JPH0741844B2 - Rear axle steering system for automobiles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear axle steering system for a vehicle, and more particularly to a rear axle for a vehicle in which a rear axle suspended by a suspension spring is turned to perform steering. The present invention relates to a steering device.

[Outline of Invention]

The present invention provides a connecting means that is expandable and contractible between a torque rod and a vehicle body that connects both sides of a rear shaft suspended by an air spring to the vehicle body, or between the torque rod and the rear shaft. By controlling the expansion and contraction of the means by the control means, the rear shaft is turned to perform steering.

[Conventional technology]

Leaf springs have been conventionally used as suspension springs for suspending an axle on a vehicle body. The suspension device composed of leaf springs has a feature that it has a simple structure, can withstand a large load, and is highly durable. However, since such a leaf spring has a large spring constant and is hard, it lacks the effect of isolating vibrations and has a drawback that the riding comfort is deteriorated. In order to solve such a drawback, an air suspension device is used in a vehicle in which ride comfort is particularly important. In such a device, the axle is supported by an air spring, either 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 cannot steer its wheels. However, the maneuverability of the vehicle changes depending on the vehicle speed. Alternatively, the maneuverability changes depending on the position of the load. Therefore, in order to make such maneuverability constant, it is preferable that the rear shaft can be steered. It is also known that by steering the rear axle, it is possible to reduce the minimum turning radius, reduce the difference between the inner and outer wheels, or reduce the wear of the tire.

The present invention has been made in view of the above problems, and improves the maneuverability, prevents the maneuverability from changing due to changes in the vehicle speed, the position of the load, etc. An object of the present invention is to provide a rear-axle steering system for an automobile, which is designed to be safe.

[Means for solving problems]

According to the present invention, both sides of a rear shaft suspended by a suspension spring are connected to a vehicle body via a torque rod, respectively, and can be expanded and contracted between the torque rod and the vehicle body or between the torque rod and the rear shaft. A common control means for expanding and contracting the left and right connecting means is provided so that the expansion and contraction of the left and right connecting means are in opposite phases, and the control means causes the left and right connecting means to be in opposite phase to each other. The present invention relates to a rear-axle steering system for a vehicle, wherein the rear-axle is steered so that the rear axle is turned to perform steering.

[Action]

When the left and right connecting means are controlled by the control means so that the expansion and contraction of the left and right connecting means are in mutually opposite phases, the control means is provided between the torque rod and the vehicle body or between the torque rod and the rear shaft. The left and right expandable and contractable connecting means are expanded and contracted so as to have opposite phases, and the rear shaft is turned to perform steering.

〔Example〕

The present invention will be described below with reference to the illustrated embodiments. 2 and 3 show a bus equipped with a rear axle steering system according to a first embodiment of the present invention. The bus is equipped with a vehicle body 10, and the vehicle body 10 is, for example, as shown in FIG. And the fifth
It is designed to be supported by a skeleton composed of a frame 11 as shown in the figure. The front end side of the vehicle body 10 is supported by the front axle 12, and the rear side of the body 10 is the rear front axle.
It is supported by 13 and a rear rear shaft 14.
Here, the rear front shaft 13 constitutes a drive shaft, and its wheels are double tires. On the other hand, rear rear axle 14
Has a driven shaft or a dead shaft, and its wheels are composed of a single tire.

Next, the structure of the suspension of the rear biaxes 13 and 14 will be described. As shown in FIGS. 4 and 5, the rear two shafts are supported by an air suspension device. That is, both ends of the rear front shaft 13 are supported by the support beams 20 provided on the left and right, respectively, and the left and right support beams 20 are suspended on the frame 11 by the front air spring 21 and the rear air spring 22, respectively. It has become so. On the other hand, the rear rear shaft 14 is suspended via the air spring 23 directly attached to the frame 11.

A pair of torque rods 24 are connected to the upper side of the rear front shaft 13. These torque rods 24 are arranged in a V shape, and their tip ends are connected to the frame 11. A pair of V-shaped torque rods are also arranged on the upper side of the rear rear shaft 14.
25 are connected, and these torque rods 25 are connected to the frame 11. Further, the rear front shaft 13 is provided with a pair of left and right torque rods 26 on its lower surface, and these torque rods 26 are connected to the frame 28. Similarly, for the rear rear shaft 14, the lower torque rod
It is adapted to be connected to the frame 28 by 27.

