JPH06179374A - Rear wheel steering device of vehicle - Google Patents

Abstract

PURPOSE:To provide a rear wheel steering device of a vehicle which is reformed to improve the reliability of the rear wheel steering further. CONSTITUTION:The rear wheel steering angle is detected in Step 101 immediately after an egnition switch is truned ON, and the rear wheel steering angle is set neutral in Step 102 to Step 104. And after a rear steering motor is stopped in Step 105, the motor rotation angle is cleared to '0' in Step 106, and after the front wheel steering angle is set neutral in Step 107, a 4WS control is started in Step 108. Thereafter, while the front wheel steering angle and the car speed are input in Step 109, the motor rotation angle is input in Step 110, and the motor angle of an electric motor is controlled depending on the rear wheel steering angle object value found in Step 111, so as to carry out the rear wheel steering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering system for a vehicle in which rear wheels are steered by an electric motor, and in particular, the position control of the electric motor is improved.

[0002]

2. Description of the Related Art In a four-wheel steering system for a vehicle, the steering angle of the front wheels is detected based on a detection signal from a steering sensor or the like, the traveling speed of the vehicle is detected, and the steering angle of the front wheel and the traveling speed of the vehicle are detected. The target steering angle of the rear wheels is calculated based on the above, and the steering control of the rear wheels is performed according to the target steering angle of the rear wheels. In such rear wheel steering control, various methods have been considered as means for steering and driving the rear wheels. For example, driving the rear wheel steering mechanism by an electric motor has been considered.

When performing such steering control of the rear wheels, it is important to detect the steering neutral position of the rear wheels with high precision in order to set and control the steering angle with high precision. That is, for example, the steering angle of the rear wheels is set to the neutral position when the engine is started, and the control reference position of the electric motor for driving the rear wheels is set based on the neutral position. I have to.

As means for detecting the neutral position of the electric motor for steering the rear wheels, an absolute type rear wheel steering angle sensor such as a potentiometer for detecting the actual steering angle of the rear wheels is used. When the detected voltage from the angle sensor is in the range of 0 to 5 V, for example, the intermediate voltage of 2.5 V is detected to bring the rear wheel to the neutral position.

When such an absolute type rear wheel steering angle sensor is used, the steering angle neutral position of the rear wheels can be detected. The rotation of the electric motor for steering the rear wheels is controlled by the rotation reduction mechanism (1). / N), the rotation angle of the motor is detected. Therefore, it is difficult to accurately control the position of the motor.

As a means for detecting the rotational angle position of such an electric motor, it is conceivable to use an increment type motor rotational angle sensor whose count value is updated for each specific rotational angle. If such an increment type rotation angle sensor is used, the control of the steered position of the rear wheels can be accurately executed based on the rotation angle of the electric motor. For example, Z that outputs one pulse per one rotation. Even with the phase-dependent rotation angle sensor, it is difficult to detect the neutral position of the rear wheels because the relationship with the steering angle of the rear wheels is not clear when the motor rotates multiple times.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and enables the steering angle control of the rear wheels to be performed with high accuracy by using an increment type motor rotation angle sensor. The neutral position of the rear wheels is detected with high accuracy, and the actual steering angle position of the rear wheels is reflected in the rotation angle position of the electric motor that reliably performs the rear wheel steering, so that highly reliable rear wheel steering control can be performed. It is an object of the present invention to provide a rear wheel steering system for a vehicle.

[0008]

According to another aspect of the invention, there is provided a rear wheel steering system for a vehicle in which a rear wheel is steered by an electric motor, and a steering angle position of the rear wheel is detected by a rear wheel steering angle sensor. However, the rotation angle of the electric motor is detected by an incremental motor rotation angle sensor, and the neutral steering angle position detection means detects the neutral position of the rear wheel based on the detection signal from the steering angle sensor. Then, in response to the detection of the rear-wheel steering angle neutral position, the rotation angle corresponding to the count value of the motor rotation angle sensor is cleared to set the rotation angle sensor to the neutral position. Then, the rear wheel steering control is performed based on the front wheel steering angle of the vehicle and the rear wheel target steering angle corresponding to the vehicle speed and the detection signal from the motor rotation angle sensor.

