JP2002025088A - Driving device for objective lens and disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that increase in lens inclination and power consumption occurs in an objective lens drive device when the dimensional error and assembling error of a part, subsidence due to self-weight of a moving part or the like are generated because the moving part is not disposed at a desired location. SOLUTION: In the objective lens drive device, a solid body having ferromagnetism is attached to a part of a coil or a lens holder disposed in a magnetic gap constituted of a magnetic circuit for objective lens drive device so that the center of its focusing direction and tracking direction almost coincide with the center of the focusing direction and tracking direction of the joint of a elastic supporting member and the lens holder about the focusing direction and tracking direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device and a disk device used for a reproducing device for an optical disk, a magneto-optical disk, and the like.

[0002]

2. Description of the Related Art Conventionally, a biaxial orthogonal translation type objective lens driving device in which a movable portion for holding an objective lens is supported by an elastic supporting member has been widely used. This configuration has the advantage that the device can be manufactured compactly and inexpensively, but because the rigidity of the elastic support member around the extending direction is low,
When a moment around this occurs, there is a problem that the objective lens is easily tilted.

When the objective lens driving device is disposed horizontally, the movable portion of the objective lens driving device sinks downward in the focusing direction due to its own weight. Therefore, an offset current for canceling the sinking of the own weight is supplied to the focusing coil. It is necessary to shed. Therefore, when the objective lens driving device is arranged horizontally, there is a problem that the power consumption of the objective lens driving device increases.

To solve the latter problem, Japanese Patent Application Laid-Open No. 10-162386 discloses that the distance from the disk surface to the tip of the objective lens when the movable portion is settled under its own weight is defined as the working distance (WD) of the objective lens. By making them coincide, an increase in power consumption in horizontal placement is suppressed.

[0005]

FIG. 5 is an external perspective view showing an example of a two-axis orthogonal translation type objective lens driving device. The objective lens driving device 1 is mounted on a slider (not shown) which is parallel to the information surface of an optical information recording medium such as a disk and is movable in the radial direction (tracking direction 14). An optical device (not shown) is arranged on the slider, and forms an optical head together with the objective lens driving device 1.

The lens holder 3 is assembled with an objective lens 2, a focusing coil 4 (hereinafter referred to as an AF coil), and a tracking coil 5 (hereinafter referred to as a TR coil) to form a movable portion 18. FIG. 6 is an external perspective view of the movable section 18 of the objective lens driving device.

The movable section 18 is supported by four elastic support members 11, whereby the movable section 18 maintains its posture, and moves in a focusing direction 15 (hereinafter referred to as an AF direction) and a tracking direction 14. (Hereinafter referred to as TR direction).

The fixed part substrate 1 is attached to the yoke 7 by screws 12.
Fixed part holder 9 with 0 is assembled,
The other end of the elastic support member 11 is fixed to the fixed part substrate 10.

Further, two magnets 8 and an upper yoke 6 are assembled to the yoke 7, and constitute a magnetic circuit of the present driving device. AF coil 4 and TR coil 5
A part thereof is arranged so as to be present in the magnetic gap of the magnetic circuit, and the current is supplied to both coils to drive the movable portion 18 in the AF direction 15 and the TR direction 14.

Note that a viscoelastic material 13 is provided on the fixed part holder 9, thereby reducing unnecessary vibration of the elastic support member 11.

FIG. 7 is an external perspective view showing an example of a disk device on which the objective lens driving device 1 is mounted. The disk device 20 is provided with a disk 21 placed on a disk tray 23.
Is sent into (or out of) the device by a disk loading mechanism (not shown). Further, the disk 21 sent into the apparatus is mounted on a turntable 22 integrally formed with a rotation shaft of a spindle motor, and is suction-fixed by a clamper 24 attached to a clamper holder 25.

The disk 21 is rotated by the spindle motor, and the information recorded on the disk 21 is read out.
This is performed by an optical head 29 mounted on the unit mechanical chassis 26. The optical head 29 mounted on the slider that can move roughly in the loading direction (TR direction) 14 of the disc tray 23 has the optical components and the objective lens driving device 1 mounted thereon as described above.

The unit mechanical chassis 26 is attached to a mechanical base 27 via vibration isolating legs 28 made of an elastic member. Further, a bottom cover 30 and a top cover 31 are attached to the entire apparatus.

The above is the configuration of the objective lens driving device and the disk device.

FIG. 8 is a plan view schematically showing the positional relationship between the magnet 8 and the movable portion 18 in the objective lens driving device 1. Here, the positional relationship in a state where no current is flowing through the coil is shown. The center of the magnet 8 in the TR direction 14 is the center of the magnetic circuit 42, and the center of the movable portion 18 in the TR direction 14 (= the center of the AF coil 4). Is the center 41 of the movable part.

