Cryocooler Spool Valve Flow Path Switching to Reduce Pressure Loss

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Solution Overview

Problem

Existing cryocoolers face challenges in reducing pressure loss in working gas flow paths, leading to increased frictional resistance and torque requirements for rotary valves, resulting in larger drive sources and increased size, particularly in large-size cryocoolers.

Innovation Solution

The implementation of a spool valve and pressure control mechanism in a cryocooler that connects the expansion chamber to compressor discharge and suction ports, generating periodic pressure fluctuations, and controlling pressure to minimize size increase in the drive source by reducing pressure loss and internal flow path expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a rotary valve is used as a flow path switching mechanism, then the flow path can be switched to properly operate the cryocooler, but the pressure loss in working gas flow paths increases and frictional resistance increases

Engineering Contradiction:

Improveflow path switching capabilityVSAvoidpressure loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent replaces the traditional rotary valve mechanical system with a spool valve system that uses gas pressure differential to drive the spool, eliminating the need for mechanical rotation and reducing frictional resistance and pressure loss in the working gas flow paths

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The spool valve is driven by a pressure control mechanism that uses compressed gas to create pressure differential across the spool, enabling flow path switching through pneumatic actuation rather than mechanical rotation, thereby reducing energy loss

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Ease of operation

If a rotary valve is used as a flow path switching mechanism, then the flow path can be switched, but torque requirements increase and drive source size increases

Engineering Contradiction:

Improveflow path switching capabilityVSAvoidtorque requirement

Core Design Contradiction:

Ease of operationVSPower

Solution Approach 1:

The patent eliminates the need for high-torque mechanical rotation by replacing the rotary valve with a spool valve system that uses low-torque pneumatic actuation through the pressure control mechanism

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The spool valve system is self-actuating through the pressure control mechanism that automatically regulates gas pressure to move the spool between positions, eliminating the need for external high-torque drive mechanisms

Inventive Principle:

Principle #25Self-service

3Loss of energy

If pressure loss is reduced in working gas flow paths, then energy efficiency improves, but the drive source size may increase due to pressure control mechanism

Engineering Contradiction:

Improvepressure lossVSAvoiddrive source size

Core Design Contradiction:

Loss of energyVSVolume of moving object

Solution Approach 1:

The patent combines the flow path switching function and pressure control function into an integrated spool valve system, where the spool serves both as the flow path switch and the pressure-controlled actuator, eliminating the need for separate drive mechanisms and reducing overall size

Inventive Principle:

Principle #5Merging (Combining)

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 size increase of the drive source and minimizes noise and vibration transmission, while maintaining cooling capacity, by using a spool valve as the flow path switching mechanism and a pressure control mechanism with opposite phase pressure fluctuations.

Implementation Method 1

the drive piston being driven in the axial direction by a pressure difference between the piston drive chamber and the expansion chamber

Methodology Applied

Scientific EffectPressure difference: Pressure Gradient

Implementation Method 2

generate a pressure fluctuation having an opposite phase to the pressure fluctuation in the expansion chamber in the piston drive chamber

Methodology Applied

Scientific EffectPressure fluctuation: Pressure Gradient

Data Source

PatentUS11530847B2Cryocooler and flow path switching mechanism of cryocooler

Publication Date: 2022.12.20 SUMITOMO HEAVY IND LTD

AI summary

A cryocooler includes a cold head including a displacer movable in an axial direction, a drive piston connected to the displacer to move the displacer in the axial direction, an expansion chamber formed with the displacer, a piston drive chamber formed with the drive piston, a spool valve including a valve drive chamber, a spool that moves between a first position and a second position in response to a pressure of the valve drive chamber, and a pressure control mechanism configured to control a pressure of the valve drive chamber so that the spool reciprocates between the first position and the second position, and to generate a pressure fluctuation having an opposite phase to the pressure fluctuation in the expansion chamber in the piston drive chamber in synchronization with the reciprocation of the spool.