Motor unit

A motor unit comprising:

• a motor configured to rotate a shaft about an axial line;
• and
• a rotation detector configured to detect rotation of the shaft, wherein
• the rotation detector comprises:
• a first support and a second support that are provided in a manner separated from each other in a direction of the axial line, one of which is rotated along with rotation of the shaft using the axial line as a rotational axis;
• a pair of magnetic field forming units that is provided on the first support in a manner facing the second support at different positions along a circumference about the axial line and having different polarities;
• at least one magnetic field detector that is formed by winding a coil around a magnetic element whose magnetized direction changes in a longitudinal direction and provided on the second support such that a longitudinal-direction side of the magnetic element faces the first support;
• and
• a first magnetic member and a second magnetic member that are each made of a magnetic material, that cover longitudinal-direction both ends of the magnetic field detector facing the first support, respectively, and that face each other with a gap interposed therebetween at a longitudinal-direction mid-portion of the magnetic field detector, and
• a dimension of each of the magnetic field forming units in a tangential direction of the circumference is larger than a dimension of the corresponding magnetic field forming unit in a radial direction and is larger than the distance of the gap.