JP2000163896A - Piezoelectric element driven type fine displacement magnetic head actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the piezoelectric driven type fine displacement magnetic head which actualizes high track density. SOLUTION: This magnetic head actuator has a mechanism 2 which covers a piezoelectric element and/or a displacement enlarging mechanism and restrains displacement nearly perpendicular to a seek direction. In order to avoid the breakage of the piezoelectric element due to a shock, part of the displacement resticting mechanism is composed of a member providing buffering action. Further, part of the displacement restricting member is composed of a member which provides conductive action as to release electric accumulated charges of the piezoelectric elements generated when a chock is received.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small displacement magnetic head actuator for driving a piezoelectric element of a magnetic disk drive, and more particularly to an actuator for positioning a magnetic head.

[0002]

2. Description of the Related Art The improvement of the recording density of a magnetic disk drive is based on the circumferential recording bit density (so-called BPI) of a magnetic disk.
And increasing the radial track density (the so-called TPI). In particular, the bit density has been remarkably improved with the adoption of a head dedicated to MR reproduction. With the development from MR heads to spin valve heads and GMR heads,
The recording density is increasing at an annual rate of 60%. However, the flying height of the magnetic head slider also approaches the medium protrusion height without limit, and the R / W channel transfer rate is considerably high with the increase of the disk rotation speed.
We are approaching an area that W-channel ICs cannot keep up with.

[0003] Therefore, recently, development has been progressing in the direction of increasing the track density. Generally, the track density has been improved by downsizing the disk. In other words, the vibration amplitude is suppressed by reducing the size of the component, and the vibration frequency is further increased, thereby increasing the control band and securing the positioning accuracy. On the other hand, for models that require large capacity and high transfer rate,
0 (rpm) or higher is required, and it is difficult to secure sufficient positioning accuracy even if the rigidity of positioning mechanism components such as actuators is increased, and it is easy to increase the track density. Was not. Therefore, instead of downsizing the actuator, mounting a small actuator corresponding to minute displacement on the main actuator to share the frequency band to be followed, thereby improving the positioning accuracy. This is the introduction of a two-stage positioning mechanism system to which a so-called microactuator is added.

[0004] The micro-displacement actuator types are first classified into a suspension drive type, a slider drive type, and a magnetic head drive type, and recently, a "Flexural Piggyback Actuator for Magnetic Diode" has been designated as a suspension drive type.
sk Drives ", Shinji Koganezawa et al. Japan Society of Mechanical Engineers, IIP'96
VCM type shown in the collection of lecture papers
DUAL STAGE ACTUATOR SYSTEM FOR MAGNETIC DISK DRIVE
S USINGA SHEAR MODE PIEZOELECTRIC MICRO-MOTOR ", S.
Koganezawa.et.al FUJITSU Ltd., Asia-Pacific Magnet
ic Recording Conference (APMRC) 1998 “PIEZOELECTRIC” as a piezoelectric element drive type and slider drive type shown in FB-03
PIGGY-BACK MICROACTUATOR FOR HARDDISK DRIVE ", Y.So
eno, et, al., TDK Cor, APMRC 1998 FB-02, "A MICRO-ACTUATOR"
FOR HEAD POSITIONING SYSTEMOF HARD DISKDRIVES ", H.
FUJITA.et.al The University of Tokyo, APMRC1998 FB
The research and development of the electrostatic type shown in -06 is actively underway. Among them, the head drive type described last is the ultimate type of the micro-displacement actuator, which can cope with a higher track density. There is a considerable limitation on the materials used since integral molding is required. The slider drive type does not need to consider the vibration characteristics of the suspension and is a solid element, so the main resonance frequency can be set quite high.However, since the piezoelectric element is connected to the back of the slider, the slider The thickness is increased, and the thickness of the entire device is increased. In order to further expand the movable range, piezoelectric elements must be laminated,
As a result, the drive frequency decreases and the drive displacement becomes non-linear. Regarding the driving frequency, it is still 20-30 (k
Hz), so there is no problem, but the effect of displacement nonlinearity on control performance is considerable.

