JP3447795B2 - Brushless motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to small magnet type motors, and more particularly to a brushless motor suitable for spindle motors and various micromotors.

[0002]

2. Description of the Related Art Conventionally, various structures have been adopted in brushless motors such as small magnet type motors and spindle motors, but most of them are polyphase in each tooth of a stator core having a plurality of slots. Is wound to form a stator, and an annular rotor magnet having a number of magnetic poles different from the number of slots of the stator, which is formed by alternately arranging different poles in the circumferential direction facing the stator, is rotatable. By selectively switching the energization to the multi-phase coil, the rotor equipped with the rotor magnet is rotated by the electromagnetic interaction between the electromagnetic poles on the magnetic pole teeth generated by the coil current and the magnetic poles of the rotor magnet. I have to.

In this case, the switching of the energization timing is controlled by detecting the polarity and the alternating position of the rotor magnet with a sensor such as a Hall element or an induced voltage of a coil.

In a brushless motor having such a structure, a starting dead point may be formed depending on the relative position between the rotor and the stator. The number of slots and the number of magnetic poles of the rotor magnet are different, and a plurality of sensors are used. Further, there is a case where the stator is provided with a supplementary pole to avoid the dead point.

Further, in a fan motor or the like using one sensor due to cost factors, a part of the tooth is cut out to make the shape of the magnetic pole teeth asymmetrical on the upstream side and the downstream side in the rotation direction, and thereby obtain the cogging torque. The rotor and the stator are mechanically displaced from the dead center.

[0006]

However, in the above-mentioned conventional brushless motor, since the number of slots of the stator and the number of magnetic poles of the rotor magnet are different, the generated torque of each magnetic pole tooth is synchronized. However, if a plurality of sensors are used or if a stator is provided with a supplementary pole, the structure becomes complicated, and the motor becomes large and expensive.

Further, in the case of a low cost design in which a part of the teeth is cut out and the shape thereof is asymmetric, high torque cannot be obtained because the magnetic resistance increases due to an increase in the average air gap length between the stator and the rotor magnet. Moreover, there is a problem that rotational ripple and vibration noise are high due to the asymmetry of the notch.

The present invention has been made in consideration of the above problems of the prior art, and its purpose is to obtain high starting reliability, without requiring a complicated structure. It is an object of the present invention to provide a new brushless motor that has both the advantages of the normal type (high-grade type) that can obtain high torque and the advantages of the low cost type, and that has solved the drawbacks of each.

[0009]

In order to achieve the above-mentioned object, the present invention comprises a stator formed by winding a coil around each tooth of a stator core having a plurality of slots,
A brushless motor including an annular rotor magnet rotatably provided facing the stator and having different poles alternately arranged in the circumferential direction, and a sensing unit for detecting a magnetic flux of the rotor magnet. In the stator core, the crystal easy axis has unidirectionality, and
The protruding direction of the teeth having at least one easy axis of magnetization
It is characterized by being constituted by an annular grain- oriented steel plate that is deviated with respect to.

In this case, before being wound around each of the teeth
The coils form one network, and the network is a single-phase
Depending on the source, the energization direction reverses with virtually no rest period
It is better to drive them at the same time by bidirectional energization.
Yes .

The easy axis of magnetization is at least one.
Matches the protruding direction of the teeth, and the easy axis of magnetization is
Of the teeth does not match the protruding direction of the teeth,
A coil wound around one tooth and the other said tooth
The coils wound on the
It is good to balance the flowing currents .

Further, according to the present invention, in order to achieve the above object , each tooth of a stator core having a plurality of slots.
And a stator formed by winding a coil around the stator,
It is rotatably installed facing each other and has different poles arranged alternately in the circumferential direction.
A row of annular rotor magnets and the rotor magnets
And a sensing means for detecting the magnetic flux of the net.
In the brushless motor, the stator core is
It has a bidirectionality in which the easy axes of crystal are perpendicular to each other.
And the teeth having at least two easy axes of magnetization.
The annular directional steel plate that is deviated from the protruding direction of
It is characterized by being configured .

