JPH04134681A - Head positioning mechanism - Google Patents

Abstract

PURPOSE:To allow positioning with high accuracy by providing an auxiliary actuator consisting of piggyback actuators which are so assembled as to have the coefft. of thermal expansion matching with the coefft. of thermal expansion of an access arm. CONSTITUTION:The access arm 12 oscillated by a main actuator 11 in the radial direction of a magnetic disk and a head supporting spring 13 supporting a head are connected by a frame structure support 15. The auxiliary actuator 19 for microdisplacement consisting of a connecting body of microdisplacing elements 27 and members 18 for compensation having the coefft. of thermal expansion matching with the coefft. of thermal expansion of another beam constituting the support 17 is provided over the entire part or part of the beam extending to the head side of the support 15 of this mechanism so that the head supporting spring 13 can be microdisplaced in the radial direction of the recording disk independently from the main actuator 11.

Description

[Detailed Description of the Invention] [Summary] Regarding a head positioning mechanism for a recording disk in a magnetic disk device, etc., a minute displacement element is incorporated into a part of an access arm so as to match the coefficient of thermal expansion of a structural member of the access arm. By providing a sub-actuator consisting of a piggyback actuator, the sub-actuator is free from abnormal thermal deformation and the data head can be positioned independently and with high precision. In a head positioning mechanism in which an access arm that swings in the radial direction by a main actuator and a head support spring that supports the head are connected by a frame structure support, the whole or part of the beam extending toward the head side of the frame structure support is A sub-actuator for micro-displacement consisting of a micro-displacement element and a connection body with a compensating member that matches the coefficient of thermal expansion of the other beams constituting the frame structure support is provided in the section, and the sub-actuator mainly controls the head support spring. The structure is such that the recording disk can be slightly displaced in the radial direction independently of the actuator.

The frame structure support body also includes a first beam connected to the head support spring, a second beam connected to the first beam and the access arm, respectively, and a third beam connecting these beams.
The third beam has a triangular frame shape, and the micro-displacement sub-actuator is incorporated in the whole or a part of the third beam.

Further, the minute displacement element incorporated in the minute displacement sub-actuator is configured to include a laminated piezoelectric element or a magnetostrictive element.

[Industrial application field]

The present invention relates to a head positioning mechanism for a recording disk in a magnetic disk device or the like.

In recent years, the recording density of magnetic disk devices used as external storage devices for computer systems has significantly improved as the amount of information processed has increased and become more diverse.In particular, higher trunk densities have led to improvements in the precision of magnetic heads. accurate positioning is essential, and it is important to improve the precision mechanism technology of the head positioning system.

In addition, with such high track density, for example, in head positioning using the servo surface servo method, the magnetic head for servo positioning with respect to the magnetic disk and the magnetic head for data may be affected by changes in temperature within the device, etc. There is a tendency for read/write errors to occur due to so-called thermal off-track, in which the data magnetic head is misaligned with respect to the magnetic disk due to slight thermal deformation. Therefore, there is a need for a mechanism that reduces thermal off-trunk of a data magnetic head with respect to such a magnetic disk and improves head positioning accuracy.

[Conventional technology]

10μ for high track density in magnetic disk drives
-The following track pitch is required, and the off-track amount is also required to be on the order of submicrons. Therefore, in order to reduce thermal off-track, which is considered to be the main cause of off-track, many mechanical technology improvements have been made to reduce and alleviate thermal distortion and deformation of the head positioning mechanism.However, When the off-track amount was on the order of submicrons, there were limits to measures to reduce it.

Therefore, as a head positioning mechanism that actively corrects such off-track, as shown in FIG. For example, a voice coil motor (VCM) is connected to the head (not shown) via a head support spring 2.
A sub actuator 5, a so-called piggyback actuator, is supported by an access arm 1 connected to a main drive actuator (not shown) and has a minute displacement element 4 such as a laminated piezoelectric element incorporated in a part of the access arm 1. A head positioning mechanism has been proposed.

In this positioning mechanism, the servo position information recorded in advance on the servo surface of the magnetic disk is read by the servo positioning magnetic head, and the main actuator is driven based on the servo position information, so that each data magnetic head 3 is moved to the target recording track on each data surface of the corresponding magnetic disk, and the sub-actuator 5 is driven to independently slightly oscillate each data magnetic head 3 in the left and right direction orthogonal to the recording track. to accurately position the head on the target recording track, or to correct positional deviation of the head due to thermal off-track.

[Problem to be solved by the invention]

By the way, the minute displacement element 4 incorporated in a part of the access arm I, for example, a laminated piezoelectric element, has a structure in which a plurality of PZT elements are laminated, and by applying a voltage between both terminals, the minute displacement element 4 can be moved on the order of several μm. Therefore, if the positional information of each data magnetic head 3 is always accurately obtained, it is possible to minutely control the displacement of each data magnetic head 3 on the order of 1 to 2 μm mist. In a structure in which the piezoelectric element is simply incorporated into a part of the access arm 1, uneven thermal deformation caused by a difference in coefficient of thermal expansion with the constituent members of the access arm 1 poses a major problem.

That is, the access arm I is generally made of an aluminum-based light alloy and has a coefficient of thermal expansion of about 20X10-6.
Ti0. The coefficient of thermal expansion of a laminated piezoelectric element consisting of a compound (equivalent to +) is 5. OX is approximately 10-6, and the portion of the access arm 1 in which the laminated piezoelectric element is incorporated is thermally deformed due to a mere temperature change, and a large thermal stress is generated, causing the data magnetic head 3 to be repositioned in the opposite direction. Therefore, there is a problem in that the sub actuator 5, which is intended to compensate for the thermal deformation of the original head positioning mechanism, becomes a thermal deformation generating means.

In view of the above-mentioned conventional problems, the present invention provides a sub-actuator, which is a piggyback actuator, in which a minute displacement element is incorporated in a part of the access arm so as to match the coefficient of thermal expansion of the structural member of the access arm. It is an object of the present invention to provide a novel head positioning mechanism which is free from uneven thermal deformation in the sub-actuator and which enables independent and highly accurate positioning of the data head.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a bend positioning mechanism in which an access arm that swings in the radial direction of a recording disk by a main actuator and a head support spring that supports a head are connected by a frame structure support. For micro-displacement, consisting of a micro-displacement element on the whole or a part of the beam extending toward the head side of the structural support, and a connection body with a compensating member that matches the coefficient of thermal expansion of the other beams that make up the frame structural support. A sub-actuator is provided, and the sub-actuator allows the head support spring to be slightly displaced in the radial direction of the recording disk independently of the main actuator.

The frame structure support body also includes a first beam connected to the head support spring, a second beam connected to the first beam and the access arm, respectively, and a third beam connecting these beams.
The third beam has a triangular frame shape, and the micro-displacement sub-actuator is incorporated in the whole or a part of the third beam.

Further, the minute displacement element incorporated in the minute displacement sub-actuator is configured to include a laminated piezoelectric element or a magnetostrictive element.

[For production]

In the present invention, an access arm that swings in the radial direction of a recording disk by a main actuator and a head support spring that supports a head are connected to a first access arm that is connected to the head support spring.
A beam, a second beam that is connected to the first beam and the access arm, and a third beam that connects these beams are framed in a triangular shape, and the entire third beam is ,
Or a micro-displacement device consisting of a connection body of a micro-displacement element made of a laminated piezoelectric element or the like using PZT in the negative part, and a compensating member that matches the coefficient of thermal expansion of the other beams constituting the frame structure support. By connecting the secondary actuators using a frame structure support, the risk of abnormal thermal deformation of the secondary actuators due to changes in environmental temperature is eliminated, and multiple data heads can be handled by the main actuator. simultaneously moving each of the magnetic disks to the target recording track, and driving the sub-actuator to independently slightly oscillate each of the magnetic heads to position them on the target recording track with high precision; It becomes possible to accurately correct positional deviations due to thermal off-track and the like.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a head positioning mechanism according to the present invention, and FIG. 2 is a plan view of essential parts for explaining a sub-actuator for minute displacement in the head positioning mechanism.

In FIG. 1, 11 is a voice coil motor (V
12 is a plurality of access arms attached to the swing type main actuator 11;
The ends of the head support springs 13 that support the plurality of access arms 12 and data magnetic heads 14 are attached to the first beams 15a connected to the head support springs 13, as shown in FIG. and a second beam 15b connected to the first beam 15a and the access arm 12, respectively.
And these first. An aluminum (A
12), and the third beam 15c has a thermal expansion coefficient of 5.0X10 due to PZT in whole or in part.
-b minute displacement element 17 consisting of a laminated piezoelectric element or the like;
In combination with the minute displacement element 17, the other first. Thermal expansion coefficient of the second beams 15a and 15b is 20X1
The coefficient of thermal expansion is 26XIO-” than Af, which is consistent with 0-’
and a large compensating metal member 18 made of, for example, a magnesium alloy, connected by a frame structure support 15 incorporating a micro-displacement sub-actuator 19 made of a connecting body in a predetermined length ratio.

A minute displacement element 17 made of a laminated piezoelectric element or the like is provided in combination with the third beam 15c of the frame structure support 15 made of triangular aluminum (A f '') described above.
As shown in FIG. 3, the compensating metal member 18 made of a magnesium alloy and a magnesium alloy has a total length that is a combination of both! , the length of the minute displacement element 17 is fp, its coefficient of thermal expansion (5, OX 10-') is αp, and the length of the compensation metal member 18 is i! m, its coefficient of thermal expansion (26XIO-')
α-1 and A2 frame structure support 15 coefficient of thermal expansion (20X
10-') is αa, then lp
/l=cαI−αa)/(αm−αp)ffip/fζ
is 0.3, so by combining the minute displacement element F and the compensating metal member 8 with a length ratio of 3=7, the thermal expansion coefficient of the frame structure support 15 made of Al and , minute displacement element 17 and compensation metal member 18
The synthetic thermal expansion coefficient is matched with
Since ΔT and the combined elongation of the minute displacement element 17 and the compensating metal member 18 (αs+j!pαρ)8T are equal, the minute displacement side actuator 19 is biased due to changes in environmental temperature, etc. There is no risk of thermal deformation or thermal stress.

When a voltage is applied to the minute displacement element 17 in the sub-actuator 19, the displacement of the minute displacement element 17 causes the head support spring 13, which supports the data magnetic head 14, to swing as shown by the broken line in FIG. do. When the width of the data magnetic head 14 is wh and the width of the triangular frame structure support 15 made of aluminum is wb, the displacement magnification rate of the data magnetic head 14 with respect to the displacement of the frame structure support 15 is Wh/ Wb is approximately 2 in the case of the dimension ratio shown in the figure.

Therefore, if the head displacement amount is 2 μm, the displacement amount of the minute displacement sub-actuator 19 may be about 1 μm.
Displacement can be easily generated by applying a voltage of about several tens of volts to the minute displacement element 17 made of a laminated piezoelectric element.

Furthermore, the first beam 15a and the second beam 15 in the frame structure support 15 constituting the minute displacement sub-actuator 19 are
By providing the hinge 16 by cutting out the part where the ends of the hinge 16 and b are connected in an arc shape, the rigidity at that part is reduced to prevent damage due to stress concentration during displacement, and to facilitate displacement. There is.

With the head positioning mechanism having such a configuration, all data magnetic heads 14 corresponding to each data surface of a plurality of rotating magnetic disks can be moved to the oscillating main actuator 11 based on servo information. The micro-displacement sub-actuator 19 is composed of a laminated piezoelectric element, which is provided between the access arm 12 and the head support spring 13 that supports the individual data magnetic heads 14. By applying a voltage to the minute displacement element 17, the sub actuator 19 can further independently record data on each data magnetic head 14 without causing abnormal thermal deformation or thermal stress due to changes in environmental temperature, etc. It is possible to make a minute rocking displacement in the direction intersecting the track, and by controlling this minute rocking displacement using the positioning information read out afterwards, each data magnetic head 14 is positioned on the target recording track with high precision. It is also possible to accurately correct positional deviations due to thermal off-track and the like.

As mentioned above, the reason why a light alloy such as magnesium is used as the compensating metal member 18 is not only for matching the coefficient of thermal expansion but also for reducing the moment of inertia of the entire actuator, as shown in FIG. As shown in FIG.
A fine displacement element 17 made of T is provided, and a compensating metal member 1 made of magnesium alloy is placed on the side far from the center of oscillation.
8, the moment of inertia of the entire actuator is reduced to almost the same as that of an all-aluminum actuator, even though the specific gravity of the minute displacement element 17 is as large as about 8. has the advantage of being larger.

In addition, in the above embodiment, the minute displacement sub-actuator 1
Although the present invention has been described using an example in which a laminated piezoelectric element is used as the minute displacement element 17 constituting the microdisplacement element 9, the present invention is not limited to this example. You can get the following effect.

Furthermore, it goes without saying that the head positioning mechanism of the present invention is applicable not only to the servo surface servo method but also to various head positioning control methods such as the data surface servo method, as well as to disk devices using optical heads and magneto-optical disks. It is also applicable to devices, etc.

〔Effect of the invention〕

As is clear from the above description, according to the head positioning mechanism according to the present invention, 1. the environmental temperature is The two-stage actuator is equipped with a sub-actuator for minute displacement that is compensated to prevent uneven thermal deformation or thermal stress caused by changes in the data head. It is possible to accurately position the recording track position of the recording track, or to correct the position of the thermal off track etc. to the predetermined recording track position with high precision, and it is an excellent feature that can realize various large capacity disk devices with high reliability and high density recording. It has many advantages.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the head positioning mechanism according to the present invention, FIG. 2 is a plan view of essential parts for explaining the sub-actuator for minute displacement according to the present invention, and FIG. 3 is a perspective view showing an embodiment of the head positioning mechanism according to the present invention. FIG. 4 is a block diagram for explaining the details of such a sub-actuator for minute displacement, and FIG. 4 is a plan view of a main part for explaining the sub-actuator for minute displacement in a conventional head positioning mechanism. 1 to 3, 11 is a swing type main actuator, 12 is an access arm, 13 is a head support spring, 14 is a data magnetic head,
15 is a frame structure support body, 15a is a first beam, 15b is a second beam
15c is a third beam, 16 is a hinge, 17 is a micro-displacement element, 8 is a compensating metal member, and 19 is a sub-actuator for micro-displacement. (Jda) ΔT Scale octopus ＾1 coffee-r Shinkushi 2・1γ74-, I-YumekanHtt
tθB force latitude N flash Figure 3

Claims (3)

[Claims] (1) The main actuator (1
1) swings the access arm (12) and the head (
In a head positioning mechanism in which a head support spring (13) supporting a head support spring (14) is connected by a frame structure support (15), the entire or part of the beam extending toward the head side of the frame structure support (15) is A sub actuator (19) for minute displacement is provided, which is a connection body of a minute displacement element (17) and a compensating member (18) that matches the coefficient of thermal expansion of another beam constituting the frame structure support (15). , the sub actuator (19)
The head support spring (13) is connected to the main actuator (1
A head positioning mechanism characterized by being capable of minute displacements in the radial direction of a recording disk independently of (1). (2) The frame structure support (15) has a head support spring (
13), a second beam (15b) connected to the first beam (15a) and the access arm (12), and these beams (15a,
15b) and a third beam (15c) connecting the third beam (15c), the micro-displacement sub-actuator (19) is incorporated in the whole or a part of the third beam (15c). The head positioning mechanism according to claim 1, characterized in that: (3) The head positioning mechanism according to claim 1 or 2, wherein the minute displacement element (17) incorporated in the minute displacement sub-actuator (19) is composed of a laminated piezoelectric element or a magnetostrictive element. .