JP2706586B2 - Motor protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor used for an air blower or the like provided in an industrial dust collector, and more particularly, to stop the operation of the motor when the temperature of the motor exceeds a set temperature. The present invention relates to a motor protection device capable of holding a stopped state.

[0002]

2. Description of the Related Art For example, at a high speed of 20,000 rpm or more,
In addition, temperature rise in a high-speed, high-input brushless motor for a blower having an input of 200 W or more easily occurs in a low air volume range. As a cause of the low air volume, the suction air path up to the suction port of the motor is blocked, dirt or the like sucked is clogged in the blower fan, or dirt or the like enters the motor and the rotor is The rotation of the rotor may be hindered, and the bearing supporting the rotor may be deteriorated and burnt to hinder the rotation of the rotor. Therefore, when the air volume decreases, it can be recognized that some abnormality has occurred in the motor. In addition, since the air cooling effect on the stator is impaired due to the decrease in the air volume, the temperature of the motor increases.

Therefore, if the operation is stopped based on the temperature rise of the motor, the motor can be protected. However, such a device has not been known in brushless motors for high-speed, high-input blowers.

[0004] By the way, thermal fuses and thermostats are known as those which operate when the set temperature is reached and cut off the current-carrying circuit. Therefore, by applying these, even in a high-speed, high-input brushless motor for a blower, it is possible to protect this motor when the air volume becomes low.

[0005]

However, since the temperature fuse cannot change the set temperature, it has no versatility, and once blown, the motor cannot be operated until a new thermal fuse is refilled thereafter. There is. In addition, adjusting the operating temperature of the thermostat cannot be performed while the thermostat is incorporated in the motor, and has to be removed once from the motor. SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor protection device which has high reliability of a protection operation, can restart the protection operation arbitrarily, and can easily adjust a set temperature.

[0006]

According to the present invention, an output of a detection sensor for detecting a rotational position of a rotor is inputted to an AND gate of a motor drive circuit through a signal distribution circuit, thereby turning on / off a switching transistor for a drive coil. It is assumed that a motor protection device is attached to a motor that controls the rotation of the rotor. And in order to solve the above-mentioned subject, the motor protection device according to the present invention is:
A temperature sensor that converts a temperature change of the motor into a voltage and outputs the voltage, and a reference voltage setting circuit having a variable resistor are connected, and a reference voltage determined according to an upper limit temperature of the motor by the circuit and the temperature sensor A comparator for comparing the output voltage of the AND gate, and a collector connected to the input terminal of the AND gate, provided when the output voltage exceeds the reference voltage.
It is turned off and turned on when the output voltage does not exceed the reference voltage, stops the operation of the motor drive circuit when in the on state, and turns off the motor drive circuit when in the off state. First to allow action
A transistor, a diode provided with an anode connected between the temperature sensor and the comparator, and a comparison output of the comparator input to a base, a collector connected to a cathode of the diode, and A lock circuit including a second transistor that is provided with an emitter connected to ground, is turned off when the output voltage exceeds the reference voltage, and is turned on when the output voltage does not exceed the reference voltage. It is provided.

[0007]

In the above configuration, since the reference voltage setting circuit for setting the reference voltage to the comparator has a variable resistor, the reference voltage can be easily adjusted, thereby changing the reference voltage and the protection device. The operating motor temperature can be set arbitrarily. The comparator compares the reference voltage with an output voltage of a temperature sensor that changes according to the temperature of the motor. The first transistor is turned on / off according to the comparison output from the comparator, and is turned on when the temperature of the motor exceeds the set temperature to stop the operation of the drive circuit of the motor. Therefore, when the temperature of the motor exceeds the set temperature based on some abnormality, the first transistor is turned on and the operation of the motor is stopped. In addition, the second transistor of the lock circuit is turned on / off according to the comparison output. Therefore, when the temperature of the motor exceeds the set temperature, the second transistor is turned on, and the lock circuit connects the ground between the temperature sensor and the comparator via the diode, thereby bypassing the comparator. Therefore, although the temperature gradually decreases after the operation is stopped, the state of the comparator is maintained without change by the lock circuit, and the operation stop state of the motor is eventually maintained. Then, the holding state can be easily canceled by turning off the power or the like, and the apparatus can be returned to a state where the protection operation can be restarted.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The electric blower 1 shown in FIG. 4 has an inner rotor type brushless motor 10. Cylindrical case 11 constituting the outer shell of this brushless motor 10
Is divided into, for example, a pair of upper and lower cases 12 and 13, and these two cases 12 and 13 are connected by screws 14. A stator 15 is housed inside the case 11. The stator 15 includes a stator core 16 and three drive coils wound around the stator core 16 (in FIG.
In FIG. 2, reference numerals 17a to 17c are shown. )
These drive coils 17a to 17c are electrically
を も っ て, for example, 100V to 200V
It is wound so that three-phase driving can be performed with a driving voltage of V.

