JPH01192025A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To make the supporting member of a movable part and the detouring of a lead wire unnecessary by arranging a permanent magnet on the movable part, provid ing a control coil at a fixed part, and holding a midpoint in a direction to control the track of the movable part and a direction of focal point by a specific method. CONSTITUTION:A ring shape permanent magnet 14 is fixed at a ring part 4 provided on the lower part of a movable holder 2. The magnet 14 is formed in such a way that four poles are magnetized in a radial direction and the magnetic pole is set at the same polarity in the same circumferential plane. Also, coils 12a and 12b for controlling a track position and a coil 11 for controlling the focal point are arranged in a gap between the magnet 14 and a base yoke 6 that is the fixed part. At this time, the travel control of a lens 1 is performed by permitting a current corresponding to the deviation of the focal point or a track to flow on the coils 12a and 12b. And a projecting part 109 and notches 9c and 9d with different width are provided at the yoke 6, and the holding of the midpoint in the focal direction and the control direction of the track is performed by applying the driving force and the recovery force of the holder 2. In such a way, the supporting member of the movable part can be unnecessitated. Also, it is not required to perform the detouring processing of the fixed part and the movable part by the above arrangement.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to controlling the track deviation and defocus of a light spot focused on the information recording surface of an optical information recording medium for recording and reproducing information. The present invention relates to an objective lens drive device suitable for use in optical playback devices and recording/playback devices.

[Prior Art] FIG. 16 is an exploded perspective view of a conventional objective lens driving device, FIG. 17 is a partially cutaway plan view of the configuration shown in FIG. 16 in an assembled state, and FIG. FIG. 2 is a cross-sectional view taken along line V-v of In each figure, (1) is an objective lens facing an information recording medium (not shown), (2) is equipped with a cylindrical bearing (3a) near the center thereof, and is eccentric by a predetermined distance from this bearing (3a). A movable holder (10) fixedly holds the objective lens (1) in position and has a focus control coil bobbin (3b); 2) Bearing (
3a), (25) is a support rubber that holds the movable holder (2), and (26) is a focus control that slides and drives the movable holder (2) along the axis of the support shaft (10). Permanent magnets (27a) and (27b) are permanent magnets for track control that rotate the movable holder (2) around the spindle (10), and (28) is a permanent magnet for driving the movable holder (2) around the spindle (10). a base yoke (29a) that holds the focus control permanent magnet (26);
), (29b) are track control permanent magnets (27a),
(27b) is the back yoke, (11) is the movable holder (2
) for slidingly driving the movable holder (2) along the axis of the support shaft (10), and (12a) and (12b) driving the movable holder (2) to rotate around the support shaft (1 center). track control coils (22a) and (22b) are support pins that fix the support rubber (25), (23) constitutes a base part, and track control permanent magnets (27a) and (2
7b) and the back yokes (29a), (29b) are engaged and held by the recesses (23a), (23b) and the support pin (22a).
), (22b) are erected and supported by holes (23c), (23
d) a fixing base with (24) a protective cover that protects the entire device;

The operation of this configuration will now be described.

The movable holder (2) slides in the direction of arrow B by passing a control current in accordance with the focal point control coil (11) to the focus control coil (11), and the objective lens (2) integrated with the movable holder (2)
1) Focus control can be performed.

Moreover, the objective lens (1) is attached to the bearing (3) of the movable holder (2).
The movable holder (2) is moved in the direction of arrow A by passing a control current in accordance with the amount of track deviation to the track control coils (12a) and (12b). The objective lens (1) rotates and becomes integrated with this! - Capable of performing rack control.

In such a configuration, the movable holder (2) which is a movable part
Since a permanent magnet for focal point control (26) and permanent magnets for track control (27a) and (27b) are arranged, it is movable by multiple lead wires in order to supply control current to these control coils. It is necessary to connect the fixed part to the fixed part.

In addition, in order to maintain the center point of the objective lens (1) in the focus control direction and the track control direction, the movable holder (2), which is a movable part, and the fixed base (23), which is a fixed part, are elastically supported. It is necessary to connect both by means of a support member.

[Problems to be Solved by the Invention] Since the conventional objective lens drive device is configured as described above, the work of routing the lead wires connecting the movable part and the fixed part and the attachment of the support members must be done carefully. In addition, there is a problem that unless the assembly is carried out precisely, assembly accuracy cannot be ensured and the operation of the device will be hindered. In addition, these operations involve relatively difficult manual labor, which is a factor in reducing productivity.

This invention was made to solve the above problems,
It is an object of the present invention to provide an objective lens drive device which eliminates the need for leading wires from a movable part that holds an objective lens and the need for supporting members for the movable part, thereby increasing productivity in assembling the device and having high reliability.