In this case, for example, with four slots,
If the stator cores are equally distributed in the same direction,
The axis of easy magnetization with respect to the protruding direction of the
It will be the same as the source.

[0014]

According to the brushless motor of the present invention described above,
When the coil wound around each tooth of the stator core is excited, the stator core is strengthened in magnetization according to the easy magnetization axis of the crystal in the steel plate, and in a certain tooth,
The center of the tip at the tip and the center of magnetization become misaligned, and a magnetic attractive force or repulsive force is generated between the electromagnetic pole generated on the tip and the magnetic pole of the rotor magnet facing it, causing the rotor magnet to move. Rotational force is generated and the rotor tries to rotate.

Here, the stator core is made of a grain-oriented steel sheet whose crystal easy axis is unidirectional, and the number of slots of the stator core is equal to the number of magnetic poles of the rotor magnet, and the axis of easy magnetization is at least one tooth. If it is deviated with respect to the projecting direction, the generated torque is high and a smoother start is possible. During rotation, since the number of slots of the stator and the number of magnetic poles of the rotor magnet are formed to be equal, the motor acts as a so-called synchronous motor,
During this rotation, torque is synchronously generated between each tooth of the stator and each magnetic pole of the rotor magnet, so that the rotational torque of the rotor as a whole becomes very large.

Further, when the angle of deviation θ of the stator core made of a unidirectional steel plate with respect to an arbitrary tooth is set,
In at least one tooth, when starting, the magnetization center of the tip deviates from the center of the tip, and the center of the opposing magnetic pole of the rotor magnet always deviates, and a rotational force acts on the rotor magnet, so that the rotor quickly moves. Rotate. This angle θ can be reduced by increasing the number of slots in the stator core.

Then, one circuit network is formed by various connections of coils wound around each tooth of the stator core,
If this circuit network is driven simultaneously by bidirectional energization in which the energization direction is reversed by the single-phase power supply without substantially including the rest period, this residual magnetism disappears after the stator core is magnetized by the excitation of the coil. Before this, the coil is excited in the opposite direction this time, so-called reverse excitation operation is obtained, the width of the magnetic change in the stator core increases,
As a result, it becomes possible to generate a large torque.

On the other hand, if the grain-oriented steel sheet is bidirectional with the axes of easy magnetization of the crystals orthogonal to each other, the number of teeth whose magnetic center of the tip deviates from the center of the tip increases,
It will be easier to start.

[0019]

Embodiments of the present invention will be described with reference to the drawings. First, the first embodiment will be described with reference to FIGS. FIG. 2 shows a case where the recording medium such as a CD-ROM is applied to a micromotor for rotationally driving the same. In FIG. 2, a substrate 1 made of a silicon steel plate or the like is fixed to a driving device.
A cylindrical sleeve 14 is fixed in the mounting hole 12 of No. 0 in a state where its axial center is orthogonal to the substrate 10 and protrudes downward, and a pair of oil-impregnated bearings 16, 1 are provided inside the sleeve 14.
A shaft 20 is rotatably supported via 8.
The upper and lower ends of the shaft 20 are led out from the sleeve 14 in the vertical direction.

A stator 26 constituted by winding a coil 24 around a stator core 22 is fixed to the outer periphery of the lower half of the sleeve 14, and the stator 2 is attached to the lower end of the shaft 20.
A cup-shaped rotor holder 28 arranged so as to surround the outer periphery of 6 is fixed by caulking or the like.
An annular rotor magnet 30 is fixed to the inner peripheral surface of the cylindrical wall. The rotor magnet 30 faces the outer peripheral surface of the stator 26 with a slight gap. A rotor 32 is constituted by the rotor holder 28 and the rotor magnet 30.

At the upper end of the shaft 20, a turntable 34 located above the substrate 10 is press-fitted and fixed, and a CD (recording medium) (not shown) is placed on the turntable 34. A sensor 36 including one Hall element is arranged at a position corresponding to the rotor magnet 30 on the lower surface of the substrate 10 and detects the magnetic flux of the rotor magnet 30.

FIG. 1 shows the relationship between the stator 26 and the rotor 32 in the micromotor. The coil 24 is omitted.

