Direct Injector Tip Temperature Estimation for Fuel Density Compensation
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Solution Overview
Problem
Existing fuel injection systems in internal combustion engines face challenges in accurately compensating for temperature variations in direct injector tips and fuel temperatures, leading to fueling errors and potential thermal degradation, especially during periods of direct injector deactivation and reactivation.
Innovation Solution
An engine controller continuously estimates the direct injector tip temperature based on heat flow and cooling flow during engine operation, including combustion and non-combustion conditions, and adjusts the direct injection fuel pulse-width to account for the differences in temperature-induced fuel density changes, ensuring accurate fuel delivery and reducing air-fuel ratio excursions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If direct injection is disabled for extended periods, then particulate matter emissions are reduced and port injection maintains combustion, but the direct injector tip temperature rises significantly causing fuel density changes and fueling errors upon reactivation
Solution Approach 1:
The system performs preliminary actions by continuously estimating the direct injector tip temperature even when direct injection is disabled, and pre-calculates the required pulse width adjustment before reactivation occurs. This allows the system to be ready with the correct compensation value immediately when direct injection resumes, eliminating the fueling error that would otherwise occur due to the temperature rise during the disabled period.
Solution Approach 2:
The system implements feedback by continuously monitoring engine operating conditions (combustion status, valve operation, port injector operation) and using this information to estimate the direct injector tip temperature in real-time. This feedback loop allows the system to dynamically adjust the direct injection pulse width based on the actual thermal state of the injector, ensuring accurate fueling despite temperature variations during port-injection-only periods.
2Manufacturing precision
If the direct injection pulse width is increased to compensate for elevated fuel temperature, then fuel density changes are addressed, but the injector tip temperature may cool faster than fuel temperature causing overcompensation and rich air-fuel ratio errors
Solution Approach 1:
The system performs preliminary estimation of the injector tip temperature continuously during the deactivation period, rather than measuring it only at reactivation. This allows the system to predict the temperature state and prepare the appropriate compensation value in advance, avoiding the need for aggressive pulse width increases that would cause overcompensation.
Solution Approach 2:
The system changes the approach from directly measuring or assuming fuel temperature to estimating the injector tip temperature based on multiple engine operating parameters (combustion conditions, valve operation, port injector operation). This parameter change allows the system to indirectly determine the thermal state more accurately and apply appropriate compensation without overcorrecting for the faster cooling rate of the injector tip compared to the fuel.
3Device complexity
If fuel rail temperature is used to estimate fuel temperature during engine transients, then temperature calculation is simplified, but the fuel rail temperature remains stable while actual fuel temperature increases causing calculation errors
Solution Approach 1:
The system extracts the temperature estimation problem from the fuel rail temperature measurement and separates it into two independent estimations: one for fuel temperature (based on fuel rail temperature) and one for injector tip temperature (based on engine operating conditions). This extraction allows the system to recognize that these two temperatures diverge during transients and apply compensation based on the injector tip temperature estimation, which accurately reflects the actual thermal state affecting fuel density.
Solution Approach 2:
The system introduces an intermediary estimation mechanism that uses engine operating conditions (combustion status, valve operation, port injector operation) as intermediate variables to infer the injector tip temperature. This intermediary approach bridges the gap between the simplified fuel rail temperature measurement and the actual fuel temperature at the injector, providing accurate compensation without requiring direct temperature sensors at the injector tip.
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 effectively reduces fueling errors and thermal damage by accurately compensating for temperature changes in the direct injector tip and fuel, improving the charge cooling effect and extending the lifespan of fuel system components.
Implementation Method 1
estimating a direct injector tip temperature different from fuel temperature based on cylinder conditions including cylinder combustion conditions
Implementation Method 2
cooling flow into the direct injector over a period of deactivation
Implementation Method 3
the density of the fuel may change over the period of deactivation based on the temperature
Data Source
AI summary
Methods and systems are provided for continuously estimating a direct injector tip temperature based on heat transfer to the injector from the cylinder due to combustion conditions, and heat transfer to the injector due to flow of cool fuel from the fuel rail. Variations in the injector tip temperature from a steady-state temperature are monitored when the direct injector is deactivated. Upon reactivation, a fuel pulse width commanded to the direct injector is updated to account for a temperature-induced change in fuel density, thereby reducing the occurrence of air-fuel ratio errors.