Vehicle Seat Longitudinal Adjuster Stiffness
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Solution Overview
Problem
Existing longitudinal adjusters for vehicle seats have limitations in rigidity and natural frequency, leading to disturbances such as rocking and vibrations, especially when the seat is empty, due to constraints in the support length and bearing elements.
Innovation Solution
Incorporating additional support elements with rotatable support rollers and vertical-direction acting support springs between the upper and lower rails, which increase the support length and rigidity by providing additional support points and minimizing friction, while compensating for manufacturing tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the support length between upper and lower rails is increased to improve stiffness, then the natural frequency of the vehicle seat increases, but the adjustment range of the longitudinal adjuster is limited by the maximum length of ball cages
Solution Approach 1:
The support function is segmented into two independent systems: ball cages for comfort adjustment and support elements with support rollers for additional stiffness. This segmentation allows each system to be optimized independently - ball cages provide adjustment within comfort range while support elements extend support length without limiting adjustment range
Solution Approach 2:
Support elements with support rollers act as intermediary components between the upper and lower rails. These intermediaries provide additional support points that increase stiffness while allowing the ball cages to maintain their full adjustment range for comfort positioning
2Strength
If ball cages are made longer to increase support length, then stiffness improves, but the length is constrained by the maximum adjustment range and rail length
Solution Approach 1:
The support function is divided between ball cages (for adjustment) and support elements (for stiffness). This allows support length to be extended through support elements without increasing ball cage length, thereby maintaining adjustment capability while improving stiffness
Solution Approach 2:
Instead of extending support length solely through longer ball cages (one dimension), the solution introduces support elements that create additional support points along the rail length, effectively utilizing the longitudinal dimension to increase support length without constraining ball cage dimensions
3Reliability
If the vehicle seat has high natural frequency to prevent vibrations, then rocking and disturbing noises are reduced, but the longitudinal adjuster requires higher stiffness which limits design flexibility
Solution Approach 1:
The longitudinal adjuster is segmented into independent functional modules: ball cages for adjustment and support elements for stiffness. This modular segmentation achieves high stiffness for vibration prevention while maintaining design flexibility, as each module can be independently optimized without compromising the other
Solution Approach 2:
The support elements are designed with rotatable support rollers that provide dynamic adaptation to load conditions. This dynamic design allows the support elements to maintain contact and provide stiffness while accommodating movement and adjustment, thereby preserving design flexibility while achieving high natural frequency
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 enhanced rigidity of the longitudinal adjuster increases the natural frequency of the vehicle seat, reducing disturbances like rocking and vibrations, and allowing for smoother adjustments within a comfort range and beyond into an easy-entry position.
Implementation Method 1
the at least one support element comprises a support spring which acts on the support roller in the vertical direction
Implementation Method 2
Because the rotatable support roller defines the additional support point, comparatively little friction is generated when the upper or lower rail slides along the support element and the support roller rolls against it
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a longitudinal adjuster for a vehicle seat (1), comprising a lower rail (5) and an upper rail (3) which is guided therein such that it can be displaced in the longitudinal direction, and at least one bearing element (30) which is arranged between the upper rail (3) and the lower rail (5) and is in contact with the upper rail (3) and the lower rail (5), wherein at least one additional supporting element (20) is provided which is in contact with the upper rail (3) and the lower rail (5) and has a rotatable supporting roller (22). Here, the supporting roller (22) can be rotated about a rotational axis (A) which runs in the vertical direction, and the at least one supporting element (20) comprises a supporting spring (26) which loads the supporting roller (22) in the vertical direction. The invention also relates to a vehicle seat (1) which comprises at least one longitudinal adjuster according to the invention.