A starter includes a coil spring disposed between a pinion gear and a motor and a buffer rubber disposed between the pinion gear and the coil spring. When the pinion gear is subjected to a reactive force from an engine, the buffer rubber absorbs the impact. Before the impact acts on the pinion gear, the coil spring is subjected to a given initial load. When the impact acts on the pinion gear, the coil spring absorbs it transmitted through the buffer rubber. The cover in which the coil spring is stored has a flange which is held from moving to the pinion gear in response to expansion of the coil spring, while it is permitted to move to the motor in response to contraction of the coil spring. This eliminates a risk that mechanical noise occurs when the pinion gear is advanced and then brought into mesh with the engine.

A motor assembly for starting an engine and driving a balance shaft may include: a motor for rotating a motor shaft which is axially movable; a clutch attached to one end of the motor shaft so as to transfer or block rotational force of the motor shaft; a balance shaft rotated by the rotational force of the motor shaft transferred through the clutch so as to reduce vibration generated by an engine; a start gear attached to the other end of the motor shaft; and an actuator for axially moving the motor shaft in a forward or backward direction.

A motor assembly for starting an engine and driving a balance shaft may include: a motor for rotating a motor shaft which is axially movable; a clutch attached to one end of the motor shaft so as to transfer or block rotational force of the motor shaft; a balance shaft rotated by the rotational force of the motor shaft transferred through the clutch so as to reduce vibration generated by an engine; a start gear attached to the other end of the motor shaft; and an actuator for axially moving the motor shaft in a forward or backward direction.

A starter for an engine is provided which includes an electromagnetic brake device and a pinion thrust mechanism. The electromagnetic brake device holds a planetary carrier from rotating. The pinion thrust mechanism converts rotational motion of an internal gear into linear motion of a pinion when the rotation of the planetary carrier is locked. The pinion thrust mechanism includes a cylindrical cam cylinder, a starter housing, a thrust collar rotatable relative to the pinion, and an engaging pin. The cam cylinder is joined to the internal gear and has a circumferential extending cam groove. The starter housing has a straight groove traversing the cam groove. The engaging pin engages both the cam groove and the straight groove and is moved linearly with rotation of the cam cylinder. This enables the linear movement of the pinion regardless of a helix angle of the spline mounted on the output shaft.

A starter for an engine is provided which includes an electromagnetic brake device and a pinion thrust mechanism. The electromagnetic brake device holds a planetary carrier from rotating. The pinion thrust mechanism converts rotational motion of an internal gear into linear motion of a pinion when the rotation of the planetary carrier is locked. The pinion thrust mechanism includes a cylindrical cam cylinder, a starter housing, a thrust collar rotatable relative to the pinion, and an engaging pin. The cam cylinder is joined to the internal gear and has a circumferential extending cam groove. The starter housing has a straight groove traversing the cam groove. The engaging pin engages both the cam groove and the straight groove and is moved linearly with rotation of the cam cylinder. This enables the linear movement of the pinion regardless of a helix angle of the spline mounted on the output shaft.