JPH0919123A - Brushless motor - Google Patents

Abstract

PURPOSE: To provide a brushless motor in which cogging torque and torque ripple are minimized while suppressing rotational fluctuation, vibration and noise significantly and enhancing the efficiency economically. CONSTITUTION: The brushless motor 1 comprises a shield yoke 8 disposed such that the cogging torque is minimized between ties 7a, 7b and a permanent magnet 3 for driving and a recess 11 is provided at the forward end of outer ties 7a, 7b on the side facing a central ties in order to concentrate the flux.

Description

Detailed Description of the Invention

[0001]

This invention relates to a CD and a CD-R.
The present invention relates to a brushless motor applied to an OM driving spindle motor or the like.

[0002]

2. Description of the Related Art A brushless motor used in a conventional spindle motor for driving a CD and a CD-ROM, etc., has an outer peripheral portion as shown in the overall configuration diagram of the conventional brushless motor of FIG. A rotor 101 having a driving permanent magnet 102 fixed thereto, an E-shaped out core 105 arranged facing the rotor 101 and provided with three teeth, and a stator 107 having an armature coil 104 wound around the rotor 101; And a magnetic shield yoke 106 formed so as to surround it.

All three teeth 103 are formed on the E-shaped out core 105 with the same width, and the tips thereof extend in the outer peripheral direction of the rotor 101, face the drive permanent magnets 102 with a predetermined gap, and have the tips. Are also formed to have the same width.

The shield yoke 106 is symmetrical to the E-shaped out core 105 on the opposite side of the rotor 101, and
The midpoint of the arc forming the shield yoke 106 and the rotor 10
There is known a brushless motor that is installed such that a straight line connecting the centers of 1 and a center line of a center tooth passing through the center of the rotor 101 overlaps with each other.

[0005]

DISCLOSURE OF THE INVENTION Conventional CD and CD
A brushless motor used in a ROM driving spindle motor or the like is composed of a stator provided with a slot-type 3 teeth E-shaped out core.

The stator has a structure in which an armature coil is directly wound around each of the three teeth, and the structure is simple and the manufacturing efficiency is improved. On the other hand, the stator having the salient pole structure is formed by the teeth and the outer circumference of the rotor. In the rotor that generates cogging with the driving permanent magnet and is required to be driven at a constant speed at a high speed response or a low speed rotation, there is a problem that the torque unevenness or the rotation unevenness characteristic of the rotor is deteriorated.

Further, the shape of the three teeth of the E-shaped out core is not magnetically uniform because the central teeth and the outer teeth have different shapes, and it is easy to generate non-uniform cogging torque. Compared to the central teeth, the teeth cannot efficiently concentrate the magnetic flux of the driving permanent magnet, so that the average starting torque of the brushless motor becomes smaller and the torque ripple becomes larger.

Further, if a shield yoke made of a magnetic material is arranged in order to shield the influence of the magnetic field of the drive permanent magnet on the outer circumference of the rotor, cogging torque is generated between the shield yoke and the drive permanent magnet.

When the period of the cogging torque generated between the three teeth of the E-shaped out core and the driving permanent magnet and the period of the cogging torque generated between the shield yoke and the driving permanent magnet match, they are combined. As a result, cogging becomes even larger.

Non-uniform cogging torque and torque ripple during rotational driving, which are complicatedly synthesized, increase vibrations and noises of the brushless motor, and there is a problem that vibrations and wow and flutter are increased particularly in a low speed rotation speed range.

The present invention has been made to solve the above problems, and an object thereof is to minimize cogging of a brushless motor, reduce torque ripple, and reduce vibration and noise. To provide.

[0012]

In order to solve the above problems, in the brushless motor according to the present invention, the shield yoke is arranged so that the cogging torque generated between the teeth and the drive permanent magnet is minimized. It is characterized by

Further, the brushless motor according to the present invention is characterized in that the ratio of the width of the tip of the central teeth to the width of the tip of the outer teeth is set to 0.6 to 0.9.

Further, in the brushless motor according to the present invention, the straight line connecting the midpoint of the arc of the shield yoke and the center of the rotor is nπ in electrical angle from the central tooth of the E-shaped out core.
At a position corresponding to ± π / 4 (n = ± 2, ± 3, ± 4),
It is characterized in that a shield yoke is arranged.

The brushless motor according to the present invention is characterized in that the ratio of the gap between the shield yoke and the drive permanent magnet and the gap between the tooth and the drive permanent magnet is set to 3 to 7.

Further, the brushless motor according to the present invention is characterized in that a concave portion for concentrating magnetic flux is provided at a tip end portion of a surface of both outer teeth of the E-shaped out core facing the central teeth.

Further, in the brushless motor according to the present invention, the areas of the surfaces of the teeth facing the driving permanent magnets are equalized, and the number of windings of the armature coil wound around the outer teeth and the armature wound around the central teeth are equalized. It is characterized in that the ratio of the number of turns of the coil is set to 1.1 to 1.4.

Further, in the brushless motor according to the present invention, the areas of the faces of the teeth facing the driving permanent magnets are equalized, and the center teeth tips and the driving tips are set with respect to the gap between the outer teeth tips and the driving permanent magnets. It is characterized in that the ratio of the gap with the permanent magnet is set to 0.4 to 0.7.

In the brushless motor according to the present invention, the area ratio of the surface of the two outer teeth facing the driving permanent magnet to the surface of the central tooth facing the driving permanent magnet is 1.2. It is characterized in that it is set to 1.6.

[0020]

In the brushless motor according to the present invention, since the shield yoke is arranged so that the cogging torque generated between the tooth and the drive permanent magnet is minimized, the shield yoke is generated between the tooth and the drive permanent magnet. The cogging torque generated and the cogging torque generated between the shield yoke and the drive permanent magnet have the same magnitude and the same period but opposite phases to each other, and the cogging torques of both can cancel each other.

Further, in the brushless motor according to the present invention, the ratio of the width of the tips of the central teeth and the width of the tips of the outer teeth is set to 0.6 to 0.9. It is possible to equalize the cycle of the cogging torque that is generated and the cycle of the cogging torque that is generated between the shield yoke and the driving permanent magnet, and to make the cycle of the cogging torque and the variation of the amplitude uniform.

Further, in the brushless motor according to the present invention, the straight line connecting the midpoint of the arc of the shield yoke and the center of the rotor is nπ in electrical angle from the central tooth of the E-shaped out core.
At a position corresponding to ± π / 4 (n = ± 2, ± 3, ± 4),
Since the shield yoke is arranged, the cycle of the cogging torque generated between the shield yoke and the drive permanent magnet is
The phase is opposite to the cycle of the cogging torque generated between the tooth and the driving permanent magnet, and the cogging torques of the two can cancel each other.

Further, in the brushless motor according to the present invention, the ratio of the gap between the shield yoke and the drive permanent magnet and the gap between the teeth and the drive permanent magnet is set to 3 to 7, so that the shield yoke and the drive permanent magnet are set. The cogging torque generated between the magnet and the magnet can be made equal to the cogging torque generated between the tooth and the drive permanent magnet.

Further, in the brushless motor according to the present invention, since the recesses for concentrating the magnetic flux are provided at the tips of the surfaces of the outer teeth of the E-shaped outcore that face the central teeth, the armature coil of the outer teeth is formed. The back electromotive force induced in the armature coil of the central tooth can be made equal to the back electromotive force induced in the armature coil of the central tooth.

Further, in the brushless motor according to the present invention, the areas of the faces of the teeth facing the driving permanent magnets are equalized, and the number of windings of the armature coil wound on the outer teeth and the armature wound on the central teeth are set. Since the ratio of the number of turns of the coil is set to 1.1 to 1.4, the number of turns of the armature coil of the outer tooth is increased to increase the counter electromotive force induced in the armature coil of the outer tooth, and the electric machine of the central tooth is increased. It can be equal to the back electromotive force induced in the child coil.

Further, in the brushless motor according to the present invention, the areas of the surfaces of the teeth facing the driving permanent magnets are equalized, and the central teeth tips and the driving tips are set with respect to the gap between the outer teeth tips and the driving permanent magnets. Since the ratio of the gap with the permanent magnet is set to 0.4 to 0.7, the magnetic flux of the armature coil axis of the central teeth becomes equal to the magnetic flux concentrated on the armature coil axis of the outer teeth, The counter electromotive forces induced in the armature coils of the central teeth and the outer teeth can be equalized.

