Closure Latch Pawl Sensor with Lost Motion Coupling
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Solution Overview
Problem
Existing closure latch assemblies for motor vehicle panels are prone to unintended pawl movement from the ratchet holding position to the releasing position due to unforeseen impact forces, such as during a crash, which can lead to improper operation and safety issues.
Innovation Solution
A latch assembly design that includes a pawl sensor arrangement with a lost motion coupling to prevent the sensor from inadvertently moving the pawl, featuring a housing member, a ratchet, a pawl, and a sensor assembly with a first and second sensor member, where the second sensor member is biased to maintain the pawl in the holding position even when the housing member is deformed, and a pawl release lever to indicate the ratchet releasing position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet or feature is fixed directly to the pawl for position detection, then the sensor can effectively indicate the pawl position, but the pawl may be inadvertently moved from the ratchet holding position to the releasing position during a crash condition
Solution Approach 1:
The sensor assembly is segmented into two separate sensor members: a first sensor member fixed to the housing member and a second sensor member fixed to the pawl. This segmentation allows the system to detect pawl position without requiring a magnet or feature directly on the pawl that could be displaced by impact forces, thereby maintaining both measurement precision and reliability under crash conditions.
Solution Approach 2:
A third component (the first sensor member fixed to the housing) is introduced as an intermediary reference point. The second sensor member's position relative to this fixed reference indicates the pawl position, eliminating the need for direct magnet-pawl attachment and preventing inadvertent movement during impact while maintaining accurate position detection.
2Reliability
If the second sensor member is moveable relative to the pawl and housing member, then the sensor assembly can indicate pawl position without fixed attachment, but the device complexity increases
Solution Approach 1:
The magnetic feature is extracted from the pawl and placed on the second sensor member instead. This extraction allows the second sensor member to move independently relative to both the pawl and housing member, enabling reliable position indication without fixed attachment while the complexity increase is minimized by using a simple magnetic coupling mechanism.
Data Source
AI summary
A latch assembly for a closure panel includes a housing member and a ratchet configured for movement relative to the housing member between a striker capture and striker release positions. A pawl is configured for movement relative to the housing member between a ratchet holding position, whereat the pawl maintains the ratchet in the striker capture position, and a ratchet releasing position, whereat the pawl releases the ratchet for movement of the ratchet to the striker release position. A pawl sensor assembly includes a first sensor member fixed relative to the housing member and a second sensor member movable from a first position to a second position. The first position indicates the pawl in the ratchet holding position, and the second position indicates the pawl in the ratchet releasing position. The second member is moveable relative to the pawl and the housing member.