JPS60182086A - Damping device - Google Patents

Abstract

PURPOSE:To suppress substantially amplitude of a bending vibration mode of a thin base to a low level by providing an overhang for the base top of an optical disk device and a vibration absorbing means consisting of a weight and an elestatic body for absorbing vibration. CONSTITUTION:A motor 8 which rotates a magnet 3, a guide 5 of an optical head 1 and an optical disk 9 is fixed on a base 6 and supported by a vibrationproof leg 7. A weight 12 for controlling vibration and a vibration absorbing member 13 of an elastic body, etc., are installed on an overhang 11 of the base 6 and both of 12 and 13 constitute a vibration absorbing means 14. When the base 6 carries out bending vibration, the vibration on the top of the overhang 11 is magnified and becomes larger, and a large amount of acceleration is applied to the weight 12. As a result, although the weight 12 is comparatively small mass, large distortion is applied to a vibration absorbing body 13; therefore a vibration control effect is large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an allocating device for an optical disk device that reduces vibration of a lightweight base.

[Background of the invention]

In an optical disk device, for example, as disclosed in Japanese Unexamined Patent Publication No. 181434/1983, a disk rotation motor, optical head moving means, etc. are fixed on a base, and usually the whole is supported by vibration isolating means. There is. Furthermore, in order to downsize the entire device, the disk rotation motor and the original head moving means are arranged at both ends of the base.

In such a structure, when the optical head moves,
The base bends and deforms due to the sword acting on the means of movement. Therefore, if the disk rotation motor and the optical head moving means are tilted in opposite directions, the original beams from the disk and the optical head will be misaligned.

This positional deviation can be corrected by the track positioning control system, but if the thickness of the base is made thinner to reduce the size and weight of the device, the control system will be forced to move around 2001h, which is the pre-oscillation frequency of the bending vibration mode of the base. oscillate. In order to prevent this oscillation, it is necessary to significantly raise or lower the resonant frequency of the bending mode of the base, or to suppress the amplitude by increasing the damping of the bending mode without changing the resonant frequency. Lowering the resonant frequency of the bending mode is not a countermeasure against the influence of other higher-order vibration modes. Furthermore, there is no generally applicable vibration damping means. For this reason, conventionally, the thickness of the base is increased to increase the bending rigidity and the resonance frequency of the first bending mode is made sufficiently high.

However, making the base thicker not only increases the weight but also increases the height, etc., making the device rod larger. This applies not only to the original disk device, but also to all devices in which bending vibration of other structures is a problem.

[Purpose of the invention]

An object of the present invention is to provide a vibration damping device that can suppress the amplitude of the bending vibration mode to a sufficiently small level even with a thin base.

[Summary of invention]

When the base supporting the disk rotation motor, optical head moving means, etc. bends and vibrates, both ends of the base become antinodes of vibration, and the angle change is large.

Therefore, the oscillating device of the present invention has an overhang at the tip to enlarge the oscillation width, and a vibration absorbing means consisting of a weight and an elastic body for absorbing the expansion is provided at the tip. This is characterized by an improved vibration absorption effect.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

1 and 2 are a side view and a plan view of an optical disk device in which an example of the allocation device of the present invention is implemented.

The optical disk device irradiates the surface of an optical disk 9 with a source beam 10 for data recording, reproduction, and positional deviation detection from the tip of an optical head 1, and moves the optical head 1 in the track direction TR by a voice coil 2 and a magnet 3. let The optical head 1 moves on a guide 5 while being supported by rollers 4. Further, the optical disc 9 is rotated by the motor 8. The magnet 3, guide 5, and motor 8 described above are fixed to the base 6, and all of them are mounted on the anti-vibration legs 7.
Supported by At the end of the base 6 on the motor fixed side, projecting portions 11 are provided at both ends in the middle direction. An allocation die 12 and a vibration absorbing member 13 such as an elastic body are attached to each of these projecting portions 11, and these constitute a vibration absorbing means 14'f.

When a force indicated by F acts on the voice coil 2 and the magnet 3 to move the optical head 1 in the track direction,
The base 6 is bent and deformed. FIG. 3 shows a deformed state when the base 6 undergoes bending vibration.

Since the swing width of the tip of the overhanging portion 11 is expanded and becomes larger, a large acceleration is applied to the weight 12. Therefore, even if the weight 12 has a relatively small mass, it can apply a large strain to the vibration absorber 13, so that the vibration damping effect is large.

In addition, since the outer peripheral side of the optical disc 9 generally protrudes outward from the base 6, this protruding part 11R-
1 rlr life 8 + single-minded #wakamujiru's power, yo V, doesn't change much. In order to avoid adverse effects on the track positioning control system of the optical head 1, it is necessary to ensure that there is no resonant frequency of the mechanical system near the cutoff frequency of the open-loop circular transmission.

