JPH0559669B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a brushless motor with a frequency generator.

TECHNICAL BACKGROUND Brushless motors with frequency generators for constant speed control are known to be useful.

A brushless motor having such a frequency generator has a stator electric motor equipped with a printed circuit board on which a comb-shaped conductive pattern for forming a frequency generator is formed at a position facing the magnetic poles for forming the frequency generator of the field magnet constituting the rotor. It is arranged on the child side.

In the above brushless motor, the frequency generator is formed by the frequency generator forming magnetic poles and the conductive pattern.

Here, using a disk-type brushless motor as an example, the circumferential speed of the field magnet, which is the rotor, is faster at the outer periphery, so the comb-shaped brushless motor is arranged face-to-face with the frequency detection magnetic pole. When the conductive pattern is formed on the outer periphery, a larger amplitude of frequency power generation pressure can be obtained, and a disk-type brushless motor can be configured that can perform constant speed control with more precision.

Further, in a normal brushless motor, a current must be passed in a predetermined direction to a predetermined armature coil depending on the position of the field magnet, so it is necessary to provide a position detecting means. Here, recent brushless motors use magnetoelectric conversion elements such as Hall elements, Hall ICs, and magnetoresistive elements as position detection elements. To arrange the position sensing element,
Although there are various methods, it is preferable to use a printed circuit board on which the comb-like conductive pattern is formed, since it is possible to inexpensively mass-produce a disk-type brushless motor having a frequency generator. The above-mentioned position detection element is required to have a very high accuracy in positioning, and the positioning can be performed with higher precision as it is disposed closer to the outer periphery of the printed circuit board on which the comb-shaped conductive pattern is formed. As for the method for installing the position sensing element on the printed circuit board, in order to easily and accurately fix the position sensing element to the back surface of the printed circuit board on which the conductive pattern is formed, a position sensing element housing is installed on the printed circuit board. One option is to drill a through hole. However, since such a through hole must be formed on a surface portion of the printed circuit board that does not face the conductive pattern, it is usually necessary to form either the through hole or the conductive pattern inside.

If the above-mentioned conductive pattern is given priority and formed on the outer periphery of the printed circuit board, the positioning of the position sensing element is difficult and cannot be mass-produced easily, and the positioning accuracy deteriorates, resulting in a decrease in performance. , and give priority to the through hole for housing the position sensing element.
When formed on the outside of the printed circuit board, the frequency power output obtained from the comb-like conductive pattern has a small amplitude, and a disk-type brushless motor with a frequency power generator that can be accurately controlled at constant speed is constructed. There were disadvantages that I could not get.

Therefore, even if both the comb-shaped conductive pattern and the through hole for housing the position sensing element are formed on the outer periphery of the printed circuit board, the above drawbacks will not occur, and the frequency power generation with large amplitude can be generated. A disc-type brushless motor with a high-precision frequency generator that can be mass-produced at a low cost can be obtained by obtaining constant pressure and performing constant speed control with high precision, and by making it possible to easily position the position detection element with high precision. It is desirable to do so.

Therefore, since the inventor of the present application has previously invented a disc-type brushless motor 1 as shown in FIGS. 1 to 7, the disc-type brushless motor 1 will be explained first.

Fig. 1 is a longitudinal cross-sectional view of a disk-type brushless motor 1 having a frequency generator, and Fig. 2 is a partial view of the brushless motor 1 shown in Fig. 1, in which a cylindrical bearing housing 2 protruding from the center is integrally formed. A stator armature 5 consisting of four groups of air-core armature coils is fixed to the upper surface of the stator yoke 3 via an insulating seal (not shown). Stator armature 5
A position sensing element housing through hole 6 is formed in the upper surface, a position sensing element 7 is stored in the through hole 6, and a terminal 8 of the element 7 is soldered to the lower surface. A printed circuit board 1 on which a ring-shaped conductive pattern 9 for forming a frequency generator is formed by etching or other means on the upper surface facing the substrate 6.
0 is fixed by adhesive or other means. Bearings 11 and 12 are mounted at both upper and lower opening ends of the bearing housing 2. Rotating shaft 13
The bearings 11 and 12 are rotatably supported. A rotor yoke 14 is fixed to the top of the rotating shaft 13, and a 2p
(p is a positive integer of 2 or more) Pole driving magnetic pole 15a
A flat annular field magnet 15 having magnetic poles 15b for forming a frequency generator, magnetized to an even number times as many as the driving magnetic poles 15a, is fixed to the outer periphery of the field magnet 15. It faces the printed circuit board 10 in a plane. The driving magnetic pole 15a of the field magnet 15 faces the stator armature 5 via the microgap 16 and the printed circuit board 10, thereby forming a disk type brushless motor. The frequency detecting magnetic pole 15b of the field magnet 15 faces the comb-shaped conductive pattern 9 via a minute gap 16, thereby forming a frequency generator.

