JP4644530B2 - motor - Google Patents

Description

  The present invention relates to a motor, and more particularly, to an arrangement of magnetic poles and core teeth or coils facing the magnet.

An example of a conventional motor will be described with reference to FIGS.
This motor is a motor mounted on a 1-inch hard disk drive (HDD) for driving a disk using a fluid bearing.
In this motor, as shown in FIG. 7, at least one hard disk 101 is mounted on a hub 102.

  The stator 103 includes a motor base 105 formed by cutting aluminum die casting or pressing a plate obtained by applying nickel plating to an aluminum plate or an iron plate, a core 106 fixed thereto, and a winding around the core 106. The coil 107 is composed of a housing 111. A housing 111 is fixed and fixed to the center hole of the motor base 105 with an adhesive so as to obtain high assembly accuracy.

The rotor 104 includes a hub 102, and a magnet 108 with electrodeposition coating is bonded and fixed to the outside on the outer peripheral side of the hub 102.
In the hub 102, a thrust ring 112 is fixed inside the outer peripheral side, and a shaft 113 portion is integrally formed at the center. It is also made of stainless steel and has a cutting finish.
The shaft portion 113 is inserted into the housing 111, and the rotor portion 104 is rotatably supported by the stator 103 via a dynamic pressure bearing.
A female screw hole 115 for fixing a clamper for clamping the hard disk 101 is provided at the upper end of the hub 102. The hub 102 is usually formed using martensite, ferrite, or austenitic stainless steel, and further has a surface coating such as electroless nickel plating for the purpose of improving wear resistance.

The core 106 is arranged such that its inner peripheral surface faces the outer peripheral surface of the magnet 108 with a slight gap.
The core 106 is formed by laminating silicon steel plates, and the surface thereof is insulation-coated by electrodeposition coating, powder coating, or the like.
The winding terminal 107 a of the coil 107 is soldered to a flexible printed circuit board (hereinafter referred to as FPC) 114 on the bottom surface of the motor base 105 through the through hole 116 of the motor base 105.
The FPC 114 is provided with a land portion (not shown) for joining a portion of the coil 107 to which the terminal 107a is soldered and a motor driving circuit on the HDD side. Are connected. Then, each phase of the coil 107 is sequentially energized by the motor drive circuit, and the rotor 104 rotates.

Next, the number of magnetic poles of the magnet and the number of slots around which the coil is wound will be described.
For motors as described above, a three-phase drive system is generally used by optimizing efficiency and circuit configuration.
That is, with respect to 3n slots (n: an integer of 1 or more) of the core 106, the number of poles of 2n or 4n at equal angular intervals (or if one pair of N and S is one pole pair, n or 2n The magnets 108 magnetized in the number of pole pairs) face each other.
Here, when viewed from the slot side, when the magnet rotates relatively, if the magnet rotates for two poles (one pole pair), it becomes magnetically the same as before rotation, Therefore, in the following description, the magnetized two poles are expressed as an electrical angle 2π [rad].

First, when 2n poles are magnetized in 3n slots, the width of the slot tip with respect to the electrical angle π [rad] of one pole is at most an electrical angle (2/3) π [rad]. ] Can only be secured.
That is, only about 67%, which is 2/3 of the magnetic flux, can be effectively used.

  Further, when 4n poles are magnetized for 3n slots, the width of the slot front end can secure a maximum electrical angle (4/3) π [rad]. For the portion exceeding the electrical angle π [rad] of the minute, it becomes an opposite pole and cancels the magnetic flux. Therefore, it is most efficient that the width of the slot tip is an electrical angle π [rad]. In this case, the range in which the slot faces the electrical angle π × 4 n [rad] of the entire magnet is an electrical angle. Since it is in the range of π × 3n [rad], only 3/4 = 75% of the magnetic flux can be effectively used as a whole.

Here, the relationship among the number of magnetic poles, the number of slots, and their arrangement pitch is shown in FIG.
In a motor mounted on the HDD, the slot interval may be partially increased in order to secure a path for the recording / reproducing head to move in the radial direction of the hard disk. FIG. 9 also includes this form.
As described above, basically, in the core and the magnet, 3n slots and 4n magnetic poles (n: an integer of 1 or more) are arranged at equal intervals, but the magnetic poles are p-poles (p: 2). Even if the above is increased, the motor can be established without providing a slot facing the portion.

