JP2517578B2 - Vehicle rear wheel steering system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rear wheel steering system for a vehicle.

(Prior Art) Conventionally, as a rear wheel steering device of a vehicle, for example, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent Publication No. 61-200064, a toe control device including a hydraulic cylinder or the like for independently controlling the toe of the left and right rear wheels and a control means for controlling the operation of the toe control device are provided, and steering of the front wheels is performed. At this time, by steering only the rear wheels on the outside of the turn in the toe-in direction, or the left and right rear wheels in the same phase as the turning direction, that is, the rear wheels on the inside of the turn in the toe-out direction and the rear wheels on the outside of the turn in the toe-in direction, respectively. By steering, lateral G at high speed
It is known to reduce the cutting action due to (lateral acceleration) to improve running stability.

(Problems to be Solved by the Invention) In a vehicle, for example, when a lane change is performed, the front wheels are steered to the left or right, and then continuously in the opposite direction.

However, in the above-mentioned conventional rear wheel steering system, during such reverse steering, there is a lack of responsiveness to follow the steering of the front wheels to quickly steer the rear wheels, and the effect of steering the rear wheels cannot be sufficiently exerted. There is. In particular, such a problem of the responsiveness of the rear wheel steering is remarkable in the type of steering both the left and right rear wheels in the same direction in the turning direction.

The present invention has been made in view of the above points, and an object thereof is to improve the toe control control of the rear wheels in the conventional rear wheel steering device to ensure traveling stability during steering. At the same time, the responsiveness of the rear wheel steering during the next reverse steering can be improved.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the solution means of the present invention is a rear wheel steering system for a vehicle, comprising a toe control device for independently controlling the toe of each of the left and right rear wheels. When the vehicle is being steered, a control means for controlling the operation of the toe control device is provided so that only the rear wheels on the outside of the turn are steered in the toe-in direction immediately after the steering, and then the rear wheels on the inside and the outside of the turn are both steered in the toe-in direction. It is configured.

(Operation) 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,
Immediately after steering, only the rear wheel on the outside of the turn is steered in the toe-in direction, so that the cutting action of the lateral G can be alleviated and the running stability can be improved. Immediately after steering, the rear wheels on the outside of the turn are steered in the toe-in direction as well as the rear wheels on the outside of the turn. Therefore, regardless of the toe-in steering of the rear wheels on the inside of the turn, the running stability can be ensured by the toe-in steering of the rear wheels on the outside of the turn.

When the front wheels are steered in the opposite direction from such a steering state, the rear wheels on the outside of the turn are already steered in the toe-in direction during the previous steering, so the response delay of the rear wheel steering with respect to the steering of the front wheels is delayed. Thus, the running stability can be improved by steering the rear wheels.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 shows a rear wheel steering system for a vehicle according to an embodiment of the present invention, in which 1L and 1R are left and right rear wheels.
L and 1R are supported by the vehicle body via the wheel support member 2 and the pair of front and rear lateral links 3a and 3b, respectively. Further, 4L and 4R are a pair of left and right hydraulic cylinders arranged between the rear lateral link 3b and the vehicle body.

As shown in detail in FIG. 2, the hydraulic cylinders 4L and 4R have the piston 6 inside the piston fitting portion 5a of the cylinder body 5.
Has a hydraulic chamber 7 and a spring chamber 8 which are slidably inserted by a predetermined stroke and partitioned by the piston 6. The cylinder body 5 is attached to the vehicle body, while the piston 6 is connected to one end of a rear lateral link 3b inserted from the spring chamber 8 side. Further, the spring chamber 8 is provided with a spring 9 that compresses and urges the piston 6 toward the end of the piston fitting portion 5a on the hydraulic chamber 7 side. When pressure oil is not supplied to the hydraulic chamber 7 and the piston 6 is positioned at the end of the piston fitting portion 5a on the hydraulic chamber 7 side due to the biasing force of the spring 9, the rear wheel
1L and 1R are in a state where the toe displacement is zero, and the supply of the pressure oil to the hydraulic chamber 7 causes the piston 6 to move the spring chamber 8 in the piston fitting portion 5a.
The rear wheels 1L and 1R are steered in the toe-in direction as they move to the side.

