Cryocooler Collar Chamber Venting for Smooth Displacer Return

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Solution Overview

Problem

In gas-driven cryocoolers with a collar bumper type, the displacer's movement from the bottom dead center to the top dead center is hindered due to a low-pressure sealed region formed when the displacer reaches the bottom dead center, causing interference and vibration issues.

Innovation Solution

Incorporating a communication passage in the collar or collar chamber to ensure communication between the upper and lower sections when the displacer is at the bottom dead center, reducing the differential pressure and facilitating the upward movement of the displacer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a collar bumper is provided to prevent interference between the displacer and cylinder end portion, then vibration and noise are reduced, but the displacer movement from bottom dead center to top dead center is hindered due to low-pressure sealed region formation

Engineering Contradiction:

Improvevibration and noiseVSAvoiddisplacer movement

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The collar chamber is divided into an upper section and a lower section by the collar, with the communication passage selectively connecting these sections. This segmentation allows the system to maintain separate pressure zones while providing a controlled pathway for pressure equalization when needed, resolving the contradiction between maintaining sealed regions for vibration reduction and enabling displacer movement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The communication passage acts as an intermediary element between the upper and lower sections of the collar chamber. It remains closed during normal operation to maintain pressure differential for vibration reduction, but opens when the displacer is at bottom dead center to equalize pressure and facilitate upward movement, thus mediating between the two conflicting requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the lower section is sealed by a second seal portion, then the collar bumper can effectively mitigate interference, but a low-pressure sealed region is formed that creates differential pressure hindering displacer movement

Engineering Contradiction:

Improvesealing performanceVSAvoiddisplacer movement

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The communication passage is designed to dynamically change its state between closed and open positions. It remains closed during most of the displacer stroke to maintain sealing performance and prevent interference, but opens when the displacer reaches bottom dead center to allow pressure equalization and enable upward movement, thus adapting the sealing behavior to the operational requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the pressure parameter in the lower section by controlling the communication passage. When the displacer is at bottom dead center, the passage opens to equalize pressure between upper and lower sections, eliminating the differential pressure that hinders movement. During other phases, the passage remains closed to maintain the pressure differential needed for reliable sealing and interference mitigation.

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

This design allows for smooth movement of the displacer from the bottom dead center to the top dead center, reducing vibration and noise by preventing interference and maintaining efficient operation of the cryocooler.

Implementation Method 1

a displacer disposed inside the cylinder and driven to reciprocate by a gas pressure

Methodology Applied

Scientific EffectGas pressure: Pressure Increase

Implementation Method 2

a lower bumper provided in the lower section to mitigate interference between the displacer and the cylinder when the displacer is located at a bottom dead center

Methodology Applied

Scientific EffectImpact mitigation: Impact Force

Data Source

PatentUS11774147B2Cryocooler

Publication Date: 2023.10.03 SUMITOMO HEAVY IND LTD

AI summary

There is provided a cryocooler including a cylinder, a displacer disposed inside the cylinder and driven to reciprocate by a gas pressure, a collar rigidly connected to the displacer to reciprocate together with the displacer, a collar chamber divided into an upper section and a lower section by the collar, a second seal portion provided between the displacer and the cylinder to seal the lower section, a lower bumper provided in the lower section to mitigate interference between the displacer and the cylinder when the displacer is located at a bottom dead center, and a communication passage formed in the collar or in the collar chamber to ensure communication between the upper section and the lower section when the displacer is located at a bottom dead center.