JPH044192B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle that steers the rear wheels in response to the steering of the front wheels.

(Prior art) Conventionally, as a four-wheel steering system for this type of vehicle,
For example, as disclosed in Japanese Unexamined Patent Publication No. 57-11173, the steering angle of the rear wheels is changed depending on the driving condition including vehicle speed and the steering angle of the front wheels. By setting the rear wheels in opposite phase and in the same phase at high vehicle speeds, it is possible to prevent wheels from skidding and improve driving stability, as well as improve maneuverability at low vehicle speeds. Things are known.

(Problem to be Solved by the Invention) However, in actual vehicle driving, there are cases where it is desired to steer the rear wheels with characteristics different from those automatically determined based on the vehicle speed and front wheel steering angle. be. For example, when parking in a garage or parallel parking, the four-wheel steering system described above only steers the rear wheels in opposite phases because the vehicle speed is extremely low. However, in some cases, it is desirable to steer the rear wheels largely in the same phase. Sometimes. In other words, if the rear wheels are steered largely in the same phase as the front wheels (by an angle equal to the steering angle of the front wheels), the vehicle will move diagonally in parallel, making it difficult to move laterally in parallel parking or in a narrow garage. This is extremely convenient when you want to move the vehicle. Also, when parking in a narrow alley in order to park close to a wall, etc.,
If the rear wheels are steered in the same phase as the front wheels, it is very easy to move the vehicle closer to the other side without having to repeatedly turn the steering wheel, which is very convenient. This kind of thing is common in actual driving, and in addition to automatic four-wheel steering according to the driving condition, it is possible to perform four-wheel steering in any different mode according to the driver's request. It is hoped that

Therefore, the present applicant has previously proposed a new four-wheel steering system for vehicles to meet such requirements (see Japanese Patent Application No. 57-190049 (Japanese Patent Application Laid-Open No. 59-81261)). That is, the proposed four-wheel steering device includes a steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a controller that controls the rear wheel steering device according to the steering angle of the front wheels. The controller has two modes: an automatic control mode and a fixed mode. In the automatic control mode, the rear wheel steering angle relative to the front wheel steering angle is changed according to the driving condition, and in the fixed mode, the steering angle is changed depending on the driving condition. It is made to change unrelatedly.

However, in the above proposal, since the controller has two modes, when the driver drives without being aware of which mode the driver is in, especially when driving in reverse, There is a risk of making mistakes. In other words, if the rear wheel steering angle characteristic as a fixed mode is set linearly to the same phase side regardless of the vehicle speed for convenience in cases such as parking in a garage or parallel parking as described above, the steering wheel in this fixed mode If you drive backwards while turning the steering wheel, unlike when using two-wheel steering or an automatic control mode that steers the rear wheels in the opposite phase at low vehicle speeds, the vehicle will drive backwards in the exact opposite direction to the direction in which you turned the steering wheel. This can cause a driver who is accustomed to two-wheel steering to make a driving mistake and collide with an obstacle at the rear of the vehicle.

On the other hand, conventionally, when a vehicle is traveling backwards, a distance sensor attached to the rear of the vehicle body detects the distance to an obstacle behind the vehicle body, and the frequency of the warning sound is changed according to the detected distance. A so-called back monitor device is known that is designed to call attention to this (see, for example, Japanese Patent Laid-Open No. 135351/1983).

However, in the four-wheel steering system proposed above, the direction of travel of the vehicle is different when backing up in the automatic control mode and when backing up in the fixed mode. It is not possible to reliably detect obstacles, and the function of the back monitor device is not fully demonstrated.

An object of the present invention is to provide two modes, a first mode for automatic control and a second mode different from the first mode, to a controller that controls the rear wheel steering device according to the steering angle of the front wheels as described above. In a four-wheel steering system for a vehicle, the vehicle is provided with a four-wheel steering system, and the object of the present invention is to improve safety during backing up by directing a backing monitor device according to the backing characteristics of the vehicle.

