JPH03193516A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To prevent the rolling at the time of high-speed turning, in the rear wheel steering device for a vehicle equipped with leaf springs, by arranging the vehicle-side pivotally supporting points of the shackle members for supporting the front and rear ends of the leaf springs in the up-and-down reverse positions, and also by inclinedly arranging the shackle members so that the lower end is positioned to the rear side of the vehicle than the upper end. CONSTITUTION:On the rear side of a vehicle frame 22, a pair of shackle members 26L, 26R, and on the front side thereof, a pair of shackle members 28L, 28R, are supported on the shafts via brackets respectively. And, the rear ends of leaf springs 30R, 30L, and the front ends thereof are pivotally supported by the lower ends of the shackle members 26L, 26R, and by the intermediate parts of the shackle members 28L, 28R respectively, in such a way that they can be movable in the front and rear directions. And, an axle member 20 is fixed to the intermediate parts of the leaf springs 30L, 30R. Further, a pair of right and left hydraulic cylinders 38L, 38R for moving the leaf springs are provided in front of the shackle members 28L, 28R.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device for a vehicle having left and right rear wheels supporting a common axle member attached to both ends thereof and a leaf spring.

(Prior Art) A vehicle suspension device proposed by the present applicant and disclosed in Japanese Patent Laid-Open No. 63-212109 has front and rear ends supported by shackle members rotatably attached to the vehicle body frame. The vehicle is equipped with a pair of left and right double shank leaf springs that are arranged to be movable in the longitudinal direction of the vehicle, and when the front wheels are steered, these left and right leaf springs are moved back and forth in opposite directions by a pair of left and right actuators. By being moved in the direction of
The rear wheels are steered in the opposite phase or in the same phase as the front wheels to improve turning performance when the vehicle is running at low speeds and to improve running stability when the vehicle is running at high speeds.

By the way, when the vehicle is steered and turns while traveling, the load moves to the outer wheel side of the turn. In this case, the outer turning wheel side of the vehicle body sinks, causing rolling. This rolling becomes more pronounced as the vehicle speed increases, and especially in freight cars loaded with a large amount of cargo, the center of gravity of the vehicle is high, resulting in large rolling, which can be dangerous.

This rolling of the vehicle body when turning can be reduced by increasing the spring constant of the leaf springs or by making the dampers harder.
Such measures have the disadvantage of worsening riding comfort.

(Object of the Invention) Therefore, the present invention provides a pair of left and right double shackle leaf springs whose front and rear ends are supported by a shank member pivotally supported on a vehicle body frame and are disposed so as to be movable in the front and rear direction of the vehicle, and a pair of these double shackle leaf springs. The rear of a vehicle is equipped with a pair of left and right actuators that steer the rear wheels by moving the leaf springs in the longitudinal direction in opposite directions (in opposite phases) to move the rear axle supported by the leaf springs and steer the rear wheels. In the wheel steering system, the shackle member that supports the front end portion of the leaf spring and the shackle member that supports the rear end portion of the leaf spring have their pivot points toward the vehicle body arranged upside down, and It is characterized by being inclined so that the lower end is closer to the rear of the vehicle body than the upper end.

(Effects of the Invention) In a vehicle equipped with a rear wheel steering device, the rear wheels are steered in the same phase as the front wheels when driving at high speed. In this case, the leaf spring of the outer wheel is moved forward by the actuator, and the leaf spring of the inner wheel is moved rearward by the actuator.

Therefore, if the shackle members that support the front and rear ends of the leaf springs are arranged as in the present invention, the leaf spring on the outer swinging wheel side will be displaced downward as it moves forward, increasing the vehicle height on the outer swinging wheel side. In addition, the leaf spring on the inner wheel of the turn moves upward as it moves rearward, lowering the vehicle height of the inner wheel of the turn, suppressing rolling of the vehicle body and preventing deterioration of ride comfort. can achieve the intended purpose.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing an embodiment of a rear wheel steering device for a vehicle according to the present invention, together with a front wheel steering mechanism of an automobile to which the device is applied. In Fig. 1, left and right front wheels 2L,
A front wheel steering mechanism 5 is provided that steers the front wheels 2R in response to steering by the steering wheel 3. The front wheel steering mechanism 5 includes a pair of knuckle members 6 that rotatably support the front wheels 2L and 2R, and a pair of tie openings each having one end connected to the knuckle arm 6a of the member 6;
and a rank-and-pinion type steering gear mechanism 10 having a rank shaft 9 to which the other ends of a pair of tie rods 8 are connected.

The left and right rear wheels 12L, 12R are each rotatably attached to both ends of an axle member 20 extending in the vehicle width direction to which the driving force of the propeller shaft 16 is transmitted via a differential gear W14.

