JP4998070B2 - Brushless motor - Google Patents

Description

  The present invention relates to a drive control technique for a brushless motor.

  As a brushless motor, for example, one described in Patent Document 1 below is known.

JP 2001-298882 A

  In a conventional brushless motor, a rectangular wave is generally used as a drive signal. When a rectangular wave drive signal is used, the motor may be overheated by an excessive current generated when the polarity of the drive signal is reversed. Therefore, a conventional brushless motor is generally provided with a circuit for limiting excess current.

  FIG. 15 shows an example of an excess current limiting circuit used in a conventional brushless motor. In this circuit, an excess current detection transistor PT and an excess current sensor ECS are provided on the ground side of the bridge circuit HB that drives the coil C of the brushless motor. When excessive current flows through the bridge circuit HB, it is detected by the excessive current sensor ECS that excessive current has flowed. The drive circuit limits the applied voltage and applied current to the coil C according to the output signal of the excess current sensor ECS.

  It is desirable to limit the excess current only in an abnormal situation such as when the load becomes excessive. However, since a considerably large current flows at the time of starting the motor, the current limit may act at the time of starting and the current may be excessively limited. Thus, if the current is excessively limited at the time of starting, there is a problem that sufficient torque may not be generated.

  An object of the present invention is to provide a technique capable of preventing overheating of a motor in a brushless motor without excessively limiting the current.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
One aspect of the present invention is a brushless motor,
A coil array having a plurality of electromagnetic coils;
A magnet array having a plurality of permanent magnets;
A magnetic sensor for detecting a relative position of the magnet array and the coil array;
A drive control circuit that uses the output of the magnetic sensor to drive the coil array using a drive element;
A temperature sensor for detecting a detection target temperature associated with one of the coil temperature of the coil array and the temperature of the drive element;
With
The drive control circuit includes:
A driver circuit composed of a plurality of drive transistors for supplying current to the coil array;
A drive signal generation circuit for generating a drive signal for controlling the plurality of drive transistors of the driver circuit;
With
The drive signal generation circuit includes:
A temperature monitoring circuit that generates a temperature monitoring signal whose signal level changes according to the detection target temperature, based on the output of the temperature sensor;
A waveform signal that generates a waveform signal that exhibits the same change as an analog change in the output of the magnetic sensor and has an amplitude proportional to the signal level of the temperature monitor signal based at least on the temperature monitor signal and the output of the magnetic sensor A generator,
A PWM control circuit that performs PWM control using the waveform signal and generates the drive signal showing the same effective voltage change as the change of the waveform signal;
Including
The drive control circuit reduces the effective value of the drive voltage supplied to the coil array when the detection target temperature detected by the temperature sensor exceeds a predetermined first threshold, and the higher the detection target temperature, the higher the detection target temperature. The drive voltage is adjusted to increase the effective value reduction range, and when the detection target temperature exceeds a predetermined second threshold value that is larger than the first threshold value, the drive voltage is supplied to the coil array. Stop.
According to this brushless motor, since the effective value of the drive voltage supplied to the coil array is reduced when the detection target temperature detected by the temperature sensor exceeds a predetermined first threshold value, an excess current limiting circuit is provided as in the prior art. Compared with the case where the current is provided, the current is not excessively limited, and overheating of the motor can be prevented. Furthermore, since the drive voltage is adjusted so that the reduction range of the effective value increases as the detection target temperature increases, for example, even when the temperature rises while the motor is rotating, the drive voltage is appropriately set. It is possible to adjust. Further, by changing the amplitude of the waveform signal used for PWM according to the detection target temperature, it is possible to appropriately prevent the motor from being overheated.

[Application Example 1] A brushless motor,
A coil array having a plurality of electromagnetic coils;
A magnet array having a plurality of permanent magnets;
A magnetic sensor for detecting a relative position of the magnet array and the coil array;
A drive control circuit that uses the output of the magnetic sensor to drive the coil array using a drive element;
A temperature sensor for detecting a detection target temperature associated with one of the coil temperature of the coil array and the temperature of the drive element;
With
The drive control circuit reduces the effective value of the drive voltage supplied to the coil array when the detection target temperature detected by the temperature sensor exceeds a predetermined first threshold, and increases the detection target temperature. A brushless motor that adjusts the drive voltage so that a reduction range of the effective value is increased.

  According to this brushless motor, since the effective value of the drive voltage supplied to the coil array is reduced when the detection target temperature detected by the temperature sensor exceeds a predetermined first threshold value, an excess current limiting circuit is provided as in the prior art. Compared with the case where the current is provided, the current is not excessively limited, and overheating of the motor can be prevented. In addition, since the drive voltage is adjusted so that the reduction range of the effective value increases as the detection target temperature increases, for example, even when the temperature rises while the motor is rotating, the drive voltage is appropriately set. It is possible to adjust.

