Piezoelectric Element Fitting Test via Capacitance

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Solution Overview

Problem

Existing methods for testing the fitted state of piezoelectric elements in head suspensions are inefficient, often relying on expensive measuring devices or unstable data from oscillation tests, and fail to accurately determine correct orientation and wiring integrity.

Innovation Solution

A method that applies a bias voltage within a predetermined range to detect changes in capacitance, using the characteristic capacitance changes to determine the correct fitting state of piezoelectric elements and identify potential wiring breakages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a mark is provided on the piezoelectric element to make it distinguishable by appearance, then the ease of operation is improved, but contamination problems occur making the method hardly adoptable

Engineering Contradiction:

Improvedistinguishability of piezoelectric elementsVSAvoidcontamination

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent applies a voltage-dependent color change effect to the piezoelectric element. When voltage is applied, the element changes color, providing a visual indicator of its operational state and orientation without requiring permanent marks that could cause contamination. This resolves the contradiction by achieving distinguishability through a functional property rather than a physical mark.

Inventive Principle:

Principle #32Color changes

2Manufacturing precision

If an actual stroke measurement is performed to determine correct fitting, then the manufacturing precision is improved, but the cost increases due to expensive measuring devices

Engineering Contradiction:

Improvefitting accuracy of piezoelectric elementsVSAvoidmeasuring device cost

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical measurement systems with an electrical field-based method. By applying voltage and observing color changes or electrical response, the fitting accuracy is determined without requiring expensive mechanical measuring devices. This substitutes a simple electrical test for complex mechanical measurement, resolving the cost contradiction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from mechanical displacement (actual stroke) to electrical/optical response (color change or capacitance). This parameter change allows for simpler, less expensive measurement while maintaining the ability to determine correct fitting, thereby reducing device complexity and cost.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If oscillation test is performed on head suspension supported alone, then the productivity is improved, but the reliability of test data deteriorates due to unstable movement of load beam

Engineering Contradiction:

Improvetest speedVSAvoidtest data stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent replaces mechanical oscillation testing with an electrical field-based test. By applying voltage and observing the response, the test avoids the unstable mechanical movement of the load beam while maintaining rapid testing capability. This substitution preserves productivity while eliminating the reliability issue associated with mechanical instability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method allows for accurate and cost-effective determination of the fitted state of piezoelectric elements, distinguishing between correctly and incorrectly fitted elements and detecting wiring issues, thereby improving the manufacturing process for head suspensions.

Implementation Method 1

the piezoelectric elements 107a and 107b deform according to a voltage applied thereto. Namely, depending on the applied voltage, the piezoelectric elements 107a and 107b oppositely deform in expanding and contracting directions

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a step detecting changes in capacitance of the piezoelectric elements with respect to changes in bias voltage applied to the piezoelectric elements

Methodology Applied

Scientific EffectCapacitance change: Capacitance

Data Source

PatentUS8878554B2Method of testing fitted state of piezoelectric element and head suspension

Publication Date: 2014.11.04 NHK SPRING CO LTD

AI summary

A method of testing a fitted state of a pair of piezoelectric elements fitted to form an actuator between a base member and a movable member, the piezoelectric elements in the actuator being arranged side by side in opposite polarity and being electrically connected in parallel with each other, and when a voltage is applied to the piezoelectric elements, minutely moving the movable member relative to the base member in a direction in which the piezoelectric members are arranged side by side. The method detects changes in capacitance of the piezoelectric elements with respect to changes in bias voltage applied to the piezoelectric elements, the bias voltage being changed within a predetermined range, and determines a fitted state of the piezoelectric elements according to a characteristic of the detected capacitance changes. The method correctly and easily determines whether or not the piezoelectric elements are correctly fitted to the actuator.