Measurement device and measurement method for measuring the vibration characteristics of a workpiece

Abstract

To provide a measuring device that can suppress the effects of crosstalk. [Solution] A suspension 10A for a hard disk drive, as an example of a workpiece, has piezoelectric elements 30R and 30L provided at a first position and piezoelectric elements 40R and 40L provided at a second position. Conductors 33 are connected to the piezoelectric elements 30R and 30L. Conductors 41 and 42 are connected to the piezoelectric elements 40R and 40L, respectively. The measuring device 100 has an excitation signal generation unit that supplies excitation signals S1 and S2 to the piezoelectric elements 40R and 40L, a vibration measurement unit that detects vibrations generated in the suspension 10A, and a ground connection unit 113. Conductors 33 that are in conductivity with the non-excitation piezoelectric elements 30R and 30L are connected to ground GND via the resistor R1 of the ground connection unit 113.

Description

Technical Field

[0001] The present invention relates to a measuring device for measuring vibration characteristics of a workpiece provided with an actuator such as a piezoelectric element, and a measuring method.

Background Art

[0002] A hard disk drive (HDD) is used in an information processing device such as a personal computer. Hereinafter, the hard disk drive is referred to as a disk drive. The disk drive includes a magnetic disk that rotates around a spindle, a carriage that pivots around a pivot axis, and the like. A suspension for a disk drive is provided on an arm of the carriage. The suspension for a disk drive is an example of a workpiece referred to in this specification. Hereinafter, the suspension for a disk drive is simply referred to as a suspension.

[0003] The suspension includes a base plate, a load beam, a flexure arranged along the load beam, and the like. A slider is provided at a gimbal portion formed near the tip of the flexure. The slider is provided with an element for accessing data recorded on the disk, such as reading and writing.

[0004] In order to increase the recording density of the disk, it is necessary to be able to position the magnetic head at a higher speed and with higher accuracy with respect to the recording surface of the disk. For this reason, a suspension equipped with a coarse movement actuator and a fine movement actuator has been developed. As a fine movement actuator, a piezoelectric element that operates according to a voltage is known.

[0005] For example, the suspension described in Patent Document 1 has an actuator mounted near the base plate of the suspension. The suspension described in Patent Document 2 has a fine-adjustment actuator mounted on the gimbal section. A multi-stage actuator type suspension equipped with both a coarse-adjustment actuator and a fine-adjustment actuator is also known.

[0006] To ensure that a suspension system functions correctly, it is necessary to accurately understand its vibration characteristics. For this reason, devices for measuring the vibration characteristics of suspension systems have been developed. For example, Patent Document 3 describes a measuring device equipped with a laser Doppler vibrometer. This measuring device includes an exciter that excites the suspension and a detector that irradiates the suspension with laser light and detects the reflected light.

[0007] In tests to measure vibration characteristics, the suspension itself is sometimes vibrated using actuators mounted on the suspension. For example, in a suspension equipped with actuators at a first position and a second position, the suspension is vibrated by supplying an excitation signal to the actuator at the first position. In this specification, the actuator to which an excitation signal is supplied during a vibration test is referred to as the excitation-side actuator, and the actuator to which an excitation signal is not supplied is referred to as the non-excitation-side actuator. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2013-246840 [Patent Document 2] Japanese Patent Publication No. 2014-22015 [Patent Document 3] Japanese Patent Publication No. 2007-192735 [Overview of the project] [Problems that the invention aims to solve]

[0009] Depending on the specifications of the disk drive, a first suspension facing a first surface of a disk and a second suspension facing a second surface of the disk may be provided. The first suspension is positioned so that the air bearing surface of the slider faces the first surface (e.g., the front surface) of the disk. The second suspension is positioned so that the air bearing surface of the slider faces the second surface (e.g., the back surface) of the disk. The first and second suspensions are mirror-symmetrical with respect to the disk.

[0010] Therefore, in vibration tests, if the excitation signal supplied to the first suspension and the excitation signal supplied to the second suspension are the same, then the vibration waveforms of the first suspension and the second suspension should be the same. However, after diligent research by the inventors, cases were observed where the vibration waveforms of the first suspension and the second suspension did not match.

[0011] The inventors diligently researched the reasons why the vibration waveforms of the first suspension and the second suspension differed from each other, and found that the cause was likely crosstalk in the wiring that was electrically connected to the actuator. When the actuator that vibrates the suspension is affected by crosstalk, the measured vibration characteristics may become inaccurate.