[Application Example 2] The brushless motor according to Application Example 1,
The drive control circuit is a brushless motor that stops supplying a drive voltage to the coil array when the temperature to be detected exceeds a predetermined second threshold value that is larger than the first threshold value.

  With this configuration, overheating of the coil can be prevented more reliably.

[Application Example 3] The brushless motor according to Application Example 1 or 2,
The drive control circuit includes:
A driver circuit composed of a plurality of drive transistors for supplying current to the coil array;
A drive signal generation circuit for generating a drive signal for controlling the plurality of drive transistors of the driver circuit;
With
The drive signal generation circuit includes:
A temperature monitoring circuit that generates a temperature monitoring signal whose signal level changes according to the detection target temperature, based on the output of the temperature sensor;
A waveform signal that generates a waveform signal that exhibits the same change as an analog change in the output of the magnetic sensor and has an amplitude proportional to the signal level of the temperature monitor signal based at least on the temperature monitor signal and the output of the magnetic sensor A generator,
A PWM control circuit that performs PWM control using the waveform signal and generates the drive signal showing the same effective voltage change as the change of the waveform signal;
Including brushless motor.

  In this configuration, it is possible to appropriately prevent overheating of the motor by changing the amplitude of the waveform signal used for PWM in accordance with the detection target temperature.

[Application Example 4] The brushless motor according to Application Example 3,
The waveform signal generation unit sets the amplitude of the waveform signal based not only on the temperature monitoring signal but also on the command value of the operating voltage of the brushless motor given from the outside.

  In this configuration, the output of the motor can be appropriately adjusted according to both the command value of the operating voltage and the detection target temperature.

[Application Example 5] The brushless motor according to any one of Application Examples 1 to 4,
The temperature sensor is a brushless motor included in a power semiconductor element on which the driving element is mounted.

  In this configuration, since the temperature of the drive element can be detected with high accuracy, overheating of the motor can be prevented without excessively limiting the current.

[Application Example 6] The brushless motor according to any one of Application Examples 1 to 4,
The temperature sensor is a brushless motor installed on a heat dissipating member provided in the drive element.

  In this configuration, since the temperature of the heat radiating member can be detected, overheating of the motor drive element can be appropriately prevented.

Application Example 7 In relation to any one of a coil array having a plurality of electromagnetic coils, a magnet array having a plurality of permanent magnets, a coil temperature of the coil array, and a temperature of a drive element that drives the coil array A temperature sensor for detecting a detection target temperature, and a brushless motor control method comprising:
A brushless motor control method.
When the detection target temperature detected by the temperature sensor exceeds a predetermined first threshold, the effective value of the drive voltage supplied to the coil array is reduced, and the effective value reduction range increases as the detection target temperature increases. A control method for a brushless motor, wherein the drive voltage is adjusted so that the current increases.

  The present invention can be realized in various forms. For example, the present invention can be realized in the form of a brushless motor, its control method (or drive method), an actuator using the same, and the like.

Next, embodiments of the present invention will be described in the following order.
A. Overview of motor configuration and operation:
B. Configuration of drive control circuit:
C. Variations:

A. Overview of motor configuration and operation:
1A to 1C are cross-sectional views showing the configuration of a motor body of a brushless motor as an embodiment of the present invention. The motor main body 100 includes a stator portion 10 and a rotor portion 30 whose outer shapes are substantially disk-shaped. The stator unit 10 (FIG. 1C) is provided with two sets of electromagnetic coils 11 and 12, two magnetic sensors 40A and 40B, and two temperature sensors 50A and 50B on a circuit board 120. . The first magnetic sensor 40A is a sensor for the first set of coils 11, and the second magnetic sensor 40B is a sensor for the second set of coils 12. Hereinafter, the two sets of electromagnetic coils 11 and 12 are referred to as “A phase coil 11” and “B phase coil 12”.

  The first temperature sensor 50A is a sensor for measuring the temperature of the A-phase coil 11, and the second temperature sensor 50B is a sensor for measuring the temperature of the B-phase coil 12. These temperature sensors 50A, 50B are preferably installed in contact with the coils 11, 12, but may be installed in the vicinity of the coils 11, 12. In addition, it is preferable to provide at least one temperature sensor for each phase coil group. By doing so, it is possible to prevent overheating of the coil when a large current flows through the coil of any phase.

  Two magnets 32 are provided in the rotor unit 30 (FIG. 1B), and the central axis of the rotor unit 30 constitutes the rotation shaft 112. The magnetization direction of these magnets 32 is a direction perpendicular to the paper surface in FIG. 1B, which corresponds to the vertical direction in FIG.

  2A to 2D are explanatory views showing the positional relationship between the magnet array and the coil array during operation of the motor. In these drawings, for the sake of illustration, the number of magnets 32 is depicted as being large, but the actual number of magnets is two as shown in FIG. However, any appropriate integer can be adopted as the number of magnets and the number of coils. As shown in FIG. 2A, the magnets 32 are arranged at a constant magnetic pole pitch Pm, and adjacent magnets are magnetized in opposite directions. Further, the two coils constituting the coil group of one phase are arranged at a constant pitch Pc and are always excited in the same direction. The adjacent phase coils are separated from each other by 1/2 of the pitch Pc between the in-phase coils. The pitch Pc between the in-phase coils is equal to the magnetic pole pitch Pm. The magnetic pole pitch Pm corresponds to π in electrical angle. The electrical angle 2π is associated with a mechanical angle or distance that moves when the phase of the drive signal changes by 2π. In this embodiment, when the phase of the drive signal changes by 2π, the rotor unit 30 moves by twice the magnetic pole pitch Pm.

  FIG. 2A shows a state where the phase is 0 or 2π. FIGS. 2B to 2D show the states at the time when the phases are π / 2, π, and 3π / 2, respectively. 2A and 2C, the hatching of the A-phase coil 11 is omitted. The polarity of the drive signal for the A-phase coil 11 is inverted at these timings (that is, the excitation direction is inverted). Because. Similarly, at the timings of FIGS. 2B and 2D, the polarity of the drive signal of the B-phase coil 12 is reversed.

  FIG. 3 is an explanatory diagram illustrating examples of sensor outputs and drive signals. FIG. 3A shows the sensor output SSA of the A-phase magnetic sensor 40A and the sensor output SSB of the B-phase magnetic sensor 40B. As the magnetic sensors 40A and 40B, Hall IC sensors having an analog output can be used. FIG. 3B shows an example of the effective drive voltage VA applied to the A-phase coil 11 and the effective drive voltage VB applied to the B-phase coil 12. These effective drive voltages VA and VB preferably have similar shapes to the respective magnetic sensor outputs SSA and SSB. FIG. 3C shows an example of a two-phase drive signal generated by PWM control using the magnetic sensor outputs SSA and SSB. The effective drive voltage VA shown in FIG. 3B is an effective voltage obtained by the A-phase drive signals DRVA1 and DRVA2. The A-phase first drive signal DRVA1 is a signal that generates a pulse only when the magnetic sensor output SSA is positive, and the second drive signal DRVA2 has a pulse only when the magnetic sensor output SSA is positive. The generated signals are shown together in FIG. 3C. For convenience, the second drive signal DRVA2 is drawn as a negative pulse. The same applies to the B phase.

B. Configuration of drive control circuit:
FIG. 4A is a block diagram showing a configuration of a drive control circuit of the brushless motor of the present embodiment. The drive control circuit 200 includes a CPU 220, a drive signal generation unit 240, two-phase driver circuits 250A and 250B, two AD conversion units 260 and 280, and a warning display unit 290. The two magnetic sensor outputs SSA and SSB are converted into digital multilevel signals by the AD converter 260 and supplied to the drive signal generator 240. Output signals TA and TB (referred to as “temperature signals”) of the temperature sensors 50A and 50B are also converted into digital multilevel signals by the AD converter 280 and supplied to the drive signal generator 240. The drive signal generator 240 generates a two-phase drive signal (FIG. 3C) based on the magnetic sensor outputs SSA and SSB and the temperature signals TA and TB. The driver circuits 250A and 250B drive the two-phase electromagnetic coil groups 11 and 12 in the motor main body 100 in accordance with these two-phase drive signals.

  FIG. 4B shows an example of the internal configuration of the magnetic sensor 40A. The B-phase magnetic sensor 40B also has the same configuration. The magnetic sensor 40 </ b> A includes a Hall element 42, a bias adjustment unit 44, and a gain adjustment unit 46. The Hall element 42 measures the magnetic flux density X. The bias adjustment unit 44 adds the bias value b to the output X of the Hall element 42, and the gain adjustment unit 46 multiplies the gain value a. The output SSA (= Y) of the magnetic sensor 40A is given by, for example, the following formula (1) or formula (2).

Y = a · X + b (1)
Y = a (X + b) (2)

  The gain value a and the bias value b of the magnetic sensor 40A are set in the magnetic sensor 40A by the CPU 220. By setting the gain value a and the bias value b to appropriate values, the magnetic sensor output SSA can be calibrated to a preferable waveform shape. The same applies to the B-phase magnetic sensor 40B.

  Note that the drive control circuit 200 of this embodiment is not provided with the current limiting circuit as described in FIG. Therefore, overheating of the coil is prevented by the functions of the temperature sensors 50A and 50B and the drive signal generator 240.

