JPH05334692A - Optical head driving device and optical disk device - Google Patents

Abstract

PURPOSE:To perform fast seek by providing a notch in a middle yoke. CONSTITUTION:The notch 7 is provided by dividing the middle yoke 2 into two bodies 2a, 2b in a center part. A magnetic field 9 when a current is permitted to flow on a coil 4 intends to pass the yokes 2a, 2b, therefore, the notch 7 functions as high magnetic resistance. When the magnetic resistance is increased, the time constant of a coil current when it rises is decreased. Thereby. since the rise of the current on the coil can be accelerated, a control band can be widened, and the fast seek can be performed.

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,
This seek improves the seek performance.

[0002]

2. Description of the Related Art FIG. 13 shows an example of an optical head driving device. A coil 4 is arranged in a magnetic circuit composed of an outer yoke 1, a middle yoke 2 and a magnet 3 such that the middle yoke penetrates the coil 4. An electromagnetic force was generated by passing a current through the coil, and the optical head 5 (only part of which is shown) was driven in the direction of arrow 6.

There is also one in which the middle yoke is covered with a good conductor.

[0004]

The conventional optical head driving device has the following problems.

(1) In order to increase the seek speed, it is necessary to speed up the rise of the current flowing through the coil, but it was not possible to increase the magnetic resistance while maintaining the magnetic flux density between the magnet and the middle yoke. ..

(2) Further, if the yoke is divided, such as by notching the yoke, assembly is difficult.

[0007]

The present invention for solving the above-mentioned problems is characterized by the following five points.

(1) In 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,
A notch is provided in a central portion of a yoke which is arranged parallel to the driving direction and penetrates the coil.

(2) An optical head driving device for controlling the position of the optical head by electromagnetic action of a coil and a magnet of an optical disk device for optically recording and reproducing information is arranged parallel to the driving direction and penetrates the coil. The yoke has a notch in the center and is covered with a pipe of good electric conductor.

(3) The optical head driving device for controlling the position of the optical head by the electromagnetic action of the coil and the magnet of the optical disk device for optically recording and reproducing information is arranged parallel to the driving direction and penetrates the coil. The yoke has a notch in the center, and the notch is filled with a non-magnetic material.

(4) In the optical head drive device for controlling the position of the optical head by the electromagnetic action of the coil and the magnet of the optical disk device for optically recording and reproducing information,
The yoke, which is arranged parallel to the driving direction of the optical head and penetrates the coil, is magnetically saturated by the magnetic force of the permanent magnet.

(5) In an optical head driving device for controlling the position of the optical head by the electromagnetic action of the coil and the magnet of the optical disk device for optically recording and reproducing information,
The yoke arranged parallel to the driving direction and penetrating the coil has a notch in the central portion, and one of the yokes is an integral part of the yoke that does not penetrate the coil.

[0013]

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. In the present invention, as shown in FIG. 1, the middle yoke 2 is provided at the center of the middle yoke 2 as compared with the middle yoke 2 of the conventional example shown in
A cutout 7 was provided by dividing into 2 bodies of 2b.

The notch acts as a large magnetic resistance against the magnetic field because the magnetic field 9 generated when a current flows through the coil 4 tries to pass through the middle yokes 2a, 2b. When the magnetic resistance increases, the time constant of the rise of the coil current decreases. As a result, as shown in the graph of FIG. 12, the current b when the magnetic resistance increases due to the notch with respect to the time t1 when the conventional current a reaches the used current
The time t2 required for the current to reach the used current is shortened.

The notch is provided substantially at the center so that the magnetic field 10 generated by the magnet 3 has no difference in magnetic flux distribution between the side of the inner yoke 2a and the side of the inner yoke 2b. Further, since the magnetic field generated by the magnet is distributed to the left and right by the middle yoke, there is a place where the magnetic flux density is 0 in the center portion of the middle yoke even if there is no notch. Therefore, notching the central portion does not weaken the magnetic field 10.

The notch 7 has a shape shown in plan view and front view in FIG.
(A) to (h) and FIGS. 9 (a) to (e).

Further, as an example, as shown in FIGS. 10A to 10F, there may be a partial connection portion.

The features of the notch shape will be described below with reference to the drawings. FIG. 8A is a simplest shape cut by a plane parallel to the middle yoke. It is easy to manage the notch width 7a. 8 (b), (c),
(D) shows that the corners of the yoke are chamfered in order to facilitate the workability and the handling of the parts in comparison with (a).

Chamfering is also effective for each of the following examples. Further, the chamfer may be a curved surface. FIG. 8 (e),
9 (a), 9 (b), 9 (f), 9 (g), 9 (h) and 9 (a) and 9 (b) show an assembling jig that is sandwiched between the notches so that the flatness and symmetry of the middle yoke can be secured when the middle yoke is assembled. It is designed so that the mounting position of parts can be managed. Figure 9
(C) and (d) are for expanding the range of the notch in the driving direction in order to make the distribution of the magnetic field generated by the magnet uniform. FIG. 9E shows a shape in which the magnetic resistance is ensured while reducing the width of the notch on the magnet side for the purpose of making the distribution of the magnetic field generated by the magnet uniform.

FIG. 10 illustrates a case where a connecting portion is partially left in the notch of the middle yoke. Although the above-mentioned connecting portion facilitates the handling of the component, it is necessary to be thin enough to be magnetically saturated by the magnetic field generated by the current flowing through the coil in order to secure the magnetic resistance. FIG. 10A shows a shape in which the left and right yokes are connected at the center for the purpose of making the magnetic field produced by the magnet uniform. 10 (b) and 10 (c) show a shape that is advantageous in punching by pressing. Figure 10
(D) and (e) are shapes that are designed so that they can be created by crushing with a press. Although FIG. 10 has been described, in all the shapes shown in FIG. 10, chamfering with a flat surface and chamfering with a curved surface are possible at the corner portions.

(Second Embodiment) FIG. 2 shows a second embodiment.
Since the shape of the notch 7 is similar to that of the first embodiment, the shape similar to that of FIG. 8A is shown as an example. As a reinforcing member for the notched middle yoke, left and right middle yokes 2a,
2b was covered and bonded with one good conductor 8. Therefore, the width of the notch of the middle yoke can be easily controlled, and the accuracy is improved. Also, since it is a single part, handling of parts is easy,
Assemblability is improved.

Since the good conductor 8 also serves the purpose of accelerating the rise of the coil current by electromagnetic induction, it is joined by closing the cylindrical side surface. The joining methods are brazing, welding,
Pressure contact and adhesion with a conductive adhesive are preferable.

It is desirable that the good conductor 8 be made of a conductive material having a low resistivity. Examples are copper, aluminum, gold, silver, tin, lead and alloys containing these as the main components.

(Embodiment 3) FIG. 3 shows a third embodiment.
Since the shape of the notch 7 is similar to that of the first embodiment, the shape similar to that of FIG. 8A is shown as an example. In this embodiment, the inner yokes 2a and 2b are thinned so that the cross-sectional area is reduced
It is characterized in that it is magnetically saturated in a region 11 in the vicinity where the inner yokes 2a, 2b come into contact with the outer yoke 1 in the magnetic field 10 generated by the magnet 3 by making the size smaller than that in FIG.

In the saturation region 11, the magnetic field 9 generated when a current flows through the coil 4 tries to pass through the inner yokes 2a, 2b, but the saturation region 11 near the contact between the inner yokes 2a, 2b and the outer yoke 1. Since it is magnetically saturated, the magnetic field does not pass through the middle yoke and acts as a large magnetic resistance against the magnetic field. When the magnetic resistance increases, the time constant of the rise of the coil current decreases. As a result,
As shown in the graph of 2, the time t2 when the current b reaches the working current when the magnetic resistance increases due to the notch,
In addition to the notch, the time t3 for the current c to reach the operating current when the magnetic resistance increases due to magnetic saturation becomes short.

(Embodiment 4) FIG. 4 shows a fourth embodiment.
In this embodiment, in addition to the third embodiment, the left and right middle yokes 2a and 2b are covered with one good conductor 8 and joined as a reinforcing member for the notched middle yoke. Like the second embodiment, the good conductor 8 is joined by closing the cylindrical side surface. Therefore, the width of the notch of the middle yoke can be easily controlled, and the accuracy is improved. Further, since it is a single part, the parts are easy to handle and the assembling property is improved.

(Embodiment 5) FIG. 6 shows a fifth embodiment.
This embodiment is a vertically symmetrical combination of the third embodiment,
Three or more middle yokes (in FIG. 7, middle yokes 2a, 2b, 2
(4 pieces of c and 2d) are collectively covered with one good conductor 8 and joined. At this time, an optical head (not shown) is attached in a direction perpendicular to the paper surface.

As described above, even when two magnetic circuits are combined with one coil, they can be easily assembled by using the middle yoke as one component.

(Embodiment 6) FIG. 7 shows a sixth embodiment.
This embodiment is different from the fifth embodiment in that the number of parts of the middle yoke is reduced and the middle yoke is separated by a notch to form two right and left parts. Further, when not separating as shown in FIG. 11, the number can be one. As described above, even when two magnetic circuits are combined with one coil, the inner yoke can be easily assembled by using one component.

(Embodiment 7) FIG. 5 shows a seventh embodiment.
In this embodiment, when the middle yoke of the first embodiment is separated by a notch, one middle yoke is integrated with the outer yoke.

Similarly, in the second, third, fourth, fifth and sixth embodiments, one middle yoke and one outer yoke may be integrated.
In this way, the notch in the central portion of the middle yoke can be realized by extending the outer yoke instead of the middle yoke.

(Embodiment 8) In the first to seventh embodiments, the cutout portion of the middle yoke is air without a member, but it may be reinforced by being filled with a filling member.

FIG. 11 is a diagram for explaining the eighth embodiment. A filling member (hatched portion) is provided for each of FIGS. 11A to 11E to fill the notch. The example shown in FIG. 11 is a representative example of the examples shown in FIGS. 8, 9, and 10.
It is possible to fill in the same manner for all the examples of FIGS. 8, 9, and 10.

A non-magnetic material is used as the material of this filling member. For example, the metal material is copper, aluminum, lead and an alloy containing these as the main components, and the non-metal material can be plastics, vinyls, glasses and rubbers.

By preliminarily joining the middle yoke with the filling member in this manner, the control of the width of the notch becomes easy and the precision of the parts is improved. Further, even in the case of the middle yoke having a partly connected portion, the parts can be easily handled and the assemblability is improved by being reinforced as shown in FIGS. 11 (c) and 11 (e).

In particular, FIGS. 8 (e), (f), (g),
(H) and FIGS. 9 (a) and 9 (b) are effective because they can be positioned by the shape of the filling member sandwiched between the notches so as to ensure the flatness and symmetry of the middle yoke when assembling the middle yoke. .. Further, FIG. 10 (f) shows a shape in which the filling member is a single component and is easily attached to the middle yoke.

(Ninth Embodiment) FIG. 14 shows an objective lens driving device according to a ninth embodiment of the present invention. Bobbin 102,
A movable portion including the focusing coil 104, the holder 105, and the objective lens 106 is sandwiched between a pair of parallel leaf spring-shaped suspensions 101 and supported by the base 103.

The structure of the objective lens driving device will be described with reference to the exploded view shown in FIG. In the movable part, two focusing coils 104 are attached to the left and right on a bobbin 102, and a holder 105 on which an objective lens 106 is placed is attached on top. Further, a balancer 107 is attached below to adjust the center of gravity of the movable part. The movable portion configured in this manner is sandwiched between the suspension 101 from above and below, and at the same time, the base 103 is also sandwiched and supported.

