JPS63192670A - Rear wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To improve turning characteristics immediately after steering operation by controlling a steering system in such a way that only a rear wheel inside a turning circle is steered toward a toe-in direction immediately after front wheel steering and only a rear wheel outside a turning circle is thereafter steered toward a toe-in direction. CONSTITUTION:When lateral acceleration just after steering operation is, for example, 0.2G-0.5G at the time of steering front wheels, a controller 24 outputs a signal of electric power supply ON to a variable orifice 17 and open/close valves 18 and 21 for left turn, and said signal to the variable orifice 17 and open/close valves 19 and 22 for right turn. According to the aforesaid constitution, pressure oil is fed to the hydraulic chamber 7 of a hydraulic cylinder 4L or 4R and only a rear wheel 1L or 1R inside a turning circle is steered toward a toe-in direction. Therefore, turning characteristics immediately after steering operation are improved. After the immediate finish of the steering operation, a signal of electric power supply ON is outputted from the controller 24 to the variable orifice 17 and the open/close valves 19 and 22 in the case of left turn, and only the rear wheel 1R outside a turning circle is steered toward a toe-in direction, thereby improving running stability.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides +! ] 'J is something. (Prior art) Conventionally, as a rear wheel steering device of a vehicle, for example,
As disclosed in Japanese Patent Publication No. 1-200064, it is equipped with a toe control device consisting of a hydraulic cylinder or the like that independently toe controls the left and right rear wheels, and a control means for controlling the operation of the toe control device. During steering, by steering only the rear wheel on the outside of the turn in the toe-in direction, or by steering the right rear wheel in the same phase in the turning direction, the rear wheel on the inside of the turn is steered in the toe-out direction, and the rear wheel on the outside of the turn is steered in the toe-in direction. It is known that the steering wheel is steered in the toe-in direction to alleviate the cutting effect caused by lateral G (lateral acceleration Iff) during high-speed driving to improve running stability. (Problems to be Solved by the Invention) By the way, in the above-mentioned conventional wheel, while the front wheels are being steered, the rear wheels are always steered in the toe-in direction, and the cutting action is such that the rear wheels are always steered in the toe-in direction to produce a lateral G.
However, even when steering the front wheels, the cutting action due to ttG rarely becomes a problem immediately after steering when the lateral G is small. On the contrary, there is a demand for improving the ability to turn the head immediately after steering. The present invention has been made in view of the above points, and its purpose is to improve the toe control control of the rear wheels in the conventional rear wheel steering system, and improve retrospective performance and running stability during steering. It is intended to effectively secure both the (Means for solving the problem) Above 1. In order to achieve the object, the solution of the present invention provides a rear wheel steering system for a vehicle equipped with a torque control device that independently toe controls the right rear wheel. Immediately after steering, only the rear wheel on the inside of the turn is steered in the toe-in direction, and then only the rear wheel on the outside of the turn is steered in the toe-in direction, and the control means is configured to operate the toe control device 11. It's b. (Function) With the above configuration, in the present invention, when steering the front wheels, the toe control device operates under the control of the control means, and immediately after steering when the lateral C is small, only the rear wheels on the inside of the turn are steered in the toe-in direction. This makes it possible to improve the ability to turn the head. In addition, immediately after steering when the lateral G increases, only the rear wheel on the outside of the turn is steered in the toe-in direction, so it is possible to alleviate the cutting effect caused by the lateral Q and improve driving stability. Moreover, in this case of 1￥f wheel steering, when transitioning from the state immediately after steering to the following states, the rear wheel on the inside of the turn is changed from the toe-in steering state to the state of zero toe displacement,
It merely changes the rear wheels on the outside of the turn from a state of zero toe displacement to a toe-in steering state, and neither of the right rear wheels changes between a toe-in steering state and a toe-out steering state. Therefore, there is no delay in the response of rear wheel steering. (Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a rear wheel steering system for 111 cars according to an embodiment of the present invention, and ILJ3 and 11 are the left and right rear wheels,
The rear wheels 1L and iR are supported by the vehicle body via a wheel support member 2 and a pair of front and rear lateral links 3a and 3b, respectively. Further, /II- and 4R are a pair of left and right hydraulic cylinders disposed between the rear lateral link 3b and the vehicle body. As shown in detail in FIG. 2, each of the above-mentioned hydraulic cylinders 4L and 4R has a piston 6 fitted into the piston@pushing part 5a of the cylinder body 5 so as to be slidable by a predetermined stroke, and partitioned by the piston 6. The hydraulic chamber 7 and spring chamber 8 are on the right. The cylinder body 5 is attached to the vehicle body, and one end of the rear lateral link 3b inserted from the spring chamber 8 side is connected to the piston 6. In addition, the piston 6 is placed in the spring chamber 8, and the piston i! ! Hydraulic chamber 7 in insertion part 5a
A spring 9 that urges movement is compressed at the side end. Then, when pressure oil is not supplied to the hydraulic chamber 7 and the piston 6 is placed in the hydraulic chamber 7 side in the piston fitting portion 5a under the biasing force of the spring 9, the rear wheel 11-, IR is in a state of zero toe displacement, and screw 1 is
The rear wheels IL and IR are steered in the toe-in direction as the spring 6 moves toward the spring chamber 8 inside the piston I insertion portion 5a. In addition, each hydraulic chamber 7 of the pair of hydraulic cylinders 4L and 4R is
An oil pump 10 for rear wheel steering is connected to a hydraulic pressure supply passage 11.
a, 11b, and Ilc, and the oil pump 10 is driven by engine output transmitted via a pulley 14 together with a front wheel steering oil pump 13 that supplies pressure oil to a front wheel steering hydraulic cylinder 12. It is supposed to be done. It branches off from the hydraulic pressure supply passage 11a.
A variable orifice 17 for regulating the hydraulic pressure discharged from the oil pump 10 toward the hydraulic cylinders 4L and 4R is interposed in the hydraulic passage 16 communicating with the f-pump tank 15, and a variable orifice 17 for regulating the hydraulic pressure discharged from the oil pump 10 toward the hydraulic cylinders 4L and 4R is provided. Opening/closing valves 18 and 19 are provided in each of the passages 11b and 11c. The variable orifice 17 is in a fully open state (i.e., there is no restriction to the passage surface g!A) when the operating portion 17a is not operated (i.e., de-energized), and the on-off valve 18
．． 19, when the operation parts 18a and 19a are not operated (
When the power is off), it is in the closed state. Furthermore, a hydraulic discharge passage 20 discharges the pressure oil in each hydraulic chamber 7 of the hydraulic cylinders 4L and 4R to the liep tank 15.
On-off valves 21.22 are interposed in each of a and 20b, and both on-off valves 21.22 are connected to the operating section 21.
a, 22a are in an open state when they are not activated (not energized). The above hydraulic cylinders 4L, 4fl and the hydraulic circuits connected to them provide toe control which independently controls the left and right rear wheels 1L, 1R from toe control 1 to roll J.

[''-le device 23 is configured. The control device W'123 has a variable orifice 17 and an on-off valve 18.19°21.2.
2, each operation section 17a, 18a, 19a. Controller 2 as a control means for 21a and 22a
The operation is controlled by inputting an energized ON-OFF switching signal from controller 4, and the above controllers 1 to 1
The <EC signal is input to the low 524 from the vehicle speed sensor I25 which detects the 01 speed and the steering wheel angle sensor 26 which detects the steering angle of the steering wheel. Toe control [1-ru installation] by the controller 1-roller 24
The operating temperature wJ (toe control control) of 23 is performed based on the flowchart II-t shown in FIG. That is, first, in step SI, the steering angle J3 of the steering wheel and the vehicle speed are read, and then in step S2, it is determined whether the steering wheel is being steered, and Y
If ES, go to step S3; if No, go back to step S1. In step S3, the lateral G (lateral acceleration) is calculated from the steering angle of the steering wheel and the vehicle speed based on a pre-stored map for lateral G performance as shown in FIG.
Determine whether μ is below 0°2 (that is, non-control area △ in Figure 4), return if YI3S, and return to N.
If it is O, go to step S4, and as in the case of step S3, the horizontal Gμ is 0.5 or more based on the map for the horizontal G cast (that is, the 22nd, 1 all region vAL32 in FIG. 4).
Determine whether or not it exists. If the determination in step S4 is YES, it is determined in step S5 whether or not the steering wheel is steering to the left, while if the determination in step S4 is NO, that is, the lateral Gμ is 1 control area B1 is 6.)
In step S6, it is determined whether the steering wheel is turned to the left. When the determination in step S5 is No, and when the determination in step S6 is YES, the process goes to step S7, and the determination in step S5 is YES.
When S and when the determination at step Ss is NO, the process goes to step S8. In step S7, the variable orifice 17 is controlled so that the oil pressure discharged from the oil pump 10 becomes a predetermined pressure, and the valve 18 is prevented from closing, and the open/close valve 21 is interlocked. Pressure oil at a predetermined pressure is supplied to the hydraulic chamber 7 of the hydraulic cylinder 4L, and only the left rear wheel 1L is steered in the toe-in direction. In addition, in step S8, the variable orifice 17 is controlled once so that the oil pressure discharged from the oil pump 10 becomes a predetermined pressure, one on-off valve is closed, and one on-off valve 22 is closed. As a result, pressure oil at a predetermined pressure is supplied to the hydraulic chamber 7 of the hydraulic cylinder 4R, and only the right rear wheel 1R is steered in the toe-in direction. Next, to explain the operation of the above embodiment, when the front wheels are not being steered and are traveling straight (when the lateral G is in the non-control area A in FIG. 4), the controller 1-CI- No signal for opening ff1 is outputted from the valve 24, the variable orifice 17 is in the open state, the on-off valves 18 and 19 are in the open state, and the open/close valves 21 and 22 are in the open state. Therefore, pressure oil is not supplied to each hydraulic chamber 7 of the hydraulic cylinders 4L and 4R, and the piston 6 is located at the end of the hydraulic chamber 7 side in the piston fitting portion 5a, thereby causing the left and right rear wheels 1L ,
1R, the toe displacement is maintained at zero as shown in Figure 5 (a). On the other hand, when the front wheels are steered, the lateral G is 0.
