JPS6011385B2 - Actuator for magnetic head drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a piezoelectric magnetic head drive actuator.

In conventional magnetic head positioning devices for movable head type magnetic disk drives, great efforts have been made to achieve higher speeds, higher densities, smaller sizes, and lower costs.

In general, the magnetic head positioning device holds floating magnetic head assemblies corresponding to each of a plurality of magnetic disk recording surfaces with a linear movement support called a carriage, and writes or moves data on the carriage using a whisk coil type actuator. At the same time as it is moved to the data track, it is positioned on the data track by a known servo technique, that is, a track-following servo.

In order to ensure high-speed and high-precision positioning, carriages are required to be lightweight and highly rigid, and magnesium alloy is now being used as the material, but its manufacturing cost is prohibitive. . Also, although we tried to reduce the weight, the weight of the carriage is still the same as the weight of the magnetic head assembly.
The frequency was about 4 times higher, and the mechanical resonance point also occurred at a considerably lower frequency. On the other hand, in a magnetic disk drive, the magnetic head and its corresponding data track may be displaced relative to the radial direction of the magnetic disk due to vibrations due to unbalanced rotation of the magnetic disk, irregular high-order vibrations, vibrations due to external shock, etc. It is happening inevitably.

In high-density devices, it is necessary to reduce the tracking error of the magnetic head with respect to this positional deviation, and the track following servo system needs to have a wide band so that it can follow the above-mentioned high-order vibrations with high precision. In the movable head type disk device using the voice coil type actuator, as mentioned above, the weight of the movable part is relatively large and the mechanical resonance point occurs at low frequencies, so there is a limit to widening the band of the track following control system. This has made it extremely difficult to realize a positioning device with higher density.

On the other hand, as a magnetic disk device that made high density possible,
There is a fixed head disk device disclosed in Japanese Patent Application Laid-Open No. 51-26505, and its configuration is shown in FIG.

In the figure, 1 is a magnetic disk, 3 is a magnetic head body consisting of a plurality of magnetic heads 2, 4 is a piezoelectric actuator, and 5 is a fixed arm. A magnetic head 2 is arranged one after another on the data track, and the magnetic head main body 3 is coupled to a piezoelectric actuator 4. The magnetic head 2 is controlled to follow the data track. However, the manufacturing cost of magnetic heads is quite high, and although the introduction of integrated circuit manufacturing technology has made it possible to manufacture highly accurate multi-heads and reduced manufacturing costs, some of them have been put into practical use. For large-capacity, low-cost devices, it is still difficult to adopt the fixed head method due to cost considerations, and an actuator mechanism is required to access a plurality of data tracks with one magnetic head.
When a conventional piezoelectric actuator shown in FIG. 1 is used in such a movable head actuator mechanism to access a data track, there is a drawback that the flying height of the magnetic head increases in proportion to the moving distance. Furthermore, since the piezoelectric element itself has a small damping coefficient, in the configuration shown in FIG. 1, the control characteristics become unstable and oscillations are likely to occur.
Therefore, the purpose of the present invention is to eliminate the above-mentioned drawbacks, adopt a high-density multi-head that can be obtained through high-precision manufacturing technology of integrated circuits, and reduce the stroke of the actuator to the necessary minimum within an allowable range of device cost. It is an object of the present invention to provide a piezoelectric actuator for driving a magnetic head that is lightweight, inexpensive, and improved in type 4 and has good follow-up control characteristics. According to the present invention, the central part of an elastic metal plate is fixed or supported, and piezoelectric bodies bored in the same direction are attached to one or both sides of the elastic metal plate, both of which are free ends and located symmetrically with respect to the center in the longitudinal direction. Bimorph type piezoelectric vibrator and magnetic head A magnetic head assembly whose gap is parallel to the vibration direction of the dimorph type piezoelectric vibrator and connected to the free end of the vibrator and the magnetic head near the free end of the vibrator is braked. A piezoelectric actuator for driving a magnetic head, which is equipped with a magnetic head element, is obtained. Next, the present invention will be explained with reference to the drawings.

FIGS. 2 and 3 show one of the pressure crab type actuators for driving a magnetic head inserted between a large number of magnetic disks 1 rotating at high speed. The piezoelectric actuator is composed of an outer magnetic head assembly 6 and a bimorph piezoelectric vibrator 14. The magnetic head assembly 6 holds an integrated head 7 including many magnetic head elements, a slider 8 that floats on the corresponding surface of the magnetic disk 1, a gimbal spring 9 that holds the slider 8, and a slider that balances the buoyancy force generated on the slider 8. It is composed of a load spring 10 for keeping the flying height of the gimbal spring 8 constant, and a support arm 11 for holding the gimbal spring 9. FIG. 4 is a perspective view showing a bimorph type piezoelectric vibrator.