The vehicle body frame 22, whose front side is omitted in FIG. 1, has a pair of shackle members 26L at predetermined left and right positions on its rear side, as is clear from FIGS. 2 and 3. 26R is body frame 2
Shaft 2 provided on a bracket 56 fixed to the lower surface of 2
7, and at predetermined left and right positions in front of the positions where the shackle members 26L and 26R are attached on the vehicle body frame 22, there are brackets 57.
is fixed to the bracket 57, and a pair of shackle members 28L and 28R are pivotally supported at their lower ends by a shaft 29. The rear ends of leaf springs 30L, 30R are attached to the lower ends of the shackle members 26L, 26R, and the leaf springs 3OL, 301'? The front end portions of the leaf springs 3OL and 30R are attached, and the leaf springs 3OL and 30R are supported movably in the longitudinal direction of the vehicle body by shackle members 26L, 26R128L and 28R.

On the upper surface of the middle part of leaf springs 30L and 30R,
The axle member 20 is fixed by a fixing member 34. In addition, on the vehicle body frame 22 above the fixing member 34,
An elastic member 36 is fixed to the fixing member 34 to prevent it from colliding with the vehicle body frame 22 due to vertical vibration of the rear wheels 12L, 12R. There is a seat between the hub carrier 35 of the rear wheels 12L and 12R and the vehicle frame 22.
A Tsuku absorber 58 is attached, and furthermore, a Watt link 59 is provided between the case of the differential gear device Y14 and the left and right fixing members 34.

Shackle members 28L, 28 in the vehicle body frame 22
A pair of left and right hydraulic cylinders 38L and 38R are located at a predetermined position in front of the position where R is installed.
, 39R, and extend from these hydraulic cylinders 38L, 38R, respectively.
0L and 40R have shackle members 28L and 2 at their ends.
Each is attached to the upper end of 8R.

Therefore, when the piston rods 40L, 40R protrude from the hydraulic cylinders 38L, 38R, the shank members 28L, 28R and the shackle members 26L, 26
R rotates about shafts 29 and 27, respectively, and as a result, leaf springs 30L and 30R move toward the rear of the vehicle body.

Further, when the piston rod 4017.40R is pulled into the hydraulic cylinders 38L, 38R, the leaf spring 3015.30R moves toward the front side of the vehicle body.

In this case, when the rear wheels 12L, 12R are not steered, that is, in the neutral position, the shank members 26L, 26R, 128L, 28R are tilted so that their lower ends are positioned toward the rear of the vehicle body than their upper ends. It is characterized by its location. With this configuration, when the leaf spring 30I7.3OR moves toward the front of the vehicle body, it also displaces downward with this movement, as is clear from FIG. become.

Hydraulic cylinders 38L and 38R are piston rods 40L
, 40R, respectively, are provided with hydraulic chambers 38a, 38b partitioned by pistons 41 fixed to the pistons 40R, and these hydraulic chambers 38a, 38b communicate with each other via an oil passage 45. The oil passage 45 is provided with oil pumps 46L and 46R that are controlled by a control unit 50.

The control unit 50 includes a steering angle sensor 5 that is arranged in relation to the front wheel steering mechanism 5 and detects the steering angle θ of the front wheels 2L and 2R.
2 and a detection signal Sv from a vehicle speed sensor 54 that detects the vehicle speed based on the rotation speed of the front wheels 2L (or 2R). Based on the detection signals Sθ and Sv, the control JTJ unit 50 outputs control signals Sl and Sr to the oil pumps 46L and 46H to operate the hydraulic cylinders 38[, 38R.

For example, the oil pumps 46L and 46R receive a control signal Sj!
, Sr take a predetermined high level, the hydraulic cylinder 38
From the hydraulic chambers 38a to 38b of each of L and 38R
The control signals Sl, Sr
takes a predetermined low level, hydraulic cylinders 38I1.
It operates to introduce oil from each hydraulic chamber 38b of 38R into the hydraulic chamber 38a.

When the vehicle equipped with the rear wheel steering device configured in this manner is running, the control unit 50 controls the steering angle sensor 52 when the detected vehicle speed from the vehicle speed sensor 54 is less than a predetermined value. If the detection signal Sθ from the oil pump 46 indicates that the vehicle is turning left, the oil pump 46
A control signal SZ that takes a predetermined high level is supplied to the oil pump 46R to operate it, and a control signal SP that takes a predetermined low level is supplied to the oil pump 46R to operate it.

Hence the hydraulic cylinder! , the pressure in the hydraulic chamber 38b in the hydraulic cylinder 38R increases, and the piston rod 40L is drawn into the hydraulic chamber 38a from the position shown by the broken line in FIG.
The pressure inside a increases and the piston rod 401'? protrudes toward the hydraulic chamber 38b from a position ζ indicated by a broken line in FIG. In such a state, the shackle members 28L, 26L are rotated toward the front of the vehicle about the shafts 29.27, so that the leaf spring 30L
moves to the front side of the vehicle, and the shackle member 28R
126R is rotated toward the rear of the vehicle about the shafts 29 and 27, thereby moving the refspring 30R toward the rear of the vehicle.

As a result, the axle member 20 supported by the leaf springs 30L and 3OR rotates clockwise in FIG. Improves turning performance when driving. In this case, the leaf spring 30L moves forward and is displaced downward, increasing the vehicle height on the left side.
Leaf spring 301? As the vehicle moves backward, it is displaced upward and the vehicle height on the right side is lowered, but this does not cause any problem as the vehicle is traveling at low speed.

Further, if the control unit does not receive a detection signal from the steering angle sensor 52 indicating that the steering angles of the front wheels 2L and 2R are zero and the vehicle has transitioned from a turning state to a straight-ahead state, A control signal SZ having a low level is supplied to the oil pump 46L.

Due to dirt, the piston rod 40L is attached to the hydraulic cylinder 38.
1, and the piston rod 40R protrudes from the hydraulic cylinder 381? When the rear wheels 12L and +2R are pulled in and returned to the position shown by the broken line in FIG. 1, the steering angles of the rear wheels 12L and +2R become zero.

On the other hand, when the vehicle is running and the detection signal Sv from the heavy speed sensor 54 is not high and the vehicle speed is above a predetermined value, the control unit 50 controls, for example, when the detection signal Sθ from the steering angle sensor 52 indicates that the vehicle is moving to the left. When changing lanes, a control signal S1 that takes a low level is supplied to the oil pump 46L to operate it, and a control signal S' that takes a high level is supplied to the oil pump 46rl. Activate this.

Therefore, the hydraulic chamber 38a in the hydraulic cylinder 38L
As the internal pressure increases, the piston rod 40L protrudes from the position shown by the broken line in FIG. 1 toward the hydraulic chamber 38b, and the hydraulic chamber 3 in the hydraulic cylinder 38R
As the pressure inside 8b increases, the piston rod 40R
It is drawn into the hydraulic chamber 38a from the position indicated by the broken line in FIG. In this state, the shackle portions +1:28L, 261- are rotated toward the rear of the vehicle about the shafts 29.27, thereby moving the leaf spring 30L toward the rear of the vehicle. In addition, the leaf spring 3
The OR moves to the front of the vehicle. As a result, the axle member 2
0 rotates counterclockwise in FIG. 1, and the rear wheels 12L, 12
R is steered in the same phase as the front wheels 21-12R, improving running stability during high-speed running. In this case, the leaf spring 30R moves forward, displacing downward to increase the vehicle height on the outer wheel of the turn, and moving rearward, the leaf spring 30L displaces upward, increasing the height of the inner wheel of the turn. By lowering the vehicle height, rolling of the vehicle body during turns is suppressed, further improving driving stability.

The control unit 50 also controls the steering angle of the front wheels 2L and 2R when the detection signal Sθ from the steering angle sensor 52 indicates that the steering angle of the front wheels 2L and 2R has become zero and the vehicle has transitioned from a lane change state to a straight-ahead driving state. supplies a high level control signal S1 to the oil pump 461, and
A control signal Sr that takes a low level is supplied to 6R. As a result, the piston port 40L is drawn into the hydraulic cylinder 38L, and the piston rod 40L is drawn into the hydraulic cylinder 38L.
1? The hydraulic cylinder 38R protrudes and is returned to the position shown by the broken line in FIG. 1, and the steering angle of the rear wheels 12L and 12R becomes zero.

In this manner, in this embodiment, rolling of the vehicle body during high-speed turns can be suppressed without deteriorating ride comfort.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an overall configuration diagram schematically showing an embodiment of a rear wheel steering device for a vehicle according to the present invention, together with a front wheel steering device for a vehicle to which the same is applied, and FIG. FIG. 3 is a perspective view of the wheel steering device, FIG. 3 is a side view thereof, and FIG. 4 is an explanatory diagram of the operation of the device according to the present invention. 2L, 2R - Front wheel 12L, 12R - Rear wheel 20 - Axle member 22 - Body frame 26L, 26R12
8L, 28 R--Shankle members 30L, 30R-Leaf springs 38L, 38R--Hydraulic cylinders 46L, 46R--Oil pump 50-Control unit 52-Rudder angle sensor 54-Vehicle speed sensor

Claims (1)

[Scope of Claims] A pair of left and right double shackle leaf springs whose front and rear ends are supported by shackle members rotatably attached to the vehicle body frame and are disposed so as to be movable in the front and back direction of the vehicle, and a pair of these left and right double shackle leaf springs. A rear wheel steering system for a vehicle comprising a pair of left and right actuators that move leaf springs in the front and rear directions in opposite phases to each other, a shackle member that supports a front end portion of the leaf spring and a shackle member that supports a rear end portion of the leaf spring. This is characterized in that the pivot points to the vehicle body are arranged upside down, and the lower ends of these shackle members are inclined so that they are closer to the rear of the vehicle body than the upper ends. Rear wheel steering system for vehicles.