Step Motor with Piezoelectric Position Compensator
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Solution Overview
Problem
Existing PM type step motors face limitations in achieving high driving resolution due to mechanical manufacturing constraints when reducing the pitch of the lead screw, and lack precise operation sensing, which restricts precise transfer capabilities for optical pickup lenses and camera lenses.
Innovation Solution
A step motor design incorporating a position compensator that finely adjusts the lead screw using a piezoelectric element and displacement amplifying members, and a rotation sensing unit that senses rotor rotation via magnetic force changes, enabling precise position compensation and operation state sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pitch of the lead screw is reduced to increase driving resolution, then transfer resolution is improved, but manufacturing precision deteriorates due to mechanical limits in mass production
Solution Approach 1:
The patent segments the pitch adjustment function into two parts: a coarse pitch lead screw for major positioning and a fine pitch lead screw for precision adjustment. This segmentation allows each component to have optimized pitch values that are manufacturable, while achieving overall high resolution through coordinated operation of both segments.
Solution Approach 2:
The patent introduces a pitch conversion mechanism as an intermediary between the coarse and fine pitch lead screws. This intermediary component converts the rotational motion from the coarse pitch screw into precise linear displacement that drives the fine pitch screw, enabling resolution enhancement without requiring the coarse screw to be manufactured at ultra-fine pitch tolerances.
2Manufacturing precision
If a lead screw with very fine pitch (0.15 mm or less) is manufactured to achieve high resolution, then transfer resolution is improved, but device complexity increases due to manufacturing difficulty
Solution Approach 1:
The patent divides the single fine pitch lead screw into two separate lead screws with different pitch values. The first lead screw has a coarser pitch for robust manufacturing and the second lead screw has a finer pitch for high resolution. This segmentation reduces the complexity of manufacturing each individual component while achieving the cumulative resolution benefit.
Solution Approach 2:
The patent adds a rotational dimension to the system by introducing a pitch conversion mechanism that rotates the coarse pitch lead screw to drive the fine pitch lead screw. This dimensional change allows the system to achieve fine resolution without requiring the coarse screw to be manufactured at fine tolerances, effectively distributing the precision requirements across different operational dimensions.
3Device complexity
If no rotation sensing unit is installed to simplify the structure, then device complexity is reduced, but measurement precision deteriorates due to inability to sense operation state
Solution Approach 1:
The patent implements feedback by installing a rotation sensing unit that continuously monitors the rotational position of the rotor. This feedback signal is used to accurately determine the position of the lead screw and enable precise control of the positioning system, allowing the motor to achieve and maintain high measurement precision through closed-loop control.
Solution Approach 2:
The rotation sensing unit enables the step motor to self-monitor its own operational state. By sensing its own rotor position and translating it to lead screw position information, the motor performs self-diagnosis and self-correction, eliminating the need for external sensing systems and reducing overall device complexity while maintaining high measurement precision.
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 allows for precise position control at the micrometer level, enhancing transfer resolution and enabling ultrafine adjustments in industrial applications, such as precise optical devices, by minimizing transfer differences through feedback compensation.
Implementation Method 1
a position compensator moving the lead screw to a desired position by finely changing a position of the lead screw while contracting and expanding
Implementation Method 2
a rotation sensing unit which is disposed at a side of the rotor (or a rotary body rotating with the rotor) and senses rotation of the rotor
Data Source
AI summary
The present invention relates to a PM (Pulse-Width Modulation) type step motor used for conveying an optical pickup lens of media devices or a mobile camera lens. In detail, the present invention relates to a step motor that is composed of a stator, a rotor rotating by interacting with the stator, a lead screw combined with the rotor and rotating with the rotation of the rotor, and a bearing supporting the lead screw and which can perform precise conveying because it can perform fine adjustment and of which the operation state can be precisely sensed by having a position correcting unit that moves the lead screw to a desired position by finely moving it while contracting and stretching and a rotation sensing unit that is disposed at a side of the rotor or a rotary member rotating with the rotor and senses rotation of the rotor.