GM Cryocooler Buffer Volume Design to Reduce Displacer Collision Noise

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Solution Overview

Problem

Gas-driven type Gifford-McMahon cryocoolers experience vibration and abnormal noise due to collisions between the displacer and the cylinder, which are not easily preventable with existing designs.

Innovation Solution

Incorporating a buffer volume and a gas spring mechanism to regulate pressure and reduce the differential pressure acting on the drive piston, thereby minimizing collisions and noise by compensating for gravitational forces and reducing the driving force during downward movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a gas-driven type GM cryocooler is used, then the refrigeration capacity is improved, but vibration and abnormal noise occur due to collisions between the displacer and cylinder

Engineering Contradiction:

Improverefrigeration capacityVSAvoidvibration and abnormal noise

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a buffer volume that stores high-pressure gas beforehand to cushion the downward movement of the drive piston. This pre-stored gas acts as a cushioning medium that reduces the impact force when the displacer approaches the cylinder, thereby reducing vibration and abnormal noise while maintaining the gas-driven refrigeration capacity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The buffer volume serves as an intermediary between the compressor and the drive piston. It mediates the pressure transmission by storing and releasing gas in a controlled manner, smoothing out pressure fluctuations and reducing the direct impact forces that cause vibration and noise in the gas-driven system.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the displacer is driven by gas pressure, then the mechanical complexity is reduced, but collisions between the displacer and cylinder become difficult to prevent

Engineering Contradiction:

Improvemechanical complexityVSAvoidcollision prevention

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The buffer volume is pre-filled with high-pressure gas to provide cushioning before the displacer reaches the cylinder. This beforehand preparation of the cushioning medium prevents collisions without requiring complex mechanical stopping mechanisms, thus maintaining low mechanical complexity while improving reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent uses pneumatic principles by introducing a buffer volume that utilizes compressed gas to control the motion of the drive piston. This pneumatic approach replaces potential mechanical collision prevention mechanisms with a gas-based cushioning system, maintaining simplicity while enhancing reliability.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Productivity

If the drive piston moves rapidly to improve cooling efficiency, then the refrigeration capacity increases, but the differential pressure fluctuations increase causing more vibration

Engineering Contradiction:

Improverefrigeration capacityVSAvoiddifferential pressure fluctuations

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The buffer volume acts as an intermediary pressure reservoir that smooths out differential pressure fluctuations. By providing a buffer zone for pressure changes, it allows the drive piston to move rapidly for high refrigeration capacity while reducing the amplitude of pressure fluctuations that cause vibration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer volume changes the pressure parameters by storing and releasing gas in a controlled manner. This transforms sharp pressure fluctuations into smoother pressure variations, enabling rapid piston movement for high efficiency while reducing vibration-causing pressure changes.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively reduces vibration and abnormal noise in gas-driven type Gifford-McMahon cryocoolers by mitigating collisions and controlling pressure fluctuations, enhancing operational stability and refrigeration capacity.

Implementation Method 1

a buffer volume connected between the auxiliary pressure switching valve and the compressor

Methodology Applied

Scientific EffectPressure regulation: Pressure Gradient

Implementation Method 2

compensating for gravitational forces and reducing the driving force during downward movement

Methodology Applied

Scientific EffectGravitational force compensation: Gravitation

Data Source

PatentUS11333407B2GM cryocooler with buffer volume communicating with drive chamber

Publication Date: 2022.05.17 SUMITOMO HEAVY IND LTD

AI summary

A GM cryocooler includes a compressor having a compressor discharge port and a compressor suction port, a displacer capable of reciprocating in an axial direction, a displacer cylinder accommodating the displacer, a drive piston connected to the displacer so as to drive the displacer in the axial direction, a drive chamber in which the drive piston is driven, a main pressure switching valve configured to alternately connect the displacer cylinder to the compressor discharge port and the compressor suction port, an auxiliary pressure switching valve configured to alternately connect the drive chamber to the compressor discharge port and the compressor suction port, and a buffer volume connected between the auxiliary pressure switching valve and the compressor.