US Patent 7696746 Motion detecting apparatus

A turbine wheel of a turbocharger has a turbine blade. The turbine blade has a fin shape of which width in the rotation direction of the turbocharger is narrow, and is projected from the base portion of the turbine wheel. An inclined part of the turbine blade is inclined with respect to the rotation direction of the turbocharger. A coil is disposed so that the inclined part passes nearby as the turbine wheel rotates in a posture that an end in the center axis direction is directed toward the turbocharger. A detector detects a change in inductance, which occurs when the inclined part of the coil passes nearby.