Parking Lock and Direct Shift Module

The hybrid parking lock of the active gearbox is not hydraulically actuated. Instead, it is actuated via an electric motor. This motor and the associated control unit are combined in one housing and called the "Direct Shift Module" (DSM). It is on the outer side of the transmission housing.

The parking lock mechanism is similar to that used in other automatic transmissions in BMW vehicles: the parking lock blocks the transmission output shaft via a parking lock pawl that meshes with the gearing of the parking lock gear.

In conventional automatic transmissions, the parking lock is engaged by spring force and disengaged hydraulically. This proven concept could not be implemented in the active gearbox, as the requirements that apply for engaging the parking lock could not have been fulfilled in this way. Therefore, the active gearbox of the E72 has an electromechanical actuator for engaging and disengaging the parking lock. This actuator and the corresponding control unit are integrated into one housing. This unit is called the "Direct Shift Module", or "DSM" for short.

The direct shift module, which is installed on the outside of the transmission housing, is connected to the parking lock mechanism in the active gearbox via a splined shaft. Using this shaft, the direct shift module can turn a notched disc inside the active gearbox, as is familiar from automatic transmissions with a mechanical selector lever. In the active gearbox of the E72, the notched disc is used only to distinguish between the engaged and disengaged parking lock. Accordingly, only the "park" (P, parking lock engaged) and "neutral" (N, parking lock not engaged) positions are used. The rotation of the notched disc moves the parking lock lever in the longitudinal direction. When the parking lock is engaged, the parking lock lever pushes the parking lock pawl into the parking lock gear via a conical sleeve. When the parking lock is disengaged, the parking lock lever is retracted and the parking lock pawl is released. A spring pulls the parking lock pawl out of the parking lock gear.

Fig 1: Identifying Direct Shift Module (Interior View)

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Identifying Parking Lock In E72

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 3: Identifying Direct Shift Module

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 4: Direct Shift Module Circuit Diagram

Courtesy of BMW OF NORTH AMERICA, INC.