FIG. 3 is a plan view of the stator armature 5. FIG.

The stator armature 5 is formed by arranging six armature coils 4-1, ..., 4-6 wound in a fan frame shape at equal intervals so as not to overlap each other in a plane. There is. The stator armature 5 is formed of six armature coils 4-1, . Each armature coil 4-
1, . . . , 4-6 are widths in which the opening angle between the conductor portions 4a and 4b contributing to the generated torque in the radial direction is approximately equal to the width per magnetic pole of the driving magnetic pole 15a of the field magnet 15; That is, since the driving magnetic poles 15a are formed into eight poles as will be clear later, they are formed into a fan frame shape with an opening angle width of 45 degrees. The circumferential conductor portions 4c and 4d of the armature coils 4-1, . . . , 4-6 are conductor portions that do not contribute to the generated torque. Since the armature coils 4-1 and 4-4 are in the same phase, the position detection element 7-1
Since the armature coils 4-2 and 4-5 are in the same phase, the position sensing element 7-2 is shared, and the armature coils 4-3 and 4-6 are in the same phase, so the position sensing element 7-2 is shared. 7-3 is shared. The position detection elements 7-1, .
Armature coils 4-1,...,4-
They are housed in through holes 6-1, .

FIG. 4 is a plan view of a printed circuit board 10 on which a comb-shaped conductive pattern 9 for forming a frequency generator is formed. On the outer periphery of the upper surface of the printed circuit board 10, radial power generation line elements 9a are formed at intervals equal to the pitch of the frequency detection magnetic poles 15b by means such as etching.
A ring-shaped conductive pattern 9 having the same number of poles as the number of poles is formed. Three position sensing elements are placed on the surface of the printed circuit board 10 facing the position sensing elements 7-1, . Through hole 6 for storage
-1,...,6-3 are formed, and the through holes 6-1,...
..., 6-3 respectively have position sensing elements 7-1,...
..., 7-3 is stored. Such a through hole 6-1,
..., 6-3 must be formed on the printed circuit board 10 facing the conductive pattern 9, but if they are formed at such a position, the conductive pattern 9 will be disconnected. Therefore, a sufficiently large through hole 6-1,...
..., 6-3, omitted portions 9b-1, ..., 9b-3 are provided in which an appropriate number of power generating line elements 9a in the radial direction are omitted, so that the conductive pattern 9 is not disconnected. Through holes 6-1, ..., 6-
It is formed through a position that avoids 3. By doing this, the position sensing elements 7-1, ..., 7-
3 and the conductive pattern 9 can be arranged preferentially on the outer periphery of the printed circuit board 10.

FIG. 5 shows an annular field magnet 1 having a driving magnetic pole 15a and a frequency generator forming magnetic pole 15b.
5 is a bottom view of FIG. The field magnet 15 is an annular magnet made of, for example, ferrite, and has eight driving magnetic poles 15 magnetized in the thickness direction so as to have N and S driving magnetic poles alternately in the circumferential direction.
a, and on the outer periphery of the same surface as the driving magnetic pole 15a, a magnetic pole 15b for forming a frequency generator of an even number multiples of the driving magnetic pole 15a, in this example 80 poles, is formed by double magnetization means. ing. N-pole driving magnetic pole 15
In a, a frequency generator-forming magnetic pole 15b having a strongly magnetized N-pole magnetized part and a weakly magnetized N'-pole magnetized part at fine evenly spaced pitches is formed, and the S-pole is driven. In the magnetic pole 15a, a magnetic pole 15b for forming a frequency generator is formed which has a strongly magnetized S-pole magnetized portion and a weakly magnetized S'-pole magnetized portion at fine, evenly spaced pitches. weakly magnetized
The N' pole acts as the S pole and is also weakly magnetized.
The S' pole acts as the N pole. For this reason, the magnetic poles 15b for forming the frequency generator are formed with fine evenly spaced pitches, and N
It is the same as having alternating poles and S poles, so
It may be magnetized in this way.

