JPH064423B2 - 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 an automobile, and more particularly to a rear axle steering system for an automobile in which a suspension shaft composed of a leaf spring suspends the rear axle.

SUMMARY OF THE INVENTION According to the present invention, a rear shaft is suspended so as to be slidable in the front-rear direction with respect to a leaf spring that constitutes a suspension spring, and both sides of the rear shaft are connected to a vehicle body through torque rods, respectively. An expansion / contraction connecting means is provided between the torque rod and the vehicle body or between the torque rod and the rear shaft, and the expansion / contraction of the connecting means is controlled by the control means to improve the maneuverability and increase the vehicle speed and load. The control means and the connecting means rotate the rear shaft to carry out steering so as to eliminate the change in the maneuverability depending on the position.

[Prior Art] Conventionally, a truck has been widely used for carrying various kinds of luggage. A suspension device including a leaf spring is widely used as a rear shaft suspension device to which a particularly large load is applied. Such a suspension device has a feature that it has a simple structure, can withstand a large load, and is highly durable.

[Problems to be Solved by the Invention] However, in a conventional truck including such a leaf suspension, the rear shaft is fixedly attached to a suspension spring by a U bolt or the like. Therefore, such a rear axle cannot turn, and the wheels attached to this axle 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 improve and maintain such maneuverability, it is preferable that the rear shaft can be steered. It is 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 a change in vehicle speed, the position of a load, etc. It is an object of the present invention to provide a rear-axle steering device for a vehicle, which is designed to obtain good properties.

[Means for Solving the Problems] The present invention provides a vehicle in which a suspension spring rear shaft composed of a leaf spring is suspended so as to be slidable in the front-rear direction with respect to the leaf spring by a low-friction sliding seat. Connecting means for suspending the rear shaft, connecting both sides of the rear shaft to the vehicle body via torque rods, and extending and contracting between the torque rod and the vehicle body or between the torque rod and the rear shaft. And a control means for controlling the expansion and contraction of the connecting means, and the control means expands and contracts the connecting means to pivot the rear shaft for steering. The present invention relates to a steering device.

[Operation] When the connecting means is expanded and contracted by the control means, both ends of the rear shaft are slid in the front-rear direction with respect to the leaf springs via the low-friction sliding seats, and the rear shaft is turned to perform steering.

[Example] The present invention will be described below with reference to an illustrated example. 2 and 3 show a truck equipped with a rear axle steering device according to an embodiment of the present invention. The truck is provided with a pair of left and right frames 10 that form the framework of the truck. A cab 11 is supported on the front end side of the. 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 shaft 13. The rear shaft 13 is composed of a drive shaft and is driven by the engine.

Next, the structure of the suspension of the rear shaft 13 composed of this drive shaft will be described. As shown in FIGS. 4 and 5, the rear shaft 13 is suspended by a suspension spring composed of a leaf spring 20. . The leaf spring 20 is supported at its front end by a center pin 22 of a front bracket 21 attached to the frame 10. On the other hand, the rear end of the leaf spring 20 is supported by the shackle 23. The shackle 23 is rotatably supported by the rear bracket 24.

The rear shaft 13 is provided on the lower surface of the leaf spring 20,
It is configured to be slidably suspended in the front-rear direction via a sliding sheet 25. And this drive shaft 13
The drive shaft 13 is connected to the frame 10 by means of torque rods 26 and 27 at the upper and lower sides in order to transmit the drive force of the drive shaft 13. The upper torque rod 26 is the rear shaft 1
3 are connected to substantially the center part and are arranged so as to form a V shape with each other, and the front end part is connected to the frame 10. On the other hand, the lower torque rod 2
7 is connected to both sides of the rear shaft 13 and is arranged below the frame 10, and is connected to the frame 10 via a bracket 28.

Next, a description will be given of the torque rod 27 that connects the left and right sides of the axle 13 to the frame 10 on the lower side thereof. As shown in FIG. 1, both ends of the torque rod 27 are composed of connecting portions 33 and 34, respectively. With
The one connecting portion 33 is connected to the piston rod 35 via a bracket. And this piston rod 3
A piston 36 attached to the tip of the piston 5 is slidably supported in a hydraulic cylinder 37. The hydraulic cylinder 37 is connected to a bracket 28 fixed to the frame 10. And this hydraulic cylinder 37
Is connected to the switching valve 38, and the oil pump 39 and the reservoir 4 are connected via the switching valve 38.
It is designed to be connected to 0.

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 is connected to a steering angle sensor 49 that detects the steering angle of the steering handle 48, a vehicle speed sensor 50, a yaw rate sensor 51, and a lateral acceleration sensor 52, respectively.

Next, the steering operation of the rear axle steering device having the above-mentioned configuration will be described. The control signal from the microcomputer 47 shown in FIG. 1 moves the spool of the switching valve 38 via the actuator 46. As a result, 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 cylinder 37 can be expanded and contracted.

Then, one of the pair of left and right hydraulic cylinders 37, for example, the left hydraulic cylinder 37 is lengthened and the right hydraulic cylinder 37 is shortened, so that the hydraulic cylinders 37 are connected via the torque rod 27. It becomes possible to turn the shaft 13 to the right, which causes the rear shaft 13 to be steered. At this time, the rear shaft 13 comes to slide on the lower surface of the sliding seat 25 having low friction. The lateral displacement of the rear shaft 13 is caused by a pair of upper V-shaped torque rods 26.
Will be prevented by.

