Pyrotechnic Actuator with Segmented Gas Generators for Reusable Hood Lifting
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Solution Overview
Problem
Conventional pyrotechnic actuators for active vehicle hoods are non-reversible, leading to high repair costs due to false triggering and inability to absorb impact effectively, causing abrupt deceleration and potential injury to pedestrians.
Innovation Solution
A pyrotechnic actuator with a cylinder and piston driven by propellant gas, featuring multiple gas generators and support chambers to enable multiple lifting movements without replacement, with an electronic ignition circuit for controlled gas release to slow down the hood's movement and absorb impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional pyrotechnic actuators are used, then the hood can be raised quickly with strong acceleration, but the actuators are non-reversible and must be replaced after each use, leading to high repair costs
Solution Approach 1:
The actuator is divided into two independent gas generators (first and second) with separate propellant charges. The first gas generator can be reignited multiple times, while the second provides additional propellant when the first is depleted. This segmentation allows the actuator to be reusable without replacement, resolving the contradiction between fast response and repairability.
Solution Approach 2:
The system changes the state of propellant gas by controlling pressure and temperature through sequential ignition of different gas generators. By monitoring propellant consumption and adjusting ignition sequences, the actuator maintains effective operation across multiple cycles, enabling reversibility while preserving performance.
2Device complexity
If a single propellant charge is used, then the actuator structure is simple, but the actuator can only be used once and requires replacement
Solution Approach 1:
The propellant system is segmented into two independent gas generators with separate propellant charges. This allows the first generator to be reignited multiple times while the second provides supplementary propellant, extending the actuator's operational duration without significantly increasing structural complexity.
Solution Approach 2:
The cylinder and piston mechanism serves multiple functions: it contains both propellant charges, accommodates sequential ignition sequences, and provides controlled gas expansion for multiple actuation cycles. This multi-functionality extends usage duration while maintaining relatively simple device structure.
3Speed
If the hood is decelerated abruptly after reaching the raised position, then the hood stops quickly, but strong vibrations are excited which can reduce the effective braking distance for pedestrians
Solution Approach 1:
The actuator employs periodic, controlled gas release through a valve mechanism that regulates propellant gas flow during deceleration. This creates a gradual, oscillating pressure reduction rather than abrupt release, dampening vibrations while maintaining effective hood deceleration and preserving pedestrian braking distance.
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
Enables multiple uses without workshop visits, reduces repair costs, and provides effective impact absorption to protect pedestrians by controlling the hood's movement and deceleration.
Implementation Method 1
a first gas generator (12) for generating the propellant gas and at least one further gas generator which can be ignited independently of the first gas generator
Implementation Method 2
a piston (15) which can be displaced in the cylinder under the influence of a propellant gas
Data Source
Figure 1
Figure 2~4
Figure 5~7
AI summary
A pyrotechnic actuator for an active hood comprises a cylinder, a piston which is displaceable in the cylinder under the influence of a propellant, and a first gas generator for generating the propellant. In one development, the actuator comprises at least one further gas generator which can be primed independently of the first gas generator. In another development, the actuator comprises a cylinder having two chambers on both sides of the piston, which chambers can be charged with propellant from the gas generator.