Portable power working machine

A portable power working machine, comprising:

• a pipe-shaped operating arm;
• a drive shaft extending through the operating arm;
• an actuating part provided at a distal end of the operating arm and driven by rotation of an electric motor through the drive shaft, the electric motor being disposed at a proximal end of the drive shaft;
• shoulder carrying means disposed near a proximal end of the operating arm;
• a motor housing connected to the proximal end of the operating arm at a front end thereof and including a tubular peripheral portion extending in a direction in which the operating arm extends, and a rear side portion closing a rear end of the tubular peripheral portion, a peripheral portion having an inlet for cooling air at a front side thereof and an outlet at a rear side thereof;
• and
• a drive unit including the electric motor, a cooling fan, and a heat sink, the electric motor being disposed near the front end of the motor housing and including a cylindrical stator, an electric motor cover attached to the stator and an output shaft projecting forward and rearward from the electric motor cover, the cooling fan being provided at a rear end of the output shaft, the heat sink being disposed between the electric motor cover and the cooling fan so as to extend from the electric motor cover and facing an inner surface of the peripheral portion with a gap therebetween,
• wherein the drive unit is disposed in the motor housing with a gap provided between the drive unit and the peripheral portion such that the stator corresponds to the inlet, the cooling fan corresponds to the outlet, and the heat sink faces the inner surface of the peripheral portion,
• wherein a front end of the output shaft is connected to the drive shaft for transferring power to the drive shaft, and
• wherein a cooling-air passage is provided between the motor housing and the drive unit for guiding the cooling air from the inlet to the outlet through the cooling fan.