A coil unit includes a first coil having an outer diameter of D1, and at least one second coil having an outer diameter of D2 (D2<D1). The at least one second coil is arranged on a transmission surface side of the first coil. A part or whole of the at least one second coil overlaps the first coil, when...http://www.google.de/patents/US20100244579?utm_source=gb-gplus-sharePatent US20100244579 - COIL UNIT, AND POWER TRANSMISSION DEVICE AND POWER RECEPTION DEVICE USING THE COIL UNIT
