JPH05137383A - Motor protector - Google Patents

Abstract

PURPOSE:To enhance reliability in protective operation by automatically interrupting operation of motor upon temperature rise of a brushless motor and sustaining the stopped state. CONSTITUTION:When air flow rate drops from steady state, temperature of the stator of a brushless motor 10 increases. Consequently, resistance and output voltage of a negative characteristic thermister 53 decrease and when the output voltage drops below a reference voltage set by a comparator 82, output of the comparator 82 goes high to turn transistors 83, 91 ON. Since a control terminal 83a goes low to close respective AND gates 70-75, switching transistors 63-68 are entirely turned OFF to interrupt DC current supply to driving coils 17a-17c thus stopping operation of the brushless motor 10. According to the constitution, positive protective operation is ensured.

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 in a blower or the like provided in an industrial dust collector, and particularly when the motor exceeds a preset temperature, the motor is stopped and The present invention relates to a motor protection device that can hold a stopped state.

[0002]

2. Description of the Related Art For example, at a high speed of 20,000 rpm or more,
Moreover, the temperature rise in a high-speed, high-input brushless motor for blowers with an input of 200 W or more is likely to occur in the low air volume range. The cause of low air volume is that the suction air passage to the suction port of the motor is blocked, dust that has been sucked is blocked by the blower fan, or dust is trapped inside the motor and the rotor is The rotation of the rotor may be hindered, or the bearing supporting the rotor may be deteriorated to cause seizure 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. Moreover, since the air cooling effect on the stator is impaired by the decrease in the air flow, the temperature of the motor rises.

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 hitherto been known for a brushless motor for a high-speed, high-input blower.

By the way, thermal fuses and thermostats are known to operate at a set temperature to turn off the energizing 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 is not versatile, and once cut, the motor cannot be operated until a new temperature fuse is replenished. There is. Further, there is an inconvenience that the operation temperature of the thermostat cannot be adjusted while it is still incorporated in the motor, and it must be removed from the motor once. An object of the present invention is to provide a motor protection device which has a high reliability of the protection operation, can arbitrarily restart the protection operation, and can easily adjust the set temperature.

[0006]

In order to achieve the above object, a motor protection device according to the present invention comprises a temperature sensor for converting a temperature change of the motor into a voltage and outputting the voltage, and a reference voltage having a variable resistance. A setting circuit is connected, and a comparator for comparing a reference voltage determined corresponding to the upper limit temperature of the motor with the output voltage of the temperature sensor by this circuit, and on / off according to the comparison output of the comparator Between the temperature sensor and the comparator, a first transistor that allows the drive circuit of the motor to operate when in the on state and stops the operation of the drive circuit when in the off state. The output of the comparator is input to the diode provided on the base and the base, the collector is connected to the cathode of the diode, and the emitter is connected to the ground. Arranged in connection, it is obtained; and a lock circuit including a second transistor for turning on and off according to the comparison output of the comparator.

[0007]

In the above structure, the reference voltage setting circuit for setting the reference voltage in the comparator has a variable resistor, so that the reference voltage can be easily adjusted, whereby the protective device can be changed by changing the reference voltage. The operating motor temperature can be set arbitrarily. The comparator compares the reference voltage with the output voltage of the temperature sensor that changes depending on 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 a set temperature to stop the operation of the drive circuit of the motor. Therefore, when the temperature of the motor exceeds the set temperature due to 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 also 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 temperature sensor and the comparator via the diode to the ground to bypass the comparator. Therefore, although the temperature gradually decreases after the operation is stopped, the state of the comparator is maintained unchanged by the lock circuit, and the operation stopped state of the motor is eventually held. Then, the holding state can be easily canceled by turning off the power supply or the like, and the device can be returned to the 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 is equipped with an inner rotor type brushless motor 10. A cylindrical case 11 that forms the outer contour of the brushless motor 10.
Is divided into, for example, a pair of upper and lower cases 12 and 13, and these cases 12 and 13 are joined by a screw 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 (indicated by a representative reference numeral 17 in FIG. 1,
In FIG. 2, reference numerals 17a to 17c are used. ),
These drive coils 17a to 17c are electrically 120
Are arranged with a phase difference of °, for example, 100V to 200
It is wound so that it can be driven in three phases with a driving voltage of V.

