Automotive Hood Joint Layout for Thermal Deformation Control
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Solution Overview
Problem
Automotive exterior components, such as hood panels, experience thermal deformation due to adhesive hardening during the baking process, leading to surface quality issues and unnatural unevenness, particularly exacerbated by thinner sheet thickness and lower rigidity in recent vehicle weight reduction efforts.
Innovation Solution
An automotive exterior component design featuring an outer panel and inner panel joined by a specific arrangement of spot-shaped joints, with first-direction and second-direction joint rows having different curvatures and intervals, and units with annular flanges, inclined walls, and bottom portions, arranged in a close-packed polygonal or circular configuration to reduce thermal deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the sheet thickness of the outer panel is reduced to decrease vehicle weight, then the weight of the vehicle is reduced, but the rigidity of the outer panel decreases and thermal deformation occurs more easily
Solution Approach 1:
The continuous adhesive bonding is segmented into discrete spot joints arranged in specific patterns. This segmentation reduces the total adhesive volume and creates isolated stress concentration points, allowing the thin outer panel to maintain rigidity without experiencing widespread thermal deformation during baking.
Solution Approach 2:
The joint arrangement creates regions of different stiffness characteristics. By strategically positioning spots with varying intervals in different directions, the structure achieves localized rigidity enhancement where needed while maintaining overall flexibility to accommodate thermal expansion without distortion.
2Strength
If adhesive is applied to join inner and outer panels, then the panels are securely connected, but thermal deformation occurs in the outer panel during baking, reducing surface quality
Solution Approach 1:
The adhesive bonding is divided into multiple discrete spot joints rather than continuous application. This segmentation limits the cumulative thermal contraction effect, preventing the large-scale surface deformation that occurs with continuous adhesive layers during the baking process.
Solution Approach 2:
The spot joints are arranged asymmetrically with different intervals in different directions (first direction vs. second direction). This asymmetric arrangement compensates for differential thermal expansion and contraction stresses, maintaining surface flatness while ensuring adequate connection strength.
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 design effectively minimizes thermal deformation, enhances panel rigidity and dent resistance, and maintains a high level of surface quality by optimizing the joint arrangement and distribution, allowing for a lighter yet robust automotive exterior component.
Implementation Method 1
an inner panel and an outer panel are joined using an adhesive... Mastic sealers and the like are known as adhesives for joining an inner panel and an outer panel... deformation that accompanies hardening of the adhesive
Implementation Method 2
During the baking, strain (thermal deformation) occurs in the outer panel due to deformation that accompanies hardening of the adhesive... the outer panel will deform so as to sink inward at places where the adhesive is applied
Data Source
AI summary
An automobile hood 1 has a first-direction joint row 30 in which a plurality of joints 20 are arranged at an interval from each other in a cross direction X, and a second-direction joint row 40 in which a plurality of the joints 20 are arranged at an interval from each other in a longitudinal direction Y. A curvature 1/R1 in a direction along the first-direction joint row 30 in a region of the outer panel 3 corresponding to the first-direction joint row 30 is smaller than a curvature 1/R2 in a direction along the second-direction joint row 40 in a region of the outer panel 3 corresponding to the second-direction joint row 40. An interval X1 between the joints 20 in the first-direction joint row 30 is greater than an interval Y2 between the joints 20 in the second-direction joint row 40.