JP3106873B2 - 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 for rotating a disk-shaped recording medium, a polygonal reflecting mirror, a VTR cylinder, and the like.

[0002]

2. Description of the Related Art As shown in FIGS. 17 and 18, a rotor 101 of a conventional brushless motor 100 has a ring-shaped magnet 104 having 16 magnetic poles facing an iron core 103 on an inner peripheral surface of a rotor yoke 102. Provided. A rotating shaft 105 is fitted in the center of the rotor 101 and is rotatably supported on a stator base 108 by a bearing 106 and a bearing holder 107.

[0003] On the other hand, the stator 109 is a member of the iron core 103.
Two slots 103a face the magnetic poles of the magnet 104, and each iron core 103 has an armature coil 110
Is provided. On the stator base 108, there are provided a position detecting means 111 for detecting the rotational position of the rotor 101 and a drive circuit 112 for controlling the drive current of the armature coil 110 according to the output signal thereof. A magnetic field corresponding to the rotational position of the rotor 101 is generated. The rotor 101 generates a continuous rotational force by the interaction between the magnetic field generated by the armature coil 110 and the magnetic pole of the magnet 104. FIG. 19 is a conceptual diagram of a conventional brushless motor 100.

[0004]

In the conventional brushless motor 100, as shown in FIGS.
Since the magnet 104 is attached to the inner peripheral surface of the rotor yoke 102, the inertia of the rotor 101 is large and the rise is slow. Similarly, it is necessary to reduce the outer diameter of the iron core 103 of the stator 109 by the thickness of the magnet 104. There is a problem that the generated torque is small.

[0005] Further, if a multi-pole magnetic pole is provided on the magnet 104, a portion having a low magnetic flux density is formed at the boundary between the poles, so that the effective total magnetic flux amount cannot be sufficiently obtained. There is also a problem that a large amount of magnetic flux is required and a special member is required to cut off the magnetic flux. Also,
In order to obtain a necessary magnetic flux with the performance improvement of the motor, it is necessary to use a rare earth magnet material having a high residual magnetic flux density, and there is also a problem that arranging the magnet all around the rotor increases the cost.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a brushless motor having a small inertia, a fast start-up, and a large torque. Things.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a position detecting means for detecting a position of a rotor, a driving circuit for controlling a driving current in accordance with an output of the position detecting means, and a driving circuit for the driving circuit. A stator having an armature coil disposed on a stator base by passing a drive current to generate a rotating magnetic field, and rotatably supported on the stator via a rotating shaft to generate a rotating force according to the rotating magnetic field The rotor has a magnetoresistive modulator with the stator in the circumferential direction, a magnet having magnetic poles is provided on the stator, and the main magnetic flux of the magnetic poles interlinks with the armature coil. In a brushless motor that takes a path passing through the magnetoresistive modulator, the stator base includes:
A part of the main magnetic flux path was constituted mainly of a magnetic material.

[0008] The stator base may be mainly composed of a magnetic material and constitute a part of a path of the main magnetic flux, and the armature coil may be arranged on an outer periphery of the rotor.

[0009]

[0010] The stator base may have a copper foil wiring path formed by etching on an iron plate via an insulating layer, and a part of the copper foil wiring path may be subjected to a terminal treatment of the armature coil.

A folded coil portion may be formed in the copper foil wiring path, and the folded coil portion may be provided so as to interlink with a part of the main magnetic flux, thereby providing a means for detecting the rotation of the rotor.

The rotary shaft may be made of a high magnetic permeability material so as to form a part of the path of the main magnetic flux.

[0013] The rotor may be provided with a magnetic path plate which is opposed to the stator base by a surface so as to be close to the stator base, and may constitute a part of a path of the main magnetic flux.

