Plastic Polygonal Mirror Deformation Control
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Solution Overview
Problem
Conventional polygonal mirrors used in light scanning units for electrophotographic image forming apparatuses, made of high-purity aluminum, have high manufacturing costs and are difficult to mass-produce, and those made of plastic materials suffer from deformation due to heat and high-speed rotation, leading to decreased optical performance.
Innovation Solution
A polygonal mirror formed from a plastic material with specific dimensions and thermal expansion coefficients, coupled to a holder frame using an adhesive to minimize deformation, and optionally featuring grooves or flow preventing steps to reduce centrifugal force effects, ensuring reduced deformation and improved planarity of reflection surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polygonal mirror is made of high-purity aluminum to achieve high reflectivity, then optical performance is improved, but manufacturing cost increases and mass production becomes difficult
Solution Approach 1:
The patent replaces expensive high-purity aluminum mirrors with inexpensive plastic mirrors that can be mass-produced through injection molding. The plastic mirrors are designed to be cost-effective substitutes that maintain adequate optical performance for the application, embodying the principle of using cheap materials to replace expensive ones.
Solution Approach 2:
The patent changes the material parameter from metal (aluminum) to plastic polymer, fundamentally altering the manufacturing approach from precision machining to injection molding. This parameter change enables mass production while maintaining functional performance through optimized plastic material selection and mirror design.
2Ease of manufacture
If a polygonal mirror is made of plastic material to reduce manufacturing cost, then ease of manufacture is improved, but deformation occurs due to heat and high-speed rotation
Solution Approach 1:
The patent optimizes plastic material parameters by selecting polymers with appropriate glass transition temperatures, thermal expansion coefficients, and mechanical properties. The mirror thickness, diameter, and rotational speed parameters are carefully controlled to minimize deformation while maintaining cost-effectiveness of plastic material usage.
Solution Approach 2:
The patent designs the plastic mirror with built-in compensation features that anticipate and counteract thermal expansion and centrifugal deformation before they occur. The mirror geometry and material selection are pre-engineered to compensate for expected thermal and rotational effects, maintaining optical performance under operating conditions.
3Area of moving object
If the size of a polygonal mirror is increased to improve light scanning coverage, then scanning performance is improved, but deformation due to centrifugal force increases
Solution Approach 1:
The patent establishes specific parameter ranges for mirror outer diameter, inner diameter, and thickness that balance scanning coverage with deformation control. The ratios between these dimensions are optimized to minimize centrifugal deformation while maintaining adequate light scanning area for the electrophotographic apparatus.
Solution Approach 2:
The patent uses composite plastic materials or multi-layer plastic structures that combine materials with different thermal and mechanical properties to create a mirror that resists centrifugal deformation while maintaining large scanning coverage. The composite structure provides enhanced stiffness-to-weight ratio.
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 effectively minimizes deformation caused by heat and rotation, maintaining optical performance within acceptable tolerances and reducing manufacturing costs, thereby enhancing the reliability and efficiency of the light scanning unit.
Implementation Method 1
coupled to a holder frame using an adhesive to minimize deformation
Implementation Method 2
A light scanning unit deflects a light beam irradiated from a light source to which an image signal is applied, and scans the light beam in a main scanning direction of an image carrier
Implementation Method 3
those made of plastic materials suffer from deformation due to heat and high-speed rotation
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A polygonal mirror, a light scanning unit using the polygonal mirror, and an image forming apparatus. The polygonal mirror is formed of a plastic and includes a plurality of reflection surfaces that are formed in an outer portion of the polygonal mirror and rotate around a rotational axis, and an internal mirror surface that defines a hole, wherein a ratio of an internal diameter d to an outer diameter D satisfies 0.1≤d/D≤0.3.