Cam Phase Detection Wall Slits for Roller Positioning
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Solution Overview
Problem
Existing image forming apparatuses face challenges in achieving a compact design due to the need for accurate detection of both contacting and separated states of the developing roller relative to the photosensitive drum, with existing solutions either compromising on accuracy or increasing the apparatus's bulkiness.
Innovation Solution
The implementation of a compact cam structure with a phase detection wall having distinct slits for detecting the contact and separated positions, allowing for precise detection without increasing the axial dimension, utilizing a photo-interrupter and a separation mechanism with a rotatable cam that includes gear, end cam, and plate cam components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the plate cam portion is provided at one surface of the cam and the phase detection wall is provided at the opposite surface of the cam, then both the contacting state and the separated state of the developing roller can be detected, but the axial dimension of the cam is inevitably increased making the image forming apparatus bulky
Solution Approach 1:
The patent transitions from a three-dimensional arrangement (phase detection wall on one surface, plate cam on the opposite surface, requiring axial space) to a two-dimensional arrangement (both phase detection wall and plate cam on the same surface, utilizing radial and circumferential dimensions). This dimensional change allows both detection functions to coexist without increasing axial dimension, resolving the contradiction between detection accuracy and compact size.
2Measurement precision
If only one flag is provided on the cam for rotational phase detection, then the cam structure is simple, but the accuracy for stopping rotation when the developing roller is in contact with the photosensitive drum is insufficient
Solution Approach 1:
The patent divides the single phase detection function into two distinct detection zones: a first detection zone with a first flag for detecting the separated state, and a second detection zone with a second flag for detecting the contacting state. This segmentation allows accurate detection of both states independently, improving rotational phase detection accuracy while maintaining relatively simple cam structure through the use of discrete, localized flags rather than complex continuous structures.
3Volume of moving object
If the cam is designed to be compact, then the image forming apparatus size is reduced, but the ability to accurately detect both contacting and separated states of the developing roller is compromised
Solution Approach 1:
The patent merges the phase detection wall and plate cam onto the same surface of the cam, combining two previously separate functional elements into a unified structure. This merging eliminates the need for axial separation, enabling compact cam design that maintains both detection capabilities within a reduced volume, thus resolving the contradiction between apparatus size and detection precision.
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 compact image forming apparatus with precise detection capabilities, ensuring accurate positioning of the developing roller, thereby reducing the overall size of the apparatus while maintaining high operational efficiency.
Implementation Method 1
The phase detection wall has a first slit and a second slit positioned away from the first slit in the circumferential direction. The first slit allows light emitted from the light emitting element to pass therethrough when the developing roller is at the separated position. The second slit allows the light emitted from the light emitting element to pass therethrough when the developing roller is at the contact position.
Data Source
AI summary
An image forming apparatus includes a developing roller, a photo-interrupter, and a separation mechanism. The developing roller is movable between a contact position and a separated position. The photo-interrupter includes a light emitting element and a light receiving element. The separation mechanism includes a cam configured to move the developing roller between the contact position and the separated position. The cam includes a phase detection wall extending in a circumference direction. The phase detection wall has a first slit and a second slit. The first slit allows the light emitted from the light emitting element to pass therethrough when the developing roller is at the separated position. The second slit allows the light emitted from the light emitting element to pass therethrough when the developing roller is at the contact position. A size of the first slit in the circumferential direction is different from that of the second slit.