[0014]

Since no magnet is provided on the rotor, the inertia of the rotor is reduced and the start-up speed is increased. Further, when the armature coil is disposed on the outer periphery of the rotor, the outer diameter of the iron core can be increased, and the generated torque can be increased. Also, if a folded coil part is formed on the copper foil wiring path,
The folded coil portion functions as a rotation detecting means of the rotor.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a longitudinal sectional view of a first embodiment of the brushless motor according to the present invention, FIG. 2 is a transverse sectional view thereof, and FIG. 3 is a longitudinal sectional view of a second embodiment of the brushless motor according to the present invention. 4 is a cross-sectional view of the same, FIG. 5 is a schematic plan view of an iron-based printed wiring board, FIG. 6 is a schematic side view showing terminal processing of an armature coil using the iron-based printed wiring board, and FIG.
FIG. 8 is a longitudinal sectional view of a third embodiment of the brushless motor according to the present invention, FIG. 8 is a transverse sectional view thereof, FIG. 9 is a conceptual diagram of the brushless motor according to the present invention, and FIGS. FIG. 14 is a longitudinal sectional view showing a magnetic flux path of the third embodiment, and FIG.
5 is a drive circuit diagram of the brushless motor according to the present invention, FIG.
6 is a timing chart.

A first embodiment of the brushless motor according to the present invention, as shown in FIGS.
A magnetoresistive modulator 5 facing the iron core 4 of the stator 10 is provided on an inner peripheral surface of a rotor yoke 3 constituting the rotor 2 of FIG. Further, the rotor 2 has a rotating shaft 6 fixed at its center,
The stator base 9 includes a pair of bearings 7 and a bearing holder 8.
It is rotatably supported on the top. On the other hand, the stator 10
Indicates that the twelve slots 4a of the iron core 4
The armature coil 11 is provided on each iron core 4.

A portion of the iron core 4 where the armature coil 11 is not provided is provided with a magnet 12 having a single magnetic pole in the thickness direction. The magnetic flux generated by the magnet 12 reaches the rotor yoke 3 mainly through the air gap G1, and further reaches the magnetoresistive modulator 5 through the inside of the rotor yoke 3,
A path is established such that the magnetic resistance modulating section 5 returns to the opposite magnetic pole of the magnet 12 through the teeth 4b of the iron core 4 while interlinking with the armature coil 11 through the slot 4a of the iron core 4 opposed thereto.

On the stator base 9, a position detecting means 13 for detecting the rotational position of the rotor 2 and a driving circuit 14 for controlling a driving current of the armature coil 11 according to an output signal thereof.
Are provided, and the armature coil 11 generates a magnetic field according to the rotational position of the rotor 2. The rotor 2 generates a continuous rotational force due to the interaction between the magnetic field generated by the armature coil 11 and the magnetic pole of the magnet 12.

The magnetoresistive modulator 5 has eight convex portions and eight concave portions arranged alternately and evenly in the circumferential direction, and has a radial distance from the opposed 12 teeth 4b of the iron core 4. Is rotor 2
It is configured to greatly change with the rotation of.
That is, the magnetic resistance decreases and the passing magnetic flux increases when the convex portion is closer to the teeth 4b, and the magnetic resistance increases and the passing magnetic flux decreases when the concave portion is closer to the teeth 4b. Note that the outer peripheral surface of the rotor yoke 3 is also
In the same manner as described above, it is formed of a convex portion and a concave portion.

The magnitude of the magnetic flux passing through one tooth 4b due to the rotation angle between the magnetoresistive modulator 5 of the rotor 2 and the tooth 4b due to the change in the magnetic resistance is shown in FIG.
As shown in a, the polarity changes in a substantially sinusoidal manner with the same polarity, and the magnetic flux passing through the other teeth 4b is also 1 electrical angle.
It changes in a substantially sinusoidal shape like b and c shown in FIG. 16 with a phase difference of 20 degrees.

Since these magnetic fluxes interlink with the armature coil 11, the number of interlinkage changes in the same manner as a, b and c, and V = N
The counter electromotive force V equal to the product of the value obtained by differentiating the change in the magnetic flux φ with time t, such as × dφ / dt, and the number of turns N of each of the coils L1, L2, L3 of the armature coil 11 is represented by d, e shown in FIG. , F
Are generated in the coils L1, L2, L3 of each phase with the following waveforms.

On the other hand, a position detecting means 13 arranged near the teeth 4b of the iron core 4, for example, a Hall element H shown in FIG.
G1, HG2, and HG3 also pass a magnetic flux that changes substantially in the same manner as the magnetic flux passing through the teeth 4b, and the Hall element HG
1, HG2 and HG3 generate outputs (voltages) such as g, h, and i shown in FIG.

FIG. 15 shows a driving circuit of the brushless motor 1 according to the present invention, and includes NPN transistors Q1 to Q1.
2, Q16 to Q18, Q25, Q26, PNP transistors Q13 to Q15, Q19 to Q24, resistor R1,
R2, R7 to R17 are provided.

The output signals g, h, and i of the Hall elements HG1, HG2, and HG3 are processed by a differential amplifier circuit (including transistors Q1 to Q6) shown in FIG.
Drive signals such as j, k, l, m, n, and o indicated by 6 and drive transistors Q13 to Q1 are supplied so that predetermined drive currents U, V, and W flow through coils L1, L2, and L3 of each phase.
8 is driven.

The resistor R17 is a current detecting resistor that collectively flows the drive currents U, V and W and converts it into a voltage drop.
A current feedback loop is formed such that negative feedback is made to the emitters of the NPN transistors Q25 and Q26 via the NPN transistor 16. The bases of the NPN transistors Q25 and Q26 are
They are commonly connected and serve as control inputs for drive currents U, V, and W.

As shown in FIG. 16, drive signals j, k,
Drive currents U, V, and W flowing through the coils L1, L2, and L3 of the respective phases of the armature coil 11 are generated in the coils L1, L2, and L3 of the respective phases of the armature coil 11 due to 1, m, n, and o. If the Hall elements HG1, HG2, and HG3 are arranged so that the phases (timings) match the back electromotive forces d, e, and f, a continuous rotational force (torque) s can be obtained without interruption in three phases.

As described above, the stator 10 is provided with the magnet 12 having magnetic poles, and the rotor 2 is provided with the magnetoresistive modulator 5 with the stator 10 in the circumferential direction. Interlinks with
The brushless motor 1 is configured by taking a path that passes through the magnetoresistive modulator 5 of the rotor 2.

In the second embodiment of the brushless motor according to the present invention, as shown in FIGS. 3 and 4, a magnet 20 is provided between the iron core 4 and the stator base 9 made of a magnetic material. The slot 4a and the armature coil 11 are the same as in the first embodiment, and the magnet 20 also has a ring shape having a single pole in the thickness direction. Further, a magnetoresistive modulator 15 facing the iron core 4 of the stator 10 is provided on the inner peripheral surface of the rotor yoke 3 constituting the rotor 2 as in the first embodiment.

The magnetoresistive modulator 15 has eight convex portions and eight concave portions arranged alternately and evenly in the circumferential direction, and has a radial distance from the opposing 12 teeth 4 b of the iron core 4. Are largely changed with the rotation of the rotor 2. That is, when the convex portion is closer to the teeth 4b, the magnetic resistance is reduced and the magnetic flux passing therethrough is increased, and the concave portion is formed as the teeth 4b.
, The magnetic resistance increases and the passing magnetic flux decreases. The outer peripheral surface of the rotor yoke 3 is formed in a circular shape unlike the first embodiment, but may be formed by a convex portion and a concave portion as in the first embodiment.

The main magnetic flux of the magnetic pole of the magnet 20 passes through the inside of the stator base 9, reaches the outer peripheral portion of the rotor 2 through the air gap G 2, and from there the slot 4 a of the iron core 4 which faces through the magnetoresistive modulator 15. And passes through the teeth 4b while interlinking with the armature coil 11 to return to the opposite magnetic pole of the magnet 20. In order to reduce the magnetic resistance, the gap G2 between the rotor 2 and the stator base 9 is configured to be as small as possible.