As shown in FIG. 4, the bimorph piezoelectric vibrator 14 has two electric bodies 13 attached to one or both sides of an elastic metal plate 12 at symmetrical positions with respect to the longitudinal center, and brake plates 15 at both ends.
is installed. The bimorph type piezoelectric vibrator is fixed at its longitudinal center portion to a stand 24 with insulating holders 16 and 17. The flexible side ends of the support arm 11 of the magnetic head assembly 6 are attached to the opposite ends of the bimorph piezoelectric vibrator 14 on the surface not provided with the brake plate 15 by gluing, welding, or a flexible support. The bimorph type piezoelectric vibrator 14 is displaced in a rotational manner around a fixed end, and in one embodiment of the present invention, the maximum displacement of the actuator is set to around 300 microns, and at the same time, the bimorph type piezoelectric vibrator of the support arm 11 Since the attachment part to the magnetic head assembly 6 is made flexible,
The influence on the head gap is almost negligible, and only a linear displacement is obtained in the part of the collecting head 7 parallel to the head gap. Furthermore, the piezoelectric bodies 13 attached to the elastic metal plate 12 have the same dimensions, and the electrical connections (not shown) to the piezoelectric bodies 13 are bimorph type when the same voltage is applied to the piezoelectric bodies 13. Both ends of the piezoelectric vibrator 14 are bent equally in the same direction. The amount of bending at both ends of the bimorph piezoelectric vibrator 14 is proportional to the voltage applied to the piezoelectric body 13, and by controlling the magnitude of this applied voltage, the magnetic head is positioned on a predetermined data track.
As mentioned above, the bimorph piezoelectric vibrator 14 itself has a very small damping coefficient, making controllability unstable.
In the present invention, a braking element 20 is added externally to improve its characteristics. In the embodiment shown in FIG. 2, braking by overcurrent is used as the braking element 20, and a braking plate 15 with non-magnetic permeability and low resistivity is attached to both ends of the piezoelectric vibrator 14, and a permanent magnet 18 and a yoke are attached. It is inserted into the gap of the magnetic circuit consisting of 19 to obtain a braking effect. It is also clear that the same effect can be obtained by using an air damper instead of using overcurrent braking. FIG. 5 shows another embodiment of the present invention, in which the longitudinal center portion of the bimorph piezoelectric vibrator 14 is supported at two points via insulating holders 22 and 23 and mounted on a stand 24. .

In this embodiment, a larger amount of bending can be obtained than when the central portion is fixed for the same applied voltage. As described above, by improving the structure and control characteristics of the conventional piezoelectric actuator, the piezoelectric actuator for driving a magnetic head according to the present invention has a simpler structure, smaller size, and extremely small weight of moving parts than a whisk coil type actuator. , has much better frequency characteristics and can sufficiently follow extremely high-frequency vibrations of the data track, making it possible to realize a magnetic head positioning device for a high-density movable head type magnetic disk drive. be able to.

Furthermore, since the stroke of the actuator is short, the average access time is also shortened, making it extremely fast for a movable head type disk device. Therefore, if the piezoelectric actuator according to the present invention is used as an actuator for driving a magnetic head, a high-performance movable head type magnetic disk device that is small, lightweight, high speed, high density, and low cost can be realized.

Modifications can be made without departing from the spirit of the present invention, and the above description does not limit the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a conventional fixed head disk device that enables high density, FIGS. 2 and 3 are plan and side views showing an embodiment of the present invention, and FIG. 4 is a bimorph FIG. 5 is a perspective view showing a type piezoelectric vibrator, and FIG. 5 is a drawing showing another embodiment of the present invention. In the figure, 1 is a magnetic disk, 2 is a magnetic head, 3 is a magnetic head body, 4 is a Shoden type actuator, 5 is a fixed arm, 6 is a magnetic head assembly, 7 is an integrated head, 8 is a slider, and 9 is a gimbal. Spring, 10 is a load spring, 11 is a support arm, 12 is an elastic metal plate,
13 is a piezoelectric body, 14 is a bimorph type piezoelectric vibrator, 15 is a brake plate, 16 and 17 are holders, 18 is a permanent magnet, 19
is a yoke, 20 is a braking element, 21 is an elastic metal plate, 22,
23 is a holder, and 24 is a stand. Figure O, Figure O, Figure 5, Figure 2, Figure O, Figure 3, Figure O, Figure 4.

Claims (1)

[Claims] 1 Bimorph type piezoelectric vibration in which the central part of an elastic metal plate is fixed or supported, both ends are free ends, and piezoelectric bodies poled in the same direction are attached to one or both sides of the plate at symmetrical positions with respect to the center in the longitudinal direction. a magnetic head assembly whose magnetic head gap width is parallel to the vibration direction of the bimorph piezoelectric vibrator and is arranged in conjunction with the free end of the bimorph piezoelectric vibrator; 1. An actuator for driving a magnetic head, comprising a damping means for damping vibration of a vibrator disposed near an end.