Fuel Injection Control System PI Integral Term Pressure Adjustment
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Solution Overview
Problem
In fuel injection control systems for internal combustion engines, the delivery pressure of the low pressure fuel pump is not adequately decreased, even when vapor is not generated, leading to increased energy consumption and potential misfires.
Innovation Solution
Implementing a proportional plus integral control system that adjusts the driving signal for the high pressure fuel pump based on the difference between target and actual delivery pressures, prohibiting adjustments when the integral term shows an increasing tendency to avoid vapor generation and ensuring the delivery pressure of the low pressure fuel pump is minimized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the delivery pressure of the low pressure fuel pump is decreased to reduce energy consumption, then energy consumption is reduced, but fuel vaporization occurs leading to misfires
Solution Approach 1:
The system implements feedback control by monitoring the integral term of the PI controller and using its rate of change to dynamically adjust the low pressure fuel pump delivery pressure. When the integral term shows an increasing tendency, the system increases feed pressure to prevent vaporization; when it shows a decreasing tendency, the system decreases feed pressure to reduce energy consumption, creating a closed-loop control system that adapts to real-time conditions.
Solution Approach 2:
The invention transforms the static feed pressure control into a dynamic control system that continuously adapts based on the rate of change of the integral term. The delivery pressure of the low pressure fuel pump is no longer fixed but varies dynamically according to the calculated tendency of the integral term, allowing the system to optimize energy consumption while preventing vaporization under varying operating conditions.
2Reliability
If the delivery pressure of the low pressure fuel pump is maintained at a high level to prevent vaporization, then fuel vaporization is prevented, but energy consumption increases
Solution Approach 1:
Instead of maintaining high feed pressure continuously, the system applies partial action by adjusting the feed pressure only when necessary based on the integral term's rate of change. The low pressure fuel pump operates at reduced pressure levels during normal conditions and only increases pressure when the integral term indicates an increasing tendency, applying exactly the right amount of pressure control needed to prevent vaporization without excessive energy consumption.
3Device complexity
If the integral term value is used directly to control feed pressure, then control simplicity is maintained, but false vapor detection occurs when target pressure changes
Solution Approach 1:
The system performs preliminary analysis by calculating the rate of change of the integral term before making control decisions. This preliminary action of computing the derivative (amount of change per unit time) allows the system to distinguish between integral term increases caused by actual vaporization versus those caused by target pressure changes, preventing false vapor detection while maintaining control simplicity.
Data Source
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AI summary
The present invention addresses the problem that in a fuel injection control system for an internal combustion engine provided with a low pressure fuel pump and a high pressure fuel pump, delivery pressure of the low pressure fuel pump can be decreased as much as possible, while avoiding the generation of vapor of fuel. In order to solve this problem, the invention resides in a fuel injection control system for an internal combustion engine in which a driving signal for a high pressure fuel pump is calculated by using proportional plus integral control based on a difference between a delivery pressure of the high pressure fuel pump and a target pressure thereof, and a delivery pressure of a low pressure fuel pump is caused to decrease when an amount of change per unit time of an integral term shows a decreasing tendency or zero, whereas the delivery pressure of the low pressure fuel pump is caused to increase when the amount of change per unit time of the integral term shows an increasing tendency, wherein in cases where an increase in the integral term resulting from a change in the target delivery pressure of the high pressure fuel pump has occurred, the increase in the delivery pressure of the low pressure fuel pump is prohibited.