Vehicle Rear Lower Structure Load Absorption via Opposing Frame Bending

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Solution Overview

Problem

In vehicles, the spare tire housing deforms and moves forward when a load is applied from the rear, potentially contacting the fuel tank or rear seat, leading to vibration and damage due to insufficient space and increased vehicle size constraints, especially in compact cars.

Innovation Solution

A lower vehicle body rear structure with a rear cross member and hook reinforcing member, where the side frame and rear floor are divided into parts with varying rigidity and deformation shapes to absorb loads effectively, preventing forward movement and vibration by bending in opposite directions, enhancing resistance and load absorption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sufficient space is secured between the spare tire housing and fuel tank to prevent contact during load, then the fuel tank contact problem is solved, but the vehicle body size increases

Engineering Contradiction:

Improveprevention of fuel tank contactVSAvoidvehicle body size

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The spare tire mounting structure is designed to be deformable under load, allowing the spare tire to tilt forward and upward when rearward force is applied. This dynamic response automatically creates the necessary clearance from the fuel tank during collision, eliminating the need for excessive static spacing in normal conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The rigidity of the spare tire mounting structure is intentionally made non-uniform, with a fragile part positioned to initiate controlled deformation. Under normal conditions, the structure maintains sufficient rigidity to hold the spare tire securely, but under load it yields at the predetermined fragile location to allow tilting movement, thus changing the positional parameter of the spare tire dynamically.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If the spare tire is mounted horizontally to simplify installation, then the mounting complexity is reduced, but the spare tire contacts the rear seat when load is applied

Engineering Contradiction:

Improvemounting simplicityVSAvoidrear seat contact

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The mounting structure transitions from a static horizontal mounting to a dynamic configuration that tilts the spare tire forward and upward under load. The fragile part acts as a hinge point, enabling the spare tire to rotate and tilt when rearward force is applied, automatically preventing contact with the rear seat without requiring complex active control mechanisms.

Inventive Principle:

Principle #15Dynamics

3Reliability

If a fragile part is provided on the spare tire bracket to enable deformation under load, then the spare tire tilting is improved, but vibrations occur during vehicle operation

Engineering Contradiction:

Improvespare tire tilting responseVSAvoidvibrations and noise

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The fragile part is designed as a separate, dedicated deformation element that is intentionally removed or yielded under load to enable the tilting motion. By concentrating the deformation function in this specific extracted component, the rest of the mounting structure can remain rigid and stable during normal operation, preventing vibrations while maintaining the ability to tilt when needed.

Inventive Principle:

Principle #2Taking out (Extraction)

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 structure effectively absorbs loads, stabilizes deformation to prevent contact with the fuel tank and rear seat, reduces vibrations, and enhances durability by managing load distribution and deformation direction, thus preventing damage and noise.

Implementation Method 1

the side frame is deformed so as to be bent in an upward convex shape or in a downward convex shape at a division position of the frame front part and the frame rear part, and also the rear floor and the hook reinforcing member are deformed so as to be bent in a downward convex shape or an upward convex shape at a division position of the reinforcing member front part and the reinforcing member rear part

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS8091941B2Lower structure of vehicle body rear part

Publication Date: 2012.01.10 SUZUKI MOTOR CORP

AI summary

A lower structure of a vehicle body rear part includes a spare tire housing formed on a rear floor, a rear cross member disposed in front of the spare tire housing to connect side frames, and a hook reinforcing member extending in the vehicle longitudinal direction. The side frame at the vehicle rear of the rear cross member is divided into a frame front part and a frame rear part in the vehicle longitudinal direction, and the hook reinforcing member is divided into a reinforcing member front part and a reinforcing member rear part in the vehicle longitudinal direction. The lower structure is configured so that when a load F is applied from the vehicle rear to a vehicle body rear part, the side frame is deformed so as to be bent in an upward convex shape at a division position of the frame front part and the frame rear part, and also the rear floor and the hook reinforcing member are deformed so as to be bent in a downward convex shape at a division position of the reinforcing member front part and the reinforcing member rear part.