JP2014238899A - Voice coil motor and magnet used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voice coil motor capable of significantly reducing unnecessary torque (flexure torque and twisting torque) and achieving low cost, and a magnet used for the voice coil motor.SOLUTION: A voice coil motor includes a magnet 1 having a pair of magnetic pole parts 1a and 1b whose polarity is different via a neutral part 1c between them. One side face from one of the magnetic pole parts 1a and 1b to the other via the neutral part 1c is flat. Width at each of the wing parts 1d and 1e of the magnetic pole parts 1a and 1b is equal to or greater than one-and-a-half times of width in the neutral part 1c. At least one of lines perpendicular to a plane in parallel to one side face passing through the wing parts 1d and 1e intersects with the one side face.

Description

  The present invention relates to a voice coil motor suitable for driving an actuator equipped with a head, and a magnet used for the voice coil motor.

  The magnetic disk apparatus records / reproduces information with respect to a predetermined track on the magnetic disk by driving an actuator equipped with the magnetic head. During the recording / reproducing operation, the magnetic head is driven by the actuator. Perform positioning. As a drive source of such an actuator, a voice coil motor having a coil disposed at one end of the actuator, a magnet installed at a position facing the coil, and a yoke member for forming a magnetic field circuit of the magnet Is used.

  The actuator is pivotally supported on a pivot shaft so as to be rotatable. When the coil is energized, a thrust is obtained by a force generated in a predetermined portion of the coil facing the magnet, and the actuator rotates about the pivot shaft by this thrust.

  Various types of such voice coil motors have been conventionally proposed (for example, Patent Documents 1, 2, and 3). All of these are flat coil type voice coils in which one or two magnets having a pair of magnetic pole portions having different polarities are arranged between the magnetic pole portions via a neutral portion so as to face the coil. It is a motor. The detailed configuration of the voice coil motor disclosed in each of these documents will be described later in comparison with the present invention.

US Patent Application Publication No. 2002/0097527 JP 2005-327407 A JP 2009-87451 A

  In the voice coil motor, a driving torque for driving the actuator is generated, and at the same time, torque other than the direction in which the actuator is rotated about the pivot shaft is also generated due to the influence of the shape of the magnet and / or the coil. . Such unnecessary torque includes bending torque in the direction of bending the coil and torsional torque in the direction of twisting the coil. Specifically, since the direction of the magnetic field is not constant in the vicinity of the neutral part of the magnet, vibrations in the direction of bending the coil and vibrations in the direction of twisting the coil are excited when the coil intersects this part. Unnecessary torque is generated.

  These unnecessary torques not only serve as noise transmission sources, but also hinder high-precision positioning of the magnetic head. Therefore, there is a problem in that the positioning accuracy of the magnetic head deteriorates due to the influence of bending torque and torsional torque generated along with the normal driving torque, and there is a demand for reducing unnecessary generated torque as much as possible. .

  Therefore, in order to sufficiently secure the driving torque necessary for positioning the magnetic head and reduce the above unnecessary torque (bending torque and torsion torque), the shape of the magnet or the shape of the coil used in the voice coil motor Attempts have been made.

  Incidentally, the magnetic disk device is widely used not only as a storage device of a computer but also in the field of household electric products such as a DVD recorder. In the field of household electrical appliances, there is an increasing demand for cost reduction in order to improve versatility.

  The present invention has been made in view of such circumstances, and by making the shape of the magnet to be used appropriate, unnecessary torque (bending torque and torsion torque) can be greatly reduced and the cost can be reduced. An object of the present invention is to provide a voice coil motor that can also be used.

  Another object of the present invention is to provide a magnet that can significantly reduce unnecessary torque (bending torque and torsion torque) when used in a voice coil motor and can also reduce costs. To do.

  A voice coil motor according to the present invention is a voice coil motor comprising a magnet having a pair of magnetic pole portions having different polarities via a neutral portion between the magnetic pole portions, a coil, and a yoke. One side surface from one of the pair of magnetic pole portions to the other of the pair of magnetic pole portions through the neutral portion is flat, and a wing portion is provided on the distal side of the pair of magnetic pole portions from the neutral portion. The width of each of the pair of magnetic pole portions in the wing portion is 1.5 times or more the width in the neutral portion, and is perpendicular to a plane parallel to the one side surface through each of the wing portions. At least one of the straight lines intersects the one side surface.

  In the voice coil motor according to the present invention, one of the two side surfaces of the magnet to be used and one side surface far from the pivot shaft described in the embodiment for carrying out the invention are flattened. In addition, the magnet in a region that does not contribute to the generation of the driving torque for driving the actuator is lost to reduce the cost, and since it is flat, there is less processing and the yield is improved. Further, the width of the wing portion of the magnetic pole portion of the magnet to be used is set to be 1.5 times or more wider than the width of the central neutral portion, so that bending torque and torsion torque are reduced. Moreover, the perpendicular from the wing | blade part of the at least 1 magnetic pole part of the magnet to be used cross | intersects said one side surface, and drive torque is obtained efficiently.

