Pyrotechnic Body Panel Lifter with Ball Ramp Energy Management

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Solution Overview

Problem

Existing pyrotechnic activated body panel lift actuators lack controlled force during downward displacement after initial deployment, limiting their effectiveness in providing pedestrian protection during head and body impacts.

Innovation Solution

A pyrotechnic activated body panel lift actuator assembly featuring a thin-walled tube and piston with a frustoconical ramp portion and balls that absorb impact by plastically deforming the tube, providing a controlled, constant force during retraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a pyrotechnic actuator is used to lift the body panel, then the deployment speed and initial lifting force are improved, but the control of downward displacement force after deployment is lost

Engineering Contradiction:

Improvedeployment speedVSAvoidcontrolled force during downward displacement

Core Design Contradiction:

SpeedVSEase of operation

Solution Approach 1:

The system transitions from a static pyrotechnic actuator to a dynamic system where the piston interacts with balls on a tapered ramp. This creates variable resistance during downward displacement, allowing controlled force generation as the balls roll up the ramp and deform the tube, converting the uncontrolled retraction into a controlled energy dissipation process.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The tapered ramp portion changes the geometric parameter of the interaction surface between the piston and balls. As the piston moves downward, the contact point moves along the tapered surface, changing the mechanical advantage and force multiplication ratio, thereby providing controlled constant force during retraction.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the hood lifter is designed to lift the body panel quickly, then pedestrian protection during impact is improved, but the energy dissipation during retraction is uncontrolled

Engineering Contradiction:

Improvepedestrian protectionVSAvoiduncontrolled energy dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The uncontrolled downward motion and energy dissipation during retraction is converted into a beneficial controlled energy absorption process. The balls rolling up the tapered ramp and plastically deforming the tube transform the harmful uncontrolled energy release into useful energy dissipation that enhances pedestrian protection by providing controlled resistance during head and body impact.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system prepares for the retraction phase by incorporating the tapered ramp and balls that will provide cushioning force during downward displacement. This beforehand design ensures that when the piston retracts after deployment, the energy dissipation is controlled through plastic deformation of the tube, creating a cushioning effect that protects pedestrians.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If a thin-walled tube is used for the actuator, then the device complexity and weight are reduced, but the control over downward displacement force is limited

Engineering Contradiction:

Improveactuator structureVSAvoidcontrolled force during retraction

Core Design Contradiction:

Device complexityVSForce

Solution Approach 1:

The thin-walled tube is designed with localized interaction zones where the balls contact and deform the tube wall during downward displacement. This local quality approach allows the majority of the tube to remain thin-walled for simplicity, while specific regions provide controlled force through plastic deformation when activated by the balls on the tapered ramp.

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 assembly achieves a controlled, constant force during retraction, enhancing pedestrian protection by managing impact energy and reducing injuries from vehicle collisions.

Implementation Method 1

pyrotechnic actuator responsive to a sensor signal indicating an impact with a pedestrian or person outside

Methodology Applied

Scientific EffectPyrotechnic combustion: Combustion

Implementation Method 2

thereafter the piston retracts under controlled substantially constant force generated by balls moving up the tapered ramp portion of the shaft thereby locally plastically deforming the thin-walled tube

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentUS10875491B2Body panel lifter mechanical energy management system

Publication Date: 2020.12.29 KEY SAFETY SYSTEMS INC

AI summary

A pyrotechnic activated body panel lift actuator assembly for a vehicle having a unique deployment profile and energy absorbing feature is disclosed. The assembly has a pyrotechnic actuator, a thin-walled tube and a piston. The tapered portion of the piston forms a recess between the piston and the tube. One or more balls sized to fit in the recess are provided. Upon activation, the piston is thrust proximally outwardly to lift a portion of a body panel to absorb an impact of a person hit by the vehicle and thereafter the piston retracts under controlled substantially constant force generated by balls moving up the tapered portion of the shaft thereby locally plastically deforming the thin-walled tube.