JP2022024275A - Motor control device - Google Patents

Abstract

To provide a motor control device capable of accurately estimating temperature of a protection object.SOLUTION: A steering control device 1 has a microcomputer 51 outputting a control signal Sc for controlling operation of a motor 21, and a drive circuit 52 supplying drive power to the motor 21 based on the control signal Sc. The microcomputer 51 operates based on control voltage set lower than drive voltage applied to a coil group 42. The microcomputer 51 calculates estimated temperature of a protection object based on substrate temperature Teb detected by a temperature sensor 63, a self temperature change amount of the protection object due to energization to the coil group 42, and a difference temperature change amount which is a difference between a heat transfer temperature change amount of the temperature sensor 63 due to heat transferred from the microcomputer 51 and the heat transfer temperature change amount of the protection object due to heat transferred from the microcomputer 51.SELECTED DRAWING: Figure 2

Description

The present invention relates to a motor control device.

Conventionally, as described in, for example, Patent Document 1, there is a motor control device that controls a motor used as a drive source of an electric power steering device. In the motor control device of the same document, the temperature of the protected object, which is the object of overheat protection, is estimated, and the upper limit of the current supplied to the motor is limited based on the estimated temperature. The temperature of the protected object is estimated based on the substrate temperature of the circuit board and the current flowing through the protected object.

Japanese Unexamined Patent Publication No. 2017-17898

By the way, in recent years, in a motor control device, it is required to estimate the temperature of a protected object more accurately. Therefore, even if the above configuration is adopted, it cannot be said that the required level has been reached. Therefore, there has been a need to create a new technology that can accurately estimate the temperature of the object to be protected.

An object of the present invention is to provide a motor control device capable of accurately estimating the temperature of a protected object.

The motor control device that solves the above problems includes a processing circuit that outputs a control signal for controlling the operation of the motor, and a drive circuit that supplies drive power to the motor based on the control signal. The processing circuit includes a control-related component that operates based on a control voltage set lower than the drive voltage applied to the coil group of the motor, and the processing circuit is a current command that is a target value of a current supplied to the coil group. The current command value calculation process for calculating the value, the estimated temperature calculation process for calculating the estimated temperature of the protected object to which the current flows when the coil group is energized, and the upper limit value of the current command value based on the estimated temperature. The current limit value calculation process for calculating the current limit value and the control signal calculation process for calculating the control signal based on the current command value limited by the current limit value are executed, and the processing circuit is executed. Is the reference temperature of the protection target detected by the temperature sensor in the estimated temperature calculation process, the self-temperature change amount of the protection target due to the energization of the coil group, and the heat transmitted from the control-related component. The estimated temperature is calculated based on at least one of the heat transfer temperature change amount of the temperature sensor and the heat transfer temperature change amount of the protection target caused by the heat transferred from the control-related component.

Since the control-related parts operate based on a control voltage different from the drive voltage, they operate even when the coil group is not energized. Therefore, even when the coil group is not energized and the protected object does not generate heat due to the current flowing through itself, the control-related parts generate heat. The temperature rise due to the heat generated by the control-related parts affects the temperature of the temperature sensor and the object to be protected. Based on this point, in the above configuration, in addition to the reference temperature and the self-temperature change amount of the protection target due to energization of the coil group, the heat transfer temperature change amount due to the heat transferred from the control-related parts is taken into consideration for protection. Calculate the estimated temperature of the target. This makes it possible to accurately estimate the temperature of the protected object.

In the motor control device, the estimated temperature calculation process is a process of calculating a value obtained by subtracting the heat transfer temperature change amount of the protection target from the heat transfer temperature change amount of the temperature sensor as a differential temperature change amount. It is preferable to include a process of calculating a value obtained by subtracting the difference temperature change amount from the sum of the reference temperature and the self-temperature change amount as the estimated temperature.

According to the above configuration, it becomes easier to calculate the estimated temperature of the protected object as compared with the case of individually calculating the heat transfer temperature change amount of the temperature sensor and the heat transfer temperature change amount of the protected object.
In the motor control device, it is preferable that the heat transfer temperature change amount is calculated so as to change based on the elapsed time from the start of application of the control voltage to the control-related parts.

According to the above configuration, based on the fact that the temperature of the control-related component gradually rises after the application of the control voltage to the control-related component is started, the temperature of the protection target is determined by using an appropriate heat transfer temperature change amount. Can be estimated accurately.

In the motor control device, it is preferable that the control-related component is the processing circuit, and the temperature sensor detects the substrate temperature of the circuit board on which the processing circuit is mounted as the reference temperature.

According to the above configuration, since the substrate temperature of the circuit board on which the processing circuit, which is a control-related component, is mounted is set as the reference temperature of the protection target, the reference temperature of the protection target is likely to change due to the influence of heat transmitted from the processing circuit. Therefore, in addition to the reference temperature and the self-temperature change amount, the effect of calculating the estimated temperature of the protection target by considering at least one of the heat transfer temperature change amount of the temperature sensor and the heat transfer temperature change amount of the protection target is great. ..

