JP2012050261A - Motor controller and electric power steering device equipped with same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller, along with an electric power steering device, capable of accurately estimating the temperature of a motor while the motor is rotating.SOLUTION: The electric power steering device estimates a temperature of a motor based on a counter electromotive constant of the motor when a rotational speed ωm of the motor is at a reference rotational speed or higher. When the rotational speed ωm of the motor is less than the reference rotational speed, the temperature of the motor is estimated based on the resistance of the motor. If the estimated value of the temperature of the motor is at the reference temperature or higher, a process for limiting a current command value Ia of the motor is executed as the control for suppressing the rising of the temperature of the motor.

Description

  The present invention relates to a motor control device and an electric power steering device that estimate the temperature of a steering force assisting motor.

  In a vehicle equipped with an electric power steering device, for example, when a steering turn-back operation is repeatedly performed by long-term garage entry, a large current continuously flows through the motor coil of the steering force assisting device. For this reason, there exists a possibility of causing the malfunction of a motor resulting from the temperature of a motor coil rising excessively.

  Therefore, in the conventional electric power steering apparatus, the temperature of the motor is estimated and the temperature of the motor is controlled based on the result. As an example, Patent Document 1 discloses a technique for estimating the temperature of a motor coil based on the resistance value of the motor coil and controlling the temperature of the motor based on the estimated temperature.

Japanese Patent Application Laid-Open No. 10-10093

  However, in a state where the motor is rotating, since the back electromotive force of the motor changes according to the rotation speed, it is difficult to estimate the resistance value of the motor. For this reason, the temperature estimation method described in Patent Document 1 cannot accurately estimate the motor temperature when the motor is rotating.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a motor control device and an electric power steering device that can accurately estimate the temperature of the motor while the motor is rotating. .

In the following, means for achieving the above object and its effects are described.
(1) The invention according to claim 1 is a motor control device that estimates the temperature of the motor of the steering force assisting device, wherein the temperature of the motor is estimated based on a back electromotive force constant or a back electromotive force of the motor. Is the gist.

  In this invention, since the temperature of the motor is estimated based on the counter electromotive force generated during the rotation of the motor or a counter electromotive force constant correlated therewith, the temperature of the motor is accurately estimated during the rotation of the motor. be able to.

  (2) The invention according to claim 2 is to estimate the temperature of the motor based on a counter electromotive force constant or counter electromotive force of the motor when the rotation speed of the motor is equal to or higher than a reference rotation speed. To do.

  Since the back electromotive force of the motor is small when the motor rotation speed is low, the estimation accuracy of the motor temperature based on the back electromotive force constant or the back electromotive force is low. In the above invention, in view of this point, the motor temperature is estimated when the rotation speed of the motor is equal to or higher than the reference rotation speed, so that the estimation accuracy of the motor temperature can be increased.

(3) The invention according to claim 3 is to estimate the temperature of the motor based on the resistance of the motor when the rotational speed of the motor is less than a reference rotational speed.
The back electromotive force of the motor affects the estimation accuracy of the motor resistance, and the estimation accuracy of the resistance decreases as the back electromotive force increases. On the other hand, when the rotational speed of the motor is low, the back electromotive force is also small, so that the estimation accuracy of the resistance of the motor is high. In view of this point, the above invention estimates the motor temperature based on the resistance of the motor when the motor rotation speed is lower than the reference rotation speed, so that the estimation accuracy of the motor temperature can be improved.

(4) The gist of the invention described in claim 4 is that when the estimated value of the temperature of the motor is equal to or higher than a reference temperature, control is performed to suppress an increase in the temperature of the motor.
In the present invention, when the estimated value of the motor temperature is equal to or higher than the reference temperature, that is, when the motor temperature is estimated to be relatively high, the motor coil is damaged in order to perform control for suppressing the increase in the motor temperature. Can occur less frequently.

  (5) The invention according to claim 5 is summarized in an electric power steering device having the motor control device of the invention.

