JP2000152684A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy-saving and low-noise brushless motor, by forming a DC motor in brushless structure and optimally controlling the switching timing of an armature coil current. SOLUTION: Connection points U and W become identical potential, no current flows between the points U and W, and the change in magnetic flux due to an armature coil current becomes gentle due to overlap control for applying a voltage between the connection points U and V shown in (a), a voltage between the connection points W and V shown in (c) from a state for allowing MOSFETs Q1 and Q5 to conduct electricity, and a voltage overlappingly with the connection points U and W as a power supply side and the connection point V as a grounding side as shown in (b), when switching to a state for allowing the MOSFETs Q3 and Q5 to conduct electricity. The amount of overlaps due to the overlap control is controlled according to the rotary speed of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer rotor type brushless D suitable for driving a blower fan for a vehicle.
The present invention relates to a brushless motor in which a switching timing of a current flowing through an armature coil in a C motor is optimized.

[0002]

2. Description of the Related Art Conventionally, a motor mounted on a vehicle such as an automobile, for example, a motor for rotating a blower fan used in an air conditioner switches the direction of an electric current flowing through an armature coil using a commutator and a brush. DC motors have been used.

In this conventional DC motor mounted on a vehicle, a battery of the vehicle is used as a power supply, and the DC motor is driven by a constant voltage power supply.
For this reason, in the rotation control of the DC motor using the brush, the power supply voltage is divided by a voltage dividing resistor and used. For example, when the battery voltage is 12 V and the DC motor is driven at 3 V, the remaining 9 V is applied to the voltage dividing resistor and is consumed as heat. For this reason, the power consumed by the voltage dividing resistor is wasted and energy efficiency is not good. Further, the sliding noise caused by the brush caused noise.

[0004]

However, when the DC motor has a brushless structure and the rotation is controlled by varying the duty of the power supply voltage (pulse width control), the natural vibration noise is generated by the repulsive force of the rotor magnetic pole and the armature coil. There was a problem that would occur. When the current flowing through the armature coil of each phase is switched, the magnitude of the natural vibration sound changes by applying a voltage to the connection point of each armature coil before and after the switching. The torque generation efficiency also changes depending on the switching timing.

[0005] The switching timing at which the torque generation efficiency is maximized is different from the switching timing at which the natural vibration sound is minimized.
If the natural vibration sound is reduced, the efficiency is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an energy-saving and low-noise brushless motor in which a DC motor used for a blower fan or the like has a brushless structure and an armature coil current switching timing is optimally controlled.

[0007]

In order to solve the above-mentioned problems, a brushless motor according to the present invention is arranged on a stator (3) in an outer rotor type brushless DC motor in which an armature is arranged on the inner peripheral side of the motor. An armature coil (4) for switching a connection to a power source to generate a rotating magnetic field;
A switching element (Q1 to Q6) for switching a current flowing through the armature coil (4) by sequentially switching between a power supply side connection point for applying a voltage to the armature coil (4) and a ground side connection point; With respect to the field permanent magnet (2) attached to (1), the sensor magnet (5) attached integrally with the rotor (1) to indicate the rotational position of the rotor (1) and the stator (3). A magnetic sensor (IC1 to IC3) that is attached and detects the direction of a magnetic field by the sensor magnet (5), and receives a change in the magnetic field direction from the magnetic sensor (IC1 to IC3) to detect the rotation speed of the rotor (1). And at the time of switching the current of the armature coil (4), an overlap for overlap control for applying a voltage to each connection point before and after the switching. An overlap control means (12a) for outputting an amount in accordance with the rotation speed, and an overlap control in accordance with the overlap amount in response to a magnetic field direction change detection from the magnetic sensors (IC1 to IC3). Timing control means (12) for controlling the current switching timing of the switching elements (Q1 to Q6).
b).

