Camshaft adjustment in "advanced" position function

W05.20-1027-79

W05.20-1052-79

General

For engine rpms at lower exhaust temperatures the camshaft positioner is driven in the position "advanced" in order to increase the exhaust temperatures. This is the prerequisite for later active purging of the diesel particulate filter.

Upon reaching the position "advanced", the rotor (8), and therefore the exhaust camshaft (5), is turned by a crank angle of up to 65°. Moving the exhaust timing in the direction "advanced" has the effect that the exhaust valves are opened earlier on the operating cycle in the downward movement of the piston. In this way exhaust which is richer in energy (warmer) is pushed in the direction exhaust system. Earlier closing of the exhaust valves in turn has the effect than the exhaust is not fully ejected out of the cylinder during the exhaust stroke. Since no valve overlap occurs, the remaining exhaust in the cylinder is compacted and flows when opening the intake valve into the charge air housing. The resonance noises arising from this in the charge air housing are dampened with the aid of the resonator.

Function

The engine management (MCM) control unit (A4) actuates the camshaft positioner solenoid (Y635) electrically so that the pressure plunger (10) pushes the control plunger (9) against the force of the compression spring (6) up to the end stop on the return flow check valve (4). There is engine oil (A) under operating pressure in the storage room (13) between the control plunger (9) and the valve housing (7). The return flow check valve (4) prevents flowing back of the engine oil (A) if the pressure drops in the feed line. The control plunger (9) frees up the bores (15) in the valve housing (7) for flow to and from the chambers B (11) so that the engine oil (A) flows out of the valve housing (7) through the bores (15) in the rotor (8) in the chambers B (11). At the same time the control plunger (9) closes the bores (16) in the valve housing (7) for flow to and from the chambers A (12) on the feed side so that no engine oil (A) can flow out of the valve housing (7) over the bores (16) in the rotor (8) into the chambers A (12). The engine oil (B) flows instead out of the chambers A (12) through the bores (16) in the rotor (8) and the freed up bores on the drain side in the valve housing (7) in the chamber upstream of the control plunger (9).

The engine oil (B) flows out of the valve housing (7) outwards through the longitudinal bore in the control plunger (9) into the return flow. There is a connection over a longitudinal groove in the drive gear (2) between one of the chambers B (11) and the fitted bore in the drive gear (2) for mounting the catch bolt (17). The engine oil (B) in the longitudinal groove (18) is has an adequate pressure applied to it so that the catch bolt (17) pushed against the force of the compression spring out of the fitted bore of the drive gear (2). The drive gear (2) is therefore no longer positively connected with the rotor (8) and the rotor (8) can be turned.

The chambers B (11) adopt their maximum fill volume as soon as the rotor (8) touches the adjuster housing (1) (arrow Y). The exhaust camshaft (5) firmly connected with the rotor (8) is now turned on the maximum direction "advanced".

The pulse wheel (3) turns with the exhaust camshaft (5). The engine management (MCM) control unit (A4) detects its changed position with the aid of the camshaft position sensor (B601).