JPH06211151A - Electric control device for rear wheel steering device - Google Patents

Abstract

PURPOSE:To make a driver recognize an abnormal condition of the rear wheels even though an alarm cannot be operated. CONSTITUTION:A microcomputer 35 controls to steer the left rear wheel RW1 and the right rear wheel RW2 to an object steering angle decided according to the car speed, the yaw rate, and the front wheel steering angle, detected by a car speed sensor 31, a yaw rate sensor 32, and a front wheel steering angle sensor 33. When an abnormal condition is generated to the steering control of the left and the right rear wheels RW1 and RW2, the steering angles of the left and the right rear wheels RW1 and RW2 are maintained while they are steered at a minute steering angle, provided that the parts of a rear wheel steering angle sensor 34 and an electric motor 21 are normal. Consequently, since the neutral position of a steering handle 11 in a straight running condition of the vehicle is slipped a little to the left or to the right from a mechanical neutral position (the neutral position of the steering handle 11 when the left and the right rear wheels RW1 and RW2 are maintained in the neutral condition), the driver can recognize the abnormal condition of the rear wheels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls a rear wheel steering device by controlling an actuator provided in a rear wheel steering device in response to vehicle state detection by various sensors such as a vehicle speed sensor, a yaw rate sensor, and a front wheel steering angle sensor. The present invention relates to an electric control device for a rear wheel steering device that steers a vehicle, and particularly relates to an electric control device for a rear wheel steering device that handles an abnormality in steering control of a rear wheel when a part of a sensor, an actuator, or the like malfunctions. For an electric control device.

[0002]

2. Description of the Related Art Conventionally, as a device of this type, for example, as disclosed in Japanese Patent Laid-Open No. 146772/1987,
If an abnormality occurs in the steering control of the rear wheel while the rear wheel is being steered in the opposite phase to the front wheel, the abnormality is detected, the rear wheel is returned to the neutral position, and the alarm device is activated to activate the driver. The above-mentioned abnormality is notified to the.

[0003]

However, in the above-mentioned conventional apparatus, when the alarm device is inoperable because of a failure such as disconnection or short circuit, the driver is There is a problem that the steering abnormality of the wheels is not noticed. The present invention has been made to address the above problems, and an object thereof is to provide an electric control for a rear wheel steering system that enables a driver to recognize a rear wheel steering abnormality even when an alarm device is inoperable. To provide a device.

[0004]

In order to achieve the above object, a structural feature of the present invention is an electric control device for a rear wheel steering system having an actuator for steering the rear wheels. An electric control for a rear wheel steering device including various sensors for detecting a vehicle state, and first steering control means for controlling an actuator and steering-controlling a rear wheel in response to vehicle state detection by the various sensors In the device, abnormality detection means for detecting steering abnormality of the rear wheels, and when the abnormality detection means detects steering abnormality of the rear wheels, the steering control by the first steering control means is stopped and the actuator is controlled to control the rear wheels. The second steering control means for controlling the steering to a predetermined small steering angle is provided.

[0005]

According to the present invention configured as described above, when the rear wheel steering becomes abnormal due to a failure in various sensors, a part of the actuator, a part of the first steering control means, etc. The detection means detects the occurrence of this abnormality, and the second steering control means stops the steering control by the first steering control means and controls the actuator to steer the rear wheels to a predetermined small steering angle. As a result, the turning position of the handlebar that is maintained to drive the vehicle straight ahead is slightly shifted to the left or right from the mechanical neutral position (the turning position of the handlebar when the rear wheels are kept in the neutral state). The driver can recognize the steering abnormality of the rear wheels even if the alarm device notifying the abnormality of the rear wheel steering does not operate due to a failure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a front wheel steering device 10 for steering left and right front wheels FW1 and FW2 and a rear wheel steering device for steering left and right rear wheels RW1 and RW2. 1 schematically shows the entire vehicle including an electric control device 20 for electrically controlling the rear wheel steering device 20.

The front wheel steering device 10 is provided with a steering handle 11 for steering the left and right front wheels FW1 and FW2 by turning operation.
The handle 11 is fixed to the upper end of the steering shaft 12.
The lower end of the steering shaft 12 meshes with the rack bar 14 in the steering gear box 13. The rack bar 14 is supported in the steering gear box 13 so as to be displaceable in the axial direction, and has tie rods 15a, 1 at both ends.
The left and right front wheels FW1, FW2 are steerably connected via the 5b and the knuckle arms 16a, 16b.

