Roller Pawl Closure Latch Assembly Friction Reduction
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Solution Overview
Problem
Automotive door latch mechanisms face high frictional forces between the ratchet and pawl, leading to increased release effort and wear, with existing solutions like double pawl configurations and low-friction lubrication having short lifespans and manufacturing complexities.
Innovation Solution
A latch assembly with a ratchet and pawl mechanism featuring a roller for pure rolling contact, cantilevered from a carrier plate, which reduces friction and wear by minimizing sliding contact between the ratchet, pawl, and roller, maintaining low friction over the latch's useful life without the need for service.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional sliding contact is used between ratchet and pawl, then the latch mechanism can be simple in structure, but high frictional forces increase release effort and wear
Solution Approach 1:
A roller element is introduced as an intermediary between the pawl and ratchet surfaces. The roller converts direct sliding contact into rolling contact, significantly reducing frictional forces during engagement and disengagement operations while maintaining the simplicity of the basic latch structure
Solution Approach 2:
The contact mode between pawl and ratchet is changed from sliding to rolling by introducing the roller element. This parameter change in the type of mechanical contact reduces the coefficient of friction and consequently reduces the release effort required to operate the latch
2Reliability
If low friction lubrication or plating is applied to reduce friction between ratchet and pawl, then friction is reduced initially, but the lubrication and plating wear away quickly
Solution Approach 1:
The roller serves as a durable intermediary component that carries the contact interface between pawl and ratchet. Instead of relying on consumable lubrication or plating layers, the roller's hard surface provides long-lasting low-friction contact that does not wear away as quickly as surface treatments
Solution Approach 2:
The solution replaces the chemical/surface-based friction reduction approach (lubrication and plating) with a mechanical approach (roller element). This substitution provides a more durable friction reduction mechanism that maintains its effectiveness over the service life of the latch assembly
3Reliability
If double pawl configuration is used to reduce friction, then friction between ratchet and pawl is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
A single roller element is used as an intermediary between one pawl and the ratchet, achieving friction reduction without the need for duplicate pawls. This approach maintains simple latch mechanism architecture while still providing the desired low-friction performance
4Reliability
If special low friction lubrication or low friction plating is applied, then friction is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The roller element provides a mechanical friction reduction solution that can be manufactured using standard rolling element bearing techniques. This avoids the need for specialized lubrication application processes or precision plating operations, simplifying manufacturing while achieving reliable friction reduction
Solution Approach 2:
The solution replaces complex surface treatment processes (special lubrication application, precision plating) with a mechanical roller element that can be manufactured and assembled using conventional methods, reducing manufacturing complexity and cost
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 solution significantly reduces the force required to actuate the latch and minimizes noise and wear, providing a long-lasting, economical, and versatile closure latch assembly suitable for various panel configurations.
Implementation Method 1
The roller is disposed between the pawl and the ratchet for selective rolling contact with the pawl and the ratchet
Implementation Method 2
minimal friction resistance between the ratchet and pawl during relative movement between the ratchet and pawl
Data Source
AI summary
A closure latch assembly having a latch mechanism is provided. The latch mechanism includes a ratchet and a pawl assembly pivotally supported for movement between a ratchet holding position whereat the pawl assembly is positioned to hold the ratchet in its striker capture position and a ratchet releasing position whereat the pawl assembly is located to permit movement of the ratchet to its striker release position. The pawl assembly has a carrier and a pawl configured for rotation relative to one another about a pawl pin and a roller carried by the carrier. The roller is disposed between the pawl and the ratchet for selective rolling movement therebetween. The roller is disposed into abutment with a closing surface of the ratchet while the pawl assembly is in the ratchet holding position and is spaced from closing surface while the pawl assembly is in the ratchet releasing position.