(Means for Solving the Problem) In order to achieve the above object, the solving means of the present invention includes a steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a rear wheel steering device that steers the front wheels. Multiple settings are made so that the wheel steering angle changes according to the vehicle speed so that they are in opposite phase at low speeds and in the same phase at high speeds, and the characteristics of the rear wheel steering angle relative to the front wheel steering angle are made to be in the same phase at least in the high speed range. control, and the characteristic is set so that the rate of increase in the rear wheel steering angle relative to the front wheel steering angle in a region where the front wheel steering angle is large is smaller than the rate of increase in the region where the front wheel steering angle is small. mode and the first
The present invention assumes a four-wheel steering device for a vehicle, which has a second mode different from the first mode, and a controller that selects the two modes and controls the rear wheel steering device according to the front wheel steering angle. . A back monitor device is installed at the rear of the vehicle body and has a distance sensor for detecting the distance to an obstacle behind the vehicle body, and the distance sensor of the back monitor device includes:
It is assumed that the vehicle is configured to be directed in the direction in which the vehicle is traveling when traveling in reverse.

(Function) As a result, even if the direction of travel of the vehicle differs when traveling backwards in the first mode and the second mode, the distance sensor is oriented according to the direction of travel, so that obstacles behind the vehicle can be detected. The distance can be accurately detected.

(Effects of the Invention) Therefore, according to the present invention, the traveling direction of the vehicle can be changed depending on whether the vehicle is traveling backwards in the first mode for automatic control or when it is traveling backwards in the second mode different from the first mode. Even if the distance sensor is completely different, the distance sensor of the back monitor device always points in the direction of travel of the vehicle and can reliably detect obstacles behind the vehicle body. It is possible to increase the safety of

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

FIG. 1 shows the overall configuration of a four-wheel steering system for a vehicle according to the present invention. In FIG. 1, reference numeral 1 denotes a steering device for steering left and right front wheels 2a, 2b.
, a rack and pinion mechanism 4, left and right tie rods 5, 5, and left and right knuckle arms 6, 6.

Reference numeral 7 denotes a rear wheel steering device for steering left and right rear wheels 8a, 8b.
and a rod 11 extending in the lateral direction of the vehicle body and connected via tie rods 10, 10. The rod 11 is moved in the lateral direction of the vehicle by the rotation of a pinion 13 that meshes with a rack 12 formed on the rod 11. The pinion 13 drives a transmission mechanism 15 consisting of a pinion shaft 14 and a pair of bevel gears 15a and 15b. It is rotatably connected to a stepping motor 16 for driving a pinion via the pinion.
Further, a hydraulic actuator 17 is connected to the rod 11, which uses the rod 11 as an operating rod. The hydraulic actuator 17 is connected to the rod 1
A left-turn hydraulic chamber 17b and a right-turn hydraulic chamber 17c are partitioned in the lateral direction of the vehicle body by a piston 17a fixed to the piston 1.
b and 17c are in communication with a control valve 18 that controls the oil supply direction and oil pressure to the hydraulic actuator 17 via hydraulic passages 17d and 17e, respectively, and the control valve 18 has an oil supply passage 19 and an oil return passage. A hydraulic pump 21 is connected via 20. The control valve 18 detects the rotational direction of the pinion shaft 14 and communicates the oil supply passage 19 with the left rotation hydraulic chamber 17b when the rear wheels 8a, 8b are steered to the left (counterclockwise in the figure). At the same time, the right turning hydraulic chamber 17c is communicated with the oil return path 20, while when the rear wheels 8a and 8b are steered to the right (clockwise in the figure), the communication state is reversed to the above, and at the same time, the hydraulic pump This function reduces the hydraulic pressure from the pinion shaft 14 to a pressure corresponding to the rotational force of the pinion shaft 14, and when the pinion 13 moves the rod 11 in the lateral direction of the vehicle body, pressure oil is supplied to the hydraulic actuator 17 to reduce the pressure of the rod 11 in the lateral direction of the vehicle body. It is designed to assist in directional movement.

Furthermore, 22 is a vehicle speed sensor that detects vehicle speed;
3 is a front wheel steering angle sensor that detects the front wheel steering angle based on the amount of steering of the steering wheel 3; 24 is a rear wheel steering angle sensor that detects the rear wheel turning angle based on the amount of rotation of the stepping motor 16 of the rear wheel steering device 7; The vehicle speed signal, front wheel steering angle signal, and rear wheel steering angle signal from each of the sensors 22 to 24 are input to a four-wheel steering controller 25, respectively. The four-wheel steering controller 25 controls the operation of the stepping motor 16 via a stepping motor driver 26.
battery power supply B and ignition power supply
IG is connected.

