JP2000156958A - Permanent magnet motor and disk apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor which reduces cogging torque, improves mechanical strength at the end of a salient pole and whose motor efficiency is enhanced, and to provide a disk apparatus which uses it. SOLUTION: This permanent magnet motor is of an outer rotation type. Twelve permanent magnets 3 and a hub 4, which fixes the permanent magnets 3, are provided at a rotor 20. A stator 10 is provided with nine salient pole parts. Stator coils 5 are wound on teeth 8. Correction grooves 6 are formed in two places near the center of the teeth 8 on the surface of salient pole ends 2 faces with permanent magnets 8. The correction grooves 6 are formed at places where n=1 and 2 at a machine angle of 5×(2n+1) deg. by using a slit 7 as a reference, i.e., at places where the angle is 15 deg. and 25 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a miniaturization,
Disk drive permanent magnet motor and DVD, CD-R for which low power consumption is important and which requires low noise and low vibration
The present invention relates to a disk drive for driving a disk such as an OM or an HDD.

[0002]

2. Description of the Related Art Conventionally, a permanent magnet motor for driving a disk used in a DVD, an HDD or the like has a low vibration in order to increase information stored in the disk, and a thin and low power consumption in a portable device. , Low noise is required.

Examples of the structure of the permanent magnet motor used here include a rotor having permanent magnets of a required number of poles arranged alternately or substantially at equal intervals, and a stator having a salient pole wound with a stator coil. And the rotor is movable with respect to the stator through a predetermined gap. As a method of reducing the cogging torque of the motor having such a configuration, a method of providing a correction groove at an extreme extreme is known.

First, the cogging torque pulsates by the least common multiple of the number of poles of the rotor and the number of stator coils of the stator per rotation of the motor. Further, the magnitude thereof is related to the magnitude of the pulsation frequency component among the harmonic components of the magnetic flux distribution of the permanent magnet of the rotor.

For example, in the case of a 4-pole 6-coil permanent magnet motor, the cogging torque is generated 12 times per rotation of the motor, and the magnitude of the cogging torque is 12 times per rotation in the magnetic flux distribution of the permanent magnet of the rotor. Related to the size of

[0006] Here, the magnetic flux distribution of the permanent magnet of the rotor is
Since the shape is close to a sine wave having half the number of poles per rotation, the higher-order component (harmonic component) decreases as the order increases. Accordingly, the magnitude of the cogging torque is reduced by providing a correction groove at the extreme pole and increasing the order of the cogging torque.

For example, it is disclosed in Japanese Patent Application Laid-Open No. 8-317622. FIG. 4 shows the structure of a conventional permanent magnet motor. The rotor is a permanent magnet motor having a 2: 3 structure in which there are four permanent magnets 3 and six salient poles 11 of the salient poles 2. Therefore, normally, 12 cogging torques are generated per rotation. In this prior art, the correction groove 6 is provided on the surface of the salient pole portion 11 of the salient pole 2 facing the permanent magnet 3. In this motor, since the slit 7 has a mechanical angle of 60 °, a correction groove 6 is provided every 20 ° in mechanical angle obtained by dividing the slit 7 by 3. Thus, the salient pole 2 behaves as if it has 18 salient poles. Therefore, the cogging torque is tripled, ie, 36 times per rotation, and the higher the order, the smaller the cogging torque. Therefore, this measure has been taken.

[0008]

However, according to such a conventional method, the mechanical strength of the salient pole 2 is weakened by the correction groove 6, or the magnetic path through which the magnetic flux passes becomes narrow, so that the effective magnetic flux decreases. There was a problem to do. This is particularly noticeable in a motor having a 4: 3 structure.

FIG. 5 shows that the number of poles of the permanent magnet 3 of the rotor is 12
This figure shows a 4: 3 structure permanent magnet motor having nine poles and two salient poles 11 of salient poles. Since the motor having this structure has a large number of poles of the rotor, the magnetic flux distribution of the permanent magnet 3 is closer to a sine wave as compared with the motor having the 2: 3 structure, and is characterized in that cogging torque is hardly generated. If the countermeasure against cogging torque is further applied to this motor according to the same principle as described above, the slit 7
It is necessary to provide the correction groove 6 every 13.3 ° in mechanical angle obtained by dividing the interval 40 ° into three equal parts. However, this angle is
Is located far from the center of the teeth 8, the portion indicated by A in FIG. 5 becomes thinner, and the mechanical strength becomes weaker.

