Mitsubishi Heavy Industries Limited

Yosuke Maruta

Hiroyoshi Kochi

Manabu Sekimukai

A forced-air-cooled engine has a main blow-out opening provided to a back plate of a cooling fan cover at a position facing a cylinder part for blowing out cooling air for cooling a cylinder part and a secondary blow-out opening provided to the back plate at a position opposite to the main blow-out opening in regard to the crankshaft center for cooling a part of a crankcase part, wherein a cooling air guide cover is equipped which is composed of a cylinder air-guide cover part which guides air blown out from the main blow-out opening to flow to cool the cylinder part and cylinder head, and a top cover part which guides air blown out from the secondary blow-out opening to flow along a side face of the crankcase part to cool there and then flow into midstream of the cooling air flow blown out from the main blow-out opening and cooling the cylinder part and cylinder head.

Forced-air-cooled engine equipped with cooling air guide cover

A structure of crankcase-integrated cylinder block for a small internal combustion engine is posed to increase strength and rigidity in order to reduce particularly vibration and noise. A cylinder part and a crankcase part are formed into a box-like shape being cast in one piece, a crankcase cover is fixed to the crankcase part to cover an opening on a side in anteroposterior thereof, a crankshaft bearing boss has a crankshaft bearing hole being provided at a central part of a back wall of the crankcase part to protrude to both inner and outer sides of the back wall for supporting an end sides of a crankshaft, wherein an inner peripheral rib is formed along the corner where the back wall of said crankcase part connects to a peripheral wall extending from the periphery of the back wall to heave inward form the corner part.

Cylinder block integrated with crankcase

The invention provides a method and construction of vibration control supporting a cooling fan cover. In a forcer-air-cooled engine having a cooling fan cover fixed directly by means of fixing bolts to the cylinder block at fixing foot parts provided at a peripheral border of the fan cover, band-like vibration damping members are disposed between the peripheral border of the fan cover and the cylinder block in each region of the peripheral border belonging to each sector part defined between two adjacent fixing points of two adjacent fixing foot parts among said plurality of fixing foot parts respectively so that each of said damping members is pressed against the cylinder block by each region of the peripheral border when the bolts are tightened, said band-like damper members are flexible damping members each of which is disposed in an essential part of loop of vibration of the periphery for preventing generation of noise due to vibration of the fan cover with the fixing points as nodes of vibration resonating to cylinder block vibration, and said band-like flexible vibration damping members are adjusted thereby to adjust elastic force and damping capacity of the damping members so that resonance of the fan cover occurs at a rotation speed of engine higher than normal rotation speed thereof.

Growing community of inventors

Sagamihara, Japan

Yosuke Maruta