JPS6280162A - Rear axle steering device for automobile having two rear axles - Google Patents

Abstract

PURPOSE:To obtain an always constant stability in steering operation irrespective of variations in vehicle speed and variations in the position of a loaded burden, by carrying out steering operation in such a way that front rear and rear rear axles are turned by means of a control means and hydraulic cylinders in order to steer the vehicle. CONSTITUTION:A spool in a change-over valve 38 is displaced by means of an actuator 46 in accordance with a control signal from a microcomputer 47, and therefore, oil pressurized by an oil pump 39 is fed into the front or rear chamber 36 defined by a piston 36 in a hydraulic cylinder 37 so that torque rods 27 are extended and retracted. Of a pair of right and left side torque rods 27, for example, the left side torque rod 27 is made to be longer while the right side torque rod 27 is made to be short to turn rear axles 13 coupled with the torque rods 27 rightward to carry out steering operation of the rear axles. With this arrangement it is possible to obtain an always constant stability in steering operation irrespective of variations in vehicle speed and variations in loaded burden.

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 a vehicle with two rear axles, and more particularly to a rear axle steering system for two rear axles in which two axles are suspended by a trunnion suspension system. [Summary of the Invention] The present invention provides a hydraulic cylinder that is connected to both sides of a rear-front shaft and a rear-rear shaft so as to be extendable and retractable, and to control the supply and discharge of oil to the hydraulic cylinder. The control means and the hydraulic cylinder rotate the rear and rear axles to perform steering so as to eliminate changes in steering stability. K. Prior Art] Trucks have been widely used in the past to transport various types of cargo. As the load on the truck increases, the load applied to the rear axle in particular increases. In order to reduce the load applied to one axle, trucks with large payloads are now adopting a structure with two rear axles. Trunnion suspension systems are widely used to distribute the load to each of the two rear axles. [Problems to be Solved by the Invention] However, in conventional trucks, both the rear front axle and the rear axle, which constitute the two rear axles, are configured so that they cannot turn, and the It was not possible to steer the wheels. 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 maintain stable handling, 1.2
Preferably, the axes are each steerable. It is known that by making both the rear two axles steerable, 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 designed to prevent changes in steering stability due to changes in vehicle speed, the position of the live load, etc., and to obtain a certain level of steering stability. 2
The object of the present invention is to provide a rear shaft steering device for an axle. Means for Solving Problem K] The present invention suspends a rear front axle and a rear rear axle by the filj OW group and the rear end of a leaf spring supported via a trunnion bracket, and In a vehicle in which a rear front axle and both sides of the rear and rear axles are respectively connected to the Φ body via torque rods, a hydraulic cylinder is connected to the 1 to 1 rods connected to both sides of the rear and front axles and the rear and rear axles. The hydraulic cylinder is provided with a control means that controls the supply and discharge of oil to the hydraulic cylinder, and the control means and the hydraulic cylinder control the rear and front axles and the rear shaft so as to eliminate changes in steering stability. Steering is performed by rotating the rear axle.

[Effect]

Therefore, according to the present invention, when the steering stability changes due to a change in vehicle speed or a change in the position of the live load, the control means operates the hydraulic cylinder to counteract this change, expands and contracts the torque rod, and The rear and rear axles are turned respectively, and these two rear axles are steered to maintain constant steering stability.

