DD15 Engine

Section 3.9 Fuel Injectors

Section 3.9
Fuel Injectors

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 1. Electrical Connector‪

 8. Check Valve‪

 2. Coil‪

 9. Solenoid Valve‪

 3. Pressure Converter Control Module‪

10. Coil‪

 4. Pressure Converter Piston‪

11. Spring‪

 5. Return Spring‪

12. Injector Needle‪

 6. High Pressure Feed‪

Y150 Injector (Cylinder 1)‪

 7. Pressure Converter‪

The fuel injectors (Y150 to Y155) are fixed by means of a hold down clamp inside the camshaft frame and located centrally between the valves of the respective cylinder. All injectors have a 6-digit code, the injector quantity compensation coding, which is located on the upper side of the injector. This code describes the quantity characterization of the respective injector. If an injector is replaced then this code must be reported to the Motor Control Module (MCM) using DDDL 7.0. ‪

The injectors have the task of injecting the fuel under high pressure into the cylinders. The injection timing, injection period, and the injection variants (e.g. with or without amplification) are established by the MCM.‪

The injectors are fitted with an amplifier circuit. This allows for two modes of injection: without amplification and with amplification.‪

In the case of injection without amplification the injection pressure is determined by the rail pressure (about 900 bar).‪

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In the case of injection with amplification the injection pressure of up to 2100 bar is generated in the injector‪

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Use of an amplifier within an injector offers the following advantages:‪

  • The leak oil losses in the high pressure area are reduced.
  • The pressure load of the high pressure pump, the fuel rail, and the high pressure lines is reduced since only a few components have high pressure applied to them.
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     A. (Square) Actuation of the amplifier control module before actuation of the needle solenoid valve‪

     B. (Ramp) Actuation of the amplifier control module parallel to actuation of the needle solenoid valve‪

     C. (Boot) Actuation of the amplifier control module after actuation of the needle solenoid valve‪

     (p). Injection pressure‪

     (t). Time‪

  • During injection with amplification the injection process is determined by actuation of the needle solenoid valve and the amplifier control module either at other times or simultaneously.

Section 3.9.1
injection without Amplification

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 1. Amplifier Control Module‪

 5. Check Valve‪

 2. Return Spring‪

 6. Needle Solenoid Valve‪

 3. High Pressure Feed‪

 7. Spring‪

 4. Amplifier‪

 8. Injector Needle‪

The amplifier control module (1) is not actuated during this process. The fuel internal to the injector is at rail pressure above and below the amplifier (4) piston. ‪

The compressed fuel from the rail enters the injector needle (8) through the center of the amplifier (4) and through the check valve (5) at the bottom of the amplifier (4). If the MCM actuates the needle solenoid valve (6) then the fuel pressure in the control compartment above the injector needle (8) is allowed to escape through the injector needle return. The injector needle (8) is then lifted due to the rail pressure being greater than the needle spring (7) pressure combined with the reduction of pressure in the control department. The fuel is injected at the specified rail pressure into the respective cylinder. If the MCM deactivates the needle solenoid valve (6), the pressure in the control compartment above the injector needle (8) builds up again. The injector needle (8) is returned to its seat with the aid of the spring (7) and fuel system pressure. At this point the injection process stops.‪

Section 3.9.2
Injection with Amplification

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 1. Amplifier Control Module‪

 5. Check Valve‪

 2. Return Spring‪

 6. Needle Solenoid Valve‪

 3. High Pressure Feed‪

 7. Spring‪

 4. Amplifier‪

 8. Injector Needle‪

Use of an amplifier (3) within an injector offers the following advantages:‪

  • The leak oil losses in the high pressure area are reduced.
  • The pressure load of the high pressure pump, the fuel rail, and the high pressure lines is reduced since only a few components have high pressure applied to them.
  • During injection with amplification (3) the injection process is determined by actuation of the needle solenoid valve (6) and the amplifier control module (1) either at other times or simultaneously.

Actuation of the amplifier control module (1) before actuation of the needle solenoid valve (6) (Square)

The amplifier control module (1) is actuated before the needle solenoid valve (6). The rail pressure applied below the amplifier (4) is routed to the injector return passage inside the injector. This difference in pressure allows the amplifier (4) to move. The fuel within the amplifier circuit is compressed by the amplifier (4) piston up to a higher fuel pressure level (red). If the MCM actuates the needle solenoid valve (6) the fuel pressure in the control compartment above the injector needle (8) is allowed to escape through the injector needle return. The injector needle (8) is then lifted due to the rail pressure being greater that the needle spring (7) pressure.‪

The fuel is injected with the fuel pressure increased by the amplifier into the respective cylinder. The level of the fuel pressure is dependent on the point in time of the initial actuation of the amplifier control module (1). If the MCM deactivates the amplifier control module (1), the pressure in the control compartment under the amplifier (4) builds up and the amplifier (4) returns to its starting position. If the MCM deactivates the needle solenoid valve (6), the pressure in the control compartment above the injector needle (8) builds up again. The injector needle (8) is returned to its seat with the aid of the spring (7) and fuel system pressure. At this point the injection process stops.‪

Actuation of the amplifier control module (1) parallel to actuation of the needle solenoid valve (6) (Ramp)

The amplifier control module (1) and the needle solenoid valve (6) are actuated at the same time by the MCM. The rail pressure applied below the amplifier (3) is routed to the injector return passage inside the injector. This difference in pressure allows the amplifier (3) to move. The injector needle (8) is lifted first by the rail pressure. Next, the fuel within the amplifier circuit is compressed by the amplifier (3) piston up to a higher fuel pressure level (red). Thus, during the complete injection phase the fuel pressure increases. If the MCM deactivates the amplifier control module (1), the pressure in the control compartment under the amplifier (3) builds up and the amplifier (3) returns to its starting position. The amplifier (3) goes back into its starting position. If the MCM deactivates the needle solenoid valve (6), the pressure in the control compartment above the injector needle (8) builds up again. The injector needle (8) is pressed onto its seat with the aid of the spring (7) and the injection process stops. ‪

Actuation of the amplifier control module (1) after actuation of the needle solenoid valve (6) (Boot)

The MCM actuates the needle solenoid valve (6) to allow the fuel pressure in the control compartment above the injector needle (8) to escape through the injector needle return. The injector needle (8) is then lifted due to the rail pressure being greater than the needle spring (7) pressure. The fuel is then injected at the prescribed rail pressure.‪

After the beginning injection, the rail pressure applied below the amplifier (3) is routed to the injector return passage inside the injector. The fuel within the amplifier circuit is compressed by the amplifier (3) piston up to a higher fuel pressure level (red). If the MCM deactivates the amplifier control module (3), the pressure in the control compartment under the amplifier (3) builds up and the amplifier (3) returns to its starting position. If the MCM deactivates the needle solenoid valve (6), the pressure in the control compartment above the injector needle (8) builds up again. The injector needle (8) is pressed onto its seat with the aid of the spring (7) and the injection process stops.‪


DD15 Fuel System Technician's Guide - DDC-SVC-MAN-0037
Generated on 10-13-2008

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