Further, in the brushless motor according to the present invention, the area ratio between the surface of the two outer teeth facing the driving permanent magnet and the area of the central tooth facing the driving permanent magnet is 1.2. Since it is set to 1.6, the magnetic flux of the armature coil shaft center of the outer teeth is made equal to the shaft center magnetic flux of the armature coil of the central teeth, and is induced in each armature coil of the outer teeth and the central teeth. The back electromotive forces can be made equal.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a brushless motor according to the present invention.

The present invention focuses on the periodicity of the cogging torque generated between the magnetic poles on the outer circumference of the rotor and the stator core, and between the magnetic poles on the outer circumference of the rotor and the shield yoke. To minimize the cogging of the brushless motor.

Further, according to the present invention, the magnetic flux concentrated on the teeth from the magnetic poles on the outer circumference of the rotor is not uniform due to the difference in the tooth shape between the center and the outside, and the back electromotive force induced in each armature coil is different. Focusing on one of the factors contributing to the torque ripple, the shape and size of the teeth tip or the armature coil is improved to minimize the torque ripple of the rotor driving torque caused by the difference in the back electromotive force.

Referring to FIG. 1, a brushless motor 1 of the present embodiment has a rotor 2 fixed to a shaft 4 and rotatable.
And a three-phase stator 9 arranged to face the rotor 2,
The shield yoke 8 arranged so as to surround the rotor 2 and the armature coil drive means 8 for controlling the exciting current flowing through the armature coil 5 to drive the rotor 2 to rotate are constituted as a whole.

The rotor 2 is provided with an eight-pole driving permanent magnet 3 fixed to the outer peripheral portion thereof, and cogging torque is generated between the teeth 7a, 7b, 7c and the driving permanent magnet 3 for the purpose of reducing the cogging torque. Permanent magnet for driving 3
The so-called sine magnetization is performed so as to avoid the sudden change of the magnetic field at the switching portion of the magnetic poles and smoothly switch.

The stator 9 has three teeth 7a and 7a.
b, 7c formed E-shaped out core 6, and the armature coil 5 wound around each tooth, the teeth 7a,
The tips of 7b and 7c extend on the outer peripheral surface of the drive permanent magnet 3 with a predetermined gap, and the outer teeth 7a and 7b are
The width is different from that of the central tooth 7c, and a recess 11 at the tip of the tooth is formed at the tip of the surface facing the central tooth.

The shield yoke 8 shields the magnetic flux of the drive permanent magnet 3 from leaking the magnetic flux so as not to affect the operation of the recording medium or the head. Therefore, the shield yoke 8 surrounds the rotor 2 and has the same circle as the center of the rotor 2. The brushless motor 1 is formed of an arcuate magnetic body and is arranged at a position where the cogging of the brushless motor 1 is minimized.

Here, in order to show the significance of the gist of the present invention with respect to the cogging characteristics, the cogging characteristics of the brushless motor of this embodiment are shown in FIGS. 2, 3 and 4.

FIG. 2 is a cogging torque characteristic diagram of only the E type out core of the brushless motor according to the present invention.
The cogging torque waveform generated in the rotor 2 when the shield yoke 8 is removed and only the rotor 2 and the E-shaped out core 6 are used is shown.

FIG. 3 is a cogging torque characteristic diagram of only the shield yoke of the brushless motor according to the present invention.
The cogging torque waveform generated in the rotor 2 when the E-shaped out core 6 is removed and only the rotor 2 and the shield yoke 8 are formed is shown.

2 and 3, when the magnitude and period of each cogging torque are the same, the position of the shield yoke 8 with respect to the E-shaped out core 6 is set such that the phases of the respective cogging torques are opposite to each other. It can be seen that the cogging of the brushless motor can be minimized if the positions can be set so as to cancel each other out.

FIG. 4 is a cogging characteristic diagram of the brushless motor according to the present invention. In FIG. 4, the cogging characteristics of the brushless motor of the present embodiment when the shield yoke 8 is arranged so that the cogging torques of both of them cancel each other out, are compared with the cogging characteristics of the conventional brushless motor of FIG. It can be seen that the cogging of the brushless motor is improved.

An embodiment in which the position of the shield yoke where the cycle / phase / amplitude of the cogging torque fluctuations of the two as described above is a predetermined condition has been obtained will be described step by step below.

Here, hereinafter, the cogging torque generated between the teeth 7a, 7b and 7c of the E-type out core 6 and the driving permanent magnet 3 is generated between the core cogging and the shield yoke 8 and the driving permanent magnet 3. The cogging torque that occurs will be referred to as shield cogging.