【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 side of the frame 10 is supported by a front shaft 12, and the rear side is supported by a rear-front shaft 13 and a rear-rear shaft 14. Note that here, the rear-front shaft 13 constitutes a drive shaft, and the rear (ν-axis 14
constitutes the driven axis or ratio axis. Next, to explain the structure of the suspension of these two rear axles 13 and 14, as shown in FIGS. 4 and 5, trunnion brackets 20 are fixed to each of the left and right frames 10, and these trunnions The bracket 20 allows the trunnion shaft 21 to be mounted perpendicularly to the frame 10. A spring seat (22) is rotatably attached to both ends of this trunnion shaft 21.Furthermore, this spring seat 22 supports a leaf spring 23 constituting a suspension spring.
It is supported via bolts 24. The rear-front shaft 13 is suspended from the rear end of the leaf spring 23 supported in this way, and the II shaft 14 is suspended from the rear end. and rear axis 1
The upper central parts of 3 are connected to each other by V as shown in FIG.
It is connected to a cross member 28 that connects the left and right frames 10 by a pair of torque rods 25 arranged in a letter shape. On the other hand, both sides of the rear and front axle 13 are connected to trunnion brackets 20 through lower torque rods 26 and 27, respectively.
It is now connected to The upper center of the rear shaft 14 is also connected to the cross member 28 by a torque rod 25, and the lower side and both sides of the rear shaft 14 are connected to the trunnion bracket 2O by left and right torque rods 26 and 27. It has become so. Next, the torque rods 26 and 27 that are connected to the trunnion brackets 20 on the left and right sides of the lower side of the axle 13 and 14 will be explained. As shown in FIG. 1, both ends of the torque rods 26 and 27 are Consisting of connecting portions 33 and 34, one connecting portion 33
A piston rod 35 is fixed to the. A piston 36 attached to the tip of the piston rod 35 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 communicated with a switching valve 38, and by switching the switching valve 38, oil is supplied from the oil pump 39, or oil is supplied from the hydraulic cylinder 37 to the reservoir 4.
It is designed to return oil to 0. An actuator 46 for switching the spool of the switching valve 38 is controlled by a microcomputer 47. And this micro combination”-
The input side of the steering wheel 47 is connected to a steering angle sensor 49 for detecting the steering angle of the steering wheel 48, a medium speed sensor 50, a yaw rate sensor 51, and a lateral acceleration sensor 52, respectively. Next, we will explain the steering operation of this rear axle steering system configured as described above.The spool of the switching valve 38 is moved via the actuator 46 by the control a Nobunori from the microcomputer 47 shown in FIG. By doing so, the oil pressurized by the oil pump 39 can be supplied to the front or rear chamber of the piston 36 of the oil L cylinder 37, and thereby the torque rod 2
6.27 can be expanded and contracted. Then, by lengthening one of the pair of left and right torque rods 26, 27, for example, the left torque rod 26 and shortening the right torque rod 27, the axle to which these torque rods 26, 27 are connected is moved to the right side. This makes it possible to turn the vehicle around, thereby steering the rear axle. The lateral deviation of the rear-front shaft 13 and the rear-rear shaft 14 is determined by the upper pair of torque rods 2 arranged in a V-shape.
5 will be prevented. Also, in this example, J
3, the rear-front axis 13. and the rear axle 14 are each independently steered. To explain in more detail the control for the subsequent two-axis steering by the microcomputer 47, as shown in the flowchart shown in FIG. . Next, the vehicle speed is read by the vehicle speed sensor 50, and based on these values, the steering angle of the η-axis 13 is calculated. 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 total n value. If the calculated value is larger, the rear-front axis 13
Turn further and steer. On the other hand, if the g1 calculated value is smaller, the rear-front shaft 13 is returned to its original state. The microcomputer 47 also performs such control for the rear shaft 14. In other words, the steering angle of the rear axle] 4 is measured, and the actual steer angle of the rear axle 14 is read. Then, the calculated value and the actual steering angle are compared, and if the total f1 value is better, the rear axle 14 is further steered, and if the calculated value is smaller, the rear axle 14 is further steered. The shaft 14 is returned to its original position. Therefore, by such control, the rear-front axle 13 and the rear-rear axle 14 are respectively steered to steering angles corresponding to the 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. Further, the microcomputer 47 reads the yaw rate, that is, the angular velocity of the yaw ink using the yaw rate sensor 51. Then, this actual yaw rate is compared with the standard yaw rate, and if the actual yaw rate is outside the standard yaw rate i~, the rear-front axle 13 and the rear-rear shaft 14 are respectively moved to the torque rod 26.
Steering correction is performed by extending and contracting a hydraulic cylinder 37 provided at 27 and turning it. 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 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 and the actual lateral acceleration are compared. If the actual lateral acceleration value exists outside the range of the standard lateral acceleration, the torque rods 26, 27 are expanded and contracted by the hydraulic cylinder 37 to correct the steering by turning the rear-front shaft 13 and the rear-rear shaft 14. Generally, the El-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 cross winds and road slopes, which changes the steering stability. However, such a change in steering stability occurs when the rear-front axis 13 and the rear-rear axis 14 are
This is corrected by independent steering using the device shown in the figure, making it possible to maintain constant steering stability. Therefore, such a vehicle can improve maneuverability especially at medium and high speeds. Furthermore, such steering of the rear two axles makes it possible to reduce the minimum turning radius and the difference between the inner and outer wheels. It becomes possible to reduce the Effects of the Invention 1 As described above, the present invention provides hydraulic cylinders to the torque rods connected to both sides of the rear-front axle and the rear-rear shaft to make them extendable and retractable, as well as supplying and discharging oil to and from the hydraulic cylinders. In order to eliminate changes in steering stability, the control means and hydraulic cylinders are used to turn the rear and rear axles to perform steering. Therefore, according to such a configuration, it is possible to always obtain constant maneuverability regardless of changes in vehicle speed or changes in the position of the bulk load.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a structure for extending and retracting rods 1 to 1 of a rear axle steering device according to an embodiment of the present invention, FIG. 2 is a plan view of a truck equipped with this rear axle steering device, and FIG. 3 is 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.
FIG. 8 is a flowchart showing the operation of this rear axle steering device, and FIG. 9 is a plan view showing the suspension device for the two rear axles. In addition, in the symbols used in the drawings, 10... Frame 13... Front axis (driving shaft) 14... Rear shaft (driven axis, ratio axis) 20... Trunnion bracket 21... Trunnion Shaft 23...Leaf spring 26.27...Torque rod 35...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)

[Claims] A rear front shaft and a rear rear shaft are respectively suspended by the front end and rear end of a leaf spring supported via a trunnion bracket, and torque rods are respectively connected to both sides of the rear front shaft and the rear rear shaft. In a vehicle that is connected to the vehicle body through A control means for controlling the discharge is provided, and the rear-front shaft and the rear-rear shaft are rotated by the control means and the hydraulic cylinder to perform steering so as to eliminate changes in steering performance. Rear axle steering device for rear two-axle vehicles.