Normally, when the objective lens driving device is assembled as designed, the center 42 of the magnetic circuit coincides with the center 41 of the movable portion in the TR direction 14 as shown in FIG. However, in actuality, there are dimensional errors and assembly errors of parts, and as shown in FIGS. 8B and 8C, the center of the magnetic circuit 42 is , Left or right.

FIGS. 9A to 9C are diagrams schematically showing the movable portion 18 of the elastic support member 11 as viewed from the extending direction 16. However, the positional relationship between the movable part 18 and the magnetic circuit corresponds to FIGS. 8A to 8C, respectively. Here, the center of the support of the movable portion 18, that is, the center of the four junctions between the movable portion 18 and the elastic support member 11 is C, the thrust center of the AF coil, that is,
The action point of the combined vector of all thrusts in the AF direction generated in the AF coil is described as PAF. The combined thrust is A
F thrust: described as FAF.

In the same figure, the middle stage shows a case where no current is flowing through the AF coil 4, that is, a case where the movable portion 18 is at the neutral position. In the upper part of FIG. 9, when a current flows only in the AF coil and the movable part 18 is displaced above the neutral position in the AF direction 15, the lower part displaces the movable part 18 below the neutral position in the AF direction 15. Each case is shown.

As shown in FIG. 8A, the magnetic circuit center 42
When the center of the thrust of the AF coil: PAF coincides with the center of support of the movable part: C in the TR direction 14, the movable part 18 is displaced in the AF direction 15. Even when the elastic support member has a moment about 16 in the rolling direction:
M does not occur.

On the other hand, as shown in FIG. 8B, when the magnetic circuit center 42 is displaced to the left from the movable part center 41, and when the movable part 18 is displaced upward in the AF direction 15, Generates a clockwise moment (M :-) in the movable part. When the movable part 18 is displaced downward in the AF direction 15, a counterclockwise moment (M: +) is generated in the movable part.

As shown in FIG. 8C, the magnetic circuit center 42
Is shifted to the right side of the center 41 of the movable portion, a positive moment is generated when displaced upward, and a negative moment is generated when displaced downward.

The above moment is at the center of the magnetic circuit.
The larger the amount of deviation between the center 42 of the movable unit and the center 41 of the movable unit, the larger the amount, and the larger the amount of displacement of the movable unit 18 in the AF direction 15, the larger the amount.

As explained above, the magnetic circuit center 42 and the movable part center 41
When there is a deviation between the movable part 18 and the elastic support member
11 moments in the direction of the rolled material 16 are generated. As described above, in the objective lens driving device shown in FIG. 5, since the rigidity of the elastic support member 11 around the extending direction 16 is low, there is a problem that a large lens tilt occurs when the above-mentioned moment is generated.

FIGS. 10 (a) and 10 (b) show a personal computer 40 (hereinafter referred to as PC) on which the disk device 20 is mounted.
It is the schematic which showed the arrangement | positioning attitude | position. On the other hand, FIG.
(d) is a schematic diagram showing the posture of the movable part 18 and the fixed part of the objective lens driving device 1 when the PC is arranged as shown in (a) and (b). However, the arrow 17 indicates the vertical direction. Normally, desktop PCs are (a)
It is used horizontally as shown in (b) or vertically as shown in (b). When the PC is placed horizontally, the objective lens driving device 1 is also placed horizontally as shown in (c). In this case, since the AF direction 15 matches the vertical direction 17, the movable unit 18
Sinks downward in the AF direction as shown in FIG. 10 (c).
In the figure, δ is the amount of settlement of the movable portion 18.

On the other hand, when the PC is placed vertically,
As shown in (d), the movable portion 18 is suspended (or lifted) by the elastic support member 11, so that the movable portion 18 does not sink in the AF direction 15 due to its own weight (vertical direction). The settlement is almost zero).

As described above, the squat amount of the movable portion 18 changes depending on the arrangement and posture of the objective lens driving device 1.

In the above publication, when the objective lens driving device is used in a horizontal position, that is, when the movable portion 18 is in the AF direction 15
When it sinks down, the distance from the disk surface to the front end of the objective lens is configured to match the working distance of the objective lens. Therefore, when the objective lens driving device is used horizontally, the power consumption does not increase.
However, when the objective lens driving device is used in a vertical position, since the movable portion 18 does not sink in the AF direction,
There is a problem that power consumption increases.