In the motor control device, it is preferable that the drive circuit and other components including the temperature sensor are mounted on the same circuit board as the processing circuit.
According to the above configuration, since the components of the motor control device are mounted on one circuit board, it is possible to reduce the size of the device as compared with the case where these components are mounted separately on a plurality of circuit boards. can. On the other hand, the temperature sensor and the protection target are likely to be arranged close to the processing circuit. Therefore, the estimated temperature to be protected is likely to change due to the influence of heat transferred from the processing circuit. Therefore, in addition to the reference temperature and the self-temperature change amount, the effect of calculating the estimated temperature of the protection target by considering at least one of the heat transfer temperature change amount of the temperature sensor and the heat transfer temperature change amount of the protection target is great. ..

In the motor control device, it is preferable that the motor applies motor torque to the steering device.

According to the present invention, the temperature of the protected object can be accurately estimated.

Schematic diagram of the electric power steering device. Block diagram of steering control device and motor. The plan view which shows the mechanical structure of a steering control device. Block diagram of the microcomputer. A graph showing the relationship between the power supply voltage and the current limit value. A graph showing the relationship between the estimated temperature and the current limit. The graph which shows the time change of a current and a self-temperature change amount. The graph which shows the relationship between the heat transfer temperature change amount of a temperature sensor, the heat transfer temperature change amount of a coil group, and the elapsed time from the start of application of a control voltage to a microcomputer. A graph showing the relationship between the amount of difference temperature change and the elapsed time from the start of application of the control voltage to the microcomputer.

Hereinafter, an embodiment of the motor control device will be described with reference to the drawings.
As shown in FIG. 1, the steering device 2 to be controlled by the steering control device 1 which is a motor control device is configured as an electric power steering device (EPS). The steering device 2 includes a steering mechanism 5 that steers the steering wheel 4 based on the operation of the steering wheel 3 by the driver. Further, the steering device 2 includes an EPS actuator 6 that imparts an assist force to assist the steering operation to the steering mechanism 5.

The steering mechanism 5 includes a steering shaft 11 to which the steering wheel 3 is fixed, a rack shaft 12 connected to the steering shaft 11, and a rack housing 13 into which the rack shaft 12 is reciprocally inserted. Further, the steering mechanism 5 includes a rack and pinion mechanism 14 that converts the rotation of the steering shaft 11 into the reciprocating motion of the rack shaft 12. The steering shaft 11 is configured by connecting the column shaft 15, the intermediate shaft 16, and the pinion shaft 17 in order from the side where the steering wheel 3 is located.

The rack shaft 12 and the pinion shaft 17 are arranged in the rack housing 13 at a predetermined crossing angle. The rack and pinion mechanism 14 is configured by engaging the rack teeth 12a formed on the rack shaft 12 and the pinion teeth 17a formed on the pinion shaft 17. Further, tie rods 19 are rotatably connected to both ends of the rack shaft 12 via ball joints 18 provided at the shaft ends thereof. The tip of the tie rod 19 is connected to a knuckle (not shown) to which the steering wheel 4 is assembled. Therefore, in the steering device 2, the rotation of the steering shaft 11 accompanying the steering operation is converted into the axial movement of the rack shaft 12 by the rack and pinion mechanism 14, and this axial movement is transmitted to the knuckle via the tie rod 19. As a result, the steering angle of the steering wheel 4, that is, the traveling direction of the vehicle is changed.

The EPS actuator 6 includes a motor 21 as a drive source, a transmission mechanism 22 for transmitting the rotation of the motor 21, and a conversion mechanism 23 for converting the rotation transmitted via the transmission mechanism 22 into reciprocating motion of the rack shaft 12. I have. Then, the EPS actuator 6 transmits the rotation of the motor 21 to the conversion mechanism 23 via the transmission mechanism 22, and the conversion mechanism 23 converts the rotation into the reciprocating motion of the rack shaft 12 to apply an assist force to the steering mechanism 5. .. The motor 21 of the present embodiment employs, for example, a three-phase surface magnet synchronous motor, the transmission mechanism 22 employs, for example, a belt mechanism, and the conversion mechanism 23 employs, for example, a ball screw mechanism. ..

Next, the electrical configuration of this embodiment will be described.
The steering control device 1 operates the motor 21. The steering control device 1 includes a central processing unit (CPU) and a memory (not shown). Various controls by the steering control device 1 are executed by the CPU executing a program stored in the memory at predetermined calculation cycles.