In the objective lens driving device assembled in this way, the base 103 shown in FIG. 14 is on the fixed side, and the movable part moves up and down.

Next, the structure of the optical head driving device will be described with reference to the drawings. The exploded view shown in FIG. 16 shows the configuration of an optical head driving device in an optical disk device. FIG.
As shown in FIG. 5, the lower yoke 205 is formed by connecting two yokes for the left and right magnetic circuits at two locations. A support spring 223 is joined to the connecting portion by caulking. The tracking magnet 203 is attached to the lower yoke 205, and the tracking coil 204 and the carriage 21 are attached.
1, a bearing 209 and an objective lens driving device 112, an optical head including a middle yoke 202 and a support shaft 206.
, The lower yoke 205
Attach to. At this time, both ends of the support shaft 206 are supported by the support springs 223 and are stabilized. Next, the upper yoke 201 having the tracking magnet 203 attached to the lower surface is connected to the middle yoke 202 penetrating the tracking coil 204.
Attach to. As a result of assembling in this way, the optical head drive device shown in FIG. 17 is completed. In FIG. 17,
Further, the spindle motor 210 and the optical disk 215 are shown and their positional relationship is shown.

FIG. 18 shows a combination state with the objective lens driving device 112 by adding a focusing magnet 222 and a focusing yoke 221 to the optical head driving device shown in FIG. The objective lens driving device 112 moves between the facing focusing magnets 222 as shown in the driving direction 208. Four focusing magnets 222 are used. Two focusing magnets 222 are combined so that magnetic poles alternate with each other, and each pair is arranged so as to face each other. Two focusing coils 104 attached to the movable part of the objective lens driving device 112 are mounted in the magnet arrangement with the linear parts facing the magnetic poles. The focusing coils 104 are connected in series, and one terminal of each coil is connected to a drive circuit (not shown).

The optical system of this embodiment is divided into a fixed optical system and an optical head. As shown in FIG. 17, the laser light emitted from the fixed optical system (not shown) is incident on the optical head as incident light 217, and the optical path is bent by the prism 216 shown in FIG. Laser light is emitted to the optical disc 215 as the emitted light 218. The irradiated laser light is used for the objective lens driving device 11
The light is condensed by 2 to form a spot 219 on the recording surface of the optical disc 215. The laser light reflected from the spot 219 reverses the above-mentioned incident optical path and returns to the fixed optical system to create a control signal and a data signal. The position of the spot 219 is controlled along the track 220 on the recording surface of the optical disc 215 by using the control signal.

Position control includes position control in the direction perpendicular to the recording surface of the optical disk 215 with respect to the objective lens driving device 112 for controlling the size of the spot 219, and movement of the optical head in the direction indicated by the driving direction 208. Position control 2
Kind done.

This embodiment relates to the position control in the direction indicated by the driving direction 208 of the optical head driving device, among the two types of position control described above.

In the optical head driving device constructed as described above, a current that rapidly changes in strength and direction flows through the tracking coil 204 for position control. The magnetic field generated by this current is the lower yoke 205 and the middle yoke 20.
2. Since it flows through the magnetic circuit formed by the upper yoke 201,
If it is the same as the conventional one, it becomes a magnetic circuit having a small magnetic resistance, and the inductance becomes large electrically, which is disadvantageous for high-speed operation as shown in the graph a of FIG. Therefore, in the present embodiment, as shown in FIG. 19, two middle yoke pieces 202a are opposed to each other and are inserted into the conductor cylinder 202b, and the middle yoke 202 is formed by forming a required gap on the opposed surfaces to solve the problem. is doing. Since the gap provided in the middle yoke 202 of the present embodiment is substantially in the center of the middle yoke 202, it becomes a magnetic resistance for the magnetic field generated by the current flowing through the tracking coil 204, but is generated by the tracking magnet 203. It does not become a magnetic resistance in the magnetic field. Therefore, the rise of the current flowing through the tracking coil can be accelerated without sacrificing the electromagnetic force for tracking, and an optical disk device capable of high-speed tracking operation can be realized.

