No Oil Pressure Crankshaft

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This idea is developed to reduce internal combustion engines' mechanical friction loss by distinctive crankshaft oil hole layout. In order to ensure adequate oil transport, from main bearing shell oil groove to connecting rod bearing via oil holes made inside crankshaft, some certain oil pressure is required to cope with centrifugal force acting on oil inside crankshaft. By elaborate oil hole layout, we can achieve very low supply oil pressure requirement.

We experimented this in firing internal combustion engine revving up to 8500rpm, with very low oil feed gallery pressure. This contains four oil bores made on one main journal, which are distributed 90° degrees apart circumferentially on one main journal. At the same time, each bore is inclined from the normal line against the journal surface to be far from crankshaft axis, to utilize dynamic pressure from crankshaft rotation. Due to four oil inlets in the main journal, the oil groove made on the main bearing shell can be quite short (90° plus). Oil will be fed to the connecting-rod bearing from these oil holes junctions inside the main journal in “#” shape.

By ensuring oil transport toward connecting rod bearings under high crankshaft speed with very low oil pressure requirement, we are able to reduce engine mechanical friction substantially, by means of crankcase churning loss reduction, bearing hydrodynamic friction reduction, and oil pump driving friction as pomp capacity can be reduced.


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  • Name:
    Hiroshi Yajima
  • Type of entry: