![]() To increase the flexibility in timing the valve opening, valve closing, and injection of fuel, and to increase power or to reduce cost, an engine may have one or more camshafts. The gears allow the rotation of the camshaft to correspond or be in time with, the rotation of the crank shaft and thereby allows the valve opening, valve closing, and injection of fuel to be timed to occur at precise intervals in the piston's travel. The camshaft is driven by the engine's crank shaft through a series of gears called idler gears and timing gears. ![]() Valve lash is the term given to the "slop" or "give" in the valve train before the cam actually starts to open the valve. This is accomplished by the use of valve lash. Therefore, the valves, valve pushrods, and rocker arms must have some method of allowing for the expansion. Because an engine experiences fairly large changes in temperature (e.g., ambient to a normal running temperature of about 190F), its components must be designed to allow for thermal expansion. The energy stored in the valve spring is then used to close the valve as the camshaft lobe rotates out from under the follower. The valves are maintained closed by springs.Īs the valve is opened by the camshaft, it compresses the valve spring. The pushrods and rocker arms transfer the reciprocating motion generated by the cam shaft lobes to the valves and injectors, opening and closing them as needed. The followers are connected to the engine's valves and fuel injectors through various types of linkages called pushrods and rocker arms. As the camshaft is rotated, the follower is forced up and down as it follows the profile of the cam lobe. Each lobe has a follower as shown on Figure 10. Major Components of a Diesel Engine illustrate the location of a camshaft in a large overhead cam diesel engine.Ī camshaft is a long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector. ![]() Figure 9 illustrates a camshaft and camshaft drive gear. To accomplish this, a component called a camshaft is used. ![]() In order for a diesel engine to operate, all of its components must perform their functions at very precise intervals in relation to the motion of the piston. Diesel Engine Camshaft, Timing Gears and Valve Mechanism ![]()
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