Lens Barrel Thermal Expansion Gap Prevention
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Solution Overview
Problem
The formation of gaps between a holding member and a lens barrel due to differing thermal expansion coefficients in injection molding leads to water ingress in image pickup apparatuses using solid-state image sensing devices.
Innovation Solution
The design includes a cylindrical lens barrel with flange portions and a holding member with corresponding fitting grooves, where the thermal expansion coefficient of the holding member is either smaller or larger than that of the lens barrel, ensuring tight contact and preventing gap formation, along with the use of adhesive materials and elastic members for enhanced sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If injection molding is used to produce the holding member and lens barrel, then production efficiency is improved, but gaps form between components due to differential thermal expansion
Solution Approach 1:
The patent changes the material parameter (thermal expansion coefficient) of the holding member by selecting a resin with a smaller thermal expansion coefficient than the lens barrel resin. This parameter change ensures that during cooling after injection molding, the lens barrel shrinks more than the holding member, maintaining tight contact at the interface and preventing gap formation while preserving the benefits of injection molding production
Solution Approach 2:
The patent employs composite material selection by using different resin materials for the holding member and lens barrel based on their thermal expansion characteristics. The holding member uses a resin with smaller thermal expansion coefficient (e.g., polyacetal, polyoxymethylene) while the lens barrel uses a resin with larger thermal expansion coefficient, creating a material system that compensates for thermal shrinkage differences and prevents water ingress
2Reliability
If a resin with smaller thermal expansion coefficient is used for the holding member, then gap formation is prevented, but material selection becomes more restricted
Solution Approach 1:
The patent systematically addresses material selection constraints by identifying and specifying resin types with appropriately small thermal expansion coefficients. It provides a structured approach by listing suitable materials (polyacetal, polyoxymethylene, and their copolymers/terpolymers) and establishing clear selection criteria based on thermal expansion coefficient ranges, thereby maintaining reliability while managing material selection flexibility
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 configuration effectively inhibits the formation of gaps between the holding member and the lens barrel, preventing water entry and improving assembly accuracy by ensuring tight contact and enhanced adhesion and sealing.
Implementation Method 1
a thermal expansion coefficient of the holding member is smaller than a thermal expansion coefficient of the lens barrel
Data Source
AI summary
An image pickup apparatus includes a circuit board, a solid-state image sensing device disposed on an upper surface of the circuit board, a cylindrical lens barrel disposed above the circuit board, a lens housed in the lens barrel, and a holding member that holds the lens barrel and the circuit board therein. The solid-state image sensing device is positioned in an enclosed space formed by the lens barrel and the circuit board. The lens barrel has a first flange portion protruding in a direction perpendicular to a central axis of the lens barrel. The holding member has a first fitting groove portion in which the first flange portion of the lens barrel is fit. A thermal expansion coefficient of the holding member is smaller than a thermal expansion coefficient of the lens barrel.