JP2015006101A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the overheat of a circuit by preventing the rotational speed of a motor from rapidly changing.SOLUTION: A motor control circuit includes: an invertor circuit 40 for modulating a voltage to be applied to a motor 52; a thermistor 50 for detecting the temperature of a substrate on which the invertor circuit 40 is mounted; and a microcomputer 32 for, when the temperature of the substrate detected by the thermistor 50 exceeds a power save threshold temperature, performing deceleration control to control the invertor circuit 40 such that the rotational speed of the motor 52 smoothly decelerates by a predetermined deceleration amount, and for, when the temperature of the substrate after deceleration control is equal to or more than a power save stop temperature, continuing deceleration control until the temperature of the substrate becomes less than the power save stop temperature, and for, when the temperature of the substrate becomes less than a power save release temperature lower than the power save stop temperature, controlling the invertor circuit 40 such that the rotational speed of the motor 52 smoothly accelerates.

Description

  The present invention relates to a motor control device.

  A semiconductor such as an FET (Field Effect Transistor) is mounted as a switching element in an inverter circuit that controls driving of the motor. These semiconductors such as FETs may be damaged when the temperature exceeds a predetermined temperature.

  In Patent Document 1, a temperature sensitive resistance element is provided in the vicinity of a heat-generating part of a motor such as an FET, and when the temperature detected by the temperature sensitive resistance element exceeds a predetermined value, energization to the motor drive winding is stopped. A motor driving device for preventing overheating of a circuit is disclosed.

Japanese Patent Laid-Open No. 2002-223581

  However, if energization of the motor drive winding is stopped when the temperature detected by the temperature sensitive resistance element exceeds a predetermined value, the rotational speed of the motor is rapidly reduced. As an example, when a motor is used for blowing air from an in-vehicle air conditioner, there is a problem that comfort in the vehicle interior is impaired due to a decrease in the amount of air blown due to a rapid decrease in the rotational speed of the motor. Furthermore, there has been a problem that a change in the operating sound of the motor accompanying a decrease in the rotational speed of the motor makes the passengers in the vehicle feel uncomfortable.

  Apart from the invention described in Patent Document 1, control is also performed to reduce the motor rotation speed by lowering the motor output voltage, which is the voltage applied to the motor, without stopping energization to the motor during overheating.

  FIG. 6 is a diagram illustrating an example of control of a blower motor for an in-vehicle air conditioner that can switch the rotation speed from a high speed rotation to a low speed rotation when the circuit is overheated. In FIG. 6, when the thermistor temperature exceeds the power save threshold temperature Tps continues for a predetermined time, the motor output voltage is lowered to reduce the blower motor even if there is no change in the speed command value that determines the duty ratio of the motor output voltage. The rotational speed is reduced from N1 to N2. The predetermined time is, for example, 1 to 2 seconds. In FIG. 6, when the thermistor temperature is lower than the power save release temperature Trps and the overheating of the circuit is resolved, the motor output voltage is increased and the rotation speed of the blower motor is returned from N2 to N1.

  However, N1 in FIG. 6 is a rotation speed of about 4000 rpm, for example, so that the air blow of the in-vehicle air conditioner becomes “strong”. N2 is a rotational speed of about 3000 rpm, for example, so that the air blow of the in-vehicle air conditioner becomes “weak”, and there is a large speed difference between N1 and N2. Furthermore, the change of the rotation speed from N1 to N2 and from N2 to N1 is performed in a short time of about 1 second, for example. Therefore, there has been a problem that a change in the amount of air flow and the operating sound of the blower motor accompanying a large and rapid change in the rotational speed makes the passengers in the passenger compartment feel uncomfortable.

  The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device that can eliminate overheating of a circuit without rapidly changing the rotational speed of the motor.

  In order to solve the above-described problem, the motor control device according to claim 1 includes a voltage modulation unit that modulates a voltage applied to the motor, a temperature detection unit that detects a temperature of a circuit including the voltage modulation unit, The voltage modulation unit is controlled based on a speed command value corresponding to an operation of a switch for switching the rotation speed of the motor, and when the temperature detected by the temperature detection unit exceeds a first threshold, the motor The temperature detection after the overheating deceleration control is performed by controlling the voltage modulation means so that the rotation speed of the motor is decelerated more slowly than the speed change corresponding to the operation of the switch by a predetermined deceleration amount. When the temperature detected by the means is equal to or higher than the first threshold value, the overheating deceleration control is continued until the temperature detected by the temperature detection means becomes less than the first threshold value, and the temperature detection is performed. When the temperature detected by the stage becomes less than a second threshold value that is lower than the first threshold value, it corresponds to the operation of the switch until the rotational speed of the motor reaches a rotational speed based on the speed command value. Voltage control means for controlling the voltage modulation means so as to increase more slowly than the speed change.

  In this motor control device, the voltage control means controls the voltage modulation means so that when the circuit is overheated, the motor rotation speed is decelerated more slowly than the change in the rotation speed based on the switch operation by a predetermined deceleration amount. Performs deceleration control.

  Further, in this motor control device, the voltage control means continues the above-described deceleration control during overheating until the overheating state of the circuit is resolved. When the overheating state of the circuit is eliminated, the voltage control means is configured to increase the speed of the motor more slowly than the change of the rotation speed by the switch until the rotation speed of the motor reaches the rotation speed based on the speed command value. Therefore, overheating of the circuit can be eliminated without abruptly changing the rotation speed of the motor.

  A motor control device according to a second aspect is the motor control device according to the first aspect, wherein the voltage control means reduces the rotational speed of the motor when the rotational speed of the motor is reduced by the overheat deceleration control. The voltage modulation means is controlled so as to be maintained for a predetermined time, and it is determined whether or not the temperature detected by the temperature detection means is equal to or higher than the first threshold after the predetermined time has elapsed.

  According to this motor control device, the rotational speed after deceleration is maintained for a predetermined time, and it is determined whether or not the circuit is in an overheated state after the predetermined time has elapsed, so that the rotational speed of the motor is not excessively reduced. Circuit overheating can be eliminated.

  According to a third aspect of the present invention, in the motor control device according to the first or second aspect, the first threshold includes an initial control threshold and a next control threshold higher than the initial control threshold, and the voltage The control means performs the first overheating deceleration control when the temperature detected by the temperature detection means exceeds the initial control threshold, and after the first overheating deceleration control, the temperature detection means When the detected temperature exceeds the next control threshold value, the overheat deceleration control is performed.

  According to this motor control device, after the first overheating deceleration control, the overheating deceleration control is performed when the circuit temperature exceeds the next control threshold value that is higher than the initial control threshold value. Overheating of the circuit can be eliminated without excessive deceleration.

It is the schematic which shows the structure of the motor unit using the motor control apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the board | substrate of the motor control apparatus which concerns on embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on embodiment of this invention. It is a figure which shows an example of control of the rotational speed of the motor according to the thermistor temperature in the motor control apparatus which concerns on embodiment of this invention. It is a flowchart which shows an example of control of the rotational speed of the motor according to the thermistor temperature in the motor control apparatus which concerns on embodiment of this invention. It is the figure which showed an example of control of the blower motor for vehicle-mounted air conditioners which can switch a rotational speed from high speed rotation to low speed rotation at the time of circuit overheating.

  FIG. 1 is a schematic diagram showing a configuration of a motor unit 10 using a motor control device according to the present embodiment. The motor unit 10 according to the present embodiment in FIG. 1 is a so-called blower motor unit used for blowing air from an in-vehicle air conditioner as an example.

  The motor unit 10 according to the present embodiment relates to a three-phase motor having an outer rotor structure in which a rotor 12 is provided outside a stator 14. The stator 14 is an electromagnet in which a lead wire is wound around a core member, and constitutes three phases of a U phase, a V phase, and a W phase.

  Each of the U-phase, V-phase, and W-phase of the stator 14 generates a so-called rotating magnetic field by switching the polarity of the magnetic field generated by the electromagnet under the control of the motor control device 20 described later.

  A rotor magnet is provided inside the rotor 12 (not shown), and the rotor magnet rotates the rotor 12 by responding to the rotating magnetic field generated by the stator 14.

  The rotor 12 is provided with a shaft 16 and rotates integrally with the rotor 12. Although not shown in FIG. 1, in this embodiment, the shaft 16 is provided with a multi-blade fan such as a so-called sirocco fan, and the multi-blade fan rotates together with the shaft 16 so that air can be blown in the vehicle-mounted air conditioner. It becomes.

  The stator 14 is attached to the motor control device 20 via the upper case 18. The motor control device 20 includes a substrate 22 of the motor control device 20 and a heat sink 24 that dissipates heat generated from elements on the substrate 22.

  A lower case 60 is attached to the motor unit 10 including the rotor 12, the stator 14, and the motor control device 20.

  Subsequently, a substrate of the motor control device according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the substrate 22 of the motor control device 20 according to the present embodiment. In FIG. 2, the board 22 is provided with an external connection connector 26 to which electric power is supplied from an in-vehicle battery and a control signal related to the in-vehicle air conditioner is input via a control device such as an ECU (Electronic Control Unit). ing.

