Automatic stop and restart device for an engine

An automatic stop and restart device for an engine that is disposed in a start and transmission system of a vehicle which comprises:

• a transmission for changing gears to transmit power of the engine to driving wheels of the vehicle;
• a transmission operation device for receiving an external transmission operation to operate a transmission state of the transmission;
• a ring gear that is provided to a crank shaft of the engine, a starter motor for starting the engine;
• a pinion gear that is capable of approaching and separating from the ring gear and is driven by the starter motor to rotate;
• pinion gear thrust unit configured to thrust the pinion gear to the ring gear so that the pinion gear engages with the ring gear to crank the engine;
• and
• ring gear rotation speed detection unit configured to detect a ring gear rotation speed,
• the automatic stop and restart device comprising a controller which comprises transmission state determination unit configured to determine whether the transmission is in a drive range or in a non-drive range, the controller performing an automatic stop process for the engine if a predetermined automatic engine stop condition is satisfied, and a restart process for the engine by controlling drive of the starter motor and the pinion gear thrust unit if a predetermined restart condition is satisfied after the predetermined automatic engine stop condition is satisfied, wherein, if the transmission operation device is changed from the drive range to the non-drive range during the restart process for the engine after the predetermined restart condition is satisfied in the automatic stop process for the engine, the controller stops the drive of the starter motor.