JP4141543B2 - Brushless motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brushless motor that optimizes the switching timing of a current flowing through an armature coil in an outer rotor type brushless DC motor suitable for driving a blower fan for a vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, DC motors that switch the direction of current flowing through an armature coil by using a commutator and a brush are used for motors mounted on vehicles such as automobiles, for example, rotational drive motors for blower fans used in air conditioners. I came.
[0003]
This conventional DC motor mounted on a vehicle uses a vehicle battery as a power source and is driven by a constant voltage power source. For this reason, in rotation control of a DC motor using a brush, the power supply voltage is divided by a voltage dividing resistor. For example, when the battery voltage is 12V and the DC motor is driven at 3V, the remaining 9V is applied to the voltage dividing resistor and consumed as heat. For this reason, the power consumed by the voltage dividing resistor is wasted and the energy efficiency is not good. Furthermore, the sliding noise caused by the brush was the cause of noise generation.
[0004]
[Problems to be solved by the invention]
However, when the DC motor has a brushless structure and rotation control is performed with the duty of the power supply voltage varied (pulse width control), the torque generation efficiency varies depending on the timing of switching the current flowing through the armature coil from the detection position of the rotor magnetic pole. To do. Also, depending on the switching timing, the loud sound due to resonance between the motor and the storage case also changes.
[0005]
Unlike the switching timing at which the torque generation efficiency is maximized and the switching timing at which the beat sound is minimized, if the priority is placed on efficiency, the beat sound increases, and if the beat sound is reduced, the efficiency decreases.
[0006]
Further, more rotational torque is required when the motor speed is increased, but relatively less rotational torque is required when decelerating.
[0007]
Accordingly, an object of the present invention is to provide a brushless motor that has a brushless structure for a DC motor used for a fan or the like, can optimally control the switching timing of the armature coil current, and can quickly change the rotation speed and is low in noise. .
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a brushless motor according to the present invention flows in an armature coil (4) disposed in a stator (3) in an outer rotor type brushless DC motor in which an armature is disposed on the inner peripheral side of the motor. Magnetic poles are provided so as to correspond to the NS magnetic poles of the switching elements (Q1 to Q6) for switching the current and the field permanent magnet (2) attached to the rotor (1), and the field permanent magnet (2) Are attached to the rotor (1) integrally with a certain delay angle, and are attached to the sensor magnet (5) indicating the rotational position of the rotor (1), the stator (3), and the sensor magnet (5). a magnetic sensor (IC1 to IC3) for detecting the direction of a magnetic field, receiving the magnetic field direction change detection signal from the magnetic sensor (IC1 to IC3), our rotational speed of the rotor (1) Calculating a change amount of the prime mover, in response to this rotational speed, the current of the armature coil with respect to the rotational position before Symbol field magnetizing the permanent magnet (2) by advancing the magnetic field direction change detection signal (4) An advance angle control means (12a) for setting an advance angle amount for advance angle control for advancing the delay angle of the switching timing, and correcting the advance angle amount with a correction value corresponding to the amount of change in the rotational speed; Timing for receiving a magnetic field direction change detection signal from the magnetic sensors (IC1 to IC3), performing advance angle control according to the corrected advance angle amount, and controlling current switching timing of the switching elements (Q1 to Q6) Control means (12b), and when the rotational speed of the rotor (1) decreases, the advance angle control means (12a) corrects with the correction value that decreases the set advance angle amount, and increases Do By correcting with the correction value that increases the set advance amount, priority is given to low noise when the motor decelerates, and high efficiency is prioritized when the motor speeds up. Control.
[0011]
Further, the advance angle control means (12a) smoothly changes the correction value of the advance amount in accordance with the change amount of the rotation speed of the rotor (1), thereby responding to the change amount of the rotation speed of the motor. Thus, the current switching timing of the switching element is changed smoothly.
[0012]
【The invention's effect】
The brushless motor according to claim 1 of the present invention controls the current switching timing of the switching element with respect to the rotational position of the field permanent magnet according to the rotational speed of the motor and the amount of change thereof , and rotates relatively. When speeding up a motor where torque is a problem, prioritize high efficiency over low noise, and when decelerating a motor where noise generation is a relative problem, lower noise than high efficiency Therefore, it is possible to provide a brushless motor that can change the rotation speed quickly and is low in noise.