The rear wheel steering device 20 includes an electric motor 21 such as a brushless motor as an actuator for steering the rear wheels. The electric motor 21 has two field windings connected in parallel, and the motor 21 is driven to rotate by energizing at least one of the windings. Electric motor 2
The rotating shaft of No. 1 is connected to a relay rod 23 supported in the steering gear box 22 via a reduction mechanism so as to be displaceable in the axial direction.
Is displaced in the axial direction according to the rotation of. The reverse efficiency of the reduction mechanism is set to be small so that the electric motor 21 is not rotationally driven by an external input from the relay rod 23 side. Tie rods 24a and 24b and knuckle arms 25a and 25b are provided at both ends of the relay rod 23.
The left and right rear wheels RW1 and RW2 are connected via the, and the left and right rear wheels RW1 and RW2 are steered according to the axial displacement of the relay rod 23.

The electric control unit 30 comprises a vehicle speed sensor 31, a yaw rate sensor 32, a front wheel steering angle sensor 33 and a rear wheel steering angle sensor 34. The vehicle speed sensor 31 detects the vehicle speed V by measuring the rotation of an output shaft of a transmission (not shown) and outputs a detection signal indicating the vehicle speed V. The yaw rate sensor 32 detects the yaw rate γ around the center of gravity of the vehicle body and outputs a detection signal indicating the yaw rate γ. The front wheel steering angle sensor 33 detects the steering angle θf of the left and right front wheels FW1 and FW2 by measuring the rotation angle of the steering shaft 12, and outputs a detection signal representing the steering angle θf. Rear wheel steering angle sensor 34
Detects the steering angle θr of the left and right rear wheels RW1 and RW2 by measuring the rotation angle of the rotary shaft of the electric motor 21, and outputs a detection signal representing the steering angle θr. The yaw rate γ, the front wheel steering angle θf, and the rear wheel steering angle θr are positive in the left rotation direction and negative in the right rotation direction.

These sensors 31 to 34 are connected to the microcomputer 35. The microcomputer 35 is composed of a CPU, a ROM, a RAM, an I / O, a timer and the like, and executes the program stored in the ROM and shown in the flowchart of FIG. Microcomputer 35
Drive circuits 36a and 36b and an alarm device 37 are connected to. The drive circuits 36a and 36b are controlled by the microcomputer 35 to flow the drive current from the battery 38 to the field windings of the electric motor 21 to control the rotation of the motor 21 independently. The battery 38
The voltage from is also supplied to each of the sensors 31 to 34, the microcomputer 35 and the alarm device 37. Alarm 37
Is composed of a lamp and a buzzer installed near the driver's seat. The left and right rear wheels R are turned on by lighting the lamp and emitting a buzzer.
The driver is warned of abnormal steering of W1 and RW2.

Next, the operation of the embodiment configured as described above will be described with reference to the flow chart shown in FIG. When an ignition switch (not shown) is turned on, the microcomputer 35 starts executing the program in step 100 of FIG. 2 and each sensor 3 in step 102.
The detection signals representing the vehicle speed V, the yaw rate γ, the front wheel steering angle θf and the rear wheel steering angle θr are input from 1 to 34, respectively. Next, at step 104, the yaw rate proportional coefficient K1 (FIG. 3) that changes according to the vehicle speed V is read from the table provided in the ROM.
(See (A)) and the steering angle proportional coefficient K2 (see FIG. 3B), and the target steering angles θr * of the left and right rear wheels RW1 and RW2 are calculated by executing the calculation of the following formula 1.

[0012]

[Mathematical formula-see original document] θr * = K1 · γ + K2 · θf After calculating this target steering angle θr *, at step 106, the deviation Δθ (= between the target steering angle θr * and the input rear wheel steering angle θr.
A control signal for reducing the deviation Δθ in accordance with θr * −θr) is supplied to the drive circuits 36a and 36b. The drive circuits 36a and 36b respectively apply a drive current corresponding to the supplied control signal to the windings of each series of the electric motor 21. As a result, the electric motor 21 rotates in a direction corresponding to the target steering angle θr *, the rotation is transmitted to the relay rod 23, and the rod 23 is displaced in the axial direction according to the rotation. The axial displacement of the relay rod 23 is caused by the tie rod 24a,
The rear wheels RW1, RW are transmitted to the left and right rear wheels RW1, RW2 via 24b and the knuckle arms 25a, 25b.
2 is steered in the direction of the target steering angle θr *.

