Vehicle Door Rail Backlash Design for Thermal Expansion
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Solution Overview
Problem
The challenge is maintaining a water-stopping function in vehicle door openings when using different materials for the frame and rail, which have varying linear expansion coefficients, leading to thermal deformations that can cause gaps between the rail and weather strip, compromising the water-stopping function.
Innovation Solution
The solution involves a rail fixed to a frame with varying backlash widths at different fixation points, allowing for thermal expansion and contraction without warping or bending, thereby maintaining the positional relationship with the weather strip, using a configuration where the second fixation points have larger backlash widths than the first, allowing for free displacement at the rail's ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If different materials (metal frame and resin rail) are used for frame and rail to reduce vehicle weight, then weight is reduced, but thermal deformation differences cause the rail to warp or bend
Solution Approach 1:
The patent applies local quality by providing different backlash widths at different fixation parts along the rail. The intermediate fixation part has a smaller backlash width to maintain stability, while the end fixation parts have larger backlash widths to accommodate thermal expansion. This localized differentiation allows the rail to handle thermal deformation without warping, resolving the contradiction between using lightweight different materials and maintaining shape stability.
2Stability of the object's composition
If the rail is rigidly fixed to the frame at all points, then the rail is stable, but thermal expansion causes the rail to warp or bend
Solution Approach 1:
The patent changes the parameter of backlash width at different fixation parts to resolve the contradiction. By setting larger backlash widths at the end fixation parts and a smaller backlash width at the intermediate fixation part, the rail can expand and contract thermally without warping, while still maintaining stable contact with the weather strip to ensure the water stopping function remains reliable.
3Reliability
If the rail is allowed to move freely at all fixation parts, then thermal expansion is accommodated, but the rail becomes unstable and gaps form with the weather strip
Solution Approach 1:
The patent applies local quality by differentiating the fixation parts along the rail's longitudinal direction. Intermediate fixation parts have smaller backlash widths to maintain stability, while end fixation parts have larger backlash widths to accommodate thermal expansion. This localized approach allows the rail to move freely where needed while remaining stable where required, preventing gaps with the weather strip.
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
This configuration stabilizes the positional relationship between the rail and weather strip, preventing gaps and maintaining the water-stopping function even with materials having different linear expansion coefficients, ensuring effective rainwater prevention.
Implementation Method 1
the rail thermally expands or thermally contracts starting from the first fixation part, and the thermal deformation amount is maximum at the opposite end parts where the second fixation parts are provided
Data Source
AI summary
A vehicle includes a vehicle body including: an elongated frame made of a first material and extending along a door opening; and an elongated rail made of a second material having a linear expansion coefficient different from that of the first material, the rail covering the frame and extending along the frame, the rail being configured to abut with a weather strip when a door closes the door opening. The rail is fixed to the frame at a plurality of fixation parts that includes: a first fixation part provided in an intermediate part of the rail in the longitudinal direction of the rail; and second fixation parts provided, respectively, in opposite end parts of the rail in its longitudinal direction. In the longitudinal direction of the rail, backlash widths at the second fixation parts are larger than a backlash width at the first fixation part.