  FIG. 5 shows the internal configuration of the driver circuit. Each phase of the driver circuits 250A and 250B includes four transistors 301 to 04 that constitute an H-type bridge circuit. Level shifters 311 and 313 are provided in front of the gate electrodes of the upper arm transistors 301 and 303. However, the level shifter may be omitted. The A-phase driver circuit 250A drives the A-phase coil 11 according to the drive signals DRVA1 and DRVA2. Arrows denoted by reference signs IA1 and IA2 indicate directions of currents flowing through the drive signals DRVA1 and DRVA2, respectively. The same applies to the other phases. As the driver circuit, circuits having various configurations including a plurality of driving transistors can be used.

  FIG. 6 is an explanatory diagram showing the internal configuration and operation of the drive signal generation unit 240 (FIG. 4A). For convenience of illustration, only the circuit element for the A phase is shown here, but the same circuit element is also provided for the B phase.

  The drive signal generation unit 240 includes a basic clock generation circuit 510, a 1 / N frequency divider 520, a PWM unit 530, a forward / reverse direction value register 540, a multiplier 550, an encoding unit 560, and a temperature monitor. Unit 570, voltage command value register 580, and excitation interval setting unit 590. The A-phase magnetic sensor output SSA is supplied to the encoding unit 560 and the excitation interval setting unit 590. The temperature signals TA and TB are supplied to the temperature monitoring unit 570.

  The basic clock generation circuit 510 is a circuit that generates a clock signal PCL having a predetermined frequency, and is composed of, for example, a PLL circuit. The frequency divider 520 generates a clock signal SDC having a frequency 1 / N of the clock signal PCL. The value of N is set to a predetermined constant value. The value of N is set in the frequency divider 520 by the CPU 220 in advance. The PWM unit 530 is supplied from the clock signals PCL and SDC, the multiplication value Ma supplied from the multiplier 550, the forward / reverse direction indication value RI supplied from the forward / reverse direction indication value register 540, and the encoding unit 560. In response to the positive / negative sign signal Pa and the excitation interval signal Ea supplied from the excitation interval setting unit 590, the A-phase drive signals DRVA1 and DRVA2 (FIG. 3C) are generated. This operation will be described later.

  In the forward / reverse direction value register 540, a value RI indicating the rotation direction of the motor is set by the CPU 220. In the present embodiment, the motor rotates forward when the forward / reverse direction instruction value RI is at L level, and reverses when it is at H level. Other signals Ma, Pa, and Ea supplied to the PWM unit 530 are determined as follows.

  The output SSA of the magnetic sensor 40A is supplied to the encoding unit 560. The encoding unit 560 converts the range of the magnetic sensor output SSA and sets the value of the middle point of the sensor output to 0. As a result, the sensor output value Xa generated by the encoding unit 560 takes a value in a predetermined range on the positive side (for example, +127 to 0) and a predetermined range on the negative side (for example, 0 to -127). However, what is supplied from the encoding unit 560 to the multiplier 550 is the absolute value of the sensor output value Xa, and the sign of the sensor output value Xa is supplied to the PWM unit 530 as the sign signal Pa.

  Voltage command value register 580 stores voltage command value Ya set by CPU 220. This voltage command value Ya functions as a value for setting the applied voltage of the motor together with the temperature monitoring signal Za (also referred to as “temperature gain Za”) generated by the temperature monitoring unit 570. Takes a value of zero. Ya = 0 means that the applied voltage is zero, and Ya = 1.0 means that the applied voltage is the maximum value.

  FIG. 7 is a graph showing the relationship between the temperature monitoring signal Za generated by the temperature monitoring unit 570 and the temperature signal. The horizontal axis indicates the temperature (also referred to as “detection target temperature”) represented by the temperature signal TA or TB, and the vertical axis indicates the level of the temperature monitoring signal Za. The temperature monitoring signal Za is maintained at 1.0 (maximum value) in a low temperature range until the detection target temperature reaches the predetermined first threshold value TT1. When the detection target temperature becomes equal to or higher than the first threshold value TT1, the level of the temperature monitoring signal Za monotonously decreases so that the temperature monitoring signal Za decreases as the detection target temperature increases. Further, when the detection target temperature becomes equal to or higher than the predetermined second threshold value TT2, the temperature monitoring signal Za becomes zero. In this embodiment, the two temperature signals TA and TB are input to the temperature monitoring unit 570, but the detected temperature temperature is one of the temperatures indicated by the two temperature signals TA and TB (the higher one). (Or the lower value) can be used. The temperature monitoring signal Za generated in this way is supplied from the temperature monitoring unit 570 to the multiplier 550.

  The multiplier 550 multiplies the sensor output value Xa output from the encoding unit 560, the voltage command value Ya, and the temperature monitoring signal Za into an integer, and supplies the multiplication value Ma to the PWM unit 530. .

  6B to 6E show the operation of the PWM unit 530 when the multiplication value Ma takes various values. The PWM unit 530 is a circuit that generates one pulse with a duty of Ma / N during one cycle of the clock signal SDC. That is, as shown in FIGS. 6B to 6E, as the multiplication value Ma increases, the pulse duty of the A-phase drive signals DRVA1 and DRVA2 increases. The first drive signal DRVA1 is a signal that generates a pulse only when the magnetic sensor output SSA is positive, and the second drive signal DRVA2 is a signal that generates a pulse only when the magnetic sensor output SSA is positive. However, in FIGS. 6B to 6E, these are described together. For convenience, the second drive signal DRVA2 is drawn as a negative pulse.

  As described above, the multiplication value Ma is a multiplication result of the three values Xa, Ya, and Za. Therefore, the multiplication value Ma shows the same change as the analog change (FIG. 3A) of the magnetic sensor output SSA, and has an amplitude proportional to the signal levels of both the voltage command value Ya and the temperature monitoring signal Za. It is a digital signal. Since the magnetic sensor output SSA is usually a signal close to a sine wave, the digital signal represented by the multiplication value Ma is also a signal having a waveform close to a sine wave. Therefore, in this embodiment, the digital signal represented by the multiplication value Ma is also referred to as a “waveform signal”. The command value register 580 may be omitted and the voltage command value Ya may not be used. In this case, the multiplication value Ma is a digital signal showing the same change as the analog change of the magnetic sensor output SSA and having an amplitude proportional to the temperature monitoring signal Za.

  The PWM unit 530 (FIG. 6) generates a drive signal that exhibits the same effective voltage change as the change in the multiplication value Ma (that is, the change in the waveform signal) by PWM control. Therefore, the effective voltage of the drive signal is proportional to the temperature monitoring signal Za. As a result, when the detection target temperature becomes equal to or higher than the first threshold value TT1 (FIG. 7), the effective voltage of the coil drive signal decreases as the detection target temperature increases, and the motor is prevented from overheating. Moreover, since the level of the temperature monitoring signal Za gradually decreases as the detection target temperature increases, it is possible to prevent the current from being excessively limited. For example, even when the motor load increases while the motor is rotating and the detection target temperature rises as a result, the drive voltage gradually decreases according to the characteristics shown in FIG. 7, thus preventing overheating. Is possible.

  In the example of FIG. 7, four warning temperature ranges with different warning levels AL are set in a temperature range in which the detection target temperature is larger than the first threshold value TT1. When the detection target temperature reaches the warning temperature range, the warning display unit 290 (FIG. 6) may display a warning according to the warning level AL. As the warning display, for example, a number indicating the warning level AL or various displays indicating the warning level AL in different colors can be used. If such warning display is performed, the motor user can immediately recognize that the motor is in an excessive state.

  8A to 8C are explanatory diagrams showing the correspondence between the waveform of the magnetic sensor output and the waveform of the drive signal generated by the PWM unit 530. FIG. In FIG. 8, waveforms are shown for Ya = 1 and Za = 1. In the figure, “Hiz” means a high impedance state in which the electromagnetic coil is in an unexcited state. As described in FIG. 6, the A-phase drive signals DRVA1 and DRVA2 are generated by PWM control using an analog waveform of the magnetic sensor output SSA. Therefore, using these A-phase drive signals DRVA1 and DRVA2, it is possible to supply an effective voltage indicating a level change corresponding to the change of the magnetic sensor output SSA to each coil.

  Further, the PWM unit 530 outputs a drive signal only in the excitation interval indicated by the excitation interval signal Ea supplied from the excitation interval setting unit 590, and does not output a drive signal in intervals other than the excitation interval (non-excitation interval). It is configured. FIG. 8C shows drive signal waveforms when the excitation interval EP and the non-excitation interval NEP are set by the excitation interval signal Ea. In the excitation interval EP, the drive signal pulse of FIG. 8B is generated as it is, and no drive signal pulse is generated in the non-excitation interval NEP. In this way, when the excitation interval EP and the non-excitation interval NEP are set, no voltage is applied to the coil in the vicinity of the middle point of the sensor output (this corresponds to the vicinity of the middle point of the back electromotive force waveform). Therefore, it is possible to further improve the efficiency of the motor. The excitation interval EP is preferably set to a symmetrical interval centered on the peak of the sensor output waveform (which is substantially equal to the back electromotive force waveform), and the non-excitation interval NEP is the middle of the sensor output waveform. It is preferable to set a symmetrical section centered on a point (center point). Note that the excitation interval setting unit 590 may be omitted.

  As can be understood from the above description, in the brushless motor of this embodiment, both the voltage command value Ya and the excitation interval signal Ea are obtained even when the value of the temperature monitoring signal Za is maintained at 1.0. It is possible to adjust the applied voltage by using it. The relationship between the desired applied voltage, the voltage command value Ya, and the excitation interval signal Ea is preferably stored in advance as a table in a memory in the drive control circuit 200 (FIG. 4A). In this way, when the drive control circuit 200 receives a target value of a desired applied voltage from the outside, the CPU 220 outputs the voltage command value Ya and the excitation interval signal Ea according to the target value, to the drive signal generation unit 240. Can be set. Note that it is not necessary to use both the voltage command value Ya and the excitation interval signal Ea to adjust the applied voltage, and only one of them may be used.

  FIG. 9 is a block diagram showing an example of the internal configuration of the PWM unit 530 (FIG. 6). The PWM unit 530 includes a counter 531, an EXOR circuit 533, and a drive waveform forming unit 535. These operate as follows.

  FIG. 10 is a timing chart showing the operation of the PWM unit 530 during normal rotation of the motor. In this figure, two clock signals PCL and SDC, forward / reverse direction indication value RI, excitation interval signal Ea, multiplication value Ma, positive / negative sign signal Pa, count value CM1 in counter 531 and counter 531 The output S1, the output S2 of the EXOR circuit 533, and the output signals DRVA1 and DRVA2 of the drive waveform forming unit 535 are shown. The counter 531 repeats the operation of down-counting the count value CM1 to 0 in synchronization with the clock signal PCL every period of the clock signal SDC. The initial value of the count value CM1 is set to the multiplication value Ma. In FIG. 10, a negative value is also drawn as the multiplication value Ma for convenience of illustration, but the absolute value | Ma | is used in the counter 531. The output S1 of the counter 531 is set to H level when the count value CM1 is not 0, and falls to L level when the count value CM1 becomes 0.

  The EXOR circuit 533 outputs a signal S2 indicating an exclusive OR of the positive / negative sign signal Pa and the forward / reverse direction instruction value RI. When the motor rotates normally, the forward / reverse direction instruction value RI is at the L level. Therefore, the output S2 of the EXOR circuit 533 is the same signal as the positive / negative sign signal Pa. The drive waveform forming unit 535 generates drive signals DRVA1 and DRVA2 from the output S1 of the counter 531 and the output S2 of the EXOR circuit 533. That is, of the output S1 of the counter 531, the signal during the period when the output S2 of the EXOR circuit 533 is at the L level is output as the first drive signal DRVA1, and the signal during the period when the output S2 is at the H level is output as the second drive signal DRVA2. Output as. In the vicinity of the right end of FIG. 10, the excitation interval signal Ea falls to the L level, and thereby a non-excitation interval NEP is set. Accordingly, in this non-excitation interval NEP, none of the drive signals DRVA1, DRVA2 is output and the high impedance state is maintained.

  FIG. 11 is a timing chart showing the operation of the PWM unit 530 during motor reverse rotation. During reverse rotation of the motor, the forward / reverse direction instruction value RI is set to H level. As a result, it can be understood that the two drive signals DRVA1 and DRVA2 are interchanged from FIG. 10, and as a result, the motor reverses.

  FIG. 12 is an explanatory diagram showing the internal configuration and operation of the excitation interval setting unit 590. The excitation interval setting unit 590 includes an electronic variable resistor 592, voltage comparators 594, 596, and an OR circuit 598. The resistance value Rv of the electronic variable resistor 592 is set by the CPU 220. Voltages V1 and V2 across the electronic variable resistor 592 are applied to one input terminal of a voltage comparator 594,596. A magnetic sensor output SSA is supplied to the other input terminal of the voltage comparators 594 and 596. Output signals Sp and Sn of the voltage comparators 594 and 596 are input to the OR circuit 598. An output Ea of the OR circuit 598 is an excitation interval signal Ea for distinguishing between excitation intervals and non-excitation intervals.

  FIG. 12B shows the operation of the excitation interval setting unit 590. Both-end voltages V1 and V2 of the electronic variable resistor 592 are changed by adjusting the resistance value Rv. Specifically, both-end voltages V1 and V2 are set to values having the same difference from the median value (= VDD / 2) of the voltage range. When the magnetic sensor output SSA is higher than the first voltage V1, the output Sp of the first voltage comparator 594 becomes H level. On the other hand, when the magnetic sensor output SSA is lower than the second voltage V2, The output Sn of the second voltage comparator 596 becomes H level. The excitation interval signal Ea is a signal obtained by taking the logical sum of these output signals Sp and Sn. Accordingly, as shown in the lower part of FIG. 12B, the excitation interval signal Ea can be used as a signal indicating the excitation interval EP and the non-excitation interval NEP. The excitation interval EP and the non-excitation interval NEP are set by the CPU 220 adjusting the variable resistance value Rv.

