Patent ID: 8751138

Claim:
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; a 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 a 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 a 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 the controller further comprises: a starter drive time measurement unit configured to measure starter motor drive time from a time point when the drive of the starter motor is started; a pinion gear rotation speed estimation unit configured to estimate a pinion gear rotation speed based on the starter motor drive time; a first pinion gear thrust timing determination unit configured to drive the pinion gear thrust unit at a timing when a difference between the ring gear rotation speed and the pinion gear rotation speed, in a case where the transmission is in the drive range, becomes a first predetermined value corresponding to a speed decrease amount of the ring gear rotation speed in the case where the transmission is in the drive range; and a second pinion gear thrust timing determination unit configured to drive the pinion gear thrust unit at a timing when a difference between the ring gear rotation speed and the pinion gear rotation speed, in a case where the transmission is in the non-drive range, becomes a second predetermined value corresponding to a speed decrease amount of the ring gear rotation speed in the case where the transmission is in the non-drive range.