JP5032615B2 - Electric motor drive device, molded motor, air conditioner, refrigerator and ventilation fan - Google Patents

Description

  The present invention relates to a drive device for an electric motor such as a DC brushless motor, and relates to a technique for preventing an excessive increase in the temperature of the motor.

  In the field of refrigeration and air conditioners, etc., three-phase DC brushless motors are used. However, when an abnormal state such as motor lock or overload occurs, the motor temperature rises excessively and the motor windings are damaged. Insulation failure may occur and various electric and electronic circuits built in the motor may be destroyed.

  As a countermeasure, in a conventional DC brushless motor drive device, when the motor temperature becomes equal to or higher than the reference temperature, the temperature discriminating unit detects, and the drive unit thereby limits the ON period of a plurality of switch elements and supplies it to the motor. The drive current is suppressed, and the situation where the temperature of the motor is erroneously excessively increased is prevented (for example, see Patent Document 1).

JP-A-10-201280 JP 2002-354870 A

  Conventional DC brushless motor drive devices use a temperature-sensitive resistor element in the overcurrent detection circuit, but due to variations in temperature-resistance change characteristics, the temperature operating range of the motor's overheat protection is wide, and overheat protection There was a problem with accuracy.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric motor drive device that has a narrow temperature operating range for overheating protection of a motor and can perform overheating protection with high accuracy. .

An electric motor drive device according to the present invention includes a DC power source connected to a power line,
An inverter circuit having a plurality of switch elements and converting the DC power of the DC power source into pseudo AC power;
An electric motor having a coil of a plurality of phases and having a drive current supplied from the inverter circuit to each phase coil;
A temperature-sensitive resistance element provided in the electric motor, the electric resistance value changes depending on the temperature, and connected to the power supply line through the transistor;
An overcurrent detection circuit having a comparison circuit that compares the detected temperature of the electric motor detected by the temperature-sensitive resistance element with a predetermined reference temperature and detects whether the detected temperature is equal to or higher than the reference temperature;
When a plurality of switch elements are individually turned on / off, and the comparison circuit detects that the temperature is higher than the reference temperature, the ON period of the plurality of switch elements is limited to reduce the drive current supplied to the motor. A drive unit to suppress,
The transistor is normally in an on state, and the transistor shifts from an on state to an off state while the detected temperature of the electric motor rises.

  With the above configuration, the motor driving device according to the present invention has a narrow temperature operation range for overheat protection, can increase the accuracy with respect to temperature changes, and can improve the accuracy of overheat protection.

FIG. 3 is a diagram illustrating the first embodiment and is a circuit diagram illustrating an electrical configuration of the driving device. FIG. 3 is a diagram illustrating the first embodiment and is a diagram illustrating an overcurrent detection circuit. FIG. 5 shows the first embodiment and is a diagram showing another example of an overcurrent detection circuit. It is a figure which shows Embodiment 1, and is a figure which shows the resistance temperature characteristic of a temperature sensitive resistive element. It is a figure which shows Embodiment 1, and is a figure which shows the relationship of a temperature-current limiting value. It is a figure which shows Embodiment 1, 2, and is a figure which shows the structure of an electric motor. It is a figure which shows Embodiment 3, and is a figure which shows a wall-hanging type air conditioner. It is a figure which shows Embodiment 3, and is a figure which shows the structure of the same indoor unit. It is a figure which shows Embodiment 4, and is a figure which shows the indoor unit of a ceiling embedded type air conditioner. FIG. 6 is a diagram illustrating the fourth embodiment, and is a diagram illustrating the outdoor unit. It is a figure which shows Embodiment 5, and is a figure which shows a refrigerator. It is a figure which shows Embodiment 6, and is a figure which shows a ventilation fan.

Embodiment 1 FIG.
1 to 6 are diagrams showing the first embodiment, FIG. 1 is a circuit diagram showing the electrical configuration of the driving device, FIG. 2 is a diagram showing an overcurrent detection circuit, and FIG. 3 is another example of the overcurrent detection circuit. FIG. 4 is a diagram showing the resistance-temperature characteristics of the temperature-sensitive resistance element, FIG. 5 is a diagram showing the relationship between temperature and current limit values, and FIG. 6 is a diagram showing the configuration of the motor.

