Window Lift Rail Layout for Bowden Cable Sag Compensation
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Solution Overview
Problem
Window regulator systems in motor vehicles face challenges in reliably moving the window pane into a closed position due to high friction forces and sagging of the Bowden cable, especially under temperature and humidity fluctuations, leading to impaired positionability and force transmission.
Innovation Solution
A window regulator system with a first guide rail and a second guide rail, where the first slider is positioned at a predetermined distance from its stop, between 0.4% and 1.2% of the Bowden cable sheath length, ensuring reliable force transmission to the second slider, even with sagging, and reducing tilting of the window pane by maintaining a small distance range between 3 mm and 8 mm, thus facilitating efficient assembly with fewer parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the Bowden cable sheath is made long to accommodate the guide rail configuration, then the system can achieve the required geometric arrangement, but the cable sags more under temperature and humidity fluctuations, impairing reliable force transmission
Solution Approach 1:
The patent applies preliminary action by pre-positioning the first slider at a specific distance (0.4%-1.2% of Bowden cable sheath length) from the first stop before the window pane reaches the closed position. This anticipatory positioning compensates for expected cable sag, ensuring the second slider maintains sufficient tension and contact with the second stop throughout the window's movement, particularly under varying temperature and humidity conditions.
Solution Approach 2:
The patent changes the parameter of slider positioning by introducing a specific distance range (0.4%-1.2% of Bowden cable sheath length, or 3-8 mm) between the first slider and the first stop. This parameter optimization ensures reliable force transmission while accommodating cable sag, resolving the contradiction between long cable sheath geometry and reliable force transmission.
2Device complexity
If both sliders are positioned at the same distance from their respective stops, then the window pane positioning is simplified, but the force transmission to the second slider becomes insufficient due to cable sag
Solution Approach 1:
The patent applies asymmetry by deliberately positioning the first slider at a different distance from the first stop compared to the second slider's distance from the second stop. The first slider is positioned at 0.4%-1.2% of the Bowden cable sheath length from its stop, while the second slider contacts its stop directly. This asymmetric configuration compensates for cable sag and ensures sufficient force transmission to the second slider.
3Shape
If the first slider is positioned close to the first stop to minimize window pane tilt, then assembly is simplified, but force transmission to the second slider is compromised under cable sag conditions
Solution Approach 1:
The patent optimizes the parameter of the first slider's distance from the first stop to a specific range (0.4%-1.2% of Bowden cable sheath length, or 3-8 mm). This optimized parameter simultaneously minimizes window pane tilt and ensures sufficient force transmission to the second slider, even when the Bowden cable sags under temperature and humidity variations.
Data Source
AI summary
A window lift system including a first guide rail including a first stop, a second guide rail which has a second stop in an upper end region, a first slider guided on the first guide rail, a second slider guided on the second guide rail, cable drum, and a drive cable driven by means of the cable drum and coupled to the sliders and extending through a Bowden cable sheath between the upper end region of the second guide rail and a lower end region of the first guide rail. The sliders are movable by the drive cable along the guide rails into a stop position in which the second slider lies against the second stop and the first slider is spaced apart from the first stop by a predefined distance ranging between 0.4 percent and 1.2 percent of the length of the Bowden cable sheath.