JPH052552B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rear axle steering system for an automobile, and more particularly to a rear axle steering system for an automobile in which the rear axle is suspended by a suspension spring consisting of an air spring. .

〓Summary of the Invention〓 The present invention provides a hydraulic cylinder on a torque rod that connects both sides of a rear axle suspended to the vehicle body by an air spring to make it extendable and retractable, and provides oil supply to the hydraulic cylinder. By controlling the discharge by a control means, the rear shaft is turned to perform steering.

〓Conventional technology〓 Leaf springs have traditionally been used as suspension springs for suspending an axle on a vehicle body. Suspension devices made of leaf springs have a simple structure, can withstand large loads, and are highly durable. However, such leaf springs have a large spring constant and are hard, so they lack the effect of isolating vibrations and have the disadvantage of deteriorating ride comfort. In order to solve these drawbacks, air suspension devices are used in vehicles where ride comfort is particularly important. In such a device, the axle is supported by an air spring.
It is designed to be supported directly or via a beam.

<Problems to be Solved by the Invention> However, in such a conventional air suspension device, the axle cannot turn, and the rear axle in particular cannot be steered. However, the maneuverability of a vehicle changes depending on the vehicle speed. Alternatively, the steering stability changes depending on the position of the load. Therefore, in order to keep such steering stability constant, it is preferable to make the rear axle steerable. Also, by steering the rear axle,
It is known that it is possible to reduce the minimum turning radius, reduce the difference between inner and outer wheels, or reduce tire wear.

The present invention has been made in view of these problems, and is designed to prevent the steering stability from changing due to changes in vehicle speed, the position of the live load, etc., and to obtain a constant steering stability. The object of the present invention is to provide a rear axle steering device for an automobile.

<Means for Solving the Problems> The present invention provides a vehicle in which the rear axle is suspended by a suspension spring consisting of an air spring, in which both sides of the rear axle are suspended via a pair of lower or upper torque rods. Hydraulic cylinders are provided on the pair of torque rods, each connected to the vehicle body and on both sides of the rear axle, so as to be extendable and retractable, and the upper or lower pair of torque rods are connected to approximately V.
The hydraulic cylinders are arranged in a letter shape, one end of which is connected to the rear axle at approximately the center in the width direction of the vehicle, and the other end of which is connected to both sides of the vehicle body, and the hydraulic cylinder is provided with the hydraulic cylinder. The present invention relates to a rear shaft steering device for a motor vehicle, characterized in that the rear shaft is rotated by extending and contracting a torque rod provided therein.

〓Operation〓 By expanding and contracting the torque rods provided with the hydraulic cylinders by the hydraulic cylinders provided on the lower or upper pair of torque rods, the rear shaft can move the upper or lower pair of torque rods. At the connected position, the vehicle is turned around approximately the center in the width direction of the vehicle, thereby performing rear axle steering. Therefore, by controlling the hydraulic cylinder with the control means,
It becomes possible to perform control to prevent changes in steering stability due to changes in vehicle speed or changes in the position of the loaded load, thereby making it possible to maintain steering stability at a constant level.

〓Example〓 The present invention will be described below with reference to an illustrated example.
FIGS. 2 and 3 show a bus equipped with a rear axle steering system according to an embodiment of the present invention, and this bus includes a vehicle body 10.
0 is supported by a framework consisting of a frame 11 as shown in FIGS. 4 and 5, for example. The vehicle body 10 is supported at its front end by a front axle 12, and at the rear by a rear-front axle 13 and a rear-rear axle 14. Note that here, the rear and front axles 13 constitute a drive shaft, and the wheels thereof are double tires. On the other hand, the rear rear shaft 14 constitutes a driven shaft or a dead shaft, and its wheels are constructed of a single tire.

Next, the structure of the suspension of these two rear axles 13 and 14 will be explained. Figures 4 and 5
As shown in the figure, the two rear axles are supported by an air suspension device. That is, the rear-front shaft 13 is supported at both ends by support beams 20 provided on the left and right sides, and the left and right support beams 20 are supported by a front air spring 21 and a rear air spring 2, respectively.
2 and is adapted to be suspended on the frame 11. On the other hand, the rear axle 14 is the frame 1
It is designed to be suspended via an air spring 23 directly attached to 1.