Even if the local resonant frequency of the projecting portion 11 is taken to be several tones above the cutoff frequency in consideration of all these points, according to the present invention, the mass of the steel 912 is small and appreciable.

Therefore, since the sum of the equivalent mass of the self-sprouting portion 11 and the quality t of the weight 12 is small, the bending rigidity of the overhanging portion 11 may be small, and the width and thickness 2t of the overhanging portion 11 may also be small. be.

In FIG. 3, if the frequency of the vibration mode is f, the kinetic energy is iE, and the amplitude of the vibration absorber consisting of the vibration absorber 13 and the weight 12 is a, then the equivalent mass of the vibration absorber m is
is expressed by equation (1).

Since the overhanging portion 11 and the vibration absorbing portion are sufficiently small compared to the entire device, the length t of the overhanging portion and the mass of the vibration absorbing portion have little effect on the overall resonant frequency f and vibration mode. Within this range, as can be seen from equation (1) above, increasing the amplitude a of the vibration absorbing section can reduce the equivalent mass level in the vibration absorbing section. According to the theory of dynamic dampers, the larger the ratio of the amount m of the dynamic damper added to the quality of the vibrating body -4m, the greater the vibration damping effect. Therefore, as shown in Fig. 3, the length tm from the bending vibration node to the vibration absorbing part is increased and the amplitude
By increasing l-thickness and reducing the uniform image mass m, the weight of the vibration absorbing part, which is a dynamic damper, can be reduced.
Even if it is small, a large allocation effect can be achieved. In order to increase the distribution effect, the mass ratio of the heavy disk 12 to the uniform mass m in the vibration absorbing section, the ratio of the resonant frequency of the vibration absorbing section to the resonant frequency of the optical disk device which is the vibrating body, and the ratio of the resonant frequency of the vibration absorbing section to the resonant frequency of the optical disk device that is the vibrating body, Conditions such as damping ratio can be found in vibration studies textbooks (
For example, it can be found in Tajima [Vibration Engineering JP 194-P198].

In one example, the length t of the overhang 11 is □ of the length of the base 6, the width is the formula of the base 6, the thickness is t'6 + of the pace 6, and the quality of the weight 912 is the gold base 6° motor. 8. By setting the mass of the magnet 3 to about ±00 and using butyl rubber as the vibration absorbing body 13, a sufficiently large vibration distribution effect was obtained.

As shown in FIGS. 1 and 2, the vibration absorbing means 14 are provided at both ends of the base 6 in the width direction.
The allocation effect can also be given to a mode in which the base 6 is twisted around the track direction.

Similarly, if only a damping effect is to be provided to the bending vibration of the base 6 in the track positioning direction, it is sufficient to provide only one overhang 11 near the center of the base 6 in the width direction.

In the above-described embodiment, the heavy seat 12 and the vibration absorber 1
3 is joined to the upper surface of the overhanging part 11, but the overhanging part 1
A similar effect can be obtained even if it is bonded to the lower surface of 1.

Although the above explanation has been made using the base of the original disk device as an example, it goes without saying that the present invention can similarly provide the above-mentioned allocation effect to any device in which bending vibration of the structure is a problem. In addition, it is possible to provide an overhang not only for bending vibration but also for torsional vibration to magnify the vibration d], and to provide a vibration distribution effect by providing a vibration absorbing section consisting of a heavy steel and a vibration absorber at the tip of the overhang. It is easy to guess what can be done.

Since the tip of the overhang generally has a large amplitude in all vibration modes, by providing the vibration absorbing portion there, there is a vibration effect in many vibration modes. However, due to the addition of the mass of the vibration absorbing section, vibration nodes are created near the vibration absorbing section in higher-order vibration modes. As a result, the amplitude a of the vibration absorbing portion becomes smaller and the damping effect is lost. Therefore, it is necessary to determine the shape and material of the overhanging portion 11 and the vibration absorbing portion so that such a vibration mode does not occur in the frequency range in which the device is used.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a large allocation effect, and it is possible to reduce the size and quantity of the device.

[Brief explanation of the drawing]

FIG. 1 is a side view of an example of the allocation device of the present invention implemented in an optical disk device, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is an optical disk device shown in FIGS. 1 and 2. FIG. 3 is a bending vibration mode diagram of FIG. l... Optical head, 9... Original disk, 6... Base, 11... Base overhang, 12... Heavy disk, 13
... Vibration absorber, 14... Vibration absorbing means. Representative Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. A vibration amplifying part that geometrically magnifies the deformation of the structure is provided at the end of the structure subject to bending vibration, and a vibration absorbing means consisting of a weight and a vibration absorber is attached to this vibration amplifying part. The claimed means is characterized in that it is a cantilever-shaped part that comes into contact with the vibration expansion part, and a vibration absorption means is provided near the tip of the part, and the vibration absorption means is provided at both ends of the structure at a distance from each other. The allocation device according to claim 1 or 2, characterized in that the allocation device is installed.