JP2015174489A - steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device which can control a steering supporting system according to a steering torque, even if an output value of a steering torque sensor cannot be used.SOLUTION: The steering device includes: a steering torque sensor 16 which outputs an output value according to a torsion angle of a torsion bar 15 which is provided in midway of a steering shaft 11; a steering angle sensor 17 which detects a steering angle of a steering wheel 10; and an EPS (Electronic Power Steering) motor rotation angle sensor 25 which detects a rotation angle of an EPS motor 24. An EPS control unit 27 calculates a steering torque using the output value of the steering angle sensor 17 and the output value of the EPS motor rotation angle sensor 25 and controls drive of the EPS motor 24, when the EPS control unit cannot normally acquire the output value of the steering torque sensor 16.

Description

  The present invention relates to a steering apparatus including an electric steering assist system.

  As is well known, as a system applied to a vehicle steering device, there is an electric steering support system that supports a driver's steering by changing a power transmission mode from a steering wheel to a steered wheel by an output of an electric motor. It is practically used. Patent Document 1 describes a steering apparatus provided with a steering assist system including a steering assist mechanism and a steering angle ratio variable mechanism. The steering assist mechanism is a mechanism that reduces the steering load on the driver by applying a steering force to the steered wheels with an electric motor, and is generally called an electric power steering (EPS) mechanism. Yes. Further, the steering angle ratio variable mechanism is a mechanism that is operated by an electric motor to change a steering angle ratio that is a ratio between a steering angle of a steering wheel and a turning angle of a steered wheel. It is called VGR (Variable steering Gear Ratio) mechanism.

  In the steering device described in the same document, normally, the steering reaction force applied to the steering is compensated by the output of the electric motor of the steering angle ratio variable mechanism, and the output of the steered wheels is controlled by the output of the electric motor of the steering assist mechanism. By steering, substantial steer-by-wire steering is realized. When the steering angle ratio variable mechanism malfunctions, the steering angle ratio variable mechanism is locked, and the steering power assist is performed by the output of the electric motor of the steering assist mechanism.

JP 2009-056888 A

  By the way, the steering device described in the same document includes a steering torque sensor that outputs an output value corresponding to torsion of a torsion bar provided in the middle of the steering shaft, and the steering assist is based on the output value of the steering torque sensor. It controls the mechanism and the rudder angle ratio variable mechanism. Therefore, when the output value of the steering torque sensor cannot be normally acquired due to a failure, the control of the steering assist mechanism and the rudder angle ratio variable mechanism cannot be continued, and the steering assist cannot be performed.

  The present invention has been made in view of such circumstances, and the problem to be solved is to control the steering assist system according to the steering torque even when the output value of the steering torque sensor cannot be used. An object of the present invention is to provide a steering device that can be used.

  A steering device that solves the above problems includes a steering shaft coupled to a steering wheel, a steered wheel that is steered according to the rotation of the steering shaft, a torsion bar provided in the middle of the steering shaft, and a steering wheel. A steering assist system that changes the power transmission mode to the steered wheels by the output of the electric motor, a steering angle sensor that detects the steering angle of the steering wheel, and a motor rotation angle sensor that detects the rotation angle of the electric motor In the steering device that controls the steering assist system according to the steering torque applied to the steering shaft, a steering torque calculation unit that calculates the steering torque from the output value of the steering angle sensor and the output value of the motor rotation angle sensor is provided. Yes.

  In the above steering device, if the ratio between the steering angle of the steering wheel and the rotation angle of the electric motor is constant, the torsion angle of the torsion bar and the steering torque applied to the steering shaft are changed from the change in the angle difference. Can be requested. Therefore, if the steering torque calculation unit as described above is provided, the steering torque can be detected even when the output value of the steering torque sensor cannot be used, and the steering assist system can be controlled according to the steering torque. become able to.

  Furthermore, in a steering apparatus including a steering torque sensor that outputs an output value corresponding to the torsion angle of the torsion bar, the steering torque calculator can be used as a backup when the steering torque sensor fails. That is, when the output value of the steering torque sensor can be normally acquired, the steering assist system is controlled based on the output value of the steering torque sensor, and when the output value of the steering torque sensor cannot be normally acquired, The steering assist system can be controlled based on the calculation result. In such a case, even if the output value of the steering torque sensor cannot be acquired normally due to a failure, the control of the steering assist system according to the steering torque can be continued.

  The steering assist system is operated by a steering assist mechanism that generates power for turning the steered wheels by an electric motor for steering assist, and an electric motor for varying the steering angle ratio, and the steering angle of the steering wheel. And a rudder angle ratio variable mechanism that can vary a rudder angle ratio that is a ratio of the steered wheel to the steered angle of the steered wheel. In such a case, the steering torque calculation unit can be configured to calculate the steering torque using the output value of the sensor that detects the rotation angle of the electric motor for steering assist as the output value of the motor rotation angle sensor. .

  Further, when the steering assist system having the steering assist mechanism and the steering angle ratio variable mechanism as described above is adopted, the steering angle ratio is fixed even when the output value of the steering torque sensor cannot be normally obtained. After locking the steering angle ratio variable mechanism, it is possible to perform steering power assist through drive control of the steering assist electric motor based on the calculation result of the steering torque calculation unit.

  According to the steering device of the present invention, the steering assist system can be controlled in accordance with the steering torque even when the output value of the steering torque sensor cannot be used.

1 is a schematic diagram schematically illustrating the configuration of an embodiment of a steering device. The flowchart which shows the switching mode of control of the steering assistance system of the steering apparatus. The block diagram which shows the normal control aspect in the steering apparatus. The block diagram which shows the control aspect at the time of failure in the steering apparatus.

Hereinafter, an embodiment of a steering device will be described in detail with reference to FIGS.
As shown in FIG. 1, the steering device of this embodiment includes a steering shaft 11 connected to a steering wheel 10. In the following, the side of the steering shaft 11 to which the steering wheel 10 is connected will be referred to as the upstream side of the steering shaft 11, and the opposite side will be referred to as the downstream side of the steering shaft 11.

  The downstream end of the steering shaft 11 is connected to a rack bar 13 via a rack and pinion mechanism 12. The rack and pinion mechanism 12 has a pinion gear fixed to the downstream end portion of the steering shaft 11 so as to be integrally rotatable, and a rack gear provided on the rack bar 13. The rotation is converted into a linear motion of the rack bar 13 in the axial direction. And the steered wheel 14 is connected with the both ends of the rack bar 13, and the steered angle of the steered wheel 14 is changed according to the linear motion of the rack bar 13.

  This steering apparatus is provided with a steering support system for supporting the steering of the driver. The steering assist system includes a steering torque sensor 16, a steering angle sensor 17, a variable steering gear ratio (VGR) mechanism 18, an electric power steering (EPS) mechanism 23, and the like.

  As shown in FIG. 1, a torsion bar 15 is provided in the middle of the steering shaft 11. The steering torque sensor 16 is installed in the vicinity of the torsion bar 15. The steering torque sensor 16 is a sensor that detects the twist angle of the torsion bar 15 by an optical, electrical, or magnetic method, and outputs an output value corresponding to the detected twist angle. 11 corresponds to the steering torque Tr applied to No. 11.

  The steering angle sensor 17 is installed on the upstream side of the torsion bar 15 in the steering shaft 11. The steering angle sensor 17 outputs an output value corresponding to the rotation angle of the steering shaft 11 at the installation portion. The output value of the steering angle sensor 17 corresponds to the steering angle θ of the steering wheel 10.

  The VGR mechanism 18 is a mechanism (steering angle ratio variable mechanism) that varies a steering angle ratio that is a ratio between the steering angle θ of the steering wheel 10 and the steering angle of the steered wheels 14, and a torsion bar 15 in the steering shaft 11. It is installed in the downstream part. The VGR mechanism 18 includes a VGR motor 19 that is an electric motor for changing the steering angle ratio, and a wave gear mechanism 20. The VGR mechanism 18 is provided with a VGR motor rotation angle sensor 21 that detects the rotation angle of the VGR motor 19 (VGR motor rotation angle θv). The VGR motor 19 is a brushless DC motor.

  The wave gear mechanism 20 includes a stator gear 20a, a driven gear 20b, a wave generator 20c, and a flexible gear 20d. The steering shaft 11 is divided in the wave gear mechanism 20. The VGR mechanism 18 is divided. The stator gear 20a is configured as an internal gear, and is connected to an upstream portion of the steering shaft 11 so as to be integrally rotatable. The driven gear 20b is configured as an internal gear having fewer teeth than the stator gear 20a, and is coupled to the downstream portion of the steering shaft 11 so as to be integrally rotatable. The stator gear 20a and the driven gear 20b are respectively meshed with the flexible gear 20d. The flexible gear 20d is configured as an externally deformable external gear, and the number of teeth is the same as that of the driven gear 20b. The flexible gear 20d is fitted to the outer ring of the wave generator 20c.

  The wave generator 20c has an elliptical cam connected to an output shaft 19a of a VGR motor 19 formed in a hollow pipe shape so as to be integrally rotatable, and the stator gear 20a and the driven gear 20b according to the rotation of the cam. The meshing position of the flexible gear 20d with respect to each of these is changed. When the cam rotates once, the relative rotation phase of the stator gear 20a and the driven gear 20b with respect to the flexible gear 20d has a difference corresponding to the difference in the number of teeth. Therefore, when the cam of the wave generator 20c is rotated by the VGR motor 19, the stator gear 20a and the driven gear 20b are differentially rotated. Therefore, when the cam of the wave generator 20c is rotated by the VGR motor 19, the steering wheel 10 and the pinion gear of the rack and pinion mechanism 12 are rotated differentially. The magnitude of the differential rotation increases or decreases depending on the rotation speed of the VGR motor 19. Therefore, the steering angle ratio can be freely changed by controlling the rotation speed of the VGR motor 19.

  Further, the VGR mechanism 18 is provided with a lock mechanism 22. The lock mechanism 22 locks the output shaft 19a of the VGR motor 19 so as not to rotate, thereby prohibiting differential rotation of the stator gear 20a and the driven gear 20b and fixing the steering angle ratio.

  The VGR motor 19 of the VGR mechanism 18 is controlled by the VGR control unit 26. Output values of the steering torque sensor 16, the VGR motor rotation angle sensor 21, and the vehicle speed sensor 28 that detects the vehicle speed v are input to the VGR control unit 26.

  The EPS mechanism 23 is a mechanism (steering assist mechanism) that generates power for turning the steered wheels 14 and includes an EPS motor 24 that is an electric motor for steering assist that generates the power. The EPS motor 24 employs a brushless DC motor. The EPS mechanism 23 is provided with an EPS motor rotation angle sensor 25 that detects the rotation angle of the EPS motor 24 (EPS motor rotation angle θe).

  As the EPS mechanism 23, a mechanism of an arbitrary system such as a column type, a pinion type, a dual pinion type, a rack direct type, or a rack parallel type can be adopted. Incidentally, the column type EPS (C-EPS) mechanism is an EPS mechanism having a configuration in which the output shaft of the EPS motor 24 is connected to the steering shaft 11 via a speed reduction mechanism. This is an EPS mechanism in which the output shaft of the EPS motor 24 is connected to the pinion gear of the rack and pinion mechanism 12 via a speed reduction mechanism. Further, the dual pinion EPS (DP-EPS) mechanism has an EPS motor 24 via a speed reduction mechanism connected to a pinion gear different from the pinion gear of the rack and pinion mechanism 12 meshed with the rack gear of the rack and pinion mechanism 12. It is the EPS mechanism of the structure which connected the output shaft. Further, the rack direct EPS (RD-EPS) mechanism transmits the power of the EPS motor 24 arranged coaxially with respect to the rack bar 13 to a portion different from the rack gear of the rack and pinion mechanism 12 in the rack bar 13. It is an EPS mechanism of the configuration. In FIG. 1, a rack parallel type EPS (RP-EPS) mechanism in which the EPS motor 24 is arranged in parallel to the rack bar 13 is shown as an example of the EPS mechanism.

  The EPS motor 24 of the EPS mechanism 23 is controlled by the EPS control unit 27. The output values of the steering angle sensor 17, EPS motor rotation angle sensor 25, and vehicle speed sensor 28 are input to the EPS control unit 27.

  Next, the control (steering support control) of the steering support system in the steering apparatus of the present embodiment configured as described above will be described. In the steering device including the steering torque sensor 16 as described above, the steering assist system can be controlled in accordance with the steering torque Tr applied to the steering shaft 11 based on the output value. However, the output value of the steering torque sensor 16 may not be acquired normally due to a failure of the steering torque sensor 16 or disconnection of its signal line. Therefore, in the steering device of the present embodiment, the control mode of the steering assist system is switched between when the output value of the steering torque sensor 16 can be normally acquired and when the output value cannot be normally acquired.

  As shown in FIG. 2, when the output value of the steering torque sensor 16 can be acquired normally (S100: YES), the steered wheels 14 are controlled through the drive control of the EPS motor 24 based on the output value (steering angle θ) of the steering angle sensor 17. Steering control is performed (S110). At this time, the compensation control of the steering reaction force applied to the steering wheel 10 is performed through the drive control of the VGR motor 19 based on the output value (steering torque Tr) of the steering torque sensor 16 (S120). And by these controls, steering by substantial steering-by-wire is realized.

  On the other hand, when the output value of the steering torque sensor 16 cannot be acquired normally (S100: NO), the VGR mechanism 18 is locked by the lock mechanism 22 so that the steering angle ratio is fixed (S130). Further, at this time, the steering torque is calculated from the output value of the steering angle sensor 17 (steering angle θ) and the output value of the EPS motor rotation angle sensor 25 (EPS motor rotation angle θe) (S140). Then, steering power assist control is performed through drive control of the EPS motor 24 based on the calculation result (steering torque calculation value Trcal) (S150).

  FIG. 3 shows concrete examples of the EPS control unit 27 and the VGR control unit 26 in the steering control of the steered wheels 14 and the compensation control of the steering reaction force that are performed when the output value of the steering torque sensor 16 can be normally acquired. The contents of the processing are shown.

  In the turning control of the steered wheels 14, the EPS control unit 27 first sets a target yaw rate γ that is a target value of the yaw rate of the vehicle based on the steering angle θ output from the steering angle sensor 17 and the vehicle speed v output from the vehicle speed sensor 28. Calculate *. Then, the EPS control unit 27 calculates the target rotation angle θe * of the EPS motor 24 according to the calculated target yaw rate γ *. Subsequently, the EPS control unit 27 determines the target value that is the target value of the current that flows to the EPS motor rotation angle sensor 25 from the difference between the EPS motor rotation angle θe output from the EPS motor rotation angle sensor 25 and the target rotation angle θe *. The current Ie * is calculated.

  Further, the EPS control unit 27 determines the EPS motor 24 based on the difference between the target current Ie * and the EPS motor current Ie, which is the current value of the current, and the EPS motor rotation angle θe output from the EPS motor rotation angle sensor 25. Calculate the motor drive duty DUTYe. The EPS control unit 27 controls the turning angle of the steered wheels 14 by controlling the driving of the EPS motor 24 according to the calculated motor driving duty DUTYe.

  On the other hand, in the compensation control of the steering reaction force, the VGR control unit 26 first calculates the target steering torque Tr * based on the steering angle θ output from the steering angle sensor 17 and the vehicle speed v output from the vehicle speed sensor 28. Then, the VGR control unit 26 calculates a target current Iv * that is a target value of the current that flows to the VGR motor 19 from the difference between the steering torque Tr output from the steering torque sensor 16 and the target steering torque Tr *.

  Further, the VGR control unit 26 determines the difference between the current (VGR motor current Iv) flowing through the current VGR motor 19 and the target current Iv *, and the current VGR motor rotation output from the VGR motor rotation angle sensor 21. Based on the angle θv, the motor drive duty DUTYv of the VGR motor 19 is calculated. The VGR control unit 26 compensates the steering reaction force by controlling the drive of the VGR motor 19 in accordance with the calculated motor drive duty DUTYv.

  FIG. 4 shows the processing contents of the EPS control unit 27 in the power assist control performed when the output value of the steering torque sensor 16 cannot be normally obtained. Note that energization of the VGR motor 19 at this time is stopped, and the VGR mechanism 18 is locked by the lock mechanism 22.

  In the power assist control, the EPS control unit 27 first calculates a steering torque calculation value Trcal based on the EPS motor rotation angle θe output from the EPS motor rotation angle sensor 25 and the steering angle θ output from the steering angle sensor 17. In this embodiment, the processing related to the calculation of the steering torque calculation value Trcal of the EPS control unit 27 at this time is the steering torque for calculating the steering torque from the output value of the steering angle sensor and the output value of the motor rotation angle sensor. This corresponds to the processing performed by the calculation unit. Further, the EPS motor rotation angle θe used for calculating the steering torque calculation value Trcal here corresponds to the output value of the motor rotation angle sensor used for calculating the steering torque of the steering torque calculation unit.

  Further, the EPS control unit 27 at this time calculates the target steering torque Tr * based on the steering angle θ output from the steering angle sensor 17 and the vehicle speed v output from the vehicle speed sensor 28. Subsequently, the EPS control unit 27 calculates the target current Ie * of the EPS motor 24 from the difference between the target steering torque Tr * and the steering torque calculation value Trcal.

  Further, the EPS control unit 27 calculates the motor drive duty DUTYe of the EPS motor 24 based on the difference between the target current Ie * and the EPS motor current Ie and the EPS motor rotation angle θe output from the EPS motor rotation angle sensor 25. To do. The EPS control unit 27 performs steering power assist by drivingly controlling the EPS motor 24 according to the calculated motor drive duty DUTYe.

Next, the operation of the steering device of the present embodiment described above will be described.
In the steering apparatus configured as described above, when the VGR mechanism 18 is locked by the lock mechanism 22, the ratio between the steering angle θ and the EPS motor rotation angle θe becomes constant, and the torsion bar 15 is twisted from the change in the angle difference. Thus, the steering torque Tr applied to the steering shaft 11 can be obtained. Therefore, in the steering device of the present embodiment, when the output value of the steering torque sensor 16 cannot be normally obtained, the VGR mechanism 18 is locked by the lock mechanism 22 and the steering torque is calculated from the steering angle θ and the EPS motor rotation angle θe. (Steering torque calculation value Trcal) is calculated. As a result, even when the output value of the steering torque sensor 16 cannot be normally obtained, the steering assist based on the steering torque, specifically, the steering power by the drive control of the EPS motor 24 based on the steering torque calculation value Trcal. Assistance can be performed.

According to the steering device of the present embodiment described above, the following effects can be obtained.
(1) In the present embodiment, the EPS control unit 27 calculates the steering torque calculation value Trcal from the steering angle θ output from the steering angle sensor 17 and the EPS motor rotation angle θe output from the EPS motor rotation angle sensor 25. Yes. Therefore, even when the output value of the steering torque sensor 16 that outputs the output value corresponding to the torsion angle of the torsion bar 15 cannot be used, the steering assist system can be controlled in accordance with the steering torque.

  (2) When the steering torque Tr output from the steering torque sensor 16 cannot be normally acquired due to failure, the VGR mechanism 18 is locked by the lock mechanism 22 so as to fix the steering angle ratio, and the steering torque is Steering power assist is performed by driving control of the EPS motor 24 based on the calculation value Trcal. Therefore, even when the steering torque Tr output from the steering torque sensor 16 cannot be normally acquired, it is possible to perform steering power assist according to the steering torque.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the specific processing contents of the steering control of the steered wheels 14, the steering reaction force compensation control, and the power assist control may be appropriately changed. For example, the target yaw rate γ * is calculated based on the steering torque θ and the vehicle speed v and also based on the steering torque sensor 16 or the target yaw rate γ * is not calculated, and the target rotation angle is calculated from the steering angle θ and the vehicle speed v. The steering control may be performed by directly calculating θe *.

  In the above embodiment, when the output value of the steering torque sensor 16 can be normally obtained, the steering control of the steered wheels 14 by the drive control of the EPS motor 24 and the compensation control of the steering reaction force by the drive control of the VGR motor 19 are performed. This was performed as steering assist control. The steering assist control at this time may be performed in a different manner.

  -Although the steering device of the said embodiment was provided with the steering assistance system which has the VGR mechanism 18 and the EPS mechanism 23, you may make it employ | adopt the steering assistance system of the structure of other than that. For example, in a steering apparatus that employs a steering assist system that does not have the VGR mechanism 18 but has only the EPS mechanism 23, the steering torque can be calculated from the steering angle θ and the EPS motor rotation angle θe. When the EPS motor 24 is driven and controlled based on the steering torque calculation value Trcal calculated from the steering angle θ and the EPS motor rotation angle θe, the steering torque Tr output from the steering torque sensor 16 cannot be normally acquired. Steering support control such as steering power assist control can be performed.

  DESCRIPTION OF SYMBOLS 10 ... Steering wheel, 11 ... Steering shaft, 12 ... Rack and pinion mechanism, 13 ... Rack bar, 14 ... Steering wheel, 15 ... Torsion bar, 16 ... Steering torque sensor, 17 ... Steering angle sensor, 18 ... VGR mechanism (rudder Angle ratio variable mechanism), 19 ... VGR motor (electric motor for variable steering angle ratio), 19a ... Output shaft (of VGR motor 19), 20 ... wave gear mechanism, 20a ... stator gear, 20b ... driven gear, 20c ... wave Generating device, 20d ... flexible gear, 21 ... VGR motor rotation angle sensor, 22 ... lock mechanism, 23 ... EPS mechanism (steering assist mechanism), 24 ... EPS motor (steering assist electric motor), 25 ... EPS motor rotation angle Sensor (motor rotation angle sensor), 26 ... VGR control unit, 2 ... EPS control unit (steering torque calculating section), 28 ... vehicle speed sensor.

Claims (4)

A steering shaft connected to the steering wheel, a steered wheel steered according to the rotation of the steering shaft, a torsion bar provided in the middle of the steering shaft, and power transmission from the steering wheel to the steered wheel A steering assist system that changes the mode according to the output of the electric motor; a steering angle sensor that detects a steering angle of the steering wheel; and a motor rotation angle sensor that detects a rotation angle of the electric motor, and the steering shaft. In the steering device that controls the steering assist system according to the steering torque applied to the vehicle,
A steering torque calculator that calculates the steering torque from the output value of the steering angle sensor and the output value of the motor rotation angle sensor;
A steering device characterized by that. A steering torque sensor that outputs an output value corresponding to a twist angle of the torsion bar;
When the output value of the steering torque sensor can be normally acquired, the steering assist system is controlled based on the output value of the steering torque sensor, and when the output value of the steering torque sensor cannot be normally acquired, the steering torque Controlling the steering support system based on the calculation result of the calculation unit;
The steering apparatus according to claim 1. The steering assist system is operated by a steering assist mechanism that generates power for turning the steered wheels by an electric motor for steering assist, and an electric motor for variable steering angle ratio, so that the steering angle of the steering wheel is increased. And a steering angle ratio variable mechanism that varies a steering angle ratio that is a ratio of a steering angle of the steered wheels, and a sensor that detects a rotation angle of the electric motor for steering assist is a motor rotation angle sensor. Prepare as
The steering apparatus according to claim 2. When the output value of the steering torque sensor cannot be normally obtained, the steering angle ratio variable mechanism is locked so as to fix the steering angle ratio, and then the steering assist based on the calculation result of the steering torque calculation unit is used. Steering power assist through electric motor drive control,
The steering apparatus according to claim 3.