Cam Phase Detection Using Slit Segmentation for Developing Roller Positioning
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately detecting the phase of a cam to stop the developing roller at the correct position, either when it contacts or separates from the photosensitive drum, particularly during initializing actions, leading to inefficiencies in the image forming process.
Innovation Solution
An image forming apparatus with a cam and cam follower mechanism that includes a phase-detector wall with distinct slits to accurately detect the position of the developing roller using a photo-interrupter, allowing the controller to initiate an initializing action by rotating the cam in reverse and stopping it based on the time period for light emission through specific slits, ensuring precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single flag is used in the cam to detect the separated condition, then the device complexity is reduced, but the measurement precision of cam phase detection deteriorates because the phase cannot be accurately detected when the developing roller is in another condition
Solution Approach 1:
The phase-detector wall is segmented into multiple slits (first slit and second slit) with different sizes instead of using a single flag. This segmentation allows the system to distinguish between different cam phases (separated condition and contacting condition) by detecting which slit is present, thereby improving measurement precision while maintaining relatively simple device complexity
Solution Approach 2:
Different regions of the phase-detector wall are given different properties through the use of slits with different sizes. The first slit and second slit have different circumferential dimensions, creating local variations in light transmission characteristics that enable accurate phase detection for different developing roller positions
2Measurement precision
If three different-sized slits are used to detect both separated and contacting conditions, then the measurement precision is improved, but the device complexity increases due to the need to handle multiple slit configurations
Solution Approach 1:
The invention extracts the essential detection function by using only two slits (first slit and second slit) with different sizes rather than three different-sized slits. This extraction simplifies the phase detection mechanism while maintaining the ability to accurately detect both separated and contacting conditions, thereby reducing device complexity while preserving measurement precision
Solution Approach 2:
The phase-detector wall with multiple slits serves multiple functions: it detects both the separated condition (when developing roller is separated from photosensitive drum) and contacting condition (when developing roller contacts photosensitive drum) through a single structural element, eliminating the need for separate detection mechanisms
3Loss of time
If the cam rotates in reverse direction during initializing action, then the initializing time is reduced, but the reliability of phase detection deteriorates because the cam may not stop accurately at the correct phase
Solution Approach 1:
The controller uses feedback from the photo-interrupter to detect which slit (first or second) is present during reverse rotation, and based on this feedback information, the controller accurately determines when to stop the cam. This feedback mechanism ensures reliable phase detection and accurate positioning even during reverse direction rotation, resolving the contradiction between fast initialization and positioning reliability
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 a shorter initializing period and accurate stopping of the cam at the correct phase, enhancing the efficiency of the image forming process by ensuring the developing roller is properly positioned relative to the photosensitive drum.
Implementation Method 1
The photo-interrupter includes a light-emitter and a light-receiver. The phase-detector wall has a first slit, through which light emitted from the light-emitter is allowed to pass
Data Source
AI summary
An image forming apparatus, having a casing, a cover, a photosensitive drum, a developing roller, a photo-interrupter, a moving mechanism to move the developing roller between a contacting position and a separated position, and a controller, is provided. The moving mechanism has a cam including, a first cam portion, a phase-detector wall including a first slit and a second slit, and a cam follower. When the cover moves from the open position to the closed position, the controller conducts a first initializing control to cause the cam to rotate in a reverse direction, and after detecting the first slit based on a time period, in which light in the photo-interrupter passes through one of the first slit and the second slit, cause the cam to stop rotating.