JPH043355B2 - - 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 according to driving conditions including vehicle speed and 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 rear wheels are not steered in opposite phases because the vehicle speed is extremely low when using four-wheel steering as described above. However, in some cases, it may be desirable to steer the rear wheels largely in the same phase. There is. 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 depending on the driving condition, four-wheel steering can be performed in any different mode according to the driver's request. It is desirable to do so.

Therefore, the present applicant has previously proposed a new four-wheel steering system for a vehicle to meet such requirements (see Japanese Patent Application No. 57-190049 (Japanese Unexamined Patent Publication 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 types of modes, when the driver drives without being aware of which mode the controller is in, the fixed mode is selected and set. If so, there is a risk of driving errors. For example, if the rear wheel steering angle characteristic as a fixed mode is set linearly to the same phase side regardless of the vehicle speed in order to facilitate parking in a garage or parallel parking as described above, when the steering wheel is turned 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 end up traveling backwards in the exact opposite direction to the direction in which you turned the steering wheel. This can lead to driving mistakes for drivers who are accustomed to two-wheel steering.

An object of the present invention is to provide a four-wheel steering system for a vehicle in which a controller for controlling a rear wheel steering system according to the steering angle of the front wheels has two modes, an automatic control mode and a fixed mode, as described above. By automatically setting the controller mode to automatic control mode when changing gears of the transmission, it is intended to prevent driving errors caused by the driver forgetting that the mode is set to fixed mode. It is something.

(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. A plurality of wheel steering angle characteristics are set so as to change according to the vehicle speed, and 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 controlled to be in phase with respect to the front wheel steering angle. The automatic control mode is set so that the ratio of increase in the rear wheel steering angle to the front wheel steering angle in a region where the front wheel steering angle is large is smaller than that increase ratio in a region where the front wheel steering angle is small. The present invention assumes a four-wheel steering system for a vehicle, which has a fixed mode to be set, and a controller that selects one of these two modes and controls the rear wheel steering system according to the front wheel steering angle. and a transmission position detecting means for detecting when the forward/reverse gear of the transmission is changed; and a fixed mode canceling means for switching the mode of the controller to the automatic control mode in response to the output of the transmission position detecting means when the fixed mode is set. It shall be equipped with the following.

(Function) As a result, in the present invention, when the fixed mode is set,
When the forward and reverse gears of the transmission are changed, the mode of the controller is switched from the fixed mode to the automatic control mode by the fixed mode release means.

(Effects of the Invention) Therefore, according to the four-wheel steering device for a vehicle of the present invention, after traveling with four-wheel steering in the fixed mode among the two modes of the controller, when moving to the next traveling, During the transition process, the transmission is automatically switched from the fixed mode to the automatic control mode by changing the forward and reverse gears, so even if the driver is not aware of which mode it is set to and drives in reverse, for example. The automatic control mode prevents the vehicle from driving backwards with the same behavior as in the case of two-wheel steering, thereby preventing driving errors and improving safety.

(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. Reference numeral 1 denotes a steering system for steering left and right front wheels 2a, 2b. It consists of a 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 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 move the rod 11 in the lateral direction of the vehicle body. I'm trying to help.

Furthermore, 22 is a vehicle speed sensor that detects vehicle speed;
3 is a front wheel steering angle detection sensor that detects the steering amount of the steering wheel 3 and detects the front wheel steering angle; 24 is a sensor that detects the rotation amount of the stepping motor 16 of the rear wheel steering device 7 to determine the rear wheel steering angle; The vehicle speed signal, the front wheel steering angle signal, and the rear wheel steering angle signal from the sensors 22 to 24 are input to the controller 25, respectively.

The controller 25 drives the stepping motor 16 via a stepping motor driver 26.
As shown in Figure 2, it has two modes that determine the ratio of the rear wheel steering angle θ _R to the front wheel steering angle θ _F (steering ratio θ _R /θ _F ). In other words, automatic control mode (AUTO) and fixed mode (CRAB) are stored in advance. In this automatic control mode (AUTO), the overall steering ratio θ _R /θ _F increases as the vehicle speed Vc increases, decreases as the vehicle speed decreases, and becomes negative (opposite phase) at extremely low speeds. In addition, when the front wheel steering angle θ _F becomes larger than the predetermined value θ _F ′ in the medium and high vehicle speed range,
Even if the front wheel turning angle θ _F increases, the rear wheel turning angle θ _R does not increase and remains constant at each vehicle speed. In other words, the characteristics of the rear wheel turning angle with respect to the front wheel turning angle are set in a plurality of settings so as to change according to the vehicle speed, and the characteristics of the rear wheel turning angle with respect to the front wheel turning angle are controlled to be in the same phase at least in the high speed range.
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, the steering ratio θ _R /θ _F remains constant on the same phase side regardless of the vehicle speed.

Further, the controller 25 is connected to a battery power supply B and an ignition power supply IG, and also has a mode selection switch 27.
is connected. Accordingly, the controller 25 selects a mode (automatic) in which the rear wheel steering angle is selected and set by the changeover switch 27 based on the vehicle speed signal from the vehicle speed sensor 22 and the front wheel steering angle signal from the front wheel steering angle detection sensor 23. The stepping motor 16 is operated while performing feedback control based on the rear wheel steering angle signal from the rear wheel steering angle detection sensor 24 so as to achieve a predetermined steering angle in the control mode or fixed mode).
(that is, the rear wheel steering device 7). Incidentally, 42 is a display means for receiving an output signal from the controller 25 and graphically displaying the steering states of the front wheels 2a, 2b and the rear wheels 8a, 8b.

