JP2013046461A - Motor control device and electrically driven power steering device incorporating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device which, when making two-phase drive of a three-phase brushless motor, can apply a drive voltage to the normal phase of the motor efficiently, and an electrically driven power steering device incorporating the motor control device.SOLUTION: When making two-phase drive of the normal phase, a signal output unit executes a control signal change process to change a manner of how the control signal is created so that a sinusoidal wave drive voltage similar to an induction voltage generated in each normal phase following the rotation of a rotor will be applied to each normal phase in such a manner as to track the induction voltage.

Description

  The present invention relates to a motor control device that performs two-phase driving of a three-phase brushless motor when any of a plurality of switching elements provided in a drive circuit is short-circuited, and an electric power steering device including the motor control device.

  2. Description of the Related Art There is known an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor according to a steering torque applied to a steering wheel by a driver. As an electric motor of this electric power steering device, a three-phase brushless motor in which driving power is supplied to three phases (U phase, V phase, W phase) is often used.

  In the electric power steering apparatus using the electric motor as a drive source as described above, even if any abnormality occurs in the system, the electric motor is continuously driven in order to continuously apply the steering assist force to the steering mechanism. Preferably it is done.

  Therefore, in the case of some kind of system abnormality, for example, when any switching element (FET or the like) provided in the drive circuit has a short circuit failure, the presence or absence of a conduction failure caused by this short circuit failure is determined for each phase of the motor (U phase, V phase, W phase). And when the phase (abnormal phase) in which the energization failure has occurred is only one phase, the so-called two-phase drive type that continuously drives the motor with two phases (normal phase) other than the abnormal phase as the energized phase Japanese Patent Application Laid-Open No. 2004-133867 discloses an electric power steering apparatus employing the motor control apparatus.

  Further, Patent Document 2 discloses a two-phase drive type motor control device that energizes only two phases of a three-phase brushless motor even if no energization failure occurs in each phase of the motor. This motor control device employs a so-called rectangular wave driving method in which a rectangular wave voltage is applied to each normal phase of the motor.

JP 200326020 A JP 2010-110147 A

  By the way, in order to continue the driving of the three-phase brushless motor by the two-phase drive type and generate the steering assist force when the above-mentioned energization failure occurs, the magnitude of the induced voltage exceeding the normal phase is larger. It is necessary to apply a driving voltage to the normal phase of the motor.

  Here, since the induced voltage is basically a sine wave, when the drive voltage is applied as a rectangular wave as described above, an excessive voltage is applied to the normal phase. As a result, an excessive current flows through the drive circuit, which may lead to a decrease in the drive efficiency of the motor and eventually heat generation of the drive circuit.

  The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide a motor control capable of efficiently applying a driving voltage to the normal phase of the motor when the three-phase brushless motor is driven in two phases. An apparatus and an electric power steering apparatus including the same are provided.

In the following, means for achieving the above object and its effects are described.
As described above, when two-phase driving of a three-phase brushless motor is performed with two phases other than the abnormal phase as a normal phase when energization failure occurs, it is preferable to apply a sinusoidal drive voltage to the normal phase.

  In the present invention, when the signal output unit drives the normal phase in two phases, each normal phase is driven in such a manner that a sine wave drive voltage similar to the induced voltage generated in each normal phase with the rotation of the rotor follows the induced voltage. The control signal changing process is executed to change the generation mode of the control signal to be applied.

  Therefore, when the normal phase is driven in two phases, the drive voltage becomes larger than necessary compared to the case where the rectangular wave drive voltage is applied to the normal phase, that is, excessive current flows in the drive circuit. Can be suppressed. In other words, it is possible to suppress a decrease in driving efficiency of the motor and heat generation in the driving circuit. In order to drive the three-phase brushless motor, of course, a sine wave drive voltage having an amplitude larger than that of the induced voltage sine wave generated in the normal phase is applied to the normal phase. Further, in the above-described two-phase drive, when the rotor is rotated in a state where all the switching elements other than the short-circuit faulty switching element of the drive circuit are turned off, the load current flows in both of the two normal phases. This is executed in the rotor rotation angle range in which the load current flows only in one of the two normal phases.

  Here, the waveform of the induced voltage generated in the normal phase at the time of the above-described energization failure, that is, in the two-phase drive, is the case where any one of the U phase, V phase, and W phase becomes energization failure. Each may be stored in the signal output unit based on the rotation angle and the rotation speed, or may be calculated based on the rotation angle and rotation speed of the rotor each time two-phase driving is performed.

