The single injection pump component description is described on engine 926.9 (6 cylinder) as an example.
Location
The single injection pumps for cylinders 1 to 6 are located on the left of the crankcase.
Y600 | Cylinder 1 single injection pump |
Y601 | Cylinder 2 single injection pump |
Y602 | Cylinder 3 single injection pump |
Y603 | Cylinder 4 single injection pump |
Y604 | Cylinder 5 single injection pump |
Y605 | Cylinder 6 single injection pump |
G07.02-A000-06
Task
The single injection pumps for cylinders 1 to 6 are directly actuated by engine management (MR) control unit (A6) and establish the necessary fuel pressure for injection and deliver the pressurized fuel to the respective fuel injector with nozzle holder combination (4).
Structure
Shown on single injection pump for cylinder 1 (Y600) |
8 | High pressure chamber |
11 | Solenoid |
12 | Anchor plate |
13 | Float needle |
21 | O-ring |
22 | Leakage drilling |
23 | Cover plate |
24 | Valve stop |
25 | Thread for union nut |
26 | Solenoid valve spring |
27 | Intermediate plate |
28 | Valve spring seat |
29 | Spring retainer |
30 | Pump housing |
31 | Sleeve |
32 | Pump element |
33 | Roller tappet spring |
34 | Spring plate (roller tappet) |
35 | Roller tappet |
36 | Oil hole |
37 | Roller |
38 | Roller tappet pin |
Y600 | Cylinder 1 single injection pump |
G07.02-A001-73
Function
I | Intake stroke |
II | Initial stroke |
III | Delivery stroke |
IV | Residual stroke |
2 | High pressure pipe |
3 | Connection fitting |
4 | Fuel injector with nozzle holder combination |
5 | Pump element |
6 | Supply passage |
7 | Solenoid valve |
8 | High pressure chamber |
9 | Diversion chamber |
10 | Return flow passage |
11 | Solenoid |
12 | Anchor plate |
13 | Float needle |
14 | Injection nozzle |
B | Fuel feed |
C | Fuel high pressure |
D | Fuel return |
W07.02-1011-76
Each single injection pump for cylinders 1 to 6 is driven via roller tappet (35) from the camshaft and is connected to injection nozzle (14) in the fuel injector with nozzle holder combination (4) by short high-pressure line (2) as well as connection fitting (3).
The single injection pumps for cylinders 1 to 6 have a fast-acting solenoid valve (7). This solenoid valve regulates the start of delivery and controls the quantity delivered. Solenoid valve (7) is actuated by the engine management (MR) control unit (A6), which calculates the start of delivery and quantity delivered according to the operating condition of the engine as soon as the engine is started and/or the engine is running.
Depending on the position of the camshaft, the single injection pumps for cylinders 1 to 6 have the following power strokes:
Intake stroke (I)
Initial stroke (II)
Delivery stroke (III)
Residual stroke (IV)
Together, these power strokes form a working cycle, which is repeated with every additional rotation of the camshaft at single injection pumps for cylinders 1 to 6 until the engine is turned off.
As soon as the engine is turned off, the engine management (MR) control unit (A6) stops actuation of solenoid valves (7). Single injection pumps for cylinders 1 to 6 deliver the almost depressurized fuel to the fuel return of the low-pressure fuel circuit and the engine switches off.
The following described processes within the individual power stroke of a cycle are transferable to all single injection pumps for 1 to 6.
Intake stroke (I)
The intake stroke (I) begins after the vertex of the cam is exceeded and pump element (5) moves downwards under the force of roller tappet spring (33).
Owing to the continuous fuel overpressure of about 2.0 to 6.5 bar in the low-pressure fuel circuit, the high-pressure chamber (8) is filled with fuel via supply passage (6) and the opened solenoid valve (7).
Therefore, the pressure in high-pressure chamber (8) filled with fuel is the same as the pressure in the low-pressure fuel circuit.
Initial stroke (II)
After the induction stroke (I), pump element (5) continues to remain in the low stop position and roller tappet (35) of the single injection pumps for cylinders 1 to 6 rolls off on the base circle of the pump cam. The initial stroke (II) begins only when the camshaft rotates further and pump element (5) begins to move in the upward direction owing to the rising pump cam.
Due to the upward movement of pump element (5) and the still open (de-energized) solenoid valve (7), the fuel in high-pressure chamber (8) is first pushed into diversion chamber (9) and then into return flow passage (10).
Delivery stroke (III)
The initial stroke (II) concludes and the delivery stroke (III) begins as soon as the engine management (MR) control unit actuates solenoid (11) in single injection pumps for cylinders 1 to 6. The solenoid (11) activates the anchor plate (12) with the float needle (13), which then locks the connection between the high pressure chamber (8) and the return flow passage (10).
If solenoid valve (7) is closed, the fuel in high-pressure chamber (8) is compressed due to the upward movement of pump element (5) (start of delivery).
With the further upward movement of pump element (5), the pressure in high-pressure chamber (8) increases and thereby the pressure in high-pressure line (2), pressure pipe connection (3) and injection nozzle (14) also increases further. At a pressure of about 330 bar, injection nozzle (14) opens and the fuel is injected into the combustion chamber (start of injection). The fuel pressure can rise up to 1800 bar during injection.
Residual stroke (IV)
If the actuation of solenoid (11) is stopped, float needle (13) of solenoid valve spring (26) is pushed back in its starting position on the shut-off stop.
The solenoid valve (7), and thereby the connection between the high pressure chamber (8) and the return flow passage (10) is opened. As a result, the fuel pressure in the high pressure chamber (8) and in the injection nozzle (14) falls sharply.
The injection nozzle (14) closes and the process of injection concludes (end of delivery).
The remainder of the fuel delivered by pump element (5) up to the vertex of the pump cam is again delivered to the low-pressure fuel circuit through diversion chamber (9) and return flow passage (10).
Diversion chamber (9) is necessary as an expansion chamber for the pressure peaks of single injection pumps for cylinders 1 to 6 during the residual stroke. This prevents the pressure behavior of the adjacent single injection pumps for cylinders 1 to 6 being affected through return flow passage (10).