[0014]
The brushless motor according to claim 3 of the present invention smoothly changes the current switching timing of the switching element with respect to the rotational position of the field permanent magnet in accordance with the amount of change in the rotational speed of the motor. The change of is gentle, you can get a smooth rotation.
[0015]
In the brushless motor according to claim 4 or 5 of the present invention, the sensor magnet has a plurality of pairs of N poles and S poles, or a plurality of magnetic sensors are arranged, so that the rotor rotates once. Thus, the change in the magnetic field direction can be detected a plurality of times, and even if the rotational speed of the rotor changes, the timing can be finely controlled with a high-speed response following the change.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a bottom view of a brushless motor according to the present invention as viewed from below. FIG. 1A shows a configuration example in which torque generation efficiency is improved, and FIG. 1B shows a configuration example in which noise is reduced. The brushless motor of this embodiment is a three-phase two-pole outer-rotor type brushless DC motor that is used for driving a fan of a vehicle air conditioner. A rotor is provided with a field permanent magnet.
[0018]
The stator 3 has armature coils 4a to 4f arranged in three phases with the projecting portions 3a to 3f as cores, and a rotor having main magnets (field permanent magnets) 2 at intervals of 90 degrees on the outside thereof. 1 is arranged. The sensor magnet 5 that indicates the rotational position of the rotor 1 is attached to a shaft 6 that 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 rotates integrally with the rotor 1. . Hall ICs 1 to 3 (magnetic sensors) for detecting the direction of the magnetic field by the sensor magnet 5 are equally arranged at intervals of 120 degrees on the inner periphery of the stator 3.
[0019]
In the brushless DC motor, the generated torque varies depending on the timing of switching the current flowing through the armature coils 4 a to 4 f from the detection position of the main magnet 2. When the sensor magnet 5 indicating the rotational position of the rotor 1 is attached to the shaft 6 with a delay angle of 30 degrees with respect to the main magnet 2 as shown in FIG. 1A, the generated torque is maximized and the efficiency is improved. As shown in FIG. 1B, when the delay angle is 42 degrees, the beat sound due to resonance between the vibration frequency of the motor and the natural vibration frequency of the motor storage case is minimized. In the present embodiment, the sensor magnet 2 is attached to the shaft 6 with a delay angle of 44 degrees as an example. This is because there is a range of delay angles at which the roaring sound is the smallest due to mechanical errors, etc., and the delay angle is usually at the angle of 44 degrees with a margin for the delay angle of 42 degrees at which the roaring sound is the smallest. This is because the error is compensated by electrical advance control. Note that (1) indicates a coil having a short current path and a current flowing twice that of other armature coils. (2) is a position for generating forward rotation torque due to the repulsive force between the armature coil 3c (3f) and the main magnet 2, and (3) is a position for generating reverse torque due to the repulsive force between the armature coil 3a (3d) and the main magnet 2. Indicates.
[0020]
FIG. 2 is a block diagram of a control circuit unit of the brushless motor according to the present embodiment. The sensor signal detection circuit 11 receives the magnetic field direction change detection signals of the sensor magnets 5 from the Hall ICs 1 to 3, generates respective inverted signals, and sends them to the microcomputer 12 as sensor signals consisting of six signals together with the non-inverted signals. input. 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 into the falling edge for detection. In the processing in the microcomputer 12, the advance angle control means 12a receives the sensor signal, calculates the rotational speed of the motor and the amount of change from the period of the magnetic field direction change detection, and corresponds to this rotational speed. In addition to setting an advance amount for advance control for advancing the delay angle of the current switching timing of the armature coils 4a to 4f with respect to the rotational position of the main magnet ( field permanent magnet ) 2 , the amount of change in rotational speed ( The advance amount is corrected with a correction value corresponding to ( rotational acceleration) . Next, the timing control means 12b receives a sensor signal, an advance amount, and a rotation instruction signal (PWM signal) for instructing the motor to rotate from an air conditioning control device (not shown), and according to the corrected advance amount. The advance angle control is performed, and the current switching timing of the MOSFETs (switching elements) Q1 to Q6 is controlled via the motor drive circuit 13.
