Vehicle Seat Fitting Four-Bar Linkage Locking
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Solution Overview
Problem
Existing vehicle seat fittings for adjusting the backrest inclination lack a weight-optimized and space-optimized locking mechanism for free pivoting, which is essential for facilitating passenger access and withstanding crash forces effectively.
Innovation Solution
A four-bar linkage mechanism is introduced, comprising a pawl, locking cam, and coupler, where the locking cam is mounted on the third fitting part, and the pawl is locked in a dead center position to effectively support crash forces, with a turning and sliding joint allowing for zero backlash and efficient locking without play, and a spring prestressing the linkage for secure locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking mechanism is added to the fitting to support crash forces, then the reliability and safety are improved, but the device complexity and weight increase
Solution Approach 1:
The locking mechanism is merged with the existing four-bar linkage mechanism. The pawl and locking cam are integrated into the linkage, sharing common components (coupler, hinge points) and working space, thereby providing crash force support without proportionally increasing overall device complexity
Solution Approach 2:
The locking mechanism utilizes the existing motion and forces in the four-bar linkage system. The pawl automatically engages with the locking cam at dead center positions where the linkage naturally experiences maximum force, using the system's own operational characteristics to provide locking without requiring separate actuation or additional energy input
2Reliability
If a locking mechanism is added to the fitting to support crash forces, then the reliability and safety are improved, but the weight of the fitting increases
Solution Approach 1:
The locking components (pawl, locking cam) are integrated into the existing four-bar linkage structure, sharing common materials and manufacturing processes. This merging approach provides crash force support capability while minimizing additional weight compared to a completely separate locking mechanism
Solution Approach 2:
The locking mechanism is designed to engage at dead center positions where the linkage geometry provides maximum mechanical advantage and force support with minimal component mass. The pawl and locking cam are sized and positioned to provide adequate crash force support while keeping weight additions minimal
3Manufacturing precision
If a four-bar linkage mechanism is used for locking, then the manufacturing precision and zero backlash are improved, but the device complexity increases
Solution Approach 1:
The four-bar linkage serves dual functions: normal backrest adjustment and secure locking at dead center positions. By merging these functions into a single mechanism rather than adding a separate locking system, the patent achieves zero backlash locking while managing overall device complexity through functional integration
Solution Approach 2:
The linkage mechanism automatically achieves precise locking at dead center positions where the geometry naturally provides maximum stability and zero backlash. The system uses its own operational characteristics and existing forces to provide precise locking without requiring additional precision components or complex control mechanisms
Data Source
AI summary
A fitting (10) for a vehicle seat has a first fitting part (11) and a second fitting part (12) that are rotatable relative to one another and are in geared connection, and a third fitting part (74) mounted on the first fitting part (11) such that it can be pivoted relative to the first fitting part (11). The third fitting part (74) can be locked to the first fitting part (11) by a pawl (80) which is mounted at a first articulation point (D1) on the third fitting part (74). The third fitting part (74), which has a locking cam (90), which is mounted at a second articulation point (D2), a coupler (98), which is connected at a third articulation point (D3) to the locking cam (90) and at a fourth articulation point (D4) to the pawl (80), and the pawl (80) define a four-bar linkage (74, 80, 98, 90).