Lens Driving Apparatus Rack Unit Impact Absorption
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Solution Overview
Problem
Conventional lens driving apparatuses require high-torque motors and large sizes due to the need for strong forces to prevent positional shifts and cogging between the rack unit and lead screw, leading to increased costs and potential damage from impacts.
Innovation Solution
A lens driving apparatus with a rack unit coupled to a lead screw, featuring a mated portion, an opposed cog, and elastic members applying forces F1, F2, and F3, where F1 < F2 < F3, to prevent positional shifts and cogging, with the opposed cog engaging only when necessary to absorb impacts and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring member applies considerable force to prevent positional shift between rack unit and lead screw, then positional shift is prevented, but motor load increases requiring larger size and higher cost
Solution Approach 1:
The rack unit is divided into two separate units: a first rack unit with a first cog that engages with the lead screw, and a second rack unit with a second cog that engages with the lead screw at a different position. This segmentation allows each cog to handle impact forces independently, preventing positional shift without requiring excessive force from a single spring member, thus reducing motor load requirements.
Solution Approach 2:
The patent introduces elastic members (springs) between the rack units and the lead screw that apply predetermined forces to cushion impact forces. The first elastic member applies a first force and the second elastic member applies a second force, both less than the maximum impact force F3. This beforehand cushioning prevents positional shift during impact without requiring the motor to handle the full impact load, resolving the contradiction between reliability and power requirements.
2Ease of operation
If a strong impact occurs at position other than end of movable range, then rack unit can be forced against lead screw, but plastic deformation and damage occur between mated portion and lead screw
Solution Approach 1:
The rack unit is segmented into two separate units with separate cogs (first cog and second cog) that can independently engage with the lead screw. This segmentation distributes impact forces across multiple engagement points, preventing plastic deformation and damage to the mated portion even when strong impacts occur during movement, thus maintaining strength while preserving ease of operation.
Solution Approach 2:
Elastic members are introduced as intermediary elements between the rack units and the lead screw. These elastic members absorb impact forces through their own deformation, acting as mediators that protect the mated portion from direct impact loads. The elastic members allow the rack unit to move freely during normal operation while cushioning strong impacts, preventing plastic deformation and damage.
3Reliability
If opposed cog is fixed to prevent cog skip, then positional shift is prevented, but impact forces cause plastic deformation and cogging
Solution Approach 1:
The patent makes the rack unit dynamic by allowing it to move along the lead screw while maintaining engagement through two separate cogs. The first cog and second cog can independently engage and disengage from the lead screw threads during movement, allowing the rack unit to adapt to impact forces dynamically. This dynamic engagement prevents both positional shift during normal operation and plastic deformation during strong impacts, resolving the contradiction between reliability and strength.
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 effectively minimizes positional shifts and cogging, reducing the need for high-torque motors and large sizes, while preventing damage to the mated portion and lead screw, thus achieving cost reduction and miniaturization.
Implementation Method 1
a first elastic member configured to force the mated portion against the lead screw with a first force F1
Implementation Method 2
a second elastic member configured to force the opposed cog unit with a second force F2 toward the lead screw
Implementation Method 3
an opposed cog arranged opposite to the mated portion with respect to the lead screw and displaceable relative to the mated portion
Data Source
AI summary
An apparatus includes a driver configured to rotate a lead screw, a rack unit including a mated portion mated with the lead screw, the rack unit being coupled with the holder and configured to move along the lead screw as the lead screw is rotated by the driver, a first elastic member configured to force the mated portion against the lead screw with a first force F1, an opposed cog arranged opposite to the mated portion with respect to the lead screw and displaceable relative to the mated portion, and a second elastic unit configured force the opposed cog unit with a second force F2 toward the lead screw. F1<F2<F3 is satisfied where a force containing F3 is a component that opposes to F2, at least one of the mated portion and the lead screw getting damaged when F3 is applied between the mated portion and the lead screw.