JPH07288961A - Brushless motor - Google Patents

Abstract

PURPOSE:To generate a rotational torque by a subcoil at a dead point by a one-phase bipolar driving by a method wherein two subcoils are wound respectively in the same direction between submagnetic poles adjacent in every other position in the circumferential direction and main coils are wound in the same direction also between the individual subcoils. CONSTITUTION:A stator core 10 is formed in such a way that a plurality of core plates stamped and formed in the same shape by means of a press or the like are laminated in the up-and-down direction. It is provided with main magnetic poles 10a1 to 10a4 and with submagnetic poles 10b1 to 10b4 installed between the main magnetic poles 10a1 to 10a4. When the circumferential width of the main magnetic poles 10a1 to 10a4 is large, a drive torque becomes large, and, when the circumferential width is small, the drive torque becomes small. On the other hand, when the circumferential width of the submagnetic poles 10b1 to 10b4 is large, an auxiliary drive torque becomes large, and, when the circumferential width direction is small, the auxiliary drive torque becomes small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to a brushless motor of a type in which a one-phase coil is driven in a bipolar manner.

[0002]

2. Description of the Related Art A DC brushless motor is, for example, a CD
A shaft rotation type brushless motor as shown in FIG. 3 which is used for rotationally driving a ROM is generally known. The motor shown in the figure has a stator bracket 1 and a rotor hub 2. ing. A hollow cylindrical portion 3 is provided at the center of the stator bracket 1, and an annular stator core 4 is fixedly provided on the outer circumference of the hollow cylindrical portion 3.

A rotating shaft 5 is vertically provided at the center of the rotor hub 2, and the rotating shaft 5 is fitted to an inner ring of a bearing 6 having an outer ring fixedly mounted in a hollow cylindrical portion 3 of a stator bracket 1 for rotation. It is supported freely. An annular yoke 7 is fixed to the rotor hub 2, and an annular magnet 8 is fixed to the inner peripheral surface side of the yoke 7. A coil 9 is wound around the stator core 4, and by supplying an exciting current to the coil 9, the rotor hub 2 rotates due to the interaction between the current magnetic field created by the coil 9 and the magnetic field of the magnet 8.

By the way, a one-phase bipolar drive system is known as a rotary drive system for a brushless motor having such a structure. In this bipolar drive system, the coil 9
Is wound around the core 4 in a one-phase state, and a direct-current exciting current in the forward and reverse directions is supplied to the coil 9 in accordance with the relationship between the magnetic pole polarity of the core 4 and the magnetic pole polarity of the magnet 8. . In order to control the supply of such an exciting current, in the conventional brushless motor, a magnetic sensor composed of a Hall element or the like is installed in the stator bracket 1,
Although the rotation of the rotor hub 2 is detected, the technical problems described below have been pointed out for such a drive system.

[0005]

That is, in the one-phase bipolar drive system as described above, as shown in FIG.
A pulsating rotational torque is generated, but with the rotational torque having such a waveform, there are dead points at which the torque becomes zero at the points shown in A, B, C, and D of FIG. Due to the presence of this dead point, a startup failure occurs.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to
It is an object of the present invention to provide a brushless motor that does not cause start-up failure in the phase bipolar drive system. Another object of the present invention is to provide a brushless motor that can reduce power consumption in a one-phase bipolar drive system.

[0007]

In order to achieve the above object, the present invention provides a stator including a coil for generating a current magnetic field in an excited state, a core around which the coil is wound, and the current magnetic field. A rotor having a magnet that obtains a rotational force by electromagnetic interaction, a magnetic sensor that detects the rotational position of the rotor, and a control circuit that controls the exciting current of the coil based on the detection signal of the magnetic sensor. In the brushless motor having, the core includes a plurality of main magnetic poles and a plurality of sub magnetic poles provided between the main magnetic poles, and the coil includes one main coil and at least two sub coils. The main coil is wound around the main magnetic poles adjacent to each other in the circumferential direction alternately in different directions, and is driven by the control circuit in a one-phase bipolar manner. Said two sub-coils, along with being wound respectively in the same direction between the sub magnetic poles adjacent to every other in the circumferential direction, characterized in that it is wound in the same direction between each sub-coil.

A plurality of the magnetic sensors are provided corresponding to the main magnetic pole and the sub magnetic pole, and an exciting current supplied to the main coil and the sub coil by the control circuit is supplied based on detection signals of these magnetic sensors. It can be switched. The main magnetic pole and the sub magnetic pole are each composed of four magnetic poles, and the magnetic poles can be arranged at equal angular intervals in the circumferential direction.

