To provide a bearing structure for a crank shaft with high durability which can keep strength of a crank bearing cap to be attached to a lower surface of a cylinder block.
In this bearing structure, companion surfaces 4b of crank bearing caps 4 each formed with a central arcuate recession to compose a bearing part 4a are tapered by angle θ to form an inverted chevron shape. The crank bearing cap 4 is fastened to a cylinder block 2 by means of a bolt 5. The crank bearing caps 4 are brought into close contact with each other with deformation. Compression stress is generated on a lower portion of the bearing portion 4a, that is, a bridge portion 6. A tensile stress at the time of fastening and a tensile stress generated on the bridge portion 6 under engine operation are cancelled by the compression stress. The tensile stress is reduced compared to the conventional cap 4. It is thus possible to reduce metal fatigue of the cap 4.
KAHARA AKIRA
KAWAMURA YASUHIRO
TAKEUCHI SHOJI
UEDA YOSHIAKI