A rotor 19 is inserted and arranged inside the stator 15. The rotor 19 includes a rotor shaft 20 and a rotor magnet 2 provided on the outer periphery of the rotor shaft 20.
1 and 1. The rotor magnet 21 is located inside the stator core 16, and a plurality of magnetic poles are magnetized at predetermined angles on an outer peripheral portion facing the stator core 16. The upper end of the rotor shaft 20 penetrates through the upper surface wall 12a of the upper case 12 and is led out of the case 11, and the upper surface wall 12a
A ball bearing 22 that rotatably supports the upper end of the “0” is provided.

A bottom member 23 is attached to the bottom of the lower case 13. A fitting hole 24 is formed in the bottom member 23. The fitting hole 24 is coaxial with the case 11, and a flange portion 25 projecting radially inward is integrally formed at an open end of the fitting hole 24. Bottom member 23
A cylindrical portion 26 extending downward is coaxially protruded from an outer peripheral portion of a lower end of the cylindrical member.

A bearing holder 28 is fitted in the fitting hole 24 of the bottom member 23. A through hole 29 is formed in the center of the bearing holder 28 so that the lower end of the rotor shaft 20 penetrates. A ball bearing that rotatably supports the lower end of the rotor shaft 20 inside the through hole 29. 30 are provided. Therefore, the rotor shaft 20 of the rotor 19
The upper and lower ends are supported by the case 11 via ball bearings 22 and 30, whereby the rotor magnet 21 is coaxially located inside the stator core 16.

The bearing holder 28 and the ball bearing 30 are
A first chamber 31 that accommodates the stator 15 and the rotor magnet 21 is partitioned from a second chamber 32 below the first chamber 31. The second chamber 32 includes the bottom member 23 and the cylindrical portion 2.
6, the open end of the tubular portion 32 is closed by a shield plate 33.

The lower end of the rotor shaft 20 penetrates the ball bearing 30 and is introduced into the second chamber 32. A bracket 35 also serving as a back yoke is coaxially fitted around the lower end of the rotor shaft 20.
On the lower surface of 5, a rotating disk 36 for detecting the rotor position is superposed coaxially. The rotating disk 36 is fastened and fixed to the lower end surface of the rotor shaft 20 via a screw 37, and is configured to rotate integrally with the rotor shaft 20. A plurality of magnetic poles are alternately magnetized at predetermined angles on the turntable 36, and eight magnetic poles are magnetized in the present embodiment because three-phase driving is performed. This turntable 36 and bracket 3
Numeral 5 is located inside the fitting hole 24, and a thrust spring 38 made of a wave washer or the like is sandwiched between the flange portion 25 of the fitting hole 24 and the bearing holder 28. . The thrust spring 38 is mounted on the bearing holder 28.
Is pressed toward the first chamber 31, and the play of the upper and lower ball bearings 22 and 30 is absorbed by the pressing.

At the upper end of the rotor shaft 20 penetrating the case 11, a centrifugal blower fan 40 is fastened and fixed via a nut 41. The area around the blower fan 40
It is covered by a fan cover 42. The fan cover 42 has a shape in which a lower surface is opened, and this opening portion is fitted to the outer periphery of a flange-shaped support wall 43 protruding from the outer peripheral surface of the upper case 12. A suction port 44 is opened at the center of the upper surface of the fan cover 42.
Is opposed to the air inlet of the blower fan 40.

When the blower fan 40 rotates, the air sucked from the suction port 44 is discharged from the outer periphery of the blower fan 40 into the fan cover 42. And upper case 1
2, a plurality of air inlets 45 are opened, and the air discharged into the fan cover 42 flows into the case 11 through the inlets 45 and flows into the case 11 on the second chamber 32 side. Then, the air is discharged to the outside 11 of the case through a plurality of discharge ports 46 opened in the lower case 13. Therefore, the stator 15 and the like are cooled by the air flowing in the case 11 by such a blowing.

