JP6413440B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device.

  Among the motors, for example, a blower motor used for blowing air from a vehicle air conditioner stops the rotation of the blower motor if the blower motor is impeded by foreign matter such as dead leaves that enter from the outside of the vehicle and the blower motor is heavily loaded. Performs load protection control. By executing such overload protection, overheating of the blower motor control device circuit and the blower motor stator coil due to overload is prevented.

  FIG. 18 is a schematic diagram illustrating an example of a motor control device that determines motor overload based on the current value between the inverter circuit 40 and the negative electrode of the battery 80. In FIG. 18, a current detection unit 94 is provided between each source of the inverters FETs 44 </ b> D, 44 </ b> E, and 44 </ b> F and the battery 80. The current detection unit 94 includes a shunt resistor 94A and an amplifier 94B that amplifies the detected current value by detecting the current value of the shunt resistor 94A. The signal output from the amplifier 94B is an overload determination unit 98 and an overcurrent determination. Are input to the unit 102.

  The overcurrent determination unit 102 compares the signal output from the amplifier 94B with the overcurrent determination value output from the overcurrent determination value output unit 100, and the overload determination unit 98 compares the signal output from the amplifier 94B with the overcurrent determination value. The overload determination value output by the load determination value output unit 96 is compared. The signals output from the overcurrent determination unit 102 and the overload determination unit 98 are input to the OR circuit 130.

  The OR circuit 130 outputs a voltage correction unit 68 when the signal output from the amplifier 94B is determined to be greater than or equal to the overcurrent determination value by the overcurrent determination unit 102 or when the overload determination unit 98 determines greater than or equal to the overload determination value. A signal that forcibly stops the output of is output. As a result, when it is determined that the circuit is in an overload state or an overcurrent state, the rotation of the motor 52 can be stopped and the circuit can be prevented from being burned out.

  In addition, a filter for preventing foreign matters from entering is provided in the intake system of the vehicle air conditioner. However, since such a filter can become an intake resistance, the vehicle air conditioner may be used with the filter removed. When the filter of the intake system is removed, the air flow rate of the air conditioner increases, but the blower motor tends to maintain the same rotation by controlling the rotation speed, and therefore the blower motor tends to have a high torque (= high load).

  In addition, the blower motor cools circuits such as the motor control device with a part of the fan airflow, but if the airflow of the fan changes greatly with the filter of the intake system removed, a part of the airflow from the fan is reduced. It cannot be introduced to the cooling of the circuit, and the circuit is likely to overheat.

  When the load of the blower motor increases, the overload protection control for stopping the rotation of the blower motor is executed as described above in order to prevent overheating of the motor control device. However, in the situation where the filter of the intake system is removed and the blower motor is likely to over-rotate, the above-described overload protection control is frequently executed, and the smooth operation of the vehicle air conditioner cannot be expected. there were.

  Patent Document 1 discloses a motor that prevents overheating of a circuit by lowering the level of a motor rotation speed command signal when the temperature of a shunt resistor arranged in a path for supplying driving power to the motor reaches a predetermined temperature. An overload protection device for a drive system is disclosed.

Japanese Patent No. 3801015

  There is a correlation between the motor load and the current supplied to the motor, and the current supplied to the motor increases as the motor load increases. However, in the invention described in Patent Document 1, since the thermistor detects the heat generated in the shunt resistor by the current and determines the load of the motor, the load of the motor is determined by the magnitude of the current supplied to the motor. Compared to the case, there is a problem that quick determination is difficult. The invention described in Patent Document 1 also has a problem that it is difficult for the thermistor to be affected by temperature changes due to the amount of current in the motor winding, and it is difficult to accurately grasp the overheating state of the circuit.

  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 quickly and accurately eliminate an overload state of a motor and a circuit without stopping the rotation of the motor.

In order to solve the above-described problem, the motor control device according to claim 1 includes a current detection unit that detects a current flowing between a power source and an inverter circuit that generates a voltage to be applied to a coil of the motor, and the motor or First temperature detection means for detecting the temperature of the circuit board, overload determination value output means for outputting an overload determination value for determining whether or not the motor is overloaded, and the overload determination value output means Connecting means for connecting the output of the first temperature detection means and the output of the overload determination value output means to adjust the overload determination value to be output; and the current value detected by the current detection means is the overload. Overload determination means for determining that the motor is overloaded when the determination value is equal to or greater than a determination value; and when the overload determination means determines that the motor is overloaded, the rotation speed of the motor is set to a predetermined speed. Reduced to Includes a rotational speed control means for controlling that, the.

  In this motor control device, the current detection means detects the current between the power supply and the inverter circuit. The overload determination means compares the current detected by the current detection means with the overload determination value to determine whether or not the motor is overloaded, so the thermistor detects the heat generated by the current flowing through the circuit. As compared with the case of determining the motor overload, the determination can be made quickly and accurately.

  Further, the motor control device performs control to rotate the motor at a predetermined rotational speed after determining the overload state quickly and accurately as described above. Such control can quickly and accurately eliminate the overload state of the motor and the circuit without stopping the rotation of the motor.

