Piezoelectric Head Unit Circuit for Noise-Resistant Nozzle Detection

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Solution Overview

Problem

Existing methods for detecting nozzle state in printing apparatuses suffer from noise superimposition during transmission of residual vibration signals from the head to the AD converter.

Innovation Solution

A head unit and liquid ejection apparatus that includes a piezoelectric element, a driving signal generation unit, a residual vibration signal generation circuit, an analog differential residual vibration signal generation circuit, a demodulation circuit, an AD converter, and a determination unit to convert and demodulate residual vibration signals into digital signals for determining the nozzle state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the residual vibration signal is transmitted from the head to the AD converter, then the nozzle state can be detected, but noise may be superimposed on the analog waveform during transmission

Engineering Contradiction:

Improvenozzle state detection accuracyVSAvoidnoise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical/electrical transmission of analog residual vibration signals with a magnetic field-based detection system. The piezoelectric element's residual vibration is converted to electromagnetic signals that can be detected and processed without physical transmission, thereby eliminating noise superimposition during signal transmission while maintaining nozzle state detection accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary magnetic field detection mechanism between the piezoelectric element and the AD converter. Instead of directly transmitting the analog residual vibration signal, the system uses magnetic field changes as an intermediary to transfer the vibration information, which prevents noise interference during the transmission process.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If analog residual vibration signals are transmitted over distance, then the control unit can process the signal, but the signal quality deteriorates due to noise

Engineering Contradiction:

Improvesignal processing capabilityVSAvoidsignal integrity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent substitutes the analog signal transmission path with a digital signal processing approach. The residual vibration signal is converted to digital form early in the process, allowing reliable transmission and processing without the degradation that plagues analog signals over distance, thus maintaining both signal integrity and processing capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If the piezoelectric element is used for both liquid ejection and residual vibration detection, then device complexity is reduced, but measurement precision may be affected

Engineering Contradiction:

Improvehead unit structureVSAvoidresidual vibration signal accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent implements multi-functionality by using the piezoelectric element for both liquid ejection and residual vibration detection. The same piezoelectric element that drives liquid ejection also serves as the sensor for detecting residual vibrations through its electromotive force changes, thereby reducing device complexity without sacrificing measurement precision through the use of magnetic field-based detection.

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

Enhances noise immunity and accuracy in detecting nozzle states by converting residual vibration signals into digital form, reducing noise interference during transmission.

Implementation Method 1

a piezoelectric element displaced according to a driving signal to cause a liquid to be ejected

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12485669B2Head unit and liquid ejection apparatus

Publication Date: 2025.12.02 SEIKO EPSON CORP

AI summary

A head unit includes a piezoelectric element displaced according to a driving signal to cause a liquid to be ejected, a driving signal generation unit that generates the driving signal, a residual vibration signal generation circuit that outputs a change in an electromotive force of the piezoelectric element according to residual vibration, in a pressure chamber in communication with a nozzle, that occurs after supply of the driving signal, as a residual vibration signal, an analog differential residual vibration signal generation circuit that converts the residual vibration signal into an analog differential residual vibration signal, a demodulation circuit that demodulates the analog differential residual vibration signal and outputs a demodulated signal, an AD converter that converts the demodulated signal into a digital signal, and a determination unit that determines, based on the digital signal, a state in the pressure chamber.