Underfloor Spare Wheel Support Structure for Fuel Tank Impact Protection

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Solution Overview

Problem

In vehicles with underfloor spare wheels, the spare wheel retaining device can tilt upwards during a rear impact, potentially damaging the fuel tank located beneath it, especially in vehicles with polymer floors that require reinforcement to ensure secure attachment.

Innovation Solution

A support structure for the spare wheel retaining device is designed with a front attachment point to the floor and reinforced with metal elements, allowing the structure to pivot in a way that prevents contact with the fuel tank during impacts, while using fewer perforations in the polymer floor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the spare wheel retaining device is fixed to the polymer floor, then the device can be securely attached, but the polymer floor requires additional reinforcement which increases complexity and weight

Engineering Contradiction:
Improveattachment strengthVSAvoidfloor reinforcement complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

A metal support structure acts as an intermediary between the polymer floor and the spare wheel retaining device. The support structure is fixed to the floor at multiple points (including front attachment points ahead of the frame) and provides a robust mounting surface for the retaining device, eliminating the need to reinforce the polymer floor itself.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution combines polymer floor material with metal support structure and metal reinforcing elements. The polymer floor provides lightweight construction while the metal support structure and L-shaped reinforcing elements provide the necessary mechanical strength for secure attachment without complicating the floor design.

Inventive Principle:
Principle #40Composite materials

2Volume of moving object

If the spare wheel retaining device is positioned under the floor, then space is optimized, but during rear impact the device may tilt upward and damage the fuel tank

Engineering Contradiction:
Improvespace utilizationVSAvoidfuel tank damage risk
Core Design Contradiction:
Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The support structure is designed with front attachment points located ahead of the frame in the longitudinal direction. This configuration creates a geometric arrangement that prevents upward rotation during rear impact before the retaining device can contact the fuel tank, effectively countering the harmful motion in advance.

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The support structure allows controlled rotation around the front attachment points during impact, transforming the rigid connection into a dynamic system that can absorb impact energy through controlled movement while maintaining protection of the fuel tank.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP3686093B1Rear structure of a motor vehicle equipped with a structure for supporting a device for retaining a spare wheel under the floor
Publication Date: 2025.07.16 RENAULT SA
  • EP3686093B1 patent drawingFigure 1~2
  • EP3686093B1 patent drawingFigure 3~4
  • EP3686093B1 patent drawingFigure 5

AI summary

The invention relates to a rear structure (10) for a motor vehicle comprising a floor (18), a spare wheel retention device, and a support structure (30) for the retention device. This support structure (30) defines a frame fixed to the floor (18) at several attachment points (31). The rear structure further has a longitudinal direction corresponding to the longitudinal direction of the vehicle, and its front and rear directions correspond to the front and rear directions of the vehicle when the rear structure is mounted on the vehicle. The support structure (30) also includes at least one front attachment point (36) to the floor located in front of a front portion of the frame along said longitudinal direction.