In order to cancel the core cogging with the shield cogging, it is necessary to equalize the cycles of the cogging torques of the both. An embodiment in which the cycle of core cogging matches the cycle of shield cogging and the cycles of both are equal will be described based on the cogging torque characteristic diagram with respect to the width ratio of the teeth in FIG.

In FIG. 6A, W1 is the width of the tips of the central teeth 7c of the E-shaped out core 6, W2 is the width of the tips of the teeth 7a, 7b on both sides of the E-shaped out core 6, and FIG. In b), α is an angle formed by a straight line connecting the center of the shaft 4 and both ends of the shield yoke 8, and is referred to as a shield yoke opening angle.

FIG. 6 (c) shows the waveforms of the core cogging and the shield cogging per pole of the driving permanent magnet. The structure at the time of measurement is as shown in FIGS. 6 (a) and 6 (b), respectively. The E-shaped out core 6 is removed in the measurement, and the shield yoke 8 is removed in the core cogging measurement.

Further, as other measurement conditions, the open angle α of the shield yoke 8 in the measurement of the shield cogging is 3π, the three teeth 7a in the measurement of the core cogging,
The distance between 7b and 7c and the drive permanent magnet 3 is constant.

Under the above measurement conditions, one period of shield cogging per one pole of the driving permanent magnet is set as a reference value π,
Ratio of the central teeth 7c and the teeth 7a, 7b on both sides (W
When 1 / W2) is 1.0, 0.75, and 0.3, the core cogging waveform in the period π has three cycles, one cycle, and two cycles, respectively, as shown in FIG. 6C.

Although not shown, in the range of (W1 / W2) of 0.6 to 0.9, the period of core cogging in the period π becomes one period, and the teeth 7a, 7b on both sides are formed.
By setting the width of the central tooth 5c to 0.6 times to 0.9 times, the period of the core cogging and the period of the shield cogging can be made equal.

Further, by making the width of the central tooth 7c having a higher magnetic flux density narrower than that of the teeth 7a and 7b on both sides,
It is also possible to reduce the non-uniformity of the magnetic flux density of the three teeth.

In this embodiment, the teeth 7a on both sides are
The width of the central tooth 7c with respect to 7b was set to 0.75 times.

In order to cancel the core cogging by the shield cogging, it is necessary to make the periods of the cogging torque of the two having the same period opposite to each other.

An example in which the position of the shield yoke 8 with respect to the E-shaped out core 6 is adjusted so that the phase of the shield cogging is opposite to the phase of the core cogging is shown in the cogging torque characteristic diagram for the arrangement of the shield yoke of FIG. It will be explained based on.

In FIG. 7, the shield cogging with respect to the angle formed by the center line of the central tooth 7c, the straight line connecting the midpoint of the arc of the shield yoke 8 and the center of the rotor 2 is shown. And the shield cogging is nπ ± π / 4 and (n + 1) π ± in electrical angle.
It is the minimum at π / 4.

At this time, the gap between the teeth 7a, 7b and 7c and the drive permanent magnet 3 is 0.3 (mm), the gap between the shield yoke 8 and the drive permanent magnet 3 is 1.0 (mm), and The yoke opening angle α is 3π, and all the angles are represented by electrical angles.

From FIG. 7, under the above conditions, the cogging is minimized at the position of the shield yoke 8 at an electrical angle of nπ and a position of (n + 1) π away from this position by π. The practical range of the position is
nπ ± π / 4 (n = ± 2, ± 3, ± 4), and the shield cogging has a phase opposite to the core cogging in this range.
In this example, n = 4 was set.

FIG. 8 is a cogging / starting torque characteristic diagram for the gap between the driving permanent magnet and the tooth.

In FIG. 8, teeth 7a, 7b, 7c
Based on the starting torque characteristic with respect to the gap between the driving permanent magnet 3 and the driving permanent magnet 3, the gap between the teeth 7a, 7b, 7c and the driving permanent magnet 3 that should be ensured with respect to the starting torque value determined by the requirements of the specification or the design reason. In consideration of manufacturing variations and the like, in the brushless motor of this embodiment, 0.
It was set in the range of 2 to 0.5 (mm).

The determined teeth 7a, 7b, 7
The value of core cogging with respect to the gap between c and the drive permanent magnet 3 is about 60 to 30 based on the cogging torque characteristic of FIG.
It can be seen that the range is (g · cm).