On the other hand, when a track density of 25,000 TPI to 40,000 TPI and a movable range of about ± 2 (μm) are targeted, the suspension itself can be used as a displacement enlarging mechanism from the viewpoint of securing a drive range. Driven micro-displacement actuators are promising. As mentioned above, the options include the VCM type and the piezoelectric element drive type. The VCM type has the same form as the first-stage actuator, and has the advantage that it can be driven by an inexpensive power supply circuit. However, since the physical quantity that can be controlled with respect to the input current is acceleration, it is necessary to perform twice integration to control the amount of displacement. Therefore, a magnetic disk for securing a control band of about 2 to 3 (kHz) is required. There is a disadvantage that the number of servo data to be recorded increases and the format efficiency decreases. On the other hand, in a piezoelectric element, since the physical quantity that can be controlled with respect to the input voltage is a displacement, the number of servo data is smaller than that of the VCM type, so the format efficiency is increased, and as a result, the recording capacity can be increased. Further, since the displacement magnifying mechanism is used, a single-layer or single-crystal piezoelectric element can be used, and the nonlinearity of the displacement can be considerably improved. However, the problem is that the drive voltage is high and
When the power supply voltage becomes 30 to 40 (V) and this power supply voltage cannot be supplied from the outside, it is necessary to newly provide a booster circuit, and the cost increases accordingly. As described above, both types have advantages and disadvantages, but when the recording density (capacity) is to be improved by increasing the TPI, the piezoelectric element drive type is advantageous.

[0006]

As a performance requirement specification of a recent magnetic disk drive, impact resistance has been particularly emphasized. In addition to transporting the device and incorporating it into a PC, the device often receives a considerable impact even in the actual use environment. Especially, a magnetic disk device of 2.5 "or less is mounted on a portable device. In order to increase the impact resistance, not only the impact resistance of each component in the device but also the relative displacement characteristics between the components are important. But
From the viewpoint of damage to recorded data, the most problem is that the slider jumps on the magnetic disk due to impact and recollides with the disk. In this case, in order to enhance the impact resistance, it is most effective to reduce the equivalent mass of the slider / suspension assembly and increase the load applied to the slider by the suspension. Further, if a head load / unload mechanism for positioning the slider / suspension portion outside the disk when the apparatus is not operating is provided, the shock resistance can be drastically improved, not only when the apparatus is not operating.

[0007] Considering the piezoelectric element driving type small displacement actuator, in the case of the shape utilizing the length mode of the piezoelectric element shown in FIG. 7, the connection with the displacement enlarging mechanism is made at both ends of the elongated rod-shaped piezoelectric element. When the suspension load is large, stress due to bending deformation or the like tends to concentrate on the bonding end of the piezoelectric element because the suspension load is large. Further, since the elastic deformation area of the piezoelectric element is considerably small, the possibility of breakage is very high if the deformation amount is large. Here, when a further shock is applied, a considerable deformation is accompanied in a short time, so that the stress applied to the piezoelectric element easily exceeds the elastic deformation limit and is very likely to be broken. In addition, when the piezoelectric element receives a stress shock, an electric charge is generated. Therefore, for example, if the shock continues to be applied while the piezoelectric element is not short-circuited when the apparatus is not operated, the electric charge is accumulated on both electrode surfaces of the piezoelectric element. And by the charge,
If the voltage at both ends of the piezoelectric element exceeds the drive voltage, an excessive voltage is applied from the piezoelectric element to the drive circuit system at the start of operation of the apparatus, and in the worst case, the drive circuit may be damaged.

On the other hand, in the case of the shape utilizing the thickness-shear mode of the piezoelectric element shown in FIG. 8, there is almost no problem with the breakage of the piezoelectric element under a high load condition, but there is a possibility that the displacement magnifying mechanism may be deformed. high. In order to solve the problem, the present invention provides a displacement restraining mechanism in a piezoelectric element portion and a displacement enlarging mechanism portion of a piezoelectric element driving type small displacement actuator to prevent plastic deformation and destruction at the time of impact, and to provide a high impact resistant magnetic material. It is intended to provide a disk device.

[0009]

SUMMARY OF THE INVENTION The present invention provides a displacement restraint for restraining a displacement in a direction substantially orthogonal to a seek direction above a piezoelectric element and / or a displacement enlarging mechanism of a piezoelectric element driven type micro displacement magnetic head actuator. A small displacement magnetic head driven by a piezoelectric element, characterized in that a mechanism is provided to impart impact resistance. As described above, the shock resistance of a piezoelectric element or the like is one of the main performances required in recent years, particularly for a magnetic disk device of 2.5 "or less. The piezoelectric element is usually installed on a base, and is connected to the base itself. Damage due to contact is not possible, but when an external force is applied, it displaces in a direction perpendicular to the base, that is, in a direction substantially perpendicular to the seek direction, causing the piezoelectric element or the like to exceed its elastic limit. In the case of contact or collision, the piezoelectric element or the like will be damaged, so in the present invention, in order to suppress deformation of the piezoelectric element or the like and to avoid collision with other parts, the surroundings of the piezoelectric element or the like are avoided. In addition, a displacement restricting mechanism for suppressing deformation of the piezoelectric element or the like and preventing collision or contact with other parts is installed in the piezoelectric element to protect the piezoelectric element or the like.

