Segmented Yoke Miniature Actuator for Lens Positioning

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Solution Overview

Problem

Designing miniature camera actuators that are lightweight and easily manufactured for use in small-sized electronic devices like cellular phones and PDAs is challenging, as existing actuators are often heavy and complex.

Innovation Solution

The actuator design features a yoke comprising multiple non-contacting subtending sections made of magnetically permeable material, which reduces material usage and weight, and includes a magnetic field generated by permanent magnets and an electric coil to displace the lens along the optical axis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If a traditional single-piece yoke is used in the actuator, then the magnetic field structure is simple, but the actuator weight increases and manufacturing complexity increases

Engineering Contradiction:

Improveactuator weightVSAvoidyoke structure complexity

Core Design Contradiction:

Weight of moving objectVSDevice complexity

Solution Approach 1:

The yoke is divided into multiple separate yoke sections (first yoke section, second yoke section, third yoke section) that are positioned around the coil assembly. Each section has a free end that extends toward the central axis, creating a segmented structure that reduces material usage and weight while maintaining magnetic field functionality. The sections are spaced apart to define gaps that allow coil windings to extend between them.

Inventive Principle:

Principle #1Segmentation

2Weight of moving object

If more yoke material is used to maintain magnetic field uniformity, then the magnetic field remains uniform, but the actuator weight increases

Engineering Contradiction:

Improveactuator weightVSAvoidmagnetic field uniformity

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The yoke sections are positioned at specific locations around the coil assembly with their free ends extending toward the central axis at defined distances. This localized positioning creates regions of concentrated magnetic permeability where needed to maintain field uniformity in the gap regions, while avoiding unnecessary material in other areas. The selective placement of magnetic material optimizes the magnetic field distribution without increasing overall weight.

Inventive Principle:

Principle #3Local quality

3Force

If the yoke sections are positioned closer to the coil assembly, then the magnetic field strength increases, but the actuator size increases

Engineering Contradiction:

Improvemagnetic forceVSAvoidactuator volume

Core Design Contradiction:

ForceVSVolume of moving object

Solution Approach 1:

The yoke sections are arranged in a radial pattern around the coil assembly, extending from the outer periphery toward the central axis. This radial arrangement allows the magnetic field to be concentrated in the radial direction within the gaps between sections, maintaining strong magnetic force in the active region while keeping the overall actuator footprint compact. The three-dimensional positioning of sections creates an efficient use of space.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 results in a lighter, easier-to-produce, and more compact actuator that effectively adjusts the lens position for autofocusing and zooming operations while maintaining a uniform magnetic field, enhancing the manufacturing efficiency and reducing the overall size of miniature cameras.

Implementation Method 1

An actuator typically includes an electrical coil disposed within a magnetic field of a permanent magnet, for example. Such an actuator may displace a lens by virtue of an interaction between a magnetic field generated by an electrical current flowing through the coil and the magnetic field of the permanent magnet.

Methodology Applied

Scientific EffectMagnetic field interaction: Lorentz Force