Deployable Rear Diffuser Linkage for Vehicle Drag Reduction

Resolve Bottlenecks,
Find Innovative Solutions
Generate Solutions

Solution Overview

Problem

Existing aerodynamic devices for vehicles are complex, inefficient, and ineffective at reducing drag coefficient at low speeds, while diffusers on sports cars are not practical for ordinary road vehicles.

Innovation Solution

An aerodynamic device with movable diffusers and an actuation mechanism, including a shaft and arms, that automatically deploys at certain speeds to reduce drag, and can be integrated harmoniously into the vehicle's design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a diffuser is mounted on the rear of the vehicle's underbody to limit turbulence, then the drag coefficient is reduced at high speeds, but the device is ineffective at low speeds and only suitable for sports cars

Engineering Contradiction:
Improvedrag coefficientVSAvoidspeed range applicability
Core Design Contradiction:
Loss of energyVSAdaptability or versatility

Solution Approach 1:

The diffuser is designed to be movable between a retracted position (at low speeds) and a deployed position (at high speeds). This dynamic adjustment allows the device to adapt to different operating conditions, being ineffective at low speeds but effective at high speeds where it is needed.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The aerodynamic performance of the diffuser is optimized for high-speed operation. By changing the operational parameter (speed threshold for deployment), the device achieves its drag-reducing function only in the speed range where it is most beneficial, accepting limited low-speed performance.

Inventive Principle:
Principle #35Parameter changes

2Loss of energy

If active aerodynamic devices with movable elements are deployed to reduce drag, then the drag coefficient is reduced, but the device complexity increases

Engineering Contradiction:
Improvedrag coefficientVSAvoidaerodynamic device complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The aerodynamic device is segmented into modular components: a first diffuser and a second diffuser that can be independently positioned. This segmentation allows for simpler individual components that work together, reducing overall complexity while maintaining aerodynamic effectiveness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The second diffuser is positioned within or alongside the first diffuser structure, creating a nested arrangement. This nesting approach allows both diffusers to function together while sharing structural support, reducing the total complexity compared to separate independent diffusers.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Shape

If an aerodynamic device is integrated into the vehicle's silhouette for aesthetic purposes, then the design is improved, but the aerodynamic effectiveness may be compromised

Engineering Contradiction:
Improvevehicle silhouetteVSAvoiddrag coefficient
Core Design Contradiction:
ShapeVSLoss of energy

Solution Approach 1:

The aerodynamic device is designed to be dynamic, remaining retracted during low-speed operation to preserve the vehicle's aesthetic silhouette, and deploying at high speeds when aerodynamic performance becomes the priority. This temporal separation resolves the conflict between appearance and function.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The device is integrated into specific locations on the vehicle (rear underbody area) rather than modifying the entire vehicle silhouette. This localized integration maintains the overall aesthetic design while providing aerodynamic benefits in the critical rear flow region.

Inventive Principle:
Principle #3Local quality

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 device effectively reduces drag coefficient by 0.005 to 0.010, enhancing energy efficiency and driving range, while maintaining a discreet and functional appearance.

Implementation Method 1

a first diffuser movable relative to the structure by means of a pivot joint around a first axis between a folded position and an unfolded position

Methodology Applied
Scientific EffectPivot joint rotation: Hinge

Implementation Method 2

a second diffuser movable relative to the first diffuser by means of a sliding joint along a second axis between a folded position and an unfolded position

Methodology Applied
Scientific EffectSliding joint translation: Friction

Implementation Method 3

an actuation mechanism comprising a shaft movable in rotation relative to the structure around a third axis parallel to the first axis, and at least one arm connecting the second diffuser to the shaft

Methodology Applied
Scientific EffectRotational actuation: Gear

Data Source

PatentEP4711252A1Aerodynamic device for a motor vehicle
Publication Date: 2026.03.18 RENAULT SA
  • EP4711252A1 patent drawingFigure 1
  • EP4711252A1 patent drawingFigure 2
  • EP4711252A1 patent drawingFigure 3

AI summary

Aerodynamic device (5) for a motor vehicle (1), characterized in that it comprises: - a structure (13) intended to be fixed to a body of the vehicle, - a first diffuser (11) movable relative to the structure by means of a pivot joint about a first axis (Y1) between a folded position and an unfolded position, - a second diffuser (12) movable relative to the first diffuser by means of a sliding joint along a second axis (A2) between a folded position and an unfolded position, and - an actuation mechanism comprising a shaft (21) movable in rotation relative to the structure about a third axis (Y3) parallel to the first axis, and at least one arm (22) connecting the second diffuser to the shaft.