[Means for Solving the Problems 1] In order to solve the above problems, the present invention provides a light spot which is slidable to control the focal position of the light spot with respect to the optical information medium and which is rotatable to control the track position with respect to the information track. an objective lens held by a movable means; a ring-shaped permanent magnet magnetized with multiple poles in a direction substantially perpendicular to the rotational axis of the movable means; The base yoke is located in the gap formed by the base yoke, at least two notches of different widths provided in the base yoke so as to face each other at the boundary between the magnetic poles of the permanent magnet, and the permanent magnet and the base yoke. To provide an objective lens driving device comprising a focus control coil fixed to a base yoke and a track position control coil fixed to the base yoke so as to be located in a gap formed by a permanent magnet and the base yoke. It is.

[Function] With the above means, the objective lens drive device of the present invention eliminates the need to route lead wires from the fixed part to the movable part, and furthermore, since the base yoke is provided facing the magnetic pole surface of the permanent magnet, the movable part It is possible to maintain the center point in the focus control direction, and since the base yoke is provided with a notch facing the magnetic pole boundary of the permanent magnet, a torque in the opposite direction to the displacement in the track control direction acts to maintain the track of the movable means. It becomes possible to maintain the midpoint in the control direction.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view of an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line 1-1 in FIG. 1, and FIG. 3 is a cross-sectional view taken along line ■-■ in FIG. 4 is a plan view of the fixed part in FIG. 1, FIG. 5 is a plan view of the permanent magnet part in the configuration of FIG. 1, and FIG. FIG. 3 is a plan view showing the positional relationship of base yokes. In each figure, (14) is fixedly held by a ring part (4) provided at the bottom of the movable holder (2), and as shown in Figure 5, four poles are magnetized in the radial direction to form magnetic poles. (14
It is a ring-shaped permanent magnet formed with a), (14b), (14c), and (14d).

These magnetic poles (14a) and (14b) and magnetic pole (14c)
and (14d) have the same circumferential surface and the same polarity. (3) is a bearing portion formed in a cylindrical shape near the center of the movable holder (2).

Further, (6) is a base yoke which is a fixed part, and this base yoke (6) has an outer protrusion part (7) and an inner protrusion part (8) so as to have a predetermined gap between it and the permanent magnet (14). )have. A permanent magnet (
A solid convex surface (109) concentric with the permanent magnet (14) and notches (9a), (9b), (9
c), (9d) is the magnetic pole (14a) of the permanent magnet (14),
Boundary (a) of (14c), magnetic pole (14a), (14d)
, the boundary (c) of the magnetic poles (14b), (14c) (F), and the boundary (d) of the magnetic poles (14b), (14d), respectively.

Note that the notches (9a) and (9b) are set to have the same width, and the notches (9c) and (9d) are set to have the same width. Furthermore, the magnetic pole (1) of the permanent magnet (14)
4c), the spacing θy that is almost the same as the magnetic pole width θm of (14d)
The notches (9a), (9C) and the notch (9
b) and (9d) are provided. (10) is a support shaft (1) that is fixedly installed approximately in the center of the base yoke (6).
0), and a bearing portion (3) of a movable holder (2) is fitted into this support shaft (10) so as to be slidable in the direction of the arrow B and rotatable in the direction of the arrow. (11) is a focus control coil fixedly disposed on the convex surface (109) of the outer protrusion (7) of the base yoke (6) facing the permanent magnet (14). In addition, (12a) and (12b) are notches (9a) and (9b) provided in the outer protrusion (7).
This is a rectangular track control coil fixed at a position facing the permanent magnet (14) so as to have sides substantially parallel to the axis of the support shaft (10).

In the above configuration, its operation will be explained next.

The focus control coil (11) is placed on the outer periphery of the permanent magnet (14), and when a current is passed through it, the electromagnetic force generated acts on the movable holder (2), causing it to move as shown in Figure 2. drive in the direction of arrow B. Therefore, the focus control coil (1
The objective lens (1) is integrated with the movable holder (2) by passing a control current in accordance with the amount of defocus through the objective lens (1).
) can be moved in the direction of arrow B to control its focus.

In addition, the track control coils (12a) and (12b) are also arranged on the outer circumferential side of the permanent magnet (14), and are arranged on the support shaft (10).
) is the magnetic pole (14a), (ltc)
and magnetic poles (14b) and (14d), so the track control coil (12a),
The polarity of interlinking magnetic flux is different between one side parallel to the axis of each support shaft (10) of (12b) and the other side. Therefore, by passing current through the track control coils (12a) and (12b), the directions of the forces generated on the sides substantially parallel to the axis of the support shaft (10) become the same direction of rotation, so that the movable holder ( 2) in the direction of arrow A in FIG. 1, the track control coils (12a) and (12
b) The objective lens (1) is integrated with the movable holder (2) by applying a control current according to the amount of track deviation to the movable holder (2).
Track control can be performed.

