JP2013079003A - Vehicle steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle steering device configured to continue turning of a vehicle by means of a steering operation even after assist stop due to a failure of an electric power steering device.SOLUTION: An ABS device 30 acquires steering torque τ that is a control state amount of an ECU 11 of the electric power steering device 1 (step S401). The ABS device 30 determines whether a fault detection signal Spsf has been input or not (step S402). When the fault detection signal Spsf has been input (step S402: YES), the ABS device determines whether the steering is in operation(step S403). When the ABS device determines that the steering is in operation (step S403: YES), braking force to be applied to a predetermined steering wheel 7 is calculated on the basis of the received steering torque τ (step S404). The normal braking force is corrected by the calculated braking force. The corrected braking force is output as a control command (step S405) to control a brake actuator 31.

Description

  The present invention relates to a vehicle steering apparatus.

  Conventionally, there is an electric power steering device (EPS) using a motor as a drive source as a power steering device for a vehicle. Usually, such an electric power steering apparatus detects a steering torque by a torque sensor, and electrically controls an assist force applied to the steering system based on the detected steering torque, vehicle speed, and the like. For example, when a failure is detected, such as when an abnormality is detected in the torque sensor, the motor that is the drive source is stopped and promptly fail-safe (for example, , See Patent Document 1).

JP 2003-182608 A

  However, when an abnormality occurs in the electric power steering apparatus, if the EPS controller stops the assist control, even if the driver tries to continue the steering operation, the steering wheel becomes very heavy and it becomes difficult to move the vehicle.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle steering device that can continue turning of a vehicle by a steering operation even after an assist stop due to an abnormality of the electric power steering device. is there.

  In order to solve the above-described problem, the invention described in claim 1 includes a steering force assisting device that applies an assisting force to a steering system using a motor as a drive source, and an abnormality detecting unit that detects an abnormality, and the abnormality is When detected, the vehicle steering system includes: an electric power steering device including a control unit that stops the operation of the steering force assisting device; and a braking control device that controls a braking force applied to each wheel. In the apparatus, when the abnormality is detected during a steering operation, the braking control device applies the braking force to a predetermined wheel based on a steering direction detected according to a state of the steering system. The gist of the vehicle is to turn the vehicle.

  According to the above configuration, when an abnormality of the electric power steering apparatus is detected and the assist operation is stopped, the control unit of the electric power steering apparatus outputs the abnormality detection signal and the assist control state quantity immediately before the abnormality is detected. Based on these pieces of information, the braking control device operates to apply a braking force to the wheel on the steering direction side during the steering operation, and the vehicle can turn in the steering direction. As a result, the steering operation can be easily performed even after the electric power steering apparatus is stopped.

  According to a second aspect of the present invention, in the vehicle steering device according to the first aspect, the braking control device is based on a steering torque detected from an output signal of a torque sensor provided in the electric power steering device. The gist is to detect the steering direction.

  According to the above configuration, the braking control device can determine the steering direction from the steering torque detected by the torque sensor provided in the electric power steering device. Thereby, the braking control device can adjust the braking force based on the information of the sensor provided in the electric power steering device without requiring a vehicle signal from another sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can continue turning of a vehicle by steering operation even after the assist stop by abnormality of an electric power steering apparatus can be provided.

The schematic block diagram of the steering apparatus for vehicles. The control block diagram of an electric power steering device. 3 is a flowchart showing a processing procedure of assist stop control when the electric power steering apparatus is abnormal in the first embodiment of the present invention. 3 is a flowchart showing a processing procedure of braking control of the braking control device when the electric power steering device is abnormal in the first embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus. As shown in FIG. 1, the vehicle steering apparatus 1 according to the present embodiment is provided with an electric power steering apparatus (EPS) 20. In the electric power steering apparatus 20 of the present embodiment, the steering shaft 3 to which the steering wheel 2 is fixed is connected to the rack shaft 5 via the rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed. The rack and pinion mechanism 4 converts the rack shaft 5 into a reciprocating linear motion. Note that the steering shaft 3 of the present embodiment is formed by connecting a column shaft 3a, an intermediate shaft 3b, and a pinion shaft 3c. The linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to the knuckle (not shown) via the tie rods 6 connected to both ends of the rack shaft 5, whereby the steered wheels (wheels) 7 are steered. The corner, that is, the traveling direction of the vehicle is changed.