  The voice coil motor according to the present invention is characterized in that a width of each of the pair of magnetic pole portions in the wing portion is three times or more than a width in the neutral portion.

  In the voice coil motor of the present invention, the width of the wing portion of the magnetic pole portion is set to be three times or more the width of the neutral portion. Therefore, the bending torque and the torsion torque can be further reduced.

  The voice coil motor according to the present invention is a voice coil motor including a pair of magnets arranged on the same plane and having different polarities, a coil, and a yoke, wherein the pair of magnets are in contact with each other, and each of the pair of magnets Is flat on one side from the side in contact with the other magnet to the distal side, and has a wing at a portion distal to the side in contact with the other magnet. At least one of the straight lines having a width of 1.5 times or more of the width in contact with the other magnet and perpendicular to a plane parallel to the one side surface through the wings of each of the pair of magnets. One crosses the one side surface.

  In the voice coil motor according to the present invention, each of the pair of magnets in contact with each other has a flat one side surface far from the pivot shaft, and generates a driving torque for driving the actuator. In addition to reducing the cost by eliminating the magnets in the region that does not contribute to the area, the flatness reduces the processing and improves the yield. In addition, the width of the wing portion distal from the side on which each of the pair of magnets is in contact is 1.5 times or more wider than the width of the contacting portion, and bending torque and torsion torque are reduced. Moreover, the perpendicular from at least one wing part of the pair of magnets used intersects one side surface, so that driving torque can be obtained efficiently.

  The voice coil motor according to the present invention is a voice coil motor including a pair of magnets having different polarities arranged on the same plane, a coil, and a yoke, wherein the pair of magnets are opposed via a gap, Each of the pair of magnets is flat on one side from the side facing the other magnet to the distal side, and has a wing at a portion distal from the side facing the other magnet. And the width of the wing portion is 1.5 times or more the width of the portion facing the other magnet, and is a surface parallel to the one side surface through the wing portion of each of the pair of magnets At least one of the straight lines perpendicular to the crossing of the one side surface.

  In the voice coil motor of the present invention, each of the pair of magnets to be used has a flat one of the two side surfaces far from the pivot shaft, and generates driving torque for driving the actuator. The cost of the non-contributing area can be reduced by reducing the cost, and the flatness can reduce the processing and improve the yield. In addition, the width of the wings distal from the opposing sides of each of the pair of magnets used is 1.5 times wider than the width of the opposing parts, and bending torque and torsion torque are reduced. To do. Moreover, the perpendicular from at least one wing part of the pair of magnets used intersects one side surface, so that driving torque can be obtained efficiently.

  The magnet used for the voice coil motor according to the present invention is a magnet used for a voice coil motor having a pair of magnetic pole portions having different polarities via a neutral portion between the magnetic pole portions. One side surface from the neutral part to the other of the pair of magnetic pole parts is flat, and each of the pair of magnetic pole parts has a wing on the distal side from the neutral part, and the pair of magnetic pole parts The width of each of the wings is 1.5 times or more the width of the neutral part, and at least one straight line passing through each of the wings and perpendicular to the plane parallel to the one side is the one of the ones. It is characterized by crossing the side.

  In the magnet used for the voice coil motor of the present invention, one side surface from one of a pair of magnetic pole portions having different polarities to the other of the magnetic pole portion through the neutral portion is flattened, and the actuator is driven. The magnets in the region that does not contribute to the generation of the driving torque can be lost, and the cost can be reduced. Since the magnets are flat, the processing is less and the yield is improved. Further, the width of the wing portion of the magnetic pole portion is made wider by 1.5 times or more than the width of the central neutral portion, and bending torque and torsion torque are reduced. In addition, the perpendicular from the wing portion at at least one magnetic pole portion intersects one side surface, so that driving torque can be obtained efficiently.

  In the present invention, the bending torque and the torsion torque, which are unnecessary torques that lead to vibration problems, can be greatly reduced, and high-accuracy drive control for the actuator can be realized. Further, the cost can be reduced by efficiently using the driving torque. Further, since the shape of the magnet becomes flat, the yield can be improved.