In the present embodiment, the teeth 7a, 7b, 7c.
And the gap between the drive permanent magnet 3 and 0.35 (mm),
The core cogging value at this time can be read as about 50 (g · cm).

In order to cancel the core cogging by the shield cogging, it is necessary to make the periods of the cogging torques of the two coincident with each other have opposite phases and further make the amplitudes of the cogging torques of the both equal.

An embodiment in which the gap between the shield yoke 8 and the drive permanent magnet 3 is adjusted so that the amplitude of the shield cogging is equal to the amplitude of the core cogging is compared with the gap between the shield yoke and the drive permanent magnet 3 shown in FIG. A description will be given based on the cogging torque characteristic diagram.

FIG. 9 shows measured values of shield cogging with respect to the gap between the shield yoke 8 and the drive permanent magnet 3 when the shield yoke open angle α is nπ and nπ ± π / 4.

The optimum value of the gap between the shield yoke 8 and the drive permanent magnet 3 for making the amplitude of the shield cogging equal to that of the core cogging is determined as follows based on FIG.

As described above, the set value of the core cogging is 60 to 30 (g) in the gap 0.2 to 0.5 (mm) between the teeth 7a, 7b and 7c and the driving permanent magnet 3.
.Cm), and in this embodiment, the gap is 0.35
(Mm) and core cogging value were set to about 50 (g · cm).

Further, as described above, the position of the shield yoke 8 in which the core cogging and the shield cogging have mutually opposite phases is nπ ± π / 4 (n = ± 2, ± 3,
The range is equivalent to ± 4), and in this embodiment, n = 4 is set.

In FIG. 9, the shield cogging is n = 4 within the range of 60 to 30 (g · cm) (hatched portion) due to the already determined set value, so that the shield cogging of α = nπ is obtained. The target value of the gap between the shield yoke 8 and the permanent magnet 3 for driving is 1.2.
The range is 5 to 3.50 (mm).

In the shield cogging that is equal to the core cogging set value of about 50 (g / cm), the gap between the shield yoke 8 and the drive permanent magnet 3 is the teeth 7a, 7a.
By making the gap between b and 7c and the driving permanent magnet 3 five times, the core cogging and the shield cogging can cancel each other. In this embodiment, the gap between the shield yoke 8 and the drive permanent magnet 3 is set to 1.75 (mm).

As described above, as shown in the cogging characteristic diagram of the brushless motor according to the present invention in FIG. 4, the fluctuation range of the cogging of the brushless motor is about 25 (g).
.Cm), which can be reduced by about 70% compared to the cogging fluctuation range of about 80 (g.cm) of the conventional brushless motor shown in FIG.

Next, in order to equalize the counter electromotive forces induced in the central and outer armature coils 5, the teeth 7a, 7
An embodiment in which the shape and size of the tips of b and 7c or the armature coil 5 is improved will be described.

FIG. 12 is a waveform diagram of the back electromotive force of the armature coil and the torque ripple of the rotor by the E-type out core according to the present invention, and the back electromotive force of the armature coil and the torque ripple of the rotor by the conventional E-type out core of FIG. It is a wave form diagram, and shows the significance of the present invention regarding the back electromotive force characteristic of stator 9 here.

12 and 13, the counter electromotive force induced in the armature coil 5 and the torque ripple generated in the rotor with respect to the rotation angle are shown. The waveforms of the counter electromotive force are shown in the center and outer armature coils 5, respectively. It is shown.

If the amplitudes of the counter electromotive forces on both the center and the outside are equal, the peak value of the torque ripple becomes constant as shown in FIG. 12, and unlike the case where the amplitudes of both are different in FIG. 13, the torque ripple is stable. The difference in counter electromotive force between the center and the outside does not appear in the torque ripple.

In order to make the counter electromotive forces of the central and outer armature coils 5 equal, the magnetic flux from the driving permanent magnet 3 concentrated by the teeth 7a, 7b, 7c is applied to the central teeth 7c and the outer teeth 7a. 7c can be made equal.

An embodiment in which the shapes and dimensions of the tips of the teeth 7a, 7b, 7c or the armature coil 5 are improved so that the counter electromotive forces induced in the central and outer armature coils 5 are equalized will be described below. 10 will be described with reference to the E-shaped out core shape diagram according to the present invention in FIG. 10 and the counter electromotive force comparison diagram of the actually measured armature coil in FIG.

