Bearing device and exhaust turbine turbocharger

A bearing device comprising:

• a rotating shaft;
• a journal bearing which is provided on the rotating shaft and rotatably supports the rotating shaft;
• a bearing accommodation portion in which the journal bearing is accommodated;
• and
• an oil discharge passage which is provided along a periphery of the rotating shaft on an outer peripheral portion of a boss portion of a turbine disk fixed to the rotating shaft and has an opened lower portion,
• wherein the journal bearing is rotatably supported by the bearing accommodation portion using a lubricating oil supplied to a portion between an outer peripheral surface of the journal bearing and an inner surface of the bearing accommodation portion and rotatably supports the rotating shaft by the lubricating oil supplied to a portion between an inner peripheral surface of the journal bearing and an outer peripheral surface of the rotating shaft, and a side surface portion of the journal bearing faces a facing portion of the boss portion with a gap in the bearing accommodation portion,
• wherein the lubricating oil reaches the oil discharge passage to communicate with the bearing accommodation portion between the side surface portion of the journal bearing and the facing portion of the boss on the outer peripheral portion of the boss, and in a region above a horizontal plane passing through a center of the rotating shaft, the oil discharge passage has the minimum cross-sectional area in a radial cross section on an anterior side in a rotation direction of the rotating shaft based on a vertical plane passing through the center of the rotating shaft and has the maximum cross-sectional area in the radial cross section on a posterior side in the rotation direction of the rotating shaft based on the vertical plane passing through the center of the rotating shaft,
• wherein the oil discharge passage is formed to be continuously enlarging from the minimum cross-sectional area to the maximum cross-sectional area with the vertical plane passing through the center of the rotating shaft as a boundary.