controller 104 as described above, and the pair of rear wheel steering actuators 48 operate in opposite directions. Actuating levers 44 each having one end connected to a piston shaft 50 of each actuator rotate in opposite directions, and a lower radius rod 38 connected to the other end of one operating lever 44 is pulled forward of the vehicle body, and Operating lever 44
The lower radius rod 38 connected to the other end of the vehicle is driven rearward of the vehicle body. As a result, the rear axle housing 16
The steering is smoothly and stably turned around the vertex of the upper radius rod 26 in the shape of a letter in the left or right direction by a set steering angle, for example, 1 °, and the high-speed steering is performed in a manner well known in the art. Steering stability at the time is improved. Since the suspension spring is the air spring 24, the rotation of the rear axle housing 16 for steering is performed extremely smoothly by flexing the rubber diaphragm 82 freely in the horizontal direction.

The vertical movement of the rear axle housing 16 with respect to the chassis frame 10 during straight running of the vehicle and turning during steering is performed with the air spring 24 receiving a load. At this time, the rear axle housing 16 is
The upper and lower radius rods 38 perform a vertical link motion. Further, the upper radius rod 26 is pivotally connected to the rear axle housing 16 and the chassis frame 10 by ball joint devices 28 and 32 (or equivalent rubber bush type joint devices), and the lower radius rod 38 is connected to a similar ball joint device 36 (or the same). Axle housing 16 with rubber bush joint device)
Therefore, even when the rear axle housing 16 tilts left or right or generates a roll displacement when traveling or turning on an uneven road, the displacement is not hindered. The lower radius rod 38 is connected to the upper end of an operating lever 44 pivotally supported by the side rail 12 of the chassis frame 10 having a sufficient ground clearance.
Driven by 48, the rear wheel steering actuator
48 and its accessories, such as hydraulic hoses, can be safely protected from flying stones, muddy water and obstacles on the ground, and have the advantage of ensuring their durability and reliability.
Further, by appropriately selecting the upper and lower lever lengths of the operation lever 44 with respect to the pivot pin 42, there is the convenience that the output capacity of the rear wheel steering actuator 48 can be appropriately set according to the actual situation. Lower radius rod 38
Since an actuator such as a hydraulic cylinder is not provided inside itself, there is an advantage that sufficient strength can be secured.

In the above-described embodiment, a vehicle having one rear axle is illustrated. However, in the case of a vehicle having two rear axles, the same rear wheel steering device as described above is provided on both the rear front axle and the rear rear axle. Can be In a rear two-axle vehicle, 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 the case of the illustrated drive wheels.

(Effect of the Invention) As described above, the rear wheel steering device of the vehicle according to the present invention includes:
Chassis frame, rear axle housing supporting rear wheels at both ends in the vehicle width direction, an air spring interposed between the rear axle housing and the chassis frame, and a vertex disposed along the center line in the vehicle longitudinal direction An upper radius rod which is pivotally attached to the center portion of the rear axle housing in the vehicle width direction and has both legs free ends pivotally attached to the chassis frame, and has a V-shaped planar shape on both sides of a longitudinal centerline of the vehicle body. A pair of left and right lower radius rods which are disposed substantially symmetrically and have one ends pivotally connected to the rear axle housing, an operation lever pivotally supported by the chassis frame with its lower ends connected to the other ends of the lower radius rods, And connected to the upper ends of the operating levers, respectively, which are operated at the time of steering during high-speed running of the vehicle, and are operated through the operating levers to lower left and right. A pair of rear wheel steering actuators for driving the radius rod in the opposite direction and moving the rear axle housing around the apex of the upper radius rod, and having a rigid rear axle tube. It is industrially beneficial because it can improve the steering stability during high-speed running of a truck or the like, and is excellent in durability and reliability with little risk of damage to the rear-wheel steering actuator and its accessories.

[Brief description of the drawings]

FIG. 1 is a perspective view of an essential part 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 view of the rear wheel steering device shown in FIG. Schematic views in plan view, FIGS. 4 and 5
The figure shows the ball joint devices 28, 32 in the device of FIG.
FIG. 6 is a cross-sectional view showing the specific structure of FIGS.
FIG. 7 is a sectional view of a rubber bush type joint device having substantially the same effect as the ball joint device shown in FIG. 5, FIG. 7 is a front view showing a suspension stopper device of the rear axle housing 16, and FIG. 4 is a schematic configuration diagram of an operation control device of a rear wheel steering actuator 48. FIG. 10 ... chassis frame, 12 ... side rail, 16 ... rear axle housing, 24 ... air spring, 26 ... upper radius rod, 28, 32 and 36 ... ball joint device, 38 ... lower radius rod, 44 ... Operating lever,
48 ... Rear wheel steering actuator.

Claims (1)

(57) [Claims] 1. A chassis frame, a rear axle housing supporting rear wheels at both ends in a vehicle width direction, an air spring interposed between the rear axle housing and the chassis frame, and arranged along a center line in the vehicle longitudinal direction. An upper radius rod having a V-shaped planar shape with its apex portion pivotally attached to the center portion of the rear axle housing in the vehicle width direction and both leg free ends pivotally attached to the chassis frame, respectively, in the front-rear direction of the vehicle body A pair of left and right lower radius rods, which are disposed substantially symmetrically on both sides of the center line and one end of which is pivotally connected to the rear axle housing, the lower ends thereof are respectively connected to the other ends of the lower radius rods, and are pivotally supported by the chassis frame. Operating lever, which is connected to the upper end of the operating lever, respectively, and operates at the time of steering during high-speed running of the vehicle, and operates the operating lever. And a pair of rear wheel steering actuators for driving left and right lower radius rods in opposite directions to move the rear axle housing around a vertex connection point of the upper radius rod. Steering gear.