JP2004289963A - Slotless brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate cogging torque, enhance torque efficiency, and lower a current. <P>SOLUTION: A slotless brushless motor (30) comprises: a stator including a three-phase coil (34); and a rotor which is rotatably disposed opposite to the stator and includes permanent magnets (7) that are alternately magnetized in the south pole and in the north pole at equal intervals on the circumference of a rotating shaft. The phase-U coil, phase-V coil, and phase-W coil constituting the three-phase coil (34) are so disposed that portions of the adjoining coils substantially equivalent to 1/2 of the width of each coil overlap each other in the circumferential direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a slotless brushless motor, and more particularly, to a slotless brushless motor used in an optical disk drive or the like and used as a spindle motor or the like for rotationally driving an optical disk inserted therein.
[0002]
[Prior art]
The optical disk drive includes a spindle motor for rotating and driving the optical disk inserted therein. As this kind of spindle motor, a brushless motor is generally used.
[0003]
Hereinafter, a general brushless motor will be described with reference to FIG. The illustrated brushless motor is disclosed in Patent Document 1.
[0004]
In FIG. 1, a spindle motor 1 is provided on a frame 2. A circuit board 3 is provided on the upper surface of the frame 2 and a bearing housing 4 is provided upright at the center. A bearing 5 is fitted to the bearing housing 4.
[0005]
The spindle motor 1 has a rotor yoke 6. As shown in FIG. 1, the rotor yoke 6 is formed in a shallow inverted concave shape, and a boss 6a is provided upright at the center. An annular rotor magnet 7 is fitted to the inner peripheral surface of the rotor yoke 6. The rotor magnet 7 is a permanent magnet in which S poles and N poles are magnetized alternately and at equal intervals. A plurality of teeth 8 are arranged radially inside the rotor magnet 7. Each of these teeth 8 is wound with a coil 9. The coil 9 is formed on the circuit board 3.
[0006]
In such a configuration, when a driving current flows through the coil 9, a magnetic field is generated around the driving current. The generated magnetic field acts on the rotor magnet 7 to rotate the spindle motor 1. As a result, the disk holder 20 fixed to the boss 6a and the optical disk (not shown) fitted to the disk holder 20 rotate clockwise.
[0007]
The rotating shaft 10 of the spindle motor 1 is rotatably mounted on the bearing 5. The rotating shaft 10 is fitted into a hole 6b of a boss 6a protruding from the rotor yoke 6, so that the rotor yoke 6 and the rotating shaft 10 can be integrally rotated.
[0008]
A fitting hole 21 formed in the center of the disc holder 20 is fitted to the outer peripheral surface of the boss 6 a of the rotor yoke 6. The laminated hole wall portion 21 a forming the fitting hole 21 is configured to protrude downward so that the fitting hole 21 can be fitted to the boss portion 6 a of the rotor yoke 6.
[0009]
Since the present invention does not relate to the disk holder 20 itself, a detailed description thereof will be omitted. However, if you want to know the details, refer to Patent Document 1.
[0010]
Anyway, a fitting hole 21 formed in the center of the disk holder 20 is fitted to the outer peripheral side surface of the boss 6a so that the disk holder 20 can be integrally rotated in synchronization with the rotation of the rotating shaft 10. It is configured.
[0011]
As described above, the teeth 8 are formed at equal intervals in the circumferential direction, and are also called salient poles.
[0012]
In the brushless motor described above, the space between the adjacent teeth 8 is a magnetic pole (hereinafter, referred to as a “magnetic pole of the rotor”) at a position facing the rotor magnet (permanent magnet) 7 as compared with the teeth 8. ) To increase the magnetic resistance. Therefore, there is a difference in the rotational torque of the rotor between when the magnetic pole of the rotor faces the space between the teeth 8 and when the magnetic pole of the rotor faces the teeth 8. Such torque fluctuations that occur during rotor rotation are referred to in the art as "cogging." The magnitude of the torque fluctuation due to cogging is called cogging torque.
