Engine starting device

An engine starting device comprising:

• a motor unit;
• a pinion gear unit which rotates according to the rotation of an output rotation shaft driven by the motor unit;
• and
• a pushing mechanism which moves the pinion gear unit towards an engagement location of a pinion gear and an engine starting gear,
• wherein an engine is started by a rotation force of the motor unit through the pinion gear and the engine starting gear which are engaged with each other,
• the pinion gear unit includes a rotation member which rotates according to the rotation of the output rotation shaft, a first pinion gear which rotates with the rotation member according to the rotation of the output rotation shaft, and moves with the rotation member when the pinion gear unit moves towards the engagement location by the pushing mechanism, to be initially engaged with the engine starting gear, and a second pinion gear which is fit to the rotation member to be adjacent to the first pinion gear through a serration unit, rotates with the rotation member according to the rotation of the output rotation shaft, and moves with the rotation member when the pinion gear unit further moves towards the engagement location by the pushing mechanism, to be engaged with the engine starting gear later than the first pinion gear, in a state where the first pinion gear is engaged with the engine starting gear, and
• an inner periphery surface portion of the first pinion gear on a side opposite to the engine starting gear is fit to an outer periphery surface portion of the second pinion gear on the engine starting gear side through an inter-pinion gear serration unit which is formed between both pinion gears, and the fitting is performed by the inter-pinion gear serration unit so that the phases of the teeth of the first pinion gear and the teeth of the second pinion gear in a circumferential direction correspond with each other.