Engine starting device

An engine starting device, comprising:

• a starter motor;
• a pinion unit which is spline-coupled to an output shaft side of the starter motor to slide in an axial direction, the pinion unit comprising a one-way clutch which spins for rotation in the same direction as a rotation direction of an engine;
• a pushing mechanism for moving the pinion unit to a position in which the pinion unit comes into meshing engagement with a ring gear;
• and
• the ring gear to be brought into meshing engagement with a pinion gear of the pinion unit pushed by the pushing mechanism, the ring gear being configured to start the engine by transmission of a rotating force of the starter motor thereto,
• the engine starting device being configured to perform restart based on a predetermined condition when a restart request is issued while the engine is rotating by inertia after the engine is stopped,
• wherein the pinion gear of the pinion unit is movable in the axial direction as a single body by having grooves for meshing engagement with a shaft core on an inner side of the pinion gear, and comprises a chamfered portion having a surface with a curved shape along a tooth surface on a non-torque transmitting surface side, the chamfered portion being provided between an end surface of the pinion gear on the ring gear side and the tooth surface on the non-torque transmitting surface side,
• wherein the curved shaped is formed as a curved shape which is a same shape as the tooth surface as viewed on a cross-section perpendicular to the axial direction,
• wherein the chamfered portion has a first length in the axial direction and a second length in a direction of rotation of the pinion gear which is perpendicular to the axial direction, and wherein the chamfered portion is provided to the pinion gear so that the first length in the axial direction is larger than the second length in the direction of rotation of the pinion gear,
• wherein a tooth of the pinion gear has an outer diameter surface located between the tooth surface on the non-torque transmitting surface side and a tooth surface located on the torque transmitting surface side, the outer diameter surface being a surface of the tooth located farthest toward the outer diameter than any other surface of the tooth,
• wherein the chamfered portion extends to the outer diameter surface.