A start signal Sig indicating on / off of a vehicle start switch 31 such as an ignition switch is input to the steering control device 1. Further, the state amount detected by various sensors is input to the steering control device 1. The steering control device 1 controls the motor 21 based on these state quantities. Various sensors include, for example, a vehicle speed sensor 32, a torque sensor 33, and a rotation angle sensor 34. The vehicle speed sensor 32 detects the vehicle speed SPD. The torque sensor 33 detects the steering torque Th input to the steering mechanism 5. The torque sensor 33 is arranged on the pinion shaft 17. The rotation angle sensor 34 detects the rotation angle θm of the motor 21 at a relative angle within the range of 360 °.

Then, the steering control device 1 operates the EPS actuator 6, that is, reciprocates the rack shaft 12 to the steering mechanism 5 by supplying driving power to the motor 21 based on each state quantity input from each of these sensors. Control the torque applied to make it.

Next, the configuration of the motor 21 will be described.
As shown in FIG. 2, the motor 21 includes a rotor 41 and a coil group 42 wound around a stator (not shown). The coil group 42 has three-phase coils of U, V, and W. The coil group 42 is connected to the steering control device 1 via the connecting line 43. In FIG. 2, for convenience of explanation, the connection lines 43 of each phase are shown together.

Next, the configuration of the steering control device 1 will be described.
The steering control device 1 includes a microcomputer 51 that outputs a control signal Sc for controlling the operation of the motor 21, and a drive circuit 52 that supplies drive power to the motor based on the control signal Sc. In this embodiment, the microcomputer 51 corresponds to a processing circuit and control-related components.

The drive circuit 52 is connected to the vehicle-mounted power supply B via the power supply line 53. As the in-vehicle power supply B, for example, one having a rated voltage of 12 V is used. The power supply line 53 is provided with a power supply relay 54, a drive relay 55, and a smoothing capacitor 56 for the purpose of smoothing the current in order from the upstream side connected to the vehicle-mounted power supply B. The power relay 54 is turned on and off according to the start signal Sig from the start switch 31. The drive relay 55 is turned on and off according to the relay signal Srl output from the microcomputer 51. Then, the drive circuit 52 can apply the power supply voltage Vb of the vehicle-mounted power supply B to the coil group 42 as the drive voltage when the power supply relay 54 and the drive relay 55 are turned on.

The microcomputer 51 is connected to the vehicle-mounted power supply B via a branch line 57 branched from the branch point P between the power supply relay 54 and the drive relay 55 in the power supply line 53. A regulator circuit 58 is provided on the branch line 57. The regulator circuit 58 generates a constant control voltage to be supplied to the microcomputer 51 based on the power supply voltage Vb of the vehicle-mounted power supply B. The control voltage is set to a value lower than the power supply voltage Vb, which is the drive voltage, for example, 5V. Then, the microcomputer 51 operates by supplying a constant control voltage from the regulator circuit 58 when the power relay 54 is turned on.

As shown in FIGS. 2 and 3, a well-known PWM inverter having a plurality of switching elements 52a to 52f such as FETs is adopted in the drive circuit 52. The control signal Sc is a gate on / off signal that defines an on / off state of each of the switching elements 52a to 52f. Then, the drive circuit 52 converts the DC power supplied from the vehicle-mounted power supply B into three-phase AC power by turning on / off the switching elements 52a to 52f according to the control signal Sc, and the coil group via the connection line 43. Supply to 42. As a result, the steering control device 1 controls the torque generated in the coil group 42 through the supply of the driving power to the coil group 42.

A current sensor 61, a voltage sensor 62, and a temperature sensor 63 are connected to the microcomputer 51. The current sensor 61 detects the actual current value Im of each phase flowing through the connection line 43. As the current sensor 61, for example, one that detects the actual current value Im based on the voltage drop of the shunt resistor can be adopted. The voltage sensor 62 detects the voltage of the power supply line 53, that is, the power supply voltage Vb of the vehicle-mounted power supply B. The temperature sensor 63 detects the substrate temperature Teb of the circuit board 64 on which the microcomputer 51 is mounted.

Here, the mechanical configuration of the steering control device 1 will be described.
As shown in FIG. 3, in the steering control device 1 of the present embodiment, various components constituting the steering control device 1 are mounted on one circuit board 64. For convenience of explanation, only the microcomputer 51, the plurality of switching elements 52a to 52f constituting the drive circuit 52, the smoothing capacitor 56, and the temperature sensor 63 are shown in the figure, and other circuit components are omitted.

The microcomputer 51 is arranged closer to the upper side of the circuit board 64. The switching elements 52a to 52f are arranged closer to the lower side of the circuit board 64. The smoothing capacitor 56 is arranged near the center of the circuit board 64. The temperature sensor 63 is arranged on the side opposite to the side where the switching elements 52a to 52f are arranged with respect to the microcomputer 51. The temperature sensor 63 is arranged closer to the microcomputer 51 than the switching elements 52a to 52f and the smoothing capacitor 56. The coil group 42 is arranged at a position farther from the temperature sensor 63 than the switching elements 52a to 52f. Therefore, in the present embodiment, the temperature sensor 63, the smoothing capacitor 56, the switching elements 52a to 52f, and the coil group 42 are arranged in this order so as to move away from the microcomputer 51.

Next, the configuration of the microcomputer 51 will be described. The microcomputer 51 calculates the control signal Sc by executing each calculation process shown in each of the following control blocks at a predetermined calculation cycle.

As shown in FIG. 2, the start signal Sig, the vehicle speed SPD, the steering torque Th, the rotation angle θm, the actual current value Im, the power supply voltage Vb, and the substrate temperature Teb are input to the microcomputer 51. Then, the microcomputer 51 outputs the control signal Sc and the relay signal Srl based on these state quantities.

Specifically, as shown in FIG. 4, the microcomputer 51 includes a motor control unit 71 that outputs a control signal Sc and a relay control unit 72 that outputs a relay signal Srl.
The start signal Sig is input to the relay control unit 72. When the start signal Sig indicates the ON state of the start switch 31, the relay control unit 72 outputs the relay signal Srl that turns the drive relay 55 into the ON state. On the other hand, when the start signal Sig indicates the off state of the start switch 31, the relay signal Srl that turns the drive relay 55 into the off state is output.

The motor control unit 71 includes a current command value calculation unit 81 that calculates the current command value Im *, and a control signal calculation unit 82 that calculates the control signal Sc. The current command value calculation unit 81 executes the current command value calculation process, and the control signal calculation unit 82 executes the control signal calculation process. Further, the microcomputer 51 is an estimated temperature calculation unit 83 that calculates the estimated temperatures Te_l, Te_c, and Te_f of the coil group 42, the drive circuit 52, and the smoothing capacitor 56 to be protected, and the upper limit value of the current command value Im *. It is provided with a current limit value calculation unit 84 that calculates a current limit value Ilim. The estimated temperature calculation unit 83 executes the estimated temperature calculation process, and the current limit value calculation unit 84 executes the current limit value calculation process.

The power supply voltage Vb and the estimated temperatures Te_l, Te_c, and Te_f calculated by the estimated temperature calculation unit 83 are input to the current limit value calculation unit 84. The current limit value calculation unit 84 calculates the current limit value Ilim_v based on the power supply voltage Vb, the current limit value Ilim_l based on the estimated temperature Te_l, the current limit value Ilim_c based on the estimated temperature Te_c, and the current limit value Ilim_f based on the estimated temperature Te_f. do. Then, among the current limit values Ilim_v, Ilim_l, Ilim_c, and Ilim_f, the smallest value is calculated as the current limit value Ilim.

Specifically, the current limit value calculation unit 84 includes a map that defines the relationship between the power supply voltage Vb and the current limit value Ilim_v. The current limit value calculation unit 84 calculates the current limit value Ilim_v according to the power supply voltage Vb by referring to this map.

As shown in FIG. 5, in this map, when the power supply voltage Vb is larger than the first voltage threshold value Vth1, the current limit value Ilim_v is constant at a value equal to the rated current Ir. That is, the current limit value Ilim_v is a value that does not limit the current supplied to the coil group 42. When the power supply voltage Vb is equal to or less than the first voltage threshold value Vth1, the current limit value Ilim_v becomes smaller based on the decrease in the power supply voltage Vb. When the value of the power supply voltage Vb is equal to or less than the second voltage threshold value Vth2, the current supplied to the coil group 42 is limited to zero.

Further, the current limit value calculation unit 84 includes a map that defines the relationship between the estimated temperature Te_l and the current limit value Ilim_l. The current limit value calculation unit 84 calculates the current limit value Ilim_l according to the estimated temperature Te_l by referring to this map.

As shown in FIG. 6, in this map, when the estimated temperature Te_l is equal to or less than the first temperature threshold value Tes1_l, the current limit value Ilim_l is constant at a value equal to the rated current Ir. That is, the current limit value Ilim_l is a value that does not limit the current supplied to the coil group 42. When the estimated temperature Te_l is larger than the first temperature threshold Tes1_l, the current limit value Ilim_l becomes smaller based on the increase of the estimated temperature Te_l. When the value of the estimated temperature Te_l is equal to or higher than the second temperature threshold value Tes2_l, the current supplied to the coil group 42 is limited to the minimum current value Imin. The minimum current value Imin is set to a value such that the temperatures of the steering control device 1 and the motor 21 do not rise even if they are supplied to the coil group 42.

The current limit value calculation unit 84 includes a map that defines the relationship between the estimated temperature Te_c and the current limit value Ilim_c, and a map that defines the relationship between the estimated temperature Te_f and the current limit value Ilim_f. Since each of these maps has the same tendency as the map shown in FIG. 6, the description thereof will be omitted. The current limit value calculation unit 84 calculates the current limit value Ilim_c according to the estimated temperature Te_c and the current limit value Ilim_f according to the estimated temperature Te_f by referring to such a map.

