Plastic Crankcase Vent Connection With Metal Screw-In Stop
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Solution Overview
Problem
Plastic components in motor vehicle crankcase ventilation devices face connection issues due to thermal stress, leading to potential material softening and weakening of connections under increased thermal loads.
Innovation Solution
A connection arrangement using a screw and nut with a metal screw-in stop limits axial force and prevents further screwing, ensuring a permanent and reliable connection by restricting the axial distance between the screw and nut, utilizing a smooth-walled sleeve or collar as the screw-in stop to prevent tilting and material flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plastic components are connected using conventional screw and nut arrangements, then the connection force increases, but the plastic material softens and flows under thermal stress, weakening the connection
Solution Approach 1:
The invention changes the geometric parameters of the screw connection by introducing a screw-in stop that limits the screwing-in depth. This parameter change restricts the axial compression force on the plastic nut, preventing material flow while maintaining adequate connection strength under thermal stress conditions.
Solution Approach 2:
The screw-in stop acts as an intermediary element between the screw and the plastic nut. It mediates the force transmission by limiting the maximum axial force that can be applied to the plastic nut, thereby preventing material deformation while still allowing sufficient connection force for secure assembly.
2Strength
If the screw is allowed to screw in completely, then the connection appears stronger, but the axial force causes plastic material to flow and weaken the connection
Solution Approach 1:
The screw-in stop modifies the geometric parameter of screw insertion depth, creating a defined stop position that prevents complete screwing in. This parameter control ensures the plastic nut maintains its structural shape while achieving adequate connection strength through optimized axial preload.
3Duration of action of stationary object
If a metal screw and nut are used to connect plastic components, then the connection durability improves, but the thermal stress causes plastic softening around the connection points
Solution Approach 1:
The screw-in stop introduces a geometric parameter that limits axial compression on the plastic nut. This parameter control allows the use of durable metal fasteners while preventing thermal stress-induced plastic softening by restricting the contact pressure between the metal components and plastic material.
Data Source
Figure 1~2
Figure 3~4
AI summary
The arrangement (4) has a screw (5) receivable in a recess (7) formed in a plastic component (2), and a nut (6), which is inserted into an undercut formed in a plastic component (3). A rotation stopper (14) is designed as a single-piece with the screw or the nut for limiting the rotation depth of the screw into the nut. The rotation stopper is designed as a smooth walled casing (12), where the winding of the screw is arranged adjacent to a screw front side. The rotation stopper is a blind hole that is formed in the nut and the screw is implemented as a collar screw.