Variable Cross-Section Connecting Element for Camshaft Joint Strength
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Solution Overview
Problem
Existing camshaft arrangements face challenges in achieving a secure and strong connection between the inner shaft and the inner shaft cam, particularly due to undefined press fits and insufficient joint strength, especially with connecting elements of constant cross-section.
Innovation Solution
The camshaft arrangement features a connecting element inserted into a receptacle in the inner shaft, with a protruding part that fits into a recess on the inner shaft cam, providing two independent interference fits for secure and strong connections, and optionally includes a shank and head part with a stepped bore or recess for reduced stress and precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a connecting element of constant cross-section is used for press fit connection, then the assembly is simple, but the joint strength and press coverage are insufficient and undefined
Solution Approach 1:
The connecting element transitions from constant cross-section to variable cross-section with a enlarged head portion that provides increased press coverage area. This local quality change ensures sufficient and defined press fit connection strength at the critical interface with the inner shaft cam, while maintaining simplicity in the shank portion for easy assembly into the inner shaft receptacle.
Solution Approach 2:
The connecting element is designed with a head portion that extends in a direction transverse to the longitudinal axis, adding a dimensional aspect that increases the contact area for press fit connection. This dimensional extension from a simple cylindrical pin to a T-shaped or L-shaped configuration provides enhanced joint strength without complicating the assembly process.
2Ease of manufacture
If multiple component bores are used to join connecting elements, then the connection can be formed, but the press coverage becomes undefined and the security of the press connection is reduced
Solution Approach 1:
The connecting element concentrates the press fit connection function in a specific localized area - the head portion - that contacts the inner shaft cam. This localized design provides defined and sufficient press coverage at the critical interface, eliminating the undefined press coverage problem that arises when multiple component bores are used to join constant cross-section connecting elements.
3Manufacturing precision
If the connecting element protrudes from the inner shaft receptacle, then alignment with the cam recess is improved, but the assembly complexity increases
Solution Approach 1:
The connecting element is segmented into functional portions: a shank portion for insertion into the inner shaft receptacle and a head portion for engagement with the cam recess. This segmentation allows each portion to be optimized for its specific function - the shank for simple insertion and the head for precise alignment - while the overall assembly remains straightforward.
Solution Approach 2:
The protruding head portion acts as an intermediary alignment feature that mediates between the inner shaft receptacle and the cam recess. This intermediary element ensures precise alignment during assembly without requiring complex alignment procedures or additional alignment features, thereby maintaining assembly simplicity while achieving high manufacturing precision.
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 design enhances the security and strength of the connection between the inner shaft and the inner shaft cam, reducing stress and surface pressure, while allowing for precise alignment and easy assembly, thus improving the overall reliability and efficiency of the camshaft arrangement.
Implementation Method 1
The connecting element is inserted into a receptacle in the inner shaft in such a way that part of the connecting element protrudes from the receptacle, and that the protruding part is at least partially inserted into a recess which is located at the joint diameter of the respective inner shaft cam
Implementation Method 2
the protruding part has at least two opposite side faces which bear with a tight fit on two corresponding inner faces of the recess of the respective inner shaft cam
Data Source
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AI summary
The invention relates to a camshaft arrangement for a drive, in particular for a motor vehicle engine, comprising two shafts (20; 30) which are arranged coaxially one inside the other, in which a hollow outer shaft (20) and an inner shaft (30) are arranged so as to be rotatable relative to one another, and both shafts (20; 30) support in each case a plurality of cams (21; 22; 31). Here, the outer shaft cams (21; 22) supported by the outer shaft (20) are rotationally fixedly attached to the outer shaft (20), while the inner shaft cams (31) supported by the inner shaft (30) are rotationally fixedly attached to the inner shaft (30) by means of in each case at least one connecting element (40; 40’). The connecting element (40; 40’) projects with play through a recess (50; 50’) in the outer shaft (20) and is fastened to the respective inner shaft cam (31) which is rotatably mounted on the outer shaft (20). The invention is characterized in that the respective connecting element (40; 40’) is inserted into a receptacle (37) in the inner shaft (30) in such a way that a part (42) of the connecting element (40; 40’) projects out of the receptacle (37), and in that that part (42) which projects out is inserted at least partially into a cutout (32) located on the join diameter of the respective inner shaft cam (31), wherein said cutout (32) is formed so as to be open at least toward one end side of the inner shaft cam (31), and in that that part (42) which projects out has at least two opposite side surfaces (43; 44) which bear with an interference fit against two corresponding inner surfaces (34; 35) of the cutout (32) of the respective inner shaft cam (31).