Then, as shown in FIG. 4, the current limit value calculation unit 84 calculates the smallest value among the current limit values Ilim_v, Ilim_l, Ilim_c, and Ilim_f as the current limit value Ilim. The current limit value Ilim calculated in this way is output to the current command value calculation unit 81.

The steering torque Th, the vehicle speed SPD, and the current limit value Ilim are input to the current command value calculation unit 81. The current command value calculation unit 81 calculates the current command value Im * based on these state quantities. The current command value Im * indicates a current corresponding to the torque to be generated by the motor 21.

Specifically, the current command value calculation unit 81 calculates a temporary current command value Im * _t having a larger absolute value as the absolute value of the steering torque Th increases and the vehicle speed SPD decreases. When the temporary current command value Im * _t is equal to or less than the current limit value Ilim, the current command value calculation unit 81 calculates this value as it is as the current command value Im *. On the other hand, when the value of the temporary current command value Im * _t is larger than the current limit value Ilim, the current command value calculation unit 81 calculates the current limit value Ilim as the current command value Im *. The current command value Im * calculated in this way is output to the control signal calculation unit 82.

The current command value Im *, the actual current value Im, and the rotation angle θm are input to the control signal calculation unit 82. The control signal calculation unit 82 executes vector control based on the actual current value Im, the current command value Im *, and the rotation angle θm in order to make the actual current value Im follow the current command value Im *, thereby performing the control signal Sc. Is calculated. Then, by outputting the control signal Sc calculated in this way to the drive circuit 52, the drive power corresponding to the control signal Sc is supplied to the coil group 42. As a result, the torque indicated by the current command value Im * is generated in the coil group 42.

The current command value Im * is a vector command value composed of a d-axis current command value Id * and a q-axis current command value Iq *, and the actual current value Im is a d-axis current value Id and a q-axis current value Iq. It is a vector value consisting of. Normally, zero is substituted for the d-axis current command value Id *, and the current command value Im * is substituted for the q-axis current command value Iq *. Since the vector control of the three-phase motor is a well-known technique, detailed description thereof will be omitted, but between the actual current value Im and the d-axis current value Id and the q-axis current value Iq, the following (1) The relation of the formula is established.

次に、推定温度演算部８３による推定温度Ｔe_l，Ｔe_c，Ｔe_fの演算について説明する。推定温度演算部８３には、実電流値Ｉm、基板温度Ｔeb及び起動信号Ｓigが入力される。推定温度演算部８３は、これらの状態量に基づいて推定温度Ｔe_l，Ｔe_c，Ｔe_fを演算する。推定温度Ｔe_l，Ｔe_c，Ｔe_fの演算方法は基本的に同様であるため、コイル群４２の推定温度Ｔe_lの演算を例に挙げて説明する。

Next, the calculation of the estimated temperatures Te_l, Te_c, and Te_f by the estimated temperature calculation unit 83 will be described. The actual current value Im, the substrate temperature Teb, and the start signal Sig are input to the estimated temperature calculation unit 83. The estimated temperature calculation unit 83 calculates the estimated temperatures Te_l, Te_c, and Te_f based on these state quantities. Since the calculation methods of the estimated temperatures Te_l, Te_c, and Te_f are basically the same, the calculation of the estimated temperature Te_l of the coil group 42 will be described as an example.

The temperature of the coil group 42 is roughly estimated by increasing or decreasing the reference temperature of the coil group 42 detected by the temperature sensor 63 according to the temperature change caused by the energization of the coil group 42. The reference temperature of the coil group 42 of the present embodiment is the substrate temperature Teb of the circuit board 64 detected by the temperature sensor 63.

That is, when the motor 21 is driven, the temperature of the coil group 42 rises as a current flows through the coil group 42 to generate heat. The self-temperature change amount ΔTes_l due to the energization of the coil group 42 is, for example, as shown in FIG. 7, when the actual current value Im flowing in the coil group 42 increases stepwise at time t1, heat is generated in the coil group 42. It increases with the tendency of the first-order delay. Further, the self-temperature change amount ΔTes_l of the coil group 42 decreases with a tendency of a first-order delay as the heat is dissipated from the coil group 42 when the actual current value Im flowing through the coil group 42 decreases to zero at time t2. In the figure, the actual current value Im is shown by a thin line, and the self-temperature change amount ΔTes_l is shown by a thick line.

In order to reflect these characteristics, the estimated temperature calculation unit 83 calculates the self-temperature change amount ΔTes_l _k in the current calculation cycle using the following equation (2) including the first-order lag filter. The subscript added to the reference code of each state quantity indicates the calculation cycle of each state quantity, and the current calculation cycle as a reference is "k".

