JP2012240537A - Electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering apparatus capable of reducing an inertia torque of a steering shaft when a rack shaft collides against a stopper.SOLUTION: The electric power steering apparatus 1 includes the steering shaft 10, the rack shaft 20, the stopper 41, an electric motor 51 which imparts a torque to the steering shaft 10, and a control device 54 that outputs a command signal for controlling the drive current of the electric motor 51. When defining that "an inertia torque" is a torque generated on the steering shaft 10 when the rack shaft 20 collides against the stopper 41, "a compensation torque" is a torque in a direction opposite to the inertia torque, "a compensation current" is a drive current of the electric motor 51 for imparting the compensation torque to the steering shaft 10, and "a compensation command signal" is a command signal for supplying the compensation current to the electric motor 51, the control device 54 outputs the compensation command signal so long as the inertial torque is present.

Description

  The present invention is directed to a steering shaft, a rack shaft, a stopper that restricts the movement of the rack shaft, an electric motor that applies torque to the steering shaft, and a drive current of the electric motor that is controlled according to the torque of the steering shaft. The present invention relates to an electric power steering apparatus that includes a control device that outputs a command signal.

  The conventional electric power steering apparatus controls the magnitude of torque applied to the shaft from the electric motor according to the torque input to the steering shaft by operating the steering wheel. Moreover, the electric power steering apparatus described in Patent Document 1 further performs control for suppressing the influence of torque input from the road surface to the steered wheels and improving steering wheel operation assist.

Japanese Patent Laid-Open No. 2004-74983

  When the force input from the road surface to the steered wheel is large, for example, when the steered wheel collides with the curb of the roadway during traveling of the vehicle, the rack shaft may collide with the stopper. When the rack shaft collides with the stopper, an excessively large inertia torque may be generated on the steering shaft. In addition, since the electric power steering apparatus of patent document 1 does not perform the control which considered that a rack shaft collides with a stopper, it is thought that the said inertia torque is not fully reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering apparatus capable of reducing the inertia torque of the steering shaft generated when the rack shaft collides with the stopper. It is in.

Means for achieving the above object will be described below.
(1) The first means is the invention according to claim 1, that is, “a steering shaft, a rack shaft, a stopper for restricting the movement of the rack shaft, an electric motor for applying torque to the steering shaft, An electric power steering apparatus including a control device that outputs a command signal for controlling a drive current of the electric motor according to the torque of the steering shaft, wherein the control device is configured to cause the rack shaft to collide with the stopper. The torque generated in the steering shaft is the inertia torque, the torque in the direction opposite to the inertia torque is the compensation torque, and the drive current of the electric motor that applies the compensation torque to the steering shaft is the compensation current. Command signal for supplying compensation current to the electric motor As compensation command signal, and the gist of the outputs of the compensation instruction signal "that when said inertial torque is generated.

  According to the present invention, when inertia torque is generated in the steering shaft, torque in the direction opposite to the inertia torque is applied to the steering shaft by the electric motor. For this reason, the inertia torque of the steering shaft generated when the rack shaft collides with the stopper can be reduced.

  (2) The second means is the invention according to claim 2, that is, “a steering shaft, a rack shaft, a stopper for restricting the movement of the rack shaft, an electric motor for applying torque to the steering shaft, An electric power steering apparatus comprising: a control device that outputs a command signal for controlling a drive current of the electric motor in accordance with a torque of the steering shaft. The control device moves the rack shaft toward the stopper. The direction of rotation of the steering shaft is a limiting direction, and a torque for rotating the steering shaft in a direction opposite to the limiting direction is a compensation torque, and the driving current of the electric motor that applies the compensation torque to the steering shaft Is the compensation current, and this compensation current is A command signal for supplying to the over data as a compensation command signal, the outputs of the compensation instruction signal when said rack shaft is colliding with the stopper "It is summarized as.

  According to this invention, when the rack shaft collides with the stopper, a torque in a direction opposite to the rotation direction of the steering shaft that moves the rack shaft toward the stopper by the electric motor is applied to the steering shaft. For this reason, the inertia torque of the steering shaft generated when the rack shaft collides with the stopper can be reduced.

  (3) The third means is the invention according to claim 3, that is, "in the electric power steering apparatus according to claim 1 or 2, the condition indicating that the rack shaft is colliding with the stopper is collided." The gist is that the compensation command signal is output when the collision occurrence condition is satisfied as the generation condition.

  (4) The fourth means is that the invention according to claim 4, that is, “in the electric power steering device according to claim 3, the reduction speed of the rotation speed of the electric motor is equal to or higher than a predetermined reduction speed. The gist is “the condition for occurrence of the collision”.

  As a phenomenon that can be confirmed when the rack shaft collides with the stopper, there is an excessively large decrease rate of the rotation speed of the electric motor. For this reason, when the decreasing speed of the rotational speed of the electric motor is equal to or higher than the predetermined decreasing speed, it can be considered that the rack shaft is likely to collide with the stopper.

  In the present invention, based on this concept, since the compensation command signal is output when the reduction speed of the rotation speed of the electric motor is equal to or higher than the predetermined reduction speed, the inertia torque generated in the steering shaft can be reduced more appropriately. Can do.

  (5) The fifth means is the invention according to claim 5, that is, “in the electric power steering apparatus according to claim 3, the absolute value of the drive current of the electric motor is changed from“ 0 ”to the electric motor. “The collision occurrence condition is that the absolute value of the drive current of the first current is changed to a state larger than“ 0 ””.

  As a phenomenon that can be confirmed when the rack shaft collides with the stopper, there is a phenomenon in which the control of the electric motor by the command signal is changed to a controllable state. For this reason, when the absolute value of the drive current of the electric motor changes from a state of “0” to a state larger than “0”, it can be considered that there is a high possibility that the rack shaft has collided with the stopper.

  In the present invention, based on this concept, a compensation command signal is output when the absolute value of the drive current of the electric motor changes from “0” to a state larger than “0”. The inertia torque to be reduced can be reduced more accurately.

  (6) The sixth means is the invention according to claim 6, that is, "in the electric power steering apparatus according to claim 3, the amount of change in torque acting on the steering shaft is greater than or equal to a predetermined amount of change." Is the above-mentioned collision occurrence condition.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the torque acting on the steering shaft is excessively large. For this reason, when the amount of change in the torque acting on the steering shaft is equal to or greater than the predetermined amount of change, it can be considered that the rack shaft is likely to collide with the stopper.

  In the present invention, based on this concept, the compensation command signal is output when the change amount of the torque acting on the steering shaft is equal to or greater than the predetermined change amount, so that the inertia torque generated on the steering shaft is reduced more accurately. be able to.

  (7) The seventh means is the invention according to the seventh aspect, that is, in the electric power steering apparatus according to the third aspect, the fact that the direction of the torque acting on the steering shaft is reversed is the collision occurrence condition. The gist is to do.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the direction of the torque acting on the steering shaft is reversed. For this reason, when the direction of the torque acting on the steering shaft is reversed, it can be considered that there is a high possibility that the rack shaft has collided with the stopper.

  In the present invention, since the compensation command signal is output when the direction of the torque acting on the steering shaft is reversed based on this concept, the inertia torque generated on the steering shaft can be reduced more accurately.

