Electromagnetic linear drive for a stirling cooler
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Solution Overview
Problem
Existing linear electric motors and generators face challenges such as high manufacturing costs, complexity, and integration difficulties, particularly when operating in pressurized environments, due to the need for large air gaps and complex magnetic circuits, which become exacerbated in larger scale applications like Stirling engines.
Innovation Solution
An electromechanical transducer design featuring a gas containment structure around the movable member but not the magnetic flux modules, with reinforcing portions outside the gaps to maintain stiffness without enlarging the gaps, and detachable coils for modular construction and thermal management, reducing material thickness and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the movable member is made thicker to increase stiffness against off-axis forces, then the radial stiffness improves, but the air gap thickness increases which reduces magnetic flux and increases energy loss
Solution Approach 1:
The invention introduces reinforcing portions that extend radially outward from the movable member, positioning the reinforcement in a different spatial dimension (radial direction) rather than increasing the axial thickness. This allows stiffness enhancement without increasing the air gap thickness in the magnetic flux path direction.
Solution Approach 2:
The reinforcing portions are strategically positioned only in regions where structural support is needed (outside the magnetic gaps), while keeping the gap regions thin to maintain magnetic flux efficiency. This localized reinforcement approach optimizes both mechanical strength and magnetic performance.
2Reliability
If the gas containment structure is made thicker to maintain radial clearance and support pressurized volume, then the structural integrity improves, but the eddy current losses increase
Solution Approach 1:
The gas containment structure is designed with variable thickness, being thinner in regions where eddy current losses would be significant and providing structural support through the reinforcing portions of the movable member. This localized thinning reduces energy losses while maintaining overall structural integrity.
Solution Approach 2:
The reinforcing portions of the movable member act as intermediary structural elements that provide radial support to the gas containment structure, allowing the containment walls to be thinner without compromising overall structural stability. The reinforcement serves as a mediator between the thin containment structure and the external forces.
3Device complexity
If coils are permanently attached to cores to simplify structure, then the device complexity reduces, but the thermal management and manufacturing flexibility deteriorate
Solution Approach 1:
The connection between coils and cores is made detachable rather than permanent, allowing the system to transition between different operational states. This dynamic connection enables coils to be removed for thermal management purposes or manufacturing adjustments, providing flexibility without permanently complicating the structure.
Solution Approach 2:
The motor is divided into separable components (coils and cores) that can be independently manufactured, assembled, and maintained. This segmentation allows for specialized manufacturing processes for each component and facilitates thermal management by enabling separate handling of heat-generating coil assemblies.
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 enhances the stiffness of the movable member against off-axis forces while maintaining electrical efficiency, reduces material thickness and costs, and facilitates easier integration and thermal management, making it suitable for various applications including Stirling cycle engines.
Implementation Method 1
Axial movement of the movable member 10 has the effect of varying the magnetic flux through the cores 4, which induces voltages in the coils 6; the polarity being opposite for neighbouring cores 4. If an alternating current of appropriate plurality is applied to the coils 6 then an alternating axial force is developed as desired.
Implementation Method 2
The movable member 10 constitutes the moving part of the motor and includes a plurality of rectangular magnets 8 arranged in a line and configured to move through the linearly aligned air gaps. The polarities of the magnets 8 alternate.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An improved electromechanical transducer is provided. In an embodiment, the transducer comprises at least two flux modules, each defining a magnetic circuit having a gap; an armature configured to move along a longitudinal axis passing through the gaps; and a gas containment structure laterally surrounding the armature, wherein: the at least two flux modules are provided outside the gas containment structure; and the armature comprises a reinforcing portion laterally outside of the gaps that is wider in a direction parallel to the flux in the gaps than at least one of the gaps.