  ADVANTAGE OF THE INVENTION According to this invention, the motor control apparatus and electric power steering apparatus which can estimate the temperature of a motor correctly during rotation of a motor can be provided.

The schematic diagram which shows typically the whole structure about the electric power steering apparatus of one Embodiment of this invention. The block diagram which shows the structure of the control system about the electric power steering apparatus of the embodiment. The flowchart which shows the procedure about the "motor temperature estimation process" performed by the electric power steering apparatus of the embodiment. The graph which shows the relationship between a back electromotive force constant and motor temperature about the electric power steering apparatus of the embodiment. The graph which shows the relationship between a motor resistance value and motor temperature about the electric power steering apparatus of the embodiment.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the overall structure of the electric power steering apparatus.
The electric power steering apparatus 1 includes a steering angle transmission mechanism 10 that transmits the rotation of the steering wheel 2 to the steered wheels 3 and a force for assisting the operation of the steering wheel 2 (hereinafter referred to as “assist force”). It includes an EPS actuator 20 to be applied, an electronic 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 operates a steering shaft 11 that rotates together with the steering 2, a rack and pinion mechanism 16 that transmits the rotation of the steering shaft 11 to the rack shaft 17, a rack shaft 17 that operates the tie rod 18, and a knuckle. And tie rod 18.

  The steering shaft 11 includes a column shaft 12 to which the steering 2 is fixed at the tip, a pinion shaft 14 that moves the rack shaft 17 in the axial direction via the rack and pinion mechanism 16, and the column shaft 12 and the pinion shaft 14. And an intermediate shaft 13 connected to each other. A torsion bar 15 is provided in the middle of the column shaft 12.

  The EPS actuator 20 includes a motor 21 that applies torque to the steering shaft 11 (column shaft 12), an angular velocity sensor 22 that detects the rotational speed of the motor 21, and a speed reduction mechanism 23 that decelerates the rotation of the motor 21. . As the motor 21, a brushless DC motor that rotates by supplying three-phase (U, V, W) driving power is provided. The rotation of the motor 21 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 2 is operated, the steering shaft 11 also rotates accordingly. The rotation of the steering shaft 11 is converted into a linear motion of the rack shaft 17 by the rack and pinion mechanism 16. The linear motion of the rack shaft 17 is transmitted to the knuckle through tie rods 18 connected to both ends of the coaxial 17. And the rudder angle of the steered wheel 3 is changed with operation | movement of a knuckle.

  The steering angle of the steering 2 is determined with reference to when the steering 2 is in the neutral position. That is, the steering angle when the steering wheel 2 is in the neutral position is set to “0”, and when the steering wheel 2 is rotated rightward or leftward from the neutral position, the steering angle increases according to the rotation angle from the neutral position.

  The electric power steering apparatus 1 is provided with a torque sensor 51, a steering sensor 52, a vehicle speed sensor 53, and the angular velocity sensor 22 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 (hereinafter, “output signal SA”) corresponding to the torque applied to the steering shaft 11 by the operation of the steering 2 to the electronic control unit 30. The steering sensor 52 outputs a signal (hereinafter referred to as “output signal SB”) corresponding to the rotation angle of the steering shaft 11 that changes with the operation of the steering 2 to the electronic control unit 30. The vehicle speed sensor 53 outputs a signal (hereinafter, “output signal SC”) corresponding to the rotational speed of the steered wheel as the rear wheel of the vehicle to the electronic control device 30. The angular velocity sensor 22 outputs a signal corresponding to the motor rotation speed (hereinafter, “output signal SD”) to the electronic control unit 30.

A specific configuration of the torque sensor 51 is shown below.
The torque sensor 51 includes two sensor elements provided at positions facing each other via the torsion bar 15, that is, the sensor element 51 </ b> A and the sensor element 51 </ b> B, and a sensor core that generates a change in magnetic flux according to the torsion of the torsion bar 15. Abbreviation). Each sensor element 51 </ b> A, 51 </ b> B is arranged on the outer periphery of the sensor core, and includes a magnetic detection element whose output changes according to the torsion bar 15 being twisted.