Here, in order to make it easy to understand the relationship between the slots from the 6th slot to the 12th slot and the magnetic poles, a schematic diagram in which these are extended linearly for convenience is shown in FIG.
In this figure, 10 poles 6 slots [FIG. 8 (b)], 12 poles 6 slots [FIG. 8 (c)], 14 poles 9 slots [FIG. 8 (e)] and 18 poles 12 slots [FIG. 8 (g)]. ], As indicated by the oblique lines at the right end of the figure, there are no slots facing the number of magnetized poles shown in FIG. 9, and the recording / reproducing head can be arranged in this vacant area to serve as the path. .

As an example, a top view of the core 106 in the case of 12 poles and 6 slots is shown in FIG. The core 106 has six slots 106a arranged at a pitch of 40 °. This corresponds to FIG. 8C as can be seen from the table of FIG.
By deleting 3 slots from 12 poles and 9 slots, a path for moving the recording / reproducing head is secured on the inner periphery of the hard disk.
As a result, recording / reproduction on both the upper and lower sides of the disk is possible, and the recording capacity of the HDD is doubled. However, the motor has characteristics of 1/3 with respect to 12 poles and 9 slots by removing the core (and coil). Will only drop.
As described above, there is sufficient room for improving the efficiency as a motor, and an improvement is desired.

As another example of the general configuration described above, there is a motor as described in Patent Document 1 in which the interval between slots of the same phase is made equal to the magnetization pitch and the interval between different phases is expanded to 75 °. .
Further, as described in Patent Document 2, there is a motor in which slots in the same phase are made equal to the magnetization pitch and slots in the middle of each phase are arranged at 120 °.
In addition, what is opposed to the magnet is an example of a spiral coil instead of a core. As described in Patent Document 3, two coils having the same opening angle as the magnetization pitch are arranged in each phase and both sides thereof are arranged. There is a motor in which coils with a narrow opening angle are arranged one by one, or three coils with an opening angle equal to the magnetization pitch and one coil with a narrow opening angle are arranged.
JP-A-6-315254 JP 2000-152581 A JP-A-6-327174

  By the way, the market demands small size and high accuracy for HDDs, and accordingly, the mounted motor is also required to be small and thin and high accuracy. Torque characteristics must be provided.

  As described above, the conventional motor has a maximum of 2/3 (about 67%) in the case of 2n pole magnetization with respect to 3n (n: an integer of 1 or more) slots, and 4n pole magnetization. In this case, only 3/4 (75%) at maximum can effectively use the magnetic flux.

  In the motor described in Patent Document 1, the width of the slot tip can be expanded to a maximum magnetization angle π [rad] of one pole. However, in a portion where slots of different phases are adjacent to each other, the mechanical angle is 75 °. In other words, the electrical angle is arranged with a pitch of (5/3) π [rad]. Therefore, in the whole motor, only the electrical angle 6π [rad] in the total slot is opposed to the electrical angle 8π [rad] in the total magnet. That is, only 6/8 (= 75%) of the magnetic flux can be effectively utilized.

In addition, in the motor described in Patent Document 2, when the tips of the slots described in the connected shape are separated for easy understanding, the portion where the interval between the slots is the narrowest is different. This is the part where the craftsmen are adjacent.
The pitch of this portion is 30 ° in mechanical angle and (2/3) π [rad] in electrical angle, and the slot tip also occupies only up to electrical angle (2/3) π [rad]. I can't. Even though the central slot in each phase can occupy up to an electrical angle π [rad], in the entire motor, the electrical angle (2/2 / 3) The ranges of π × 6 + π × 3 = 7π [rad] are opposite to each other, and only 7/8 (= 88%) of the magnetic flux can be effectively used.

Further, in the motor described in Patent Document 3, in the case of a highly efficient motor in which three coils having the same opening angle as the magnetization pitch and one coil having a narrow opening angle are arranged, the entire motor has a total of magnets. The electrical angle π × 9 + (2/3) π × 3 = 11π [rad] is opposed to the electrical angle 12π [rad] in FIG. 11 to effectively use 11/12 = 92% of the magnetic flux. It will be.
However, as described in that document, the torque becomes 3.898 / 4 times due to the occurrence of a phase shift, so that the substantial effective utilization ratio is (11/12) × (3.898 / 4). ) = 89%.