  As shown in FIG. 1, the driving device 21 includes an inverter circuit 28, a gate drive circuit 29, a three-phase distribution circuit 30, a PWM circuit 32, an overcurrent detection circuit 35, and a DC power supply 40. Yes.

  The drive unit includes a gate drive circuit 29 and a three-phase distribution circuit 30.

  The electric motor 22 has three phases, and a stator having three coils 23, 24, and 25 to which U-phase, V-phase, and W-phase drive signals Iu, Iv, and Iw are supplied, and a pair of magnetic poles. The rotor 26 which consists of a permanent magnet etc. which has is provided.

  In addition, the electric motor 22 includes a hall element or the like for detecting the rotational speed of the rotor 26, and includes a magnetic pole detection element 27 that outputs magnetic pole signals Hu, Hv, and Hw for each phase.

  The coils 23, 24, and 25 of the electric motor 22 are connected to an inverter circuit 28 that supplies U-phase, V-phase, and W-phase drive signals Iu, Iv, and Iw, respectively. The inverter circuit 28 is provided with six transistors Q1, Q2, Q3, Q4, Q5, and Q6. Diodes D1, D2, D3, D4, D5, and D6 are connected in parallel to each of the transistors Q1 to Q6. The anodes of the diodes D1 to D6 are connected to the emitters of the transistors Q1 to Q6, and the transistors Q1 to Q6 are connected to the DC power supply 40.

  U-phase, V-phase, and W-phase drive signals Iu, Iv, and Iw are output from the connection points of the transistors Q1, Q4; Q2, Q5; Q3, Q6, respectively. The collectors of the transistors Q1 to Q3 are connected to the DC power supply 40 via the power supply line 39, and the emitters of the transistors Q4 to Q6 are connected to the negative electrode of the DC power supply 40 via the power supply line 39.

  The magnetic pole detection element 27 is connected to the three-phase distribution circuit 30. The output of the three-phase distribution circuit 30 is input to a gate drive circuit 29 that outputs a control signal for turning on / off each of the transistors Q1, Q2, Q3, Q4, Q5, and Q6. On the other hand, a PWM (pulse width conversion) circuit 32 and an overcurrent detection circuit 35 are connected to the three-phase distribution circuit 30.

  In the PWM circuit 32, the signal from the speed command input unit is compared with the triangular wave from the triangular wave generation circuit by the comparison circuit, and the PWM signal in the ON period corresponding to a predetermined rotational speed is output to the three-phase distribution circuit 30.

  The outline of the configuration of the overcurrent detection circuit 35 is as follows.

  That is, the overcurrent detection circuit 35 includes, as an example, a comparison circuit 36 (described later) in which a voltage between terminals of a current detection resistor 41 connected in series to the power supply line 39 is input to one input terminal, and a comparison circuit 36. And a reference power source 37 for inputting a predetermined reference voltage to the other input terminal. The output of the comparison circuit 36 is input to the three-phase distribution circuit 30.

  Hereinafter, a detailed configuration example of the overcurrent detection circuit 35 will be described with reference to FIG.

  As shown in FIG. 2, the overcurrent detection circuit 35 includes a power supply line 39 and a resistor, a capacitor, a reference potential, a digital transistor, a temperature sensitive resistance element, and a comparison circuit connected thereto.

  The power supply line 39 is connected to a current detection resistor 41 in which resistance values R13 and R14 are connected in parallel, and one end thereof is grounded. At this time, the potential V1 between the current detection resistor 41 and the power supply line 39 becomes V0 via the resistor R159 and is connected to the comparison circuit 36.

  The potential of V0 is grounded by the capacitor C1512. On the other hand, one end of the temperature sensitive resistance element RT1 42 is grounded from the reference voltage VB2, and the other end is grounded from the resistance voltage dividing resistor R171 and the capacitor C1811. At this time, the reference potential VB3 is connected to the base side of a digital transistor (transistor with transistor) Q75, the collector side is connected to the reference potential VB3 via the resistor R166, and the emitter is grounded. The reference potential VB2 and the reference potential VB3 are the same voltage.

  At this time, the reference potential VB2 is connected to the potential V0 by the resistor R127. The potential of V0 is taken into the comparison circuit 36. Further, the other input terminal of the comparison circuit 36 is connected to a reference power source 37 having a reference potential Vref.

  The temperature sensitive resistance element RT1 42 is mounted on, for example, a substrate in a mold of the electric motor 22 whose temperature is to be detected (see FIG. 6).

  As the temperature sensitive resistance element RT1 42, for example, an n-type valence control type semiconductor in which a trace amount of rare earth element is added to barium titanate is suitable. As an example of such a temperature sensitive resistance element RT <b> 1 42, the use of Posister (registered trademark, Murata Manufacturing Co., Ltd.) is optimal. An example of the temperature-resistance change ratio characteristic of the temperature-sensitive resistance element RT1 42 used in this embodiment is shown in the graph of FIG.

  In the overcurrent detection circuit of FIG. 2, an example in which the digital transistor (transistor-containing transistor) Q75 is used is shown, but a combination of the transistor Q8 and a resistor may be used as shown in FIG.

  The overcurrent detection circuit 35 shown in FIG. 2 was mounted on the driving device 21 shown in FIG. 1 to perform an overheat protection test of the motor.

  The electric motor used in the test is a DC brushless motor in which a stator and a substrate on which a temperature sensitive resistance element RT1 42 is mounted are integrally molded with a mold resin 25 as shown in FIG. is there.

  Further, the above-described Posister (registered trademark, Murata Manufacturing Co., Ltd.) PRF18BE471 was used for the temperature sensitive resistance element RT1 42.

  With respect to the DC brushless motor, the relationship between the motor input current and the motor temperature was investigated by locking the rotor of the DC brushless motor in an atmosphere of room temperature to 110 ° C.

  The results are shown in the graph of FIG.

  FIG. 5 shows current limit value temperature characteristics in curves A, B, and C in a conventional driving device (for example, Patent Document 1). A, B, and C correspond to those in FIG.

  On the other hand, the current limit value temperature characteristics according to the present embodiment are as shown by curves 17, 23 and 18 in FIG.

  As can be seen, the current limiting range 20 by the driving device of the present embodiment is narrower and the slope becomes steeper than the current limiting range 19 by the conventional driving device. This makes it possible to limit the current with high accuracy and little variation. As a result, the temperature range of the operation operation of the indoor unit 46 of the drive device of the present embodiment is wider than the operation temperature range 45 of the conventional drive device, and the temperature range of the stable operation of the motor is widened. It became clear that performance improved.

  The above result is obtained by the driving device 21 of the present embodiment. When the temperature of the electric motor 22 rises due to locking or overloading and exceeds the Curie temperature of the temperature sensitive resistance element RT1 42, the resistance change ratio of the temperature sensitive resistance element RT1 42 rapidly increases. As a result, the reference potential VB3 at one end of the temperature sensitive resistance element RT1 42 in FIG. 2 is lowered, and the normally-on digital transistor Q75 is turned off, thereby raising the potential V0. When the voltage V0 exceeds the reference potential Vref of the reference power source 37, an overcurrent detection signal is output from the comparison circuit 36, the overcurrent detection circuit 35 outputs an overcurrent detection signal, and the three-phase distribution circuit 30 detects this detection signal. Is output to the gate drive circuit 29 to shorten the on-time of each of the transistors Q1 to Q6 of the inverter circuit 28 and suppress the drive current.

  Thereby, the situation where the temperature of the electric motor 22 rises excessively can be prevented. That is, an equilibrium state is reached at a temperature at which the temperature of the electric motor 22 that generates heat by the suppressed supply of drive current and the detected temperature of the temperature sensitive resistance element RT1 42 corresponding to the current limit value are balanced.

  However, even if the drive current is suppressed, if the temperature of the electric motor 22 continues to rise due to some external factor, the drive current is further suppressed and finally the supply of the drive current is stopped.

  Further, when the electric motor 22 is released from the locked state or the overload state, the temperature of the electric motor 22 is lowered, so that the resistance value of the temperature sensitive resistance element RT1 42 returns to a normal value, and a predetermined output is obtained to the electric motor 22. Automatically returns to a state where a sufficient current can be supplied.

  The limit signal is output to the gate drive circuit 29, and the on-time of each of the transistors Q1 to Q6 of the inverter circuit 28 is shortened to suppress the drive current.

  Further, the element used as the temperature-sensitive resistance element RT1 42 in this embodiment exhibits a substantially constant resistance until the external temperature reaches the Curie temperature from the normal temperature, and becomes steep when the external temperature exceeds the Curie temperature. Since it shows a positive temperature-resistance change, when the motor 22 is rotating normally, it is set as the specification of the motor 22 until the temperature of the motor 22 reaches an excessively high temperature such as a temperature exceeding the Curie temperature. A sufficient current can be supplied to the electric motor 22 to obtain the current output.

  Further, when the electric motor 22 becomes excessively high in temperature, the resistance element RT1 42 rapidly increases the resistance value, so that the overcurrent detection circuit 35 quickly limits the driving current value supplied to the electric motor 22, or Cut off. Thereby, the overcurrent detection circuit 35 of the present embodiment can reliably protect the electric motor 22 from an excessively high temperature.

  On the other hand, when the electric motor 22 rotates normally and its temperature is normal temperature, the temperature of the temperature-sensitive resistance element RT1 42 is less than the Curie temperature, and the current limit value in the driving device 21 is relatively large. Sufficient current is supplied to obtain the output.

  That is, in this case, the three-phase distribution circuit 30 outputs an energization on signal to the electric motor 22. Thereby, the gate drive circuit 29 turns on / off each of the transistors Q1 to Q6 at a timing corresponding to a predetermined rotation speed when the electric motor 22 is not locked and therefore no overcurrent flows.

  In the present embodiment, the configuration of the overcurrent detection circuit shown in FIG. 2 makes it possible to limit the current with high accuracy by narrowing the temperature range of the overheat protection of the electric motor 22 and widen the operating temperature range of the electric motor 22. I can take it.

  By indirectly disconnecting one end of the temperature sensitive resistance element RT1 42 from the power supply line 39 via the digital transistor Q75, an effect of preventing destruction of the temperature sensitive resistance element RT1 42 due to surge or noise is obtained.

  Further, by indirectly disconnecting from the power supply line 39, the degree of freedom of arrangement of the temperature sensitive resistance element RT1 42 is increased, and circuit design and mounting wiring are facilitated.

  In addition, by connecting one end of the temperature-sensitive resistance element RT1 42 to the reference voltage VB2, the voltage is stabilized and the accuracy of the voltage drop rate due to the temperature of the temperature-sensitive resistance element RT1 42 is improved, so that the overheat protection is highly accurate. it can.

Embodiment 2. FIG.
FIG. 6 is also a diagram showing the second embodiment, and shows an example of an electric motor using the drive device of the first embodiment.

  In the figure, the driving device of the first embodiment is mounted on the main body substrate 8. The main body substrate 8 is integrally formed with a mold resin 25 together with a stator having a stator core 13. Drive signals Iu, Iv, and Iw are supplied from the connector 14 to the electric motor.

  The outer shell material may be a steel plate.

  By using the main body substrate 8 on which the driving device of the first embodiment is mounted, a good quality molded motor can be obtained.

Embodiment 3 FIG.
7 and 8 are diagrams showing Embodiment 3, FIG. 7 is a diagram showing a wall-mounted air conditioner, and FIG. 8 is a diagram showing a configuration of the indoor unit.

  7, the wall-mounted air conditioner includes an indoor unit 46 and an outdoor unit 47. The indoor unit 46 uses an indoor unit blower 48b (see FIG. 8), and the outdoor unit 47 uses an outdoor unit blower 31a. ing.

  The outdoor unit blower 31a and the indoor unit blower 31b are driven by the electric motor of the second embodiment.

  In recent years, noise reduction has progressed in air conditioners, and it is preferable to use the electric motor of Embodiment 2 as a blower motor that is a main part of the air conditioner.

  By configuring in this way, the quality of the blower of the wall-mounted air conditioner is improved.

Embodiment 4 FIG.
FIGS. 9 and 10 are diagrams showing Embodiment 4, FIG. 9 is a diagram showing an indoor unit of a ceiling-embedded air conditioner, and FIG. 10 is a diagram showing the outdoor unit.

  As shown in FIG. 9, the indoor unit of the ceiling embedded air conditioner uses a blower 49. The quality of the blower 49 and the ceiling-embedded air conditioner is improved by mounting the electric motor shown in the second embodiment on the blower 49.

  As shown in FIG. 10, the outdoor unit of the ceiling-embedded air conditioner also uses the blower 50. By mounting the electric motor shown in the second embodiment on the blower 50, the quality of the blower 50 and the ceiling-embedded air conditioner is improved.

Embodiment 5 FIG.
FIG. 11 is a diagram showing the fifth embodiment and is a diagram showing a refrigerator.

  As shown in the figure, the refrigerator includes a blower 51 in the cooling chamber for sending the cold air generated by the cooler to the cooling chamber to the refrigerator compartment, the freezer compartment, and the like.

  By installing the electric motor shown in the second embodiment on the blower 51, the quality of the blower 51 and the refrigerator is improved.

Embodiment 6 FIG.
FIG. 12 is a diagram showing the sixth embodiment and is a diagram showing a ventilation fan.

  As shown in the figure, the ventilation fan includes a blower 52 for performing a ventilation operation.

  By mounting the electric motor shown in the second embodiment on the blower 52, the quality of the blower 52 and the ventilation fan is improved, and noise reduction can be realized.

  1 resistor R17, 2 reference potential VB, 3 reference potential VB, 4 resistor R16, 5 digital transistor Q7, 7 resistor R12, 8 body substrate, 9 resistor R15, 11 capacitor C18, 12 capacitor C15, 13 stator core, 14 connector , 21 Driving device, 22 Electric motor, 25 Mold resin, 28 Inverter circuit, 29 Gate drive circuit, 30 Three-phase distribution circuit, 35 Overcurrent detection circuit, 36 Comparison circuit, 37 Reference power supply, 39 Power supply line, 40 DC power supply, 41 Resistance for current detection, 42 Temperature sensitive resistance element RT1, 46 Indoor unit, 47 Outdoor unit, 48a Blower for outdoor unit, 48b Blower for indoor unit, 49-52 Blower.

Claims (7)

DC power supply connected to the power line,
An inverter circuit having a plurality of switch elements and converting the DC power of the DC power source into pseudo AC power;
An electric motor having a coil of a plurality of phases, and a drive current is supplied to each phase coil from the inverter circuit;
A temperature-sensitive resistance element provided in the electric motor, the electric resistance value of which varies with temperature;
An overcurrent detection circuit having a comparison circuit that detects whether or not the detected temperature is equal to or higher than the reference temperature by comparing the detected temperature of the electric motor detected by the thermosensitive resistance element with a predetermined reference temperature;
The plurality of switch elements are individually turned on / off, and when the comparison circuit detects that the reference temperature is higher than the reference temperature, the ON period of the plurality of switch elements is limited and supplied to the electric motor. A drive unit that suppresses the drive current generated;
Equipped with a,
The overcurrent detection circuit includes a transistor,
The comparison circuit has two input terminals;
One end of the temperature-sensitive resistance element is connected to the reference potential VB , the other end is grounded via a resistor and a capacitor, and is connected to the base side of the transistor,
It said reference potential VB through a resistor to the collector of the transistor is connected to the emitter of the transistor is grounded, the collector side of the transistor is connected to one input terminal of the comparator circuit via a resistor,
The power supply line to which the current detection resistor is connected is connected to the one input terminal of the comparison circuit via a resistor ,
A reference potential V _ref is connected to the other input terminal of the comparison circuit,
The transistor is a normally on state, the electric motor of the detected temperature is the way the transistor driving device to that electric motive means shifts from the ON state to the OFF state to increase. The motor drive device according to claim 1, wherein one input terminal of the comparison circuit is grounded via a capacitor.   3. The motor driving apparatus according to claim 1, wherein the transistor is a digital transistor.   4. A molded electric motor comprising a substrate on which the electric motor driving device according to claim 1 is mounted together with a stator in a mold resin.   An air conditioner comprising the molded motor according to claim 4 mounted as a blower motor.   A refrigerator comprising the molded motor according to claim 4 as a blower motor.   A ventilation fan comprising the molded electric motor according to claim 4 mounted as an electric motor for a blower.

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