Bearing device

A bearing device comprising:

• a bearing including an outer ring, an inner ring, and a rolling element;
• and
• a retaining member, wherein
• the retaining member is fixed to any one ring of the outer ring and the inner ring,
• the retaining member includes a side plate portion having a width in a radial direction and extending in a circumferential direction,
• at least part of a power supply that generates electric power and a circuit board are fixed to the retaining member,
• the circuit board is fixed to, in an axial direction, a surface of the side plate portion not facing the rolling element,
• at least one gas sensor and a wireless communication circuit are mounted on the circuit board, the at least one gas sensor detecting a state of the bearing, the wireless communication circuit wirelessly transmitting an output of the at least one gas sensor to outside,
• the power supply is an electromagnetic generator including a magnetic ring fixed to the other ring different from the any one ring of the outer ring and the inner ring, and a coil attached to the retaining member so as to face the magnetic ring in a radial direction of the bearing,
• the retaining member is part of a stator,
• the stator includes a first stator and a second stator that are facing each other,
• a bobbin and the coil are attached between and surrounded by the first stator and the second stator,
• the first stator, the second stator, the bobbin and the coil are arranged so as not to extend axially outward beyond an end face of the outer ring and an end face of the inner ring, and
• the circuit board is retained by the first stator.