[0013]
When the cogging torque is large, the rotation speed of the brushless motor fluctuates, the smoothness of rotation is impaired, and high performance cannot be achieved.
[0014]
In order to reduce cogging torque, a slotless brushless motor without teeth has been proposed (for example, see Patent Document 2). In Patent Document 2, a stator structure of a slotless brushless motor that can be downsized is obtained by forming a conductive winding on an insulating film to form a conductive printed coil. More specifically, the conductive printed coil is formed in a square and spiral shape, and a U-phase coil, a V-phase coil, and a W-phase coil are sequentially and independently formed.
[0015]
Further, as a prior art document related to the present invention, there is a drive coil structure of a motor that uses an air-core coil as a drive coil to obtain a large torque and to smoothly rotate (for example, see Patent Document 3). In Patent Literature 3, the drive coil includes a first air-core coil portion and a second air-core coil portion. The first air-core coil portion and the second air-core coil portion are superposed so as to be shifted in the circumferential direction so that a part of the inner peripheral portion of the coil overlaps. The inner peripheral portions of the superposed coils are electrically connected, and the outer peripheral portion of the first air core coil portion and the outer peripheral portion of the second air core coil portion are used as external connection electrodes.
[0016]
[Patent Document 1]
JP 2002-288910 A
[Patent Document 2]
JP-A-2002-78264
[Patent Document 3]
JP-A-9-19094
[Problems to be solved by the invention]
In the slotless brushless motor disclosed in Patent Literature 2, the U-phase coil, the V-phase coil, and the W-phase coil are formed independently of each other without being overlapped with each other. Therefore, it is difficult to increase the torque efficiency as will be described later in detail with reference to the drawings.
[0020]
On the other hand, the motor disclosed in Patent Literature 3 divides each drive coil into two coil portions and superimposes the two divided coils so as to be shifted from each other. Not a combination.
[0021]
Therefore, an object of the present invention is to provide a slotless brushless motor that does not have cogging, has high winding efficiency, and can achieve low current.
[0022]
[Means for Solving the Problems]
According to the present invention, a stator (4, 31, 32, 33, 34) including a three-phase coil (34), and an S-pole and an N-pole arranged on the outer periphery of the rotating shaft so as to be rotatable facing the stator. And a rotor (6, 7) including permanent magnets (7) magnetized alternately and at equal intervals, and a slotless brushless motor (30) comprising a three-phase coil (34). The adjacent ones of the phase coil, the V-phase coil and the W-phase coil are arranged so that portions corresponding to substantially half the width of each coil overlap with each other in the circumferential direction. A brushless motor is obtained.
[0023]
The slotless brushless motor is an outer rotor type slotless brushless motor in which a rotor is disposed outside a stator. In this case, the three-phase coil (34) is wound around the outer peripheral surface of the laminated core (31) via the insulating film (33), for example.
[0024]
The slotless brushless motor may be an inner rotor type slotless brushless motor in which a rotor is arranged inside a stator.
[0025]
It should be noted that the reference numerals in the parentheses are provided to facilitate understanding of the present invention, and are merely examples, and it is a matter of course that the present invention is not limited to these.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0027]
A slotless brushless motor 30 according to one embodiment of the present invention will be described with reference to FIG. The illustrated slotless brushless motor 30 is used for an optical disk drive, and is used as a spindle motor for rotating and driving an optical disk inserted therein. The illustrated slotless brushless motor 30 has substantially the same configuration as the brushless motor 1 shown in FIG. 1 except that the configuration of the stator (stator assembly) is different. To play. Therefore, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0028]
The stator assembly (stator) of the slotless brushless motor 30 has a laminated core 31 disposed inside the rotor magnet 7. The laminated core 31 is configured by laminating a plurality of annular iron cores 311. The laminated core 31 is held by a core holder 32. A plurality of coils 34 are provided on the outer peripheral surface of the laminated core 31 via a cylindrical insulating film 33 in a circumferential direction as described later. The plurality of coils 34 constitute a three-phase coil. The coil 34 and the rotor magnet 7 are opposed to each other with a predetermined gap as shown in FIG.