[0047]

According to the present invention, by providing the notch in the middle yoke, the magnetic resistance of the magnetic circuit with respect to the electromagnetic induction generated by passing the current through the coil is increased, so that the rising of the current flowing through the coil is prevented. Can be fast. As a result, the control band is widened and high-speed seek can be realized.

Next, by making the cross-sectional area of the middle yoke small and using it in a magnetically saturated state, it becomes difficult for the magnetic field generated by the current flowing through the coil to pass through the middle yoke, so that a current flows through the coil. It is possible to increase the magnetic resistance of the magnetic circuit against the electromagnetic induction generated thereby. As a result, the control band is widened and high-speed seek can be realized.

Further, since the good conductor, which has conventionally covered the middle yoke, is joined also for the purpose of reinforcing the middle yoke, the accuracy of parts and the assemblability are improved.

In terms of reinforcement, the notch may be filled with a non-magnetic material. As a result, component accuracy and assemblability are improved.

If such an optical head driving device is mounted, a high-performance optical disk device having a high access speed can be supplied at a low price.

[Brief description of drawings]

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

FIG. 2 is a plan view illustrating a second embodiment of the present invention.

FIG. 3 is a plan view illustrating a third embodiment of the present invention.

FIG. 4 is a plan view illustrating a fourth embodiment of the present invention.

FIG. 5 is a plan view illustrating a seventh embodiment of the present invention.

FIG. 6 is a plan view illustrating a fifth embodiment of the present invention.

FIG. 7 is a plan view illustrating a sixth embodiment of the present invention.

FIG. 8 is an explanatory view of a notch shape of the present invention.

FIG. 9 is an explanatory view of a notch shape of the present invention.

FIG. 10 is an explanatory view of a notch shape of the present invention.

FIG. 11 is an explanatory view of the shape of a filling member for explaining an eighth embodiment of the present invention.

FIG. 12 is an explanatory diagram of an effect of the present invention.

FIG. 13 is a plan view illustrating a conventional example.

FIG. 14 is a perspective view of an objective lens driving device for explaining a ninth embodiment of the present invention.

FIG. 15 is an exploded view of an objective lens driving device for explaining a ninth embodiment of the present invention.

FIG. 16 is an exploded view of an optical head driving device for explaining a ninth embodiment of the present invention.

FIG. 17 is a perspective view of an optical head driving device for explaining a ninth embodiment of the present invention.

FIG. 18 is an explanatory diagram of an optical disc device for explaining a ninth embodiment of the present invention.

FIG. 19 is a detailed view of the middle yoke for explaining the ninth embodiment of the present invention.

[Explanation of symbols]

 1 outer yoke 2, 2a, 2b, 2c, 2d middle yoke 3 magnet 4 coil 5 optical head 6 driving direction 7 notch 7a notch width 8 good conductor 9 magnetic field generated by current flowing in coil 10 created by magnet Magnetic field 11 Saturation region

Claims (7)

[Claims] 1. 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, and a yoke which is arranged parallel to a driving direction and penetrates the coil. An optical head drive device having a notch in the central part of the. 2. The optical head driving device according to claim 1, wherein the yoke having a notch in the center is covered with a pipe made of a good conductor. 3. The optical head drive device according to claim 1, wherein the notch portion of the yoke according to claim 1 is filled with a non-magnetic material. 4. 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, wherein the coil is arranged parallel to a driving direction of the optical head. An optical head drive device characterized in that a yoke passing through is magnetically saturated by a magnetic force of a permanent magnet. 5. 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 the optical head drive device is arranged parallel to a drive direction and penetrates the coil. An optical head driving device, wherein the yoke has a notch in a central portion, and one of the yokes is an integral part with the yoke that does not penetrate the coil. 6. An optical disk device comprising the optical head driving device according to claim 2. 7. An optical disk device comprising the optical head driving device according to claim 3.