Double Pawl Closure Latch for Crash-Resistant Ratchet Retention
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Solution Overview
Problem
Existing closure latches for vehicle doors struggle to maintain the ratchet in primary and secondary striker capture positions during normal and crash conditions, with inadequate support for the primary pawl during deformation.
Innovation Solution
A closure latch assembly with a double pawl mechanism, featuring a primary pawl supported by a primary pivot post during normal conditions and both primary and secondary pivot posts during crashes, and a secondary pawl to backstop the primary pawl's movement during crashes, ensuring the ratchet remains in the primary striker capture position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single pawl is used to hold the ratchet in the primary striker capture position, then the latch structure is simpler, but the reliability during crash conditions deteriorates
Solution Approach 1:
The latch mechanism is segmented into multiple functional pawls: a primary pawl for normal operation and a secondary pawl specifically for crash conditions. This segmentation allows each pawl to be optimized for its specific function, with the secondary pawl providing additional support during crash conditions when the primary pawl may deform.
Solution Approach 2:
The secondary pawl acts as a pre-positioned protective element that engages before the primary pawl can deform under crash loads. By having this backup pawl already in place and properly positioned, the system provides beforehand cushioning against crash conditions, preventing ratchet release before failure occurs.
2Adaptability or versatility
If a double pawl mechanism is used to maintain both primary and secondary striker capture positions, then the latch can maintain multiple positions, but the complexity of the mechanism increases
Solution Approach 1:
The ratchet mechanism is designed with a single ratchet surface that can be engaged by both the primary pawl and secondary pawl. This universal design allows the same ratchet structure to serve multiple functions: normal operation with the primary pawl and crash protection with the secondary pawl, reducing overall system complexity.
Solution Approach 2:
The primary and secondary pawls are merged into a unified latch mechanism that shares common components including the ratchet, pivot posts, and biasing members. This merging approach allows the system to maintain multiple positions (primary and secondary striker capture positions) while minimizing the increase in complexity through shared structural elements.
3Strength
If the primary pawl is supported by only one pivot post, then the structure is simpler, but the load-bearing capacity during crash conditions deteriorates
Solution Approach 1:
The support structure for the primary pawl is extended from a single pivot post to two pivot posts (primary and secondary pivot posts). This dimensional change in the support structure provides additional load-bearing paths, distributing crash forces across multiple structural elements and significantly increasing the load-bearing capacity during crash conditions.
Solution Approach 2:
The secondary pivot post and secondary pawl are pre-positioned and prepared in advance to provide additional support during crash conditions. This preliminary arrangement ensures that when crash forces apply, the extra support structure is already in place to immediately分担 the load, enhancing strength without requiring complex real-time adjustment mechanisms.
Data Source
AI summary
A closure latch assembly for a closure member of a motor vehicle, including a latch mechanism including a ratchet, a double pawl mechanism having a primary pawl for holding the ratchet in a primary latched position, and a secondary pawl for holding the ratchet in a secondary latch position, wherein the primary pawl is configured to abut the secondary pawl during a crash condition to prevent the ratchet to move to its striker release position.