In the second embodiment, as in the first embodiment, the rotor 2 generates a continuous torque due to the interaction between the magnetic field generated by the armature coil 11 and the magnetic poles of the magnet 20.

The stator base 9 is not formed of a single magnetic material, but is etched on a magnetic substrate (iron plate, silicon steel plate) 21 via an insulating layer 22, as shown in FIG. 5 or FIG. As a result, a so-called iron-based printed wiring board having a copper foil wiring path 23 can be formed. And
If the terminal treatment of the armature coil 11 is performed using a part of the copper foil wiring path 23, the number of components can be reduced, and the stator 10 can be made thin and lightweight. In addition,
11a is a terminal of the armature coil 11, and 24 is solder.

Further, as shown in FIG.
A folded coil portion 25 is formed in the vicinity of a gap between the rotor 2 and the stator base 9 so that the folded coil portion 25 interlinks with a part of the main magnetic flux, for example, without providing a special FG magnet. The unit 25 can output an FG signal (a rotation detection signal having a frequency proportional to the rotation speed of the rotor 2) by interlinking with a part of a main magnetic flux as a rotation detection unit.

In a third embodiment of the brushless motor according to the present invention, as shown in FIGS. 7 and 8, three teeth 31 are formed on an iron core 30 and arranged outside a rotor 32. On the outer peripheral surface of the rotor yoke 33, there is provided a magnetoresistive modulator 34 in which eight convex portions and eight concave portions facing the iron core 30 are alternately and uniformly formed in the circumferential direction.

A magnet 36 having a single magnetic pole in the thickness direction is provided between the iron core 30 and a stator base 35 made of a magnetic material. The path of the main magnetic flux of the magnetic pole of the magnet 36 passes through the teeth 31 while passing through the slots of the iron core 30 and interlinking with the armature coil 37 as shown by an arrow A in FIG. A path is reached so as to reach the magnetoresistive modulating section 34, pass through the inside of the stator base 35 via the gap G4, and return to the opposite magnetic pole of the magnet 36.

The drive circuit 14 is arranged on the stator base 35 inside the rotor yoke 33. In the third embodiment, as in the first embodiment, the rotor 32 generates a continuous torque due to the interaction between the magnetic field generated by the armature coil 37 and the magnetic pole of the magnet 36.

FIGS. 11 to 13 are longitudinal sectional views of a brushless motor in which a magnetic path is formed for the purpose of reducing the magnetic resistance of the magnetic circuit in the third embodiment. FIG. 11 shows a configuration in which a magnetic path plate 40 is provided on the rotor 32 so as to be close to the stator base 35 and faces the surface thereof, and forms a part of the path of the main magnetic flux to reduce the magnetic resistance of the magnetic circuit. . Here, the path of the main magnetic flux of the magnetic pole of the magnet 36 forms a loop indicated by an arrow B.

FIG. 12 shows a magnetic circuit having a reduced magnetic resistance by using a part of the rotor yoke 33 as a magnetic path plate 41 approaching and facing the stator base 35. Here, the path of the main magnetic flux of the magnetic pole of the magnet 36 forms a loop indicated by an arrow C. FIG.
1 and the rotor 32 shown in FIG.
8 cannot be arranged on the stator base 35 inside the rotor yoke 33, so it is arranged outside the rotor yoke 33.

FIG. 13 shows a structure in which the rotating shaft 39 is formed of a material having high magnetic permeability and forms a part of a main magnetic flux path to reduce the magnetic resistance of the magnetic circuit. If the bearing (bearing and bearing holder) 42 is also formed of a material having a high magnetic permeability, the magnetic resistance is further reduced. Here, the path of the main magnetic flux of the magnetic pole of the magnet 36 forms a loop indicated by an arrow D.

