Variable Valve Timing for Turbocharged Engine Knock Control
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Solution Overview
Problem
Internal combustion engines with exhaust-gas turbocharging face challenges in managing engine knock, which leads to reduced fuel economy and limited maximum torque due to necessary spark retardation and the compromise of fixed long intake cams.
Innovation Solution
A supercharged internal combustion engine with partially variable valve drives and a knock regulator, allowing for adjustable intake valve timing based on load and engine conditions, reduces the need for spark retardation by elongating the inlet valve opening duration and retarding the closing of the second inlet valve, thereby increasing efficiency and reducing knock limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spark timing is retarded to address engine knock, then knock is reduced, but fuel economy deteriorates and maximum torque is limited
Solution Approach 1:
The patent implements variable valve timing mechanisms that dynamically adjust intake valve opening and closing timing based on engine operating conditions. This dynamic adjustment allows the effective compression ratio to be varied, enabling the engine to operate at higher compression ratios when knock is not present, thereby improving fuel economy without sacrificing knock control capability.
Solution Approach 2:
The patent changes the parameter of compression ratio by adjusting valve timing rather than maintaining a fixed geometric compression ratio. By retarding the closing of the second inlet valve, the effective compression ratio is reduced when knock occurs, and can be increased when knock is absent, thus optimizing both knock control and fuel economy across different operating conditions.
2Object-affected harmful factors
If fixed long intake cams are used for knock control, then knock is reduced, but maximum torque is limited due to compromise between part and full load conditions
Solution Approach 1:
The patent replaces fixed intake cam timing with dynamic variable valve timing control. The intake valve timing is continuously adjusted based on real-time engine operating conditions, allowing optimization for both part load and full load conditions independently, rather than being constrained by a fixed compromise timing setting.
Solution Approach 2:
The patent uses multiple inlet valves with independent timing control for each valve. This segmentation allows different timing strategies to be applied to different valves based on operating conditions, enabling optimized torque production across the entire operating range while maintaining knock control capability.
3Use of energy by moving object
If compression ratio is increased to improve efficiency, then fuel economy is improved, but engine knock increases
Solution Approach 1:
The patent implements dynamic control of the effective compression ratio through variable valve timing. The compression ratio is increased when engine conditions permit (improving fuel economy) and reduced when knock risk is detected (preventing knock), thus resolving the contradiction between efficiency and knock prevention.
Solution Approach 2:
The patent changes the effective compression ratio parameter dynamically by adjusting the closing timing of inlet valves. By retarding the closing of the second inlet valve, the effective compression ratio is reduced to prevent knock, while allowing higher compression ratios during normal operation to improve fuel economy.
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 approach enhances fuel economy, increases torque, and minimizes the need for ignition spark retardation, optimizing engine operation by adapting valve timing to prevent knocking and maintain efficiency across varying loads.
Implementation Method 1
at least one exhaust-gas turbocharger, each exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system
Implementation Method 2
a valve spring means for may preload the valves in the direction of the valve closed position
Implementation Method 3
each actuating device comprising a cam which is arranged on a camshaft and which, as the camshaft rotates, may be brought into engagement with at least one cam follower element, whereby the associated valve is actuated
Data Source
AI summary
A turbocharged internal combustion engine is provided with at least a partially variable valve train on an intake side wherein the intake valves are controlled to optimize the actuation of a second inlet valve in relation to a first inlet valve for different load conditions.