[0012] The object of the present invention is to provide a measuring device and a measuring method that can accurately measure the vibration characteristics of a workpiece in a test to measure the vibration characteristics of a workpiece having an actuator. [Means for solving the problem]

[0013] One embodiment of the measuring device is a measuring device for measuring the vibration characteristics of a workpiece having an actuator provided at a first position, a conductor that is electrically connected to the actuator at the first position, an actuator provided at a second position, and a conductor that is electrically connected to the actuator at the second position. The measuring device comprises an excitation signal generation unit, a vibration measurement unit, and a ground connection unit that is connected to ground. The excitation signal generation unit supplies an excitation signal to either the actuator at the first position or the actuator at the second position. The vibration measurement unit detects the vibration generated in the workpiece by the actuator to which the excitation signal is supplied. The ground connection unit connects the non-exciting actuator, which is not supplied with the excitation signal, to ground.

[0014] In one embodiment of the measuring device, the ground connection portion may have a resistor, and the non-excitation side actuator may be connected to the ground via the resistor. Furthermore, the actuator at the first position and the actuator at the second position may each have a piezoelectric element. Preferably, the impedance of the resistor may be smaller than the impedance of the piezoelectric element to which the excitation signal is supplied. If the stroke of the piezoelectric element at the first position is greater than the stroke of the piezoelectric element at the second position, the piezoelectric element at the first position may be connected to the ground connection portion, and the excitation signal may be supplied to the piezoelectric element at the second position.

[0015] One embodiment of the measurement method is a method for measuring the vibration characteristics of a workpiece having an actuator such as a piezoelectric element provided at a first position, a conductor that is electrically connected to the actuator at the first position, an actuator such as a piezoelectric element provided at a second position, and a conductor that is electrically connected to the actuator at the second position. Of the actuators at the first and second positions, the non-exciting actuator to which an excitation signal is not supplied is connected to ground. Of the actuators at the first and second positions, an excitation signal is supplied to the excitation actuator, and vibrations generated in the workpiece by the excitation actuator are detected.

[0016] In one embodiment of the measurement method, the excitation signal may be supplied to the excitation actuator while a resistor is provided between the non-excitation actuator and the ground. Preferably, the impedance of the resistor is smaller than the impedance of the excitation actuator. [Effects of the Invention]

[0017] According to a measuring device and measuring method according to one embodiment of the present invention, in a test to measure the vibration characteristics of a workpiece having an actuator, the effect of crosstalk is suppressed, and the vibration characteristics of the workpiece can be measured more accurately. [Brief explanation of the drawing]

[0018] [Figure 1] A perspective view showing an example of a disk drive. [Figure 2] A schematic cross-sectional view of the disk drive. [Figure 3] A plan view showing an example of the first suspension. [Figure 4] A plan view showing an example of a second suspension. [Figure 5] A schematic plan view showing the measuring device and the first suspension according to the first embodiment. [Figure 6]A plan view schematically showing a measuring device according to the first embodiment and a second suspension. [Figure 7] A block diagram showing an example of an electric circuit of the measuring device. [Figure 8] A diagram showing the vibration waveform of the first suspension shown in FIG. 5 and the vibration waveform of the second suspension shown in FIG. 6. [Figure 9] A diagram showing the relationship between the excitation signal and the crosstalk voltage of the first suspension shown in FIG. 5. [Figure 10] A diagram showing the relationship between the excitation signal and the crosstalk voltage of the second suspension shown in FIG. 6. [Figure 11] A diagram showing the vibration waveforms of the first suspension and the second suspension according to the second embodiment. [Figure 12] A diagram showing the relationship between the excitation signal and the crosstalk voltage of the first suspension according to the second embodiment. [Figure 13] A diagram showing the relationship between the excitation signal and the crosstalk voltage of the second suspension according to the second embodiment. [Figure 14] A plan view schematically showing a part of a measuring device according to the third embodiment and a first suspension. [Figure 15] A plan view schematically showing the first suspension of Comparative Example 1. [Figure 16] A diagram showing the vibration waveforms of the first suspension and the second suspension of Comparative Example 1. [Figure 17] A plan view schematically showing the first suspension of Comparative Example 2. [Figure 18] A diagram showing the vibration waveforms of the first suspension and the second suspension of Comparative Example 2. [Figure 19] A plan view schematically showing a part of a measuring device according to the fourth embodiment and a first suspension. [Figure 20] A plan view schematically showing a part of a measuring device according to the fourth embodiment and a second suspension.

MODE FOR CARRYING OUT THE INVENTION

[0019] First, the first suspension 10A and the second suspension 10B will be described with reference to Figures 1 to 4. The first suspension 10A and the second suspension 10B are examples of symmetrical objects (workpieces) for which vibrations are measured. However, the present invention can also be applied when measuring the vibration characteristics of either the first suspension 10A or the second suspension 10B.

