Electrohydraulic Valve Train Cold Start Refilling
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Solution Overview
Problem
Existing methods for improving the starting behavior of internal combustion engines, particularly during the cold start phase, are inadequate in efficiently regulating gas-exchange valve lift and heating the hydraulic system.
Innovation Solution
An electrohydraulic valve train with a camshaft, hydraulic system, and electrically controlled hydraulic valve is used to control the gas-exchange valve, allowing for improved refilling of the pressure chamber and heating of the hydraulic system by closing and opening the hydraulic valve between successive lifts of the first hydraulic piston during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the hydraulic valve is closed during a lift of the first hydraulic piston to regulate gas-exchange valve lift, then the valve lift is controlled within minimum and maximum limits, but the refilling of the pressure chamber with pressurized medium is insufficient during cold start phase
Solution Approach 1:
The hydraulic valve is opened and closed periodically between two immediately successive lifts of the first hydraulic piston during startup phase. This periodic action allows the pressure chamber to be refilled with pressurized medium in cycles, ensuring sufficient medium volume while maintaining valve lift control through the electronic control means.
2Reliability
If the hydraulic system operates during cold start phase, then the engine can start, but the hydraulic system is insufficiently heated leading to poor starting behavior
Solution Approach 1:
The electrical energy required to operate the electrically controlled hydraulic valve during startup phase is converted into heat energy through the valve's electromagnetic coil. This Joule heating effect warms the pressurized medium and hydraulic components, improving fluid viscosity and system responsiveness, thereby enhancing cold start reliability.
3Quantity of substance
If the hydraulic valve is opened and closed frequently between successive lifts, then the pressure chamber refilling is improved and hydraulic system is heated, but the energy consumption increases
Solution Approach 1:
The hydraulic valve is opened and closed in advance between two immediately successive lifts of the first hydraulic piston, before the actual valve actuation is needed. This preliminary action ensures the pressure chamber is pre-filled with sufficient pressurized medium and the hydraulic system is pre-heated, preventing energy-intensive operations during critical startup moments.
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 method enhances the starting behavior and cold start performance by improving pressure chamber refilling and heating the hydraulic system, leading to better engine operation and efficiency.
Implementation Method 1
electrical energy of the electrically controlled hydraulic valve is converted into heat energy and fed to the valve piston, the valve seat of the hydraulic valve, and the pressurized medium
Data Source
AI summary
A method for operating an internal combustion engine (4) with an electrohydraulic valve train (1) for variable-lift drive of a gas exchange valve (3), including a camshaft (6) and a hydraulic system arranged in a drive path between the camshaft and the gas exchange valve, said hydraulic system being connected to a pressure medium supply (14) of the internal combustion engine, a first hydraulic piston (8) which is driven by a cam (5) of the camshaft and a second hydraulic piston (9) which drives the gas exchange valve in an opening direction, a variable-volume pressure chamber (10) which is delimited by the hydraulic piston and a control channel (12) which connects the pressure chamber to a pressure relief chamber (11), an electrically actuated hydraulic valve (15) which is arranged in the control channel and which, in an open position, permits a flow of hydraulic medium through the control channel and, in a closed position, blocks a flow of hydraulic medium through the control channel, and an electronic controller (16) for the actuation of the hydraulic valve as a function of operating parameters of the internal combustion engine. To improve the cold-start behavior of the internal combustion engine, it is provided that, during the starting phase, the hydraulic valve is closed and opened again at least once between two immediately successive lifts of the first hydraulic piston.