As described above, each conventional motor has room for improving the utilization efficiency of the magnetic flux and increasing the torque. In order to increase the torque of the motor, there are various methods other than improving the efficiency of using the magnetic flux, but all have disadvantages.
Specifically, increasing the current to flow increases power consumption, and if the magnet material generates a stronger magnetic force, it becomes expensive.If the number of turns of the coil is increased, the coil becomes larger and space efficiency is increased. Etc.

Further, in the motor mounted on the HDD, in order to secure the maximum recording capacity of the hard disk, it is necessary to consider the structure so that the recording / reproducing head can be moved to the inner periphery of the disk.
In this case, as described above, it is necessary to increase the magnetic poles of the magnet and secure a space in which the recording / reproducing head can move.

When a fluid dynamic pressure bearing is used as the radial bearing and a bearing having a clearance in the shaft is used as the thrust bearing, the rotor motion due to the clearance occurs.
However, if the core is provided with a slot-free portion to secure the recording / reproducing head path described above, the generated radial magnetic force will be unbalanced and a lateral pressure will be applied to the shaft, resulting in vibration and scratching motion. Can be prevented.
However, if it is attempted to delete a part of the slots in the 12-pole 9-slot, which has a long track record of use, in order to secure the passage, it is necessary to delete the 3 slots and operate as 6 slots for the convenience of motor control.
In this case, a passage space of approximately 120 ° is obtained as the mechanical angle for the four magnetized poles, but only 50%, which is 2/3 of the effective utilization rate of magnetic flux with 9 slots, can be used. .
As described above, in the conventional motor, if a part of the slot is deleted for reasons such as securing a space for moving the head or applying a lateral pressure, the efficiency of the motor is reduced and the torque constant is reduced. Improvement was desired.

  Therefore, the problem to be solved by the present invention is that, even if the core is an annular shape or an arc shape with a part of the slot removed, the utilization efficiency of the magnetic flux of the magnet is improved, the size is small, and the power consumption is small. An object of the present invention is to provide a motor that can obtain a large torque while being inexpensive.

In order to solve the above problems, the present invention has the following configuration as means.
[1] An annular magnet (8) in which a plurality of magnetic poles are provided at equal angular widths, and 3n pieces (n: 2 or more) arranged in an arc shape at a predetermined pitch facing the magnet (8). A core (6) having an integer number of slots (6S) and 3n coils (7) wound around the slots (6S), respectively, by energizing the 3n coils (7) In the motor configured such that the magnet (8) and the core (6) are concentric and relatively rotate,
The 3n coils (7) are configured as three phases (U, V, W) in which the adjacent n coils are one phase, and the predetermined pitch is set to the three phases (U, V, W). The n slots (6S) around which the n coils (7) of each phase in FIG. 2 are wound are set to the same angular pitch as the equiangular width, while adjacent slots between different phases are The motor (51) is characterized in that the angle pitch is approximately 4/3 times the equiangular width.
[2] An annular magnet (8) in which a plurality of magnetic poles are provided at equal angular widths, and 3n (n: an integer of 2 or more) coils (17) formed by winding a conductor in a flat annular shape, The 3n coils (17) are arranged in a circular arc shape at a predetermined pitch so as to face the magnet (8), and the magnet (8) and the n are energized by energizing the coil (17). In the motor that is configured so that the coils (17) and the coils (17) are relatively coaxial and rotationally moved,
The 3n coils (17) are configured as three phases (U, V, W) in which the adjacent n coils (17) are one phase, and the predetermined pitch is set to the three phases (U, The n coils (17) of each phase in V, W) have the same angular pitch as the equiangular width, while coils adjacent to each other in different phases are approximately 4/3 of the equiangular width. The motor is characterized by having a double angle pitch.

  According to the present invention, the utilization efficiency of the magnetic flux of the magnet is improved, and there is an effect that a large torque can be obtained with a small size, low power consumption, and low cost.

The preferred embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a sectional view showing a first embodiment of the motor of the present invention.
FIG. 2 is a plan view for explaining a main part of the first embodiment of the motor of the present invention.
FIG. 3 is a schematic view for explaining each embodiment of the motor of the present invention.
FIG. 4 is a table for explaining each embodiment of the motor of the present invention.
FIG. 5 is a sectional view showing a second embodiment of the motor of the present invention.
FIG. 6 is a plan view for explaining a main part of a second embodiment of the motor of the present invention.

