EGR Valve Assembly With Tapered Sealing and Misalignment Compensation
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Solution Overview
Problem
Inefficient control of exhaust gas recirculation in internal combustion engines leads to air/fuel mixtures that are too rich or too lean for efficient combustion, resulting in improper engine performance and emissions.
Innovation Solution
A valve assembly with a valve housing, a shaft, and a flap that can move between open and closed positions, featuring sealing members with tapered ends to inhibit gas flow, and a spider assembly to accommodate misalignment between drive and driven shafts, along with a coining process to ensure precise fit and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sealing member with a flat end surface is used, then the manufacturing process is simpler, but the sealing precision deteriorates due to misalignment between shafts
Solution Approach 1:
The sealing member's end surface geometry is changed from flat to tapered, transforming the contact interface parameters. This tapered configuration (with specific angle ranges like 15-45 degrees) allows the sealing surface to conform to the flap even when shafts are misaligned, maintaining sealing precision while accommodating manufacturing tolerances and assembly variations
Solution Approach 2:
The tapered geometry of the sealing member provides a built-in compensation mechanism that anticipates and cushions against misalignment issues before they cause sealing failures. The gradual taper allows for self-adjustment and maintains contact pressure across the sealing surface despite positional deviations between shafts
2Reliability
If a rigid connection between drive shaft and flap is used, then the force transmission is more efficient, but the system cannot accommodate misalignment between shafts
Solution Approach 1:
The sealing member is designed with a tapered end surface that can dynamically adjust its contact angle and position relative to the flap. This dynamic geometry allows the sealing interface to adapt to misalignment conditions while maintaining effective sealing, combining rigid force transmission with flexible alignment accommodation
Solution Approach 2:
The tapered end surface creates an asymmetric geometry that is specifically optimized for sealing contact. This asymmetric shape (rather than a symmetric flat surface) allows the sealing member to engage the flap at varying angles, providing tolerance for shaft misalignment while ensuring reliable sealing contact
3Reliability
If multiple sealing members are used to improve sealing, then the sealing effectiveness increases, but the device complexity and manufacturing cost increase
Solution Approach 1:
The sealing member is divided into multiple functional surfaces (tapered end surface, lateral surfaces, circumferential end surface) that work together to provide comprehensive sealing. This segmentation of sealing functions within a single component achieves effective sealing across multiple potential leak paths without requiring multiple separate sealing members
Solution Approach 2:
The sealing member is designed as a multi-functional component that simultaneously provides sealing contact, alignment tolerance compensation, and force distribution. The tapered geometry enables this single component to perform multiple sealing-related functions that would otherwise require several separate components, reducing overall device complexity
Data Source
AI summary
An exhaust gas recirculation (EGR) valve assembly includes a valve housing with a wall defining a flow passage. The valve housing defines a bore communicating with the flow passage. A shaft is supported in the bore and extends into the flow passage. A flap is supported on the shaft in the flow passage. The flap is movable relative to the flow passage between a closed position and an open position. A sealing member projects from the wall into the flow path. The sealing member has a sealing surface that interacts with the flap in the closed position to inhibit gas flow through the flow passage, an opposite surface tapering toward the wall, and a circumferential end surface proximate and tapered away from the bore. The flap is coined against the sealing surface. A spider assembly is positioned between the shaft and a drive shaft of an actuator assembly.