JP2679879B2 - Speed control device for brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor control method and apparatus, and more particularly to a brushless motor control method and apparatus capable of driving a brushless motor with high efficiency.

[0002]

2. Description of the Related Art Conventionally, as a control method for a brushless motor, an excitation signal with a duty ratio of 1/3 is usually applied over the entire low speed range to the high speed range, and the rotation speed is controlled by the current value.

In this case, in order to increase the number of revolutions in the high speed range, the current value is increased or the number of turns of the stator coil is reduced to increase the current value. However, if the number of turns is reduced, the current is wasted in the low speed range. However, there was a problem that the efficiency deteriorated.

[0004]

The problem to be solved is that the efficiency is high in the low speed range and the high speed range, and the rotation speed is further increased in the high speed range.

[0005]

According to the present invention, at least two kinds of signals having different duty ratios and / or signals having different lead angles (advance angles) with respect to the magnetic poles of the rotor are prepared as excitation signals for the stator coil of the brushless motor. Then
As the motor speed increases, the excitation signal is switched to one with a larger duty ratio and / or one with a larger lead angle.

[0006]

According to the applicant, in the low speed range, the smaller the duty ratio of the excitation signal and the smaller the lead angle, the more efficiently the rotational speed can be increased with a small current value, and in the high speed range, the larger the duty ratio and the larger the lead angle. Focusing on the fact that the number of revolutions can be increased efficiently, from this point, the duty ratio of the excitation signal and / or the lead angle can be switched to a larger one as the speed increases without decreasing the number of turns of the coil. It is possible to control the motor up to a higher rotation speed with high efficiency without supplying useless current in the range.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention.
A to 2C are signal waveform diagrams in each part of FIG. FIG.
2, a magnetic pole position detector of the rotor, for example, three Hall sensors 6a to 6c is provided on the inner periphery of the stator facing the rotor of the brushless motor 2, and a magnetic pole piece is provided on the outer periphery of the rotor.

The Hall sensors 6a to 6c output pulses in response to the magnetic flux from the magnetic pole pieces. These output pulses are input to the Hall signal generating circuit 10. The Hall sensors 6a to 6c rotate around the rotor. For example, as shown in FIG. 4A, they are provided at intervals of 30 degrees along the direction. still,
FIG. 4 illustrates a 4-pole motor.

The hall signal generating circuit 10 outputs a hall signal which is a three-phase rectangular signal shown in FIG. 2A in response to the output pulses of the hall sensors 6a to 6c, and one of them outputs to the division signal generating circuit 12. And to the speed detector 8 and, on the other hand, 1/2 to the terminal 14a of the switch 14.
It is given as a duty signal (C in FIG. 2). Here, it is assumed that one wavelength of the Hall signal corresponds to, for example, a rotation angle of 45 degrees of the rotor.

The division signal generation circuit 12 is used to generate U for each hall signal.
The duty ratio of the phase, the V phase, and the W phase is converted to 1/3, and the divided signals of the U phase, the V phase, and the W phase, that is, 1/3 duty signals are output (B in FIG. 2). That is, the fall of the U-phase hall signal is synchronized with the rise of the V-phase hall signal, the fall of the V-phase hall signal is synchronized with the rise of the W-phase hall signal, and the fall of the W-phase hall signal is performed. Is synchronized with the rise of the U phase. The 1/3 duty signal is provided to the terminal 14b of the switch 14.

The switch 14 selects one of the Hall signal and the 1/3 duty signal applied to the terminals 14a and 14b in response to the output of the speed detector 8. Speed detector 8
Detects the rotation speed of the motor 2 based on the cycle (frequency) of the output pulse of the hall sensor 6a and outputs a signal indicating whether the rotation speed is equal to or higher than a predetermined speed to the switch 14. The switch 14 selects the hall signal when the rotation speed exceeds a predetermined speed, and selects the 1/3 duty signal when the rotation speed is less than the predetermined speed and gives the same to the output control unit 16.

Therefore, the output control unit 16 supplies a predetermined excitation signal to the excitation coils 18U, 18V, 18W of the stator of the motor 2 when the rotation speed exceeds a predetermined speed, the duty ratio being 1/2 as shown in C of FIG. When the speed is equal to or lower than the speed, an excitation signal having a duty ratio of 1/3 shown in FIG. 2B is given.

FIG. 3 shows the motor rotation speed (r
pm) and torque (kg, cm),
A curve 31 shows the characteristics of the excitation signal with a duty ratio of 1/2, and a curve 32 shows the characteristics of the excitation signal with a duty ratio of 1/3. As is apparent from the figure, in the low speed range, the excitation signal with a duty ratio of 1/3 has a higher rotational speed than the excitation signal with a duty ratio of 1/2 with respect to the same torque value, and the reverse is true in the high speed range. .

By the way, comparing the duty signals of the same phase of B and C in FIG. 2, for example, the U phase, the center phase P ₂ of the high level section of the 1/2 duty signal is the 1/3 duty signal. The lead angle (angle α in FIG. 5) because the phase is advanced by β compared to the phase P ₃ at the center of the high-level section
Is also considered to have advanced by β. This also applies to the other phases.

Therefore, in the low speed region as described above, the excitation signal having the duty ratio of 1/3 is applied to make the lead angle smaller than that of the excitation signal having the duty ratio of 1/2, and the current value is made small so that the rotation speed can be increased with high efficiency. It can be increased, and in the high-speed range, by giving an excitation signal with a duty ratio of 1/2, the current value is made larger than that of an excitation signal with a duty ratio of 1/3, and the lead angle is made large so that the rotation speed can be increased with high efficiency. It is possible to obtain a high-efficiency motor by reducing the waste of current. Incidentally, the speed v shown in FIG. 3 is preferable as the predetermined speed for switching the duty ratio and / or the lead angle.

Next, a second embodiment will be described with reference to FIG. In this embodiment, the divided signal generating circuit 12 is not provided, and two types of Hall sensors are provided for the 1/2 duty ratio and the 1/3 duty ratio. In the figure, those having the same functions as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 4, Hall sensors 6a to 6c are for generating a 1/2 duty ratio signal, and the Hall sensor 7
a to 7c are for generating a 1/3 duty ratio signal. The Hall sensors 7a to 7c are arranged on the inner peripheral surface of the stator along the rotation direction of the rotor at intervals of 30 degrees as shown in FIG. 4B, for example. It is arranged offset. The direction of deviation may be the opposite direction of the drawing.

The output pulses of the Hall sensors 7a to 7c are applied to the Hall signal generator 20 to generate a signal having a duty ratio of 1/3 shown in B of FIG. The following operation is the same as that of the first embodiment, and the same effect as that of the first embodiment can be obtained.

In the above embodiments, the duty ratios of the excitation signals at low speed and high speed are set to 1/3 and 1/2, respectively, but other values such as 1 / n and 1 / m may be used. Both n and m are positive integers and may be n> m.

In each of the above embodiments, the duty ratio and / or the lead angle is switched in two stages according to the speed, but it may be switched in three or more stages, and the duty ratio is increased or / and the lead angle is increased as the speed increases. Should be increased. Also,
In the case of reversing the motor, the same effect can be obtained by reversing the duty signal used.

[0020]

As described above, in the present invention, by providing an excitation signal having a small duty ratio or / and a small lead angle at low speed, higher rotation can be obtained with a small current value, and at high speed the duty ratio or Higher rotation can be obtained by applying an excitation signal having a large lead angle and / or lead angle, and thus waste of current can be omitted, and a highly efficient motor can be obtained. That is, the motor can be efficiently controlled by switching the duty ratio and the lead angle according to the rotation speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a timing chart showing a signal waveform in each part of FIG.

FIG. 3 is a characteristic diagram showing the relationship between the duty ratio of the excitation signal to the motor and the torque-rotation speed of the motor.

4A and 4B are diagrams showing the positions of the Hall sensor and the magnetic pole of the rotor in the first and second embodiments, respectively.

FIG. 5 is a diagram for explaining a lead angle.

FIG. 6 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

[Explanation of symbols]

 2 Brushless motors 6a to 6c Hall sensor 8 Speed detector 10 Hall signal generator 12 Divided signal generation circuit 14 Switch 16 Output control unit 18U, 18V, 18W Stator coil

Claims (10)

(57) [Claims] 1. A speed detecting means (8) for detecting a rotation speed of a brushless motor, and each of said motors generating a hall signal of a predetermined duty ratio in response to a predetermined rotation angle position of said motor. Multiple Hall sensors with the same number as the number of phases (6, 7)
A means (10, 12, 20) for generating duty signals of at least two different duty ratios and different lead angles from the plurality of Hall signals; and the higher the speed detected by the speed detecting means, Means (14) for selecting a duty signal having a large duty ratio and a large lead angle from among the duty signals
And a means (16) for generating an excitation signal to the motor based on the selected duty signal, the speed control device for a brushless motor. 2. A speed detection means (8) for detecting the rotation speed of a brushless motor, and Hall sensors (6) the same in number as the number of phases of the motor.
Then, in response to the specified rotation angle position of the motor, each phase
The hall signal with the first duty ratio to the first duty
First duty signal generating means for generating a signal
(6, 10) and in response to the first duty signal,
Has a second duty ratio different from the duty ratio of 1.
The lead angle different from that of the first duty signal above.
A second Deyute <br/> I signal generating means (12) for generating a second duty signal having the higher speed detected by the speed detecting means, for each phase the first, second Means (14) for selecting a duty signal having a large duty ratio and a large lead angle among the duty signals, and means (16) for generating an excitation signal to the motor based on the selected duty signal for each phase. A speed control device for a brushless motor, comprising: 3. The first duty signal generating means
(6, 10) is the above-mentioned first duty of 1/2 duty for each phase.
1 for each phase , and the second duty signal generating means (12) for each phase
Has a 1/3 duty and the first duty signal
No. 2 lead angle smaller than the lead angle
Generates I signal, said selecting means, for each phase, the detection speed of the motor selects the second duty signal when less than the predetermined value, when the above predetermined value the first de Yuti signal 3. The brushless motor speed control device according to claim 2, wherein 4. When the number of phases of the motor is n and the number of poles is m (n and m are both positive integers), the number of Hall sensors is n, and the Hall sensors are the inner circumference of a stator of the motor. 3. The speed control device for a brushless motor according to claim 2, wherein the motors are arranged at an angular interval of 360X2 / nXm from each other along the rotation direction of the rotor of the motor. 5. The number of phases of the motor is 3, the number of poles of the motor is 8, the number of Hall sensors is 3, and the Hall sensors are arranged along the inner circumference of a stator of the motor. 3. The speed control device for a brushless motor according to claim 2, wherein the speed control devices are arranged at an angular interval of 30 degrees from each other along the rotation direction of the rotor of the motor. 6. The number of phases of the motor is 3, and
The number of hall sensors is 3,The first duty signal generating means (6, 10) is
 U, V, W phaseFirst duty aboveGenerate a signal,The second Duty signal generationmeans(12) isIn synchronization with the fall of the U-phase first duty signal
Fall, the rising of the first duty signal of the W phase
Second duty signal of U phase rising in synchronization with falling
Issue AndIn synchronization with the fall of the first duty signal of the V phase
Fall of the U-phase first duty signal
V-phase second duty signal that rises in synchronization with falling
Issue In synchronization with the fall of the first duty signal of the W phase
Falling of the first duty signal of the V phase
The second D of the W phase that rises in synchronization with the fall Tee Shin
Issue The brushless motor according to claim 3, wherein
Data speed control device. 7. a speed detecting means for detecting a rotational speed of the brushless motor (8), 1 for each phase in response to a predetermined rotational angle position of the motor
A first set of Hall sensors (6) having the same number as the number of phases of the above-mentioned motor, which generate a first Hall signal of / 2 duty .
And 1 for each phase in response to the predetermined rotation angle position of the motor.
A second set of Hall sensors (7) that generate a second Hall signal with a / 2 duty and are equal in number to the number of phases of the motor.
And the first set of Hall sensors and the second set of Hall sensors are arranged at a predetermined angle offset from each other along the rotation direction of the rotor of the motor, and are responsive to the first and second Hall signals. Duty signal generating means (1) for generating first and second duty signals having different duty ratios and different lead angles for each phase.
And 0,20), the higher the speed detected by the speed detecting means, each
The first for each phase, and means (14) for selecting the larger duty signal of large and lead angle of the duty ratio of the second duty signal, the excitation to the motor based on the duty signal for each phase, which is the selected A brushless motor speed control device comprising means (16) for generating a signal. 8. The duty signal generating means (10, 2)
0) is 1 / for each phase in response to the first Hall signal.
A first duty generating a first duty signal of two duty
The Hall signal generator (10) and the second Hall signal
In response, the second duty of 1/3 duty for each phase
A second Hall signal generator (20) for generating a signal
And, said selection means, for each phase, that the detection speed of the motor selects the second duty signal when less than the predetermined value, selecting the first duty signal when above predetermined value The speed control device for a brushless motor according to claim 7 . 9. When the number of phases of the motor is n and the number of poles is m (n and m are positive integers), the respective numbers of the Hall sensors of the first and second sets are n,
The Hall sensors of the first and second sets are arranged at an angular interval of 360X2 / nXm with respect to each other along the inner circumference of the stator of the motor and along the rotation direction of the rotor of the motor. 8. The brushless motor according to claim 7, wherein the Hall sensor and the second set of Hall sensors are arranged at a predetermined angle of 360X2X2 / nXmXm from each other along the rotation direction of the rotor of the motor. Speed control device. 10. The number of phases of the motor is three, the number of poles of the motor is eight, and the number of Hall sensors of each of the first and second sets is three. The two sets of Hall sensors are arranged along the inner circumference of the stator of the motor along the rotation direction of the rotor of the motor at angular intervals of 30 degrees from each other, and the Hall sensors of the first set and the second set of Hall sensors are arranged. 8. The speed control device for a brushless motor according to claim 7, wherein the Hall sensors of the pair are arranged at a predetermined angle of 7.5 degrees from each other along the rotation direction of the rotor of the motor.