  Further, in the above-described two-phase driving, the phase difference of induced voltages generated in the respective normal phases tends to be smaller than that in the case where no conduction failure has occurred in all three phases (normal time). Therefore, by matching the cycle of the sine wave of the drive voltage applied to the normal phase with the cycle of the sine wave of the induced voltage generated in the normal phase during the two-phase drive, Thus, the effect of suppressing the heat generation of the drive circuit can be made more remarkable.

  Moreover, there is a possibility that the drive power is not sufficiently supplied to the three-phase brushless motor only by applying the drive voltage having the same period as the period of the induced voltage generated in the normal phase. Therefore, by applying a drive voltage with a sine wave period slightly larger than the sine wave period of the induced voltage generated in the normal phase to the normal phase, sufficient drive power can be obtained even when performing two-phase drive. Phase brushless motor can be supplied.

  According to the present invention, when a three-phase brushless motor is driven in two phases, it is possible to provide a motor control device capable of efficiently applying a drive voltage to the normal phase of the motor and an electric power steering device including the motor control device. .

BRIEF DESCRIPTION OF THE DRAWINGS (a) is a schematic diagram which shows typically the whole structure, (b) is a schematic diagram which shows the structure of a motor about the electric power steering apparatus concerning one Embodiment which actualized this invention. The block diagram which shows the structure of the control system about the electric power steering apparatus. The circuit diagram which shows the circuit structure of the drive circuit of a motor control apparatus. The flowchart which shows the process sequence of "abnormal phase determination processing." The circuit diagram which shows the closed circuit formed in a drive circuit at the time of abnormality. (A) is a graph showing the theoretical waveform of the induced voltage generated in each phase when no short-circuit failure has occurred in any of the FETs, and (b) is a case where the lower FET of the W phase has a short-circuit failure. The graph which shows the theoretical waveform of the induced voltage generate | occur | produced in U phase and V phase. The flowchart which shows the process sequence of a "control signal change process." The graph which shows the waveform of the drive voltage after execution of a control signal change process. The electric power steering apparatus concerning other embodiment of this invention WHEREIN: The graph which shows the waveform of the drive voltage in the case of a control signal change process.

An embodiment of the present invention will be described with reference to FIGS.
First, the entire structure of the electric power steering apparatus will be described with reference to FIG.
The electric power steering apparatus includes a steering angle transmission mechanism 10 that transmits the rotation of the steering wheel 1 to the steered wheels 2, and an EPS actuator 20 that applies a force (assist force) for assisting the operation of the steering wheel 1 to the steering angle transmission mechanism 10. And a motor control device 30 for controlling the EPS actuator 20 and a plurality of sensors for detecting the state of each device.

  The steering angle transmission mechanism 10 includes a steering shaft 11 that rotates together with the steering 1, a rack and pinion mechanism 15 that transmits the rotation of the steering shaft 11 to the rack shaft 16, a rack shaft 16 that operates the tie rod 17, and a knuckle (not shown). And a tie rod 17 for operating.

  The steering shaft 11 includes a column shaft 12 to which the steering 1 is fixed at one end, a pinion shaft 14 that moves the rack shaft 16 in the axial direction via a rack and pinion mechanism 15, and the column shaft 12 and the pinion shaft 14. An intermediate shaft 13 to be connected is provided.

  The EPS actuator 20 includes a motor 21 that applies torque to the steering shaft 11 (column shaft 12), a rotation angle sensor 22 that detects the rotation angle of the motor 21, and a speed reduction mechanism 23 that reduces the rotation of the motor 21. It is configured.

  As the motor 21, as shown in FIG. 1B, a so-called three-phase brushless motor that rotates by supplying three-phase (U-phase, V-phase, W-phase) driving power is used. The motor 21 includes a U-phase field coil 21U, a V-phase field coil 21V, a W-phase field coil 21W, and a rotor 21A that is rotated by a magnetic field formed by these field coils. The rotation of the motor 21 (rotor 21 </ b> A) is decelerated by the reduction mechanism 23 and transmitted to the steering shaft 11. At this time, torque applied from the motor 21 to the steering shaft 11 acts as an assist force.

  The steering angle transmission mechanism 10 operates as follows. That is, when the steering 1 is operated, the steering shaft 11 is also rotated accordingly. The rotation of the steering shaft 11 is converted into a linear motion of the rack shaft 16 by the rack and pinion mechanism 15. The linear motion of the rack shaft 16 is transmitted to the knuckle through tie rods 17 connected to both ends of the coaxial 16. And the steering angle of the steered wheel 2 is changed with the operation | movement of this knuckle.

  In the electric power steering apparatus, a torque sensor 51, a steering sensor 52, a vehicle speed sensor 53, and a rotation angle sensor 22 are provided as a plurality of sensors. Each of these sensors outputs a signal corresponding to a change in the state of the monitoring target as follows.

  The torque sensor 51 outputs a signal (output signal SA) corresponding to the torque applied to the steering shaft 11 by the operation of the steering 1 to the motor control device 30. The steering sensor 52 outputs a signal (output signal SB) corresponding to the rotation angle of the steering shaft 11 that changes according to the operation of the steering 1 to the motor control device 30. The vehicle speed sensor 53 outputs a signal (output signal SC) corresponding to the rotation speed of the steered wheels of the vehicle to the motor control device 30. The rotation angle sensor 22 outputs a signal (output signal SD) corresponding to the rotation angle of the motor 21 to the motor control device 30.

The motor control device 30 calculates the following calculated values based on the outputs of the sensors.
Based on the output signal SA of the torque sensor 51, a calculation value (steering torque τ) corresponding to the magnitude of torque input to the steering shaft 11 as the steering 1 is operated is calculated.

A calculation value (steering angle θs) corresponding to the steering angle of the steering 1 is calculated based on the output signal SB of the steering sensor 52.
Based on the output signal SC of the vehicle speed sensor 53, a calculation value (vehicle speed V) corresponding to the traveling speed of the vehicle is calculated.

  Based on the output signal SD of the rotation angle sensor 22, a calculation value (rotation angle θm) corresponding to the rotation angle of the motor 21, that is, the rotation angle of the rotor 21 </ b> A is calculated. The rotation angle θm of the rotor 21A is the rotation angle of the rotor 21A with respect to the stator (not shown) of the motor 21. Each of these calculated values is used for various controls performed by the motor control device 30.

The motor control device 30 performs power assist control for adjusting the assist force according to the traveling state of the vehicle and the operation state of the steering 1.
This power assist control is based on the steering torque τ calculated based on the output signal SA of the torque sensor 51 and the vehicle speed V calculated based on the output signal SC of the vehicle speed sensor 53. Target assist force) is calculated. Then, drive power corresponding to the target assist force is supplied to the motor 21. Specifically, a drive voltage is applied to each of the three-phase field coils. As a result, the EPS actuator 20 applies a torque corresponding to the target assist force to the steering shaft 11.

Next, a detailed configuration of the motor control device 30 will be described with reference to FIG.
The motor control device 30 includes the following control blocks.
That is, a drive circuit 31 that supplies drive power to the motor 21 and a signal output unit 32 that generates a signal (control signal Sm) that indicates the magnitude of the drive power supplied to the motor 21 are provided.

  Further, based on the steering torque τ and the vehicle speed V, the current value (current command value Ia) necessary for causing the EPS actuator 20 to generate a torque corresponding to the target assist force, that is, the target of the current supplied to the motor 21. A current command value calculation unit 33 for calculating a value is provided.

  Furthermore, the steering torque detector 34 that calculates the steering torque τ based on the output signal SA from the torque sensor 51, the vehicle speed detector 35 that calculates the vehicle speed V based on the output signal SC from the vehicle speed sensor 53, and the rotation A rotation angle detector 36 for calculating the rotation angle θm of the rotor 21A based on an output signal SD from the angle sensor 22;

  In addition, a voltage sensor (not shown) that outputs a signal corresponding to the voltage between the terminals of the motor 21 is provided, and a voltage detector 37 that calculates the phase voltages Vu, Vv, Vw of each phase based on the output signal of the sensor. I have. Similarly, a current sensor that outputs a signal corresponding to the current supplied to the motor 21 (not shown), and calculates the phase currents Iu, Iv, Iw of each phase based on the output signal of the sensor. 38.

  Furthermore, when an energization failure occurs in any of the three phases (U phase, V phase, W phase) of the motor 21, an “abnormal phase identification process” is performed to identify the abnormal phase in which the energization failure has occurred. The specifying unit 40 is provided.

The current command value calculator 33 calculates the current command value Ia as follows.
As the steering torque τ input from the torque sensor 51 increases, a larger value is calculated as the current command value Ia. That is, the target assist force is increased as the steering torque τ increases.
-As the vehicle speed V decreases, a larger value is calculated as the current command value Ia. That is, the target assist force is increased as the vehicle speed V decreases.

  The signal output unit 32 generates assist force generated in the motor 21 based on the current command value Ia, the phase currents Iu, Iv, Iw of each phase, and the rotation angle θm of the rotor 21A detected by the rotation angle sensor 22. A control signal Sm is generated and output to the drive circuit 31 so as to match the target assist force.

  The drive circuit 31 supplies a three-phase drive voltage to the motor 21 based on the control signal Sm captured from the signal output unit 32. That is, a drive voltage for causing the EPS actuator 20 to generate a torque corresponding to the target assist force is applied to each field coil.

Next, the detailed configuration of the drive circuit 31 will be described with reference to FIG.
The drive circuit 31 is a so-called three-phase bridge inverter circuit, and corresponds to a U-phase series circuit 60 corresponding to the U-phase of the motor 21, a V-phase series circuit 70 corresponding to the V-phase of the motor 21, and a W-phase of the motor 21. W-phase series circuit 80 is provided. These series circuits 60 to 80 are connected in parallel with each other between the DC power supply 91 and the ground point 92.

  The U-phase series circuit 60 includes an upper stage FET 61 provided on the DC power supply 91 side, a lower stage FET 62 provided on the ground point 92 side, and an upper stage diode 63 and a lower stage diode 64 provided corresponding to these FETs 61 and 62, respectively. Has been. These diodes 63 and 64 are respectively connected in such a direction that current flows in the direction (forward direction) from the ground point 92 side to the DC power supply 91 side.

  The V-phase series circuit 70 includes an upper stage FET 71 provided on the DC power supply 91 side, a lower stage FET 72 provided on the ground point 92 side, and an upper stage diode 73 and a lower stage diode 74 provided corresponding to these FETs 71 and 72, respectively. Has been. These diodes 73 and 74 are connected in such a direction that current flows in the forward direction.

  The W-phase series circuit 80 includes an upper stage FET 81 provided on the DC power supply 91 side, a lower stage FET 82 provided on the ground point 92 side, and an upper stage diode 83 and a lower stage diode 84 provided respectively corresponding to these FETs 81 and 82. Has been. These diodes 83 and 84 are connected in such a direction that current flows in the forward direction.

  The U-phase field coil 21U of the motor 21 is connected to a point between the pair of FETs 61 and 62 corresponding to the U-phase. Similarly, the V-phase field coil 21V is connected to a point between the pair of FETs 71 and 72 corresponding to the V-phase, and the W-phase field coil 21W is connected to the pair of FETs 81 and 82 corresponding to the W-phase. Connected to a point. In the following, these six FETs are simply referred to as FETs unless otherwise distinguished.

The signal output unit 32 performs sine wave driving for energizing the motor 21 by 180 ° by performing PWM control of each of these FETs in a normal state.
Specifically, the signal output unit 32 causes the assist force to approach the target assist force based on the input phase voltages Vu, Vv, and Vw and the rotation angle θm of the rotor 21A. Then, the control amount is calculated, and this control amount is PWM converted and output to each FET as the control signal Sm.

  More specifically, the signal output unit 32 stores a sine wave table in which the rotation angle θm of the rotor 21A is associated with the sine wave generation level for generating the drive voltage of each phase of the motor 21. The signal output unit 32 refers to the sine wave table and acquires a sine wave generation level corresponding to the rotation angle θm of the rotor 21A. Based on the rotation angle θm of the rotor 21A, first, a control amount corresponding to the U phase, that is, a U phase drive voltage is calculated. For the V-phase drive voltage and the W-phase drive voltage, the control amounts obtained by advancing the phase by 120 ° and 240 ° are calculated from the U-phase drive voltage.

  On the other hand, when each FET is abnormal, the phase corresponding to the short-circuited FET becomes an energization failure, that is, an abnormal phase. Therefore, in this case, the signal output unit 32 executes the two-phase driving of the motor 21 by performing PWM control on the FETs corresponding to the remaining two phases which are normal phases. Note that which FET has a short-circuit fault and which phase is an abnormal phase is specified based on the above-described “abnormal phase specifying process” executed by the specifying unit 40.

Here, the abnormal phase specifying process will be described with reference to FIG.
The identification unit 40 executes this abnormal phase identification process when detecting that an operation failure has occurred in the motor 21. Whether or not an operation failure has occurred in the motor 21 is determined by monitoring the waveforms of the phase voltages Vu, Vv, and Vw of the respective phases that are input from the voltage detection unit 37 to the specifying unit 40.

  First, in step S <b> 110, the specifying unit 40 outputs a motor stop command signal to the signal output unit 32. When receiving the motor stop command signal, the signal output unit 32 stops the 180 ° energization sine wave drive and temporarily turns off all the FETs of the drive circuit 31. Thereby, the drive of the motor 21 is temporarily stopped.

  Next, in step S120, whether or not the phase voltages Vu, Vv, and Vw of each phase of the motor 21 satisfy the first condition, that is, the phase voltages Vu, Vv, and Vw of each phase are voltages Vg having a predetermined ground level. It is determined whether or not: If this first condition is satisfied, it is determined in step S130 that any one of the lower FETs 62, 72, and 82 has a short circuit failure.

  On the other hand, if the first condition is not satisfied, it is determined in step S140 whether the second condition is satisfied, that is, whether the phase voltages Vu, Vv, Vw of each phase are equal to or higher than a predetermined power supply level Vb. judge. If this second condition is satisfied, it is determined in step S150 that any one of the upper FETs 61, 71, 81 is short-circuited.

  In Step S130 or Step S150, when it is specified that the FET in which the short-circuit fault has occurred is either the upper stage FET or the lower stage FET, in Step S160, which FET is specifically faulty is specified. . That is, the induced voltage of each phase generated by the rotation of the motor 21 (rotor 21A) accompanying the steering of the steering 1 is monitored, and the FET in which the short-circuit failure has occurred is specified based on those waveforms. If it is determined in step S140 that the second condition is not satisfied, it is determined that a current-carrying failure has occurred for a reason other than a short-circuit failure of each FET, and the abnormal phase identification process is terminated.

Next, with reference to FIG. 5, the load current flowing in the drive circuit 31 at the time of abnormality will be described.
As shown in FIG. 5, for example, when the W-phase lower stage FET 82 is short-circuited, the driver steers the steering wheel 1 and the rotor 21A rotates with all other FETs turned off. . In this case, an induced voltage is generated in the motor 21, and a load current flows through the first closed circuit 100 and the second closed circuit 110 of the drive circuit 31 due to the induced voltage.

The first closed circuit 100 includes a W-phase lower FET 82, a U-phase lower diode 64, a U-phase field coil 21U, and a W-phase field coil 21W that are short-circuited.
On the other hand, the second closed circuit 110 includes a W-phase lower FET 84, a V-phase lower diode 74, a V-phase field coil 21V, and a W-phase field coil 21W that are short-circuited.

  In the following, when a short-circuit failure occurs in the lower-stage FET 82 of the W phase, the rotation angle range of the rotor 21A in which the load current flows through both the first closed circuit 100 and the second closed circuit 110 is set as an unusable range. The rotation angle range of the other rotor 21A is set as a controllable range.

Next, the waveform of the induced voltage generated in each phase of the motor 21 will be described with reference to FIG.
As shown in FIG. 6A, the phase difference between the induced voltages Vu ′, Vv ′, and Vw ′ of the sine wave generated in each phase in the normal state is 120 °.

  However, at the time of abnormality, for example, when the W-stage lower FET 82 is short-circuited, as shown in FIG. 6B, the phase difference between the induced voltages Vv ′ and Vu ′ of sine waves generated in the V-phase and the U-phase. Is smaller than normal. Therefore, at the time of abnormality, it is necessary to apply a sinusoidal drive voltage to the normal phase in consideration of the change in the phase difference of the induced voltage generated in the normal phase. That is, it is necessary to change the generation mode of the control signal Sm.

Next, the control signal change process will be described with reference to FIG.
The specifying unit 40 outputs the result of the abnormal phase specifying process described above to the signal output unit 32. The signal output unit 32 receives the result of the abnormal phase identification process and executes the following control signal change process.

  First, in step S210, it is determined whether or not the motor 21 can be driven in two phases. That is, based on the result of the abnormal phase identification process, it is determined whether or not the phase in which the energization failure has occurred is one phase.

  If it is determined in step S210 that the motor 21 can be driven in two phases, the induced voltage generated in each normal phase is specified in step S220. For example, when the FET that is short-circuited is the upper FET 81 of the W phase or the lower FET 82 of the W phase, the sine wave of the induced voltage generated in the U phase and V phase that are normal phases is specified. More specifically, the signal output unit 32 generates a sine wave of an induced voltage generated in each normal phase in each case where any one of the U phase, the V phase, and the W phase fails to be energized. A sine wave table stored in association with the rotation angle θm is provided. Therefore, the signal output unit 32 specifies the sine wave of the induced voltage generated in each normal phase based on the sine wave table and the rotation angle θm of the rotor 21A. Then, the amplitude of the identified induced voltage is determined based on the rotational speed θs of the rotor 21A.

  In step S230, the generation mode of the control signal Sm is changed so that a sinusoidal driving voltage similar to each specified induced voltage is applied to each normal phase in a mode that follows each induced voltage in a controllable range.

  If it is determined in step S210 that the two-phase drive of the motor 21 is not possible, that is, if two or more FETs have a short-circuit failure, in step S240, two or more phases in which a conduction failure has occurred are generated. This control signal changing process is terminated.

Next, the waveform of the drive voltage applied to each normal phase as a result of the control signal change process described above with reference to FIG. 8 will be described.
As shown in FIG. 8, for example, when the W-stage lower FET 82 is short-circuited, the induced voltage Vv ′ generated in the V phase and the induced voltage Vu ′ generated in the U phase have a sine wave having the same cycle. The drive voltage Vvo and the drive voltage Vuo are applied to the V phase and U phase, which are normal phases. In addition, the improper range in the figure is the rotation angle range of the rotor 21A in which the load current flows through both the first closed circuit 100 and the second closed circuit 110 as described above. More specifically, this is the rotation angle range of the rotor 21A in which the V-phase induced voltage Vv ′ and the induced voltage Vu ′ are lower than the W-phase induced voltage Vw ′ at the time of abnormality. In other words, the rotation angle range of the rotor 21A excluding this unusable range becomes a controllable range when the W-stage lower FET 82 is short-circuited.

  Even when the same energization failure occurs in the U phase or the V phase, the processing mode is basically the same. The closed circuit through which the load current to be considered when determining the impossible range is as follows. That is, for example, when the U-phase lower FET 62 is short-circuited, the short-circuited U-phase lower FET 62, the V-phase lower diode 74, the U-phase field coil 21U, and the V-phase field coil 21V A closed circuit is formed. Furthermore, a closed circuit is formed by the U-phase lower stage FET 62, the W-phase lower stage diode 84, the U-phase field coil 21U, and the W-phase field coil 21W that are short-circuited.

  When the V-phase lower FET 72 is short-circuited, the V-phase lower FET 72, the U-phase lower diode 64, the U-phase field coil 21U, and the V-phase field coil 21V are closed. A circuit is formed. Further, a closed circuit is formed by the V-phase lower FET 72, the W-phase lower diode 84, the V-phase field coil 21V, and the W-phase field coil 21W that are short-circuited.

This is basically the same when the upper FET of each phase is short-circuited.
According to this embodiment described above, the following effects can be obtained.
(1) As described above, when performing two-phase driving in which only the normal phase of the motor 21 is energized, it is preferable to apply a sinusoidal driving voltage to the normal phase.

  The signal output unit 32 of the motor control device 30 according to the present embodiment is similar to the induced voltage Vu ′ and the induced voltage Vv ′ generated in each normal phase as the rotor 21A rotates when the normal phase is driven in two phases. A control signal changing process is executed to change the generation mode of the control signal so as to apply the drive voltages Vuo and Vvo of the waves to the respective normal phases in a manner to follow the induced voltages Vu ′ and Vv ′. Therefore, it can suppress that each drive voltage Vuo and Vvo applied to each normal phase becomes larger than necessary. That is, it is possible to suppress an excessive current from flowing through the drive circuit 31, and it is possible to suppress a decrease in drive efficiency of the motor 21 and heat generation of the drive circuit 31.

(2) Further, when each normal phase is driven in two phases, as shown in FIG. 6B described above, the phase difference of the induced voltage generated in the normal phase tends to be smaller than that in the normal phase. Therefore, by making the cycle of the drive voltage coincide with the cycle of the induced voltage generated in the normal phase, the effect of suppressing the reduction in the drive efficiency of the motor 21 and the heat generation of the drive circuit 31 described above is further remarkable. It can be.
(Other embodiments)
In addition, the embodiment of the present invention is not limited to the embodiment exemplified in the above-described embodiment, and the embodiment may be modified as shown below, for example. The following modifications are not applied only to the above-described embodiment, and different modifications can be combined with each other.

  The period of the drive voltage to be applied is matched with the period of the induced voltage generated in the normal phase, but as shown in FIG. 9, in the controllable range, the period of the induced voltage generated in the normal phase A sinusoidal driving voltage having a large period may be applied to the normal phase. Thereby, even when two-phase driving is executed, a driving voltage can be sufficiently applied to the normal phase.

When the U phase is an abnormal phase, two-phase driving of the V phase and the W phase can be performed. When the V phase is an abnormal phase, two-phase driving of the U phase and the W phase can be performed.
The rotation angle range of the rotor in which the load current flows in both the first closed circuit 100 and the second closed circuit 110 is set as an unusable range, but at least of the first closed circuit 100 or the second closed circuit 110 On the other hand, the range in which the load current flows can be set as an unusable range.

  In the above embodiment, the present invention is applied to the column type electric power steering apparatus, but the present invention can be applied to pinion type and rack assist type electric power steering apparatuses.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering wheel, 10 ... Steering angle transmission mechanism, 11 ... Steering shaft. DESCRIPTION OF SYMBOLS 12 ... Column shaft, 13 ... Intermediate shaft, 14 ... Pinion shaft, 15 ... Rack and pinion mechanism, 16 ... Rack shaft, 17 ... Tie rod, 20 ... EPS actuator, 21 ... Motor, 21A ... Rotor, 21U ... U phase field Magnetic coil, 21V ... V phase field coil, 21W ... W phase field coil, 22 ... Rotational angle sensor, 30 ... Motor control device, 31 ... Drive circuit, 32 ... Signal output unit, 33 ... Current command value calculation unit, 34 ... Steering torque detector, 35 ... Vehicle speed detector, 36 ... Rotation angle detector, 37 ... Voltage detector, 38 ... Current detector, 40 ... Specific part, 51 ... Torque sensor, 52 ... Steering sensor, 53 ... Vehicle speed Sensor: 60 U phase series circuit 61 Upper FET 62 Lower FET 63 Upper diode 64 Lower diode 70 V phase Circuit: 71 ... Upper FET, 72 ... Lower FET, 73 ... Upper Diode, 74 ... Lower Diode, 80 ... W Phase Series Circuit, 81 ... Upper FET, 82 ... Lower FET, 83 ... Upper Diode, 84 ... Lower Diode, 91 ... DC power source, 92 ... grounding point, 100 ... first closed circuit, 110 ... second closed circuit.

Claims (5)

A signal output unit that generates and outputs a control signal of a brushless motor having a rotor and a three-phase field coil, a drive circuit that supplies drive power to the field coil based on the control signal, and a drive circuit A specific unit that identifies an in-phase as an abnormal phase when any one of the plurality of switching elements provided is short-circuited and an energization failure occurs in any one phase of the brushless motor, and when the energization failure occurs, In the motor control device that drives these two phases with the two phases other than the abnormal phase as the normal phase,
When the normal phase is driven in two phases, the signal output unit follows the induced voltage with a sinusoidal driving voltage similar to the induced voltage generated in each normal phase as the rotor rotates. A motor control device that executes control signal change processing for changing a generation mode of the control signal to be applied to a phase. The signal output unit calculates, as the control signal change processing, an induced voltage generated in each normal phase at the time of the energization failure based on a rotation angle and a rotation speed of the rotor, and a mode of generating the calculated induced voltage The motor control device according to claim 1, wherein the control signal is generated based on the control signal. In the control signal changing process, the control signal is applied to each normal phase in such a manner that a sine wave drive voltage having the same period as that of the induced voltage generated in each normal phase at the time of the energization failure follows the induced voltage. The motor control device according to claim 1, wherein the generation mode is changed. The control signal changing process changes the generation mode of the control signal so as to apply a driving voltage of a sine wave having a period longer than that of the induced voltage generated in each normal phase at the time of the energization failure so as to follow the induced voltage. The motor control device according to claim 1, wherein the motor control device is a device.   The electric power steering apparatus provided with the motor control apparatus as described in any one of Claims 1-4.

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