| 摘要 |
A cutout portion (p1) is formed in a part of a ferrite (72) provided in a disc-type coil (71). Formation of the cutout portion (p1) causes a change in the density of magnetic flux produced by a main coil (74), resulting in the formation of a general portion with a predetermined magnetic flux density and a magnetic flux changed portion with a magnetic flux density different from that of the general portion. If a frame-shaped foreign body is present on the upper surface side of the disc-type coil (71), the ratio between the magnetic flux density detected in the general portion and the magnetic flux density detected in the magnetic flux changed portion will change compared with a situation in which the foreign body is not placed thereon. Accordingly, the presence of a frame-shaped foreign body can be detected on the basis of the change. |
