2. Outline 2.1 Features of System The common rail system was developed primarily to cope with exhaust gas regulations for diesel engines, and aimed for 1. further improved fuel economy; 2. noise reduction; and 3. high power output. [1] System Characteristics The common rail system uses a type of accumulation chamber called a rail to store pressur- ized fuel, and injectors that contain electronically controlled solenoid valves to spray the pres- surized fuel into the cylinders. Because the engine ECU controls the injection system (including the injection pressure, injection rate, and injection timing), the system is unaffected by the engine speed or load.
This ensures a stable injection pressure at all times, particularly in the low engine speed range, and dramatically decreases the amount of black smoke ordi- narily emitted by a diesel engine during start-up and acceleration. As a result, exhaust gas emissions are cleaner and reduced, and higher power output is achieved. (1) Injection Pressure Control a. Enables high-pressure injection, even in the low engine speed range. b. Optimizes control to minimize particulate matter and NOx emissions. (2) Injection Timing Control a. Optimally controls the timing to suit driving conditions. (3) Injection Rate Control a. Pilot injection control sprays a small amount of fuel before the main injection.
Common Rail System Injection Timing Control Injection Rate Control Optimization Pilot Injection Speed Injection Rate Common Rail System Main Injection Injection Timing Crankshaft Angle Injection Quantity Control Conventional Pump Cylinder Injection Volume Correction Speed 㧝㧟㧠㧞 QD0734E (4) EGR (Exhaust Gas Recirculation) Control a. By recirculating the exhaust gas into the intake side of the engine, the combustion temperature is reduced and NOx is decreased. 2 Injection Pressure Control Optimization, H Common Rail System Pressure Injection Conventional Pump Speed igh Pressurization Particulate NOx Injection Pressure imization, H igh Pressu