Piston-Operated Bypass Valve Control for Screw Compressor Vibration

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Solution Overview

Problem

Conventional screw compressors experience over-compression leading to repetitive opening and closing of the valve body, resulting in hit sound and vibration due to the imbalance of pressures acting on the valve body, which defeats the spring's biasing force and causes immediate balancing with discharge chamber pressure.

Innovation Solution

A screw compressor design incorporating a valve body with a piston and rod system, cylinder chambers, and electromagnetic valves controlled by a controller using suction and discharge pressure sensors to manage over-compression by opening and closing the valve body based on detected pressure ratios, eliminating the need for a spring and reducing vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a spring is used to bias the valve body to close the valve hole, then the valve body can be opened and closed to reduce over-compression, but the valve body repeats opening and closing rapidly causing hit sound and vibration

Engineering Contradiction:

Improveover-compression reductionVSAvoidhit sound and vibration

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the spring-based mechanical biasing system with a piston-cylinder chamber system that uses pressure differential control. Instead of relying on spring force, the valve body is moved by pressure differences between the compression work chamber and the cylinder chamber, eliminating the rapid repetitive opening/closing and associated vibrations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a cylinder chamber connected to the compression work chamber through a communication hole, using gas pressure (pneumatics) to control valve body movement. The pressure differential between the compression work chamber and cylinder chamber drives the piston and valve body, providing smooth control without mechanical spring rebound.

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Stress or pressure

If the valve body is opened to reduce over-compression, then compressed gas can be discharged through the bypass flow path, but pressure balancing causes immediate closing due to spring force

Engineering Contradiction:

Improvecompression work chamber pressureVSAvoidvalve body opening duration

Core Design Contradiction:

Stress or pressureVSDuration of action of moving object

Solution Approach 1:

The patent establishes a communication path between the compression work chamber and cylinder chamber before the valve body opens. This preliminary action allows pressure to equalize in advance, so when the valve body opens, there is no sudden pressure differential causing rapid closing. The pressure balancing occurs gradually through the communication hole rather than abruptly.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If pressure from the compression work chamber acts on the valve body, then over-compression can be detected, but the valve body immediately balances pressure and closes due to spring biasing

Engineering Contradiction:

Improveover-compression detectionVSAvoidvalve body operation smoothness

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent introduces the cylinder chamber and piston as intermediary elements between the compression work chamber and the valve body. Instead of pressure acting directly on the valve body, the pressure differential first moves the piston, which then moves the valve body. This intermediary mechanism provides smoother, more controlled operation without direct pressure冲击 on the valve body.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 hit sound and vibration by controlling the valve body's operation to prevent over-compression, ensuring reliable opening and closing regardless of compressor operation conditions, thereby improving performance and reducing unnecessary power consumption.

Implementation Method 1

a piston reciprocally moving in the cylinder chambers; a rod connecting together the piston and the valve body

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

a plurality of valve means provided at the pressure discharge path or the communication path, the valve means changing pressure in the cylinder chambers

Methodology Applied

Scientific EffectElectromagnetic actuation: Electromagnet

Implementation Method 3

a controller detecting whether or not over-compression is occurring in the compression work chamber

Methodology Applied

Scientific EffectPressure detection: Pressure Gradient

Data Source

PatentUS9169840B2Piston operated bypass valve for a screw compressor

Publication Date: 2015.10.27 HITACHI JOHNSON CONTROLS AIR CONDITIONING INC

AI summary

A screw compressor includes a valve hole formed at a discharge side end surface of a discharge casing and at a position opening to a compression work chamber; a bypass flow path having the valve hole and a discharge chamber communicate with each other; and a valve body arranged in the valve hole. The screw compressor also includes cylinder chambers provided on a rear surface side of the valve body; a piston reciprocally moving in the cylinder chambers; a rod connecting the piston and the valve body; communication paths for introducing a fluid on a discharge side into the cylinder chamber on a side opposite to a valve body side of the piston and on the valve body side; a pressure discharge path; a plurality of valve means; and a controller controlling the plurality of valves means.