Active Spare Tire Assembly for Underbody Drag Reduction
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Solution Overview
Problem
Conventional spare tires mounted under vehicle underbodies do not contribute significantly to vehicle aerodynamic performance and often require inconvenient or inaccessible locations, impacting battery range in electric vehicles and fuel economy in gas-powered vehicles.
Innovation Solution
An active aerodynamic vehicle underbody spare tire assembly that includes a carrier, actuator, and cover, which moves the spare tire between stowed and deployed positions based on vehicle speed, enhancing aerodynamic performance by acting as a diffuser at the vehicle rearend.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the spare tire is mounted high against the underside and rearend of the vehicle in a conventional fixed position, then the spare tire is easily accessible and securely mounted, but it does not contribute to vehicle aerodynamic performance and increases aerodynamic drag
Solution Approach 1:
The spare tire assembly is designed to move between a stowed position (high against the underbody) and a deployed position (lowered to act as a diffuser). An actuator mechanism enables this dynamic repositioning based on driving conditions, allowing the system to optimize between accessibility and aerodynamic performance.
Solution Approach 2:
The spare tire assembly serves multiple functions: it acts as a conventional spare tire storage when in the stowed position, and functions as an active aerodynamic diffuser when deployed. This multi-functionality resolves the contradiction by making the same component serve both accessibility and aerodynamic needs at different times.
2Loss of energy
If the spare tire is moved to a deployed position with lowered location to act as a diffuser, then vehicle aerodynamic performance is improved by minimizing drag and facilitating wake closure, but the spare tire becomes less accessible and requires additional actuation mechanisms
Solution Approach 1:
The system dynamically repositions the spare tire assembly between stowed and deployed states based on vehicle speed and driving conditions. The actuator mechanism enables this movement, and the controller automates the decision-making process, reducing the operational burden on the user while maintaining accessibility when needed.
Solution Approach 2:
The controller receives input from various sensors including vehicle speed sensors and determines the optimal position of the spare tire assembly. This feedback-based control system automatically adjusts the assembly position to optimize aerodynamic performance without requiring manual intervention, thereby maintaining ease of operation.
3Loss of energy
If an actuator mechanism is added to move the spare tire between stowed and deployed positions, then active aerodynamic performance is achieved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The actuator mechanism is integrated into the existing spare tire mounting system, allowing the same component to serve both as a mounting mechanism and an active aerodynamic control mechanism. This reduces overall system complexity compared to adding a completely separate actuation system.
Solution Approach 2:
The controller automatically determines when to deploy or stow the spare tire assembly based on vehicle speed and driving conditions, eliminating the need for manual control inputs. The system self-regulates its aerodynamic performance without requiring complex user interfaces or manual operation.
4Device complexity
If the spare tire remains in a fixed stowed position, then the device complexity is minimized, but aerodynamic wake closure is not facilitated and fuel economy or battery range is reduced
Solution Approach 1:
The spare tire assembly transitions from a static fixed-position design to a dynamic repositioning system that can lower the spare tire to act as a diffuser. This dynamic capability enables wake closure and improved aerodynamic efficiency, directly impacting fuel economy or battery range without requiring a complete redesign of the mounting system.
Data Source
AI summary
An active aerodynamic vehicle underbody spare tire assembly improves airflow dynamics and reduces drag at an underbody and rearend of a vehicle, ultimately extending vehicle battery range in an electric vehicle and providing better fuel economy in a gas-powered vehicle. The active aerodynamic vehicle underbody spare tire assembly moves the spare tire between a stowed position and a deployed position based on vehicle speed. At lower vehicle speeds, the spare tire is kept at the stowed position. And at higher vehicle speeds, the spare tire is moved to the deployed position. In varying implementations, the active aerodynamic vehicle underbody spare tire assembly can include a spare tire carrier, an actuator, and a spare tire cover.