The Economic Implications of Exaptation

Bearing 1 comprises a porous bearing body 1a having a bearing surface 1b disposed to oppose an outer circumferential surface of the rotating shaft 3 via a bearing clearance 4, a lubricating oil or lubricating grease impregnated in the bearing body 1a, and hydrodynamic pressure generating grooves 1c formed on the bearing surface 1b of the bearing body 1a. The rotating shaft 3 is supported, without making contact with the bearing 1, by a hydrodynamic pressure oil film formed in the bearing clearance and the oil is circulated, via openings made in the surface of the bearing body 1a, between the inside of the bearing body 1a and the bearing clearance 4.