[0009]

According to the rear wheel steering system having the above-described structure, when the ignition switch for starting the engine is operated, the rear wheels are neutralized based on the detection signal from the rear wheel steering angle sensor. Set to position. If such a rear wheel neutral position is set corresponding to the detection signal from the rear wheel steering angle sensor, the count value expressing the rotation angle of the increment type motor rotation angle sensor is cleared in accordance with this, Since the motor rotation angle sensor is set to the neutral reference, the rear wheel steering angle can be calculated corresponding to the actual steering angle based on the count value from this rotation angle sensor. The rear wheel steering corresponding to the target steering angle will be performed with high accuracy and reliability.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a system configuration of four-wheel steering, in which a front wheel 12 is steered by a steering wheel 11 and a rear wheel 13 is steered by a rear wheel steering mechanism 14. 14 has an electric motor 15 as a drive source. The power supply motor 15 is rotationally controlled by a command from an electronic control unit (ECU) 16, and rear wheel steering is executed according to the rear wheel steering angle target obtained by the ECU 16.

Here, the rear wheel steering mechanism 14 is provided with a rear wheel steering angle sensor 17, and the electric motor 15 is provided with a motor rotation angle sensor 18. Detection signals from these sensors 17 and 18 are sent to the ECU 16 And the rear wheels 13 are controlled so as to correspond to the rear wheel steering angle target.

A steering sensor 19 is provided on the steering 11.
The vehicle speed sensor 20 is set in the vehicle, and the steering angle detection signal from the steering sensor 19 and the vehicle speed signal from the vehicle speed sensor 20 are E
The steering angle target of the rear wheels 13 is calculated based on the steering angle information and the vehicle speed information which are input to the CU 16. Reference numeral 21 is a warning lamp for issuing a warning to the driver when the ECU 16 detects an abnormality in the sensors.

Here, the motor rotation angle sensor 18 is of an increment type and is constructed as shown in FIG. 2, for example. That is, the rotation angle sensor 18 includes a disc 32 that is rotated integrally with the rotation shaft 31 of the electric motor 15, and the disc 32 has a large number of slits at equal intervals along the circumference centered on the shaft 31. 331, 332, ... Are formed. Further, a notch 34 is formed at one place on the outer circumference of the disk 32, and the detection reader 35 is set so as to surround a part of the outer circumference of the disk 32.

FIG. 3A is an enlarged view of a part of the disk 32. The slits 331, 332, ... Have their circumferential lengths and mutual intervals set equal to each other. Point A on the trailing edge of 331 and slits 332 and 33
The photointerrupter of the detection reader 35 is set to correspond to the point B at the intermediate position with respect to 3. Specifically, if the arrangement period of the slits 331, 332, ... Is set at the angle θ, the angular difference between the points A and B is “θ + θ /
4 ".

When the photo interrupter of the detection reader 35 is set in this manner, A from the points A and B respectively
The phase signal and the B phase signal are respectively generated with a pulse width of θ / 2 as shown in (B) of the figure, so that there is a phase difference of θ / 4 between the A and B phase detection signals. Become.
Further, one Z-phase signal is detected corresponding to one rotation of the disk 32 corresponding to the cutout 34, that is, one rotation of the steering wheel, and this Z-phase signal is output at the neutral position of the steering wheel. Is set to.

In such a rotation angle sensor 18, the A-phase signal and the B-phase signal are generated as shown in FIG. 4 corresponding to the forward rotation and the reverse rotation of the electric motor 15. Then, for example, when the B-phase signal falls while the A-phase signal is at the low level, and when the A-phase signal falls when the B-phase signal is at the high level, a count-up (increment) indicating the rotation angle of the electric motor is performed. ) Signal is generated, the rotation angle of the motor 15 is output corresponding to the count value, and the count value increases when the motor 15 rotates in the normal direction.

On the contrary, for example, when the A-phase signal is high level and the B-phase signal falls, and when the B-phase signal is low level and the A-phase signal falls, a countdown (decrement) signal is generated. The counter value is reduced when the motor 15 rotates in the reverse direction, and the rotational angular position of the electric motor 15 is obtained based on the counter value.

FIG. 5 shows the flow of processing performed in the ECU 16 for steering the rear wheels. When the ignition switch is turned on (IG-ON) and the vehicle is started, step 101 is performed. Rear wheel steering angle sensor
Read the signal from 17. An analog signal of a voltage corresponding to the steering angle is input from the sensor 17, and is input as a voltage value corresponding to the rear wheel steering angle θr, for example, as shown in FIG. It is converted into a digital signal by the D converter and read as a steering angle value of the rear wheels.

In step 102, it is judged whether or not the rear wheel steering angle signal has a value corresponding to the neutral position. The steering angle signal voltage θr is smaller than α indicating the neutral position range, corresponding to FIG. It is determined whether or not it is larger than β, and the steering direction of the rear wheels is determined. When it is determined in step 102 that “θr <α”, step 10
If the process proceeds to step 3, the rear wheel steering electric motor 15 is commanded to rotate to the right, and if it is determined that “θr> β”, step 10
Proceed to step 4 to issue a command to rotate the electric motor 15 to the left, and
Make sure 13 is steered towards the neutral position.

By such an operation, the steering angle of the rear wheel 13 is controlled so as to be set to the neutral position.
If the neutral position is confirmed in step 2, step
Proceeding to 105, the electric motor 15 for steering the rear wheels is stopped.
That is, immediately after the ignition switch is operated, the steering angle of the rear wheel 13 is set and controlled to the neutral position. Rear wheel 13
If the steering angle of is set to the neutral position, step 106
Clears the rotation angle θm of the motor rotation angle sensor 15 to “0”.

At the time of starting such a vehicle, the front wheels 12
The steering wheel is also set to the neutral position for initial setting, and based on the detection signal from the steering sensor 19, it is determined in step 107 whether the neutral position of the front wheel steering angle is detected. Then, if it is confirmed that the steering angle of the front wheels 12 is set to the neutral position, the four-wheel steering (4WS) control is started in step 108.

That is, in step 109, the vehicle speed and the front wheels are
The steering angle of the rear wheels 13 is confirmed by inputting the steering angle of 12 and the output value from the rotation angle sensor 15 of the electric motor 15 for steering the rear wheels in step 110. And step 111
In step 109, the target steered angle of the rear wheels 13 is calculated based on the vehicle speed and the steered angle of the front wheels 12 input in step 109.

When the target steered angle θr of the rear wheels 13 is calculated in this manner, the target steered angle θr is compared with the rotation angle θm of the electric motor 15 in step 112, and the steps are repeated until the two match. At 113, the electric motor 15 for steering the rear wheels is rotationally controlled, and the rear wheels are steered so that the rear wheels 13 are set to this target turning angle. Then, in step 113, the target turning angle and the motor 15
If the rotation angle θm of the rear wheel 13 coincides with the rotation angle θm, the stop control of the electric motor 15 for steering the rear wheel 13 is performed in step 114, and the rear wheel steering corresponding to the vehicle running state is ended.

That is, immediately after the ignition switch is turned on and the starting operation of this vehicle is performed, the rear wheels are
The electric motor 15 steers the steering angle to a neutral position, and the steering is stopped with the neutral position being set. Then, with the steering angle neutral position of the rear wheel 13 set, the electric motor 15 for steering the rear wheel 13 is initially set, and the motor rotation angle "0" is set.
The rotation angle of the motor 15 is read by the motor rotation angle sensor 18 based on the initial reference position, and the rear wheel steering control is performed based on the rotation angle read value from the motor rotation angle sensor 18.

After the reference rotation angle corresponding to the rear wheel steering angle of the electric motor 15 for steering the rear wheels 13 is set in this manner,
The rear wheel steering control is performed by comparing the rear wheel steering angle target value calculated based on the steering angle of 12 and the vehicle traveling speed with the rotation angle of the electric motor 15 that steers the rear wheels 13. The steering angle control of the rear wheels 13 can be executed accurately and reliably.

In the above example, the rear wheels 13 are returned to the neutral position immediately after the ignition switch is turned on, and after the rear wheel steering angle sensor 17 detects that the steering angle of the rear wheels 13 is set to the neutral position. The detection control of the steering angle position of the rear wheel 13 is performed based on the detection signal from the rotation angle sensor 18.

However, immediately after the ignition switch is turned on, the current steering angle position of the rear wheels 13 is detected by the rear wheel steering angle sensor 17, and this rear wheel steering angle θr is detected by the motor rotation angle sensor.
It may be converted into a count value (θm) indicating the rotation angle of 18 and thereafter the rear wheel steering angle position may be controlled based on the detection signal from the motor rotation angle sensor 18. In this case, the detected steering angle (θm) from the rear wheel steering angle sensor 17 is at the neutral position (α ≦
When θr ≤ β), check whether the count value (θm) of the motor rotation angle sensor 18 is “± 0”,
If the value is deviated, a motor rotation angle neutral correction means is provided so as to clear the count value (θm) of the motor rotation angle sensor 18 to “0”.

[0028]

As described above, according to the vehicle rear wheel steering system of the present invention, when the rear wheels are steered by the electric motor, the rotation angle position of the electric motor and the steering angle position of the rear wheels are controlled. Is always set correspondingly, and the rear wheel steering control can be performed with high accuracy by driving and controlling the electric motor based on the target value of the rear wheel steering angle, and the reliability of the four-wheel steering of the vehicle is improved. .

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a vehicle in which a rear wheel steering system according to an embodiment of the present invention is set.

FIG. 2A is a side view illustrating a motor rotation angle sensor installed in the vehicle, and FIG. 2B is a front view of the same.

FIG. 3A is an enlarged view of a part of a disk of the rotation angle sensor, and FIG. 3B is a view explaining a detection signal from the sensor.

FIG. 4 is a diagram illustrating a rotation angle detection operation of the rotation angle sensor.

FIG. 5 is a flowchart illustrating a rear wheel steering process of the rear wheel steering device.

FIG. 6 is a diagram illustrating an output of a rear wheel steering angle sensor.

[Explanation of symbols]

11 ... Steering, 12 ... Front wheel, 13 ... Rear wheel, 14 ... Rear wheel steering mechanism, 15 ... Electric motor, 16 ... Electronic control unit, 17 ...
Rear wheel steering angle sensor, 18 ... Motor rotation angle sensor, 19 ... Steering sensor, 20 ... Vehicle speed sensor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Nakamura 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. An electric motor for steering a rear wheel, a rear wheel steering angle sensor for detecting a steering angle position of the rear wheel, an increment type motor rotation angle sensor for detecting a rotation angle of the electric motor, and a vehicle. And a neutral steering angle position detecting means for detecting that the rear wheel steering angle is set to the neutral position based on the detection signal from the steering angle sensor, and the rear wheel steering angle neutral position detection. And a rotation angle sensor neutral setting means for clearing a rotation angle corresponding to the count value of the motor rotation angle sensor, and a rear wheel target steering angle and a motor rotation angle corresponding to a front wheel steering angle and a vehicle speed of the vehicle. A rear wheel steering device for a vehicle, wherein steering control of rear wheels is performed based on a detection signal from a sensor.