Concentric Yoke Lens Drive Eliminates Ball Screw Loss

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Solution Overview

Problem

Conventional lens driving apparatuses for small-sized portable cameras experience increased drive loss and reduced responsivity due to the mismatch between the direction of thrust and the moving direction of the lens, leading to slower movement speeds and reduced mobility.

Innovation Solution

A lens driving apparatus utilizing concentric yokes and coils to generate electromagnetic forces that align the thrust direction with the lens movement, eliminating the need for gears and cam mechanisms, thereby minimizing drive loss and enhancing mobility and responsivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If rotational movement is converted to linear movement using a ball screw, then the lens can be moved in the direction of the optical axis, but drive loss increases and responsivity becomes slow

Engineering Contradiction:

Improvelens moving speedVSAvoiddrive loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent replaces the mechanical ball screw system with an electromagnetic drive system. The coil and magnet generate electromagnetic force that directly moves the lens support member in the optical axis direction, eliminating the need for rotational-to-linear conversion and reducing drive loss while improving lens moving speed and responsivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If a ball screw mechanism is used to move the lens, then linear movement is achieved, but the structure becomes complex and space-consuming

Engineering Contradiction:

Improvelens movement efficiencyVSAvoiddrive mechanism complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the complex mechanical ball screw mechanism with a compact electromagnetic drive system consisting of a coil, magnet, and yoke. This substitution simplifies the drive mechanism structure and reduces the space required for lens actuation while maintaining efficient lens movement capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and eliminates unnecessary mechanical conversion components (ball screw, rotational joints) from the drive system, retaining only the essential electromagnetic components needed for direct linear actuation of the lens support member

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If gears and cam mechanisms are used to move the lens, then movement control is achieved, but rattle occurs due to accuracy errors

Engineering Contradiction:

Improvelens positioning accuracyVSAvoidrattle

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces mechanical gear and cam mechanisms with an electromagnetic drive system that directly actuates the lens support member. This eliminates mechanical meshing and contact interfaces that cause rattle due to manufacturing accuracy errors, providing smoother and more precise lens positioning

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enables efficient lens movement in a narrow space with reduced drive loss and improved responsivity, suitable for small-sized cameras, while also allowing for miniaturization and preventing rattle due to the absence of gears and cams.

Implementation Method 1

The lens support member is linearly moved in the direction of an optical axis of a lens by an electromagnetic force caused by passing current through the coil

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentUS7394603B2Lens driving apparatus

Publication Date: 2008.07.01 NEW SHICOH MOTOR CO LTD(JP)

AI summary

A lens driving apparatus includes: a first yoke having an inner peripheral wall and an outer peripheral wall placed to be concentric with each other and forming a rectangular U-shape cross section and a cylindrical shape; a second yoke placed at an outer side of the first yoke to be concentric with the first yoke and forming a rectangular U-shape cross section and a cylindrical shape; a base; a first magnet and a first coil arranged in a rectangular U-shape interior of the first yoke; a second magnet and a second coil arranged in a rectangular U-shape interior of the second yoke; a first lens support member; and a second lens support member. The second lens support member is placed at an inner peripheral side of the second yoke and has the second coil fixed onto an outer periphery thereof. The first lens support member is linearly moved in a direction of an optical axis of a lens by an electromagnetic force caused by passing current through the first coil. The second lens support member is linearly moved in a direction of an optical axis of a lens by an electromagnetic force caused by passing current through the second coil.