GF07.15-W-4004C | Determination of the compression cycle on the 1st cylinder - function | 19.12.03 |
ENGINE 541.9 in MODELS 950, 952, 953, 954
ENGINE 542.9 in MODELS 950, 952, 954
W07.15-1246-79
1 Flywheel
2 Camshaft sprocket
3 Pins for detecting the engine speed (only when required)
A6 MR/PLN control unit
B15 Crankshaft angle position sensor
B16 Cylinder 1 TDC sensor
4 Additional pin for detecting the compression stroke on the 1st cylinder
General information
Detection of the compression stroke on the 1st cylinder takes place as soon as the engine is started. The position of the crankshaft alone is not sufficient, the engine control (MR) also uses signal from the TDC sensor on cylinder 1 (B16).
If the compression stroke on the 1st cylinder is once known, however, then all further compression strokes can be calculated just on the basis of signals from the crankshaft angle position sensor (B15).
Signals from the TDC sensor for cylinder 1 (B16) are used exclusively to determine the rotational speed or the compression stroke on the 1st cylinder if the crankshaft angle position sensor (B16) fails.
The reason for this is that the crankshaft angle position sensor (B15) delivers more precise values over the crankshaft position than the TDC sensor on cylinder 1 (B15); this means that the start of injection can be determined more exactly.
Function
The camshaft is fitted with a wheel with 12 pins (3) on its circumference each at 30° angular distance to each other. They trigger an pulse in the TDC sensor for cylinder 1 (B16) positioned on the camshaft sprocket (2) which is comparable with that from the crankshaft angle position sensor (B15).
The use of an additional pin (4) at a 55° crankshaft angle before top dead center on the 1st cylinder can also determine the compression stroke on the 1st cylinder.
If the engine is now started, the engine control (MR) uses pulses from the crankshaft angle position sensor (B15) from the position of the crankshaft as well the current engine speed. It simultaneously waits until the compression stroke on the 1st cylinder has been recognized based on pulses from the TDC sensor on cylinder 1 (B16). It then synchronizes the values of both sensors, so that the signals on the crankshaft angle position sensor (B15) can be used to determine the start of injection.