Shaftless Scanner Mirror Drive Using Voice Coil Actuation
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Solution Overview
Problem
Existing scanner devices for laser material processing face challenges in achieving rapid and accurate repositioning of the deflection mirror due to high torque inertia and limited connecting rigidity, particularly in systems with torque-transmitting shafts.
Innovation Solution
A scanner device design featuring a pivotable mirror with an armature element made of soft magnetic material, an iron core with an air gap, and a coil that induces a magnetic field to interact with permanent magnets, allowing for shaftless torque transmission and precise repositioning without the limitations of traditional shaft-based systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a torque-transmitting shaft is used to connect the drive to the mirror, then the connection rigidity is improved, but the torque inertia of the system increases
Solution Approach 1:
The patent extracts and eliminates the torque-transmitting shaft from the system. The drive unit is directly coupled to the mirror mounting, removing the intermediate shaft that caused both rigidity limitations and inertia problems. This direct coupling achieves both stiff connection and low inertia simultaneously.
2Measurement precision
If the mirror is mounted on a shaft for rotation, then the positioning accuracy is improved, but the repositioning speed is reduced due to high moment of inertia
Solution Approach 1:
The patent removes the traditional shaft-based rotation mounting. Instead, the mirror is mounted directly on the drive unit with the deflection axis aligned to the drive's rotation axis. This eliminates the shaft's moment of inertia while maintaining precise angular positioning capability through the direct drive coupling.
Solution Approach 2:
Rather than mounting the mirror on a shaft and driving it through the shaft, the patent inverts the approach by integrating the mirror mounting directly into the drive unit. The drive rotor itself becomes part of the mirror mounting structure, reversing the traditional architecture to achieve lower inertia.
3Force
If a rotary magnet drive with permanent magnets is used to increase torque, then the drive torque is improved, but the moment of inertia increases due to magnet mass
Solution Approach 1:
The patent replaces the traditional rotary magnet drive with a voice coil motor (electromagnetic actuator). The voice coil generates electromagnetic force directly on a movable coil assembly, eliminating the need for heavy permanent magnets and mechanical rotor structures. This substitution provides sufficient torque with significantly reduced moving mass.
Solution Approach 2:
The patent changes the drive mechanism from magnetic interaction between permanent magnets and coils to direct electromagnetic force generation by a voice coil. This parameter change in the drive principle allows achieving the required torque with much lower moment of inertia by using lightweight coil and magnet assemblies that move minimally.
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 enables fast and accurate repositioning of the mirror with reduced inertia and a compact, non-interfering contour, achieving a high torque-to-moment ratio through flux concentration and weight-saving design, while maintaining high positioning accuracy.
Implementation Method 1
a coil which can be charged with a current and by means of which a magnetic field can be induced in the air gap and the iron core
Implementation Method 2
The scanner device comprises at least one pair of permanent magnets, each pair having a first and a second permanent magnet... disposed in the air gap such that a component of the magnetization of the first magnet points in the direction of the first coil-field-direction
Data Source
AI summary
The invention relates to a scanner device having a mirror arranged so as to be pivotable about an axis of rotation, an iron core with an air gap, a coil arranged about a portion of the iron core, and two permanent magnets. The two magnets have differently directed magnetizations and are arranged inside the air gap at different angular rotation positions with respect to the axis of rotation. An armature made of a soft-magnetic material is arranged on the mirror in such a manner that the armature is residing inside the air gap and, by means of application of electric current to the coil, the armature is moved toward one of the two magnets, depending on the direction of the current, and the mirror rotates.