A pair of torque rods 24 are connected to the upper side of the rear and front shafts 13. These torque rods 24 are arranged in a V-shape, and their tip ends are connected to the frame 1.
1. A pair of V-shaped torque rods 25 are also connected to the upper side of the rear axle 14, and are connected to the frame 11 by these torque rods 25. Furthermore, the rear-front shaft 13 is provided with a pair of left and right torque rods 26 on its lower surface, and is connected to the frame 11 by these torque rods 26. Similarly, the rear axle 14 is also connected to the frame 11 by a lower torque rod 27.

Next, we will explain the torque rods 26 and 27 that connect the left and right sides of the lower side of the axles 13 and 14 to the frame 11, respectively.As shown in FIG.
Each of the piston rods is composed of connecting portions 33 and 34, and a piston rod 35 is fixed to one of the connecting portions 33. And this piston rod 35
A piston 36 attached to the tip of the hydraulic cylinder 37 is slidably supported within a hydraulic cylinder 37. The hydraulic cylinder 37 is connected to the other connecting portion 34 . The hydraulic cylinder 37 is connected to a switching valve 38, and by switching the switching valve 38, oil is supplied from the oil pump 39, or oil is returned from the hydraulic cylinder 37 to the reservoir 40. It's becoming like that.

The actuator 46 for switching the spool of the switching valve 38 is operated by a microcomputer 47.
It has come to be controlled by The input side of this microcomputer 47 includes a steering angle sensor 49 that detects the steering angle of the steering wheel 48, a vehicle speed sensor 50, and a yaw rate sensor 5.
1 and a lateral acceleration sensor 52, respectively.

Next, to explain the steering operation of this rear axle steering system configured as described above, the switching valve 38 is controlled via the actuator 46 by a control signal from the microcomputer 47 shown in FIG.
By moving the spool, oil pressurized by the oil pump 39 can be supplied to the front or rear chamber of the piston 36 of the hydraulic cylinder 37, and thereby the torque rod 26,
27 can be expanded and contracted. By lengthening one of the pair of left and right torque rods 26, for example, by lengthening the left torque rod 26 and shortening the right torque rod 26, the axle 13 to which these torque rods 26 are connected can be turned to the right. This allows the rear axle to be steered. In this embodiment, the rear-front shaft 13 and the rear-rear shaft 14 are each independently steered.

To explain in more detail the control for the two-axis steering by the microcomputer 47, the microcomputer 47 controls the steering wheel 4 as shown in the flowchart shown in FIG.
8 is read by the sensor 49. Next, the vehicle speed is read by the vehicle speed sensor 50, and the steering angle of the rear and front axles 13 is calculated based on these values. Further, based on the stroke of the piston rod 35 of the hydraulic cylinder 37, the steering angle of the rear and front shafts 13 is read by the stroke sensor 53. This actual steering angle is then compared with the calculated value. If the calculated value is larger, the rear-front shaft 13 is further turned and steered. On the other hand, if the calculated value is smaller, the rear-front shaft 13 is returned to its original state.

Such control is performed by a microcomputer 47.
This is also done for the rear axle 14. In other words, the steering angle of the rear axle 14 is calculated, and the steering angle of the rear axle 1 is calculated.
4. Read the actual steering angle. Then, the calculated value is compared with the actual steering angle, and if the calculated value is larger, the rear axle 14 is further steered, whereas if the calculated value is smaller, the rear axle 14 is further steered. I'm trying to get it back. Therefore, by such control, the rear-front shaft 13 and the rear-rear shaft 14
are steered to steering angles corresponding to vehicle speed.

Furthermore, this rear axle steering system maintains constant steering stability by steering the two rear axles in response to changes in vehicle speed and load. This operation is performed based on the flowchart shown in FIG. The microcomputer 47 reads the steering angle of the steering wheel 48 and calculates a standard yaw rate according to this steering angle. Furthermore, the microcomputer 47 reads the yaw rate, that is, the angular velocity of yawing, using the yaw rate sensor 51. This actual yaw rate is then compared with the standard yaw rate, and if the actual yaw rate is outside the range of the standard yaw rate, the rear-front axle 13 and the rear-rear axle 14 are controlled by hydraulic cylinders 37 provided on the torque rods 26 and 27, respectively. Steering corrections are made by extending and contracting and turning.

In addition, instead of steering correction using yaw rate,
It is also possible to perform steering correction based on the detection of lateral acceleration as shown in the flowchart shown in the figure. In this case, the steering angle of the steering handle 48 is read by the steering angle sensor 49, and the reference 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 is outside the standard lateral acceleration range, the torque rods 26 and 27 are connected to the hydraulic cylinder 3.
7 to expand and contract the rear-front axis 13 and the rear-rear axis 1.
Perform steering correction by turning in step 4.

