Compression-Limiting Fastener for Plastic Intake Manifold
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Solution Overview
Problem
Lightweight metals like magnesium and aluminum used in engine components face challenges such as thermal expansion mismatches and creep, leading to fastener loosening and material damage, while plastic components suffer from creep and brittle nature, requiring improved fastening solutions to ensure secure attachment without damage.
Innovation Solution
A compression limiting fastener assembly with a molded compliance ring and spring stem compression limiter is used to attach a plastic intake manifold flange to a cam cover, preventing over-compression and ensuring 100% compression without damaging the plastic components, even under extreme vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lightweight metals like magnesium and aluminum are used to reduce weight, then fuel economy improves, but thermal expansion mismatches and creep cause fastener loosening and attachment failure
Solution Approach 1:
The patent introduces a compliant ring as an intermediary component between the fastener and the plastic engine component. This compliant ring mediates the thermal expansion and creep effects by providing a flexible interface that accommodates dimensional changes without compromising fastener retention, thus resolving the reliability issue while maintaining the weight benefits of lightweight materials
Solution Approach 2:
The patent changes the physical parameters of the fastening system by using a compliant ring with specific elastic properties that allow it to deform under thermal load and creep conditions. This parameter change enables the fastening system to maintain clamping force despite temperature variations and long-term dimensional instability of the lightweight metal or plastic components
2Ease of manufacture
If plastic components are used instead of metals, then manufacturing cost and ease of production improve, but creep causes fasteners to back out over time
Solution Approach 1:
The compliant ring serves as a mediator between the fastener and the plastic component, compensating for the plastic's creep tendency. The ring's elastic properties allow it to maintain constant pressure on the fastener, preventing backout despite the plastic material's dimensional changes over time
Solution Approach 2:
The compliant ring provides beforehand cushioning by being pre-installed in a state that allows it to compensate for future creep effects. The ring's elastic deformation capacity is designed to anticipate and counteract the plastic component's tendency to creep, maintaining fastener security throughout the component's service life
3Strength
If spring stem fasteners are used to attach plastic components, then attachment strength improves, but over-compression or under-compression occurs due to tolerance variations
Solution Approach 1:
The compliant ring introduces dynamic adaptability to the fastening system. Instead of a rigid connection that is sensitive to tolerance variations, the compliant ring dynamically adjusts its deformation to accommodate manufacturing tolerances, ensuring optimal compression is always achieved regardless of dimensional variations in the assembled 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 provides robust joint attachment without additional parts, reducing material costs and assembly time, ensuring the fastener remains secure and prevents loosening, enhancing the reliability of plastic component connections in engine applications.
Implementation Method 1
a molded compliance ring formed on the attachment side of the intake manifold flange
Implementation Method 2
a spring stem compression limiter that, when fully threaded into its attachment position, prevents over-compression while providing 100% compression
Data Source
AI summary
A compression limiting fastener assembly includes a plastic intake manifold having an attachment flange and a molded and tuned compliance ring formed on the attachment side of the flange, a plastic cam cover having a threaded attachment insert, a compression limiting bolt fastener for attaching the intake manifold to the cam cover, and a spring stem compression limiter that, when fully threaded into its attachment position, prevents over-compression and possible damage to the plastic components while providing 100% compression. The compliance ring of the intake manifold is concentric with a fastener bore formed through the intake manifold attachment flange. The spring stem compression limiter includes a tubular body having an upper end and a lower end. A spring stem flange is attached to the upper end of the tubular body while a depth limiting flange is attached to the lower end.