JPS63282936A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To expand the data area of a disk by making a coil bobbin to provide an objective lens into a square, arranging an inner yoke side at the recessed part on a long side and positioning a focus coil and a tracking coil at a cavity between the inner yoke side and an outer yoke side. CONSTITUTION:The device has a moving part composed of a coil bobbin 1, an objective lens 6, a focus coil 7 and a tracking coil 8 and a fixing part composed of a base 10, an outer yoke 10a, an inner yoke 10b and a permanent magnet 9, and the inner yoke 10b is arranged at a recessed part 1a of the coil bobbin 1 and at the cavity between the inner yoke 10b and the outer yoke 10a, the focus coil 7 and the tracking coil 8 are positioned. Consequently, the outer shape dimension of the direction along the short side of the coil bobbin 1 can be minimized, the magnetic flux density of a magnetic circuit is enlarged by the yoke including the inner yoke 10b and the outer yoke 10a oppositely arranged and as the result, a large focus driving force and a tracking turning movement can be obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an objective lens drive device for an optical head that is incorporated into an optical disk device or a magneto-optical disk device, and in particular, the invention relates to an objective lens drive device for an optical head that is incorporated into an optical disk device or a magneto-optical disk device. It is made to be moisturized.

[Conventional technology]

As a first conventional example, an objective lens drive device used in an optical head of an optical disk device will be described with reference to a plan view in FIG. 5 and a side sectional view in FIG. This conventional example mainly consists of an objective lens holding section and a yoke section. The objective lens holder includes an objective lens holder 21, a bearing 22 made of a non-magnetic material provided at the center of the objective lens holder 21, and wound around the outer peripheral surface of a cylindrical portion 21b of the objective lens holder 21. It consists of a focus coil 27 and four approximately rectangularly wound tracking coils 28A to 28D bonded to the outer surface of the focus coil 27 in a layered manner. Note that the objective lens 6 is inserted through the lens frame 5 at an intermediate position from the center to the outer circumference of the end portion 21a of the objective lens holder 21.
is provided, the optical axis of which is parallel to the axis of the bearing 22. Further, the yoke portion is provided on the inner circumferential surface of the end portion of the outer yoke 30a on both sides of the yoke 30 made of a high magnetic permeability material and integrally formed from a pair of outer yokes 10a, a pair of inner yokes 30b, and a base yoke 30c. A permanent magnet 29 is provided, and a support shaft 24 made of a magnetic material is provided at the center of the yoke 30.
, an elastic connector 33 provided on the inner base surface 30f of the yoke 30 via a mounting plate 32, and a connector 35. In FIG. 6, at the center of the inner base surface 30f of the yoke 30, a buffer stand 34 made of a ring-shaped elastic material, such as a rubber material, is provided which fits onto the support shaft 24. A connecting body 33 is provided. Now,
The elastic connector 33 connects the yoke 30 and the objective lens holder 21.
are connected. This elastic connector 33 is made up of a flat ring-shaped rubber plate having a rectangular peripheral edge with a narrow width, and protrusions integrally connected to the center of each of its opposing long sides, one of the protrusions being It is fixed to the mounting plate 32, and the other protruding piece is provided with a hole, and the objective lens holder 2 is connected to the hole.
A support pin 31 is installed between the inner side of the end portion 21a of 1 and the inner side of the end portion 21a. That is, both ends of the support bottle 31 are fixed to the end portion 21a and the elastic connector 33, respectively. The operation of this conventional example is as follows. Permanent magnet29. Within the magnetic gap between the inner yokes 30b, the permanent magnet 2 is perpendicular to the cylindrical portion 21b of the objective lens holder 21.
9 to the inner yoke 30b, the current flowing in the focus coil 27, that is, the current flowing in the clockwise circumferential direction in FIG. 5, centered on the axis of the support shaft 24, The objective lens holder 21 is electromagnetically driven in a vertically downward direction of the plane of the paper, which is the focus direction. Conversely, when a current flows counterclockwise through the focus coil 27, the objective lens holder 21 is electromagnetically driven vertically upward from the plane of the paper. This is how the focus adjustment operation is performed. Furthermore, in this case, tracking coils 28A to 28D perform trunking drive as follows. The objective lens holder 21 is moved along the axis of the support shaft 24, which corresponds to the tracking direction, by the current flowing in the axial direction of the support shaft 24 in one side of each of the tracking coils 28A to 28D located in the magnetic gap described above. It is electromagnetically driven in the direction of rotation. In addition, the elastic connecting body 33 determines its position in balance with the electromagnetic driving force or electromagnetic driving moment in the focusing direction or tracking direction that acts on the objective lens holder 21, and when these forces are released. This is a type of centering mechanism that has the function of automatically returning the objective lens holder 21 to the neutral position. Note that when the focus driving force is released, that is, becomes zero, the lower end surface of the bearing 22 comes into contact with the upper surface of the buffer table 34 due to the weight of the objective lens holder 21, and the impact at that time is absorbed and alleviated. Ru. Further, a second conventional example will be explained with reference to FIGS. 7 and 8. Note that FIG. 7 is a plan view thereof, and FIG. 8 is a side sectional view thereof. In these figures, reference numeral 41 indicates a substantially rectangular coil bobbin, and reference numeral 42 indicates a bearing provided at the center of the coil bobbin 41. Further, an objective lens 6 is provided on the coil bobbin 41 at an intermediate portion between the center and the outer periphery via the lens frame 5, and a focus coil 47 is wound around the outer periphery, and tracking coils 48A and 48B are further wound on the outer periphery of the coil bobbin 41.
, 48C, and 48D are provided across four ridgeline portions of the coil bobbin 41, respectively. On the other hand, 50 is a base, which is a rectangular plate-like member made of a magnetic material. Reference numeral 50a denotes an outer yoke, which is a thick circular arc-shaped member that protrudes from both ends of the base 50 in the thickness direction of the base 50.
It is integrated with 0. Reference numeral 49 denotes a thick-walled arc-shaped permanent magnet, which is fixed to the inner periphery of the outer yoke 50a. Note that in this conventional example, unlike the first conventional example, the focus coil 47
．． The tracking coils 48A to 48D are connected to the outer yoke 50a.
There is no inner yoke that is sandwiched between the two. This is because the objective lens 6 is provided near the outer periphery of one short side of the coil bobbin 41, and there is no space for providing an inner yoke. A support shaft 44 is erected at the center of the base 50, and a bearing 42 of a coil bobbin 41 is fitted onto the support shaft 44 so as to be rotatable around the center line and movable in the direction of the center line. The coil bobbin 41 and the base 50 are connected by engaging a support pin 51 fixed to the lower surface of the former with an elastic connector 33 fixed to the upper surface of the latter. . The operation of this second conventional example is the same as that of the first conventional example, so a description thereof will be omitted.

