Engine Valve Actuation Handoff Control via Selective Coupling
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Solution Overview
Problem
Existing valve actuation systems in internal combustion engines experience high velocity mismatches during handoff between main and auxiliary valve actuation motions, leading to impacts that accelerate wear, fatigue, and potential failure of valve train components, particularly due to sharp transitions and physical constraints that prohibit larger auxiliary cams.
Innovation Solution
A valve actuation system with a selectable coupling mechanism that includes a selectively extendable actuator, allowing for smooth transition between main and auxiliary valve actuation motions by ensuring the difference in valve actuation velocities does not exceed a threshold, thereby minimizing impacts during handoff, and incorporating cam profiles for first and second valve actuation motion sources to achieve cooperative valve events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If main and auxiliary valve actuation motions are combined through a selectable coupling mechanism, then cooperative valve events (such as late intake valve closing and early exhaust valve opening) are achieved, but high velocity mismatches during handoff cause impacts that accelerate wear and fatigue of valve train components
Solution Approach 1:
The cam profiles are designed with dynamically adjusted parameters including modified rise portions, fall portions, and dwell periods. The auxiliary cam profile includes a delayed rise portion that begins after the main cam's rise portion completes, creating a smooth velocity transition during handoff. This dynamic timing adjustment ensures velocity matching between main and auxiliary motions, eliminating impacts while maintaining cooperative valve events capability
Solution Approach 2:
The invention changes critical parameters of the cam profiles including rise time, fall time, dwell duration, and peak lift values. The auxiliary cam profile is specifically designed with a rise portion that starts after the main cam's rise completes, and includes a dwell period that maintains valve position during handoff. These parameter changes ensure continuous velocity matching while achieving desired valve timing events, thereby preventing component wear and fatigue
2Power
If larger auxiliary cams are used to provide sufficient actuation motion, then auxiliary valve events are enhanced, but physical constraints in the engine valley prohibit such larger cams
Solution Approach 1:
The valve actuation function is segmented between main and auxiliary cam systems, each performing specific portions of the valve event. The main cam handles primary valve opening and closing, while the auxiliary cam provides supplemental motion for specific events like late intake valve closing or early exhaust valve opening. This segmentation allows compact auxiliary cam design that fits within spatial constraints while maintaining effective actuation capability through coordinated operation
Solution Approach 2:
The auxiliary cam profile is designed with preliminary action features including a delayed rise portion that prepares for handoff by matching velocity with the main cam's fall portion. The dwell period in the auxiliary cam profile maintains valve position during the transition, ensuring smooth handoff without impacts. This preliminary velocity matching enables compact auxiliary cam design that achieves full actuation capability without requiring larger physical dimensions
Data Source
AI summary
A valve actuation system comprises a first motion transfer mechanism operatively connected to a first valve actuation motion source and to the at least one engine valve, a second motion transfer mechanism operatively connected to a second valve actuation motion source; and a selectable coupling mechanism between the first and second motion transfer mechanisms. The coupling mechanism is operable in a first state where first valve actuation motions are conveyed to the at least one engine valve via the first motion transfer mechanism, and a second state where second valve actuation motions are additionally conveyed to the at least one engine valve via the second motion transfer mechanism, the coupling mechanism and the first motion transfer mechanism. During a handoff between the first and second valve actuation motions or vice versa, a difference in valve actuation velocities of the first and second valve actuation motions does not exceed a threshold.