Automotive Door Lock Noise Reduction via Plastic Cam
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Solution Overview
Problem
Existing motor vehicle door locks experience noise issues due to the interaction of metal components during closing and opening movements, which current friction brake devices fail to adequately address, particularly in terms of manufacturing complexity and noise behavior.
Innovation Solution
Incorporating a cam that forms part of a plastic casing for the rotary latch, which acts as a noise-dampening element, and designing the friction brake device as a spring lip or buffer pocket with a plastic cam that interacts with the end stop, allowing for a quasi one-piece configuration or separate components, effectively decoupling acoustic noise and reducing frictional forces post-main detent position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a leaf spring friction brake device is used to damp impact noises, then closing noises are effectively damped, but opening noises still occur due to steel-on-steel contact between the fork latch and leaf spring
Solution Approach 1:
The patent introduces a plastic cam as an intermediary element between the fork latch and the leaf spring friction brake device. This plastic cam acts as a mediator that prevents direct metal-to-metal contact during opening movements, thereby eliminating opening noises while preserving the noise-dampening function during closing movements.
Solution Approach 2:
The patent changes the material parameter of the cam from metal to plastic. This material parameter change fundamentally alters the acoustic properties of the interaction, allowing the cam to function as both a mechanical actuator for the friction brake and an acoustic decoupler that prevents noise generation.
2Object-generated harmful factors
If the cam is integrated into the plastic casing of the rotary latch, then noise development is significantly reduced through acoustic decoupling, but the structural complexity increases
Solution Approach 1:
The patent merges the cam function with the plastic casing of the rotary latch by integrating the cam directly into the casing structure. This merging eliminates the need for separate cam components and reduces assembly steps, thereby preventing the structural complexity from increasing despite the added noise-dampening functionality.
Solution Approach 2:
The plastic casing is given multiple functions: it serves as both the protective housing for the rotary latch and as the carrier for the cam mechanism. This multi-functionality approach allows the cam to be defined within the existing casing structure without requiring additional dedicated components.
3Ease of manufacture
If the friction brake device and cam are designed as separate components, then manufacturing flexibility is improved, but the noise damping effectiveness is reduced compared to an integrated design
Solution Approach 1:
Even when designed separately, the plastic cam maintains its role as an intermediary noise-dampening element. The separate design allows for optimized manufacturing of each component while the plastic material continues to provide acoustic decoupling between the metal fork latch and the leaf spring friction brake device.
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
This solution significantly reduces noise development by using plastic components for the cam and friction brake device, ensuring reliable noise suppression during both closing and opening movements while maintaining a simple structure and low production costs, with restoring forces facilitating the return of the locking mechanism to the main position.
Implementation Method 1
the cam acting on the friction brake device is acoustically decoupled from it by its plastic covering
Implementation Method 2
a flexible friction braking device for the locking mechanism, which only becomes effective during a closing movement of the locking mechanism
Implementation Method 3
restoring forces that are already built up with the overtravel as a result of elasticities that are inevitably present
Data Source
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AI summary
The invention relates to an automotive door lock which comprises at least one ratchet mechanism (1, 2), constituted substantially by a rotary latch (1) and a detent pawl (2) and a flexible frictional brake device (10) for the ratchet mechanism (1, 2). When the ratchet-type mechanism (1, 2) performs a closing movement, the frictional brake device (10) becomes effective only shortly before a rigid limit stop (13) is reached. For this purpose, the ratchet mechanism (1, 2) is provided with at least one cam which interacts with the frictional brake device (10) when the closed position is reached. The invention is characterized in that the cam (14) and optionally the rotary latch (1) are noise-reduced.