  (8) The eighth means is the invention according to the eighth aspect, that is, “in the electric power steering apparatus according to any one of the first to seventh aspects, the rack shaft collides with the stopper. The gist is that the condition is the expected collision condition and the compensation command signal is output when the expected collision condition is satisfied.

  According to the present invention, it is possible to suppress the output of the compensation command signal over a long period of time even though the operation state of the electric motor is in a controllable state. For this reason, after the rack shaft collides with the stopper, appropriate assist for the steering wheel can be resumed promptly.

  (9) The ninth means is the invention according to claim 9, that is, “in the electric power steering apparatus according to claim 8, the collision expectation condition that the operation state of the electric motor is in a predetermined operation state. The gist of this is.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the operating state of the electric motor is in a state corresponding to the occurrence of the collision. For this reason, when the operation state of the electric motor is a predetermined operation state, it can be considered that the possibility that the rack shaft collides with the stopper is high.

  In the present invention, since the compensation command signal is output when the operation state of the electric motor is in a predetermined operation state based on this concept, the inertia torque generated in the steering shaft can be reduced more accurately.

  (10) The tenth means is the invention according to the tenth aspect, that is, in the electric power steering apparatus according to the eighth or ninth aspect, the rotational speed of the electric motor is equal to or higher than a predetermined rotational speed. The gist is "Consider conditions for collision."

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the rotational speed of the electric motor is excessively high. For this reason, when the rotation speed of the electric motor is equal to or higher than a predetermined rotation speed, it can be considered that the rack shaft is highly likely to collide with the stopper.

  In the present invention, since the compensation command signal is output when the rotational speed of the electric motor is equal to or higher than the predetermined rotational speed based on this concept, the inertia torque generated in the steering shaft can be reduced more accurately.

  (11) The eleventh means is the invention according to the eleventh aspect, that is, “in the electric power steering apparatus according to the eighth or ninth aspect, the difference between the drive current of the electric motor and the command current of the command signal is The gist is that the collision expectation condition is that the difference is equal to or greater than a predetermined difference.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the drive current of the electric motor and the command current of the command signal are excessively deviated. For this reason, when the difference between the drive current of the electric motor and the drive current commanded by the command signal is greater than or equal to a predetermined difference, it can be considered that the rack shaft is likely to collide with the stopper.

  In the present invention, based on this concept, since the compensation command signal is output when the difference between the drive current of the electric motor and the drive current commanded by the command signal is greater than or equal to a predetermined difference, the inertia torque generated in the steering shaft Can be reduced more accurately.

  (12) The twelfth means is the invention according to claim 12, that is, “in the electric power steering device according to claim 8 or 9, the collision expectation that the drive current of the electric motor is“ 0 ”. The stipulation is “Condition”.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the electric motor cannot be controlled by the control device. For this reason, when the drive current of the electric motor is “0”, it can be considered that the possibility that the rack shaft collides with the stopper is high.

  In the present invention, since the compensation command signal is output when the drive current of the electric motor is “0” based on this concept, the inertia torque generated in the steering shaft can be reduced more accurately.

  (13) A thirteenth aspect is the invention according to the thirteenth aspect, that is, “in the electric power steering apparatus according to the eighth aspect, the collision expectation that the moving speed of the rack shaft is equal to or higher than a predetermined moving speed. The stipulation is “Condition”.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the movement speed of the rack shaft is excessively high. For this reason, when the moving speed of the rack shaft is equal to or higher than the predetermined moving speed, it can be considered that the rack shaft is likely to collide with the stopper.

  In the present invention, based on this concept, the compensation command signal is output when the movement speed of the rack shaft is equal to or higher than the predetermined movement speed, so that the inertia torque generated in the steering shaft can be reduced more accurately.

  (14) The fourteenth means is the invention according to the fourteenth aspect, that is, in the electric power steering device according to any one of the first to thirteenth aspects, the control device outputs the compensation command signal. And when the difference between the drive current of the electric motor and the command current of the command signal is equal to or less than a reference difference, the command signal is output according to the torque of the steering shaft.

  A phenomenon that can be confirmed when the control of the electric motor by the control device is possible is that the difference between the drive current of the electric motor and the command current of the command signal is small. For this reason, when the difference between the drive current of the electric motor and the command current of the command signal is equal to or less than the reference difference, it can be considered that the electric motor can be controlled.

  In the present invention, based on this concept, when the difference between the drive current of the electric motor and the drive current commanded by the command signal is equal to or smaller than the reference difference, the output of the command signal corresponding to the torque of the steering shaft is started. For this reason, switching from the control of the electric motor based on the compensation command signal to the control of the electric motor based on the command signal corresponding to the torque is performed at an appropriate time.

  (15) The fifteenth aspect is the invention according to the fifteenth aspect, that is, "in the electric power steering apparatus according to the fourteenth aspect, the control device includes a driving current of the electric motor and a command current of the command signal; The difference is that the difference is less than or equal to the reference difference, and when the allowable deviation state continues for a predetermined time or more, the command signal is output in accordance with the torque of the steering shaft. To do.

  When the difference between the drive current of the electric motor and the command current of the command signal changes from a state larger than the reference difference to a state below the reference difference, the current difference immediately changes to a state larger than the reference difference. Sometimes. Therefore, in order to switch the control of the electric motor based on the compensation command signal to the control of the electric motor based on the command signal according to the torque at a more appropriate time, the state where the current difference is equal to or less than the reference difference It is preferable to confirm whether or not has continued for a predetermined time or more.

  In the present invention, based on this concept, a state where the difference between the drive current of the electric motor and the command current of the command signal is equal to or less than a reference difference is defined as an allowable divergence state, and the allowable divergence state continues for a predetermined time or more. At this time, output of a command signal corresponding to the torque of the steering shaft is started. For this reason, switching from the control of the electric motor based on the compensation command signal to the control of the electric motor based on the command signal corresponding to the torque can be performed at a more appropriate time.

  (16) The sixteenth means is the invention according to the sixteenth aspect, that is, in the electric power steering apparatus according to any one of the first to thirteenth aspects, the control device outputs the compensation command signal. When the rotation direction of the electric motor is reversed, the command signal is output according to the torque of the steering shaft.

  A phenomenon that can be confirmed when the rack shaft collides with the stopper is that the rotation direction of the electric motor acting on the steering shaft is reversed. For this reason, when the rotation direction of the electric motor is reversed, it can be considered that there is a high possibility that the rack shaft has collided with the stopper. In addition, when the rack shaft collides with the stopper, the rotation speed of the electric motor is reduced, so there is a high possibility that the control device has changed from being unable to control the electric motor to being capable of being controlled.

  In the present invention, based on this concept, a compensation command signal is output when the rotation direction of the electric motor is reversed. For this reason, switching from the control of the electric motor based on the compensation command signal to the control of the electric motor based on the command signal corresponding to the torque can be performed at a more appropriate time.

  (17) The seventeenth means is the invention according to the seventeenth aspect, that is, the electric power steering apparatus according to any one of the first to sixteenth aspects, wherein the control device detects a torque of the steering shaft. The gist is to output the command signal set in advance as the compensation command signal without reflecting the output of the torque sensor.

  (18) The eighteenth means is the invention according to the eighteenth aspect, that is, "the electric power steering apparatus according to any one of the first to seventeenth aspects, wherein the control device outputs the compensation command signal." The gist is that, instead of the control, a control for stopping the driving of the electric motor is performed.