In FIG. 10, the teeth 7a, 7b, 7
A rotor 2 having the same shape as the four types of E-shaped out cores 6 each having a different shape and size of the tip of c is drawn. In the figure, W1 and W2 are rotors 2 at the tips of the teeth 7a, 7b and 7c. The widths of the portions facing each other, G1 and G2, respectively represent the sizes of the gaps between the rotor 2 and the tips of the teeth 7a, 7b, 7c facing the rotor 2, and T1 and
T2 is the number of turns of the armature coil 5 of the central teeth 7c and the outer teeth 7a and 7b.

As shown in the figure, two outer teeth 7
As for the shape of the tips of a and 7b, a concave portion 11 of the tips of the teeth is provided on the side facing the central tooth 7c,
A width W2 of a portion of the tips of the teeth 7a and 7b, which are symmetric with respect to the center line of the central tooth 7c and face the rotor 2,
Are the same and teeth 7 facing the rotor 2 as well.
The gap between the tips of a and 7b and the rotor 2 has the same dimensional value.

Next, the constitutional conditions of the stator 9 shown in each drawing of FIG. 10 will be described. In FIG. 10A, W2 = W1, G
2 = G1 and T2 = T1, and a concave portion 11 at the tooth tip is provided at the outer tooth tip of the conventional E-shaped out core.

In FIG. 10B, W2 = W1, G2 = G
The number of turns of 1 and T2 is 1.1 to 1.4 times the number of turns of T1, and this relationship is hereinafter expressed as T2 = (1.1 to 1.4) * T1. FIG. 10C shows W2 = W1, T2 = T1, G2.
Is 0.4 times to 0.7 times G1, and this relationship is expressed as G2 = (0.4 to 0.7) * G1. FIG. 10 (d)
Is G2 = G1, T2 = T1, and W2 is 1.2 to 1.6 times W1, and thereafter, this relationship is W2 = (0.4 to 0.
7) * W1.

FIG. 11 is a waveform diagram in which the counter electromotive force induced in the armature coil 5 of the central teeth 7c and the outer teeth 7a and 7b is actually measured under the above-mentioned stator configuration conditions, and the waveform A is the outer teeth 7a. , 7b, the counter electromotive force induced in the armature coil 5 and the waveform B are the central teeth 7c.
The counter electromotive force induced in the armature coil 5 of FIG.

FIG. 11A shows the counter electromotive force of the armature coil by the E-shaped out core of the conventional brushless motor shown in FIG. 14, and the outer teeth 7a and 7b are for driving as compared with the central teeth 7c. Since the magnetic flux of the permanent magnet 3 cannot be efficiently concentrated, the counter electromotive force (waveform A) of the armature coil 5 attached to the outer teeth 7a and 7b is equal to the counter electromotive force (waveform B of the armature coil 5 of the central tooth 7c). ) Is about 30-40% smaller.

FIG. 11 (b) shows FIGS. 10 (a) and 10 (b).
The waveform of the counter electromotive force according to the stator configuration condition of (c), the amplitude of the waveform A is slightly smaller than that of the waveform B, and the difference of the counter electromotive force of the armature coil 5 of the outer teeth 7a and 7b and the central tooth 7c is You can see that it is decreasing.

FIG. 11C is a waveform of the counter electromotive force according to the stator configuration condition of FIG. 10D, which is the waveform A and the waveform B.
There is almost no difference in the amplitude of the outer teeth 7a, 7
It can be seen that the back electromotive forces of the armature coils 5 of b and the central teeth 7c are almost equal.

In order to make the counter electromotive forces more exactly equal in the stator configurations shown in FIGS.
Of the stator configuration conditions of (b), the number of turns of the armature coil 5, T2 = (1.1 to 1.4) * T1 may be performed.

As described above, the teeth 7
The shape and size of the tips of a, 7b, 7c or the armature coil 5 is improved so that the magnetic flux concentrated in the teeth 7a, 7b, 7c is made uniform, and the reverse of the armature coil 5 of the outer teeth 7a, 7c and the central tooth 7c. By making the electromotive forces equal, fluctuations in torque ripple can be minimized, as shown in FIG.

