Autofocus Actuator Friction Management Using Homogeneous Plastic Guide Pin and Spheres
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Solution Overview
Problem
Existing SMA-based autofocus actuators in camera modules face issues with frictional forces and wear between metal or ceramic rolling members and plastic guide channels, leading to premature failures and increased costs when attempting to address these issues with metal or ceramic coatings in the manufacturing process.
Innovation Solution
The autofocus actuator design incorporates a metal or ceramic guide pin and spheres with slots on the lens carrier, allowing for sliding contact that maintains optimal friction and prevents wear, along with a flexure for anti-rotation, ensuring precise movement and stability of the lens carrier without complex manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If metal or ceramic rolling members are used in guide channels, then friction management is improved, but wear increases due to surface hardness difference
Solution Approach 1:
The invention uses plastic material for both the guide channels and the rolling members, eliminating the surface hardness difference between dissimilar materials. This homogeneity prevents the wear issue that occurs when hard ceramic or metal rolling members contact plastic guide channels, while still maintaining adequate friction management for the actuator operation.
2Reliability
If metal or ceramic coating is applied to guide channels, then wear resistance is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The invention eliminates the need for complex coating processes by using uniform plastic material for both guide channels and rolling members. This approach achieves adequate wear resistance through material selection and design rather than through complex manufacturing processes like metal or ceramic coating, thereby maintaining manufacturing simplicity and cost-effectiveness.
3Ease of manufacture
If plastic guide channels are used with metal or ceramic rolling members, then manufacturing ease is maintained, but premature failure occurs due to wear
Solution Approach 1:
The invention maintains manufacturing simplicity by using plastic material for both guide channels and rolling members, which can be easily molded and assembled. Simultaneously, it improves actuator lifetime by eliminating the wear problem associated with hard ceramic or metal rolling members contacting plastic, achieving both ease of manufacture and enhanced reliability through material homogeneity.
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 enhances the lifespan and performance of the autofocus actuator by maintaining optimal friction and preventing wear, while simplifying the manufacturing process and reducing costs, thereby improving the reliability and efficiency of the camera module's autofocus functionality.
Implementation Method 1
The controlled heating via Joule effect of the SMA wire causes its contraction and the movement of the lens carrier with respect to the housing
Implementation Method 2
a return elastic element causes the lens carrier to move back to its rest position when the SMA wire is deactivated
Data Source
AI summary
Autofocus actuator for camera modules comprising a SMA wire (17) as actuating element and at least six spheres (27) as sliding aids contained in at least three slots (26) formed in a lens carrier (12) and symmetrically arranged around a guide pin (15) mounted on a bottom plate (13), whereby the guide pin (15), slots (26) and spheres (27) form a linear bearing for the sliding axial movement of the lens carrier (12) on the bottom plate (13), whereby two sets of additional spheres, each set comprising at least two spheres, are kept in position by a sphere stopping structure.