Therefore, the magnetic flux density waveform 17 of the gap 16 formed by the field magnet 15 becomes as shown in FIG. 6a.

As shown in FIG. 6a, the driving magnetic pole 15a
The magnetic flux density waveform 18 formed by the frequency generator forming magnetic pole 15b is superimposed on the magnetic flux density waveform 17 formed by the driving magnetic pole 15.
A finely uneven waveform is formed at the peaks or valleys of the magnetic flux density waveform 17 formed by a. Therefore,
As shown in FIG. 6b, the frequency for power generation can be obtained by extracting the magnetic flux density waveform 18 formed by the magnetic pole 15b for forming a frequency generator. If you convert it into generated voltage using , you can obtain the voltage for speed control.

FIG. 7 shows the driving magnetic pole 15 of the field magnet 15.
FIG. 4 is a developed view of a stator armature 5 consisting of groups of six armature coils 4-1, . . . , 4-6. As is clear from this developed view, the six armature coils 4-1, . . . , 4-6 are arranged at equal intervals so as not to overlap each other. Each armature coil 4-
Both terminals 1, . . . , 4-6 are connected to a three-phase one-way energization control circuit 19. Armature coil 4-1
The terminals of one of the conductor portions of 4-4 and 4-4 are connected in common, and are connected to the collector of the transistor _Tr1 in the circuit 19. Armature coil 4-2 and 4-
The terminals of one of the conductor portions of the transistors 5 are commonly connected and connected to the collector of the transistor Tr ₂ in the circuit 19. The terminals of one of the conductor portions of the armature coils 4-3 and 4-6 are commonly connected and connected to the collector of the transistor _Tr3 in the circuit 19. The terminals of the other conductor portions of the armature coils 4-1, ..., 4-6 are commonly connected to the positive power supply terminal 2.
Connected to 0. Transistor Tr ₁ ,...,
The emitters of Tr ₃ are commonly connected to the negative power supply terminal 2.
Connected to 1. Transistors Tr ₁ , Tr ₂ ,
The base of Tr ₃ is connected to the output terminals of position detection elements 7-1, 7-2, and 7-3 via resistors R ₁ , R ₂ , and R ₃ , respectively. Position sensing element 7-1,...
..., 7-3 positive power supply terminal 22-1, ..., 22
-3 are commonly connected and connected to the positive side power supply terminal 20. The negative power terminals 23-1, . . . , 23-3 of the position detection elements 7-1, . . . , 7-3 are commonly connected to the negative power terminal 21.

Therefore, when the position detection elements 7-1, . . . , 7-3 detect either the N pole or the S pole of the driving magnetic pole 15a of the field magnet 15, the transistors Tr ₁ , . . . , Tr ₃ are activated. Continuity, armature coil 4-
1, . . . , 4-6 are energized in a predetermined direction to obtain rotational torque in a predetermined direction. The generation of such rotational torque causes the field magnet 15 to rotate in a predetermined direction.

Incidentally, when every other power generation line element 9a group in the radial direction of the conductive pattern 9 faces, for example, N or S of the frequency generator forming magnetic pole 15b, the line element 9a group between them is N'. or opposite S′. As a result, an electromotive force is generated in the same direction according to the rotation speed of the frequency generator forming magnetic pole 15b by each wire element 9a, and a frequency corresponding to the rotation speed of the rotor is detected from the output terminals 9c and 9d of the conductive pattern 9. I get the output.

Although the pulsed magnetic flux generated by the frequency generator forming magnetic pole 15b appears intermittently, the conductive pattern 9
are formed all around the circumference as shown in FIG. 4, so the detection output is obtained as a continuous wave. Moreover, even if there is pitch unevenness in the magnetic pole 15b for forming the frequency generator,
Pitch unevenness is averaged out by the conductive pattern 9 having a plurality of groups of power generating line elements 9a, and when the rotational speed of the rotor is constant, a detection output of a constant frequency is obtained. A variation in the rotor rotational speed is extracted as a frequency modulation component of the detection output. Since the disc-type brushless motor 1 has the above-mentioned configuration, when the position detection elements 7-1, . 1, .

Further, the rotation speed is determined by feeding back a signal from the frequency generator formed by the frequency generator forming magnetic pole 15b and the conductive pattern 9 to the rotation speed control circuit, so that the field magnet 15 is kept at a constant rotation speed. It can be rotated.