The control circuit can supply the exciting current to the sub-coil only when the motor is started.

[0010]

According to the brushless motor having the above structure, the core around which the coil is wound has a plurality of main magnetic poles and a plurality of sub magnetic poles provided between the main magnetic poles, and one coil is provided. Of the main coil and at least two sub-coils, the main coil is wound in different directions alternately between the main magnetic poles that are adjacent in the circumferential direction, and is driven by the control circuit in a one-phase bipolar manner. The sub-coils are wound in the same direction between every other sub-poles adjacent to each other in the circumferential direction, and the sub-coils are also wound in the same direction, so that an exciting current is supplied to the main coil. When the exciting current is supplied to the sub-coil during the one-phase bipolar drive, the sub-coil can generate the rotational torque at the dead point point of the one-phase bipolar drive. That.

Further, according to the structure of claim 4, the control circuit supplies the exciting current to the sub-coil only at the time of starting the motor, so that the power consumption of the motor at the time of steady rotation can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 show an embodiment of a brushless motor according to the present invention. In the following description, the same or corresponding parts as those of the conventional example described above are designated by the same reference numerals. The basic structure of the brushless motor shown in the figure is the same as that of the conventional example shown in FIG. 4, and has a stator bracket 1 and a rotor hub 2. At the center of the stator bracket 1,
A hollow cylindrical portion 3 is provided, and an annular stator core 10 is fixedly provided on the outer circumference of the hollow cylindrical portion 3.

A rotating shaft 5 is vertically provided at the center of the rotor hub 2. The rotating shaft 5 is fitted to an inner ring of a bearing 6 having an outer ring fixedly mounted in a hollow cylindrical portion 3 of a stator bracket 1 for rotation. It is supported freely. An annular yoke 7 is fixed to the rotor hub 2, and an annular magnet 8 is fixed to the inner peripheral surface side of the yoke 7. A coil 12 is wound around the stator core 10, and by supplying an exciting current to the coil 12, the coil 12 is
The rotor hub 2 rotates due to the interaction between the magnetic field of the current created by the magnet and the magnetic field of the magnet 8. Further, a magnetic sensor 14 is arranged on the stator bracket 1, and the exciting current supplied to the coil 12 is controlled by the control circuit 16 based on the detection signal of the magnetic sensor 14.

The basic structure of the brushless motor as described above is the same as that of the conventional brushless motor of this type, but the brushless motor of the present invention has a remarkable feature in the following points. That is, in the brushless motor of the present invention, the stator core 10 is formed in the shape shown in FIG. The stator core 10 shown in the drawing is configured by laminating core plates that are stamped by a press on a plurality vertically in the same shape, a plurality of main magnetic poles 10a ₁ 10 A _4, these main poles 10a~ 1
0a ₄ between the plurality of sub magnetic poles 10b _{1 to} 10b
Have ₄ and.

In this embodiment, the main magnetic poles 10a _{1 to} 10a ₄ radially extend outward from the disk-shaped base portion 10c, and _four main magnetic poles 10a _{1 to} 10a 4 are provided at equal angular intervals of about 90 °.
The sub magnetic pole 10b ₁ ~10b ₄ is disc-shaped base 1
Four pieces extend radially from 0c outward and are provided at equal angular intervals of about 90 °. Main magnetic pole 10a ₁ to 1
0a ₄ is for obtaining the main drive torque,
Therefore, increasing the circumferential width of the main pole 10a ₁ 10 A _4, the drive torque is increased and the driving torque and to reduce the width of the circumferential direction is reduced.

On the other hand, the sub magnetic pole 10b₁-10b_FourIs the de
To obtain auxiliary drive torque to eliminate the dead point.
Therefore, this sub magnetic pole 10b is₁-10
b_FourWhen the circumferential width of is increased, the auxiliary drive torque becomes
Becomes larger (in this way, increasing the auxiliary drive torque
As a result, the main magnetic pole 10a₁-10a _Four
Of the main drive torque is small.
And the auxiliary drive torque is reduced when the width in the circumferential direction is reduced.
Becomes smaller (in this way, the auxiliary drive torque is made smaller
As a result, the main magnetic pole 10a₁-10a
_FourAnd the main drive torque generated is large.
Become).

In consideration of the above reason, in this embodiment, the main magnetic poles 10a _{1 to} 10a ₄ and the sub magnetic pole 10b _{1 are used.}
The ratio of the circumferential direction of the ～10B ₄ approximately 3: 1. The width of the main pole 10a ₁ 10 A ₄ may be set to about 2 to 5 times greater than the width of the sub magnetic pole 10b ₁ ~10b _4. On the other hand, the coil 12 is composed of one main coil M and two sub-coils S _{1 and} S ₂ . The main coil M is the main magnetic pole 1 shown in FIG.
Each of the main magnetic poles is wound in a divided state into 0a _{1 to} 10a _4, and the main magnetic poles circumferentially adjacent to each other are wound in different directions. That is, for example, assuming that the main magnetic pole 10a ₁ is wound counterclockwise, the main magnetic pole 10a ₂ adjacent in the circumferential direction is clockwise.
The main magnetic pole 10a ₃ is wound counterclockwise, and the main magnetic pole 10a ₄ is wound clockwise, and these are connected in series.

Two subcoils S_1,S₂Shown in Figure 1
Sub magnetic pole 10b₁-10b_FourDivided into
It is wound with the sub coil S₁Is the sub magnetic pole 10b
₁And 10b₃It is wound so that it is in the same direction as
Coil S₂Is the sub magnetic pole 10b ₂Same as 10b_FourSame as
Each is wound so that they are facing each other, and these winding directions
Is the subcoil S₁Same as S₂And are in the same direction
It

That is, now, for example, the sub magnetic pole 10b ₁
In If sub coils S ₁ is being wound in the counterclockwise direction, the sub magnetic pole 10b _2, the sub-coils S ₂ is wound counterclockwise, the sub magnetic pole 10b _3, sub coil S ₁
Is wound counterclockwise, and in the sub magnetic pole 10b ₄ , the sub coil S ₂ is wound counterclockwise. On the other hand, in the present embodiment, the magnetic sensor 14 includes two magnetic sensors 14a,
14b, and these magnetic sensors 14
The main magnetic poles 10a _{1 to} 10a ₄ and the sub magnetic pole 10b are denoted by a and 14b, as shown in the relative positional relationship in FIG.
In correspondence with the angular relationship of _{1 ~10b 4,} it is provided a pair at an angle interval of 45 °. In the embodiment, the sub magnetic pole 10b
One magnetic sensor 14a is arranged on the outer side of ₂ , and the other magnetic sensor 14b is arranged on the outer side of the main magnetic pole 10a ₃ .

In the brushless motor configured as described above, the coil 12 (main coil M, sub-coils S _1, S
₂ ) When the rotor hub 2 is rotated without supplying an exciting current to the rotor, a counter electromotive voltage is generated in each coil 12 that links the magnet 8, and the generated waveform is shown in FIG. In this embodiment, the main pole 10a ₁ 10 A ₄ are arranged at equal angular intervals of 90 °, the magnetic pole 10a ₁ ~10a _{4 1}
Since the main coil M of the phase is wound and the winding direction of the coil M is alternately different in the circumferentially adjacent portions, the counter electromotive voltage induced in the main coil M is indicated by the solid line in FIG. As shown, a substantially sine wave state is obtained, which is sequentially inverted at an angle interval of 90 °.

In the embodiment, the rotor magnet 8
Is magnetized to 4 poles, and the N and S poles are substantially 90 °
Are arranged at intervals. On the other hand, in the sub coil S _{1 in} which the sub magnetic poles 10b ₁ and 10b ₃ are wound,
As indicated by the alternate long and short dash line, a back electromotive force in a substantially sinusoidal state, which has a peak at an angle delayed by 45 ° from the back electromotive force induced in the main coil M, is generated. In addition, the sub magnetic pole 10b
_{In the} sub coil S ₂ wound with ₂ and the same 10 b ₄ , a peak appears at an angle delayed by 135 ° from the back electromotive force induced in the main coil M, as shown by a chain double-dashed line in FIG. A back electromotive force in a sine wave state is generated.

Therefore, in the present invention, the magnetic sensor 14a is used.
Switches the exciting current supplied to the main coil M
The magnetic sensor 14b on the other hand is
IL S _1,S₂For switching the excitation current supplied to
Detection of these magnetic sensors 14a, 14b
Based on the signal, the main and sub coils M, S_1,S₂
An exciting current described below is supplied from the control circuit 16 to
I did it.

That is, first, when the detection signal of the magnetic sensor 14a is "H", an exciting current in the positive direction is supplied to the main coil M so that the detection signal of the magnetic sensor 14a is "H".
An exciting current in the opposite direction is supplied when L ". When such an exciting current is supplied to the main coil M, the main coil M is driven in a one-phase bipolar manner, and the solid line shown in FIG. In the waveform, the main drive torque is generated in the state where the − direction part is reversed to the + direction.
The _1, when the detection signal of the magnetic sensor 14b is "H", the conjunction exciting current is supplied to the sub coil S _2, when the detection signal of the magnetic sensor 14b is "L", the exciting current is supplied To be done.

