PROBLEM TO BE SOLVED: To realize at least one of compact-size, light weight and low cost features of a handheld engine work machine of which power source is a 4-cycle engine.SOLUTION: This invention relates to a trimming machine having an engine as a power source in which an intake valve and an exhaust valve are opened or closed in cooperation with a rotation of a crank shaft and this trimming machine has a speed reduction mechanism for reducing a rotational speed of the crank shaft by 1/2. The speed reduction mechanism comprises a small diameter gear arranged at the crank shaft and a large diameter gear arranged at a cam shaft and engaged with the small diameter gear. The intake valve, exhaust valve and blade are driven by a driving force outputted from the speed reduction mechanism that is commonly applied to these elements.COPYRIGHT: (C)2015,JPO&INPIT【課題】4サイクルエンジンを動力源とする手持ち式エンジン作業機の小型化、軽量化、低コスト化の少なくとも1つを実現する。【解決手段】クランク軸の回転に連動して吸気弁および排気弁が開閉されるエンジンを動力源とする刈込機であって、クランク軸の回転速度を1/2に減速させる減速機構を有する。前記減速機構は、クランク軸に設けられた小径ギヤと、カム軸に設けられ、小径ギヤと噛み合う大径ギヤとを含み、吸気弁,排気弁およびブレードがこれらに共通である前記減速機構から出力される駆動力によって駆動される。【選択図】図5
