Starter

A starter comprising:

• a motor unit configured to generate a rotational force by conducting electricity;
• an output shaft configured to receive the rotational force of the motor unit and to rotate;
• a pinion mechanism slidably installed on the output shaft and helically engageable with a ring gear of an engine;
• a clutch mechanism installed between the output shaft and the pinion mechanism and configured to transmit the rotational force of the output shaft to the pinion mechanism;
• and
• an electromagnetic device configured to perform conducting electricity and blocking electricity to the motor unit and to bias a pressing force toward the ring gear to the clutch mechanism and the pinion mechanism, and having an exciting coil and a gear plunger sliding in the output shaft direction based on electricity connected to the exciting coil and configured to bias the pressing force to the clutch mechanism, wherein:
• the pinion mechanism comprises a pinion inner part fitted onto the output shaft and slidable along the output shaft,
• the clutch mechanism comprises a clutch outer part disposed at the gear plunger side, and a clutch inner part installed inside in the radial direction of the clutch outer part concentrically with the clutch outer part and integrally formed with the pinion inner part,
• the gear plunger comprises:
• a plunger inner part fitted onto the output shaft and slidable along the output shaft;
• a plunger outer part separately from the plunger inner part, installed concentrically with the plunger inner part, and interlocked with the plunger inner part to be slidable along the output shaft, outside in the radial direction of the plunger inner part;
• and
• a backlash absorption mechanism installed between the plunger inner part and the plunger outer part,
• the backlash absorption mechanism is installed to elastically contact a point of action of the gear plunger with the clutch outer part constantly installed at the electromagnetic device,
• the backlash absorption mechanism abuts on the plunger inner part on one side edge of the backlash absorbing mechanism, and abuts on the plunger outer part on the other side edge of the backlash absorbing mechanism,
• the pinion mechanism comprises:
• a pinion gear concentrically installed with the pinion inner part and helically engageable with the ring gear, outside in a radial direction of the pinion inner part;
• and
• a pinion spring disposed between the pinion inner part and the pinion gear, and configured to absorb shock when the pinion gear and the ring gear are helically engaged,
• the gear plunger is concentrically installed with the output shaft, slidable along the output shaft based on conducting electricity to the exciting coil, and configured to bias a pressing force to the clutch mechanism,
• the point of action is formed at an end section of the gear plunger near the ring gear, and
• wherein the gear plunger comprises a plunger spring installed between the plunger inner part and the plunger outer part, the plunger outer part is configured to be slidable based on conducting electricity that is delivered to the exciting coil and the plunger inner part is configured to be interlocked with the slide movement of the plunger outer part to be slidable, and the plunger spring functions as the backlash absorption mechanism,
• provided that a spring load of the plunger spring is a and an attractive force generated at the plunger outer part by a magnetic field generated through conducting electricity to the exciting coil of the electromagnetic device is β,
• the spring load α, and the attractive force β of the electromagnetic device are set to satisfy α<β,
• a diameter-enlarged section having a diameter enlarged via a step difference section is formed at an inner circumferential surface of the pinion gear,
• a housing unit is formed between the pinion inner part and the pinion gear,
• the pinion spring configured to surround an outer circumferential surface of the pinion inner part is put in the housing unit, and
• the pinion spring put in the housing unit is compressed and deformed by the step difference section of the diameter-enlarged section of the pinion gear and a step difference section of the pinion inner part,
• wherein the plunger inner part abuts the clutch outer part and a pressing force is biased to the pinion mechanism via the clutch outer part,
• an outer flange section is formed at one end of the plunger inner part and an inner flange section is formed at one end of the plunger outer part,
• the plunger spring is put in a spring housing unit formed between the outer flange section and the inner flange section, and
• the plunger spring is a coil spring concentrically fitted onto the plunger inner part, and a winding direction of the plunger spring toward the clutch mechanism is set to be the same as a rotation direction of the pinion mechanism,
• wherein a claw section protruding outward in the radial direction and elastically deformable inward in the radial direction is formed at the plunger inner part at a position corresponding to the inner flange section of the plunger outer part, and the inner flange section is configured to be engageable with the claw section, and
• a gap between an inner circumferential surface of the claw section and an outer circumferential surface of the output shaft is set to be smaller than a height of the claw section.