[0020] Figure 1 is a perspective view showing an example of a hard disk drive (HDD) 1. Hereafter, the hard disk drive will be simply referred to as the disk drive. Figure 2 is a schematic cross-sectional view of the disk drive 1. The disk drive 1 includes a case 2, a disk 4 that rotates around a spindle 3, a carriage 6, and a positioning motor 7. The carriage 6 pivots around a pivot axis 5. The motor 7 functions as an actuator to pivot the carriage 6. The case 2 is sealed by a lid (not shown).

[0021] As shown in Figure 2, the first suspension 10A is attached to the first surface of each arm 6a of the carriage 6. The second suspension 10B is attached to the second surface of the arm 6a (the surface opposite to the first surface). The first suspension 10A and the second suspension 10B face each other with the disk 4 in between.

[0022] Figure 3 is a plan view showing an example of the first suspension 10A. Figure 4 is a plan view showing an example of the second suspension 10B. The first suspension 10A and the second suspension 10B are configured to be mirror-symmetric with respect to the disk 4. For this reason, the configurations of the first suspension 10A and the second suspension 10B are substantially equivalent.

[0023] The first suspension 10A shown in Figure 3 includes a base plate 11, a load beam 12, a flexure 13, an actuator mounting section 14 located at a first position, and an actuator mounting section 15 located at a second position. The first position is a position close to the base plate 11 in the longitudinal direction of the suspension 10A. The second position is near the tip of the suspension 10A. The base plate 11 and the load beam 12 are made of, for example, stainless steel plates. A circular boss portion 16 is formed on the base plate 11. The boss portion 16 is fixed to the arm 6a of the carriage 6 (shown in Figure 2).

[0024] The flexi-sha 13 includes a metal base 20 and a wiring section 21. The metal base 20 is made of a stainless steel plate thinner than the load beam 12. The wiring section 21 is arranged along the metal base 20. A swingable gimbal section 25 is formed near the tip of the flexi-sha 13. A slider 26, which functions as a magnetic head, is mounted on the gimbal section 25. The slider 26 is equipped with elements for magnetically recording data on the disk 4 and elements for reading data recorded on the disk 4.

[0025] A pair of piezoelectric elements 30R and 30L, which function as actuators, are arranged in the actuator mounting section 14 at the first position. The piezoelectric elements 30R and 30L are made of PZT (lead zirconate titanate) or the like.

[0026] In Figure 3, a conductor 33 is connected to one electrode of the piezoelectric element 30R located on the right side via terminal 31 of the wiring section 21. The other electrode of the piezoelectric element 30R is electrically connected to a metal part (e.g., base plate 11) that constitutes the ground-side circuit of the first suspension 10A.

[0027] In Figure 3, a conductor 33 is connected to one electrode of the piezoelectric element 30L located on the left side, via terminal 32 of the wiring section 21. The other electrode of the piezoelectric element 30L is electrically connected to the metal part that constitutes the ground-side circuit of the first suspension 10A.

[0028] The piezoelectric elements 30R and 30L have a common configuration, but are arranged on the actuator mounting section 14 with their polarities (positive and negative) reversed. Therefore, when a common voltage is applied to terminals 31 and 32, piezoelectric elements 30R and 30L expand and contract in opposite directions. This allows the tip of the first suspension 10A to move by a small amount in the sway direction (indicated by the double-headed arrow A1 in Figure 3). For example, when piezoelectric element 30R contracts and piezoelectric element 30L expands, the tip of the first suspension 10A moves in the first direction. When piezoelectric element 30R expands and piezoelectric element 30L contracts, the tip of the first suspension 10A moves in the second direction.

[0029] A pair of piezoelectric elements 40R and 40L are arranged on the actuator mounting section 15 at the second position. The piezoelectric elements 40R and 40L are made of PZT (lead zirconate titanate) or the like. In Figure 3, the right-side conductor 41 of the wiring section 21 is connected to one electrode of the piezoelectric element 40R located on the right side. The other electrode of the piezoelectric element 40R is electrically connected to the ground-side circuit of the first suspension 10A.

[0030] In Figure 3, the left-side conductor 42 of the wiring section 21 is connected to one electrode of the piezoelectric element 40L located on the left side. The other electrode of the piezoelectric element 40L is in electrical contact with the ground-side circuit of the first suspension 10A.