The stator core 22 of the stator 26 has a 6-slot structure made of a unidirectional silicon steel plate, and 6 teeth 38 are arranged at equal intervals in the circumferential direction. The coils 24 are respectively wound around the teeth 38. The coils 24 are excited so that the coils 24 of the adjacent teeth 38 have opposite magnetic poles, and are connected in series to form one circuit network. Are configured. Therefore, when the coils 24 are energized, the tips of the adjacent teeth 38, that is, the tips 40, are magnetized to have opposite magnetic poles.

The axis of easy magnetization of the crystal of the stator core 22 is
As shown in FIG. 1, it has a deviation angle θ with respect to the protruding direction of any one tooth 38. This declination θ has the effect of doubling the angle because of the electrical angle relationship based on the number of slots in the stator core 22.

On the other hand, the rotor magnet 30 has a 6-pole structure having the same number as the slots of the stator core 22.
N poles and S poles are alternately arranged in the circumferential direction to form six magnetic poles. The sensor 36 includes two adjacent teeth 3 of the stator core 22 on the lower surface of the substrate 10.
It is arranged so as to face the rotor magnet 30 on the outer side in the radial direction at the center between the eight.

FIG. 3 shows a schematic configuration of the motor control circuit 42. This motor control circuit uses a DC power supply 4
4, a power supply controller 46 that supplies a direct current to the coil 24 and a switching element connected to the coil 24,
For example, it has an exciting current control unit 48 that controls switching of the transistors T1 to T4.

The power supply control unit 46 controls the current supplied to the coil 24 by the CLV signal obtained when reproducing the CD, and controls the rotation speed of the rotor 32. In addition, the exciting current control unit 48, as shown in the current waveform schematically shown in FIG. 4, bidirectionally reverses the energization direction while the magnetization of the stator core 22 remains substantially without the coil 24 being in the idle period. Each electromagnetic pole of the stator core 22 that is driven simultaneously by energization and is formed by energization is connected to the rotor magnet 30.
The coil 24 is excited using the detection signal of the sensor 36 so as to have a polarity opposite to that of the opposite magnetic pole.

In the thus constructed micromotor, when the coil 24 of the stator 26 is driven by the motor control circuit 42, each tooth 3 of the stator core 22.
8 is magnetized so that the tips 40 adjacent to each other have different polarities.

When the rotor 32 is not energized, each magnetic pole of the rotor magnet 30 is moved to the stator core 22.
Although the mechanical angle facing each tip 40 is slightly deviated based on the deviation θ, when the stator core 22 is magnetized by energizing the coil 24 at the start, the magnetization center of each tip 40 is deviated from the center of the tip 40. By a large amount θ, and therefore the centers of the magnetic poles of the rotor magnet 30 deviate from the magnetization centers of the tips 40, and the rotor magnet 6
Rotational force based on these deviation angles acts on 2 and the rotor 32 rotates quickly. Therefore, there is no inconvenience that the stator 26 and the rotor 32 form a so-called dead point and cannot be started.

When the rotor 32 is activated, the sensor 36 detects the rotational position of the rotor magnet 30, that is, the boundary between the magnetic poles, and the detection signal is used to switch the energizing direction to the coil 24 so that each tip 40 has a magnetic pole opposed to the rotor magnet 30. An electromagnetic pole with the opposite polarity is formed,
It becomes possible to continuously apply a rotational force to the rotor 32.

Here, since the number of poles of the stator 26, that is, the number of teeth 38 and the number of magnetic poles of the rotor magnet 30 are formed equal, the motor acts as a so-called synchronous motor, and at the time of this rotation, the tip of each tooth 38 is formed. Since torque is generated between each of the magnetic poles of the rotor 40 and the rotor magnet 30, the rotational torque of the rotor 32 as a whole becomes extremely large.

Particularly, in the case of the CD-ROM motor,
Although a rising speed of rotation is required, in the above-described micromotor, the startup is performed promptly, and when the rotor 32 starts to rotate, the motor immediately shifts to the synchronous motor. Is extremely short,
It is suitable for driving a CD-ROM.

