PM Stepping Motor Stator Assembly Coaxial Alignment
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Solution Overview
Problem
Conventional small permanent magnet stepping motors face challenges in aligning bearings coaxially with the stator units, leading to uneven gaps between the rotor magnet and pole teeth, which affects motor stability and performance.
Innovation Solution
The stator units are axially coupled with resin molding, forming protrusions from the outer flanges to engage with bearings, allowing for precise coaxial alignment and stable retention, minimizing the gap between the rotor magnet and stator pole teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bearings are attached to front and rear plates individually, then assembly is simplified, but coaxial alignment precision deteriorates
Solution Approach 1:
The patent merges the bearing support function into the stator unit structure itself by forming bearing engagement holes directly in the pole teeth of the inner and outer yokes. This eliminates the need for separate front and rear plates, allowing bearings to be positioned precisely relative to the pole teeth while simplifying the overall assembly structure.
Solution Approach 2:
The patent introduces bearing engagement holes as intermediary structures formed in the pole teeth, which serve as precise reference features for bearing positioning. These holes act as mediators that ensure accurate coaxial alignment between bearings and pole teeth without requiring complex plate attachments.
2Ease of manufacture
If pole teeth are formed by bending process, then manufacturing is easier, but bearing retention stability deteriorates
Solution Approach 1:
The patent applies local quality by forming bearing engagement holes with precise dimensions and positions in the pole teeth. These localized features provide stable bearing retention while the rest of the pole teeth maintain their bent shape for magnetic function. The holes are positioned to ensure uniform gaps between rotor magnet and pole teeth surfaces.
Solution Approach 2:
The bearing engagement holes are formed in advance during the pole teeth manufacturing process, before bearing installation. This preliminary action ensures that the holes are precisely positioned and sized to provide stable bearing retention, eliminating the need for subsequent adjustments or modifications.
3Power
If gap between rotor magnet and pole teeth is minimized, then motor performance is improved, but alignment difficulty increases
Solution Approach 1:
The bearing engagement holes are designed to automatically guide bearing installation and ensure proper positioning. The precise dimensions and positions of these holes enable bearings to be installed without complex alignment procedures, while still achieving uniform minimal gaps between the rotor magnet and pole teeth surfaces.
Solution Approach 2:
The patent replaces complex mechanical alignment systems with precisely formed bearing engagement holes. Instead of using multiple adjustment mechanisms or complex fixture systems, the holes themselves provide the necessary geometric constraints to achieve accurate alignment and uniform gaps through their precise formation during manufacturing.
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 approach ensures uniform and minimized gaps between the rotor magnet and stator pole teeth, enhancing motor stability and performance while allowing for downsizing of the motor diameter.
Implementation Method 1
two bobbins are formed of the molding resin material to be consolidated with the two inner yokes
Implementation Method 2
a magnet 132 magnetized circumferentially... the outer circumferential surface of the magnet 132 opposes the pole teeth 131 and 123 of the inner and outer yokes 111 and 122 with a gap provided in between
Data Source
AI summary
A PM stepping motor includes: a stator assembly composed of two stator units which are axially coupled to each other with a molding resin material, and each of which includes: inner and outer yokes each having a plurality of pole teeth; a bobbin including inner and outer flanges; and a coil wound around the bobbin, thus providing two such inner yokes, outer yokes, bobbins and coils in total; a rotor assembly which includes a shaft and a magnet, and which is rotatably disposed in the hollow of the stator assembly; and two bearings to rotatably support the shaft of the rotor assembly, wherein the two bobbins are formed of the molding resin material to be consolidated with the two inner yokes, and wherein a plurality of protrusions are formed of the molding resin material to extend integrally from the outer flange of each of the two bobbins.