Liquid Ejecting Head Detection Resistor Noise and Moisture Management

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Solution Overview

Problem

Existing liquid ejecting heads face challenges in reducing noise interference on temperature detection resistors while minimizing moisture adsorption by the piezoelectric body.

Innovation Solution

The liquid ejecting head incorporates a detection resistor positioned on the lower side of the piezoelectric bodies, overlapping with the common electrode in certain regions and not overlapping in others, formed from the same material as the individual and common electrodes, and configured to change resistance value with liquid temperature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the common electrode is laminated on the piezoelectric body to suppress moisture adsorption, then moisture adsorption is suppressed, but noise interference on the detection resistor increases due to drive current flowing on the common electrode

Engineering Contradiction:

Improvemoisture suppressionVSAvoidnoise interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The detection resistor is divided into two segments: a first detection resistor disposed on the lower side of the piezoelectric bodies overlapping with drive wiring, and a second detection resistor disposed not overlapping with the drive wiring. This segmentation allows the system to maintain moisture suppression functionality while reducing noise interference by using the second resistor for temperature detection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an insulating film between the detection resistor and the drive wiring (common electrode) to reduce capacitive coupling and noise interference. This intermediary layer allows the common electrode to maintain its moisture suppression function while minimizing its harmful noise effect on the detection resistor.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the detection resistor is positioned to avoid overlapping with drive wiring to reduce noise, then noise interference is reduced, but moisture adsorption by the piezoelectric body increases due to restricted common electrode coverage

Engineering Contradiction:

Improvetemperature detection accuracyVSAvoidmoisture suppression

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The common electrode serves multiple functions: it provides moisture suppression by laminating on the piezoelectric body, and it maintains sufficient coverage area to perform this function effectively, while the detection resistor configuration ensures accurate temperature detection by positioning at least part of it away from noise sources.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 configuration effectively reduces noise interference on the detection resistor and suppresses moisture adsorption, thereby improving temperature detection accuracy.

Implementation Method 1

piezoelectric bodies laminated on the plurality of individual electrodes, respectively, and driven in order to apply a pressure to a liquid inside the plurality of pressure chambers

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a detection resistor... configured to change a resistance value in response to a temperature of the liquid inside the plurality of pressure chambers

Methodology Applied

Scientific EffectTemperature-dependent resistance change: Thermistor

Data Source

PatentUS20250033355A1Liquid ejecting head and liquid ejecting apparatus

Publication Date: 2025.01.30 SEIKO EPSON CORP

AI summary

A liquid ejecting head includes a detection resistor disposed on a lower side of the piezoelectric bodies in a direction of lamination and at a position not overlapping the individual electrodes, formed from the same material as that of the individual electrodes and the common electrode, and configured to change its resistance value in response to a temperature of the liquid inside the pressure chambers. The detection resistor includes an overlapping region overlapping the common electrode and a non-overlapping region not overlapping the common electrode at a cross-section where the pressure chamber substrate is sectioned at a position where the pressure chamber is present on a plane parallel to a longitudinal direction of the pressure chambers and the direction of lamination.