[0021]
FIG. 3A is a timing chart when the advance angle control of the control circuit unit of the brushless motor of this embodiment is not performed, and FIG. 3B is a diagram of MOSFETs (Q1 to Q6) controlled at this timing. Indicates the connection relationship. Since the sensor magnet 5 has the N pole and the S pole arranged every 90 degrees, the magnetic field direction change detection signal from the Hall IC changes for two periods while the rotor 1 makes one rotation. This makes it possible to control the rotation of the rotor twice as finely as possible. Further, by arranging three Hall ICs at equal intervals, it is possible to control the rotation of the rotor three times finely. Based on the magnetic field direction change detection from the Hall ICs 1 to 3 arranged at equal intervals, the MOSFETs (Q1 to Q6) are switched on / off a total of 12 times while the rotor 1 makes one rotation, and the MOSFETs that are turned on are switched on. The direction of the current flowing through the armature coils 4a to 4f is switched depending on the combination.
[0022]
FIG. 4 shows a correspondence relationship between (a) the rotor rotational position and (b) the Hall IC signal used for control at that time and the conduction state of the MOSFET. When the rotor rotation angle is 0 degree, a signal from the Hall IC 3 is used to turn on the MOSFETs (Q1) and (Q5). The 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.
[0023]
FIG. 5 shows the energization state of each coil when the Hall IC 3 is switched and the delay angle of the current switching timing of the armature coils 4a to 4f with respect to the rotational position of the main magnet 2 (hereinafter, for the sake of simplicity, the main It is a figure which shows the position by the (delay angle of the sensor magnet 5 with respect to the magnet 2 ) . MOSFETs (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), and current path S2 is U side (+) → coil 4e → coil 4b → coil 4a → coil 4d → V side (GND). Then, since the resistance value of the current path S1 is half, the current value is doubled ( circle 1 in FIG. 1 ). A repulsive force that is particularly strong compared to other coils is generated between the coil having the current value doubled and the main magnet 2, and a strong rotational torque that cancels the reverse torque is generated.
[0024]
6A shows the case where the rotor rotation angle is 30 degrees, and FIG. 6B shows the correspondence between the Hall IC signal used for the control at that time and the conduction state of the MOSFET. When the rotor rotation angle is 30 degrees, the signal from the Hall IC 1 is used to turn on the MOSFETs (Q3) and (Q5). The MOSFET (Q3) is on the power supply side and the MOSFET (Q5) is on the ground side, and a voltage is applied between the connection point W and the connection point V.
[0025]
FIG. 7 is a diagram illustrating the energization 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. MOSFETs (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), and current path S4 is U side (+) → coil 4b → coil 4e → coil 4f → coil 4c → V side (GND). Then, since the resistance value of the current path S3 is half, the current value is doubled.
[0026]
FIG. 8 shows a flow of control for correcting the advance amount by a correction value corresponding to the amount of change in the rotational speed. First, it is determined whether the rotation speed is increasing (ST1), (ST2) as an increase amount A correction value X if increased, Ete the correction value X on the advance amount C ₁ before correction pressurized new The advance amount is C (ST3). If the rotational speed does not increase, and further determines whether or not reduced (ST4), as a decrease amount B correction value X if reduction (ST5), uncorrected advance amount C ₁ in the correction value X is added to obtain a new advance amount C (ST3). If the rotational speed is not decreased, (ST6) a correction value X 0, i.e. as C = C _1, no correction.
[0027]
FIG. 9 shows a change of the correction value X with respect to the rotation speed change amount. When the amount of change increases, the correction value X is set to a positive value and gradually increases as the amount of increase increases. When the amount of change decreases, the correction value X is set to a negative value and gradually increases as the amount of decrease increases. Let it be a small value (a negative value with a large absolute value). Then, by smoothing the change of the correction value X with respect to the increase / decrease of the change amount, the change of the advance amount can be made smooth. As a result, the rotational torque changes gently and a smooth rotation can be obtained.
[0028]
FIG. 10 is a timing chart for outputting a MOSFET output switching control signal based on a signal from the Hall IC. FIG. 10A shows an input signal from the sensor (Hall IC), and FIG. 10B shows a gate signal of the MOSFET. .
[0029]
SAH and SAL shown in (a) indicate a signal from the Hall IC 1 and its inverted signal, respectively. Similarly, SBH and SBL indicate a signal from the Hall IC 2 and SCH and SCL respectively indicate a signal from the Hall IC 3 and its inverted signal. With the above six signals, the timing can be finely controlled for every 30 ° rotation of the rotor.
[0030]
(B) shows the gate signal output to the MOSFET at the time of advance control, AT, BT, CT show the gate signal for the high side (power supply side), AB, BB, CB show the gate signal for the low side (ground side) MOSFET. . In the present embodiment, the timing of the gate signal of the MOSFET is controlled by the falling of the 6 signals of the sensor input. In this case, corresponding to the fall of each sensor signal, the timing corresponding to the next fall (corresponding to 30 ° rotation of the rotor 1) is predicted, and the gate signal of the MOSFET is controlled on / off. At that time, the rotational speed of the rotor and the amount of change thereof are calculated from the time between the falling edges of the sensor signal, and the advance amount for advance control is set corresponding to this rotational speed. The advance amount is corrected with a correction value corresponding to the amount of change. Then, when ON / OFF control of the gate signal of the MOSFET is performed, advance control is performed according to the corrected advance amount, and timing control is performed. The same control can be performed using the rising edge of the sensor signal.
[0031]
FIG. 11 shows the correspondence relationship of the advance control amount with respect to the rotational speed of the motor, where (a) represents the advance amount in angle, and (b) represents the advance amount in time. As shown in (a), the advance amount is set to 0 until the rotational speed of the motor reaches 1800 rpm, and the output of the MOSFET is controlled on / off with a mechanically fixed delay angle D (for example, 44 degrees). This is because when the motor is started, the rotation speed of the motor is not stable, the rotation speed of the rotor is calculated from the time between the falling edges of the sensor signal, and the advance angle control corresponding to the rotation speed is performed. This is because the predictive control for predicting the next falling edge from the detection of the falling edge of the sensor signal causes a deviation from the actual rotational speed, and the advance angle amount does not match the actual rotational speed. In other words, if the advance angle control is performed while the rotational speed is not stable, the rotational torque fluctuates and causes uneven rotation. Therefore, a mechanically fixed delay angle, that is, low noise is obtained until a constant rotational speed is reached. The MOSFET output is on / off controlled by the delay angle, and the advance angle control is not performed.
[0032]
When the number of rotations of the motor reaches 1800 rpm, the advance angle control is started. First, as the advance amount set corresponding to the rotational speed, the delay angle is linearly and continuously changed linearly from D to D-8 up to 2500 rpm. If the delay angle is changed suddenly, the rotational torque also changes suddenly, causing uneven rotation. To avoid this, the delay angle is changed smoothly and continuously. When the rotational speed of the motor is 2500 rpm or more, 8 degree advance control is performed and the delay angle is set to D-8 (36 degrees).
[0033]
Further, the advance amount is corrected with a correction value corresponding to the amount of change in the rotational speed. That is, when the amount of change increases, the correction value X is set to a positive value, and gradually increases as the amount of increase increases. When the amount of change decreases, the correction value X is set to a negative value to increase the amount of decrease. Along with the correction, gradually correct with a small value (a negative value with a large absolute value).
[0034]
In order to perform control according to the rotation speed by software control of the microcomputer, advance time control corresponding to the motor rotation speed shown in (b) is performed. First, since the advance angle control is not performed until the motor rotational speed reaches 1800 rpm, when the falling edge of the sensor signal is detected, the output of the MOSFET is controlled on / off immediately after the detection.
