JPH04219637A - Actuator yoke oscillation preventing construction of optical head - 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]

0001

[Industrial Application Field] This invention relates to an optical head of an optical disk device that writes, reads, and erases information by irradiating an information storage medium with light that is converged into a minute spot by an objective lens, and in particular focuses the objective lens. This invention relates to a vibration isolation structure for the yoke portion of an actuator that corrects errors and tracking errors.

0002

[Background Art] Magneto-optical storage devices that utilize magneto-optical effects have recently appeared, and their use in the computer field is attracting attention as large-capacity rewritable external storage devices that replace hard disks and floppy disks. There is. Additionally, phase change optical storage devices and the like are being developed that utilize reversible phase change from crystalline to amorphous due to changes in the temperature of the storage medium. Further, operations such as recording, reproducing, and rewriting information in these storage devices are all performed by irradiating the storage medium with a laser beam focused on a minute spot using an optical head. Incidentally, in order to record and reproduce high-quality information, it is necessary to project a well-focused light spot onto the information track formed on the storage medium. An optical head is now known in which an objective lens is supported by an actuator, and the actuator is minutely driven based on focus error detection signals and tracking error detection signals to correct the focus shift and track the information track. It is being

FIG. 2 is a sectional view showing a conventional objective lens actuator. On the base 20 of the optical head, which has a seat 21 to which a preamplifier board 22 is screwed, etc., there is an actuator that engages with a recess 23 to position the actuator. An actuator yoke 1 is provided, and the actuator yoke 1 has a magnetic circuit consisting of a fixed shaft 9 projecting perpendicularly from the center thereof, and two sets of outer yokes 2 and inner yokes 4 projecting symmetrically from each other on both sides of the fixed shaft 9. A magnet 3 is attached to the outer yoke 2 on the side facing the inner yoke. Further, the fixed shaft 9 is provided with an objective lens driving section 10 that is slidably guided by a bearing 6 on the fixed shaft, and a focus coil 7 is provided on a portion of the movable bobbin 5 coupled to the bearing 6 that faces the magnet 3. A track coil 8 is attached to the movable bobbin 5, and an objective lens and a balancer (not shown) are supported in front and behind the fixed shaft 9 of the movable bobbin 5.

In the objective lens actuator configured as described above, when a drive current based on a focus error signal is supplied to the focus coil 7, the drive unit 10
moves slightly in the axial direction of the fixed shaft 9 to correct the focal shift of the light spot. Furthermore, when a drive current based on the tracking error signal is supplied to the track coil 8, the drive unit 1
0 slightly rotates around the fixed axis 9 to track the information track on the storage medium and correct positional deviation. By the way, as optical disks as information storage media rotate at higher speeds, it has become important to improve the followability of the actuator and the vibration characteristics of the drive unit. The weight has been reduced, the rigidity has been strengthened, and the high resonance frequency has been improved.

[0005]

[Problems to be Solved by the Invention] On the other hand, with the progress of vibration analysis, vibrations generated in the drive unit when the focus coil and track coil are excited by drive current are parasitic to the actuator yoke via the fixed shaft and magnetic circuit. It has become clear that this parasitic vibration is further propagated to the base of the optical head and adversely affects the servo control characteristics of the actuator. As a method for suppressing the above-mentioned parasitic vibration, it is considered effective to provide a dynamic weight 30 with a weight 32 attached to the outer surface of the outer yoke 2 using a flexible adhesive layer 31, but the long-term reliability of the adhesive layer There is a problem that there are concerns about the quality of the adhesive and that the number of manual bonding steps increases.

An object of the present invention is to provide an actuator that can easily and stably suppress parasitic vibrations of an actuator yoke and thus has stable servo control performance.

[0007]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a magnetic circuit consisting of a fixed shaft and an inner yoke and an outer yoke arranged symmetrically on both sides of the fixed shaft is provided. an actuator yoke positioned on the base of the optical head, a movable bobbin that is slidably supported on the fixed shaft and supports the objective lens, and a portion of the movable bobbin that faces the magnetic pole surface of the outer yoke. A focus coil that is mounted to slightly drive the movable bobbin in the axial direction of the fixed shaft, and a track coil that slightly rotates the movable bobbin, and a track coil that protrudes from the optical head side and is elastic on the outer surface of the outer yoke. The actuator yoke is provided with a vibration isolator that contacts the actuator yoke and suppresses vibration of the actuator yoke.

It is also assumed that the vibration isolating device is comprised of a leaf spring whose one end is screwed to the base of the optical head, and whose other curved end is formed so as to come into resilient contact with the outer surface of the outer yoke.

Furthermore, the plate spring is screwed together with the preamplifier board to a mounting seat for fixing the preamplifier board to the optical head.

0010

[Operation] By configuring a vibration isolator that comes into elastic contact with the outer surface of the actuator yoke and protrudes from the base side of the optical head, the natural frequency of the actuator yoke can be changed by selecting the spring constant of the vibration isolator. This makes it possible to suppress parasitic vibrations. In addition, if the main portion of the vibration isolator is composed of a leaf spring, a vibration isolator with a simple structure having an arbitrary spring constant can be easily obtained. Furthermore, by screwing the vibration isolator made of a leaf spring to the base of the optical head using the mounting seat of the preamplifier board, the vibration isolator can be assembled without requiring any special mounting seat or installation man-hours.