<First embodiment>
The motor of the first embodiment is a motor 51 that includes a fluid dynamic pressure bearing and is mounted on a 1-inch hard disk drive (HDD) for driving a disk. The motor 51 rotates the disk at a rotational speed of 7200 times / minute.
First, the motor 51 will be described with reference to FIG.
The hard disk 71 shown in FIG. 1 is mounted when the motor 51 is mounted on an HDD, and recording / reproducing heads 71A and 71B facing the upper and lower surfaces of the hard disk 71 are provided on the HDD side. It is what was done.

The motor 51 includes a stator S and a rotor R, and has a three-phase drive structure of an inner rotor.
The stator S is fixed to a motor base 5, a substantially cylindrical housing 11 having a flange portion 11 a at one end thereof fixed to a through hole 5 a formed near the center thereof, and fixed to the motor base 5 concentrically with the housing 11. A substantially annular core 6 is included.
The motor base 5 is formed by cutting an aluminum die casting or pressing an aluminum plate or an iron plate plated with nickel.
The housing 11 is fixed by an adhesive because high accuracy is obtained in assembly.

The core 6 has the form shown in FIG. In other words, a part of the ring is missing, and a plurality of slots 6S projecting inward at an equal angle are provided. In this figure, the wound coils 7-1 to 7-9 are also described.
This slot is provided with nine poles, that is, slots 6S1 to 6S9. In this figure, the numbers of the respective poles are shown as [1] to [9], and the slots 61 to 6S9 correspond to the respective pole numbers.
As described above, the motor 51 is driven in three phases, and coils are wound so that the slots 6S1 to 6S3, the slots 6S4 to 6S6, and the slots 6S7 to 6S9 correspond to the respective phases. Details of this winding will be described later.
The slots of each phase are arranged at a pitch of 30 °, and the gaps between adjacent phase slots, that is, between 6S3 and 6S4 and between 6S6 and 6S7 are set to 10 °. In other words, the pitch of adjacent slots of different phases is set to 40 °.
With such an arrangement, the angle range of the missing portion L is approximately 70 °.

The core 6 is shown in FIG. 1 so that the missing portion L is located on the left side with respect to the rotation axis C. In this vacant space, recording / reproducing heads 71A and 71B on the HDD side are arranged, and the disk 71 It is possible to move in the radial direction.
Since the recording / reproducing heads 71A and 71B are provided corresponding to the upper and lower surfaces of the hard disk 71, the recording capacity of the hard disk is double that of the single-side recording.

The core 6 having such a shape is fixed to the inner peripheral surface of the wall portion 5 b that is provided in a ring shape on the motor base 5.
The core 6 is made of laminated silicon steel plates, and the surface is coated with an insulating coating such as electrodeposition coating or powder coating. In each of the slots 6S1 to 6S9, coils 7-1 to 7-9 are wound corresponding to the respective phases.
The winding terminal 7 a (U, V, W, COM) of the coil 7 is soldered to a flexible printed circuit board (hereinafter referred to as FPC) 14 attached to the opposite side through a through hole 5 c formed in the motor base 5. ing.
The FPC 14 is provided with a land portion (not shown) for joining a portion where the winding terminal 7a of the coil 7 is soldered and a motor drive circuit (not shown) on the HDD side. And the land portion are electrically connected by a wiring pattern.
Then, each phase of the coil 7 is sequentially energized by the motor drive circuit, and the rotor R rotates with respect to the stator S.

On the other hand, the rotor R is fixed to the inner peripheral surface, the substantially cup-shaped hub 2 having the shaft portion 1, the ring-shaped magnet 8 magnetized with a predetermined number of magnetic poles and fixed to the outer peripheral surface of the hub 2. The thrust ring 12 is configured to include the outer cylinder portion 13 inserted into the outer peripheral surface of the shaft portion 1.
The surface of the magnet 8 is electrodeposited, and the hub 2 is made of stainless steel and finished by cutting.
The hub 2 has a mounting portion 2a on the outer periphery of which the hard disk 71 is mounted, and a female screw 2b for fixing a clamper (not shown) for clamping the disc is provided on the upper surface. Yes.
The hub 2 is formed using martensite, ferrite, or austenitic stainless steel, and the surface is coated with electroless nickel plating or the like for the purpose of improving wear resistance.
In addition, the thickness of this surface coating is about 3 to 50 μm. In order to prevent the diameter of the female screw 2b from being reduced by coating, the tapping of the female screw 2b is performed after the electroless nickel plating treatment. ing. As a result, there is no dimensional change due to cutting or peeling of the coating material, and the generation of particles is reduced.

