Selective DLC Coating of Cam Lobes for Lower Friction
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Solution Overview
Problem
The high cost and complexity of applying DLC coatings to camshafts in internal combustion engines, particularly in the automotive industry, limit their widespread adoption due to the need for coating the entire camshaft, which is inefficient given that only a small fraction of the surface is in contact with levers or pushers, and the presence of oils with additives like MoDTC can lead to accelerated degradation of the DLC coating through tribocorrosion.
Innovation Solution
A method for selectively coating only the cams of a camshaft with a DLC coating using a carousel-based vacuum deposition process, where the cams are arranged to align their lengths radially and are coated only on the fraction oriented towards the outside, reducing the need for rotational movements and allowing for a denser arrangement, thereby reducing processing time and material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire camshaft is coated with DLC coating, then the friction reduction performance is improved, but the manufacturing cost and complexity increase significantly
Solution Approach 1:
The patent applies DLC coating selectively only to the cam lobes and nose portions that are in actual contact with valve train components, rather than coating the entire camshaft. This localized coating approach maintains friction reduction performance in critical areas while avoiding unnecessary coating on non-contact surfaces, thereby reducing material costs and processing complexity.
Solution Approach 2:
The camshaft is divided into distinct segments: the cam lobes and nose portions receive DLC coating, while the journal portions and other non-contact areas remain uncoated. This segmentation allows differential treatment of different camshaft regions based on their functional requirements, optimizing both performance and cost.
2Reliability
If the entire camshaft surface is coated with DLC, then wear resistance is improved, but the processing time and material usage increase
Solution Approach 1:
The coating process is configured to deposit DLC material only on the cam lobes and nose portions through selective positioning and masking techniques. This local quality approach ensures wear resistance is enhanced only where contact occurs, reducing the total processing time and DLC material consumption compared to full-surface coating.
Solution Approach 2:
Instead of applying excessive coating coverage to the entire camshaft, the patent uses partial action by limiting the coating to the minimum necessary areas (cam lobes and noses). This reduces material usage and processing time while still providing adequate wear protection for the functional contact zones.
3Loss of energy
If DLC coating is applied to camshafts, then fuel consumption is reduced, but the cost becomes prohibitive for general automotive manufacturing
Solution Approach 1:
By applying DLC coating only to the critical cam lobe and nose surfaces that directly contact valve train components, the patent reduces the amount of coating material required and simplifies the manufacturing process. This localized approach makes the technology economically viable for mass production while still achieving sufficient friction reduction to lower fuel consumption.
Solution Approach 2:
The patent modifies the coating application parameters by limiting coverage area and adjusting deposition conditions to optimize material usage. These parameter changes reduce both material costs and processing expenses, making DLC-coated camshafts affordable for general automotive applications rather than just high-performance or racing vehicles.
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 approach lowers the cost of DLC coating application, enabling its widespread use in the automotive industry while maintaining friction reduction performance even with oils containing MoDTC additives, by focusing the coating on the most critical contact areas and minimizing unnecessary coating, thus reducing wear and friction effectively.
Implementation Method 1
the enclosure being placed under vacuum so as to enable stripping of the cams, the carousel being rotated around its axis relative to a source of carbon material so as to deposit a coating on the fraction of the periphery of the cams which is oriented towards the outside of the carousel
Data Source
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AI summary
In order to treat the cams of a camshaft for an internal combustion vehicle, so as to reduce the friction coefficient thereof relative to a counterpart in an area provided with a hard coating made from amorphous Diamond-Like Carbon or DLC, the method involves disposing the cams on a support, bringing the support and the cams into a chamber placed under vacuum so as to clean said cams, bringing said support into relative movement along a trajectory of travel relative to a coating source, and taking said cams off the support before assembling them on a camshaft; the method involves disposing the cams on the support in a fixed configuration which, together with the trajectory, is defined in such a way that said cams are brought successively opposite the source with orientations and at distances substantially identical relative to said source, so as to deposit a hard coating made from amorphous Diamond-Like Carbon or DLC, selectively on the fraction of the section of the cams that is oriented towards the source.