The electrical circuit of the changeover switch 27 is shown in FIG. That is, in FIG. 3, 28 is a first switch for automatic control mode selection, 29 is a second switch for fixed mode selection, 3
0 is a latch relay connected to both the switches 28 and 29, and the latch relay 30 is connected to the first
When the switch 28 is turned on, it receives the ON operation signal and connects the common terminal 30b of the relay contact 30a.
While connecting the AUTO terminal 30c and outputting the AUTO signal to the controller 25, when the second switch 29 is turned on, it receives the ON operation signal and connects the common terminal 30b of the relay contact 30a.
Connect CRAB terminal 30d to controller 2
5 to output a CRAB signal.

In addition, 31 turns on the ignition power supply IG when the transmission is changed to reverse gear.
A back-clamp switch 33 applies current from the back-clamp switch 31 to the back-clamp 32 to light the back-clamp 32;
The delay circuit 34 receives the ON operation signal directly and
a first exclusive OR circuit that receives the first exclusive OR circuit 33 via the first exclusive OR circuit 33;
The switch detects the ON-OFF switching of the back clamp switch 31 based on ON operation signals from different paths, and outputs an "H" level signal at the ON-OFF switching. Further, 35 is an inhibitor switch that is turned ON when the transmission is changed to parking or neutral, and 36 is a second exclusive OR circuit that receives the ON operation signal from the inhibitor switch 35 directly and via a delay circuit 37. Then, the second exclusive OR circuit 36 determines and detects when the inhibitor switch 35 is switched between ON and OFF based on ON operation signals from different paths, and performs the ON-OFF switching of the inhibitor switch 35.
It outputs an "H" level signal when switched off. Therefore, the first and second exclusive OR circuits 33 and 36 allow the
Transmission position detection means 3 for detecting when reverse gear is changed
8 are made up.

Further, 39 outputs an "H" level signal when receiving the output signal from the transmission position detection means 38 (that is, the "H" level signal from the first or second exclusive OR circuit 33, 36). OR circuit, 40 is "H" from the OR circuit 39
The level signal is amplified by a predetermined amount, and the amplified "H" level signal is applied to the first latch relay 30.
This is a transistor that outputs to the switch 28 connection side, and when fixed mode selection is set (latch relay 30
Common terminal 30b of relay contact 30a and CRAB
(when the terminal 30d is in the connected state), the first switch 28 of the latching relay 30 receives an output signal from the transmission position detection means 38 and outputs an "H" level signal.
output to the connection side, and connect the common terminal 30b of the relay contact 30a of the latch relay 30 to the CRAB terminal 30d.
A fixed mode canceling means 41 is constituted, which outputs an AUTO signal to the controller 25 and switches the mode of the controller 25 to the automatic control mode by switching the connection from the AUTO terminal 30c to the AUTO terminal 30c.

Therefore, in the above embodiment, when the controller 25 moves to the next run after driving with four-wheel steering in the fixed mode of the two modes, the gear change is performed when the gear of the transmission is changed in the transition process. The machine position detection means 38 detects this and outputs an output signal. For example, when changing the transmission from forward gear to reverse gear, the first exclusive OR circuit 33 outputs an "H" level signal, and when changing the transmission from forward gear to parking, the second exclusive OR circuit 33 outputs an "H" level signal. Exclusive OR circuit 3
6 outputs an "H" level signal.

Then, the fixed mode release means 41 receives the output signal from the transmission position detection means 38, and the output signal from the fixed mode release means 41 is sent to the controller 25.
An AUTO signal is output, which causes the controller 25 to switch from fixed mode to automatic control mode. In other words, the driver presses the first switch 2.
The same result as when turning on 8 will occur.

Therefore, even if the driver forgets that the controller 25 was set to the fixed mode during the previous drive and drives in reverse, for example, the automatic control mode causes the vehicle to behave in the same way as when the vehicle is in two-wheel steering. This causes the vehicle to travel backwards, thereby preventing driving errors and improving safety.

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 rear wheel steering device 7 is configured to use both the stepping motor 16 and the hydraulic actuator 17 to steer the rear wheels 8a and 8b. The configuration may be such that only one of the rear wheels 8a, 8b is used to steer the rear wheels 8a, 8b, or the steering force of the front wheels 2a, 2b is transmitted to the rear wheels 8a, 8b via a link mechanism etc. The wheels 8a and 8b may be steered.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram, FIG. 2 is a diagram showing rear wheel steering angle characteristics with respect to front steering angle, and FIG. 3 is an electric circuit diagram of a changeover switch. be. 1... Steering device, 2a, 2b... Front wheels, 7... Rear wheel steering device, 8a, 8b... Rear wheels,
25...Controller, 38...Transmission position detection means, 41...Fixed mode release means.

Claims (1)

[Claims] 1 A steering device that steers the front wheels, a rear wheel steering device that steers the rear wheels, and a plurality of rear wheel steering angle characteristics relative to the front wheel steering angle are set so as to change according to vehicle speed, and at least at high speed. The characteristics of the rear wheel steering angle relative to the front wheel steering angle are controlled to be in the same phase in the region where the front wheel steering angle is large. It has an automatic control mode that is set to be smaller than the rate of increase in a small area, and a fixed mode that sets this characteristic regardless of the driving state, and the rear wheel steering device can select between these two modes. A four-wheel steering system for a vehicle, comprising: a controller for controlling a front wheel according to a front wheel steering angle;
A four-wheel steering system for a vehicle, comprising fixed mode release means for switching a controller mode to an automatic control mode in response to an output from the transmission position detection means.