As is clear from the above, the disk type brushless motor 1 has a portion 9b in which two radial power generation line elements 9a contributing to power generation of the comb-shaped conductive pattern 9 are omitted, and the power generation line element 9a is omitted. Omitted part 9
By forming a through hole for accommodating the position sensing element in the portion facing b and accommodating the position sensing element in the through hole, priority can be given to both the positioning accuracy of the position sensing element and the formation of the conductive pattern.

However, when the above-mentioned power generation line element omitted portion is provided in a position that was not previously used, the terminal 9 of the conductive pattern 9
There was a drawback that the output waveform of the frequency generator obtained from c and 9d was sloppy and flutter became worse.

For example, the 8-pole driving magnetic pole 15a shown in FIG.
A field magnet 15 having 80 magnetic poles 15b for forming a frequency generator, and a conductive pattern in which two power generating line elements 9a as shown in FIG. 8 are omitted to form one power generating line element omitted portion 9b. Taking a disc-type brushless motor using 9 as an example, the output waveform by the frequency generator forming magnetic pole 15b is not affected in any way, but there is an even number of power generating line elements 9a formed by the conductive pattern 9 shown in FIG. In this case, when the field magnet 15 rotates, when half of the power generating line elements 9a group generates power in a certain direction, the remaining half of the power generating line elements 9a group generates power in the opposite direction. . For this reason, the driving magnetic pole 15a does not generate a frequency power generation output, but the boundary between the N and S poles of the driving magnetic pole 15a face each other near the center of the generating line element omitted portion 9b. At this time, the N pole or S pole faces an odd number of power generating line elements 9a, and the N pole or S pole faces one more power generating line element 9a than the other magnetic pole, so that the frequency of FIG. The power generation pressure waveforms 18'a and 18'b appear largely in a certain direction, causing irregularities in the frequency power generation pressure waveform 18' as a whole, and as a result, there is a drawback that the disk type brushless motor 1 has poor flutter.

FIG. 10 is a plan view of a conductive pattern 9 in which four power generating line elements 9a are omitted and a power generating line element omitted portion 9b is formed at one location. Frequency power generation pressure waveform 1 when using the conductive pattern 9 shown in FIG.
8' has roughness as shown in FIG.

In Fig. 12, 10 power generation line elements 9a are omitted, and 3
FIG. 7 is a plan view of a conductive pattern 9 in which generating line element omitted portions 9b are formed at certain locations. When the conductive pattern 9 shown in FIG. 12 is used, a rough frequency power generation voltage waveform 18' appears as shown in FIG. 13.

In this way, the rough frequency power generation pressure waveform 18'
In this case, there is a drawback that the disk type brushless motor 1 has poor flutter, but the same problem occurs when the conductive pattern 9 shown in FIG. 4 is used.

As described above, conventionally, when some of the power generation line elements 9a of the conductive pattern 9 are omitted for reasons such as disposing the position detection element 7, the frequency may vary depending on the position of the field magnet. The problem was that the generated pressure waveform became uneven, which caused flutter to worsen. This also applies to cylindrical brushless motors.

(Object of the present invention) The present invention has been made in view of the above circumstances, and for reasons such as attaching a position detection element, a part of the power generation line elements of the conductive pattern is omitted to form a power generation line element omitted part. Even so, it is necessary to obtain a brushless motor with a uniform frequency power generation pressure waveform and good flutter, and especially in a disc-type brushless motor having a frequency generator, conductive patterns and position sensing elements should be mounted on a printed circuit board. By making it possible to arrange and form them on mutually opposing parts of the outer periphery, and obtaining a large-amplitude frequency power generation pressure waveform, and by making it possible to easily position and arrange the position sensing element, it is possible to achieve highly accurate frequency power generation. The purpose of this design was to enable low-cost mass production of disk-type brushless motors.

(Means for Achieving the Object of the Present Invention) The object of the present invention is to provide a 2p (p is a positive integer of 1 or more) driving magnetic pole having N and S magnetic poles alternately, and a multiplier that is an even multiple of the driving magnetic pole. A field magnet having magnetic poles for forming a frequency generator formed by polar magnetization is provided as a rotor that rotates relative to the stator armature, and a frequency generator is provided at a position facing the magnetic poles for forming the frequency generator. In a brushless motor having a frequency generator in which an insulator such as a printed circuit board on which a ring-shaped comb-shaped conductive pattern is disposed on the stator armature surface facing the field magnet, the conductive pattern is When one or more radial power generation line elements are omitted, the power generation line element of the conductive pattern is omitted at a point that is 180 degrees out of phase in electrical angle from the omitted part of the power generation line element, or at the same position. This is achieved by providing a brushless motor with a frequency generator characterized in that it is short-circuited.

