Cam Lobe Roller Mounting for Load Distribution
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Solution Overview
Problem
Cam structures with rollers face issues of durability due to peak acceleration of the valve being received by a narrow valve lifting portion, limited flexibility in roller diameter selection, and poor lubrication and foreign matter discharge, which can lead to reduced durability and increased risk of foreign matter adherence.
Innovation Solution
A cam structure design where the base cam portion receives the peak acceleration, with a roller mounted in a cutout portion having a curved opposing face with a larger radius of curvature, allowing for increased contact area and improved lubrication and foreign matter discharge, and connected to the camshaft via a pin with an oil path for enhanced lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a roller is provided at the distal end portion of the valve lifting portion, then friction and cam driving torque are reduced, but the peak acceleration load is concentrated on the narrow valve lifting portion, reducing durability
Solution Approach 1:
The invention applies local quality by creating a specific structural configuration where the valve lifting portion has a larger contact area with the follower. This is achieved by positioning the roller at the distal end portion and designing the valve lifting portion with sufficient thickness and contact area to handle the peak acceleration loads, while the roller itself maintains its function of reducing friction during the valve lift phase. The localized structural enhancement ensures that the narrow valve lifting portion can still receive peak acceleration loads effectively.
2Stability of the object's composition
If the opposing face of the cutout portion and the roller are centered with the same radius of curvature, then a constant gap is formed, but the gap opening becomes narrow, limiting flexibility in roller diameter selection and poor lubrication supply
Solution Approach 1:
The invention applies parameter changes by modifying the radius of curvature parameters of the opposing face and the roller. Specifically, the opposing face is designed with a different radius of curvature than the roller, creating a variable gap width rather than a constant gap. This allows the gap opening to be sufficiently large for lubrication supply and foreign matter discharge, while still maintaining appropriate clearance. The parameter change enables flexibility in roller diameter selection without compromising the functional requirements of the cam-roller-follower system.
3Area of stationary object
If the opposing face of the cutout portion is formed with a small radius of curvature, then the gap opening is narrow, but this causes poor discharge of foreign matters and increased risk of foreign matter adherence to the roller
Solution Approach 1:
The invention applies spheroidality by designing the opposing face of the cutout portion with a specific radius of curvature that is coordinated with the roller's radius of curvature. The opposing face is formed as a curved surface (circular arc) with a radius that creates an appropriately sized gap opening. This curved geometry ensures that the gap is wide enough to effectively discharge foreign matters and prevent their adherence to the roller, while maintaining the structural integrity and functional requirements of the cam lobe assembly.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A cam structure includes a camshaft and a cam lobe. The cam lobe includes a base cam and a roller which is provided at a distal end portion of a valve lifting portion. A first plus peak of acceleration of a valve is caused on starting a valve lift, a second plus peak is caused on finishing the valve lift, and the acceleration of the valve becomes minus between the first peak and the second peak. An outside diameter and mounting position of the roller are set so that a follower portion of a valve mechanism rides on to the roller from the valve lifting portion at a side of the starting of the valve lift and rides on to the valve lifting portion from the roller at a side of the finishing of the valve lift between the first and second peaks.