JPH06144273A - Electrical control unit for rear wheel steering system - Google Patents

Abstract

PURPOSE:To allow rear wheels to be steered appropriately without interfering with other devices even in the idle state of an engine in the lowered state of battery voltage in a rear wheel steering system steering rear wheels by a motor. CONSTITUTION:In the case of requiring to steer lateral rear wheels RW1, RW2 due to the difference between the target steering angle and the actual steering angle in the state of the voltage of a battery detected by a voltage detector 35 being lower than the specified reference value, a microcomputer 36 outputs a command signal, indicating the idling-up of an engine, to an engine rotation control circuit 51 so as to increase the idling engine speed. In the case of the voltage of the battery 40 being high or in the case of not requiring to steer the lateral rear wheels RW1, RW2 due to the coincidence of the target steering angle with the actual steering angle, the microcomputer 36 outputs a command signal, indicating no need of idling-up, to the engine rotation control circuit 51 so as not to increase the idling engine speed for rear wheel steering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a vehicle equipped with a rear wheel steering device that steers rear wheels by the rotation of an electric motor, and is driven by a battery according to the difference between a target steering angle and an actual steering angle. The present invention relates to an electric control device for a rear wheel steering device that applies a current to an electric motor to steer the rear wheels to a target steering angle.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in JP-A-34476, when the battery voltage is detected and the voltage drops, the target steering angle at which the rear wheels should be steered is regulated and the power consumption of the battery for steering the rear wheels. To prevent it from interfering with other devices.

[0003]

However, in the above-mentioned conventional device, when the battery voltage drops, the target steering angle of the rear wheels is regulated, but the rear wheels are steered, so the battery voltage drops. If the engine is in the idle state at the same time, the illuminance of the headlight may decrease, the engine may stall, or the life of the battery may decrease.
The present invention has been made to address the above-described problems, and an object thereof is to be able to appropriately steer the rear wheels and to hinder other devices even when the engine is in an idle state when the battery voltage is low. It is an object of the present invention to provide an electric control device for a rear wheel steering device which is prevented.

[0004]

In order to achieve the above object, a structural feature of the present invention is that it has engine rotation control means for controlling the idle speed of the engine, and the rear wheel is controlled by the rotation of an electric motor. It is applied to a vehicle having a rear wheel steering device that steers, and a target rudder angle determining unit that determines a target rudder angle of a rear wheel, an actual rudder angle detection unit that detects an actual rudder angle of the rear wheel,
An electric control device for a rear wheel steering system, comprising: a drive means for flowing a drive current from a battery to an electric motor according to a difference between a target rudder angle and an actual rudder angle to control rotation of the electric motor. A voltage detector for detecting a voltage and an instruction means for instructing the engine rotation control means to idle up the engine when the electric motor is driven and the detected battery voltage is less than a predetermined value are provided.

[0005]

According to the present invention configured as described above, when the electric motor is driven to steer the rear wheels and the battery voltage detected by the voltage detector is low, the indicating means is the engine. The rotation control means is instructed to idle up the engine. As a result, the engine rotation control means increases the idle speed of the engine,
Even when the battery voltage drops and the engine is in the idle state at the same time, the increase in the idle speed secures the power required for steering the rear wheels, which reduces the illuminance of the headlight, stalls the engine, or shortens the battery life. It is possible to steer the rear wheels without affecting other devices such as deterioration.

[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, 15 at both ends.
The left and right front wheels FW1, FW2 are steerably connected via b and knuckle arms 16a, 16b.