1 is a schematic view of a magnetic disk device using a voice coil motor according to the present invention. It is sectional drawing of the LL 'line | wire which shows the structure of the voice coil motor which concerns on this invention. It is a top view which shows the positional relationship of the magnet and coil in a voice coil motor. It is a top view which shows the magnet which concerns on this invention. It is sectional drawing which shows the structure of the voice coil motor using one magnet. It is a top view which shows the magnet and coil in the conventional voice coil motor. It is a graph which shows the characteristic of the bending torque which generate | occur | produces in the voice coil motor (invention example) of this invention, and the conventional voice coil motor (conventional example). It is a graph which shows the characteristic of the torsion torque which generate | occur | produces in the voice coil motor (invention example) of this invention, and the conventional voice coil motor (conventional example). It is a top view which shows the magnet and coil in the example of this invention. It is a top view which shows the magnet and coil in patent document 2. FIG. It is a graph which shows the characteristic of the bending torque with respect to ratio (b / a) of the width | variety (a) in the neutral part of the center of a magnet, and the width | variety (b) in the wing | blade part of one side. It is a graph which shows the characteristic of the torsion torque with respect to ratio (b / a) of the width (a) in the neutral part of the center of a magnet, and the width (b) in the wing | blade part of one side. It is a top view which shows the shape of the magnet when the value of b / a is set to infinity. It is a top view which shows the magnet and coil disclosed by patent document 1. FIG. It is a top view which shows the magnet and coil which were disclosed by patent document 2. FIG. It is a top view which shows the magnet and coil disclosed by patent document 3. FIG. It is a graph which shows the characteristic of the drive torque in an example of the present invention and patent documents 1, 2, and 3. It is a graph which shows the characteristic of the bending torque generate | occur | produced in the example of this invention and patent documents 1, 2, and 3. FIG. It is a graph which shows the characteristic of the torsion torque which generate | occur | produces in the example of this invention and patent document 1, 2, 3. It is a top view which shows the magnet and coil in the modification (1st modification) of this invention. It is a top view which shows the magnet and coil in the modification (2nd modification) of this invention. It is a top view which shows the magnet and coil in the modification (3rd modification) of this invention. It is a top view which shows the magnet and coil in the modification (4th modification) of this invention. It is a top view which shows the magnet and coil in the modification (5th modification) of this invention. It is a top view which shows the magnet and coil in the modification (6th modification) of this invention. It is a top view which shows the magnet and coil in the modification (7th modification) of this invention. It is a top view which shows the magnet and coil in other embodiment of this invention. It is a top view which shows the magnet and coil in other embodiment of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

  FIG. 1 is a schematic view of a magnetic disk apparatus using a voice coil motor according to the present invention. The magnetic disk device 10 includes a disk-shaped magnetic disk 20, a magnetic head 30 that moves in a radial direction with respect to the magnetic disk 20 to record / reproduce information, an actuator 40 that positions the magnetic head 30, and an actuator 40 And a voice coil motor 50 for driving the motor.

  The central portion of the magnetic disk 20 is attached to the spindle motor 60, and the magnetic disk 20 is rotated as the spindle motor 60 is driven. The information recording / reproducing area on the magnetic disk 20 is an area between the outermost circumference position (OD) and the innermost circumference position (ID) as shown by a one-dot chain line in FIG. There is an intermediate circumferential position (MD) in between.

  The actuator 40 is pivotally supported on a pivot shaft 41. A voice coil motor 50 is provided on the proximal end side of the actuator 40. The voice coil motor 50 includes a magnet 1, a coil 2, and a yoke 3.

  FIG. 2 is a cross-sectional view taken along line LL ′ showing the configuration of the voice coil motor 50 according to the present invention. The voice coil motor 50 includes two magnets 1, a coil 2, and a yoke 3 including a top yoke 3a and a bottom yoke 3b. The circular coil 2 is arranged to be parallel to the surface of the magnetic disk 20. Above the coil 2, a magnet 1 attached to a top yoke 3 a that forms a part of the yoke 3 is disposed with a predetermined gap facing the coil 2. Also, below the coil 2, a magnet 1 attached to a bottom yoke 3 b that forms a part of the yoke 3 is disposed with a predetermined gap facing the coil 2. Although the shape of these two magnets 1 is the same, the positional relationship of different polarities (N, S) of the magnetic pole portions is reversed (see FIG. 2).

  FIG. 3 is a plan view showing the positional relationship between the magnet 1 and the coil 2 in the voice coil motor 50. In FIG. 3, point A represents the position where the pivot shaft 41 is installed, in other words, the position of the rotation center of the actuator 40 (coil 2). Hereinafter, the point A is referred to as a pivot axis A. In FIG. 3, the solid line represents the position of the coil 2 when the actuator 40 is located at the center, and the alternate long and short dash line represents the position of the coil 2 when the actuator 40 has moved to the maximum angle on one side and the other side. Yes.