  The inertia torque of the steering shaft generated when the rack shaft collides with the stopper acts in the direction of pressing the rack shaft against the stopper. For this reason, in the electric power steering apparatus that performs torque assist control, torque in the same direction as the inertia torque is applied from the electric motor to the steering shaft in accordance with the inertia torque. At this time, since the movement of the rack shaft is restricted by the stopper, when the electric motor is driven in the direction in which the torque is generated, a component for transmitting power between the electric motor and the steering shaft and the electric An excessively large load is applied to the motor. That is, when the rack shaft collides with the stopper, there is a possibility that at least one of the same component and the electric motor may be damaged due to the torque assist control of the electric motor.

  In the present invention, when the inertia torque is generated due to the collision between the rack shaft and the stopper, the driving of the electric motor is stopped, so that it is possible to suppress the occurrence of the above-described problem due to the torque assist control.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus which can make small the inertia torque of the steering shaft which generate | occur | produces when a rack shaft collides with a stopper can be provided.

The schematic diagram which shows the whole structure about the electric power steering apparatus of one Embodiment of this invention. The flowchart which shows the procedure of the "inverse input inertia compensation control" performed by the control apparatus about the electric power steering apparatus of the embodiment. The flowchart which shows the procedure of the "collision expectation condition determination control" performed by the control apparatus about the electric power steering apparatus of the embodiment. The flowchart which shows the procedure of the "compensation stop condition determination control" performed by the control apparatus about the electric power steering apparatus of the embodiment. FIG. 4 is a timing chart showing (a) a change in the rotation speed of the electric motor, (b) a change in torque acting on the steering shaft, and (c) a change in the drive current of the electric motor for the electric power steering device of the comparative example. FIG. 4 is a timing chart showing (a) a change in the rotational speed of the electric motor, (b) a change in torque acting on the steering shaft, and (c) a change in the drive current of the electric motor in the electric power steering apparatus of the embodiment.

The configuration of the electric power steering apparatus 1 will be described with reference to FIG.
The electric power steering apparatus 1 includes a steering shaft 10 that rotates in response to an operation of the steering wheel 2 and a rack shaft 20 that linearly moves by rotation transmitted from the steering shaft 10. In addition, a rack and pinion mechanism 30 that transmits the rotation of the steering shaft 10 to the rack shaft 20, a rack housing 40 that supports the rack shaft 20, and an assist device 50 that applies torque to the steering shaft 10 are provided. Yes.

  The steering shaft 10 includes a column shaft 11 to which the steering wheel 2 is fixed, a pinion shaft 13 that transmits rotation to the rack and pinion mechanism 30, and an intermediate shaft 12 that connects the column shaft 11 and the pinion shaft 13 to each other. I have.

  The rack and pinion mechanism 30 includes a pinion 31 formed on the pinion shaft 13 and a rack 32 formed on the rack shaft 20. The pinion 31 and the rack 32 are meshed with each other in the rack housing 40.

  In the rack shaft 20, the right end including the right end and the left end including the left end protrude from the rack housing 40. A right rack end 21 is provided at the right end of the rack shaft 20. A left rack end 22 is provided at the left end of the rack shaft 20.

  A right stopper 41 facing the right rack end 21 in the axial direction is provided at the right end of the rack housing 40. A left stopper 42 facing the left rack end 22 in the axial direction is provided at the left end of the rack housing 40.

  In the electric power steering apparatus 1, the movement of the rack shaft 20 with respect to the rack housing 40 is limited as follows. That is, when the rack shaft 20 moves to the left in the axial direction with respect to the rack housing 40 and the right rack end 21 comes into contact with the right stopper 41, the movement to the left in the axial direction with respect to the rack housing 40 is restricted. . On the other hand, when the rack shaft 20 moves to the right in the axial direction with respect to the rack housing 40, when the left rack end 22 contacts the left stopper 42, the movement to the right in the axial direction with respect to the rack housing 40 is restricted. .

  The assist device 50 decelerates the rotation of the electric motor 51 and transmits it to the column shaft 11, an electric motor 51 as a drive source, a rotation angle sensor 51 A that outputs a signal corresponding to the rotation angle of the rotor of the electric motor 51. A reduction gear 52, a torque sensor 53 that outputs a signal corresponding to the torque acting on the steering shaft 10, and a control device 54 that controls the electric motor 51 are provided.

  The speed reducer 52 includes a worm shaft 52 </ b> A that rotates integrally with the output shaft of the electric motor 51 and a worm wheel 52 </ b> B that rotates integrally with the column shaft 11. The worm wheel 52B is made of resin.

  The control device 54 calculates a calculation value corresponding to the rotation speed of the electric motor 51 based on the output of the rotation angle sensor 51A. Further, based on the output of the torque sensor 53, a calculation value corresponding to the torque acting on the steering shaft 10 is calculated. Various controls including torque assist control, reverse input inertia compensation control (FIG. 2), collision expectation condition determination control (FIG. 3), and compensation stop condition determination control (FIG. 4) are performed.

  In the torque assist control, a command signal corresponding to the torque of the steering shaft 10 (hereinafter referred to as “normal command signal”) based on the current flowing in the electric motor 51 (hereinafter referred to as “drive current”) and the calculated value of the torque. Is output to the drive circuit of the electric motor 51.

  In reverse input inertia compensation control, when the collision expectation condition success / failure state is changed from not established to established by the collision expectation condition determination control, a preset command signal (hereinafter referred to as “compensation instruction signal”) is used regardless of the calculated torque value. )) Output starts. Moreover, when the success / failure state of the compensation stop condition is changed from not established to established by the compensation stop condition determination control, the output of the compensation command signal is stopped.

  In the collision expectation condition determination control, it is determined whether or not a collision expectation condition, that is, a condition indicating that the rack shaft 20 may collide with the right stopper 41 or the left stopper 42 is satisfied. Further, based on the rotational speed of the electric motor 51 as one of the operating states of the electric motor 51, it is determined whether or not a collision expectation condition is satisfied.

  In the compensation stop condition determination control, whether or not a compensation stop condition, that is, a condition indicating that the operation state of the electric motor 51 has changed from an inoperable state based on a command signal of the control device 54 to a possible state is established. Determine. Further, based on the drive current of the electric motor 51 as one of the operation states of the electric motor 51, it is determined whether or not the compensation stop condition is satisfied. The command signal here means all command signals generated by the control device 54 including the normal command signal and the compensation command signal.

  The drive circuit of the electric motor 51 supplies the electric motor 51 with a drive current corresponding to a current specified by a command signal from the control device 54 (hereinafter referred to as “command current”). The drive current that can be supplied to the electric motor 51 by the drive circuit has an upper limit value in each of the positive direction and the negative direction. For this reason, the control device 54 controls the command current corresponding to the upper limit drive current in the positive direction (hereinafter, “positive guard current value IPmax”) and the command current corresponding to the upper limit drive current in the negative direction (hereinafter referred to as “following”). A command signal is generated using “negative guard current value INmax”) as a guard value of the command current.

The operation of the electric power steering apparatus 1 will be described.
When torque is input to the steering wheel 2 by the driver, the steering shaft 10 rotates together with the steering wheel 2. The rotation of the steering shaft 10 is converted into a linear motion in the axial direction of the rack shaft 20 by the rack and pinion mechanism 30. The rack shaft 20 moves in the axial direction by the force transmitted from the rack and pinion mechanism 30. As the rack shaft 20 moves in the axial direction, the steering angle of the steered wheels 3 is changed.