The rear wheel steering device 20 includes an electric motor 21 such as a brushless motor for steering the rear wheels.
The rotating shaft of the electric motor 21 is the steering gear box 2
The relay rod 23 is supported in the shaft 2 via a speed reduction mechanism so as to be displaceable in the axial direction, and the rod 23 is displaced in the axial direction according to the rotation of the motor. The left and right rear wheels RW1 and RW are provided at both ends of the relay rod 23 via tie rods 24a and 24b and knuckle arms 25a and 25b.
2 are connected, 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, a rear wheel steering angle sensor 34 and a voltage detector 35. Vehicle speed sensor 3
Reference numeral 1 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 measures the rotation angle of the steering shaft 12 to determine the steering angle θ of the left and right front wheels FW1 and FW2.
It detects f and outputs a detection signal representing the same steering angle θf. The rear wheel steering angle sensor 34 measures the rotation angle of the rotating shaft of the electric motor 21 to determine the steering angle θr of the left and right rear wheels RW1 and RW2.
Is detected and a detection signal representing the same steering angle θr is output. 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. The voltage detector 35 detects the voltage V _{BT of the} battery 40 and outputs a detection signal representing the voltage V _BT . The battery 40 is supplied with electric power from a generator driven by an internal combustion engine 52 (engine) described later.

A microcomputer 36 is connected to the sensors 31 to 34 and the voltage detector 35.
The microcomputer 36 includes a CPU, ROM, RAM,
It is composed of I / O, a timer, etc., and executes the program stored in the ROM and corresponding to the flowchart of FIG.
A drive circuit 37 is connected to the microcomputer 36, and the drive circuit 37 controls the rotation of the electric motor 21 by supplying a drive current from the battery 40 to the electric motor 21 according to a control signal from the microcomputer 36. Electric power is supplied from the battery 40 to circuits other than the drive circuit 37. An engine rotation control circuit 51 is connected to the microcomputer 36. The engine rotation control circuit 51 has a known function of controlling the idle speed of the engine in the internal combustion engine 52, and when the engine is in an idle state, for example, increases the amount of air supplied to the engine by the internal combustion engine 52. By doing so, the idle speed of the engine is increased.

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 36 starts executing the program in step 100 of FIG.
The detection signals representing the vehicle speed V, the yaw rate γ, the front wheel steering angle θf, the rear wheel steering angle θr, and the battery voltage V _BT are input from the voltage detectors 1 to 34 and the voltage detector 35, respectively. Next, step 1
At 04, the yaw rate proportional coefficient K1 (see FIG. 3 (A)) and the steering angle proportional coefficient K2 (see FIG. 3 (B)) that change according to the vehicle speed V are read out from the table provided in the ROM, and the following mathematical formula 1 is used. The target steering angles θr * of the left and right rear wheels RW1 and RW2 are calculated by executing the calculation of

[0012]

[Equation 1] θr * = K1 · γ + K2 · θf After calculating the target steering angle θr *, it is determined in step 106 whether the target steering angle θr * is equal to the input rear wheel steering angle θr. . In this case, if the target steering angle θr * and the rear wheel steering angle θr are not equal and it is necessary to steer the left and right rear wheels RW1 and RW2, it is determined to be “NO” in step 106 and the program proceeds to step 108. . In step 108, it is determined whether or not the battery voltage V _BT is equal to or higher than a predetermined reference voltage Vref. If the voltage of the battery 40 is normal and the battery voltage V _BT is equal to or higher than the reference voltage Vref, it is determined "YES" in step 108 and the program proceeds to step 110. In step 110, an instruction signal indicating that the idle-up is unnecessary is output to the engine rotation control circuit 51. Engine rotation control circuit 5
Reference numeral 1 updates the stored instruction signal relating to idle-up to an instruction signal indicating that the idle-up is unnecessary, and controls the idle speed of the engine based on the updated instruction signal. In this case, the engine rotation control circuit 51 controls the internal combustion engine 52 so as not to increase the idle speed of the engine for steering the rear wheels.

After the processing of step 110, step 1
At 12, the control signal representing the deviation θr * −θr between the calculated target steering angle θr * and the rear wheel steering angle θr is output to the drive circuit 37. The drive circuit 37 controls the rotation of the electric motor 21 by supplying a drive current from the battery 40 to the electric motor 21 for a predetermined time according to the control signal. The rotation of the electric motor 21 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 rods 24a, 24b and the knuckle arms 25a, 25b and the left and right rear wheels RW1, RW2.
And the rear wheels RW1 and RW2 are steered to the target steering angle θr *.