[0029]
As shown in FIG. 3, each coil 34 is formed in a spiral shape. Then, as shown in FIG. 4, each coil 34 is shaped so as to change the radius of curvature by the thickness of the coil at approximately half the position.
[0030]
As shown in FIGS. 5 and 6, the coils 34 adjacent to each other are arranged such that the width portions substantially corresponding to half of each coil overlap each other in the circumferential direction.
[0031]
As shown in FIG. 7, each coil 34 forms one of a U-phase coil, a V-phase coil, and a W-phase coil of a three-phase coil. FIG. 7 shows an example in which there are 18 three-phase coils. That is, the three-phase coil has six U-phase coils, six V-phase coils, and six W-phase coils. In FIG. 7, the six U-phase coils are distinguished from the first stage (first stage) to the last stage (sixth stage) by U1 coils, U2 coils,..., U6 coils, respectively. Similarly, the six V-phase coils are indicated by V1 coils, V2 coils,..., V6 coils from the first stage (first stage) to the last stage (sixth stage). The six W-phase coils are indicated by W1 coils, W2 coils,..., W6 coils from the first stage (first stage) to the last stage (sixth stage). The winding end terminal and winding start terminal of adjacent U-phase coils, the winding end terminal and winding start terminal of adjacent V-phase coils, and the winding end terminal and winding start terminal of adjacent W-phase coils are electrically connected to each other. And the winding end terminals of the U-phase coil (U6 coil), V-phase coil (V6 coil), and W-phase coil (W6 coil) of the final stage are electrically connected in common. Is connected.
[0032]
As shown in FIG. 5, in the illustrated example, since the number of coils 34 is 18, the circumferential width of each coil 34 is substantially 40 ° in terms of angle. Then, the adjacent coils 34 are arranged in a state of being superposed in the circumferential direction by a width substantially corresponding to an angle of 20 °.
[0033]
The coil wire constituting each coil 34 is formed of a self-fusing wire whose surface is insulated. Therefore, the 18 coils 34 are fixed to form a circular (cylindrical) shape as a whole, as shown in FIG. 5, by pressure-compression bonding in a state of being overlapped as described above. Thereafter, the connection is made as shown in FIG.
[0034]
Thus, in the slotless brushless motor 30 according to the present invention, the adjacent ones of the U-phase coil, the V-phase coil, and the W-phase coil constituting the three-phase coil 34 correspond to substantially half the width of each coil. Since the portions to be overlapped with each other in the circumferential direction are arranged, the torque efficiency (winding efficiency) can be increased.
[0035]
Hereinafter, referring to FIG. 8, a slotless brushless motor in which adjacent coils are overlapped with each other as in the present invention, and each of the coils as in Patent Document 2 are formed independently (the overlapping of adjacent coils is not limited). No) Compare torque efficiency with slotless brushless motor.
[0036]
8A is a diagram for explaining the torque efficiency of the slotless brushless motor disclosed in Patent Document 2, and FIG. 8B is a diagram illustrating the torque of the slotless brushless motor 30 according to the embodiment of the present invention. It is a figure for explaining efficiency. In this example, one circumference (360 °) of the rotor magnet is indicated by a serial number of 1 to 36 at an angle of 10 °. The number 1 indicates an angle range of 0 ° to 10 ° of the rotor magnet.
[0037]
In the slotless brushless motor, two of the U-phase coil, the V-phase coil, and the W-phase coil, which constitute a three-phase coil, are rotated by the rotor in a predetermined rotation direction (forward rotation). The current flowing in the three-phase coil is controlled so that the current flows in the opposite direction and does not flow in the remaining coils. In FIG. 8, the direction of the current flowing through each coil is indicated by an upward arrow “↑” and a downward arrow “↓”. The coils through which no current flows are marked with a horizontal bar "-". In each coil, the portions that contribute to the torque are the portions on both sides in the circumferential direction, and the current flow directions are opposite to each other on both side portions. The illustrated example shows a state in which currents flow in the U-phase coil and the V-phase coil in directions opposite to each other, and no current flows in the W-phase coil.