Generally, the yaw rate or lateral acceleration of a vehicle changes depending on the vehicle speed. In addition, the steering stability changes depending on the position of the cargo, and furthermore, the vehicle receives lateral forces due to external disturbances such as crosswinds and road slopes, which changes the steering stability. It turns out. However, such changes in steering stability can be corrected by independently steering the rear-front axle 13 and the rear-rear shaft 14 using the devices shown in FIG. 1, thereby maintaining a constant level of steering stability. becomes possible.
Therefore, such a vehicle can improve maneuverability, especially at medium and high speeds. Furthermore, by steering the rear two axes in this manner, the minimum turning radius can be reduced, and the difference between the inner and outer wheels can be reduced.
Also, it becomes possible to reduce the wear of the tires on the rear axle 14.

Although the present invention has been described above with reference to an illustrated embodiment,
The present invention is not limited to the above embodiments, and various modifications can be made based on the technical idea of the present invention. For example, the above embodiment relates to a rear axle steering system for a bus in which both rear axles are suspended by air suspension devices, but the present invention is also applicable to a bus with an air suspension system having only one rear axle. be. Furthermore, it is also applicable to rear axle steering devices of vehicles other than buses.

Effects of the Invention As described above, the present invention suspends the rear axle using an air spring, connects both sides of the rear axle to the vehicle body via a pair of lower or upper torque rods, and The pair of torque rods connected on both sides are provided with hydraulic cylinders to make them expandable and retractable, and the upper or lower pair of torque rods are arranged in a substantially V-shape, with one end placed at approximately the center in the width direction of the vehicle. It is connected to the rear axle, and the other end is connected to both sides of the vehicle body, and the torque rod to which this hydraulic cylinder is attached is expanded and contracted by a hydraulic cylinder to rotate the rear axle and perform steering. be.

Therefore, by controlling such rear axle steering according to vehicle running conditions and vehicle body conditions, it is possible to always obtain constant steering stability regardless of changes in vehicle speed or the position of the loaded load.

Also, the center of rotation of the rear axle during rear axle steering is the connecting position of the upper or lower pair of torque rods arranged in a substantially V-shape with the rear axle, and is approximately at the center of the rear axle in the width direction of the vehicle. Become a club. Therefore, the rear axle can be turned without causing any lateral displacement, and the pair of torque rods arranged in a V-shape on the upper or lower side, which do not extend or contract, prevent the rear axle from lateral displacement.

Moreover, since the V-shaped torque rods on the upper or lower side are connected to the rear axle at approximately the center in the width direction of the vehicle, the pair of torque rods on the upper or lower side that do not extend or contract are There is no resistance when turning, which makes it possible to steer the rear axle with a small steering force, and no large load is placed on the hydraulic cylinder incorporated in the lower or upper torque rod.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a structure for extending and retracting the torque rod of a rear axle steering device according to an embodiment of the present invention, FIG. 2 is a plan view of a bus equipped with this rear axle steering device, and FIG. 3 is the same. 4 is a plan view showing the suspension device of the rear axle of this bus, FIG. 5 is a side view of the same, and FIGS. 6 to 8 are flowcharts showing the operation of the rear axle steering device. . In addition, in the symbols used in the drawings, 10... Vehicle body, 13... Rear shaft (drive shaft), 14... Rear shaft (driven shaft, dead shaft), 21, 22, 23... Air spring, 24, 25 ...Torkurod, 26,2
7...Torque rod, 33, 34...Connection part, 3
5... Piston rod, 36... Piston, 37
...Hydraulic cylinder, 38...Switching valve, 39...
Oil pump, 46... Actuator, 47...
... microcomputer, 49 ... steering angle sensor, 50 ... vehicle speed sensor, 51 ... yaw rate sensor, 52 ... lateral acceleration sensor.

Claims (1)

[Scope of Claims] 1. In a vehicle in which a rear axle is suspended by a suspension spring consisting of an air spring, both sides of the rear axle are connected to the vehicle body through a pair of lower or upper torque rods, and Hydraulic cylinders are provided on the pair of torque rods connected to both sides of the rear shaft to make them expandable and retractable, and the upper or lower pair of torque rods are connected to approximately V.
The hydraulic cylinders are arranged in a letter shape, one end of which is connected to the rear axle at approximately the center in the width direction of the vehicle, and the other end of which is connected to both sides of the vehicle body, and the hydraulic cylinder is provided with the hydraulic cylinder. 1. A rear shaft steering device for an automobile, characterized in that the rear shaft is rotated by expanding and contracting a torque rod provided therein.