Часть второй
Distribution and Injection
Illustration 6g01140974
The rear view of the Bosch VP30 fuel injection pump
(6) Fuel solenoid valve (15) Delivery valve (11) Timing solenoid valve
The distribution of fuel to the fuel injection nozzles (10) takes place through the rotating movement of the distributor plunger (8). The fuel solenoid valve (6) meters the amount of fuel by the following operations:
- Time of closure
- Duration time
- Start of injection
- Amount of fuel
Illustration 7g01140988
Delivery of fuel from the delivery valve
Illustration 8g01141216
Closing of the delivery valve
The delivery valve (15) ensures that the pressure waves do not allow a reopening of the fuel injection nozzle (10). The pressure waves are created at the end of the injection process. The valve cone is lifted by the fuel pressure.
The fuel is forced through the fuel line to the fuel injection nozzle (10). The delivery ends and the fuel pressure drops. The valve spring presses the valve cone onto the valve seat. The reopening of a fuel injection nozzle (10) has a negative effect on emissions.
Timing
Retarding of the fuel injection is the direct relationship between the start of injection and the position of the piston. The timing compensates for the higher RPM of the engine by advancing the start of injection.
Illustration 9g01141217
Timing advance for timing mechanism (side view and top view)
Illustration 10g01366794
Timing retard for timing mechanism (side view and top view)
The timing advance or the timing retard of the fuel injection pump is shown in the following steps:
- The ECU (2) sends a signal to the timing solenoid valve (11).
- The timing mechanism is triggered by the timing solenoid valve (11) .
- The timing solenoid valve (11) changes the pressure in the timing advance mechanism (12) .
- The timing advance mechanism (12) changes the position of the cam ring (5) .
- The cam ring (5) changes the position of the rollers (13) .
- The rollers (13) change the position of the cam plate (14) .
- The cam plate (14) changes the timing of the fuel delivery.
Shutoff
The engine shuts off by interrupting the fuel supply. The engine Electronic Control Module (ECM) (1) specifies the amount of fuel. The fuel solenoid valve (6) is switched by the ECU (2) on the fuel injection pump to zero.
Control
Illustration 11g01141220
Electronic control for the fuel system (typical example)
The ECU (2) for the injection pump uses the command from the ECM (1) and the measured values from the secondary speed/timing sensor (4) to actuate the fuel solenoid valve (6).
Illustration 12g01141235
The timing wheel and the secondary speed/timing sensor
(4) Secondary speed/timing sensor (23) Timing wheel
The ECU (2) for the fuel injection pump is mounted on the top of the pump. The ECU has a connection to the engine ECM (2) and a connection to the speed/timing sensor (4). The ECU has a connection for the two solenoid valves (6). The ECM functions as a control computer. The ECU calculates the optimal parameters from the ECM data. The fuel solenoid (6) actuates the valve accordingly.
The secondary speed/timing sensor (4) in the fuel injection pump determines the precise angular position and the speed of the fuel injection pump shaft. Timing wheel (23) is permanently connected to the fuel injection pump shaft. The secondary speed/timing sensor (4) gets information from the timing wheel (23). The sensor then sends electrical impulses to the ECU (2). The ECU also uses the information to determine the average speed of the pump and momentary speed of the pump.
Note: The engine will not run if the secondary speed/timing sensor (4) fails.
The signal of the speed/timing sensor (4) is constant. Power command signals are routed over the CAN data link from the engine ECM (1) to the ECU (2) on the fuel injection pump.
Illustration 13g01141251
Operating principle
(24) Angle of fuel delivery
(25) Lift of the cam
(26) Stroke
(27) Pulse for actuating the fuel solenoid
(28) Valve lift (29) Angle of the speed/timing sensor
The amount of fuel is proportional to the stroke of the piston. The effective stroke is proportional to the angle of fuel delivery. A temperature compensation takes place in the ECU (2). The compensation takes place in order to inject the precise amount of fuel.
Fuel Injection Nozzles
Illustration 14g01144089
Fuel injection nozzle
Each fuel injection nozzle is held into the cylinder head by a clamp around the fuel injection nozzle. The fuel injection nozzles are not serviceable but the nozzles can be removed in order to clean the orifice.
The fuel injection pump forces the fuel to flow under high pressure to the hole in the fuel inlet. The fuel then flows around a needle valve within the nozzle holder which causes the nozzle to fill with fuel. The pressure of the fuel pushes the needle valve and a spring. When the force of the fuel pressure is greater than the force of the spring, the needle valve will lift up.
When the needle valve opens, fuel under high pressure will flow through the nozzle orifices into the cylinder. The fuel is injected into the cylinder through the orifices in the nozzle end as a very fine spray. When the fuel is injected into the cylinder, the force of the fuel pressure in the nozzle body will decrease. The force of the spring will then be greater than the force of the fuel pressure that is in the nozzle body. The needle valve will move quickly to the closed position. The needle valve has a close fit with the inside of the nozzle. This makes a positive seal for the valve.