PURPOSE: To provide a working device capable reducing the variation of the combustion characteristic including the misfire attributable to insufficient mixture of air with the fuel, the errors in measurement of the fuel, etc.
CONSTITUTION: A portable working device of a combustion force operation type, for example, a tool for driving a fastening element, is provided with a combustion chamber 9 to burn the air-fuel mixture, and pistons 7, 7a which are guided by a guide cylinder 8 and driven by the operational pressure generated by the combustion of the air-fuel mixture. The combustion chamber volume of the combustion chamber 9 is variable by the displacement of at least one combustion chamber wall 11. A metering chamber 67 is provided to prepare the air-fuel mixture, and the gaseous fuel of the prescribed quantity is prepared in the metering chamber. The air and the gaseous fuel is sucked in the combustion chamber 9 with the negative pressure generated in the combustion chamber 9 when the combustion chamber volume is increased.
MARUKUSU SHIYUPURENGAA