Linear Motor Magnet Layout for Uniform Thrust in Lens Barrels
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Solution Overview
Problem
Existing voice coil motors (VCMs) used in lens barrels for focusing mechanisms in cameras face challenges in power efficiency and size enlargement, with magnetic efficiency being uneven across the driving stroke and requiring separate fixing members, leading to increased electric power consumption and motor enlargement.
Innovation Solution
A linear motor design with a coil arrangement coinciding with the main axis direction, featuring a center yoke, main and sub magnets with inclined magnetization directions, and back and side yokes to enhance magnetic efficiency without increasing size, utilizing an applied Hulbach array configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a VCM is used as a focusing mechanism in a lens barrel, then the linear motor can be installed in the lens barrel with finite track, but the magnetic efficiency varies across the driving stroke and power efficiency deteriorates
Solution Approach 1:
The patent applies local quality by configuring different magnetization directions for main magnets and sub magnets in different regions of the magnetic circuit. The sub magnets are arranged with magnetization directions inclined at specific angles (α and -α) relative to the main magnets, creating localized magnetic field variations that compensate for the natural decline in magnetic efficiency at stroke ends, thereby equalizing magnetic efficiency across the entire driving stroke while improving overall power efficiency.
2Reliability
If the magnetic efficiency is equalized across the driving stroke by deteriorating the magnetic efficiency in the central part, then the magnetic efficiency becomes uniform, but the power efficiency worsens as a whole
Solution Approach 1:
The patent employs parameter changes by precisely controlling the magnetization directions of sub magnets relative to main magnets through specific inclination angles (α and -α). This parameter optimization ensures that the magnetic flux distribution is improved at stroke ends without excessive deterioration at the central part, achieving a balance where magnetic efficiency is equalized across the stroke while minimizing overall energy loss and improving power efficiency.
3Stability of the object's composition
If a fixing member is added to fix the magnet array, then the magnet array stability is improved, but the outside size of the linear motor becomes large
Solution Approach 1:
The patent applies merging by integrating the sub magnets directly adjacent to the main magnets in a compact arrangement where the sub magnets serve dual purposes: they modify the magnetic flux distribution to equalize magnetic efficiency while simultaneously being structurally supported by the same magnetic circuit framework. This eliminates the need for separate fixing members, maintaining magnet array stability without increasing the outside size of the linear motor.
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
The improved magnetic efficiency enhances power efficiency and reduces electric power consumption while maintaining a compact size, suitable for camera focusing mechanisms, particularly in autofocus operations.
Implementation Method 1
a linear motor that generates thrust in a main axis direction, including a coil unit (230a), a magnetic circuit (230b)... that generates Lorentz force with a combination of a permanent magnet and a coil
Implementation Method 2
it is important to heighten efficiency of a magnetic circuit that consists of a permanent magnet and a yoke... heighten density of a magnetic flux that contributes to generation of the thrust in a coil area
Data Source
AI summary
A linear motor capable of improving power efficiency while preventing enlargement. A winding core direction of a coil coincide with a thrust direction of the linear motor. A center yoke is arranged inside the coil extending in the thrust direction. A magnet faces the center yoke outside the coil so that its magnetization direction is perpendicular to the thrust direction. A back yoke adjoins the main magnet at an opposite side of the center yoke. Two sub magnets adjoin the main magnet and their magnetization directions are inclined by 90° to that of the main magnet. Two side yokes adjoin the center and back yokes at both sides a magnet group in the thrust direction. Surfaces of the main magnet that adjoin the sub magnets incline inward toward the back yoke. Surfaces of the sub magnets that adjoin the main magnet incline inward toward the center yoke.