Vehicle Door Latch Roller Pawl for Low-Force Release
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Solution Overview
Problem
Existing automotive door latch mechanisms face issues with high frictional forces between the ratchet and pawl, leading to undesirable high door latch release effort, and existing solutions like double pawl configurations and low friction lubrication have limitations such as short lifespan and manufacturing complexity.
Innovation Solution
A closure latch assembly with a primary pawl assembly and a secondary pawl, featuring a rolling member and a ratchet with a secondary striker capture position, designed to reduce friction and maintain reduced friction over the latch assembly's life, including a secondary pawl pivotally supported for engagement with a ratchet rivet during crash states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ratchet and pawl mechanism is used for door latch, then the door can be securely held in closed position, but high static and dynamic frictional forces are generated between ratchet and pawl during relative movement
Solution Approach 1:
A roller element is introduced as an intermediary between the pawl and ratchet teeth. The roller reduces direct sliding contact to rolling contact, significantly lowering frictional forces during engagement and disengagement while maintaining the secure holding function through the ratchet-pawl mechanism
2Ease of operation
If low friction lubrication or plating is applied to reduce friction between ratchet and pawl, then friction is reduced, but the lubrication and plating wear away over time resulting in short lifespan
Solution Approach 1:
The roller serves as a durable intermediary component that transfers wear from the lubricated/plated ratchet and pawl surfaces to the roller itself. This protects the critical mating surfaces from wear while the roller can be easily replaced or is designed with sufficient service life
Solution Approach 2:
The invention replaces sliding friction mechanics with rolling friction mechanics. By substituting the sliding contact mechanism with a rolling element, the fundamental nature of friction is changed from high static/dynamic sliding friction to much lower rolling friction, eliminating the need for heavy reliance on lubrication
3Ease of operation
If double pawl configuration or special low friction lubrication is used, then friction is reduced, but manufacturing complexities and cost increase
Solution Approach 1:
The roller is a simple, single-component intermediary that can be manufactured using standard processes. It eliminates the need for complex double pawl mechanisms or specialized low-friction coatings, providing friction reduction through a straightforward rolling contact design that is easier and cheaper to manufacture
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 assembly achieves reduced manual and electrical release efforts in normal conditions and prevents unintended opening during crashes by maintaining the ratchet in a secondary striker capture position, enhancing safety and durability.
Implementation Method 1
a rolling member rotatably between the primary pawl and the ratchet
Implementation Method 2
the secondary pawl is configured to engage a ratchet rivet extending laterally outwardly from the main body of the ratchet to hold the ratchet in the secondary striker capture position
Data Source
AI summary
A latch assembly for a vehicle closure member including a frame plate, a ratchet rotatably mounted to the frame plate, a pawl assembly rotatably mounted to the frame plate for holding the ratchet in a primary striker capture position and for releasing the ratchet to allow the ratchet to rotate toward a striker releasing position during a non-crash state of the latch assembly, and a secondary pawl rotatably mounted to the frame plate for holding the ratchet in a secondary striker capture position during a crash state of the latch assembly.