Source: http://www.google.com/patents/US6246552?dq=5708422
Timestamp: 2014-10-23 06:53:51
Document Index: 75597802

Matched Legal Cases: ['arts 43', 'arts 43', 'art 43', 'art 44', 'arts 44', 'art 44', 'arts 43', 'art 44', 'art 43', 'art 43', 'art 43']

Patent US6246552 - Read/write head including displacement generating means that elongates and ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA read/write head includes a slider provided with an electromagnetic transducer element (or an optical module), an actuator, and a suspension. The actuator includes a fixed part, a movable part, and at least two beam members for coupling them together. The beam members have a displacement generating...http://www.google.com/patents/US6246552?utm_source=gb-gplus-sharePatent US6246552 - Read/write head including displacement generating means that elongates and contracts by inverse piezoelectric effect of electrostrictive effectAdvanced Patent SearchPublication numberUS6246552 B1Publication typeGrantApplication numberUS 09/091,363Publication dateJun 12, 2001Filing dateSep 30, 1997Priority dateOct 31, 1996Fee statusPaidAlso published asCN1145957C, CN1206488A, WO1998019304A1Publication number09091363, 091363, US 6246552 B1, US 6246552B1, US-B1-6246552, US6246552 B1, US6246552B1InventorsYoshikazu Soeno, Shinji Ichikawa, Takamitsu Tsuna, Isamu SatoOriginal AssigneeTdk CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (12), Non-Patent Citations (2), Referenced by (99), Classifications (24), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetRead/write head including displacement generating means that elongates and contracts by inverse piezoelectric effect of electrostrictive effectUS 6246552 B1Abstract A read/write head includes a slider provided with an electromagnetic transducer element (or an optical module), an actuator, and a suspension. The actuator includes a fixed part, a movable part, and at least two beam members for coupling them together. The beam members have a displacement generating means that elongates and contracts by inverse piezoelectric effect or electrostrictive effect. The fixed part is fixed to the suspension, and the movable part is fixed to the slider. Upon the elongation and contraction of the displacement generator, the displacement generator deflects and the movable part displaces linearly, circularly or rotationally with respect to the fixed part, and the electromagnetic transducer element displaces in a linear or circular orbit, so that the electromagnetic transducer element intersects recording tracks. In the actuator, the fixed part, movable part and beam members are formed as an integrated single piece by providing a hole and/or a cutout in a sheet-like member constructed of a piezoelectric or electrostrictive material. The actuator of the structure illustrated is used for the positioning of a direction intersecting recording tracks. In this case, the total sum of voltages applied on the displacement generating means is controlled in such a manner that it is constant at any time, thereby controlling position fluctuations of the electromagnetic transducer element in the direction vertical to the recording medium surface.
FIELD OF THE INVENTION The present invention relates to a read/write head, a read/write head positioning mechanism, and a read/write system such as a magnetic or optical disk drive.
DISCUSSION OF THE BACKGROUND FIG. 32 is a plan schematic illustrative of a flying type magnetic head and a positioning mechanism therefor used in a conventional magnetic or hard disk drive (HDD).
The electromagnetic transducer element 1 comprises a magnetic pole and coil for converting electric signals to magnetic signals, and vice versa, and a magnetoresistance effect element for transforming magnetic signals into a voltage change, etc., each being fabricated by thin film techniques, assembly techniques, etc. The slider 2 is formed of non-magnetic ceramics such as Al2O3�TiC or CaTiO3 or a magnetic material such as ferrite, and has a generally cuboidal shape. The surface (air bearing surface) of the slider 2 opposite to a disk medium 6 is processed into a shape suitable for generating pressure to fly the slider 2 on the disk medium 6 at a small spacing. The suspension 3 is formed by bending, punching or otherwise processing a resilient stainless sheet.
For slider displacement, it has also been put forward to use an electrostatic force microactuator (�Magnetic Recording Head Positioning at Very High Track Densities Using a Microactuator-Based, Two-Stage Servo System�, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol. 42, No. 3, pp. 222-233, June 1995) or an electromagnetic force microactuator (�Silicon Microstructures and Microactuators for Compact Computer Disk Drives�, IEEE CONTROL SYSTEMS, pp. 52-57, December 1994). However, it is found that with the electrostatic force actuator it is difficult to generate driving force large enough to displace the slider, and with the electromagnetic force actuator there is concern that the magnetic signal on a disk medium is affected by flux leakage. A problem common to both actuators is that they are sensitive to extraneous disturbances because the slider must be held in place by means of a support member that has small resiliency and can be deformed by electrostatic force, and electromagnetic force generated from the actuators. Such a problem is also found in JP-A 8-180623 disclosing that a slider is driven by an electrostatic actuator.
