JPH08154395A - Brushless dc motor - Google Patents

Abstract

PURPOSE: To obtain a brushless DC motor which smoothes a torque ripple and reduces a noise due to the pulsation of a fuel or the like by a method wherein the level of an exciting current at every phase is changed at every angle of rotation of a rotor. CONSTITUTION: Four-phase motor coils 13a to 13d are excited at one phase or two phases by a drive circuit 200. Exciting currents 11 to 14 for respective phases have a duty ratio of 100% during an exciting period at one phase, they have a duty ratio of 50% during an exciting period at two pjases. The electrifying period of the exciting current at one phase becomes a cutoff period in the exciting current at the other phase. The number of generated torque ripples per rotation of a rotor 1 is eight. In addition, since the magnitude of a torque ripple during the exciting period at one phase is suppressed, the torque ripple becomes small, and the magnitude of individual torque ripples becomes nearly equal. In this manner, when the level of the exciting current at every phase is changed at every angle of rotation of the rotor at an integral multiple of the number of phases, the torque ripples are smoothed, and a noise due to the pulsation of a fuel or the like can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor, and more particularly, to a brushless DC motor used as a power source for an electric fuel pump or the like for smoothing torque ripple.
Regarding motors.

[0002]

2. Description of the Related Art Conventionally, in the case of a brushless DC motor, for example, a four-phase two-pole motor, as shown in FIG. 10, four Hall elements 3a, 3b, 3c for detecting a rotation angle of a rotor 2 having a permanent magnet. , 3d, the drive circuit (not shown) causes the cores 12a, 12 of the stator 1 to rotate.
Phases I, II, III wound around b, 12c, 12d,
IV phase motor coils 13a, 13b, 13c, 13d
Is configured to be excited by one phase.

[0003]

However, according to the above-mentioned conventional brushless DC motor, as shown in FIG. 10, four large torque ripples are generated per rotation, so that, for example, fuel is pumped while pulsating. In addition, there is a problem that noise due to fuel pulsation is relatively large.

Therefore, in order to smooth the torque ripple, it is possible to drive the motor by the 1-2 phase excitation method as shown in FIG. However, according to this driving method, as shown in FIG. 11, there is a problem that a large torque ripple is generated during the two-phase excitation period, and smoothing of the torque ripple cannot be sufficiently achieved.

An object of the present invention is to solve the above problems, to provide a brushless DC motor capable of sufficiently achieving smoothing of a torque ripple and sufficiently reducing noise due to pulsation of fuel or the like.

[0006]

According to a first aspect of the present invention, there is provided a rotation angle detecting means for detecting a rotation angle of a rotor, and a drive circuit for exciting 1-2 phase of an n-phase motor coil based on a signal from the rotation angle detecting means. And a rotation angle detecting means, wherein the rotation angle detecting means is “n × N” (N; integer of 2 or more).
Of the brushless DC motor, wherein the drive circuit changes the exciting current level of each phase for each “n × N” rotor rotation angle. .

According to a second aspect of the present invention, the drive circuit changes the exciting current level of each phase by duty control, and the brushless DC motor according to the first aspect is adopted.

In the third aspect, the exciting current of each phase has a pulse waveform, and is 100 during the one-phase exciting period.
% Duty ratio (ratio between energization time and interruption time), and in the two-phase excitation period, with a duty ratio of 50%, the energization period of the excitation current waveform of one phase is The brushless DC motor according to claim 2, wherein the excitation current waveform of the phase is cut off.

In the present invention, the exciting current of each phase has a pulse waveform, and the exciting current is 100 during the one-phase exciting period.
% Duty ratio (ratio between energization time and interruption time), and in the two-phase excitation period, there are a plurality of duty ratios that are switched in stages, and the energization period of the excitation current waveform of one phase is The brushless DC motor according to claim 2, wherein the excitation current waveform of the other phase is cut off.

According to a fifth aspect of the present invention, the rotation angle detecting means is composed of “n × N / 2” Hall elements arranged at equal intervals in the circumferential direction only on one semicircular region side of the stator. The brushless DC motor according to any one of claims 1 to 4 is adopted.

[0011]

According to the brushless DC motor of the first aspect of the present invention, since the exciting current level of each phase is changed for every "n × N" rotor rotation angle, "n × N" per revolution. Torque ripple occurs. Since the number of occurrences of this torque ripple “n × N” is “n” in the case of the above-mentioned conventional case, it is “N” times that of the conventional case, and the torque ripple becomes small. Further, by changing the exciting current level of each phase, it becomes possible to make the magnitudes of the individual torque ripples substantially the same. Therefore, smoothing of the torque ripple can be sufficiently achieved, and noise due to pulsation of fuel or the like can be sufficiently reduced.