[0035]
When the motor rotation speed reaches 1800 rpm, the advance angle control is started. As shown in FIG. 10, the sensor signal is received every 30 degrees rotation of the rotor 1 and the timing corresponding to the next falling (30 of the rotor 1). The gate signal of the MOSFET is turned on / off by predicting the degree of rotation). That is, as the advance angle control time corresponding to the rotation speed, when the motor rotation speed is 1800 rpm (cycle: 33.3 msec), the time required for the rotor to rotate 30 degrees is 2.78 msec, and when 2500 rpm (cycle: 24 msec) Since the time required for the rotor to rotate 30 degrees is 2 msec, after the time required for the rotation of 30 degrees has elapsed from the falling edge of the sensor signal, the MOSFET gate signal is controlled on / off. In order to perform 8 degree advance control at 2500 rpm, the advance time by software is (2−0.533) msec. Furthermore, the advance amount of 0.533 msec for the advance angle of 8 degrees is corrected with a correction value corresponding to the change amount of the rotation speed. That is, when the speed is increased, the advance angle amount is increased so as to be larger than 0.533 msec. At the time of deceleration, the advance angle amount is decreased so as to be smaller than 0.533 msec. As a result, the advance time is set to a value smaller than (2−0.533) msec during acceleration, and the advance time is set to a value greater than (2−0.533) msec during deceleration.
[0036]
FIG. 12 shows the relationship between the delay angle of the sensor magnet 5 with respect to the main magnet 2 and the noise level. When the rotation speed is 2400 rpm, the beat sound component due to the delay angle is masked due to the influence of the blowing sound, and the noise level becomes constant. When the rotation speed is 900 rpm, the blowing sound becomes small, and therefore the beat sound component becomes relatively large, and the noise becomes small as the delay angle becomes large. For this reason, particularly in the low rotational speed region, the effect of reducing noise by increasing the delay angle is great.
[0037]
FIG. 13 shows the relationship between the delay angle of the sensor magnet 5 with respect to the main magnet 2 and the motor efficiency. The motor efficiency is maximized at a delay angle of about 30 degrees, and as a result, the rotational torque is maximized. Considering the above relationship between the delay angle and the noise level, noise does not change even if the delay angle is changed in the high rotation speed range. Obtainable.
[0038]
From the above, low noise and high efficiency are optimally controlled by the number of revolutions by controlling the amount of advance of the delay angle less when the rotational speed of the rotor is low and by controlling the amount of advance of the delay angle when the rotor speed is high. It is possible to control in proportion.
[0039]
Furthermore, when the rotational speed is increased, the rotational torque is given priority to control the amount of advancement, and when the speed is reduced, no rotational torque is required. Therefore, priority is given to low noise, and the amount of advancement is reduced. To do. As a result, the rotation speed can be changed quickly and a low noise motor can be obtained.
[0040]
FIG. 14 shows a change in the relationship between the motor speed and the twelfth component of the noise depending on the delay angle. For example, at 1000 rpm, that is, 16.7 revolutions per second, the 12th-order component is 200 Hz, and the beat noise is maximized due to resonance between the motor and its storage case. When the rotational speed is further increased, the blowing sound is larger than the roaring sound and masked.
[0041]
FIG. 15 shows a change in the relationship between the motor rotation speed and the 24th order component of the noise depending on the delay angle. For example, at 500 rpm, that is, at 8.3 revolutions per second, the 24th-order component is 200 Hz, and the beat noise is maximized due to resonance between the motor and its storage case. When the rotational speed is further increased, the blowing sound is larger than the roaring sound and masked.
[0042]
As described above, by using the brushless motor of the present invention for driving a fan of a vehicle air conditioner, when the speed is reduced, that is, when the amount of air is reduced, the noise is low, and when the speed is increased, that is, when the amount of air is increased Operates at high efficiency, that is, with high torque, and in response to an instruction to change the rotational speed, it performs control that achieves both high torque torque and low noise rotation as needed, depending on the amount of change in the rotational speed. Optimal correction control can be performed to obtain a comfortable air-conditioning environment.
[0043]
Although the present embodiment has been described as a brushless motor for driving a blower fan of a vehicle air conditioner, it can be similarly applied to a radiator cooling fan of a vehicle engine, and further, a blower fan of an indoor air conditioner, etc. Can also be used.
[Brief description of the drawings]
1A and 1B are bottom views of a brushless motor according to the present invention, in which FIG. 1A is a configuration example in which torque generation efficiency is improved, and FIG.
FIG. 2 is a block diagram of a control circuit unit of the brushless motor of the present invention.
FIG. 3A is a timing chart of a control circuit unit of a brushless motor, and FIG. 3B is a diagram showing a connection relationship of MOSFETs.
4A is a diagram illustrating a correspondence relationship between a rotor rotational position and FIG. 4B is a Hall IC signal and a conduction state of a MOSFET.
FIG. 5 is a diagram showing a state of energization of each coil when the Hall IC 3 is switched and a position according to a delay angle of the sensor magnet with respect to the main magnet.
6A shows a case where the rotor rotation angle is 30 degrees, and FIG. 6B shows a correspondence relationship between the Hall IC signal and the conduction state of the MOSFET.
FIG. 7 is a diagram showing a state of energization of each coil at the time of switching Hall IC 1 and a position according to a delay angle of a sensor magnet with respect to a main magnet.
FIG. 8 is a flowchart showing a flow of control for correcting the advance amount.
FIG. 9 is a diagram illustrating a change of a correction value with respect to a rotation speed change amount.
10A is a timing chart showing an input signal from a sensor (Hall IC), and FIG. 10B is a timing chart showing a MOSFET gate signal.
11A and 11B are diagrams showing an advance control amount with respect to the rotational speed of the motor, in which FIG. 11A shows the advance amount in angle, and FIG. 11B shows the advance amount in time.
FIG. 12 is a diagram showing a relationship between a delay angle of a sensor magnet with respect to a main magnet and a noise level.
FIG. 13 is a diagram illustrating a relationship between a delay angle of a sensor magnet with respect to a main magnet and motor efficiency.
FIG. 14 is a diagram showing the relationship between the motor rotation speed and the twelfth order component of the noise.
FIG. 15 is a diagram illustrating a relationship between a motor rotation speed and a 24th-order component of noise.
[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 to 3 ... Hall IC (magnetic sensor), (1) ... Coil through which double current flows, (2) ... Positive rotation torque generation position, (3) ... Reverse torque generation position.

Claims (4)

In the outer rotor type brushless DC motor in which the armature is arranged on the inner peripheral side of the motor,
Switching elements (Q1 to Q6) for switching a current flowing through the armature coil (4) arranged in the stator (3);
A magnetic pole is provided so as to correspond to the NS magnetic pole of the field permanent magnet (2) attached to the rotor (1), and the rotor (1) has a constant delay angle with respect to the field permanent magnet (2). A sensor magnet (5) attached integrally with the rotor and indicating the rotational position of the rotor (1);
Magnetic sensors (IC1 to IC3) attached to the stator (3) and detecting the direction of the magnetic field by the sensor magnet (5);
In response to the magnetic field direction change detection signal from the magnetic sensor (IC1 to IC3), calculates the rotational speed and the amount of change in the rotor (1), in response to the rotation speed, the magnetic field direction change detection signal proceeds sets the advance amount for the advance control to advance the delay angle of the current switching timing of the armature coils relative to the rotational position before Symbol field magnetizing the permanent magnet (2) by corner (4), said rotating Advance angle control means (12a) for correcting the advance amount by a correction value corresponding to the amount of change in speed;
Timing control for detecting a change in the magnetic field direction from the magnetic sensors (IC1 to IC3), performing advance angle control according to the corrected advance amount, and controlling the current switching timing of the switching elements (Q1 to Q6). Means (12b) ,
When the rotational speed of the rotor (1) decreases, the advance angle control means (12a) corrects with the correction value that decreases the set advance angle amount, and when it increases, the set advance angle amount. A brushless motor, wherein the correction is made with an increasing correction value . The brushless motor according to claim 1, wherein the advance angle control means (12a) smoothly changes the correction value of the advance amount in accordance with the change amount of the rotational speed of the rotor (1) . The brushless according to claim 1 or 2, wherein the sensor magnet (5) has a plurality of pairs of N poles and S poles arranged at an equal angle with respect to the rotation center of the rotor (1). motor. The brushless motor according to any one of claims 1 to 3, wherein a plurality of the magnetic sensors (IC1 to IC3) are arranged at equal angles around the stator (3) .

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