Interior Mirror Base Securing Element With Thermal Expansion Compensation
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Solution Overview
Problem
Existing securing elements for attaching components in motor vehicles experience plastic elongation and loosening due to temperature variation, leading to unreliable attachments and noise issues like creaking and rattling.
Innovation Solution
A hermetic plastic body with a cavity containing a filling medium having a higher thermal expansion coefficient than the plastic, which expands and contracts more than the plastic, maintaining a prestressed position and ensuring secure attachment through elastic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hook is used to attach components, then the attachment is simple and easy to manufacture, but the attachment becomes loose and unreliable when temperature varies due to plastic elongation
Solution Approach 1:
The patent introduces a filling medium with a higher thermal expansion coefficient than the plastic body to compensate for thermal expansion of the hook material. This parameter change in the filling medium's physical property (thermal expansion coefficient) counteracts the thermal deformation of the hook, maintaining attachment reliability across temperature variations without compromising manufacturing simplicity
Solution Approach 2:
The patent creates a composite structure by enclosing a filling medium (gas, liquid, or powder) within a hermetic plastic body. This composite system combines the structural function of the plastic hook with the thermal compensation function of the filling medium, achieving both ease of manufacture and temperature-independent reliability
2Device complexity
If a hook is used to attach components, then the structure is simple, but noises such as creaking and rattling occur due to loosening from plastic elongation
Solution Approach 1:
By changing the physical parameter of the filling medium (selecting materials with specific thermal expansion coefficients higher than the plastic), the patent prevents thermal loosening that causes noise. The filling medium expands more than the plastic body when heated, maintaining constant pre-stress on the hook and eliminating creaking and rattling noises without increasing structural complexity
Solution Approach 2:
The patent converts the harmful effect of thermal expansion into a beneficial effect by using a filling medium that expands more than the plastic body. This excessive expansion of the filling medium compensates for the plastic's thermal deformation, transforming the potential harm of thermal effects into a benefit that maintains tight attachment and eliminates noise
3Temperature
If the hook is heated beyond softening temperature, then plastic elongation occurs, but this causes loosening of the attachment and reduces reliability
Solution Approach 1:
The patent changes the physical parameter of the filling medium to have a thermal expansion coefficient significantly higher than the plastic body. This parameter change ensures that even when the plastic approaches its softening temperature, the filling medium's expansion compensates for the plastic's deformation, maintaining attachment reliability across the entire temperature range up to the softening point
Solution Approach 2:
The hermetic body enclosing the filling medium acts as a pre-configured compensation mechanism that cushions against thermal deformation before it causes harm. The filling medium is positioned in advance to expand and compensate for plastic elongation, preventing loosening and maintaining reliability even when temperature approaches the softening point
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 provides a secure and noise-free attachment by compensating for thermal expansion, maintaining reliability and reducing noise, with optional vibration damping and controlled deformation through partition walls and connecting webs.
Implementation Method 1
The coefficient of thermal expansion and therefore the thermal expansion of the filling medium, at least up to a softening temperature of the plastic of the body, is greater than the coefficient of thermal expansion, and the thermal expansion, of the plastic
Implementation Method 2
The powder in the filling medium results in acoustic damping of the securing element
Data Source
AI summary
A securing element for a motor vehicle has a hermetic body made of plastic which encloses a cavity. The cavity is filled with a filling medium. The thermal expansion coefficient of the filling medium is, up to a softening temperature of the plastic, greater than the thermal expansion coefficient of the plastic. A cover for an interior mirror base of a motor vehicle includes such a securing element.