JP3284455B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

[0003] All three teeth 103 are formed on the E-shaped out core 105 with the same width, and the leading end extends in the outer peripheral direction of the rotor 101, faces the driving permanent magnet 102 with a predetermined gap, and has a leading end. Are formed with the same width.

[0004] The shield yoke 106 is symmetrical to the E-shaped out core 105 on the opposite side of the rotor 101,
The midpoint of the arc forming the shield yoke 106 and the rotor 10
A brushless motor is known which is installed and configured such that a straight line connecting the centers of the first and second teeth overlaps a center line of a center tooth passing through the center of the rotor 101.

[0005]

SUMMARY OF THE INVENTION Conventional CDs and CDs
-A brushless motor used for a ROM drive spindle motor or the like is constituted by a stator having a slot-type three-teeth E-shaped out core.

The stator has a structure in which an armature coil is wound directly around each of the three teeth, and the structure is simplified, thereby improving the manufacturing efficiency. Cogging occurs with the driving permanent magnet, and there is a problem in that a rotor that requires high-speed response and constant-speed driving at low speed rotation deteriorates torque unevenness or uneven rotation characteristics of the rotor.

[0007] Further, the shape of the three teeth of the E-shaped out core is not magnetically uniform because the center teeth and the outer teeth are different in shape, so that an uneven cogging torque is easily generated. In the case of the taste, the magnetic flux of the driving permanent magnet cannot be concentrated efficiently as compared with the center taste, so that there is a problem that the average starting torque of the brushless motor decreases and the torque ripple increases.

Furthermore, if a shield yoke made of a magnetic material is arranged to shield the influence of the magnetic field of the drive permanent magnet on the outer periphery 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, the two are combined. As a result, cogging becomes even larger.

The intricately combined non-uniform cogging torque and the torque ripple during the rotation drive increase the vibration and noise of the brushless motor, and have the problem of increasing the vibration and wow and flutter especially in the low-speed rotation region.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object of the present invention is to minimize the cogging of a brushless motor, reduce torque ripple, and reduce vibration and noise. Is to provide.

[0012]

In order to solve the above-mentioned problems, a brushless motor according to the present invention has the following configuration. (1) A rotor which is rotatable and has a driving permanent magnet fixed to an outer peripheral portion thereof, and a stator which is disposed opposite to the rotor and has an armature coil wound around each of an E-shaped out core having three teeth. A brushless motor comprising: a magnetic shield yoke formed so as to surround the rotor; and a three-phase excitation current flowing through the armature coil, and armature coil driving means for rotating the rotor. The cogging torque generated between the three teeth and the driving permanent magnet and the cogging torque generated between the shield yoke and the driving permanent magnet are:
The shield yoke and the three teeth are configured to have the same period , and the arc of the shield yoke is
The straight line connecting the midpoint to the center of the rotor and the E-shaped
The angle between the center line of the center teeth and the electrical angle is nπ
At the position where ± π / 4 (n = ± 2, ± 3, ± 4),
A brushless motor characterized by disposing a metal yoke. (2) The ratio (W1 / W2) of the width (W1) of the center tooth tip to the width (W2) of the outer tooth tip is 0.6 to 0.
9. The brushless motor according to claim 1, wherein the brushless motor is set to 9.

[0013]

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 pays attention to the periodicity of the cogging torque generated between the magnetic pole on the outer periphery of the rotor and the stator core and between the magnetic pole on the outer periphery of the rotor and the shield yoke, and replaces the former cogging torque with the latter cogging torque. To minimize 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 periphery of the rotor is not uniform due to the difference between the central and outer teeth shapes, and the back electromotive force induced in each armature coil is different. Focusing on contributing to the torque ripple, the shape and size of the teeth tip or the armature coil are improved, and the torque ripple of the rotor drive torque caused by the difference in the back electromotive force is minimized.

In FIG. 1, a brushless motor 1 according to the present embodiment has a rotatable rotor 2 fixed to a shaft 4.
A three-phase stator 9 disposed opposite to the rotor 2,
A shield yoke 8 arranged so as to surround the rotor 2 and armature coil driving means 8 for controlling an exciting current flowing through the armature coil 5 to rotate the rotor 2 are provided, and the whole is configured.

