Cam Carrier Flexible Structure for Thermal Deformation
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Solution Overview
Problem
In internal combustion engines with a monolithic cam carrier on the cylinder head, thermal expansion differences lead to relative displacement and thermal deformation, causing fretting, wear, and seizing of cam bearings, which affects coaxial machining accuracy and engine reliability.
Innovation Solution
A flexible structure is introduced on the longitudinal frames of the cam carrier, reducing axial stiffness to absorb thermal expansion differences, either through a convex-shaped or slit-shaped configuration, allowing deformation to mitigate thermal deformation impacts on cam bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a monolithic cam carrier is fixed on the cylinder head, then coaxial machining accuracy of cam bearings is improved, but thermal deformation and relative displacement occur due to differential thermal expansion between the cam carrier and cylinder head
Solution Approach 1:
The cam carrier is divided into multiple longitudinal frames (at least two) that are connected to each other. This segmentation allows each frame to independently accommodate thermal expansion, preventing the cumulative thermal deformation that would occur in a completely monolithic structure while still maintaining sufficient rigidity for coaxial machining accuracy.
Solution Approach 2:
The connection structure between longitudinal frames is designed with specific structural parameters (connection portions with reduced stiffness or compliance) that allow controlled thermal deformation. This parameter optimization enables the structure to absorb thermal expansion differences between the cam carrier and cylinder head while maintaining operational precision.
2Strength
If the cam carrier is made as a monolithic structure, then structural rigidity is improved, but fretting occurs on contact surfaces due to relative displacement from thermal expansion differences
Solution Approach 1:
By dividing the cam carrier into multiple longitudinal frames connected through connection portions, the structure maintains overall rigidity while allowing localized movement at the connection points. This prevents the buildup of thermal stress that would cause fretting on the contact surfaces with the cylinder head.
Solution Approach 2:
The connection portions between longitudinal frames act as intermediaries that accommodate thermal expansion differences. These connection structures absorb the relative displacement caused by differential thermal expansion, preventing direct transmission of movement to the contact surfaces and thus eliminating fretting damage.
3Ease of manufacture
If the cam carrier is made as a monolithic structure, then manufacturing simplicity is improved, but thermal deformation changes the position and inclined angle of cam bearings relative to the camshaft
Solution Approach 1:
The segmented structure of multiple longitudinal frames allows thermal expansion to be accommodated locally without affecting the overall positioning accuracy. Each frame can expand independently while the connection portions maintain the relative positions and angles of cam bearings with respect to the camshaft.
Solution Approach 2:
The connection portions are designed with specific geometric parameters and material properties that allow thermal deformation without compromising the critical positioning parameters. This enables the structure to change its thermal state while maintaining the precision required for cam bearing alignment.
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 flexible structure absorbs relative displacement and thermal deformation, preventing fretting and wear of contact surfaces, maintaining coaxial machining accuracy and reducing wear or seizing of cam bearings, thus enhancing engine performance and durability.
Implementation Method 1
a difference in temperature between the cylinder head and the cam carrier occurs, such as a running condition in which the engine is suddenly transmitted from a low load running such as a cold state to a high load running
Implementation Method 2
a flexible structure for suppressing amounts of change in a relative position and an inclined angle of the cam bearings with respect to the camshaft due to a thermal expansion
Data Source
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AI summary
A cam carrier 20 includes a pair of longitudinal frames 21 provided parallel to an axial direction of a camshaft 30 and a plurality of transversal frames 22 connected to the pair of longitudinal frames 21 to be spaced from each other and supporting the camshaft 30 via cam bearings 31. A flexible structure 40 suppressing amounts of change in a relative position and an inclined angle of the cam bearings 31 relative to the camshaft 30 due to a thermal expansion is provided on at least one of wall surfaces 23 of the longitudinal frames 21, the wall surfaces 23 being located between adjacent transversal frames 22.