JPS621132A - Actuator for optical disk device - Google Patents

Abstract

PURPOSE:To obtain an actuator which is excellent in its damping performance, by providing a hole on a lower damper, especially, of a damper for supporting a bobbin which moves as one body with an objective lens, and also varying variously a size, a shape, etc. of the provided hole. CONSTITUTION:A lower damper 31 is provided with plural pieces of round holes 32, and others are the same as conventional one. According to the actuator for an optical disk device having the above constitution, a viscous resistance coefficient by air is varied and a Q value can be controlled by providing the round holes 32 on the lower damper 31. That is to say, the Q value is varied variously and controlled by the number of the holes provided on the lower damper, the size, the shape or the arranging method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an actuator for an optical disc device that focuses a laser beam onto a disc-shaped recording medium (hereinafter referred to as a disc) into a minute beam and records or reproduces information on the disc. It is something.

2. Description of the Related Art In recent years, optical disk devices have attracted attention from various quarters as future storage devices due to their large storage capacity and high-speed random access function, and some have already been put into practical use.

An example of a conventional actuator for an optical disc device will be described below with reference to the drawings.

FIG. 4, FIG. 5, and FIG. 6 show the structure of a conventional actuator. Reference numeral 1 denotes an objective lens that condenses the beam into minute light and forms an image on a disc (not shown); 2 a bobbin that houses and fixes the objective lens; two pairs of arms to
a and 2b, and coils 3a and ab are wound around each of them.

A focus pobbin 4 is adhesively fixed to the bobbin 2, and a coil 6 is similarly wound around its outer periphery. Further, the bobbin 2 is provided with grooves 2c and 2d on its upper and lower sides, respectively, and an upper damper and a lower damper, which will be described later, are mounted thereon. 6
are E-shaped yokes provided opposite the arms 2a and 2b of the bobbin 2, and are fixed to the base 15 (at 4 locations).In addition, two chip-shaped magnets are attached to each of the E-shaped yokes. 7 are adhesively fixed, a magnetic circuit is formed between the coils 3a and 3b of the bobbin 2, and the coils 3a,
The bobbin 2 is driven and controlled in the track direction 8 and the circumferential direction 9 according to the direction of the current flowing through the coil 3b. Reference numeral 1o denotes a center yoke facing the focus bobbin 4, to which a donut-shaped magnet, throat 11 and top yoke 12 are bonded, and similarly forms a magnetic circuit with the coil 6 of the focus bobbin 4, and the coil The bobbin 2 is driven and controlled in the focus direction 14 in the direction of the current flowing through the bobbin 5. A lower bolt 13 supports one side of the bobbin 2, and is made of rubber having a uniform thickness and is set to be easily deformed in the focus direction 14. In addition, this lower Danno (13 is adhesively fixed to the center yoke 10 and supports the other bobbin 2 through the groove 2d of the bobbin 2. Similarly, the lower Danno (13) supports the other bobbin 2 through the groove 2C. The upper damper is also made of rubber, and unlike the lower damper 13, it has a structure that is easily deformed in the track direction 8 and the circumferential direction 9.The upper damper 16 is adhesively fixed to the holder 17. This holder 17 is further fixed to the base 15. Reference numeral 18 is a printed board on which the soldering of the coil is performed, and 19 is a cap.

The operation of the actuator configured as above will be described below.

As mentioned above, the actuator allows the light spot of the objective lens 1 to accurately follow the surface runout and eccentricity of the disk, but the objective lens 1 is driven by energizing a coil in a magnetic circuit. For example, in Figure 6, l
- When the coil 3a in the rack direction is energized in a fixed direction, the left hand side of the mink 71 causes the bobbin 2 to move in either of the track directions 8, and when the coil 3a is energized in the opposite direction, the direction of movement is also reversed. Similarly, in the focus direction 14, the movement of the bobbin 2 in the focus direction 14 can be controlled by causing the coil 5 wound around the focus bobbin 4 to perform the same operation as described above.

Problems to be Solved by the Invention Regarding actuator characteristics and performance evaluation, it is generally easiest to express them in the Bode diagram shown in FIG. 7, where the resonant frequency ω. , the resonance width value (hereinafter referred to as Q value), the presence or absence of higher-order resonance, etc. can be evaluated.