FIG. 14 shows a modification of the third embodiment, in which a magnet 44 is arranged inside a rotor yoke 33 on a stator base 35 via a magnet holder 45 so as to face the teeth of the iron core 30. This is a circuit configuration. The magnet holder 45 is formed of a high magnetic permeability material. Here, the path of the main magnetic flux of the magnetic pole of the magnet 44 forms a loop indicated by an arrow E. In addition, if the magnet 44 is used for the portion of the stator holder 46, the magnetic flux further increases and the torque increases.

Although the magnetoresistive modulator in this embodiment is formed integrally with the rotor yoke, it goes without saying that it may be formed separately by two pieces. In this embodiment, the position detecting means 1 detects the rotational positions of the rotors 2 and 32.
Although the configuration using the Hall elements HG1, HG2, and HG3 is used as 3, the configuration can be made by another method. For example, a method of detecting the rotational positions of the rotors 2 and 32 according to the induced electromotive force of the armature coils 11 and 37, and a frequency generator for detecting the speed are separately provided. A method of detecting the rotational position may be used.

[0042]

As described above, according to the present invention, since no magnet is provided on the rotor, a brushless motor having a small inertia and a fast rise can be constructed. Further, since the magnet is not provided on the rotor, the space for mounting the magnet is not required, so that the outer diameter of the iron core of the stator can be increased accordingly, and the generated torque increases.

Further, since the magnetic pole of the magnet is a single pole, there is no portion having a low magnetic flux density at the boundary between the poles, and the total magnetic flux can be increased to 2 / π times that in the case of a multipole, so that the generated torque increases.

In the case where the armature coil is disposed on the outer periphery of the rotor, it is not necessary to dispose the magnet on the entire periphery of the rotor, so that the volume of the magnet can be reduced, the leakage magnetic flux is reduced, and the weight of the rotor is reduced. Can be achieved. Further, since the frequency of the magnetic flux passing through the iron core of the armature is small, iron loss can be reduced.

Further, when the armature coil is arranged on the outer periphery of the rotor, the radial attraction between the rotor and the stator is different between the side where the iron core is arranged and the opposite side, and the gap between the rotating shaft and the bearing is different. Even when a sliding bearing having a large diameter is used, the gap always moves in a certain direction, and the rotation accuracy of the rotating shaft is improved. Also,
Since the armature coil and the iron core that generate heat as the motor are located outside the rotor, heat radiation is improved.

As a stator base, an iron-based printed wiring board having a copper foil wiring path is formed on a steel sheet by etching via an insulating layer, and the armature coil is terminated using a part of the copper foil wiring path. If this is the case, the number of parts can be reduced, and the stator can be made thin and lightweight.

If a folded coil portion is formed in the copper foil wiring path and the folded coil portion is arranged so as to interlink with a part of the main magnetic flux, the folded coil portion can be rotated without providing a special FG magnet. An FG signal can be output by interlinking with a part of the main magnetic flux as the detecting means.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of a brushless motor according to the present invention.

FIG. 2 is a cross-sectional view of the first embodiment of the brushless motor according to the present invention.

FIG. 3 is a longitudinal sectional view of a second embodiment of the brushless motor according to the present invention.

FIG. 4 is a cross-sectional view of a second embodiment of the brushless motor according to the present invention.

FIG. 5 is a schematic plan view of an iron-based printed wiring board.

FIG. 6 is a schematic side view showing terminal processing of an armature coil using an iron-based printed wiring board.

FIG. 7 is a longitudinal sectional view of a third embodiment of the brushless motor according to the present invention.

FIG. 8 is a cross-sectional view of a third embodiment of the brushless motor according to the present invention.

FIG. 9 is a conceptual diagram of a brushless motor according to the present invention.

FIG. 10 is a longitudinal sectional view showing a magnetic flux path of a third embodiment of the brushless motor according to the present invention.

FIG. 11 is a longitudinal sectional view showing a magnetic flux path of a third embodiment of the brushless motor according to the present invention.

