The process for determining the compression stroke function of cylinder 1 is described using engine 926.9 (6 cylinders) as an example.
G07.15-A028-79
A6 | Engine management (MR) control unit | B16 | Camshaft position sensor | |
B15 | Crankshaft position sensor | A | Input signals |
G07.15-A027-79
1 | Flywheel | B15 | Crankshaft position sensor | |
2 | Camshaft sprocket | B16 | Camshaft position sensor | |
3 | Hole | A | Input signals | |
4 | Additional bore (for detecting the compression stroke at cylinder 1) | X | Rotation direction | |
A6 | Engine management (MR) control unit |
General
Detection of the compression stroke at cylinder 1 takes place as soon as the engine has started. Since the position of the crankshaft alone is not sufficient for this, the engine management (MR) control unit also uses signals from the camshaft position sensor.
However, if the compression stroke at cylinder 1 is just known the one time then all further compression strokes are just calculated based on signals from the crankshaft position sensor.
Signals from the camshaft position sensor are exclusively used to determine the engine speed or the compression stroke at cylinder 1 if the crankshaft position sensor fails.
The reason for this is that the crankshaft position sensor provides more precise values for the crankshaft position than the camshaft position sensor. Thus the start of actuation of the single injection pumps for cylinders 1 to 6 (Y600 to Y605) can be determined more exactly.
Function
The camshaft sprocket (2) located on the exhaust camshaft has 12 bores (3) that are distributed around the entire circumference of the camshaft sprocket (2) at intervals of 30° in each case. They each trigger a pulse in the camshaft position sensor positioned on the camshaft sprocket (2).
With the aid of an additional bore (4) at a 55° crankshaft angle before top dead center for cylinder 1, the compression stroke of cylinder 1 can be determined.
As soon as the exhaust camshaft turns, the bores (3) and the additional bore (4) in the camshaft position sensor generate changes in the magnetic field that are converted into shift signals by an electronic analysis system and are passed on to the engine management (MR) control unit.
If the engine is started, the engine management (MR) control unit uses the additional bore (4) to check when cylinder 1 is in its compression stroke.
Because the engine management (MR) control unit determines the position of the crankshaft via the crankshaft position sensor at the same time, it can synchronize the position of the additional bore (4) with the position of the gap on the flywheel (1) so that the signals from the crankshaft position sensor alone are then sufficient for determining the compression stroke of cylinder 1 and thus the start of actuation of the single injection pumps for cylinders 1 to 6.