While explanation has been made with reference to a magnetic head out of read/write heads, it is understood that the problems mentioned in connection with magnetic head positioning are all true of a recording/reproducing head for optical disk systems. A conventional optical disk system makes use of an optical pickup comprising an optical module including at least a lens. This optical pickup is so designed that the lens can be mechanically controlled so as to be focused on the recording surface of the optical disk. In recent years, near field recording has been proposed to achieve ever-higher optical disk recording densities. In this regard, see �NIKKEI ELECTRONICS�, Jun. 16, 1997 (No. 691), page 99. This near field recording makes use of a flying head which uses a slider like a slider used with a flying type magnetic head. Built in this slider is an optical module comprising a hemispherical lens called a solid immersion lens or SIL, a magnetic field modulation recording coil, and a prefocusing lens. Another flying head for near field recording is disclosed in U.S. Pat. No. 5,497,359. An optical disk used in combination with such a flying head has very high recording track densities. Accordingly, when positioning is effected with respect to recording tracks, the same problems as mentioned with reference to the flying type magnetic head arise.
SUMMARY OF THE INVENTION One object of the present invention is to achieve high-precision yet fast positioning of an electromagnetic transducer element or an optical module mounted in a read/write head in read/write systems such as magnetic or optical disk devices. Another object of the present invention is to achieve easy control of position fluctuations, upon such positioning, of the electromagnetic transducer element or optical element in a direction vertical to a recording medium surface.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective schematic illustrative of one typical basic construction of the magnetic head according to the present invention, and the positioning mechanism for an electromagnetic transducer element.
DISCUSSION OF THE PREFERRED EMBODIMENTS Features and advantages of the read/write head according to the present invention will now be explained specifically with reference to a magnetic head.
Conceptually, the term �read/write head� used herein shall include a read/write head, a write-only head, and a read-only head. Likewise, the term �read/write system� used herein shall include a read/write system, a write-only system, and a read-only system. The term �recording medium� used herein, too, shall include a read-only type medium such as a read-only optical disk in addition to a recordable medium.
Embodiment of the Invention Wherein the Actuator is Located on the Back Surface of the Slider FIG. 2 is an exploded perspective schematic illustrative of one exemplary construction of the magnetic head according to the present invention. The actuator depicted in FIG. 2 is provided with fixed and movable parts 43 and 44. Two rod-like beam members for making connections between the parts 43 and 44 are located in parallel with each other, and are each provided with an electrode layer 45 to form displacement generating means 41. The fixed part 43 is in a frame form in which the displacement generating means 41 and movable part 44 are enclosed. The movable and fixed parts 44 and 43 are coupled to the slider 2 and suspension 3, respectively, as by bonding.
When, in each embodiment, voltage is applied on both displacement generating means in such a manner that they contract concurrently or elongate at the same time, the movable part 44 effects rotational motion around the aforesaid axis of symmetry, so that an electromagnetic transducer element 1 can displace in a circular orbit. These actuator embodiments are less likely to have an adverse influence on the vibration characteristics of the magnetic head because the slider is rotationally driven and so reaction to driving is limited. Even with the embodiment shown in FIG. 3, similar advantages and features are achievable because it is possible to drive the slider rotationally. It is here noted that by the wording �rotational driving of the slider� is intended the rotation of the slider around an axis passing therethrough.
Embodiments of the Invention Wherein the Actuator is Located on the Side of the Slider An actuator shown in FIG. 11 comprises two rod-like displacement generating means 41 for coupling fixed and movable parts 43 and 44 together, with the sides of the movable part 44 bonded to the sides of a slider 2. This actuator is similar in construction to the actuator shown in FIG. 2 with the exception that the fixed part 43 is not in a frame form.
Embodiments of the Invention Wherein the Actuator is Located in a Space Formed by a Step Provided on the Slider Referring to FIG. 14, cutting or the like is used to provide a step on a back surface of a cuboidal slider 2 in such a manner that there is left a room available for the formation of an electromagnetic transducer element 1, and an actuator 4 is located within a space 21 defined by the step. This embodiments is effective for reducing the thickness increase of the magnetic head due to the provision of the actuator, and reducing the mass of the slider as well.
Embodiments of the Invention Wherein the Suspension is Located Between the Slider and the Actuator When positioning operation is performed by swinging a magnetic head by means of VCM, it is not preferable that there is a mass imbalance between the upper and lower surfaces of a suspension because the undisturbed, and stable operation of a slider is not achieved due to distortion or moment. According to a magnetic head embodiment shown in FIG. 16 wherein an actuator 4 is located on an upper surface of a suspension 3 and a slider 2 is located on a lower surface of the suspension 3, the aforesaid imbalance is so eliminated to such an extent that the stable operation of the slider 2 is ensured. If, in this embodiment, the mass of the actuator 4 is much the same as that of the slider 2, it is then possible to substantially eliminate the aforesaid imbalance because, as illustrated in FIG. 17, the center of gravity G of a structure comprising slider 2 and actuator 4 is positioned in the vicinity of a line extending from the surface of the suspension 3. This embodiment may be applied to other actuators as well.
Embodiments of the Invention Wherein the Actuator is Coupled to the Gimbal Part of the Suspension Usually, a gimbal mechanism such as a flexure is mounted in the vicinity of a tip of the suspension to allow the slider to follow fluctuations in the surface of the disk medium. Some exemplary applications of the present invention to a magnetic head having such a gimbal mechanism are illustrated in FIGS. 18A, 19A, 20A and 21A.