The assist device 50 assists the operation of the steering wheel 2 as follows.
When torque is input to the steering wheel 2 by the driver, a signal corresponding to the torque input to the steering shaft 10 is output from the torque sensor 53 to the control device 54.

  The control device 54 generates a command signal for the electric motor 51 based on the output of the torque sensor 53, and outputs this command signal to the drive circuit of the electric motor 51. The drive circuit supplies a command current indicated by a command signal from the control device 54 to the electric motor 51. As a result, a drive current corresponding to the command current flows through the electric motor 51.

  The rotation of the electric motor 51 is decelerated by the speed reducer 52 and transmitted to the steering shaft 10, whereby torque is applied to the steering shaft 10. Thereby, the force required for operating the steering wheel 2 to move the rack shaft 20 in the axial direction is reduced. That is, the assist device 50 assists the force required for operating the steering wheel 2.

With reference to FIG. 2, the procedure of the inertia compensation control at the time of reverse input is demonstrated.
This control is repeatedly performed at predetermined control cycles by the control device 54 of FIG. That is, after the process of the last step is completed, the execution of the control is suspended until a predetermined control cycle elapses, and the main control is performed again from the first step when the predetermined control cycle elapses.

The control device 54 processes each step as follows.
In step S11, it is determined whether or not the determination result that the success / failure state of the collision expected condition has changed from not established to established is obtained by the collision expectation condition determining control of FIG. When it is determined in step S11 that the determination result is obtained, the process proceeds to step S16. On the other hand, when it is determined in step S11 that the determination result is not obtained, the process proceeds to step S12.

  In step S12, it is determined whether a compensation command signal is being output. When it is determined in step S12 that the compensation command signal is being output, the process proceeds to step S13. On the other hand, when it is determined in step S12 that the compensation command signal is not being output, the process proceeds to step S14.

  In step S13, it is determined whether or not the determination result that the success / failure state of the compensation stop condition has changed from not established to established is obtained by the compensation stop condition determining control of FIG. When it is determined in step S13 that the determination result is obtained, the process proceeds to step S15. On the other hand, when it is determined in step S13 that the determination result is not obtained, the process proceeds to step S16.

  In step S14, the output of the normal command signal is started or continued. In step S15, the output of the compensation command signal is stopped and the output of the normal command signal is started. In step S16, the output of the compensation command signal is started or continued.

The content of the collision expectation condition determination control will be described with reference to FIG.
This control is repeatedly performed at predetermined control cycles by the control device 54 of FIG. That is, after the process of the last step is completed, the execution of the control is suspended until a predetermined control cycle elapses, and the main control is performed again from the first step when the predetermined control cycle elapses.

  In step S21, it is determined whether or not the rotational speed of the electric motor 51 is equal to or higher than a predetermined rotational speed (hereinafter, “upper limit rotational speed RC”). When a positive determination is made in step S21, the process proceeds to step S22. On the other hand, when a negative determination is made in step S21, the process proceeds to step S24.

  The upper limit rotation speed RC is set in advance as a determination value for determining whether or not the rotation speed of the electric motor 51 is in the undetectable region. The undetectable region indicates a region of the rotation speed of the electric motor 51 where the rotation angle sensor 51A cannot detect the rotation angle of the electric motor 51, and can be grasped in advance by performing a test or the like.

  When the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, the rotation angle of the electric motor 51 is not detected by the rotation angle sensor 51A. As a result, it becomes impossible to perform feedback control of the drive current of the electric motor 51, so that the drive current corresponding to the command signal of the control device 54 is not supplied to the electric motor 51.

  For this reason, when the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, the drive current of the electric motor 51 gradually decreases with the passage of time, and finally becomes “0”. That is, when the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, the control device 54 cannot control the electric motor 51 with the command signal.

  Hereinafter, the operation state of the electric motor 51 in which the control of the electric motor 51 by the command signal is disabled is referred to as “control disabled state”. In addition, the operation state of the electric motor 51 that can control the electric motor 51 by the command signal is referred to as a “controllable state”.

  In step S22, a state in which the rotational speed of the electric motor 51 is equal to or higher than the upper limit rotational speed RC is set as an “excess speed state”, and a time during which the excessive speed state is continued (hereinafter, “excess speed continuing time TA”) is determined. It is determined whether or not it is greater than or equal to TAX. When a positive determination is made in step S22, the process proceeds to step S23. On the other hand, when a negative determination is made in step S22, the process proceeds to step S24.

  The determination time TAX is determined based on the rotational speed of the electric motor 51 as to whether or not the rack shaft 20 may collide with the right stopper 41 or the left stopper 42 due to the excessive speed state of the electric motor 51. Is set in advance as a determination value.

  In step S23, it is determined that the collision expectation condition is satisfied, that is, the condition that the rack shaft 20 collides with the right stopper 41 or the left stopper 42 is satisfied. In step S24, it is determined that the collision expectation condition is not satisfied.

  A phenomenon that can be confirmed when the rack shaft 20 collides with the right stopper 41 or the left stopper 42 is that the operation state of the electric motor 51 is in an excessive speed state. For this reason, when the operation state of the electric motor 51 is an excessive speed state, that is, when the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, there is a high possibility that the rack shaft 20 collides with the right stopper 41 or the left stopper 42. Can be considered. Further, as the time during which the excessive speed state is continued increases, the possibility that the rack shaft 20 collides with the right stopper 41 or the left stopper 42 becomes higher.

  For this reason, in this collision expectation condition determination control, the excess speed duration TA of the electric motor 51 is counted, and when this excess speed duration TA is equal to or longer than the determination time TAX, it is determined that the collision expectation condition is satisfied. .

The content of compensation stop condition determination control will be described with reference to FIG.
This control is repeatedly performed at predetermined control cycles by the control device 54 of FIG. That is, after the process of the last step is completed, the execution of the control is suspended until a predetermined control cycle elapses, and the main control is performed again from the first step when the predetermined control cycle elapses.

  In step S31, it is determined whether or not the difference between the drive current of the electric motor 51 and the command current of the command signal is greater than or equal to a predetermined difference (hereinafter, “determination deviation DX”). When an affirmative determination is made in step S31, the process proceeds to step S32. On the other hand, when a negative determination is made in step S31, the process proceeds to step S34.

  The determination deviation amount DX is set in advance as a determination value for determining whether or not the difference between the drive current and the command current is in the deviation area when control is not possible. The non-controllable deviation area indicates a difference area between the drive current and the command current generated when the electric motor 51 is in a non-controllable state, and can be grasped in advance by performing a test or the like.

  In step S32, a state in which the difference between the drive current of the electric motor 51 and the command current of the command signal is less than the determination divergence amount DX is defined as an “permissible divergence state”. It is determined whether or not the deviation continuation time TB ") is equal to or longer than the determination time TBX. When a positive determination is made in step S32, the process proceeds to step S33. On the other hand, when a negative determination is made in step S32, the process proceeds to step S34.

  The determination time TBX is set in advance as a determination value for determining whether or not the operation state of the electric motor 51 has shifted from the uncontrollable state to the controllable state based on the allowable deviation continuation time TB. .

