Three-Plate Capacitive Toner Level Sensor
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Solution Overview
Problem
Existing toner level sensing methods in image forming devices are not sensitive enough to small changes in toner level, often inaccurate, and increase component complexity, which is undesirable in terms of manufacturing costs and reliability.
Innovation Solution
A three-plate capacitive toner level sensor is implemented within the toner sump, using a central sense plate and two side electrodes connected together, forming two parallel capacitors that provide enhanced sensitivity and accuracy by maximizing surface area and minimizing separation distance, while utilizing existing components like the doctor blade and gutter for electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two parallel plates are used for detecting toner volume levels, then a capacitance-based sensing mechanism is provided, but the sensitivity to small changes in toner level is insufficient
Solution Approach 1:
The sensor is divided into three separate plates (first plate, second plate, third plate) instead of using a single two-plate configuration. This segmentation allows the sensor to detect capacitance changes at multiple levels simultaneously, significantly improving sensitivity to small toner level changes while maintaining a relatively simple overall structure.
Solution Approach 2:
The sensor arrangement transitions from a single capacitance measurement between two plates to a multi-level capacitance measurement system with three plates positioned at different heights. This dimensional arrangement enables detection of toner level changes across multiple thresholds, enhancing measurement precision without substantially increasing structural complexity.
2Measurement precision
If electrical sensors measuring motive force of an agitator are used, then toner level can be determined, but component complexity and opportunities for errors increase
Solution Approach 1:
The mechanical agitator-based sensing system is replaced with a static capacitive sensing system using three plates. This substitution eliminates the need for moving mechanical parts while providing accurate toner level detection through capacitance measurements, thereby reducing component complexity and potential failure points.
Solution Approach 2:
The sensor plates utilize the toner material itself as part of the capacitive sensing mechanism. The toner acts as a dielectric medium between the plates, and changes in toner level automatically alter the capacitance values, providing self-service sensing without requiring additional mechanical actuators or complex measurement systems.
3Measurement precision
If optical devices including mirrors and toner dust wipers are used, then toner level can be sensed, but component complexity and opportunities for errors increase
Solution Approach 1:
The opto-mechanical sensing system involving mirrors and moving dust wipers is replaced with a static electrical capacitive sensing system. This substitution eliminates complex optical paths and mechanical moving parts, reducing component complexity while maintaining accurate toner level sensing through non-contact capacitance measurements.
4Ease of manufacture
If estimates of toner use and accumulation based on print or time counts are used, then toner level can be determined, but accuracy is reduced due to variability in environmental factors
Solution Approach 1:
The indirect estimation method based on print counts and time calculations is replaced with direct physical measurement using capacitive sensing. This substitution provides real-time actual toner level measurements rather than calculated estimates, significantly improving accuracy by eliminating the influence of environmental variables and usage pattern variations.
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 three-plate capacitive sensor offers improved sensitivity and resolution for toner level monitoring, reducing errors and maintaining device performance without significantly increasing manufacturing costs.
Implementation Method 1
A first plate and two second plates form a capacitive sensor having a capacitance that varies in response to an amount of toner that exists between the first plate and the two second plates
Implementation Method 2
the capacitance varies with the amount of toner existing between the two parallel plates
Data Source
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AI summary
A toner container including a first electrode disposed within the toner container, a second electrode electrically connected to the first electrode and disposed within the toner container, and a sense electrode disposed between the first electrode and the second electrode. The sense electrode and the first electrode form a first capacitor having a first capacitance that changes in response to a change in toner amount existing therebetween. The sense electrode and the second electrode form a second capacitor having a second capacitance that changes in response to a change in toner amount existing therebetween