After the processing of step 112, the program is returned to step 102, and steps 102 to 11 are executed.
The processing of No. 2 is executed again to steer the left and right rear wheels RW1 and RW2 to the target steering angle θr *. Such steps 102-
If the target steering angle θr * and the rear wheel steering angle θr become equal during the processing of 112, it is determined to be “YES” in step 106 and the program proceeds to step 116. After outputting to the instruction signal indicating that the idle-up is unnecessary in step 116 as in step 110, the program is returned to step 102. As described above, when the target steering angle θr * and the rear wheel steering angle θr are equal and it is not necessary to steer the left and right rear wheels RW1 and RW2, the drive current from the battery 40 is not supplied to the electric motor 21, and However, it is not idled up for steering the rear wheels.

On the other hand, since the target steering angle θr * and the rear wheel steering angle θr are not equal, it is necessary to steer the left and right rear wheels RW1 and RW2, and the voltage of the battery 40 drops and the battery voltage V
_{When BT} becomes less than the reference voltage Vref, steps 106, 1
Both are determined to be “NO” at 08 and the program proceeds to step 114. In step 114, an instruction signal indicating idle up is output to the engine rotation control circuit 51. The engine rotation control circuit 51 updates the previously stored instruction signal indicating that idle up is unnecessary by this instruction signal indicating idle up, and controls the idle speed of the engine based on the instruction signal. In this case, if the engine is in the idle state, the engine rotation control circuit 5
1 increases the idle speed of the engine. As a result, the electric power required for steering the left and right rear wheels RW1, RW2 is secured, so that the drive circuit 37 can supply a sufficient current (electric power) to the electric motor 21, and the motor 21 can supply the voltage of the battery 40. The left and right rear wheels RW1 and RW2 can be steered to the target rudder angle θr * even if is decreased. Further, by securing this electric power, even if the left and right rear wheels RW1 and RW2 are steered, other devices such as reduction in illuminance of headlights, engine stall, or reduction in battery life will not be hindered.

Even during such engine idle-up, the target steering angle θr * and the rear wheel steering angle θr are equalized by the steering control of the left and right rear wheels RW1 and RW2.
If it becomes unnecessary to steer the left and right rear wheels RW1 and RW2,
In step 106, the determination is “YES” and the program proceeds to step 116 described above. Therefore, when the left and right rear wheels RW1 and RW2 are not steered, that is, when it is not necessary to supply current (electric power) to the electric motor 21,
The engine rotation control circuit 51 does not perform control for increasing the idle speed of the engine for steering the rear wheels. As a result, the idle-up of the engine can be minimized, and wasteful consumption of fuel can be suppressed.

[Brief description of drawings]

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

2 is a flowchart of 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.

[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 ... Voltage Detector, 36 ... Microcomputer, 37 ... Drive circuit, 40 ... Battery, 51 ... Engine rotation control circuit, 52 ... Internal combustion engine.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location B62D 127: 00 137: 00 (72) Inventor Hiroaki Aizawa 2-1, Asahi-cho, Kariya city, Aichi prefecture Aishi Within Seiki Co., Ltd.

Claims (1)

[Claims] 1. The present invention is applied to a vehicle having engine rotation control means for controlling an idle speed of an engine and having a rear wheel steering device for steering a rear wheel by rotation of an electric motor, wherein a target steering angle of the rear wheel is set. Target rudder angle deciding means for deciding, real rudder angle detecting means for detecting the real rudder angle of the rear wheels, and driving current from the battery to the electric motor according to the difference between the target rudder angle and the real rudder angle. In a electric control device for a rear wheel steering system including a drive means for controlling rotation of the motor, a voltage detector for detecting a battery voltage and a battery voltage for which the electric motor is driven and the detected battery voltage is An electric control device for a rear wheel steering system, wherein the engine rotation control means is provided with an instruction means for instructing engine idle-up when the value is less than a predetermined value.