JPS63206148A - Linear motor for optical head - Google Patents

Abstract

PURPOSE:To prevent vibration from generating by providing a pair of movable coils so wired as to operate driving forces which have equal magnitudes and reverse directions on a pair of movable units opposed to a magnet forming a magnetic circuit. CONSTITUTION:A coll 26A is disposed slightly separate above adjacent magnets 24A, 25A. Similarly, a coil 26B is disposed slightly separate below magnets 24B, 25B of low side. When the coils 26A, 26B are connected in series, it is so wired that, if a driving force which operates when a current flows in one coil 26A moves the coil 26A, for example, rightward, it moves the other coil 26B leftward. With this configuration, even if an acceleration is operated at the time of accessing or the like, a reaction force which operates on a stator side can be set to substantially zero as a whole, thereby preventing a vibration from generating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a linear motor for an optical head that has a structure that is almost immune to the influence of reaction during access.

[Prior Art] In recent years, instead of using a magnetic head, information has been recorded by irradiating a condensed light beam onto a recording medium, or by receiving the return light of a condensed light beam irradiated onto a recording medium. Optical information recording and reproducing devices that can reproduce information recorded on a computer have come into practical use.

In the optical information recording and reproducing apparatus described above, information is recorded along concentric or spiral tracks on a disk-shaped recording medium that is rotationally driven. Therefore, when accessing a target track to record or reproduce information, it is necessary to move the optical head using an optical head feeding mechanism. For example, a linear motor shown in FIGS. 8 and 9 has been used as a feeding mechanism for this optical head.

Figure 8: Linear motors are especially voice coil motors (VC
It is called M).

In the VCM 1, a cylindrical yoke 4 is attached to, for example, the N pole side of the cylindrical magnet 3, and the yoke 4 and the magnet 3 are surrounded by a cylindrical yoke 5. One end of the yoke 5 is It is integrated with the disc-shaped yoke portion to which the S pole of the magnet 3 is attached. A movable coil 6 is loosely fitted between the inner yoke and the outer yoke 5, and the optical head is attached to the coil 6, and the optical head is moved together with the coil 6 by the current flowing through the coil 6. It's like moving.

In addition, in the linear motor 2 shown in FIG. 9, the central yoke 1
A moving coil 12 is fitted into the moving coil 1, and magnets 13 and 13 are arranged on both sides of the moving coil 12. Each magnet 13 shares the central yoke 11 and forms an 8-shaped closed loop on both sides of the yoke 11. For example, each S pole side is fixed to each yoke 14. The magnetic flux emitted from the N pole of each magnet 13 crosses the coil 12 to form the inner yoke 11.
The magnetic flux passing through this yoke 11 is directed to the yoke 14.1
4 and return to the south pole side.

[Problems to be Solved by the Invention] In the VCML shown in FIG. 8 above, since the coil 6 is arranged in the gap between the inner yoke 4 and the outer yoke 5, only the coil 6 is small compared to the size of the magnetic circuit. Cannot be placed. Therefore, the driving force for moving the optical head is small.

In addition, the loss due to overcurrent is large in usage conditions such as repeated start, stop, forward, and backward operations, and high frequency response IJJ work.
Drive efficiency decreases. In order to prevent this, a short ring 7 made of a copper plate or the like is used, but this short ring 7 makes the gap even larger and the leakage magnetic flux increases, so the overall shape is made larger to compensate for the decrease due to the leakage magnetic flux. There will be a need to supplement. For this reason, each component becomes large-sized and disadvantageous in terms of cost.

In addition, in order to increase the driving force, when the coil 6 is accelerated or decelerated by increasing the current flowing through the coil 6, a magnetic reaction acts on the stator side, producing a force in the opposite direction to the moving direction of the moving coil. receive. This effect causes the optical pickup mounted on the movable coil and the disk on the stator side to vibrate with each other, which is extremely harmful to tracking pull-in during high-speed access.

