Variable Valve Cam Profile for Wider Closing Timing Control
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Solution Overview
Problem
Existing variable valve apparatuses for internal combustion engines face challenges in facilitating valve closing control and promoting variable response of valve closing timing, particularly in increasing the change region of the lift finish point, while also alleviating seating impact and noise.
Innovation Solution
A variable valve apparatus with a cam shaft, drive cam, and rocker arm mechanism where the down section of the cam lift face is longer than the up section, and the cam projected face curvature is smaller on the down section side, allowing for a larger change region of the lift valve closing time point and reduced impact through constant positive acceleration in the down section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the down section of the cam lift face is made longer than the up section, then the change region of the lift valve closing time point is increased, but the cam structure becomes more complex
Solution Approach 1:
The cam lift face is designed with asymmetric sections where the down section (from cam top to base circle) is intentionally made longer than the up section (from base circle to cam top). This asymmetry allows the valve closing timing to vary over a larger crank angle range while maintaining a relatively simple cam structure without requiring additional components or mechanisms.
2Object-affected harmful factors
If the cam projected face curvature is made smaller on the down section side, then seating impact is reduced, but the lift amount control precision is compromised
Solution Approach 1:
The cam projected face is designed with different curvature characteristics in different sections: the down section has a smaller curvature radius to reduce seating impact and noise, while the up section maintains appropriate curvature for precise lift amount control. This local differentiation allows each section to optimize its function without compromising the other.
Data Source
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AI summary
A variable valve apparatus of an internal combustion engine includes a cam shaft (9), a drive cam (14) formed integrally with the cam shaft (9), and a rocker arm mechanism for transmitting an opening/closing force from an operating end portion thereof to an intake or an exhaust valve (5, 6) by receiving the opening/closing force by a drive cam opposed roller (32) brought into contact with the drive cam (14) . For displacing a lift time period, in which the drive cam opposed roller (32) receives the opening/closing force, frontward/rearward in a direction of rotating the drive cam (14), a down section of a cam lift face of the drive cam (14) is formed to be longer than an up section thereof such that a change region of a lift valve closing time point of the lift time period becomes larger than a change region of a lift valve opening time point thereof.