| US 7,525,324 B2 | ||
| Inspection method, inspection apparatus, and polarization method for piezoelectric element | ||
| Takao Ohnishi, Kiyosu (Japan); Tomohiro Yamada, Kasugai (Japan); and Takatoshi Nehagi, Seto (Japan) | ||
| Assigned to NGK Insulators, Ltd., Nagoya-City (Japan) | ||
| Filed on Sep. 17, 2007, as Appl. No. 11/856,351. | ||
| Application 11/856351 is a continuation of application No. PCT/JP2006/305906, filed on Mar. 17, 2006. | ||
| Claims priority of application No. 2005-078645 (JP), filed on Mar. 18, 2005; application No. 2005-189326 (JP), filed on Jun. 29, 2005; and application No. 2005-330589 (JP), filed on Nov. 15, 2005. | ||
| Prior Publication US 2008/0030102 A1, Feb. 07, 2008 | ||
| Int. Cl. G01R 29/22 (2006.01) | ||
| U.S. Cl. 324—727 [310/313 R; 310/358; 324/718; 438/3] | 20 Claims |
| 1. An inspection method for a piezoelectric element for determining whether or not the piezoelectric element is anomalous,
the method comprising at least:
first-inspection-signal application step of applying to the piezoelectric element a first inspection signal having a first
predetermined voltage waveform, the first predetermined voltage waveform is a voltage waveform composed of a first number
of successive basic waveforms each increasing from zero to a predetermined voltage value and then decreasing from the predetermined
voltage value to zero;
first-characteristic-value measurement step of measuring, as a first characteristic value, an electrical characteristic value
of the piezoelectric element after application of the first inspection signal;
second-inspection-signal application step of applying to the piezoelectric element a second inspection signal having a second
predetermined voltage waveform and an electrical power greater than that of the first inspection signal, the second predetermined
voltage waveform is a voltage waveform composed of a second number of the successive basic waveforms or successive second
waveforms each including the basic waveform, the second number being larger than the first number;
second-characteristic-value measurement step of measuring, as a second characteristic value, the electrical characteristic
value of the piezoelectric element after application of the second inspection signal; and
anomaly determination step of determining whether or not the piezoelectric element is anomalous on the basis of a value corresponding
to the difference between the measured second characteristic value and the measured first characteristic value,
wherein the basic waveform is a voltage waveform in which at least one of an increasing time, which is a time required to
increase from zero to the predetermined voltage value, and a decreasing time, which is a time required to decrease from the
predetermined voltage value to zero, substantially coincides with the resonance period of the piezoelectric element.
|