The output of the torque sensor 51 changes as follows.
When torque is input to the column shaft 12 as the steering 2 is operated, the torsion bar 15 is twisted according to the magnitude of the torque. As a result, the magnetic flux passing through the sensor elements 51A and 51B of the torque sensor 51 changes, so that the voltage output from the sensor elements 51A and 51B, that is, the output signal SA of the torque sensor 51 also changes in accordance with the change of the magnetic flux. To do.

A specific configuration of the vehicle speed sensor 53 is shown below.
The vehicle speed sensor 53 includes two sensors provided corresponding to the right rear wheel and the left rear wheel, that is, a right rear wheel sensor 53A and a left rear wheel sensor 53B. Each sensor 53A, 53B outputs one pulse as an output signal SC each time the corresponding rear wheel makes one rotation. That is, the vehicle speed sensor 53 outputs a signal corresponding to the rotational speed of the right rear wheel and a signal corresponding to the rotational speed of the left rear wheel.

The electronic control unit 30 calculates the following calculated values based on the output of each sensor.
Based on the output signal SA of the torque sensor 51, a calculated value (hereinafter referred to as “steering torque τ”) corresponding to the magnitude of the torque input to the steering shaft 11 as the steering 2 is operated is calculated.

  Based on the output signal SB of the steering sensor 52, a calculated value corresponding to the steering angle of the steering 2 (hereinafter referred to as “steering angle θs”) is calculated. Further, a calculated value corresponding to the rotational speed of the steering shaft 11 (hereinafter referred to as “steering speed ωs”) is calculated based on the calculated steering angle θs.

  Based on the output signal SC of the vehicle speed sensor 53, that is, based on the output signal SC of the right rear wheel sensor 53A and the output signal SC of the left rear wheel sensor 53B, a calculated value (hereinafter referred to as “vehicle speed”). V ").

  Based on the output signal SD of the angular velocity sensor 22, a calculated value corresponding to the motor rotational speed (hereinafter referred to as “motor rotational speed ωm”) is calculated. These calculated values are used for various controls performed by the electronic control unit 30.

  The electronic control unit 30 includes power assist control for adjusting the assist force in accordance with the traveling state of the vehicle and the operation state of the steering 2, and steering torque shift control for correcting the steering torque τ used for the power assist control. I do.

  In the power assist control, based on the steering torque τ calculated by the steering torque shift control and the vehicle speed V calculated based on the output signal SC of the vehicle speed sensor 53, a target value of the assist force (hereinafter referred to as “target assist force”). )). Then, drive power corresponding to the target assist force is supplied to the motor 21. As a result, the EPS actuator 20 applies a torque corresponding to the target assist force to the steering shaft 11.

A detailed configuration of the electronic control device 30 will be described with reference to FIG.
The electronic control unit 30 includes the following control elements.
That is, it includes a drive circuit 31 that supplies drive power to the motor 21 and a control signal output unit 32 that generates a signal (hereinafter, “motor control signal Sm”) that indicates the magnitude of drive power supplied to the motor 21. .

  Further, based on the steering torque τ and the vehicle speed V, a current value (hereinafter referred to as “current command value Ia”) necessary for causing the EPS actuator 20 to generate a torque corresponding to the target assist force, that is, supplied to the motor 21. A current command value calculator 33 for calculating a target value of the current to be generated.

  In addition, a steering torque detector 34 that calculates the steering torque τ based on the output signal SA from the torque sensor 51, a vehicle speed detector 35 that calculates the vehicle speed V based on the output signal SC from the vehicle speed sensor 53, and an angular velocity sensor And a motor rotation speed detection unit 36 that calculates the motor rotation speed ωm based on the output signal SD from the motor 22.

  In addition, a voltage sensor that outputs a signal corresponding to the voltage between the terminals of the motor 21 (hereinafter referred to as “motor voltage”) is provided. ”) Is included.

  In addition, a current sensor that outputs a signal corresponding to a current supplied to the motor 21 (hereinafter referred to as “motor current”) is provided. Im ") is included.

