BOSCH Common Rail Injection

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The fuel in the pressure accumulator of this injection system is constantly under pressure. It is no longer necessary to build up the pressure again for each injection.

Its function

The fuel for the individual cylinders comes from the common pressure accumulator where it is stored continually at high pressure. At the heart of the system are the solenoid-valve-controlled injectors, one of which is assigned to each of the engine’s cylinders. A triggering signal from the ECU energises them for each injection process. The accumulator pressure is generated by a high-pressure radial-piston pump as a function of the engine’s operating status, and precisely controlled by the ECU. This means that the duration of injection and the pressure, and therefore the injected fuel quantity, can be changed at any instant in time. For passenger cars, the maximum system pressure is 1,350 bar, and for commercial-vehicle engines 1,400 bar.

Special features

 Low-emission, economic, and quiet engines
 The optimum fuel pressure is always available for every engine operating status
 The modular design facilitates adaptation to the diesel engine in question
 Conventional injection installations can be replaced by Common Rail systems without far-reaching engine modifications
Components

Essentially, the complete system comprises the following major components:
 Quantity-controlled high-pressure pump
 Common rail
 Pressure-control valve
 Pressure sensor
 Injectors
 ECU
 Further sensors and actuators

 

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BOSCH Single Unit Injectors:

The high-performance single-cylinder injection pump systems with short high-pressure lines generate very high injection pressures in a short time.
Its function

Together with engine design engineers, Bosch has developed the Unit Injector System with solenoid injector (UIS) and the Unit Pump System (UPS). On the UIS, the injector nozzle and the plunger-and-barrel assembly are in the form of a compact unit which is installed in the engine cylinder head and driven via the engine’s camshaft. Maximum injection pressure is 1,800 bar for commercial vehicles and 2,000 bar for passenger cars. The high-speed solenoid valve not only defines the start of injection, but also the injected fuel quantity. The UIS electronic control permits the incorporation of auxiliary functions such as temperature-controlled start of injection, and active surge damping. With the UIS for passenger-cars, pilot injection is possible for even further reducing the combustion noise.

The UPS was conceived for use in commercial vehicles and trucks. It generates peak pressures of up to 1,800 bar, and features outstanding levels of fuel economy and environmental compatibility. The pump is connected to the injection nozzle by a very short injection line and is driven from underneath by a bottom-mounted camshaft.

Special features

 Very high injection pressures: Up to 2,000 bar with the UIS for passenger cars
 Compact design, therefore minimum installation space
 The UPS modular design makes it easy to incorporate in existing diesel-engine concepts
 High-speed solenoid valve for precise control of start of injection and injected fuel quantity

 

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BOSCH DISTRIBUTOR PUMP:

Small, light, fast, clean: the new injection pumps for diesel engines reach a pressure of up to 1,500 bar.

Its function

The major assemblies are the high-pressure solenoid valve, the ECU (which is directly attached to the pump in the VP 44 version), and the angle-of-rotation sensor. The engine’s available torque curve can be put to full effect by means of the sensor data and maps which are stored in the ECU. The start-of-injection control guarantees outstanding fuel economy and low levels of exhaust-gas emissions. The electronic control also provides for new safety and comfort functions, as well as permitting the exchange of data with other systems in the vehicle.

The next development target is the radial-piston distributor pump with integrated pilot injection.

Special features

 Easily adaptable
 High performance: VP 44 1,500 bar at the nozzle
 Low weight
 Low volume