[Problems to be solved by the invention]

As explained above, in the first conventional example, the coil bobbin around which the focus coil and the tracking coil are wound is circular, and the objective lens is arranged on the radius of the coil bobbin, so the radius inevitably becomes large. Therefore, even if the optical head is brought close to the disk drive motor until it comes into contact with the disk drive motor, the distance between the center of the objective lens and the center of the disk increases, resulting in a problem in that the data area of the disk is narrowed. Furthermore, in the second conventional example, since the coil bobbin is rectangular, it is dimensionally small in the short side direction, and the condition that the data area can be expanded is satisfied. However, because the inner yoke cannot be installed structurally, the magnetic flux density of the magnetic circuit becomes small, resulting in a small focus driving force and tracking rotation moment; therefore, it is susceptible to friction and other effects (good focus control, There is a problem that tracking control cannot be performed.An object of the present invention is to solve the above-mentioned problems of the conventional technology, and to reduce the width of the outer shape of the disk in at least one direction when viewed from the disk axis direction. It is an object of the present invention to provide an objective lens driving device that can expand a data area and provide a large focus driving force and tracking rotation moment.

[Means for Solving the Problems] In order to achieve the above object, the inventive device includes a columnar coil bobbin having a rectangular cross section with a recess on each long side, and the recess formed on the outer periphery of the coil bobbin. a focus coil wound so as to straddle the coil bobbin; a set of two tracking coils wound approximately in a rectangular shape provided on the outer periphery of the focus coil corresponding to each long side of the coil bobbin; a movable part comprising an objective lens provided on the coil bobbin, the optical axis being a straight line parallel to the center line of the coil bobbin and parallel to the long sides of the rectangle by a predetermined distance; a base; and respective movable parts facing each other. It consists of two sets of a rectangular inner yoke and an outer yoke, each set corresponds to each long side of the coil bobbin, and the inner yoke side is located in each recess of the coil bobbin, and A yoke is provided on the base so that a portion of the focus coil and a tracking coil that is installed across the coil bobbin recess is located in the gap between the yokes, and whether the inner yoke or the outer yoke of each of the yokes is a fixing part comprising substantially rectangular permanent magnets provided on opposing surfaces of one side; the coil bobbin is rotatable about its center line with respect to the fixing part; The coil bobbin is supported so as to be movable in the direction of the center line, and currents flowing through the focus coil and the tracking coil apply a rotational moment about the center line and a driving force in the direction of the center line to the coil bobbin, respectively. In an embodiment, the base is integrated with the yoke. In another embodiment, the base is made of a non-magnetic material, and the inner yoke and the outer yoke form a U-shaped yoke that is integrated with the connecting portion thereof. [Function] The coil bobbin is made rectangular, and a recess is provided on each long side of the bobbin.The inner yoke is installed in the recess, and the focus coil and tracking coil are positioned in the gap between the inner yoke and the outer yoke. ■The external dimensions of the coil bobbin in the direction along the short side can be reduced;
■The magnetic flux density of the magnetic circuit is increased by the yokes, which include an inner yoke and an outer yoke (permanent magnets are provided on either of them), which are arranged facing each other, and as a result, a large focus driving force and tracking rotation moment can be obtained. .

