JPH05298838A - Optical head driving device - Google Patents

Abstract

PURPOSE:To provide the optical disk device which is thin and small. CONSTITUTION:A rare earth magnet of a praseodymium system is used as the magnet of the optical head driving device which controls the position of the optical head by the electromagnetic effect of the coil and magnet of the optical disk device which optically records and reproduces information. Then, the size and thickness of a magnetic circuit are reduced by the rare earth magnet of the praseodymium system and the resonance of the yoke and the magnet is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device,
The optical head driving device is made thinner and smaller.

[0002]

2. Description of the Related Art Television Society Journal Vol. 44, N
o. 10 (1990), "Structure of head / motor assembly in FIG. 2" described in the article "3.5 inch rewritable optical disk apparatus using DBF method and its medium compatibility".

[0003]

In the conventional optical head driving device, when the optical disk device is made thinner and smaller, the magnet of the optical head driving device cannot be made thinner, so that it is made thinner.
It was difficult to miniaturize. In addition, there is a problem that resonance of the yoke occurs when it is made thin.

An object of the present invention is to realize a thin and compact optical disc device and to solve the resonance problem.

[0005]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is an optical head driving device for controlling the position of an optical head by electromagnetic action of a coil and a magnet of an optical disk device for optically recording and reproducing information. A praseodymium rare earth magnet was used as the magnet, the thickness of the praseodymium rare earth magnet was 1 mm or less, and the length of the praseodymium rare earth magnet was 31 mm.
It is characterized in that it is set to mm or more.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiments. The same reference numerals represent the same members.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. A coil 4 is arranged in a magnetic circuit composed of an outer yoke 1, a middle yoke 2, and a praseodymium rare earth magnet 3 such that the middle yoke 2 penetrates through the coil 4.

As shown in the explanatory view of FIG. 2, the magnetic field 7 generated by the praseodymium rare earth magnet 3 is uniformly distributed between the praseodymium rare earth magnet 3 and the inner yoke 2, and a current is passed through the coil 4. The optical head 13 is driven in the drive direction 8 by the generated electromagnetic force.

According to the praseodymium rare earth magnet 3 as compared with the case of using the conventional ferrite magnet, the thickness b of the magnet can be made smaller, so that the width a of the magnetic circuit can be made smaller. As a result, the entire optical head driving device can be downsized as shown in FIG.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. A coil 4 is arranged in a magnetic circuit composed of an outer yoke 1, a middle yoke 2, and a praseodymium rare earth magnet 3 such that the middle yoke 2 penetrates the coil 4. This embodiment is the first
The difference from the embodiment is the arrangement of the outer yoke 1.

A thin plate-shaped magnet having a thickness b of 1 mm or less, which was difficult to produce with conventional ferrite magnets and rare earth magnets obtained by sintering, can be easily produced with praseodymium rare earth magnets produced by rolling. Therefore, it is possible to connect the outer yoke 1 to the beam emission direction 1 of the coil 4.
It can be arranged on the four side. With this arrangement, thinning and miniaturization can be realized.

Further, according to the praseodymium rare earth magnet, even if the thickness b of the magnet is 1 mm or less, the coil 4
Since a magnetic flux density of 1500 Gauss or more is obtained in the coil portion between the middle yoke 2 and the above, there is no adverse effect that the magnetic flux density becomes weak.

(Embodiment 3) FIG. 4 shows a third embodiment of the present invention. This embodiment is different from the second embodiment in that the outer yoke 1,
A magnetic circuit constituted by the praseodymium rare earth magnet 3 is additionally arranged on the side opposite to the beam emitting direction 14 of the coil 4.

In the present embodiment, the driving force for driving the optical head 13 is increased by increasing the number of magnetic circuits to improve the seek performance, but the magnet thickness b is 1 m.
According to the thin plate-shaped praseodymium rare earth magnet 3 having a thickness of m or less, it is possible to realize thinning and downsizing.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention. This embodiment is an application example in which the thickness is further reduced in comparison with the third embodiment.

