Cryocooler Pressure-Based Displacer Control to Reduce Cost and Size
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Solution Overview
Problem
Existing cryocoolers face challenges in optimizing the movement speed of the displacer without the need for expensive position detectors, which can increase manufacturing costs and device size.
Innovation Solution
A cryocooler system that includes an expander motor with a motor rotary shaft connected to a displacer for linear reciprocation, a rotary valve for gas control, and a controller that detects pressure fluctuations to synchronize motor drive waveforms with feature points, optimizing displacer movement without requiring position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a position detector is added to optimize displacer movement speed, then the cooling efficiency is improved, but the manufacturing cost and device size increase
Solution Approach 1:
The patent replaces the mechanical position detection system with a pressure-based detection system. The pressure detector monitors pressure fluctuations in the expansion space, which naturally occur during the refrigeration cycle, to infer the displacer position and optimize motor speed without requiring additional mechanical sensors or detectors.
Solution Approach 2:
The system uses the existing pressure variations within the refrigeration cycle itself as the detection signal. The pressure fluctuations that naturally occur during compression and expansion phases serve as the basis for position detection, eliminating the need for separate detection mechanisms.
2Productivity
If a position detector is added to optimize displacer movement speed, then the cooling efficiency is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical position detection system with a pressure-based detection system. The pressure detector monitors pressure fluctuations in the expansion space, which naturally occur during the refrigeration cycle, to infer the displacer position and optimize motor speed without requiring additional mechanical sensors or detectors.
Solution Approach 2:
The system uses the existing pressure variations within the refrigeration cycle itself as the detection signal. The pressure fluctuations that naturally occur during compression and expansion phases serve as the basis for position detection, eliminating the need for separate detection mechanisms.
3Use of energy by moving object
If the motor rotation speed is optimized based on pressure fluctuations, then the energy consumption is reduced, but the control complexity increases
Solution Approach 1:
The patent implements a feedback control system where the pressure detector continuously monitors pressure fluctuations and feeds this information to the controller. The controller adjusts the motor rotation speed in real-time based on the detected pressure signals, creating a closed-loop system that optimizes energy consumption while maintaining effective control through straightforward pressure-speed correlation.
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
Enables efficient operation of the cryocooler by optimizing displacer movement, reducing manufacturing costs and size, while maintaining cooling capacity and efficiency, and optimizing energy consumption and reducing the rotation speed of the motor drive waveform in synchronization with the feature point that periodically appears in the measured pressure.
Implementation Method 1
a pressure sensor that measures a pressure of the working gas and outputs a measurement signal indicating the measured pressure
Implementation Method 2
an expander provided with an expander motor having a motor rotary shaft, a displacer that is connected to the motor rotary shaft to reciprocate linearly by rotation of the motor rotary shaft
Implementation Method 3
a refrigeration cycle is configured in the cryocooler by changing the pressure in the expansion space appropriately in synchronization with the periodic volume fluctuation in the expansion space
Data Source
AI summary
A cryocooler includes an expander provided with an expander motor including a motor rotary shaft, a displacer that changes a volume of an expansion space of a working gas by reciprocating linearly by the motor rotation shaft rotating, and a rotary valve that controls intake and exhaust of the working gas into the expansion space by rotating by the motor rotation shaft rotating, a pressure sensor that measures a pressure of the working gas and outputs a measurement signal indicating the measured pressure, and a controller that receives the measurement signal, detects a feature point appearing periodically in the measured pressure during an operation of the cryocooler, acquires a motor drive waveform indicating a command rotation speed of the motor rotary shaft determined to vary within one rotation of the motor rotary shaft, and outputs the motor drive waveform in synchronization with the feature point appearing periodically.