A brushless DC motor according to claim 2 is
Since the excitation current level of each phase is changed by duty control, simplification of the drive circuit and power saving can be expected.

According to the brushless DC motor of the third aspect, the exciting current of each phase has a duty ratio of 100% in the one-phase exciting period and 50% in the two-phase exciting period.
In addition to having the duty ratio, the energizing period of the exciting current of one phase becomes the cutoff period of the exciting current of the other phase, so that the current level of the one-phase exciting period and the current level of the entire two phases of the two-phase exciting period are Are equal. Therefore, it is possible to make the sizes of the individual torque ripples substantially the same, it is possible to sufficiently achieve smoothing of the torque ripples, and it is possible to sufficiently reduce noise due to pulsation of fuel and the like.

According to the brushless DC motor of the fourth aspect, since the torque ripple is generated by switching the duty ratio in the two-phase excitation period, the number of torque ripples is increased. Therefore, the torque ripple is further smoothed, and noise due to pulsation of fuel etc.
It can be expected to be further reduced.

In the brushless DC motor according to the fifth aspect, the output pattern of the "n × N / 2" Hall elements arranged at equal intervals in the circumferential direction only in one semicircular region of the stator is the rotor 1 There are “n × N” combinations per rotation. For this reason, all the rotor rotation angles can be detected by half of the rotor rotation angles to be detected, so that the number of Hall elements used can be halved.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a four-phase two-pole, 1-
1 shows the overall configuration of a two-phase excitation brushless DC motor.

In FIG. 1, reference numeral 1 denotes a stator of the motor body 100 shown in FIG. Motor body 10
As shown in FIGS. 2 (A) and 2 (B), 0 has a disk-shaped stator substrate 11, on the upper surface of which four cores 12a, 12b, 12c, 12d are circumferentially arranged. The cores 12a, 12b, 12c, 12d at equal intervals
A four-phase motor coil, that is, an I-phase motor coil 13a,
The II-phase motor coil 13b, the III-phase motor coil 13c, and the IV-phase motor coil 13d are wound. On the other hand, in the rotor 2, on the lower surface of the disk-shaped rotor substrate 21,
A disk-shaped permanent magnet 22 is arranged. The permanent magnet 22 is magnetized so that the lower surface of one semicircular region has an N pole and the lower surface of the other semicircular region has an S pole. And
A rotary shaft 23 is fixed to the center of the rotor substrate 21, and the rotary shaft 23 is rotatable by a bearing 14 provided at the center of the stator substrate 11.

Further, four Hall elements 3a, 3b, 3c and 3d are arranged on the upper surface of the stator substrate 11. These Hall elements 3a, 3b, 3c, 3d are arranged at equal intervals (45 ° intervals) in the circumferential direction only in one semicircular region of the disk-shaped stator substrate 11. The Hall elements 3 a, 3 b, 3 c, 3 d are arranged so that
It outputs a Hi level signal when it faces the pole. Therefore, as shown in FIG. 3, four Hall elements 3
The output patterns of a, 3b, 3c and 3d are 4
It changes every 5 ° rotation, and there are 8 combinations per rotor rotation.

Each Hall element 3a, 3b, 3c, 3d is
Four-phase motor coils 13a, 13b, 13 of the stator 1
It is connected to a drive circuit 200 that excites the c and 13d in the 1-2 phase.

The drive circuit 200 includes hall elements 3a and 3a.
four amplifiers 41a for amplifying the outputs of b, 3c and 3d,
41b, 41c, 41d and the amplifiers 41a, 41b,
The signal generation unit 40 includes four inverter circuits 42a, 42b, 42c, 42d that invert the outputs of 41c, 41d. The signal generator 40 includes the Hall elements 3a,
Hall element outputs a1, a2, a3, a4 for every 3b, 3c, 3d
(See FIG. 4) and the inverter circuits 42a, 42b, 42
Two signals consisting of the hall element outputs a1, a2, a3, a4 inverted by c and 42d are separately output. Eight AND circuits 5 are provided on the output side of the signal generator 40.
1a, 51b, 51c, 51d, 51e, 51f, 51
A rotation angle detector 50 composed of g and 51h is connected.

