Linear Stepper Motor Stator Overmould for Minimal Air Gap
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Solution Overview
Problem
Existing stators for linear stepper motors are costly due to their complex construction with numerous components, leading to high assembly times, inaccuracies, and reduced efficiency from larger air gaps, and they suffer from wobbling movements and axial play issues.
Innovation Solution
A novel stator design using a minimal number of stator sheets with integrated polar arms and a manufacturing process involving press-fitting, overmoulding, and insert-moulding to form an integral stator with a metallic sleeve, eliminating additional bearings and ensuring precise dimensional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple individual components are used to construct the stator, then the stator can provide radial support and axial positioning, but the number of components increases leading to high manufacturing costs, long assembly times, and accumulated tolerances
Solution Approach 1:
The patent merges multiple separate stator components into a single integral stator body through injection molding. The stator includes a stator body, stator yoke, and stator core that are formed as one piece, eliminating the need for separate assembly of these components. This reduces the number of parts, simplifies manufacturing, and eliminates accumulated tolerances while maintaining the necessary radial support and axial positioning functions.
Solution Approach 2:
The integral stator body performs multiple functions simultaneously: it provides radial support through its structural design, axial positioning through integrated features, magnetic flux path through the stator yoke and core, and mechanical support for the rotor. This multi-functionality in a single component reduces overall device complexity while maintaining reliability.
2Ease of manufacture
If a larger air gap is chosen to accommodate tolerance accumulation from multiple components, then assembly is easier, but the accuracy of the actuating force and efficiency of the linear stepper drive are reduced
Solution Approach 1:
By combining the stator body, yoke, and core into a single injection-molded component, the patent eliminates the tolerance accumulation that would otherwise occur between multiple assembled parts. This allows for a smaller, more precise air gap while maintaining ease of manufacture through the automated injection molding process, thereby improving actuating force accuracy without sacrificing manufacturing ease.
3Reliability
If traditional bearing arrangements with multiple components are used, then radial and axial support is provided, but assembly time increases and manufacturing costs rise
Solution Approach 1:
The patent integrates bearing functions directly into the integral stator body through molded-in bearing races and support features. This eliminates separate bearing components and their associated assembly steps, reducing assembly time and manufacturing costs while maintaining reliable radial and axial support for the rotor.
Solution Approach 2:
The injection-molded stator body incorporates flexible yet precise geometric features that provide bearing surfaces and support structures. These molded features replace traditional rigid bearing components while maintaining the necessary support functions, enabling faster assembly through automated molding processes.
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 new stator design reduces manufacturing complexity, costs, and increases actuating force while maintaining high precision and eliminating wobbling, allowing for efficient and cost-effective production in large quantities.
Implementation Method 1
The loaded mandrel is then placed in an injection-moulding tool and the stator sheets are overmoulded and insert-moulded to form an integral stator overmould
Implementation Method 2
at least four largely similar or identical stator sheets oriented towards each other and provided with inside bent portions forming polar arms
Data Source
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AI summary
The invention relates to a stator for a linear stepper motor and method for its manufacture. A stator (1) for a linear stepper motor includes four stator sheets (2) and two stator windings (4). The four stator sheets (2) are oriented towards each other, provided with bent polar arms, and have two inner stator sheets (2) each defining a sheet recess (3) and two outer stator sheets (2) that are arranged in an offset manner. The four stator sheets (2) are joined into an integral coil body by a stator overmould (6). One of the stator windings (4) is wound onto the coil body between one inner stator sheet (2) and one outer stator sheet (2) and connected with connector pins (12). The four stator sheets (2) and the stator overmould (6) including a stator flange (5) and a pin socket are integrally formed such that radial envelope surfaces of the at least four stator sheets (2) are free from the stator overmould (6). A stator recess (7) inside the stator (1) is arranged centrically in the stator overmould (6).