  An inverter circuit 40 for controlling power supplied to the U phase, V phase, and W phase of the stator 14 is mounted on the substrate 22. The inverter circuit 40 of the motor control device 20 according to the present embodiment is a voltage-type inverter that operates as a voltage source by connecting large-capacitance capacitors 42A, 42B, 42C, and 42D in parallel to a DC side circuit.

  The inverter circuit 40 includes inverter FETs 44A, 44B, 44C, 44D, 44E, and 44F as switching elements. Inverter FETs 44A and 44D perform switching of power to be supplied to the U phase, inverters FETs 44B and 44E to V phase, and inverters FETC 44C and 44F to W phase, respectively. The electric power controlled by the switching of the inverters FET 44A to 44F is supplied to the stator 14 through the electric power supply terminals 28A, 28B, 28C.

  On the DC side of the inverter circuit 40 on the substrate 22, a noise removing coil 46 is provided, and a reverse connection prevention FET 48 and a large-capacitance capacitor 42E are provided. A microcomputer 32 for controlling the inverter circuit 40 is mounted on the substrate 22. The reverse connection prevention FET 48 is an FET for protecting the inverter circuit 40 when the vehicle battery is connected with the opposite polarity.

  In the substrate 22 shown in FIG. 2, the inverter FETs 44A to 44F, the coil 46, and the reverse connection prevention FET 48 generate significant heat during operation. In the present embodiment, the heat sink 24 is attached by the fixing bolt 30 on the back side of the portion where the element that generates significant heat during operation is mounted.

  The substrate 22 is provided with a thermistor 50, which is a temperature sensor that senses the temperature related to heat generation of the mounted circuit, near the inverter FET 44B. In the present embodiment, when there is a possibility that the temperature of the thermistor 50 becomes equal to or higher than a predetermined threshold, the duty ratio of the pulse output from the inverter circuit 40 is reduced to prevent damage to the element due to heat. Note that the thermistor 50 may be provided at a location other than the vicinity of the inverter FET 44B as long as the temperature related to the heat generation of the circuit mounted on the substrate 22 can be detected. Further, an infrared temperature sensor can be used instead of the thermistor. The infrared temperature sensor may be provided at a location other than the substrate 22 as long as it can receive infrared rays from the substrate 22.

  FIG. 3 is a diagram schematically illustrating the motor control device according to the present embodiment. The inverter circuit 40 switches power supplied to the coil of the stator 14 of the motor 52. For example, the inverter FETs 44A and 44D switch the power supplied to the U-phase coil 14U, the inverter FETs 44B and 44E switch to the V-phase coil 14V, and the inverter FETs 44C and 44F switch the power supplied to the W-phase coil 14W.

  The drains of the inverter FETs 44A, 44B, and 44C are connected to the positive electrode of the on-vehicle battery 80 via a noise removing coil 46. The sources of the inverters FET 44D, 44E, and 44F are connected to the negative electrode of the battery 80 through the reverse connection prevention FET 48.

  In the present embodiment, the Hall element 12B detects the magnetic field of the sensor magnet 12A provided coaxially with the shaft 16. The microcomputer 32 detects the position (rotational position) of the rotor 12 based on the magnetic field detected by the hall element 12B, and controls switching of the inverter circuit 40 according to the rotational position of the rotor 12.

  Further, the microcomputer 32 receives a control signal including a speed command value related to the rotational speed of the motor 52 from the air conditioner ECU 82 that controls the air conditioner in response to the switch operation of the air conditioner, and a resistance value signal from the thermistor 50. The microcomputer 32 controls switching of the inverter circuit 40 based on these input signals.

  FIG. 4 is a diagram illustrating an example of control of the rotation speed of the motor according to the thermistor temperature in the motor control apparatus according to the present embodiment. In FIG. 4, the change in thermistor temperature, the speed command value that determines the duty ratio of the voltage applied to the motor, the change in the motor output voltage, which is the voltage applied to the motor, and the change in the rotation speed of the motor are compared on the same time axis. Let me show you.

  In FIG. 4, during the period t0, a motor output voltage corresponding to the duty ratio determined based on the speed command value is applied to the motor, and the motor rotates at the rotational speed N1. In this embodiment, the control of the rotational speed based on the speed command value is referred to as a normal control mode.

  N1 shown in FIG. 4 is 4000 rpm as an example. Further, in FIG. 4, the speed command value is constant exceeding 60%, but the speed command value is changed in response to the switch operation of the air conditioner in the passenger compartment. For example, when the air blow of the air conditioner switch is set to “strong”, the motor output voltage increases due to the increase of the speed command value, and the rotation speed of the motor increases. In addition, when the air blow of the air conditioner switch is set to “weak”, the motor output voltage decreases due to a decrease in the speed command value, and the rotation speed of the motor becomes low.