A rotor 19 is inserted through the inside of the stator 15. The rotor 19 includes a rotor shaft 20 and a rotor magnet 2 provided on the outer circumference of the rotor shaft 20.
It is composed of 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 the outer peripheral portion facing the stator core 16. The upper end of the rotor shaft 20 penetrates the upper surface wall 12a of the upper case 12 and is led out to the outside of the case 11. The upper surface wall 12a has the upper end wall 12a.
A ball bearing 22 that rotatably supports the upper end portion of 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 the opening end of the fitting hole 24 is integrally formed with a flange portion 25 projecting radially inward. Bottom member 23
A cylindrical portion 26 extending downward is coaxially provided on the outer peripheral portion of the lower end of the.

A bearing holder 28 is fitted in the fitting hole 24 of the bottom member 23. A through hole 29 through which the lower end of the rotor shaft 20 passes is formed in the center of the bearing holder 28, and 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 thereof are supported by the case 11 via ball bearings 22 and 30, whereby the rotor magnet 21 is positioned coaxially inside the stator core 16.

The bearing holder 28 and the ball bearing 30 are
A first chamber 31 that houses the stator 15 and the rotor magnet 21 is separated from a second chamber 32 below the first chamber 31. The second chamber 32 includes the bottom member 23 and the tubular portion 2
It is located inside 6, and the open end of this 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.
A rotor disk 36 for detecting the rotor position is coaxially superposed on the lower surface of the shaft 5. The turntable 36 is fastened and fixed to the lower end surface of the rotor shaft 20 via a screw 37 so as to rotate integrally with the rotor shaft 20. On the turntable 36, a plurality of magnetic poles are alternately magnetized at every predetermined angle. In the case of the present embodiment, three-phase drive is performed, so eight magnetic poles are magnetized. This turntable 36 and bracket 3
Reference numeral 5 is located inside the fitting hole 24, and a thrust spring 38, such as a wave washer, is sandwiched between the flange portion 25 of the fitting hole 24 and the bearing holder 28. .. The thrust spring 38 is used for 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 this 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 is
It is covered by the fan cover 42. The fan cover 42 has a shape in which the lower surface is opened, and this opening portion is fitted to the outer periphery of a flange-shaped support wall 43 which is provided so as to project on 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.
Faces 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 to the side of the second chamber 32 of the case 11. The gas then flows and is discharged to the outside of the case 11 through the discharge ports 46 formed in the lower case 13. Therefore, the stator 15 and the like are cooled by the wind that flows in the case 11 by such blowing.

A circuit board 50 is housed in the second chamber 32. The circuit board 50 is fastened and fixed to the lower surface of the bottom member 23 with a screw 49, and the central portion thereof is close to the lower surface of the turntable 36. On the lower surface of the circuit board 50, there are provided three Hall element-made detection sensors 51a to 51c, which are located at a portion facing the turntable 36 and magnetically detect the rotational position of the rotor 19.
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,
The change of the magnetic poles of the turntable 36 is detected, and the rotor 1
The rotation position of 9 is determined, and the detection sensor 5
The outputs of 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 characteristic thermistor 53 is attached to 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, 61 is a rectifying stack as an AC-DC converter connected to a commercial AC power source 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 rectifying stack 61 is
The third switching transistor 65 is connected to the ground through the collector and the emitter, and the collector and the emitter of the fourth switching transistor 66 whose collector is connected to the emitter, and the output terminal is connected to the fifth switching transistor. It is connected to the ground via the collector-emitter of 67 and the collector-emitter of the sixth switching transistor 68 whose collector is connected to the emitter.

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 drive 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 drive coil 17c is connected to the emitter of the fifth switching transistor 67 and the sixth switching transistor 67. It is connected to a connection point with the collector of the switching transistor 68.

Output terminals of the detection sensors 51a to 51c are connected to a signal distribution circuit 69, respectively. This circuit 69
Is an IC and has the same number of output terminals as the transistors 63 to 68. These AND gates 70 to 75 are provided respectively corresponding to the transistors 63 to 68, respectively.
Is connected to one input end. Each AND gate 70
Output terminals of the protection circuit 81 are respectively connected to the other input terminals of the to 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 the negative characteristic thermistor 53.
Together with this, it constitutes a motor protection device, the construction 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 the inverting input (minus) terminal of the comparator 82, and
The positive power supply terminal is connected via the resistor 85. The non-inverting input (plus) terminal of the comparator 82 has a variable resistor 85 and a resistor 86 connected between the plus power supply terminal and the ground.
Both resistors 8 in the reference voltage setting circuit 87 including
5,86 interconnection points are connected. The reference voltage setting circuit 87 arbitrarily determines the 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 sets the reference voltage to the non-inverting input terminal of the comparator 82. To be set to.

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

The lock circuit 84 is composed of 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 the second transistor 9
It is connected to the ground via the collector-emitter of 1. The base of the second transistor 91 is connected to the output terminal of the comparator 82 via the resistor 92. Regarding the total resistance value of the resistor 89 and the diode 90 of the lock circuit 84, the voltage of the non-inverting input terminal of the comparator 82 is kept smaller than the reference voltage of the inverting input terminal when the second transistor 91 is in the ON state. Is set to a value like

The collector of the second transistor 91 is connected to the plus power supply terminal via the display circuit.
The display circuit includes 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 structure, the brushless motor 10 is at room temperature at that time, and
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 a 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 plus power supply terminal 93 is in the high level state, and the power supply voltage is supplied to the AND gates 70 to 75, so that the motor drive circuit of FIG. 2 is operated.

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

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

During this operation, when the air volume decreases from the steady state due to, for example, the suction passage being clogged, the temperature of the stator 15 of the brushless motor 10 rises. Since the temperature of the negative characteristic thermistor 53 also rises as the temperature rises, 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 the first transistor 83 and the second transistor 91 are both 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-emitter of the first transistor 83, and the control terminal 83a becomes low. Therefore, since the AND gates 70 to 75 are all closed, the switching transistors 63 to 68 are all turned off, the direct current supply to the drive coils 17a to 17c is cut off, and the operation of the brushless motor 10 is stopped. It

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 characteristic thermistor 53 becomes cold after the operation of the motor 10 is stopped and its resistance value and output voltage increase, the voltage at the inverting input terminal of the comparator 82 becomes the reference voltage due to the bypass in the lock circuit 84. The above is prevented. Therefore, the comparison output of the comparator 82 remains at the low level, so that the operation stopped state can be maintained.

As described above, when the air volume of the brushless motor 10 is remarkably reduced from the normal state due to some abnormality and the temperature of the motor 10 rises, not only the operation can be stopped but also the subsequent temperature decrease. Regardless, driving will not be restarted. Therefore, under abnormal conditions, the motor 10
The protection operation is highly reliable because it is not operated repeatedly.

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 to notify the stop of the operation.
Moreover, at this time, the diode 93 of the lock circuit 84 can prevent the current for turning on 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, it is possible to guarantee the operation of holding the operation stop state described above.

Then, by turning off the power source and resetting the comparator 82, the holding state can be easily canceled, whereby the protection operation can be restarted.
Can return 1. When this restoration 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. You may make it lower than this.

Further, in the motor protection device having the above construction, 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 the conventional thermostat, it is advantageous in incorporating it in the motor 10.

Moreover, in the motor protection device having the above structure, the reference voltage setting circuit 8 for setting the reference voltage to the comparator 82 included in the protection circuit 61 installed outside the motor 10.
Since 7 has the variable resistor 85, the reference voltage of the comparator 82 can be easily adjusted outside the motor 10, and therefore, there is no trouble of removing the protective 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 usage conditions of the brushless motor 10 used.

The present invention is not limited to the above embodiment. For example, as the temperature sensor, a positive characteristic thermistor may be used instead of the negative characteristic thermistor. In that case, an inverting circuit may be inserted at the output end of the comparator and connected to the first and second transistors, or PNP type transistors 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 the 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 set arbitrarily and easily by adjusting the reference voltage of the comparator, and the protection operation can be restarted arbitrarily by resetting the comparator. be able to.

[Brief description of 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 a cross-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 shown in the direction of arrow Z in FIG. 3 with the shield plate removed.

[Explanation of symbols]

10 ... Brushless motor, 53 ... Negative characteristic thermistor (temperature sensor), 70-75 ... AND gate, 81 ... Protection circuit, 82 ... Comparator, 83 ... First transistor 83, 84 ... Lock circuit, 85 ... Variable resistance, 87 ... reference voltage setting circuit, 90 ... diode, 91 ... second transistor, 93 ... plus power supply terminal.

Claims (1)

[Claims] 1. A temperature sensor for converting a temperature change of a motor into a voltage and outputting the voltage, and a reference voltage setting circuit having a variable resistance are connected, and a reference determined in correspondence with the upper limit temperature of the motor by this circuit. A comparator that compares the voltage with the output voltage of the temperature sensor, and turns on / off according to the comparison output of this comparator, while permitting the operation of the drive circuit of the motor while in the on state, and turning it off. A first transistor for stopping the operation of the drive circuit at a certain time, a diode provided with an anode connected between the temperature sensor and the comparator, and a comparison output of the comparator is input to a base. A second transistor having a collector connected to the cathode of the diode and an emitter connected to the ground, and turned on / off according to the comparison output of the comparator. A motor protection device having a lock circuit including a transistor.