Screw Compressor Capacity Control Valve Guide Body
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Solution Overview
Problem
Conventional screw compressors experience fluid leakage and reduced pressure maintenance due to the inclination of the piston rod, leading to increased wear and the need for frequent part replacement, as the piston rod and rod hole contact results in abrasion and gap formation during capacity control operations.
Innovation Solution
A guide body with a high hardness, possibly achieved through heat treatment, is integrated into the cylinder end wall to guide the piston rod, utilizing O-rings for sealing to prevent fluid leakage and maintain pressure within the cylinder, allowing the capacity control valve to be accurately positioned and enhancing control performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the piston rod is allowed to move in a large range to enlarge capacity control range, then the capacity control range is improved, but the contact between piston rod and rod hole increases causing increased abrasion and fluid leakage
Solution Approach 1:
A guide body is introduced as an intermediary component between the piston rod and the cylinder end wall. The guide body includes a guiding hole that guides the piston rod, preventing direct contact between the piston rod and the rod hole in the cylinder end wall. This mediator reduces abrasion and prevents fluid leakage while allowing the piston rod to move through a large range for enlarged capacity control.
Solution Approach 2:
The guiding function is segmented from the cylinder end wall structure. Instead of having the piston rod move directly through a hole in the end wall, the guiding function is separated into a distinct guide body component. This segmentation allows the guide body to be optimized specifically for guiding and sealing functions, reducing wear and preventing leakage.
2Ease of operation
If the piston rod and rod hole are brought into contact to guide the piston rod, then the guiding function is achieved, but abrasion occurs in the rod hole causing gap formation and fluid leakage
Solution Approach 1:
The guide body acts as an intermediary between the piston rod and the cylinder end wall. The guiding hole in the guide body provides the necessary guiding function, while the seal member (O-ring) prevents fluid leakage. This intermediary structure eliminates direct contact between the piston rod and the rod hole, preventing abrasion and gap formation.
Solution Approach 2:
The mechanical contact-based guiding system (piston rod directly contacting rod hole) is replaced with a sealed guiding system. The guide body with its guiding hole provides mechanical guidance, while the elastomeric seal member (O-ring) provides sealing without requiring tight mechanical contact, thus preventing abrasion.
3Reliability
If pressure fluid leaks from the gap between rod hole and piston rod, then the cylinder pressure cannot be maintained, but the capacity control valve position control is affected
Solution Approach 1:
The guide body with seal member acts as an intermediary sealing system between the piston rod and the cylinder end wall. This intermediary sealing structure prevents pressure fluid from leaking through the gap, maintaining cylinder pressure and ensuring accurate capacity control valve positioning.
Solution Approach 2:
An elastomeric seal member (O-ring) is used to provide sealing between the piston rod and the guide body. The flexible nature of the elastomeric material allows it to conform to the piston rod surface and maintain sealing effectiveness, preventing pressure fluid leakage and maintaining cylinder pressure for precise valve control.
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 prevents fluid leakage, maintains pressure within the cylinder, and improves the reliability and longevity of the capacity control valve, reducing the need for frequent part exchanges and allowing for increased capacity control range without compromising performance.
Implementation Method 1
an O-ring which seals an outer peripheral surface of the piston rod
Implementation Method 2
a guide body having a guiding hole for guiding the piston rod
Implementation Method 3
the guide body may be made high in hardness by means of heat treatment as compared with the cylinder end wall
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A capacity control device for a screw compressor comprising a capacity control valve (7), a piston rod (18) connected to the capacity control valve (7), a piston (17), and a cylinder (16) that guides the piston (17) slidably, and wherein a guide body (24) for permitting and guiding inclined movements of the piston rod (18) is provided on that end wall (22) toward the piston rod (18), which forms the cylinder (16).