  In the period t1, when a state in which the thermistor temperature exceeds the power save threshold temperature Tps continues for a predetermined time of 1700 milliseconds, the inverter circuit that is the voltage modulation means is controlled even if the speed command value does not change. The motor output voltage is lowered from M1 to M2_1. As a result, the rotational speed of the motor is decelerated from N1 to N2_1 by a predetermined deceleration amount. In this embodiment, the control for reducing the rotation speed of the motor during overheating is called a power save mode.

  As an example, a predetermined deceleration amount that is a difference in rotational speed between N1 and N2_1 is 100 rpm. In this embodiment, when the duty ratio of the speed command value exceeds 60% and the thermistor temperature exceeds the power save threshold temperature Tps continues for 1700 msec, the rotation speed is changed from N1 to N2_1 at a rate of 50 rpm per second. The motor output voltage is controlled to decelerate. The power save threshold temperature Tps varies depending on the element mounted on the substrate and the mounting position of the thermistor, but is 90 ° C. as an example.

  In the present embodiment, the deceleration of the rotation speed of the motor in the period t1 by a predetermined deceleration amount is more gradual than the change in the rotation speed of the motor due to the switch operation of the air conditioner. By slowing down the rotational speed with a predetermined deceleration amount during overheating, the passenger in the vehicle compartment can be prevented from noticing that the motor speed and the air blower of the air conditioner have changed.

  In the period t2, even after the rotational speed is reduced to N2_1, the thermistor temperature exceeds the power save threshold temperature Tps and the power save stop temperature Tsps, which are threshold values indicating an overheat state. In the present embodiment, it is determined that further reduction of the rotation speed is necessary when the thermistor temperature is equal to or higher than the power save stop temperature Tsps after maintaining the rotation speed after deceleration for a predetermined time. The predetermined time is 20 seconds as an example. As an example, the power save stop temperature Tsps is 95 ° C. when the power save threshold temperature Tps is 90 ° C.

  In the present embodiment, it is determined whether further reduction of the rotational speed is necessary based on the power save stop temperature Tsps that is higher than the power save threshold temperature Tps. Since the thermistor 50 detects the temperature of the substrate 22 as shown in FIG. 2, even if the temperature of the element actually decreases due to a decrease in the rotation speed, there is a time lag until the thermistor 50 detects the decrease in temperature. Occurs. When such a time lag occurs, if it is determined whether further reduction of the rotation speed is necessary based on the power save threshold temperature Tps, the rotation speed of the motor may be excessively reduced. Then, control based on the power save stop temperature Tsps is performed.

  Depending on the board configuration or the mounting position of the thermistor, it may not be necessary to consider the temperature lag time lag. In such a case, is it necessary to further reduce the rotational speed based on the power save threshold temperature Tps? It may be determined whether or not.

  In the period t3, the motor output voltage is controlled based on the determination in the period t2, and the rotational speed is reduced from N2_1 to N2_2. The rate of deceleration is reduced by 100 rpm, for example, at a rate of 50 rpm per second, as in the period t1.

  Hereinafter, in periods t4 and t6, it is determined whether or not the thermistor temperature is equal to or higher than the power save stop temperature Tsps for 20 seconds after the rotational speed is reduced as in the period t2. In the periods t5 and t7, the motor output voltage is controlled as in the periods t1 and t3 to reduce the rotational speed by 100 rpm at a rate of 50 rpm per second.

  In the present embodiment, the control for gradually reducing the rotational speed of the motor by a predetermined deceleration amount is continued until the state where the thermistor temperature is equal to or higher than the power save stop temperature Tsps is less than 20 seconds.

  In the period t8, when the thermistor temperature is higher than the power save stop temperature Tsps for less than 20 seconds and the thermistor temperature is lower than the power save release temperature Trps for 200 milliseconds, the overheating of the circuit is resolved. Is determined. The power save cancel temperature Trps is 75 ° C. as an example.

  In period t9, the rotational speed of the motor is returned to N1 corresponding to the speed command value. As an example, the motor output voltage is controlled so that the increase in rotational speed is 50 rpm per second. When the rotational speed of the motor returns to N1 during the period t10, the power save mode is terminated and the normal control mode is entered.