  In addition, the electric power steering device 20 is an EPS actuator (steering force assisting device) 10 as a steering force assisting device that applies an assisting force for assisting the steering operation to the steering system, and a control that controls the operation of the EPS actuator 10. ECU (control means) 11 as means is provided.

  The EPS actuator 10 of the present embodiment is configured as a so-called column type EPS actuator in which a motor 12 as a driving source is drivingly connected to a column shaft 3 a via a speed reduction mechanism 13. In the present embodiment, the motor 12 is a DC motor with a brush. The EPS actuator 10 is configured to apply motor torque as an assist force to the steering system by decelerating the rotation of the motor 12 and transmitting it to the column shaft 3a.

  On the other hand, the ECU 11 is connected to a torque sensor 14, a vehicle speed sensor 15, and a steering sensor (steering angle sensor) 16 that constitutes a steering angle detection means. And ECU11 detects steering torque (tau), vehicle speed V, and steering angle (theta) s based on the output signal of each sensor.

  In the present embodiment, the torsion bar 17 is provided in the middle of the column shaft 3a, more specifically, on the steering wheel 2 side with respect to the speed reduction mechanism 13 constituting the EPS actuator 10. The torque sensor 14 of the present embodiment includes sensor elements 14a and 14b that output sensor signals Sa and Sb that can calculate the steering torque τ transmitted through the steering shaft 3 based on the twist of the torsion bar 17. It is prepared for.

  In such a torque sensor, for example, two magnetic detection elements (for example, Hall ICs) are arranged as sensor elements 14a and 14b on the outer periphery of a sensor core (not shown) that generates a magnetic flux change based on torsion of the torsion bar 17. Can be formed.

  That is, when the torsion bar 17 is twisted by torque input to the steering shaft 3 that is the rotating shaft, the magnetic flux passing through the sensor elements 14a and 14b changes. The torque sensor 14 of the present embodiment is configured to output the output voltages of the sensor elements 14a and 14b, which change with the change of magnetic flux, to the ECU 11 as sensor signals Sa and Sb, respectively.

  Further, the steering sensor 16 of the present embodiment includes a rotor 18 fixed to the column shaft 3a on the steering wheel 2 side of the torque sensor 14, and a sensor element (for example, detecting a change in magnetic flux accompanying the rotation of the rotor 18). Hall IC) 19 and a magnetic rotation angle sensor.

  In the present embodiment, the ECU 11 as the torque calculation means detects the steering torque τ based on the sensor signals Sa and Sb output from the sensor elements 14a and 14b as output elements of the torque sensor 14. The ECU 11 calculates a target assist force based on the steering torque τ and the vehicle speed V detected by the vehicle speed sensor 15, and drives the motor 12 as a drive source to generate the target assist force in the EPS actuator 10. By supplying power, the assist force applied to the steering system is controlled. (Power assist control)

  Further, as shown in FIG. 1, the vehicle steering apparatus 1 of the present embodiment is equipped with an ABS (anti-lock brake) device (braking control device) 30. Each steered wheel (wheel) 7 is provided with a brake actuator 31, and the braking force applied to the brake actuator 31 of each steered wheel 7 is controlled by the operation of the ABS device 30. The ABS device 30 detects the locked state of each steered wheel 7 during braking, and automatically controls the braking force, thereby avoiding that each steered wheel 7 is completely locked.

  Each state quantity (steering torque τ, motor rotation angular velocity ω, and steering angle θs) indicating the operating state of the electric power steering device 20 is input from the ECU 11 to the ABS device 30 through CAN communication. The input information is used for calculating a control command for the brake actuator 31 when the assist is stopped due to an abnormality in the electric power steering device 20. And the ABS apparatus 30 becomes a structure which controls the braking force given to the predetermined steered wheel 7 based on such information.

Next, an aspect of assist control in the electric power steering apparatus of the present embodiment will be described.
FIG. 2 is a control block diagram of the electric power steering apparatus 20 of the present embodiment. As shown in FIG. 2, the ECU 11 supplies driving power to a microcomputer (hereinafter referred to as a CPU) 21 that outputs a motor control signal and a motor 12 that is a driving source of the EPS actuator 10 based on the motor control signal. And a drive circuit 22.

  Each control block shown below is realized by a computer program executed by the CPU 21. Then, the CPU 21 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control block at every predetermined period.

  Specifically, the CPU 21 calculates the current command value I * corresponding to the target assist force to be generated by the EPS actuator 10, and the current command value I calculated by the current command value calculator 23. And a motor control signal output unit 24 that outputs a motor control signal based on *.

  Further, the CPU 21 includes a steering torque calculator 25 that calculates the steering torque τ based on the sensor signals Sa and Sb output from the torque sensor 14. That is, the torque sensor 14 of the present embodiment is a magnetic torque sensor using a magnetic detection element (for example, Hall IC) for each of the sensor elements 14a and 14b as described above. For this reason, the steering torque calculator 25 is configured to calculate the steering torque τ with high accuracy by performing correction processing (temperature characteristics and the like) using these two systems of sensor signals Sa and Sb. Then, the current command value calculator 23 is based on the steering torque τ calculated by the steering torque calculator 25 and the vehicle speed V detected by the vehicle speed sensor 15, and the assist control amount (assist Torque) is calculated.

  More specifically, the steering torque τ and the vehicle speed V are input to the assist control unit 26 provided in the current command value calculation unit 23. Further, a motor rotation angular velocity ω and a steering angle θs obtained by calculation from the motor rotation angle θ and the back electromotive force of the motor or by time differentiation of the motor rotation angle θ are input to the assist control unit 26. Then, the assist control unit 26 calculates a basic assist control amount (not shown), which is a basic component for generating an assist force corresponding to the input steering torque τ.

  Specifically, the assist control unit 26 calculates a basic assist control amount having a larger absolute value so that a larger assist force is applied to the steering system as the absolute value of the steering torque τ increases. . In the present embodiment, the calculation of the basic assist control amount serving as a basic component for generating the assist force is performed using a vehicle speed sensitive three-dimensional map. As a result, the assist control unit 26 calculates a basic assist control amount having a larger absolute value as the vehicle speed V is smaller.

  As described above, the current command value calculation unit 23 calculates the current command value I * to be supplied to the motor 12 using the basic assist control amount calculated by the assist control unit 26 as a basic component of the target assist force of the assist control. The motor control signal output unit 24 is supplied with the actual current value I of the motor 12 detected by the current sensor 27 together with the current command value I * calculated by the current command value calculation unit 23. The motor control signal output unit 24 of this embodiment generates a motor control signal by executing current feedback control so that the actual current value I follows the current command value I *.

  In the ECU 11 of the present embodiment, the CPU 21 outputs the motor control signal generated in this way to the drive circuit 22, and the drive circuit 22 supplies drive power based on the motor control signal to the motor 12. The operation of the actuator 10 is controlled to perform assist control.

  Here, the CPU 21 of the present embodiment is provided with abnormality detecting means for detecting abnormality of each sensor signal Sa, Sb output from the torque sensor 14, for example, and the ECU 11 (CPU 21) is based on the abnormality detection. The abnormality of the torque sensor 14 is determined. And ECU11 as a control means and an abnormality detection means becomes a structure which performs assist control according to the abnormality generation mode of the torque sensor 14 detected. When it is determined that an abnormality has occurred in each of the sensor elements 14a and 14b, control for gradually decreasing the assist force is executed (assist stop control) in order to quickly stop the assist control and achieve failsafe.

  Furthermore, as shown in FIG. 2, in this embodiment, the abnormality detection results of the sensor signals Sa and Sb executed by the steering torque calculator 25 and the abnormality detection results of the corresponding sensor elements 14a and 14b are detected as abnormal detection. The current command value calculation unit 23 inputs the signal Str. The current command value calculation unit 23 receives the current command value I when the abnormality detection signal Str indicating that both of the sensor elements 14a and 14b corresponding to the sensor signals Sa and Sb have both failed. * Output is stopped.

  In the present embodiment, the assist control unit 26 has a function as a detection unit (abnormality detection unit) that detects an abnormality of the electric power steering apparatus 20, and detects any abnormality by an abnormality detection determination described later. If it is, the CPU 21 immediately stops the assist control and outputs an abnormality detection signal Spsf indicating that an abnormality has been detected.

  Next, the fail safe control of the electric power steering apparatus in the present embodiment will be described. FIG. 3 is a flowchart showing a processing procedure of assist stop control when the electric power steering apparatus is abnormal in the first embodiment of the present invention. The ECU 11 of this embodiment has a function as a detection unit that detects an abnormality of the electric power steering apparatus 20. If any abnormality (for example, a motor, an ECU, a torque sensor, etc.) is detected by the abnormality detection determination, the operation of the electric power steering device 20 is stopped in order to make the fail safe.

  Specifically, as shown in the flowchart of FIG. 3, when the CPU 21 detects any abnormality in the electric power steering apparatus 20 based on the abnormality determination (step S301: YES), first, the control of the ECU 11 is performed immediately before the abnormality is detected. The steering torque τ calculated as the state quantity is stored (step S302). Then, an abnormality detection signal Spsf indicating that an abnormality has been detected is output (transmitted) (step S303), and the immediately preceding steering torque τ stored at the time of abnormality detection is output (transmitted) (step S304). Then, assist stop control is executed to stop the operation of the electric power steering device 20 (step S305). After this processing, the process returns to the main routine. If no abnormality is detected in step S301 (step S301: NO), the processes in steps S302 to S305 are not executed.

  Further, when the abnormality is detected, the abnormality detection signal Spsf and the steering torque τ output from the ECU 11 are input to the ABS device 30 via the CAN bus (see FIG. 1). Then, when receiving the abnormality detection signal Spsf during the steering operation, the ABS device 30 applies a braking force so that a turning force is generated in the steering direction. As a result, the steering operation is performed even after the electric power steering apparatus 20 stops operating, thereby stabilizing the vehicle behavior.

  FIG. 4 is a flowchart showing a processing procedure of braking control of the braking control device when the electric power steering device is abnormal in the first embodiment of the present invention. As shown in FIG. 4, the ABS device 30 acquires a steering torque τ, which is an assist control state quantity of the ECU 11 of the electric power steering device 20 (step S401). Next, it is determined whether or not there is an input of the abnormality detection signal Spsf (step S402). If there is an input of the abnormality detection signal Spsf (step S402: YES), whether or not a steering operation is subsequently being performed. Is determined (step S403). If it is determined that the steering operation is being performed (step S403: YES), the braking force applied to the predetermined steered wheel (wheel) 7 is calculated based on the received steering torque τ (step S404). Here, the braking force component calculated for the normal braking force is corrected. Then, the braking force is output as a control command (step S405), and the brake actuator 31 is controlled. After this processing, the process returns to the main routine.

  If no abnormality detection signal Spsf is input in step S402 (step S402: NO), or if it is determined in step S403 that the steering operation is not being performed (step S403: NO), the above steps S404 and The process of S405 is not executed.

  Next, a second embodiment embodying the present invention will be described. Here, this embodiment is different from the first embodiment only in the control state quantity of the ECU 11. That is, the steering torque τ in FIGS. 3 and 4 is replaced with the motor rotational angular velocity ω, and the CPU 21 outputs (transmits) the immediately preceding steering torque τ stored at the time of abnormality detection, and the ABS device 30 The motor rotation angular velocity ω, which is the assist control state quantity of the ECU 11 of the electric power steering device 20, is acquired, and the braking force applied to a predetermined steered wheel (wheel) 7 is calculated based on the received motor rotation angular velocity ω. The other processing procedures are the same as those in FIGS. 3 and 4 and will not be described.

As described above, according to the present embodiment, the following operations and effects can be obtained.
When an abnormality of the electric power steering device 20 is detected during the steering operation and the assist operation is stopped, the ECU 11 of the electric power steering device 20 detects the abnormality detection signal Spsf and the steering torque τ immediately before the abnormality is detected, or the motor Output (communication) the control state quantity of the rotational angular velocity ω. Based on these pieces of information, the ABS device 30 operates to apply a braking force to the steered wheels 7 on the steering direction side in addition to the normal braking force, and controls the brake actuator 31. Thus, the vehicle can turn in the steering direction and can easily perform a steering operation even after the operation of the electric power steering apparatus 20 is stopped.

  Further, according to the above configuration, the steering direction immediately before the abnormality is detected can be determined from the steering torque τ detected by the torque sensor 14 or the rotational angular velocity ω calculated from the motor rotational angle θ. Thus, the ABS device 30 does not require vehicle signals (steering angle, yaw rate, etc.) from other sensors, and controls based on information from the sensors (torque sensor, rotation angle sensor, etc.) provided in the electric power steering device 20. The power can be adjusted.

  As described above, it is possible to provide a vehicle steering apparatus that can continue turning of a vehicle by a steering operation even after an assist stop due to an abnormality of the electric power steering apparatus.

In addition, you may change each said embodiment as follows.
In the above embodiment, an example in which the steering direction is determined based on a signal from the torque sensor 14 input to the electric power steering device 20 or the rotation angle sensor 28 provided in the motor 12 has been described. The steering direction may be determined based on the steering angle θs detected by the equipped steering sensor 16.

Further, the above embodiment is not limited to the abnormality of the torque sensor 14, but may be applied when an abnormality occurs in the electric power steering apparatus 20 (motor 12, ECU 11, etc.).
Furthermore, the embodiment described above may be applied not only to the electric power steering device 20 but also to a hydraulic power steering device as long as the operation is stopped by fail-safe.

  In the above embodiment, a brushed DC motor is used as the motor 12 that is the drive source of the EPS actuator 10. However, the present invention is not limited to this, and an electric power steering apparatus using a brushless motor as a drive source may be embodied.

  Further, in the above embodiment, the present invention is embodied in the so-called column type electric power steering apparatus 20, but the present invention may be applied to a so-called pinion type or rack assist type electric power steering apparatus.

1: vehicle steering device, 2: steering wheel, 3: steering shaft,
3a: column shaft, 3b: intermediate shaft, 3c: pinion shaft,
4: rack and pinion mechanism, 5: rack shaft, 6: tie rod, 7: steered wheel,
10: EPS actuator (steering force assist device), 11: ECU (control means),
12: Motor, 14: Torque sensor, 14a, 14b: Sensor element, 15: Vehicle speed sensor,
16: Steering sensor, 17: Torsion bar, 18: Rotor, 19: Sensor element,
20: Electric power steering device (EPS), 21: CPU (microcomputer),
22: drive circuit, 23: current command value calculation unit, 24: motor control signal output unit,
25: Steering torque calculation unit, 26: Assist control unit, 27: Current sensor,
28: rotation angle sensor, 30: ABS (anti-lock brake) device (braking control device),
31: Brake actuator,
I *: current command value, I: actual current value, Sa, Sb: sensor signal, Str: abnormality detection signal,
τ: steering torque, V: vehicle speed, θ: motor rotation angle, ω: motor rotation angular velocity, θs: steering angle

Claims (2)

A steering force assist device that applies assist force to the steering system using a motor as a drive source;
An electric power steering apparatus comprising: an abnormality detecting means for detecting an abnormality; and a control means for stopping the operation of the steering force assisting device when the abnormality is detected;
In a vehicle steering apparatus comprising: a braking control device that controls a braking force applied to each wheel;
When the abnormality is detected during the steering operation, the braking control device applies the braking force to a predetermined wheel based on the steering direction detected according to the state of the steering system. A vehicle steering apparatus characterized by turning. The vehicle steering apparatus according to claim 1,
The vehicular steering apparatus, wherein the braking control apparatus detects the steering direction based on a steering torque detected from an output signal of a torque sensor provided in the electric power steering apparatus.

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