Injector Corrosion Isolation Seal Design
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Solution Overview
Problem
Corrosive liquids, such as saltwater, can seep past the O-ring seal in a Reductant Delivery Unit (RDU) fluid injector due to differing thermal expansion rates of plastic and metallic components, leading to corrosion and electrical shorting.
Innovation Solution
A fluid injector design featuring a metal housing with a molded plastic body and a carrier with a stepped portion integral to the distal end, where a secondary seal member, like an elastomer O-ring, contacts both the stepped portion and the carrier to prevent liquids from entering the space between the housing and the body, thereby isolating vulnerable metal components from corrosive environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single O-ring seal is used between the metal housing and carrier, then the structure remains simple, but corrosive liquids can seep into the internal space causing corrosion and electrical shorting
Solution Approach 1:
The seal structure is divided into two separate O-rings: a first O-ring seal positioned between the metal housing and carrier, and a second O-ring seal positioned between the plastic body and carrier. This segmentation allows each seal to perform a specific function - the first seal handles primary sealing while the second seal prevents liquid migration into the internal space, thereby resolving the contradiction between maintaining structural simplicity and achieving reliable corrosion protection.
Solution Approach 2:
The carrier acts as an intermediary component between the metal housing and plastic body, providing a interface that accommodates both seals. The carrier's stepped configuration creates distinct sealing surfaces that allow the two O-rings to function independently, mediating the interaction between dissimilar materials (metal and plastic) while preventing corrosive liquid intrusion.
2Reliability
If plastic body and metal housing are directly connected, then manufacturing remains simple, but thermal expansion differences create gaps allowing liquid ingress
Solution Approach 1:
The carrier serves as an intermediary component between the plastic body and metal housing, providing a mechanical interface that accommodates differential thermal expansion. The carrier's stepped configuration creates sealing surfaces that maintain seal integrity despite expansion/contraction movements, eliminating the need for direct plastic-to-metal connection while preserving manufacturing simplicity.
Solution Approach 2:
The seal structure is designed to accommodate parameter changes in the form of thermal expansion and contraction. The two O-ring configuration allows the seals to compress and expand within their grooves as temperatures vary, maintaining seal integrity throughout the operating temperature range without requiring complex expansion joints or adjustable mechanisms.
3Reliability
If the O-ring seals only between housing and carrier, then the seal installation remains simple, but liquid can be drawn into the injector interior causing corrosion
Solution Approach 1:
The sealing function is segmented into two distinct locations: the first O-ring seals between the metal housing and carrier, while the second O-ring seals between the plastic body and carrier. This segmentation ensures that even if liquid bypasses the first seal, the second seal provides a secondary barrier preventing liquid entry into the injector interior, thereby achieving enhanced corrosion resistance through functional segmentation.
Solution Approach 2:
The dual O-ring configuration provides beforehand cushioning against corrosion by creating a redundant sealing system. The second O-ring acts as a backup seal that prevents liquid intrusion even when the first seal is compromised, providing prior protection against the harmful effect of corrosive liquids before they can cause damage to internal components.
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 corrosion and electrical shorting by ensuring that corrosive liquids are kept out of the injector's internal space, allowing for normal expansion and contraction of the seal without causing O-ring failure, thus maintaining the injector's operability.
Implementation Method 1
A seal member is in contact with at least the stepped portion and a surface of the carrier to prevent liquid from entering a space between the housing and the body
Data Source
AI summary
A fluid injector includes a valve assembly constructed and arranged to control flow of fluid from an inlet to an outlet of the injector. A metal housing surrounds at least a portion of the valve assembly. A plastic body is molded over at least a portion of the housing. A distal end of the body defines an integral stepped portion extending from the body. A carrier surrounds at least the distal end of the body. A seal member is in contact with at least the stepped portion and a surface of the carrier to prevent liquid from entering a space between the housing and the body.