The present invention has been made in view of the above problems, and has almost the same configuration as that of the conventional device, that is,
It is an object of the present invention to provide an objective lens driving device and a disk device in which an increase in lens tilt is reduced and an increase in power consumption is reduced while maintaining small size and low cost.

[0029]

The increase in the lens inclination and the increase in the power consumption described above are caused by the fact that the position of the movable portion 18 is different from the design position (desired position) due to various causes. Has occurred.

In order to solve the above problems, an objective lens driving device according to the present invention provides an objective lens for condensing a beam generated from a laser source on an information recording surface of a disk, and a lens for holding the objective lens. A holder, a focusing coil provided for driving the objective lens in the focusing direction, a tracking coil provided for driving in the tracking direction, a magnetic circuit including a magnetic yoke and a magnet, and the lens holder are supported. A plurality of elastic support members, and a fixing portion for fixing the plurality of elastic support members, and a solid having ferromagnetism in a part of the coil or the lens holder disposed in a magnetic gap of the magnetic circuit. Attach.

Further, the center of the focusing direction and the tracking direction of the ferromagnetic solid is defined as the center of the joining point between the elastic support member and the lens holder in the focusing direction and the tracking direction, and the focusing direction and the tracking direction. Attached to the coil or the lens holder so that they substantially match.

As the solid having ferromagnetism, a solid containing iron as a main component is used.

Further, a disk device having the above-mentioned objective lens driving device is mounted.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail.

The objective lens driving device of this embodiment is shown in FIG.
The configuration is almost the same as that of the example shown in FIG. 6, and the disk device of this embodiment has almost the same configuration as the example shown in FIG. Therefore, here, the same parts as those in FIGS. 5 to 7 are denoted by the same reference numerals, and only different parts are illustrated and described.

Hereinafter, the objective lens driving device of the present invention will be described.

FIG. 1 is an external perspective view showing a movable portion 51 of the objective lens driving device of the present invention. The solid 53 having ferromagnetism is mounted on the AF coil 4 of the movable portion 51 of the objective lens driving device of the present invention. The ferromagnetic solid 53 is disposed in a magnetic gap in the magnetic circuit of the objective lens driving device, that is, between the opposing magnets, as apparent from FIG. The centers of the ferromagnetic solid 53 in the AF direction 15 and the TR direction 16 are arranged so as to be on the center line 19.

Next, the center line 19 will be described with reference to FIG.
FIG. 2 is an external perspective view of the movable section 51 of the objective lens driving device of the present invention when viewed from a direction different from FIG. The fixed points of the elastic support member in the main movable portion 51 are four points 52 in the figure. The center position of the fixed point 52 in the AF direction 15 and the TR direction 14 is the support center C of the movable portion 18. In the figure,
The center line 19 is a line passing through the support center C and perpendicular to the AF direction 15 and the TR direction 14. That is, the ferromagnetic solid 19 is mounted such that the center in the AF direction 15 and the TR direction 14 substantially coincides with the support center C of the movable portion 18 in the AF direction and the TR direction.

The effect of attaching the ferromagnetic solid to the movable part will be described below. As described above, the increase in the lens tilt and the increase in power consumption occur because the position of the movable portion 18 in a state where no current is flowing through the coil is different from the design position (desired position) due to various causes. . Therefore, in order to reduce these, the position of the movable part 18 matches the design position (desired position).
Alternatively, the structure may be such that it is closer to the design position (desired position).

FIG. 11 is a schematic diagram illustrating a magnetic gap in the objective lens driving device 1 shown in FIG.
The figure shows a case where a part of the magnetic circuit in the objective lens driving device 1 is viewed from the TR direction 14,
The space between 8 is the magnetic gap 47. In the present objective lens driving device 1, a part of an AF coil and a TR coil (not shown) are arranged in a magnetic gap.

FIG. 12 is a schematic diagram for explaining the magnetic flux density distribution in the magnetic gap in the objective lens driving device 1 shown in FIG. AF direction 15 in the magnetic gap
Graph shows the relationship between the position of
The graph 46 shows the relationship between the position in the TR direction 14 and the magnitude of the magnetic flux density. Here, among the magnetic flux densities, the magnitude of 16 components in the direction of the elongation of the elastic support member is shown. Also, the magnet 8 in the AF direction 15 and the TR direction 14
Is represented by O.

As shown in the graph 45, in the AF direction 15, the magnetic flux density becomes maximum at the center O of the magnet 8;
The center of the magnet 8: It becomes smaller as it moves up and down from O. Similarly, also in the TR direction 14, the magnetic flux density becomes maximum at the center O of the magnet 8, and decreases as the distance from the center O of the magnet 8 to the left and right increases.

