JP2007220219A - Vcm (voice coil motor) device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a VCM (voice coil motor) device which effectively reduces leakage magnetic flux to the side of a body to be driven such as a magnetic head by devising the yoke structure of a VCM magnetic circuit. <P>SOLUTION: The device is provided with: a pair of plate-like yokes 2 and 3 opposing each other; plate-like permanent magnets 8 and 9 fixed to opposing surfaces of the yokes 2 and 3; a driving coil 12 arranged movably between the opposing surfaces of the yokes 2 and 3; and an arm 11 to which the driving coil 12 is attached. At peripheries of pull-out sides of the arms of the yokes 2 and 3 or in the neighborhood of them, auxiliary yokes 6 and 7 extended in the direction of the thickness of the permanent magnets 8 and 9 are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a VCM (voice coil motor) device used for driving a magnetic head in an HDD (hard disk drive) device, and more particularly to a driven member (magnetic head, etc.) side of an oscillating VCM device. The present invention relates to a yoke structure that effectively attenuates the leakage magnetic flux.

  VCM devices are used not only for HDD devices for PC (personal computer) peripheral devices but also for home appliances and portable terminals in recent years.

  In recent years, high capacity and high speed are desired for HDD devices, and there is a demand to increase the magnetic flux density in the air gap of the VCM magnetic circuit in order to increase the coil drive torque. In order to increase the magnetic flux density, there are methods of narrowing the gap, increasing the thickness of the permanent magnet, or increasing the magnetic characteristics of the permanent magnet.

  On the other hand, miniaturization of the HDD device has progressed, the distance between the VCM device and the hard disk as the recording medium has become smaller, and the distance between the magnetic head as the driven body and the VCM magnetic circuit has also become narrower. For this reason, the influence of the leakage magnetic flux from the VCM magnetic circuit on the recording medium and the magnetic head has become a problem.

The following Patent Document 1 and Patent Document 2 are known documents relating to leakage magnetic flux reduction of the VCM magnetic circuit.
JP-A-5-74074 JP-A-5-122917

  In Patent Document 1, in a swing type (rotary type) VCM apparatus, a shield plate is arranged on the outer arc surface side of a permanent magnet arranged in a substantially arc shape, thereby reducing leakage magnetic flux to a magnetic head. A structure is disclosed. However, the countermeasure against leakage magnetic flux on the pulling direction side of the arm to which the magnetic head is attached is not taken into consideration.

  In Patent Document 2, in an oscillating type (rotary type) or linear type VCM device, auxiliary yokes (height equivalent to the thickness of the permanent magnet) are arranged in contact with the permanent magnets at both end surfaces in the coil moving direction of the permanent magnets. Thus, a structure for reducing the leakage magnetic flux at the end of the permanent magnet is disclosed. However, in this configuration, since the auxiliary yoke is in contact with the side surface of the permanent magnet, the magnetic flux that can be interlinked with the driving coil flows to the auxiliary yoke. In the vicinity of the auxiliary yoke arrangement portion, the magnetic flux in the air gap of the VCM magnetic circuit The density is thought to decrease. In addition, the countermeasure against leakage magnetic flux on the drawing direction side of the arm to which the magnetic head is attached is not taken into consideration.

  Contrary to the increase in the seek time of HDD devices and the increase in storage capacity, the permanent magnets are improved in characteristics, and the yoke is becoming thinner and smaller, the magnetic circuit becomes smaller, and the size is reduced. As a result, the influence of the leakage magnetic flux cannot be ignored, so that at the time of recording / reproducing the magnetic head, there is a possibility that the signal cannot be recorded / reproduced by the magnetic head due to the leakage magnetic flux. As the HDD device itself becomes smaller (the space between the head and the VCM device becomes narrower), and the information recording on the hard disk is increased in density and perpendicular recording, it is only necessary to provide a shield plate outside as in Patent Document 1 above. Alternatively, the configuration in which magnetic flux leakage is fed back from the auxiliary yoke to the permanent magnet due to the arrangement of the auxiliary yoke that contacts both end faces of the permanent magnet as in Patent Document 2 has not been able to cope with it sufficiently.