With the above configuration, when the current of the armature coil is switched, the amount of overlap in which voltage is applied to each of the connection points before and after the switching is controlled in accordance with the rotation speed of the motor, and the amount of overlap is controlled. Controls current switching timing.

Further, the overlap control means (1)
2a) controlling the amount of overlap to be large when the rotation speed of the rotor (1) is low and controlling the amount of overlap to be small when the rotation speed of the rotor (1) is low; When the motor is rotating at a high speed, priority is given to giving priority to high efficiency.

The overlap control means (12)
a) smoothly changes the overlap amount according to the rotation speed of the rotor (1), thereby smoothly changing the current switching timing of the switching element according to the rotation speed of the motor.

The overlap control means (12
a) performs overlap control of applying a voltage to each connection point before and after switching at the time of switching between the power supply side connection point and the ground side connection point of the armature coil (4), At the time of switching all the currents of the armature coil, overlap control is performed.

[0012]

In the brushless motor according to the first aspect of the present invention, when the current of the armature coil is switched, the overlap amount for applying the voltage to each of the connection points before and after the switching is determined by the amount of rotation of the motor. Since the control is performed according to the speed and the current switching timing of the switching element is controlled, the switching timing of the current flowing through the armature coil can be optimally controlled in consideration of noise due to natural vibration noise and motor efficiency.

[0013] In the brushless motor according to the second aspect of the present invention, when the motor in which the generation of noise is relatively low-speed rotates at a low speed, priority is given to low noise rather than high efficiency. When the motor whose efficiency is of high concern rotates at high speed, control is performed with priority given to high efficiency over low noise, so that a brushless motor with low energy consumption and low noise can be provided.

[0014] In the brushless motor according to the third aspect of the present invention, since the current switching timing of the switching element is smoothly changed according to the rotation speed of the motor, the change in the rotation torque is gentle and smooth rotation is obtained. Can be

In the brushless motor according to a fourth aspect of the present invention, the overlap control is performed when all the currents of the armature coils are switched, so that the natural vibration noise can be further reduced.

In the brushless motor according to the fifth or sixth aspect of the present invention, since the sensor magnet has a plurality of pairs of N poles and S poles or a plurality of magnetic sensors are arranged, the rotor has one rotor. A change in the direction of the magnetic field can be detected a plurality of times during rotation, and even if the rotation speed of the rotor changes, high-speed response and fine-grained timing control can be performed following the change.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a bottom view of the brushless motor of the present invention as viewed from below. The brushless motor according to the present embodiment is used for driving a fan of a vehicle air conditioner, and is a three-phase two-pole wound outer rotor type brushless DC motor. The rotor is provided with a permanent magnet for field.

The stator 3 has armature coils 4a to 4f for generating a rotating magnetic field with each of the protrusions 3a to 3f as a core.
Are arranged in three phases, and a rotor 1 provided with main magnets (field permanent magnets) 2 is arranged at 90-degree intervals outside the three phases. The sensor magnet 5 indicating the rotational position of the rotor 1 has two pairs of N poles and S poles arranged at an equal angle with respect to the rotation center of the rotor 1 and is attached to a shaft 6 that rotates integrally with the rotor 1. . Hall ICs 1-3 for detecting the direction of the magnetic field by the sensor magnet 5
(Magnetic sensors) are evenly arranged on the inner periphery of the stator 3 at intervals of 120 degrees.

In the brushless DC motor, the generated torque changes depending on the timing of switching the current flowing through the armature coils 4a to 4f from the detection position of the main magnet 2. In the present embodiment, the sensor magnet 5 indicating the rotational position of the rotor 1 is attached to the shaft 6 with a delay angle of 42 degrees with respect to the main magnet 2, and further performs electrical advance control. Here, indicates a coil in which a current path is short and a current twice as large as that of the other armature coils flows. Is a position where a forward rotation torque is generated by a repulsive force between the armature coil 3c (3f) and the main magnet 2,
Indicates a reverse torque generating position due to a repulsive force between the armature coil 3a (3d) and the main magnet 2.

FIG. 2 is a block diagram of a control circuit of the brushless motor according to the present embodiment. The sensor signal detection circuit 11 receives the detection of a change in the magnetic field direction of the sensor magnet 5 from the Hall ICs 1 to 3, generates respective inversion signals, and inputs the inverted signals together with the non-inversion signal to the microcomputer 12 as sensor signals consisting of six signals. I do. This is because the microcomputer 12 used in the present embodiment detects only the falling edge of the input signal and converts the rising edge to the falling edge for detection.

In the processing in the microcomputer 12, the overlap control means 12a receives the sensor signal, calculates the rotational speed of the motor from the period of the magnetic field direction change detection, and switches the current of the armature coil 4. At times, an overlap amount for overlap control in which a voltage is applied to each of the connection points U, V, and W before and after the switching is output according to the rotation speed. Next, the timing control unit 12b receives a sensor signal, an overlap amount, and a rotation instruction signal (PWM signal) for instructing rotation of the motor from an air-conditioning control device (not shown), and receives an overlap according to the overlap amount. Control, and MOSFETs (switching elements) Q1 to Q1
The current switching timing of Q6 is controlled.

FIG. 3A is a timing chart when the overlap control of the control circuit of the brushless motor according to the present embodiment is not performed, and FIG. 3B shows the MOSFETs (Q1 to Q1) controlled at this timing. The connection relation of Q6) is shown. The sensor magnet 5 has N pole and S pole of 90
Since it is arranged every degree, the magnetic field direction change detection signal from the Hall IC changes for two periods while the rotor 1 makes one rotation. Thus, the timing of the rotation of the rotor can be controlled twice as finely. Further, by arranging three Hall ICs at equal intervals, it is possible to control the rotation of the rotor three times more precisely. Based on the detection of the change in the magnetic field direction from the Hall ICs 1 to 3 arranged at equal intervals, the MOSFETs (Q1 to Q1)
Q6) is switched on / off 12 times in total, and the armature coil 4
By sequentially switching between a power supply side connection point and a ground side connection point for applying a voltage to the armature coils 4a to 4f.
The direction of the current flowing through 4f is switched. As a result, a rotating magnetic field is generated.

FIG. 4A shows the rotational position of the rotor, and FIG.
Is the Hall IC signal and MOS used for the control at that time.
4 shows a correspondence relationship with a conduction state of an FET. Rotor rotation angle 0
In the case of the temperature, the signal from the Hall IC 3 is used, and the MOSFE
T (Q1) and (Q5) become conductive. MOSFET
(Q1) is on the power supply side and the MOSFET (Q5) is on the ground side, and a voltage is applied between the connection point U and the connection point V.

FIG. 5 is a diagram showing the energized state of each coil when the Hall IC 3 is switched and the position of the sensor magnet 5 with respect to the main magnet 2 depending on the delay angle. MOSFE
T (Q1) and (Q5) are turned on, the U side (Q1) becomes the power supply voltage, and the V side (Q5) is grounded. Current path S1 is U side (+) → coil 4f → coil 4c → V side (GND)
Assuming that the current path S2 is U side (+) → coil 4e → coil 4b → coil 4a → coil 4d → V side (GND), the current value is doubled because the resistance value of the current path S1 is half. (Of FIG. 1). A particularly strong repulsive force is generated between the coil whose current value is doubled and the main magnet 2 as compared with the other coils, and a strong rotational torque for canceling the reverse torque is generated.

FIG. 6A shows the case where the rotor rotation angle is 30 degrees, and FIG. 6B shows the Hall IC used for control at that time.
The correspondence between the signal and the conduction state of the MOSFET is shown. When the rotor rotation angle is 30 degrees, the MOSFETs (Q3) and (Q5) are turned on using the signal from the Hall IC1. MOSFET (Q3) is the power supply side, MOSFET
(Q5) is on the ground side, and a voltage is applied between the connection point W and the connection point V.