Furthermore, according to this motor control device, the voltage on the overload determination value output means side is divided to the first temperature detection means side via the connection means. As a result, the overload judgment value output by the overload judgment value output means is adjusted so as to decrease. Therefore, when the current value detected by the current detection means shows an upward trend, the overload judgment value is output quickly. The state can be determined.

The motor control device according to claim 2 is the motor control device according to claim 1 , wherein the first temperature detection unit is configured such that a voltage is applied to one end via a resistor and the other end is grounded to increase the temperature. The resistance value of the thermistor decreases as the temperature rises, and the voltage of the overload determination value is divided to the thermistor side via the connecting means in response to the resistance value of the thermistor decreasing as the temperature rises. Thus, the overload judgment value is adjusted. Can be determined.

  According to this motor control device, since the resistance value of the thermistor decreases as the circuit temperature increases, the voltage of the overload determination value output from the overload determination value output means is distributed to the thermistor side via the connection means. Pressed. This partial pressure also reduces the overload judgment value, which is the current value output by the overload judgment value output means, so that if there is a possibility of overheating of the circuit, the motor can be quickly operated based on the lower overload judgment value. Overload can be determined.

A third aspect of the present invention is the motor control device according to the second aspect , further comprising a resistor connected in parallel to the first temperature detecting means.

  According to this motor control device, the first temperature detection means in the low temperature range is relaxed by the resistance of the first temperature detection means whose resistance value changes due to temperature change by the resistance connected in parallel to the first temperature detection means. An increase in the resistance value is suppressed. Thereby, the voltage of the overload determination value output by the overload determination value output means at a temperature lower than that of the motor control device according to claim 2 is likely to be divided to the first temperature detection means side via the connection means. Therefore, it is possible to quickly determine the motor overload state prior to the temperature rise due to overheating of the circuit.

The invention according to claim 4, in the motor control device according to claim 3, a second temperature sensing means for sensing said first temperature sensing means and independently the temperature of the motor or circuit board, wherein the motor is overheated An overheat state determination value output means for outputting an overheat state determination value for determining whether or not the motor is overheated when the temperature detected by the second temperature detection means is equal to or higher than the temperature indicated by the overheat state determination value. And an overheat state determining means for determining that the state is a state.

  According to this motor control device, the first temperature detection means connected in parallel with the parallel resistance is not connected to the overheat state determination value output means, and the second temperature detection means separate from the first temperature detection means is connected. Has been. Further, the second temperature detecting means is not connected to a parallel resistor as in the first temperature detecting means. As a result, it is possible to determine the overheating state of the motor without considering the influence of the parallel resistance connected to the first temperature detecting means.

According to a fifth aspect of the present invention, in the motor control device according to the fourth aspect , the second temperature detecting means is a thermistor whose resistance value changes according to temperature.

  According to this motor control device, it is possible to determine the overheated state of the motor using the thermistor which is a general-purpose element.

A sixth aspect of the present invention is the motor control device according to any one of the first to fifth aspects, wherein one end of the connection means is connected to an output of the first temperature detection means, and the other end is the overload. A resistor connected to the output of the judgment value output means.

  According to this motor control device, the resistance value of the first temperature detecting means, which is a thermistor, decreases as the circuit temperature rises. Therefore, the voltage of the overload determination value output by the overload determination value output means Through the first temperature detecting means. In addition, by using a resistor for the connection means, it is possible to appropriately suppress a sudden drop in voltage due to voltage division. Since the overload determination value, which is the current value output by the overload determination value output means, is also reduced by the appropriately suppressed partial pressure in this way, a lower overload determination value can be used when there is a possibility of overheating of the circuit. Based on this, it is possible to quickly determine the motor overload.

A seventh aspect of the present invention is the motor control device according to any one of the first to sixth aspects, wherein an overcurrent determination value output means for outputting an overcurrent determination value exceeding the overload determination value, and the current detection Overcurrent determination means for determining that the motor is in an overcurrent state when the current value detected by the means is greater than or equal to the overcurrent determination value, and the rotational speed control means includes the overcurrent determination means. When it is determined that the motor is in an overcurrent state, the rotation of the motor is stopped for a predetermined time.

  According to this motor control device, when the current detected by the current detection means is equal to or greater than the overcurrent determination value that is larger than the overload determination value, the motor is determined to be in a more critical overcurrent state than the overload state. To do. In the case of the determination, since the rotation of the motor is stopped for a predetermined time, the motor and the circuit can be prevented from being burned out.

