BRACKET AS 6S6741 - Caterpillar

Valves And Valve Mechanism
Illustration 18 g01741288
Valve system components
(70) Rocker arm
(71) Pushrod
(72) Valve bridge
(73) Valve spring
(74) Valve
(75) Lifter The valve system components control the flow of inlet air into the cylinders and out of the cylinders during engine operation. The valve mechanism also operates the fuel injector.The camshaft must be timed to the crankshaft in order to get the correct relation between the piston movement and the valve movement.The camshaft has three camshaft lobes for each cylinder. Two lobes operate the inlet and exhaust valves and one lobe operates the electronic unit injector mechanism. As the camshaft turns, lobes on the camshaft cause lifters (6) to move pushrods (71) up and down. Upward movement of the pushrods against rocker arms (70) results in downward movement (opening) of valves (74).Each cylinder has two inlet valves and two exhaust valves. The valves are actuated at the same time by a valve bridge (72). Valve springs (73) close the valves when the lifters move down.
Illustration 19 g01741306
Front gear train
(76) Camshaft gear
(77) Timing mark
(78) Crankshaft gear
(79) Idler gear The 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 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. The camshaft gear (76) is driven by an idler gear. The idler gear (79) is driven by the crankshaft gear (78). The timing marks (77) must be aligned in order to provide the correct relationship between the piston and the valve movement.Variable Valve Actuator
The Intake Valve Actuation system (IVA) uses pressurized engine oil to delay the closing of the intake valves. The system is controlled by the Engine Control Module (ECM). The system contains the following components:Check Valve (82) - Pressurized engine oil flows to a rail inside the valve cover base. A check valve prevents oil from flowing from the rail back to the main oil gallery.Pressure Sensor (81) - A pressure sensor is threaded into the rail. The sensor converts the rail pressure into an electrical signal. The ECM monitors the signal in order to determine the pressure of the oil in the rail.Control Valve (80) - A control valve is threaded into the rail. The control valve contains a coil and a cartridge assembly. The cartridge assembly contains a spool. The spool is normally closed. When the spool is closed, the oil is contained in the rail. The ECM sends a signal to the coil in order to fully open the spool. The oil is released into the space underneath the valve cover and the rail pressure is reduced.Actuator (83) - The actuators are located under the valve covers. Pressurized engine oil flows from the rail to each actuator. The actuators use the pressurized engine oil and electrical