10/28/2019 Bosch Common Rail Injection System Pdf
No other combustion engine is as versatile as the diesel engine. Its versatility can be attributed primarily to a high degree of efficiency and associated cost effectiveness. The requirements for diesel engine injection systems are constantly increasing: higher pressures, faster switching times and the flexible adaptation of the injection pattern to suit operating conditions make the diesel engine both economical and powerful. Bosch consistently further develops diesel drive systems, including components for fuel injection (diesel common-rail system) and fuel supply as well as the engine and air control, turbocharging, exhaust-gas treatment, glow system, brake system and engine lubrication. Diesel drive systems with common-rail injection systems combined with efficient exhaust-gas treatment can form the basis for economical vehicles. The primary advantage of the diesel common-rail system is the enormous flexibility of the injection pressure and the injection timing, which is achieved by separating the pressure generation and injection systems.
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The fuel is permanently maintained at a high pressure ready for injection. The pressure is generated by the high-pressure pump. The fuel rail mounted on the engine serves as a high-pressure accumulator. From here, the fuel is distributed to the individual injectors. An injector with injection nozzle is integrated into each engine cylinder.
The injection timing and fuel quantity are calculated and controlled individually for each cylinder. The common-rail system with piezo injectors by Bosch enables the flexible injection of fuel at pressures up to 2,700 bar. Even greater economy and precision The “Digital Rate Shaping” strategy (DRS) contributes to a very small delay between pre-injection and main injection. DRS can be used for realizing a smoother combustion process with less interruptions that can further reduce noise, emissions and fuel consumption.
The innovative “Needle Closing Control” (NCC) function can significantly increase injection accuracy over lifetime, in particular. Characteristic injector variables are measured from a sensor and exchanged with the electronic control unit. Air control In order to contribute to an efficient combustion while conserving resources, the amount of injected fuel must always be adapted accurately to the air mass that enters the cylinder. The air mass is measured accurately by a hot film air-mass sensor. Electrification and downsizing Together with the variable injection start and the option of multiple pre- and post-injections as well as short intervals between injections, the system is optimally designed for downsizing concepts with turbocharging as well as for combining with hybrid technology to electrify the powertrain. SYSTEM BENEFITS FOR MANUFACTURERS. For very high specific engine outputs up to 100 kw/l.
Common Rail Injection Pump
Supports compliance with Euro 6, Real Driving Emissions and comparable standards. Efficient and versatile for passenger cars and light duty vehicles due to modular design. A permanently available injection pressure that is independent of the speed and load allows the flexible selection of the injection start, quantity and duration. High flexibility of multiple injections. Simple mounting of the common-rail system on the engine.
Common rail injection: advanced technology for diesel engines Bosch launched the first common rail system in 1997. The system is named after the shared high-pressure reservoir (common rail) that supplies all the cylinders with fuel.
With conventional diesel injection systems, the fuel pressure has to be generated individually for each injection. With the common rail system, however, pressure generation and injection are separate, meaning that the fuel is constantly available at the required pressure for injection.
Common rail systems have a modular design. Each system consists of a high-pressure pump, injectors, a rail, and an electronic control unit. Mode of operation With conventional diesel injection systems, the fuel pressure has to be generated individually for each injection.
With the common rail system, however, pressure generation and injection are separate, meaning that the fuel is constantly available at the required pressure for injection. Pressure generation takes place in the high-pressure pump. The pump compresses the fuel and feeds it via a high-pressure pipe to the inlet of the rail, which acts as a shared high-pressure reservoir for all injectors – hence the name “common rail”. From there, the fuel is distributed to the individual injectors, which inject it into the cylinder’s combustion chamber. The injector in a common rail system consists of the nozzle, an actuator for Piezo injectors or a solenoid valve for solenoid valve injectors, as well as hydraulic and electrical connections for actuation of the nozzle needle. It is installed in each engine cylinder and connected to the rail via a short high-pressure pipe.
The injector is controlled by the Electronic Diesel Control (EDC). This ensures that the nozzle needle is opened or closed by the actuator, be it solenoid valve or Piezo. Injectors with Piezo actuators are somewhat narrower and operate at a particularly low noise level.
Both variants demonstrate similarly short switching times and enable pre-injection, main injection and secondary injection to ensure efficient fuel combustion at every operating point.
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