When evaluating actuator performance using Bode diagrams,
The Q value at the resonance frequency ω is an important factor in servo technology, and if this Q value is too large, it becomes vulnerable to external vibrations, especially focus, track 2. In the king servo, there is a problem that it becomes difficult to obtain stable pull-in during random access, for example, and it is said that the smaller the Q value, the better. In order to reduce the Q value, the spring constant of the damper may be reduced as shown in the theoretical formula described later, but there is a risk that center runout of the objective lens may occur, especially when driving in the focus direction.

In addition, most of the Q value is determined by the material hardness, thickness, shape, etc. of the damper used, so if there is a discrepancy between the target value and the actual value, change the material, shape, thickness, etc. of the damper mentioned above. It became necessary to change and re-experiment, and it was difficult to obtain a target Q value with excellent damping performance in a short time.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an actuator for an optical disc device that allows easy control of the Q value.

Means for Solving the Problems In order to solve the above problems, the actuator for an optical disk device of the present invention includes an objective lens, a bobbin that moves together with the objective lens, and upper and lower dampers that respectively support both ends of the bobbin. A hole is provided in the lower damper of the actuator consisting of a damper.

Operation According to the present invention, the viscous drag coefficient of the fluid (air in this case) changes, and the Q value can be freely controlled by the above-described configuration.

Embodiment Hereinafter, an actuator for an optical disk device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the structure of an actuator for an optical diffuser according to a first embodiment of the present invention, in which numeral 31 denotes a lower damper in which a plurality of round holes 32 are provided. The rest is the same as that shown in the conventional example shown in FIG. 4, and the explanation will be omitted. FIG. 1 shows the actuator for an optical disk device configured as described above.

The operation will be explained using FIGS. 2 and 3.

The dynamic model of the actuator in the embodiment shown in FIG. 1 is shown in FIG. 2, and its equation of motion is expressed as follows.

F=mx+cx+kx ・−・−−−−・
...(1) When this is Laplace-transformed to obtain the transfer function G(s), the Bode diagram represented by this changes with ζ in equation (2) as a parameter, as shown in Figure 3. .

That is, in the dynamic model shown in FIG. 2, Q is sufficient, but in this embodiment, the viscous drag coefficient C due to air is made smaller by providing a round hole 32 in the lower damper 31.

As described above, according to this embodiment, the round hole 3 is provided in the lower damper 31.
2, it is possible to change the viscous drag coefficient due to air and control the Q value.

Here, the holes provided in the lower damper are not limited to the embodiment shown in Fig. 1, and it goes without saying that the Q value can be controlled in various ways depending on the number, size, shape, arrangement method, etc. of the holes provided. be.

Effects of the Invention As described above, the present invention is achieved by providing a hole in the damper, particularly the lower damper, which supports the bobbin that moves together with the objective lens, and by changing the size of the hole provided.

By variously changing the shape etc., the Q value can be delicately controlled, and by optimizing the holes provided, it is possible to easily provide an actuator for an optical disk device with excellent damping performance.

[Brief explanation of drawings]

Figure 1 is an exploded view of an actuator according to an embodiment of the present invention, Figure 2 is a diagram showing its dynamic model, Figure 3 is a Bode diagram with ζ as a parameter, and Figure 4 is an exploded view of a conventional actuator. 5 is a plan view of the actuator in FIG. 4, FIG. 6 is a front sectional view thereof, and FIG. 7 is a Bode diagram. 1...Objective lens, 2...Bobbin, 4
...Focus bobbin, 16...Upper damper, 31...Lower tick/c, 32...
Round hole. Name of agent: Patent attorney Toshio Nakao and 1 other person G4
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] An objective lens that condenses a light beam into a minute beam and forms an image on a disk-shaped recording medium, a bobbin that houses this objective lens and moves together with it, an upper damper and a lower damper that respectively support both ends of this bobbin, and the objective lens. An actuator for an optical disk device, comprising magnetic circuits for driving a lens in a focus direction and a track direction of the disk-shaped recording medium, and further comprising a hole in the lower damper.