[0011]

EXAMPLES The present invention will be explained below based on examples. FIG. 1 is a sectional view showing an actuator yoke vibration isolation structure of an optical head according to an embodiment of the present invention, and the same reference numerals are used for the same parts as in the conventional device, and a detailed explanation will be omitted. In the figure, the vibration isolator 11 is a leaf spring 12
is the main component, one end of which is the base 20 of the optical head.
The preamplifier board 22 is fixed to a seat 21 protruding from the base 21 with a screw 13 via a pad 15 and a washer 14. The other end of the bent leaf spring 12 is configured to elastically contact the outer surface of the outer yoke 2 of the actuator yoke 1 while maintaining a predetermined pressure. Note that it goes without saying that the vibration isolator 11 may be provided at multiple locations.

In the vibration isolating device 11 configured as described above, the influence on the natural frequency of the actuator yoke 1 can be varied over a fairly wide range by determining the spring constant of the leaf spring 12. The vibration generated in the drive part when excited by the drive current can be suppressed from propagating to the actuator yoke via the fixed shaft 9 and the magnetic circuit and inducing parasitic vibration.
It is possible to avoid a situation in which this parasitic vibration further propagates to the base of the optical head and adversely affects the servo control characteristics of the actuator. Further, by using a leaf spring, a vibration isolating device having an arbitrary spring constant can be easily obtained, and this leaf spring can be attached to the base 20 of the optical head together with the preamplifier board by using the mounting seat 21 of the preamplifier board.
By screwing the vibration isolator, the number of man-hours required for assembling the vibration isolator can be reduced to almost zero. Therefore, it is possible to obtain a vibration isolating device that has a simple structure, requires no assembly man-hours, and has excellent long-term stability.

[0013]

[Effects of the Invention] As described above, the present invention has a structure in which a vibration isolator that comes into elastic contact with the outer surface of the actuator yoke protrudes from the base side of the optical head, thereby making it possible to select the spring constant of the vibration isolator. Depending on the method, the natural frequency of the actuator yoke can be changed and parasitic vibration can be suppressed.
The conventional problem that parasitic vibration propagates to the base of the optical head and adversely affects the servo control characteristics is eliminated, and it is therefore possible to provide an optical head equipped with an actuator that has excellent responsiveness to high-speed access.

Furthermore, if the main part of the vibration isolator is composed of a leaf spring, a vibration isolator with a simple structure having an arbitrary spring constant can be easily obtained, and the conventional adhesive layer can be eliminated, resulting in long-term stability. Accordingly, it is possible to provide an optical head equipped with a vibration isolating device having excellent properties.

Furthermore, if a vibration isolator made of a leaf spring is screwed to the optical head using the mounting seat of the preamplifier board, the vibration isolator can be formed without requiring a special mounting seat or installation man-hours, so dynamic The economic disadvantage caused by the increase in assembly man-hours, which was a problem with the conventional method using weights, is eliminated, and there is an advantage that it can contribute to reducing the manufacturing cost and improving the performance of the optical head.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an actuator yoke vibration isolation structure of an optical head according to an embodiment of the present invention.

[Figure 2] Cross-sectional view showing the actuator yoke vibration isolation structure of a conventional optical head

[Explanation of symbols]

1 Actuator yoke 2 Outer yoke 3 Magnet 4 Inner yoke 5 Movable bobbin 6 Bearing 7 Focus coil 8 Track coil 9 Fixed axis 10　　　Drive part 11 Vibration isolation device 12 Leaf spring 20 Base of optical head 21 Mounting seat 22 Preamplifier board 30 Dynamic weight

Claims (3)

[Claims] Claim 1: A magnetic circuit comprising a fixed shaft, an inner yoke and an outer yoke arranged symmetrically across the fixed shaft, an actuator yoke positioned on the base of an optical head, and a magnetic circuit arranged on the fixed shaft. a movable bobbin that is movably supported to support an objective lens; a focus coil that is attached to a portion of the movable bobbin that faces the magnetic pole surface of the outer yoke to minutely drive the movable bobbin in the axial direction of the fixed shaft; and a track coil for micro-rotation drive, further comprising a vibration isolator that protrudes from the base side of the optical head, comes into elastic contact with the outer surface of the outer yoke, and suppresses vibrations of the actuator yoke. An optical head actuator yoke anti-vibration structure characterized by: 2. The vibration isolator comprises a leaf spring having a predetermined spring constant, one end of which is screwed to the base of the optical head;
2. The actuator yoke vibration isolation structure for an optical head according to claim 1, wherein the other curved end is formed to elastically contact the outer surface of the outer yoke. 3. The actuator yoke vibration isolation structure for an optical head according to claim 2, wherein the leaf spring is screwed together with the preamplifier board to a mounting seat for fixing the preamplifier board to the optical head.