Diesel Engine Control Device Adjusting Pilot Main Injection Interval
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Solution Overview
Problem
Existing diesel engine control devices face challenges in managing cylinder pressure when reducing supercharging pressure, leading to potential excessive cylinder pressure rises due to the inertia of turbochargers and other factors, which can result in engine noise and inefficiencies.
Innovation Solution
A control device and method for a diesel engine that adjusts the interval between the start timings of pilot and main injections based on the degree of accelerator pedal opening and actual supercharging pressure, retarding the main injection start timing if the actual supercharging pressure is higher than a predetermined value to slow down combustion and reduce cylinder pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the start timing of main injection is retarded to reduce cylinder pressure, then engine silence is improved, but combustion efficiency may deteriorate
Solution Approach 1:
The fuel injection is divided into two distinct phases: pilot injection (first fuel injection) and main injection (second fuel injection). The pilot injection is performed first to initiate combustion and heat the cylinder, then the main injection is retarded to reduce noise. This segmentation allows each injection to serve a specific function, resolving the contradiction between noise reduction and combustion efficiency.
Solution Approach 2:
The pilot injection is performed as a preliminary action before the main injection. By injecting a small amount of fuel first to create preliminary combustion and heat the cylinder, the main injection can be retarded without causing excessive noise or combustion inefficiency. The preliminary combustion prepares the cylinder environment for the delayed main injection.
2Object-affected harmful factors
If the interval between pilot injection and main injection is broadened to reduce cylinder pressure, then engine silence is enhanced, but fuel premixing time may be insufficient
Solution Approach 1:
The pilot injection serves as a preliminary action that heats the cylinder and initiates combustion before the main injection. This preliminary heating ensures that even with a broadened interval, the fuel from main injection can still mix and combust efficiently. The preliminary combustion creates favorable thermal conditions for the delayed main injection.
Solution Approach 2:
The injection timing parameters are dynamically adjusted based on operating conditions. The interval between pilot and main injection is broadened specifically when supercharging pressure is high and accelerator opening is decreasing, while maintaining appropriate timing under other conditions. This parameter change resolves the contradiction by adapting to specific operational contexts.
3Speed
If supercharging pressure is reduced quickly in response to accelerator pedal closure, then engine response is improved, but excessive cylinder pressure rise occurs due to turbocharger inertia
Solution Approach 1:
The pilot injection is performed as a preliminary action before the main injection when supercharging pressure is high. This preliminary combustion helps control the overall combustion process and prevents excessive cylinder pressure rise even when the accelerator is closed quickly. The pilot injection prepares the combustion environment to handle the transient pressure conditions.
Solution Approach 2:
The injection timing strategy is dynamically adjusted based on real-time operating conditions including supercharging pressure and accelerator opening. When supercharging pressure is high and accelerator opening decreases, the interval between pilot and main injection is broadened. This dynamic adjustment allows the system to respond quickly to driver input while preventing excessive cylinder pressure due to turbocharger inertia.
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 cylinder pressure, enhances engine silence, and improves emission performance by ensuring sufficient fuel premixing without reducing fuel injection amounts, while maintaining a simpler control mode.
Implementation Method 1
a fuel-injector that is configured to inject fuel into a combustion chamber
Implementation Method 2
a supercharger that is configured to supercharge gas to be introduced into the combustion chamber
Implementation Method 3
main injection that allows injected fuel to start combusting from near a compression top dead center
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The silence of a diesel engine is enhanced. A PCM 10 detects an actual supercharging pressure of a gas, and controls an injection mode of a fuel through an injector 18, thereby executing main injection that is started near a compression top dead center or pilot injection that is executed prior to the main injection depending on an operating state of an engine 1. If the degree of opening of an accelerator pedal decreases during operation of a large turbocharger 61, and the actual supercharging pressure is equal to or higher than a predetermined value, the PCM 10 executes cylinder pressure control that allows an interval between a start timing of the pilot injection and a start timing of the main injection to be broader than if the actual supercharging pressure is less than a predetermined value.