Variable Valve Timing Control for Engine Braking Load Management
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Solution Overview
Problem
Existing control arrangements for variable valve timing in four-stroke internal combustion engines face challenges in accommodating changes under current engine operating conditions, leading to high loads on engine hardware such as the valve train, which can result in unfavorable engine states and potential damage.
Innovation Solution
A control arrangement that performs sequential changes in the timings of the exhaust and intake camshafts based on current maximum cylinder pressure, allowing for transitions from one camshaft timing setting to another while considering current engine operating conditions to avoid high valvetrain loads and maintain optimal engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If variable valve timing is applied to achieve engine braking effects, then engine braking performance is improved, but loads on the valve train increase
Solution Approach 1:
The control arrangement performs preliminary actions by sequentially adjusting camshaft timings before and during engine braking operations. The system pre-establishes timing sequences that prepare the valve train for upcoming high-load conditions, distributing the mechanical stress over multiple cycles rather than applying it all at once, thereby preventing excessive valve train loads while maintaining effective engine braking performance
2Speed
If camshaft timing changes are performed rapidly, then response time to operating conditions is improved, but valvetrain loads increase
Solution Approach 1:
The control arrangement segments the camshaft timing changes into multiple discrete sequential steps rather than executing them as a single rapid transition. Each timing adjustment is performed in a controlled sequence, allowing the valve train to gradually adapt to changing conditions. This segmentation reduces the instantaneous mechanical shock and excessive loads on valve train components while still achieving timely response to engine operating condition changes
3Power
If variable valve timing is used during compression release braking, then braking efficiency is improved, but engine hardware loads increase
Solution Approach 1:
The control arrangement dynamically adjusts camshaft timings based on real-time engine operating conditions during compression release braking. The system continuously monitors engine parameters and adapts the timing sequence accordingly, optimizing the balance between braking efficiency and hardware load protection. This dynamic control allows the valve train to operate within safe load limits while maintaining effective braking performance through optimized timing adjustments
Data Source
AI summary
The disclosure concerns variable valve timing of a four-stroke ICE. The ICE comprises: an exhaust valve and an intake valve an exhaust camshaft an intake camshaft and a cylinder arrangement. The cylinder arrangement comprises a combustion chamber a cylinder bore and a piston. The control arrangement is configured to: perform a first sequence of changes in the timings of the exhaust and intake camshafts in order to arrive from a first camshaft timing setting at a second camshaft timing setting based on a first current maximum cylinder pressure within the combustion chamber around top dead centre fire and/or around to dead centre gas exchange.