Motor drive circuits are designed to transmit rotation:
- camshafts (21, 22, see fig. 4.11) intake valves of both cylinder heads from the crankshaft (main chain, 1);
- exhaust camshaft from intake camshaft (intermediate chain, 10, see fig. 4.10);
- oil pump (see fig. 4.13) from the crankshaft of the engine.
The engine uses a valve timing mechanism with intake and exhaust overhead camshafts, the cams of which act on the valves through hydraulic tappets.
The intake camshaft is driven by a roller chain from the crankshaft sprocket, and the exhaust camshaft is driven from the intake sprocket, thanks to the intermediate chain. The intake camshaft has a mechanism for changing the angle of the initial position (turn), the VANOS system, which leads to a change in the opening phase of the intake valves.
The gas distribution mechanism includes a cylinder head, camshafts, intake and exhaust valves, valve guides, valve springs with fastening parts, hydraulic pushers, camshaft drive chains with tension parts.
The chain tension is regulated by an automatic tensioner with a hydraulic damping mechanism. The camshaft and crankshaft sprockets are mounted on segment keys and fixed with bolts.
Camshaft
The design of the camshafts is shown in fig. 4.12.
The camshaft is five-bearing, rotates in plain bearings. The intake camshaft has two drive chain sprockets.
Axial movement of the camshaft:
- nominal - 0.20 - 0.36 mm;
- the maximum allowable is 0.45 mm.
Radial runout of the shaft journals for engine models during its assembly, not more than 0.040 - 0.074 mm. The limit value in operation is 0.1 mm.
Thrust bearing width - 22.1 - 22.2 mm.
The gap between the necks of the shafts and their bearings is 0.040 - 0.074 mm.
Camshaft lobe height:
- inlet - 47.7±0.05 mm;
- outlet - 47.3±0.05 mm.
Valve lift:
- intake - 9.7 mm;
- graduation - 9.4 mm.