The structure will be described with reference to the exploded view shown in FIG. The praseodymium rare earth magnet 3 is attached to the lower yoke 5, the middle yoke 2 and the support shaft 6 are inserted into the optical head composed of the coil 4, the carriage 11, the bearing 9 and the actuator 12 according to the dashed line in the figure, and then the lower yoke 5 is inserted. Attach to. Next, the upper yoke 1 having the lower surface of the praseodymium rare earth magnet 3 attached thereto is attached to the middle yoke 2 penetrating the coil 4. As a result of assembling in this way, the optical head driving device shown in FIG. 5 is completed. In FIG. 5, the spindle motor 10 and the optical disk 15 are further illustrated, and the positional relationship between them is shown.

The optical system of this embodiment is separated into a fixed optical system and an optical head. As shown in FIG. 5, the laser light emitted from the fixed optical system (not shown) is incident on the optical head as incident light 17, and the prism 16 shown in FIG. Emitted light 18
As a result, the optical disk 15 is irradiated with laser light. The irradiated laser light is condensed by the actuator 12 and a spot 1 is formed on the recording surface of the optical disc 15.
9 is formed. The laser light reflected from the spot 19 goes back through the above-mentioned incident optical path and returns to the fixed optical system to generate a control signal and a data signal. The position of the spot 19 is controlled along the track 20 on the recording surface of the optical disc 15 by using the control signal.

The position control includes position control in a direction perpendicular to the recording surface of the optical disk 15 with respect to the actuator 12 for controlling the size of the spot 19, and the optical movement in a direction indicated by a driving direction 8. Two types of head position control are performed.

The present invention relates to position control of the optical head in the driving direction 8 of the position controls. As shown in FIG. 5, the optical head is driven in the drive direction 8 by the electromagnetic action of the magnetic field generated by the praseodymium rare earth magnet 3 between the praseodymium rare earth magnet 3 and the middle yoke 2 and the current flowing through the coil. It is driven as shown in. Since the optical head moves on all tracks on the recording surface of the optical disk 15, and when it stays on a specific track, it moves following the eccentricity of the optical disk, so that the drive current becomes an oscillating current.

In this embodiment, since the height c of the magnetic circuit is made small, the lower yoke 5 and the upper yoke 1 are thin. Therefore, the magnetic field generated by the oscillating current flowing in the coil 4 excites the resonance between the lower yoke 5 and the upper yoke 1 via the vibration of the attractive force that attracts the yoke. The resonance is harmful in controlling the position of the optical head, but the thickness b of the magnet shown in FIG. 6 of the present embodiment is 1 mm or less, and the length d of the magnet shown in FIG. 5 is 31 mm or more. By attaching the praseodymium rare earth magnet 3 to the lower yoke 5 and the upper yoke 1, the lower yoke 5 and the upper yoke 1 are reinforced, so that the resonance is suppressed.

[0021]

According to the present invention, not only each magnetic circuit can be miniaturized and thinned, but also the optical head drive device and the optical disk device as a whole can be miniaturized and thinned.

Further, resonance of the yoke, which is an adverse effect of thinning, can be suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a first embodiment of the present invention.

FIG. 2 is an explanatory diagram explaining an operation of the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a second embodiment of the present invention.

FIG. 4 is a perspective view illustrating a third embodiment of the present invention.

FIG. 5 is a perspective view illustrating a fourth embodiment of the present invention.

FIG. 6 is an exploded view for explaining a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Outer yoke 2 Middle yoke 3 Praseodymium rare earth magnet 4 Coil 5 Lower yoke 6 Support shaft 7 Magnetic field created by magnet 8 Driving direction 9 Bearing 10 Spindle motor 11 Carriage 12 Actuator 13 Optical head 14 Light emitting direction 15 Optical disk 16 Prism 17 Incident Light 18 Emitted light 19 Spot 20 Track a Magnetic circuit width b Magnet thickness c Magnetic circuit height d Magnet length

Claims (3)

[Claims] 1. An optical head drive device for controlling the position of an optical head by electromagnetic action of a coil and a magnet of an optical disk device for optically recording and reproducing information, wherein a praseodymium-based rare earth magnet is used as the magnet. Optical head drive device. 2. The thickness of the praseodymium rare earth magnet is 1
The optical head driving device according to claim 1, wherein the optical head driving device is less than or equal to mm. 3. The length of the praseodymium rare earth magnet is 3
The optical head drive device according to claim 2, wherein the optical head drive device has a length of 1 mm or more.