Lens Driver Bobbin Magnet Structure for Coupling Without Interference
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Solution Overview
Problem
Existing lens moving apparatuses face challenges in miniaturization for subminiature, low-power camera modules, particularly in increasing coupling force between components and reducing magnetic field interference, while also addressing issues like board breakage during assembly and sensor tilting due to burrs or improper mounting.
Innovation Solution
The design includes a sensing magnet that projects from the bobbin's surface towards the housing, with a width decrease towards the housing, and a seating groove with specific openings to enhance coupling force and reduce magnetic field interference, facilitating easier assembly and positioning despite burrs or tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the sensing magnet is made larger to increase coupling force with the position sensor, then the coupling force increases, but the magnetic field interference with the drive magnet increases
Solution Approach 1:
The sensing magnet is designed with an asymmetric width profile that decreases toward the drive magnet side. This dimensional variation in the width direction creates a gradient structure that allows the magnet to maintain strong coupling with the position sensor while progressively reducing magnetic field strength toward the drive magnet, thereby minimizing interference.
Solution Approach 2:
Different regions of the sensing magnet are designed with different width characteristics. The region facing the position sensor maintains sufficient width for strong coupling, while the region facing the drive magnet has reduced width to minimize magnetic field interference. This local differentiation resolves the contradiction between needing strong signal detection and avoiding interference.
2Volume of moving object
If the camera module is miniaturized to reduce size, then the device becomes more compact, but the coupling force between components decreases
Solution Approach 1:
The sensing magnet's width parameter is varied along its length, creating a non-uniform structure. This parameter change allows the magnet to achieve optimal coupling force within a reduced volume by concentrating magnetic flux where needed rather than requiring a uniformly large magnet throughout.
Solution Approach 2:
The combination of the asymmetric sensing magnet structure with the bobbin and position sensor creates a composite magnetic coupling system that achieves high coupling force density in a compact package, effectively resolving the size-force contradiction.
3Manufacturing precision
If the board is inserted tightly into the housing pocket to improve positioning accuracy, then positioning precision increases, but the difficulty of assembly increases due to burrs and misalignment
Solution Approach 1:
The elastic member is pre-installed between the board and housing to provide cushioning and tolerance compensation before final assembly. This beforehand preparation allows the board to be positioned accurately while accommodating burrs and minor misalignments, reducing assembly difficulty.
Solution Approach 2:
The elastic member changes its physical state from compressed to relaxed, providing dynamic adjustment capability. This parameter change in the elastic member's compression state allows it to compensate for dimensional variations and burrs while maintaining precise positioning.
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 increases the coupling force between the bobbin and sensing magnet, minimizes magnetic field interference, reduces board breakage during assembly, and improves assembly ease and productivity by stabilizing sensor placement.
Implementation Method 1
a position sensor (170) disposed in the housing (140) and configured to detect a position of the sensing magnet (180)
Implementation Method 2
a coil (120) disposed in the housing (140) and configured to generate an electromagnetic force
Data Source
Figure 1
Figure 2~3A
Figure 3B~3c
AI summary
An embodiment comprises: a housing comprising a first corner part and a second corner part opposite to the first corner part; a bobbin disposed in the housing; a magnet comprising a first magnet disposed in the first corner part of the housing and a second magnet disposed in the second corner part of the housing; a coil disposed on the bobbin and opposite to the magnet; a circuit board disposed on one surface of the housing and including a position sensor; and a sensing magnet disposed in the bobbin and opposite to the position sensor, wherein a protrusion part is formed to protrude from one surface of the bobbin, opposite to one surface of the housing, toward the one surface of the housing, and the sensing magnet is at least partially placed within the protrusion part of the bobbin.