The displacement restricting mechanism preferably has an inverted L-shape extending in a beam shape from the surface on the base side of the base to above the piezoelectric element or the like, but has a function of minimizing the displacement of the piezoelectric element. Therefore, the shape is not limited to this, but may be a shape extending above the piezoelectric element from the side surface of the base. Further, since the piezoelectric element is fixed to the base and is displaced together with the base in the bending direction of the base, the piezoelectric element is displaced in a direction substantially orthogonal to the seek direction as described above, and a displacement restricting mechanism is installed in that direction. The displacement restricting mechanism not only restricts the displacement but also protects the displaced piezoelectric element and the like. Therefore, if the displacement restricting mechanism is made of a material that damages the piezoelectric element when the piezoelectric element collides, there is no point in installing the mechanism. In particular, when the displacement restraining mechanism is formed of a hard material, a structure (shock absorbing material) made of a soft or elastic material and having a shock buffering function is attached to a portion of the displacement restraining mechanism that comes into contact with the piezoelectric element, or the like. Form. As described above, electric charges may be generated in the piezoelectric element, and if the electric charges are accumulated, the driving circuit may be damaged. In order to avoid this, in the present invention, a conductive material is provided at a position where the displacement restricting mechanism comes into contact with the piezoelectric element, and the electric charge can be released by bringing the piezoelectric element into contact with the conductive material.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing a first embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to claim 1 of the present invention. The piezoelectric element displacement restraining mechanism 2 is a cantilever having one end fixed to the base side of the joint between the tip of the first-stage VCM arm 3 and the base 4 of the piezoelectric element driving type micro-displacement magnetic head actuator 1. It has a structure. The fixed portion may be any portion as long as it does not significantly displace in response to an impact, and may be fixed to the tip end side of the VCM arm. The cantilever portion 5 of the displacement restricting mechanism 2 of the piezoelectric element covers almost the upper part of the piezoelectric element 6, and when a displacement occurs in a direction substantially orthogonal to the seek direction due to an impact, the piezoelectric element 6 first
Collides with the lower surface of the beam portion, and any further displacement is restrained or decelerated depending on the spring characteristic of the beam portion 5,
Destruction in the plastic deformation region due to excessive displacement and speed can be suppressed.

FIG. 2 is a view showing a second embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to the first aspect of the present invention. In this embodiment, at the time of impact, the piezoelectric element 10 itself is displaced and
Does not collide with the movable part 13 of the piezoelectric element driven type micro displacement magnetic head actuator 1. Thereby, the possibility of breaking a piezoelectric element (ceramic) which is more brittle with respect to the suspension material can be suppressed. In this case, it is possible to protect the weak spring portion from being plastically deformed by directly restraining the vertical displacement and the torsional displacement by colliding with the displacement enlarging mechanism portion instead of the movable portion 13. . Further, a greater effect can be expected by combining with the case of FIG.

FIG. 3 is a view showing a third embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to the first aspect of the present invention. In this case, by disposing the displacement restraint mechanism 22 on both the upper and lower sides of the piezoelectric element 21, it is possible to perform effective displacement restraint even for repetition of bound / rebound at the time of impact. It is possible to increase the possibility of avoiding destruction of the element 21. Similarly, by providing the displacement restricting mechanism on both sides of the spring portion of the displacement enlarging mechanism, it is possible to suppress the plastic deformation.

FIG. 4 is a view showing a first embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to the second aspect of the present invention. An impact absorbing material 33 is disposed on a portion of the displacement constraint mechanism 31 facing the piezoelectric element 32. When an impact is applied, the impact absorbing material 33 collides with the piezoelectric element 32 in this embodiment, but the impact force and the impact velocity are reduced by the effect of the impact absorbing material 33, so that the impact destruction of the piezoelectric element 32 is prevented. Things become possible. The same effect can be expected even when the shock absorbing material 33 collides with the displacement enlarging mechanism or the movable part.

FIG. 5 is a view showing a second embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to the second aspect of the present invention. In this case, a shock absorbing material 44 is connected between the side surface of the beam portion 42 of the displacement restraining mechanism 41 and the base portion 43. As a result, it is possible to increase the damping characteristics of the beam portion 42 and improve the bound / rebound vibration damping characteristics of the vertical displacement of the piezoelectric element 45 due to the impact, and to enhance the non-destructive characteristics of the piezoelectric element 45 due to the impact. Can be. In this case, the non-destructive reliability can be further improved by using the collision portion together with the displacement enlarging mechanism and the movable portion.