  Furthermore, the motor temperature estimation part 40 which calculates the temperature (henceforth "motor temperature") of the motor 21 and the memory | storage part (illustration omitted) for memorize | stored the result obtained by various calculations, etc. are included. Each control block provided in the electronic control device 30 is configured by a computer program.

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 control signal output unit 32 performs feedback control of the current command value Ia based on the current command value Ia and the motor current Im. Specifically, the rotation angle θm is calculated based on the motor rotation speed ωm, and the phase current value (Iu, Iv, Iw) of the motor 21 calculated as the motor current Im is converted to d / q based on the rotation angle θm. To do. That is, the phase current value of the motor 21 is converted into the d-axis current value and the q-axis current value in the d / q coordinate system based on the rotation angle θm.

  Next, a d-axis voltage command value and a q-axis voltage command value are calculated based on the d-axis current value, the q-axis current value, and the q-axis current command value. Further, the phase voltage command values (Vu, Vv, Vw) are calculated by performing d / q inverse conversion on the d-axis voltage command value and the q-axis voltage command value. The motor control signal Sm is generated based on the phase voltage command value, and the generated motor control signal Sm is output to the drive circuit 31.

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

  Based on the motor voltage Vm, the motor current Im, and the motor rotation speed ωm, the motor temperature estimation unit 40 calculates values corresponding to the counter electromotive force constant Kt of the motor 21 and the resistance of the motor 21 (hereinafter, “motor resistance Rm”). Is calculated. In addition, based on the back electromotive force constant Kt and the motor resistance Rm, a calculated value corresponding to the motor temperature (hereinafter, “motor temperature Tm”) is calculated. The calculation of the motor temperature Tm is specifically performed according to the procedure of “motor temperature estimation process” in FIG.

The counter electromotive force constant Kt is calculated from the following equation (1).

Kt = (Vm−Rma × Im) / ωm (1)

“Vm” indicates the motor voltage Vm input from the voltage detection unit 37.
“Im” indicates the motor current Im input from the current detection unit 38.
“Ωm” indicates the motor rotation speed ωm input from the motor rotation speed detection unit 36.
“Rma” indicates a reference value of resistance of the motor 21 stored in advance in the storage unit (hereinafter, “reference motor resistance Rma”). As the reference motor resistance Rma, a value corresponding to a resistance unique to the motor 21 is used.

The motor resistance Rm is calculated from the following equation (2).

Rm = (Vm−Kta × ωm) / Im (2)

“Vm” indicates the motor voltage Vm input from the voltage detection unit 37.
“Im” indicates the motor current Im input from the current detection unit 38.
“Ωm” indicates the motor rotation speed ωm input from the motor rotation speed detection unit 36.
“Kta” indicates a reference value of the counter electromotive force constant Kt of the motor 21 stored in advance in the storage unit (hereinafter referred to as “reference counter electromotive force constant Kta”). As the reference counter electromotive force constant Kta, a value corresponding to a counter electromotive force constant unique to the motor 21 is used.

  The content of the “motor temperature estimation process” will be described with reference to FIG. This process is stored in advance in the storage unit, and is repeatedly performed by the motor temperature estimation unit 40 every predetermined calculation cycle.

The motor temperature estimation unit 40 performs the following processes as “motor temperature estimation process”.
In step S110, it is determined whether the motor rotation speed ωm is equal to or higher than the reference rotation speed ωX. The reference rotational speed ωX is set in advance as a value for determining whether or not the estimation accuracy of the back electromotive force constant Kt or the back electromotive force is greatly reduced due to the small back electromotive force of the motor 21. . The counter electromotive force of the motor 21 can be calculated as a result of multiplying the motor rotational speed ωm and the counter electromotive force constant Kt.