  The voice coil motor 50 generates a driving torque necessary for moving the magnetic head 30 to a target radial position of the magnetic disk 20 by passing a current through the coil 2 existing in the magnetic field generated by the magnet 1. The region where the driving torque is generated is a region where the magnet 1 and the coil 2 intersect mainly.

  Next, the shape of the magnet 1, which is a characteristic part of the present invention, and actions and effects resulting from the shape will be described in detail.

  FIG. 4 is a plan view showing the magnet 1 according to the present invention. The magnet 1 has a pair of magnetic pole portions 1a and 1b having different polarities (N, S) via a neutral portion 1c which is a magnetic pole changing portion between the magnetic pole portions 1a and 1b. Is a configuration integrally including a magnetic pole portion 1a having the polarity of the N pole on one end side, a magnetic pole portion 1b having the polarity of the S pole on the other end side, and a neutral portion 1c at the center portion. Each of the magnetic pole portions 1a and 1b has wing portions 1d and 1e on the distal side from the neutral portion 1c.

  In the magnet 1, the shapes of two side surfaces from the one magnetic pole portion 1a through the neutral portion 1c to the other magnetic pole portion 1b are different from each other. The side surface close to the pivot axis A is inclined such that the width decreases from the wing portion 1d having the maximum width toward the central neutral portion 1c, and the width increases toward the wing portion 1e from the neutral portion 1c. It has become. Note that the inclination angle of the inclined surface has two steps: a steep angle at both ends and a gentle angle at the center. On the other hand, the side surface far from the pivot axis A is a flat surface over the entire area from the magnetic pole portion 1a to the magnetic pole portion 1b through the neutral portion 1c.

  Further, when the width of the neutral portion 1c of the magnet 1 is a, the width of the wing portion 1d (maximum width of the magnetic pole portion 1a) is b, and the width of the wing portion 1e (maximum width of the magnetic pole portion 1b) is c. B / a ≧ 1.5 and c / a ≧ 1.5 are satisfied. Specifically, a and b and c are a = 0 to 14 mm and b and c = 6 to 22 mm, respectively, and the horizontal distance w between the neutral portion 1c and the wing portions 1d and 1e is w = 7-20 mm.

  In addition, the leg of the perpendicular line which is lowered from the apex of the wing portion 1d to a plane parallel to the side surface far from the pivot axis A intersects this side surface. That is, in the plan view in FIG. 4, the perpendicular foot C dropped from the apex B of the wing 1 d intersects the straight line F. Similarly, the leg of the perpendicular line dropped from the apex of the wing 1e to a plane parallel to the side surface far from the pivot axis A intersects this side surface. That is, in the plan view in FIG. 4, the perpendicular foot E dropped from the vertex D of the wing 1 e intersects the straight line F.

  In the present invention, since the magnet 1 having the shape as described above is used, the driving torque that contributes to driving the actuator 40 can be efficiently generated. Further, at this time, unnecessary torque such as bending torque and torsion torque, which become a vibration source, can be reduced without contributing to driving of the actuator 40.

  In the vicinity of the neutral portion 1c of the magnet 1, the direction of the magnetic field is not constant. Therefore, in the arrangement in which the coil 2 intersects with this portion, unnecessary torque is generated that excites vibrations in the bending direction and the torsional direction. In the present invention, the width of the wing portions 1d and 1e of each of the pair of magnetic pole portions 1a and 1b is 1.5 times or more the width of the neutral portion 1c, thereby reducing the width of the neutral portion 1c. Generation of large torque (bending torque and torsion torque) is reduced.

  In the above-described example, the voice coil motor 50 is configured using two magnets 1, but may be configured to use one magnet 1. FIG. 5 is a cross-sectional view showing a configuration of a voice coil motor 50 using such a single magnet 1. In FIG. 5, the same parts as those in FIG. In this configuration example, the magnet 1 attached to the top yoke 3a is disposed only above the coil 2 so as to face the coil 2 with a predetermined gap. In the example of FIG. 5, the magnet 1 is disposed above the coil 2, but the present invention is not limited thereto, and may be disposed only below the coil 2.

  Hereinafter, the effect of reducing the bending torque and torsion torque in the voice coil motor of the present invention will be described in comparison with a conventional voice coil motor. FIG. 6 is a plan view showing a magnet 1 and a coil 2 in a conventional voice coil motor. The magnet 1 in the conventional voice coil motor has a generally fan-shaped shape as disclosed in, for example, a magnet used in the conventional voice coil motor of Patent Document 2.

