Exhaust Valve Timing Control for High Temperature
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Solution Overview
Problem
Existing methods for increasing exhaust gas temperature in internal combustion engines, such as those disclosed in DE 103 48 107 A1 and EP 3 115 581 A1, can lead to undesired excitations in the crank drive and are limited in effectiveness under low-load conditions.
Innovation Solution
The method involves shortening and delaying the opening time of the exhaust valve and reducing its lift during the exhaust stroke, which increases the work of the gas exchange loop, resulting in higher exhaust gas temperature without deactivating cylinders, thus avoiding unwanted excitations in the crank mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cylinders are deactivated to increase exhaust gas temperature, then exhaust gas temperature increases, but unwanted excitations occur in the crank mechanism
Solution Approach 1:
The exhaust valve control is segmented into different phases: a first exhaust valve control during a first part of the exhaust stroke with reduced opening duration and/or retarded opening timing, and a second exhaust valve control during a second part of the exhaust stroke with normal or different timing. This segmentation allows selective compression of exhaust gas in specific phases without complete cylinder deactivation, avoiding crank mechanism excitations while still increasing exhaust gas temperature.
2Temperature
If existing methods are used to increase exhaust gas temperature, then temperature increases, but effectiveness is limited under low-load conditions
Solution Approach 1:
The exhaust valve timing and duration are made dynamic and adaptive based on operating conditions. The control system adjusts the opening duration and timing of the exhaust valve according to the current load condition, allowing the method to be effective across a wide range of operating points including low-load conditions where previously it was limited.
3Temperature
If exhaust valve opening duration is shortened and opening timing is retarded, then exhaust gas temperature increases, but gas exchange work increases
Solution Approach 1:
The method changes the parameters of exhaust valve control (opening duration and opening timing) to optimize the balance between exhaust gas temperature increase and gas exchange work. By retarding the opening timing and reducing opening duration in a controlled manner, the method achieves sufficient temperature increase for aftertreatment while managing the additional gas exchange work within acceptable limits.
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 allows for efficient exhaust gas temperature increase, even under low-load conditions, maximizing exhaust gas enthalpy and preventing excessive loading on the intake valves and valve trains, enabling effective regeneration of exhaust gas aftertreatment systems like particulate filters without cylinder deactivation.
Implementation Method 1
shortening an opening time of an exhaust valve of a cylinder in the exhaust stroke compared to a normal opening time of the exhaust valve and retarding an opening time of the exhaust valve in the exhaust stroke compared to a normal opening time of the exhaust valve
Implementation Method 2
operating the internal combustion engine by firing the cylinder
Data Source
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AI summary
The invention relates to a method for operating an internal combustion engine (10) to increase the exhaust gas temperature, comprising shortening the opening time of an exhaust valve (16) of a cylinder (12) of the internal combustion engine (10) during the exhaust stroke compared to a normal opening time of the exhaust valve (16). The method further comprises delaying the opening time of the exhaust valve (16) during the exhaust stroke compared to a normal opening time of the exhaust valve (16). The method also includes operating the internal combustion engine (10) by firing the cylinder (12) and actuating the exhaust valve (16) according to the shortened opening time and the delayed opening time. In particular, the method enables the generation of a maximum exhaust gas enthalpy under low-load conditions without undesirable excitation in the crankshaft due to cylinder deactivation.