FIG. 5 is a second embodiment showing the case of 4 poles and 3 slots. Stator core 5 of stator 50
2 has a three-slot structure, and three teeth 54 are arranged at equal intervals in the circumferential direction, that is, every 120 degrees. This stator core 52 is made of a unidirectional silicon steel plate, and the axis of easy magnetization of crystals in the steel plate is displaced by a mechanical angle θ with respect to any one tooth 54 as shown by the arrow in the figure. 5
6 is a tip located at the tip of each tooth 54.
In addition, for example, one coil is sequentially wound around each tooth 54.

On the other hand, the rotor 58, which is rotatably provided so as to face the stator 50, is constructed by attaching an annular rotor magnet 62 to the inner peripheral surface of the peripheral wall of the rotor holder 60. The rotor magnet 62 has a 4-pole structure, and N poles and S poles are alternately arranged at equal intervals in the circumferential direction. A sensor (not shown) such as a Hall element is arranged facing the rotor magnet 62.

In the brushless motor having such a configuration, when stopped, the state shown in FIG. 5, that is, a certain tip 56 faces a certain magnetic pole of the rotor magnet 62, and the remaining two tips 56 are each the rotor magnet 62.
The two magnetic poles are opposed to each other and are balanced in this state. When power is supplied to the coil at start-up and each tip 56 is magnetized, the stator core 52 has directionality in its easy magnetization direction, so the magnetization center of each tip 56 deviates from the center of the tip 56, and thus the rotor 56 The center of each magnetic pole of the magnet 62 is deviated from the center of magnetization of each tip 56, so that a rotational force acts on the rotor magnet 62 and the rotor 58 rotates rapidly.

When the rotor 58 starts to rotate, the sensor detects the rotational position of the rotor magnet 62, that is, the position of the magnetic pole, and by switching the energization direction to the coil by this detection signal, the rotor 58 continuously rotates. The force can be applied, and the rotation of the rotor 58 is continued thereafter.

Next, a third embodiment of the present invention will be described with reference to FIGS. 6 and 7. Similar to the second embodiment, this embodiment shows a case where the present invention is applied to a brushless motor with four poles and three slots, and the stator core 72 of the stator 70 has three
It has a slot structure, and three teeth 74 are arranged at equal intervals in the circumferential direction, that is, every 120 degrees. The stator core 72 is made of a unidirectional silicon steel plate, and the axis of easy magnetization of crystals in the steel plate coincides with the protruding direction of any one tooth 74 as shown by the arrow in the figure. Therefore, the easy axis of magnetization of the crystal has a deviation angle of +120 degrees and −120 degrees with respect to the protruding direction of the other two teeth 74. 76 is a tip located at the tip of each tooth 74.

On the other hand, the rotor 78, which is rotatably provided so as to face the stator 70, is constructed by attaching an annular rotor magnet 82 to the inner peripheral surface of the peripheral wall of the rotor holder 80. The rotor magnet 82 has a 4-pole configuration, and N poles and S poles are alternately arranged at equal intervals in the circumferential direction. A sensor (not shown) such as a Hall element is arranged so as to face the rotor magnet 82.

Further, each tooth 7 of the stator core 72
The coils 84a, 84b, 84c are wound around the coil 4, respectively. The coil 84a wound around any one of the teeth 74 and the coils 84b and 84c wound around the other two teeth 74 have winding directions set so that the polarities of the generated magnetic poles when energized are different. As shown in FIG. 7, the coil 84a and the series circuit of the coils 84b and 84c are connected in parallel, and this parallel circuit network is driven by a single-phase power supply.

The brushless motor having such a structure has three
It is an improved version of the phase brush motor. That is,
A three-phase brush motor has a rotating three-phase armature provided with a three-phase commutator connected to each phase coil (Δ connection), and a pair of brushes connected to a single-phase power source and two commutators. The alternative is to slide. In the energization process in this case, the one-phase coil and the other two-phase coils connected in series are connected in parallel to the single-phase power supply, and the overcurrent of the one-phase coil is larger than the others. Causes excessive Joule heat, and the three-phase magnetic characteristics are not equivalent, but the coil connection state switches sequentially as the armature rotates,
On average, equal currents are supplied to the coils of each phase, so that on average Joule heat is generated and the magnetic characteristics are uniform.

