Ignition device

An ignition device for igniting a mixture of air and fuel gas by plasma to generate an initial flame, comprising:

• a spark plug having an inner conductor, a cylindrical outer conductor that holds the inner conductor inside, and a dielectric provided between the inner conductor and the outer conductor, and the spark plug configured to emit an electromagnetic wave to a plasma formation space between the inner conductor and the outer conductor to generate a plasma;
• an electromagnetic wave power supply that generates the electromagnetic wave and delivers an electromagnetic wave power to the spark plug;
• and
• a power supply control unit that controls the electromagnetic wave power supply, wherein
• the electromagnetic wave power supply is configured to generate high frequency power at a number of different frequencies, and
• the power supply control unit is configured to output at least one of the plurality of high frequency powers generated by the electromagnetic wave power supply as the electromagnetic wave power;
• wherein
• the power supply control unit adjusts the combined ratio of the plurality of high frequency powers in time series in one discharge cycle, and inputs it to the spark plug as the electromagnetic wave power;
• and
• a first state that is a state in which plasma is not formed in the plasma formation space, a second state that is a state in which plasma is formed in the plasma formation space, and a third state is a state in which an initial flame is formed in the plasma formation space by plasma are states of the plasma formation space that sequentially change in time series in a short time during each discharge cycle.