Auxiliary Spring for Pedestrian Protection Flap Reliability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing spring devices on motor vehicle flaps, particularly the front flap, fail to maintain the pedestrian protection position in the event of a malfunction where the gas spring loses pressure, potentially leading to suboptimal impact absorption and increased injury risk during pedestrian collisions.

Innovation Solution

A spring device comprising a gas spring and an additional prestressed spring, which can hold the front flap in the raised pedestrian protection position even if the gas spring loses pressure, utilizing a sensor-activated actuator to initially raise the flap and ensuring the additional spring's pretensioning force is sufficient to maintain this position during impacts, with a low-design effort suspension and damping system to absorb the impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the gas spring is used alone to hold the front flap in the raised pedestrian protection position, then the device is simple and cost-effective, but the front flap cannot be held in the raised position when the gas spring loses pressure

Engineering Contradiction:

Improveability to hold front flap in raised position during gas spring malfunctionVSAvoidspring device structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies beforehand cushioning by introducing an additional spring that is pre-loaded to compensate for potential gas spring failure. This auxiliary spring is prepared in advance and automatically engages when the gas spring loses pressure, ensuring continuous support for the front flap in the raised position without requiring complex active control systems.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent utilizes parameter changes by designing the additional spring with specific pre-load characteristics and stiffness properties that allow it to take over the support function when the gas spring fails. The pre-load force and spring constant are carefully selected to maintain the front flap in the raised position while allowing manual closing when needed.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the additional spring is pre-loaded with high force to maintain the raised position during gas spring failure, then reliability is improved, but manual closing of the front flap becomes difficult

Engineering Contradiction:

Improveability to hold front flap in raised position during malfunctionVSAvoidmanual closing of front flap

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies parameter changes by carefully selecting the pre-load force and spring constant of the additional spring. The pre-load is set to a specific range that provides sufficient support during gas spring failure but does not create excessive resistance during normal manual closing operations. This optimization balances reliability with ease of operation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies partial action by designing the additional spring to provide just enough pre-load force to maintain the raised position during malfunction, rather than using excessive force. This partial pre-loading ensures reliability while minimizing the impact on manual closing ease, avoiding over-engineering the spring force.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If the additional spring is used to hold the front flap in the raised position, then reliability during malfunction is improved, but the design effort and preloading requirements increase

Engineering Contradiction:

Improveability to hold front flap in raised position during gas spring failureVSAvoidspring device design and preloading

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies beforehand cushioning by using a pre-loaded additional spring that automatically compensates for gas spring failure. This approach provides reliable backup support without requiring complex active control systems, sensors, or actuators, thereby limiting the increase in design complexity despite the added reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Ensures the front flap is in an optimal position for impact absorption, reducing pedestrian injuries and allowing easy manual return to the closed position after the event, with a low preloading requirement for the additional spring.

Implementation Method 1

an additional spring (2), which is pretensioned with a pretensioning force (11)

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a gas spring (1) with a piston (5) that can be adjusted axially in a cylinder (3)

Methodology Applied

Scientific EffectGas pressure: Pressure Increase

Data Source

PatentEP2394870B1Spring device on a pivoting flap of a motor vehicle

Publication Date: 2012.10.17 STABILUS GMBH

Figure 1~2
Figure 3~4

AI summary

The device has an auxiliary spring (2) provided between a body of a motor car and a flap and pre-tensioned with pre-tensioning force which is sufficient during an event in which a gas spring (1) exhibits reduced or low gas pressure, to maintain a front flap in a raised pedestrian protection system against crash. An actuator is activated by a sensor device and enables raising of the flap in the protection system against impact of a pedestrian on the flap. The auxiliary spring is designed as a metallic helical spring. The gas spring has a piston (5) that is adjustable in a cylinder (3).