Fuel Injection Pressure Compensation for Propagation Delay
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Solution Overview
Problem
Existing fuel injection systems for internal combustion engines face challenges in accurately measuring the pressure of fuel discharged from the pump due to the propagation delay of pressure changes from the pump outlet to the pressure sensor, leading to errors in fuel quantity control.
Innovation Solution
A fuel injection system that includes a pressure sensor located closer to the fuel injector than the pump outlet, a calculator that compensates for pressure propagation delays by calculating the pump discharge pressure based on the sensor's output, and a controller that adjusts the flow rate control valve operation to ensure accurate fuel discharge, using tasks such as pressure change compensation and quantity change conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure sensor is installed in the fuel path closer to the fuel injector than to the pump outlet, then the measurement reliability is improved, but the measurement precision of pump discharge pressure deteriorates due to pressure propagation delay
Solution Approach 1:
The system performs preliminary sampling of pressure sensor output at a first time point before the calculation start time. This advance sampling allows the calculator to account for pressure propagation delay by using the sampled value in combination with the calculated pressure change, thereby resolving the contradiction between reliable measurement location and precise pump discharge pressure measurement.
Solution Approach 2:
The calculator acts as an intermediary that processes the pressure sensor output and adds the calculated pressure change to derive the pump discharge pressure. This intermediary computation compensates for the time delay inherent in pressure propagation through the fuel path, maintaining measurement precision while allowing the sensor to be positioned for reliable operation.
2Device complexity
If the pressure sensor is positioned closer to the fuel injector, then the system avoids the need for additional pressure sensors, but the pressure measurement becomes delayed relative to the actual pump discharge pressure
Solution Approach 1:
The system replaces the need for a second pressure sensor (which would be required to measure pump discharge pressure directly) with a computational approach. The calculator computes the pressure change based on fuel quantity changes and adds it to the sampled sensor output, thereby substituting mechanical measurement with computational compensation to eliminate time delay while maintaining device simplicity.
Solution Approach 2:
The system changes the parameter being measured from direct pump discharge pressure to a derived value combining sampled pressure sensor output with calculated pressure change. This parameter transformation allows the use of a single pressure sensor positioned for operational reliability while compensating for time delay through mathematical processing.
3Measurement precision
If the pressure sensor output is sampled before the calculation start time, then the calculation accuracy is improved by accounting for propagation delay, but the response time to pressure changes is reduced
Solution Approach 1:
The system performs preliminary sampling of the pressure sensor output at a first time point before the calculation start time. This advance sampling, combined with calculation of pressure change based on fuel quantity, provides accurate pump discharge pressure determination while maintaining responsive control through the calculator's ability to process this data quickly.
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 solution enables precise control of fuel discharge pressure and flow rate, improving the reliability and accuracy of fuel injection, even when the operating time ratio is high, and reduces production costs by eliminating the need for additional pressure sensors.
Implementation Method 1
a pressure sensor 10 installed in a portion of the fuel path 4 which is located closer to the fuel injector 6 than to the outlet of the pump 3, the pressure sensor 10 producing an output indicating a pressure of the fuel in the fuel path 4
Implementation Method 2
the pressure of fuel at the outlet of the pump usually starts to rise at the moment the fuel is discharged from the pump, but it is impossible for the pressure sensor to measure such a pressure change until it propagates to the pressure sensor
Data Source
AI summary
A fuel injection system for an internal combustion engine is provided which works to correct the pressure of fuel, as measured by a pressure sensor, using a pressure change corresponding to a change in quantity of the fuel in a common rail within a pressure change compensating time Tp to determine a pump discharge pressure Ptop. This compensates for an error in determining the pump discharge pressure Ptop which arises from propagation of the pressure of fuel from a pump to the pressure sensor. The pressure change compensating time Tp is the sum of a time T1 elapsed between sampling the output of the pressure sensor before a calculation start time when the pump discharge pressure is to start to be calculated and the calculation start time and a time T2 required for the pressure to transmit from the outlet of the pump to the pressure sensor.