It is the schematic which shows the structure of the motor unit using the motor control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the temperature characteristic of the chip | tip thermistor used for the motor control apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the overload protection control in the motor control apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on the 2nd Embodiment of this invention. (A) is the schematic which showed the chip thermistor and overload judgment value output part in 1st Embodiment, (B) is the chip thermistor and overload judgment value output part in 2nd Embodiment. It is the schematic which shows these connections. It is the schematic which shows the relationship between the electric current value in the bridge circuit of the chip | tip thermistor which concerns on the 2nd Embodiment of this invention, and an overload determination value, a voltage value, and resistance value. It is a figure which shows an example of the change of the overload threshold voltage VP corresponding to the change of the resistance value of bridge resistance RB in the 2nd Embodiment of this invention. It is a figure which shows an example of the change of the chip | tip thermistor voltage VT corresponding to the change of the resistance value of bridge | bridging resistance RB in the 2nd Embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on the 3rd Embodiment of this invention. (A) is the schematic which shows the connection of the chip thermistor and overload determination value output part in 2nd Embodiment, (B) is the chip thermistor and overload determination value output part in 3rd Embodiment. It is the schematic which shows the connection. It is a figure which shows an example of the change of the overload threshold voltage VP corresponding to the change of the resistance value of the parallel resistance RP in the 3rd Embodiment of this invention. FIG. 13 is an enlarged view around the equilibrium temperature of FIG. 12. It is a figure which shows an example of the change of the chip | tip thermistor voltage VT corresponding to the change of the resistance value of the parallel resistance RP in the 3rd Embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on the 4th Embodiment of this invention. (A) is the schematic which shows the connection of the chip thermistor and overload determination value output part in 3rd Embodiment, (B) is the chip thermistor and overload determination value output part in 4th Embodiment. It is the schematic which shows the connection. It is a figure which shows an example of the change of the chip | tip thermistor voltage VT with respect to the chip | tip thermistor temperature in the 4th Embodiment of this invention. It is the schematic which shows an example of the motor control apparatus which determines the overload of a motor based on the electric current value between an inverter circuit and the negative electrode of a battery.

[First Embodiment]
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 a 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 the present 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, thereby blowing air in the vehicle air conditioner. It becomes possible.

  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 28 is attached to the motor unit 10 including the rotor 12, the stator 14, and the motor control device 20.

  FIG. 2 is a diagram schematically illustrating the motor control device according to the present embodiment. The inverter circuit 40 shown in FIG. 2 switches the electric power supplied to the coil of the stator 14 of the motor 52 by FET (Field Effect Transistor). 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 inverters FETs 44A, 44B, and 44C are connected to the positive electrode of the on-vehicle battery 80 via the choke coil 82. The sources of the inverters FET 44D, 44E, and 44F are connected to the negative electrode of the battery 80.

  Further, on the board of the motor control device 20 of the present embodiment, in addition to the inverter circuit 40 described above, a comparator 54, an actual rotation number calculation unit 56, a command rotation number calculation unit 58, a standby circuit 60, a main power supply energization unit 62, an energization control drive waveform determination unit 64, a PI control unit 66, a voltage correction unit 68, an FET driver 70, and the like are mounted.

  A choke coil 82 and smoothing capacitors 84A and 84B are mounted on the substrate of the motor control device 20 of the present embodiment, and an air conditioner ECU (Electronic Control Unit) 78 and a battery 80 are connected. The choke coil 82 and the smoothing capacitors 84A and 84B together with the battery 80 constitute a substantially DC power source. The air conditioner ECU 78 is an electronic control unit for a vehicle air conditioner. When the user turns on the air conditioner by the air conditioner ECU 78, the motor 52 is operated under the control of the motor control device 20. When the user adjusts the air volume of the vehicle air conditioner, a signal for instructing the rotational speed of the motor 52 (rotor 12) is input via the air conditioner ECU 78.

  In the present embodiment, the Hall element 12B detects the magnetic field of the sensor magnet 12A provided coaxially with the shaft 16. The comparator 54 is a device that converts the analog output of the Hall element 12 </ b> B into a digital signal, and the actual rotational speed calculation unit calculates the actual rotational speed of the rotor 12 based on the digital signal output from the comparator 54. The command rotation number calculation unit calculates a target rotation speed based on an instruction from the air conditioner ECU 78 or the like. In the present embodiment, the target rotation speed is approximately 1000 to 5000 rpm.

  The PI controller 66 changes the coil of the stator 14 when changing the actual rotational speed to the target rotational speed from the target rotational speed calculated by the command rotational speed calculator 58 and the actual rotational speed calculated by the actual rotational speed calculator 56. The voltage applied to is calculated by so-called PI control. The PI control unit 66 includes a deviation proportional unit 66P that calculates a voltage at the target rotational speed based on a proportional relationship between a deviation between the target rotational speed and the actual rotational speed and a deviation between the voltage at the target rotational speed and the voltage at the actual rotational speed. Including. Further, the PI control unit 66 includes a deviation integration unit 66I that eliminates the residual deviation by deviation integration when the residual deviation is generated only by the proportional relationship. The voltage correction unit 68 corrects the voltage applied to the coil of the stator 14 based on the calculation result by the PI control unit 66.

  The standby circuit 60 is a circuit that controls power supply from the battery 80 to each unit. The main power supply energization unit 62 turns on the power to the motor control device according to the control of the standby circuit 60. Further, the main power supply energizing unit 62 issues a command to the forced 500 rpm command unit 88 via the OR circuit 86 when the motor 52 is started, that is, when the motor 52 is rotated from a rotation speed of 0 rpm. The forced 500 rpm command unit 88 controls the command rotational speed calculation unit 58 so that the target rotational speed becomes 500 rpm at a predetermined time when the motor 52 is started, and the command rotational speed calculation unit 58 performs PI control on a signal related to 500 rpm. The data is output to the unit 66. The predetermined time is 500 to 1000 milliseconds as an example.

