Automotive Shift Cable Isolators for High Temperature Lash Control
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Solution Overview
Problem
Current motor vehicle transmission shift cable assemblies face challenges with elevated temperature resistance, dimensional tolerance variations, and vibration mitigation, leading to issues like lash inaccuracy and wear at mounting points, which are exacerbated by harsh engine compartment conditions.
Innovation Solution
The development of automotive transmission shift cable assemblies featuring a conduit subassembly with a core wire and polymeric isolators, including a core wire adjuster and conduit end fitting isolators made from materials like polyester-type thermoplastic polyurethane and polymeric silicone, which maintain durometer and resist deformation at high temperatures, reducing lash and installation/extraction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional isolators made of soft resilient material are used to absorb vibration, then vibration absorption is improved, but the isolators suffer wear and breakdown in concentrated load areas
Solution Approach 1:
The patent uses a composite material structure where a polymeric isolator is combined with a metal reinforcement insert. The polymeric material provides vibration absorption while the metal insert reinforces concentrated load areas to prevent wear and breakdown. This composite approach allows the isolator to simultaneously achieve softness for vibration damping and hardness for wear resistance at critical contact points.
2Ease of manufacture
If dimensional tolerance range of strand and attachment pins is large, then manufacturing ease is improved, but lash and inaccuracy in transmission shift system occur
Solution Approach 1:
The patent introduces an isolator as an intermediary component between the attachment pin and the terminal sub-assembly. This isolator compensates for dimensional tolerance variations in the strand and attachment pins by providing a compliant interface that maintains proper engagement while absorbing tolerance build-up, thereby reducing lash without requiring tight manufacturing tolerances.
Solution Approach 2:
The patent employs materials with specific durometer ranges (e.g., 50-70 Shore A) for the polymeric isolator that allow it to deform elastically within a controlled range. This parameter control enables the isolator to accommodate tolerance variations while maintaining sufficient rigidity to prevent excessive lash, effectively translating material property parameters into tolerance compensation.
3Strength
If high installation loads are used to achieve high extraction loads, then connection strength is improved, but assembly difficulty increases
Solution Approach 1:
The patent uses a dynamic isolation approach where the polymeric isolator provides progressive resistance to loading. During installation, the isolator deforms elastically to accommodate the attachment pin with moderate forces. During extraction, the same isolator maintains high resistance due to its viscoelastic properties and geometric configuration, achieving high extraction loads without requiring high installation forces.
4Adaptability or versatility
If cable assembly is exposed to elevated temperatures in engine compartment, then operational capability is improved, but material deformation and performance degradation occur
Solution Approach 1:
The patent selects polymeric materials with specific thermal properties including durometer stability at elevated temperatures (e.g., maintaining 50-70 Shore A at 100°C). The material composition and crosslinking density are controlled to minimize thermal expansion and prevent deformation within the operating temperature range, allowing the isolator to maintain its functional properties in the engine compartment environment.
Solution Approach 2:
The patent combines polymeric isolator material with metal reinforcement elements to create a composite structure that leverages the thermal stability of metal and the vibration-damping properties of polymer. This composite construction allows the assembly to operate at elevated temperatures while maintaining dimensional stability and mechanical performance.
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
These cable assemblies demonstrate performance stability at 165°C, meeting stringent tests such as Lash 200,000 Cycles, Attachment Pin Installation/Extraction 200,000 Cycles, and In-Vehicle Routing 165°C Cable Strength, without the need for heat shields, ensuring reliable operation and ease of assembly.
Implementation Method 1
designed to absorb vibration
Implementation Method 2
The material of the isolator, however, must be adequately resistant to deflection or compression set over extended usage periods
Implementation Method 3
which maintain durometer and resist deformation at high temperatures
Implementation Method 4
The material of the isolator, however, must be adequately resistant to deflection or compression set over extended usage periods
Data Source
AI summary
Automotive push-pull type transmission shift cable assemblies are disclosed that meet new specifications for extended performance at high temperatures, including certain embodiments suitable for use at elevated temperatures of at least 165° C. The cable comprises a conduit and a core wire extending through the ends of the conduit to a shifter end portion and transmission end portion. The transmission end portion comprises a core wire length adjuster and a conduit end fitting. The core wire length adjuster comprises a core wire adjuster isolator and a retainer cap. At least certain embodiments of the transmission shift cable assemblies pass one or a combination of the following tests:a. Lash 200,000 Cycles Test,b. Attachment Pin Installation 200,000 Cycles Test,c. Attachment Pin Extraction 200,000 Cycles Test, andd. Cable Efficiency Teste. In-Vehicle Routing 165° C. Cable Strength Test.