JPH0438272A - Rear-wheel steering angle controller for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To improve the reliability of clutch-off control by making a clutch so as to be turned off through a theoretical circuit in the case where there is either of a trouble detection signal out of a trouble detector of a microcomputer or that of an electric motor or a clutch-off command out of the microcomputer. CONSTITUTION:A four-wheel steering vehicle is being reset to a state of two- wheel steerage at a time when a clutch 16 interposed between an electric motor 14 and rear wheels 18 is off, and usually (four-wheel steering time), the clutch 16 is turned to OFF by a clutch control signal 10. In this state, when a microcomputer trouble detector 4 detects something wrong in a microcomputer 7 by a microcomputer monitoring signal 5, a trouble detection signal 6 is turned over by a NOT circuit 12b, and further a logical product is taken by the clutch control signal 10 through an AND circuit 12d, whereby output 11 of this AND circuit 12d is turned to OFF, and the clutch 16 is turned to OFF. Likewise, when a motor trouble detector 15 detects something wrong in the motor 14, the clutch 16 is turned to OFF by this trouble detection signal 9 through a NOT circuit 12c and the AND circuit 12d.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to rear wheel steering angle control of a four-wheel steering vehicle in which the rear wheel steering angle is controlled by an electric motor according to vehicle driving conditions such as steering angle. Regarding equipment.

BACKGROUND OF THE INVENTION Conventionally, a rear wheel steering angle control device for a four-wheel steering vehicle has been used, for example.
As shown in Japanese Patent Application Laid-Open No. 01-22675,
When the vehicle is running at a speed lower than the predetermined vehicle speed value, the steering angle ratio between the front wheels and the rear wheels is set to a value where the rear wheel steering angle is in the opposite phase to the front wheel steering angle. A system has been proposed in which the steering ratio is set to a value where the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle is running at a higher speed than a predetermined vehicle speed value. .

The main advantage of four-wheel steering vehicles is that the cornering force of the front and rear tires can be generated almost simultaneously, so the vehicle can move laterally after steering wheel operation faster than a vehicle with only front-wheel steering.

In other words, if the front wheels and rear wheels are steered at an appropriate steering angle ratio such that the front and rear wheels are out of phase at low speeds and in phase at high speeds, the rotational motion starts earlier, thereby reducing the delay in lateral acceleration response to steering. Practical effects include improved maneuverability at low speeds and improved ability to avoid emergency situations at high speeds.

For example, the method of steering the rear wheels is to mechanically transmit the steering angle of the front wheels to the rear wheels, tilt the rotating surface of the yoke incorporated therein, and continuously change the steering direction and steering ratio. In the past, a method of steering the rear wheels using hydraulic pressure was proposed, but in recent years, a method of directly steering the rear wheels using an electric motor (the subject of the present invention) has been proposed in search of various possibilities for rear wheel steering control. has been done.

The configuration and operation of the conventional example will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a rear wheel steering angle control device and a rear wheel steering mechanism of a conventional four-wheel steering vehicle. Inside the control device 13 is a microcomputer 7 that controls the electric motor 14.
(hereinafter referred to as a microcomputer), a microcomputer abnormality detector 4 that monitors abnormalities (runaway, etc.) of the microcomputer 7, and a low voltage detector 1 that monitors a voltage drop in the power input 2. is provided with a motor abnormality detector 16 that monitors abnormalities (overspeed, overcurrent, overload, etc.) of the electric motor 14 itself. Furthermore, an electric motor 14 and a rear wheel 18 (tire)
During this period, the transmission of the output of the electric motor 14 to the rear wheels 18 is controlled (
A clutch 16 is provided for turning the vehicle on and off, and a mechanism for returning the rear wheels to a two-wheel steering (2WS) state when the clutch 16 is off.

The operation of the clutch 16 in this configuration (ONlo
FF) will be explained. Before turning on the power, the control device 13
is not operating, the clutch 16 is turned off, and even when the power is turned on, while the low voltage detector 1 is detecting the low voltage of the power source 2, the low voltage detection signal 3 is output to the OR circuit 12a. is input to the reset terminal of microcomputer 7 through
When the microcomputer 7 is initialized, the clutch control signal 10 is also turned off, and the clutch and notch 16 remain turned off. When the voltage of the power source 2 rises and is no longer judged as low voltage, the reset terminal is turned OFF and the microcomputer 7
The program is executed. As a result, the microcomputer outputs a motor control signal 8 and a clutch control signal 1 according to various inputs (sensor input, switch input, etc.) according to the program.
Output o.

