Capacitive Toner Level Sensing Circuit Ground Reference
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Solution Overview
Problem
Existing toner level sensing systems in imaging devices are not robust or cost-effective, particularly when using capacitive sensors, as they require flexible circuits and are prone to errors due to moving hardware and toner agitation, leading to inaccurate toner level measurements.
Innovation Solution
A capacitive toner level sensing system that couples the AC signal generator between system ground and local ground, using the local ground as the ground reference, allowing for a more robust and cost-effective connection between the capacitor and the sensing circuitry, where one plate of the capacitor also serves as a doctor blade, and includes a sample and hold circuit to generate an output voltage based on the capacitance ratio, reducing offset voltages through active circuit elimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flexible circuits are used to connect capacitive sensor plates, then the sensor can be integrated into the toner container, but the system becomes more complex and less robust
Solution Approach 1:
The patent merges the capacitive sensor plate with existing structural components of the toner container (such as the doctor blade or container walls), eliminating the need for separate flexible circuit connections. This integration reduces component count and simplifies the overall system architecture while maintaining sensing functionality.
Solution Approach 2:
The sensor plate is designed to serve multiple functions: it acts as both a structural component of the toner container and a capacitive sensing element. This multi-functionality eliminates the need for dedicated connection circuits while achieving both mechanical support and electrical sensing requirements.
2Measurement precision
If moving hardware is added to the sensing system, then toner level can be detected, but component complexity and error opportunities increase
Solution Approach 1:
The patent replaces mechanical sensing mechanisms (such as moving flags or physical level indicators) with a capacitive sensing system that uses electrical fields to detect toner level. This substitution eliminates moving parts while maintaining measurement capability, as the capacitive sensor detects changes in dielectric properties caused by toner presence.
Solution Approach 2:
The sensing system utilizes the toner itself as part of the sensing mechanism. The toner particles contribute to the capacitive effect by altering the dielectric properties between sensor plates, meaning the object being measured becomes part of the measurement system, eliminating the need for separate moving detection hardware.
3Stability of the object's composition
If toner agitation is used to prevent packing, then toner flows better, but unwanted toner dust is created
Solution Approach 1:
The patent replaces mechanical agitation methods (such as rotating augers or vibrating mechanisms) with an electrical field-based capacitive sensing approach. This substitution allows for toner level detection without physical disturbance of the toner, preventing dust generation while still monitoring toner distribution through changes in capacitive properties.
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 solution provides a robust and cost-effective capacitive toner level sensing system that accurately measures toner levels in imaging devices, reducing errors and component complexity, while maintaining the dual functionality of the capacitor as both a sensor and doctor blade.
Implementation Method 1
Other techniques for sensing or determining toner level include use of a capacitive sensor disposed within a toner container, such as a waste toner container, and circuitry for sensing the capacitance of the capacitive sensor as toner levels in the container change
Data Source
AI summary
A circuit and system for sensing a capacitance of a capacitive sensor disposed in a toner container of an electrophotographic imaging apparatus. The circuit and system may include an AC signal generator and conversion circuitry, coupled to the capacitive sensor, for detecting an AC current appearing on the capacitive sensor and converting the detected AC current to a substantially DC voltage, relative to a local ground, the local ground serving as a ground reference for the conversion circuitry. The AC signal generator is coupled between the local ground and a system ground. Physically separating the AC signal generator from the capacitive sensor allows for parts of the capacitive sensor to be used to perform other functions in the toner container.