Hydraulically operated valve gearing system modified from conventional mechanically driven type was tested in the test bench. This system aims at reducing mechanical noise of the main engine. Since noise from mechanical valve gearing is produced mainly by knocking of metal parts such as the push rods, the rocker arm the valve stem. In order to reduce mechanical noise, the valve driving mechanism in which the valves are driven hydraulically is developed eliminating the parts touching metal to metal.
The assembly drawing of the hydraulically operated valve gearing system is shown in Fig.8.
Fig.8 HYDRAULIC VALVE GEARING
The servo pistons locating on the cambox are pushed up by the intake and the exhaust cams through the roller guides. Thus, hydraulic oil pressure inside the valve operating oil pipe is raised pushing down the valve piston to open the intake or the exhaust valve against the valve spring force.
The intake valve and the exhaust valve are closed by the valve spring as soon as the oil pressure inside the pipe is released.
The hydraulic oil is common with the engine system oil. The notched butt end ring is used for the servo piston. In order to compensate the valve timing delay due to oil leakage through this butt end of the ring, the mechanism supplying oil to the system all the time through the throttle valve is employed.
Fig.9 shows the lift of the intake and the exhaust valve.
