JPH01186473A - Bear wheel steering of vehicle - Google Patents

Abstract

PURPOSE:To permit the sure drive out from a narrow longitudinal arrangement parking space by releasing the delay control in retreat and carrying out the reverse phase steering for rear wheels from the start of retreat, in the constitution in which the rear wheels are steered in reverse phase under the delay control, during the front wheel steering in advance operation. CONSTITUTION:A front wheel steering mechanism steers front wheels 1R and 1L through a rack 7, etc., interlocked with the operation of a steering wheel 3, and a steering power is assisted by a power cylinder 9. A rear wheel steering mechanism steers rear wheels 2L and 2R by swinging a suspension member 14 by a rear wheel steering actuator 17. The power cylinder 9 and the actuator 17 are connected with the hydraulic pressures 18-21 equipped with a rear wheel direction selector valve 22, and said selector valve 22 is controlled so that the rear wheels are steered in the reverse phase under the delay control during the steering in advance operation. In this case, the above-described delay control is released in retreat, and the rear wheel is controlled so as to be reverse-phase-steered in correspondence with the front wheel steering angle from the start of the retreat.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for steering the rear wheels of a four-wheel steering vehicle, which also steers the rear wheels when the front wheels are steered.

(Conventional technology) Rear wheel steering technology includes a technology that steers the rear wheels in the opposite phase to the front wheels in order to improve turning performance when driving at low speeds, and a technology that steers the rear wheels in the opposite phase to the front wheels to improve turning stability when driving at high speeds. There is a technology that steers the wheels in the same phase as the front wheels.

The present invention relates to the former rear wheel steering technology, but in this technology, when the vehicle starts from a parked state where the side of the vehicle is along an obstacle such as a wall while steering the front wheels, the rear part of the vehicle body due to reverse phase steering of the rear wheels. The overhanging trajectory causes the rear part of the vehicle to collide with the above-mentioned obstacle.

Therefore, in order to solve the above-mentioned problem, the applicant of the present application previously disclosed in Japanese Patent Application Laid-Open No. 60-176867 and Japanese Patent Application Laid-Open No. 61-75057 to 75059 that the rear wheels are steered in reverse phase after moving forward a certain distance. We have already proposed a technique for delaying rear wheel reverse phase steering, which gradually increases the reverse phase steering angle of the rear wheels according to the forward distance.

(Problem to be Solved by the Invention) However, in this case, as shown in Fig. 5, there are obstacles such as walls in front of the vehicle, and the following problem occurs when it is necessary to move forward and then turn back. arise.

That is, in the case where the above-mentioned delay technique starts reverse-phase steering of the rear wheels after the vehicle has moved forward a certain distance, the vehicle stopped at position A-1 in FIG. 5 is initially at position A-2 when moving forward. Only the front wheels are steered by two-wheel steering (2WS) until then, and then the front and rear wheels are steered by four-wheel steering (4WS) to reach the l-3 position, improving cornering performance while keeping the overhang of the rear of the vehicle small. Therefore, when the vehicle is reversed from the A-3 position, the rear wheels are kept in a non-steering neutral state, and the vehicle is driven backward at 2WS. Therefore, the vehicle is A-3
It traces a trajectory from position 8 to position C, bulges out toward the obstacle, and falls into a state where it cannot move forward or backward.

(Means for Solving the Problems) The present invention attempts to provide a rear wheel steering method that does not cause such a problem while reversing. When steering the rear wheels while reversing in a vehicle that has been designed to perform phase steering to improve cornering performance while keeping the overhang of the rear body small, the delay control is canceled during reversing and the front wheels are steered from the beginning of reversing. It is characterized by a rear wheel steering method of a vehicle that provides a rear wheel reverse phase steering angle depending on the angle.

(Function) When the front wheels are steered while moving forward, the rear wheels are steered in reverse phase under delay control, allowing the vehicle to turn in a small way without increasing the overhang of the rear of the vehicle body. Therefore, even when starting from a stopped state with the side of the vehicle along an obstacle, the rear of the vehicle will not collide with the obstacle, and its maneuverability allows the vehicle to escape even from relatively narrow parallel parking spaces. be able to.