Now, assuming that a solid having ferromagnetism with a constraint that it can move only in the AF direction 15 and the TR direction 14 is disposed in the magnetic gap, as apparent from the above magnetic flux density distribution, A thrust toward the center of the magnet is generated in the ferromagnetic solid, and when there is no resistance such as friction, the ferromagnetic solid moves to a position coinciding with the center of the magnet.

Similarly, when a ferromagnetic solid is attached to a portion of the movable portion of the objective lens driving device which is disposed in the magnetic gap, a thrust toward the center of the magnet is generated in the ferromagnetic solid. I do. Therefore, the A of this ferromagnetic solid
The centers in the F direction and the TR direction substantially coincide with the center in the AF direction and the TR direction (the support center of the movable portion: C) at the junction between the elastic support member and the lens holder in the AF direction and the TR direction. If a ferromagnetic solid is attached, the center of support of the movable part: C will be closer to the center of the magnet: O. In other words, it is possible to reduce the deviation between the center of support of the movable part: C and the center of the magnet: O due to dimensional errors of components, assembly errors, the arrangement posture of the objective lens driving device, and the like. , Lens tilt and increase in power consumption can be suppressed.

The ferromagnetic solid 53 in this embodiment is an iron alloy, and its size is 1.5 mm in length, 1.5 mm in width, and 0.3 mm in thickness. Note that the shape of the ferromagnetic solid 53 does not need to be a rectangular parallelepiped, but may be a cylindrical shape or the like. The ferromagnetic solid 53 is preferably made of a material containing iron as a main component and having a high saturation magnetic flux density and a low cost.

Next, another embodiment according to the present invention will be described.

FIG. 3 is an external perspective view of an objective lens driving device of a type having magnetic circuits on both sides of a lens. However, in FIG. 3, the upper yoke 6 is shown away from the main body to make it easier to see the inside of the apparatus. As shown in the figure, the objective lens driving device 55 includes an objective lens 2, a lens holder 3, an AF coil 4, a TR coil 5, a yoke 7, an upper yoke 6, a magnet 8, a fixed part holder 9, a fixed part substrate 10, , 4
The elastic support member 11 includes a viscoelastic material 13. The function of each unit is the same as that of the objective lens driving device 1 shown in FIG.
The function of each part is the same.

FIG. 4 is an external perspective view showing the movable portion 54 of the objective lens driving device 55 of the present invention. Also in the objective lens driving device 55 of the present invention, the AF wound around the lens holder 3
A solid 53 having ferromagnetism is mounted on the coil 4. However, in the objective lens driving device 55 of the present invention, since the magnetic gap exists on both sides of the lens, two
A plurality of ferromagnetic solids 53 (the other magnetic solid is not shown) are attached. In the objective lens driving device 55,
The space between the magnet 8 and the yoke 7 is a magnetic gap.

The center of the ferromagnetic solid 53 in the AF direction 15 and the TR direction 14 is the center of the junction between the elastic support member 11 and the lens holder 3 in the AF and TR directions (support center of the movable portion: C); They are attached so that they substantially coincide in the AF direction and the TR direction.

As a result, the position of the movable portion in a state where no current flows through the coil is corrected, and as a result, an increase in lens tilt and an increase in power consumption are suppressed.

As described above, the objective lens driving device of the present invention has almost the same configuration as that of the conventional objective lens driving device. Therefore, the objective lens driving device is small and inexpensive, and the increase in lens tilt and the increase in power consumption are suppressed. Can be Further, the disk device of the present invention on which the objective lens driving device of the present invention is mounted can realize low cost, low power consumption, and good jitter characteristics.

The same applies to an objective lens system in which an optical element such as a wave plate and a dichroic filter is added to the objective lens instead of the objective lens described in the present embodiment.

Further, the disk device of the present invention is a CD-ROM, a DVD,
The present invention is not limited to disk devices such as ROM and DVD-RAM, but is also applied to magneto-optical disk devices and the like.

[0054]

As described above, in the objective lens driving device of the present invention, an increase in lens tilt and an increase in power consumption caused by dimensional errors of components, subsidence of a movable portion under its own weight, and the like can be achieved. It can be effectively suppressed. Further, the configuration of the present objective lens driving device is almost the same as the configuration of the conventional device, so that the present device can be realized at a small size and at low cost.

Further, in the disk device of the present invention on which the objective lens driving device of the present invention is mounted, a device with good jitter characteristics and low power consumption can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a movable section of the objective lens driving device of the present invention.