Hereinafter, embodiments of the present invention will be described with reference to FIG. 14 and subsequent figures.

(Embodiments of the Present Invention) As the brushless motor of the present invention, the disc-type brushless motor 1 shown in FIG. 1 may be adopted, so only the conductive pattern 9 in which the present invention differs from the conventional one will be described. Further, the present invention is advantageous for a 2p field magnet 15 having N and S magnetic poles alternately, such as the field magnet 15 shown in FIG.
(p is a positive integer of 2 or more) The driving magnetic pole 15a of the pole (the field magnet 15 in FIG. 5 has 8 poles) and the number of even multiples of the driving magnetic pole 15a (in addition, In the example shown below, the field magnet 15 shown in Fig. 5 is used. Only conductive patterns convenient for application will be described.

FIG. 14 is a plan view of a conductive pattern 9-1 showing a first embodiment of the present invention, which eliminates the drawbacks of the conductive pattern 9 shown in FIG. In the conductive pattern 9-1, when the two power generating line elements 9a protruding toward the outside of the circle are omitted to form a power generating line element omitted part 9b-1, the power generating line element omitted part 9b-1 is When the boundary between the N pole and the S pole of the drive magnetic pole 15a is opposed to each other in the middle part, as explained for the conductive pattern 8 in FIG. A power generation line element omitted part 9b-2 is also formed in a portion of the conductive pattern 9-1 which is 180 degrees electrically shifted from the element omitted part 9b-1. Note that the power generation line element omitted portion 9b-2 may be formed at a position of the conductive pattern portion 9e under equal conditions with the power generation line element omitted portion 9b-2. If the power generation line element omitted part 9b-2 is provided separately from 9b-1 in the above condition position, the power generation line element omitted part 9b-
Since the opposing relationship between the N and S poles of the drive magnetic poles 15a of 1 and 9b-2 is reversed, the power generation line element omitted part 9
The voltage generated at b-2 is the power generation line element omitted part 9b-1
A voltage in the opposite direction is generated, and the frequency generated voltage waveform obtained by the conductive pattern 9-1 is the driving magnetic pole 1.
5a, a uniform frequency power generation pressure waveform 18'' shown in FIG. 15 is obtained.As shown in FIG. 15, a uniform frequency power generation pressure waveform 18'' is obtained. By using 18'' as the speed control voltage, a disc-type brushless motor 1 with good flutter can be obtained.

FIG. 16 is a plan view of a conductive pattern 9-2 showing a second embodiment of the present invention.
are the two power generating wire elements 9 sticking out towards the inside of the circle.
A is omitted to form a power generation line element omitted part 9b-1, and a power generation line element omitted part 9b-2 is also formed in a part of the conductive pattern 9-2 whose phase is shifted by 180 degrees in electrical angle from the omitted part 9b-1. It has become a thing of the past. With such a conductive pattern 9-2, a desirable frequency power generation voltage waveform 18'' can be obtained similarly to the conductive pattern 9-2 shown in FIG. 14 above.

FIG. 17 shows a plan view of a conductive pattern 9-3 showing a third embodiment of the present invention, which eliminates the drawbacks of the conductive pattern 9 shown in FIG.
Generating line element omitted parts 9b-1, ..., 9b-5
is formed. Omitted part 9b-1, ..., 9b-
3 has a through hole 6- in the printed circuit board facing this.
1,...,6-3 are provided, and the through holes 6-1,...,
Position detection elements 7-1, ..., 7 for each of 6-3
-3 was provided to accommodate the 3. The omitted section 9b-1 is obtained by omitting the four power generation line elements 9a, and in order to prevent the flutter from worsening due to the formation of the omitted section 9b-1, the omitted section 9b-1 is omitted.
A power generation line element omitted portion 9b-5 in which four power generation line elements 9a are omitted is formed at a position 180 degrees out of phase in electrical angle from . In order to prevent the flutter from worsening due to the formation of the power generation line element omitted part 9b-2 in which two power generation line elements 9a are omitted, 6 A power generating line element omitted portion 9b-3 is formed by omitting the actual power generating line element 9a. In addition, in order to prevent the flutter from worsening due to the formation of the omitted portion 9b-3, four power generating line elements 9a are placed at positions 180 degrees out of phase in electrical angle.
A power generation line element omitted section 9b-4 is provided in which the generation line element is omitted. With such a conductive pattern 9-3, a desirable frequency power generation pressure waveform 18'' can be obtained similarly to the conductive pattern 9-2 shown in FIG. 7-3 can be arranged on the outer periphery of the printed circuit board facing the conductive pattern 9-3 without any problem.

