JP2002083476A - Head actuator and hard disk drive using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head actuator capable of obtaining larger head displacement with a lower voltage, and achieving head positioning control in a broad band by increasing a mechanical resonant frequency. SOLUTION: This head actuator is provided with a head slider for supporting a head, and a head supporting member for supporting the head slider. The head supporting member is provided with a first area for installing the head slider, a second area for installing a driving element, and a third area for connecting the first and second areas to each other. The driving element has a geometric center surface. The head supporting member has a second neutral surface in the second area, and a third neutral surface in the third area. The third neutral surface is displaced to the same side of the geometric center surface with respect to the second neutral surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an information recording / reproducing apparatus used for recording / reproducing information, and more particularly to a head actuator for positioning a head on a desired track of a recording medium.

[0002]

2. Description of the Related Art In recent years, information recording / reproducing apparatuses using a disk-shaped recording medium such as a magnetic disk apparatus and an optical disk apparatus have become widespread. Above all, magnetic disk devices are widely used as external storage devices for personal computers, taking advantage of the characteristic of high-speed data transfer.

[0003] In a small-sized magnetic disk device that has been widely used in recent years, concentric recording tracks are formed on a magnetic disk, and a magnetic head is positioned at a desired recording track on the magnetic disk by an oscillating head actuator. In general, information is recorded and reproduced. In order to further improve the recording density,
There has been proposed a method of improving the head positioning accuracy by providing a secondary micro head actuator at the tip of an oscillating head actuator, and several micro head actuators have been proposed for that purpose.

As an example, in the example described in Japanese Patent Application Laid-Open No. 5-47126, a head supporting spring is constituted by two beams, the ends of the two beams are connected to support the head near the connection point, and And at least one thin plate-like displacement element that expands and contracts according to an externally applied voltage on at least one of the beams.
A configuration that is integrally fixed to a surface is disclosed (hereinafter referred to as Conventional Example 1). Japanese Patent Application Laid-Open No. 7-224838 discloses a configuration in which a piezoelectric element is provided on the surface of a load beam on which a head is mounted (hereinafter referred to as Conventional Example 2).

[0005] Conventional example 1 and conventional example 2 are common in the basic configuration. Hereinafter, a configuration in which a displacement element or a piezoelectric element is provided on one surface will be described with reference to FIGS. FIG. 15 is a schematic diagram showing a configuration of a conventional head actuator 1200. The head slider 52 is fixed to one end of the head support member 50. A plate-like displacement element 51 is fixed to the surface near the center of the head support member 50.

In FIG. 15, a region to which the displacement element 51 of the head supporting member 50 is fixed is defined as a region 1201 and a region to which the displacement element 51 is not fixed is defined as a region 1202. NB1 is the head support member 50
Coincides with the geometric center plane. Also, the area 1201
In the above, since the displacement element 51 is integrally fixed to the head support member 50, the neutral plane NA1 is inevitably deviated toward the displacement element 51 from the neutral plane NB1. (Hereinafter, the difference D1 between the neutral planes NA1 and NB1 is referred to as "neutral plane step."
Called. In addition, the geometric center plane L1 of the displacement element 51 alone is on the opposite side of the neutral plane NB1 with respect to the neutral plane NA1, and the distance between L1 and NA1 is H1.

In this configuration, when a voltage is applied to the displacement element 51, the head support member 50 expands and contracts in the longitudinal direction, and the head slider 52 is slightly displaced.

[0008]

Generally, the basic performance required of a micro head actuator is that a large displacement can be obtained at a lower voltage, and that a mechanical resonance frequency is high and a wide band positioning control is possible. Two points.

However, in the conventional head actuator 1200 described above, the displacement caused by the expansion and contraction of the head support member 50 in the longitudinal direction caused by the displacement element 51 is lost due to the deflection of the head support member 50, and an effective displacement is obtained. There are two problems that the mechanical resonance frequency mainly depends on the rigidity of the head support member 50 in the bending direction and that it is difficult to increase the resonance frequency.

First, a problem relating to the amount of displacement will be described. FIGS. 16A to 16C show static models of a conventional head actuator. From the viewpoint of statics, the conventional head actuator 1200 shown in FIG. 15 represents the head support member 50 by its neutral planes NA1 and NB1, and displaces it, as shown in FIG. It can be represented by a model in which the force by the element 51 acts as an external force. Now, consider a state in which a voltage is applied in the direction in which the displacement element 51 extends in FIG. At that time, the expansion and contraction force F1 by the displacement element 51 acts outward as shown in FIG. Further, as described above, since the central plane L1 of the displacement element 51 alone is deviated from the neutral plane NA1, the bending moment M
1 occurs. The bending moment M1 is a magnitude obtained by multiplying the stretching force F1 by the distance H1. Central plane L1 is neutral plane NA
1 is deviated upward (only by H1) on the plane of the paper, so that the bending moment acts in a direction in which the neutral plane NA1 becomes convex upward on the plane of the paper. This state includes a state in which only the stretching force F1 is applied (FIG. 16B) and a state in which the bending moment M1 is applied.
This can be considered as a superimposition with the state where only is added (FIG. 16C). Focusing on the length of the region 1201, that is, the distance between the point A and the point B, as shown in FIG. 16B, the point A is displaced by the displacement amount X1 in the direction extending in the plane due to the stretching force F1. On the other hand, as shown in FIG. 16 (c), the bending moment M1 acting in the upward convex direction
As a result, deflection angles θA and θB are generated at both ends of the beam, respectively, and a longitudinal displacement corresponding to the deflection angles θA and θB multiplied by the neutral surface step D1 is generated. Only the displacement. FIG.
As is clear from (b) and FIG. 16 (c), the displacement amount X1 and the displacement amount X2 are in opposite directions, and the difference between them becomes the total displacement amount. Similarly, when a voltage in the contracting direction is applied to the displacement element 51, the displacement amount X1 and the displacement amount X2 are in opposite directions, and the difference between the two becomes the total displacement amount. That is,
In the structure of the conventional head actuator, the displacement X1 in the in-plane direction caused by the expansion and contraction force is lost by the displacement X2 in the longitudinal direction caused by the deflection angle, so that a sufficient displacement for positioning the head can be obtained. There was a problem that there was no.

Next, a problem concerning the mechanical resonance frequency will be described. FIG. 17 is a dynamic model of a conventional head actuator. The head support member 50 in FIG. 15 can be represented by a model in which an equivalent mass MA1 is concentrated at the center of a beam 1401 having equivalent bending rigidity. Note that K1 is the equivalent rigidity of the head support member 50 in the expansion and contraction direction, and MS is the equivalent mass of the movable body 1402 around the head slider 52. In this dynamic model, a natural vibration mode is formed in which the degree of freedom φS of the movable body 1402 and the degree of freedom φY of the beam 1401 in the bending direction are coupled. That is, the inertial force caused by the vibration of the mass MS in the φS direction causes the moment M1 due to the neutral plane step D1.
Acts on the beam 1401 as S. The inertial force resulting from the vibration of the mass MS in the φS direction is equivalent to the equivalent mass M of the beam 1401.
The natural vibration mode is formed in a state dynamically balanced with the inertial force caused by the vibration of A1 in the φY direction. The natural frequency of this natural vibration mode mainly depends on the mass MS of the movable body 1402.
And the elastic force in the bending direction of the beam, that is, the head support member 50. Therefore, in order to increase the natural frequency, the head supporting member 50 corresponding to the beam 1401 is required.
It is necessary to increase the stiffness. However, increasing the rigidity of the head support member 50 requires the displacement element 5
The resistance to 1 expansion and contraction force will be increased,
This leads to a reduction in the amount of displacement. That is, the displacement amount and the mechanical resonance frequency are in a trade-off relationship, and there has been a problem that the natural frequency, that is, the mechanical resonance frequency cannot be increased in order to secure a predetermined displacement amount. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a head actuator capable of obtaining a large head displacement at a lower voltage and realizing high-precision head positioning control by increasing a mechanical resonance frequency. The purpose is to provide.

[0013]

A head actuator according to the present invention comprises: a head slider for supporting a head for recording or reproducing information on or from a recording medium; and a head support member for supporting the head slider. The head support member includes a substrate and a drive element provided on at least one surface of the substrate, and generates a stretching force in a longitudinal direction in response to an external signal. Extend the head support member in the longitudinal direction,
A head actuator for positioning the head in a radial direction of the recording medium, wherein the head support member includes:
A first area where the head slider is provided, a second area where the driving element is provided, and the first area and the second area.
And a third region connecting the region to the driving region, wherein the driving element comprises:
A geometric center plane, wherein the head support member has a first neutral plane in the second area and a second neutral plane in the third area.
A neutral surface, wherein the second neutral surface is offset to the same side as the geometric center plane with respect to the first neutral surface, thereby achieving the above object. .

[0014] The first neutral plane may exist on the substrate side with respect to the geometric center plane.

[0015] The head support member may further include a neutral plane deviation means for displacing the second neutral plane with respect to the first neutral plane on the same side as the geometric center plane.

[0016] The neutral plane deviation means may include a reinforcing member provided at least in the third region.

[0017] The first neutral plane may be on an opposite side of the substrate with respect to the geometric center plane.

[0018] The head support member may further include a geometric center plane displacing means for displacing the first neutral plane on the opposite side of the substrate with respect to the geometric center plane.

The geometric center plane displacing means includes a holding member formed on the same side as the substrate with respect to the driving element, and the holding member increases rigidity of the head support member in a bending direction. And a function of increasing the natural frequency of the head support member.

[0020] The holding member is provided on the driving element, and has a low rigidity layer having a smaller longitudinal elastic modulus than the driving element, and is provided on the low rigidity layer, and has a lower longitudinal elasticity coefficient than the lower rigidity layer. A large high-rigidity layer.

The low rigidity layer contains a polyimide resin,
The high rigidity layer may include stainless steel.

[0022] The head support member may further include a first neutral plane deviation means for displacing the second neutral plane with respect to the first neutral plane on the same side as the geometric center plane. Good.

[0023] The first neutral plane deviation means may include a reinforcing member provided at least in the third region.

[0024] The reinforcing member may be provided on a side opposite to the driving element with respect to the substrate.

The driving element has a first extensional stiffness, the substrate has a second extensional stiffness, and the first extensional stiffness is
It may be larger than the second elongation rigidity.

[0026] The driving element may have a plate shape.

[0027] The driving element may include a piezoelectric element unit in which electrodes are mounted on a thin-film piezoelectric body.

[0028] The driving element may include a first driving element and a second driving element to which voltages in opposite directions are applied.

The substrate includes a first telescopic portion provided with the first driving element, a second telescopic portion provided with the second driving element, a rotating portion provided with the head slider, and the rotating portion. A first hinge portion connecting the rotation portion and the second expansion portion, and a second hinge portion connecting the rotation portion and the second expansion portion.

[0030] The head actuator may further include a load beam for supporting the head support member.

Another head actuator according to the present invention includes a head slider for supporting a head for recording or reproducing information on or from a recording medium, and a head support member for supporting the head slider. Includes a substrate and a driving element provided on at least one surface of the substrate and generating a stretching force in a longitudinal direction in response to an external signal, and applying the external signal to the driving element to form the head support member. A head actuator that expands and contracts in a longitudinal direction and positions the head in a radial direction of the recording medium, wherein the head support member includes a first area where the head slider is provided, and a second area where the drive element is provided. And a third region connecting the first region and the second region, wherein the head support member includes a third region in the second region. A neutral surface and a second neutral surface in the third region, wherein the first neutral surface and the second neutral surface are substantially continuous, thereby achieving the above object. You.

[0032] The head support member may include continuation means for making the first neutral surface substantially continuous with the second neutral surface.

[0033] The continuous means may include an intermediate layer provided between the substrate and the driving element.

[0034] The continuation means may include a reinforcing member provided at least in the third region.

[0035] The continuous means may include a wiring portion provided around the driving element.

The driving element has a first extensional stiffness, the substrate has a second extensional stiffness, and the first extensional stiffness is
It may be larger than the second elongation rigidity.

[0037] The driving element may have a plate-like shape.

[0038] The driving element may include a piezoelectric element unit in which electrodes are formed on a thin-film piezoelectric body.

[0039] The driving element may include a first driving element and a second driving element to which voltages in opposite directions are applied.

[0040] The substrate has a first expandable portion provided with the first drive element, a second expandable portion provided with the second drive element, a rotating portion provided with the head slider, and the rotating portion. A first hinge portion connecting the rotation portion and the second expansion portion, and a second hinge portion connecting the rotation portion and the second expansion portion.

The head actuator may further include a load beam for supporting the head support member.

The hard disk drive according to the present invention comprises:
A head actuator according to the present invention, a motor that drives the recording medium to rotate, and a head actuator that is radially moved across the surface of the recording medium so that the head can access a predetermined data track on the recording medium. And control means for applying the external signal to the drive element so as to expand and contract the head support member in the in-plane direction and position the head in the radial direction of the recording medium. Therefore, the above object is achieved.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a head actuator according to the present invention will be described with reference to FIGS. 1 to 14 by taking a head actuator used in a magnetic disk drive as an example.

(Embodiment 1) A head actuator according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of a main part of a head actuator according to a first embodiment of the present invention. In FIG.
The head actuator 100 is a recording medium (not shown)
A magnetic head 1 for recording and reproducing information comprises a head slider 11 provided on one end surface, a flexure 30 having the head slider 11 fixed to one end, and a load beam 20 supporting the flexure 30. The main feature of the first embodiment resides in the flexure 30 and the head slider 1
As the load beam 1 and the load beam 20, a general beam used in a magnetic disk device that is currently widely used can be used.

FIG. 2 is an exploded perspective view of a portion K in FIG. FIG. 3 is a schematic diagram showing a cross section GG in FIG. 4, and is shown in an enlarged manner in the thickness direction.

In this specification, the longitudinal direction means a direction indicated by an arrow V in FIG. 3 and a direction corresponding to this direction in other drawings. The flexure according to the present invention extends in this longitudinal direction.
In this specification, the thickness direction means a direction indicated by an arrow U in FIG. 3 and a direction corresponding to this direction in other drawings. Further, in the present specification, the bending direction means a direction substantially the same as the thickness direction. The thickness direction and the bending direction are substantially perpendicular to the longitudinal direction.

Referring to FIG. 2 and FIG.
Includes a flexible substrate 31, a piezoelectric element unit 40, a reinforcing plate 32, a spacer 33, and a back plate 34. The piezoelectric element unit 40 includes the first piezoelectric element unit 4
0A and the second piezoelectric element unit 40B. The flexible substrate 31 has two beam-shaped elastic portions 31A and 31B extending from the fixed portion 31D, and the elastic portions 31A and 31B.
Is connected to the rotating part 31E by a hinge part 31C formed at the tip. The flexible substrate 31 has a wiring pattern formed of a copper thin film on a base material made of a polyimide resin having a thickness of about 10 micrometers. A reinforcing plate 32 made of stainless steel and having a similar planar shape and having a thickness of about 25 μm is adhered to the rotating portion 31E and the hinge portion 31C of the flexible substrate 31, and the head slider 11 is further interposed through a spacer 33. Glued.

The flexible portion 31 of the flexible substrate 31
A and 31B respectively have first and second piezoelectric element units 4
0A and 40B are adhered. The first and second piezoelectric element units 40A and 40B are formed by forming platinum electrodes having a thickness of about 0.1 μm on both sides of a thin-film piezoelectric body made of PZT having a thickness of about 2.5 μm. It expands and contracts in the longitudinal direction by the piezoelectric effect according to the voltage applied to the electrodes. The electrodes of the first and second piezoelectric element units 40A and 40B are bonded to the wiring of the flexible substrate 31, and a voltage is supplied by an external driver (not shown). The first and second piezoelectric element units 40 are provided on the fixing portion 31D of the flexible substrate 31.
A back plate 34 made of stainless steel is adhered to the surface opposite to the surface to which A and 40B are adhered, and the back plate 34 is joined to the load beam 20 (FIG. 1) by spot welding. Further, a dimple receiver 31F is provided on the rotating portion 31E of the flexible substrate 31, and the dimple 21 provided on the load beam 20 abuts on the back surface thereof to form a pivot bearing.

In FIG. 3, the elastic portions 31A and 31B of the flexible substrate 31 are defined as a region 301, and the hinge portion 31C is defined as a region 302. An adhesive layer (not shown) having a small thickness is formed between the flexible substrate 31 and the piezoelectric element unit 40 to join them. The product of the longitudinal elastic modulus and the cross-sectional area of PZT in the piezoelectric element unit 40 is about 1.5 times larger than the sum of the product of the longitudinal elastic modulus and the cross-sectional area of each of the flexible substrate 31 and the adhesive layer.

In FIG. 3, the neutral plane NA2 of the flexure 30 in the area 301 is located inside the flexible substrate 31 and the neutral plane N2 of the flexure 30 in the area 302.
B2 is inside the reinforcing plate 32, and the neutral surface step D2 is about 1
6 micrometers. Also, the piezoelectric element unit 4
0 is the neutral plane N2 of the area 301
A2 is in the same direction as the neutral plane NB2 of the region 302 with respect to A2, and the distance H2 between the geometric center plane L2 and the neutral plane NA2 is about 7 micrometers. Note that the geometric center plane means a plane that is the geometric center in the cross section of the piezoelectric element unit 40.

The operation of the thus configured head actuator according to the first embodiment of the present invention will be described below. FIG. 4 is a plan view showing a state of deformation of the head actuator according to the first embodiment of the present invention. In FIG. 4, a solid line E indicates a non-operation state, and a broken line F indicates an operation state. In the operation state, voltages having the same absolute value are applied to the two piezoelectric element units 40A and 40B (FIG. 2) in opposite directions by a driver. For example, when a voltage is applied in the direction in which the piezoelectric element unit 40A compresses and the direction in which the piezoelectric element unit 40B expands, as shown in FIG.
1B is deformed in the direction of arrow Q, and a displacement amount in the longitudinal direction of displacement amount XA and displacement amount XB is generated in hinge portion 31C. Both displacements have opposite directions and the same absolute value. Therefore, the rotation portion 31E rotates in the direction of arrow R with the middle point of the hinge portion 31C as a fulcrum.
A displacement of YH occurs in a direction substantially perpendicular to Q. The amount of displacement YH of the head position is proportional to the amount of expansion and contraction of the expansion and contraction portions 31A and 31B, and is therefore proportional to the voltage applied to the piezoelectric element units 40A and 40B. If the proportionality constant between the applied voltage and the head displacement is known, the position of the head is controlled by controlling the voltage supplied from the driver.

As shown in FIG. 3, in this embodiment, in order to efficiently convert the piezoelectric strain generated in the piezoelectric element unit 40 into longitudinal displacement, the piezoelectric element The unit 40 is held only by the flexible substrate 31 which is sufficiently softer, and the product of the longitudinal elastic modulus and the sectional area of the PZT in the piezoelectric element unit 40 is determined by the longitudinal elastic modulus and the sectional area of each of the flexible substrate 31 and the adhesive layer. Is larger than the sum of the products. Generally, the elongational rigidity of a material is determined by the product of the longitudinal elastic modulus and the cross-sectional area. In the first embodiment, the portion (the flexible substrate 31) that resists the stretching force with respect to the stretching stiffness of the PZT in the piezoelectric element unit 40 that generates the stretching force.
And the adhesive layer) have a low elongational rigidity,
Most of the piezoelectric strain generated in the ZT can be taken out as displacement in the longitudinal direction. Therefore, since the input voltage can be efficiently converted into the displacement, a large head displacement can be obtained with a lower voltage.

Next, the operation of the first embodiment for increasing the amount of displacement in the longitudinal direction will be described. FIG.
FIG. 5C is a static model of the head actuator according to the first embodiment of the present invention. From the viewpoint of statics, the head actuator of the first embodiment is the same as that of FIG.
As shown in (a), the flexure 30 is moved to its neutral plane N.
A2 and NB2 can be represented by a model in which the force generated by the piezoelectric element unit 40 acts as an external force. Now, in FIG. 3, the piezoelectric element unit 4
Consider a state in which a voltage is applied in the direction in which 0 extends. At this time, the stretching force F2 by the piezoelectric element unit 40 is as shown in FIG.
It acts in the pulling direction as shown in FIG. Further, as described above, the geometric center plane L2 of the single piezoelectric element unit 40 is H above the neutral plane NA2 toward the paper surface.
Since it is displaced by two, a bending moment M2 is generated by the stretching force F2. The bending moment M2 is a magnitude obtained by multiplying the stretching force F2 by the distance H2.

Since the center plane L2 of the piezoelectric element 40 is deviated upward, the bending moment M2 acts so that the neutral plane NA2 bends downward toward the paper surface. This state is a state in which only the stretching force F2 is applied (FIG. 5B).
And only the bending moment M2 is applied (FIG. 5)
(C)) can be considered as superposition. Focusing on the position of point A, as shown in FIG.
2, the point A is displaced in the longitudinal direction by the displacement X3.
On the other hand, as shown in FIG. 5C, a bending angle θ2 is generated at the tip of the beam due to the bending moment M2. Thereby, a displacement in the longitudinal direction corresponding to the deflection angle θ2 multiplied by the neutral surface step D2 occurs. That is, the point A is the displacement amount X in the longitudinal direction.
Displaced by four. The directions of the displacement amount X3 and the displacement amount X4 are the same. Therefore, the sum of the two displacement amounts is the total displacement amount. Similarly, when a voltage in the contracting direction is applied to the piezoelectric element unit 40, the displacement X3 and the displacement X4 are in the same direction, and the sum of the two becomes the actual displacement.

In the first embodiment, the displacement X3 in the longitudinal direction is on the order of 10 −7 m. The deflection angle θ2 is on the order of 10 −2 radians, the neutral plane step D2 is on the order of 10 −5 meters, and the displacement X4, which is the product thereof, is on the order of 10 −7 meters. That is, in the first embodiment, since the displacement X4 caused by the deflection angle θ2 is added to the original longitudinal displacement X3 of the piezoelectric element unit 40, the actual displacement can be increased.

As in the first embodiment, the direction of the displacement X3 in the longitudinal direction of the piezoelectric element unit 40 and the deflection angle θ
The condition that the direction of the displacement amount X4 in the longitudinal direction due to 2 is the same as that of the neutral plane NA2 in the area 301 and the geometric center of the neutral plane NB2 in the area 302 and the piezoelectric element unit 40 alone. That is, the plane L2 is displaced in the same direction (hereinafter, referred to as “displacement addition condition”).

As described above with reference to FIG. 15, the conventional head actuator has a structure in which the displacement element 51 is only fixed to a part of the surface of the head supporting member 50, and therefore, is necessarily in contact with the neutral plane NA1. Since the neutral plane NB1 and the central plane L1 are located in opposite directions, the above-described change addition condition is not satisfied. On the other hand, according to the first embodiment,
By fixing the reinforcing plate 32 to the region 302, the position of the neutral plane NB2 is shifted in the direction of the reinforcing plate 32, and the displacement addition condition is satisfied.

That is, in the configuration of the conventional head actuator, the displacement X1 in the longitudinal direction caused by the expansion and contraction force F1 is opposite to the direction of the displacement X1 caused by the deflection angle θA as described above with reference to FIG. While there was a problem that the displacement was lost due to the displacement amount X2 and a sufficient displacement for positioning the head was not obtained, according to the first embodiment, as described above with reference to FIG. The displacement amount X4 in the longitudinal direction caused by the deflection angle θ2 is added to the displacement amount X3 in the longitudinal direction, so that the effect of increasing the actual displacement amount can be obtained.

(Second Embodiment) A head actuator according to a second embodiment of the present invention will be described below with reference to FIGS. FIG. 6 is an exploded perspective view of a main part of a head actuator according to a second embodiment of the present invention.
FIG. 7 is a schematic diagram showing a cross-sectional configuration of FIG.
The thickness direction is shown enlarged. The head actuator of the second embodiment differs from the first embodiment in that the configuration of the flexure 30 shown in FIGS. 6 and 7 is different from that of the first embodiment in the points described later. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

6 and 7, the flexure 30A of the second embodiment differs from the configuration of the first embodiment in the following three points. The first difference is that, in the above-described embodiment, as shown in FIG.
Embodiment 1 is overlapped with the first embodiment.
In the first embodiment, the reinforcing plate 32 is not overlapped with the piezoelectric element unit 4 of the flexible substrate 31 as shown in FIG.
0 is fixed to the same surface as the fixed surface, whereas the second embodiment is fixed to the opposite surface as shown in FIG. In the second embodiment, as shown in FIG. 7, the holding members 41A and 41B are fixed on the piezoelectric element units 40A and 40B, respectively. As shown in FIG. 7, the holding members 41A and 41B
A high-rigidity layer 43 made of stainless steel and having a thickness of about 10 micrometers is bonded to a low-rigidity layer 42 made of a polyimide resin having a thickness of about 150 micrometers.

In FIG. 7, as in the first embodiment, the stretchable portions 31A and 31B (FIG. 6) of the flexible substrate 31 are defined as a region 401, and the hinge portion 31C (FIG. 6) is defined as a region 402. In the second embodiment, the holding member 41 is provided on the piezoelectric element unit 40, and the material and the material of the low-rigid layer 42 and the high-rigid layer 43 are set so that the neutral plane NA3 of the region 401 exists inside the low-rigid layer 42. The thickness is set. The neutral plane NB3 in the region 402 is the flexible substrate 31
Inside the reinforcing plate 32 fixed to the lower surface of the plate. In the second embodiment, the neutral surface step D3 is about 103 micrometers. The distance H3 between the central plane L3 of the single piezoelectric element unit 40 and the neutral plane NA3 is about 78 micrometers. As described above, also in the second embodiment,
With respect to the neutral plane NA3 in the area 401, the area 402
The neutral plane NB3 and the central plane L3 of the piezoelectric element unit 40 alone are displaced in the same direction, satisfying the displacement addition condition described in the first embodiment.

FIGS. 8A to 8C show static models of the head actuator according to the second embodiment of the present invention. Comparing the model of the second embodiment shown in FIG. 8A with the model of the first embodiment described above with reference to FIG. 5A, the two have a mirror-symmetric relationship with respect to the vertical direction of the drawing. You can see that. Therefore, by the same operation as that described in the first embodiment, as shown in FIGS. 8B and 8C, the direction of the displacement X5 due to the longitudinal stretching force F3 and the displacement due to the deflection angle θ3. The direction of the amount X6 is the same direction, and the actual amount of displacement is the sum of the amount of displacement X5 and the amount of displacement X6.

That is, according to the second embodiment, similarly to the first embodiment, the longitudinal displacement X6 caused by the deflection angle θ3 is added to the longitudinal displacement X5 caused by the stretching force F3. This has the effect that the actual displacement can be increased.

In the second embodiment, as shown in FIG. 7, the neutral surface step D3 is changed to the neutral surface step D2 in the first embodiment.
Since it can be larger than (FIG. 3), the deflection angle can be converted to a larger longitudinal displacement.
In the second embodiment, since the holding members 41A and 41B are provided on the piezoelectric element units 40A and 40B, the in-plane expansion and contraction amount is slightly reduced as compared with the first embodiment. Since the displacement in the direction can be made sufficiently large, the actual displacement amount is larger than that in the first embodiment.

In addition, regarding the dynamic characteristics, the holding member 4
Since 1A and 41B act to increase the rigidity of the flexure 30A in the bending direction, the natural frequency of the head actuator can be increased. Therefore, there is an effect that the mechanical resonance frequency of the head actuator can be improved and head positioning control in a wide band can be performed.

In particular, the holding members 41A, 41 of the second embodiment
B is fixed to the piezoelectric element units 40A and 40B by separating the high rigidity layer 43 having the same rigidity as the piezoelectric element units 40A and 40B with the low rigidity layer 42 having sufficiently lower rigidity than the high rigidity layer 43. With such a configuration, the thickness of the members necessary for achieving the predetermined neutral plane deviation amount can be reduced. Therefore, the bending stiffness in the bending direction can be increased without significantly increasing the elongation stiffness in the longitudinal direction, so that a further effect is exhibited in both of increasing the displacement amount and increasing the mechanical resonance frequency. .

(Embodiment 3) Hereinafter, a head actuator according to Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 9 is a schematic diagram showing a cross-sectional configuration of the head actuator according to the third embodiment of the present invention, which is shown in an enlarged manner in the thickness direction. The other components and operations of the head actuator of the third embodiment are the same as those of the first embodiment except that the intermediate layer 44 is provided on the flexure 30B shown in FIG. And the description is omitted.

In FIG. 9, the piezoelectric element unit 40 is
It is bonded to the flexible substrate 31 via an intermediate layer 44 made of a polyimide resin having a thickness of about 18 micrometers. As in the first embodiment, the elastic portions 31A and 31B (FIG. 2) of the flexible substrate 31 are defined as a region 501 and the hinge portion 31C (FIG. 2) is defined as a region 502. In the third embodiment, the thickness of intermediate layer 44 is selected such that neutral plane NA4 of region 501 is continuous with neutral plane NB4 of region 502.

The head actuator according to the third embodiment includes:
With the configuration described above, the mechanical resonance frequency is significantly increased. As described above with reference to FIG. 17, the conventional head actuator has a natural vibration mode in which the inertial force caused by the vibration of the head slider having a large mass and the elastic force in the bending direction of the head support member are balanced. And that set the lowest mechanical resonance frequency. In addition, there is a problem that it is difficult to increase the mechanical resonance frequency because it is difficult to increase the bending rigidity of the head support member.

In the third embodiment, as described above, the region 50
1 and the neutral plane NB4 in the region 502 are continuous with each other and the neutral plane step is not generated, so that the flexure 30B vibrates in the direction perpendicular to the longitudinal direction, that is, in the bending direction. However, the first natural vibration mode which does not affect the positioning of the head 1 provided on the head slider 11 is formed, and the head slider 11 having a large mass vibrates in the longitudinal direction. A mechanical resonance frequency of the head actuator by forming a second natural vibration mode in which the inertial force generated by the vibration is applied by the longitudinal elastic force of the flexure 30B having relatively high rigidity. It is.

Hereinafter, the two vibration modes will be sequentially described with reference to FIGS. 10 (a) and 10 (b). FIGS. 10A and 10B are dynamic models of the head actuator according to the third embodiment of the present invention. Flexure 30B can be represented by a model in which equivalent mass MA1 is concentrated at the center of beam 1001 having equivalent bending rigidity. K1 is flexure 30
MS is the equivalent rigidity of the movable body 1002 with the head slider 11 as the center.

The first natural vibration mode in this model is a mode in which the flexure 30B vibrates in a direction perpendicular to the longitudinal direction, that is, in a bending direction, as shown in FIG. In the third embodiment, the configuration is such that a neutral surface step does not occur. Therefore, even if the flexure 30B vibrates in the bending direction as shown in FIG. 10A, a force is applied to the movable body 1002 around the head slider 11 in the direction of the arrow 1003 as in the prior art described above with reference to FIG. Has no effect. Therefore, the mass MS of the movable body 1002 does not vibrate in the direction of the arrow 1003.
That is, the degree of freedom φY in the bending direction of the flexure 30B does not affect the degree of freedom φS of the movable body 1002. Therefore, even if the first natural vibration mode occurs, the vibration is not detected by the head provided on the head slider 11, so that the head positioning control is not affected. In the third embodiment, the natural frequency of the first natural vibration mode is 20.7 kHz.

Next, the second natural vibration mode is shown in FIG.
As shown in (b), the movable body 1002 and the flexure 3
0B is a mode that vibrates integrally in the longitudinal direction, that is, in the direction of arrow 1003. The mass MS of the movable body 1002 is supported by the equivalent rigidity K1 in the longitudinal direction, which is higher in rigidity than the bending rigidity in the bending direction, and has a high natural frequency. In the third embodiment, the natural frequency of the second natural vibration mode is 22.9 kHz.

FIGS. 11A and 11B are graphs showing the dynamic characteristics of the head actuator according to the third embodiment of the present invention. FIG. 11 (a) and FIG.
In (b), the horizontal axis represents the frequency of the supply voltage supplied to the head actuator, and the vertical axis represents the displacement of the head.
FIG. 11A shows dynamic characteristics in a configuration in which the above-described neutral surface step does not occur. FIG. 11B for comparison.
In addition, the intermediate layer 44 is made thicker so that
9 shows dynamic characteristics in a configuration provided with 6 micrometers. Except that the thickness of the intermediate layer 44 is different, the configurations of the two are the same. In FIG. 11B, the lowest mechanical resonance frequency is 15.1 kHz (the position indicated by the arrow 111), which is due to the natural vibration mode of the dynamic model similar to that described with reference to FIG. It is. On the other hand, in FIG. 11A, the lowest mechanical resonance frequency is 22.9 kHz (the position indicated by the arrow 112) due to the second natural vibration mode described above. Although the first natural vibration mode exists at a frequency of 20.7 kHz (the position indicated by the arrow 113), no vibration is detected and does not affect the head positioning control.

As described above, in the head actuator according to the third embodiment, the intermediate layer 44 is provided, and the region 501 and the region 50 are provided.
By configuring so that the neutral planes of the two are continuous, the mechanical resonance frequency can be significantly increased. Thereby,
There is an effect that highly accurate head positioning control can be performed in a wider band.

In the third embodiment, the intermediate layer 44 is provided so that the neutral planes of the region 501 and the region 502 are continuous. However, the present invention is not limited to this. 7, the neutral surfaces of the region 501 and the region 502 may be continuous by providing the holding members 41A and 41B on the piezoelectric element unit 40 as described with reference to FIG.

FIG. 12 is a schematic diagram showing a cross-sectional configuration of another head actuator according to the third embodiment. As shown in FIG. 12, instead of the intermediate layer 44, by providing the reinforcing member 32A at least in the region 502, the neutral surface NA6 in the region 501 and the neutral surface NB6 in the region 502 are made continuous. Good.

FIG. 13A is a schematic diagram showing a cross-sectional structure of still another head actuator according to the third embodiment. FIG. 13B shows a cross section SS in FIG.
And also the cross section JJ in FIG. FIG.
As shown in FIG.
With respect to the piezoelectric element units 40A and 40B provided on 1A and 31B, respectively, the piezoelectric element units 40A and 40B overlap with the piezoelectric element units 40A and 40B in the thickness direction (the direction perpendicular to the surfaces of the elastic portions 31A and 31B of the flexible substrate 31). As described above, the wiring 34A, the wiring 34B,
When the wiring 34C, the wiring 34D, and the wiring 34E are provided, the neutral plane NA5 in the region 501 is changed to the piezoelectric element unit 40.
By moving to the sides A and 40B, the neutral plane NA5 in the region 501 can be made continuous with the neutral plane NB5 in the region 502. That is, wiring is provided around each of the piezoelectric element units 40A and 40B without providing the above-described intermediate layer 44 between each of the elastic portions 31A and 31B of the flexible substrate 31 and each of the piezoelectric element units 40A and 40B. Thereby, the neutral plane NA5 in the area 501 can be made continuous with the neutral plane NB5 in the area 502. Therefore, the mechanical resonance frequency can be remarkably increased, and the same effect as the above-described effect that high-precision head positioning control can be performed in a wider band can be obtained.

Note that the neutral plane NA4 of the region 501 and the region 5
02 is not necessarily strictly continuous with the neutral plane NB4, and is different from the distance between the neutral plane NA4 of the region 501 and the center plane of the piezoelectric element unit. If the step between the neutral planes is sufficiently small, the neutral planes NA4 and NB4 have substantially the same effect as being continuous, and the two neutral planes are substantially continuous. Can be considered.

In each of the first to third embodiments, the configuration in which the piezoelectric element unit is provided on the head slider side of the flexible substrate has been described as an example. However, the configuration is provided on the surface opposite to the head slider. Is also good. Also,
A configuration provided on both sides of the flexible substrate may be used.

Further, in all of the first to third embodiments, the piezoelectric element unit has been described using a single-layer piezoelectric element as an example, but a plurality of piezoelectric elements may be stacked.

Further, in all of the first to third embodiments, the example in which the head slider provided with the magnetic head is mounted on the head actuator has been described, but the optical pickup element is mounted instead of the head slider provided with the magnetic head. You may.

FIG. 14 is a perspective view of a hard disk drive 1500 on which the head actuator according to any of the first to third embodiments is mounted. The hard disk drive 1500 includes a head actuator 1510 including the slider 11 provided with the head 1, and a head carriage 1501 holding the head actuator 1510.
A linear or rotary voice coil motor 1502 for moving the head 1 via a head carriage 1501 and a head actuator 1510;
And a flexible substrate of a head actuator 1510 are expanded and contracted in the longitudinal direction, and the head 1 is moved in the radial direction of the disk 1503.
To position the head actuator 1510
15 for giving a signal to the piezoelectric element unit included in
05.

The spindle motor 1504 is connected to the disk 1
503 is driven to rotate at a predetermined speed. The voice coil motor 1502 is provided with a head actuator 15 including a slider 11 provided with the head 1 so that the head 1 can access a predetermined data track on the disk 1503.
10 is moved radially across the surface of the disk 1503. The piezoelectric element unit expands and contracts the flexible substrate in the longitudinal direction according to a signal given by the control unit 1505, and positions the head 1 in the radial direction of the disk 1503. The head 1 records and reproduces information on the disk 1503.

The slider 11 holding the head 1 is, for example, an air bearing slider. In this case, the slider 11 is used to activate the hard disk drive 1500.
During the stop operation, the disk contacts the surface of the disk 1503. During the information recording / reproducing operation of the hard disk drive 1500, the slider 11 is maintained on the surface of the disk 1503 by an air bearing formed between the rotating disk 1503 and the slider 11.

[0086]

As described above, according to the head actuator of the present invention, a large head displacement can be obtained at a lower voltage and the mechanical resonance frequency can be increased. Thereby, highly accurate head positioning control can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a head actuator according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a portion A in FIG.

FIG. 3 is a schematic diagram showing a configuration of a cross section of FIG. 2;

FIG. 4 is a plan view showing a state of deformation of the head actuator according to the first embodiment of the present invention.

FIG. 5 is a static model of a head actuator according to the first embodiment of the present invention.

FIG. 6 is an exploded perspective view of a main part of a head actuator according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram showing a configuration of a cross section of FIG. 6;

FIG. 8 shows a static model of a head actuator according to a second embodiment of the present invention.

FIG. 9 is a schematic diagram showing a cross-sectional configuration of a head actuator according to a third embodiment of the present invention.

FIG. 10 is a dynamic model of a head actuator according to a third embodiment of the present invention.

FIG. 11 is a graph showing dynamic characteristics of a head actuator according to a third embodiment of the present invention.

FIG. 12 is a schematic diagram showing a cross-sectional configuration of another head actuator according to the third embodiment of the present invention.

FIG. 13A is a schematic diagram showing a cross-sectional configuration of still another head actuator according to the third embodiment of the present invention, and FIG. 13B is a cross-sectional view taken along line SS in FIG.

FIG. 14 is a perspective view of a hard disk drive on which the head actuator according to the first to third embodiments is mounted.

FIG. 15 is a schematic diagram showing a cross-sectional configuration of a conventional head actuator.

FIG. 16 shows a static model of a conventional head actuator.

FIG. 17 shows a dynamic model of a conventional head actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic head 11 Head slider 20 Load beam 21 Dimple 30 Flexure 31 Flexible board 31A, 31B Elastic part 31C Hinge part 31D Fixed part 31E Rotating part 31F Dimple receiver 32 Reinforcement plate 33 Spacer 34 Back plate 40A, 40B Piezoelectric element unit 41A 41B Holding member 42 Low rigidity layer 43 High rigidity layer 44 Intermediate layer 50 Head support member 51 Displacement element 100 Head actuator

Claims (31)

[Claims] A head slider that supports a head that records or reproduces information on a recording medium; and a head support member that supports the head slider. The head support member includes a substrate, A drive element provided on at least one surface and generating a stretching force in the longitudinal direction in response to an external signal, by applying an external signal to the drive element to expand and contract the head support member in the longitudinal direction, A head actuator for positioning the head in a radial direction of a medium, wherein the head support member includes a first area where the head slider is provided, a second area where the driving element is provided, the first area and the first area. A third region connecting the second region and the third region, wherein the driving element has a geometric center plane, and the head support member is disposed in the second region. A first neutral surface and a second neutral surface in the third region, wherein the second neutral surface is biased toward the same side as the geometric center plane with respect to the first neutral surface. Head actuator. 2. The head actuator according to claim 1, wherein the first neutral plane exists on the substrate side with respect to the geometric center plane. 3. The head support member further includes a neutral plane deviation means for displacing the second neutral plane with respect to the first neutral plane on the same side as the geometric center plane. The head actuator according to claim 2. 4. The head actuator according to claim 3, wherein said neutral plane deviation means includes a reinforcing member provided at least in said third region. 5. The head actuator according to claim 1, wherein the first neutral plane is on an opposite side of the substrate with respect to the geometric center plane. 6. The head support member further includes a geometric center plane deviation means for displacing the first neutral plane to the opposite side of the substrate with respect to the geometric center plane. 5
The head actuator according to any one of the preceding claims. 7. The geometric center plane deviation unit includes a holding member formed on the same side as the substrate with respect to the driving element, wherein the holding member has a rigidity in a bending direction of the head support member. 7. The head actuator according to claim 6, wherein the head actuator has a function of increasing the natural frequency of the head support member. 8. The low-stiffness layer provided on the drive element and having a lower longitudinal elastic coefficient than the drive element, the holding member is provided on the low-stiffness layer, and the longitudinal elasticity is lower than the low-stiffness layer. The head actuator according to claim 7, further comprising a high rigidity layer having a large coefficient. 9. The head actuator according to claim 8, wherein the low rigidity layer includes a polyimide resin, and the high rigidity layer includes a stainless steel. 10. The head support member further includes a first neutral plane deviation means for displacing the second neutral plane with respect to the first neutral plane on the same side as the geometric center plane. The head actuator according to claim 6, comprising: 11. The first neutral plane deviation means includes a reinforcing member provided at least in the third region.
0 head actuator. 12. The head actuator according to claim 11, wherein the reinforcing member is provided on a side opposite to the driving element with respect to the substrate. 13. The driving element has a first extension rigidity, the substrate has a second extension rigidity, and the first extension rigidity is larger than the second extension rigidity.
The head actuator according to claim 1. 14. The head actuator according to claim 1, wherein the driving element has a plate shape. 15. The head actuator according to claim 1, wherein the drive element includes a piezoelectric element unit in which an electrode is mounted on a thin film piezoelectric body. 16. The head actuator according to claim 1, wherein the driving elements include a first driving element and a second driving element to which voltages in opposite directions are applied. 17. The substrate, wherein: a first telescopic portion provided with the first drive element; a second telescopic portion provided with the second drive element; a rotating portion provided with the head slider; 17. The head actuator according to claim 16, further comprising: a first hinge unit that connects a moving unit and the first elastic unit; and a second hinge unit that connects the rotating unit and the second elastic unit. 18. The head actuator further includes a load beam that supports the head support member.
The head actuator according to claim 1. 19. A head slider that supports a head that records or reproduces information on or from a recording medium, and a head support member that supports the head slider, wherein the head support member includes a substrate, A drive element provided on at least one surface and generating a stretching force in the longitudinal direction in response to an external signal, by applying an external signal to the drive element to expand and contract the head support member in the longitudinal direction, A head actuator for positioning the head in a radial direction of a medium, wherein the head support member includes a first area where the head slider is provided, a second area where the driving element is provided, the first area and the first area. A third region connecting the second region and the head support member, wherein the head support member has a first neutral surface in the second region and a third neutral surface in the third region. And a neutral plane, the first neutral surface and the second neutral surface and the head actuator is substantially continuous. 20. The head actuator according to claim 19, wherein said head support member includes a continuation means for making said first neutral plane substantially continuous with said second neutral plane. 21. The head actuator according to claim 20, wherein the continuous unit includes an intermediate layer provided between the substrate and the driving element. 22. The continuation means includes at least the third
The head actuator according to claim 20, further comprising a reinforcing member provided in the region. 23. The head actuator according to claim 20, wherein the continuation unit includes a wiring portion provided around the driving element. 24. The driving element has a first extensional rigidity, the substrate has a second extensional rigidity, and the first extensional rigidity is larger than the second extensional rigidity.
The head actuator according to claim 19. 25. The head actuator according to claim 19, wherein the driving element has a plate shape. 26. The head actuator according to claim 19, wherein the drive element includes a piezoelectric element unit in which an electrode is formed on a thin-film piezoelectric body. 27. The head actuator according to claim 19, wherein the driving elements include a first driving element and a second driving element to which voltages in opposite directions are applied. 28. The substrate, wherein: a first telescopic portion provided with the first drive element; a second telescopic portion provided with the second drive element; a rotating portion provided with the head slider; 28. The head actuator according to claim 27, comprising: a first hinge unit that connects a moving unit and the first elastic unit; and a second hinge unit that connects the rotating unit and the second elastic unit. 29. The head actuator further includes a load beam supporting the head support member.
The head actuator according to claim 19. 30. The head actuator according to claim 1, a motor for driving the recording medium to rotate, and the head actuator to the recording medium so that the head can access a predetermined data track on the recording medium. Drive means for moving in a radial direction across the surface of the recording medium, so as to expand and contract the head support member in the in-plane direction, to position the head in the radial direction of the recording medium,
A hard disk drive comprising: a control unit that supplies the external signal to the drive element. 31. The head actuator according to claim 19, a motor for driving the recording medium to rotate, and the head actuator so that the head can access a predetermined data track on the recording medium. Drive means for moving in a radial direction across the surface of the recording medium, so as to expand and contract the head support member in the in-plane direction, to position the head in the radial direction of the recording medium,
A hard disk drive comprising: a control unit that supplies the external signal to the drive element.