Inkjet Printhead Alignment via Transmitted Light Detection

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Solution Overview

Problem

Conventional inkjet printheads face challenges in accurately and precisely positioning piezoelectric actuators relative to cavity units due to low contrast images from detection portions, often affected by surface flaws, leading to inaccuracies in detecting holes for alignment.

Innovation Solution

Incorporating detection portions in the cavity unit that allow light to pass through, enabling high contrast imaging and precise detection, and using corresponding detection portions in the piezoelectric actuator for accurate alignment, thereby improving the positioning of pressure chambers and pressure producing portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If detection portions are formed as holes in the cavity unit and imaged by reflecting light from the inner surface, then positioning between actuator and cavity unit can be achieved, but image contrast is low and detection accuracy is reduced due to surface flaws and streaks

Engineering Contradiction:

Improvedetection accuracy of holesVSAvoidsurface flaws and streaks affecting image quality

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Instead of illuminating the inner surface of the cavity unit and detecting reflected light (which causes low contrast due to surface flaws), the patent inverts the approach by illuminating from the outer surface and detecting light that has transmitted through the holes. This inversion of the light path allows the holes to appear as bright spots against a dark background, dramatically improving image contrast and detection accuracy while eliminating the harmful effect of surface flaws.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces light as an intermediary to pass through the detection portions (holes) from the outer surface to the inner surface. By using transmitted light rather than reflected light, the holes themselves become the mediator that carries the optical signal, creating high-contrast images where the holes are clearly visible as illuminated regions against the non-transparent cavity unit background, thereby improving detection precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If conventional imaging methods are used with reflected light from the cavity unit inner surface, then detection portions can be located, but positioning accuracy between pressure chambers and pressure producing portions is insufficient

Engineering Contradiction:

Improvealignment accuracy of pressure chambers and pressure producing portionsVSAvoidimage contrast for detection portions

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent inverts the conventional imaging approach by changing from reflected light imaging to transmitted light imaging. Light is shone from the outer surface through the holes (detection portions) to the inner surface, causing the holes to appear as high-contrast bright spots. This inversion dramatically improves measurement precision of the detection portions, which directly enhances the manufacturing precision of aligning pressure chambers with pressure producing portions during assembly.

Inventive Principle:

Principle #13The other way round (Inversion)

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 approach enhances the accuracy and precision of aligning pressure chambers and pressure producing portions, resulting in improved ink ejection performance and reliability of the inkjet printhead.

Implementation Method 1

The first detection portion allows light as radiated from a second side of the cavity unit that is opposite to the first side, to pass through the first detection portion to the first side

Methodology Applied

Scientific EffectLight transmission: Light

Implementation Method 2

a piezoelectric actuator having a plurality of active portions respectively corresponding to the pressure chambers

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7520597B2Inkjet printhead and method of assembling the same

Publication Date: 2009.04.21 BROTHER KOGYO KK

AI summary

There is disclosed an inkjet printhead comprising a cavity unit and an actuator. The cavity unit includes a plurality of nozzles each for ejecting a droplet of ink, a plurality of pressure chambers formed on a surface of the cavity unit on a first side thereof to respectively correspond to the nozzles, and a first detection portion formed in a given positional relationship with the pressure chambers. The actuator is disposed on the cavity unit, and includes a plurality of pressure producing portions that correspond to the respective pressure chambers so as to selectively apply a pressure to the ink in each of the pressure chambers. The first detection portion allows light as radiated from a second side of the cavity unit that is opposite to the first side, to pass through the first detection portion to the first side, and is used for positioning of the cavity unit relatively to the actuator so that the pressure chambers and the respectively corresponding pressure producing portions are positioned relatively to each other.