In such a rotor R, the outer cylinder portion 13 is inserted into the through hole 11b of the housing 11 of the stator S, and is supported rotatably with respect to the stator S via the radial dynamic pressure bearing RB and the thrust dynamic pressure bearing SB. .
The radial dynamic pressure bearing RB is configured to include an outer peripheral surface of the outer cylindrical portion 13, an inner peripheral surface of the housing 11 facing the outer cylindrical portion 13, and a lubricating oil interposed in a gap therebetween. The upper surface of the thrust ring 12, the lower surface of the flange portion 4 a of the housing 11 facing the thrust ring 12, and the lubricating oil interposed between the two are configured.

Next, the relationship between the number of magnetic poles of the magnet 8, the number of coils 7 wound around the core 6, and the missing portion L (hereinafter also referred to as a space L) will be described with reference to FIGS.
FIG. 4 shows a part of the relationship such as the number of slots that can be taken in the motor 51 of the first embodiment, the number of magnetic poles of the magnet, and the arrangement pitch thereof.
In this embodiment, n slots (n: an integer of 2 or more) that are always energized at the same timing (phase) are arranged at the same pitch as the magnetized pitch of the magnets 8.
Also, the arrangement pitch of adjacent slots in different phases is 4/3 times the magnetized pitch of the magnet.
Thus, the angle range occupied by one phase is (n−1) + (4/3) = n + (1/3) in terms of the number of magnetic poles for n slots, and is a three-phase motor. The angle range occupied by the entire slot is 3 × {n + (1/3)} = 3n + 1.

FIG. 4 shows a configuration in which the number of magnetic poles of the magnet is increased by m poles (m is an integer equal to or larger than 0), and a configuration in which a slot facing the increased portion is not arranged is included [where m is 0 ( In the case of (zero), the configuration is such that slots are arranged over the entire circumference.]
In this configuration, when the total number of poles (3n + 1 + m) is an odd number, the N poles and the S poles cannot be alternately arranged over the entire circumference. Is the case.

In FIG. 4, the ranges of n ≦ 4 and m ≦ 3 are described, but there are combinations that are similarly established as motors for ranges exceeding this range.
4 (a) to 3 (f) are schematic diagrams showing the magnet and the core in a straight line for easy understanding of the range shown in FIG. 4 that is established as a motor. .
In this figure, the hatched range at the right end is the range where there are no slots opposite to the number of poles shown in FIG. 4, that is, the range corresponding to the space L. can do.
In the case of 10 poles and 9 slots shown in FIG. 3C, slots are arranged over the entire circumference of the core and the space L cannot be secured, but the efficiency as a motor is high and a motor with a high torque constant can be easily obtained. It is a form that can be done.

Next, the case where the magnet is 12-pole magnetized will be described with reference to FIG. In the description, the three phases will be referred to as U, V, and W, respectively.
In the case of this 12-pole magnetization, the largest number of slots can be arranged in the case of 9 slots, as shown in FIG.
In this figure, if the slots in which coils of each phase are wound are U1, U2, U3, V1, V2, V3, and W1, W2, W3, , Each arranged at a pitch of π [rad] (mechanical angle 30 °) in electrical angle, and adjacent slots in different phases, ie, U3 and V1 and V3 and W1 are respectively (4/3) π in electrical angle. They are arranged at a pitch of [rad] (45 ° mechanical angle).
As a result, in total, including the gap between the range L indicated by the hatched portion and the slot adjacent thereto, a space Lt of 2π + (1/3) [rad] in electrical angle, that is, 70 ° in mechanical angle, is obtained. It can be secured.
The arrangement pitch (4/3) π [rad] of the slots adjacent to each other in the different phases can satisfy the required characteristics within the error range of ± 1% in the cored motor as in this embodiment. Usually acceptable. That is, it may be approximately (4/3) π [rad].

