Plastic Screw Fixing Light Metal Headlight Module
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Solution Overview
Problem
Existing fastening systems for motor vehicle light modules, particularly those involving light metal and plastic components, face issues with high costs and reliability due to the use of screws specifically designed for light metals, which often exert excessive pressure on plastic components, leading to failure in shock and heat-humidity cycle tests.
Innovation Solution
A self-tapping plastics technology screw with a second diameter greater than the first diameter, calculated using the formula D=An+K*(d0-1), is used to create a reliable screw connection by ensuring the screw can be processed into a pre-drilled hole in the light metal component without breaking, thereby reducing pressure and ensuring the screw connection meets the IEC 60068-2-38 standard.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If screws specifically designed for light metals are used, then the screw connection can be made in light metal components, but the screws exert excessive pressure on plastic components causing them to fail in shock and heat-humidity cycle tests
Solution Approach 1:
The patent applies parameter changes by modifying the hole diameter parameter in the fastening system. Specifically, the hole diameter is set to a larger value (greater than the screw diameter by a specific amount) to reduce the contact pressure between the screw and the plastic component. This parameter adjustment allows the use of standard plastic screws while preventing excessive pressure that would cause failure in shock and heat-humidity cycle tests.
2Reliability
If screws specifically designed for light metals are used, then the screw connection can be made in light metal components, but the cost increases
Solution Approach 1:
The patent applies universality by making the fastening system compatible with standard plastic screws that can be used across multiple material types (plastic, light metal, and combinations thereof). By designing the hole with a universal diameter that is larger than the screw diameter, the system can use off-the-shelf plastic screws rather than requiring specialized light metal screws, thereby reducing costs while maintaining reliability across different material combinations.
3Object-affected harmful factors
If the hole diameter is increased beyond the screw diameter, then the pressure on plastic components is reduced, but the precision of the screw connection may be affected
Solution Approach 1:
The patent applies parameter changes by establishing specific relationships between hole diameter and screw diameter parameters. The hole diameter is set to be greater than the screw diameter by a controlled amount, which optimizes the balance between reducing contact pressure on plastic components and maintaining sufficient manufacturing precision for reliable screw connections.
Data Source
Figure 1
AI summary
Fastening system (1) for a motor vehicle lighting module comprising a thread-forming plastic screw (4a, 4b) with a first diameter (d0) and a light metal component (2) of a motor vehicle lighting module, wherein the light metal component (2) has a pre-drilled hole (6a, 6b), wherein the pre-drilled hole (6a, 6b) is associated with the plastic screw (4a, 4b) and has a second diameter (D), wherein the second diameter (D) is larger than a predetermined value and the value of the second diameter (D) depends at least on the value of the first diameter (d0), wherein the thread-forming plastic screw (4a, 4b) can be screwed into the pre-drilled hole (6a, 6b).