Next, the torque rods 26 and 27, which are connected to the frame 28 on the left and right sides of the lower sides of the axles 13 and 14, will be described. As shown in FIG.
Both ends of each are composed of connecting portions 33 and 34, respectively, and the piston rod 35 is connected to one connecting portion 33.
Connected through 32. And this piston rod
A piston 36 attached to the tip of 35 is slidably supported in a hydraulic cylinder 37. The hydraulic cylinder 37 is connected to the frame 28. The hydraulic cylinder 37 is connected to a switching valve 38. By switching the switching valve 38, oil is supplied from an oil pump 39, or another hydraulic cylinder is used.
It is designed to return oil from 37 to reservoir 40.

An actuator 46 for switching the spool of the switching valve 38 is controlled by a microcomputer 47. The input side of the microcomputer 47 has 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,
The lateral acceleration sensor 52 and the stroke sensor 53 are respectively connected.

Next, the steering operation of the rear axle steering device having the above-described configuration will be described. The actuator 46 is controlled by the control signal from the microcomputer 47 shown in FIG.
By moving the spool of the switching valve 38 via the, the oil pressurized by the oil pump 39 can be supplied to the front chamber or the rear chamber of the piston 36 of the hydraulic cylinder 37, whereby the torque rods 26, 27 Can be moved back and forth. Then, one of the pair of left and right torque rods 26, for example, by moving the left torque rod 26 rearward and moving the right torque rod 26 forward, the axle 13 to which these torque rods 26 are connected is moved. It is possible to turn to the right,
As a result, the rear axle is steered. In this embodiment, the rear front shaft 13 and the rear rear shaft 14 are independently steered.

The control for the steering of the two axes by the microcomputer 47 will be described in detail below. As shown in the flowchart of FIG. 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. Furthermore, 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 of the two rear axles is performed in response to changes in vehicle speed and changes in load, thereby improving maneuverability and maintaining constant maneuverability. 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 uses the yaw rate sensor 51 to control the yaw rate,
That is, the yaw angular velocity is read. Then, this actual yaw rate is compared with the reference yaw rate, and if the actual yaw rate is outside the range of the reference yaw rate, the rear front shaft 13 and the rear rear shaft 14 are connected to the hydraulic cylinders 37 connected to the torque rods 26 and 27, respectively. Steering is corrected by expanding and contracting and turning.

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
The front and rear axles are made by expanding and contracting the hydraulic cylinder 37 connected to 26 and 27.
Steering correction is performed by turning 13 and rear-rear axle 14.

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 devices 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, it is possible to reduce the minimum turning radius, and it is possible to reduce the inner ring difference and the outer ring difference, and in particular, wear of the tires of the rear front shaft 13 and the rear rear shaft 14 is prevented. It can be reduced.

Further, according to the rear axle steering apparatus according to the present embodiment, the rear two axles 13 and 14 to which the rear wheels are attached are turned as a whole, and the rear wheels are rotatably supported by the kingpin and steered. It has a different structure from the steering mechanism for the front wheels. That is, the rear front axis 13 and the rear rear axis 14
The rear front shaft 13 and the rear rear shaft 14 can be pivoted as a whole by supporting the air spring 23 or the air spring 23 so as to be displaceable in the front-rear direction. Therefore, the rear two-axle steering can be carried out with a very simple structure, the number of parts for that is small, the weight hardly increases, and the rear-axle steering device is constructed very advantageously in terms of cost. It becomes possible to do.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, the parts corresponding to those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description of the parts having the same configuration is omitted. A feature of the second embodiment is that a geared motor 60 and a feed screw 61 are used as an expandable / contractible connecting means for connecting the bracket 28 on the vehicle body side and the torque rod 26. The output shaft of the geared motor 60 attached to the bracket 28 is configured as a feed screw 61, and is engaged with the female screw hole 63 of the bracket 62 attached to the connecting portion 33 of the torque rod 26. The geared motor 60 is driven by a drive circuit 64 controlled by the microcomputer 47. Also in this embodiment, the left and right geared motors 60 are connected to the drive circuit 64 so as to rotate in opposite directions.

Therefore, by driving each of the left and right geared motors 60 via the drive circuit 64 based on the instruction of the microcomputer 47, for example, the right side connecting means is extended and the left side connecting means is contracted. As a result, the rear front shaft 13 turns to the right, and rear shaft steering is performed. Therefore, even with such an embodiment, it is possible to obtain the same effects as the above embodiment. Further, according to this embodiment, since the rear front shaft 13 can be steered only by driving the geared motor 60 by the drive circuit 64, it is not necessary to mount a means for generating hydraulic pressure on the vehicle.

[Application example]

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 bracket 28 and the torque rod on the vehicle body side
Although a connecting means which can be expanded and contracted is provided between the torque rod and the wheel 26, the connecting means may be interposed between the torque rod and the axle. The present invention is also applicable to a vehicle in which a rear shaft is suspended by a suspension spring composed of a combination of a leaf spring and an air spring. For example, the front end portion or the rear end portion of the leaf spring is formed by the air spring. It can also be used in a vehicle that is supported by a frame. In the second embodiment, the geared motor 60 that drives the feed screw can be replaced with a hydraulic motor.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, according to the present invention, both sides of the rear shaft suspended by the suspension springs are connected to the vehicle body via the torque rods respectively, and can be expanded and contracted between the torque rod and the vehicle body or between the torque rod and the rear shaft. And a common control means for expanding and contracting the left and right connecting means such that the expansion and contraction of the left and right connecting means are in opposite phases.
The left and right connecting means are expanded and contracted by the control means so that they are in opposite phases to each other, and the rear axle is turned to perform steering.

Therefore, the rear shaft is pivoted by providing expandable and contractible connecting means between the left and right torque rods and the vehicle body or between the torque rod and the rear shaft, and controlling such connecting means by common control means. Steering will be performed. By such rear axle steering, it is possible to suppress a change in maneuverability or reduce the minimum turning radius, reduce the difference between the inner and outer wheels, and reduce the wear of the tire.

Particularly, according to the present invention, since the left and right connecting means are expanded and contracted by the common control means so that the expansion and contraction of the left and right connecting means are in mutually opposite phases, the control device can be commonly used for the left and right. This makes it possible to simplify the control device. Therefore, it is possible to provide a rear-axle steering system for an automobile that is low in cost and has a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a structure for expanding and contracting a connecting means of a rear axle steering device according to a first embodiment of the present invention, and FIG. 2 is a plan view of a bus equipped with the rear axle steering device. The figure is a side view of the same, FIG. 4 is a plan view showing a suspension device on the rear side of the bus, FIG. 5 is a side view of the same, and FIGS. 6 to 8 are flow charts showing the operation of the rear axle steering device. FIG. 9 is a block diagram showing a structure for expanding and contracting the connecting means of the rear axle steering system according to the second embodiment. In the reference numerals used in the drawings, 10 ... frame 13 ... rear front shaft (driving shaft) 14 ... rear rear shaft (driven shaft) 21-23..air springs 26, 27 ... torque rod 28..frame 35 …… Piston rod 36 …… Piston 37 …… Hydraulic cylinder 38 …… Switching valve 39 …… Oil pump 46 …… Actuator 47 …… Microcomputer 49 …… Steering sensor 50 …… Vehicle speed sensor 51 …… Yaw rate sensor 52 ...... Lateral acceleration sensor 60 ...... Geared motor 61 ...... Feed screw 62 ...... Connection arm 63 ...... Female screw hole 64 ...... Drive circuit.

Claims (1)

[Claims] 1. A rear shaft suspended by a suspension spring is connected to a vehicle body through torque rods on both sides, and is expanded and contracted between the torque rod and the vehicle body or between the torque rod and the rear shaft. In addition to providing possible connecting means, a common control means for expanding and contracting the left and right connecting means is provided so that expansion and contraction of the left and right connecting means are in opposite phases, and the left and right connecting means are in opposite phase by the control means. A rear axle steering system for an automobile, wherein the rear axle is steered so that the rear axle is swung to perform steering.