Further, an oil pump 10 for steering the rear wheels is provided in each of the hydraulic chambers 7 of the pair of hydraulic cylinders 4L, 4R.
11c, the oil pump 10 is driven by the engine output transmitted via the pulley 14 together with the front wheel steering oil pump 13 that supplies pressure oil to the front wheel steering hydraulic cylinder 12. Has become. In the hydraulic passage 16 which branches from the hydraulic supply passage 11a and communicates with the reserve tank 15, the hydraulic cylinders 4L, 4R are connected from the oil pump 10 to the hydraulic passage 16.
A variable orifice 17 for adjusting the hydraulic pressure discharged toward the hydraulic pressure supply passage 11b, 11c is provided.
The on-off valves 18 and 19 are provided in each of them. The variable orifice 17 is in a fully opened state (that is, there is no restriction to the passage surface passage) when the operating portion 17a is not operated (that is, when not energized), and the opening / closing valves 18 and 19 are Is also in the closed state when the operation parts 18a and 19a are not operated (not energized).

Further, hydraulic pressure discharge passages 20a, 20b for discharging the pressure oil in the hydraulic chambers 7 of the hydraulic cylinders 4L, 4R to the reserve tank 15.
On-off valves 21 and 22 are provided in each of them, and both of the on-off valves 21 and 22 are in an open state when the operating parts 21a and 22a are not operated (when not energized). With the above hydraulic cylinders 4L, 4R and the hydraulic circuit connected to them, the left and right rear wheels 1L, 1R
Toe control device 2 for independent toe control of R
3 are configured.

Further, the toe control device 23 includes the variable orifice 17 and the operating portions 17a, 18 of the on-off valves 18, 19, 21, 22.
Controller 24 as control means for a, 19a, 21a, 22a
The operation is controlled by inputting an ON-OFF switching signal from the controller.
Signals from a vehicle speed sensor 25 that detects the vehicle speed and a steering wheel steering angle sensor 26 that detects the steering angle of the steering wheel are input to the.

The operation control (toe control control) of the toe control device 23 by the controller 24 is performed based on the flowchart shown in FIG. That is, first, in step S ₁ , after reading the steering angle and vehicle speed of the steering wheel, it is determined in step S ₂ whether or not the steering wheel is being steered. If YES, the process proceeds to step S ₃ and NO If so, the process returns to step S ₁ . In step S _3, on the basis of the lateral G calculation map, as shown in FIG. 4 which is previously stored, the lateral G from the steering angle and the vehicle speed of the steering wheel
It is determined whether (lateral acceleration) μ is 0.2 or less (that is, the non-control area A in FIG. 4). If YES, the process returns, and if NO, the process goes to step S ₄ and step S ₃ . Similar to the case, it is determined whether the lateral Gμ is 0.5 or more (that is, the second control area B _{2 in} FIG. 4) based on the lateral G calculation map.

When the determination in step S ₄ is YES, the process proceeds to step S ₅ , while when it is NO (that is, when the lateral Gμ is in the first control region B ₁ in FIG. 4), the process proceeds to step S ₆ and steering is performed. It is determined whether the steering wheel is steered to the left. If this determination is YES, go to step S ₇ , and if NO, step S _7.
Go to ₈ .

In step S _7, and controls the variable orifice 17 as hydraulic pressure discharged from the oil pump 10 becomes a predetermined pressure, the opening and closing valve 19 is opening operation, by opening and closing valve 22 thereby closing operation, the hydraulic cylinder 4R A predetermined pressure oil is supplied to the hydraulic chamber 7 to steer only the right rear wheel 1R in the toe-in direction. Further, in step S _8, the oil pump 10
The variable orifice 17 is controlled so that the hydraulic pressure discharged from the hydraulic pressure control device is at a predetermined pressure, and the opening / closing valve 18 is opened and the opening / closing valve 21 is closed, so that the hydraulic chamber 7 of the hydraulic cylinder 4L has a predetermined pressure. Supply oil and steer only the left rear wheel 1L in the toe-in direction. Furthermore, in step S ₅ ,
The variable orifice 17 is controlled so that the hydraulic pressure discharged from the oil pump 10 reaches a predetermined pressure, and the on-off valves 18, 19
Is opened and the on-off valves 21 and 22 are closed to supply pressure oil of a predetermined pressure to the hydraulic chambers 7 of the hydraulic cylinders 4L and 4R to steer both the left and right rear wheels 1L and 1R in the toe-in direction. To do.

Next, the operation of the above-described embodiment will be described. When the front wheels are not steered and are in a straight traveling state (when the lateral G is in the non-control area A in FIG. 4), the controller 24 turns on the power. Signal is not output at all, the variable orifice 17 is fully open, the open / close valves 18 and 19 are closed, and the open / close valve 2
1,22 are open. Therefore, the pressure oil is not supplied to the hydraulic chambers 7 of the hydraulic cylinders 4L and 4R, and the piston 6 is located at the end of the piston fitting insertion portion 5a on the side of the hydraulic chamber 7, whereby the left and right rear wheels 1L are , 1R is maintained in a state where the toe displacement is zero as shown in FIG. 5 (a).

