Piezoelectric Liquid Ejection Head Detection Circuit Noise Reduction

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Solution Overview

Problem

Existing liquid ejection apparatuses, such as inkjet printers, face challenges in accurately detecting the potential of piezoelectric elements due to switching noise from detection switches, which affects the ejection state checking process.

Innovation Solution

The proposed solution involves a liquid ejection apparatus with a detection circuit that includes a first amplifier circuit. This circuit has a first amplifier with input and output terminals, resistors coupling nodes within the circuit, and wires supplying drive signals to the piezoelectric element, allowing for accurate detection of the element's potential without switching noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a detection switch is turned on to detect the potential of the piezoelectric element, then the ejection state can be checked, but switching noise is superimposed on the detection signal reducing measurement accuracy

Engineering Contradiction:

Improveejection state checkingVSAvoidpotential detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent segments the detection process into two distinct phases: a drive period where the piezoelectric element is driven to eject liquid, and a detection period where the element is driven to vibrate and the potential is detected. By temporally separating these functions, the detection switch remains off during drive operations (avoiding noise) and is only activated during vibration detection, thus resolving the contradiction between reliable ejection state checking and accurate potential measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic alternating operations between drive mode and detection mode. The piezoelectric element is periodically driven for liquid ejection, then periodically driven at a different frequency to induce vibration for detection. This periodic action allows the detection switch to be turned on only during vibration detection periods, eliminating switching noise contamination while maintaining the ability to check ejection state through vibration analysis.

Inventive Principle:

Principle #19Periodic action

2Device complexity

If the detection circuit directly connects to the piezoelectric element during drive signal supply, then the circuit is simple, but the drive signal interferes with the potential detection

Engineering Contradiction:

Improvedetection circuit structureVSAvoidsignal detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent uses periodic action to alternate between drive signal supply and vibration-induced potential detection. During drive periods, the drive signal is supplied to the piezoelectric element. During detection periods, the element is driven to vibrate and the resulting potential variations are detected. This temporal separation eliminates signal interference while maintaining circuit simplicity, as the same physical connection is used but at different times for different purposes.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies preliminary action by first driving the piezoelectric element to eject liquid, then subsequently driving it to vibrate for detection. This sequential arrangement ensures that the drive signal has completed its ejection function before the detection phase begins, preventing interference between the strong drive signal and the subtle vibration detection signals, thereby maintaining both circuit simplicity and detection accuracy.

Inventive Principle:

Principle #10Preliminary action

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 enables accurate detection of the piezoelectric element's potential, improving the reliability of ejection state checking and reducing the occurrence of ejection abnormalities in liquid ejection apparatuses.

Implementation Method 1

an ejection portion including a piezoelectric element driven by a drive signal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a detection circuit detecting a potential of the element electrode varying according to a vibration remaining in the piezoelectric element after the driving of the piezoelectric element

Methodology Applied

Scientific EffectElectrical potential detection: Electric Field

Data Source

PatentUS20250042150A1Liquid ejection apparatus and liquid ejection head

Publication Date: 2025.02.06 SEIKO EPSON CORP

AI summary

A liquid ejection apparatus includes an ejection portion including a piezoelectric element driven by a drive signal, a first wire to which a first drive signal of the drive signal is supplied, a second wire electrically coupled to an element electrode of the piezoelectric element, and a detection circuit detecting a potential of the element electrode varying according to a vibration remaining in the piezoelectric element after driving of the piezoelectric element, wherein a first amplifier circuit of the detection circuit includes a first amplifier having a first input terminal, a second input terminal, and a first output terminal, a first resistor electrically coupling a first node electrically coupled to the first input terminal and a second node electrically coupled to the first output terminal, and a second resistor electrically coupling the first node and the second wire, and the first wire is electrically coupled to the second input terminal.