[0031] When a voltage is applied to the piezoelectric element 40R through the R-side conductor 41 and to the piezoelectric element 40L through the L-side conductor 42, the piezoelectric elements 40R and 40L expand and contract in accordance with the voltage. This allows the tip of the first suspension 10A to be moved by a small amount in the sway direction (indicated by the double-headed arrow A1 in Figure 3).

[0032] For example, when piezoelectric element 40R contracts and piezoelectric element 40L extends, the tip of the first suspension 10A moves in the first direction. When piezoelectric element 40R extends and piezoelectric element 40L contracts, the tip of the first suspension 10A moves in the second direction. The stroke of the piezoelectric elements 40R and 40L in the second position is smaller than the stroke of the piezoelectric elements 30R and 30L in the first position.

[0033] Figure 4 shows the second suspension 10B. The second suspension 10B has a mirror-symmetric shape to the first suspension 10A. Therefore, the second suspension 10B will be briefly explained.

[0034] The second suspension 10B shown in Figure 4 includes a base plate 51, a load beam 52, a flexure 53, an actuator mounting section 54 located at a first position, and an actuator mounting section 55 located at a second position. The first position is a position close to the base plate 51 in the longitudinal direction of the second suspension 10B. The second position is near the tip of the second suspension 10B. A circular boss portion 56 is formed on the base plate 51. The boss portion 56 is fixed to the arm 6a of the carriage 6 (shown in Figure 2).

[0035] The flexi-sha 53 includes a metal base 60 and a wiring section 61. A pivotable gimbal section 65 is formed near the tip of the flexi-sha 53. A slider 66 is mounted on the gimbal section 65.

[0036] A pair of piezoelectric elements 70R and 70L are arranged on the actuator mounting section 54 at the first position. In Figure 4, a conductor 73 is connected to one electrode of the piezoelectric element 70R located on the right side via terminal 71 of the wiring section 61. The other electrode of the piezoelectric element 70R is electrically connected to the metal part that constitutes the ground-side circuit of the second suspension 10B.

[0037] In Figure 4, a conductor 73 is connected to one electrode of the piezoelectric element 70L located on the left side, via terminal 72 of the wiring section 61. The other electrode of the piezoelectric element 70L is electrically connected to the metal part that constitutes the ground-side circuit of the second suspension 10B.

[0038] The piezoelectric elements 70R and 70L have a common configuration, but are arranged on the actuator mounting section 54 with opposite polarities. Therefore, when a common voltage is applied to terminals 71 and 72, the piezoelectric elements 70R and 70L extend and contract in opposite directions. This allows the tip of the second suspension 10B to be moved by a small amount in the sway direction (indicated by the double-headed arrow A2 in Figure 4).

[0039] A pair of piezoelectric elements 80R and 80L are arranged on the actuator mounting section 55 at the second position. In Figure 4, the right-side conductor 81 of the wiring section 61 is connected to one electrode of the piezoelectric element 80R located on the right side. The other electrode of the piezoelectric element 80R is electrically connected to the ground-side circuit of the second suspension 10B.

[0040] In Figure 4, the left-side conductor 82 of the wiring section 61 is connected to one electrode of the piezoelectric element 80L located on the left side. The other electrode of the piezoelectric element 80L is in electrical contact with the ground-side circuit of the second suspension 10B.

[0041] When a voltage is applied to the piezoelectric element 80R through the R-side conductor 81 and to the piezoelectric element 80L through the L-side conductor 82, the piezoelectric elements 80R and 80L expand and contract in accordance with the voltage. This allows the tip of the second suspension 10B to be moved by a small amount in the sway direction (shown by the double-headed arrow A2 in Figure 4). The stroke of the piezoelectric elements 80R and 80L in the second position is smaller than the stroke of the piezoelectric elements 70R and 70L in the first position.

[0042] [First Embodiment] The measuring device 100 and the measurement method for measuring vibration characteristics will be described below with reference to Figures 5 to 10. Figure 5 schematically shows a part of the measuring device 100 and the first suspension 10A. Figure 6 schematically shows a part of the measuring device 100 and the second suspension 10B.

[0043] As shown in Figure 5, terminals 91, 92, and 93 are provided on the wiring section 21 of the first suspension 10A. Terminal 91 is electrically connected to the piezoelectric elements 30R and 30L at the first position via the conductor 33. Terminal 92 is electrically connected to the piezoelectric element 40R at the second position via the right-side conductor 41. The right-side conductor 41 is adjacent to the conductor 33 and is arranged along the conductor 33. For illustrative purposes, the right-side conductor 41 and terminal 92 are shown with hatching in Figure 5.

