Dynamic Time Constant Filtering for Engine High-Pressure Control
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Solution Overview
Problem
Internal combustion engines with existing injection systems face issues during sudden load rejection, leading to impermissible high pressures and deteriorated emission behavior due to rapid changes in fuel injection volume flow, causing excessive stress and emission deviations.
Innovation Solution
A method is developed to filter the target volume flow with a selected time constant based on its temporal development, allowing for delayed reduction or rapid increase of the fuel injection, thereby controlling high-pressure dynamics to prevent excessive pressure increases and maintain optimal engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the target volume flow is rapidly reduced after load rejection, then the high pressure drops quickly, but the high pressure rises suddenly again due to high-pressure control inertia, causing impermissible load and deteriorated emission behavior
Solution Approach 1:
The patent applies dynamics by making the time constant dynamic rather than fixed. The filtering time constant is adapted based on the current operating state and rate of change of the target volume flow. When the target volume flow changes rapidly (high derivative), a larger time constant is used to smooth the controlled volume flow and prevent excessive pressure fluctuations. When changes are gradual, a smaller time constant allows faster response. This dynamic adaptation resolves the contradiction between fast response and stable emission behavior.
Solution Approach 2:
The patent changes the parameter of the time constant based on the derivative of the target volume flow. By monitoring how quickly the target volume flow is changing and adjusting the filtering time constant accordingly, the system optimizes the balance between response speed and pressure stability. This parameter change approach allows the control system to handle both rapid transients and steady-state operations effectively.
2Stress or pressure
If the target volume flow is delayed reduced, then the high pressure increase is limited, but the response to protect the engine from impermissible load is slower
Solution Approach 1:
The dynamic time constant adjustment enables the system to provide immediate protection when needed. When the derivative of the target volume flow indicates a rapid change (such as sudden load rejection), the control system responds quickly by applying an appropriately sized time constant that limits pressure spikes while maintaining fast response. This resolves the contradiction between protection speed and pressure limitation.
3Speed
If a fixed small time constant is used for filtering, then the response to pressure changes is fast, but the high pressure rises suddenly during rapid target volume flow changes, causing impermissible load
Solution Approach 1:
The patent resolves this contradiction by making the time constant dynamic. During rapid transients when the derivative of target volume flow is large, a larger time constant is automatically applied to prevent excessive pressure rises. During normal operation with gradual changes, a smaller time constant maintains fast response. This dynamic adaptation eliminates the need to choose between fast response and pressure limitation.
Solution Approach 2:
The system changes the time constant parameter based on operating conditions. By monitoring the rate of change of the target volume flow and adjusting the filtering time constant accordingly, the system achieves both fast response during steady-state and pressure limitation during transients, resolving the contradiction between response speed and pressure control.
Data Source
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AI summary
The invention relates to a method for operating an internal combustion engine (1) having an injection system (3) which has a high-pressure accumulator (13), high pressure in the high-pressure accumulator (13) being controlled via a suction throttle (9) on the low-pressure side, acting as a first pressure control element in a first high-pressure control loop (25). During normal operation, a high-pressure disturbance variable is produced by means of a pressure regulating valve (19, 20) on the high-pressure side, acting as an additional pressure control element, via which fuel is re-directed from the high-pressure accumulator (13) into a fuel reservoir (7), the at least one pressure regulating valve (19, 20) being controlled, during normal operation, on the basis of a set volumetric flow rate (Vs) for the fuel to be re-directed. According to the invention, a temporal development of the set volumetric rate (Vs) is sensed and the set volumetric flow rate (Vs) is filtered, a time constant (Tv) for the filtering of the set volumetric flow rate (Vs) being selected as a function of the sensed temporal development.