Cam Follower M-Shape Trough Design for Fatigue Strength
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Solution Overview
Problem
The production of cam followers with a trough shape for internal combustion engine gas exchange valves is hindered by high material forming complexity, leading to material cracks and insufficient fatigue fracture strength, resulting in a high reject rate and potential engine damage.
Innovation Solution
The cam follower design features an M-shape trough adjacent to the joint socket with clearances open toward the gas exchange valve, reducing forming complexity and incorporating large bending radii for stress compatibility, which enhances fatigue strength and process reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a trough shape with closed U-section is formed in the follower body, then rigidity is increased and mass moment of inertia is reduced, but material cracks occur during cold-forming and fatigue fracture strength is insufficient
Solution Approach 1:
The closed U-section trough shape is segmented into two separate U-shaped profiles that do not fully connect. The first U-shaped profile has a bottom portion and sidewalls, while the second U-shaped profile has a bottom portion and sidewalls that are spaced apart from the first profile. This segmentation eliminates the need for complex 180° bending operations that cause material cracks, while still providing enhanced rigidity compared to a simple open U-shape.
Solution Approach 2:
Large bending radii are introduced at the transitional regions where the bottom portions connect to the sidewalls. This curvature design reduces stress concentration and notch effects during cold-forming operations, preventing material cracks while maintaining the structural rigidity provided by the U-shaped profiles.
2Weight of moving object
If wall thickness is reduced to decrease mass moment of inertia, then contact and friction forces are reduced, but follower body rigidity becomes insufficient
Solution Approach 1:
The U-shaped profiles with their curved sidewalls and bottom portions provide efficient structural rigidity with minimal material. The curvature distributes stresses more effectively than straight edges, allowing thin-walled construction that reduces mass moment of inertia while maintaining sufficient rigidity for valve drive dynamics.
Solution Approach 2:
The segmented U-shaped profiles create a lightweight structure that reduces mass moment of inertia. By using two separate U-shaped profiles rather than a fully enclosed tube, the structure achieves adequate rigidity with less material, thereby reducing contact and friction forces in the valve drive system.
3Reliability
If high degree of cold-forming is applied to create trough shape, then joint socket geometric design is improved with greater overlap angle, but material cracks and reject rate increase
Solution Approach 1:
The joint socket is formed within the segmented U-shaped profiles rather than requiring a single complex forming operation. The two separate U-shaped profiles provide adequate geometric design and overlap angle for joint socket reliability without requiring the excessive 180° bending that causes material cracks and high reject rates.
Solution Approach 2:
Large bending radii in the U-shaped profiles reduce stress concentration during cold-forming operations, enabling the joint socket to achieve the necessary geometric design and overlap angle with lower forming complexity and improved process reliability.
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 allows for cost-effective, reliable production of cam followers with increased rigidity and reduced mass, minimizing material cracks and fatigue issues while maintaining functional advantages.
Implementation Method 1
an elongate follower body which is cold-formed from sheet metal material
Implementation Method 2
a joint socket serving for the pivotably moveable mounting of the cam follower
Data Source
AI summary
A cam follower for actuating a gas exchange valve of an internal combustion engine, which has a lifting body cold formed from sheet metal and that forms, on a valve-sided lifting section which has two lateral walls and a first base section connecting the walls, a cross-sectional profile which is open towards the gas exchange valve in a U-shaped manner, and on a joint-sided lifting section that has lateral walls and a second base section connecting the walls, a modifiable cross-sectional profile which is initially open towards the gas exchange valve in a U-shaped manner the U-shape adopting a trough shape that has a protruding annular cavity. The trough shape adjacent to an annular cavity on the side of the valve-sided lifting section is M-shaped and has two free recesses open towards the gas exchange valve and extend respectively between one of the lateral walls and the second base section.