[0044] The terminal portion 93 shown in Figure 5 is electrically connected to the piezoelectric element 40L at the second position via the left-side conductor 42. The left-side conductor 42 is arranged along the right-side conductor 41. In Figure 5, the left-side conductor 42 and the terminal portion 93 are shown with a sandy texture.

[0045] As shown in Figure 6, terminals 95, 96, and 97 are provided on the wiring section 61 of the second suspension 10B. Terminal 95 is electrically connected to the piezoelectric elements 70R and 70L at the first position via the conductor 73. Terminal 96 is electrically connected to the piezoelectric element 80R at the second position via the R-side conductor 81. For illustrative purposes, the R-side conductor 81 and terminal 96 are shown with hatching in Figure 6.

[0046] The terminal portion 97 shown in Figure 6 is electrically connected to the piezoelectric element 80L at the second position via the left-side conductor 82. The left-side conductor 82 is adjacent to the conductor 73 and is arranged along the conductor 73. In contrast, the right-side conductor 81 is arranged along the left-side conductor 82. In Figure 6, the left-side conductor 82 and the terminal portion 97 are shown with a sandy texture.

[0047] Figure 7 is a block diagram showing an example of the measuring device 100. The measuring device 100 includes an excitation signal generation unit 110, a vibration measurement unit 111, a frequency response analysis unit 112, a ground connection unit 113, and the like. The excitation signal generation unit 110 and the frequency response analysis unit 112 may be part of an information processing unit 114 such as a computer that has measurement software, etc.

[0048] The excitation signal generated by the excitation signal generation unit 110 passes through the digital-to-analog converter 115 to become the excitation signal voltage V1. The excitation signal voltage V1 is amplified by the amplifier 116 to generate a drive voltage V2 for driving the piezoelectric element. The drive voltage V2 is supplied to the piezoelectric element on the excitation side of the first suspension 10A or the piezoelectric element on the excitation side of the second suspension 10B.

[0049] As shown in Figure 5, when performing a vibration test on the first suspension 10A, terminal 91, which is in contact with the piezoelectric elements 30R and 30L at the first position, is connected to ground (signal ground) GND via resistor R1. Under these conditions, excitation signals S1 and S2 are supplied to terminals 92 and 93, which are in contact with the piezoelectric elements 40R and 40L at the second position, respectively.

[0050] The extension and retraction stroke of the piezoelectric elements 30R and 30L located at the first position is greater than the extension and retraction stroke of the piezoelectric elements 40R and 40L located at the second position. In this case, preferably, the ground connection portion 113 is connected to the piezoelectric elements 30R and 30L at the first position. Then, excitation signals S1 and S2 are supplied to the 40R and 40L at the second position.

[0051] Excitation signals S1 and S2 are generated by the excitation signal generation unit 110, causing the piezoelectric elements 40R and 40L at the second position to vibrate. An oscilloscope 101 may be used to measure the waveform of the excitation signal and the crosstalk waveform. In this specification, the piezoelectric element to which the excitation signal is supplied is referred to as the excitation-side piezoelectric element, and the piezoelectric element to which the excitation signal is not supplied is referred to as the non-excitation-side piezoelectric element.

[0052] When an excitation signal is supplied to the piezoelectric elements 40R and 40L at the second position, causing the first suspension 10A to vibrate, the vibration velocity of the first suspension 10A is detected by the vibration measurement unit 111 (shown in Figure 7). An example of the vibration measurement unit 111 is a laser Doppler velocimeter. The vibration measurement unit 111 detects the vibration velocity and other parameters based on the laser irradiation light B1 and the laser reflected light B2.

[0053] The output of the vibration measurement unit 111 (voltage V3 related to vibration velocity) is converted into a measurement signal via the analog / digital converter 117 and input to the frequency response analysis unit 112. The frequency response analysis unit 112 determines the vibration characteristics of the first suspension 10A based on measurement software such as the frequency response function.

[0054] As shown in Figure 6, when performing a vibration test on the second suspension 10B, terminal 95, which is in contact with the piezoelectric elements 70R and 70L at the first position, is connected to ground (signal ground) GND via resistor R2. Under these conditions, excitation signals S1 and S2 are supplied to terminals 96 and 97, which are in contact with the piezoelectric elements 80R and 80L at the second position, respectively.

[0055] The stroke of the piezoelectric elements 70R and 70L located at the first position is greater than the stroke of the piezoelectric elements 80R and 80L located at the second position. In this case, preferably, the ground connection portion 113 is connected to the piezoelectric elements 70R and 70L at the first position. Then, excitation signals S1 and S2 are supplied to the piezoelectric elements 80R and 80L at the second position. The vibration characteristics of the second suspension 10B can be determined by the measuring device 100, similar to the first suspension 10A.