[0084]

As described above, in the brushless motor according to the present invention, the shield yoke is arranged so that the cogging torque generated between the tooth and the drive permanent magnet is minimized, and the tooth and the drive magnet are arranged. The cogging torque generated between the permanent magnet and the cogging torque generated between the shield yoke and the drive permanent magnet should be of the same magnitude and the same period but opposite phases, so that the cogging torques of the two cancel each other out. Therefore, it is possible to minimize vibration, noise, and rotation irregularity due to cogging of the brushless motor.

Further, in the brushless motor according to the present invention, the ratio of the width of the tips of the central teeth and the width of the tips of the outer teeth is set to 0.6 to 0.9, and the brushless motor is generated between the teeth and the drive permanent magnet. It is possible to equalize the cycle of the cogging torque generated between the shield yoke and the drive permanent magnet, and to make the cycle of the cogging torque and the variation of the amplitude uniform. It is possible to minimize the fluctuation of the cogging.

Furthermore, in the brushless motor according to the present invention, the straight line connecting the midpoint of the arc of the shield yoke and the center of the rotor is nπ in electrical angle from the central tooth of the E-shaped out core.
At a position corresponding to ± π / 4 (n = ± 2, ± 3, ± 4),
The shield yoke is arranged, and the cycle of the cogging torque generated between the shield yoke and the drive permanent magnet has a phase opposite to that of the cogging torque generated between the teeth and the drive permanent magnet. Since the cogging torques can cancel each other out, it is possible to reduce vibrations, noises, and rotational unevenness due to cogging of the brushless motor.

In the brushless motor according to the present invention, the ratio of the gap between the shield yoke and the driving permanent magnet and the gap between the teeth and the driving permanent magnet is set to 3 to 7, and the shield yoke and the driving permanent magnet are set. Since the cogging torque generated between the brushless motor and the teeth can be made equal to the cogging torque generated between the teeth and the drive permanent magnet, the amplitude of the cogging fluctuation of the brushless motor can be made constant.

Further, in the brushless motor according to the present invention, a recess for concentrating magnetic flux is provided at the tip of the surface of the outer teeth of the E-shaped outer core facing the central teeth, and induced in the armature coil of the outer teeth. The generated back electromotive force can be increased to be equal to the back electromotive force induced in the armature coil of the central tooth, reducing irregular torque ripple during rotational drive of the brushless motor, reducing vibration and noise. Rotational unevenness can be reduced.

Further, in the brushless motor according to the present invention, the areas of the surfaces of the teeth facing the driving permanent magnets are made equal, and the number of windings of the armature coil wound around the outer teeth and the armature wound around the central teeth. The ratio of the number of turns of the coil is set to 1.1 to 1.4, the number of turns of the armature coil of the outer tooth is increased to increase the counter electromotive force induced in the armature coil of the outer tooth, and the armature of the central tooth is increased. Since it can be made equal to the counter electromotive force induced in the coil, the torque ripple during rotational driving of the brushless motor can be further reduced, and vibration, noise, and rotational irregularity can be reduced.

Further, in the brushless motor according to the present invention, the areas of the surfaces of the teeth facing the driving permanent magnets are made equal, and the central teeth tips and the driving tips are set with respect to the gap between the outer teeth tips and the driving permanent magnets. The ratio of the gap with the permanent magnet is set to 0.4 to 0.7, and the magnetic flux of the armature coil shaft center of the central teeth becomes equal to the magnetic flux concentrated on the armature coil shaft center of the outer teeth. Since the back electromotive forces induced in the armature coils of the teeth and outer teeth can be made equal, the torque ripple during rotational driving of the brushless motor can be further reduced, and vibration, noise, and rotational irregularity can be reduced. it can.

In the brushless motor according to the present invention, the area ratio of the surface of the two outer teeth facing the driving permanent magnet to the surface of the central tooth facing the driving permanent magnet is 1.2. Set to 1.6 to make the magnetic flux of the armature coil shaft center of the outer teeth equal to the shaft center magnetic flux of the armature coil of the central teeth, and the reverse induced in each armature coil of the outer teeth and the center teeth. Since the electromotive forces can be made equal, the torque ripple during rotational driving of the brushless motor is minimized, and vibration and uneven rotation can be further reduced.

Therefore, as described above, according to the present invention, the cogging and the torque ripple, which are the problems of the brushless motor having the slot type stator, are minimized, and the vibration, noise and wow and flutter are greatly reduced. In addition to improving the motor efficiency, it is possible to provide a brushless motor that achieves a significant improvement in performance economically.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a brushless motor according to the present invention.

