Free piston Stirling refrigerator
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Solution Overview
Problem
Conventional free piston Stirling refrigerators require complex and costly systems for detecting physical quantities to control piston and displacer amplitudes, leading to potential collisions and increased system complexity.
Innovation Solution
A free piston Stirling refrigerator configuration that uses an inverter circuit to generate alternating current, a current detection circuit to detect turbulence, and a control circuit to adjust the linear motor output based on detected turbulence, allowing for collision restriction through a simple and inexpensive setup by calculating difference values and averaging waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical quantity detection units are added to control piston and displacer amplitudes, then collision restriction is improved, but device complexity increases
Solution Approach 1:
The patent extracts the collision detection function from complex physical quantity detection units and implements it through simple current detection. By monitoring current fluctuations in the linear motor, the system detects piston-displacer collisions without requiring additional sensors for position, velocity, or acceleration measurement.
Solution Approach 2:
The current detection circuit serves multiple functions: it monitors the operation status of the linear motor, detects piston-displacer collisions, and provides feedback for control adjustments. This multi-functional approach eliminates the need for separate detection units for each parameter.
2Reliability
If complex calculation systems are implemented for continuous position tracking, then collision restriction is improved, but device complexity increases
Solution Approach 1:
The patent extracts the collision detection function from complex calculation systems and implements it through simple current fluctuation analysis. By monitoring current variations directly, the system identifies collisions without requiring continuous position calculations or complex control algorithms.
3Measurement precision
If multiple detection units are added for continuous position calculation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts collision detection capability from complex position measurement systems and implements it through simple current monitoring. The current fluctuations directly indicate collision events, providing sufficient measurement precision for collision detection without requiring multiple sensors or complex calculation systems.
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 effectively restricts collisions and maintains stability by controlling the linear motor output based on turbulence detection, reducing system complexity and cost while maintaining operational stability across varying conditions.
Implementation Method 1
a linear motor for reciprocating the piston
Implementation Method 2
a current detection circuit for detecting the alternating current outputted from the inverter circuit
Data Source
AI summary
A free piston Stirling refrigerator of the present invention has a cylinder provided inside a casing; a piston and a displacer that are provided in a way such that they are capable of reciprocating inside the cylinder; a linear motor for reciprocating the piston; and a control unit for controlling the operation of the linear motor. Particularly, the control unit has an inverter circuit for generating an alternating current with a given frequency and then supplying the alternating current to the linear motor; a current detection circuit for detecting the current outputted from the inverter circuit; and a control circuit for controlling the output from the inverter circuit based on a turbulence in the current detected by the current detection circuit. Thus, collisions between the piston and the displacer (i.e. hitting) can be restricted through an inexpensive configuration and a simple control.