Fuel Injector Back End Rate Shaping via Dwell Time Control
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Solution Overview
Problem
Existing fuel injection systems struggle to effectively produce back end rate shapes, which are crucial for meeting stringent emissions standards, as they require precise control over fuel injection timing and pressure variations.
Innovation Solution
A fuel injector system with a rate shaping control unit that adjusts the dwell time between the opening and closing of the spill valve and check control valve, allowing for cycle-to-cycle variation of the back end rate shape by manipulating the electrical energy states of the actuators, thereby controlling the fuel injection rate into the engine cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fuel injection systems are used, then basic fuel delivery is achieved, but precise control over back end rate shape is insufficient for meeting emissions standards
Solution Approach 1:
The fuel injection system is segmented into multiple independently controlled valves: a spill valve for controlling plunger pressure and a check control valve for controlling nozzle outlet pressure. This segmentation allows independent optimization of different phases of fuel injection, enabling precise back end rate shape control while maintaining manageable system complexity through modular design
Solution Approach 2:
The system employs dynamically adjustable valve actuation timings that can be modified cycle-to-cycle based on operating conditions. The spill valve and check control valve are actuated at different timings during the injection event, with their duty cycles and timing parameters being dynamically adjustable to shape the back end injection rate according to emissions requirements
2Measurement precision
If multiple valves with independent control are implemented, then precise injection rate control is achieved, but system complexity increases
Solution Approach 1:
Both the spill valve and check control valve are integrated into a single fuel injector assembly, sharing common structural elements such as the valve body, spring mechanisms, and actuator mounting. This multi-functional integration allows precise control of both plunger pressurization and nozzle outlet pressure within one compact unit, achieving high measurement precision without proportionally increasing overall device complexity
Solution Approach 2:
The spill valve acts as an intermediary element that indirectly controls the back end injection rate by regulating plunger pressure, rather than directly controlling nozzle outlet pressure. This intermediary approach provides an additional degree of freedom for rate shaping while maintaining a relatively simple direct control path through the check control valve
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 over the back end rate shape of fuel injections, improving combustion efficiency and reducing emissions by allowing for tailored injection patterns based on engine operating parameters, enhancing compliance with stringent emissions standards.
Implementation Method 1
a spill valve assembly including a spill valve electrical actuator, and a spill valve positioned fluidly between the plunger cavity and the fuel inlet passage
Implementation Method 2
a check control valve assembly including a control valve electrical actuator and a check control valve positioned fluidly between the check control chamber and the low pressure outlet
Implementation Method 3
a plunger having a tappet and being movable between a retracted position, and an advanced position in the plunger cavity
Implementation Method 4
The method further includes advancing a plunger in a plunger cavity in a fuel injector in response to rotation of a cam
Implementation Method 5
a direct-operated nozzle check positioned fluidly between the nozzle supply passage and the nozzle outlet
Data Source
AI summary
A fuel system includes a mechanically actuated fuel injector having a spill valve assembly and a control valve assembly. A rate shaping control unit is coupled with a spill valve actuator and a control valve actuator, and structured to adjust a dwell time, cycle to cycle, between opening of a spill valve and closing of a check control valve. Adjusting the dwell time enables varying a back end rate shape, cycle to cycle, of fuel injections from a fuel injector into a cylinder in an internal combustion engine.