  After the predetermined time has elapsed, the control to the command rotational speed calculation unit 58 by the forced 500 rpm command unit is finished, and the command rotational speed calculation unit 58 outputs a signal related to the target rotational speed calculated based on an instruction from the air conditioner ECU 78. Output to the PI controller 66.

  When power is supplied via the standby circuit 60 and the main power supply energization unit 62, the energization control drive waveform determination unit 64 determines the position of the rotor 12 based on the digital signal output from the comparator 54, and determines the position of the rotor 12. Based on the target rotational speed calculated by the command rotational speed calculation unit 58, the drive waveform of the voltage applied to the coil of the stator 14 is determined.

  The FET driver 70 generates a PWM signal for controlling the switching of the inverter circuit 40 based on the drive waveform determined by the energization control drive waveform determination unit 64 and the voltage value corrected by the voltage correction unit 68 to generate an inverter. Output to the circuit 40.

  Further, on the substrate of the motor control device 20 according to the present embodiment, a chip thermistor that detects the temperature of the substrate as a resistance value is applied with a control voltage Vcc at one end via a resistor R3 and the other end grounded. RT is implemented. FIG. 3 is a diagram illustrating an example of temperature characteristics of the chip thermistor used in the motor control device according to the present embodiment. The chip thermistor RT used in the present embodiment is an NTC (Negative Temperature Coefficient) thermistor whose resistance decreases with increasing temperature, and as shown in FIG. 3, the resistance value of the chip thermistor RT increases with increasing temperature. Decrease. Note that a PTC (Positive Temperature Coefficient) thermistor whose resistance value increases as the temperature rises by using an inverting circuit together may be used.

  The chip thermistor RT and the resistor R3 form a kind of voltage dividing circuit, and a voltage that changes based on the resistance value of the chip thermistor RT is output from one end of the chip thermistor RT connected to the resistor R3. . The voltage output from one end of the chip thermistor RT is compared with the overheat determination value output from the overheat determination value output unit 104 in the overheat state determination unit 106, and the voltage output from one end of the chip thermistor RT is equal to or less than the overheat determination value. The command rotational speed calculation unit 58 is controlled so as to force the target rotational speed to 0 rpm. As described above, since the chip thermistor RT according to the present embodiment is a type in which the resistance decreases as the temperature rises, the chip thermistor that is also the output terminal of the voltage dividing circuit composed of the resistor R3 and the chip thermistor RT. The voltage output from one end of RT decreases as the temperature increases. The overheat state determination unit 106 determines that the circuit is overheated when the voltage output from one end of the chip thermistor RT is equal to or less than the overheat determination value. The overheat determination value varies depending on the element mounted on the substrate, the position of the chip thermistor RT, and the like. As an example, the overheat determination value is a voltage output by a voltage dividing circuit of the chip thermistor RT and the resistor R3 at 145 ° C.

  In addition, a current detection unit 94 is provided between the source of each of the inverters FETs 44D, 44E, and 44F and the battery 80. The current detection unit 94 includes a shunt resistor 94A having a resistance value as small as about 0.2 mΩ to several Ω, and an amplifier 94B that detects the current value of the shunt resistor 94A and amplifies the detected current value. The signals are input to the overload determination unit 98 and the overcurrent determination unit 102, respectively. The overcurrent determination unit 102 compares the signal output from the amplifier 94B with the overcurrent determination value output from the overcurrent determination value output unit 100. If the signal output from the amplifier 94B is greater than or equal to the overcurrent determination value, the overcurrent determination value is compulsory. Thus, by stopping the output of the voltage correction unit 68, the rotation of the motor 52 is stopped. The overload determination unit 98 compares the signal output from the amplifier 94B with the overload determination value output from the overload determination value output unit 96, and when the signal output from the amplifier 94B is equal to or greater than the overload determination value. Sends a command to the forced 500 rpm command section 88 via the OR circuit 86 to control the motor 52 to forcibly reduce the rotational speed of the motor 52 to a predetermined rotational speed of 500 rpm.

  In the present embodiment, the overcurrent determination value is a value that exceeds the overload determination value, and is a current value that requires the rotation of the motor 52 to be urgently stopped for circuit protection. Since the specific values of the overcurrent determination value and the overload determination value depend on the specifications of the motor 52, they are specifically determined for each motor specification through simulation and experiment at the time of design. Various circuit configurations of the overcurrent determination value output unit 100 and the overload determination value output unit 96 are conceivable. As an example, a voltage dividing circuit as shown on the right in FIG. 6A is used.

  After determining the overcurrent state and stopping the rotation of the motor 52, the application of voltage to the coil of the stator 14 is interrupted for a predetermined time to prevent the circuit from burning out. The predetermined time is, for example, 100 milliseconds, and the application of voltage to the coil is interrupted for 100 milliseconds. Thereafter, the voltage application is resumed. If the overcurrent determination value is exceeded, the voltage application is interrupted again. If the state is repeated a predetermined number of times, it is determined that there is a high risk of circuit burnout, and the application of voltage again is stopped.