In contrast to the conventional motor with 12 poles and 9 slots, an extra space could not be provided, but according to this embodiment, a space was secured despite the same number of 9 slots. Moreover, the characteristics of the motor are not sacrificed (details will be described later).
Details of the core and coil in the 12-pole 9-slot motor of the first embodiment described above will be described again with reference to FIG.

There are nine slots 6 </ b> S toward the inner periphery of the core 6. The front end surfaces (inner peripheral surfaces) of these slots 6S1 to 6S9 are arranged to face the outer peripheral surface of the magnet 8 with a predetermined gap therebetween.
Three slots of the same phase are arranged at a mechanical angle of 30 ° (electrical angle π) from the center, and a slot between other adjacent phases is 10 ° mechanical angle (3 / π electrical angle). ) Spaced apart.
In other words, three slots of the same phase are arranged at a mechanical angle of 30 ° pitch, and adjacent slots between different phases are arranged at a mechanical angle of 45 °.
Therefore, the space L is obtained in the range of a mechanical angle of 70 °.

Next, the coils 7-1 to 7-9 wound around the slots 6S1 to 6S9 will be described.
First, the U phase starts at the terminal U, turns a predetermined number of turns clockwise from the center side with respect to the slot 6S1, and then turns a predetermined number of turns counterclockwise with respect to the adjacent slot 6S2. The predetermined number of turns in the clockwise direction again with respect to the slot 6S3 to be completed is completed.
The V phase starts at the terminal V and turns a predetermined number of turns clockwise from the center side with respect to the slot 6S4, and then turns a predetermined number of turns counterclockwise with respect to the adjacent slot 6S5. 6S6 is again wound a predetermined number of times in the clockwise direction, and the process ends.
The W-phase starts from the terminal W, turns a predetermined number of turns clockwise from the center side with respect to the slot 6S7, then turns a predetermined number of turns counterclockwise to the adjacent slot 6S8, and then turns to the adjacent slot 6S9 is again wound a predetermined number of times in the clockwise direction, and the process ends.
The winding end of each phase is connected to a common COM terminal.

These coil windings are continuously wound in series in adjacent slots of the same phase. Therefore, since there is no so-called crossover, no wasteful electric wires, coils are short-circuited or disconnected, and high reliability can be obtained without increasing costs.
Further, in order to secure the space L, the slots 6S1 to 6S9 are arranged to be biased. Therefore, the magnetic flux is biased between the portion where the slot is arranged and the portion where the slot is not arranged, and the attractive force is different. Thereby, the rotor R is always sucked in a constant radial direction, and the effect of preventing the grinding motion is obtained. When this motor is mounted on the HDD, the space L can be used as a moving path of the recording / reproducing head as described above.

<Second embodiment>
A second embodiment of the motor of the present invention will be described. This embodiment is an 8-pole 6-coil flat-plate-facing three-phase slotless motor, an example of which is shown in FIG. In the motor of the second embodiment, the magnet is surface-magnetized to 8 poles with a ring-shaped flat plate, and the coil is opposed to the magnetized surface with a minute gap. The motor has a structure in which six spiral coils are used and a core (slot) is omitted.

In FIG. 5, the motor 52 is attached to the motor base 32, a generally U-shaped capstan holder 33 erected on the motor base 32 and provided with a pair of bearings B, and one surface of the motor base 32. A stator S including a flexible substrate (FPC) 34, and a plurality of flat ring-shaped coils 17 attached to the FPC 34 in an arc shape; a shaft 35 rotatably supported by the bearing B; A flat hub 36 fixed to the front end side thereof, and a magnet 18 fixed to the inner surface of the hub 36 and formed in a flat ring shape so as to face the coils 17 arranged in an arc shape. And a rotor R constituted by
The motor 52 is configured such that the rotor R is free to rotate with respect to the stator with the coil 17 and the magnet 18 having a predetermined gap d.

FIG. 6 schematically shows the relationship between the position of each coil 17 and the position of each magnetic pole of the magnet 18 opposed thereto in this motor.
Such a flat slotless motor can be considered based on the same principle by replacing the slot with a coil in the cored motor of the first embodiment.
In the conventional motor, in the case of an 8-pole 6-coil, as shown in FIG. 8A, the coil is arranged over the entire circumference, and it is not possible to secure a space by deleting some of the coils. The recording / reproducing head could not be arranged on the same plane.