FIG. 2 is a cogging torque characteristic diagram of only the E-type out core of the brushless motor according to the present invention.

FIG. 3 is a cogging torque characteristic diagram of only the shield yoke of the brushless motor according to the present invention.

FIG. 4 is a cogging characteristic diagram of the brushless motor according to the present invention.

FIG. 5 is a cogging characteristic diagram of a conventional brushless motor.

FIG. 6 is a cogging torque characteristic diagram with respect to a width ratio of teeth.

FIG. 7 is a cogging torque characteristic diagram with respect to the arrangement of the shield yoke.

FIG. 8 is a cogging / starting torque characteristic diagram for the gap between the tooth and the drive permanent magnet.

FIG. 9 is a cogging torque characteristic diagram with respect to a gap between a shield yoke and a drive permanent magnet.

FIG. 10 is an E-shaped out core shape diagram according to the present invention.

FIG. 11 is a comparison diagram of counter electromotive forces of armature coils by actual measurement.

FIG. 12 is a torque ripple waveform diagram of a back electromotive force of an armature coil and a rotor by an E-type out core according to the present invention

FIG. 13 is a diagram of a counter electromotive force of an armature coil and a torque ripple waveform of a rotor by a conventional E-type out core.

FIG. 14 is an overall configuration diagram and an E-type outcore shape diagram of a conventional brushless motor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Brushless motor, 2 ... Rotor, 3 ... Driving permanent magnet, 4 ... Shaft, 5 ... Armature coil, 6 ... E-shaped out core, 7a ... Outer teeth, 7b ... Outer teeth, 7c
... center teeth, 8 ... shield yoke, 9 ... stator,
10 ... Armature coil driving means, 11 ... Recess at the tip of the tooth.

Claims (8)

[Claims] 1. An armature coil is wound around each of a rotor that is rotatable and has a drive permanent magnet fixed to its outer peripheral portion, and an E-shaped out core that is arranged to face the rotor and has three teeth. A brushless provided with a stator, a magnetic shield yoke formed so as to surround the rotor, and armature coil driving means for rotating and driving the rotor by controlling a three-phase exciting current flowing in the armature coil. In the motor, the brushless motor is characterized in that the shield yoke is arranged so that a cogging torque generated between the tooth and the driving permanent magnet is minimized. 2. The brushless motor according to claim 1, wherein the ratio of the width of the tips of the central teeth to the width of the tips of the outer teeth is set to 0.6 to 0.9. 3. A straight line connecting the midpoint of the arc of the shield yoke and the center of the rotor is nπ ± π / 4 (n = ± 2, ± 3, ±) in electrical angle from the central tooth of the E-shaped out core.
The brushless motor according to claim 1, wherein the shield yoke is arranged at a position corresponding to 4). 4. The brushless motor according to claim 1, wherein a ratio of a gap between the shield yoke and the drive permanent magnet and a gap between the tooth and the drive permanent magnet is set to 3 to 7. . 5. An armature coil is wound around each of a rotor that is rotatable and has a drive permanent magnet fixed to the outer periphery thereof, and an E-shaped out core that is arranged facing the rotor and that has three teeth. A brushless provided with a stator, a magnetic shield yoke formed so as to surround the rotor, and armature coil driving means for rotating and driving the rotor by controlling a three-phase exciting current flowing in the armature coil. In the motor, the brushless motor is characterized in that a concave portion for concentrating magnetic flux is provided at a tip end portion of a surface of each of the outer teeth of the E-shaped outer core facing the central teeth. 6. The ratio of the number of turns of the armature coil wound on the outer tooth to the number of turns of the armature coil wound on the central tooth is set to 1 with the areas of the faces of the teeth facing the drive permanent magnets made equal. A brushless motor characterized by being set to 0.1 to 1.4. 7. The areas of the faces of the teeth facing the drive permanent magnets are equalized, and the ratio of the gap between the center teeth tips and the drive permanent magnets to the gap between the outer teeth tips and the drive permanent magnets is set to be the same. , 0.4 to 0.7 are set, and the brushless motor according to claim 5. 8. The area ratio of the surface of the two outer teeth facing the driving permanent magnet to the surface of the central tooth facing the driving permanent magnet is set to 1.2 to 1.6. The brushless motor according to claim 5, wherein: