Bearing structure and turbocharger

A bearing structure, comprising:

• a housing;
• a bearing hole formed in the housing and provided with a bearing for pivotally supporting a shaft;
• a clearance groove formed on an inner circumferential surface of the bearing hole, having an opposing wall portion radially opposed to the shaft;
• an oil drainage passage provided below a shaft center of the shaft;
• a communicating opening formed in the housing, communicating the clearance groove with the oil drainage passage;
• a scattering space formed in the housing, positioned between an impeller provided at one end of the shaft and the clearance groove, and communicating with the oil drainage passage;
• an annular protrusion formed in the housing, positioned between the clearance groove and the scattering space, and annularly surrounding the large diameter portion of the shaft;
• and
• a wide portion in the opposing wall portion of the clearance groove with a theoretical boundary right above the shaft center of the shaft, provided in a front side in a rotation direction of the shaft, having a wider gap from the shaft than that in a rear side in the rotation direction of the shaft, wherein a curvature radius of the wider gap increases in the rotational direction toward the communicating opening.