FIG. 2 is a schematic view showing an embodiment of a movable portion of the objective lens driving device of the present invention.

FIG. 3 is a schematic view showing an embodiment of the objective lens driving device of the present invention.

FIG. 4 is a schematic view showing an embodiment of a movable portion of the objective lens driving device of the present invention.

FIG. 5 is a schematic perspective view showing an example of a two-axis orthogonal translation type objective lens driving device.

FIG. 6 is a schematic perspective view showing an example of a movable section of the objective lens driving device.

FIG. 7 is a schematic perspective view showing an example of a disk device.

FIG. 8 is a schematic plan view showing a positional relationship between a magnetic circuit and a movable part.

FIG. 9 is a schematic diagram illustrating a moment generated when the movable unit is displaced in the AF direction.

FIG. 10 is a schematic diagram showing the arrangement posture of a personal computer equipped with a disk device and an objective lens driving device.

FIG. 11 is a schematic diagram illustrating a magnetic gap.

FIG. 12 is a schematic diagram showing a magnetic flux density distribution in a magnetic gap.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Object lens drive device, 2 ... Object lens, 3 ... Lens holder, 4 ... Focusing coil, 5 ... Tracking coil, 6 ... Upper yoke, 7 ... Yoke, 8 ... Magnet, 9
... Fixed part holder, 10 ... Fixed part substrate, 11 ... Elastic support member, 12 ... Screw, 13 ... Viscoelastic material, 14 ... Tracking direction, 15 ... Focusing direction, 16 ... Extension direction of elastic support member, 17 ... Vertical Direction, 18 movable part, 19 center line of ferromagnetic solid, 20 disk device, 21 disk, 22 turntable, 23 disk tray, 2
4: Clamper, 25: Clamper holder, 26: Unit mechanical chassis, 27: Mechanical base, 28: Anti-vibration leg, 29: Optical head, 30: Bottom cover, 31: Top cover, 40: Personal computer, 41: Center of movable part , 42: magnetic circuit center, 43: AF direction axis, 4
4 ... TR axis, 45 ... AF direction magnetic flux density distribution, 46 ...
TR direction magnetic flux density distribution, 47: magnetic gap, 51: movable part, 52: junction of elastic support members, 53: ferromagnetic solid, 54: movable part, 55: objective lens driving device.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D118 AA08 AA12 AA15 BA01 DC03 EA02 EB13 ED03 FA29 FA46 5D119 AA36 AA37 BA01 JA43 JC06 JC07

Claims (6)

[Claims] 1. An objective lens for converging a beam generated from a laser source on an information recording surface of a disc, a lens holder for holding the objective lens, and the lens holder for driving the objective lens in a focusing direction. A focusing coil provided in the, a tracking coil provided in the lens holder for driving in the tracking direction, and a magnetic circuit including a magnetic yoke and a magnet, and a plurality of elastic support members for supporting the lens holder, And a fixing portion for fixing the plurality of elastic support members, wherein a solid having ferromagnetism is attached to a part of the coil or the lens holder arranged in a magnetic gap of the magnetic circuit. Objective lens drive. 2. The ferromagnetic solid attached to the coil or the lens holder has a center in a focusing direction and a tracking direction, and a center in a focusing point and a tracking point at a junction between the elastic support member and the lens holder. 2. The objective lens driving device according to claim 1, wherein the center of the direction substantially coincides with the focusing direction and the tracking direction. 3. The objective lens driving device according to claim 1, wherein the solid having ferromagnetism contains iron as a main component. 4. A motor for rotating a disk, a laser source for generating a beam, a lens for condensing the beam on an information recording surface of the disk, a lens holder for holding the lens, and driving the objective lens in a focusing direction. A focusing coil provided on the lens holder, a tracking coil provided on the lens holder for driving in a tracking direction, a magnetic circuit including a magnetic yoke and a magnet, and a plurality of elastic supports for supporting the lens holder. A member, an optical head including a fixing portion for fixing the plurality of elastic support members, and a slider for moving the optical head in a radial direction of the disk, wherein the coil or the coil disposed in a magnetic gap of the magnetic circuit. Attach ferromagnetic solid to part of the lens holder Disk reproducing apparatus, characterized in that the. 5. The solid having ferromagnetism attached to the coil or the lens holder has a center in a focusing direction and a tracking direction, and a focusing direction and a tracking point at a junction between the elastic support member and the lens holder. 5. The disk device according to claim 4, wherein the center of the direction substantially coincides with the focusing direction and the tracking direction. 6. The disk device according to claim 4, wherein the solid having ferromagnetism contains iron as a main component.