PUMP GP-PISTON 2308001 - Caterpillar

The valve train controls the flow of inlet air into the cylinders and the flow of exhaust gases out of the cylinders during engine operation. Specifically machined lobes on camshaft (74) are used in order to control the following aspects of valve function:
Height of valve lift
Timing of valve lift
Duration of valve liftThe crankshaft gear drives the camshaft gear through the front gear train. The camshaft must be timed to the crankshaft in order to get the correct relation between the piston position and the valve position.The camshaft has three camshaft lobes for each cylinder. Each cylinder has two inlet valves and two exhaust valves. One camshaft lobe operates both of the inlet valves for each cylinder. One camshaft lobe operates both of the exhaust valves for each cylinder. There is also one camshaft lobe that operates the unit injector for each cylinder. Camshaft follower (73) rolls against the surface of the camshaft lobe. The follower is used in order to transfer the lift that is machined into the camshaft lobe to rocker arm (65) .The camshaft lobe lifts the camshaft follower of the rocker arm. This actuates valve (78). As the camshaft lobe lifts the follower, the rocker arm pivots at rocker shaft (72). This applies the lifting action to valve bridge (75). The valve bridge is used to transfer the lift from the rocker arm to the valves. Valve adjustment screw (71) is used in order to adjust the valve lash.Valve springs (77) are used to hold the valves in the closed position when lift is not being transfered from the camshaft lobe. The springs provide the force on the valve in order to ensure that the valves will close at high rpm. The springs also ensure that the valves will remain closed under conditions of high boost pressures.Valve rotators (76) cause the valves to rotate while the engine is running. The rotation of the valves in the valve seat prevents valve damage by constantly changing the contact area of the valve face and valve seat (79). This rotation gives the valves longer service life.
Illustration 21 g01521777
Front gear train (80) Timing mark (81) Camshaft gear (82) Adjustable idler gear (83) Idler gear (84) Timing mark (85) Cluster gear (86) Crankshaft gearThe inlet valves and the exhaust valves are opened by the valve mechanism. The inlet valves and the exhaust valves are also closed by the valve mechanism. This occurs as the rotation of the crankshaft causes a relative rotation of the camshaft. Camshaft gear (81) is driven by a series of two idler gears. Adjustable idler gear (82) is driven by idler gear (83). This idler gear is driven by cluster gear (85). The cluster gear is driven by crankshaft gear (86). Timing mark (84) and timing mark (80) are aligned in order to provide the correct relationship between the piston and the valve movement.The adjustable idler gear is designed to be adjusted so that backlash can be adjusted for the front gear train. The backlash adjustment is