  An object of the present invention is to provide a VCM device capable of effectively reducing leakage magnetic flux toward a driven body such as a magnetic head by devising a yoke structure of a VCM magnetic circuit in view of the above points.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, a VCM device according to the present invention comprises a pair of opposing plate-like yoke portions, a flat plate-like permanent magnet fixed to at least one of the opposing surfaces of the plate-like yoke portion, and the plate-like magnets. A drive coil disposed movably between the opposing surfaces of the yoke portion, and an arm to which the drive coil is attached;
An auxiliary yoke portion extending in the thickness direction of the permanent magnet is provided at or near the arm drawer side periphery of the plate-like yoke portion.

  In the VCM device, the length of the auxiliary yoke portion extending from the opposing surface of the plate-like yoke portion may be longer than the thickness of the permanent magnet.

  In the VCM device, the thickness of the arm at the portion facing the auxiliary yoke portion is thinner than the thickness of the driving coil, and the extension length of the auxiliary yoke portion is set so as to cover the driving coil. Also good.

  In the VCM apparatus, the auxiliary yoke portion may be located on an inner side of the arm drawer side periphery of the plate-like yoke portion.

  In the VCM device, the auxiliary yoke portion may be non-contact with a side surface of the permanent magnet.

  According to the VCM device of the present invention, since the auxiliary yoke portion extending in the thickness direction of the permanent magnet is provided at or near the arm drawing side periphery of the plate-like yoke portion, the pair of plate-like yoke portions and the auxiliary yoke are provided. The magnetic circuit can be effectively terminated at the section (the gap in the magnetic circuit can be narrowed), and the arm on which the driving coil is attached, that is, toward the driven body such as the magnetic head Leakage can be sufficiently reduced. In addition, since a magnetic circuit that feeds back the leakage magnetic flux from one yoke part to the other yoke part is assembled, the original magnetic characteristics of the permanent magnet effectively act on the driving coil, and the driven body such as the magnetic head High speed driving can be achieved.

  In the following, as the best mode for carrying out the present invention, an embodiment of a VCM apparatus will be described with reference to the drawings.

  An example of a swing type VCM apparatus according to the first embodiment of the VCM apparatus according to the present invention will be described with reference to FIGS. In these drawings, reference numeral 1 denotes a yoke structure made of a soft magnetic material, a pair of opposed plate-like yoke portions 2 and 3, a rear yoke portion 4, side yoke portions 5 on both end sides, and an auxiliary yoke portion. 6 and 7. Flat plate-like permanent magnets 8 and 9 are fixed to opposing surfaces (inner side surfaces) of the plate-like yoke portions 2 and 3, respectively. A driving coil 12 is attached and fixed to a carriage arm 11 that is supported by a fulcrum shaft 10 so as to be rotatable (swingable). The driving coil 12 can move in a gap between the flat permanent magnets 8 and 9. Yes, by energizing the drive coil 12, a driving force for rotating the carriage arm 11 is generated by the interaction with the magnetic flux in the gap between the permanent magnets 8 and 9. The opposite side of the carriage arm 11 from the drive coil mounting side is a magnetic head mounting end 11a as a driven body.

  The auxiliary yoke parts 6, 7 are provided so as to extend in the thickness direction of the permanent magnets 8, 9 substantially perpendicularly from the arm drawer side periphery of the plate-like yoke parts 2, 3. In this case, the auxiliary yoke parts 6 and 7 are continuously formed along the peripheral edge of the arm drawer side, and the length (height) extending from the opposing surfaces of the plate-like yoke parts 2 and 3 of the auxiliary yoke parts 6 and 7 is a permanent magnet. It is set larger than the thickness of 8,9. Further, the thickness of the portion of the carriage arm 11 facing the auxiliary yoke portions 6 and 7 is thinner than the thickness of the driving coil 12, and the extension length of the auxiliary yoke portions 6 and 7 is set so as to cover the driving coil 12. Has been.

  The gap D between the side surfaces of the permanent magnets 8 and 9 and the auxiliary yoke portions 6 and 7 is preferably narrow from the viewpoint of miniaturization, but the auxiliary yoke portions 6 and 7 are in direct contact with the side surfaces of the permanent magnets 8 and 9. Then, since the closed circuit is constituted only by the side surface of the permanent magnet 8 and the auxiliary yoke portion 6 or the side surface of the permanent magnet 9 and the auxiliary yoke portion 7, it is not preferable.

  According to the first embodiment, the following effects can be obtained.