If the auxiliary groove 6 does not cause an effect equivalent to the magnetic effect of the slit 7, it does not act as if the salient pole portion 11 has increased, so the depth of the auxiliary groove 6 must be increased. Instead, the mechanical strength of this part weakens,
There were problems such as saturation of magnetic flux.

When the portion indicated by B in FIG. 5 is made thicker, the number of turns of the stator coil 5 is reduced, and when the number of turns is secured and the winding is made thinner, the winding resistance increases. The problem of the decrease occurs.

An object of the present invention is to provide a permanent magnet motor having reduced cogging torque and improved mechanical strength and motor efficiency of the salient pole 2, and a disk device using the same.

[0013]

The feature of the present invention that achieves the above object is that the least common multiple of the number of poles M of the rotor and the number of poles S of the stator is L, and the slit between adjacent salient poles is L. From the center, mechanical angle (360 / L) x (2n + 1) / 2 degrees (however,
That is, two or more grooves are provided at positions near the center of the salient poles among the positions (n is an integer).

According to this feature, the cogging torque generated by the slit is exactly 180 ° out of phase, the cogging torque can be corrected, smooth rotation can be obtained, and noise can be reduced. Further, since the cogging torque is compensated by a plurality of grooves, the depth of the grooves can be reduced, and
Since the groove is close to the center of the tooth, the thickness of the protruding end of the auxiliary groove can be made larger than before. As a result, the cogging torque of the permanent magnet motor can be reduced, the efficiency can be improved, and the mechanical strength of the extreme pole can be improved.

The circumferential width of the groove is a mechanical angle (360 degrees).
/ L) / 2, the correction torque can be generated most efficiently, the depth of the groove can be made smaller, the cogging torque of the permanent magnet motor can be reduced, and the efficiency can be reduced. Further, the mechanical strength of the extreme pole can be further improved.

By using the permanent magnet motor of the present invention, smooth rotation with little speed fluctuation can be obtained with high efficiency.
Since the noise due to rotation can be reduced, it is particularly effective as a spindle motor for a disk drive for driving a disk such as a CD-ROM, DVD, or HDD used in portable information equipment. In the disk device having such a configuration, fluctuations in the rotation speed of the disk can be extremely reduced, so that recording and reproduction of magnetic information can be stabilized, reliability can be improved, and recording density can be improved.

[0017]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
1 shows a permanent magnet motor according to an embodiment of the present invention. The permanent magnet motor according to the present embodiment is of an abduction type, and is a 4: 3 structure permanent magnet motor having a rotor 20 having 12 poles and a stator 10 having 9 poles.
The rotor 20 has twelve permanent magnets 3 and a hub 4 for fixing the permanent magnets 3. The stator 10 has nine salient pole portions 11
And the stator coil 5 is wound around the teeth 8. On the surface of the salient pole 2 facing the permanent magnet 3, two correction grooves 6 are provided near the center of the teeth 8. The method of detecting the position of the magnetic pole of the permanent magnet 3 is not an essential problem, and is omitted. However, a brushless type such as providing a Hall element in the housing 1 or detecting an induced voltage generated in the stator coil 5 or a mechanical method There is a type having a simple brush. In the permanent magnet motor without the correction groove 6, the number of poles of the rotor 20 is 12 and the number of poles of the stator is 9, so that the cogging torque of 36, which is the least common multiple of 12 and 9, becomes 1 rotation. It happens around. This cogging torque has a cycle of 10 ° in mechanical angle.

In this embodiment, in order to correct this cogging torque, the mechanical angle is 5 × (2n + 1) ゜ (where n = 0, 0) with reference to the slit 7 between the adjacent salient poles 2.
(1, 2, 3...)), A groove having the same shape as the slit 7, that is, a correction groove 6 is provided. By providing the correction groove 6, a torque 180 ° out of phase with the case of the permanent magnet motor having no correction groove 6 is generated,
Cogging torque is corrected to obtain smooth rotation. This is because the cogging torque due to the slit 7 is generated at a mechanical angle of 10 ° cycle, and if the correction groove 6 is provided at an odd multiple of 5 ° in mechanical angle, the cogging torque due to the slit 7 is exactly 180 ° in phase. This is because different torques can be generated. That is, the correction groove 6 sets the cycle of the cogging torque to Tc.
(Tc is the number of poles of the permanent magnet as M, the number of slots as S, M
And Tc = 360 / L ゜ when the least common multiple of S is L, and Tc (2n
+1) / 2 = (360 / L) × (2n + 1) / 2 degrees (however,
(n is an integer).

In this embodiment, in order to solve the problems of the mechanical strength and the motor efficiency of the salient pole 2 shown in the conventional example, the mechanical angle is 5 × (2n + 1) ゜ with respect to the slit 7. Correction grooves 6 were provided at n = 1 and 2, that is, at 15 ° and 25 °. As a result, the following features are obtained.

(1) By setting n to 1 and 2, the position of the correction groove 6 is closer to the center of the tooth 8 by about 1.7 ° in mechanical angle than the position of the correction groove 6 shown in FIG. be able to.

(2) In order to cancel the magnetic effect of the slit 7, the two correction grooves 6 of 15 ° and 25 ° share and correct the magnetic effect. The depth of the groove, which may have a significant effect, may be used. That is,
The depth of the correction groove 6 can be reduced as compared with the conventional example.

Therefore, from (1) and (2), the thickness of the portion indicated by A in FIG. 1 can be made thicker than before, thereby reducing the cogging torque and the motor efficiency.
The mechanical strength of the salient pole 2 can be ensured.

Next, the position, width W and depth D of the correction groove 6
The relationship between and torque will be described. FIG.
FIG. 3 is a diagram in which one salient pole of a permanent magnet motor having 12 poles and a stator 10 having 9 poles is developed in a parallel movement state. Since the cogging torque due to the slits 7 has a mechanical angle of 10 ° cycle, four cycles of cogging torque are generated between adjacent slits 7 (40 °). In order to generate a correction torque having a phase opposite to that of the cogging torque, a groove may be provided at a position indicated by C in FIG. In this embodiment, the correction grooves 6 are provided at two places closer to the center of the teeth. Thereby, the depth D of the groove can be made smaller than in the case of one location. Therefore, the mechanical strength of the salient pole 2 can be secured.

The width D of the correction groove 6 can be made smaller by dividing the angle (40 °) of the adjacent slits 7 into eight equal parts (5 °). it can.
This is similar to the cogging torque because the adjacent slits 7
The correction torque that needs to be generated for four periods between the slits has a width equivalent to eight between the adjacent slits 7, so that the width of the groove exactly matches the half period of the correction torque, and the pulsation torque is most efficiently obtained. This is because

That is, the width W of the correction groove 6 is such that the period of the cogging torque is Tc (where Tc is M, the number of poles of the rotor is S, S is the number of poles of the stator, and L is the least common multiple of M and S). Tc
= 360 / L}, Tc / 2 = (36
By providing a width having an angle of 0 / L) / 2 °, the correction torque can be generated most efficiently, and the depth D of the correction groove 6 can be reduced.

As described above, when the permanent magnet motor of this embodiment is used, smooth rotation with little speed fluctuation can be obtained with high efficiency, and noise due to rotation can be reduced. CD-ROM, DV
It is effective as a spindle motor of a disk drive for driving a disk such as D or HDD.

In this embodiment, a rotary motor has been described, but the present invention can also be applied to a motor that performs a linear operation. For example, in a linear motor having n equally spaced cores moving in parallel to a surface facing permanent magnets with alternating poles at equal intervals, the number of poles of the permanent magnets is the number of poles facing the moving core. The correction groove 6 may be provided at a position based on the same idea as described above using the number. For example, if there are nine equally spaced cores moving in parallel and the number of permanent magnets facing the moving core is 12, the correction groove 6 may be provided at the position shown in FIG.