  In step S33, it is determined that the compensation stop condition is satisfied, that is, the condition indicating that the electric motor 51 is in an operating state that can be controlled according to the command signal. In step S34, it is determined that the compensation stop condition is not satisfied.

  A phenomenon that can be confirmed when the operation state of the electric motor 51 is in a controllable state is that the operation state of the electric motor 51 is in an allowable deviation state. For this reason, when the operation state of the electric motor 51 is an allowable deviation state, that is, when the difference between the drive current and the command current is less than the determination deviation amount DX, it is highly likely that the electric motor 51 is in a controllable state. Can do. Further, as the time during which the allowable deviation state is continued increases, the possibility of being in the controllable state becomes higher.

  For this reason, in this compensation stop determination control, the allowable deviation duration time TB of the electric motor 51 is counted, and when the allowable deviation duration time TB is equal to or greater than the determination time TBX, it is determined that the compensation stop condition is satisfied.

  With reference to FIG. 5, control of the electric motor 51 performed by an electric power steering device (hereinafter, “virtual steering device”) as a comparative example will be described. This virtual steering device has the same configuration as the electric power steering device 1 of the present embodiment except that it does not execute reverse input inertia compensation control, collision expectation condition determination control, and compensation stop condition determination control. To do.

  5A shows the rotation speed of the electric motor 51, FIG. 5B shows the torque acting on the steering shaft 10, and FIG. 5C shows the drive current of the electric motor 51. Also, the two-dot chain line in FIG. 5C indicates the command current of the command signal, and the solid line in FIG. 5C indicates the drive current of the electric motor 51.

  At time t11, that is, when the steered wheel 3 of the vehicle collides with the curb of the travel path, the rack shaft 20 moves in one axial direction based on the torque input to the steered wheel 3. Further, torque is input to the steering shaft 10 via the rack and pinion mechanism 30 as the rack shaft 20 moves.

  For this reason, as shown in FIG. 5B, the torque acting on the steering shaft 10 rapidly increases according to the torque input from the rack shaft 20. Further, the output of the torque sensor 53 changes according to the torque of the steering shaft 10.

  The control device 54 generates a command signal according to the output of the torque sensor 53 as shown by the solid line in FIG. For this reason, the drive current of the electric motor 51 rapidly increases in the negative direction according to the command current of the command signal. Further, as the drive current increases, the rotation speed of the electric motor 51 rapidly increases as shown in FIG.

  After the time t11, when the command current reaches the negative guard current value INmax as the torque of the steering shaft 10 increases, a command signal having the negative guard current value INmax as the command current is generated. In the example shown in FIG. 5C, a command signal having a negative guard current value INmax as a command current is generated over a predetermined period due to the large torque of the steering shaft 10.

  At time t <b> 12, that is, when the rotation speed of the electric motor 51 exceeds the upper limit rotation speed RC, the drive circuit of the electric motor 51 cannot supply a drive current corresponding to the command signal of the control device 54 to the electric motor 51. For this reason, as shown in FIG. 5C, the drive current (solid line) of the electric motor 51 changes rapidly from the magnitude corresponding to the command current (two-dot chain line) of the control device 54 toward “0”. To do. Then, after a predetermined time has elapsed after the rotation speed of the electric motor 51 exceeds the upper limit rotation speed RC, the drive current of the electric motor 51 becomes “0”.

  At time t13, that is, when the torque input to the steered wheels 3 from the outside reaches a peak, the torque acting on the steering shaft 10 also shows a peak accordingly. Corresponding to this increase in torque, the rotational speed of the electric motor 51 also exhibits the largest rotational speed in the range of changes accompanying the input of torque from the steering shaft 10.

  After the time t13, when the torque input to the steered wheels 3 from the outside decreases beyond the peak, the torque of the steering shaft 10 decreases accordingly. On the other hand, since the rack shaft 20 continues to move in one axial direction based on the torque input to the steered wheels 3 after time t11, the torque is continuously applied to the steering shaft 10 from the rack shaft 20. Is entered. Thereby, as an operation state of the electric motor 51, a state of rotating based on the torque input from the steering shaft 10 is maintained.

  As shown in FIG. 5C, the control device 54 generates a command signal corresponding to the output of the torque sensor 53 even after the time t13. On the other hand, since the operation state of the electric motor 51 is in an uncontrollable state, the command signal is output from the control device 54, but the state where the drive current of the electric motor 51 is "0" is continued.

  At time t14, that is, when the rack shaft 20 collides with the right stopper 41 or the left stopper 42, the movement of the rack shaft 20 is stopped. Therefore, as shown in FIG. Inertia torque acts in the opposite direction to the torque that has been applied. Further, as the moving speed of the rack shaft 20 rapidly decreases, the inertia torque acting on the rack shaft 20 increases rapidly. Further, since the rotation of the electric motor 51 is hindered by the steering shaft 10, the rotation speed of the electric motor 51 rapidly decreases.

  As shown in FIG. 5C, the control device 54 generates a normal command signal for rotating the electric motor 51 in a direction opposite to that before the time t14 in accordance with the output of the torque sensor 53 after the time t14. To do. On the other hand, since the operation state of the electric motor 51 is still uncontrollable during the period from time t14 to time t15, the state where the drive current of the electric motor 51 is “0” is maintained.

  At time t15, that is, when the rotation speed of the electric motor 51 is changed from the state where the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC to the state where the rotation speed of the electric motor 51 is lower than the upper limit rotation speed RC, Change to possible state. For this reason, as shown in FIG. 5B, the drive current of the electric motor 51 increases rapidly toward the command current of the command signal. That is, the electric motor 51 starts to rotate according to the command current.

  At this time, as the command signal, a stopper that restricts the movement of the rack shaft 20 is inputted to input torque to the steering shaft 10 so that the rack shaft 20 is pressed against the stopper.

  Specifically, when the rack shaft 20 collides with the right stopper 41 at time t14, the command signal generated after time t14 is torque to the steering shaft 10 so that the rack shaft 20 is pressed against the right stopper 41. Will be entered. On the other hand, when the rack shaft 20 collides with the left stopper 42 at time t14, a command signal generated after time t14 inputs torque to the steering shaft 10 so that the rack shaft 20 is pressed against the left stopper 42. It will be a thing.

  From the above, the state after time t14 is the state where the inertial torque acting on the steering shaft 10 is increased by the torque assist control of the electric motor 51, that is, due to the execution of the torque assist control. 10 can be seen as a state where a larger load is applied.

  After the time t15, when the command current reaches the positive guard current value IPmax as the torque of the steering shaft 10 increases, a command signal having the positive guard current value IPmax as the command current is generated. In the example shown in FIG. 5 (c), due to the large inertia torque of the steering shaft 10, a command signal having the positive guard current value IPmax as a command current is generated over a predetermined period.

  At time t16, that is, when the rotational speed of the electric motor 51 reaches “0”, the inertia torque acting on the steering shaft 10 reaches the peak due to the inertia torque of the electric motor 51. At this time, the magnitude of the torque acting on the electric motor 51 due to the reaction from the steering shaft 10 exceeds the magnitude of the inertia torque acting on the electric motor 51 so far. For this reason, the electric motor 51 rotates in the direction opposite to the rotation direction before time t16. That is, as shown in FIG. 5A, the rotation speed of the electric motor 51 is a negative rotation speed after time t16.