(Effects) As is clear from the above configuration, the present invention has devised the conductive pattern, so some of the power generating line elements of the conductive pattern are omitted for reasons such as attaching a position detection element. Even if the omitted portion is formed, a uniform frequency power generation pressure waveform can be obtained, so that a brushless motor with good flutter can be obtained. In particular, in a disk-type brushless motor having a frequency generator, since the conductive pattern and the position sensing element can be arranged and formed on mutually opposing parts of the outer periphery of the printed circuit board, a frequency-generated voltage waveform with a large amplitude can be obtained. Since the position detection element can be easily positioned and arranged, a disc-type brushless motor having a highly accurate frequency generator can be mass-produced at low cost.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a disk-type brushless motor with a frequency generator shown as an example, Fig. 2 is a partial view of Fig. 1, Fig. 3 is a plan view of a stator armature, and Fig. 4 is an example of a disc-type brushless motor. Fig. 5 is a plan view of a printed circuit board on which a comb-shaped conductive pattern for forming a frequency generator is formed; Fig. 5 is a bottom view of a field magnet on which driving magnetic poles and magnetic poles for forming a frequency generator are magnetized; Fig. 6; a is a magnetic flux density waveform diagram of the air gap (micro gap) obtained by the field magnet shown in FIG. 5, FIG. 6b is a magnetic flux density waveform diagram of the air gap area obtained by the magnetic poles for forming a frequency generator, Fig. 7 is a developed view of the stator armature consisting of the driving magnetic poles of the field magnet and the armature coil group, and Fig. 8 is a section where two generating line elements are omitted at one location. FIG. 9 is a plan view of a comb-shaped conductive pattern for forming a frequency generator provided with a frequency generator, and FIG.
The figure is a plan view of a comb-like conductive pattern for forming a frequency generator that has a power generation line element omitted section in which four power generation line elements are omitted in one place, and Figure 11 is a plan view of a comb-like conductive pattern for forming a frequency generator. 12 is a plan view of a comb-shaped conductive pattern for forming a frequency generator with generation line element omissions formed at three locations, and FIG. 13 is a conductive pattern of FIG. 12. 14 is a plan view of a comb-like conductive pattern for forming a frequency generator according to the first embodiment of the present invention, which eliminates the drawbacks of the conductive pattern shown in FIG. FIG. 15 shows a frequency power generation voltage waveform obtained by the conductive pattern shown in FIG. 14, and FIG. 16 is a plan view of a comb-like conductive pattern for forming a frequency generator showing a second embodiment of the present invention. 1
FIG. 7 is a plan view of a comb-shaped conductive pattern for forming a frequency generator according to a third embodiment of the present invention, which eliminates the drawbacks of the conductive pattern shown in FIG. 12. 4... Armature coil, 5... Stator armature,
6... Through hole for storing position detection element, 7... Position detection element, 9, 9-1,..., 9-3... Comb tooth-shaped conductive pattern for forming frequency generator, 9a...
Power generation line element, 9b-1,..., 9b-5...Omitted portion of power generation line element, 10...Printed circuit board, 15...Field magnet, 15a...Driving magnetic pole, 15b...
Magnetic poles for forming frequency generator, 18', 18''...Frequency power generation voltage waveform.

Claims (1)

[Claims] 1 A driving magnetic pole of 2p (p is a positive integer of 1 or more) pole having N and S magnetic poles alternately, and a frequency generator forming magnetic pole formed by magnetizing a multi-pole that is an even number multiple of the driving magnetic pole. A field magnet is provided as a rotor that rotates relative to the stator armature, and a comb-like conductive pattern for forming a frequency generator is formed in a ring shape at a position facing the magnetic pole for forming a frequency generator. In a brushless motor having a frequency generator in which an insulator such as a printed circuit board is disposed on the stator armature surface facing the field magnet,
When one or more radial power generating line elements are omitted, the above conductive pattern is measured in electrical angle from the omitted part of the generating line element.
A brushless motor having a frequency generator characterized in that a generating line element of a conductive pattern at a position 180 degrees out of phase or at a position equivalent to the position is omitted to form a short circuit.