Here, the midpoint holding mechanism of the movable holder (2) will be explained.

First, regarding the center point holding til+M in the focus control direction, the seventh
The description will be made according to the characteristic diagram of focus control direction displacement shown in the figure. Incidentally, FIG. 7 shows the relationship between the restoring force F in the focus control direction and the displacement X in the focus control direction. Movable holder (2
) is at the midpoint position in the focus control direction.
4) Magnetic poles (14a), (14b), (14c)
, (14d) and a convex surface (109) concentric with the permanent magnet (14) is provided on the peripheral surface of the outer protrusion (7) of the base yoke (6) facing the permanent magnet (14).
As shown in FIG. 7, a restoring force X' acting in the opposite direction to the displacement X of the movable holder (2) in the focus control direction acts on the permanent magnet (14) near the center of the convex surface (109) in the height direction. It is possible to maintain the center point of the movable holder (2) in the focus control direction by setting the point at the center point.

This is because the permanent magnet (14) is stabilized at the position where the magnetic energy is maximum. In other words, this is because the magnetic flux density in the air gap is stabilized at the position where it becomes maximum. As a result, if the focus control coil (11) is provided on the convex surface (109), it will be placed at the part where the maximum magnetic flux density in the air gap can be obtained, resulting in a larger driving force in the focus control direction. will be obtained. In addition, even if the permanent magnet (14) is displaced with the focus control operation, the magnetic flux is
109), the focus control coil (
11) The change in the magnetic flux density interlinking with the magnetic flux density is small, and the change in the focus control direction driving force accompanying the focus control direction operation is small.

Next, the midpoint holding mechanism in the track control direction will be described with reference to the characteristic diagram of the rotation angle in the track control direction shown in FIG. Incidentally, FIG. 8 is a characteristic diagram showing the relationship between the rotation angle and the restoring force in the track control direction. In this case, as shown in diagram m6, the magnetic pole (14a) of the permanent magnet (14)
), (14b), (14c), (14d) boundary (a)
, (B), (C), and (D), the base yoke (6
) have notches (9a), (9b), (
9c) and (9d), the restoring force T in the direction opposite to the rotation angle θ1 of the movable holder (2) as shown in FIG.
() acts on the permanent magnet (14), making it possible to maintain the center point of the movable holder (2) in the track control direction. This is based on the same principle as the center point holding mechanism in the focus control direction, and is because the permanent magnet (14) is stabilized at the position where the magnetic energy is maximum.

Here, magnetic poles (14a), (14b), (14C), (
A notch (9a
), (9b), (9C), and (9d) in the ninth section.
Figure 1. This will be explained according to the plan view of FIG. Incidentally, FIGS. 9 and 10 show a general configuration for controlling the track position using two notches (9x) and (9y). As shown in FIG. 9, the base yoke (6
), if notches (9X) and (9y) are provided in the outer protrusion (7) of The magnet (14) rotates and interference occurs.

This becomes a problem in -l-, which drives the objective lens (1).

In order to eliminate this magnetic operation interference, the magnetic poles (14a), (14) of the permanent magnet (14) are
When notches (9x) and (9y) are provided in the outer protrusion (7) of the base yoke (6) facing the boundaries (a) and (b) of b), (14c), and (14d), Permanent magnet (14)
Since the magnetic flux density distribution in the air gap between the base yoke (6) and the base yoke (6) is not point symmetrical, a radial force is generated on the permanent magnet (14), which acts as a normal force on the bearing (3) of the movable holder (2). The frictional force on the sliding surface increases, the sliding characteristics deteriorate, and the focus control operation is adversely affected.

For the above reasons, in the configuration of this embodiment,
Magnetic poles (14a), (14b), (1
4c), (14d) boundaries (a), (b), (c), (
Notches (9a), (9b), (9C), (9d) are formed on the outer protrusion (7) of the base yoke (6) so as to face the base yoke (6).
) has been established.

Next, according to the plan view of FIG. 11, the notch (9a), (
9b), (9C), and (9d), the relationship between the sizes of the notches, that is, the widths will be explained. In order to eliminate the magnetic interference mentioned earlier, the rate of increase/decrease in the magnetic flux density distribution in the air gap due to the magnetomotive force of the focus control coil (11) must be
10) Linear symmetry (
(excluding point symmetry). In addition, in order to reduce the radial force used on the permanent magnet (14), the magnetic flux density distribution in the air gap must approach point symmetry, so the outer protrusion (7) of the base yoke (6) is
The relationship between the width θ1 of the notches (9a) and (9b) provided in ) and the width θ of the notches (9c) and (9d) must be θl>θ2. In this case, as the values of θ1 and 02 become closer, the radial force acting on the permanent magnet (14) decreases.

