JP2017007460A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance steering feeling during failure of a torque sensor.SOLUTION: An electric power steering device comprises: an electric motor 10 which gives a steering assistant torque for assisting a steering operation by an operator based on a detection result of a torque sensor 12 at a normal time of the torque sensor 12; a failure determination part 32 which determines failure of the torque sensor 12; a steering angle acquisition part 15 which acquires a steering angle in association with the steering operation; a turning angle acquisition part 33 which acquires a turning angle of a wheel 6; and a motor control part 31 which sets a target turning angle of the wheel 6 based on an acquisition result of the steering angle acquisition part 15 in the case that the failure determination part 32 determines failure of the torque sensor 12, and so controls drive of the electric motor 10 that the turning angle acquired by the turning angle acquisition part 33 is coincident with the target turning angle.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electric power steering apparatus.

  As a conventional electric power steering apparatus, in Patent Document 1, when the steering torque sensor is normal, the drive of the electric motor is controlled based on the vehicle speed signal and the steering torque signal from the steering torque sensor. In the case where it is determined that there is a failure, there is disclosed a device that controls the driving of an electric motor using a steering torque estimated based on a vehicle speed signal and a steering angle signal.

JP 11-59447 A

  In the electric power steering device described in Patent Literature 1, assist control by the electric motor is continued even when the torque sensor fails. In that case, since the drive of the electric motor is controlled using the steering torque estimated based on the vehicle speed signal and the steering angle signal, the steering feeling greatly depends on the estimation accuracy of the steering torque. However, since the estimation accuracy of the steering torque based on the vehicle speed signal and the steering angle signal is not high, there is a problem that a good steering feeling cannot be obtained when the torque sensor fails.

  The present invention has been made in view of the above-described problems, and an object thereof is to improve the steering feeling when a torque sensor fails.

  The present invention relates to an electric power steering device, wherein when the torque sensor is normal, an electric motor for applying a steering assist torque for assisting a steering operation by a driver based on a detection result of the torque sensor and a failure of the torque sensor are determined. When the failure determination unit determines a failure of the torque sensor, the steering angle acquisition unit that acquires the steering angle associated with the steering operation, the turning angle acquisition unit that acquires the turning angle of the wheel, and the failure determination unit The target turning angle of the wheel is set based on the acquisition result of the steering angle acquisition unit, and the drive of the electric motor is controlled so that the turning angle acquired by the turning angle acquisition unit matches the target turning angle. And a motor control unit.

  According to the present invention, when the torque sensor fails, the electric motor is set such that the turning angle acquired by the turning angle acquisition unit matches the target turning angle set based on the acquisition result of the steering angle acquisition unit. Is controlled. Thus, when the torque sensor is out of order, the turning angle control is performed based on the steering angle associated with the steering operation, not the assist control. Therefore, it is possible to improve the steering feeling when the torque sensor fails.

It is a lineblock diagram of an electric power steering device concerning an embodiment of the present invention. It is a control block diagram of the electric power steering device according to the embodiment of the present invention.

  Hereinafter, an electric power steering apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an electric power steering apparatus 100 includes an input shaft 2 that rotates in response to an operation of a steering wheel 1 by a driver (hereinafter referred to as “steering operation”), and a rack that steers wheels 6. An output shaft 3 linked to the shaft 5 and a torsion bar 4 connecting the input shaft 2 and the output shaft 3 are provided. A steering shaft 7 is configured by the input shaft 2, the output shaft 3, and the torsion bar 4.

  A pinion gear 3 a that meshes with a rack gear 5 a formed on the rack shaft 5 is formed below the output shaft 3. When the steering wheel 1 is operated, the steering shaft 7 rotates, and the rotation is converted into a linear motion of the rack shaft 5 by the pinion gear 3a and the rack gear 5a, and the wheel 6 is steered through the knuckle arm 14.

  The electric power steering apparatus 100 includes an electric motor 10 that is a power source for assisting the driver in steering the steering wheel 1, and a speed reducer 11 that decelerates and transmits the rotation of the electric motor 10 to the steering shaft 7. , A torque sensor 12 for detecting the torque acting on the torsion bar 4 by the relative rotation of the input shaft 2 and the output shaft 3 accompanying the steering operation by the driver, and driving of the electric motor 10 based on the detection result of the torque sensor 12 And a controller 30 for controlling.

  The electric motor 10 is provided with a motor rotation angle sensor 10 a that detects the rotation angle of the electric motor 10. The motor rotation angle sensor 10a is configured by a resolver.

  The speed reducer 11 includes a worm shaft 11a connected to the output shaft of the electric motor 10 and a worm wheel 11b connected to the output shaft 3 and meshing with the worm shaft 11a. The torque output from the electric motor 10 is transmitted from the worm shaft 11a to the worm wheel 11b and applied to the output shaft 3 as a steering assist torque.

  Instead of the configuration in which the torque output from the electric motor 10 is applied to the output shaft 3 via the speed reducer 11, the torque output from the electric motor 10 may be applied to the rack shaft 5 through the speed reducer. As described above, the electric motor 10 applies steering assist torque to the steering system.

  A steering torque applied to the input shaft 2 in accordance with the steering operation by the driver is detected by the torque sensor 12, and the torque sensor 12 outputs a voltage signal corresponding to the steering torque to the controller 30. The controller 30 calculates the torque output from the electric motor 10 based on the voltage signal from the torque sensor 12, and controls the driving of the electric motor 10 so that the torque is generated. As described above, the electric power steering apparatus 100 detects the steering torque applied to the input shaft 2 with the torque sensor 12, and controls the drive of the electric motor 10 with the controller 30 based on the detection result. Assist steering operation.

  The torque sensor 12 is connected to the controller 30 through two systems, a main system and a sub system.

  The input shaft 2 is provided with a steering angle sensor 15 as a steering angle acquisition unit that acquires a steering angle (absolute steering angle) that is a rotation angle of the steering wheel 1. Since the rotation angle of the input shaft 2 is equal to the steering angle of the steering wheel 1, the steering angle of the steering wheel 1 can be obtained by detecting the rotation angle of the input shaft 2 by the steering angle sensor 15. The detection result of the steering angle sensor 15 is output to the controller 30.

  Although not shown, the steering angle sensor 15 includes a center gear that rotates integrally with the input shaft 2 and two outer gears that mesh with the center gear. Based on the change in magnetic flux accompanying the rotation of the two outer gears, The rotation angle of the center gear, that is, the rotation angle of the input shaft 2 is calculated.

  The controller 30 is detected by a CPU that controls the operation of the electric motor 10, a ROM that stores control programs and setting values necessary for the processing operation of the CPU, and various sensors such as the torque sensor 12 and the steering angle sensor 15. And a RAM for temporarily storing information.

  Next, the controller 30 will be described with reference to FIG. FIG. 2 is a control block diagram of the electric power steering apparatus.

  The controller 30 includes a motor control unit 31 that controls driving of the electric motor 10, a failure determination unit 32 that determines failure of the torque sensor 12, and a turning angle acquisition unit 33 that acquires the actual turning angle of the wheel 6. .

  The motor control unit 31 controls the drive of the electric motor 10 based on the detection result of the torque sensor 12 when the torque sensor 12 is normal, and acquires the detection result and the turning angle of the steering angle sensor 15 when the torque sensor 12 fails. The drive of the electric motor 10 is controlled based on the turning angle of the wheel 6 acquired by the unit 33.

  When the torque sensor 12 is normal, a voltage signal output from the main system is used to control the electric motor 10. The voltage signal output from the sub system is not used for controlling the electric motor 10 but is used for determining a failure of the torque sensor 12.

  The failure determination unit 32 compares the output voltage output from the main system and the output voltage output from the sub system, and determines that the difference is greater than or equal to a predetermined tolerance, the torque sensor 12 Is determined to be malfunctioning.

  Next, steering control by the electric power steering apparatus 100 will be described with reference to FIGS.

  While the failure determination unit 32 determines that the torque sensor 12 is normal, the motor control unit 31 controls the drive of the electric motor 10 based on the detection result of the torque sensor 12.

  When the difference between the output voltage output from the main system of the torque sensor 12 and the output voltage output from the sub system is equal to or greater than a predetermined tolerance, and the failure determination unit 32 determines that the torque sensor 12 has failed, The motor control unit 31 switches the control method of the electric motor 10 from assist control based on the detection result of the torque sensor 12 to turning angle control based on the detection result of the steering angle sensor 15. Below, turning angle control at the time of failure of the torque sensor 12 is demonstrated.

  The motor control unit 31 sets the target turning angle of the wheel 6 based on the detection result of the steering angle sensor 15. On the other hand, the turning angle acquisition unit 33 calculates the actual turning angle of the wheel 6 based on the detection result of the motor rotation angle sensor 10a. Specifically, the turning angle acquisition unit 33 calculates the rotation angle of the output shaft 3 based on the detection result of the motor rotation angle sensor 10a and the reduction ratio of the speed reducer 11, and the rotation angle of the output shaft 3 and the pinion gear 3a. And the amount of movement of the rack shaft 5 in the axial direction is calculated from the reduction ratio of the rack gear 5a, and the actual turning angle of the wheel 6 is calculated based on the amount of movement. And the motor control part 31 controls the drive of the electric motor 10 so that the actual turning angle of the wheel 6 acquired by the turning angle acquisition part 33 may correspond with a target turning angle.

  In this way, when the torque sensor 12 fails, the assist control based on the detection result of the torque sensor 12 is switched to the turning angle control based on the steering angle of the steering wheel 1 accompanying the steering operation. In the turning angle control at the time of failure of the torque sensor 12, immediately after the driver starts turning the steering wheel 1, the torsion bar 4 is twisted, so that the steering of the steering wheel 1 is not so heavy and the steering wheel 1 is several times. Rotate. If the steering wheel 1 rotates several degrees, the rotation angle is detected by the steering angle sensor 15, so the target turning angle is set by the motor control unit 31 and the electric motor 10 is controlled. Therefore, even in the electric power steering apparatus 100 in which the steering wheel 1 and the rack shaft 5 are mechanically connected, the turning angle control is possible.

  According to the above embodiment, there exist the effects shown below.

  When the torque sensor 12 fails, the actual turning angle of the wheel 6 acquired by the turning angle acquisition unit 33 matches the target turning angle set based on the detection result of the steering angle sensor 15. The drive of the electric motor 10 is controlled. Thus, when the torque sensor 12 is out of order, not the assist control but the turning angle control is performed based on the steering angle of the steering wheel 1 accompanying the steering operation. In the turning angle control, the target turning angle is set in accordance with the steering operation of the driver, and the drive of the electric motor 10 is controlled so that the actual turning angle of the wheel 6 matches the target turning angle. Further, it is possible to improve the steering feeling when the torque sensor 12 fails.

  Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.

  In the present embodiment, the electric power steering apparatus 100 includes an input shaft 2 that rotates in accordance with a steering operation by a driver, an output shaft 3 that is linked to a rack shaft 5 that steers wheels 6, an input shaft 2, and an output shaft. 3, a torque sensor 12 that detects torque acting on the torsion bar 4, and a steering assist that assists the driver in steering operation based on the detection result of the torque sensor 12 when the torque sensor 12 is normal. The electric motor 10 that applies torque, the failure determination unit 32 that determines failure of the torque sensor 12, the steering angle sensor 15 that acquires the steering angle associated with the steering operation, and the turning angle that acquires the turning angle of the wheel 6 When the acquisition unit 33 and the failure determination unit 32 determine that the torque sensor 12 has failed, the acquisition of the steering angle sensor 15 is performed. A motor control unit that sets the target turning angle of the wheel 6 based on the result and controls the drive of the electric motor 10 so that the turning angle acquired by the turning angle acquisition unit 33 matches the target turning angle. 31.

  In this configuration, when the torque sensor 12 fails, the electric motor is set such that the turning angle acquired by the turning angle acquisition unit 33 matches the target turning angle set based on the acquisition result of the steering angle sensor 15. 10 drive is controlled. Thus, when the torque sensor 12 fails, the turning angle control is performed based on the steering angle associated with the steering operation, not the assist control. Therefore, it is possible to improve the steering feeling when the torque sensor fails.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above-described embodiment, the configuration in which the pinion gear 3 a formed at the lower portion of the output shaft 3 meshes with the rack gear 5 a formed on the rack shaft 5 has been described. Instead of this, a pinion shaft that meshes with the rack gear 5a may be provided separately from the output shaft 3, and the output shaft 3 and the pinion shaft may be connected via a universal joint.

  In the above-described embodiment, the mode in which the target turning angle of the wheel 6 is set based on the detection result of the steering angle sensor 15 has been described. Instead of this, if the vehicle speed information and the like are taken into account in addition to the detection result of the steering angle sensor 15, a more accurate target turning angle can be set.

  In the said embodiment, the turning angle acquisition part 33 demonstrated the form which calculates the actual turning angle of the wheel 6 based on the detection result of the motor rotation angle sensor 10a. Instead of this, a turning angle sensor for detecting the actual turning angle of the wheel 6 may be provided, and the actual turning angle of the wheel 6 may be directly acquired instead of the calculation.

DESCRIPTION OF SYMBOLS 100 ... Electric power steering device, 1 ... Steering wheel, 2 ... Input shaft, 3 ... Output shaft, 4 ... Torsion bar, 5 ... Rack shaft, 6 ... Wheel, DESCRIPTION OF SYMBOLS 10 ... Electric motor, 10a ... Motor rotation angle sensor, 12 ... Torque sensor, 15 ... Steering angle sensor (steering angle acquisition part), 30 ... Controller, 31 ... Motor control part 32 ... Failure determination unit, 33 ... Steering angle acquisition unit

Claims (1)

An input shaft that rotates in accordance with the steering operation by the driver;
An output shaft linked to the rack shaft that steers the wheels;
A torsion bar connecting the input shaft and the output shaft;
A torque sensor for detecting torque acting on the torsion bar;
An electric motor for applying a steering assist torque for assisting a steering operation by a driver based on a detection result of the torque sensor when the torque sensor is normal;
A failure determination unit for determining a failure of the torque sensor;
A steering angle acquisition unit for acquiring a steering angle associated with a steering operation;
A turning angle acquisition unit for acquiring a turning angle of the wheel;
When the failure determination unit determines that the torque sensor has failed, the target turning angle of the wheel is set based on the acquisition result of the steering angle acquisition unit, and is acquired by the turning angle acquisition unit. An electric power steering apparatus comprising: a motor control unit that controls driving of the electric motor such that a turning angle coincides with the target turning angle.

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