Further, 27 is a changeover switch for selectively setting the four-wheel steering controller 25 to one of two modes to be described later;
This is a display device that graphically displays the steering status of the rear wheels 8a, 2b and rear wheels 8a, 8b and the behavior of the vehicle, and the display device 28 and the changeover switch 27 are each provided on the driver's seat side in the vehicle interior. .

In addition, reference numeral 29 denotes a back monitor controller as a control section of a back monitor device A provided to prevent collisions with obstacles at the rear of the vehicle body when backing up. An output signal from the steering controller 25 (a rear wheel turning phase signal to be described later) and a rear wheel turning angle signal from the rear wheel turning angle sensor 24 are respectively input. As shown in FIG. 2, the back monitor device A is attached to the rear of the vehicle body C together with the back monitor controller 29 in such a manner that it can detect the entire area behind the vehicle body, and detects the distance to an obstacle D located at the rear of the vehicle body. A plurality of (three in the figure) distance sensors 30, 30,
30, and a buzzer 31 installed on the driver's seat side inside the vehicle. The above distance sensor 30, 30, 3
0 is provided so that its detection direction can be changed in the left-right direction by the operation of the drive motor.

The electrical control circuits of the four-wheel steering controller 25 and back monitor controller 29 are specifically shown in FIG. That is, the four-wheel steering controller 25 uses the front wheel steering angle sensor 23
a calculation unit 32 that calculates a desired rear wheel turning angle according to a pre-stored mode based on a front wheel turning angle signal from the front wheel, a vehicle speed signal from the vehicle speed sensor 22, and a selection mode signal from the changeover switch 27; Arithmetic unit 3
Rear wheel steering angle calculated in 2 and rear wheel steering angle sensor 2
a comparison circuit 33 that compares the magnitude with the actual rear wheel turning angle based on the signal from 4 and outputs a deviation signal;
A control signal generating section 34 outputs control signals (rotation direction switching signal and correction pulse signal) to the stepping motor drive 26 based on the deviation signal from the comparison circuit 33, and a control signal generating section 34 outputs control signals to the stepping motor driver 26. The stepping motor 16 (that is, the rear wheel steering device 7) is feedback-controlled by the output of the stepping motor driver 26 so that the rear wheel steering angle becomes a desired steering angle. Here, the modes stored in the calculation unit 32 of the four-wheel steering controller 25 include an automatic control mode (AUTO) as a first mode and a fixed mode (CRAB) as a second mode, as shown in FIG. There are two. In automatic control mode (AUTO), the ratio of the rear wheel steering angle θ _R to the front wheel steering angle θ _F , that is, the steering ratio θ _R /θ _F
As a whole, the higher the vehicle speed V, the larger it becomes, and the lower the vehicle speed, the smaller it becomes, and at very low speeds (e.g.
30km/h or less), the front wheel steering angle θ _F
When becomes larger than a predetermined value θ _F ', even if the front wheel steered angle θ _F increases, the rear wheel steered angle θ _R does not increase much and remains constant at each vehicle speed. In other words, the automatic control mode has multiple settings so that the rear wheel steering angle relative to the front wheel steering angle changes depending on the vehicle speed so that they are in opposite phase at low speeds and in the same phase at high speeds, and at least in the high speed range. The characteristics of the rear wheel steering angle with respect to the wheel steering angle are controlled to be in the same phase,
The characteristics are set such that the rate of increase in the rear wheel turning angle relative to the front wheel turning angle in a region where the front wheel turning angle is large is smaller than the increase rate in a region where the front wheel turning angle is small. On the other hand, in the fixed mode (CRAB), unlike the automatic control mode, the steering ratio θ _R /θ _F remains constant on the same phase side regardless of the vehicle speed V.

