4.2.5 Piston
Ductile cast iron unit of thin-walled light weight which can bear high combustion pressure and thermal stress is introduced to the piston. For strength analysis a three-dimensional model can be automatically made out through newly developed system by only inputting main dimension of piston, while giving sufficient strength to temperature and stress design-wise.
Ductile cast iron piston bears up against sleeving and is rich in wear and abrasion resistance with less thermal expansion rate, for this reason it can make clearance to the cylinder liner smaller and prevent blow-bye, thus lubrication consumption.
The upper and lower part of No.1 & No.2 piston-ring groove is laser hardened to improve wear and abrasion resistance. Also, the piston ring is composed of 2 pcs of compression ring and 1 pce of oil ring for model 6N18(A)L and 3 pcs of compression ring and 1 pce of oil ring for model 6/8N21(A)L, and, all for above, gas tight ring is used for No.1 ring and chrome plated is given to each ring rubbing portion to keep reliability and durability.
4.2.6 Cylinder head
The cylinder head is so designed as to make total height dimension larger against increasing combustion pressure and thermal load as output increases. The upper part and side face are walled thick and lower part thin and at the same time it is structurized to improve gas sealing and reduce thermal load by arranging effective oblique rid.
The suction and exhaust valve arrangement is by tandem arrangement, suction and exhaust ports are put together on the non-operating side to make maintenance and check of the devices such as fuel injection pump, etc on the operating side easier.
Suction connecting duct to connect air inlet duct of the cylinder block is unified with the cylinder head. Packing between cylinder block and cylinder head air inlet is adopted V-type packing because of boltless structure.
For 4 pcs of cylinder head bolt, hydraulic tightening method is introduced to keep stabilization of the axial force and to improve reliability against gas leakage because face pressure of the cylinder head portion gets equal.
