Voice Coil Motor Bobbin Coupling for Precise Lens Gap Control
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Solution Overview
Problem
Conventional voice coil motors (VCMs) face challenges in accurately adjusting the gap between a lens and an image sensor due to manufacturing tolerances, leading to reliability issues and increased manufacturing costs.
Innovation Solution
The proposed VCM design includes a bobbin with protrusions, a coil block, a magnet, and elastic members with specific configurations to securely couple the elastic members to the bobbin, preventing disengagement from external shocks or vibrations, and enhancing the coupling power between the coil and the elastic members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing methods are used for the bobbin and elastic member, then manufacturing cost is reduced, but gaps are frequently generated between the bobbin and elastic member due to manufacturing tolerances
Solution Approach 1:
The elastic member is pre-formed with a coupling hole that matches the protrusion shape, and the protrusion is pre-formed on the bobbin. This preliminary preparation of coupling features eliminates gaps that would otherwise occur due to manufacturing tolerances, while maintaining standard manufacturing processes and costs.
Solution Approach 2:
The protrusion on the bobbin acts as an intermediary coupling element between the bobbin and the elastic member. This intermediate feature fills the gap that would exist due to manufacturing tolerances, providing precise positioning and eliminating the need for more expensive tight-tolerance manufacturing.
2Strength
If the leaf spring is coupled to the bobbin by insert method, then coupling strength is improved, but manufacturing process becomes complicated to increase manufacturing cost
Solution Approach 1:
The coupling hole in the elastic member and the protrusion on the bobbin are designed to fit together as an integrated coupling mechanism. This merged design provides strong coupling through the interference fit while maintaining a simple manufacturing process that does not require separate assembly steps or complex operations.
3Strength
If the leaf spring is coupled to the bobbin by thermal fusion method, then coupling strength is improved, but the leaf spring is disengaged from the bobbin due to vibration and shock
Solution Approach 1:
The coupling hole and protrusion are pre-designed with appropriate clearance and interference fit characteristics. This preliminary design ensures that the elastic member remains securely coupled to the bobbin under vibration and shock conditions, eliminating the disengagement problem associated with thermal fusion methods while maintaining strong coupling.
4Strength
If adhesive is coated between the bobbin and leaf spring, then coupling strength is improved, but adhesive coated area is small to limit coupling strength improvement
Solution Approach 1:
The protrusion on the bobbin serves as an intermediary mechanical coupling feature that provides large-area contact with the elastic member. This mechanical coupling through the protrusion-coupling hole interface provides substantial coupling strength without relying on adhesive, eliminating the limitation of small adhesive coated area.
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 design effectively eliminates gaps between the bobbin and elastic members, allowing for precise adjustment of the lens-image sensor interval, increases reliability by reducing manufacturing costs, and enhances the durability of the VCM.
Implementation Method 1
a force from a magnetic field generated by a magnet and a magnetic field generated by a coil block facing the magnet
Implementation Method 2
an elastic member elastically supporting a magnet opposite to the coil block and the bobbin
Data Source
AI summary
A VCM (voice coil motor) is disclosed, the VCM including: a rotor including a cylindrical bobbin for accommodating a lens and protruded at a bottom end with a boss, and a coil block arranged at a periphery of the bobbin; a stator including a magnet facing the coil block and a yoke fixing the magnet; and an elastic member including a first elastic member formed with a through hole coupled to the boss of the bobbin and a second elastic member coupled to an upper end facing the bottom end of the bobbin; wherein the boss is formed with a disengagement prevention unit inhibiting the first elastic member from being disengaged from the boss, and the first elastic member is formed with a coupling unit contacting a joint where the disengagement prevention unit and the coupling unit meet.