JPH04184740A - Magneto-optical disc device - Google Patents

Abstract

PURPOSE:To increase an output per a unit space of a voice coil motor by making the height of a coil surrounding a center yoke approximately the same as that of a side yoke, on the inside of which a permanent magnet is installed, while the sectional area of the side yoke is made the same as or larger than that of the center yoke. CONSTITUTION:A magnetic circuit is composed of a center yoke 12 surrounded by a coil 11, a permanent magnet 13 oppositely faced to the coil 11 from the outside of the coil 11 and a side yoke 14 on the outside of the magnet 13. The height Hc of the coil 11 is made approximately the same as that Hy of the side yoke 14 while the sectional area Am of the center yoke 12 is made the same as or smaller than that As of the side yoke 14 at that time. When currents are conducted through the coil 11, electromagnetic force is generated by the line of magnetic force generated by the center yoke 12, the permanent magnet 13 and the side yoke 14 constituting the magnetic circuit, a carriage 2 can be driven in the direction orthogonal to a paper surface. Accordingly, an output from a voice coil motor per a unit space is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical disk device having a voice coil motor for moving a carriage carrying an optical pickup using electromagnetic force.

[Prior Art] FIG. 6 shows an example of a drive system of a conventional apparatus for recording and reproducing information using the magneto-optic effect.

The laser beam emitted from the fixed optical system l is sent to the carriage 2.
The light enters the objective lens 3 through an optical axis bending mirror (not shown) provided in the. Actuator 4 is objective lens 3
By driving the disc D, auto-focusing and auto-tracking are performed on the rotating disc D, and information is recorded and reproduced on the disc D using a laser beam.

If only the actuator 4 is driven, the range in which information can be recorded and reproduced on the disc is narrow. Therefore, the actuator 4 that drives the objective lens 3 is mounted on the carriage 2 and moved in the radial direction of the disc D, thereby changing the arrangement of information. A recordable and reproducible range is secured over substantially the entire circumference of the disc D.

The carriage 2 is rolled and supported by bearings, and is driven by electromagnetic force generated by a voice coil motor composed of a magnetic circuit formed by a combination of a yoke 5 and a permanent magnet 6, and a coil 7 attached to the carriage 2. Ru.

Here, FIG. 7 shows the configuration of a general voice coil motor, in which the magnetic circuit consists of a yoke 5 which is a ring body made up of a combination of rectangular parallelepipeds made of yoke members made of iron-based materials.
A permanent magnet 6 is provided inside one long side of the yoke 5, and a coil 7 is provided around the long side of the yoke 5 facing the permanent magnet 6. The coil 7 is energized to generate an electromagnetic force through interaction with the magnetic force generated by the magnetic circuit, thereby obtaining a driving force F for moving the object.

FIG. 8 shows an example of a cross-sectional view of a voice coil motor commonly used in a magneto-optical disk device, in which a carriage 2 is arranged approximately in the middle of the device, and the voice coil motors are arranged symmetrically on both sides of the carriage 2. has been done. Carriage 2
Coils 7 are attached to both sides of the coil 7.
A center yoke 5a is inserted inside the coil 7, and a permanent magnet 6 and a side yoke 5b are arranged outside the coil 7, and these constitute two sets of magnetic circuits.

Further, the height of the side yoke 5b is indicated by Hy, the height of the coil 7 is indicated by Hc, and the height of the center yoke 5a is indicated by H■.

[Problem to be Solved by the Invention 1] However, in the conventional example described above, the maximum height of the voice coil motor is determined by the height Hc of the coil 7. This is because the height H of the center yoke 5a is matched to the inner dimension of the coil 7, and the height Hy of the side yoke 5b is determined accordingly. Therefore, an empty space is created by the difference in height between the side yoke 5b and the coil 7 (Hc-Hy), resulting in wasted space. This does not result in efficient use of space, and it is not possible to obtain a voice coil motor with the highest possible efficiency within a given space.

In addition, the output of the voice coil motor is determined by the product of the magnetic force generated by the magnetic circuit, the number of turns of the coil 7, the value of the current flowing, and the effective length that the coil 7 crosses the lines of magnetic force.In the conventional example, the effective length is approximately equal to the side yoke. It is equal to the height Hy of 5b, and the effective length is shorter than approximately the coil height Hc. For this reason,
A length longer than the effective length of the coil 7 is wasted, leading to a decrease in the output per unit volume of the voice coil motor.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a magneto-optical disk device in which the voice coil motor has a large output per unit space.

[Hands to solve problems! ] In order to achieve the above object, in the magneto-optical disk device according to the present invention, in the magnetic circuit of the voice coil motor that drives the carriage, the height of the coil surrounding the center yoke is adjusted such that a permanent magnet is provided inside. The height of the side yokes is approximately equal to that of the center yoke, and the cross-sectional area of the side yoke is equal to or larger than the cross-sectional area of the center yoke in order to ensure magnetic flux passing through the magnetic path. It is something.

