Variable Valve Timing Camshaft Oil Transfer Design
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Solution Overview
Problem
Existing adjustable camshafts face mechanical weakening due to elongated radial openings in the outer shaft, which are necessary for effective oil transfer between the inner and outer shafts, especially during angle adjustments, compromising the camshaft's strength and oil flow efficiency.
Innovation Solution
The design incorporates radial openings in the outer and inner shafts with optimized cross-sectional geometries, including beveled and conically widened sections, to ensure full coverage and oil flow without extending the opening's circumference range, thereby minimizing mechanical weakening and maintaining strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elongated radial openings are provided in the outer shaft to ensure complete coverage of radial openings in the inner shaft during angle adjustment, then oil flow reliability is improved, but the mechanical strength of the outer shaft is significantly weakened
Solution Approach 1:
The invention transitions from a two-dimensional planar coverage problem to a three-dimensional solution by providing different cross-sectional geometries at different radial positions. The radial opening has a first cross-sectional geometry at the inner shaft interface and a second cross-sectional geometry at the outer shaft interface, allowing coverage to be achieved through dimensional transformation rather than extending the opening's circumferential expanse.
Solution Approach 2:
The invention applies different cross-sectional geometries to different locations of the same radial opening. The first cross-sectional geometry (at the inner shaft side) is optimized for coverage, while the second cross-sectional geometry (at the outer shaft side) is optimized for maintaining structural strength. This local differentiation allows the opening to fulfill multiple functional requirements simultaneously.
2Reliability
If circumferential grooves are added to transfer fluid between radial openings, then coverage of radial openings is improved, but the mechanical ability of the shaft to withstand stress is weakened
Solution Approach 1:
The invention extracts the fluid transfer function from the circumferential groove concept and integrates it directly into the radial opening structure itself. By designing the radial opening with optimized cross-sectional geometries that enable coverage and fluid transfer without requiring separate circumferential grooves, the solution eliminates the additional stress-concentrating features while maintaining fluid connection reliability.
3Reliability
If radial openings are made very long in the circumference direction to guarantee oil flow at boundary positions, then oil flow coverage is improved, but the camshaft strength reaches critical lower limits
Solution Approach 1:
The invention changes the geometric parameters of the radial opening by providing different cross-sectional geometries at different positions along the opening. Instead of uniformly increasing the circumferential length, the solution modifies the cross-sectional shape and size parameters locally, allowing sufficient coverage area to be achieved with minimal circumferential extension, thereby preserving camshaft strength.
Data Source
AI summary
An adjustable camshaft may include an outer shaft that is hollow and an inner shaft received in the outer shaft and rotatable in the outer shaft. The inner shaft may include a cavity into which oil can be applied. At least a first radial opening may be configured in the outer shaft and at least a second radial opening may be configured in the inner shaft. Thus oil can flow between the cavity and an outside of the outer shaft during overlap of the first radial opening and the second radial opening. The first radial opening on an inside of the outer shaft may have a greater cross-section than on the outside of the outer shaft.