ただし、「Ｋs_l」はコイル群４２に応じて設定されるゲインを示し、「τs_l」はコイル群４２に応じて設定される遅れフィルタの時定数を示し、「ｔ」は演算周期の時間間隔を示す。なお、ゲインＫs_l及び時定数τs_lは、コイル群４２への通電を行った状態で、コイル群４２の温度を測定した実験結果等に基づいて予め設定されている。

However, "Ks_l" indicates the gain set according to the coil group 42, "τs_l" indicates the time constant of the delay filter set according to the coil group 42, and "t" indicates the time interval of the calculation cycle. show. The gain Ks_l and the time constant τs_l are set in advance based on the experimental results of measuring the temperature of the coil group 42 while the coil group 42 is energized.

By the way, the microcomputer 51 operates based on the control voltage supplied from the regulator circuit 58, unlike the drive voltage for supplying the drive power to the coil group 42. That is, the microcomputer 51 operates even when the coil group 42 is not energized. Therefore, even when the coil group 42 is not energized and the coil group 42 does not generate heat due to the current flowing through itself, the microcomputer 51 generates heat. The temperature rise due to the heat generated by the microcomputer 51 affects the substrate temperature Teb detected by the temperature sensor 63 and the temperature of the coil group 42. That is, the substrate temperature Teb and the temperature of the coil group 42 rise even when the motor 21 is not driven. Since the temperature sensor 63 is arranged closer to the microcomputer 51 than the coil group 42 as described above, the amount of change in the substrate temperature Teb detected by the temperature sensor 63 is the temperature of the coil group 42. It is larger than the amount of change.

Based on this point, the estimated temperature calculation unit 83 considers heat dissipation from the microcomputer 51 in addition to the substrate temperature Teb and the self-temperature change amount ΔTes_l of the coil group 42 due to energization of the coil group 42. Calculate the estimated temperature Te_l of group 42.

Specifically, the estimated temperature calculation unit 83 describes the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 due to the heat transferred from the microcomputer 51 and the heat transfer temperature change amount ΔTep_l of the coil group 42 caused by the heat transferred from the microcomputer 51. Calculate the difference temperature change amount ΔTed_l which is the difference from. Then, the estimated temperature calculation unit 83 calculates the value obtained by subtracting the difference temperature change amount ΔTed_l from the sum of the substrate temperature Teb and the self-temperature change amount ΔTes_l as the estimated temperature Te_l of the coil group 42, as shown in the following equation (3). do.

Te_l = Teb + ΔTes_l－ΔTed_l… (3)
That is, the estimated temperature Te_l of the coil group 42 subtracts the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 from the sum of the substrate temperature Teb and the self-temperature change amount ΔTes_l, and the heat transfer temperature change amount of the coil group 42. It is a value obtained by adding ΔTep_l.

Here, as shown in FIG. 8, the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 is the elapsed time from the turn-on state of the start switch 31, that is, the application of the control voltage to the microcomputer 51 is started. As the elapsed time E from, the temperature increases with a tendency of a first-order delay. Similarly, the heat transfer temperature change amount ΔTep_l of the coil group 42 increases with a tendency of a first-order delay with the elapsed time E from the start of application of the control voltage to the microcomputer 51. Therefore, as shown in FIG. 9, the differential temperature change amount ΔTed_l obtained by subtracting the heat transfer temperature change amount ΔTep_l from the heat transfer temperature change amount ΔTep_s increases with a tendency of a first-order delay.

In order to reflect these characteristics, the estimated temperature calculation unit 83 calculates the difference temperature change amount ΔTed_l using the following equation (4). The estimated temperature calculation unit 83 measures the time after the start signal Sig indicating the ON state is input, and the time is set as the elapsed time E. Further, the estimated temperature calculation unit 83 starts the calculation after the start signal Sig is input. Therefore, “k” indicating the calculation cycle in the following equation (4) is a numerical value corresponding to the elapsed time E.

このように（４）式に示される差分温度変化量ΔＴed_lは、経過時間Ｅに基づいて変化するように演算される。ただし、（４）式中の係数は、「Ｋp_l」は回路基板６４及びコイル群４２に応じて設定されるゲインを示し、「τp_l」は回路基板６４及びコイル群４２に応じて設定される遅れフィルタの時定数を示し、「ｔ」は演算周期の時間間隔を示す。なお、ゲインＫp_l及び時定数τp_lは、マイクロコンピュータ５１に制御電圧を供給しつつ、コイル群４２への通電を停止した状態で、基板温度Ｔeb及びコイル群４２の温度を測定した実験結果等に基づいて予め設定されている。

In this way, the difference temperature change amount ΔTed_l shown in Eq. (4) is calculated so as to change based on the elapsed time E. However, as for the coefficient in the equation (4), "Kp_l" indicates the gain set according to the circuit board 64 and the coil group 42, and "τp_l" indicates the delay set according to the circuit board 64 and the coil group 42. The time constant of the filter is indicated, and "t" indicates the time interval of the calculation cycle. The gain Kp_l and the time constant τp_l are based on the experimental results of measuring the substrate temperature Teb and the temperature of the coil group 42 while supplying the control voltage to the microcomputer 51 and stopping the energization of the coil group 42. Is preset.

