Variable Valve Timing for Engine Cylinder Switching
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Solution Overview
Problem
Existing methods for switching between full-cylinder and partial-cylinder operation in four-stroke internal combustion engines with fully variable valve trains are inefficient, leading to suboptimal combustion and increased load changes, which affect engine performance and efficiency.
Innovation Solution
The method involves temporarily setting all intake valves to the maximum lift position during switchover, advancing or postponing the point of maximum valve lift, and maintaining constant air mass flow to optimize combustion efficiency, while keeping the throttle valve open and adjusting the ignition angle as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the valve lift is adjusted during switchover between full-cylinder and partial-cylinder operation, then the cylinder operation mode can be changed, but combustion efficiency deteriorates and load changes increase
Solution Approach 1:
The patent applies preliminary action by setting all intake valves to maximum lift position before the actual switchover occurs. This preparatory step ensures that when cylinders are deactivated, the remaining active cylinders have already optimized their valve timing and lift, maintaining combustion efficiency throughout the transition process rather than adjusting valves during the critical switchover moment.
2Stability of the object's composition
If the throttle valve is used to limit cylinder adjustment during switchover, then load changes can be avoided, but throttle losses increase and efficiency decreases
Solution Approach 1:
The patent extracts the throttle valve from the load control function during switchover. By removing the throttle valve's role in limiting cylinder adjustment, the system allows full valve lift operation while deactivating cylinders, eliminating throttle losses. Load stability is maintained through the coordinated valve timing adjustments and ignition angle optimization rather than throttle restriction.
3Power
If the ignition angle is adjusted during switchover to compensate for load changes, then torque stability can be maintained, but combustion efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by optimizing the ignition angle for maximum combustion efficiency before the switchover occurs. When cylinders are deactivated, the pre-optimized ignition timing ensures that active cylinders burn fuel efficiently without requiring compensatory ignition angle adjustments that would sacrifice combustion efficiency for torque stability.
Data Source
Figure 1~2
Figure 3a1~3b3
AI summary
According to a claimed method for operating a four-stroke internal combustion engine comprising a fully variable valve train and at least one phase shifter for changing the time of the maximum valve stroke of the inlet valves, during the switching of the internal combustion engine between a full cylinder operation and a partial cylinder operation, a) the valve stroke is increased in an early switching phase on all cylinders and simultaneously the time of the maximum valve stroke is shifted by means of the phase shifter to an earlier time, and/or b) in a late switching phase at least on the cylinders which are to continue running after switching, the valve stroke is reduced and the time of the maximum stroke is shifted to a later time.