Normally (during four-wheel steering), the clutch control signal 1o is turned on, and the clutch 16 is also turned on. In this state, when the microcomputer abnormality detector 4 detects an abnormality in the microcomputer by the microcomputer monitoring signal 5, the microcomputer abnormality detection signal 6 is input to the reset terminal of the microcomputer 7 through the OR circuit 121L, and the clutch It is turned off at 16.

Furthermore, when the motor abnormality detector 16 detects an abnormality in the electric motor 14, it returns a motor abnormality detection signal 9 to the microcomputer 7.
Turn off the clutch 16.

In this way, in the conventional rear wheel steering angle control device, when an abnormality occurs in the microcomputer or electric motor, the clutch control signal is turned off through the microcomputer to turn off the clutch, and
The WS return mechanism returns the vehicle to two-wheel steering to avoid unstable operation of the rear wheels in abnormal situations, improving safety.

Problem to be Solved by the Invention However, in the conventional rear wheel steering angle control device configured as described above, even if the abnormality detector of the microcomputer detects an abnormality, the abnormality detection signal is input to the reset terminal of the microcomputer. The clutch is not turned off until the clutch control signal output terminal is initialized. Similarly,
Even if the abnormality detector of the electric motor detects an abnormality, the clutch will not be turned off until the abnormality detection signal is input to the microcomputer and an OFF signal is output to the output terminal as a result of processing the input. In this way, it takes microcomputer initialization time and processing time from when an abnormality is detected until the clutch is turned off, and in addition to the time it takes to detect each abnormality, the rear wheel There is a problem in that there is a time when the control becomes unstable. Furthermore, if the microcomputer cannot be initialized normally (microcomputer failure, etc.),
If the microcomputer is abnormal at the time when an abnormality in the electric motor is detected (an abnormality has not yet been detected), the above-mentioned time becomes longer and the above-mentioned problem becomes more serious.

In order to solve this problem, there is a way to prevent the above situation by using a highly reliable microcontroller.
Generally, it is difficult to select a highly reliable microcontroller.
Also, the cost is correspondingly higher.

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the conventional structure and provide a more reliable rear wheel steering angle control device for a four-wheel steering vehicle.

Means for Solving the Problems In order to achieve the above object, the rear wheel steering angle control device for a four-wheel steering vehicle of the present invention includes an abnormality detector such as runaway of a microcomputer that receives electric motor control within the control device. , and the electric motor that controls the rear wheel steering angle is equipped with an abnormality detector such as overspeed, overcurrent, overload, etc., and the abnormality detection signal from the abnormality detector of the microcomputer is input to the reset terminal of the microcomputer, and the abnormality detection of the electric motor is performed. The abnormality detection signal from the device is input to the microcontroller, and the logical inversion signal (normal signal) of each abnormality detection signal is input.
and a control signal (ON signal) from the microcomputer to a clutch provided to disconnect the electric motor and the rear wheels, and the clutch is controlled using the result.

In the above configuration, when an abnormality is detected by the abnormality detector of the microcomputer or the abnormality detector of the electric motor, the present invention returns this abnormality detection signal to the microcontroller, and also sends a logical inversion signal of this abnormality detection signal to the microcontroller. By taking a logical product with the clutch control signal from It will be turned off. In addition, as in the past, the clutch is controlled to be turned off via a microcomputer. This reduces the time from when an abnormality is detected until the clutch is turned off, and the clutch can be turned off using a highly reliable circuit, creating an unstable state in rear wheel control and reducing safety. Can solve problems in a simple way.

Embodiments Hereinafter, the configuration and operation of embodiments of the present invention will be explained with reference to the accompanying drawings. FIG. 1 shows a block diagram of a rear wheel steering angle control device and a rear wheel steering mechanism of a four-wheel steering vehicle according to an embodiment of the present invention. Since the basic configuration is the same as the conventional example, explanation of the same functional parts will be omitted.

Operation of the clutch 16 in this configuration (ONloFF
), the clutch 16 is OFF because the control device 13 is not operating before the power is turned on, and the low voltage detector 1 detects the low voltage of the power input 2 even after the power is turned on. During this period, the low voltage detection signal 3 is input to the reset terminal of the microcomputer 7, the microcomputer 7 is initialized, and the clutch control signal 1o is also turned OFF, so that the clutch 16 remains OFF. When the voltage of power supply input 2 rises and is no longer judged as a low voltage, the reset terminal becomes 0.
The program of the FFL microcomputer 7 is executed.

