The Getrag 7HDT300 gearbox is a transmission that uses electric actuators for lubrication, for engaging and disengaging the two clutches, and for selecting and engaging odd and even gears. The five actuators have the same characteristics; they are equipped with three-phase motors powered at 12 volts by the DTCM gearbox control unit. Each motor is equipped with a position sensor, powered at 5 volts, to detect the position of the rotor with respect to the stator polarities. The clutch assembly consists of two oil-bath multi-plate concentric clutches, the inner clutch dedicated to even gears, the outer clutch to odd gears. The clutch assembly is protected by a shell in which the fluid circulates to cool the oil that bathes the clutch plates. Each clutch is moved by hydraulic actuators each activated by its own electric pump powered and controlled by the DCTM gearbox control unit. The oil flows through holes in the sleeve on which the clutch assembly is engaged.

This transmission requires specific viscosity and stability requirements of hydraulic fluids. Pentosin FFL-7 A, specified by the manufacturer, guarantees low viscosity, stability against wear and oxidation, and high compatibility with electronic materials and components.

A logical diagram of the transmission of motion follows:

Such a gearbox, despite integrating a 48V electric motor, only allows driving in electric mode by keeping both clutches open to isolate the motor from the kinematic chain and engaging 2nd or reverse gear.

This is provided that:

• The state of charge of the 48 V battery (SOC) is sufficient;
• The vehicle speed is below about 25 km/h;
• The driver requires low drive torque;
• The gear selector is set to R or D;
• The 48 V battery, motor P2 and inverter temperature is below the maximum threshold;
• The air conditioning brought the cabin to the required temperature;
• Absence of specific DTC fault codes.

For further information, please consult the technical manual of the MM1 2023 'Alfa Romeo Tonale MHEV' course or visit the portal Magneti Marelli Campus.

• Kinematic chain
• Logical scheme
• Getrag 7HDT300