Such an exciting current is applied to the subcoils S ₁ , S
_When it is supplied to ₂ , the sub coil S _1,
Auxiliary driving torque is generated by S _2, so 1
The occurrence of dead points in the phase bipolar drive system is eliminated, and the starting characteristics of the motor can be greatly improved.

The subcoils S _{1 and} S ₂ are provided in order to eliminate the dead point of the motor, and in order to reduce the power consumption, the excitation current is not supplied to the subcoils S _{1 and} S ₂ . , It is preferable to set it only at the start. For example, in the case of a motor having a rated rotation speed of 800 rpm, the supply of the exciting current to the subcoils S _{1 and} S ₂ is stopped when the rotation speed reaches 400 rpm, which is about ½.

The subcoils S _{1 and} S ₂ are for eliminating dead points at the start,
Thus, may be supplied to the exciting current to the sub-coils S _1, S ₂ after startup, but split consuming power, since the torque generated is small, it is desirable to control as described above. Such a low power consumption type brushless motor is particularly suitable for rotating a load, and is conveniently applied to drive, for example, a CD-ROM, an LBP mirror, a HDD magnetic disk, or the like. In the motors that rotate these, since the load acts as inertia, sufficient torque can be obtained without supplying current to the sub-coils S ₁ and S ₂ after starting.

Although the main and sub magnetic poles 10a _{1 to} 10a _{4 and} 10b _{1 to} 10b ₄ each have four poles in the above embodiment, the present invention is not limited to this. It is applicable if the number of magnetic poles is an even number of 4 or more. Further, in the above embodiment, the shaft rotation type is illustrated as the brushless motor, but the present invention can be applied to the shaft fixed type brushless motor.

[0028]

As described above in detail in the embodiments,
According to the brushless motor of the present invention,
Since the dead point at the time of the phase bipolar drive is eliminated, the starting reliability of the motor becomes very high. Further, according to the configuration of claim 4, since the sub-coil for eliminating the dead point supplies the exciting current only at the time of starting, it is possible to reduce the power consumption.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a wound state of a core and a coil of a brushless motor according to the present invention.

FIG. 2 is a waveform diagram of a counter electromotive voltage induced in each coil of the brushless motor.

FIG. 3 is a sectional view of a brushless motor to which the present invention is applied.

FIG. 4 is a waveform diagram of torque generated when a conventional brushless motor is driven in one-phase bipolar mode.

[Explanation of symbols]

1 stator bracket 2 rotor hub 3 hollow cylindrical portion 5 rotating shaft 6 bearing 7 yoke 8 magnet 10 stator core 10a ₁ 10 A ₄ main pole 10b ₁ ~10b ₄ sub magnetic pole 12 coils M main coil S _1, S ₂ sub-coils

Claims (4)

[Claims] 1. A stator including a coil that generates a current magnetic field in an excited state, a core around which the coil is wound, and a rotor including a magnet that obtains a rotational force by electromagnetic interaction with the current magnetic field. A brushless motor having a magnetic sensor for detecting a rotational position of the rotor and a control circuit for controlling an exciting current of the coil based on a detection signal of the magnetic sensor, wherein the core has a plurality of main magnetic poles, A plurality of sub magnetic poles provided between these main magnetic poles, wherein the coil is composed of one main coil and at least two sub coils, and the main coils are the main coils that are adjacent in the circumferential direction. The magnetic poles are alternately wound in different directions, and driven by the control circuit in a one-phase bipolar manner. The two subcoils are adjacent to each other in the circumferential direction. Brushless motor wherein together are wound respectively in the same direction between the sub-magnetic poles, characterized in that it is wound in the same direction between each sub-coil to. 2. A plurality of the magnetic sensors are provided corresponding to the main magnetic pole and the sub magnetic pole, and the excitation circuit supplies the main coil and the sub coil by the control circuit based on detection signals of these magnetic sensors. The brushless motor according to claim 1, wherein the current is switched. 3. The brushless motor according to claim 1, wherein each of the main magnetic pole and the sub magnetic pole is composed of four magnetic poles, and the magnetic poles are arranged at equal angular intervals in the circumferential direction. 4. The brushless motor according to claim 1, wherein the control circuit supplies an exciting current to the sub coil only when the motor is started.