[0056] Figure 8 shows the vibration waveform G1 of the first suspension 10A and the vibration waveform G2 of the second suspension 10B, as measured by the measuring device 100. In Figure 8, the horizontal axis represents frequency and the vertical axis represents gain.

[0057] In Figure 8, G1 represents the vibration waveform of the first suspension 10A when the piezoelectric elements 40R and 40L of the first suspension 10A are vibrated. The excitation signal was supplied to the piezoelectric elements 40R and 40L via the R-side conductor 41 and the L-side conductor 42. In contrast, no excitation signal was supplied to the piezoelectric elements 30R and 30L at the first position. These piezoelectric elements 30R and 30L are connected to ground GND via a resistor R1 with low impedance (e.g., 50Ω).

[0058] In Figure 8, G2 represents the vibration waveform of the second suspension 10B when the piezoelectric elements 80R and 80L of the second suspension 10B are vibrated. The excitation signal was supplied to the piezoelectric elements 80R and 80L via the R-side conductor 81 and the L-side conductor 82. In contrast, no excitation signal was supplied to the piezoelectric elements 70R and 70L at the first position. These piezoelectric elements 70R and 70L are connected to ground GND via a resistor R2 with low impedance (e.g., 50Ω).

[0059] Since the first suspension 10A and the second suspension 10B are mirror images of each other, if a common excitation signal S1 and S2 is supplied to both, their vibration waveforms should be the same. However, in reality, as shown in Figure 8, slight differences were observed in the vibration waveforms G1 and G2 around 20,000 Hz and around 25,000 Hz. Noticing this difference, the inventors focused on the crosstalk occurring in the first suspension 10A and the crosstalk occurring in the second suspension 10B.

[0060] Figure 9 shows the excitation signal (input voltages RV1, LV1) and crosstalk voltage CV1 of the first suspension 10A as observed by oscilloscope 101. A small crosstalk voltage CV1 was observed depending on the input voltages RV1, LV1.

[0061] Figure 10 shows the excitation signal (input voltages RV2, LV2) and crosstalk voltage CV2 of the second suspension 10B as observed by oscilloscope 101. A small crosstalk voltage CV2 was observed in response to the input voltages RV2, LV2. It was considered that the difference in crosstalk voltages CV1, CV2 was the cause of the difference in vibration waveforms G1, G2 (shown in Figure 8).

[0062] [Second Embodiment] In the second embodiment, a high-impedance resistor R1 (1 MΩ) was connected to the terminal portion 91 of the first suspension 10A (shown in Figure 5). Additionally, a high-impedance resistor R2 (1 MΩ) was connected to the terminal portion 95 of the second suspension 10B (shown in Figure 6).

[0063] Figure 11 shows the vibration waveform G3 of the first suspension 10A connected to a 1MΩ resistor R1 and the vibration waveform G4 of the second suspension 10B connected to a 1MΩ resistor R2 in the second embodiment. The difference between these vibration waveforms G3 and G4 was greater than the difference between the vibration waveforms G1 and G2 in the first embodiment (shown in Figure 8).

[0064] Figure 12 shows the excitation signal (input voltages RV1, LV1) and crosstalk voltage CV3 supplied to the first suspension 10A (shown in Figure 5) in the second embodiment. A relatively large crosstalk voltage CV3 was observed depending on the input voltages RV1, LV1.

[0065] This crosstalk voltage CV3 occurs with the same period as the peaks and troughs of the input voltage RV1 waveform. As shown in Figure 5, the conductor 33 of the first suspension 10A was positioned along the right-side conductor 41. Furthermore, in the second embodiment, a resistor R1 with a large impedance (e.g., 1 MΩ) was connected to the terminal portion 91. As a result, crosstalk occurred in the conductor 33 corresponding to the waveform of the input voltage RV1 of the right-side conductor 41.

[0066] Figure 13 shows the excitation signal (input voltages RV2, LV2) and crosstalk voltage CV4 supplied to the second suspension 10B (shown in Figure 6) in the second embodiment. A relatively large crosstalk voltage CV4 was observed depending on the input voltages RV2, LV2.

[0067] This crosstalk voltage CV4 occurs with the same period as the peaks and troughs of the input voltage LV2 waveform. As shown in Figure 6, the conductor 73 of the second suspension 10B was positioned along the left-side conductor 82. Furthermore, in the second embodiment, a resistor R2 with a large impedance (e.g., 1 MΩ) was connected to the terminal portion 95. As a result, crosstalk occurred in the conductor 73 in accordance with the waveform of the input voltage LV2 of the left-side conductor 82.