FIG. 12 is a longitudinal sectional view showing a magnetic flux path of a third embodiment of the brushless motor according to the present invention.

FIG. 13 is a longitudinal sectional view showing a magnetic flux path of a third embodiment of the brushless motor according to the present invention.

FIG. 14 is a longitudinal sectional view of a modification of the third embodiment of the brushless motor according to the present invention.

FIG. 15 is a drive circuit diagram of a brushless motor according to the present invention.

FIG. 16 is a timing chart of the brushless motor according to the present invention.

FIG. 17 is a longitudinal sectional view of a conventional brushless motor.

FIG. 18 is a cross-sectional view of a conventional brushless motor.

FIG. 19 is a conceptual diagram of a conventional brushless motor.

[Explanation of symbols]

1: brushless motor, 2, 32: rotor, 3, 33 ...
Rotor yoke, 4,30 ... iron core, 4a ... iron core slot, 4b, 31 ... iron core teeth, 5,15,34 ... magnetic resistance modulator, 6,39 ... rotary shaft, 9,35 ... stator base, 10: stator, 11, 37: armature coil,
11a: Terminal of armature coil, 12, 20, 36, 44
... magnet, 13 ... position detecting means, 14 ... drive circuit,
Reference numeral 21: magnetic substrate (iron plate), 22: insulating layer, 23: copper foil wiring path, 25: folded coil portion, 40, 41: magnetic path plate,
HG1, HG2, HG3 ... Hall element, L1, L2, L
3. Each phase coil of the armature coil.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02K 29/00, 21/00 H02P 6/08

Claims (6)

(57) [Claims] 1. A position detecting means for detecting a position of a rotor, a driving circuit for controlling a driving current in accordance with an output of the position detecting means, and a driving current for the driving circuit is supplied to generate a rotating magnetic field to generate a rotating magnetic field on a stator base. A stator having an armature coil disposed therein; and a rotor rotatably supported on the stator via a rotating shaft to generate a rotating force in accordance with the rotating magnetic field. In a brushless motor having a magnetoresistive modulation section with a magnetic pole on the stator and a main magnetic flux of the magnetic pole linking the armature coil and taking a path passing through the magnetoresistive modulation section, The brushless motor according to claim 1, wherein the stator base mainly includes a magnetic material and forms a part of a path of the main magnetic flux. 2. A position detecting means for detecting a position of a rotor, a driving circuit for controlling a driving current in accordance with an output of the position detecting means, and a driving current for the driving circuit is supplied to generate a rotating magnetic field to generate a rotating magnetic field on a stator base. A stator having an armature coil disposed therein; and a rotor rotatably supported on the stator via a rotating shaft to generate a rotating force in accordance with the rotating magnetic field. In a brushless motor having a magnetoresistive modulation section with a magnetic pole on the stator and a main magnetic flux of the magnetic pole linking the armature coil and taking a path passing through the magnetoresistive modulation section, The stator base mainly forms a part of a path of the main magnetic flux mainly using a magnetic material, and the armature coil includes:
A brushless motor provided on the outer periphery of the rotor. 3. The stator base has a copper wiring path formed by etching on an iron plate via an insulating layer,
3. The brushless motor according to claim 1, wherein a terminal treatment of the armature coil is performed in a part of the copper foil wiring path. 4. A rotation detecting means for the rotor, wherein a folded coil portion is formed in the copper foil wiring path, and the folded coil portion is disposed so as to interlink with a part of the main magnetic flux. The brushless motor as described. 5. The device according to claim 1, wherein a high permeability material is used for the rotating shaft so as to form a part of a path of the main magnetic flux.
The brushless motor according to 2, 3, or 4. 6. The rotor according to claim 1, wherein the rotor is provided with a magnetic path plate approaching the surface of the stator base and facing the stator base, and constituting a part of a path of the main magnetic flux. The brushless motor as described.