  After time t16, the inertia torque acting on the steering shaft 10 that does not cause the rotation direction of the electric motor 51 to reverse is rapidly reduced. Then, at time t17 when a predetermined time has elapsed from time t16, the direction of the inertia torque acting on the steering shaft 10 is reversed. Thereafter, as the rotational speed of the electric motor 51 decreases, the inertia torque acting on the steering shaft 10 also decreases.

  At a time t18, that is, when a predetermined time has elapsed from the time t14 when the rack shaft 20 collides with the right stopper 41 or the left stopper 42, the rotation speed of the electric motor 51 becomes “0”. Then, after the rotation of the electric motor 51 stops, the torque acting on the steering shaft 10 becomes “0”.

  As shown in FIG. 5C, the control device 54 generates a command signal corresponding to the output of the torque sensor 53 even after the time t16. Further, since the operation state of the electric motor 51 is in a controllable state, the drive current of the electric motor 51 changes according to the normal command signal output from the control device 54.

  After time t17, when the command current reaches the negative guard current value INmax as the inertia torque of the steering shaft 10 increases in the negative direction, a command signal having the negative guard current value INmax as the command current is generated. Is done. In the example shown in FIG. 5C, a command signal having a negative guard current value INmax as a command current is generated over a predetermined period due to a large inertia torque of the steering shaft 10.

With reference to FIG. 6, an example of an execution mode of the inertia compensation control at the time of reverse input will be described.
Here, on the premise of the same situation as the above-described example describing the control of the electric motor 51 in the virtual steering device shown in FIG. 5, the generation mode of the command signal by the reverse input inertia compensation control performed at that time Will be described. In addition, about the time which has shown the state similar to each time shown by FIG. 5, description of the overlapping point is abbreviate | omitted.

  After the time t22, the counting of the excessive speed duration time TA is started by the collision expectation condition determination control of FIG. Further, it is determined whether or not the excessive speed continuation time TA is equal to or longer than the determination time TAX.

  At time t24, that is, when the collision expectation condition is satisfied when the excessive speed duration time TA becomes equal to or greater than the determination time TAX, output of a compensation command signal is started. Specifically, when the predetermined time Δt1 has elapsed from time t22 with reference to time t22 when the rotational speed of the electric motor 51 has changed from a state less than the upper limit rotational speed RC to a state greater than or equal to the upper limit rotational speed RC, the control device 54 Is changed from the normal command signal to the compensation command signal. At this time, as the compensation command signal, a preset signal is output without reflecting the output of the torque sensor 53 that detects the torque of the steering shaft 10.

  When the collision expectation condition is satisfied, the difference between the drive current of the electric motor 51 and the command current of the command signal is greater than a predetermined difference. Further, the moving speed of the rack shaft 20 is greater than a predetermined moving speed. Further, the drive current of the electric motor 51 indicates “0”.

That is, the control device 54 outputs the compensation command signal based on the fact that the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, and as a result, at least one of the following conditions is satisfied. Sometimes a compensation command signal is output.
(A) The difference between the drive current and the command current of the command signal is larger than a predetermined difference.
(B) The moving speed of the rack shaft 20 is not less than a predetermined moving speed.
(C) The drive current of the electric motor 51 is “0”.

  As shown in FIG. 6C, the control device 54 outputs a compensation command signal using the negative guard current value INmax as a command current after time t24. On the other hand, during the period from time t24 to time t26, since the operation state of the electric motor 51 is in a non-controllable state, the state where the drive current of the electric motor 51 is “0” is maintained.

  The direction of the command current of the compensation command signal is determined according to the direction of torque acting on the steering shaft 10. Therefore, when the direction of the torque acting on the steering shaft 10 is opposite to the example shown in FIG. 6C, a compensation command signal having the positive guard current value IPmax as the command current is output. Further, although the maximum value of the command current is set here as the magnitude of the command current of the compensation command signal, a command current smaller than the maximum value can be set.

  At time t25, that is, when the collision occurrence condition is satisfied, the rotational speed of the electric motor 51 starts to rapidly decrease as the rack shaft 20 collides with the right stopper 41 or the left stopper 42. Further, the direction of the torque acting on the steering shaft 10 is reversed.

  When the collision occurrence condition is satisfied, the reduction speed of the rotation speed of the electric motor 51 is greater than or equal to a predetermined reduction speed. Further, the absolute value of the drive current of the electric motor 51 is changed from “0” to a state larger than “0”. Further, the amount of change in torque acting on the steering shaft 10 is greater than or equal to a predetermined amount of change. Further, the direction of torque acting on the steering shaft 10 is reversed.

That is, the control device 54 outputs the compensation command signal based on the fact that the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC, and as a result, at least one of the following conditions is satisfied. Sometimes a compensation command signal is output.
(A) The reduction speed of the rotation speed of the electric motor 51 is greater than or equal to a predetermined reduction speed.
(B) The drive current has changed from “0” to a state larger than “0”.
(C) The amount of change in torque of the steering shaft 10 is greater than or equal to a predetermined amount of change.
(D) The direction of torque of the steering shaft 10 is reversed.

  At time t26, that is, when the rotation speed of the electric motor 51 changes from the state where the rotation speed of the electric motor 51 is equal to or higher than the upper limit rotation speed RC to the state where the rotation speed of the electric motor 51 is lower than the upper limit rotation speed RC, the operation state of the electric motor 51 is controlled from the uncontrollable state. Change to possible state. For this reason, as shown in FIG. 6B, the drive current of the electric motor 51 increases rapidly toward the command current of the command signal. That is, the electric motor 51 starts to rotate according to the command current.

  At this time, as the compensation command signal, a stopper that restricts the movement of the rack shaft 20 is inputted to input torque to the steering shaft 10 so that the rack shaft 20 is separated from the stopper. That is, the electric motor 51 is controlled so that torque in the direction opposite to the inertia torque acting on the steering shaft 10 is input to the steering shaft 10.

  After time t26, when the electric motor 51 is driven by the compensation command signal, the inertial torque that acts on the steering shaft 10 after the rack shaft 20 collides with the right stopper 41 or the left stopper 42 acts on the virtual steering device. It becomes smaller than torque. That is, as shown in FIG. 6 (b), the inertial torque (solid line) acting on the steering shaft 10 during the period from time t25 to t29 in the electric power steering apparatus 1 of the present embodiment is changed from the time t14 to the virtual steering apparatus. It becomes smaller than the inertia torque (broken line) acting on the steering shaft 10 in the period of t18.

  At time t27, that is, when the drive current of the electric motor 51 shows the same magnitude as the command current of the compensation command signal, counting of the allowable divergence duration TB is started by the compensation stop condition determination control of FIG. In addition, the determination of whether or not the allowable deviation continuation time TB is equal to or longer than the determination time TBX is started.

  When the compensation stop condition is satisfied when the time t29, that is, the allowable deviation continuation time TB is equal to or greater than the determination time TBX, the output of the compensation command signal is stopped. Specifically, when a predetermined time Δt2 has elapsed from time t27 with reference to time t27 when the difference between the drive current and the command current changes from a state larger than the predetermined difference to a state equal to or smaller than the predetermined difference, the compensation command The signal output is stopped. Further, generation of a normal command signal based on the output of the torque sensor 53 is started.