On the other hand, during reversing, the delay control is canceled and the rear wheels are steered by applying a rear wheel reverse phase steering angle corresponding to the front wheel steering angle from the beginning of reversing. As a result, when the vehicle is started forward from the above-mentioned stopped state and then reversed to move backward, the vehicle body will be moved to a position further from the obstacle than the initial stopping position, making it necessary to reverse the vehicle. This allows you to reliably escape from narrow parallel parking spaces, and avoid the worst-case scenario where you are forced to move backwards and forwards.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 illustrates a four-wheel (3-wheel) steering system of a vehicle used to carry out the method of the present invention, in which IL and IR represent left and right front wheels, 2L and 2R represent left and right rear wheels, respectively, and 3 represents a steering wheel. Front wheels IL and IR are each knuckle arm 4L
, side rod 5L between 4R.

The steering wheel 3 is connected to the steering wheel 3 through a rack 7 of the steering gear 6 via the steering gear 5R, and a binion (not shown) that meshes with this rack is connected to the steering wheel 3.
front wheel IL due to the stroke of rack 7 during steering operation.
, 1'R can be steered in the steering direction by the steering angle.

The steering gear 6 is provided with a power steering control valve 8 and a power cylinder 9. During the above-mentioned front wheel steering, the control valve 8 supplies hydraulic pressure (power steering assist pressure) as shown in FIG. For example, hydraulic pressure (power steering assist pressure) as shown in the figure is supplied to the chamber 9b of the power cylinder 9 to power assist left steering, thereby enabling light power steering.

The rear wheels 2L and 2R are rotatably supported by wheel support members 10L and IOH, respectively, and these members are connected to a parallel link IIL.
, IIR in the vehicle width direction, radial rods 12L and 12R to support the vehicle body in the longitudinal direction, and struts 13L and 13R to elastically support the vehicle body in the vertical direction.

The rear suspension member 14, which supports the parallel links IIL and 11R, has its negative end pivoted to the vehicle body by a pin 15 so that it can swing horizontally, and the other end has an elastic bush 16 to enable this swing. Support through.

By causing the suspension member 14 to swing as described above, the rear wheel 2
Rear wheel steering actuator 17 for steering L and 2R
This actuator rotates the suspension member 14 in the direction of the solid line arrow around the pin 15 to steer the rear wheel to the right when extended by supplying hydraulic pressure to the chamber 17a, and contracts by supplying hydraulic pressure to the chamber 17b. At this time, the suspension member 14 is rotated in the direction of the dotted arrow to steer the rear wheels to the left.

A rear wheel steering direction switching valve 22 is connected and provided between oil passages 18.19 from the power cylinders 9a, 9b and oil passages 20.21 from the actuator chambers 17a, 17b.

This valve is a 2-position solenoid valve, and the solenoid 22a is turned OFF.
When the solenoid 22a is in the neutral position, the oil passages 18 and 19 are shut off and the oil passages 20 and 21 are communicated, and when the solenoid 22a is in the ON/N phase position, the oil passages 18 and 21 and 19° and 20 are communicated.

The controller 24 turns ON and OFF the solenoids 22 and 1.
This controller controls the signal from the vehicle speed sensor 25 that detects the vehicle speed and the gear position G of the on-vehicle transmission.
Based on the signal from the gear position sensor 26 that detects the third
The functions shown in the figure shall be performed as follows.

That is, first, in step 101, the running direction of the vehicle is determined from the gear position G. If it is determined that it is moving forward,
For now, turn off the solenoid 22a in step 102.
With this, the switching valve 22 is set to the neutral position, and the oil passages 18 and 19 are shut off, while the oil passages 20 and 21 are communicated with each other. As a result, both chambers 17a and 17b of the rear wheel steering actuator 17 are communicated with each other, so that the rear suspension member 14 is kept in a non-rotating position by the elastic bushing 16, and the rear wheels are held in a neutral position where they are not steered.

In the next step 103, depending on whether the vehicle speed ■ is less than V0,
It is determined whether the vehicle speed is low at which the rear wheels should be steered in reverse phase or whether the vehicle speed is high at which the rear wheels should not be steered. In the case of a low vehicle speed, in step 104 the mileage after the forward start is calculated from the vehicle speed V and the elapsed time after the start, and in the next step 105 it is checked whether the vehicle has traveled a predetermined distance from this mileage. After the start, the control is returned to step 104 until the vehicle has traveled a predetermined distance, and by continuing the non-steering state of the rear wheels in step 102, only the front two wheels are steered.
Drive with wheel steering (2WS) (rear wheel reverse phase steering delay control m
).

