Fuel Injection Control for Pressure Variation Compensation
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Solution Overview
Problem
In fuel injection systems with a common rail, it is challenging to accurately control fuel injection quantity due to variations in fuel pressure, especially in asynchronous systems where feed durations overlap with injection durations, leading to inconsistent fuel delivery among injectors.
Innovation Solution
A control apparatus that includes an estimator to determine the actual injection duration, a determiner to calculate the fuel pressure during injection, and a setter to adjust the manipulated variable for each injector based on real-time pressure data, ensuring accurate fuel injection quantity control despite pressure variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feed durations overlap with injection durations in asynchronous fuel injection system, then fuel pump can continuously supply fuel to accumulator, but fuel pressure in accumulator varies during injection causing inaccurate fuel injection quantity control
Solution Approach 1:
The control apparatus determines the fuel pressure at a specific timing (middle of estimated actual injection duration) before setting the command injection duration. This preliminary determination of pressure allows the system to pre-calculate the appropriate injection duration that will deliver the commanded fuel quantity, compensating for pressure variations that occur during overlapping feed and injection periods.
Solution Approach 2:
The system uses feedback from the pressure sensor to continuously monitor fuel pressure in the accumulator. The control apparatus adjusts the command injection duration based on the detected fuel pressure, creating a closed-loop control system that compensates for pressure variations caused by overlapping feed and injection operations, thereby maintaining accurate fuel injection quantity control.
2Speed
If command injection duration is set based on fuel pressure sensed at start of energization, then control response is fast, but fuel pressure variation during injection causes deviation from command injection quantity
Solution Approach 1:
The control apparatus performs preliminary determination of fuel pressure at the middle of the estimated actual injection duration, and based on this preliminary pressure value, sets the command injection duration. This allows the system to account for pressure variations that will occur during the injection process, rather than relying solely on the initial pressure reading at energization start.
Solution Approach 2:
The system dynamically adjusts the timing for determining fuel pressure from a fixed point (start of energization) to a dynamic point (middle of estimated actual injection duration). This dynamic timing adjustment allows the control apparatus to capture the representative fuel pressure during the injection process, improving the accuracy of injection quantity control while maintaining responsive control.
3Device complexity
If fuel pressure in accumulator is not compensated, then control system is simple, but injection quantity varies among injectors whose injection durations overlap with feed durations
Solution Approach 1:
The control apparatus applies local quality control by individually determining the fuel pressure and calculating the command injection duration for each injector based on its specific injection timing. Injectors whose injection durations overlap with feed durations receive compensated control based on actual pressure conditions during their injection period, while other injectors use standard control, thereby achieving consistent injection quantity across all injectors without uniformly complicating the entire control system.
Data Source
AI summary
A control apparatus is provided to control a fuel injection apparatus. The fuel injection apparatus includes an accumulator that accumulates high-pressure fuel, at least one injector that injects the high-pressure fuel accumulated in the accumulator into a cylinder of an internal combustion engine, and a pressure sensor that senses fuel pressure in the accumulator and outputs a signal indicative of the sensed fuel pressure. The control apparatus includes an estimator, a determiner, and a setter. The estimator estimates an actual injection duration of the injector. The determiner determines, during the actual injection duration estimated by the estimator, a value of the fuel pressure in the accumulator based on the signal output from the pressure sensor. The setter sets a manipulated variable for controlling fuel injection quantity of the injector based on the value of the fuel pressure determined by the determiner.