A circuit board 50 is accommodated in the second chamber 32. The circuit board 50 is fastened and fixed to the lower surface of the bottom member 23 via a screw 49, and a central portion thereof is close to the lower surface of the turntable 36. On the lower surface of the circuit board 50, three Hall element detection sensors 51 a to 51 c for magnetically detecting the rotation position of the rotor 19 are provided at a portion facing the rotating disk 36.
The detection sensors 51a to 51c are arranged on the lower surface of the circuit board 50 with a phase difference of 120 ° as shown in FIG. Therefore, by the detection sensors 51a to 51c,
When the switching of the magnetic pole of the turntable 36 is detected, the rotor 1
9 is determined, and the detection sensor 5
The outputs 1a to 51c are sent to the motor drive circuit shown in FIG.

A temperature sensor for converting the temperature of the motor 10 into a voltage, for example, a negative temperature coefficient thermistor 53 is mounted on the lower surface of the circuit board 50. The thermistor 53 detects the ambient temperature of the detection sensors 51a to 51c and sends temperature information for preventing the temperature of the motor 10 from exceeding a set upper limit temperature to a protection circuit described later.

FIG. 2 shows a drive circuit of the brushless motor 10. In the figure, reference numeral 61 denotes a rectifying stack as an AC-DC converter connected to a commercial AC power supply 62.
The output terminal of the rectifying stack 61 is connected to the ground via the collector and the emitter of the first switching transistor 63 and the collector and the emitter of the second switching transistor 64 whose collector is connected to the emitter. Similarly, the output end of the rectification stack 61 is
The third switching transistor 65 is connected to the ground via the collector and the emitter of the third switching transistor 65 and between the collector and the emitter of the fourth switching transistor 66 whose collector is connected to the emitter. The sixth switching transistor 68 whose collector is connected to the emitter is connected to the ground via the collector and the emitter of the sixth switching transistor 68.

The drive coil 17a is connected to a connection point between the emitter of the first switching transistor 63 and the collector of the second switching transistor 64.
Similarly, the driving coil 17b is connected to a connection point between the emitter of the third switching transistor 65 and the collector of the fourth switching transistor 66, and the driving coil 17c is connected to the emitter of the fifth switching transistor 67 and the sixth switching transistor 67. It is connected to the connection point of the switching transistor 68 with the collector.

The output terminals of the detection sensors 51a to 51c are connected to a signal distribution circuit 69, respectively. This circuit 69
Is composed of ICs and has the same number of output terminals as the number of transistors 63 to 68. These are AND gates 70 to 75 provided respectively corresponding to the transistors 63 to 68, respectively.
Is connected to one of the input terminals. Each AND gate 70
The output terminals of the protection circuit 81 are respectively connected to the other input terminals of .about.75. The output terminals of the AND gates 70 to 75 are separately connected to the bases of the transistors 63 to 68, respectively.

The protection circuit 81 is provided with the negative characteristic thermistor 53.
Together with a motor protection device, the configuration of which is shown in detail in FIG. The protection circuit 81 includes a comparator 82, a first transistor 83, and a lock circuit 84.

A negative characteristic thermistor 53 is connected to an inverting input (minus) terminal of the comparator 82.
A positive power supply terminal is connected via a resistor 85. A non-inverting input (plus) terminal of the comparator 82 has a variable resistor 85 and a resistor 86 connected between a plus power supply terminal and the ground.
The two resistors 8 in the reference voltage setting circuit 87
5,86 interconnection points are connected. The reference voltage setting circuit 87 arbitrarily determines a reference voltage having a value corresponding to the upper limit temperature of the brushless motor 10 by changing the resistance value of the variable resistor 85, and outputs the reference voltage to the non-inverting input terminal of the comparator 82. Is set to

The base of the first transistor 83 is a comparator 8
2 is connected via a resistor 95 to the output terminal. The emitter of the transistor 83 is connected to the ground , and the collector is connected to a positive power supply terminal 93 via a resistor 88. Further, the first transistor 83
Is connected to a control terminal 83a.
aThey are connected to the other input terminals of the AND gates 70 to 75 of the motor drive circuit, respectively.

The lock circuit 84 includes a resistor 89, a diode 90, and a second transistor 91. One end of the resistor 89 is connected to the inverting input terminal of the comparator 82, and the other end is connected to the anode of the diode 90. The cathode of the diode 90 is connected to the second transistor 9
It is connected to ground via one collector and emitter. The base of the second transistor 91 is connected to the output terminal of the comparator 82 via the resistor 92. The total resistance of the resistor 89 and the diode 90 of the lock circuit 84 is such that the voltage at the non-inverting input terminal of the comparator 82 is kept lower than the reference voltage at the inverting input terminal when the second transistor 91 is on. Is set to such a value.

The collector of the second transistor 91 is connected to a positive power supply terminal via a display circuit.
The display circuit is formed by a resistor 96 and a light emitting diode 97. The motor drive circuit and the protection circuit 81 shown in FIGS. 1 and 2 are provided on a control panel (not shown) arranged outside the case 11.

When the power is turned on in the above configuration, the brushless motor 10 is at room temperature at that time,
Since the resistance value of the negative characteristic thermistor 53 for detecting the motor temperature is usually about 400 KΩ, the output voltage from the thermistor 53 is naturally higher than the reference voltage set in the comparator 82.

Therefore, the comparison output of the comparator 82 is at the low level, and both the first transistor 83 and the second transistor 91 maintain the off state. Therefore, the control terminal 83a connected to the positive power supply terminal 93 is at a high level, and the power supply voltage is supplied to each of the AND gates 70 to 75, so that the motor drive circuit of FIG. 2 operates.

That is, two AND gates input with a drive signal based on the detection of the position of the rotor 19 by the detection sensors 51a to 51c via the signal distribution circuit 69 are opened, and a switching transistor connected thereto is turned on. The signal distribution circuit 69 supplies a drive signal to any one of the switching transistors 63, 65, and 67 and any one of the switching transistors 64, 66, and 68 to perform an operation of turning them on. The program is executed according to a predetermined order.

Therefore, the rectifying stack 61 is connected to two drive coils inserted in series between the two switching transistors that are turned on.
The DC converted from the AC is supplied, and the rotation of the rotor 19 and the blower fan 40 is started. Hereinafter, based on the detection of the position of the rotor 19 by the detection sensors 51a to 51c, the drive coils 17a to 17c are excited by three-phase bipolar driving, and the operation of the brushless motor 10 is continued.

During this operation, if the air flow decreases from the steady state due to, for example, a blockage of the suction passage, the temperature of the stator 15 of the brushless motor 10 increases. Since the temperature of the negative characteristic thermistor 53 also rises with this temperature rise, the resistance value of the thermistor 53 and the output voltage correspondingly decrease. Then, when the output voltage of the negative characteristic thermistor 53 becomes lower than the reference voltage set in the comparator 82, the comparison output of the comparator 82 becomes high level from that point, and both the first transistor 83 and the second transistor 91 become active. Turned on.

Then, when the first transistor 83 is turned on, the power supply voltage of the positive power supply terminal 93 is dropped to the ground through the collector and the emitter of the first transistor 83, and the control terminal 83a is set to the low state. Therefore, since all the AND gates 70 to 75 are closed, all of the switching transistors 63 to 68 are turned off, the supply of DC to the drive coils 17 a to 17 c is cut off, and the operation of the brushless motor 10 is stopped. You.

Since the second transistor 91 is also turned on at the same time, the inverting input terminal of the comparator 82 is connected to the ground via the lock circuit 84 bypassing the comparator 82.
Therefore, even if the negative temperature coefficient thermistor 53 cools down after the operation of the motor 10 is stopped and the resistance value and the output voltage increase, the voltage at the inverting input terminal of the comparator 82 is reduced by the bypass in the lock circuit 84. The above is prevented. Therefore, since the comparison output of the comparator 82 remains at the low level, the operation stop state can be maintained.

As described above, when the air volume of the brushless motor 10 is significantly reduced due to some abnormality and the temperature of the motor 10 rises, not only can the operation be stopped, but also the subsequent temperature decrease. Regardless, operation is not restarted. Therefore, under abnormal conditions, the motor 10
Is not repeatedly operated, so that the reliability of the protection operation is high.

When the operation of the motor 10 is stopped, the light emitting diode 97 is turned on at the same time when the second transistor 91 is turned on, so that the stop of the operation can be notified.
Moreover, at this time, the diode 93 of the lock circuit 84 can prevent the current for lighting the light emitting diode 97 from flowing backward through the lock circuit 84 and being supplied to the inverting input terminal of the comparator 82. Therefore, the operation of maintaining the operation stop state described above can be guaranteed.

Then, by turning off the power and resetting the comparator 82, the holding state can be easily eliminated, and the protection circuit 8 can be restarted so that the protection operation can be resumed.
1 can be restored. When the return is performed in the power supply state, a switch is provided between the non-inverting input terminal of the comparator 82 and the ground, and the switch is closed to change the voltage of the non-inverting input terminal to the voltage of the inverting input terminal. Alternatively, it may be set lower.

In the motor protection device having the above-described structure, only the negative characteristic thermistor 53 as a temperature sensor is incorporated in the motor 10. Since the negative characteristic thermistor 53 is much smaller than a conventional thermostat, it is advantageous in incorporating it into the motor 10.

Further, in the motor protection device having the above-mentioned configuration, the reference voltage setting circuit 8 for setting the reference voltage to the comparator 82 provided in the protection circuit 61 provided outside the motor 10.
7 has a variable resistor 85, so that the reference voltage of the comparator 82 can be easily adjusted outside the motor 10, so that there is no trouble in removing the protection device from the motor 10 and adjusting it. Thereby, the motor temperature at which the protection device operates can be arbitrarily set by changing the reference voltage according to the use conditions of the brushless motor 10 to be used.

The present invention is not limited to the above embodiment. For example, a positive temperature coefficient thermistor may be used instead of a negative temperature coefficient thermistor. In that case, an inversion circuit may be inserted into the output terminal of the comparator and connected to the first and second transistors, or a PNP transistor may be used for both transistors.

[0040]

As described above in detail, according to the present invention, when the temperature of the brushless motor rises, the operation of this motor can be automatically stopped and the stopped state can be maintained. The reliability of the protection operation against the rise is high, and the motor temperature at which the protection device operates can be arbitrarily and easily set by adjusting the reference voltage of the comparator, and the protection operation can be arbitrarily restarted by resetting the comparator. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a protection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a motor drive circuit according to the embodiment.

FIG. 3 is an exemplary sectional view showing the configuration of an electric blower including the motor according to the embodiment;

FIG. 4 is a bottom view of the electric blower as viewed from the direction of arrow Z in FIG. 3 with the shield plate removed.

[Explanation of symbols]

10: brushless motor, 17a to 17c: drive coil
, 51a to 51c: detection sensor, 53: negative characteristic thermistor (temperature sensor), 69: signal distribution circuit, 63 to 68
... Switching transistor, 70-75 ... And gate, 81 ... Protection circuit, 82 ... Comparator, 83 ... First transistor, 83,84 ... Lock circuit, 85 ... Variable resistance, 8
7 ... Reference voltage setting circuit, 90 ... Diode, 91 ... Second
Transistor, 93 ... plus power supply terminal.

Claims (1)

(57) [Claims] An output of a detection sensor for detecting a rotational position of a rotor is input to an AND gate of a motor drive circuit through a signal distribution circuit, thereby turning on / off a switching transistor for a drive coil to control the rotation of the rotor. A motor protection device attached to a motor to be connected, wherein a temperature sensor that converts a temperature change of the motor into a voltage and outputs the voltage and a reference voltage setting circuit having a variable resistor are connected, and the circuit is used to adjust the upper limit temperature of the motor. A comparator for comparing a correspondingly determined reference voltage with the output voltage of the temperature sensor, provided with a collector connected to the input terminal of the AND gate, and turned off when the output voltage exceeds the reference voltage Is turned on when the output voltage does not exceed the reference voltage, and the motor is driven when the output voltage is in the on state. A first transistor that stops the operation of the circuit and allows the operation of the motor drive circuit when in the off state, a diode provided with an anode connected between the temperature sensor and the comparator, and A comparison output of the comparator is input to the base, a collector is connected to the cathode of the diode, and an emitter is connected to the ground. The output is turned off when the output voltage exceeds the reference voltage. And a lock circuit including a second transistor that is turned on when the output voltage does not exceed the reference voltage.