Free-Piston Stirling Cooler Electromagnetic Layout for Smaller Diameter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional free-piston Stirling cycle machines have a large outer diameter due to the placement of the mover and stator, leading to increased weight and manufacturing costs, and reducing the number of coil turns to minimize diameter results in decreased performance and efficiency due to weaker magnetic fields and increased copper loss.
Innovation Solution
The electromagnetic mechanism is redesigned with the mover and piston axially aligned, the stator and cylinder also axially aligned, and the mover's outer diameter reduced to match or be less than the piston's, with the stator's inner diameter matching or exceeding the cylinder's, and the mover side of the piston made of electrically insulating material to minimize eddy currents and copper loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the mover and stator are disposed outside the piston and cylinder respectively, then the electromagnetic mechanism can be simply structured, but the outer diameter of the entire machine becomes larger
Solution Approach 1:
The mover is nested inside the cylinder by disposing it axially aligned with the piston, and the stator is nested such that its inner diameter matches or exceeds the cylinder's inner diameter. This nesting arrangement allows the electromagnetic mechanism components to occupy space within the existing cylinder-stator envelope, eliminating the need for additional outer diameter clearance while maintaining structural simplicity.
Solution Approach 2:
The arrangement transitions from a radial disposition (mover outside piston, stator outside cylinder) to an axial dimension alignment (mover axially aligned with piston, stator axially aligned with cylinder). This dimensional reconfiguration allows the electromagnetic mechanism to fit within the existing radial envelope of the cylinder-stator assembly, reducing the overall outer diameter while preserving the simple structural relationship between components.
2Area of stationary object
If the number of turns of electromagnetic coil is reduced to decrease outer diameter of stator, then the outer diameter decreases, but the magnetic field becomes weak and performance deteriorates
Solution Approach 1:
The patent changes the geometric parameters of the electromagnetic system by axially aligning the mover with the piston and positioning the stator with its inner diameter matching or exceeding the cylinder's inner diameter. This parameter change allows the magnetic field to be concentrated more effectively within the working volume, maintaining sufficient field strength with fewer coil turns, thus preserving power output while reducing stator outer diameter.
3Area of stationary object
If the wire is slenderized to ensure number of turns while forming smaller outer diameter, then the outer diameter decreases, but copper loss increases and efficiency decreases
Solution Approach 1:
By transitioning to an axial alignment configuration, the patent optimizes the three-dimensional arrangement of the electromagnetic components. This allows the coil windings to be positioned more efficiently in space, reducing the required wire length for a given number of turns. The axial configuration enables better utilization of the available winding space, maintaining adequate wire diameter to minimize copper loss while achieving a compact stator outer diameter.
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 configuration reduces the outer diameter of the Stirling cycle machine, minimizes axial extension, enhances magnetic flux density, and improves efficiency by reducing copper loss and eddy currents, while allowing for easier assembly and preventing mechanical damage.
Implementation Method 1
an electromagnetic mechanism comprised of a stator and a mover, wherein said mover is comprised of an inner yoke made of magnetic flux conducting material and a permanent magnet provided outside said inner yoke
Implementation Method 2
said mover is comprised of an inner yoke made of magnetic flux conducting material
Implementation Method 3
the mover side of the piston made of electrically insulating material to minimize eddy currents and copper loss
Data Source
AI summary
To provide a less expensive and high-efficient free-piston Stirling cycle machine with an outer diameter of entire machine being relatively small. In a Stirling cycle cooler as a free-piston Stirling cycle machine including a cylinder 7, a piston 18 which is reciprocable inside said cylinder 7 and an electromagnetic driving mechanism 19 for reciprocating said piston 18, said electromagnetic driving mechanism 19 is comprised of a mover 20 and a stator 35, said piston 18 and said mover 20 formed by disposing a permanent magnets 24 outside an inner yoke 23 made of magnetic flux conducting material are disposed in an axial alignment, and said stator 35 and said cylinder 7 are disposed in an axial alignment. By this disposition, the outer diameter Rm of said mover 20 of said electromagnetic driving mechanism 19 can be reduced, and consequently the inner diameter Rs and the outer diameter of said stator 35 provided outside said mover 20, eventually the outer diameter of entire Stirling cycle cooler can also be reduced.