Valve

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PowerPoint Presentation:

Don Bosco Center For Learning Presentation Created by : Mr. Namo

Today’s Topic:

Today’s Topic 5.1 Valves 5.2 Valve Operating Mechanism 5.3 Valve Seat 5.4 Valve Spring 5.5 Valve Guide

Objective:

Objective Knowledge of function, type, construction and working of valves Knowledge of valve operating mechanism.

5.1 Components of an Engine (Valves):

5.1 Components of an Engine (Valves) Valves

PowerPoint Presentation:

Valves Functions of valves To open and close the inlet and exhaust passages of the cylinder. To dissipate heat through its seat to the cylinder head. Components of an Engine (Valves)

Components of an Engine (Valves) :

Components of an Engine (Valves) Construction :- The head of the valve is ground with a margin to provide strength. The valve face is ground to 30 0 or 45 0 angle which matches with the seat angle to avoid leakage. Head Face 45 o Stem

Components of an Engine (Valves):

Components of an Engine (Valves) Construction :- The valve stem is of a round shape. The length of the stem varies from engine to engine. At the end of the stem, a groove is provided to hold the spring lock. Groove for spring lock

PowerPoint Presentation:

Types :- Poppet-valves These valves pop on their seat. Three types of poppet-valves are in use. Standard valve. Tulip valve. Flat top valve. Components of an Engine (Valves)

5.2 Valve Operating Mechanisms:

5.2 Valve Operating Mechanisms Two types of valve operating mechanism are used in engines. They are as follows :- Side valve mechanism Overhead valve mechanism.

Valve Operating Mechanisms :

Valve Operating Mechanisms Side valve mechanism:- In the side valve mechanism both the inlet and exhausts valves are fitted in the cylinder block.

Valve Operating Mechanisms:

Valve Operating Mechanisms Side valve mechanism:- WORKING :- The camshaft rotates the cam lobe. When the cam lobe reaches the maximum height, the valve opens fully. Further rotation of the cam causes the tappet to move down and the valve is closed by the tension of the valve spring.

Valve Operating Mechanisms:

Valve Operating Mechanisms Side valve mechanism:- Working (Contd.) :- The spring presses the valve against its seat, which helps in preventing leakage of the gases through the valve. Tappet clearance is provided between the valve tip and the tappet. This clearance can be adjusted by an adjusting screw and lock-nut on the tappet.

PowerPoint Presentation:

Overhead Valve Mechanism The valves are located in the cylinder head. Push rods and rocker arms are used in addition to the side valve mechanism. Valve Operating Mechanisms

Valve Operating Mechanisms:

Valve Operating Mechanisms Overhead valve mechanism:- WORKING :- When the camshaft rotates, the cam lobe lifts the tappet upward. When the tappet moves up, it pushes the push rod and one end of the rocker arm upwards. The other end of the rocker arm’s tip, moves downward and the valve opens against the spring’s tension.

Valve Operating Mechanisms:

Valve Operating Mechanisms Overhead valve mechanism:- Working (contd.) When the cam lobe reaches the maximum height, the valve opens fully. Further rotation of the camshaft causes the tappet to move down and the valve is closed by the tension of the spring. Tappet clearance is provided in between the valve tip and rocker arm’s tip. The clearance can be adjusted by the adjusting screw and the lock-nut.

5.3 Valve Seats:

5.3 Valve Seats Definition :- The face of the valve and the cylinder head meet at some contact. This area of contact is known as the valve seat. The valve face forms a prefect seal with the valve seat when the valve is closed.

5.4 Valves Springs:

5.4 Valves Springs Function:- The function of valve springs is to close the valve with adequate force to seal the gases of combustion. A weak valve spring causes rough engine idling and harder valve hammering on the valve seat. A valve spring with much tension causes wear to the cam lobes. Installation of valve springs is done with the help of a valve spring compressor.

5.5 Valve Guides:

5.5 Valve Guides Function:- Valve guides allow the valves to move up and down and position the valve face correctly over the valve. The valve stem applies a side thrust which wears the guide in an oval shape. The wear in the exhaust valve guide is more because it runs at high temperature. Valve guide is lubricated by oil which goes to the upper gallery, rocker shaft, rockers and springs.

Tomorrow’s Topic:

Tomorrow’s Topic Valves timing. Manifolds. Combustion chamber.

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