(Embodiment 2) FIG. 3 shows an HDD device using a permanent magnet motor according to a second embodiment of the present invention.

The permanent magnet motor used in the HDD device of this embodiment is the same as the abduction type permanent magnet motor described in the first embodiment, except that the rotor 20 has four fixed poles. The difference is that the number of poles of the child 10 is six. The salient pole 2 is provided with a correction groove 6 based on the principle shown in the first embodiment. Therefore, as in the case of the permanent magnet motor of the first embodiment, it is possible to obtain smooth rotation with little speed fluctuation and low noise with high efficiency.

In the HDD device having such a configuration, the fluctuation of the rotation speed of the disk 30 on which the magnetic information is recorded can be extremely reduced, so that the recording and reproduction of the magnetic information can be stabilized and the reliability can be improved. The recording density can be improved. In this example, the HDD device is shown. However, even when the present invention is applied to a CD-ROM device or a DVD device for recording / reproducing information on / from the disk 30 with a laser beam, fluctuations in the rotational speed of the disk 30 can be extremely reduced. Therefore, recording and reproduction of information with a laser beam can be stabilized, reliability can be improved, and recording density can be improved.

[0031]

According to the permanent magnet motor of the present invention, smooth rotation can be obtained by correcting cogging torque and noise can be reduced. In addition, the thickness of the protruding extreme portion of the auxiliary groove portion can be made thicker than before. As a result, the cogging torque of the permanent magnet motor can be reduced, the efficiency can be improved, and the mechanical strength of the extreme pole can be improved.

The circumferential width of the groove is set to a mechanical angle (360 /
By making the angle of L) / 2, the correction torque can be generated most efficiently, so that the depth of the groove can be made shallower, and the cogging torque of the permanent magnet motor can be further reduced.
The efficiency can be further improved, and the mechanical strength of the extreme pole can be further improved.

In the disk drive using the permanent magnet motor of the present invention, fluctuations in the rotational speed of the disk can be extremely reduced, so that the recording and reproduction of magnetic information is stabilized, the reliability is improved, and the recording density is improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a permanent magnet motor according to a first embodiment.

FIG. 2 is a diagram showing a relationship between cogging torque and torque by a correction groove 6;

FIG. 3 is a view showing a longitudinal section of an HDD device according to a second embodiment.

FIG. 4 is a diagram showing a conventional permanent magnet motor (2: 3 structure).

FIG. 5 is a diagram showing a conventional countermeasure method (4: 3 structure).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Salient pole, 3 ... Permanent magnet, 4 ... Hub, 5 ... Stator coil, 6 ... Correction groove, 7 ... Slit,
8: Teeth, 10: Stator, 11: Salient pole, 20: Rotor, 30: Disk.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumio Tajima 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. Hitachi, Ltd. Automotive Equipment Division (72) Inventor Nobuyuki Kumasaka 1410 Inada, Hitachinaka-shi, Ibaraki Prefecture F-Terminator, Hitachi, Ltd. AV Equipment Division F-term (reference) 5H002 AA04 AB06 AC06 AD04 AD06 AE06 AE07 5H621 AA02 BB07 GA01 GA04 GA14 GA15 HH05 JK02 JK05 JK15

Claims (3)

[Claims] A rotor having a plurality of permanent magnets arranged along a circumferential direction; and a stator having a plurality of salient poles on which a stator winding is wound. In the permanent magnet motor having a plurality of grooves on the side facing the permanent magnet, the minimum common multiple of the number of poles M of the rotor and the number of poles S of the stator is L, and the distance between adjacent salient poles is L. Mechanical angle (360 / L) × (2n + 1) / 2 degrees from the center of the slit (however,
wherein the groove is provided at two or more positions near the center of the salient pole among the positions (n is an integer). 2. The circumferential width of the groove is a mechanical angle (360 /
2. The permanent magnet motor according to claim 1, wherein the width is an angle of L) / 2. 3. A disk device using the permanent magnet motor according to claim 1.