  In the example shown in FIG. 6C, since the output of the torque sensor 53 indicates “0” when the output of the compensation command signal is stopped, the drive current is set to the negative guard current value INmax as the normal command signal. To change from “0” to “0”. At time t29, when the output of the torque sensor 53 is greater than “0”, a normal command signal corresponding to the output is generated.

According to the electric power steering apparatus 1 of the present embodiment, the following effects can be obtained.
(1) The electric power steering apparatus 1 outputs a compensation command signal when the rack shaft 20 collides with the right stopper 41 or the left stopper 42 and inertia torque is generated in the steering shaft 10.
According to this configuration, when inertia torque is generated in the steering shaft 10, torque (compensation torque) in a direction opposite to the inertia torque is applied to the steering shaft 10 by the electric motor 51. For this reason, the inertia torque of the steering shaft 10 can be reduced.

  (2) In the virtual steering device, after time t14, that is, after the rack shaft 20 collides with the right stopper 41 or the left stopper 42, a larger load is applied to the steering shaft 10 due to execution of torque assist control of the electric motor 51. Will be put on.

  In the electric power steering apparatus 1 of the present embodiment, after time t25, that is, after the rack shaft 20 collides with the right stopper 41 or the left stopper 42, the compensation command signal is output as described in (1) above. That is, for the stopper that restricts the movement of the rack shaft 20, a compensation command signal for inputting torque to the steering shaft 10 in the direction opposite to the direction in which the rack shaft 20 is pressed against the stopper is output to the electric motor 51. Yes. For this reason, the load concerning the steering shaft 10 becomes small compared with a virtual steering device.

  (3) The electric power steering device 1 starts outputting a compensation command signal when the collision expectation condition is satisfied. According to this configuration, when the operation state of the electric motor 51 changes from the uncontrollable state to the controllable state after the rack shaft 20 collides with the right stopper 41 or the left stopper 42, the compensation current is supplied based on the compensation command signal. Get started quickly. For this reason, the inertia torque of the steering shaft 10 can be reduced more accurately.

  (4) The electric power steering device 1 stops outputting the compensation command signal when the compensation command signal is being output and when the compensation stop condition is satisfied. According to this configuration, it is possible to suppress the output of the compensation command signal over a long period of time even though the operation state of the electric motor 51 is in a controllable state. For this reason, after the rack shaft 20 collides with the right stopper 41 or the left stopper 42, it is possible to promptly resume appropriate assist for the steering wheel 2.

(Other embodiments)
The embodiment of the present invention is not limited to the above embodiment, and can be modified as shown below, for example. The following modifications are not applied only to the above-described embodiment, and different modifications can be implemented in combination.

  In the above embodiment (FIG. 3), the state where the rotational speed of the electric motor 51 is equal to or higher than the upper limit rotational speed RC is defined as the excessive rotational speed state, and when the excessive rotational speed state continues for a predetermined time or more, Although the output is started, the output start time of the compensation command signal can be changed as follows. That is, when the rotational speed of the electric motor 51 is equal to or higher than the upper limit rotational speed RC, the output of the compensation command signal can be started regardless of the duration of the excessive rotational speed.

  In the above embodiment (FIG. 3), it is determined whether or not the collision expectation condition is satisfied based on the rotation speed of the electric motor 51 and the upper limit rotation speed RC, but the collision expectation condition determined by the control device 54 The contents of can also be changed as follows. The following (A) to (F) correspond to determining whether or not the collision expectation condition is satisfied based on whether or not the operation state of the electric motor 51 is in a predetermined operation state. The following (G) to (I) correspond to determining whether or not the collision expectation condition is satisfied based on an event different from the operation state of the electric motor 51.

  (A) It is set as a collision expectation condition that the difference between the drive current of the electric motor 51 and the command current of the command signal is equal to or greater than a predetermined difference. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (B) In (A) above, a state where the difference between the drive current of the electric motor 51 and the command current of the command signal is equal to or greater than a predetermined difference is defined as a current divergence state, and the duration of this current divergence state is equal to or greater than a predetermined period. Is set as a collision expectation condition. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (C) The fact that the difference between the drive current of the electric motor 51 and the command current of the command signal has changed from a state less than a predetermined difference to a state greater than or equal to the predetermined difference is set as a collision expectation condition. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

(D) The fact that the drive current of the electric motor 51 is “0” is set as a collision expectation condition. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.
(E) In (D) above, a state in which the drive current of the electric motor 51 is “0” is set as a zero current state, and the duration of this zero current state is set as a collision expectation condition that is equal to or longer than a predetermined period. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (F) The fact that the absolute value of the drive current of the electric motor 51 has changed from “0” to “0” is set as a collision expectation condition. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (G) It is set as a collision expectation condition that the moving speed of the rack shaft 20 is equal to or higher than a predetermined moving speed. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (H) In (G) above, a state where the movement speed of the rack shaft 20 is equal to or higher than a predetermined movement speed is set as an excessive movement speed state, and the duration of this excessive movement speed state is set as a collision condition as a collision condition. To do. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied.

  (I) The fact that the moving speed of the rack shaft 20 has changed from a state below the predetermined moving speed to a state above the predetermined moving speed is set as a collision expectation condition. Then, the control device 54 determines whether or not the same collision expectation condition is satisfied. The moving speed of the rack shaft 20 can be calculated based on the output of a position sensor that detects the position of the rack shaft 20, for example.

  In the above embodiment (FIG. 4), it is determined whether or not the compensation stop condition is satisfied based on the drive current of the electric motor 51 and the command current of the command signal. The content of the condition can be changed as follows. The following (A) to (D) correspond to determining whether the compensation stop condition is satisfied based on whether the operation state of the electric motor 51 is in a predetermined operation state. The following (E) to (G) correspond to determining whether the compensation stop condition is satisfied based on an event different from the operation state of the electric motor 51.

(A) The fact that the rotation direction of the electric motor 51 is reversed is set as a compensation stop condition. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.
(B) It is set as a compensation stop condition that the reduction speed of the rotation speed of the electric motor 51 is greater than or equal to a predetermined reduction speed. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  (C) It is set as a compensation stop condition that the reduction speed of the rotation speed of the electric motor 51 has changed from a state less than the predetermined reduction speed to a state higher than or equal to the predetermined reduction speed. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  (D) A change in the driving current of the electric motor 51 from “0” to a state larger than “0” is set as a compensation stop condition. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  (E) It is set as a compensation stop condition that the amount of change in torque acting on the steering shaft 10 is equal to or greater than a predetermined amount. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  (F) It is set as a compensation stop condition that the amount of change in torque acting on the steering shaft 10 has changed from a state less than a predetermined amount of change to a state greater than or equal to a predetermined amount of change. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  (G) The fact that the direction of the torque acting on the steering shaft 10 is reversed is set as a compensation stop condition. Then, the control device 54 determines whether or not the compensation stop condition is satisfied.

  In the above embodiment (FIG. 2), the compensation command signal is output when inertia torque is generated by the inertia compensation control at the time of reverse input, but the drive of the electric motor 51 is stopped instead of the control that outputs the compensation command signal. It is also possible to perform control. According to this configuration, the following effects can be obtained.

