Single-Screw Compressor Pin Mechanism for Pressure Relief

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Solution Overview

Problem

Single-screw compressors face issues with internal pressure buildup due to liquid compression, leading to potential gate rotor breakage and costly maintenance, as existing solutions require high sampling frequencies and dedicated detectors, increasing manufacturing costs and operational downtime.

Innovation Solution

Incorporating a pin mechanism that press-fits into gate-rotor support holes, allowing the pin to disengage when a target pressure difference is reached, thereby reducing internal pressure by communicating the compression chamber with a low-pressure space, preventing gate rotor breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a dedicated detector and high sampling frequency are used to detect internal pressure and control discharge timing, then liquid compression can be detected early and gate rotor breakage can be prevented, but manufacturing cost increases

Engineering Contradiction:
Improvegate rotor breakage preventionVSAvoiddetector and control system
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The pin mechanism automatically activates when liquid compression occurs, releasing the compression chamber content without requiring external detection or control systems. The system serves itself by using the pressure buildup to trigger the safety mechanism, eliminating the need for dedicated detectors and complex control circuits.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The harmful high pressure buildup from liquid compression is converted into a beneficial trigger signal that activates the pin mechanism. The pressure that would otherwise cause damage is instead used to push the pin and open the release valve, transforming the harmful effect into a protective action.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

2Ease of manufacture

If the gate rotor is made of synthetic resin material to avoid metal-to-metal contact, then wear and damage are reduced, but the gate rotor becomes vulnerable to breakage under high pressure

Engineering Contradiction:
Improvematerial selectionVSAvoidgate rotor strength
Core Design Contradiction:
Ease of manufactureVSStrength

Solution Approach 1:

The pin mechanism is pre-positioned to block the hole in the gate rotor, creating a safety barrier before liquid compression occurs. When abnormal pressure builds up, the pin is pushed out to release the pressure, preventing the gate rotor from experiencing destructive forces that would cause breakage.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The pin acts as an intermediary element between the compression chamber and the external environment. It mediates the pressure buildup by remaining in place during normal operation and automatically releasing pressure when needed, protecting the gate rotor from direct exposure to damaging high pressures.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of repair

If maintenance is performed by complete disassembly and removal of fracture fragments, then the compressor can be restored, but operational downtime and costs increase significantly

Engineering Contradiction:
Improvecompressor restorationVSAvoidoperational downtime
Core Design Contradiction:
Ease of repairVSLoss of time

Solution Approach 1:

The pin is designed as a sacrificial component that can be easily replaced. When liquid compression occurs, the pin is pushed out and can be quickly removed and replaced without disassembling the entire compressor, making it a disposable safety element that minimizes maintenance time and complexity.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The safety mechanism is segmented into separate replaceable components (pin, hole, release valve) rather than being integrated into the main compressor structure. This segmentation allows the safety mechanism to be independently maintained or replaced without affecting the rest of the compressor system, reducing operational downtime.

Inventive Principle:
Principle #1Segmentation

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 pin mechanism effectively reduces internal pressure and prevents gate rotor breakage, enhancing operational safety and reducing maintenance costs by allowing for earlier detection and management of pressure spikes, thus maintaining compressor functionality.

Implementation Method 1

a pin 14 is provided in the gate-rotor support hole 80 in such a way as to be press-fitted therein

Methodology Applied
Scientific EffectPress-fit: Friction

Implementation Method 2

the pin comes off the gate-rotor support hole 80 when a target pressure difference between the compression chamber and the low-pressure space is achieved

Methodology Applied
Scientific EffectPressure difference: Pressure Gradient

Data Source

PatentEP3557064B1Single-screw compressor and refrigeration/air-conditioning device equipped with same
Publication Date: 2020.09.23 MITSUBISHI ELECTRIC CORP
  • EP3557064B1 patent drawingFigure 1~2
  • EP3557064B1 patent drawingFigure 3~4
  • EP3557064B1 patent drawingFigure 5~6

AI summary

A single-screw compressor includes: a casing which forms an outer periphery thereof; a screw including spiral tooth grooves formed in its outer peripheral surface; a gate rotor which defines along with the casing and the screw a compression chamber, and which includes gate-rotor teeth formed to fit in the tooth grooves; and a gate-rotor support which supports the gate rotor, and includes gate-rotor support teeth provided to face the gate-rotor teeth. A gate-rotor hole is formed in at least one of the gate-rotor teeth to extend therethrough in a thickness direction thereof. A support hole is formed in the gate-rotor support teeth to extend through at least one of the gate-rotor support teeth in a thickness direction thereof, and has ends one of which communicates with the gate-rotor hole and the other of which communicates with a low-pressure space provided in the casing. A pin is provided in the support hole in such a way as to be press-fitted therein. The pin comes off the support hole when an internal pressure of the compression chamber is raised to a level, thereby causing the compression chamber to communicate with the low-pressure space.