Fuel Post Injection Timing for DPF Regeneration

The patent applies parameter changes by precisely controlling the fuel post injection timing within a specific crank angle range (within 40 degrees before and after top dead center). This timing parameter optimization ensures that fuel is injected when the piston is near the top of its stroke, allowing the fuel to be drawn into the exhaust system through the exhaust valve rather than remaining in the cylinder where it would cause wall wetting and oil dilution. The exact timing parameter control resolves the contradiction between generating sufficient exhaust temperature for regeneration and avoiding harmful fuel deposition in the cylinder.

The patent implements dynamics by adapting the fuel post injection strategy specifically for cylinder deactivation and engine braking conditions. The system dynamically adjusts injection timing based on the operational state, ensuring that during these specific conditions where combustion is discontinued, the injection timing precisely targets the exhaust system entry point. This dynamic adaptation allows exotherm generation while preventing the fuel from settling on cylinder walls or mixing with oil.

The patent applies the extraction principle by removing the fuel from the cylinder environment at the critical moment when the piston approaches top dead center. By timing the injection to coincide with the piston at or near TDC and leveraging the exhaust valve opening, the fuel is extracted from the cylinder space and directed into the exhaust system. This extraction prevents the fuel from remaining in the cylinder where it would otherwise continue to combust incompletely or deposit on walls, thereby resolving the contradiction between complete combustion and avoiding wall wetting.

The exhaust system acts as an intermediary medium that receives the post-injected fuel. By timing the injection to occur when the exhaust valve is open or about to open, the fuel uses the exhaust gas flow as a carrier to transport it out of the cylinder and into the exhaust system where combustion can complete in the DPF or downstream catalyst. This intermediary mechanism allows the fuel to combust completely without contacting cylinder walls or mixing with oil.

The patent applies preliminary action by injecting the fuel just before or at the moment the exhaust valve opens, during the brief period when the piston is at top dead center. This timing ensures that the fuel is introduced into the cylinder at the optimal moment to be swept into the exhaust system, generating exotherms that raise exhaust temperature for DPF regeneration. This preliminary, precisely-timed injection enables temperature maintenance during fuel economy modes without requiring continuous combustion in all cylinders.

The patent implements periodic action through the cyclic nature of the fuel post injection, which occurs once per engine cycle in the specific crank angle window. This periodic injection, synchronized with the engine's natural cycle and exhaust valve timing, creates regular exothermic events that maintain exhaust temperature throughout the regeneration process while allowing cylinders to remain in fuel economy mode between injection events.