JPS6280164A - Rear axle steering device for automobile - Google Patents

Abstract

PURPOSE:To make possible to steer a rear axle with a simple arrangement, by forming fluid chambers in rubber bushings provided in both end couplings of a torque rod which supports a longitudinally movable rear axle so that the effective length between the couplings are changed by feeding and discharging fluid to and from these fluid chambers. CONSTITUTION:In a rear axle steering device in which the rear axle of a vehicle such as a truck or the like, is suspended by means of a suspension spring composed of leaf springs, the rear axle is suspended slidably in the longitudinal direction, and both ends of the rear axle are coupled to a vehicle body through the intermediary of torque rods 27, respectively. Rubber bushings 35 are fitted in right-like couplings 33, 34 formed at both ends of each torque rod 27, and connecting pins 37 are oscillatably supported in the center sections of the bushings 35. Further, a pair of hydraulic chambers 41, 42 are formed in each rubber bushing 35 at a position on an axial extension of the torque rod 27, and pressure oil is fed to or discharged from the chambers 41, 42 through a change-over valve 33 so that the effective length L between the couplings 33, 34 are changed to steer the rear axle.

Description

[Detailed description of the invention]

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 rear axle is suspended by a suspension spring made of a leaf spring.

[Summary of the invention]

In the present invention, a rear axle is suspended so as to be movable in the front-rear direction with respect to a leaf spring that constitutes a suspension spring, and both sides of the rear axle are connected to the vehicle body via torque rods.
Furthermore, by providing a fluid chamber in at least one rubber bushing of the connecting portions at both ends of the torque rod connected to both sides of the rear shaft, and supplying fluid to this fluid chamber or discharging fluid from this fluid chamber, By changing the effective length between the connecting parts at both ends, the rear axle can be turned to perform steering. K. Prior Art Σ Trucks have been widely used in the past to transport various types of cargo. As suspension devices for rear axles that are subject to particularly large loads, suspension devices made of leaf springs are widely used. Such a suspension device 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 having such a leaf suspension, the rear axle is fixed to the suspension spring using 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 a vehicle changes depending on the vehicle speed. Alternatively, the maneuverability changes depending on the position of the cargo. Therefore, in order to keep such steering stability constant, it is preferable to make the rear axle steerable. 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 tire wear. The present invention has been made in view of these problems, and is an automobile that prevents changes in steering stability due to changes in vehicle speed, the position of the loaded load, etc., and achieves a certain level of steering stability. The object of the present invention is to provide a rear axle steering device. Means for Solving Problem K] The present invention provides a vehicle in which a rear axle is suspended by a suspension spring consisting of a leaf spring, in which the rear axle is suspended so as to be slidable in the longitudinal direction with respect to the leaf spring. Both sides of the rear axle are connected to the vehicle body via torque rods, and a fluid chamber is provided in at least one rubber bushing of the connecting portions at both ends of the torque rods connected to both sides of the rear axle. By supplying or discharging fluid into the fluid chamber, the effective length between the connecting portions at both ends is changed, thereby turning the rear shaft to perform steering.

[effect] Therefore, according to the present invention, when the steering stability is about to change due to a change in vehicle speed or a change in the position of the live load, fluid is supplied to the fluid chamber provided in the rubber bush of the torque rod so as to counteract this change. Alternatively, fluid may be drained from this fluid chamber, thereby changing the effective length between the connections at the ends of the torque rod. Therefore, the rear axle is turned to perform steering, and the steering stability is maintained constant. K Example]