[0038]
Further, the following is assumed here. When the north pole of the rotor magnet and the direction of the current indicated by the upward arrow “↑” of the coil face each other, and when the S pole of the rotor magnet and the current direction indicated by the downward arrow “↓” of the coil face each other, the slot is used. A torque (hereinafter, referred to as “forward rotation torque”) for rotating (forward rotation) in a predetermined rotation direction (forward rotation direction) acts on the rotor of the brushless motor. On the other hand, when the north pole of the rotor magnet and the current direction indicated by the downward arrow "↓" of the coil face each other, and when the S pole of the rotor magnet faces the current direction indicated by the upward arrow "↑" of the coil, A torque (hereinafter referred to as "reverse rotation torque") for rotating (reverse rotation) in a direction (reverse rotation direction) opposite to a predetermined rotation direction acts on the rotor of the slotless brushless motor.
[0039]
First, the torque efficiency of the slotless brushless motor disclosed in Patent Document 2 will be described with reference to FIG. Here, the following is assumed. It is assumed that the number of N and S poles of the rotor magnet is 6 poles and 12 poles as a whole. In other words, the magnetic poles of the rotor magnet are reversed at an angular interval of 30 °. On the other hand, there are three U-phase coils, three V-phase coils, and three W-phase coils that constitute the three-phase coil, and there are nine coils in total. Therefore, the width of each coil has an angular range of 40 °, and the nine coils are arranged independently in the circumferential direction at an angular interval of 40 °.
[0040]
As is clear from the bottom row of FIG. 8A, when the rotor magnet is in the angle range of 0 ° to 50 °, the normal rotation torque Tn acts on the rotor magnet. Similarly, the reverse rotation torque Ti acts in the angle range of 50 ° to 60 °, the normal rotation torque Tn acts in the angle range of 60 ° to 80 °, and the normal rotation torque Tn acts in the angle range of 120 ° to 180 °. The reverse rotation torque Ti is in the range of 180 ° to 190 °, the normal rotation torque Tn is in the range of 190 ° to 210 °, and the normal rotation torque Tn is 290 ° to 300 ° in the range of 240 ° to 290 °. The reverse rotation torque Ti acts on the rotor magnet in the angle range, and the normal rotation torque Tn acts on the rotor magnet in the angle range of 300 ° to 320 °. Therefore, the torque efficiency of the slotless brushless motor disclosed in Patent Document 2 is 50%.
[0041]
Next, the torque efficiency of the slotless brushless motor according to the embodiment of the present invention will be described with reference to FIG. Here, the following is assumed. The number of N and S poles of the rotor magnet 7 is assumed to be 6 poles and 12 poles as a whole. In other words, the magnetic poles of the rotor magnet 7 are reversed at angular intervals of 30 °. On the other hand, there are six U-phase coils, six V-phase coils, and six W-phase coils that constitute the three-phase coil, and there are 18 coils in total. Therefore, the width of each coil has an angular range of 40 °, and the 18 coils are arranged in a state of being superposed in the circumferential direction at an angular interval of 20 °.
[0042]
As is clear from the bottom row of FIG. 8B, the forward rotation torque Tn acts on the rotor magnet 7 when the rotor magnet 7 is in the angle range of 0 ° to 40 °. Similarly, in the angle range of 40 ° to 50 °, the reverse rotation torque Ti, in the angle range of 50 ° to 100 °, the forward rotation torque Tn, and in the angle range of 100 ° to 110 °, the reverse rotation torque Ti becomes 110 ° to 110 °. In the angle range of 160 °, the forward rotation torque Tn, in the angle range of 160 ° to 170 °, the reverse rotation torque Ti, in the angle range of 170 ° to 220 °, the forward rotation torque Tn, and in the angle range of 220 ° to 230 °, When the reverse rotation torque Ti is in the angle range of 230 ° to 280 °, the forward rotation torque Tn is in the angle range of 280 ° to 290 °, and in the angle range of 290 ° to 340 °, the forward rotation torque Tn is 340. The reverse rotation torque Ti acts on the rotor magnet 7 in the angle range of ° to 350 °, and the forward rotation torque Tn acts in the angle range of 350 ° to 360 ° (0 °). Therefore, the torque efficiency of the slotless brushless motor according to the embodiment of the present invention is about 66.7%.
[0043]
Thus, it can be seen that the slotless brushless motor 30 according to the embodiment of the present invention has higher torque efficiency than the slotless brushless motor disclosed in Patent Document 2.
[0044]
In addition, the slotless brushless motor according to the embodiment of the present invention illustrated in FIG. 2 has lower current consumption and smaller torque loss than the conventional brushless motor illustrated in FIG. For example, when the rotation speed is 9000 rpm, only 10 g · cm of torque is required. In the conventional brushless motor (FIG. 1), since the current consumption is 20 g · cm, there is a torque loss of 10 g · cm. On the other hand, in the slotless brushless motor (FIG. 2) according to the embodiment of the present invention, the current consumption is 13 to 14 g · cm, and there is only a torque loss of 3 to 4 g · cm.
[0045]
The present invention is not limited to the above-described embodiment, and it goes without saying that various changes and modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the outer rotor type slotless brushless motor in which the rotor is located outside the stator is described as an example, but the inner rotor type slot where the rotor is located inside the stator is described. It is needless to say that the present invention can be similarly applied to a brushless motor. In addition, the slotless brushless motor according to the present invention can be used not only for a spindle motor for an optical disk drive but also for other uses.
[0046]
【The invention's effect】
As is apparent from the above description, according to the present invention, the adjacent ones of the U-phase coil, the V-phase coil and the W-phase coil constituting the three-phase coil of the stator are substantially half the width of each coil. Are arranged such that the portions corresponding to each other overlap in the circumferential direction, so that there can be provided a slotless brushless motor having no cogging, high torque efficiency, and low current.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a conventional brushless motor (spindle motor).
FIG. 2 is a cross-sectional view showing a configuration of a slotless brushless motor (spindle motor) according to one embodiment of the present invention.
3A and 3B are diagrams showing one coil used in the slotless brushless motor shown in FIG. 2, wherein FIG. 3A is a front view and FIG. 3B is a plan view.
FIGS. 4A and 4B are diagrams in which the shape shown in FIG. 3 is processed (deformed) so as to be superimposable, wherein FIG. 4A is a front view and FIG. 4B is a plan view.
FIG. 5 is a plan view showing a three-phase coil used in the slotless brushless motor shown in FIG.
6 is a front view showing a part of the three-phase coil shown in FIG.
FIG. 7 is a connection diagram showing a connection state of the three-phase coil shown in FIG. 5;
FIG. 8 is a diagram for explaining torque efficiency of a conventional slotless brushless motor and a slotless brushless motor according to the present invention.
[Explanation of symbols]
Reference Signs List 4 bearing housing 5 bearing 6 rotor yoke 7 rotor magnet 10 rotating shaft 20 disk holder 30 slotless brushless motor 31 laminated core 32 core holder 33 insulating film 34 three-phase coil

Claims (4)

A stator including a three-phase coil, and a rotor including a permanent magnet rotatably arranged facing the stator and having an S pole and an N pole alternately and equidistantly magnetized on the outer periphery of a rotation shaft. A slotless brushless motor,
Adjacent ones of the U-phase coil, the V-phase coil, and the W-phase coil constituting the three-phase coil are arranged so that portions corresponding to substantially half the width of each coil overlap in the circumferential direction. A slotless brushless motor. The slotless brushless motor according to claim 1, wherein the slotless brushless motor is an outer rotor type slotless brushless motor in which the rotor is disposed outside the stator. The slotless brushless motor according to claim 2, wherein the three-phase coil is wound around an outer peripheral surface of the laminated core via an insulator. The slotless brushless motor according to claim 1, wherein the slotless brushless motor is an inner rotor type slotless brushless motor in which the rotor is disposed inside the stator.

Images