  FIG. 7 is a graph showing characteristics of bending torque generated in the voice coil motor of the present invention (example of the present invention) and the conventional voice coil motor (conventional example). FIG. 7 shows the characteristics of a configuration in which both the present invention example and the conventional example have two magnets. Further, in FIG. 7, d indicates the characteristic of the present invention example, and e indicates the characteristic of the conventional example. Further, in FIG. 7, the horizontal axis represents the coil angle (°) rotated between the innermost circumferential position side (ID side) and the outermost circumferential position side (OD side), and the vertical axis represents the normal driving torque. The ratio of the bending torque to is expressed.

  When the present invention example is compared with the conventional example, it can be seen that the bending torque generated on the ID side and the OD side can be reduced to about half that of the conventional example.

  FIG. 8 is a graph showing the characteristics of torsion torque generated in the voice coil motor of the present invention (example of the present invention) and the conventional voice coil motor (conventional example). FIG. 8 shows the characteristics of the configuration of the present invention and the conventional example having two magnets. In FIG. 8, d indicates the characteristic of the present invention example, and e indicates the characteristic of the conventional example. Further, in FIG. 8, the horizontal axis represents the coil angle (°) rotated between the innermost circumferential position side (ID side) and the outermost circumferential position side (OD side), and the vertical axis represents the normal driving torque. The ratio of torsional torque with respect to.

  When the present invention example is compared with the conventional example, it can be seen that the torsion torque generated on the ID side and the OD side can be reduced to about 1/5 of the conventional example.

  7 and 8, the characteristics on the innermost peripheral position side (ID side) and the outermost peripheral position side (OD side) are focused on the unnecessary torque that becomes the vibration source on the ID side and OD side. This is because the bending torque and torsion torque in the case become a problem.

  In the voice coil motor of the present invention, since one side surface of the magnet is flat, the distance between the coil and the magnet can be increased, and generation of unnecessary torque can be suppressed. Further, by reducing the width in the neutral portion where unnecessary torque is frequently generated, it is possible to reduce the generated unnecessary torque. The decrease in driving torque due to the reduction in the width of the neutral part is compensated by increasing the thickness of the wing part of the magnetic pole part.

  Hereinafter, the superiority of one characteristic shape (one side surface is a flat shape) of the magnet 1 of the present invention will be described in more detail. FIG. 9 is a plan view showing the magnet 1 and the coil 2 in the example of the present invention, and FIG. 10 is a plan view showing the magnet 1 and the coil 2 in Patent Document 2.

  In Patent Document 2, the direction of the torque generated in the coil shown in FIG. 10 when the coil 2 is energized is the direction indicated by the arrow G. On the other hand, the direction of torque that contributes to driving of the actuator 40 is the direction indicated by the arrow H. Here, since the directions of both torques have a substantially orthogonal relationship, the generated torque hardly contributes to driving of the actuator 40, and there is a concern that unnecessary torque is generated.

  From the above, a part of the side surface of the magnet 1 far from the pivot axis A (part K hatched in FIG. 10) hardly contributes to an increase in driving torque, and on the contrary, a large unnecessary torque is generated. There is a concern to do. Therefore, the magnet 1 of the present invention has a configuration in which such an unnecessary portion is lost. Therefore, in the present invention, it is possible to reduce the bending torque and the torsion torque while reducing the cost, and to efficiently generate the necessary and sufficient driving torque. Further, since one side surface is flat and the shape of the magnet 1 is simpler than that of the conventional example, less processing is required, leading to an improvement in yield.

  Next, one characteristic shape of the magnet 1 of the present invention (b / a ≧ 1.5, c / a where a is the width in the neutral portion 1c and b and c are the widths in the wing portions 1d and 1e) The operation / effect of ≧ 1.5) will be described. Since the relationship between the width a and the width b and the relationship between the width a and the width c are the same, the relationship between the width a and the width b will be described below.

  FIG. 11 is a graph showing the characteristic of the bending torque with respect to the ratio (b / a) between the width (a) of the neutral portion 1c at the center of the magnet 1 and the width (b) of the wing portion 1d on one side. In FIG. 11, f indicates the characteristic at the innermost peripheral position side (ID side), and g indicates the characteristic at the outermost peripheral position side (OD side). In FIG. 11, the horizontal axis represents the ratio b / a of the width b of the wing 1d to the width a of the neutral portion 1c, and the vertical axis represents the ratio of the bending torque to the driving torque.

  FIG. 12 is a graph showing the characteristics of torsional torque with respect to the ratio (b / a) of the width (a) of the neutral portion 1c at the center of the magnet 1 and the width (b) of the wing portion 1d on one side. In FIG. 12, f indicates the characteristic on the innermost peripheral position side (ID side), and g indicates the characteristic on the outermost peripheral position side (OD side). In FIG. 12, the horizontal axis represents the ratio b / a of the width b of the wing 1d to the width a of the neutral portion 1c, and the vertical axis represents the ratio of torsion torque to drive torque.

  By setting the value of the ratio b / a to 1.5 or more, the bending torque and the torsion torque can be suppressed to a low level. Further, by setting the value of the ratio b / a to 3 or more, it is possible to realize a significant reduction in bending torque and torsion torque.

  Note that setting the value of the ratio b / a to ∞ means setting the value of a to 0 as much as possible. FIG. 13 is a diagram showing the shape of the magnet 1 when the value of b / a is ∞.

  Hereinafter, a comparison between the three documents cited as the prior art documents (Patent Document 1, Patent Document 2, and Patent Document 3) and the present invention will be described.

  FIG. 14 is a plan view showing a magnet and a coil disclosed in Patent Document 1. FIG. The magnet 71 includes two first sectors 72 and second sectors 73 having different magnetism, and a transition portion 74 between the first sector 72 and the second sector 73. The widths of the first sector 72 and the second sector 73 are larger than the width of the central transition portion 74 (corresponding to the neutral portion of the present invention). The side surface 75 on the side close to the pivot axis A has an arc shape, and the side surface 76 on the side far from the pivot axis A has a substantially linear shape. However, the perpendicular line dropped from the wings of the first sector 72 and the second sector 73 to a plane parallel to the side surface 76 on the side far from the pivot axis A does not intersect the side surface 76. This point is different from the configuration of the magnet 1 of the present invention. A long and thin special-shaped coil 77 is opposed to the magnet 71 having such a shape. The magnet 71 in Patent Document 1 is formed only by a combination with a long and thin special-shaped coil 77.

  FIG. 15 is a plan view showing a magnet and a coil disclosed in Patent Document 2. FIG. The magnet 81 has two magnetic pole portions 82 and 83 having different magnetism and a magnetic pole changing portion 84 (corresponding to the neutral portion of the present invention) between the magnetic pole portions 82 and 83. The width of the magnetic pole portions 82 and 83 is larger than the width of the magnetic pole changing portion 84 at the center. The side surface 85 on the side close to the pivot axis A and the side surface 86 on the side far from the pivot axis A have the same arc shape. A circular coil 87 is opposed to the magnet 81 having such a shape. The magnet 81 is decisively different from the configuration of the magnet 1 of the present invention in that the side surface 86 on the side far from the pivot axis A is not flat.

  FIG. 16 is a plan view showing a magnet and a coil disclosed in Patent Document 3. As shown in FIG. The magnet 91 has two magnetic pole portions 92 and 93 having different magnetism, and a neutral portion 94 between the magnetic pole portions 92 and 93. The magnet 91 has a rectangular shape and the width thereof is the same over the entire region, and this is different from the configuration of the magnet 1 of the present invention. A circular coil 95 is opposed to the magnet 91 having such a shape.

  For the voice coil motor of the present invention (example of the present invention) and the voice coil motors of Patent Documents 1, 2, and 3, adjust the shape of the magnet so that the weight of the magnet is equal, and rotate the coil around the pivot axis Thus, the magnitude of the normal driving torque for driving the actuator and the unnecessary torque (bending torque and torsional torque) serving as the vibration source were evaluated. The evaluation result will be described below.

  FIG. 17 is a graph showing the characteristics of the drive torque in the present invention example and Patent Documents 1, 2, and 3. In FIG. 17, h, i, j, and k indicate the characteristics of the example of the present invention, the characteristics of Patent Document 1, the characteristics of Patent Document 2, and the characteristics of Patent Document 3, respectively. In FIG. 17, the horizontal axis represents the rotated coil angle (°), and the vertical axis represents the normal drive torque magnitude (mNm / A).

  In the example of the present invention, it can be seen that, compared with Patent Documents 1, 2, and 3, a large driving torque is obtained with the same weight. In Patent Document 3, the driving torque at the center is large, but the uniformity of the driving torque over the entire moving range of the coil is poor, and particularly the driving torque at both ends is remarkably lowered, making it difficult to control the actuator. On the other hand, in the present invention example, a uniform and large driving torque is obtained over the entire moving range of the coil. Compared to Patent Document 1, the example of the present invention has a large driving torque and a wide coil angle. Moreover, with respect to Patent Document 2, the coil angle with a large driving torque is wide. Therefore, in the present invention example, the efficiency of the magnetic circuit is good, and the cost can be reduced.

  FIG. 18 is a graph showing the characteristics of bending torque generated in the present invention example and Patent Documents 1, 2, and 3. In FIG. 18, h, i, j, and k indicate the characteristics of the present invention example, the characteristics of Patent Document 1, the characteristics of Patent Document 2, and the characteristics of Patent Document 3, respectively. In FIG. 18, the horizontal axis represents the rotated coil angle (°), and the vertical axis represents the ratio of the bending torque to the normal driving torque.