On the other hand, according to the second embodiment, as shown in FIG. 3A, six coils are arranged with the same characteristics, and a space L of π in electrical angle, that is, 45 ° in mechanical angle can be obtained. it can.
In addition, when including the gap with the adjacent coil, a space Lt of (4/3) π [rad] in electrical angle, that is, 60 ° in mechanical angle is obtained (however, this figure shows U1 to U1 in the above description). U3, V1 to V3, and W1 to W3 are slots, but here, these are applied to the coil for explanation).
As described above, also in the second embodiment, it is possible to secure an empty space where the coil is not arranged while having the same torque characteristic. Accordingly, when this motor is mounted on the HDD, this empty space can be used as a moving path of the recording / reproducing head.

Referring to FIG. 6 showing an example of the coil in the second embodiment, the six coils 17-1 to 17-6 have 17-1 and 17-2 as U phases, and 17-3 and 17-. The wire is wound with 4 as the V phase and 17-5 and 17-6 as the W phase.
Each coil is formed such that its width occupies a range of π in electrical angle, that is, 45 ° in mechanical angle, and is arranged in an arc shape.
Further, between adjacent coils of different phases, that is, between 17-2 and 17-3, and between 17-4 and 17-5, an electrical angle of π / 3, that is, a mechanical angle of 15 °. An angular gap is provided.
In other words, two coils of the same phase are arranged at a mechanical angle of 45 ° pitch (electrical angle π), and adjacent coils between different phases have a mechanical angle of 60 ° [electrical angle (4/3) π ] Are arranged at a pitch. Therefore, the space L is obtained in a mechanical angle range of 60 °.
The arrangement pitch (4/3) π [rad] of the coils adjacent in this different phase has the required characteristics within the error range of ± 5% in the flat motor without core as in this embodiment. Satisfactory and usually acceptable. That is, it may be approximately (4/3) π [rad].

Next, the winding direction and connection method of the coils 17-1 to 17-6 will be described.
In this second embodiment, all the coils 17-1 to 17-6 are wound in the CW (clockwise) direction as viewed from the front side of the figure (paper). Taking -1 and 17-2 as an example, in order to reverse the direction of current flow in both coils, the winding start lines (st) that are inside the coils are connected to each other.
Similarly, the winding start lines (st) are connected to the coils 17-3 and 17-4 that are the V phase, and the winding start lines (st) are also connected to the coils 17-5 and 17-6 that are the W phase. Connected.

In order to drive the motor in three phases, U, V, and W must be separated by {(2/3) + 2a} π [rad] and {(4/3) + 2a} π [rad] in electrical angle, respectively. Yes (a: any integer).
In the embodiment, the entrance of the U phase is on the winding end line (f) side, which is the outside of the coil 17-1.
In addition, since the coil 17-3 is separated by {(1/3) +2} [rad] in electrical angle at the entrance of the V phase, {(4/3) not in the end of winding of the coil 7-3 but in electrical angle. ) +2} [rad] It is on the winding end line (f) side of the coil 17-4 that is separated.
In addition, the coil 17-5 has an electrical angle of {(2/3) +4} [rad] away from the coil 17-1 at the entrance of the W phase, so the winding end line (f) of the coil 17-5 On the side.
Furthermore, in each phase, the winding end lines which are outside the coil (17-2, 17-3, 17-6) which is not used as the entrance of the above-mentioned phase are connected to each other to be a middle point (COM). By connecting in this way, the same coil wound in the same manner can be used as each coil, so that mass productivity is high and there is no defect in the arrangement.

The coil winding and connection method differs depending on the number of coils forming each phase.
That is, when n shown in FIG. 4 is an odd number, windings are made in the same manner for three phases as in the first embodiment, and the same side of each phase is used as an entrance. When n is an even number, the three phases are wound in the same manner as shown in the second embodiment, and the entrance and the middle point are connected reversely only for the intermediate phase, or The same side is the entrance and only the middle phase is wound in the opposite direction.

