JP4810818B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus having an abnormality / failure detection function, and more particularly to an electric power steering apparatus provided with an alarm / display means for notifying a driver of the degree of abnormality / failure.

  An electric power steering device that assists an automobile or a vehicle steering device with an auxiliary load by the rotational force of a motor is a steering shaft or rack that transmits the driving force of the motor by a transmission mechanism such as a gear or a belt via a reduction gear. An auxiliary load is applied to the shaft. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist force). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the motor current detection value becomes small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 6. The column shaft 2 of the steering handle 1 is connected to the steering wheel via the reduction gear 3, the universal joints 4 a and 4 b, and the pinion rack mechanism 5. It is connected to the tie rod 6. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is connected to the column shaft 2 via the reduction gear 3. ing. The control unit 30 that controls the power steering device is supplied with electric power from the battery 14 via the ignition key 11 and the relay 13, and the control unit 30 is detected by the steering torque T detected by the torque sensor 10 and the vehicle speed sensor 12. The steering assist command value I of the assist command is calculated based on the vehicle speed V, and the current supplied to the motor 20 is controlled based on the calculated steering assist command value I.

  The control unit 30 is mainly composed of a CPU (including an MPU). FIG. 7 shows general functions executed by a program inside the CPU.

  The function and operation of the control unit 30 will be described. The steering torque T detected and input by the torque sensor 10 is phase-compensated by the phase compensator 31 in order to improve the stability of the steering system, and the phase-compensated steering torque. TA is input to the steering assist command value calculator 32. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines a steering assist command value I that is a control target value of the current supplied to the motor 20 based on the input steering torque TA and vehicle speed V. The steering assist command value I is input to the subtractor 30A, and is also input to the feedforward differential compensator 34 for increasing the response speed. The deviation (Ii) of the subtractor 39A is input to the proportional calculator 35. At the same time, it is input to an integration calculator 36 for improving the characteristics of the feedback system. Together with the output of the differential compensator 34, the outputs of the proportional calculator 35 and the integral calculator 36 are also added to the adder 39B, and the current control value E, which is the addition result of the adder 30B, is used as a motor drive circuit. 37. The current i of the motor 20 is detected by the motor current detection circuit 38 and fed back to the subtractor 39A.

  In such an electric power steering apparatus, a fail-safe function has been provided in order to further improve safety. As an electric power steering device having a conventional fail-safe function, for example, there are those shown in JP-A-10-167086 (Patent Document 1) and JP-A-2001-18820 (Patent Document 2).

  The device described in Patent Document 1 includes a motor current detection circuit and a failure detection circuit that detects a failure of the current detection circuit, and opens a feedback system when the failure detection circuit detects a failure of the current detection circuit. Switching to a loop system.

Moreover, the thing of patent document 2 detects that the wheel became the locked state or the idling state based on the rotation angle or the rotational speed of the wheel detected by the sensor, and the abnormality of the idling state of the wheel is detected. The automatic steering control is stopped when the abnormal state is severe, and the automatic steering control is continued when the abnormal state is severe, thereby preventing the vehicle from deviating from the correct movement locus. is there.
JP-A-10-167086 JP2001-18820

  In the electric power steering device described in Patent Document 1 described above, the assist is continued with the fail lamp lit even after a failure. Moreover, in the electric power steering apparatus described in Patent Document 2, an alarm is issued to the driver after the occurrence of an abnormality, and the control is stopped or continued after judging the degree of failure. In either case, since the driver is not informed of the degree of failure, the driver feels that the operation of the electric power steering device is strange when the assist is limited, which may cause anxiety.

  For example, if the current is limited to protect against overheating, the assisting power will be reduced, so the driver will be worried that the electric power steering device may be out of order. However, this is not a malfunction and there is no need to go to a repair shop such as a dealer. If the assist power is reduced even though the fail lamp is not lit, it becomes uneasy that it is a failure. If the fail lamp is lit, it will be sent to a dealer or the like for repair although it is not necessary. In some cases, the current may be limited due to a failure. In this case, it is necessary to bring the product to a repair shop for repair.

  Both of the above two cases appear as the same symptom that the assist force is reduced, and therefore it is impossible to distinguish whether the driver is faulty or not. However, if the distinction is made according to whether the fail lamp is turned on or off, the driver is anxious as described above.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to visually or auditorily notify the driver of the degree of abnormality / failure (information that assist limitation is applied but not failure). Accordingly, it is an object of the present invention to provide an electric power steering device that does not give a driver anxiety even when assist limitation is controlled.

The present invention relates to an electric power steering apparatus that calculates a steering assist command value based on a torque signal and a vehicle speed and applies an assist force by a motor to a steering system based on the steering assist command value. the above object of the abnormality-failure detecting means for detecting an abnormality or failure of the electric power in the steering device, the degree of the abnormality or malfunction, there is no need Assist protection operation about repair, there is a need for repairs a assist sustainable degree of limiting the cyst, and abnormal or failure about discriminating means for discriminating either of the extent to stop the assist impossible continuation in need of及beauty repair, determination of the abnormality or failure about discriminating means This is achieved by providing display means for performing display according to the result.

  Further, the object of the present invention is to provide the display means in the driver's vision, or to provide a switching unit in the electric power steering system, and to control the switching unit based on the determination result, at least two or more. By turning on or blinking the lamp or LED, or according to the failure / abnormal state of the electric power steering system, it has a function of outputting a message using characters, symbols, drawings, etc. Alternatively, the display means can be achieved more effectively by using a voice message or an alarm sound.

  According to the electric power steering apparatus according to the present invention, the driver can visually confirm the degree of the failure visually or audibly, so that even if the assist restriction control is performed, the driver does not feel anxiety due to a vehicle abnormality or failure. .

  The conventional fail-safe function in the electric power steering apparatus stops the assist immediately when something breaks down. Recently, however, the assistance has been continued as much as possible after any abnormality or failure. One of the reasons is an increase in the size of a vehicle using an electric power steering device. A vehicle such as a conventional light vehicle can be sufficiently steered even in a manual steering state in which the assist is stopped. However, in a 2000 cc class vehicle that has recently been equipped with an electric power steering device, the assist is stopped. Then, it is difficult to steer because the steering wheel is too heavy.

  In order to continue the assist as much as possible even if something abnormal occurs / fails, it is necessary to reliably determine whether the abnormality / failure that allows the assist to continue or the abnormality / failure that cannot be continued. For example, an abnormality or failure of the torque sensor that controls the motor is fatal, so it is necessary to immediately stop the assist for any large vehicle. However, either the main torque sensor or the sub torque sensor If a failure occurs, the output of the normal torque sensor can be used, so there is no problem in continuing the assist.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an embodiment of a control unit 30A according to the present invention corresponding to FIG. 6. The control unit 30A has an abnormality / failure detection unit 301 for detecting an abnormality or failure of the torque sensor 10, the motor 20, and the like. The level of the abnormality / failure detected by the abnormality / failure detection unit 301, that is, the abnormality / failure of the assist protection operation level, or the abnormality / failure in which the assist can be continued by limiting the assist, or the assist cannot be continued. An abnormality / failure degree determination unit 302 is provided for determining whether an abnormality / failure should be stopped. The determination signal DC determined by the abnormality / failure level determination unit is input to the assist control unit 304, controls the assist of the motor 20, and is input to the display control unit 303, and is provided on the meter panel 40 in front of the driver's seat. The display of the display unit 41 is controlled.

  FIG. 2 shows an example of the display unit 41. Two LEDs (light emitting diodes) 411 (for example, two light emitting colors) 411 (for example, between the speedometer 42 of the meter panel 40 and an engine rotation meter (including other meters) 43 are provided. Red) and 412 (for example, blue) are provided. FIG. 2 is an example, and the display unit 41 can be installed at an arbitrary position in the meter panel 40.

  FIG. 3 shows a connection example of the display unit 41. The LEDs 411 and 412 are connected to the power source + Vcc through the resistor 413, and the other ends are connected to the contacts a and b of the switching unit 310, respectively. Driving signals DS of LEDs 411 and 412 are applied from the display control unit 303 to the switching unit 310, and the contacts a and b are switched by a switching signal SW from the display control unit 303. In FIG. 3, the switching unit 310 has a mechanical configuration, but may be configured by a non-contact type electronic switch.

  In such a configuration, the operation will be described with reference to the flowchart of FIG.

  The abnormality / failure detection unit 301 always detects an abnormality / failure in the torque sensor 10 or the like (step S1), and when an abnormality / failure is detected, the abnormality / failure degree determination unit 302 is detected based on the detection signal DT. Then, the degree of abnormality / failure is determined (step S2). As a result, when the operation is assist protection (step S3), the drive signal DS is generated, and the contact point b of the switching unit 310 is connected by the switching signal SW to turn on the blue LED 412 (step S4). Examples of abnormalities / failures in the assist protection operation include overheat protection, battery voltage drop, and lock end protection.

  Further, when the assist is limited and continued by determining the degree of abnormality / failure (step S5), a pulsed drive signal DS is generated and the contact a of the switching unit 310 is connected by the switching signal SW. The red LED 411 blinks (step S6). When the assist is stopped (step S7), the drive signal DS is generated and the contact a of the switching unit 310 is connected by the switching signal SW to turn on the red LED 411. (Step S8). After that, it waits for a return. Assist restriction abnormalities / failures include vehicle speed sensor 12 abnormalities / failures, CAN (Controller Area Network) communication system abnormalities / failures, etc., and assist stop abnormalities / failures include serious failures such as motor 20 and torque sensor 10. There is.

  In this example, the LEDs are of two colors, but the LEDs of the same color can be distinguished by lighting and flashing, and can be displayed as three or more colors.

  In this example, the LED notifies the driver of the occurrence of an abnormality / failure or the assist state, but a lamp may be used as a display element. If it is a lamp, it can be displayed in any color. In the above example, the LED has two colors, and one mode blinks. However, it is also possible to notify with three colors of LEDs and lamps.

  Further, the display unit 41 of the present invention may display the assist state in a message format on a liquid crystal panel or the like as shown in FIG. In this case, for example, “power steering protection function in operation” is displayed in the assist protection operation, “power steering function failure” is displayed in the assist restriction, and “failure or repair is required” is displayed in the assist stop.

  In the above example, an alarm is notified by turning on or blinking an LED or a lamp, or displaying a message. However, in addition to the visual sense or independently, it is notified by an auditory sound such as a voice message or an alarm sound. It is also possible to make it. Further, the installation location of the LED, the lamp, etc. is not limited to the meter panel, but may be at least a location within the driver's field of view.

  According to the present invention, it is possible to visually (or / and audibly) notify the driver of the degree of abnormality / failure, so that a high-performance electric power steering device that gives the driver a sense of security can be realized.

It is a block block diagram which shows one Example of this invention. It is a figure which shows an example of the meter panel which concerns on this invention. It is a figure which shows the example of a connection of a display control part and a display part. It is a flowchart which shows the operation example of this invention. It is a figure which shows the other example of the meter panel which concerns on this invention. 1 is a structural diagram showing an outline of a general electric power steering apparatus. It is a block block diagram which shows an example of a control unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Column shaft 3 Reduction gear 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 13 Relay 14 Battery 20 Motor 30, 30A Control unit 40 Meter panel 41 Display part 301 Abnormality / failure detection part 302 Abnormality / failure degree determination part 303 Display control unit 304 Assist control unit 310 Switching unit 411, 412 LED

Claims (5)

A steering assist command value is calculated based on a torque signal and a vehicle speed, and an assist force by a motor is applied to a steering system based on the steering assist command value. and abnormality-failure detecting means for detecting an abnormality or failure, the degree of abnormality or malfunction, there is no need assist protection operation about repairs need is to limit assist degree of assist possible continuation of repair, and abnormal or failure about discriminating means for discriminating either of the extent to stop the Assist impossible continuation in need of及beauty repair, and display means for performing display in accordance with the discrimination result of the abnormality or failure about discriminating means An electric power steering apparatus characterized by comprising. The electric power steering apparatus according to claim 1, wherein the display means is provided in a driver's vision. 2. The electric power steering according to claim 1, wherein a switching unit is provided in the electric power steering system, and the switching unit is controlled based on the determination result to light or blink at least two or more lamps or LEDs. apparatus. The electric power steering apparatus according to claim 2, wherein the electric power steering apparatus has a function of outputting a message using characters, symbols, drawings, and the like in accordance with a failure / abnormal state of the electric power steering system. The electric power steering apparatus according to claim 1, wherein the display means is a voice message or an alarm sound.

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