The rotor 2 has an eight-pole driving permanent magnet 3 fixed to an outer peripheral portion thereof. The cogging torque generated between the teeth 7a, 7b, 7c and the driving permanent magnet 3 is reduced. Permanent magnet 3 that is a source of
That is, so-called sine magnetization is applied so as to avoid a sudden change in the magnetic field at the portion where the magnetic poles are switched, and to switch smoothly.

The stator 9 has three teeth 7a, 7
b, 7c, and an armature coil 5 wound around each tooth.
The tips of 7b and 7c extend on the outer peripheral surface of the driving permanent magnet 3 via a predetermined gap, and the outer teeth 7a and 7b
The central teeth 7c have a width different from that of the central teeth 7c, and a concave portion 11 at the distal end of the teeth is formed at the distal end of the surface facing the central teeth.

The shield yoke 8 is a circle having the same shape as the center of the rotor 2 so as to surround the rotor 2 in order to shield the leakage of the magnetic flux so that the magnetic flux of the driving permanent magnet 3 does not affect the operation of the recording medium and the head. The brushless motor 1 is formed of an arc-shaped magnetic material and is arranged at a position where cogging of the brushless motor 1 is minimized.

Here, in order to show the significance 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.

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

FIG. 3 is a cogging torque characteristic diagram of only the shield yoke of the brushless motor according to the present invention.
7 shows a cogging torque waveform generated in the rotor 2 when the E-shaped out core 6 is deleted and the rotor 2 and the shield yoke 8 are used alone.

In FIGS. 2 and 3, when the magnitude and the 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 determined so that the phases of the respective cogging torques are opposite to each other. It can be seen that if the positions can be set to cancel each other, cogging of the brushless motor can be minimized.

FIG. 4 is a cogging characteristic diagram of the brushless motor according to the present invention. FIG. 4 shows the cogging characteristics of the brushless motor of the present embodiment when the shield yoke 8 is arranged so that the cogging torques of the two cancel each other, and is compared with the cogging characteristic diagram 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 arrangement position of the shield yoke in which the period, phase and amplitude of the cogging torque fluctuation satisfy predetermined conditions as described above will be described in order.

Here, the cogging torque generated between the teeth 7a, 7b, 7c of the E-shaped out core 6 and the driving permanent magnet 3 is generated between the core yoke and the shield yoke 8 and the driving permanent magnet 3. This cogging torque is referred to as shield cogging.

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

In FIG. 6A, W1 is the width of the tip of the central tooth 7c of the E-shaped outcore 6, and W2 is the width of the tip of the teeth 7a, 7b on both sides of the E-shaped outcore 6. 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. 6C shows the waveforms of the core cogging and the shield cogging per one pole of the driving permanent magnet, and the configurations at the time of measurement are as shown in FIGS. In the measurement, the E-shaped out core 6 was removed, and in the measurement of core cogging, the shield yoke 8 was removed.

Further, as other measurement conditions, the opening angle α of the shield yoke 8 in the measurement of shield cogging is 3π, and in the measurement of core cogging, three teeth 7a are used.
The distance between the driving permanent magnets 3 and the driving permanent magnets 3 is constant.

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

Although not shown, when (W1 / W2) is in the range of 0.6 to 0.9, the period of the core cogging in the period π is one, and both-side teeth 7a, 7b
By setting the width of the central teeth 7c to 0.6 times to 0.9 times, the periods of the core cogging and the shield cogging can be made equal.

In addition, the width of the central teeth 7c having a high magnetic flux density is narrowed as compared with the teeth 7a and 7b on both sides,
The non-uniformity of the magnetic flux density of the three teeth can also be reduced.

In this embodiment, both-side teeth 7a,
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 torques of both periods coincide with each other in opposite phases.

An embodiment in which the position of the shield yoke 8 with respect to the E-shaped out core 6 is adjusted and the shield cogging phase is reversed from the core cogging phase is shown in the cogging torque characteristic diagram for the shield yoke arrangement of FIG. It will be described based on the following.

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

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

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

FIG. 8 is a graph showing cogging and starting torque characteristics with respect to the gap between the driving permanent magnet and the teeth.

In FIG. 8, teeth 7a, 7b, 7c
Starting torque characteristics with respect to the gap between the driving permanent magnet 3 and the driving permanent magnet 3 are determined based on the starting torque value determined based on the specification requirements and design reasons. In the brushless motor according to the present embodiment, 0.1 is taken into consideration in consideration of manufacturing variations and the like.
It was set in the range of 2 to 0.5 (mm).

The determined teeth 7a, 7b, 7
The value of the core cogging with respect to the gap between c and the driving permanent magnet 3 is approximately 60 to 30 according to the cogging torque characteristic of FIG.
(G · cm).

In this embodiment, the teeth 7a, 7b, 7c
And the gap between the driving 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 periods opposite to each other and to make the amplitudes of the two cogging torques equal to each other.

An embodiment in which the gap between the shield yoke 8 and the driving permanent magnet 3 is adjusted so that the amplitude of the shield cogging is equal to the amplitude of the core cogging is shown in FIG. 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 driving permanent magnet 3 when the shield yoke opening angle α is nπ and nπ ± π / 4.

The optimum value of the gap between the shield yoke 8 and the driving permanent magnet 3 for making the amplitude of the shield cogging equal to 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, 7c and the driving permanent magnet 3.
· Cm), and in this embodiment, the gap is 0.35
(Mm) and the core cogging value were set to about 50 (g · cm).

As described above, the position of the shield yoke 8 where the core cogging and the shield cogging are in opposite phases is nπ ± π / 4 (n = ± 2, ± 3,
± 4), and in this embodiment, n = 4.

In FIG. 9, the shield cogging in FIG. 9 is within the range of 60 to 30 (g.cm) (shaded area), and n = 4. For the curve, the possible value of the gap between the shield yoke 8 and the driving permanent magnet 3 is 1.2
It is in the range of 5 to 3.50 (mm).

In the shield cogging which is equal to the core cogging set value of about 50 (g / cm), the gap between the shield yoke 8 and the driving permanent magnet 3 is defined by the teeth 7a, 7
The core cogging and the shield cogging can be canceled by setting the gap between the b and 7c and the driving permanent magnet 3 to five times. In the present embodiment, the gap between the shield yoke 8 and the driving 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 is about 70% smaller than the variation range of cogging of the conventional brushless motor shown in FIG. 5 of about 80 (g · cm).

Next, in order to equalize the back electromotive force induced in the central and outer armature coils 5, the teeth 7a, 7
An embodiment in which the shapes and dimensions of the tips b and 7c or the armature coil 5 are improved will be described.

FIG. 12 is a waveform diagram of the back electromotive force of the armature coil and the rotor ripple due to the E-shaped out core according to the present invention, and FIG. 13 is the back electromotive force of the armature coil and the torque ripple of the rotor due to the conventional E-shaped out core. FIG. 4 is a waveform diagram showing the significance of the present invention regarding the back electromotive force characteristics of the stator 9.

12 and 13, the back 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 back electromotive force are shown in the center and outer armature coils 5 respectively. It is shown.

If the amplitudes of the back electromotive force at 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 the back electromotive force between the center and the outside does not appear in the torque ripple.

To equalize the back electromotive force of the central and outer armature coils 5, the magnetic flux from the driving permanent magnet 3 concentrated by the teeth 7a, 7b, 7c is transferred to the central tooth 7c and the outer teeth 7a, 7b may be 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 back electromotive forces induced in the central and outer armature coils 5 are equalized. 10 will be described with reference to the E-shaped out-core shape diagram of the present invention shown in FIG. 10 and the back electromotive force comparison diagram of the armature coil measured by FIG.

In FIG. 10, teeth 7a, 7b, 7
c, four types of E-shaped out cores 6 having different shapes and dimensions at the tips of the rotors 2 are depicted, and W1 and W2 in the figure are rotors 2 at the tips of the teeth 7a, 7b, and 7c. , G1 and G2 respectively represent the dimensions of the gaps between the tips of the teeth 7a, 7b and 7c facing the rotor 2 and the rotor 2;
T2 is the number of turns of the armature coil 5 of the center tooth 7c and the outer teeth 7a, 7b.

As shown in the figure, two outer teeth 7
The shape of the tip of a, 7b is such that a recess 11 at the tip of the tooth is provided on the side facing the central tooth 7c,
The width W2 of a portion symmetrical with respect to the center line of the central teeth 7c and opposed to the rotor 2 at the tips of the teeth 7a and 7b.
Are equal and the teeth 7 also face the rotor 2
The gaps between the tips a and 7b and the rotor 2 have the same dimensions.