  As described above, in the brushless motor of the above embodiment, overheating of the coils 11 and 12 of each phase is prevented by the action of the temperature sensors 50A and 50B and the temperature monitoring unit 570 (FIG. 6). Therefore, there is no need to provide a current limiting circuit as in the prior art. Further, since it is possible to prevent the current from being excessively limited even at the time of starting, it is possible to prevent a problem that a sufficient torque cannot be generated at the time of starting. That is, when power is supplied by rectangular waveform driving in a region where the SN poles intersect as in the prior art, a short-circuit current occurs and a current limiting circuit is essential. However, in this embodiment, in the intersecting region, as shown in FIG. 8, power supply by sinusoidal waveform driving is suppressed and no short-circuit current is generated, so that no current limiting circuit is required. Further, at the time of starting, since the starting current for obtaining the starting torque and the impedance of the electromagnetic coil are determined by design, excessive current protection is not required by design. In addition, when an unexpected excessive load occurs in design, an excessive current exceeding the design time can be suppressed by temperature detection.

  FIG. 13 is a block diagram illustrating an example of another configuration of the drive control circuit of the brushless motor. In the drive control circuit 200a, temperature sensors 60A and 60B are provided in the driver circuits 250A and 250B of the drive control circuit 200 shown in FIG. Further, the motor main body 100a is obtained by omitting the temperature sensors 50A and 50B from the motor main body 100 of FIG. Other structures are the same as those of the circuit illustrated in FIG. The temperature sensors 60A and 60B are for detecting the temperature of the drive elements (drive transistors) constituting the driver circuits 250A and 250B.

  FIG. 14A shows a mounting example of the temperature sensor 60A. In this example, a power semiconductor element constituting the driver circuit 250A is placed on the heat dissipation board 252, and a temperature sensor 60A is mounted in the power semiconductor element. Similarly, the temperature sensor 60B is mounted on the other driver circuit 250B (not shown). For example, a diode element can be used as the temperature sensors 60A and 60B. Since the current-voltage characteristic of the diode element depends on temperature, it is possible to detect the temperature by measuring the current-voltage characteristic of the diode element. In this case, it is preferable that a temperature determination circuit for determining the temperature from the current-voltage characteristics of the diode element is provided in the temperature monitoring unit 570 (FIG. 6). The temperature monitoring unit 570 generates the temperature monitoring signal Za shown in FIG. 7 based on the outputs of the temperature sensors 60A and 60B. Note that the temperature determination circuit in the temperature monitoring unit 570 preferably has a temperature compensation function for compensating its own temperature characteristics.

  FIG. 14B shows another mounting example of the temperature sensor. In this example, the heat sink 254 is provided in the driver circuits 250 </ b> A and 250 </ b> B, and the temperature sensor 60 is installed on the heat sink 254. In this example, one temperature sensor 60 is provided, but one temperature sensor may be provided in the vicinity of each of the driver circuits 250A and 250B. The temperature sensor 60 is not for measuring the temperature of the drive elements of the driver circuits 250A and 250B, but for measuring the temperature of the heat sink 254 that varies with the temperature of the drive elements. As can be understood from this example, it is not necessary to measure the temperature of the drive element itself, and the detection target temperature associated with the temperature of the drive element (that is, the temperature that rises and falls with the temperature of the drive element) is detected to limit overheating. You may make it perform. This also applies to the coil temperature described above.

C. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C1. Modification 1:
In the above embodiment, the level of the temperature monitoring signal Za is changed according to the detection target temperature (coil temperature or drive element temperature), and the effective drive voltage of the coil is reduced accordingly. The effective drive voltage applied to the coil may be reduced using Such a circuit configuration, for example, re-adjusts the resistance value Rv of the variable resistor 592 in accordance with the level of the detection target temperature (or the temperature monitoring signal Za) in the configuration of the excitation interval setting unit 590 shown in FIG. This can be realized by providing a resistance value adjusting circuit.

C2. Modification 2:
In the above embodiment, an analog magnetic sensor is used, but a digital magnetic sensor having a multi-valued analog output may be used instead of the analog magnetic sensor. An analog magnetic sensor and a digital magnetic sensor having a multi-value output are common in that they have an output signal indicating an analog change. In this specification, “an output signal indicating an analog change” includes both a digital output signal having multiple levels of three or more and an analog output signal, not an on / off binary output. Used in a broad sense.

C3. Modification 3:
As the PWM circuit, various circuit configurations other than the circuit shown in FIG. 6 can be adopted. For example, a circuit that performs PWM control by comparing the sensor output with a reference triangular wave may be used. Further, the drive signal may be generated by a method other than PWM control. A circuit that generates a drive signal by a method other than PWM control may be employed. For example, it is possible to employ a circuit that amplifies the sensor output and generates an analog drive signal.

C4. Modification 4:
In the above embodiment, an example of a two-pole two-phase motor has been described. However, any number of poles and phases of the motor can be employed.

C5. Modification 5:
The present invention is applicable to motors of various devices such as a fan motor, a timepiece (hand drive), a drum-type washing machine (single rotation), a roller coaster, and a vibration motor.

It is sectional drawing which shows the structure of the motor main body of the brushless motor in an Example. It is explanatory drawing which shows the positional relationship of the magnet row | line | column and coil row | line | column at the time of operation | movement of a motor. It is explanatory drawing which shows the example of a sensor output and a drive signal. It is a block diagram which shows the structure of the drive control circuit of the brushless motor of a present Example. It is a figure which shows the internal structure of a driver circuit. It is explanatory drawing which shows the internal structure and operation | movement of a drive signal production | generation part. It is a graph which shows the relationship between the temperature monitoring signal Za and a temperature signal. It is explanatory drawing which shows the correspondence of a magnetic sensor output waveform and a drive signal waveform. It is a block diagram which shows the internal structure of a PWM part. It is a timing chart which shows operation | movement of the PWM part at the time of motor forward rotation. It is a timing chart which shows operation | movement of the PWM part at the time of motor reverse rotation. It is explanatory drawing which shows the internal structure and operation | movement of an excitation area setting part. It is a block diagram which shows the other structure of the drive control circuit of a brushless motor. It is explanatory drawing which shows the other mounting example of a temperature sensor. It is explanatory drawing which shows an example of the excess current limiting circuit used for the conventional brushless motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Stator part 11 ... A phase coil 12 ... B phase coil 30 ... Rotor part 32 ... Magnet 40A, 40B ... Magnetic sensor 42 ... Hall element 44 ... Bias adjustment part 46 ... Gain adjustment part 50A, 50B ... Temperature sensor (coil temperature) For detection)
60, 60A, 60B ... temperature sensor (for element temperature detection)
DESCRIPTION OF SYMBOLS 100 ... Motor body 112 ... Rotating shaft 120 ... Circuit board 200 ... Drive control circuit 220 ... CPU
240 ... Drive signal generator 250A, 250B ... Driver circuit 252 ... Heat dissipation board 254 ... Heat sink 260 ... AD converter 280 ... AD converter 290 ... Warning indicator 510 ... Basic clock generator 520 ... Divisor 530 ... PWM part 531 ... Counter 533 ... EXOR circuit 535 ... Drive waveform forming unit 540 ... Register 550 ... Multiplier 560 ... Encoding unit 570 ... Temperature monitoring unit 580 ... Register 590 ... Excitation section setting unit 592 ... Electronic variable resistor 594,596 ... Voltage Comparator 598 ... OR circuit

Claims (4)

A brushless motor,
A coil array having a plurality of electromagnetic coils;
A magnet array having a plurality of permanent magnets;
A magnetic sensor for detecting a relative position of the magnet array and the coil array;
A drive control circuit that uses the output of the magnetic sensor to drive the coil array using a drive element;
A temperature sensor for detecting a detection target temperature associated with one of the coil temperature of the coil array and the temperature of the drive element;
With
The drive control circuit includes:
A driver circuit composed of a plurality of drive transistors for supplying current to the coil array;
A drive signal generation circuit for generating a drive signal for controlling the plurality of drive transistors of the driver circuit;
With
The drive signal generation circuit includes:
A temperature monitoring circuit that generates a temperature monitoring signal whose signal level changes according to the detection target temperature, based on the output of the temperature sensor;
A waveform signal that generates a waveform signal that exhibits the same change as an analog change in the output of the magnetic sensor and has an amplitude proportional to the signal level of the temperature monitor signal based at least on the temperature monitor signal and the output of the magnetic sensor A generator,
A PWM control circuit that performs PWM control using the waveform signal and generates the drive signal showing the same effective voltage change as the change of the waveform signal;
Including
Said drive control circuit, said when detected temperature detected by the temperature sensor exceeds a predetermined first threshold to reduce the effective value of the driving voltage supplied to the coil array, wherein the higher the detected temperature is higher The drive voltage is adjusted to increase the effective value reduction range, and when the detection target temperature exceeds a predetermined second threshold value that is larger than the first threshold value, the drive voltage is supplied to the coil array. A brushless motor that stops . The brushless motor according to claim 1 ,
The waveform signal generation unit sets the amplitude of the waveform signal based not only on the temperature monitoring signal but also on the command value of the operating voltage of the brushless motor given from the outside. The brushless motor according to claim 1 or 2 ,
The temperature sensor is a brushless motor included in a power semiconductor element on which the driving element is mounted. The brushless motor according to any one of claims 1 to 3 ,
The temperature sensor is a brushless motor installed on a heat dissipating member provided in the drive element.

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