On the other hand, the back monitor controller 29 is
The buzzer 31 sends warning signals of different frequencies depending on the distance signals from the distance sensors 30, 30, 30.
The vehicle is equipped with a warning signal generator 35 that outputs a warning signal to the obstacle D, and changes the intermittent interval of the warning sound from the buzzer 31 depending on the distance to the obstacle D.
In addition, the back monitor controller 29 includes the above-mentioned 4
A rear wheel steering phase signal from the calculation unit 32 of the wheel steering controller 25 (that is, a signal indicating whether the rear wheels 8a, 8b are steered in the same phase or in opposite phases) and a rear wheel steering signal from the rear wheel steering angle sensor 24. A calculation unit 36 that calculates a turning angle such that the distance sensors 30, 30, 30 face in the traveling direction of the vehicle when traveling in reverse based on the steering angle signal, and a turning angle and distance calculated by the calculation unit 36. The distance sensor 30,
A deflection angle sensor 38 that detects the deflection angle of 30, 30.
a comparison circuit 39 that compares the magnitude of the deflection angle with the actual deflection angle based on the deflection angle signal from the deflection angle signal and outputs a deviation signal;
and a control signal generating section 41 that outputs control signals (rotation direction switching signal and correction pulse signal) to the drive motor driver 40 based on the deviation signal from the comparison circuit 39, and outputs the control signal to the drive motor driver 40. The drive motor driver 40
The drive motor 37 is feedback-controlled via the drive motor 37 so that the distance sensors 30, 30, 30 are directed in the direction in which the vehicle is traveling when traveling backwards.

Therefore, in the embodiment described above, when the vehicle is traveling backwards, the distance sensors 30, 30, 30 of the backward monitor device A always monitor the vehicle's progress by the rotational drive of the drive motor 37 controlled by the backward monitor controller 29. Therefore, even if the traveling direction of the vehicle is completely different when traveling backwards in the automatic control mode of the four-wheel steering controller 25 and when traveling backwards in the fixed mode, the distance sensor 30, 30, 30
Accordingly, the obstacle D behind the vehicle body can be reliably detected. Therefore, the function of the back monitor device A, that is, the function of alerting the driver to the approach of the obstacle D by the warning sound of the buzzer 31, is fully and reliably performed, and safety can be improved. can.

It should be noted that the present invention is not limited to the above embodiments, but includes various other modifications. For example, in the above embodiment, the distance sensor 3 is
4 is used as an element for calculating the turning angle such that 0, 30, 30 points in the direction of travel of the vehicle when traveling backwards.
Although a combination of the rear wheel steering phase based on the signal from the calculation unit 32 of the wheel steering controller 25 and the rear wheel turning angle based on the signal from the rear wheel steering angle sensor 24 was used,
A combination of the rear wheel steering phase, the front wheel steering angle based on the signal from the front wheel steering angle sensor 23, and the vehicle speed based on the signal from the vehicle speed sensor 22 may be used, or the front wheel steering angle and the rear wheel steering angle may be used. You may also use a combination with.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram, FIG. 2 is a schematic plan view showing the arrangement of each component of the back monitor device, and FIG. 3 is a four-wheel steering controller and a back monitor. FIG. 4, an electrical control circuit diagram of the controller, is a diagram showing the rear wheel steering angle characteristics with respect to the front wheel steering angle. 1... Steering device, 2a, 2b... Front wheels, 7... Rear wheel steering device, 8a, 8b... Rear wheels,
25... Four-wheel steering controller, A... Back monitor device, 30... Distance sensor.

Claims (1)

[Claims] 1 A steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a rear wheel steering angle that changes depending on the vehicle speed so that it is in opposite phase at low speeds and in the same phase at high speeds. The characteristics of the rear wheel steering angle with respect to the front wheel steering angle are controlled to be in the same phase at least in the high speed range, and the characteristics are set such that the characteristics of the rear wheel steering angle with respect to the front wheel steering angle are a first mode in which the increasing rate of the steering angle is set to be smaller than the increasing rate in a region where the front wheel turning angle is small;
A four-wheel steering device for a vehicle, comprising a second mode different from the first mode, and a controller that selects the two modes and controls the rear wheel steering device according to the front wheel steering angle, A back monitor device is installed at the rear of the vehicle body and has a distance sensor for detecting a distance to an obstacle behind the vehicle body, and the distance sensor of the back monitor device is configured to be directed in the direction of travel of the vehicle when backing up. A four-wheel steering device for a vehicle characterized by: