JP2008135156A - System and method for discriminating problem of piezoelectric element of micro-actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and a method for discriminating a problem of a piezoelectric element of a micro-actuator. <P>SOLUTION: Vibration of a reference unit and a test unit is caused by applying voltage such as sine wave voltage to the reference unit (S602). Then, it is confirmed whether a problem exists in the test unit or not by comparison (e.g. using a processor) of corresponding resonance properties (e.g. frequency, amplitude, phase, or the like) (S604, S606, S608). The reference unit can possess a head gimbal assembly or a head suspension assembly of a hard disk drive device. Also, the test unit includes parts used for detection. A problem of the piezoelectric element can be detected by this technology even when only one piezoelectric element is included in each micro-actuator. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information recording disk drive device, and more particularly to a technique for identifying a problem related to a piezoelectric element of a microactuator installed in a head suspension assembly of a disk drive device.

  A disk drive device is often used as a device for recording data using a magnetic medium. This disk drive apparatus is an apparatus for selectively recording / reproducing data from / on a magnetic medium by a movable recording / reproducing head provided above the magnetic medium.

  Conventionally, users have requested disk drive devices to have higher recording density, faster recording / reproducing operations, and higher accuracy. For this reason, manufacturers of disk drive devices, for example, reduce the track width and track pitch of the magnetic disk and indirectly increase the recording capacity of the track of the magnetic disk, thereby increasing the recording density of the magnetic disk drive device. We have been intensively developing. However, in order to perform a recording / reproducing operation quickly and with high accuracy for a disk drive device that has been increased in density with an increase in track density, high accuracy has been required for position control for the recording / reproducing head. . However, it has become extremely difficult to quickly and highly accurately arrange a recording / reproducing head on a track of a magnetic disk using conventional techniques as the track density increases. With such an increase in track density, a technique for improving the positioning control of the recording / reproducing head is being studied.

  Each manufacturer employs a second driver (i.e., microactuator) to improve the positioning control of the recording / reproducing head. This microactuator is driven together with one main driver to improve the recording / reproducing head positioning accuracy and speed up the operation. A disk drive equipped with this microactuator is called a two-driver system.

  Conventionally, various two-driver systems have been developed in order to increase the speed of the recording / reproducing operation and to realize the high-precision positioning control of the recording / reproducing head on the high-density magnetic disk. Such a two-driver system includes a voice coil motor (VCM) that is one main driver and a microactuator (for example, a piezoelectric element microactuator) that is one sub-driver. The voice coil motor is controlled by a servo control system, which rotates the drive arm. The drive arm carries a recording / reproducing head, and thereby positions the recording / reproducing head on a specific track of the recording medium. A piezoelectric element (PZT element) microactuator is used together with a voice coil motor driver, thereby realizing a rapid recording / reproducing operation and a high-precision recording / reproducing head positioning control. That is, the voice coil motor driver coarsely adjusts the positioning of the recording / reproducing head with low accuracy, and the piezoelectric element microactuator finely adjusts the positioning of the recording / reproducing head with respect to the recording medium with high accuracy. By using these two drivers, information can be recorded / reproduced from a high-density magnetic disk quickly and accurately.

  Currently, the microactuator used for positioning of the recording / reproducing head has a configuration including a piezoelectric element. Such a piezoelectric element microactuator has an electronic circuit structure for driving the piezoelectric element so as to selectively expand or contract the piezoelectric element on the microactuator. Since the piezoelectric element microactuator has such a structure, the microactuator can be driven by the expansion or contraction or expansion of the piezoelectric element, and the recording / reproducing head can be operated. The operation of the recording / reproducing head can adjust the position of the recording / reproducing head more quickly and with higher accuracy than a magnetic disk drive unit using only a voice coil motor driver. Such piezoelectric element microactuators related to the conventional example are disclosed in, for example, the following Patent Documents 1 to 4. Here, the contents of these patent documents will be described in combination.

  FIGS. 1 and 2 are diagrams showing a conventional disk drive unit. A magnetic disk 101 is mounted on a spindle motor 102 and is rotated by driving the spindle motor 102. A head gimbal assembly (HGA) 227 is mounted on the voice coil motor arm 104. The head gimbal assembly 227 includes a microactuator 105 having a slider 203. The slider 203 includes a recording / reproducing head. Is arranged. The voice coil motor (VCM) controls the operation of the voice coil motor arm 104 and further controls the movement of the slider 203 from one track to another track on the surface of the magnetic disk 101. As a result, the recording / reproducing head can record / reproduce information with respect to the magnetic disk 101.

  However, when only one servo motor system is used, due to the inherent error caused by the voice coil motor and head suspension assembly, the quick and accurate positioning of the slider cannot be controlled, and recording that records and reproduces information from the magnetic disk. / The accuracy performance of the playback head was affected. Therefore, by providing a microactuator, the positioning accuracy of the slider 203 and the recording / reproducing head is improved. Specifically, the piezoelectric microactuator adjusts the position of the slider with a smaller width than the voice coil motor to compensate for the resonance error of the voice coil motor or the head suspension assembly. This piezoelectric microactuator can be applied to a smaller track pitch, and the track density (TPI value, the number of tracks per inch) of the disk drive device is improved by 50%, and the seek time and positioning time of the magnetic head. Can be shortened. Thereby, the piezoelectric microactuator can significantly increase the surface recording density of the recording disk.

  FIG. 2A is a perspective view showing a conventional U-shaped microactuator. As shown in FIG. 2A, the microactuator 105 has a ceramic frame 100, and the ceramic frame 100 includes side arms 107 and 108. Piezoelectric elements 107a and 108a are mounted on the side arms 107 and 108, respectively. The microactuator 105 is connected to the suspension tongue of the head gimbal assembly through the bottom of the ceramic frame 100. Further, the presence of a parallel gap (not shown) allows the piezoelectric microactuator 105 to move the slider 203 smoothly when a voltage is applied to at least one of the piezoelectric elements 107a and 108a.

  FIG. 2B is a perspective view showing another conventional U-shaped microactuator. As shown in FIG. 2B, the microactuator 105 ′ includes a metal frame 213, and the metal frame 213 includes a top support arm 214, a bottom support arm 215, and side arms 211 and 212. Piezoelectric elements 207 and 208 are mounted on the side arms 211 and 212, respectively. The bottom support arm 215 is attached to the suspension tongue. Further, the presence of a parallel gap (not shown) allows the piezoelectric microactuator 105 ′ to move the slider 203 smoothly when a voltage is applied to at least one of the piezoelectric elements 207 and 208.

  FIG. 2C shows a head gimbal assembly 227 including two drivers of the conventional disk drive unit shown in FIGS. More specifically, FIG. 2C is an enlarged perspective view showing a head gimbal assembly of the conventional disk drive unit shown in FIGS. The microactuator shown in FIG. 2B is positioned by a head gimbal assembly. Of course, the microactuator shown in FIG. 2A is also positioned on the head gimbal assembly, but a detailed description thereof will be omitted. Briefly, the microactuator 105 ′ is coupled to a suspension trace 117 at one end of each piezoelectric element 207, 208 via an electrical connection pad 109. The electrical connection pad 109 is appropriately formed by, for example, gold ball bonding (GBB), solder ball bonding (SBB), or other similar methods. The slider 203 is attached to the top support arm 214 of the metal frame 213, and the slider 203 and the suspension trace are connected using a plurality of electrical connection pads (connected by gold ball connection, solder ball connection, or other similar methods). 110 is coupled to provide an electrical connection between the recording / reproducing transducers. When a driving voltage is applied via the suspension trace 117, the piezoelectric elements 207 and 208 in the side arms 211 and 212 are expanded or contracted to bend the side arms 211 and 212 along the same one side direction. As described above, the slider 203 is connected to the two side arms, so that the slider 203 is moved in the lateral direction. Thereby, fine adjustment of the position control of the slider can be realized.

  Such microactuators are highly universal in the industry and are also very important as hard disk drive functions, so consider how to identify problems or failures related to microactuators' piezoelectric elements. There was a need. Examples of this problem include formation of microcracks and deformation of piezoelectric elements. In the prior art, in order to detect a problem of the piezoelectric element, the piezoelectric element is visually inspected. However, this inspection has drawbacks. For example, since there is a limitation due to the size and complexity of the piezoelectric element and the head gimbal assembly, the problem may not be detected by visual inspection alone.

  As another technique, voltage is applied to the piezoelectric element and laser Doppler vibrometers (LDV) are used to measure the capacitance or resonance of other piezoelectric elements to obtain mechanical resonance characteristics. In some cases, a deviation from the planned standard was detected. This technique is exemplified in Patent Document 5, which will be described with reference to the contents of the same.

  FIG. 3A is a diagram illustrating a test apparatus 300 that detects an error of a head gimbal assembly including two piezoelectric elements. The test apparatus 300 includes a user interface 314 with an associated input mechanism 318 and a display 316, a test control processor 312, a signal generator 308 and a signal analyzer 310. Among them, the signal generator 308 is electrically connected (304) to the first microactuator 207 of the first side arm of the head gimbal assembly. The signal analyzer 310 is electrically connected (306) to the second microactuator 208 of the second side arm. The test control processor 312 instructs the signal generator 308 to output a reference signal at a predetermined voltage (eg, sweep, sine, period chirp, random noise, etc.) To do. This reference signal activates the piezoelectric element 207 and causes the first side arm to bend. Since the first side arm and the second side arm are interconnected and the second piezoelectric element is located on the second side arm, the second piezoelectric element 208 is also curved, As a result, a response voltage is generated in the piezoelectric element 208. Further, in order to predict the characteristics of the microactuator, the response voltage is detected by the signal analyzer 310, and the test control processor 312 compares the reference signal characteristics and the response signal characteristics.

  FIG. 3B is a diagram for explaining the output status of the conventional system shown in FIG. 3A. Here, the control data can be represented by a bode plot useful for reflecting the steady state frequency response of the electronic filter. In this figure, a logarithm of increased profit versus logarithmic frequency is shown. In the figure, R1 is the output value of the electrical signal of the piezoelectric element 207 or 208, and R2 is the expected response signal. If the response signal R1 and the expected response signal R2 do not match (for example, main peak frequency drift, profit increase amplitude mismatch, etc.), it means that the response characteristics of the piezoelectric element have already changed, and the piezoelectric element is damaged or defective. Indicates that it may have occurred.

As described above, in the head gimbal assembly having the structure including the two piezoelectric elements, the conventional capacitance measurement and the measurement by the laser Doppler vibrometer can be used well. However, if there was only one piezoelectric element in the system, they could not work at all. Such a situation can occur in a hard disk drive sensor system. Therefore, it has been desired to provide an improved system that can overcome the above disadvantages.
JP 2002-133803 A US Pat. No. 6,671,131 US Patent Publication No. 6700749 US Published Patent Publication No. 2003-0168935 US Published Patent Publication No. 2003-0076121

  In the present invention, based on some embodiments, a technique for detecting a defect of a piezoelectric element of a microactuator disposed in a hard disk drive unit, and a defect when at least one piezoelectric element is mounted on the microactuator are detected. Provide technology.

  The present invention provides a system for identifying problems with piezoelectric elements of microactuators. The voltage distributor can be connected to one reference microactuator, and has a structure for causing the reference microactuator to vibrate in a state of standard resonance. The test microactuator is induced by vibration from the reference microactuator and vibrates in the state of the resonance under test. The processor is configured to compare at least one characteristic of the reference resonance with at least one corresponding characteristic of the resonance under test.

  Also, according to a specific embodiment of the present invention, a method for identifying a problem of a piezoelectric element of a microactuator according to the present invention is provided. First, a reference microactuator and a test microactuator are prepared. Next, a voltage is applied to the reference microactuator so that it is induced in the reference microactuator to form a reference resonance. Then, the reference resonance and the resonance under test are measured. Furthermore, a comparison operation is performed for at least one characteristic of the reference resonance and at least one corresponding characteristic of the resonance under test.

  In yet another embodiment, a method for identifying a problem with a piezoelectric element of a microactuator in a disk drive device is provided. The disk drive apparatus includes a head suspension assembly having a set of head gimbal assemblies, each head gimbal assembly further including a slider provided with a recording / reproducing head and a drive arm connected to the head gimbal assembly. This method applies a voltage to the head suspension assembly so that it is induced in each microactuator to form a resonance. Next, the inductive resonance in each microactuator is measured. Then, a reference resonance is formed. Furthermore, a comparison operation is performed for at least one characteristic of the reference resonance and at least one corresponding characteristic of the resonance under test.

  Hereinafter, with reference to the drawings, some embodiments will be described with respect to a technique for identifying problems (for example, formation of microcracks, deformation, etc.) occurring in a piezoelectric element of a microactuator. A voltage (such as a sinusoidal voltage) can be applied to the reference unit to cause vibration of the reference unit and the test unit. Then, by comparing (for example, using a processor) with corresponding resonance characteristics (for example, frequency, amplitude, phase, etc.), it can be confirmed whether there is a problem with the test unit. The reference unit may be disposed in a head gimbal assembly or a head suspension assembly of the hard disk drive device. The test unit also includes parts used for detection. According to such a technique, even if each microactuator includes only one piezoelectric element, it is possible to detect a problem that has occurred in the piezoelectric element.

  4A and 4B are diagrams showing an exemplary source device 401 of the test system according to the embodiment of the present invention, and FIGS. 4C and 4D are illustrations of the test system according to the embodiment of the present invention. It is a figure which shows a typical receiver. The source device 401 includes a voltage distributor 402 that is used to provide a voltage to the reference microactuator 403 of the reference head gimbal assembly 411. The receiving device 408 includes a sensor 405, a processor 407, and a test microactuator 404 connected to the test head gimbal assembly 411 ′.

  When the reference microactuator 403 of the reference head gimbal assembly 411 is driven by the source device 401, the piezoelectric element of the reference microactuator 403 generates a vibration waveform having a fixed frequency while vibrating. As shown in FIG. 4A, this vibration waveform propagates in the air. Then, the waveform is received by the piezoelectric element of the test microactuator 404 in the test head gimbal assembly 411 ′ connected to the receiving device 408. Here, since the frequencies of the test head gimbal assembly 411 ′ and the reference head gimbal assembly 411 are the same, the test head gimbal assembly 411 ′ seizes the waveform, and within the piezoelectric element of the test microactuator 404. A response resonance occurs. This response resonance represents the characteristics of the head gimbal assembly 411 ′ and the test microactuator 404. For example, if a change in resonance frequency or an increase / decrease in amplitude occurs, it indicates that the piezoelectric element of the test microactuator 404 in the test head gimbal assembly 411 ′ is broken or defective ( It is possible to display by the response characteristic of the piezoelectric element).

  FIG. 5A is a diagram illustrating an example of test data obtained from the test system according to the embodiment of the present invention. When a sinusoidal drive voltage 501 is applied to the piezoelectric element of the reference microactuator 403, the reference microactuator 403 vibrates and generates a resonance waveform. In the present embodiment, the frequency is set to about 25 kHz, but of course, other frequencies may be set. This waveform propagates in the air. Further, the test microactuator 404 located in the receiving device 408 confines the waveform and is induced to respond to the resonance 502. The induced resonance 502 has the same frequency as the drive voltage applied by the voltage divider 402 and the resonance frequency of the reference microactuator 403.

  FIG. 5B is a diagram showing another example of test data obtained from the test system according to the embodiment of the present invention. The resonances of the induced voltage 503 and the test head gimbal assembly 411 ′ correspond to each other. As shown in FIG. 5B, the frequency of the induction resonance voltage 503 is 12.5 KHz, and this frequency is lower than the resonance frequency of the reference microactuator 403. Here, since this microactuator 403 is used as a reference object, the above difference means that a microcrack or another defect exists in the test microactuator 404.

  FIG. 6 is an exemplary flowchart illustrating a method for performing a test operation on a microactuator according to an embodiment of the present invention. First, in step S602, a voltage is applied to the reference microactuator. This causes resonance in the reference microactuator, and this resonance causes resonance in the test microactuator. Next, resonances induced in the reference microactuator and the test microactuator are measured in step S604 and compared in step S606. Based on this comparison, it can be confirmed in step S608 whether there is a problem with the test microactuator. Examples of this comparison include changes in amplitude, frequency, and phase.

  As described above, the voltage divider is applied to a single head gimbal assembly, but the present invention is not limited to this. For example, in other embodiments, the entire head suspension assembly can be tested. FIG. 7 is a local perspective view of the head suspension assembly 800. The testing techniques relating to embodiments of the present invention can also be used for such head suspension assemblies. Since the head suspension assembly 800 includes a magnetic head, a part or all of the microactuators 203a located in the head gimbal assemblies 277a to 277e of the head suspension assembly 800 when the voltage distributor is operated. To e can be induced. In addition, response resonance also occurs in each of the microactuators 203a to 203e. And the characteristic for every piezoelectric element of each microactuator is identified, and it can also compare as a different object, respectively. Therefore, in another embodiment of the present invention, the entire head suspension assembly 800 can be favorably applied as a reference object. Also, in other embodiments of the present invention (described below with reference to FIG. 8, for example), other comparisons can be performed, thereby supplementing or replacing the above-described comparison techniques.

  FIG. 8 is an exemplary flowchart of a method for testing a microactuator of an overall head suspension assembly according to an embodiment of the present invention. First, in step S802, a voltage is applied to the head suspension assembly to induce resonance in each microactuator in the head gimbal assembly of the head suspension assembly. Next, the resonance induced in each microactuator is measured in step S804, and a comparison operation is performed on one or several induction resonances in step S806. These comparisons include a series of paired comparisons, comparisons with the average of induction resonances, comparisons with scheduled reference resonances, and the like. Preferably, one or several resonances are all designated as reference resonances so that all other detected resonances are compared to it. In addition, the reference resonance may be swung around the induction resonance so as to include comparing each induction resonance with each other induction resonance. Subsequently, based on the comparison, it can be confirmed in step S808 whether there is a problem with one or several microactuators.

  As shown in FIG. 9, the technique described in combination with FIGS. 7 and 8 can also be applied to a head suspension assembly arranged in a hard disk drive. FIG. 9 is a diagram showing a disk drive unit including a magnetic disk 901 attached to a spindle motor 902. The spindle motor 902 is used for rotating the magnetic disk 901. The voice coil motor arm 904 supports a head suspension assembly 800 including a set of head gimbal assemblies, and each head gimbal assembly includes a microactuator and a slider. A recording / reproducing head is incorporated in this slider. A voice coil motor (VCM) controls the operation of the arm 904 of the voice coil motor so that the slider 903 moves between tracks on the surface of the disk 901, so that the recording / reproducing head is moved relative to the disk 901. Read and write information. Next, by applying a voltage, the characteristics of each induction resonance can be detected and compared.

  Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention, and the present invention has been described in detail. Of course, it is not limited to.

It is a perspective view of the conventional disk drive unit. FIG. 2 is a local perspective view of the conventional disk drive unit shown in FIG. 1. It is the figure which showed the conventional U-shaped microactuator. It is the figure which showed the other conventional U-shaped microactuator. FIG. 3 is an enlarged perspective view of a conventional head gimbal assembly in the disk drive unit shown in FIGS. It is the figure which showed the conventional test device for detecting the error of the head gimbal assembly containing two piezoelectric elements. It is the figure explaining the output condition of the conventional system shown by FIG. 3a. 1 is a diagram illustrating an exemplary source device of a test system according to an embodiment of the present invention. 1 is a diagram illustrating an exemplary source device of a test system according to an embodiment of the present invention. It is the figure which showed the exemplary receiver of the test system which concerns on embodiment of this invention. It is the figure which showed the exemplary receiver of the test system which concerns on embodiment of this invention. It is the figure which showed an example of the exemplary test data obtained from the test system which concerns on embodiment of this invention. It is a figure which shows another example of the example test data obtained from the test system which concerns on some embodiment of this invention. 4 is a flowchart of an exemplary method for testing a microactuator according to an embodiment of the present invention. 1 is a local perspective view of a head stack assembly (HSA) (testing techniques relating to embodiments of the present invention are also applicable to this head suspension assembly). FIG. 4 is a flowchart of an exemplary method for testing a microactuator of a head suspension assembly according to an embodiment of the present invention. 1 is a perspective view of a disk drive unit (testing techniques according to some embodiments of the present invention are also applicable to this disk drive unit). FIG.

Explanation of symbols

401: Source device 402: Voltage distributor 403: Reference microactuator 404: Test microactuator 405: Sensor 407: Processor 408: Receiver device 411: Reference head gimbal assembly
800: head suspension assembly 901: magnetic disk, 902: spindle motor, 903: slider, 904: arm

Claims (17)

A voltage distributor that is connected to one reference microactuator and vibrates the reference microactuator in a state of standard resonance;
A test microactuator that is induced by vibration from the reference microactuator and vibrates in a state of resonance under test;
A processor for comparing at least one characteristic of the reference resonance with at least one characteristic of the resonance under test corresponding to the characteristic;
A system for identifying problems with piezoelectric elements of microactuators, comprising: The system according to claim 1, wherein the voltage distributor is configured to apply a sine wave voltage to the reference microactuator. The system according to claim 1, wherein at least one characteristic of the reference resonance and at least one corresponding characteristic of the resonance to be tested are one or more selected from frequency, amplitude, and phase. Each of the microactuators is disposed in one disk drive device, and the disk drive device includes a head suspension assembly including a set of head gimbal assemblies, a disk, and a spindle motor.
Each head gimbal assembly further includes a slider provided with a recording / reproducing head and a drive arm connected to the head gimbal assembly.
The disk performs data recording or reproduction via the recording / reproducing head,
The system according to claim 1, wherein the spindle motor is used to drive the disk. The system according to claim 1, wherein the reference microactuator is one microactuator in the head suspension assembly, and all other microactuators are test microactuators. Providing a reference microactuator and a test microactuator;
Causing a voltage to be applied to the reference microactuator so that it is induced in the reference microactuator to form a reference resonance, thereby causing a resonance under test in the test microactuator by the reference resonance When,
Measuring the reference resonance and the resonance under test;
Performing a comparison operation on at least one characteristic of the reference resonance and at least one corresponding characteristic of the resonance under test;
A method of identifying a problem with a piezoelectric element of a microactuator comprising: The method according to claim 6, further comprising the step of checking whether there is a problem with the test microactuator based on the comparing step. The method of claim 6, wherein the voltage is a sinusoidal voltage. 7. The method according to claim 6, wherein at least one characteristic of the reference resonance and at least one corresponding characteristic of the resonance under test are one or several selected from frequency, amplitude and phase. In a method for identifying a problem of a piezoelectric element of a microactuator in a disk drive device,
The disk drive apparatus includes a head suspension assembly including a set of head gimbal assemblies, each head gimbal assembly further including a slider provided with a recording / reproducing head, and a drive arm connected to the head gimbal assembly. A device comprising
The method comprises
Applying a voltage to the head suspension assembly such that it is induced in each microactuator to form a resonance;
Measuring inductive resonance in each microactuator;
Forming a reference resonance;
Comparing at least one characteristic of the inductive resonance with at least one corresponding characteristic of a reference resonance;
A method of identifying a problem of a piezoelectric element of a microactuator in a disk drive device comprising: 11. The method of claim 10, further comprising the step of checking if there is a problem with the one or several microactuators based on the comparing step. The method of claim 10, wherein the voltage is a sinusoidal voltage. The method according to claim 10, wherein at least one characteristic of the inductive resonance is one or more selected from frequency, amplitude, and phase. The method of claim 10, further comprising estimating the reference resonance based on at least a portion of the applied voltage. The method of claim 10, further comprising averaging the inductive resonance to obtain the reference resonance. The method according to claim 10, wherein at least one inductive resonance is designated as a reference resonance. The method of claim 10, wherein the reference resonance is swiveled around the inductive resonance such that the comparing step includes comparing each inductive resonance with each other inductive resonance.

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