On the other hand, when the lateral G is 0.2 or more and 0.5 or less immediately after the steering of the front wheels (that is, in the first control region B ₁ in FIG. 4), the controller 24 causes the variable orifice 17 and An energization ON signal is output to the opening / closing valves 19 and 22, and in the case of right steering, an energization ON signal is output from the controller 24 to the variable orifice 17 and the opening / closing valves 18 and 21. As a result, the variable orifice 17 controls the hydraulic pressure discharged from the oil pump 10 to a predetermined pressure due to its passage area throttling action, the opening / closing valve 19 or 18 is opened, and the opening / closing valve 22 or 21 is closed. By doing so, pressure oil is supplied to the hydraulic chamber 7 of the hydraulic cylinder 4R or 4L, and the piston 6 moves from the hydraulic chamber 7 side end to the spring chamber 8 side inside the piston fitting insertion portion 5a. Only the rear wheels (corresponding to the right rear wheel 1R in the case of left steering turn and the left rear wheel 1L in the case of right steering turn) are steered in the toe-in direction as shown in FIG. 5 (b). As a result, the cutting action by the lateral G can be alleviated, and the running stability immediately after steering can be improved.

Further, immediately after the steering, when the lateral G is 0.5 or more (that is, in the second control region B ₂ in FIG. 4), the variable orifice 17 and the on-off valves 18, 19, 21, 22 are fed from the controller 24.
In response to this, a signal indicating that the energization is ON is output, which causes the rear wheels on the inside of the turn to be steered in the toe-in direction in the same manner as when the rear wheels on the outside of the turn are steered in the toe-in direction immediately after steering.
The left and right rear wheels 1L, 1R are both steered in the toe-in direction as shown in FIG. 5 (c).

In this case, the road surface resistance acting on the rear wheel on the outside of the turn, for example, on the right rear wheel 1R in the case of left turn as shown in FIG. 5 (c), is much higher than that of the left (inward turn) rear wheel 1L. Therefore, irrespective of the toe-in steering of the left rear wheel 1L, by the toe-in steering of the right rear wheel 1R, the cutting action by the lateral G can be alleviated as in the case immediately after steering, and the traveling stability can be improved. Moreover, when steering the front wheels to the right from such a left turning steering state (when changing lanes, etc.), the outside of the turn, that is, the left rear wheel 1L has already been steered in the toe-in direction during the previous steering. Therefore, there is no delay in the response of the rear wheel steering with respect to the steering of the front wheels, and it is possible to further improve the traveling stability by the rear wheel steering.

In the above embodiment, the toe control device 23 for toe-controlling the left and right rear wheels 1L, 1R is described as being constituted by the hydraulic cylinders 4L, 4R and the hydraulic circuit.However, the present invention uses an electric motor or the like. It can be similarly applied to the case of using other toe control devices such as those constructed. In short, in the control of the toe control device, when steering the front wheels, it is only necessary to steer only the rear wheels on the outside of the turning in the toe-in direction immediately after steering, and then to steer both the rear wheels on the inside and the outside of the turning in the toe-in direction. is there.

(Effects of the Invention) As described above, according to the vehicle rear wheel steering system of the present invention, when the front wheels are steered, only the rear wheels on the outside of the turn are steered in the toe-in direction immediately after the steering, and thereafter the inside and outside of the turn are steered. By steering the rear wheels together in the toe-in direction, it is possible to effectively ensure the driving stability during steering, and also to improve the responsiveness during the next reverse steering operation, such as when changing lanes. It can be done safely and quickly.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic overall configuration diagram of a rear wheel steering system of a vehicle, FIG. 2 is a vertical sectional side view of a hydraulic cylinder, and FIG. 3 is a flow chart diagram of toe control control. FIG. 4 is a diagram showing a lateral G calculation map,
FIG. 5 is an explanatory diagram for explaining steering of the rear wheels. 1L, 1R …… rear wheel, 23 …… toe control device, 24 ……
controller.

Claims (1)

(57) [Claims] 1. A rear wheel steering system for a vehicle, comprising a toe control device for independently controlling the left and right rear wheels, wherein only the rear wheels on the outside of the turning direction in the toe-in direction when the front wheels are steered. A rear wheel steering system for a vehicle, comprising: a control unit that controls the operation of the toe control device so that the rear wheels are steered and then both the inner and outer rear wheels are steered in the toe-in direction.