The inertia torque of the steering shaft 10 generated when the rack shaft 20 collides with the right stopper 41 acts in a direction in which the rack shaft 20 is pressed against the right stopper 41. Further, the inertia torque of the steering shaft 10 generated when the rack shaft 20 collides with the left stopper 42 acts in a direction in which the rack shaft 20 is pressed against the left stopper 42.
For this reason, in the electric power steering apparatus 1 that performs torque assist control, torque in the same direction as the inertia torque is applied from the electric motor 51 to the steering shaft 10 in accordance with the inertia torque. At this time, since the movement of the rack shaft 20 is restricted by the stoppers 41 and 42, when the electric motor 51 is driven in the direction in which the same torque is generated, the movement between the electric motor 51 and the steering shaft 10 is performed. An excessively large load is applied to the power transmission component (for example, the worm wheel 52B) and the electric motor 51. That is, when the rack shaft 20 collides with the stoppers 41 and 42, there is a possibility that at least one of the same component and the electric motor 51 may be damaged due to the torque assist control of the electric motor 51. Therefore, by stopping the driving of the electric motor 51 when the inertia torque is generated due to the collision between the rack shaft 20 and the stoppers 41 and 42, the above problem caused by the torque assist control is suppressed. be able to.

  In this regard, according to the modified example in which the driving of the electric motor 51 is stopped instead of the control for outputting the compensation command signal, it is possible to suppress the occurrence of the above problem due to the torque assist control.

-In the said embodiment (FIG. 1), although the thing made from resin is provided as the worm wheel 52B, it can also change into a metal worm wheel.
In the above embodiment (FIG. 1), an example in which the present invention is applied to the column assist type electric power steering apparatus 1 in which the electric motor 51 is attached to the column shaft 11 is shown, but the present invention can be applied. Such an electric power steering device is not limited to that exemplified in the above embodiment.

  For example, the present invention is applied to a pinion assist type electric power steering apparatus in which an electric motor is attached to a pinion shaft of a rack and pinion mechanism, or a rack assist type electric power steering apparatus in which an electric motor is attached to a rack shaft of a rack and pinion mechanism. It can also be applied.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering wheel, 3 ... Steering wheel, 10 ... Steering shaft, 11 ... Column shaft, 12 ... Intermediate shaft, 13 ... Pinion shaft, 20 ... Rack shaft, 21 ... Right rack end, 22 ... left rack end, 30 ... rack and pinion mechanism, 31 ... pinion, 32 ... rack, 40 ... rack housing, 41 ... right stopper, 42 ... left stopper, 50 ... assist device, 51 ... electric motor, 51A ... rotation angle sensor , 52 ... reducer, 52A ... worm shaft, 52B ... worm wheel, 53 ... torque sensor, 54 ... control device.

Claims (18)

A steering shaft, a rack shaft, a stopper for restricting the movement of the rack shaft, an electric motor for applying torque to the steering shaft, and a drive current for controlling the electric motor according to the torque of the steering shaft; In an electric power steering apparatus comprising a control device that outputs a command signal,
The control device uses the torque generated in the steering shaft when the rack shaft collides with the stopper as an inertia torque, sets the torque in the direction opposite to the inertia torque as the compensation torque, and applies the compensation torque to the steering shaft. The compensation command signal is output when the inertia torque is generated, with the drive current of the electric motor providing the compensation current as the compensation current, and the command signal for supplying this compensation current to the electric motor as the compensation command signal. An electric power steering device. A steering shaft, a rack shaft, a stopper for restricting the movement of the rack shaft, an electric motor for applying torque to the steering shaft, and a drive current for controlling the electric motor according to the torque of the steering shaft; In an electric power steering apparatus comprising a control device that outputs a command signal,
The control device uses a rotation direction of the steering shaft for moving the rack shaft toward the stopper as a limiting direction, and a torque for rotating the steering shaft in a direction opposite to the limiting direction as a compensation torque, The rack shaft collides with the stopper, using the drive current of the electric motor that applies this compensation torque to the shaft as a compensation current and a command signal for supplying this compensation current to the electric motor as a compensation command signal. An electric power steering apparatus characterized in that the compensation command signal is sometimes output. In the electric power steering apparatus according to claim 1 or 2,
The electric power steering apparatus according to claim 1, wherein a condition indicating that the rack shaft is colliding with the stopper is used as a collision occurrence condition, and the compensation command signal is output when the collision occurrence condition is satisfied. In the electric power steering device according to claim 3,
The electric power steering apparatus according to claim 1, wherein the collision occurrence condition is that a reduction speed of a rotation speed of the electric motor is equal to or higher than a predetermined reduction speed. In the electric power steering device according to claim 3,
The collision occurrence condition is that the absolute value of the drive current of the electric motor is changed from a state where the absolute value of the drive current of the electric motor is “0” to a state where the absolute value of the drive current of the electric motor is larger than “0”. Power steering device. In the electric power steering device according to claim 3,
The electric power steering apparatus according to claim 1, wherein the collision occurrence condition is that a change amount of a torque acting on the steering shaft is a predetermined change amount or more. In the electric power steering device according to claim 3,
The electric power steering apparatus characterized in that the condition of occurrence of a collision is that the direction of torque acting on the steering shaft is reversed. In the electric power steering device according to any one of claims 1 to 7,
An electric power steering apparatus characterized in that a condition indicating that the rack shaft collides with the stopper is used as a collision expectation condition, and the compensation command signal is output when the collision expectation condition is satisfied. The electric power steering apparatus according to claim 8,
The electric power steering apparatus characterized in that the collision expectation condition is that the operation state of the electric motor is in a predetermined operation state. The electric power steering apparatus according to claim 8 or 9,
The electric power steering apparatus characterized in that the collision expectation condition is that a rotation speed of the electric motor is equal to or higher than a predetermined rotation speed. The electric power steering apparatus according to claim 8 or 9,
The electric power steering apparatus, wherein the collision expectation condition is that a difference between a driving current of the electric motor and a command current of the command signal is a predetermined difference or more. The electric power steering apparatus according to claim 8 or 9,
The electric power steering apparatus characterized in that the collision expectation condition is that the drive current of the electric motor is “0”. The electric power steering apparatus according to claim 8,
The electric power steering apparatus characterized in that the collision expectation condition is that the movement speed of the rack shaft is equal to or higher than a predetermined movement speed. In the electric power steering device according to any one of claims 1 to 13,
The control device outputs the compensation command signal, and when the difference between the drive current of the electric motor and the command current of the command signal is equal to or less than a reference difference, according to the torque of the steering shaft. An electric power steering device characterized by outputting a command signal. The electric power steering apparatus according to claim 14,
When the difference between the drive current of the electric motor and the command current of the command signal is equal to or less than the reference difference as the allowable divergence state, the control device, when the allowable divergence state continues for a predetermined time or more, The electric power steering device characterized in that the command signal is output according to the torque of the steering shaft. In the electric power steering device according to any one of claims 1 to 13,
The control device outputs the command signal according to the torque of the steering shaft when the compensation command signal is output and when the rotation direction of the electric motor is reversed. apparatus. In the electric power steering device according to any one of claims 1 to 16,
The said control apparatus outputs the said command signal set beforehand as the said compensation command signal, without reflecting the output of the torque sensor which detects the torque of the said steering shaft. The electric power steering apparatus characterized by the above-mentioned. In the electric power steering device according to any one of claims 1 to 17,
The electric power steering apparatus, wherein the control device performs control to stop driving of the electric motor instead of the control to output the compensation command signal.

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