  When it is determined in step S110 that the motor rotational speed ωm is equal to or higher than the reference rotational speed ωX, the back electromotive force constant Kt of the motor 21 is calculated based on the above formula (1) in step S120. In the next step S130, the motor temperature Tm is calculated by applying the back electromotive force constant Kt calculated in step S120 to the map of FIG. In the map of FIG. 4, the relationship between the motor temperature Tm and the counter electromotive force constant Kt is defined so that the counter electromotive force constant Kt decreases as the motor temperature Tm increases.

  When it is determined in step S110 that the motor rotational speed ωm is less than the reference rotational speed ωX, the motor resistance Rm is calculated based on the above equation (2) in step S140. In the next step S150, the motor temperature Tm is calculated by applying the motor resistance Rm calculated in step S140 to the map of FIG. In the map of FIG. 5, the relationship between the motor temperature Tm and the motor resistance Rm is defined so that the motor resistance Rm increases as the motor temperature Tm increases.

  After calculating the motor temperature Tm in step S130 or step S150, it is determined in step S160 whether the motor temperature Tm is equal to or higher than the reference temperature TX. The reference temperature TmX is set in advance as a value for determining whether or not the motor temperature is high enough to cause damage to the motor coil.

  When it is determined in step S160 that the motor temperature Tm is equal to or higher than the reference temperature TX, in step S170, the output signal SX for controlling the increase in the motor temperature, that is, the process for limiting the current command value Ia is controlled. The signal is output to the signal output unit 32. When receiving the output signal SX, the control signal output unit 32 calculates a value obtained by subtracting the correction value Iz from the current command value Ia as a correction command value Ib, and generates a motor control signal Sm using the correction command value Ib. To do.

  When it is determined in step S160 that the motor temperature Tm is lower than the reference temperature TX, in step S180, an output signal SY for performing a return process of the current command value Ia is output to the control signal output unit 32. When receiving the output signal SY, the control signal output unit 32 ends the current command value Ia obtained by subtracting the correction value Iz, and generates the motor control signal Sm using the current command value Ia. Even when the output signal SY is received when the current command value Ia is not limited, the motor control signal Sm is generated using the current command value Ia without performing the correction with the correction value Iz.

According to this embodiment, the following effects can be obtained.
(1) In the “motor temperature estimation process” of the present embodiment, the temperature of the motor 21 is estimated based on the counter electromotive force constant Kt of the motor 21. According to this configuration, since the motor temperature Tm is estimated based on the counter electromotive force constant Kt correlated with the counter electromotive force Kr generated during the rotation of the motor 21, the motor temperature Tm during the rotation of the motor 21 is estimated. Can be estimated accurately.

  (2) When the motor rotational speed ωm is lower than the reference rotational speed ωX, the back electromotive force constant Kt or the back electromotive force Kr is estimated based on the equation (1) because the back electromotive force Kr of the motor 21 is small. descend.

  In view of this point, in the “motor temperature estimation process” of the present embodiment, when the motor rotational speed ωm is equal to or higher than the reference rotational speed ωX, that is, when the counter electromotive force Kr of the motor 21 is large, the motor is based on the counter electromotive force constant Kt. Since the temperature Tm is calculated, the estimation accuracy of the motor temperature Tm can be increased.

  (3) The back electromotive force Kr of the motor 21 affects the estimation accuracy of the motor resistance Rm, and the estimation accuracy of the motor resistance Rm decreases as the back electromotive force Kr increases. On the other hand, when the motor rotation speed ωm is low, the back electromotive force Kr is also small, so that the estimation accuracy of the motor resistance Rm is high.

  In view of this point, in the “motor temperature estimation process” of the present embodiment, when the motor rotation speed ωm is less than the reference rotation speed ωX, that is, when the counter electromotive force Kr of the motor 21 is small, the motor temperature Tm is based on the motor resistance Rm. Therefore, the estimation accuracy of the motor temperature Tm can be increased.

  (4) In the “motor temperature estimation process” of this embodiment, when the motor temperature Tm is equal to or higher than the reference temperature TX, control for suppressing the temperature rise of the motor 21 is performed. According to this configuration, when the motor temperature Tm is estimated to be relatively high, the control for suppressing the increase in the motor temperature Tm is performed, so that the frequency of occurrence of damage to the motor coil can be reduced.

