4.2.7 Cam shaft, valve mechanism
Axial diameter of cam shaft is made larger sufficiently to bear load increase for high pressure injection. Fuel cam, suction and exhaust cam are prepared optimum profile and valve timing by means of performance simulation, in particular the profile of fuel cam is adopted to be effective injection characteristics for low fuel consumption and reduced NOx. In regard to the fuel cam.
Both suction and exhaust valves are made of heat resisting steel with satellite padding on the valve seat portion. For exhaust valve, corrosion resisting nimonic material is used in case of specification for heavy fuel oil and equipped with cooling type valve seat in standard specifications.
4.2.8 Fuel injection pump, fuel injection valve
High pressure injection pump of 150MPa is introduced to make high pressure short-injection
possible.
To reduce deformation against high pressure, plunger barrel is closed type and fixed to the pump body.
A two-way delivery valve is included in the discharge valve to prevent cavitation in the injection system.
In the case of specification for heavy fuel oil, a lubricating system to the pinion sleeve is adopted. In this system lubricating oil diverged from the system oil route is discharged to the drain tank after lubricating the fuel variable rack, plunger guide and spring bearing on the method of drip-feed lubrication to the pinion sleeve.
Fuel injection valve is the low inertia type and can bear gas leakage by means of high injection valve opening pressure. Cooling of the fuel injection valve is made by indirect cooling system where cooling water in the cylinder head jacket cools the sleeve with flame protector outside the nozzle holder.
Comparing with the conventional cooling system, it has a simple structure which does not require exclusive cooling piping for the fuel injection valve.
