Stepper Motor Internal Vibration Damper
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Solution Overview
Problem
Stepper motors face challenges in reducing inherent vibration and noise due to their stepping motion, as existing solutions like external and internal dampers either increase motor size or expose additional rotating parts, and magnetic coupling-based solutions are not fully effective in eliminating vibrations.
Innovation Solution
Incorporating a mechanical damper within the rotor itself by positioning a permanent magnet in the stator assembly, allowing for an internal viscous damper with a dummy weight and viscous material that oscillates out-of-phase with the rotor, thereby reducing vibrations without increasing the rotor's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an external damper is attached to the motor's axial drive shaft, then vibration is effectively reduced and smooth motion is obtained, but an additional rotating part is exposed outside of the motor
Solution Approach 1:
The damper is nested within the rotor assembly, specifically positioned between the rotor and the stator. This internal placement eliminates the need for external rotating parts while maintaining the vibration damping function. The dummy weight and viscous material are contained within the rotor's internal space, effectively hiding the damping mechanism inside the motor structure.
2Device complexity
If an internal damper is introduced to avoid external rotating parts, then device complexity is reduced, but extra space inside the motor is required, increasing overall motor size
Solution Approach 1:
The damper utilizes the radial dimension of the motor by positioning the dummy weight and viscous material in the radial space between the rotor and stator. This radial placement allows the damping mechanism to fit within the existing motor envelope without significantly increasing the overall motor size, effectively using unused radial space for the damping function.
3Force
If the permanent magnet is located in the rotor, then magnetic coupling is strong, but no space is available for internal damper incorporation
Solution Approach 1:
The permanent magnet is extracted from the rotor and relocated to the stator assembly. This extraction creates two benefits: it maintains strong magnetic coupling through the stator-rotor interface, and it frees up internal space within the rotor structure to accommodate the dummy weight and viscous material damper mechanism without compromising magnetic performance.
4Object-affected harmful factors
If varying stator pitch angles is used to reduce detent torque, then noise and vibration are reduced, but magnetic coupling between stator and rotor creates inherent vibration that is almost impossible to eliminate
Solution Approach 1:
The inherent magnetic coupling that creates vibration is converted into a benefit by using the same magnetic field to drive a dummy weight in the damper. The magnetic force that causes rotor vibration also drives the dummy weight to oscillate out-of-phase, and the viscous material dissipates this energy, transforming the harmful magnetic vibration into a controlled damping mechanism.
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 internal damper effectively reduces motor vibrations by providing counterweight and viscosity-induced delay, minimizing detent torque and noise, as shown in rotational velocity graphs, while maintaining compact motor design.
Implementation Method 1
The damping element may be a viscous damper, wherein a dummy weight, situated together with viscous material within the rotor's housing, oscillates out-of-phase with respect to the rotor.
Implementation Method 2
The internal damper effectively reduces motor vibrations by providing counterweight and viscosity-induced delay
Data Source
AI summary
A stepper motor has a stator winding assembly with a permanent ring magnet located radially outside of electromagnetic windings for the stator poles. The permanent ring magnet remotely magnetizes a rotor seated by bearings on an axial shaft so as to rotate within the stator winding assembly, thereby freeing up space within the rotor for an internal damper. The rotor has a cylindrical damping weight enclosed within, but not fixed to, the rotor. The weight ideally has a rotational moment of inertia that substantially matches that of the rotor. The weight is elastically coupled to the rotor by a viscous material contained in the rotor and filling the space between the weight and the rotor and between the weight and the axial shaft. The viscosity of this material is selected such that motion of the weight is delayed, preferably so as to be substantially 180° out-of-phase with, but at the same frequency as, the stepping rotation of the rotor. The weight thereby serves as a counterweight to the rotor so as to cancel vibrations generated by stepping of the rotor.