The control for steering the rear shaft 13 by the microcomputer 47 will be described in more detail. As shown in the flow chart of FIG.
Reads the steering angle of the steering handle 48 by the sensor 49. Next, the vehicle speed is read by the vehicle speed sensor 50, and the steer angle of the rear axle 13 is calculated based on these values. Further, the piston rod 3 of the hydraulic cylinder 37
From the stroke of 5, the stroke sensor 53 reads the steer angle of the rear shaft 13. Then, this actual steer angle is compared with the calculated value. When the calculated value is larger, the rear shaft 13 is further turned and steered. On the other hand, when the calculated value is smaller, the rear shaft 13 is rotated in the returning direction.

Further, in this rear axle steering device, the rear axle 13 is steered in response to changes in vehicle speed and changes in load,
The maneuverability is improved and kept constant. This operation is performed based on the flowchart shown in FIG.
The microcomputer 47 has a steering handle 48.
The steering angle of is read and the standard yaw rate is calculated 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 if the actual yaw rate is out of the range of the reference yaw rate, the hydraulic cylinder 37 connecting the rear shaft 13 to the torque rod 27 is expanded / contracted to turn the steering wheel. Make corrections.

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. When the actual lateral acceleration value is outside the range of the reference lateral acceleration, the steering cylinder is corrected by turning the rear shaft 13 by expanding and contracting by the hydraulic cylinder 37 connected to the torque rod 27.

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 steering the rear shaft 13 by the device shown in FIG. 1, and it becomes possible to maintain a certain maneuverability. Therefore, such a vehicle can improve the maneuverability particularly at medium speed and high speed. Further, such steering of the rear shaft 13 can reduce the minimum turning radius, reduce the difference between the inner ring and the outer ring, and particularly reduce the wear of the tire on the rear shaft 13. Become.

Further, according to the rear axle steering apparatus of the present embodiment, the rear axle 13 to which the rear wheels are attached is turned as a whole, and the front wheels are rotatably supported by the kingpin for steering. It has a different structure from the steering mechanism. That is, by interposing the sliding seat 25 between the rear shaft 13 and the leaf spring 20, the rear shaft 13 can be turned as a whole. Therefore, the rear axle can be steered with a very simple structure, the number of parts for the rear axle is small, the weight hardly increases, and the rear axle steering device is very advantageous in terms of cost. It will be possible.

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. The 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 27. Geared motor 6 mounted on bracket 28
The output shaft of No. 0 is constituted by the 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 27. 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 an instruction from the microcomputer 47, for example, the right connecting means is extended and the left connecting means is contracted. As a result, the rear axle 13 turns to the left while sliding on the sliding seat 25, and the rear axle is steered. 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 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 Although the present invention has been described above with reference to the illustrated embodiment, 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-mentioned embodiment, the expandable and contractable connecting means is arranged between the bracket 28 on the vehicle body side and the torque rod 27, but this connecting means is interposed between the torque rod and the axle. You may do it. The present invention is also applicable to a vehicle in which a rear shaft is suspended by a suspension spring formed by combining a leaf spring and an air spring. For example, the front end or the rear end of the leaf spring 20 may be an air spring. It can also be used in a vehicle that is supported by the frame 10. Further, in the second embodiment described above, the geared motor 60 that drives the feed screw may be replaced with a hydraulic motor.

As described above, according to the present invention, the rear shaft is suspended by the low-friction sliding seat so as to be slidable in the front-rear direction with respect to the leaf spring, and both sides of the rear shaft are attached to the vehicle body through the torque rods. In addition to providing a connecting means which is connected and is expandable between the torque rod and the vehicle body or between the torque rod and the rear shaft, a control means for controlling the expansion and contraction of this connecting means is provided, and the connecting means is expanded and contracted by the control means. Then, the rear axle is turned to perform steering.

Therefore, by extending and contracting the extendable connecting means connected to the torque rod by the control means, both ends of the rear shaft are slid in the front-rear direction with respect to the leaf springs by the low friction sliding seats, which causes the rear shaft to move. It is turned and steering is performed. It is thus possible to achieve rear axle steering with a very simple construction. Moreover, since the rear shaft is slidably suspended with respect to the leaf spring by the low-friction sliding seat, the driving force required for steering can be reduced, and the axle and the leaf spring are prevented from wearing. It will be possible.

[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 truck equipped with the rear axle steering device, and FIG. The figure is a side view of the same, FIG. 4 is a plan view showing a suspension device on the rear side of this truck, FIG. 5 is the same side view, and FIGS.
FIG. 9 is a flow chart showing the operation of the rear axle steering system, and FIG. 9 is a block diagram showing the 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 shaft (driving shaft) 20 ... Leaf spring 25 ... Sliding sheet 27 ... Torque rod 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 63 ... Female screw hole 64 ... Drive circuit

Claims (1)

[Claims] 1. A vehicle in which a rear shaft is suspended by a suspension spring composed of a leaf spring, and the rear shaft is suspended by a low-friction sliding seat so as to be slidable in the front-rear direction with respect to the leaf spring, Both sides of the rear shaft are connected to the vehicle body through torque rods, respectively, and a connecting means that is expandable / contractible is provided between the torque rod and the vehicle body or between the torque rod and the rear shaft. A rear-shaft steering apparatus for a vehicle, comprising: a control means for controlling expansion / contraction, wherein the control means expands / contracts the connecting means to pivot the rear shaft for steering.