Crankcase structure of internal combustion engine

摘要

A bearing holding portion supporting a crankshaft in a manner to rotate freely via a bearing and fittingly holding the bearing is formed in a crankcase. A second cross section passing through a crankshaft axis line and along an orthogonal direction to a cylinder axis line is set to have a larger cross-sectional area than a first cross section passing through the crankshaft axis line and along a direction of the cylinder axis line in the bearing holding portion.

主权项

1. A crankcase structure of an internal combustion engine, the crankcase structure comprising:
a bearing holding portion formed in a crankcase, the bearing holding portion supporting a crankshaft in a manner to rotate freely via a bearing and fittingly holding the bearing, wherein the bearing holding portion is formed integrally with the crankcase and continuously formed in a crushed round shape along a whole outer periphery of the bearing so as to surround the bearing, wherein a second cross section passing through a crankshaft axis line and along an orthogonal direction to a cylinder axis line is set to have a larger cross-sectional area than a cross-sectional area of a first cross section passing through the crankshaft axis line and along a direction of the cylinder axis line in said bearing holding portion, wherein a length along the orthogonal direction to the cylinder axis line of the second cross section is set larger than a length along the direction of the cylinder axis line of the first cross section, and wherein cross sections located on one side and another other side across the crankshaft axis line in the second cross section are each set larger in cross-sectional area than either larger one of cross sections located on one side and another side across the crankshaft axis line in the first cross section.