JPH0698936B2 - Rear axle steering system for rear two-axle vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear axle steering device for a rear two-axle vehicle, and more particularly to a vehicle rear axle steering device in which the rear two axles are suspended by a trunnion suspension system.

[Outline of Invention]

The present invention divides a torque rod that connects both ends of a rear front shaft and a rear rear shaft to a vehicle body into two parts and connects them with a feed screw so that the torque rod can expand and contract, and a motor for driving the feed screw is provided. By driving the feed screw by this motor, the effective length of the torque rod is changed to rotate the rear front shaft and the rear rear shaft for steering.

[Conventional technology]

Conventionally, trucks have been widely used to carry various kinds of luggage. When the load on the truck increases, the load applied to the rear axle also increases. In order to reduce the load applied to one shaft, the structure of the rear two shafts is adopted in a truck having a large load. A trunnion suspension is widely used to distribute the load to each of the two rear axles.

[Problems to be solved by the invention]

However, in the conventional truck, both the front and rear axles and the rear and rear axles that form the rear two axles are incapable of turning, and the wheels attached to these axles cannot be steered. However, the maneuverability of the vehicle changes depending on the vehicle speed. Alternatively, the maneuverability changes depending on the position of the cargo. Therefore, in order to keep such maneuverability constant,
It is preferred that each axis be steerable. Further, it is known that if the two rear axles can be steered together, the minimum turning radius can be reduced, the inner ring difference and the outer ring difference can be reduced, or tire wear can be reduced.

The present invention has been made in view of the above problems, and prevents the maneuverability from changing due to changes in the vehicle speed, the position of the load, and the like, and obtains a certain maneuverability. Two
An object of the present invention is to provide a rear axle steering device for an axle.

[Means for solving problems]

The present invention suspends a rear front shaft and a rear rear shaft at a front end portion and a rear end portion of a leaf spring supported via a trunnion bracket, respectively, and supports both sides of the rear front shaft and the rear rear shaft. In a vehicle in which the torque rods are respectively connected to a vehicle body, the torque rods are divided into two parts, which are extensiblely connected by a feed screw, and a motor for driving the feed screw is provided. By driving the feed screw, the effective length of the torque rod is changed to pivot the rear front shaft and the rear rear shaft for steering.

[Action]

Therefore, according to the present invention, when the maneuverability changes due to, for example, a change in vehicle speed or a change in the position of the load, the motor drives the feed screw to expand and contract the torque rod to change its effective length. It becomes possible to turn the rear and front axles and the rear and rear axles, whereby steering correction is performed.

〔Example〕

The present invention will be described below with reference to an embodiment shown in the drawings. 2 and 3 show a truck equipped with a rear axle steering device according to an embodiment of the present invention, and the truck is provided with a pair of left and right frames 10 constituting its skeleton,
A cab 11 is supported on the front end side of the frame 10. The front end side of the frame 10 is supported by the front shaft 12, and the rear side thereof is supported by the rear front shaft 13 and the rear rear shaft 14. Here, the rear front shaft 13 constitutes a drive shaft, and the rear rear shaft 14 constitutes a driven shaft or a dead shaft.

Next, the structure of the suspensions of the rear two shafts 13 and 14 will be described. As shown in FIG. 4 and FIG.
A trunnion bracket 20 is fixed to each of the pair of left and right frames 10, and a trunnion shaft 21 is attached by these trunnion brackets 20 so as to be orthogonal to the frame 10. Spring seats 22 are rotatably attached to both ends of the trunnion shaft 21, respectively. Further, the spring seat 22 supports a leaf spring 23 constituting a suspension spring via a U bolt 24.

The rear front shaft 13 is suspended on the front end of the leaf spring 23 thus supported, and the rear rear shaft 14 is suspended on the rear end. Then, as shown in FIG. 9, the central portion on the upper side of the rear front shaft 13 is provided with a pair of torque rods 25 arranged in a V shape so that the left and right frames 10 can be connected.
Is connected to a cross member 28 for connecting the. On the other hand, both sides of the rear front shaft 13 are
It is adapted to be connected to the trunnion bracket 20 via 6 and 27. Also in the rear-rear shaft 14, the central portion on the upper side is connected to the cross member 28 by the torque rod 25, and on the lower side of the rear-rear shaft 14, both sides are left and right torque rods.
It is adapted to be connected to the trunnion bracket 20 by 26 and 27.

Next, on the lower side of the axles 13 and 14, the right and left sides of the torque rod 2 which are respectively connected to the trunnion bracket 20.
Referring to 6 and 27, as shown in FIG. 1, both ends of the torque rods 26 and 27 are composed of connecting portions 33 and 34, respectively. A geared motor is attached to one connecting portion 33.
35 is fixed, the output shaft of the geared motor 35 is composed of a feed screw 36. On the other hand, a disc 37 is fixed to the tip of the other connecting portion 34, and the feed screw 36 is screwed into a female screw hole 38 formed in the disc 37. And geared motor 35
Is connected to the drive circuit 39.

The drive circuit 39 for driving the geared motor 35,
It is controlled by the microcomputer 47. The input side of the microcomputer 47 is connected to a steering angle sensor 49 for detecting the steering angle of the steering handle 48, a vehicle speed sensor 50, a yaw rate sensor 51, a lateral acceleration sensor 52, and a stroke sensor 53, respectively. There is.

Next, the steering operation of the rear axle steering device having the above-described configuration will be described. The control signal from the microcomputer 47 shown in FIG. 1 causes the geared motor 35 to rotate normally or reversely via the drive circuit 39. By doing so, the feed screw 36 will rotate forward or reverse,
Moreover, the feed screw 36 is engaged with the female screw hole 38 of the disk 37. Therefore, the torque rods 26 and 27 are expanded and contracted. Then, one of the pair of left and right torque rods 26, 27, for example, by making the left torque rod 27 long and shortening the right torque rod 26, the axle shaft 13 to which these torque rods 26, 27 are connected is It becomes possible to turn to the right, which causes the rear shaft 13 to be steered. The lateral displacement of the rear front shaft 13 and the rear rear shaft 14 is prevented by the pair of upper V-shaped torque rods 25. Further, in this embodiment, the rear front shaft 13 and the rear rear shaft 14 are independently steered.

The control for the subsequent two-axis steering by the microcomputer 47 will be described in more detail. As shown in the flowchart of FIG. 6, the microcomputer 47 reads the steering angle of the steering handle 48 by the sensor 49. Then, the vehicle speed is read by the vehicle speed sensor 50, and the steering angle of the rear front shaft 13 is calculated based on these values.
Further, from the stroke of the piston rod 35 of the hydraulic cylinder 37, the stroke sensor 53 reads the steer angle of the rear front shaft 13. Then, this actual steer angle is compared with the calculated value. When the calculated value is larger, the rear front shaft 13 is further turned and steered. On the other hand, when the calculated value is smaller, the rear front shaft 13 is returned to the original state.

The microcomputer 47 controls the rear axle 14
Also do. That is, the steering angle of the rear-rear shaft 14 is calculated, and the actual steering angle of the rear-rear shaft 14 is read. Then, the calculated value is compared with the actual steer angle, and if the calculated value is larger, the rear-rear-axis 14 is further steered, whereas if the calculated value is smaller, the rear-rear-axis 14 is I'm trying to bring it back. Therefore, by such control, the rear front shaft 13 and the rear rear shaft 14 are steered to the respective steering angles according to the vehicle speed.

Further, in this rear axle steering device, steering stability is kept constant by steering the rear two axles in response to changes in vehicle speed and changes in load. This operation is performed based on the flowchart shown in FIG. The microcomputer 47 reads the steering angle of the steering handle 48 and calculates a standard yaw rate according to this steering angle. Further, the microcomputer 47 causes the yaw rate sensor 51 to read the yaw rate, that is, the angular velocity of yawing. Then, this actual yaw rate is compared with the reference yaw rate, and when the actual yaw rate is out of the range of the reference yaw rate, the torque rods 26 and 27 are expanded and contracted using the geared motor 35 and the feed screw 36, respectively. Steering is corrected by turning the front shaft 13 and the rear rear shaft 14.

Instead of the steering correction by the yaw rate, it is possible to perform the steering correction based on the detection of the lateral acceleration as shown in the flowchart of FIG. In this case, the steering angle of the steering handle 48 is read by the steering angle sensor 49, and the standard lateral acceleration at this steering angle is calculated. Then, the actual lateral acceleration obtained by the lateral acceleration sensor 52 is read, and the calculated value is compared with the actual lateral acceleration. If the actual lateral acceleration value exists outside the specified lateral acceleration range, the torque rod
Steering correction is performed by turning the front and rear shafts 13 and 14 by expanding and contracting the screws 26 and 27 with the feed screw 36.

Generally, the yaw rate or lateral acceleration of a vehicle changes depending on the vehicle speed. Further, the maneuverability changes depending on the position of the load, and further, the lateral force is applied by a disturbance such as a side wind received by the vehicle or the inclination of the road surface, which causes the maneuverability to change. However, such a change in maneuverability is corrected by independently steering the rear front shaft 13 and the rear rear shaft 14 by the device shown in FIG. 1, and it becomes possible to maintain a certain maneuverability. Become. Therefore, such a vehicle can improve the maneuverability particularly at medium speed and high speed. Further, by steering such two rear axles, the minimum turning radius can be reduced, the inner ring difference and the outer ring difference can be reduced, and in particular, the wear of the tires of the rear front shaft 13 and the rear rear shaft 14 can be prevented. It can be reduced.

The present invention has been described above with reference to the illustrated embodiment, but the present invention is not limited to the above embodiment, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiment, the geared motor 35 is used as the drive source for expanding and contracting the torque rod, but a hydraulic motor can be used instead of such an electric motor.

〔The invention's effect〕

As described above, according to the present invention, the torque rod is divided into two and is connected to the feed screw so that the torque rod can expand and contract, and a motor for driving the feed screw is provided. The effective length is changed to turn the front and rear axles for steering. Therefore, according to such a configuration,
It is possible to steer the rear two axes independently with a simple structure.

Further, according to the present invention, the effective length of the torque rod is changed by driving the feed screw by the motor, and the rear front shaft and the rear rear shaft are turned to perform steering. Therefore, by utilizing the boosting action of the feed screw, the rear shaft steering can be achieved by the motor having a relatively small output. Moreover, it is possible to precisely control the turning amounts of the rear front shaft and the rear rear shaft by using the motor and the feed screw.

[Brief description of drawings]

FIG. 1 is a block diagram showing a structure for expanding and contracting a torque rod of a rear axle steering system according to an embodiment of the present invention, FIG. 2 is a plan view of a truck equipped with the rear axle steering system, and FIG. The same side view, FIG. 4 is a side view showing the rear two-axle suspension device of this truck, FIG. 5 is the same front view, and FIGS. 6 to 8 are flowcharts showing the operation of the rear axle steering device.
FIG. 9 is a plan view showing a rear biaxial suspension device. In the reference numerals used in the drawings, 10 ... frame 13 ... rear front shaft (drive shaft) 14 ... rear rear shaft (driven shaft, dead shaft) 20 ... trunnion bracket 21 ... trunnion shaft 23 ... leaf spring 26, 27 …… Torque rod 33,34 …… Coupling 35 …… Geared motor 36 …… Feed screw 37 …… Disk 38 …… Female screw hole 39 …… Drive circuit 47 …… Microcomputer 49 …… Steering angle sensor 50 …… Vehicle speed sensor 51 …… Yaw rate sensor 52 …… A lateral acceleration sensor.

Claims (1)

[Claims] 1. A rear front shaft and a rear rear shaft are respectively suspended by a front end and a rear end of a leaf spring supported through a trunnion bracket, and both sides of the rear front shaft and the rear rear shaft are suspended. In a vehicle in which the torque rods are respectively connected to the vehicle body, the torque rods are divided into two and are connected to each other by a feed screw so that they can expand and contract.
A motor for driving the feed screw is provided, and by driving the feed screw by the motor, the effective length of the torque rod is changed to rotate the rear front shaft and the rear rear shaft to perform steering. A rear axle steering device for a rear two-axle vehicle, which is characterized in that