[Function] The magneto-optical disk device having the above-mentioned configuration can efficiently use the given space, and since the effective length of the coil becomes long, the ratio of wasted portions of the coil length is reduced, and the unit The output efficiency of the voice coil motor per space is high.

[Example] The present invention will be described in detail based on the example illustrated in FIGS. 1 to 5. Note that the same reference numerals as in the conventional example represent the same members.

Fig. 1 shows a cross-sectional view of the first embodiment, and Fig. 2 shows a distribution diagram of magnetic lines of force. A magnetic circuit is arranged on the carriage 2, and coils 11 are attached to the left and right sides of the carriage 2. The magnetic circuit is composed of a center yoke 12 surrounded by a coil 11, a permanent magnet 13 facing the coil 11 from the outside of the coil 11, and a side yoke 14 further outside. Here, the height of the coil 11 is Hc, the height of the side yoke 14 is Hy, the height of the center yoke 12 is Hsa, the cross-sectional area of the center yoke 12 is A, and the cross-sectional area of the side yoke 14 is As. , satisfies the following relational expression.

HC>Hll...filHc#
Hy... (2)
Age4 As or All<AS-f31
The formula fi1 is a necessary condition because the center yoke 12 is surrounded by the coil 11, the formula (2) is a condition for the height of the side yoke 14, and the formula (3) is a condition for the cross-sectional area of the side yoke 14. be.

By applying current to the coil 11, electromagnetic force is generated by magnetic lines of force generated by the center yoke 12, permanent magnets 13, and side yokes 14 that constitute a magnetic circuit, and the carriage 2 can be driven in a direction perpendicular to the plane of the paper. .

Here, since the magnitude of the magnetic flux passing through the cross-sectional area Am of the center yoke 12 and the magnetic flux passing through the cross-sectional area As of the side yokes are almost equal, the cross-sectional area Am of the center yoke 12 and the cross-sectional area As of the side yokes 14 are If the cross-sectional area As of the side yoke 14 is approximately equal to or larger than the cross-sectional area Am of the center yoke 12, a closed magnetic path with almost no magnetic field leakage can be constructed, so that the magnetic flux in the magnetic circuit can be utilized. Increased efficiency.

The effective length of the coil 11 is approximately equal to the coil height Hc, and from the distribution of magnetic lines of force shown in FIG.
Since the magnetic flux passing through the side yoke 14 can be utilized almost entirely, the proportion of wasted portions of the coil length is reduced.
High output per unit space.

FIG. 3 shows a second embodiment in which the magnetic circuit is connected to the carriage 2.
The permanent magnet 2 is arranged above the coil 21 in a direction perpendicular to the plane of the paper, which is the moving direction of the coil 21, and in a plane parallel to the vertical direction.
2 is arranged, and a side yoke 23 is arranged thereon. In this case as well, the same effects as in the first embodiment can be obtained.

FIG. 4 shows a third embodiment, in which the center yoke 31, the coil 32, and the permanent magnet 33 have curvature, so that the gap length between the permanent magnet 33 and the center yoke 31 is approximately equal, and a uniform distribution is obtained. It will be done.

FIG. 5 shows a fourth embodiment, in which the magnetic circuit shown in the second embodiment is provided not only on the upper side but also on the lower side, and arranged symmetrically above and below. In this case, the effective length simply doubles, so
If the magnetic flux in the upper and lower magnetic circuits is about the same as in the second embodiment, the output will be doubled.

In the above-described embodiment, the magnetic circuits were arranged symmetrically on both sides of the carriage 2, but a similar configuration may be provided only on one side of the carriage 2.

[Effects of the Invention] As explained above, the magneto-optical disk device according to the present invention has a large voice coil motor output per unit space (
Since the magnetic circuit has a good space factor, the device can be made smaller.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the magneto-optical disk device according to the present invention, FIG. 1 is a sectional view of the voice coil motor of the first embodiment, FIG. 2 is a distribution diagram of lines of magnetic force, and FIG. Figure 3,
4 and 5 are sectional views of voice coil motors of second, third, and fourth embodiments, respectively, and FIG. 6 is a perspective view of a voice coil motor of a conventional magneto-optical disk device.
The figure is a configuration diagram of a general voice coil motor, and FIG. 8 is a sectional view of a conventional voice coil motor. 2 is the carriage, 4 is the actuator, 11.21
．． 32 is the coil, 12.31 is the center yoke, 13.2
2.33 is a permanent magnet, and 14.23 is a side yoke. Patent applicant Canon Co., Ltd. Figure 2 Figure 3

Claims (1)

[Claims] 1. In the magnetic circuit of the voice coil motor that drives the carriage, the height of the coil surrounding the center yoke is approximately equal to the height of the side yokes with permanent magnets installed inside, and the magnetic flux passing through the magnetic path is A magneto-optical disk device characterized in that the cross-sectional area of the side yokes is equal to or larger than the cross-sectional area of the center yoke in order to ensure the following.