Externally Driven Axial Cam for Engine Valve Actuation
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Solution Overview
Problem
Radial cams used in internal combustion engines are bulky, complex, and require precise bearing alignment, with high Hertzian loads and lubrication challenges, making them costly and prone to degradation, while axial cams are more compact and durable but often longer due to the need for external drive mechanisms.
Innovation Solution
An axial cam with oppositely facing cam surfaces fixed to a rotating exterior shell, allowing followers to be driven within the cam's central cavity, reducing length and complexity, and utilizing a belt drive or gears for operation, with lubricating oil forming a centrifugal layer to enhance contact efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a radial cam is used to actuate engine valves, then the cam can drive multiple followers, but the cam becomes massive and requires several closely aligned bearings along the cylinder head
Solution Approach 1:
The patent transitions from a radial cam configuration to an axial cam configuration, changing the dimensional orientation of the cam lobes from radial to axial. This allows the cam to drive multiple followers without requiring bearings along the cylinder head length, as the axial cam drives followers through its rotational axis, eliminating the bearing alignment complexity while maintaining multi-follower capability
2Reliability
If a radial cam is used, then the cam can actuate valves, but the cam surfaces experience high Hertzian loads and require precise surface lubrication
Solution Approach 1:
By changing from radial to axial cam configuration, the contact geometry between cam surfaces and followers is fundamentally altered. The axial cam configuration reduces the Hertzian loads on contact surfaces by changing the orientation of force application, thereby reducing the severity of lubrication requirements while maintaining reliable valve actuation
3Weight of moving object
If an axial cam is used, then the cam becomes compact and lightweight, but the cam needs to be stiff against deflection requiring extra axial thickness
Solution Approach 1:
The patent employs a composite construction where a lightweight cam body is enclosed within a stiffening shell or cage structure. This composite approach allows the cam to maintain compact dimensions and reduced weight while the outer shell provides the necessary stiffness to prevent deflection during operation, eliminating the need for increased axial thickness
4Ease of operation
If a radial cam is used, then the cam can be driven by the crankshaft, but the cam requires oil galleries bored through the cam for lubrication
Solution Approach 1:
The axial cam configuration changes the lubrication requirements by allowing oil to be delivered through the camshaft journal and distributed to contact surfaces through centrifugal force during rotation. This eliminates the need to bore oil galleries through the cam body, simplifying manufacturing while maintaining ease of operation with crankshaft drive
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 axial cam design provides a compact, lightweight, and cost-effective solution for actuating engine valves with minimal complexity and bulk, offering improved stiffness and reduced Hertzian loading, while allowing for efficient lubrication and easy phasing adjustments.
Implementation Method 1
Lubricating oil forms a layer that is centrifugally flung against the inside surface of the rotating shell, contact between the oil layer and the followers splashing oil continuously against the cam contact faces
Data Source
AI summary
An axial cam with a plurality of followers mounted within its diameter drives the followers in both axial directions. The followers operatively actuate valves such as those of an internal combustion engine. The cam can be driven about its exterior perimeter, providing an axially compact embodiment. The phasing of select followers can be established by modifying the azimuth positions of those followers with the cam in operation. By providing the cam with a symmetric actuating profile its followers can be linked to alternately actuate same-function valves in different engine cylinders.