FIG. 6 is a view showing an embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to claim 3 of the present invention. A conductive material 53 is disposed on a portion of the displacement constraint mechanism 51 facing the piezoelectric element 52. When the piezoelectric element 52 is deformed by an impact, electric charges are generated on both electrodes 54 and 55 of the piezoelectric element 52 by the piezoelectric effect. When bending or twisting due to very fast acceleration, the generated charge is high and the potential difference between both ends is 100
(V) or higher. As in the present embodiment, when an electric charge is generated in the piezoelectric element 52, an unnecessary electric charge can be removed by immediately contacting the electrode portion of the piezoelectric element 52 with the grounded conductive material 53. Can be prevented from being damaged. In general, a piezoelectric element also has a pyroelectric effect, and may generate an electric charge in response to a temperature change. Such a case can be dealt with by activating the displacement restricting mechanism 51, bringing the piezoelectric element 52 into contact with the conductive material 53 at a predetermined time when the apparatus is activated, and operating the apparatus, and grounding the electrode 54. It is.

Although not particularly shown in the present embodiment, the displacement restricting mechanism of the present invention may be any mechanism that absorbs the impact of the piezoelectric element-driven micro-displacement magnetic head actuator and suppresses its destruction. As for the constituent material, any material having the characteristics shown in the claims may be used, and modifications in accordance with the gist of the present invention are possible.

[0018]

As described above in detail, by using the piezoelectric element-driven small displacement actuator having the displacement restraining mechanism according to the present invention (claim 1),
It is possible to configure a two-stage actuator mechanism system having high shock resistance, and it is possible to provide a highly reliable magnetic disk device having a higher track density and a large storage capacity. Also, depending on the material of the displacement restricting mechanism, the piezoelectric element or the like may be damaged by the displacement restricting mechanism. To avoid this, a structure having an impact buffering function should be provided at a position where the displacement restricting mechanism comes into contact with the piezoelectric element. It may be formed (claim 2). Further, electric charges are easily accumulated in the piezoelectric element, and the accumulated electric charges may damage the driving circuit. In order to avoid this, a structure having conductivity is provided at a portion of the displacement restricting mechanism that comes into contact with the piezoelectric element, and the structure is maintained at the same potential as the electrical ground of the device. Item 3),
Thereby, the charge generated in the piezoelectric element can be removed from the piezoelectric element through the structure.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to claim 1 of the present invention.

FIG. 2 is a view showing a second embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to claim 1 of the present invention.

FIG. 3 is a view showing a third embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to claim 1 of the present invention.

FIG. 4 is a view showing a first embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to claim 2 of the present invention.

FIG. 5 is a view showing a second embodiment of the piezoelectric element driving type small displacement magnetic head actuator according to claim 2 of the present invention.

FIG. 6 is a view showing an embodiment of a piezoelectric element driving type small displacement magnetic head actuator according to claim 3 of the present invention.

FIG. 7 is a schematic view showing an example of a conventional piezoelectric element driving type micro displacement magnetic head actuator (length mode displacement).

FIG. 8 is a schematic view showing an example of a conventional piezoelectric element driving type micro displacement magnetic head actuator (slip mode displacement).

[Explanation of symbols]

 1. Piezoelectric element driven type micro-displacement magnetic head actuators 2, 11, 22, 31, 41, 51, displacement restraint mechanism 3, VCM arms 4, 43, bases 5, 12, 23, 42, beams 6, 10, 21 , 32, 42, 52, piezoelectric elements 33, 44, shock absorbing material 53, conductive materials 54, 55, electrodes

Claims (3)

[Claims] 1. A displacement magnifying mechanism that mounts a piezoelectric element and the piezoelectric element and magnifies the displacement, a suspension that is connected to the displacement magnifying mechanism and that is a part of the displacement magnifying mechanism, and that is connected to a tip of the suspension. In a piezoelectric element-driven small displacement magnetic head actuator composed of a magnetic head for recording and reproducing information, a seek direction of the piezoelectric element and / or the displacement magnifying mechanism is set around the piezoelectric element and / or the displacement magnifying mechanism. A micro-displacement magnetic head actuator driven by a piezoelectric element, wherein a shock-resisting property is provided by installing a displacement restraining mechanism for restraining displacement in a direction perpendicular to the magnetic head. 2. The actuator according to claim 1, wherein the piezoelectric element and / or the displacement of the displacement restricting mechanism are located around the piezoelectric element and / or the displacement enlarging mechanism and restrict the displacement in a direction substantially orthogonal to the seek direction. A small displacement magnetic head actuator driven by a piezoelectric element, wherein at least a part of a portion that can come into contact with the enlargement mechanism is formed of a structure having an impact buffering function. 3. The actuator according to claim 1, wherein a portion of the displacement restraint mechanism facing the piezoelectric element is formed of a conductive structure, and the structure is connected to an electrical ground of the device. A small displacement magnetic head actuator driven by a piezoelectric element, which is maintained at the same potential.