Furthermore, the linear motor 2 also has the disadvantage that it cannot eliminate the influence of magnetic reaction due to acceleration that occurs during access.

The present invention has been made in view of the above-mentioned points, and provides a linear motor for an optical head that can eliminate the occurrence of inconvenient phenomena such as vibration caused by acceleration even when acceleration is applied during access operations. The purpose is to

[Means and effects for solving the problem] In the present invention, a pair of almost symmetrical magnetic circuits are formed on both sides of a central yoke, and movable coils are arranged opposite to the magnets forming each magnetic circuit. Furthermore, by connecting these moving coils in such a way that driving forces of equal magnitude are generated in opposite directions when current is passed through them, even if acceleration is applied during access, etc., the side of the member that supports both moving coils remains intact. so that the reaction forces cancel each other out,
Prevents vibration from occurring.

[Example] Hereinafter, the present invention will be specifically described with reference to the drawings.

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure shows a side sectional view of the first embodiment, FIG. 2 shows a plan view taken along the line AA' in FIG. 1, FIG. 3 shows a side view of FIG. 5 shows an exploded perspective view of the mounting portion of the optical pickup, and FIG. 5 shows a drive circuit for driving the first embodiment.

The linear motor 21 (for optical head) of the first embodiment is as follows:
As shown in FIG. 1, vertically symmetrical magnetic circuits are formed on both upper and lower sides of the central plate-like yoke 22.

That is, a plate-shaped upper yoke 23A1 and a lower yoke 23B are arranged opposite to the central plate-shaped yoke 22, and both of these yokes 2
3A and 23B are both ends in the longitudinal direction, and are fixed to yoke portions vertically provided on the plate surface of the yoke 22 at both ends of the yoke 22 to form a flat closed magnetic path.

The central yoke 22 in both the yokes 23A and 23B
There are two magnets 2 on each inner surface facing the
4A, 25A: 24B, 25B are fixed adjacently so that the magnetic pole directions are opposite.

In other words, if the N pole of one magnet 24A (or 25B) is facing downward, the adjacent magnet 24A (or 25B)
5A (or 24B) is oriented upward. Also, the magnets 24A, 24B or 25A facing vertically
, 25B are attached so that the same magnetic poles face each other. Therefore, for example, if the magnetic flux of the magnet 24Δ is in the downward direction, the magnetic flux of the opposing magnet 24B is in the upward direction.

Between the adjacent magnets 24A, 25A and the center yoke 22, and the adjacent magnets 24B, 25B
and the central yoke 22 are each provided with a flat coil 2.
6A and 26B are coil support plates 27A and 27B, respectively.
is fixed.

Each coil support plate 27A, 27B is made of a non-magnetic material that is lightweight and has sufficient strength.
8A, 28A: 28B, 28B are installed, guide shaft 29A, 29A: 29B.

This allows for smooth movement on 29B.

Both ends of the upper coil support plate 27A are bent to surround the upper yoke 23A as shown in FIGS. 3 and 4, and an optical pickup is attached to the folded horizontal portion via the head fixing plate 31. (Optical head) 32 can be attached.

Both the coils 26A and 26B are connected in series to the output end of the drive circuit 33 as shown in FIG. are connected to generate driving forces in opposite directions. For example, in FIG. 1, when a driving force of the same magnitude is generated in the coil 26A in a direction to the right in the drawing as shown by the symbol a, a driving force of the same magnitude is generated in the coil 26B to the left in the drawing as already shown in the drawing. That's what I do.

Coils 26A that are moved by driving forces in mutually opposite directions;
Coil support plates 27A and 27 to which 26B are fixed respectively
B is the roller 34.34 on the outside of both ends of the central yoke 22.
The intervening parts are fixed to the upper and lower parts and the lower part of the passed steel belt 35 with an adhesive 36 or the like.

Each coil 26 is fixed to the steel belt 35 at a fixed position.
A and 26B are arranged to coincide at the center position of their movement range (the state shown in FIG. 1), and then move in opposite directions with a light load from this center position. The moving range is shown relative to the center of the coil 26B in FIG.