(Other embodiments)
In addition, the embodiment of the present invention is not limited to the embodiment exemplified in the above-described embodiment, and can be implemented by changing it 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.

In the above embodiment, the motor rotation speed ωm is calculated based on the output signal SD of the angular velocity sensor 22, but the motor rotation speed ωm can also be calculated based on the following equation (3).

ωm = ωs × π / 180 × n (3)

“N” indicates a reduction ratio between the motor 21 and the column shaft 12.

“Ωs” indicates a steering speed calculated based on the output signal SB of the steering sensor 52.
When this configuration is employed, a motor with a brush that is not provided with the angular velocity sensor 22 can be employed as the motor of the EPS actuator 20.

  In the above embodiment, the motor temperature Tm is estimated based on the counter electromotive force constant Kt of the motor 21, but the counter electromotive force Kr is calculated based on the following equation (4), and based on the counter electromotive force Kr. The motor temperature Tm can also be calculated.

Kr = Vm−Rma × Im (4)

“Vm” indicates the motor voltage Vm input from the voltage detection unit 37.

“Im” indicates the motor current Im input from the current detection unit 38.
“Rma” indicates a reference motor resistance Rma stored in advance in the storage unit.
When this configuration is adopted, a map that defines the relationship between the counter electromotive force Kr and the motor temperature Tm is stored in the storage unit in advance. In this map, the relationship between the motor temperature Tm and the counter electromotive force Kr is defined so that the counter electromotive force Kr decreases as the motor temperature Tm increases.

  In the “motor temperature estimation process” of the above-described embodiment, a parameter for calculating the motor temperature Tm based on the relationship between the motor rotational speed ωm and the reference rotational speed ωX is any of the back electromotive force constant Kt and the motor resistance Rm. However, it can be changed as follows. That is, the motor temperature Tm can be calculated based on the back electromotive force constant Kt regardless of the relationship between the motor rotation speed ωm and the reference rotation speed ωX.

  In the “motor temperature estimation process” of the above embodiment, the motor temperature Tm is calculated based on the back electromotive force constant Kt when the motor rotation speed ωm is equal to or higher than the reference rotation speed ωX. On the other hand, when the motor rotation speed ωm is less than the reference rotation speed ωX, the motor temperature Tm is calculated based on the motor resistance Rm. The calculated motor temperature Tm is determined as an estimated value of the motor temperature Tm in the current calculation cycle, but can be changed as shown in (A) to (F) below.

  (A) In the current calculation cycle, the motor temperature Tm calculated based on the counter electromotive force constant Kt when the motor rotation speed ωm is equal to or higher than the reference rotation speed ωX is defined as “current temperature Tma”. In the previous calculation cycle, the motor temperature Tm calculated based on the motor resistance Rm when the motor rotation speed ωm is lower than the reference rotation speed ωX is defined as “previous temperature Tmb”. In the current calculation cycle, the motor temperature Tm is newly calculated based on the current temperature Tma and the previous temperature Tmb, and the calculated motor temperature Tm is determined as an estimated value of the motor temperature Tm in the current calculation cycle. In this case, the determination process of step S160 is performed based on the determined motor temperature Tm.

  (B) In (A) above, a new motor temperature Tm is calculated by a weighted average of the current temperature Tma and the previous temperature Tmb. In this case, as the current motor rotation speed ωm becomes a value close to the reference rotation speed ωX, the weight of the previous temperature Tmb relative to the weight of the current temperature Tma is increased. On the contrary, as the current motor rotation speed ωm becomes a value away from the reference rotation speed ωX, the weight of the previous temperature Tmb with respect to the weight of the current temperature Tma is decreased.

  (C) In (A) above, an average value of the current temperature Tma and the previous temperature Tmb is calculated as a new motor temperature Tm, and this motor temperature Tm is determined as an estimated value of the motor temperature Tm in the current calculation cycle.

