Flexible Flat Cable Projections for Piezoelectric Actuator Isolation

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Solution Overview

Problem

In ink-jet heads, the flexible flat cable (FPC) contacts the piezoelectric sheet during heat treatment, causing deformation that hinders ink discharge due to continued contact after cooling, leading to deteriorated ink discharge properties.

Innovation Solution

A liquid discharging head design featuring a flexible flat cable with projections that cover the piezoelectric deformation portions, ensuring these projections contact areas different from the pressure chambers, preventing contact with the piezoelectric deformation portions and maintaining ink discharge efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If solder or thermosetting electroconductive adhesive is used to join the FPC to the piezoelectric sheet, then electrical connection is achieved, but the FPC undergoes downward deformation due to heat treatment and contacts the piezoelectric sheet, hindering deformation and ink discharge

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidink discharge property

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The FPC is segmented into multiple sections: a first section that contacts the piezoelectric sheet for electrical connection, and a second section that extends away from the piezoelectric sheet. This segmentation allows the FPC to maintain electrical connection while preventing the deformation portion from contacting the piezoelectric sheet, thus resolving the contradiction between connection reliability and ink discharge performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A land (thicker electroconductive member) is introduced as an intermediary between the FPC contact and the piezoelectric sheet. The land serves as a mediator that provides the necessary electrical connection while physically separating the FPC from the piezoelectric deformation portion, preventing harmful contact during operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the FPC is made thinner to avoid contacting the piezoelectric sheet, then deformation hindrance is reduced, but electrical connection and joining become more difficult

Engineering Contradiction:

Improveink discharge propertyVSAvoidjoining ease

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The FPC is designed with different local characteristics: the first section has properties suitable for electrical connection (conductive, planar), while the second section has properties that prevent contact with the piezoelectric sheet. This local differentiation allows the FPC to fulfill multiple functions simultaneously, resolving the contradiction between manufacturing ease and ink discharge performance.

Inventive Principle:

Principle #3Local quality

3Reliability

If dummy electrodes are formed and joined to FPC contacts, then electrical connection is established, but heat treatment causes FPC deformation and contact with piezoelectric sheet, hindering ink discharge

Engineering Contradiction:

Improveelectrical connectionVSAvoiddeformation hindrance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The FPC is divided into sections that perform different functions: the first section establishes electrical connection with the piezoelectric sheet, while the second section extends away from the sheet to avoid deformation hindrance. This segmentation resolves the contradiction between electrical connection reliability and prevention of harmful deformation effects.

Inventive Principle:

Principle #1Segmentation

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

The solution effectively isolates the flexible flat cable from the piezoelectric deformation portions, preventing hindrance to the deformation necessary for ink discharge, thus maintaining stable ink discharge characteristics and improving printing quality.

Implementation Method 1

the piezoelectric sheet undergoes unimorph deformation by a piezoelectric transverse effect at a time of an ink discharge

Methodology Applied

Scientific EffectPiezoelectric transverse effect: Piezoelectric Effect

Implementation Method 2

at the time of the heat treatment, the FPC undergoes a downward deformation due to heat

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS7527364B2Printer, liquid discharging head, and flexible flat cable of liquid discharging head

Publication Date: 2009.05.05 BROTHER KOGYO KK

AI summary

An ink-jet head includes a head main body including a channel unit in which a pressure chamber is formed, and a piezoelectric actuator having a piezoelectric deformation portion facing the pressure chamber, and an FPC which has a substrate and a plurality of wires, and which is arrange on an upper side of the piezoelectric actuator. A plurality of projections bent to form a projection toward the head main body is formed in the FPC. A front end of the projections is in contact with an area not facing the pressure chamber, on a surface of the piezoelectric actuator. Accordingly, it is possible to suppress hindering of a deformation of the piezoelectric deformation portion accompanied by a liquid discharge, due to a contact with a flexible flat cable.