[0068] Here, if the impedance of resistor R1 is greater than 1 MΩ, the crosstalk voltage CV3 shown in Figure 12 was expected to be even larger, as indicated by the dashed line X1. If terminal 91 is in an open state and not connected to ground GND, the resistance value becomes almost infinite, so the crosstalk voltage may become even larger. Similarly, if the impedance of resistor R2 is greater than 1 MΩ, the crosstalk voltage CV4 shown in Figure 13 was expected to be even larger, as indicated by the dashed line X2. If terminal 95 is in an open state and not connected to ground GND, the resistance value becomes almost infinite, so the crosstalk voltage may become even larger.

[0069] From the above, it was found that when supplying an excitation signal to the excitation-side piezoelectric element through a conductor, crosstalk can be reduced by connecting the conductor portion that is in contact with the non-excitation-side piezoelectric element to ground (GND) via a resistor with low impedance.

[0070] For example, when vibrating the piezoelectric elements 40R and 40L of the first suspension 10A shown in Figure 5, the terminal 91 is connected to ground GND via a resistor R1 with low impedance. For example, if the impedances of the piezoelectric elements 40R and 40L are 300kΩ / 1kHz, the impedance of resistor R1 should be less than 300Ω. Also, when vibrating the piezoelectric elements 80R and 80L of the second suspension 10B shown in Figure 6, the terminal 95 is connected to ground GND via a resistor R2 with low impedance. For example, if the impedances of the piezoelectric elements 80R and 80L are 300kΩ / 1kHz, the impedance of resistor R2 should be less than 300Ω.

[0071] [Third Embodiment] Figure 14 schematically shows a part of the measuring device 100 and the first suspension 10A of the third embodiment. In this embodiment, the terminal portion 91 that is in conductivity with the non-excitation side piezoelectric elements 30R and 30L is connected to ground GND via the conductor 200. As the other configurations are common to the first embodiment, the third embodiment is given common part numbers and the explanation is omitted. The resistance value of the conductor 200 is extremely small but can be considered as resistance.

[0072] [Comparative Example 1] Figure 15 shows the first suspension 10C of Comparative Example 1. In the first suspension 10C, the conductor 33, which is in contact with the piezoelectric elements 30R and 30L, is cut at the cut portions 210 and 211. The terminal portion 91, which is in contact with the conductor 33, is not connected to ground and is in an open state. In other respects, the first suspension 10C of Comparative Example 1 is the same as the first suspension 10A of the first embodiment. The second suspension of Comparative Example 1 is not shown, but it is mirror-symmetric to the first suspension 10C.

[0073] As shown in Figure 15, in Comparative Example 1, the first suspension 10C has a conductor 33 that is in contact with the piezoelectric elements 30R and 30L that is disconnected. However, when excitation signals S1 and S2 are supplied to the excitation-side piezoelectric elements 40R and 40L, crosstalk occurs in the non-excitation-side conductor 33.

[0074] Figure 16 shows the vibration waveform G5 of the first suspension 10C in Comparative Example 1 and the vibration waveform G6 of the second suspension which is mirror-symmetric to the first suspension 10C. Crosstalk caused a shift in the vibration waveforms G5 and G6.

[0075] [Comparative Example 2] Figure 17 shows the first suspension 10D of Comparative Example 2. In the first suspension 10D, the conductors 41 and 42 that are in contact with the piezoelectric elements 40R and 40L are cut at the cut portions 220 and 221. The terminal portion 91 that is in contact with the conductor 33 is not connected to ground and is in an open state. In all other respects, the first suspension 10D of Comparative Example 2 is the same as the first suspension 10A of the first embodiment. The second suspension of Comparative Example 2 is not shown, but it is mirror-symmetric to the first suspension 10D.

[0076] As shown in Figure 17, in Comparative Example 2, the first suspension 10D has conductors 41 and 42 that are in contact with the excitation-side piezoelectric elements 40R and 40L disconnected. However, when excitation signals S1 and S2 are supplied to these conductors 41 and 42, crosstalk occurs in conductor 33, causing the non-excitation-side piezoelectric elements 30R and 30L to vibrate slightly.

[0077] Figure 18 shows the vibration waveform G7 of the first suspension 10D and the vibration waveform G8 of the second suspension, which is mirror-symmetric to the first suspension 10D. A slight shift was observed between vibration waveforms G7 and G8 near the extremely low gain level of approximately -40 dB.

