Optical Waste Liquid Detection for Inkjet Printers
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Solution Overview
Problem
Conventional liquid droplet jetting apparatuses face challenges in accurately detecting the full liquid state of the absorbing body, particularly when using liquids with low conductivity, leading to potential overflow issues due to detection failures or imprecise estimation of evaporation rates.
Innovation Solution
A liquid droplet jetting apparatus that includes a liquid kind detecting section to differentiate between liquids based on conductivity, a waste liquid recovery device with a waste liquid detection mechanism measuring electric current at a full-liquid detection position, and a full liquid judging section that assesses the full liquid state using either conductivity detection or estimated waste liquid amount based on discharge operations, ensuring precise detection regardless of liquid conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a waste liquid detection mechanism using electrodes is used to detect the full liquid state, then detection precision is improved for conductive liquids, but detection reliability deteriorates when liquid conductivity is low
Solution Approach 1:
The patent changes the detection parameter from electrical conductivity to optical properties. By using a light source and light receiving element, the system detects liquid presence through light absorption or scattering characteristics, which are effective regardless of liquid conductivity. This parameter change resolves the contradiction by providing reliable detection for both conductive and non-conductive liquids.
Solution Approach 2:
The patent replaces the electrical detection mechanism (electrodes measuring conductivity) with an optical detection mechanism (light source and light receiving element). This substitution allows the system to detect liquid presence through optical properties rather than electrical properties, thereby maintaining detection reliability for low conductivity liquids while preserving detection precision.
2Reliability
If the full liquid state is judged based on estimated waste liquid amount, then detection reliability is improved for low conductivity liquids, but measurement precision deteriorates due to evaporation estimation errors
Solution Approach 1:
The patent replaces the estimation-based judgment method with direct optical detection. Instead of calculating liquid amount based on evaporation models and discharge counts, the system directly detects liquid presence at the full liquid detection position using light absorption/scattering, providing both reliability and precision simultaneously.
Solution Approach 2:
The patent introduces light as an intermediary to detect liquid presence. The light source emits light that passes through or reflects off the liquid, and the light receiving element detects changes in light intensity caused by liquid absorption or scattering. This intermediary enables direct, accurate detection without relying on evaporation estimation.
3Reliability
If a large margin is set in the estimated waste liquid amount to prevent overflow, then detection reliability is improved, but productivity deteriorates due to premature full liquid state detection
Solution Approach 1:
The patent replaces the estimation-based judgment with direct optical detection at the actual full liquid detection position. This eliminates the need to set large margins in estimation, allowing the system to detect the true full liquid state accurately without premature detection, thereby maintaining both reliability and productivity.
Solution Approach 2:
The patent implements direct feedback from the optical detection mechanism to the control system. When the light receiving element detects liquid at the full liquid detection position, the system immediately receives accurate feedback about the actual liquid state, enabling timely and accurate responses without relying on margin-based estimation.
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
Enables precise detection of the full liquid state in both conductive and non-conductive liquids, preventing overflow and ensuring accurate judgment of the absorbing body's state, even when using low-conductivity inks, thereby preventing detection failures and maintaining efficient waste liquid management.
Implementation Method 1
a waste liquid detection mechanism which measures an electric current value in the absorbing body at a predetermined full-liquid detection position when a predetermined voltage is applied, and which detects whether or not the liquid arrives at the full-liquid detection position of the absorbing body based on the measured electric current value
Implementation Method 2
an absorbing body (absorbing member) which is formed of a porous material, which is accommodated in the waste liquid case and which absorbs the waste liquid
Data Source
AI summary
A liquid droplet jetting apparatus includes: a liquid droplet jetting head; a liquid kind detecting section detecting whether a liquid, used in the liquid droplet jetting head, is a first liquid having a conductivity of not less than a predetermined value or a second liquid having a conductivity of less than the predetermined value; a discharge mechanism discharging the liquid inside the liquid droplet jetting head therefrom; a waste liquid recovery device recovering the liquid discharged by the discharge mechanism, and including: a waste liquid case, an absorbing body accommodated in the waste liquid case, and a waste liquid detection mechanism measuring an electric current value in the absorbing body and thereby detecting whether or not the liquid arrives at a full-liquid detection position of the absorbing body; and a waste liquid absorb amount estimating section estimating an amount of the waste liquid absorbed in the absorbing body.