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

FIG. 10B shows that W2 = W1, G2 = G
1, the number of turns of T2 is 1.1 times 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 that W2 = W1, T2 = T1, G2
Is 0.4 to 0.7 times G1. This relationship is hereinafter 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) Expressed as * W1.

FIG. 11 is a waveform diagram in which the back electromotive force induced in the armature coil 5 of the center tooth 7c and the outer teeth 7a, 7b under the above-mentioned stator configuration conditions is shown. , 7b, the back electromotive force induced in the armature coil 5 and the waveform B are the center teeth 7c
Respectively represent the back electromotive force induced in the armature coil 5.

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

FIG. 11 (b) shows the state shown in FIG.
(C) is a waveform of the back electromotive force according to the stator configuration condition. The amplitude of the waveform A is slightly smaller than the waveform B, and the difference between the back electromotive forces of the armature coils 5 of the outer teeth 7a and 7b and the center tooth 7c is It can be seen that it has decreased.

FIG. 11C shows the waveforms of the back electromotive force under the stator configuration conditions shown in FIG.
Of the outer teeth 7a, 7
It can be seen that the back electromotive force of the armature coil 5 of b and the center teeth 7c is substantially equal.

In order to make the back electromotive force more strictly equal in the stator configuration shown in FIGS.
The number of turns of the armature coil 5, T2 = (1.1 to 1.4) * T1, may be implemented in the stator configuration condition of (b).

As described above, the teeth 7
a, 7b, 7c and the shape or size of the tip or the armature coil 5 is improved, the magnetic flux concentrated on the teeth 7a, 7b, 7c is made uniform, and the outer teeth 7a, 7b and the armature coil 5 of the center tooth 7c are reversed. By making the electromotive forces equal, fluctuations in torque ripple can be minimized as shown in FIG.

[0069]

As described above, the brushless motor according to the present invention has a cogging torque generated between three teeth and a driving permanent magnet, and a cogging torque generated between a shield yoke and a driving permanent magnet. Therefore, the vibration, noise, and uneven rotation due to the cogging of the brushless motor can be minimized. In addition, the complicated cogging fluctuation of the brushless motor can be minimized.

[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 an E-shaped 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 graph showing a cogging torque characteristic with respect to a tooth width ratio.

FIG. 7 is a graph showing cogging torque characteristics with respect to the arrangement of a shield yoke.

FIG. 8 is a characteristic diagram of cogging and starting torque with respect to a gap between a tooth and a driving permanent magnet.

FIG. 9 is a graph showing a cogging torque characteristic with respect to a gap between a shield yoke and a driving permanent magnet.

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

FIG. 11 is a comparison diagram of back electromotive force of an armature coil by actual measurement.

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

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

FIG. 14 is an overall configuration diagram and an E-shaped out-core shape diagram of a conventional brushless motor.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 brushless motor 2 rotor 3 drive permanent magnet 4 shaft 5 armature coil 6 E-shaped out core 7 a outer teeth 7 b outer teeth 7 c
... Center teeth, 8 ... Shield yoke, 9 ... Stator,
10: armature coil driving means, 11: concave portion at the tip of the tooth.

Claims (2)

(57) [Claims] An armature coil is wound around each of a rotatable rotor having a driving permanent magnet fixed to an outer peripheral portion thereof, and an E-shaped out core having three teeth disposed opposite to the rotor. A brushless motor comprising: a stator; a shield yoke made of a magnetic material formed so as to surround the rotor; and an armature coil driving unit that controls a three-phase excitation current flowing through the armature coil to rotate the rotor. The cogging torque generated between the three teeth and the driving permanent magnet and the cogging torque generated between the shield yoke and the driving permanent magnet have the same circumference.
The shield yoke and the three teeth are configured so that the
Inside the straight line connecting the center of the rotor and the E-shaped out core
The angle between the center line of the central tooth and the center line is an electrical angle, nπ ± π /
4 (n = ± 2, ± 3, ± 4)
A brushless motor having a yoke arranged therein . 2. The ratio (W1 / W2) of the width (W1) of the center tooth tip and the width (W2) of the outer tooth tip is 0.6 to 0.6.
2. The brushless motor according to claim 1, wherein the value is set to 0.9.