  FIG. 19 is a graph showing characteristics of torsional torque generated in the present invention example and Patent Documents 1, 2, and 3. In FIG. 19, h, i, j, and k indicate the characteristics of the present invention example, the characteristics of Patent Document 1, the characteristics of Patent Document 2, and the characteristics of Patent Document 3, respectively. In FIG. 19, the horizontal axis represents the rotated coil angle (°), and the vertical axis represents the ratio of the torsional torque to the normal driving torque.

  In the example of the present invention, it can be seen that the bending torque generated as an unnecessary torque can be greatly reduced as compared with Patent Document 1. Moreover, it turns out that the bending torque which generate | occur | produces as an unnecessary torque can be reduced compared with patent document 2, 3. FIG. Moreover, in the example of this invention, compared with patent document 1, it turns out that the torsion torque which generate | occur | produces as an unnecessary torque can be reduced significantly. Further, it can be seen that the torsional torque generated as unnecessary torque can be reduced as compared with Patent Document 3. Moreover, it turns out that it is a torsional torque comparable as patent document 2.

  Here, the advantage of one characteristic shape of the magnet 1 of the present invention (perpendiculars of a perpendicular line extending to a plane parallel to the side surface far from the pivot axis A from the apex of the wing portions 1d and 1e intersects this side surface) The characteristics will be described in comparison with the voice coil motor of Patent Document 1 that does not have this characteristic shape.

  In Patent Document 1, a long and thin special coil 77 is used so that the entire magnet 71 can be used effectively. However, as can be seen from the characteristic results shown in FIG. 17, the efficiency of the driving torque obtained with respect to the magnet weight is lower than that of the voice coil motor of the present invention. Coils generally used for voice coil motors are trapezoidal, circular, and elliptical, and when these coils are combined with the magnets in Patent Document 1, all contribute to driving torque. There are few magnets and there is a useless magnet in a part that does not contribute to the driving torque. In such a configuration, the efficiency of the obtained driving torque is further reduced. In the present invention, at least one straight line that passes through each wing portion and is perpendicular to a plane parallel to one side surface intersects one side surface, thereby increasing the efficiency of the driving torque.

  On the other hand, in the voice coil motor of the present invention, since the magnet 1 has the characteristic shape as described above, the coil 1 has a shape widely used in voice coil motors such as a circle, a trapezoid, and an ellipse. On the other hand, the inconvenience as in Patent Document 1 does not occur, and the drive torque can be obtained efficiently.

  Next, a modified example of the present invention will be described. 20 to 26 are plan views showing a magnet 1 and a coil 2 in a modification of the present invention. 20 to 26 show the position of the coil 2 on the ID side and the OD side.

  In the magnet 1 of the first modification shown in FIG. 20, the magnetic pole part 1a and the magnetic pole part 1b are not the same shape, and the perpendicular from the wing part 1d of one magnetic pole part 1a intersects the side surface on the side far from the pivot axis A. However, the perpendicular from the wing 1e of the other magnetic pole portion 1b does not intersect this side surface.

  The first modification shown in FIG. 20, the second modification shown in FIG. 21, and the third modification shown in FIG. 22 are different functions from the generation of the drive torque (for example, the actuator is more reliably disposed on the outer peripheral side than the OD. In order to fulfill the function of fixing to the magnetic pole portion 1, the magnetic pole portion 1 b of the magnet 1 is further provided with a surplus portion.

  A fourth modification shown in FIG. 23 and a fifth modification shown in FIG. 24 are examples in which the shape of the magnet 1 is changed. In the magnet 1 of the fourth modified example, the central portion 1h (near the neutral portion 1c) on the side surface close to the pivot axis A is not an inclined surface but a flat surface. In the magnet 1 of the fifth modification, the inclination angle from the wing portion 1d (1e) on the side surface close to the pivot axis A to the neutral portion 1c is constant over the entire region.

  The sixth modification shown in FIG. 25 and the seventh modification shown in FIG. 26 are examples in which the shape of the coil 2 is changed. The coil 2 of the sixth modification has a substantially rectangular shape instead of a circular shape, and the coil 2 of the seventh modification has a trapezoidal shape.

  Even with the voice coil motor configured as described above, as with the voice coil motor described above, unnecessary torque (bending torque and torsion torque) can be reduced and drive torque can be obtained efficiently, and cost reduction can be achieved. Can be achieved.

  Next, another embodiment of the present invention will be described. FIG. 27 is a plan view showing a magnet and a coil according to another embodiment of the present invention. The magnet 1 of this embodiment is configured by contacting a pair of magnets 1f and 1g having different polarities. A coil 2 is opposed to the magnet 1 with a predetermined gap.