  (D) In this calculation cycle, the motor temperature Tm calculated based on the motor resistance Rm when the motor rotation speed ωm is lower than the reference rotation speed ωX is defined as “current temperature Tma”. Further, in the previous calculation cycle, the motor temperature Tm calculated based on the counter electromotive force constant Kt when the motor rotation speed ωm is equal to or higher than the reference rotation speed ωX is defined as “previous temperature Tmb”. In the current calculation cycle, the motor temperature Tm is newly calculated based on the current temperature Tma and the previous temperature Tmb, and the calculated motor temperature Tm is determined as an estimated value of the motor temperature Tm in the current calculation cycle. In this case, the determination process of step S160 is performed based on the determined motor temperature Tm.

  (E) In (D) above, a new motor temperature Tm is calculated by a weighted average of the current temperature Tma and the previous temperature Tmb. In this case, as the current motor rotation speed ωm becomes a value close to the reference rotation speed ωX, the weight of the previous temperature Tmb relative to the weight of the current temperature Tma is increased. On the contrary, as the current motor rotation speed ωm becomes a value away from the reference rotation speed ωX, the weight of the previous temperature Tmb with respect to the weight of the current temperature Tma is decreased.

  (F) In (D) above, an average value of the current temperature Tma and the previous temperature Tmb is calculated as a new motor temperature Tm, and this motor temperature Tm is determined as an estimated value of the motor temperature in the current calculation cycle.

In the “motor temperature estimation process” of the above embodiment, the current command value Ia is reduced by the correction value Iz as the current command value Ia limit process. However, the content of the limit process is changed as follows. You can also
(A) The current command value Ia is decreased by multiplying the current command value Ia by a coefficient less than “1”.
(B) An upper limit guard value is set for the current command value Ia. As the upper guard value, for example, the current command value Ia when it is determined that the motor temperature Tm is equal to or higher than the reference temperature TX can be used. A preset upper limit guard value can also be used.

  In the above embodiment, the present invention is applied to the column-type electric power steering device 1, but the present invention can also be applied to pinion-type and rack-assist type electric power steering devices. Also in this case, the effect according to the effect of the embodiment can be obtained by adopting the configuration according to the embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Steering, 3 ... Steering wheel, 10 ... Steering angle transmission mechanism, 11 ... Steering shaft, 12 ... Column shaft, 13 ... Intermediate shaft, 14 ... Pinion shaft, 15 ... Torsion bar, 16 DESCRIPTION OF SYMBOLS ... Rack and pinion mechanism, 17 ... Rack shaft, 18 ... Tie rod, 20 ... EPS actuator, 21 ... Motor, 22 ... Angular velocity sensor, 23 ... Deceleration mechanism, 30 ... Electronic control unit, 31 ... Drive circuit, 32 ... Control signal output 33, current command value calculation unit, 34 ... steering torque detection unit, 35 ... vehicle speed detection unit, 36 ... motor rotation speed detection unit, 37 ... voltage detection unit, 38 ... current detection unit, 40 ... motor temperature estimation unit, 51 ... Torque sensor, 51A, 51B ... Sensor element, 52 ... Steering sensor, 53 ... Vehicle speed sensor, 5 A ... right rear wheel sensor, 53B ... left rear wheel sensor.

Claims (5)

In the motor control device that estimates the temperature of the motor of the steering force assist device,
A motor control device that estimates the temperature of the motor based on a back electromotive force constant or a back electromotive force of the motor. The motor control device according to claim 1,
When the rotational speed of the motor is equal to or higher than a reference rotational speed, a temperature of the motor is estimated based on a back electromotive force constant or a back electromotive force of the motor. The motor control device according to claim 1 or 2,
When the rotational speed of the motor is less than a reference rotational speed, the temperature of the motor is estimated based on the resistance of the motor. In the motor control device according to any one of claims 1 to 3,
When the estimated value of the temperature of the motor is equal to or higher than a reference temperature, control for suppressing an increase in the temperature of the motor is performed.   An electric power steering device having the motor control device according to any one of claims 1 to 4.

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