Capacitive Sheet Cassette Detection in Image Forming Apparatus
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Solution Overview
Problem
Existing printers face challenges in accurately detecting the position of a sheet cassette and the remaining amount of sheets within it, often relying on complex combinations of sensors and actuators, which can lead to false detections and inefficiencies.
Innovation Solution
An image forming apparatus utilizing a single capacitive sensor with an electrode and a wire, where the capacitance value is used to determine the presence, position, and quantity of sheets in the sheet cassette, allowing for accurate detection without the need for multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors and actuators are used to detect sheet cassette position and remaining sheets, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple detection functions (sheet cassette presence, sheet presence, and remaining sheet quantity detection) into a single capacitive sensor system. The capacitive sensor measures capacitance changes that correspond to different states: whether the sheet cassette is present, whether sheets are present, and how many sheets remain. This merging of multiple detection functions into one sensor resolves the contradiction by maintaining detection accuracy while reducing device complexity.
Solution Approach 2:
The capacitive sensor serves multiple functions simultaneously: it detects the presence of the sheet cassette, the presence of sheets within the cassette, and the quantity of remaining sheets. By making a single sensor universal across these different detection needs, the system achieves comprehensive monitoring capability without requiring separate sensors for each function, thus resolving the contradiction between detection accuracy and device complexity.
2Device complexity
If a single sensor is used to detect sheet cassette position and remaining sheets, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent utilizes changes in capacitance parameters to distinguish between different detection states. As sheets are added to or removed from the sheet cassette, the capacitance value changes in a predictable manner. By monitoring these parameter changes, the single capacitive sensor can accurately determine the number of remaining sheets, thereby maintaining measurement precision while using only one sensor.
Solution Approach 2:
The patent extends the detection capability of the single capacitive sensor by utilizing the dimensional aspect of capacitance variation. Instead of using multiple sensors at different positions, the system uses one sensor that measures capacitance across different states (empty cassette, partial sheets, full sheets). This dimensional approach to parameter measurement allows a single sensor to provide information that would traditionally require multiple sensors.
3Difficulty of detecting and measuring
If optical sensors and actuators are used for detection, then detection capability is achieved, but false detection occurs due to signal timing delays
Solution Approach 1:
The patent replaces optical sensors and mechanical actuators with a capacitive sensing system. Capacitive sensors detect changes in electrical field caused by the presence and quantity of sheets, eliminating the need for optical components and mechanical movement. This substitution removes the source of signal timing delays and false detections associated with optical systems, thereby improving reliability while maintaining detection capability.
Solution Approach 2:
The capacitive sensor system is self-regulating and provides immediate feedback based on the electrical properties of the sheets and cassette. Unlike optical systems that require complex signal processing and timing synchronization, the capacitive system directly measures the physical state through capacitance changes, automatically adapting to different conditions without generating false signals. This self-service capability eliminates false detections while maintaining full detection functionality.
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 enables precise detection of the sheet cassette's position and remaining sheets using a single sensor, improving accuracy and reducing false detection issues compared to traditional methods.
Implementation Method 1
a capacitance detector configured to output a signal indicating a value corresponding to a quantity of electricity stored in the electrode
Data Source
AI summary
An image forming apparatus includes a main body, a sheet cassette attachable to the main body and configured to support one or more sheets to be supplied to the image forming unit, and a controller. The main body includes an electrode movable relative to the main body, a capacitance detector configured to output a signal indicating a value corresponding to a quantity of electricity stored in the electrode, and a wire. The sheet cassette includes a metal member, and a sheet supporting plate made of metal, movable relative to the sheet cassette in an up-down direction, and configured to support one or more sheets from below. The controller is configured to determine whether the sheet cassette is at an installation position in the main body from a level of the value of the signal outputted from the capacitance detector connected to the electrode via the wire.