  The effective utilization rate (utilization efficiency) of the magnetic flux in each embodiment described above will be described below. Specifically, the effective utilization rate of the magnetic flux in the example was calculated in the same manner as obtained for the motor described in each patent document, which is a conventional motor. In the calculation, the greater the number of poles, the higher the effective utilization rate. However, in an actual motor, if there are too many poles, a magnetic flux loop is formed between adjacent poles and the magnetic flux that does not reach the slot increases. It needs to be a number. Here, a comparative explanation will be given within the range of upper limit of 12 poles (12 coils) described in Patent Document 3 having the highest effective utilization rate of 89% in the conventional example.

In each embodiment, the number of magnetic poles is 12 or less and the coils are arranged over the entire circumference is a configuration of 10 poles and 9 coils, which corresponds to FIG.
In this case, the electric angle of 10π [rad] is occupied as the total of the magnets, while the range of the electric angle 9π [rad] is opposed to the magnets in total of the coils, and 9/10 of the magnetic flux, that is, 90% is effectively utilized. Has been. Therefore, it can be seen that this is an improvement over the conventional 89%.
As is clear from FIG. 3 (c), the remaining 10% is a gap of each electrical angle (1/3) π [rad] between three different phases. If the number of poles can be increased, the gap between the different phases does not change with the electrical angle, but decreases with the mechanical angle, and further improvement in the effective utilization rate of the magnetic flux can be expected.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

It is sectional drawing which shows 1st Example of the motor of this invention. It is a top view explaining the principal part of 1st Example of the motor of this invention. It is a schematic diagram explaining each Example of the motor of this invention. It is a table | surface explaining each Example of the motor of this invention. It is sectional drawing which shows 2nd Example of the motor of this invention. It is a top view explaining the principal part of 2nd Example of the motor of this invention. It is sectional drawing explaining the conventional motor. It is a schematic diagram explaining the conventional motor. It is a table | surface explaining the conventional motor. It is a top view explaining a part of conventional motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft part 2 Hub 2a Mounting part 2b Female screw 5 Motor base 5a Through-hole 5b Wall part 6 Core 6S Slot 7, 17 Coil 7a Winding terminal 11 Housing 11a Flange part 13 Outer cylinder part 14 Flexible printed circuit board (FPC)
17 (17-1 to 17-6) Coil 18 Magnet 21 Outer cylinder portion 32 Motor base 33 Capstan holder 34 FPC
35 Shaft 36 Hub 51, 52 Motor 71 Hard disk 71A, 71B Recording / reproducing head B Bearing L Missing part (space)
R Rotor S Stator U, V, W phase

Claims (3)

An annular magnet in which a plurality of magnetic poles are provided at equal angular widths;
A core having 3n (n: an integer greater than or equal to 2) slots arranged in an arc shape at a predetermined pitch facing the magnet;
3n coils wound respectively in the slots,
In the motor configured such that the magnet and the core are relatively coaxial and rotationally moved by energizing the 3n coils,
The number of magnetic poles of the magnet is an even number greater than 3n + 1,
The 3n coils are configured as three phases with n adjacent coils as one phase,
For the n slots in which the n coils of each phase in the three phases are wound, the predetermined pitch is set to the same angular pitch as the equiangular width, while slots adjacent to each other in different phases. for the motor, characterized in that said equal Ri substantially formed as 4/3 times the angular pitch of the angular width, provided with the slot is no space for more than one magnetic pole of the magnet. A rotor having the magnet;
A stator having the core,
The motor according to claim 1, wherein the rotor is rotatably supported with respect to the stator via a dynamic pressure bearing. An annular magnet in which a plurality of magnetic poles are provided at equal angular widths;
3n coils (n: an integer of 2 or more) formed by winding a conductor in a flat annular shape,
The 3n coils are arranged in an arc shape at a predetermined pitch so as to face the magnet, and the magnet and the n coils are relatively coaxially rotated by energization of the coils. Motor
The number of magnetic poles of the magnet is an even number greater than 3n + 1,
The 3n coils are configured as three phases with n adjacent coils as one phase,
The predetermined pitch is set to the same angular pitch as the equiangular width for the n coils of each phase in the three phases, while about 4 of the equiangular width for coils adjacent to each other in different phases. / 3 times the Ri formed as angular pitch, motor, characterized in that a said coil is no space for more than one magnetic pole of the magnet.

Images