Since the temperature sensor 63 is arranged closer to the microcomputer 51 than the coil group 42 as described above, the difference temperature change amount ΔTed_l is a positive value. That is, by considering the heat transferred from the microcomputer 51, the estimated temperature Te_l of the coil group 42 becomes lower than in the case where it is not taken into consideration.

In the calculation of the estimated temperature Te_c of the smoothing capacitor 56, the gain Ks_c and the time constant τs_c set according to the smoothing capacitor 56 are used when applying the above equation (2). Further, in the calculation of the estimated temperature Te_c of the smoothing capacitor 56, the gain Kp_c and the time constant τp_c set according to the circuit board 64 and the smoothing capacitor 56 are used when applying the above equation (4).

In the calculation of the estimated temperature Te_f of the drive circuit 52, the gain Ks_f and the time constant τs_f set according to the drive circuit 52 are used when applying the above equation (2). In the calculation of the estimated temperature Te_f of the drive circuit 52, the gain Kp_f and the time constant τp_f set according to the circuit board 64 and the drive circuit 52 are used when applying the above equation (4). In the present embodiment, the estimated temperature Te_f of the drive circuit 52 is the estimated temperature of the switching element arranged at the position where the temperature is most likely to rise among the switching elements constituting the drive circuit 52.

Next, the operation and effect of this embodiment will be described.
(1) The microcomputer 51 calculates the estimated temperature of the protected object in consideration of the substrate temperature Teb, the self-temperature change amount of the protected object, and the heat transferred from the microcomputer 51 to the temperature sensor 63 and the protected object. This makes it possible to accurately estimate the temperature of the protected object.

(2) The microcomputer 51 calculates a value obtained by subtracting the difference temperature change amount from the sum of the substrate temperature Teb and the self-temperature change amount of the protected object as the estimated temperature. Therefore, the calculation of the estimated temperature of the protection target becomes easier than the case where the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 and the heat transfer temperature change amount of the protection target are calculated individually.

(3) The difference temperature change amount is calculated so as to change based on the elapsed time E from the start of application of the control voltage to the microcomputer 51. Therefore, based on the fact that the temperature of the microcomputer 51 gradually rises after the application of the control voltage to the microcomputer 51 is started as described above, the temperature of the object to be protected is accurately determined by using an appropriate difference temperature change amount. Can be estimated to.

(4) The temperature sensor 63 detects the substrate temperature Teb of the circuit board 64 on which the microcomputer 51 is mounted as a reference temperature to be protected. Therefore, the reference temperature to be protected is likely to change due to the heat transferred from the microcomputer 51. Therefore, the effect of calculating the estimated temperature of the protected object in consideration of the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 and the heat transfer temperature change amount of the protected object is great.

(5) Since various components constituting the steering control device 1 are mounted on one circuit board 64, the size of the steering control device 1 is reduced as compared with the case where each component is separately mounted on a plurality of circuit boards. be able to. On the other hand, the temperature sensor 63 and the protection target are likely to be placed close to the microcomputer 51. Therefore, the estimated temperature of the object to be protected is likely to change due to the influence of heat transferred from the microcomputer 51. Therefore, in addition to the substrate temperature Teb and the self-temperature change amount, the effect of calculating the estimated temperature of the protection target in consideration of the difference temperature change amount is great.

This embodiment can be modified and implemented as follows. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
-In the above embodiment, the components of the steering control device 1 are mounted on one circuit board 64, but the present invention is not limited to this, and the components of the steering control device 1 may be mounted separately on a plurality of circuit boards. ..

In the above embodiment, the temperature sensor 63 is arranged closer to the microcomputer 51 than the coil group 42, the drive circuit 52, and the smoothing capacitor 56, but the present invention is not limited to this, and for example, the temperature sensor 63 is placed closer to the smoothing capacitor 56 than the smoothing capacitor 56. It may be arranged away from the microcomputer 51. In this case, the difference temperature change amount ΔTed_c, which is the difference between the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 and the heat transfer temperature change amount ΔTep_c of the smoothing capacitor 56, becomes a negative value. That is, by considering the heat transferred from the microcomputer 51, the estimated temperature Te_c becomes higher than in the case where it is not taken into consideration.

-In the above embodiment, the substrate temperature Teb is used as the reference temperature of the protection target, but the present invention is not limited to this, and for example, the atmospheric temperature in the steering control device 1 may be used as the reference temperature of the protection target.
In the above embodiment, the estimated temperature Te_l of the coil group 42 is set to a value obtained by subtracting the difference temperature change amount ΔTed_l from the sum of the substrate temperature Teb and the self-temperature change amount ΔTes_l, but the present invention is not limited to this. For example, the value obtained by subtracting the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 from the sum of the substrate temperature Teb and the self-temperature change amount ΔTes_l and adding the heat transfer temperature change amount of the protection target is estimated as the protection target. It may be the temperature. Further, for example, the value obtained by subtracting only the heat transfer temperature change amount ΔTep_s of the temperature sensor 63 or only the heat transfer temperature change amount of the protection target from the sum of the substrate temperature Teb and the self-temperature change amount ΔTes_l is the protection target. It may be an estimated temperature. Such a change in the calculation method of the estimated temperature is also applicable to the calculation of the estimated temperature Te_c of the smoothing capacitor 56 and the estimated temperature Te_f of the drive circuit 52.