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1 is a perspective view thereof, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. 1. In FIG. 1, the objective lens driving device is roughly divided into a movable part and a fixed part. One movable part mainly consists of the coil bobbin 1. It consists of an objective lens 6, a focus coil 7, and a tracking coil 8, and the other fixed part is mainly a base 10. Outer yoke 10a, inner yoke 10b,
and a permanent magnet 9. As for the movable part, 1 is a coil bobbin whose cross section is so-called I-shaped, with rectangular recesses 1a removed from each long side of the rectangular outline. Note that the short side of the cross section is arcuate. Bearing 2 in the center
is provided, and an objective lens 6 is provided via a lens frame 5 at a position near the outer periphery on the short side (see FIG. 3). Also,
A focus coil 7 is wound around the outer periphery of the coil bobbin 1. This focus coil 7 has a recess 1a on each long side.
It takes the form of straddling the . A tracking coil 8 wound in a rectangular shape is laminated and fixed on the surface of each focus coil near each end of the recess 1a, with one side parallel to the center line of the coil bobbin 1. As for the fixed part, a rectangular plate-shaped base 10 made of a magnetic material is used as a base, and an outer yoke 10a and an inner yoke 10b each having a rectangular shape are erected thereon. A pair of outer yokes 10a and inner yokes 10b are arranged to face each other, and a rectangular permanent magnet 9 is fixed to the outer yoke 10a. The inner yoke 10b is located inside the recess 1a of the coil bobbin 1, and the focus coil 7 and the tracking coil 8 are located in the opposing gap between the inner yoke 10b and the permanent magnet 9 (see FIG. 2). Further, a support shaft 4 is erected at the center of the base 10, and the support shaft 4 and the bearing 2 of the coil bobbin 1 are fitted to be rotatable around the axis and movable in the axial direction. A support pin 11 is provided on the lower surface of the coil bobbin 1, and an elastic connector 13 is provided on the upper surface of the base 10, and the tip of the support pin 11 fits into a hole made in the elastic connector 13 (
(See Figure 3). When the coil bobbin 1 rotates relative to the base 10,
Before the focus coil 7 and the tracking coil 8 come into contact with the inner yoke 10b or the permanent magnet 9, the recess 1a
The bottom surface of the inner yoke 10b comes into contact with each opposing ridgeline of the inner yoke 10b. This is a safety structure to prevent damage to the focus coil 7 and tracking coil 8 due to this contact. The basic operation of this objective lens driving device is the same as that already described in the first conventional example. However, in this case, in particular, unlike the first conventional example, the outer dimensions of the coil bobbin in the direction along the short side can be reduced, and unlike the second conventional example, the inner yoke 10b disposed oppositely can be permanently The magnetic flux density of the magnetic circuit is increased by the outer yoke 10a including the magnet 9, and as a result, a large focus driving force and tracking rotation moment can be obtained. Next, another embodiment will be described with reference to FIG. This figure is a dispersed perspective view of the base and yoke parts, and the structure of the base and yoke is different from the previous embodiment. The base 20 is a rectangular plate-like member made of a non-magnetic material such as aluminum, and has a support shaft 24 in the center and carved portions 20a on both sides thereof. In the previous example,
Outer yoke 10a. Outer yoke 21a and inner yoke 2 corresponding to inner yoke 10b
1b forms a U-shaped yoke 21 together with the bottom yoke 21c. In this yoke 21, a rectangular permanent magnet 9 is fixed to the outer yoke 21a side, and is fitted into the carved portion 20a. In this embodiment, the base 20 is made of aluminum, so it is lightweight, and the yoke 21 is made separately from the base 20 as a unit, and has a simple shape, so it is easy to manufacture and is advantageous in terms of cost. It is. of course,
In terms of performance, it is exactly the same as the previous embodiment.

【Effect of the invention】

As described above, in the present invention, the outer dimensions of the coil bobbin in the direction along the short side can be reduced, and the inner yokes are arranged to face each other. The yoke including the outer yoke (one of which is provided with a permanent magnet) increases the magnetic flux density of the magnetic circuit, and as a result, a large focus driving force and tracking rotation moment can be obtained. Therefore, the present invention has the following superior effects compared to the conventional technology. (1) By installing the objective lens drive device so that the straight line that passes through the center of the objective lens and is in equilibrium with the short side of the coil bobbin coincides with the disk radius, the center of the objective lens can be moved without changing the disk drive motor. It can be brought closer to the center of the disk, and the data area of the disk can be expanded accordingly. (2) Also, focus driving force and tracking rotation moment are increased, and good focus control and tracking control can be obtained. (3) Since the shapes of the inner yoke, outer yoke, and permanent magnet are changed from the conventional thick-walled arc shape (shape obtained by dividing a thick-walled cylinder) to the rectangular shape, manufacturing becomes easier and costs can be reduced. (4) According to the embodiment, the yoke is U-shaped and attached to the base, which further facilitates manufacturing and reduces costs.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment according to the present invention, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1, and Fig. 4 is a cross-sectional view taken along line A-A in Fig. 1. FIG. 5 is a plan view of the first conventional example; FIG. 6 is a side sectional view thereof; FIG. 7 is a plan view of the second conventional example; The figure is also a side sectional view. Code explanation 1: Coil bobbin, 2: Bearing, 4.24: Support shaft, 6:
Objective lens, 7: Focus coil, 8A, 8B, 8C
, 8D: ) racking coil, 9: permanent magnet, 1
0,20:Base, 10a:Outer yoke, 10b:Inner yoke, 21:Yoke, 21a:Outer yoke, Ryo 1st 2nd side 3rd figure 7

Claims (1)

[Scope of Claims] A columnar coil bobbin having a rectangular cross section with recesses on each long side; a focus coil wound around the outer periphery of the coil bobbin so as to straddle the recesses; 2 coils each wound in a substantially rectangular shape are provided on the outer periphery corresponding to each long side of the coil bobbin.
A movable part comprising a set of tracking coils, and an objective lens provided on the coil bobbin, the optical axis of which is a straight line parallel to the center line of the coil bobbin and parallel to the long sides of the rectangle by a predetermined distance. It consists of a base and two sets of an inner yoke and an outer yoke each facing each other and having a rectangular shape, each set corresponding to each long side of the coil bobbin, and each inner yoke side facing the coil bobbin. a yoke provided on the base so that the focusing coil and the tracking coil are located in the respective recesses of the coil bobbin recesses, and portions of the focus coil and the tracking coil that straddle the coil bobbin recesses are located in the gaps of the respective yokes; a fixed part comprising substantially rectangular permanent magnets provided on opposing surfaces of either the inner yoke or the outer yoke; The coil bobbin is supported to be rotatable around the center line and movable in the direction of the center line, and a rotation moment around the center line and a driving force in the direction of the center line are applied to the coil bobbin by the current flowing through the focusing coil and the tracking coil. An objective lens driving device characterized in that each of these is provided. 2) The objective lens driving device according to claim 1, wherein the base is integrated with the yoke. 3) The device according to claim 1, wherein the base is made of a non-magnetic material, and the inner yoke and the outer yoke constitute a U-shaped yoke that is integrated with the connecting portion thereof. Objective lens drive device.