After the vehicle has traveled a predetermined distance after starting, the control is advanced from step 105 to step 106, where the solenoid 22a is turned on to set the switching valve 22 to the reverse phase position and the oil passages 20 and 21 are communicated with the oil passages 19 and 18, respectively. Here, when the front wheels IL and IR are steered by the steering wheel 3, the interior 9a (when steering to the right)
Or, the power steering assist pressure corresponding to the front wheel steering angle shown in Fig. 2 generated at 9b (during left steering) is
7a, the rear wheels 2L and 2R are steered as requested by an angle corresponding to the front wheel steering angle in the opposite phase to the front wheels to perform four-wheel steering (four-wheel steering).
WS) can be done. From step 106, control returns to step 103 and repeats the above loop.

In this way, in the case where the vehicle starts forward from the stopped state shown by A-1 in FIG. 4, as described above with reference to FIG. As a result, turning performance can be improved without increasing the overhang at the rear of the vehicle body.

If it is determined in step 101 that the vehicle is moving backward, the control proceeds to step 107, where the same processing as in step 106 is performed to reverse the rear wheels by an angle corresponding to the front wheel steering angle without the delay control described above when the front wheels are steered. Phase change. This results in
Regarding the case where the vehicle is turned back from position A-3 in Fig. 4, the rear wheels of the vehicle are initially steered in reverse phase by an angle corresponding to the front wheel steering angle, and the vehicle is steered backward by the 4WS. , it reaches the middle position in Fig. 4 and is further away from the obstacle than the initial stop position A-1. Therefore, it is possible to escape from a parallel parking space that requires a turnaround by further retreating the vehicle, for example, to position E in FIG.

In normal driving after such escape, V>V. When the vehicle speed reaches a high speed of
The oil passage 20.21 is set to the neutral position with the switching valve 22 by FF.
At the same time, the oil passages 18 and 19 are blocked. As a result, both chambers 17a and 17b of the rear wheel steering actuator 17
Since the rear suspension member 14 is in communication with the rear suspension member 14, the elastic bushing 16 keeps the rear suspension member 14 in a non-rotating position, and holds the rear wheel in a neutral position where it is not steered.

(Effects of the Invention) As described above, the rear wheel steering method of the present invention always steers the rear wheels in the opposite phase from the beginning during reversing, so that when the vehicle turns back and reverses, the vehicle will be able to avoid lateral obstructions from the initial stopping position. By moving to a position further away from objects, it is possible to reliably escape from a narrow parking space that requires a turnaround, and the worst situation where the vehicle is forced to move back and forth can be avoided.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view illustrating a vehicle steering system used to implement the method of the present invention, Fig. 2 is a characteristic diagram of power steering assist pressure, and Fig. 3 is a functional flowchart showing the rear wheel steering procedure of this embodiment. , FIG. 4 is a diagram showing the motion trajectory of the vehicle according to this embodiment, and FIG. 5 is a diagram showing the motion trajectory of the vehicle by conventional rear wheel steering. LL, IR...Front wheel 2L, 2R...Rear wheel 3.
... Steering wheel 6 ... Steering gear 7 ... Rack 8 ... Control pulp 9 ... Power cylinder 11L, IIR ... Parallel links 12L, 12R ... Radius slot 14 ... Rear suspension member 15 ... Pivot pin 16 ... Elastic bush 17 ... Rear wheel steering actuator 22 ... Rear wheel steering direction switching valve 24 ... Controller 25 ... Vehicle speed sensor 26 ... Gear position sensor Patent application People Nissan Motor Co., Ltd.

Claims (1)

[Scope of Claims] 1. When the front wheels are steered while moving forward, the rear wheels are steered in reverse phase under delay control to improve turning performance while keeping the overhang of the rear part of the vehicle small. A method for steering rear wheels of a vehicle, characterized in that, when steering the middle and rear wheels, the delay control is canceled during reversing and a reverse phase steering angle of the rear wheels corresponding to the front wheel steering angle is applied from the beginning of the start of reversing.