The present invention will be explained below with reference to an illustrated embodiment. 2 and 3 show a truck equipped with a rear axle steering device according to an embodiment of the present invention, and this truck is equipped with a pair of left and right frames 10 constituting its framework. A cab 11 is supported on the front end side. The front end of the frame 10 is supported by a front shaft 12, and the rear end is supported by a rear shaft 13. Note that the rear shaft 1.3 is composed of a drive shaft and is driven by an engine. Next, the structure of the suspension of the rear axle 13, which is the drive shaft, will be explained. As shown in FIGS. 4 and 5, the rear axle 13 is suspended by a suspension spring consisting of a leaf spring 20. . The front end of the leaf spring 20 is supported by a center pin 22 of a front bracket 21 attached to the frame 10. On the other hand, leaf spring 20
The rear end portion of is supported by a shackle 23. The cisicle 23 is rotatably supported by the rear bracket 1-24. The rear shaft 13 is attached to the lower surface of the leaf spring 20,
It is suspended so as to be slidable in the front-rear direction via a sliding seat 25. In order to transmit the driving force of the drive shaft 13, the drive shaft 13 is connected to the frame 10 at its upper and lower ends by torque rods 26 and 27. The upper torque rods 26 are connected to approximately the center of the rear shaft 13, and are arranged in a V-shape with each other, with the front ends connected to the frame 10. On the other hand, the lower torque rod 27 is connected to both sides of the rear axle 13 and disposed below the frame 10, and is connected to the frame 10 via a bracket 28. . The torque rods 27 that are located at both ends of the rear axle 13 and connect them to the vehicle body will be explained in more detail.
As shown in FIG. 1, ring-shaped connecting portions 33 and 34 are formed at both ends of the torque rod 27, respectively. These connections 33, 34 have circular openings in their centers and receive rubber bushings 35. A joint ring 36 is supported on the center side of the rubber bush 35, and supports the connecting pin 37 so as to be swingable. Inside the rubber bush 35, a pair of hydraulic chambers 41 and 42 are provided symmetrically with respect to the center at positions on the axial extension of the torque rod 27. These hydraulic chambers 41, 42 are connected to the switching valve 38 via an oil conduit. The switching valve 38 is further connected to an oil pump 39 and a 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 is connected to a steering angle sensor 49 that detects the steering angle of the steering wheel 48, a vehicle speed sensor 50, a yaw rate sensor 51, a lateral acceleration sensor 52, and a stroke sensor 53. There is. In the above configuration, the torque rod 27 that connects the rear shaft 13 to the frame 10 via the brackets 28 at both ends thereof has hydraulic rods connected to the left and right connecting portions 33 and 34, respectively, as shown in FIG. 41.42 are provided. Therefore, when pressurized oil is supplied to the hydraulic chambers 41 of the left connecting portion 33 and the hydraulic chambers 41 of the right connecting portion 34, and oil is discharged from the hydraulic chambers 42 of the connecting portions 33 and 34, respectively, the connecting The joint rings 3G engaged with the pin 37 move away from each other, thereby increasing the distance between the centers of the connecting portions 33, 34, and causing the torque rods 26, 27 to extend. Become. On the other hand, by supplying oil into the hydraulic chamber 42 of the connecting part 33.34 and discharging oil from the other hydraulic chamber 41, the connecting part 33.
34 becomes shorter. By lengthening one of the pair of left and right torque rods, for example, by lengthening the left torque rod 27 and shortening the right torque rod 27, the axle to which these one torque rod is connected can be turned to the right. This allows the rear axle 13 to be steered. Note that at this time, the rear shaft 13 comes to slide on the lower surface of the sliding seat 25. Lateral displacement of the rear shaft 13 is prevented by the upper pair of torque rods 26 arranged in a V-shape. To explain in more detail the control for steering the rear axle 13 by the microcomputer 47, as shown in the flowchart shown in FIG.
The steering angle of the steering wheel 48 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 axle 13 is calculated based on these values. Furthermore, the stroke sensor 53 detects the rear shaft 1.
Read the steer angle of 3. And this actual steering angle is i
Compare with the tc7 value. If the calculated value is larger,
The rear shaft 13 is further turned and steered. On the other hand, if the word 0 value is smaller, the rear shaft 13 is rotated in the returning direction. Furthermore, this rear axle steering system maintains constant steering stability by steering the rear axle 13 in response to changes in vehicle speed and load. This action is the seventh
The process is carried out based on the flowchart shown in the figure. 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
A yaw rate sensor 51 reads the yaw rate, that is, the yaw angular velocity. Then, this actual yaw rate is compared with the standard yaw rate, and if the actual yaw rate is outside the standard yaw rate, the rear axle 13 is rotated by expanding or contracting the hydraulic chambers 41 and 42 provided in the torque rod 27. Steering correction is performed by Note that instead of the steering correction based on the yaw rate, it is also possible to perform the steering correction based on the detection of lateral acceleration as shown in the flowchart shown in FIG. In this case, the steering angle of the steering wheel 48 is read by the steering angle sensor 49, and the l-range 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 and the actual lateral acceleration are compared. If the actual lateral acceleration value is outside the range of the standard lateral acceleration, the distance between the connecting portions 33 and 34 of the torque rod 27 is changed to correct the steering by turning the rear axle 13. Generally, the yaw rate or lateral acceleration of a vehicle changes depending on the vehicle speed. Furthermore, the steering stability changes depending on the position of the cargo, and furthermore, the vehicle receives lateral forces due to external disturbances such as cross winds and road slopes, which causes the steering stability to change. However, such changes in steering stability can be corrected by steering the rear axle 13 using the device shown in FIG. 1, making it possible to maintain a constant level of steering stability. Therefore, such a vehicle can improve maneuverability especially at medium and high speeds. Further, by steering the rear axle in this manner, the minimum turning radius can be reduced, the difference between the inner and outer wheels can be reduced, and the wear of the tires on the rear axle 13 in particular can be reduced. . 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 embodiment, the connecting portions 33 at both ends of the torque rod 27
．． Although the hydraulic chambers 41 and 42 are provided in each of the connecting portions 33 and 34, the hydraulic chambers 41 and 42 may be provided in either one of the connecting portions 33 or 34. This reduces the change in the effective length between the connecting portions 33 and 34 to half that of the above embodiment, but such a configuration can also be used if the steering angle is small. Further, in the above embodiment, the rear end of the leaf spring 20 is supported by the frame 10 via the shackle 23, but the rear end of the leaf spring 20 may also be supported by the frame 10 via an air spring. good. [Effects of the Invention] As described above, the present invention provides a fluid seedling in at least one rubber bushing of the connecting portions at both ends of a torque rod,
By supplying or discharging fluid to or from the fluid chamber, the effective length between the connecting portions at both ends is changed, thereby turning the rear shaft to perform steering. Therefore, according to the present invention, rear axle steering is possible with a simple configuration,
This makes it possible to perform automatic corrective steering in response to vehicle speed, cargo position, or external disturbances. Further, such rear axle steering makes it possible to reduce the minimum turning radius, reduce the difference between the inner and outer wheels, and reduce the amount of tire wear.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a structure for changing the effective length of the connecting portion of the torque rod of a rear axle steering device according to an embodiment of the present invention, and FIG. 2 is a plan view of a truck equipped with the rear axle steering device. , Fig. 3 is a side view of the same, Fig. 4 is a plan view showing the rear axle suspension device of this truck, Fig. 5 is a side view of the same, and Figs. 6 to 8 show the first year of rear axle steering. FIG. In addition, in the symbols used in the drawings, 10...Frame 13...Rear shaft (drive shaft) 20...Leaf spring 25...Sliding seat 27...Torque rod 33.34...Connection part 35 ... Rubber bush 36 ... Joint ring 37 ... Connection bin 38 ... Three switching valves ... Oil pump 41.42 ... Hydraulic chamber 46 ... Actuator 47 ... Microcomputer 49 ... Steering angle sensor 50 ... Vehicle speed sensor 51 ... Yaw rate sensor 52 ... Lateral acceleration sensor.

Claims (1)

[Claims] In a vehicle in which a rear axle is suspended by a suspension spring consisting of a leaf spring, the rear axle is suspended so as to be slidable in a longitudinal direction relative to the leaf spring, and both sides of the rear axle are connected via torque rods. A fluid chamber is provided in at least one rubber bush of the connecting portions at both ends of the torque rod connected to the vehicle body and connected to both sides of the rear axle, and both ends are fixed by supplying or discharging fluid into the fluid chamber. A rear shaft steering device for an automobile, characterized in that the effective length between the connecting portions of the vehicle is changed, thereby turning the rear shaft to perform steering.