Fuel Vapor Retention Filter Loading via Scavenge Pump Differential Pressure
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Solution Overview
Problem
Modern internal combustion engines with hybrid drive and start/stop functionality face challenges in regenerating fuel vapor retention filters due to reduced scavenge rates and insufficient pressure in the intake manifold, leading to inaccurate determination of fuel vapor loading, which can result in increased emissions, fuel consumption, and poor drivability.
Innovation Solution
A method and control device that accurately determine the loading of a fuel vapor retention filter by measuring differential pressure across a scavenge air pump, using pressure sensors or a differential pressure sensor, and correlating this with the degree of loading, allowing for precise injection correction and enhanced regeneration even under reduced pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the internal combustion engine is shut down temporarily for hybrid drive and start/stop functionality, then fuel consumption and emissions are reduced, but the scavenge rate for regenerating the fuel vapor retention filter is significantly reduced
Solution Approach 1:
The control device determines the degree of loading of the fuel vapor retention filter before the regeneration process starts. This preliminary determination allows the system to prepare appropriate injection correction values and scavenge flow rates in advance, ensuring effective regeneration even when the engine is operating in hybrid mode or during start/stop cycles.
Solution Approach 2:
The control device continuously monitors the actual scavenge flow rate and compares it with the target scavenge flow rate. Based on this feedback, the control device adjusts the tank venting valve opening and injection correction values to maintain optimal regeneration conditions, ensuring the fuel vapor retention filter is effectively regenerated despite reduced engine operating time.
2Power
If dethrottling is implemented to eliminate the throttle valve and control airflow using intake valves and exhaust gas turbocharging, then engine efficiency is improved, but the reduced pressure in the intake manifold pipe becomes insufficient for effective scavenging
Solution Approach 1:
The control device introduces an intermediary measurement approach by using the differential pressure across the scavenge air pump as a proxy indicator for the degree of loading. This intermediary parameter allows the system to accurately determine filter loading conditions even when direct pressure measurements in the intake manifold are insufficient due to dethrottling operations.
Solution Approach 2:
The control device changes the measurement parameter from direct intake manifold pressure (which is insufficient under dethrottling) to differential pressure across the scavenge air pump (which correlates with fuel vapor concentration). This parameter transformation enables accurate loading determination despite the altered pressure conditions caused by dethrottling.
3Device complexity
If conventional methods using lambda probe signal deviation are used to determine the degree of loading, then the system can operate with existing sensors, but the determination leads to erroneous results and requires a relatively long learning phase
Solution Approach 1:
The control device replaces the indirect mechanical/electrical measurement method (lambda probe signal analysis) with a direct physical measurement approach (differential pressure measurement across the scavenge air pump). This substitution provides more accurate and immediate determination of the degree of loading without requiring complex signal processing or prolonged learning phases.
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 enables accurate determination of fuel vapor loading, improving scavenge rates, reducing lambda drift, and minimizing drivability issues, while ensuring compliance with emission limits and efficient fuel management.
Implementation Method 1
a value for a differential pressure is determined across the scavenge air pump. A value for the degree of loading of the fuel vapor retention filter is then assigned to the differential pressure
Implementation Method 2
The purpose of such devices is to accommodate and temporarily store fuel vapor that forms in a fuel tank as a result of vaporization, so that the fuel vapor cannot escape into the environment. As storage for the fuel vapor, a fuel vapor retention filter is provided in the fuel vaporization restraint system; this uses, for example, activated carbon as a storage medium.
Implementation Method 3
a value is detected for the pressure in the regeneration line upstream of the scavenge air pump and a value is detected for the pressure in the regeneration line downstream of the scavenge air pump. From these pressure values a value for a differential pressure is determined across the scavenge air pump
Data Source
AI summary
Various embodiments may include a method and a control device for operating a tank venting system of an internal combustion engine. For example, a method for operating an engine may include: activating a scavenge air pump disposed in a regeneration line with a fuel vapor retention filter; upon reaching a constant speed of an impeller of the scavenge air pump conveying the scavenge air, detecting a pressure upstream of the scavenge air pump and a pressure downstream of the scavenge air pump; calculating a differential pressure across the scavenge air pump; determining the degree of loading of the fuel vapor retention filter based at least in part on the differential pressure; and adjusting a fuel injection time based on the degree of loading.