However, in this type of brushed motor, all coils are energized at all times as compared with an ordinary three-phase brushless motor, so that there is an advantage that the utilization efficiency of the coil and the armature core is high. Since a commutator and a brush are required to rotate the child, the height of the motor in the axial direction is correspondingly increased, and the number of parts is increased and noise is excessively generated.

On the other hand, in the case of the third embodiment, despite the fact that it is brushless, it is possible to overcome the drawbacks of the brush and to satisfy the high efficiency characteristics of the brush. it can. That is, in any one tooth 74 around which the coil 84a is wound, the projecting direction thereof coincides with the easy axis of magnetization, and the other coil 8 connected in series.
In the other teeth 74 on which the windings 4b and 84c are respectively wound, the protruding direction thereof has an angle of 120 degrees with the easy magnetization axis. For this reason, the magnetic flux generated in any one tooth 74 can be made twice as much as the magnetic flux generated in the other tooth 74. In other words, the generation of Joule heat of the coil 84a of any one tooth 74 is caused to occur in the other tooth 74. The coils 84a, 84b, and 84c can be halved, and the current of the coil 84a becomes 1/2 of the current of the other coils, so that the coils 84a, 84b, and 84c have the same coil current without rotating the stator 70.

Here, when the rotor 78 is stopped, the magnetic poles of the rotor magnet 82 and the tips 76 of the stator core 72 are magnetically balanced, and at the time of start-up, the stator 70 and the rotor 78 form a so-called dead center and start-up. It may be impossible to do this, but due to the difference in the number of poles and slots and the magnetic potential based on the directionality of the stator core, there is a difference in the winding state (arrangement, space factor) in each tooth 74, and each tip 76 is different. There is a difference in attraction and repulsion between the tips 76 and the magnetic poles of the rotor magnet 82 in (1), and the rotor 78 starts rotating.

When the rotor 78 starts to rotate, the sensor detects the rotational position of the rotor magnet 82, that is, the boundary between the magnetic poles, and the detection signal causes the coils 84a, 84b,
By switching the energizing direction to 84c, an electromagnetic pole having a polarity opposite to the opposing magnetic pole of the rotor magnet 82 is formed in each tip 76, and it becomes possible to continuously apply the rotational force to the rotor 78.

Next, a fourth embodiment will be described with reference to FIG. What is shown in this embodiment is a brushless motor having four poles and four slots, and a stator core 8 of a stator 86.
Reference numeral 8 denotes a four-slot structure in which four teeth 90 are arranged at equal intervals in the circumferential direction, that is, at every 90 degrees. The stator core 88 is made of bidirectional silicon steel plates which are orthogonal to each other, and the axes of easy magnetization of crystals in the steel plates are deviated by a mechanical angle θ with respect to a pair of teeth 90 facing each other with the center therebetween as shown by the arrow in the figure. While being positioned, it is displaced by the mechanical angle θ with respect to the other pair of teeth 90. This declination θ
Is set to 7 degrees, for example. 92 is each tooth 90
It is a tip located at the tip of. Also, each tooth 9
For example, one coil is wound around 0 in order.

On the other hand, the rotor 94, which is rotatably provided so as to face the stator 86, is constructed by attaching an annular rotor magnet 98 to the inner peripheral surface of the peripheral wall of the rotor holder 96. The rotor magnet 98 has a 4-pole structure, and N poles and S poles are alternately arranged at equal intervals in the circumferential direction. One sensor (not shown) such as a Hall element is arranged between arbitrary slots facing the rotor magnet 62.

In the brushless motor having such a configuration, when stopped, the state shown in FIG. 8, that is, each tip 92 slightly opposes each magnetic pole of the rotor magnet 98,
Although balanced in this state, when the coils 92 are magnetized by starting energization at the time of start-up, the stator core 88 has directionality in its easy magnetization direction. Since the centers of the magnetic poles of the rotor magnet 98 and the centers of magnetization of the tips 92 deviate from each other substantially equally, the rotational force acts on the rotor magnet 98 and the rotor 94 rotates rapidly.

