JP4142803B2 - 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]
SUMMARY OF THE INVENTION An object of the present invention is to provide a brushless motor which has a brushless structure for a DC motor used for a fan or the like, and optimally controls the switching timing of the armature coil current, thereby saving energy and reducing noise.
[0007]
[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. A switching element (Q1 to Q6) for switching current and a field permanent magnet (2) attached to the rotor (1) are integrally attached to the rotor (1) at a fixed delay angle, and the rotor (1) A magnetic sensor (IC1 to IC3) that is attached to the stator (3) and detects the direction of the magnetic field by the sensor magnet (5), and this magnetic sensor (IC1 to IC3). ), The rotational speed of the rotor (1) is calculated, and the field permanent magnet for the sensor magnet (5) corresponding to the rotational speed is calculated. The advance control means (12a) for outputting an advance amount for advance control for advancing the delay angle with respect to the stone (2) and the change in magnetic field direction from the magnetic sensors (IC1 to IC3) are detected, and the advance Timing control means (12b) for controlling the advance angle according to the angular amount and controlling the current switching timing of the switching elements (Q1 to Q6), and the advance angle control means (12a) calculates the rotational speed. Is performed based on the time interval of the change in the magnetic field direction of the sensor magnet (5) corresponding to the rotation period of the rotor (1) .
[0008]
With the above configuration, the current switching timing of the switching element is controlled with respect to the rotational position of the field permanent magnet according to the rotational speed of the motor, and in particular, the rotational speed is calculated by the advance angle control means (12a). This is performed based on the time interval of the change in the magnetic field direction of the sensor magnet (5) corresponding to the rotation period of the rotor (1), and the cause of the calculation error of the rotation speed generated within the rotation period is canceled out.
[0009]
Further, the advance angle control means (12a) controls a small advance amount of the delay angle when the rotational speed of the rotor (1) is low, and controls a large advance amount of the delay angle when the rotational speed is high. When the motor rotates at a low speed, priority is given to low noise, and when the motor rotates at a high speed, priority is given to high efficiency.
[0010]
Further, the advance angle control means (12a) smoothly changes the advance amount of the delay angle in accordance with the rotational speed of the rotor (1), so that the current of the switching element depends on the rotational speed of the motor. Change the switching timing smoothly.
[0012]
【The invention's effect】
Since the brushless motor according to the first aspect 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, the motor efficiency and noise are taken into consideration. Thus, the switching timing of the current flowing through the armature coil can be optimally controlled.
[0013]
In the brushless motor according to the second aspect of the present invention, when the motor that is relatively problematic in generating noise is rotating at a low speed, priority is given to low noise over high efficiency, and the efficiency is relatively low. When the motor in question rotates at high speed, control is performed with priority given to high efficiency over low noise, so that a brushless motor with energy saving and low noise can be provided.
[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 according to the rotational speed of the motor. A gentle and smooth rotation can be obtained.
[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]
The brushless motor according to claim 6 of the present invention calculates the rotational speed based on the time interval of the change in the magnetic field direction of the sensor magnet corresponding to the rotation period of the rotor by the advance angle control means, and within the rotation period. Since the factor of the calculation error of the generated rotation speed is canceled, control based on the accurate rotation speed is possible.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a brushless motor according to the present invention will be described below in detail with reference to the drawings.
[0018]
FIG. 1 is a bottom view of a brushless motor to which a first embodiment of a brushless motor according to the present invention is applied, as viewed from below. FIG. 1A is a configuration example in which torque generation efficiency is improved, and FIG. The structural example which becomes low noise is shown. The brushless motor shown in the figure is a brushless DC motor of a three-phase two-pole winding outer rotor type that is used for driving a blower fan of an air conditioner for vehicles, and has an armature coil and an outer rotor on an inner peripheral side stator. Are provided with permanent magnets for the field.
[0019]
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.
[0020]
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.
[0021]
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 change in the magnetic field direction of the sensor magnet 5 from the Hall ICs 1 to 3, generates respective inverted signals, and inputs them to the microcomputer 12 as sensor signals consisting of six signals together with the non-inverted signals. To 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 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 rotation speed of the motor from the period of the magnetic field direction change detection, and the sensor magnet 5 according to this rotation speed. An advance amount for advance control for advancing the delay angle with respect to the field permanent magnet 2 is output. 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 controller (not shown), and an advance angle corresponding to the advance amount. Control is performed to control the current switching timing of the MOSFETs (switching elements) Q1 to Q6 via the motor drive circuit 13.
[0022]
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.
[0023]
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.
[0024]
FIG. 5 is a diagram showing the energization 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. 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 ((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.
[0025]
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.
[0026]
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.
[0027]
FIG. 8 is a timing chart for outputting a MOSFET output switching control signal based on a signal from the Hall IC. FIG. 8A shows an input signal from the sensor (Hall IC), and FIG. 8B shows a gate signal of the MOSFET. .
[0028]
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. In addition, control with high responsiveness to changes in the rotational speed is possible.
[0029]
(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 is calculated from the time between the falling edges of the sensor signal, and the advance amount for the advance control corresponding to the rotational speed is obtained. When the on / off control of the gate signal of the MOSFET is performed, the timing is controlled by performing control according to the advance amount. The same control can be performed using the rising edge of the sensor signal.
[0030]
FIG. 9 shows the correspondence of the advance angle 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.
[0031]
When the number of rotations of the motor reaches 1800 rpm, the advance angle control is started, and the delay angle is linearly and smoothly changed continuously 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).
[0032]
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.
[0033]
When the motor rotational speed reaches 1800 rpm, the advance angle control is started. As shown in FIG. 8, a sensor signal is received every 30 degrees of rotation of the rotor 1, and the timing corresponding to the next fall (30 of the rotor 1). The gate signal of the MOSFET is turned on / off by predicting the degree of rotation). That is, when the motor 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), the time required for the rotor to rotate 30 degrees is 2 msec. Therefore, after the time required for this 30-degree rotation has elapsed from the falling edge of the sensor signal, the MOSFET gate signal is on / off controlled. In order to perform 8 degree advance control at 2500 rpm, the advance time by software is (2−0.533) msec.
[0034]
As described above, in the first embodiment, the rotor rotation speed is calculated from the time required for 30-degree rotation, and the advance time is determined according to the calculated rotation speed, so that high-speed response is possible. Therefore, fine control is possible.
[0035]
Here, in FIG. 10A, the magnetic signal from the sensor magnets detected by the Hall ICs 1 to IC3 is converted into a binary signal by the comparator (not shown) inside the Hall IC in FIG. The output signals that are output after being converted to the same are shown.
[0036]
As shown in this figure, the threshold level of the comparator that inputs the magnetic signal is allowed within a predetermined variation range with respect to the standard value as shown by the arrow 14a in this figure. There is also a possibility that variations occur in the switching timing. Therefore, when the rotational speed is detected based on the edge of the output signal from a different Hall IC, the threshold values of the comparators are not the same, which causes an error in the calculated rotational speed. .
[0037]
Further, as shown by a solid line in FIG. 8A, each magnetic signal should ideally be input to the Hall IC with a phase difference of 120 degrees from each other, but in reality, as shown by a broken line, Shows a different waveform. The factors include the following.
[0038]
As a first factor, due to variations in operations such as soldering, ideally, the intervals between the Hall ICs that should be arranged and fixed at equal intervals become non-uniform. Thereby, the shift | offset | difference with respect to the time axis as shown by the arrow 14b of this figure has arisen. A second factor is that the magnetized state of the sensor magnet becomes uneven due to variations in the magnetization process. For this reason, the magnetic signal is distorted as shown by the arrow 14c in the figure.
[0039]
Therefore, as shown in this figure, the variation of the edge timing with respect to the ideal in the output signal of the actual Hall IC is obtained by adding the above mechanical factor to the electrical factor due to the threshold level of the comparator. Become. For this reason, the actual period with respect to the ideal inter-edge period (in this case, 30 degrees) varies. In this way, when the motor rotation speed is calculated from the cycle between edges where the rotation angle is less than 360 degrees, the calculation error may increase, and it may be difficult to control the advance angle at an accurate rotation speed. There is.
[0040]
Therefore, a second embodiment of the brushless motor of the present invention configured to calculate the number of rotations from the rotation cycle of the rotor, that is, the cycle between edges corresponding to 360 ° rotation will be described. In this embodiment, the number of rotations is calculated from the period between edges corresponding to the rotation angle of the rotor of 360 degrees, and the first is manifested by detection at a period between edges shorter than this (for example, 30 degrees). And the influence of the second factor is prevented. In addition, the detection by the same Hall IC cancels the error in the rotational speed due to the difference in threshold level between the comparators.
[0041]
FIG. 11 is a timing chart for explaining the principle that can reduce the rotational speed error in the second embodiment.
[0042]
As shown in the figure, an output signal having an equal phase difference is ideally obtained from the Hall IC1 to IC3, and one period should be exactly 360 degrees, but this embodiment In fact, within one cycle time of the rotor corresponding to two electrical angles, there are actually deviations a and c at the falling edge and deviations b and d at the rising edge due to the factors described above. .
[0043]
However, by adopting a method for detecting the period between edges corresponding to one period of the rotor, these deviations cancel each other out, and as shown in this figure, an accurate period substantially corresponding to a rotation angle of 360 degrees can be detected. It becomes.
[0044]
FIG. 12 is a flowchart showing the operation of calculating the rotational speed in the advance angle control means 12a, which is repeatedly executed as a previous stage for determining the advance amount.
[0045]
In step S1 in this figure, the advance angle control means 12a detects a signal edge (rise or fall) from the sensor signal detection circuit 11 at a predetermined interrupt port of the microcomputer 12 in a state where a rotation instruction is input. When this is done, the internal timer is reset and a variable i for integrating the number of edges is initialized to 0 (zero). When this processing is interrupted by the edge (rising or falling) of the signal input to the above-described interrupt port, the advance angle control means 12a increments the variable i and accumulates the number of edges in step S3. Then, in step S5, it is determined whether or not the variable i is a predetermined number (4 in this embodiment) corresponding to one cycle of the rotor. In step S3, the next interruption is performed again. On the other hand, if it is determined as YES in step S5, the advance angle control means 12a stops the internal timer and measures the rotor 1 cycle in the next step S7. In step S9, the reciprocal (rotation speed) of the measured rotor 1 cycle is calculated. In step S11, the advance time t is determined by software according to the calculated rotation speed, and the next advancement is determined. Used for angle control. At that time, the advance time t (sec) is expressed as follows: α (degree) as the advance amount and T (sec) as the period of the rotor 1
t = T × (30−α) / 360
Asking. The above operations are sequentially executed while the brushless motor is operating.
[0046]
As is clear from the above description, in the second embodiment, since the rotation speed is calculated based on the period between edges corresponding to the rotation period of the rotor, accurate rotation speed calculation with less error can be performed, It is possible to control the advance angle at an accurate rotational speed.
[0047]
Hereinafter, characteristics common to the first embodiment and the second embodiment of the brushless motor according to the present invention will be described.
[0048]
FIG. 13 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.
[0049]
FIG. 14 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.
[0050]
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.
[0051]
FIG. 15 shows a change in the relationship between the motor rotation 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.
[0052]
FIG. 16 shows the 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.
[0053]
As described above, by using the brushless motor of the present invention for driving the fan of a vehicle air conditioner, the noise is low when the rotation is low, that is, when the amount of air is low, and when the rotation is high, that is, when the amount of air is large. Energy efficient and high torque rotational force can be obtained by high-efficiency operation, and this can be controlled to an optimal ratio according to the rotational speed to obtain a comfortable air-conditioning environment.
[0054]
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]
FIGS. 1A and 1B are bottom views of a brushless motor according to a first embodiment of the present invention, in which FIG. 1A is a configuration example in which torque generation efficiency is improved, and FIG. is there.
FIG. 2 is a block diagram of a control circuit unit in the form shown in FIG.
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.
8A is a timing chart showing an input signal from a sensor (Hall IC), and FIG. 8B is a timing chart showing a MOSFET gate signal.
FIGS. 9A and 9B are diagrams showing the amount of advance control with respect to the number of rotations of the motor, in which FIG. 9A shows the amount of advance, and FIG. 9B shows the amount of advance as time.
FIG. 10 is a diagram illustrating a cause of a motor rotation speed calculation error.
FIG. 11 is a timing chart illustrating the principle of reducing the rotation speed calculation error in the second embodiment of the brushless motor according to the present invention.
12 is a flowchart illustrating a process for calculating the rotation speed in the embodiment shown in FIG.
FIG. 13 is a diagram illustrating a relationship between a delay angle of a sensor magnet with respect to a main magnet and a noise level.
FIG. 14 is a diagram showing a relationship between a delay angle of a sensor magnet with respect to a main magnet and motor efficiency.
FIG. 15 is a diagram illustrating a relationship between a motor rotation speed and a twelfth component of noise.
FIG. 16 is a diagram showing the relationship between the motor rotation speed and the 24th order component of the 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 (5)

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 sensor magnet (5) which is integrally attached to the rotor (1) at a certain delay angle with respect to the field permanent magnet (2) attached to the rotor (1), and indicates 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);
Upon receiving the magnetic field direction change detection from the magnetic sensors (IC1 to IC3), the rotational speed of the rotor (1) is calculated, and the field permanent magnet (2) of the sensor magnet (5) according to this rotational speed. An advance angle control means (12a) for outputting an advance amount for advance angle control for advancing the delay angle with respect to
Timing control means (12b) that receives a change in the magnetic field direction from the magnetic sensors (IC1 to IC3), performs advance angle control according to the advance angle amount, and controls current switching timing of the switching elements (Q1 to Q6). ); and a,
The advance angle control means (12a) calculates the rotational speed based on the time interval of the change in the magnetic field direction of the sensor magnet (5) corresponding to the rotation period of the rotor (1). motor.   The advance angle control means (12a) controls a small advance amount of the delay angle when the rotational speed of the rotor (1) is low, and controls a large advance amount of the delay angle when the rotation speed is high. The brushless motor according to claim 1.   The brushless motor according to claim 1 or 2, wherein the advance angle control means (12a) smoothly changes the advance amount of the delay angle according to the rotational speed of the rotor (1).   The sensor magnet (5) according to any one of claims 1 to 3, wherein a plurality of pairs of N poles and S poles are arranged at an equal angle with respect to the rotation center of the rotor (1). The brushless motor described.   The brushless motor according to any one of claims 1 to 4, wherein a plurality of the magnetic sensors (IC1 to IC3) are arranged around the stator (3) at an equal angle.

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