FIG. 14 is a plan view of an objective lens driving device according to another embodiment of the present invention, FIG. 12 is a plan view of a focus control coil assembly applied to the configuration of FIG. 14, and FIG. FIG. 15 is a sectional view taken along line IV--IV in FIG. 14.

The difference between the configuration of this embodiment and the embodiments shown in FIGS. 1 to 6 is that the focus control coil (11) is formed by winding it in an air-core state and is fixed to the base yoke (6). Instead, the focus control coil (11) is wound around a coil holder (115) made of a non-magnetic abrasive or magnetic material, and this is attached to a permanent magnet (7) on the outer protrusion (7) of the base yoke (6). 14) was fixed so as to face it.

In this way, a coil holder with relatively high mechanical strength (
By winding the focus control coil (11) around the focus control coil (115), there is no need to worry about breakage due to handling errors, which has traditionally been a problem when assembling the focus control coil (11), and handling can be simplified. This can improve work efficiency.

As for the material of the coil holder (115), if a non-magnetic material such as engineering plastic is used, it will not be possible to maintain the center point of the movable holder (2) in the focus control direction, but if a magnetic material such as iron is used, In this case, it is possible to maintain the center point of the movable holder (2) in the focus control direction.

[Effects of the Invention] As described in Section 2 below, according to the objective lens drive device of the present invention, the permanent magnet is arranged in the movable part and the control coil is arranged in the fixed part, so that the lead from the movable part is There is no need for wire routing processing, and the focus direction of the movable part can be controlled by a convex surface provided on the circumferential surface facing the permanent magnet of the base yoke, which is the fixed part, or by a yoke provided on the base yoke of the fixed part, facing the permanent magnet. This makes it possible to maintain the center point of the moving part, and since the base yoke is provided with notches that face each of the boundaries of the magnetic poles of the permanent magnet, it is possible to maintain the center point of the moving part in the track control direction. Since there is no need for a support member or other delicate work to connect the movable part and the fixed part, it is possible to realize a device with good assembly productivity and high reliability. Furthermore, since the control coil is provided on the convex surface or is wound around the yoke, there is little change in driving force associated with focus control operation, and the control coil is placed opposite the magnetic pole boundary of the permanent magnet. Since the notch is provided, the vertical force applied to the sliding surface is reduced, resulting in the effect that stable control operation can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an objective lens driving device according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line 1-1 in Fig. 1, and Fig. 3 is a sectional view taken along line The resulting sectional view, Figure 4 is a plan view of the fixed part in Figure 1, Figure 5 is a plan view of the permanent magnet part in the configuration of Figure 1, and Figure 6 is the permanent magnet and base of Figure 5. A diagram showing the positional relationship of the yokes, Figure 7 is a characteristic diagram of displacement in the focus control direction, Figure 8 is a characteristic diagram of rotation angle in the track control direction, and Figures 9 and 10 are track position control using two notches. FIG. 11 is a plan view illustrating the relationship between the size of the notch, that is, the width, and FIG. 12 is an objective lens drive device according to another embodiment. 13 is a sectional view taken along the line ■-■ in FIG. 12; FIG. 14 is a plan view of the objective lens drive device according to the embodiment in FIG. 12; Figure 15 is IV-I of Figure 14.
16 is an exploded perspective view of a conventional objective lens drive device, and FIG. 17 is a partially cutaway plan view of the configuration shown in FIG. 16 in an assembled state. 18 is a sectional view taken along line V-V in FIG. 17. In the figure, (1) is the objective lens, (2) is the movable holder, (3) is the bearing, (6) is the base yoke, (7) is the outer protrusion, (8) is the inner protrusion, and (9a) , (9b),
(9c), (9d) are notches, (10) is a support shaft, (11
) is a focus control coil, (12a), (12b) is a track control coil, (109) is a convex surface, (14) is a permanent magnet, (14a), (14b), (14c), (14d)
) is a magnetic pole, and (115) is a coil holder. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Patent Attorney Masuo Oiwa (and 2 others) Figure 1 Figure 3 Figure 4 Figure 6 Figure 5 Figure 6 Figure 9C'' 14C Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 1 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18

Claims (1)

[Claims] (1) An objective lens held by a movable means that is slidable to control the focal position of the light spot with respect to the optical information medium and rotatable to control the track position with respect to the information track, and rotation of the movable means. A ring-shaped permanent magnet magnetized with multiple poles in a direction substantially perpendicular to the axis, a base yoke provided opposite to the inner circumferential surface and outer circumferential surface of the permanent magnet, and at least two of the boundaries between the magnetic poles of the permanent magnet. a focus control coil fixed to the base yoke so as to be located in the gap formed by the permanent magnet and the base yoke; An objective lens driving device comprising a track position control coil fixed to a base yoke so as to be located in a gap formed by the yoke.