  When it is determined that the motor 52 is in an overload state and the rotation speed of the motor 52 is 500 rpm, the rotation speed of the motor 52 is controlled to 500 rpm until the current value detected by the current detection unit 94 falls below the overload determination value. After the current value detected by the current detector 94 falls below the overload determination value, the voltage applied to the coil of the stator 14 is set so that the motor 52 rotates at the target rotational speed calculated by the command rotational speed calculator 58. Control.

  FIG. 4 is a flowchart showing overload protection control in the motor control apparatus according to the present embodiment. The overload protection control is started when the overload determination unit 98 determines that the current value detected by the current detection unit 94 is equal to or higher than the overload determination value. In step 400, the rotation speed of the motor 52 is controlled to 500 rpm. In step 402, it is determined whether or not the current value detected by the current detection unit 94 in the overload determination unit 98 is equal to or greater than the overload determination value. If the determination is affirmative, the procedure is returned to step 400, and the control for setting the rotation speed of the motor 52 to 500 rpm is continued. If the determination in step 402 is negative, the overload protection control is terminated by controlling the rotational speed of the motor 52 to the target rotational speed in step 404.

  In the present embodiment, the circuit overcurrent state and the circuit overload state are determined depending on whether or not the current value detected by the current detection unit 94 provided between the inverter circuit 40 and the battery 80 is equal to or greater than a predetermined threshold value. Each is judged. Since the overcurrent state and overload state of the circuit are determined based on the actually measured current value in this way, the determination is quicker than when the circuit overcurrent state or the circuit overload state is determined from the heat generation state of the circuit. Is possible.

  Furthermore, in the present embodiment, in the overload state where the circuit current value is not as large as the overcurrent state, the motor 52 continues to rotate at 500 rpm, which is lower than the target rotation speed, until the overload state is resolved. Even in an overload state, the operation of the vehicle air conditioner can be continued.

[Second Embodiment]
FIG. 5 is a diagram showing an outline of a motor control device according to the second embodiment of the present invention. In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description of the same components as those in the first embodiment is omitted. In this embodiment, a bridge circuit is configured in which the end (output end) of the chip thermistor RT to which the resistor R3 is connected and the output end of the overload determination value output unit 96 are connected via the bridge resistor RB. This is different from the first embodiment. As long as the bridge circuit can be configured, other connection means such as a conductor or a diode may be used in addition to the bridge resistor RB.

  FIG. 6A is a schematic diagram showing the chip thermistor RT and the overload determination value output unit 96 in the first embodiment. The overload determination value output unit 96 includes resistors R1 and R2, and constitutes a voltage dividing circuit that outputs the control voltage Vcc as the overload threshold voltage VP. The chip thermistor RT is also a resistor whose resistance value changes with temperature, and forms a voltage dividing circuit that outputs the control voltage Vcc as the chip thermistor voltage VT together with the resistor R3.

  FIG. 6B is a schematic diagram showing the connection between the chip thermistor RT and the overload determination value output unit 96 in the present embodiment. The overload judgment value output unit 96 and the chip thermistor RT each form a voltage dividing circuit as in the first embodiment, but in this embodiment, both voltage dividing circuits are connected by a bridge resistor RB. doing.

The resistance values of the resistors shown in FIGS. 6A and 6B are as follows as an example, except for the chip thermistor RT whose resistance value varies with temperature. Further, the bridge resistance RB is changed stepwise in the range of 10 to 90 kΩ as will be described later, and an optimum resistance value is selected in order to eliminate the overload state.
R1: 49.9kΩ
R2: 30.1kΩ
R3: 3.57 kΩ
RB: 10 to 90 kΩ

FIG. 7 is a schematic diagram illustrating a relationship among a current value, a voltage value, and a resistance value in a bridge circuit between the chip thermistor RT and the overload determination value output unit 96 according to the present embodiment. The resistance value of the resistor R1 _{R 1,} the resistance value of the resistor R2 _{R 2,} the resistance value of the resistor R3 _{R 3,} the resistance value of the chip thermistor RT _{R T,} the resistance value of the bridge resistor RB and _{R B.} The current value of the current I1 flowing through the resistor R1 is I ₁ , the current value of the current IB flowing through the bridge resistor RB is I _B , the current value of the current I3 flowing through the resistor R3 is I ₃ , and the voltage value of the overload threshold voltage VP Is V _P , and the voltage value of the chip thermistor voltage VT is V _T , the following equations (1) to (5) are derived.

Further, from FIG. _{7, I 3 = (Vcc-} V T) / R 3, I B = (V P -V T) / from _R is _B, and these _I 3, the _{I B} of the formula (5) When substituted, the following equation (6) is obtained.

From the above formula (6) and the above formulas (1) to (4), the following formulas (7) and (8) are obtained.

  FIG. 8 is a diagram illustrating an example of a change in the overload threshold voltage VP corresponding to a change in the resistance value of the bridge resistor RB in the present embodiment. Using the above equation (7), Vcc is 5 V, the resistance value of the bridge resistor RB is 10, 20, 30, 40, 50, 60, 70, 80, 90 kΩ and the resistance value is infinite when the bridge resistor RB is not mounted. The overload threshold voltage VP is calculated by changing each largely.

  As shown in FIG. 8, the overload threshold voltage VP is high when the temperature of the chip thermistor RT is low, and it is excessive when the temperature of the chip thermistor RT is high, compared to an infinite case where the bridge resistor RB is not mounted. The load threshold voltage VP is lowered. The chip thermistor RT used in the present embodiment is an NTC thermistor whose resistance decreases as the temperature rises, as in the first embodiment. Therefore, when the temperature of the circuit rises and the resistance value of the chip thermistor RT decreases, the voltage of the overload determination value output unit 96 is easily divided to the chip thermistor RT side via the bridge resistor RB, and the overload threshold voltage VP Decreases.

  If the overload threshold voltage VP decreases, the overload determination value that is a current value also decreases, and the overload state can be determined more quickly. In particular, an overload often accompanies circuit overheating, so if the overload threshold voltage VP decreases when the temperature of the chip thermistor RT is high, the overload threshold voltage VP does not decrease at a high temperature more quickly. It is possible to quickly determine whether the circuit is burned out.

  When this embodiment is mounted on a vehicle air conditioner, an overload threshold voltage VP at a safe temperature at which the circuit does not burn out is obtained from the results or experiments of FIG. By selecting the bridge resistance, it is possible to determine overload to prevent circuit burnout. For example, if the safe temperature at which the circuit does not burn out is 140 ° C. and the overload threshold voltage VP is set to 1.5 V or less at 140 ° C., the resistance value of the bridge resistor RB is set to 20 kΩ.

  FIG. 9 is a diagram illustrating an example of a change in the chip thermistor voltage VT corresponding to a change in the resistance value of the bridge resistor RB in the present embodiment, and is calculated using the above equation (8). As shown in FIG. 9, even if the value of the bridge resistor RB changes, the value of the chip thermistor voltage VT does not change greatly. Even in the present embodiment in which the bridge circuit is configured, the circuit by the overheat state determination unit 106 There is no hindrance in judging the overheating state.

  As described above, in the present embodiment, the overload judgment value output unit 96 and the chip thermistor RT, each of which constitutes a voltage dividing circuit, are connected by the bridge resistor RB, so that overload is likely to occur. When the temperature is high, the overload state can be quickly determined.

[Third Embodiment]
FIG. 10 is a diagram showing an outline of a motor control device according to the third embodiment of the present invention. In FIG. 10, the same components as those in the first embodiment and the second embodiment described above are denoted by the same reference numerals, and the same components as those in the first embodiment and the second embodiment. The detailed description of is omitted. The present embodiment is different from the second embodiment in that a parallel resistor RP is provided in the chip thermistor RT.

  FIG. 11A is a schematic diagram showing the connection between the chip thermistor RT and the overload determination value output unit 96 in the second embodiment. The overload judgment value output unit 96 and the chip thermistor RT each constitute a voltage dividing circuit, and both voltage dividing circuits are connected by a bridge resistor RB. FIG. 11B is a schematic diagram showing the connection between the chip thermistor RT and the overload determination value output unit 96 in the present embodiment. The overload judgment value output unit 96 and the chip thermistor RT each constitute a voltage dividing circuit, and both voltage dividing circuits are connected by a bridge resistor RB, but are connected in parallel to the chip thermistor RT. A parallel resistor RP is separately provided.

The resistance values of the resistors shown in FIG. 11A are the same as those in FIG. The resistance values of the resistors shown in FIG. 11B are as follows as an example, except for the chip thermistor RT whose resistance value varies with temperature. Further, the parallel resistance RP is changed stepwise in the range of 10 to 90 kΩ as will be described later, and an optimum resistance value is selected in order to eliminate the overload state.
R1: 49.9kΩ
R2: 30.1kΩ
R3: 3.57 kΩ
RB: 20 kΩ
RP: 10-90kΩ

  In the present embodiment, the chip thermistor RT and the parallel resistor RP are regarded as one combined resistor, and the overload threshold voltage VP and the chip thermistor voltage VT are calculated using the aforementioned equations (7) and (8).

  FIG. 12 is a diagram illustrating an example of a change in the overload threshold voltage VP corresponding to a change in the resistance value of the parallel resistor RP in the present embodiment. In FIG. 12, the resistance value of the bridge resistor RB is 20 kΩ, the resistance value of the parallel resistor RP is 10, 20, 30, 40, 50, 60, 70, 80, 90 kΩ, and the resistance value is infinite when the parallel resistor RP is not mounted. The overload threshold voltage VP is calculated by changing each largely. In any case, the overload threshold voltage VP is lower in a higher temperature range than in the case of no bridge where the bridge resistor RB is not mounted. However, the overload threshold voltage VP is the same temperature as in the case of no bridge. A difference is observed between the equilibrium temperature and the overload threshold voltage VP in a low temperature range below the equilibrium temperature. In the present embodiment, a parallel resistance RP is connected in parallel to the chip thermistor RT, whereby a change in resistance value due to the temperature of the chip thermistor RT is suppressed by the parallel resistance RP. As a result, in the low temperature range below the equilibrium temperature, the overload threshold voltage VP is lower than that without the parallel resistor RP. The overload threshold voltage VP in the low temperature region decreases as the resistance value of the parallel resistor RP decreases, and approaches the overload threshold voltage VP in the low temperature region when the bridge resistor RB is not mounted.

  When the bridge resistor RB is mounted, the overload threshold voltage VP can be lowered in the high temperature range as in the second embodiment. However, in the low temperature range, the overload threshold voltage VP becomes higher than that in the case where the bridge resistor RB is not mounted, and there is a possibility that the control of the overload determination in the low temperature range may be hindered. In the present embodiment, since the increase of the overload threshold voltage VP in the low temperature range below the equilibrium temperature is suppressed, the risk of hindering the control of the overload determination in the low temperature range can be reduced.

  Further, the lower the resistance value of the parallel resistor RP, the lower the equilibrium temperature. FIG. 13 is an enlarged view around the equilibrium temperature of FIG. In FIG. 13, when the parallel resistance RP is not mounted, the equilibrium temperature is 110 ° C., but when the parallel resistance RP of 20 kΩ is mounted, the parallel temperature RP of 106 ° C. and 10 kΩ is mounted. In this case, the equilibrium temperature becomes 102 ° C.

  When the bridge resistor RB is mounted, the overload threshold voltage VP is lower than the case without the bridge when the temperature is equal to or higher than the equilibrium temperature regardless of the presence or absence of the parallel resistor RP, but the equilibrium temperature may be decreased by mounting the parallel resistor RP. it can. By reducing the equilibrium temperature, it is possible to lower the overload threshold voltage VP from a lower temperature than when no bridge is present, and it is possible to quickly determine an overload state prior to a temperature rise due to circuit overheating. .

  FIG. 14 is a diagram illustrating an example of a change in the chip thermistor voltage VT corresponding to a change in the resistance value of the parallel resistor RP in the present embodiment. When the parallel resistor RP is mounted, the chip thermistor voltage VT is reduced in a low temperature range. However, in this embodiment, 145 ° C. is set as a temperature for determining the overheat state. There is no problem in the determination of the overheating state of the circuit by 106.

  As described above, according to the present embodiment, by providing the chip thermistor RT with the parallel resistor RP, the characteristics of the chip thermistor RT whose resistance value increases in the low temperature region are alleviated by the parallel resistor RP. An increase in the load threshold voltage VP is suppressed. Therefore, since the overload threshold voltage VP can be lowered from a lower temperature range than when the parallel resistor RP is not mounted, it is possible to quickly determine the overload state prior to the temperature rise due to overheating of the circuit.

[Fourth Embodiment]
FIG. 15 is a diagram schematically showing a motor control device according to the fourth embodiment of the present invention. In FIG. 15, the same components as those in the first to third embodiments are denoted by the same reference numerals, and detailed description of the same components as those in the first to third embodiments is omitted. In the present embodiment, apart from the chip thermistor RT1, a chip thermistor RT2 is provided, in which a control voltage Vcc is applied to one end via a resistor R4 and the other end is grounded, and the temperature of the substrate is detected as a resistance value. Is different from the third embodiment.

  The chip thermistor RT2 used in the present embodiment is an NTC thermistor whose resistance decreases with increasing temperature, and forms a kind of voltage dividing circuit together with the resistor R4. Further, one end of the chip thermistor RT2 connected to the resistor R4 is connected to the overheat state determination unit 106.

  FIG. 16A is a schematic diagram showing the connection between the chip thermistor RT and the overload determination value output unit 96 in the third embodiment. FIG. 16B is a schematic diagram showing the connection between the chip thermistor RT1 and the overload determination value output unit 96 in the present embodiment. In FIG. 16B, the overload determination value output unit 96 and the chip thermistor RT1 corresponding to the chip thermistor RT of FIG. 16A each constitute a voltage dividing circuit, and both voltage dividing circuits are connected by a bridge resistor RB. This is the same as FIG. 16A in that a parallel resistor RP connected in parallel to the chip thermistor RT1 is additionally provided. However, in the present embodiment shown in FIG. 16B, the chip thermistor RT2 and the resistor R4 provided separately from the chip thermistor RT1 form a voltage dividing circuit. In addition, the voltage output from the voltage dividing circuit constituted by the chip thermistor RT2 and the resistor R4 is input to the overheat state determination unit 106 as the chip thermistor voltage VT.

  The overheat state determination unit 106 determines that the motor is in an overheat state when the temperature detected by the chip thermistor RT2 is equal to or higher than the temperature indicated by the overheat state determination value. For example, when the chip thermistor RT2 is an NTC thermistor, the voltage output from the voltage dividing circuit composed of the chip thermistor RT2 and the resistor R4 decreases as the substrate temperature rises. Therefore, the overheat state determination unit 106 determines that the temperature detected by the chip thermistor RT2 is equal to or higher than the temperature indicated by the overheat state determination value when the voltage output from the voltage dividing circuit is equal to or lower than the voltage of the overheat state determination value. To do.