Further, the steel belt 35 is passed between the outer periphery of each row 534 through a slit-shaped through hole through which the steel belt 35 can be passed near both ends of the central yoke 22.

Note that each guide shaft 29A or 29B is fixed at both ends with shaft fixing members 39, 39.

The drive circuit 33 amplifies the input drive signal with an operational amplifier 41 as shown in FIG. Both coils connected 26A
, 26B.

The drive signal is input to the non-inverting input terminal of the operational amplifier 41, and the inverting input terminal of the amplifier 41 is grounded via a resistor R1, and is connected via a resistor R2 to the emitters of both transistors 42a and 42b, i.e. It is connected to the output end of the drive circuit 33.

The amplification factor (R1+R2)/
R1 is set. The output terminal of the operational amplifier 41 is connected to the bases of NPN and PNP transistors 42a and 22b, and the collectors are connected to positive and negative power supply terminals +Vc and -Vc, respectively.

For example, a driving force acts on each coil 26A, 26B connected in series to the output end of the drive circuit 33 as follows.

In FIG. 2, magnetic flux passes through two sides (indicated by symbols Ll and L2) perpendicular to the moving direction of one coil 26B in an upward direction and a downward direction in the direction perpendicular to the plane of the paper, respectively. Therefore, each side L1. When a current flows through L2 as shown by symbol I, each coil bottom L1. As already indicated by the reference numeral, a leftward driving force acts on L2, and the coil support plate 27B to which this coil 26B is attached is moved leftward. In this case, the other coil 26A is wired so that a driving force that moves in the opposite direction, that is, to the right, acts on the other coil 26A.

Therefore, in order to move the optical pickup 32 attached to the upper part of the upper coil support plate 27A and access the target track, when current is applied to both the coils 26A and 26B,
Driving forces of equal magnitude act on both coils 26A and 26B in opposite directions, and these driving forces are connected by a steel belt 35, so the sum of the forces on both sides moves the optical pickup 32 in one direction. It moves and can be moved with high power.

Furthermore, since the two movable parts are driven in opposite directions, the reaction forces acting on the stator side cancel each other out. In other words, when the optical pickup 32 is moved or stopped after being moved, acceleration acts on each coil 26A, 26B and the coil support plates 27Δ, 27B to which these coils 26A, 26B are attached, but these act on each other. In the opposite direction, the sizes are almost the same (the main difference is the influence of ffff1 of the optical pickup 32),
Stator side member, that is, yoke 22, this yoke 2
2, and almost no reaction force acts on the near motor 21 body side as a whole. For this reason, in the conventional example, the reaction force acting on the stator side during access causes mutual vibration between the optical pickup and the disk attached to the rotating shaft of the spindle motor fixed to the stator side member. This first embodiment does not cause such inconvenience. Also, each coil 26A,
Since 26B is a flat coil, gap loss can be reduced and there is no overcurrent loss, so a thin high-output linear motor can be realized.

In the above first practical example, the upper coil support plate 27A is bent and the optical pickup 32 is attached to the upper surface thereof, but as in the second embodiment shown in FIG. One side of the plate 27A' extends horizontally, and an optical pickup 3 is mounted on the upper part of the horizontal plate surface.
You may also make it possible to say 2. Also, since one side of the coil support plate 27A' is extended, the bearing 28A
etc. are shifted horizontally. In the illustration, one side of the lower coil support plate also extends, but the present invention is not limited to this. The other configurations are the same as those of the first embodiment, and the effects are also almost the same.

FIG. 7 shows a side view of a linear motor according to a third embodiment of the present invention.

In this embodiment, for example, in the first embodiment, the coil 26A
This is a structure in which the arrangement of the magnets 24A, 25A, the coil 26B, and the magnets 24B, 25B are replaced.

That is, magnets 2 are placed on the upper and lower surfaces of the central yoke 22.
4A', 25A: 24B, 25B are fixed. A coil 26A is arranged slightly apart from the upper side facing the adjacent magnets 24A and 25A.
A is attached to the steel belt 35' and is also fixed to the coil support plate 27A. Similarly, a coil 26B is arranged at a slight distance below the lower magnets 24B and 25B, and this coil 26B is attached to the steel belt 35' and is also fixed to the coil support plate 27B.

The above steel belt 35' has number puller rollers 34 installed at the four corners.
', 34', 34', 34' are provided with hooks, and each roller 34' is fitted onto each shaft 37'.
' is rotatably supported at both ends by bearings 38', 38'.

The upper coil support plate 27A is bent upward, and an optical pickup 32 is attached to the upper surface of the coil support plate 27A via a head fixing plate 31.

In this embodiment, for example, the magnetic poles of magnets 24A and 24B are arranged so as to form an upward magnetic flux,
Adjacent magnets 2'5A and 25B are arranged so as to form a downward magnetic flux.

Also in this embodiment, for example, both coils 26A.

26B are connected in series, one coil 26AI,
:The driving force that moves when current is passed through this coil 26A
For example, if the coil 26B is to be moved to the right, the other coil 26B is wired so as to be moved to the left. Therefore, even in this embodiment, even if acceleration is applied when the coils 26A and 26B are moved by applying current or stopped from the transfer state in order to access the optical pickup 32 toward the target track, the stator The side is so that the reaction force in that case is canceled out.

In other words, the effects of this embodiment are similar to those of the other embodiments described above.

In addition, in each of the above-mentioned examples, the steel belt 35.3
Steel wire or the like may be used instead of 5'.

Moreover, the coil support plate 2 to which the optical pickup 32 is attached
6A, by attaching a member having the same mass to the other coil support plate 26B, both coils 26A, 26
When a current is passed through B, the direction is opposite and the magnitude of the acceleration is equal, so the magnitude of the reaction force in that case is also opposite in direction and the magnitude of the reaction force is equal to each other, and these completely cancel each other out. You can do it like this.

Incidentally, the present invention is not limited to one in which an optical pickup is attached to one coil support plate side, but may be one in which optical pickups are attached to both coil support plates.

In addition, when current is passed through both coils 26A and 26B, they are not limited to being connected in series, but may be connected in parallel.

[Effects of the Invention] As described above, according to the present invention, a pair of magnetic circuits having a symmetrical structure and a pair of movable parts disposed opposite to the magnets forming this magnetic circuit have equal sizes. A pair of moving coils are connected so that driving forces act in opposite directions, so even if acceleration is applied during access, the reaction force acting on the stator side is reduced to almost zero as a whole. It is possible to prevent vibration from occurring.

[Brief explanation of the drawing]

FIGS. 1 to 5 relate to the first embodiment of the present invention.
The figure is a side sectional view of the first embodiment, and the second figure is A-A of the first embodiment.
A plan view cut along the ' line, Figure 3 is a side view of Figure 2,
FIG. 4 is an exploded perspective view showing the outline of the components for mounting the optical head, FIG. 5 is a circuit diagram showing the drive circuit of the first embodiment, and FIG.
The figure is a plan view showing a second embodiment of the present invention, FIG. 7 is a side view showing a third embodiment of the present invention, FIG. 8 is a configuration diagram showing a conventional example, and FIG. 9 is a diagram showing another conventional example. FIG. 21... Linear motor 22... Yoke 23A,
23B... Yoke 24△, 25A, 24B, 25B... Magnet 26
A, 26B...Coil 27A, 27B...Coil support plate 32...Optical pickup 35...Steel belt Fig. 4 S2 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9

Claims (1)

[Claims] A pair of almost symmetrical magnetic circuits and a magnet forming the pair of magnetic circuits are arranged on both sides of the central yoke, and an optical head is attached to at least one of them, and a drive current 1, which are connected in such a way that driving forces of equal magnitude and opposite directions are applied when
A linear motor for an optical head, comprising a pair of moving coils and a movable support mechanism that movably supports the pair of moving coils.