Prestressing Fixture for PSIR Chute Vibration Welding
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Solution Overview
Problem
Vibration welding of Passenger Side Inflatable Restraint (PSIR) chutes to automotive instrument panels results in visible distortion due to uneven material shrinkage during the cooling process, affecting the aesthetic appeal of the instrument panel.
Innovation Solution
A pre-stressed instrument panel with a substrate layer, intermediate foam layer, and cover layer, along with a weld fixture using convex pre-stressors to create compression and tension, ensuring that the thermal shrinkage matches the surface stretch and eliminating visible distortion by vibration welding the weld bars to the substrate layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If vibration welding is used to attach PSIR chute to instrument panel, then bonding strength is improved, but visible distortion occurs due to uneven shrinkage during cooling
Solution Approach 1:
The patent applies preliminary action by pre-stressing the instrument panel before vibration welding. The fixture creates controlled compression and tension zones in advance, so that when welding and subsequent shrinkage occur, the pre-established stress distribution compensates for uneven shrinkage and prevents visible distortion on the exposed surface.
Solution Approach 2:
The patent changes the physical state and stress parameters of the instrument panel material through pre-stressing. By applying controlled mechanical stress before welding, the material's internal stress distribution is modified, which counteracts the thermal shrinkage stresses that will occur during and after welding, thereby eliminating visible distortion.
2Shape
If pre-stressing fixture with convex pre-stressors is applied, then visible distortion is eliminated, but device complexity increases
Solution Approach 1:
The patent segments the pre-stressing function into multiple discrete convex pre-stressors positioned at specific locations on the fixture. Each pre-stressor creates a localized stress zone, allowing complex stress distribution patterns to be achieved through simple, modular components rather than a single complex mechanism.
Solution Approach 2:
The patent introduces a vacuum system as an intermediary to apply the pre-stressing force. The vacuum creates uniform suction that presses the instrument panel against the convex pre-stressors, providing a simple yet effective mechanism to generate the required compression and tension zones without complex mechanical actuation systems.
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 solution effectively eliminates visible distortion in the area of vibration welded PSIR chutes, maintaining a flat or contoured appearance of the instrument panel, enhancing its aesthetic appeal and functionality.
Implementation Method 1
Vibration welding joins components by 'rubbing' them together, creating heat through the friction, melting the connection points, and applying/holding pressure until the components cool together
Implementation Method 2
During the cooling process, there is known to be shrinkage/deformation of materials. Namely, during the known vibration welding of an instrument panel and PSIR chute, there is a visible deflection of the instrument panel at the connection points between the components caused by uneven shrinkage during the cooling process
Data Source
AI summary
An automotive interior component including an airbag chute having at least one weld bar, and a pre-stressed instrument panel having a substrate layer for bonding to the weld bar. The pre-stressing provides tensile stress at weld bar bonding areas to reduce any deformation visible on an exposed surface of the instrument panel.