After the processing of step 106, step 1
At 08, it is determined whether or not an abnormality has occurred in the rear wheel steering due to a failure of the vehicle speed sensor 31, the yaw rate sensor 32, the front wheel steering angle sensor 33, the microcomputer 35, the drive circuits 36a and 36b, the electric motor 21, and the like. In the determination of this abnormality, for example, it is determined whether or not the abnormality has occurred based on the following conditions. The detected vehicle speed V shows a value that is not possible when the vehicle is running. The detected yaw rate γ shows a value that is not possible when the vehicle is running. The detected front wheel steering angle θf shows a value that is not possible during vehicle traveling. Detected vehicle speed V, detected yaw rate γ, and detected front wheel steering angle θf
Is in a relationship that is impossible for the vehicle to travel. The target rudder angle θr * or the detected rear wheel rudder angle θr shows a value that is impossible for the vehicle running, or the deviation Δ between the two rudder angles θr * and θr
The absolute value | Δθ | of θ is very large.

The change rate dθr * / dt of the target rudder angle θr * or the change rate dθr / dt of the detected rear wheel rudder angle θr indicates that the vehicle cannot travel, or both change rates dθr * / dt and dθr / dt. The absolute value of deviation | dθr * / dt−dθr / dt | is very large.

If the steering of the rear wheels is normal, step 10
In step 8, the program is judged to be “NO” and step 102 is executed.
Return to. Then, unless the abnormality occurs, the circulation processing including steps 102 to 108 is repeatedly executed to steer the left and right rear wheels RW1 and RW2 to the target steering angle θr *.

Next, the vehicle speed sensor 31, the yaw rate sensor 32, the front wheel steering angle sensor 33, and the microcomputer 3
5, a case where an abnormality occurs in the drive circuits 36a and 36b, the electric motor 21, and the like will be described. In this case, it is determined "YES" in step 108 and the program is advanced to step 110 and the subsequent steps. In step 110, the rear wheel steering angle θr is read from the rear wheel steering angle sensor 34, and step 1
At 12, it is determined whether the absolute value | θr | of the rear wheel steering angle θr read in is greater than a predetermined small steering angle θro. This small rudder angle θro is a rudder angle that does not cause any inconvenience in the running of the vehicle, and the rotational position for maintaining the steering wheel 11 to drive the vehicle straight ahead is a mechanical neutral position (left and right rear wheels RW1, RW2. Is a rear wheel steering angle (for example, about 1 degree) to the extent that the driver notices that the steering wheel 11 is offset from the rotational position of the steering wheel 11 in the state of being kept neutral. If the absolute value | θr | of the rear wheel steering angle θr is less than or equal to the minute steering angle θro, it is determined to be “NO” in step 112 and the program proceeds to step 120. In step 120, the operation signal is output to the alarm device 37, and the data indicating the type of abnormality detected by the determination process in step 108 is stored in the microcomputer 35. The alarm device 37 responds to the actuation signal by lighting a lamp or emitting a buzzer sound to generate left and right rear wheels RW1, RW.
Notify the driver that steering abnormality has occurred in 2. Further, the abnormal data stored in the microcomputer 35 is used for later repair, investigation of the cause of failure, and the like. After the execution of step 120, the execution of the program is stopped in step 122. In this case, since the reduction efficiency of the reduction gear mechanism in the steering gear box 22 is small, the relay rod 23 is not displaced in the axial direction by the external force applied to the left and right rear wheels RW1, RW2 from the road surface, and the rear wheels RW1, RW1, RW2 is maintained at the minute steering angle θro.

On the other hand, if the absolute value | θr | of the rear wheel steering angle θr is larger than the minute steering angle θro, at step 112, "YE
S ”is determined and the program proceeds to step 114.
In step 114, it is determined whether or not steering (returning) in the neutral direction of the left and right rear wheels RW1, RW2 is possible. This determination process is to determine whether or not the minimum operation of the devices necessary for steering the left and right rear wheels RW1 and RW2 to a predetermined small steering angle θro is normal. It is determined whether the angle sensor 34, at least one winding of the electric motor 21, at least one of the drive circuits 36a and 36b, and the portion of the microcomputer 35 that controls the left and right rear wheels RW1 and RW2 are normal. If these devices are not normal, the determination in step 114 is "NO" and the program proceeds to steps 120 and 122.
As in the case described above, data indicating the type of abnormality is stored in the microcomputer 35, the alarm 37 is activated, and the execution of the program is stopped.

If the minimum operation of the devices required to steer the left and right rear wheels RW1 and RW2 to a predetermined small steering angle θro is normal, "YES" is determined in step 114.
Then, the program proceeds to step 116. In step 116, the drive circuits 36a and 36b are controlled based on the input rear wheel steering angle θr to drive the drive circuit 3
The left and right rear wheels RW1 and RW2 are steered in the neutral direction based on the operation of the electric motors 6a and 36b. This step 1
After the processing of 16, it is determined in step 118 whether or not the absolute value | θr | of the rear wheel steering angle θr is less than or equal to the minute steering angle θro,
If the absolute value | θr | is larger than the small steering angle θro, it is determined to be “NO” at step 118 and the program is returned to step 100. The steps 110 to 118 are repeatedly executed until the absolute value | θr | of the rear wheel steering angle θr reaches the minute steering angle θro or less, and the absolute value | θr | becomes the minute steering angle θro.
When the following is reached, it is determined to be “YES” in step 118, and the execution of the program is stopped by the processing of steps 120 and 122 described above.

As can be understood from the above description of the operation, according to the above embodiment, the vehicle speed sensor 31, the yaw rate sensor 32, the front wheel steering angle sensor 33, and the microcomputer 35.
Of one of the drive circuits 36a and 36b, one winding of the electric motor 21, or the like, and the left and right rear wheels RW.
When the steering of 1 and RW2 becomes abnormal, the left and right rear wheels RW1 and R
The rear wheels RW1 and RW2 are steered to the minute steering angle θro and maintained at the same steering angle θro, provided that W2 can be steered to the minute steering angle θro. Therefore, according to the above-described embodiment, when the steering of the left and right rear wheels RW1, RW2 is abnormal as described above, the neutral position of the steering handle 11 during straight running of the vehicle is the mechanical neutral position (the left and right rear wheels RW).
1, steering wheel 11 when RW2 is kept in a neutral state
Even if the alarm 37 does not operate due to a failure, the driver can recognize the steering abnormality of the rear wheels.

In the above embodiment, as shown in FIG. 4, when the left and right rear wheels RW1 and RW2 are abnormally steered, they are steered at a small steering angle ± θro with reference to the neutral position of the rear wheels RW1 and RW2. However, the neutral position may be shifted to the left or right depending on the position of the driver, for example, in the case of a right-hand drive vehicle, the neutral position may be shifted to the left as shown by the broken line in the figure. Accordingly, it is possible to correct the difference in the tolerance of the driving vehicle with respect to the right deflection or the left deflection of the vehicle depending on the position of the steering wheel 11. Further, in the above embodiment, even if steering abnormality occurs in the left and right rear wheels RW1 and RW2, the rear wheel steering angle θ
If r is within the small rudder angle θro, the rear wheels RW1 and RW2 are not steered.
Even if r is within the small steering angle θro, the left and right rear wheels RW1, R
W2 may be steered up to the minute steering angle θro.

Further, in the above embodiment, the left and right rear wheels RW
1, as a means to notify the driver of steering abnormality of RW2,
When the abnormality occurs, the power steering device or the suspension device may be controlled to make the operation of the steering wheel 11 heavy or to add means for changing the vehicle height.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of a vehicle according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a program executed by the microcomputer of FIG.

3A is a change characteristic diagram of a yaw rate proportional coefficient with respect to a vehicle speed, and FIG. 3B is a change characteristic diagram of a steering angle proportional coefficient with respect to a vehicle speed.

FIG. 4 is an explanatory diagram for explaining a steering angle range of rear wheels.

[Explanation of symbols]

FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 10 ...
Front wheel steering device, 20 ... Rear wheel steering device, 21 ... Electric motor, 30 ... Electric control device, 31 ... Vehicle speed sensor, 32 ... Yaw rate sensor, 33 ... Front wheel steering angle sensor, 34 ... Rear wheel steering angle sensor, 35 ... Micro Computer, 36a, 36
b ... Drive circuit, 37 ... Alarm device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shinichi Tagawa 2-1-1 Asahi-cho, Kariya City, Aichi Prefecture Aisin Seiki Co., Ltd. (72) Hideki Kasuriya 2--1 Asahi-cho, Kariya City, Aichi Aisin Seiki Co., Ltd. Within the corporation

Claims (1)

[Claims] 1. An electric control device for a rear wheel steering system having an actuator for steering a rear wheel, comprising: various sensors for detecting a state of a vehicle; and a response to detection of the state of the vehicle by the various sensors. An electric control device for a rear wheel steering system, comprising: a first steering control means for controlling the actuator to control the steering of the rear wheels; and an abnormality detection means for detecting steering abnormality of the rear wheels, and the abnormality detection means. Second steering control means for stopping steering control by the first steering control means when the steering abnormality of the rear wheels is detected by the means, and controlling the actuator to steer the rear wheels to a predetermined small steering angle. An electric control device for a rear wheel steering device characterized by being provided.