2 or more and 0.5 or less (that is, when in the first control region B1 in FIG.
In the case of right steering, the variable orifices 17 and 17 are output from the controller 24.
An energization ON signal is output to the 0 leap valve 19.22. As a result, the variable orifice 17 controls the hydraulic pressure discharged from the oil pump 10 to a predetermined pressure by its passage area narrowing action, the on-off valve 18 or 19 closes, and the on-off valve 21 or 22 closes. By doing
Pressure oil is supplied to the hydraulic chamber 7 of the hydraulic cylinder 4L or 4R, and the screw I-ne 6 moves inside the piston insertion part 5a from the hydraulic chamber 7 side end to the spring chamber 8 side. Only the rear wheels (in the case of a left steering turn, the left rear wheel 1L corresponds, and in the case of a right steering turn, the right rear wheel 1R corresponds) are steered in the toe-in direction as shown in FIG. 5(b). Ru. As a result, it is possible to improve the ability to look back immediately after steering. In addition, when the lateral G is 0.5 or more immediately after the steering (that is, in the second control area B2 in Figure 4), the left steering In the case of controller 24 to TI epidemic: 4 refills 17 and 19.2
In the case of right steering, the controller 24 outputs an energization ON signal to the variable orifice 17 and the GTL closing valve 18.21. In the case of right rear wheel 1R
(in the case of a right steering turn, the left rear wheel 1L corresponds) is steered in the toe-in direction as shown in 5th fi4 (c). As a result, the cutting action caused by the lateral Q can be alleviated, and the running stability immediately after steering can be improved. Moreover, when transitioning from the state immediately after the front wheel is steered to the subsequent state, the rear wheel on the inside of the turn is changed from the 1-in steering state to the zero toe displacement state, and the rear wheel on the outside of the turn is shifted from the 1-in steering state to the zero toe displacement state. Although the rear wheels are changed from a state of zero toe displacement to a toe-in steering state, neither of the left and right rear wheels (1 m) or IR can be changed between a toe-in steering state and a toe-out steering state. There is no delay in the response of rear wheel steering, and driving stability immediately after steering can be ensured with good response. In the above embodiment, a case was described in which the toe control device 'a23 for toe control i-rolling of the left and right rear wheels IL, In was constituted by hydraulic cylinders/IL, 4R and a hydraulic circuit. The present invention can be similarly applied to cases where other control devices such as those constructed by electric motors or the like are used. In short, in controlling the toe control roll device, when steering the front wheels, immediately after steering, only the rear wheel on the inside of the turn is steered in the toe-in direction, and then only the rear wheel on the outside of the turn is steered in the toe-in direction. (Effects of the Invention) As described above, according to the rear wheel steering device of the present invention, when steering the front wheels, only the rear wheel on the inside of the turn is steered in the toe-in direction immediately after steering with a small lateral G, and the lateral G is reduced. By steering only the rear wheel on the outside of the turn in the toe-in direction immediately after the steering becomes large, it is possible to improve the ability to look back immediately after the steering, and to ensure responsive driving stability immediately after the steering. It has excellent practical effects.

[Brief explanation of the drawing]

The drawings do not show the embodiments of the present invention, and FIG. 1 is a schematic overall configuration diagram of a rear wheel steering system of a vehicle, FIG. 2 is a vertical side view of a hydraulic cylinder, and FIG. 3 is a flowchart of toe control control. , FIG. 4 is a diagram showing a map for lateral G play,
FIG. 5 is an explanatory diagram for explaining the steering of the rear wheels. 1L, IR...Rear wheel, 23...Toe control device, 24...Controller. Patent applicant: Mazda Motor Corporation
Before Rinto 1) Hiroshi,
-゛几卛゛、1、1- Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) A rear wheel steering device for a vehicle equipped with a toe control device that independently toe controls left and right rear wheels,
Control means is provided for controlling the operation of the toe control device so that when the front wheels are steered, immediately after the steering, only the rear wheels on the inside of the turn are steered in the toe-in direction, and then only the rear wheels on the outside of the turn are steered in the toe-in direction. A rear wheel steering device for a vehicle characterized by: