Great attention is focused on electrical powered vehicles such as an electric vehicle and hybrid vehicle as environment-friendly vehicles. These vehicles incorporate an electric motor for generating a driving force for running, and a rechargeable power storage device for storing electric power to be supplied to the electric motor. A hybrid vehicle refers to a vehicle incorporating an internal combustion engine as a power source, in addition to an electric motor, or a vehicle further incorporating a fuel cell in addition to a power storage device as the direct current power source for driving the vehicle. A hybrid vehicle incorporating an internal combustion engine and an electric motor as the power source is already put into practice.
Among the hybrid vehicles there is known a vehicle that allows charging of the vehicle-mounted power storage device from a power source external to the vehicle, likewise with an electric vehicle. The so-called “plug-in hybrid vehicle” that allows the power storage device to be charged from a general household power supply by connecting the plug socket located at an establishment with the charging inlet provided at the vehicle is known.
As a method for power transfer, attention is recently focused on wireless electrical power transmission not using power supply cords and/or cables for electrical transmission. Three promising approaches of this wireless power transfer technique are, known, i.e. power transfer using electromagnetic induction, power transfer using radio waves, and power transfer through the resonance method.
The resonance method thereof is directed to power transfer taking advantage of the resonance of the electromagnetic field, allowing electric power as high as several kW to be transferred over a relatively long distance (for example, several meters) (refer to Non-Patent Document 1).
Patent Document 1: Japanese Patent Laying-Open No. 2001-8380
Patent Document 2: Japanese Patent Laying-Open No. 8-126106
Non-Patent Document 1: Andre Kurs et al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances” [online], Jul. 6, 2007, Science, vol. 317, pp. 83-86, [retrieved on Sep. 12, 2007], Internet <URL:http://www.sciencemag.org/cgi/reprint/317/5834/83.pdf>