  FIG. 28 is a plan view showing a magnet and a coil according to still another embodiment of the present invention. The voice coil motor of this embodiment has a pair of magnets 11 and 12 having different polarities. The pair of magnets 11 and 12 are arranged on the same plane in a manner facing each other with a gap. The coil 2 faces the magnets 11 and 12 with a predetermined gap.

  Each of the magnets 11 and 12 has a shape similar to the magnetic pole portions 1a and 1b of the magnet 1 of the above-described embodiment. The side surface of the magnet 11 that is close to the pivot axis A is an inclined surface that decreases in width as it goes from the wing portion 11 d having the maximum width toward the side facing the magnet 12. On the other hand, the side surface far from the pivot axis A is a flat surface over the entire area.

  Further, when the width of the portion of the magnet 11 facing the magnet 12 is a and the width of the wing portion 11d is b, the condition of b / a ≧ 1.5 is satisfied. In addition, the leg of the perpendicular line which is lowered from the apex of the wing part 11d to a plane parallel to the side surface far from the pivot axis A intersects this side surface. That is, in the plan view in FIG. 28, the perpendicular foot C dropped from the apex B of the wing part 11d intersects the straight line F. In addition, since the shape of the magnet 12 is the same as the shape of the magnet 11, the description is omitted.

  Even in such an embodiment having a pair of magnets having different polarities, the actuator is used after reducing unnecessary torques of bending torque and torsion torque as a vibration source as in the above-described embodiment. The driving torque that contributes to the driving of 40 can be efficiently generated, and the side surfaces are flattened, so that the cost can be reduced.

  In addition, as described in the claims of the present invention, “one side surface from one of the pair of magnetic pole portions to the other of the pair of magnetic pole portions through the neutral portion is flat”, “ “One side from the contact side to the distal side is flat” and “One side from the side facing the other magnet to the distal side is flat” means “flat” Even if the side surface is uneven, the width between the minimum and maximum of the unevenness includes a shape that is within 3% of the length of the side surface of the magnet.

1, 1f, 1g Magnet 1a, 1b Magnetic pole part 1c Neutral part 1d, 1e Wing part 1h Central part 2 Coil 3 Yoke 10 Magnetic disk device 11, 12 Magnet 11d Wing part 30 Magnetic head 40 Actuator 41 Pivot shaft 50 Voice coil motor

Claims (5)

In a voice coil motor comprising a magnet having a pair of magnetic pole portions having different polarities, a neutral portion between the magnetic pole portions, a coil, and a yoke,
The magnet
One side surface from one of the pair of magnetic pole parts to the other of the pair of magnetic pole parts through the neutral part is flat,
Each of the pair of magnetic pole portions has a wing on the distal side from the neutral portion;
The width of each of the pair of magnetic pole portions in the wing portion is 1.5 times or more the width in the neutral portion;
A voice coil motor characterized in that at least one straight line passing through each wing portion and perpendicular to a plane parallel to the one side surface intersects the one side surface.   2. The voice coil motor according to claim 1, wherein a width of each of the pair of magnetic pole portions in the wing portion is three times or more a width of the neutral portion. In a voice coil motor comprising a pair of magnets with different polarities, coils, and yokes arranged on the same plane,
The pair of magnets are in contact with each other,
Each of the pair of magnets is
One side from the side in contact with the other magnet to the distal side is flat,
It has a wing at the part distal to the side that is in contact with the other magnet,
The width of the wing portion is 1.5 times or more the width of the portion in contact with the other magnet,
A voice coil motor, wherein at least one straight line perpendicular to a plane parallel to the one side surface through the wing portion of each of the pair of magnets intersects the one side surface. In a voice coil motor comprising a pair of magnets with different polarities, coils, and yokes arranged on the same plane,
The pair of magnets are opposed to each other through a gap,
Each of the pair of magnets is
One side from the side facing the other magnet to the distal side is flat,
It has a wing in the part distal to the side facing the other magnet,
The width of the wing portion is 1.5 times or more the width of the portion facing the other magnet,
A voice coil motor, wherein at least one straight line perpendicular to a plane parallel to the one side surface through the wing portion of each of the pair of magnets intersects the one side surface. In a magnet used for a voice coil motor having a pair of magnetic pole parts having different polarities via a neutral part between the magnetic pole parts,
One side surface from one of the pair of magnetic pole parts to the other of the pair of magnetic pole parts through the neutral part is flat,
Each of the pair of magnetic pole portions has a wing on the distal side from the neutral portion;
The width of each of the pair of magnetic pole portions in the wing portion is 1.5 times or more the width in the neutral portion;
A magnet used for a voice coil motor, characterized in that at least one straight line passing through each wing portion and perpendicular to a plane parallel to the one side surface intersects the one side surface.

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