-In the above embodiment, the difference temperature change amount is calculated to change based on the elapsed time E, but the calculation is not limited to this, and the difference temperature change amount is calculated to be a constant predetermined value regardless of the elapsed time E. You may.

-In the above embodiment, the coil group 42, the smoothing capacitor 56, and the drive circuit 52 are protected, but the present invention is not limited to this. In addition to or in place of these circuit elements, a circuit element through which a large current flows, such as a current sensor 61, may be protected. Further, the microcomputer 51 may be protected.

-In the above embodiment, the microcomputer 51 is used as a control-related component, but the present invention is not limited to this, and it operates even when the coil group 42 is not energized, for example, a dedicated hardware circuit (for example, ASIC) that executes a specific process. Other circuit elements may be used as control-related components.

-In the above embodiment, the steering device 2 is configured as an EPS, but the present invention is not limited to this. For example, a motor in which the steering device 2 is configured as a steer-by-wire type in which the power transmission between the steering section and the steering section is separated, and the steering control device 1 applies steering torque for steering the steering wheel 4, or The operation of the motor that applies the steering reaction force to the steering wheel 3 may be controlled. Further, the operation of the motor that applies the motor torque to the device other than the steering device may be controlled.

-In the above embodiment, the motor 21 to be controlled by the steering control device 1 may have a plurality of coil groups. In this case, the steering control device 1 includes a plurality of energization systems including individual drive circuits corresponding to each of the plurality of coil groups and supplies drive power for each coil group, and a plurality of control devices for controlling the operation of the plurality of drive circuits. It is provided with at least one processing circuit for outputting the control signal of. Then, the estimated temperature of the protection target is calculated for each of the plurality of energization systems as in the present embodiment.

-In the above embodiment, the steering control device 1 is not limited to the one provided with a CPU and a memory to execute software processing. For example, a dedicated hardware circuit (eg, ASIC, etc.) that processes at least a part of the software processing executed in the above embodiment may be provided. That is, the steering control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a ROM for storing the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit for executing the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the processing may be performed by a processing circuitry comprising at least one of one or more software processing circuits and one or more dedicated hardware circuits.

1 ... Steering control device 21 ... Motor 42 ... Coil group 51 ... Microcomputer (processing circuit)
52 ... Drive circuit 63 ... Temperature sensor

Claims (6)

A motor control device including a processing circuit that outputs a control signal for controlling the operation of the motor and a drive circuit that supplies drive power to the motor based on the control signal.
It is equipped with control-related components that operate based on a control voltage set lower than the drive voltage applied to the coil group of the motor.
The processing circuit is
The current command value calculation process for calculating the current command value, which is the target value of the current supplied to the coil group, and the current command value calculation process.
Estimated temperature calculation processing that calculates the estimated temperature of the protected object to which current flows when the coil group is energized, and
A current limit value calculation process for calculating a current limit value which is an upper limit value of the current command value based on the estimated temperature, and a current limit value calculation process.
A control signal calculation process for calculating the control signal based on the value obtained by limiting the current command value by the current limit value is executed.
The processing circuit is used in the estimated temperature calculation process.
The reference temperature of the protection target detected by the temperature sensor and
The amount of self-temperature change of the protection target due to energization of the coil group and
The estimated temperature is based on at least one of the heat transfer temperature change amount of the temperature sensor due to the heat transferred from the control-related component and the heat transfer temperature change amount of the protection target due to the heat transferred from the control-related component. Motor control device that calculates. In the motor control device according to claim 1,
The estimated temperature calculation process is
Processing to calculate the difference temperature change amount, which is the difference between the heat transfer temperature change amount of the temperature sensor and the heat transfer temperature change amount of the protection target,
A motor control device including a process of calculating a value obtained by subtracting the difference temperature change amount from the sum of the reference temperature and the self-temperature change amount as the estimated temperature. In the motor control device according to claim 2,
A motor control device whose differential temperature change amount is calculated to change based on the elapsed time from the start of application of the control voltage to the control-related parts. In the motor control device according to any one of claims 1 to 3.
The control-related component is the processing circuit.
The temperature sensor is a motor control device that detects the substrate temperature of the circuit board on which the processing circuit is mounted as the reference temperature. In the motor control device according to claim 4,
The drive circuit and other components including the temperature sensor are motor control devices mounted on the same circuit board as the processing circuit. In the motor control device according to any one of claims 1 to 5.
The motor is a motor control device that applies motor torque to the steering device.

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