To shorten an ignition cycle more than usual, and promote cooling of a combustion chamber by arranging a fan in the combustion chamber to facilitate scavenging of combustion gas after combustion, and arranging an auxiliary fan outside the combustion chamber to cool an outside surface of the combustion chamber.

A fan 46 is rotatably arranged in a combustion chamber 36, and mixing of fuel and air is promoted, and cooling and scavenging are promoted, and combustion is promoted. Cooling air flows in the combustion chamber 36 and also flows on the outside of a cylinder 60 as an arrow 90 by rotating an auxiliary fan 92 when a tool 10 is put in an opening position as shown by a drawing. In this way, the auxiliary fan 92 promotes scavenging of combustion gas from the combustion chamber 36. The combustion chamber 36 is cooled from the outside when in a closing position and is also cooled from the inside when in an opening condition by air flowing in the tool 10 by the auxiliary fan 92. The outside of a lower part of the cylinder 60 is also cooled.