Bearing structure and air blower

An air blower comprising:

• a rotor;
• a stator;
• a case that accommodates the rotor and the stator;
• and
• a bearing structure that is provided between the rotor and the stator, the bearing structure comprising:
• a shaft;
• an oil-impregnated bearing that supports the shaft to be rotatable and includes a first sintered metal material having a first density;
• a bearing holder that supports an outer circumferential surface of the oil-impregnated bearing;
• and
• a seal member that is provided at an opening of the bearing holder,
• wherein the shaft is provided with an annular groove having a side surface portion that has an outer diameter that decreases as the side surface portion separates away from one end surface of the oil-impregnated bearing,
• wherein the seal member includes a second sintered metal material having a second density that is lower than the first density of the first sintered metal material, and
• wherein the seal member includes a contact surface that contacts with the one end surface of the oil-impregnated bearing, a large-diameter inner circumferential surface arranged to face the annular groove of the shaft, and a small-diameter inner circumferential surface that provides a seal clearance along the outer circumferential surface of the shaft.