Minimizing the oil pump capacity of an engine while
maintaining reliability is one of the most effective
ways of reducing mechanical loss of an engine. Care
is required to assure reliability, because an excessively
low oil flow may result in poor lubrication that can
cause engine components to seize.
The oil flow was observed by visualization and the
pressure was measured in two types of oil passage
that link main bearings and con-rod bearings, namely,
"V type" which has an oil passage in the main journal,
and "I type" which does not have this passage. The
oil flow in the passage was observed using a CCD camera
and a crankshaft made of acrylic resin. The oil flow
rate was measured at the same time as the flow was
observed. The pressure at which the oil supply failed
due to the occurrence of aeration differed with the
oil passage types.
Then, the oil flow rate from the oil pump through
the main bearing to the con-rod bearing was predicted
by using a model that combined a mass-conserved elastohydrodynamic
lubrication calculation with an oil flow equation
to calculate the effect of the oil supply conditions
on aeration. Consequently, the validity of the model
was confirmed by attaining a good agreement with the
measured oil flow rates, as well as the limit pressure
without aeration in the two oil passage types.
エンジンの信頼性を確保しつつオイルポンプ容量を最小限にすることは，エンジンの機械損失を低減する重要な手法の一つである。しかし，潤滑油不足は焼付きなどの問題に直結するため十分な配慮が必要である。
ここでは，エンジン主軸受からコネクティングロッド大端部軸受 ( 以後，コンロッド軸受 ) 間の油流れ可視化と給油圧の測定を，貫通路のある"V形油路"と貫通路のない"I形油路"の2種類の油路形状について行った。主軸受はアクリル製とし，コンロッド軸受間の油路内流れをCCDカメラで観察した。その結果，エアレーションによってコンロッド軸受への油供給ができなくなる限界給油圧は，油路形状によって異なることがわかった。
そこで，ポンプから主軸受を通してコンロッド軸受に流れる油流量を，質量保存弾性流体潤滑モデルと油路流れの式を連立したモデルを作成し，エアレーションの影響を考慮して予測した。この予測結果からエアレーションを発生しない限界給油圧は油路形状で異なることがわかり，実験と良い相関が得られた。
