Variable Camshaft With Segmented Contours For Valve Timing
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Solution Overview
Problem
Existing camshafts for internal combustion engines face limitations in achieving a wide adjustment angle while maintaining high cam lift, leading to kinematic and dynamic discontinuities in valve lift, speed, and acceleration profiles, which can result in reduced valve lift and potential piston/valve contact.
Innovation Solution
The camshaft design features two part cams with different maximum lift heights, where one cam's contour section is a circular arc extending beyond the base circle, and the active flank region of the higher lift cam ensures a consistent transition at the transfer point, avoiding kinematic discontinuities by forming a tangent with the lower lift cam's circular arc section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the part cams are rotated with respect to one another to vary the valve opening period, then the valve opening time can be extended, but the maximum rotation angle is limited to a very low value due to kinematic discontinuity
Solution Approach 1:
The cam element is divided into two part cams (first part cam and second part cam) that can be rotated independently with respect to one another. This segmentation allows each part cam to have different cam contour configurations, enabling extended valve opening periods while maintaining smooth kinematic transitions through proper design of the cam peak sections.
2Adaptability or versatility
If the part cams are flattened in the manner of a plateau to allow wide spreading, then the adjustment angle can be increased, but the valve lift is reduced
Solution Approach 1:
The cam peak section of the second part cam is designed with a circular arc section that has different geometric properties than conventional plateau designs. This local modification allows the cam contour to maintain high lift values while still enabling wide rotation angles, as the circular arc geometry provides smooth transitions without requiring flattening that would reduce valve lift.
3Duration of action of moving object
If the cam contour is varied by rotating cam elements, then the valve opening time can be adjusted, but kinematic discontinuities occur in valve lift, speed and acceleration profiles
Solution Approach 1:
The cam peak section of the second part cam incorporates a circular arc section instead of straight-line or plateau geometries. This curved geometry ensures that when the part cams are rotated relative to each other, the transitions in valve lift, speed, and acceleration profiles remain continuous and smooth, eliminating kinematic discontinuities that would otherwise occur.
Data Source
AI summary
A camshaft for an internal combustion engine, having a hollow outer shaft and an inner shaft which is concentrically mounted inside the outer shaft to be rotatable about an angle and a multi-part cam element having a first cam section that is mounted on the outer shaft in a rotationally fixed manner and a second cam section that is connected to the inner shaft in a rotationally fixed manner and rotationally mounted on the outer shaft. The two cam sections have different cam contours, the relative movement of the two cam sections in opposite directions allowing the resulting cam contour of the cam element interacting with a cam follower to be changed to adjust the variable valve opening period. The two cam sections have different maximum lifts, the cam top section of the cam section having the smaller maximum lift being substantially formed by an annular sector.