Variable Valve Drive for Engine Overrun Drag Torque Control
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Solution Overview
Problem
Existing internal combustion engine technologies face challenges in managing drag torque during overrun operation, leading to increased emissions, fuel consumption, and potential damage to engine components due to oxygen enrichment and uncontrolled particulate filter regeneration.
Innovation Solution
A method utilizing a variable valve drive with electro-mechanically adjustable camshaft adjusters to optimize intake and exhaust camshaft phase positions, reducing drag torque and air mass flow during overrun phases, while avoiding critical negative pressures and oxygen enrichment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the throttle valve is opened during overrun operation to reduce drag torque, then the drag torque decreases, but oxygen-rich fresh air flows through the cylinders causing charge-exchange losses and lowering exhaust system temperature
Solution Approach 1:
The control device prepares the catalytic converter for the upcoming combustion engine operation by controlling the throttle valve and valve timing before the transition. This preliminary action ensures the catalytic converter is ready to handle the exhaust gas composition change, preventing oxygen saturation issues and maintaining optimal temperature in the exhaust after-treatment system.
Solution Approach 2:
The system dynamically adjusts the throttle valve position and valve timing based on the operating phase. During overrun operation, the throttle valve is opened to minimize drag torque, while during combustion operation, it is closed to control air mass flow. The control device continuously adapts these parameters to optimize both drag torque reduction and emission control throughout the transition.
2Object-generated harmful factors
If the throttle valve is closed during overrun operation to prevent air flow, then charge-exchange losses are reduced, but critical negative pressure develops in the combustion chamber causing air-oil volume flow
Solution Approach 1:
The control device dynamically adjusts the throttle valve position based on real-time operating conditions. During overrun operation, the throttle valve is opened to a specific position that prevents critical negative pressure while still reducing charge-exchange losses. The system continuously monitors and adapts the throttle position to maintain pressure stability and prevent air-oil volume flow.
Solution Approach 2:
The variable valve timing system acts as an intermediary mechanism between the throttle valve and the combustion chamber. By adjusting the inlet and exhaust valve timing, the system mediates the pressure conditions in the combustion chamber, preventing critical negative pressure buildup while still achieving the goal of reducing charge-exchange losses during overrun operation.
3Object-generated harmful factors
If variable valve drive deactivates all valve lifts to prevent air scavenging, then oxygen enrichment is avoided, but the system complexity increases
Solution Approach 1:
Instead of completely deactivating all valve lifts, the control device applies partial action by selectively controlling the inlet and exhaust valves. The system closes the inlet valve before top dead center and the exhaust valve after bottom dead center during overrun operation, which is sufficient to prevent air scavenging and oxygen enrichment without requiring complete valve deactivation. This partial action reduces the complexity burden while achieving the same protective effect.
4Productivity
If the engine is restarted immediately after overrun operation, then productivity is improved, but torque peaks occur due to oxygen saturation in the catalytic converter
Solution Approach 1:
The control device performs preliminary action by controlling the throttle valve and valve timing during the transition from overrun to combustion operation. This preliminary control prepares the catalytic converter by managing the oxygen content and temperature in the exhaust system before combustion resumes, preventing oxygen saturation and the subsequent torque peak when the engine restarts.
Solution Approach 2:
The system uses feedback control to monitor the operating phase and continuously adjust the throttle valve position and valve timing. During the transition from overrun to combustion operation, the control device receives feedback about the engine state and adapts the valve control strategy to prevent torque peaks, enabling smooth engine restart while maintaining productivity.
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
The method effectively reduces drag torque and emissions, prevents torque peaks during engine restart, and minimizes fuel consumption by controlling valve timing and lift, ensuring smooth and efficient engine operation.
Implementation Method 1
A method utilizing a variable valve drive with electro-mechanically adjustable camshaft adjusters to optimize intake and exhaust camshaft phase positions
Implementation Method 2
A method for operating an internal combustion engine with a variable valve drive, in that a valve timing is assigned for the inlet valves and/or the exhaust valves
Implementation Method 3
In the event of deceleration, the combustion engine is dragged along via the closed drive train by the inertia of the motor vehicle
Data Source
AI summary
The disclosure relates to a method for operating an internal combustion engine. The internal combustion includes an intake manifold via which a cylinder can be supplied with fresh air, an inlet valve via which, when it is open, the fresh air can flow from the intake pipe into the cylinder, and a variable valve drive by means of which the opening duration or the relative timing of the inlet valve event is variable in relation to a crankshaft position. During a starting of the internal combustion engine, when the intake manifold pressure differs from the intake manifold desired pressure, a filling pilot control of the cylinder is undertaken by the variable valve drive by the fresh air supply being reduced in comparison to the fresh air supply at the intake manifold desired pressure. The disclosure further relates to a control device for an internal combustion engine that enables low-emission operation.