Capacitance Sheet Size Detection in Image Formers
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Solution Overview
Problem
Existing image forming apparatuses face high costs and reliability issues due to the use of exposed detectors that can be damaged by user handling and require multiple sensors for detecting different sheet sizes.
Innovation Solution
An image forming apparatus with a capacitance detection system using a first and second electrode and a conductor in the sheet cassette, where the electrodes are positioned to detect the sheet guide's movement, allowing the controller to determine sheet size without a movable member, thus reducing the risk of damage and using a single sensor for multiple sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector is disposed at an outer surface of the sheet cassette to detect sheet size, then sheet size detection is enabled, but the detector may be damaged by user handling
Solution Approach 1:
The patent replaces the mechanical contact-based detector with a capacitance sensor that detects sheet size through electrical field interaction. The capacitance sensor measures changes in capacitance caused by the dielectric properties of different sheet materials and thicknesses, eliminating the need for physical contact between the detection component and the sheet cassette exterior, thus preventing damage from user handling.
Solution Approach 2:
The patent introduces the sheet cassette body as an intermediary element that transmits detection signals from the interior to the exterior. The capacitance sensor is positioned inside the sheet cassette, and the sheet cassette structure itself serves as the medium through which detection information is conveyed to the controller, eliminating the need for exposed detectors on the outer surface.
2Measurement precision
If multiple detectors or sensors are used to detect different sheet sizes, then accurate detection for various sheet sizes is achieved, but the cost increases
Solution Approach 1:
The patent implements a universal detection system using a single capacitance sensor that can detect multiple sheet sizes through a unified detection mechanism. The capacitance sensor measures capacitance variations that correspond to different sheet sizes, allowing one sensor to perform the function of multiple sensors would have been required in traditional mechanical detection systems.
Solution Approach 2:
The patent utilizes changes in capacitance parameters to differentiate between various sheet sizes. By measuring capacitance variations caused by different sheet dimensions, materials, and thicknesses, the system achieves multi-size detection capability with a single sensor, avoiding the need for multiple detectors and reducing manufacturing costs.
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 solution provides an inexpensive and failure-resistant method for detecting sheet sizes, eliminating the need for multiple sensors and reducing the risk of mechanical failure, while accurately determining sheet sizes using a single capacitive sensor.
Implementation Method 1
a capacitance detector configured to output a signal indicating a value corresponding to a quantity of electricity stored in the first electrode and the second electrode
Data Source
AI summary
An image forming apparatus includes a main body, a sheet cassette, and a controller. The main body includes a first electrode, a second electrode, and a capacitance detector configured to output a signal indicating a value corresponding to a quantity of electricity stored in the first electrode and the second electrode. The sheet cassette includes a sheet guide, and a conductor disposed in an upper portion of the sheet guide. In a state in which the sheet cassette is at an installation position defined in the main body, the first electrode and the second electrode face the conductor in an up-down direction and are at different positions in a moving direction in which the sheet guide is movable. The controller is configured to detect a position of the sheet guide from the value of the signal outputted from the capacitance detector.