Embodiments of the Invention Wherein the Amount of Displacement is Amplified The amount of displacement (the amount of contraction of displacement generating means) generated by inverse piezoelectric effect or electrostrictive effect is very small. In the present invention, however, when the movable part is displaced making use of the deflection of the displacement generating means, it is possible to make the amount of displacement of a juncture between the slider and the actuator (the movable part in the actuator) larger than the amount of elongation and contraction of the displacement generating means. In other words, the actuator itself can have displacement enlarging function. When the movable part displaces circularly or rotationally in the practice of the present invention, it is possible to mechanically enlarge the displacement of the electromagnetic transducer element by allowing the movable part and electromagnetic transducer element to have an appropriate position relation. By such displacement enlargement, it is possible to bring the amount of displacement of the electromagnetic transducer element up to practical levels.
Details of the Actuator An actuator shown in FIG. 24 comprises a frame form of fixed part 43 similar in construction to that shown in FIG. 2, and two holes in the fixed part 43, which are filled with a flexible filler 46 in such a manner that it is confined in a plane of the actuator.
By the term �piezoelectric or electrostrictive material� used herein is intended a material that elongates and contracts due to inverse piezoelectric effect or electrostrictive effect. The piezoelectric or electrostrictive material used in the present invention may be any material that can be applied to the displacement generating means in an actuator. However, it is usually preferable to use ceramic piezoelectric or electrostrictive materials such as PZT [Pb(Zr, Ti)O3], PT (PbTiO3), PLZT [(Pb, La)(Zr, Ti)O3], and barium titanate (BaTiO3) because of their high rigidity. An actuator, when it is constructed of a ceramic piezoelectric or electrostrictive material, can be easily fabricated using thick film technologies such as sheet-making, and printing processes. It is noted that the actuator may also be fabricated using thin film technologies. When the piezoelectric or electrostrictive material has a crystal structure, the crystal structure may comprise either polycrystals or single crystals.
Fabrication Process Embodiments of the process of fabricating actuators used in the present invention will now be explained specifically with reference to the use of ceramic piezoelectric or electrostrictive materials.
Actuator Prototype An actuator of the structure shown in FIG. 2 was made, using PZT (where the piezoelectric constant is d31=−250�10−12 m/V) as a piezoelectric or electrostrictive material and utilizing the aforesaid thick film process.
Driving Control Method in the Magnetic Head Positioning Mechanism A preferred control method for driving a magnetic head of such structure as shown in FIG. 26 is now explained. The driving control method explained herein is preferably applied to the presently invented magnetic head wherein an actuator is overall constructed of a piezoelectric or electrostrictive material in the form of an integrated single piece. However, it is understood that this driving control method may also be applicable to a magnetic head comprising an actuator of such structure that independently fabricated fixed and movable parts, and displacement generating means are assembled together, or an actuator that has such assembly structure and includes fixed and movable parts made up of a material other than the piezo-electric or electrostrictive material.
Experimental Example of the Driving Control Method An actuator of the structure shown in FIG. 26 was made, using PZT (where the piezoelectric constant is d31=−250�10−12 m/V) as a piezoelectric or electrostrictive material and utilizing the aforesaid thick film process.
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Ltd.Optical pickup deviceEP1304683A2 *Mar 13, 2002Apr 23, 2003Fujitsu LimitedRecording medium drive and head assembly thereforEP1315151A2 *Mar 6, 2002May 28, 2003Fujitsu LimitedMagnetic head sliderEP1318551A2 *Dec 5, 2002Jun 11, 2003Matsushita Electric Industrial Co., Ltd.Composite piezoelectric element and method of fabricating the sameEP1406319A1 *Oct 3, 2003Apr 7, 2004Sagem S.A.Valve actuatorEP1427031A2 *Dec 3, 2003Jun 9, 2004Matsushita Electric Industrial Co., Ltd.Thin film piezoelectric element, its manufacturing method, and actuator using the sameEP1555661A2 *Dec 24, 2004Jul 20, 2005Lg Electronics Inc.Optical writing and reading device* Cited by examinerClassifications U.S. Classification360/294.4, G9B/21.025, G9B/5.202, G9B/7.086, G9B/21.018, G9B/5.193, G9B/5.221International ClassificationG11B7/09, G11B5/58, G11B21/10, G11B5/55, G11B21/20Cooperative ClassificationG11B21/20, G11B7/0937, G11B5/5552, G11B5/59627, G11B5/58, G11B21/10European ClassificationG11B5/55D2, G11B7/09D7, G11B5/58, G11B21/20, G11B21/10, G11B5/596ELegal EventsDateCodeEventDescriptionOct 1, 2012FPAYFee paymentYear of fee payment: 12Nov 13, 2008FPAYFee paymentYear of fee payment: 8Nov 3, 2004FPAYFee paymentYear of fee payment: 4Aug 5, 2003CCCertificate of correctionFeb 25, 1999ASAssignmentOwner name: TDK CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SOENO, YOSHIKAZU;ICHIKAWA, SHINJI;TSUNA, TAKAMITSU;AND OTHERS;REEL/FRAME:009783/0071Effective date: 19980901RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google