FIG. 7 is a diagram showing the energized state of each coil when the Hall IC 1 is switched and the position of the sensor magnet 5 with respect to the main magnet 2 depending on the delay angle. MOSFE
T (Q3) and (Q5) are turned on, the W side (Q3) becomes the power supply voltage, and the V side (Q5) is grounded. Current path S3 is U side (+) → coil 4a → coil 4d → V side (GND)
Assuming that the current path S4 is U side (+) → coil 4b → coil 4e → coil 4f → coil 4c → V side (GND), the current value is doubled because the current path S3 has a half resistance value. .

FIG. 8 is an explanatory diagram of the overlap control according to the present invention. A voltage is applied between the connection point U and the connection point V using the signal from the Hall IC 3 shown in FIG.
From the state where the OSFETs (Q1) and (Q5) are turned on,
Using the signal from the Hall IC 1 shown in FIG.
And a connection point V, a voltage is applied between the MOSFET (Q
When switching to a state where 3) and (Q5) are conducted, (b)
As shown in (1), the connection points U and W are both set to the power supply side, and the connection point V is set to the ground side to apply the voltage in duplicate. By the overlap control, in the overlap voltage application state shown in FIG. 3B, the connection points U and W have the same potential, and no current flows between U and W. For this reason, by changing from the state shown in (a) to the state shown in (c) through the overlapping voltage application state shown in (b), the change in current becomes gentle,
As a result, the change in magnetic flux due to the armature coil current becomes gentle. For this reason, the change of the repulsive force between the rotor magnetic pole and the armature coil becomes gentle, and the natural vibration sound generated by the repulsive force is also reduced. On the other hand, the period during which an effective rotation torque is generated is shortened, and the torque generation efficiency is reduced.

FIG. 9 shows the U phase by the overlap control.
The overlap voltage application width (lap margin) of the V-phase and W-phase signals is shown.
When switching the voltage application to each connection point of the armature coil, a time width for applying the voltage redundantly is provided.

FIG. 10 is a timing chart for outputting an output switching control signal of the MOSFET based on the signal from the Hall IC. FIG. 10A shows an input signal from the sensor (Hall IC), and FIGS. Indicates a gate signal of the MOSFET.

SAH and SAL shown in (a) indicate a signal from the Hall IC 1 and its inverted signal, respectively. Similarly, SBH and SBL are output from Hall IC2, respectively.
SCH and SCL indicate a signal from the Hall IC 3 and its inverted signal, respectively. With these six signals, the timing can be finely controlled every 30-degree rotation of the rotor.

AT, BT, and CT shown in (b) are high-side (power supply) MOSFETs during overlap control.
And gate signals AB and B shown in FIG.
B and CB indicate gate signals output to the low-side (ground side) MOSFET.

In this embodiment, the timing of the gate signal of the MOSFET is controlled by the falling edge of the six sensor input signals. In this case, the timing corresponding to the next falling (corresponding to 30-degree rotation of the rotor 1) is predicted corresponding to the falling of each sensor signal, and the MOSFE
On / off control of the T gate signal. At this time, the rotation speed of the rotor is calculated from the time between the falling edges of the sensor signal, and the amount of overlap for overlap control corresponding to the rotation speed is obtained. When the gate signals of the high-side and low-side MOSFETs are controlled to be turned on / off, overlap control is performed according to the overlap amount, and timing control is performed. The same control can be performed by using the rising edge of the sensor signal.

In the overlap control, the effect of reducing the natural vibration noise can be obtained by controlling the switching timing of only the output of the high-side MOSFET and delaying the output off timing, but the output of the low-side MOSFET can be reduced. By delaying the switching timing, the overlap control is performed at the time of switching all the currents of the armature coil, and the natural vibration sound can be further reduced.

FIG. 11 shows the relationship between the number of rotations of the motor and the overlap control amount (overlap time). Motor rotation speed is 0 ~ 450rpm and 450 ~
Overlap time 670μs up to 1125rpm
c, The overlap time is set to 670 to 75 μsec for 1125 to 1800 rpm, and the overlap time is set to 75 μsec for 1800 rpm or more, and the polygonal line control according to the rotation speed is performed.

In the above overlapping polygonal line control,
450 ~ 1125rpm and 1125 ~ 1800r
The overlap time is linearly and smoothly changed continuously between pm. When the overlap time is changed suddenly,
The rotation torque also changes abruptly and causes uneven rotation. To avoid this, the overlap time is smoothly and continuously changed.

Under the software control of the microcomputer, the overlap time is controlled according to the motor speed. For example, when the motor rotation speed is 1800 rpm (period: 3)
At 3.3 msec), the time required for the rotor to rotate 30 degrees is 2.78 msec, so after the time required for this 30 degree rotation has elapsed from the falling edge of the sensor signal,
Assuming that the overlap time is 75 μsec,
On / off control of the T gate signal.

FIG. 12 shows the relationship between the amount of overlap and the noise level. Until the overlap amount is about 150 μsec, the noise level also decreases as the overlap amount decreases. The noise level gradually decreases as the amount of overlap is further reduced.

FIG. 13 shows the relationship between the overlap amount and the motor efficiency. When the overlap amount is 0, the motor efficiency is maximum, that is, the rotational torque is maximum. As the overlap amount increases, the motor efficiency decreases.

When the motor rotates at a high speed, the natural vibration sound component is masked by the influence of the blowing sound, and the noise due to the natural vibration sound does not cause a relatively problem. On the other hand, when the number of rotations of the motor is low, the blowing sound is small, so that the natural vibration sound component is relatively large. For this reason, particularly in the low rotation speed region, the effect of reducing the noise by increasing the amount of overlap is great.

From the above, by controlling the amount of overlap to be large when the rotation speed of the rotor is low and by controlling the amount of overlap to be small when the rotation speed of the rotor is high, low noise and high efficiency can be achieved at an optimum ratio depending on the number of rotations. Control.

As described above, by using the brushless motor of the present invention for driving the fan of a vehicle air conditioner, low noise is obtained when the rotation speed is low, that is, when the air volume is small, and the noise is high when the rotation speed is high, that is, the air volume is small. When the number is large, energy-saving and high-torque torque can be obtained by high-efficiency operation, and this can be controlled to an optimal ratio by the number of revolutions, so that a comfortable air-conditioning environment can be obtained.

Although the present embodiment has been described as a brushless motor for driving a blower fan of a vehicle air conditioner, for example, the present invention can be similarly applied to a radiator cooling fan of a vehicle engine. It can also be used for blower fans and the like.

[Brief description of the drawings]

FIG. 1 is a bottom view of a brushless motor according to the present invention.

FIG. 2 is a block diagram of a control circuit section of the brushless motor of the present invention.

FIG. 3A is a timing chart of a control circuit section of a brushless motor, and FIG. 3B is a diagram illustrating a connection relation of MOSFETs.

4A is a rotor rotational position, and FIG. 4B is a Hall IC.
FIG. 3 is a diagram illustrating a correspondence relationship between a signal and a conduction state of a MOSFET.

FIG. 5 shows the energized state of each coil when switching the Hall IC 3;
It is a figure showing a position by a delay angle of a sensor magnet to a main magnet.

FIG. 6A shows a case where the rotor rotation angle is 30 degrees,
(B) is a diagram showing the correspondence between the Hall IC signal and the conduction state of the MOSFET.

FIG. 7 shows the energized state of each coil when the Hall IC 1 is switched,
It is a figure showing a position by a delay angle of a sensor magnet to a main magnet.

8A and 8B are explanatory diagrams of the overlap control according to the present invention, in which FIG. 8A shows the application of a voltage between the connection points U and V, FIG. 8B shows the connection points U and W on the power supply side, and FIG. FIG. 7C is a diagram showing a state of voltage application between connection points W and V, and FIG.

FIG. 9 is a diagram illustrating a wrap margin of U-phase, V-phase, and W-phase signals by overlap control.

FIG. 10A is a timing chart showing an input signal from a sensor (Hall IC), and FIGS. 10B and 10C are timing charts showing a gate signal of a MOSFET.

FIG. 11 is a diagram illustrating a correspondence relationship between an overlap time and a rotation speed of a motor.

FIG. 12 is a diagram illustrating a relationship between an overlap amount and a noise level.

FIG. 13 is a diagram showing a relationship between an overlap amount and motor efficiency.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... rotor, 2 ... main magnet (field permanent magnet), 3 ... stator, 4a-f ... armature coil, 5 ... sensor magnet, 6 ... shaft, 11 ... sensor signal detection circuit, 12 ... microcomputer, 13 ... Motor drive circuit, IC1-3 ... Hall IC (magnetic sensor), ... 2
Coil where current is flowing twice, ... forward rotation torque generation position, ... reverse torque generation position.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsuyoshi Sekine 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonic Corporation (72) Inventor Eiji Takahashi 5-24-15 Minamidai, Nakano-ku, Tokyo Calsonic F term in reference (reference) 5H019 BB05 CC04 DD01 EE14 5H560 AA01 BB04 BB08 BB12 DA03 DA19 EB01 EC02 JJ12 RR04 SS02 UA05 XA05 XA12 XB01

Claims (6)

[Claims] 1. An outer rotor type brushless DC motor in which an armature is arranged on an inner peripheral side of a motor, wherein an armature coil (4) arranged on a stator (3) for switching a connection to a power source to generate a rotating magnetic field. A switching element (Q1 to Q6) for switching a current flowing through the armature coil (4) by sequentially switching between a power supply side connection point for applying a voltage to the armature coil (4) and a ground side connection point; A sensor magnet (5) attached to the rotor (1) integrally with the field permanent magnet (2) attached to the rotor (1) to indicate the rotational position of the rotor (1); ) And a magnetic sensor (I) for detecting the direction of the magnetic field by the sensor magnet (5).
C1 to IC3) and the change in the magnetic field direction from the magnetic sensors (IC1 to IC3), the rotation speed of the rotor (1) is calculated, and when the current of the armature coil (4) is switched, An overlap control means (12a) for outputting an overlap amount for overlap control for applying a voltage redundantly to each subsequent connection point in accordance with the rotation speed.
Timing control means for receiving a change in the magnetic field direction from the magnetic sensors (IC1 to IC3), performing overlap control according to the overlap amount, and controlling the current switching timing of the switching elements (Q1 to Q6). (12b) A brushless motor comprising: 2. The overlap control means (12a).
2. The brushless motor according to claim 1, wherein when the rotation speed of the rotor is low, the amount of overlap is controlled to be large, and when the rotation speed is high, the amount of overlap is controlled to be small. 3. The overlap control means (12a).
The brushless motor according to claim 1 or 2, wherein the amount of overlap changes smoothly in accordance with the rotation speed of the rotor (1). 4. The overlap control means (12a)
However, at the time of switching between the power supply side connection point and the ground side connection point of the armature coil (4), overlap control for applying a voltage to each of the connection points before and after the switching is performed. The brushless motor according to claim 1. 5. The sensor magnet according to claim 1, wherein a plurality of pairs of north poles and south poles are arranged at an equal angle with respect to the center of rotation of the rotor. 5. The brushless motor according to 4. 6. The magnetic sensor (IC1 to IC3)
The brushless motor according to claim 1, wherein a plurality of the motors are arranged around the stator at an equal angle.