Vehicle Seat Detent Fitting Four-Bar Chain Locking Mechanism
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Solution Overview
Problem
Existing detent fittings for vehicle seats lack a secure and play-free locking mechanism that is optimized for weight and construction space, particularly in providing an additional free-pivoting function for facilitating rear seat access.
Innovation Solution
The detent fitting incorporates a four-bar chain mechanism with a locking cam, coupler, and pawl, where one hinge point is a turning and sliding joint, allowing the pawl to be locked in a dead center position to support crash forces effectively and reduce construction space requirements, while a spring prestresses the chain to maintain contact without play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional locking mechanism is used for the free-pivoting function, then the structure is simple, but the locking is not secure and has play
Solution Approach 1:
The locking cam is designed to move between locked and unlocked positions dynamically, allowing the pawl to be secured in the locked position through mechanical engagement while permitting free movement when unlocked. This dynamic mechanism provides secure locking without requiring complex additional components.
2Strength
If additional space is allocated for crash force support, then crash forces are supported effectively, but construction space increases
Solution Approach 1:
The locking cam serves dual functions: it locks the pawl in the locked position to support crash forces, and it enables free-pivoting when unlocked. By merging these functions into a single component, the mechanism provides effective crash force support without requiring additional space for separate support structures.
3Volume of stationary object
If a four-bar chain mechanism is used, then construction space is reduced, but the mechanism requires precise prestressing to eliminate play
Solution Approach 1:
The spring prestressing force is optimized to eliminate play in the four-bar chain mechanism while maintaining compact dimensions. By carefully selecting the spring parameters (force, stiffness), the mechanism achieves play-free operation without requiring excessive prestressing that would increase component sizes.
4Strength
If the pawl is locked in dead center position, then crash forces are supported effectively, but the mechanism becomes more complex
Solution Approach 1:
The locking cam is designed to automatically position the pawl in the dead center locked position before crash forces act, preparing the mechanism in advance to support crash forces effectively. This preliminary positioning action is achieved through the natural mechanical engagement of the cam and pawl geometry.
Data Source
AI summary
A detent fitting for a motor vehicle seat includes a first fitting part (11) and a relatively rotatable second fitting part (12) and catches (16) guided by one fitting part between a locked state and an unlocked state to lock the detent fitting upon interacting with a gear ring of another fitting part. A third fitting part (74) is pivotably mounted and is lockable with a detent plate (115) fixed to the first fitting part or with the first fitting part by a pawl (80) which is mounted in a hinge point on the third fitting part. The third fitting part, a locking cam (90) with a hinge point on the third fitting part, a coupling (98) connected to the locking cam with a hinge point and the pawl with a hinge point define a four-link chain. A vehicle seat with at least one such detent fitting is also provided.