[0078] [Fourth Embodiment] Figure 19 schematically shows a part of the measuring device 100 and the first suspension 10A according to the fourth embodiment. The first suspension 10A shown in Figure 19 is the same as that of the first embodiment (shown in Figure 5). Figure 20 schematically shows a part of the measuring device 100 and the second suspension 10B according to the fourth embodiment. The second suspension 10B shown in Figure 20 is the same as that of the first embodiment (shown in Figure 6).

[0079] As shown in Figure 19, when measuring the vibration characteristics of the first suspension 10A, an excitation signal S3 is supplied to the piezoelectric elements 30R and 30L at the first position through the conductor 33. Conductors 41 and 42, which are in contact with the piezoelectric elements 40R and 40L at the second position, are connected to ground GND via resistors R3 and R4, respectively. The impedances of resistors R3 and R4 should be smaller than the impedances of the excitation-side piezoelectric elements 30R and 30L, respectively.

[0080] As shown in Figure 20, when measuring the vibration characteristics of the second suspension 10B, an excitation signal S3 is supplied to the piezoelectric elements 70R and 70L at the first position through the conductor 73. Conductors 81 and 82, which are in contact with the piezoelectric elements 80R and 80L at the second position, are connected to ground GND via resistors R5 and R6, respectively. The impedances of resistors R5 and R6 should be smaller than the impedances of the excitation-side piezoelectric elements 70R and 70L, respectively.

[0081] It goes without saying that in carrying out the present invention, the specific configurations of each element constituting the workpiece and measuring device can be changed in various ways. In the embodiments described above, an example of a workpiece was a suspension for a hard disk drive, but the present invention can also be applied to vibration testing of workpieces other than suspensions. The actuator mounted on the workpiece can be any member driven by an excitation signal, and vibration generators other than piezoelectric elements may be used. [Explanation of Symbols]

[0082] 1...Disk drive, 10A...First suspension (workpiece), 10B...Second suspension (workpiece), 14...Actuator mounting section at the first position, 15...Actuator mounting section at the second position, 21...Wiring section, 30R, 30L...Piezoelectric element, 33...Conductor, 40R, 40L...Piezoelectric element, 41, 42...Conductor, 54...Actuator mounting section at the first position, 55...Actuator mounting section at the second position, 61...Wiring section, 70R, 70L...Piezoelectric element, 73...Conductor, 80R, 80L...Piezoelectric element, 81, 82...Conductor, 100...Measuring device, 101...Oscilloscope, 110...Excitation signal generation section, 111...Vibration measurement section, 112...Frequency response analysis section, S1, S2, S3...Excitation signal, R1, R2, R3, R4, R5, R6...Resistor.

Claims

1. An actuator provided at the first position, A conductor that is in contact with the actuator at the first position, An actuator located at the second position, A conductor that is in contact with the actuator at the second position, A measuring device for measuring the vibration characteristics of a workpiece having the following features: An excitation signal generation unit that supplies an excitation signal to either the actuator at the first position or the actuator at the second position, A vibration measuring unit that detects vibrations generated in the workpiece by the actuator to which the excitation signal is supplied, A ground connection section that connects the actuator at the first position and the non-excitation actuator at the second position, to which the excitation signal is not supplied, to ground, A measuring device characterized by being equipped with the following.

2. In the measuring device according to claim 1, The aforementioned ground connection part has resistance, A measuring device in which the actuator on the non-vibration side is connected to the ground via the resistor.

3. In the measuring device according to claim 2, A measuring device in which the actuator at the first position and the actuator at the second position each have a piezoelectric element.

4. In the measuring device according to claim 3, A measuring device in which the impedance of the resistor is smaller than the impedance of the piezoelectric element to which the excitation signal is supplied.

5. In the measuring device according to claim 3, A measuring device in which the stroke of the piezoelectric element at the first position is greater than the stroke of the piezoelectric element at the second position, the piezoelectric element at the first position is connected to the ground connection, and the excitation signal is supplied to the piezoelectric element at the second position.

6. An actuator provided at the first position, A conductor that is in contact with the actuator at the first position, An actuator located at the second position, A conductor that is in contact with the actuator at the second position, A measurement method for measuring the vibration characteristics of a workpiece having the following characteristics: The actuator at the first position and the non-excitation actuator at the second position, to which the excitation signal is not supplied, are connected to ground. An excitation signal is supplied to the actuator at the first position and to the actuator at the second position that is on the excitation side. A measurement method characterized by detecting vibrations generated in the workpiece by the actuator on the vibration side.

7. In the measurement method described in claim 6, A measurement method for supplying the excitation signal to the excitation actuator while a resistor is provided between the non-excitation actuator and the ground.

8. In the measurement method described in claim 7, A measurement method in which the impedance of the resistor is smaller than the impedance of the actuator on the excitation side.

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