Polygon Mirror Protrusion Design for Uniform Axial Pressing
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Solution Overview
Problem
The existing polygon mirrors made of plastic deform unevenly when pressed, leading to reduced moldability and increased mold releasing resistance, and the thickness variations during molding affect the liquidity of the resin, resulting in deteriorated moldability and deformation of reflecting surfaces.
Innovation Solution
A polygon mirror design with a first surface having protrusions equally distant from the axis between vertices, a recessed portion at the center, and connecting surfaces with a gentle curvature to reduce deformation and mold releasing resistance, and a pressing member that contacts these protrusions to maintain uniform pressure, ensuring even deformation and improved moldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the polygon mirror is pressed by the pressing member at the vertices, then the polygon mirror can be fastened to the light deflector, but the reflecting surfaces deform by different amounts due to thickness variations
Solution Approach 1:
The pressing member is designed to contact the polygon mirror at multiple positions including both vertices and midpoints of sides, rather than only at vertices. This distributes the pressing force more uniformly across the polygon mirror's surface, compensating for thickness variations and preventing differential deformation of reflecting surfaces while maintaining adequate fastening strength
2Device complexity
If the polygon mirror has a recessed portion for motor insertion, then the motor can be integrated into the polygon mirror, but the thickness reduction decreases resin liquidity and deteriorates moldability
Solution Approach 1:
The gate position in the mold is strategically positioned to ensure adequate resin flow paths and pressure distribution during injection molding. The gate is located to feed resin into thicker sections of the polygon mirror first, allowing the resin to fill the mold cavity progressively and compensate for the thickness reduction at the recessed portion, thereby maintaining good moldability despite the integrated motor recess
3Manufacturing precision
If two adjacent reflecting surfaces are directly connected to form a sharp edge, then the polygon mirror achieves precise optical geometry, but the mold releasing resistance increases and moldability deteriorates
Solution Approach 1:
Instead of forming sharp edges where adjacent reflecting surfaces meet, the polygon mirror incorporates rounded corners or filleted transitions at these junctions. This curvature modification reduces the mold releasing resistance by allowing the molded product to be easily extracted from the mold cavity, while the rounded edges are subsequently precision-machined or optically figured to achieve the required precise optical geometry
Data Source
AI summary
A light deflector includes: a polygon mirror made of plastic and having a plurality of reflecting surfaces; a motor including a rotor and configured to rotate the polygon mirror; and a pressing member configured to press the polygon mirror toward the rotor in an axial direction of the motor. The polygon mirror has a first surface having a polygonal shape, and a second surface opposite to the first surface in the axial direction and having a polygonal shape. The second surface faces the rotor. The polygon mirror includes a plurality of first contact portions configured to be in contact with and pressed by the pressing member, and the first contact portions are provided on the first surface at positions equally distant from an axis of the motor between each of vertices of the first surface and the axis of the motor.