(1) Auxiliary yoke portions 6 and 7 extending in the thickness direction of the permanent magnets 8 and 9 on the arm drawing side peripheral edges of the pair of plate-like yoke portions 2 and 3 are substantially opposite to the opposing surfaces of the plate-like yoke portions 2 and 3. The gap between the auxiliary yoke parts 6 and 7 can be sufficiently narrowed. As a result, the magnetic circuit can be substantially terminated by the pair of plate-like yoke portions 2 and 3 and the auxiliary yoke portions 6 and 7, and has occurred when the auxiliary yoke portions 6 and 7 are not provided in FIG. The flow of the magnetic flux of the magnetic flux line φ can be prevented. Therefore, the magnetic flux leakage toward the drawing side of the carriage arm 11 to which the driving coil 12 is attached, that is, the direction of the magnetic head as the driven body can be sufficiently reduced, and the magnetic head mounting at the tip position of the carriage arm 11 can be reduced. The magnetic field due to the leakage magnetic flux with respect to the end portion 11a can be made sufficiently small so as not to adversely affect the recording and reproduction of the magnetic head. In addition, the influence of leakage magnetic flux on the hard disk as a recording medium can be reduced. As a result, it is possible to prevent malfunctions in the recorded information (erroneous recording, erroneous erasure, etc.).

(2) Since a magnetic circuit for returning leakage magnetic flux from one auxiliary yoke portion 6 and the plate-like yoke portion 2 to the other auxiliary yoke portion 7 and the plate-like yoke portion 3 is assembled, the original magnetism of the permanent magnets 8 and 9 is established. The characteristic effectively acts on the driving coil 12, and the magnetic head can be driven at high speed.

(3) The length (height) extending from the opposing surfaces of the plate-like yoke parts 2 and 3 of the auxiliary yoke parts 6 and 7 is larger than the thickness of the permanent magnets 8 and 9, and the auxiliary yoke part 6 of the carriage arm 11. , 7 is thinner than the drive coil 12 and the extension length of the auxiliary yoke portions 6, 7 is set so as to cover the drive coil 12. The leakage magnetic flux toward the extraction side (magnetic head direction) can be further reduced.

  FIG. 4 shows a second embodiment of the present invention. In this figure, the auxiliary yoke parts 16 and 17 are provided so as to incline slightly inward from the arm drawer side periphery of the plate-like yoke parts 2 and 3 and extend in the thickness direction of the permanent magnets 8 and 9. In this case, the length in the vertical direction extending from the opposing surfaces of the plate-like yoke parts 2 and 3 of the auxiliary yoke parts 16 and 17 is set to be larger than the thickness (height) of the permanent magnets 8 and 9. The thickness of the portion of the carriage arm 11 facing the auxiliary yoke portions 16 and 17 is smaller than the thickness of the driving coil 12, and the extension length of the auxiliary yoke portions 16 and 17 is set so as to cover the driving coil 12. Has been.

  Other configurations are the same as those of the first embodiment described above, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  In the second embodiment, since the auxiliary yoke parts 16 and 17 are inclined slightly inward from the arm drawer side peripheral edge of the plate-like yoke parts 2 and 3, the space between the auxiliary yoke parts 16 and 17 is the arm drawer. The distance between the auxiliary yoke portions 16 and 17 where the leakage magnetic flux leaks and the magnetic head mounting end portion 11a of the carriage arm 11 can be increased so that the leakage magnetic flux can be further increased. It is effective for reduction.

  FIG. 5 shows a third embodiment of the present invention. In this figure, the auxiliary yoke portions 26 and 27 are provided so as to rise substantially vertically from the inner side of the arm drawer side periphery of the plate-like yoke portions 2 and 3 and extend in the thickness direction of the permanent magnets 8 and 9. . In this case, the length (height) extending from the opposing surfaces of the plate-like yoke portions 2 and 3 of the auxiliary yoke portions 26 and 27 is set larger than the thickness of the permanent magnets 8 and 9. Further, the thickness of the portion of the carriage arm 11 facing the auxiliary yoke portions 26 and 27 is smaller than the thickness of the driving coil 12, and the extension length of the auxiliary yoke portions 26 and 27 is set so as to cover the driving coil 12. Has been.

