JPS621133A - Actuator for optical disk device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an actuator for an optical disk device that focuses a laser beam onto a disk-shaped recording medium (hereinafter referred to as a disk) into a very small beam and records or reproduces information on the disk. 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 disk device will be described below with reference to the drawings.

Figure 4! 5 and 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 disk (not shown); 2 a bobbin that houses and fixes this objective lens; Pair of arms 2a
, 2b, and coils sa and 3b are wound around each of them.

A focus bobbin 4 is adhesively fixed to the bobbin 2, and a coil 6 is similarly wound around its outer periphery.

The bobbin 2 also has grooves 2c on its upper and lower sides, respectively.

2d, and an upper damper and a lower damper, which will be described later, are mounted thereon. Reference numeral 6 denotes an E-shaped yoke that is provided facing each of the arms 2a and 2b of the bobbin, and is fixed to the base 15 (at four locations). Further, two chip-shaped magnets 7 are adhesively fixed to each of the E-shaped yokes, and the coils 3a of the bobbin 2 are connected to each other.

A magnetic circuit is formed between the coil 3a and the coil 3a.

The bobbin 2 is driven and controlled in the track direction 8 and the circumferential direction 9 in the direction of the current flowing through the bobbin 3b. Reference numeral 10 denotes a seven-point 7 yoke facing the focus bobbin 4, to which a donut-shaped magnet 11 and a top yoke 12 are respectively bonded. Similarly, a magnetic circuit is formed 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 6. A lower damper 13 supports one side of the bobbin 2, and is made of rubber with a uniform thickness and is set to be easily deformed in the focus direction 14. The lower damper 13 is adhesively fixed to the center yoke 1o, and supports the bobbin 2 via the groove 2d of the bobbin 2. Reference numeral 16 designates an upper damper that similarly supports the other side of the bobby/2 through the groove portion 2C, and is also made of rubber, and unlike the lower damper 13, the upper damper
and has a structure that is easily deformed in the circumferential direction 9. Further, the upper damper 16 is adhesively fixed to a holder 17, and this holder 17 may be further fixed to the base 16.
19 is the printed board on which the soldering of the coil described above is carried out.
is a cap, and 2o is an optical bench on which the actuator is fixed.

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 FIG. 5, if the coil 3a in the track direction is energized in a fixed direction, the bobbin 2 on Fleming's left hand side will move in one of the track directions 8, and if the coil 3a is energized in the opposite direction, the direction of movement will be reversed. Become. Similarly, in the focus direction 14, the movement of the bobbin 2 in the focus direction 12 can be controlled by causing the coil 5 wound around the focus bobbin 4 to perform the same operation as described above.

In addition, actuator characteristics and performance evaluation are generally easiest to understand by representing them in the Bode diagram shown in Figure 7.
The resonance 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 a Bode diagram, the resonant frequency ω
The Q value in is an important factor in servo technology,
If this Q value is too large, it becomes susceptible to external vibrations, and in particular, in focus and tracking servos, it becomes difficult to obtain stable pull-in during random access, for example, so it is said that the smaller the Q value, the better.

Problems to be Solved by the Invention However, in the above configuration, when the actuator is fixed to the optical bench 20 in FIG.
3, the air portion 21 between the optical table 20 and the optical bench 20 becomes sealed, and as shown in the theoretical formula described later, the viscous refractive coefficient of the air increases and the Q value becomes large.

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 disk 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, an upper damper that supports both ends of the bobbin, and an upper damper that supports both ends of the bobbin. In the lower damper and the base that houses them, holes communicating with the outside air are provided, particularly in the exposed portion of the base that is sealed from air by the lower damper.

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

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 disk device according to a first embodiment of the present invention, in which 31 is a base, and a plurality of circles are arranged so as to release the air 21 sealed by the lower damper 13 to the outside. A hole 32 is provided. The rest is the same as that shown in the conventional example shown in FIG. 4, and the explanation will be omitted. The operation of the actuator for an optical disk device constructed as described above will be explained below with reference to FIGS. 1, 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 ・・・・・・−・φ・・・
・・・・・・・・・・・・(1) Laplace transform this to find the transfer function G(sl), and as shown in Figure 3, the Bode diagram expressed by this is as shown in equation (2). It changes with ζ as a parameter.

That is, in the mechanical model shown in FIG. 2, the viscous drag coefficient C due to air is reduced by providing a round hole 32 in the base 31 so that the sealed air escapes to the outside. be.

As described above, according to this embodiment, by providing the round holes 32 in a corresponding portion of the base 31 that is airtight, it is possible to change the viscous drag coefficient due to air and control the Q value. Here, the holes provided in the base 31 are not limited to the embodiment shown in FIG. 1, and it goes without saying that the Q value can vary and be controlled by changing the number, size, shape, arrangement method, etc. of the holes provided. It is.

Effects of the Invention As described above, the present invention provides holes in a considerable portion of the base 31 so that the air sealed by the lower damper can escape to the outside, and the size, shape, etc. of the holes provided can be varied in various ways. By doing this, 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]

Fig. 1 is a front cross-sectional view of an actuator according to an embodiment of the present invention, Fig. 2 is a diagram showing its dynamic model, Fig. 3 is a Bode diagram with ζ as a parameter, and Fig. 4 is a diagram 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, 13 ... Lower damper, 16 ... Upper damper, 21 ... Sealed air section, 31 ... Base Stand, 32...
...Round hole. Name of agent: Patent attorney Toshio Nakao and 1 other person +-
-g￥'aL>7" 2-, bobbin 4---F1-nosr"--t>4-3-g Fig. 1
1l---)-i-/? '7゛m2 1
2--Top 7" 3-ri 13--F

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. Consisting of magnetic circuits that drive the lens in the focus direction and track direction of the disk-shaped recording medium, and a base that houses these,
An actuator for an optical disc device, characterized in that a hole communicating with outside air is provided in a substantial portion of the base that is sealed from air by the lower damper.