In particular, in this case, since the stator core 88 has two directions, the declination angle of the easy axis of magnetization with respect to the protruding direction of each tooth 90 becomes equal, and the rotational force at the time of starting is equally generated in each magnetic pole of the rotor magnet 98. As a result, the rotor 94 is started up extremely quickly.

According to this structure, since the conventional notch of the stator is unnecessary, not only the equivalent gap can be reduced to improve the motor efficiency, but also the vibration noise during rotation due to the notch is reduced. Has the effect of doing.

Although various embodiments of the brushless motor according to the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are made without departing from the gist of the present invention. It goes without saying that modifications are possible.

[0051]

Since the present invention is configured as described above, it has the following effects. Since the stator core of the stator is made of the grain-oriented steel plate, it is possible to eliminate the occurrence of a dead center at the time of starting the motor and realize a smooth start. Therefore, there is no need for a structural ingenuity such as using a plurality of sensors with the number of slots of the stator and the number of magnetic poles of the rotor magnet being different from each other as in the prior art, and the number of slots of the stator and the rotor magnet according to the motor characteristics The number of magnetic poles can be set arbitrarily, there is no need to provide supplementary poles on the stator, and there is no need to make the teeth asymmetrical so that the rotor and stator are mechanically displaced from the dead center, and the structure is simple. Therefore, it is possible to obtain inexpensive and highly efficient motor characteristics. .

[Brief description of drawings]

FIG. 1 is a plan view of a stator and a rotor showing a main part of a first embodiment of a brushless motor of the present invention.

FIG. 2 is a cut front view showing the overall configuration of the brushless motor of FIG.

FIG. 3 is a circuit diagram showing the coil drive circuit of FIG.

4 is a waveform diagram of a coil current in the drive circuit of FIG.

FIG. 5 is a plan view of a stator and a rotor showing a main part of a second embodiment of the present invention.

FIG. 6 is a plan view of a stator and a rotor showing a main part of a third embodiment of the present invention.

7 is a circuit diagram of the coil shown in FIG.

FIG. 8 is a plan view of a stator and a rotor showing a main part of a fourth embodiment of the present invention.

[Explanation of symbols]

22, 52, 72, 88 Stator core 24, 84a, 84b, 84c coil 26, 50, 70, 86 Stator 30, 62, 82, 98 Rotor magnet

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-17557 (JP, A) JP-A-63-217940 (JP, A) JP-A-57-208832 (JP, A) Practical application Sho-55- 59545 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02K 29/00 H02K 21/22 H02P 6/20

Claims (4)

(57) [Claims] 1. A stator configured by winding a coil around each tooth of a stator core having a plurality of slots,
A brushless motor including an annular rotor magnet rotatably provided facing the stator and having different poles alternately arranged in the circumferential direction, and a sensing unit for detecting a magnetic flux of the rotor magnet. In the stator core, the crystal easy axis has unidirectionality, and
The protruding direction of the teeth having at least one easy axis of magnetization
A brushless motor characterized by being constituted by an annular grain- oriented steel plate that is deviated with respect to. 2. The coil wound around each tooth.
Form a network, which is powered by a single-phase power supply
Both of which the energization direction is reversed without substantially including the rest period
The brushless motor according to claim 1, wherein the brushless motors are simultaneously driven by a counter current . 3. The easy axis of magnetization is at least one of the above.
Matches the protruding direction of the teeth, and the axis of easy magnetization is in front of the other.
At least one of the above does not match the protruding direction of the teeth.
The coil wound around the tooth and the other said tooth
The turned coil is connected in parallel and flows to each coil.
The brushless motor according to claim 1, wherein the electric currents are balanced . 4. A stator core having a plurality of slots
A stator configured by winding a coil around each tooth,
Rotatably provided facing the stator and having different poles in the circumferential direction
An annular rotor magnet in which the
Sensing hand for detecting the magnetic flux of the rotor magnet
A brushless motor comprising:
Tacoa is composed of two crystals whose axes of easy magnetization are perpendicular to each other.
Directional and having at least two easy axes
Annular direction deviated from the protruding direction of the teeth
A brushless motor characterized by being made of a flexible steel plate .