  Other configurations are the same as those of the first embodiment described above, and the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  In the third embodiment, since the auxiliary yoke portions 26 and 27 are raised from the inner position of the plate-like yoke portions 2 and 3 from the peripheral edge of the arm drawing side, the space between the auxiliary yoke portions 26 and 27 where the leakage magnetic flux leaks. The space between the auxiliary yoke portions 26 and 27 and the magnetic head mounting end portion 11a of the carriage arm 11 can be increased, and the magnetic head mounting end portion 11a can be increased. This is effective in further reducing the magnetic field due to the leakage magnetic flux.

  The auxiliary yoke portion may be formed integrally with a soft magnetic material such as an iron plate by bending the plate-like yoke portion during pressing, or an auxiliary yoke portion that is a separate component from the plate-like yoke portion. The plate-like yoke portion may be connected and integrated by welding or the like. Further, the auxiliary yoke portion may be divided (non-continuously) instead of being continuously provided along the arm drawer side periphery.

In order to verify the effect of the auxiliary yoke portion shown in each of the above embodiments, there is no auxiliary yoke portion at the side edge of the upper and lower plate-shaped yoke portions (permanent magnet fixed to the opposing surface) as shown in FIG. And a magnetic flux density at the measurement points P1, P2, and P3 in FIG. 7 are simulated by preparing an auxiliary yoke portion on the side edges of the upper and lower plate-like yoke portions as shown in FIG. (Unit: 10 ⁻⁴ T = Gauss). The results are shown in Table 1 below.

In Table 1, the height Z (mm) is a height with reference to the bottom surface (outer surface) of the lower plate-like yoke portion at each measurement point P1, P2, P3. In FIG. 7, the rotation center C of the hard disk is a position 33 mm away from the side edge of the plate-shaped yoke portion, and the measurement point P1 is on the side of the plate-shaped yoke portion on the circumference with a radius of 30.9 mm from the rotation center C. The positions P2 and P3 that are approximately 2 mm away from the edge are slightly shifted from P1 on the same circumference.

  From the measurement results of Table 1, a good effect of reducing the leakage magnetic flux is obtained at a particularly important height Z = 2 to 2.5 mm with respect to the yoke total height of 5 mm.

  In each of the above embodiments, a magnetic circuit configuration having a pair of opposing plate-like yoke portions and a flat plate-like permanent magnet fixed to each of the opposing surfaces of the pair of plate-like yoke portions has been shown. Any magnetic circuit configuration in which a flat permanent magnet is fixed to at least one of the opposing surfaces of the pair of plate-like yoke portions may be used.

  Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.

1 is a front sectional view showing a first embodiment of a VCM apparatus according to the present invention. FIG. FIG. 4 is a perspective view showing a yoke structure in the first embodiment. It is a front sectional view showing Embodiment 2 of the present invention. It is a front sectional view showing Embodiment 3 of the present invention. FIG. 4 is a perspective view showing a yoke structure for verifying the effect of the auxiliary yoke portion, in which (A) shows the case without the auxiliary yoke portion and (B) shows the case with the auxiliary yoke portion. It is a top view which shows the measurement point of the leakage magnetic flux when it is set as the yoke structure of FIG. 6 (A), (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Yoke structure 2, 3 Plate-shaped yoke part 4 Back yoke part 5 Side yoke part 6, 7, 16, 17, 26, 27 Auxiliary yoke part 8, 9 Flat permanent magnet 10 Supporting shaft 11 Carriage arm 12 Driving coil

Claims (5)

A pair of opposed plate-shaped yoke portions, a flat plate-like permanent magnet fixed to at least one of the opposed surfaces of the plate-shaped yoke portion, and a driving coil movably disposed between the opposed surfaces of the plate-shaped yoke portion And a VCM device comprising an arm to which the driving coil is attached,
An auxiliary yoke portion extending in the thickness direction of the permanent magnet is provided at or near the arm drawer side periphery of the plate-like yoke portion.   2. The VCM device according to claim 1, wherein a length of the auxiliary yoke portion extending from an opposing surface of the plate-like yoke portion is longer than a thickness of the permanent magnet.   The thickness of the arm at the portion facing the auxiliary yoke portion is thinner than the thickness of the driving coil, and the extension length of the auxiliary yoke portion is set so as to cover the driving coil. The VCM apparatus according to claim 1 or 2.   4. The VCM apparatus according to claim 1, wherein the auxiliary yoke portion is located on an inner side of an arm drawer side periphery of the plate-like yoke portion.   The VCM device according to claim 1, wherein the auxiliary yoke portion is not in contact with a side surface of the permanent magnet.

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