Thereby, the microcomputer 7 outputs a motor control signal 8 and a clutch control signal 10 according to various inputs (sensor input, switch input, etc.) according to the program. Normally (during four-wheel steering), clutch control signal 1° is turned on, and clutch 1
6 is also ON. In this state, when the microcomputer abnormality detector 4 detects an abnormality in the microcomputer 7 based on the microcomputer monitoring signal 5, this abnormality detection signal 6 is logically inverted by the N0T12b circuit, and the AN
Since the logical product is taken through the D circuit 12C1, A
The output 11 (final control output to the clutch) of the ND circuit 12d is turned off, and the clutch 16 is also turned off immediately.

Similarly, when the motor abnormality detector 15 detects an abnormality in the electric motor 14, this abnormality detection signal 9 causes the NOT circuit 12 to
C・MuND [Turn OFF the clutch 16 immediately through J road 12d. Further, in order to improve reliability in consideration of a failure of the NOT circuit, each abnormality detection signal 6 is returned to the microcomputer and turned off using the conventional method.

In this embodiment, the microcomputer 7 or the electric motor 14
If an abnormality occurs, the clutch is turned OFF via the microcomputer.
Before F, the clutch is turned off through a simple gate (NOT/AND) circuit, and the 2WS return mechanism returns to the single-wheel steering state.

Effects of the Invention As described above, in the conventional technology, when an abnormality occurs in the microcomputer or the electric motor, the microcomputer returns an abnormality detection signal to the microcomputer, and the microcomputer switches the output port of the clutch control signal to O.
Because the shift latch was turned OFF by turning the FF, there is a possibility that the microcomputer cannot be initialized normally (microcomputer failure, etc.), or that the microcomputer is malfunctioning when a motor malfunction is detected (the malfunction has not yet been detected). In this case, the time from when an abnormality is detected until the clutch is turned off, that is, the time when the electric motor's torque is transmitted to the rear wheels and the steering angle control of the rear wheels becomes unstable, becomes a major problem. come. In such a situation, this problem is solved by directly turning off the clutch control signal with the abnormality detection signal through the logic circuit, shortening the unstable time of rear wheel control and improving driving safety. By using the present invention in conjunction with clutch OFF control, a highly reliable rear wheel steering angle control device for a four-wheel steering vehicle can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a rear wheel steering angle control device and a rear wheel steering mechanism of a four-wheel steering vehicle according to an embodiment of the present invention, and FIG. 2 is a block diagram of a rear wheel steering angle control device and a rear wheel steering mechanism of a four-wheel steering vehicle of a conventional example. FIG. 3 is a block diagram of a rear wheel steering mechanism. 1...Low voltage detector, 2...Power input, 3...Low voltage detection signal, 4...Microcomputer abnormality detector, 5... ...Microcomputer monitoring signal, 6
...Microcomputer abnormality detection signal, 7...Microcomputer, 8...Motor control signal, 9...
・Electric motor abnormality detection signal, 1o...Clutch control signal, 11...Final control output to the clutch, 1
2b, 12C...NOT circuit, 12d...
...MuND circuit, 13...Control device, 14...
...Electric motor, 16...Motor abnormality detector,
16...Clutch, 1...Differential and 2WS return mechanism, 18...Rear tire.

Claims (1)

[Claims] In a rear wheel steering angle control device for a four-wheel steering vehicle, the rear wheel steering angle is controlled by an electric motor according to the driving state of the vehicle detected from a sensor such as a steering wheel angle. The rear wheel steering mechanism is equipped with a clutch that operates a mechanism that steers the rear wheels by transmitting the signal, and when the electric motor is turned off, disconnects the electric motor and the rear wheels to return the rear wheels to two-wheel steering. and an abnormality detection signal from the abnormality detector of the electric motor is returned to the microcomputer, and if an abnormality is detected in either of them, the clutch control signal is turned OFF through the microcomputer, and the clutch control (O
FF) signal, an abnormality detection signal of a microcomputer, or an abnormality detection signal of an electric motor, the rear wheel steering angle control device for a four-wheel steering vehicle is configured to turn off the clutch through a logic circuit.