The rotation angle detecting section 50 has one AND circuit 51 according to the eight outputs from the signal generating section 40.
a, 51b, 51c, 51d, 51e, 51f, 51g
Or, only 51h outputs a logic "1" signal, and eight AND circuits 51a, 51b, 51c, 51d, 51e, 51 are provided.
The present rotor rotation angle can be indicated depending on which of f, 51g, and 51h outputs the logical "1" signal. That is, the AND circuit 51a outputs a signal indicating "1000" out of the eight output patterns of the four Hall elements 3a, 3b, 3c, 3d.
b1 is output, and the AND circuit 51b outputs "110".
The signal b2 indicating "0" and the AND circuit 51c are "1110".
Signal b3 indicating that the AND circuit 51d is a signal b4 indicating “1111”, the AND circuit 51e is a signal b5 indicating “0111”, and the AND circuit 51f is a signal b indicating “0011”.
6, the AND circuit 51g has a signal b7 indicating "0001",
The AND circuit 51h outputs the signal b8 indicating "0000" (see FIG. 4). Of the rotation angle detector 50,
A duty generator 60 is connected to the output sides of the AND circuits 51b, 51d, 51f, 51h.

The duty generator 60 includes an AND circuit 5
AND circuits 61a, 61b, 61c, 61d that output a 50% duty signal when a logical "1" signal of 1b, 51d, 51f, 51h is input, and input from these AND circuits 61a, 61b, 61c, 61d It is composed of AND circuits 62a, 62b, 62c, and 62d with an inverter that invert the incoming 50% duty signal. The output side of the duty generator 60 has 4
Four OR circuits 71a, 71 for controlling switching of the power supply transistors 4a, 4b, 4c, 4d for supplying exciting current to the phase motor coils 13a, 13b, 13c, 13d
A switching control unit 70 including b, 71c, and 71d is connected.

Each OR circuit 71 of the switching control unit 70
a, 71b, 71c, 71d are logical "1" signals from the AND circuits 51a, 51c, 51e, 51g of the rotation angle detection unit 50, and AND circuits 61a, 61b, 61c, 61.
50% duty signal from d, AND circuit 62a,
Signals c1, c2, c3, c consisting of inverted signals of 50% duty signals from 62b, 62c, 62d or logic "0" signals
4 (see FIG. 4) to the feeding transistors 4a, 4b, 4c,
It is applied to the base of 4d.

Since the drive circuit 200 is configured as described above, the outputs a1, a2, a3, a4 of the amplifiers 41a, 41b, 41c, 41d and the AND circuits 51a, 51b, 51 are formed.
Output b of c, 51d, 51e, 51f, 51g, 51h
1, b2, b3, b4, b5, b6, b7, b8 and respective OR circuits 71a, 71
The outputs c1, c2, c3, c4 of b, 71c, 71d are as shown in FIG. The OR circuit outputs c1, c2, shown in FIG.
c3, c4 That is, as is apparent from the base voltage of the power supply transistor, the four-phase motor coils 13a, 13b, 13
c and 13d are excited by 1-2 phase by the drive circuit 200, and the excitation currents I1, I2, I3, and I4 of each phase have a duty ratio of 100% in the one-phase excitation period, and the two-phase excitation period. Has a 50% duty ratio, and the energizing period of the exciting current of one phase becomes the cutoff period of the exciting current of the other phase.

FIG. 5 shows the rotor rotation angle and the exciting currents I1, I2, I3, I4 of the brushless DC motor configured as described above.
The relationship between (motor coil applied voltage) and torque ripple is shown. As shown in FIG. 5, the number of torque ripples generated per one rotation of the rotor is "8", and the magnitude of the torque ripple during the two-phase excitation period is suppressed, so that the torque ripple becomes small, and The magnitudes of the individual torque ripples are substantially the same.

FIG. 6 shows the rotor rotation angle and the exciting currents I1, I2 in the second embodiment in which six Hall elements are used and the duty ratio in the two-phase exciting period is set in two stages of 30% and 70%. , I3, I4 and the torque ripple are shown. As shown in FIG. 6, since the number of torque ripples generated per one rotation of the rotor is "12", the torque ripple is further reduced.

FIG. 7 shows the rotor rotation angle and the exciting current in the third embodiment in which eight Hall elements are used and the duty ratio in the two-phase excitation period is set to three stages of 30%, 50% and 70%. The relationship between I1, I2, I3, I4 and torque ripple is shown. As shown in FIG. 7, since the number of torque ripples generated per one rotation of the rotor is "16", the torque ripple is further reduced.

FIG. 8 is a three-phase two-pole type 1-
The overall structure of a brushless DC motor with two-phase excitation is shown, and the reference numerals in the figure correspond to those in FIG.

According to this embodiment, each amplifier 41a, 4a
Outputs a1, a2, a3 of 1b, 41c, and AND circuits 51a, 5
Outputs b1, b2, b of 1b, 51c, 51d, 51e, 51f
The outputs c1, c2, c3 of 3, b4, b5, b6 and the OR circuits 71a, 71b, 71c are as shown in FIG. 9, and the number of generated torque ripples is "6".

As described above, according to the brushless DC motors according to the above-mentioned embodiments, "n × N", that is, "4 × 2", "4 × 3", "4 × 4" or "3 ×".
Since the exciting current level of each phase is changed for each rotor rotation angle of "2", "8", "12" per rotation,
A torque ripple of "16" or "6" occurs. In the case of the above-mentioned conventional case, the number of occurrences of this torque ripple is "n", so that it is "N" times that of the conventional case.
Torque ripple is reduced.

In the first embodiment, the exciting current of each phase has a duty ratio of 100% during the one-phase excitation period and a duty ratio of 50% during the two-phase excitation period. Since the energization period of the excitation current of one phase is a cutoff period for the excitation current of the other phase, the current level of the one-phase excitation period becomes equal to the current level of all the two phases of the two-phase excitation period. Therefore, it is possible to make the sizes of the individual torque ripples substantially the same, it is possible to sufficiently achieve smoothing of the torque ripples, and it is possible to sufficiently reduce noise due to pulsation of fuel and the like.

Further, in the second and third embodiments, since the torque ripple is generated by switching the duty ratio in the two-phase excitation period, the number of torque ripples is increased. Therefore, the torque ripple can be further smoothed, and noise due to pulsation of fuel or the like can be expected to be further reduced.

Further, in each of the above-mentioned embodiments, only "n × N /", which is arranged in one circumferential region of the stator at equal intervals in the circumferential direction.
The output patterns of 2 ”Hall elements are“ n × N ”combinations per one rotation of the rotor. For this reason, all the rotor rotation angles can be detected by half of the rotor rotation angles to be detected, so that the number of Hall elements used can be halved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a 4-phase 2-pole, 1-2-phase excitation brushless DC motor according to a first embodiment.

FIG. 2 shows a configuration of a motor main body 100, and FIG.
The longitudinal sectional view, FIG. 2B is a sectional view taken along line BB in FIG. 2A.

FIG. 3 is a diagram showing an output pattern of four Hall elements 3a, 3b, 3c, 3d.

FIG. 4 is a timing chart for explaining the operation of the drive circuit 200.

FIG. 5 is a diagram showing the relationship between rotor rotation angle, exciting currents I1, I2, I3, I4 (motor coil applied voltage) and torque ripple.

FIG. 6 is a rotor rotation angle and exciting current in the second embodiment.
Diagram showing the relationship between I1, I2, I3, I4 (motor coil applied voltage) and torque ripple

FIG. 7 is a rotor rotation angle and exciting current in the third embodiment.
Diagram showing the relationship between I1, I2, I3, I4 (motor coil applied voltage) and torque ripple

FIG. 8 is an overall configuration diagram of a brushless DC motor with 3-phase 2-pole and 1-2-phase excitation according to a fourth embodiment.

FIG. 9 is a timing chart for explaining the operation of the drive circuit 200.

FIG. 10 is a diagram for explaining a problem of a conventional brushless DC motor.

FIG. 11: Brushless D considered as a premise of the present invention
Figure for explaining the problem of C motor

[Explanation of symbols]

1 Stator 2 Rotor 3a, 3b, 3c, 3d Hall element (rotation angle detecting means) 13a, 13b, 13c, 13d Motor coil 200 Drive circuit I1, I2, I3, I4 Excitation current for each phase

Claims (5)

[Claims] 1. A brushless DC motor comprising: a rotation angle detecting means for detecting a rotation angle of a rotor; and a drive circuit for exciting a n-phase motor coil by 1-2 phase based on a signal from the rotation angle detecting means. The rotation angle detecting means is configured to detect a rotor rotation angle of “n × N” (N; an integer of 2 or more), and the drive circuit sets the rotor rotation angle of “n × N”. , A brushless DC motor characterized by changing the exciting current level of each phase. 2. The brushless DC motor according to claim 1, wherein the drive circuit changes the exciting current level of each phase by duty control. 3. The exciting current of each phase has a pulse waveform, has a duty ratio of 100% (ratio between energization time and interruption time) in the one-phase excitation period, and
3. The phase excitation period has a duty ratio of 50%, and the energization period of the excitation current waveform of one phase is a cutoff period of the excitation current waveform of the other phase. Brushless DC motor. 4. The excitation current of each phase has a pulse waveform, has a duty ratio of 100% (ratio between energization time and cutoff time) in a one-phase excitation period, and
The phase excitation period has a plurality of duty ratios that are switched in stages, and the energization period of the excitation current waveform of one phase is a cutoff period of the excitation current waveform of the other phase. The brushless DC motor according to 1. 5. The rotation angle detecting means are arranged at equal intervals in the circumferential direction only on one semi-circular region side of the stator, “n ×”.
The brushless DC motor according to any one of claims 1 to 4, wherein the brushless DC motor comprises N / 2 "Hall elements.