Vehicle Seat Fitting Eccentric Cam Locking Mechanism
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Solution Overview
Problem
Existing vehicle seat fittings are sensitive to tolerances and difficult to assess reliably, especially under unfavorable load conditions, leading to potential undesired opening due to cyclical or vibratory stresses.
Innovation Solution
A fitting design featuring a toothed ring and radially displaceable locking bars with eccentric cams, where the first eccentric cam has a concentric cam portion to ensure secure locking and allow clear measurement of rotational angular deviation, reducing sensitivity to tolerances and enhancing locking security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional eccentric with self-locking contour is used, then the fitting can be locked securely under static conditions, but the eccentric may rotate undesiredly under cyclical or vibratory stresses leading to fitting opening
Solution Approach 1:
The eccentric is divided into two functionally distinct cams: a first cam with a self-locking contour for preventing reverse rotation under load, and a second cam with a concentric portion for providing a reliable angular reference position. This segmentation allows each cam to specialize in one aspect of locking reliability without compromising the other.
Solution Approach 2:
The concentric cam portion is designed to establish a predetermined angular reference position of the eccentric relative to the locking bar before any load is applied. This preliminary positioning ensures that the eccentric starts from a known, reliable angular position that is less sensitive to tolerance variations.
2Measurement precision
If the eccentric angle is used to monitor the fully locked position, then the locking state can be detected, but measurement inaccuracies lead to false assessment of the fitting state
Solution Approach 1:
The concentric cam portion establishes a predetermined angular reference position of the eccentric relative to the locking bar before any load is applied. This preliminary positioning ensures that the eccentric starts from a known, reliable angular position that is less sensitive to tolerance variations.
Solution Approach 2:
The concentric cam portion creates a geometric copy or reference of the ideal angular position relationship between the eccentric and locking bar. By having the eccentric return to this predetermined angular position after loading, the system provides a reliable reference that can be used to assess whether the fitting is properly locked, compensating for manufacturing tolerances.
3Reliability
If a first and second wedge angle system is used to compensate tolerances and block rotation, then locking reliability improves, but the system becomes very sensitive to tolerances in practice
Solution Approach 1:
The eccentric is divided into two functionally distinct cams: a first cam with a self-locking contour for preventing reverse rotation under load, and a second cam with a concentric portion for providing a reliable angular reference position. This segmentation allows each cam to specialize in one aspect of locking reliability without compromising the other.
Solution Approach 2:
The patent changes the geometric parameter of the cam profile from a conventional wedge angle to a concentric portion with a predetermined angle. This parameter change creates a more robust system where the angular reference position is determined by the geometry of the concentric portion rather than by sensitive wedge angle measurements, reducing tolerance sensitivity.
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 design provides a reliable assessment of the locked state and improved locking security, even under adverse conditions, with a slight increase in operating force during unlocking, indicating when the fitting is released, thus ensuring safer vehicle seat functionality.
Implementation Method 1
a rotatably mounted eccentric which during the transition from the unlocked state into the locked state by being rotated in a closing direction subjects the locking bar to a force for clamping the locking bar against the toothed ring
Implementation Method 2
at least one locking bar which is radially displaceably guided by means of the guide segments between a locked state and an unlocked state
Data Source
AI summary
A vehicle seat fitting has a fitting parts (11, 12) have a sprocket (17) and guide segments (14), a bar (16) guided by the guide segments between a locked and unlocked state that interact with the sprocket. The bar has bar cams (16a, 16b). An eccentric (27) is rotatably mounted around a rotation axis (A) and in a transition from unlocked to the locked, engages the bar with a force for clamping the bar against the sprocket. The eccentric has eccentric cams (28, 128) interacting with the bar cams. The first eccentric cam has a cam section (28.2) which runs in the peripheral direction concentrically around the axis. The cam section is arranged upstream in the closing direction of a further cam section (28.4) that has a cam contour running radially outwards downstream in the closing direction relative to the concentrically peripheral contour for clamping the bar against the sprocket.