  FIG. 5 is a flowchart showing an example of control of the rotation speed of the motor according to the thermistor temperature in the motor control device according to the present embodiment. In the motor control device according to the flowchart of FIG. 5, when the circuit is not overheated, the motor rotates at 4000 rpm when the blower is “strong” and at 3000 rpm when the blower is “weak”. The voltage applied to the motor is controlled.

  In step 500 of FIG. 5, it is determined whether or not the thermistor temperature exceeds the power save threshold temperature Tps for a predetermined time. In this embodiment, the predetermined time is 1700 milliseconds, for example.

  If the determination in step 500 is affirmative, it is determined in step 502 whether or not the duty ratio of the speed command value exceeds 60%, for example. If the determination in step 502 is affirmative, the rotational speed of the motor is decelerated by 100 rpm at a rate of 50 rpm per second in step 504, but the lower limit value of the rotational speed after deceleration is 3000 rpm.

  In step 506, it is determined whether or not the state where the thermistor temperature is equal to or higher than the power save stop temperature Tsps continues for 20 seconds, for example. If the determination is affirmative, the procedure returns to step 504 and the motor rotation speed is set to 50 rpm. Decelerate at a rate of 100 rpm.

  If a negative determination is made in step 506, it is determined in step 508 whether or not the state where the thermistor temperature is lower than the power save release temperature Trps has continued for, for example, 200 milliseconds. If the determination in step 508 is affirmative, in step 510, the rotational speed of the motor is increased to a rotational speed corresponding to the speed command value, and the process ends.

  If the determination in step 502 is negative, the upper limit of the rotational speed is set to 3000 rpm (speed command value = 60%) in step 512.

  In step 514, it is determined whether or not the state where the thermistor temperature has become lower than the power save release temperature Trps has continued for, for example, 200 msec. If the determination is affirmative, the procedure proceeds to step 510 and the process ends.

  As described above, in the present embodiment, when the circuit is overheated, the rotational speed of the motor is slow and slow, and when the thermistor temperature after deceleration is still high, the rotational speed is further reduced. Thus, overheating of the circuit can be eliminated without abruptly changing the rotation speed of the motor.

DESCRIPTION OF SYMBOLS 10 ... Motor unit, 12 ... Rotor, 12A ... Sensor magnet, 12B ... Hall element, 14 ... Stator, 14U, 14V, 14W ... Coil, 16 ... Shaft, 18 ... Upper case, 20 ... Motor controller, 22 ... Substrate, 24 ... Heat sink, 26 ... External connector, 28A, 28B, 28C ... Power supply terminal, 30 ... Fixing bolt, 32 ... microcomputer, 40 ... inverter circuit, 42A, 42B, 42C, 42D, 42E ... capacitor, 44A, 44B, 44C, 44D, 44E, 44F ... inverter FET, 46 ... -Coil, 48 ... Reverse connection prevention FET, 50 ... Thermistor, 52 ... Motor, 60 ... Lower case, 80 ... Battery, 82 ... Air conditioner CU

Claims (3)

Voltage modulation means for modulating the voltage applied to the motor;
Temperature detecting means for detecting the temperature of the circuit including the voltage modulating means;
The voltage modulation unit is controlled based on a speed command value corresponding to an operation of a switch for switching the rotation speed of the motor, and when the temperature detected by the temperature detection unit exceeds a first threshold, the motor The temperature detection after the overheating deceleration control is performed by controlling the voltage modulation means so that the rotation speed of the motor is decelerated more slowly than the speed change corresponding to the operation of the switch by a predetermined deceleration amount. When the temperature detected by the means is equal to or higher than the first threshold, the overheating deceleration control is continued until the temperature detected by the temperature detection means becomes less than the first threshold, and the temperature detection means detects If the measured temperature becomes lower than the second threshold value, which is lower than the first threshold value, the operation of the switch is handled until the rotational speed of the motor reaches the rotational speed based on the speed command value. And voltage control means for controlling the voltage modulation means so as to gradually speed higher than the speed change,
A motor control device comprising:   The voltage control means controls the voltage modulation means so as to maintain the reduced rotational speed for a predetermined time when the rotational speed of the motor is reduced by the overheat deceleration control, and after the predetermined time has elapsed. The motor control device according to claim 1, wherein it is determined whether the temperature detected by the temperature detection unit is equal to or higher than the first threshold value. The first threshold includes a threshold for initial control and a threshold for next control higher than the threshold for initial control,
The voltage control means performs the first overheating deceleration control when the temperature detected by the temperature detection means exceeds the initial control threshold, and after the first overheating deceleration control, the temperature detection The motor control device according to claim 1 or 2, wherein the overheat deceleration control is performed when a temperature detected by the means exceeds the next control threshold value.

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