  As shown in FIGS. 15 and 16B, in this embodiment, the voltage output from the circuit including RT1 to which the parallel resistor RP is connected is not used for the determination of the overheat state, and the parallel resistor is connected. The voltage output from the voltage dividing circuit including the chip thermistor RT2 that has not been used is used to determine the overheated state. As a result, the voltage dividing circuit constituted by the chip thermistor RT2 and the resistor R4 is not affected by the parallel resistor RP, so that the chip thermistor voltage VT does not decrease in the low temperature region as in the third embodiment.

  FIG. 17 is a diagram illustrating an example of a change in the chip thermistor voltage VT with respect to the chip thermistor temperature in the present embodiment. In the present embodiment, as shown in FIG. 17, the chip thermistor voltage VT is not affected by the resistance value of the parallel resistor RP. Therefore, in this embodiment, when the resistance value of the parallel resistor RP is changed, it is not necessary to consider the change in the chip thermistor voltage VT.

  As described above, in the third embodiment, when the resistance value of the parallel resistor RP is changed to adjust the overload threshold voltage VP, the chip thermistor voltage VT also changes depending on the resistance value of the parallel resistor RP. Therefore, it is difficult to arbitrarily change the resistance value of the parallel resistor RP. However, in the present embodiment, as described above, the chip thermistor voltage VT is not affected by the parallel resistance RP, so that the resistance value of the parallel resistance RP is arbitrarily changed in order to adjust the overload threshold voltage VP. Becomes easy.

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, 28 ... Lower case, 40 ... Inverter circuit, 44A, 44B, 44C, 44D, 44E, 44F... Inverter FET, 52... Motor, 54... Comparator, 56... Real rotation speed calculation section, 58... Command rotation speed calculation section, 60. Main power supply energization section, 64 ... energization control drive waveform determination section, 66 ... PI control section, 66I ... deviation integration section, 66P ... deviation proportional section, 68 ... voltage correction section, 70 ··Dora , 78 ... air conditioner ECU, 80 ... battery, 82 ... choke coil, 84A, 84B ... smoothing capacitor, 86 ... logical sum circuit, 88 ... forced 500rpm command section, 94 ..Current detection unit, 94A ... shunt resistor, 94B ... amplifier, 96 ... overload judgment value output unit, 98 ... overload judgment unit, 100 ... overcurrent judgment value output unit, DESCRIPTION OF SYMBOLS 102 ... Overcurrent determination part, 104 ... Overheat determination value output part, 106 ... Overheat state determination part, 130 ... OR circuit, R1, R2, R3, R3, R4 ... Resistance, RB ... Bridge resistance, RP ... Parallel resistance, RT, RT1, RT2 ... Chip thermistor, Vcc ... Control voltage, VP ...... Overload threshold voltage, VT ... Chip thermistor voltage

Claims (7)

Current detection means for detecting a current flowing between the power source and an inverter circuit for generating a voltage to be applied to the motor coil;
First temperature detection means for detecting the temperature of the motor or circuit board;
Overload determination value output means for outputting an overload determination value for determining whether or not the motor is overloaded;
Connecting means for connecting the output of the first temperature detection means and the output of the overload judgment value output means in order to adjust the overload judgment value output by the overload judgment value output means;
Overload determination means for determining that the motor is overloaded when the current value detected by the current detection means is greater than or equal to the overload determination value;
A rotation speed control means for performing control to reduce the rotation speed of the motor to a predetermined speed when the overload determination means determines that the motor is overloaded;
A motor control device comprising: The first temperature detecting means is a thermistor in which a voltage is applied to one end via a resistor and the other end is grounded, and the resistance value decreases as the temperature rises.
The overload determination value is adjusted by dividing the voltage of the overload determination value to the thermistor side via the connecting means in response to a decrease in resistance value of the thermistor as temperature rises. Item 2. The motor control device according to Item 1 . The motor control device according to claim 2 , further comprising a resistor connected in parallel to the first temperature detection means. Second temperature detection means for detecting the temperature of the motor or circuit board independently of the first temperature detection means;
An overheat state determination value output means for outputting an overheat state determination value for determining whether or not the motor is in an overheat state;
An overheat state determination unit that determines that the motor is in an overheat state when the temperature detected by the second temperature detection unit is equal to or higher than the temperature indicated by the overheat state determination value;
The motor control device according to claim 3 , further comprising: The motor control device according to claim 4 , wherein the second temperature detection unit is a thermistor whose resistance value changes according to temperature. It said connection means being connected at one end to an output of said first temperature sensing means and the other end according to any one of the overload judgment value is a resistor connected to an output of the output means according to claim 1 to 5, Motor control device. An overcurrent determination value output means for outputting an overcurrent determination value exceeding the overload determination value;
Overcurrent determination means for determining that the motor is in an overcurrent state when the current value detected by the current detection means is greater than or equal to the overcurrent determination value;
Further comprising
The rotational speed control means when said overcurrent determination means determines that the motor is in an overcurrent state, according to any one of claims 1 to 6 rotating stopping predetermined time of the motor Motor control device.