Brief component description: Decoupler

A separation clutch is integrated in the housing of the electrical machine. The separating clutch is designed as a wet multi-plate clutch. The separating clutch is used in certain operating states to disconnect the combustion engine from the electrical machine and the remaining power train. This takes place for example with purely electrical driving as well as in the "coasting" driving condition.

So that the connection and disconnection of the combustion engine is not noticeable, the separating clutch has high actuating precision. As soon as the separation clutch is closed, the electrical machine, transmission input shaft and the combustion engine are turning at the same engine speed.

In the same way as all clutches and multi-plate brakes of the automatic gearbox, the separating clutch is operated by the mechatronics module. At static pressure, the separating clutch is opened. This means that gearbox oil pressure is required to close the separation clutch. The transmission oil pressure is provided either by the electric gearbox oil pump or the mechanical oil pump. With the separating clutch opened, the mechanical oil pump is driven by the electric motor. In the event of an electrical machine malfunction and a transmission oil temperature below 0 °C, the separation clutch can no longer be closed. Drive-off is thereby no longer possible.

Fig 1: Identifying Decoupler

Courtesy of BMW OF NORTH AMERICA, INC.