EGR Valve Stem Sealing Assembly for High-Temperature Leak Tightness
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Solution Overview
Problem
Existing EGR valve assemblies face challenges in maintaining leak-tightness over the life of the valve, particularly in high-temperature environments, leading to potential exhaust gas leakage.
Innovation Solution
The assembly features a valve body, a slidable valve stem, a guide with a recess, and a seal with inner and outer lips that provide three leaktight supports, made from materials like PTFE and bronze, which are subjected to axial stress to ensure effective sealing, even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single sealing support is used in the EGR valve assembly, then the device complexity is reduced, but the sealing quality deteriorates leading to exhaust gas leakage
Solution Approach 1:
The sealing structure is divided into two separate sealing supports (first sealing support on the valve body and second sealing support on the guide) that work together to provide comprehensive sealing. This segmentation allows each support to address specific sealing zones, ensuring complete exhaust gas containment while maintaining a manageable structural complexity through modular design.
2Reliability
If the seal is not subjected to axial stress, then the ease of manufacture is improved, but the sealing effectiveness deteriorates at high temperatures
Solution Approach 1:
The seal is pre-stressed in the axial direction during assembly through the configuration of the first and second sealing supports. This preliminary action ensures that the seal maintains optimal contact pressure with the valve stem throughout operation, particularly at high temperatures where thermal expansion could otherwise compromise sealing effectiveness. The pre-stressing is achieved through the natural assembly process rather than requiring additional manufacturing steps.
3Reliability
If the inner lip does not extend into the recess, then the ease of manufacture is improved, but the sealing against the stem deteriorates
Solution Approach 1:
The inner lip of the seal is designed to extend into the recess of the guide only in the specific local area where stem sealing is required. This localized geometric modification provides enhanced sealing contact between the inner lip and valve stem where needed, while the rest of the seal maintains its standard geometry for ease of manufacture. The recess acts as a localized feature that improves sealing without requiring complex modifications throughout the entire seal structure.
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 significantly reduces leakage by maintaining leaktightness throughout the valve's operation, ensuring minimal exhaust gas escape, even at temperatures up to 230 degrees Celsius.
Implementation Method 1
the seal has a lip, in particular an inner lip, extending at least partially into the recess formed by the guide. This allows the seal to be deformed to subject it to a certain axial stress, along the sliding axis of the rod. During this stressing process, the seal deforms somewhat
Implementation Method 2
The seal is made in particular from PTFE-based material, for example marketed under the brand name Rulon ®. This valve is specifically designed to operate at high temperatures, particularly in a temperature range up to 230 degrees.
Data Source
Figure 1~3
AI summary
The invention relates to an assembly (2) for a valve (1) of a motor vehicle, said assembly comprising: a valve body (3), a shutter rod (4) able to slide relative to the valve body, a guide (5) arranged to guide the rod as this rod slides, packing (10) arranged to provide sealing around the rod, said packing being placed between the valve body and the guide and coming into contact with the valve body at two separate sealing seats (11, 12).