3.4.3. Valvate mechanism
The valvate mechanism consists of the following elements:
— guides of valves;
— saddles of valves;
— valvate springs;
— plates and crackers of fixing of assembly of the valve with a spring;
— two camshafts.
Valves (fig. 3.7)
are manufactured of the heat resisting alloyed steel. Working facets of final valves are covered stellity. Key parameters of valves are specified in tab. 3.3.
Saddles of valves
Saddles (fig. 3.8)
of valves are pressed in block head combustion chambers. Key parameters of saddles of valves are specified in tab. 3.4.
Machining of the surfaces covered stellity is not allowed.
plugs of valves
The directing plugs of valves are pressed in the lower section of a head of the block and have the parameters specified in tab. 3.5.
The maximum gap in operation between guides and inlet (final) valves — 0,15 mm.
Fig. 3.9. Valvate springs
Outer diameter of valvate springs (fig. 3.9)
— 27,7 — 28,1 mm, internal diameter — 20,08 — 20,12 mm.
The condition of valvate springs is checked by external survey and measurement of height at a free state and under loading. Sizes of loading and values of heights corresponding to them have to correspond to these tab. 3.6.
pushers of valves
Fig. 3.10. Hydraulic pusher of the valve: 1 — a spring; 2 — the pusher cylinder; 3 — a groove;
4 — a plunger; 5 — the backpressure valve
Pushers (fig. 3.10)
hydraulic, self-regulating, are filled with oil. The spring located in the pusher cylinder supports him in contact with the camshaft; the effort of this spring is lower than effort of a spring of the valve that provides linear movement of the last.
The backpressure valve prevents expression of oil at impact of a cam of the camshaft on a pusher and at excess of pressure of oil in the pusher cylinder over oil pressure in the engine lubrication system.
The hydraulic pusher has three operating modes.
Fig. 3.11. Mode of 1 work of a hydraulic pusher
The mode 1 (fig. 3.11)
— when a pusher is in contact with a basic circle of a cam of the camshaft, oil from the channel of the case of the bearing of the camshaft comes to a pusher through a flute and an opening in a side surface. Oil passes through the groove located in the top part of a pusher and comes to the pusher cylinder. When the pusher is not influenced by a cam contour, oil pressure in the engine is higher than oil pressure in the cylinder of a pusher and oil passes through the backpressure valve of the cylinder of a pusher.
Fig. 3.12. Mode 2 works of a hydraulic pusher
The mode 2 (fig. 3.12)
— when a pusher is wrung out down, oil pressure in its cylinder becomes higher than pressure of oil in the engine, the backpressure valve is closed and the pusher works as a solid body.
Fig. 3.13. Mode 3 works of a hydraulic pusher
The mode 3 (fig. 3.13)
— at return of a pusher to contact with a basic circle of a cam of the camshaft oil pressure in the engine is higher than oil pressure in the pusher cylinder. The backpressure valve opens, passing oil that provides pressing of a pusher to the camshaft.
Fig. 3.14. Key parameters of a hydraulic pusher of the valve