Vehicle Seat Rail Locking Layout to Prevent Tooth-On-Web Jamming
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Solution Overview
Problem
Existing adjustment devices for vehicle seats in a longitudinal direction face challenges such as delayed or hindered positive-fit locking due to 'tooth-on-web' positions, especially in electrically actuated systems, and difficulty in meeting safety standards with small sheet thicknesses.
Innovation Solution
An adjustment device with an ancillary locking system featuring locking structures on both sides of the seat rails, arranged at regular distances with an offset in the longitudinal direction, ensuring that if a 'tooth-on-web' position occurs on one side, it cannot exist on the other side, facilitating quick and reliable locking during crashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-sided toothing and hole pattern are used in the ancillary locking device, then the structure is simpler, but a 'tooth-on-web' position may occur which delays or hinders positive-fit locking
Solution Approach 1:
The locking device is segmented into two independent sides, each with its own toothing and hole pattern. The first toothing and first hole pattern are arranged such that their locking elements do not align, preventing simultaneous tooth-on-web positioning on both sides. This segmentation ensures that if one side experiences a tooth-on-web condition, the other side can still achieve positive-fit locking.
Solution Approach 2:
The first and second hole patterns are positioned asymmetrically relative to each other in the longitudinal direction. This asymmetric arrangement ensures that the locking elements (teeth and recesses) on opposite sides do not correspond in position, making it impossible for both sides to be in a tooth-on-web state simultaneously. The asymmetry breaks the symmetry of the problem that causes tooth-on-web positioning.
2Reliability
If the locking structures are arranged at regular distances with offset positioning, then crash safety is enhanced by preventing tooth-on-web positions, but the device complexity increases
Solution Approach 1:
The hole patterns are pre-positioned at regular distances along the longitudinal direction with a specific offset between opposite sides. This preliminary arrangement of locking structures ensures that during normal operation and in crash scenarios, the geometry prevents tooth-on-web positioning from occurring simultaneously on both sides, enabling reliable positive-fit locking when force is applied.
3Weight of moving object
If small sheet thickness is used to match the locking increment, then the device is lighter, but it becomes difficult to comply with safety standards
Solution Approach 1:
The solution moves from a single-dimensional constraint (matching locking increment to sheet thickness) to a two-dimensional solution by utilizing the longitudinal offset arrangement of hole patterns on opposite sides. This allows the use of smaller sheet thicknesses while maintaining safety through the geometric arrangement of locking elements in both longitudinal and transverse dimensions, rather than relying solely on increased thickness.
Data Source
AI summary
Disclosed is an adjustment device (103) for the adjustment of the position of a vehicle seat in a longitudinal direction, comprising at least one pair of rails comprising a first, fixed rail (3) and a second rail (5) movably guided thereto in a longitudinal direction (x), and an ancillary locking device (107) which comprises a plurality of first locking structures (24, 25) formed on or connected to the second rail (5), and a plurality of second locking structures (36, 37) formed corresponding to the first locking structures and formed on or connected to the first rail (3). The ancillary locking device is not active in a normal mode and, after introduction of forces in the event of a crash, causes an additional locking of the second rail (5) to the first rail (3) by positively locking of the first and second locking structures (24, 25; 36, 37) to one another.In order to ensure a locking of the longitudinal position of the pair of seat rails in the event of a crash by the ancillary locking device in any longitudinal positions, the first and second locking structures (24, 25; 36, 37) are arranged on both sides of the respective pair of rails and at regular distances (a) from one another in the longitudinal direction (x), wherein the first locking structures (24a, 25a; 24b, 25b) or the second locking structures (36a, 37b; 36b, 37b) are arranged offset from one another in the longitudinal direction (x) on the two sides of the respective pair of rails.