| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a crankcase integrated cylinder block in which a communication hole having a maximum opening area is formed in a bulkhead that partitions a cylinder bore and a crank chamber without dividing a honing release surface formed continuously with the cylinder bore. <P>SOLUTION: A honing release surface 48a continuously with a cylinder bore 21 and formed in a cylindrical surface shape having a diameter larger than that of the cylinder bore 21 is formed in an upper crankcase 6 and the upper bulkhead 23, and an arcuate recess 49 is thereby formed in the upper bulkhead 23. A communication hole 38 including an opening edge 45a extending in a direction substantially perpendicular to the cylinder axis C, an opening edge 45b having a decreasing opening width with distance from the cylinder bore 21, and an opening edge 45c extending substantially parallel to the cylinder axis C and connecting between the opening edge 45a and the opening edge 45b is formed from the cylinder bore 21 to the recess 49. Accordingly, division of the honing release surface 48a is thereby prevented. <P>COPYRIGHT: (C)2012,JPO&INPIT |
