Plastic Underbody Assembly With Sealed Junctions for Micro-City EVs

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Solution Overview

Problem

Two-seater electric vehicles, or 'micro-city' cars, are prone to water infiltration and damage to electrical components due to gaps between underbody parts, especially when passing through fords, leading to degradation from mud and gravel.

Innovation Solution

The underbody assembly consists of left and right sub-assemblies made of a single piece of plastic, with interlocking profiles and a sealing gasket to minimize gaps, reducing the number of parts and enhancing sealing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If multiple separate parts are assembled to form the underbody, then the assembly can be manufactured and assembled in a modular way, but water infiltration occurs through the junctions between parts

Engineering Contradiction:
Improvemodular assemblyVSAvoidwater infiltration resistance
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent merges multiple separate underbody parts (front apron, side sills, rear apron, wheel arches) into a single integrated plastic underbody assembly. This eliminates the junctions between parts where water infiltration occurred, while maintaining manufacturability through single-piece molding technology.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent uses plastic material to create the integrated underbody assembly, replacing traditional multi-material assemblies (metal panels, rubber seals, fasteners). The plastic material provides both structural integrity and water tightness in a single component.

Inventive Principle:
Principle #40Composite materials

2Ease of manufacture

If multiple separate parts are assembled to form the underbody, then the assembly can be manufactured and assembled in a modular way, but electrical components are damaged by mud and gravel entering through junctions

Engineering Contradiction:
Improvemodular assemblyVSAvoiddamage to electrical components
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

By integrating all underbody components into a single plastic assembly, the patent eliminates the junctions that allowed mud and gravel to penetrate and damage electrical components mounted on the underbody.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The plastic underbody assembly acts as a continuous protective shell, forming a barrier that prevents mud and gravel from reaching electrical components, replacing the discontinuous protection provided by multiple separate parts with gaps between them.

Inventive Principle:
Principle #30Flexible shells and thin films

3Reliability

If the number of parts is reduced to single-piece sub-assemblies, then water infiltration and damage to electrical components are reduced, but the manufacturing complexity of each part increases

Engineering Contradiction:
Improveprotection against water and debrisVSAvoidsingle-piece sub-assembly complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the underbody into two symmetrical half-assemblies (left and right), each manufactured as a single piece. This segmentation allows each complex half to be molded separately and then assembled, reducing the complexity of individual molding operations while maintaining the benefits of integration.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Each half-assembly is designed as a universal component that incorporates multiple functions (structural support, water tightness, mud guard, wheel arch) into a single molded part, simplifying the overall system despite the complexity of each individual component.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Reliability

If the number of parts is reduced to single-piece sub-assemblies, then water infiltration and damage to electrical components are reduced, but the assembly process becomes more complex

Engineering Contradiction:
Improveprotection against water and debrisVSAvoidassembly process
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The underbody is segmented into two manageable half-assemblies that can be assembled symmetrically, simplifying the assembly process compared to joining multiple smaller parts while maintaining water tightness.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The half-assemblies incorporate self-aligning features and integrated fastening mechanisms that simplify the assembly process, allowing the complex single-piece components to be joined easily without requiring complex alignment procedures.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4353571B1Motor vehicle assembly and motor vehicle comprising such an assembly
Publication Date: 2025.11.12 STELLANTIS AUTO SAS
  • EP4353571B1 patent drawingFigure 1~2
  • EP4353571B1 patent drawingFigure 3~4

AI summary

The invention relates to a motor vehicle assembly (3) (1) forming the underbody of said motor vehicle (1), comprising a left sub-assembly (7g) and a right sub-assembly. According to the invention, the left (7g) and right sub-assemblies each consist of a single piece made of plastic material and are joined together at a junction area (9). The invention also relates to a motor vehicle comprising such an assembly.