New clutch allows hybrids to run manual gearboxes

by Hilton Holloway, Autocar UK Jul 07, 2017

German components firm Schaeffler has unveiled a new hybrid clutch system that opens the way for electrified cars to be offered with manual transmissions.

The so-called ‘P2 module’ is expected to go into production at the end of this year in China. The P2 module fits between the engine and the transmission — making it especially useful for transversely engined vehicles — and combines a 12kW electric motor and a pair of clutches. A disconnect clutch allows the car’s engine to be decoupled from the transmission. An impact clutch is used to smooth out vibrations when the engine is restarted.

Schaeffler said the P2 module would allow a car to drive electrically at low speeds in stop-start traffic, automatic parking could be performed in electric-only mode and the system also allows ‘active sailing’ at speeds up to 30mph. The active sailing system allows a vehicle to take advantage of rolling momentum or downhill stretches of road by either idling or shutting down the engine and disconnecting it from the transmission in order to save fuel.

The new unit is designed to work with a 48V electrical system, which many car makers are rushing to adopt for future models. The 48V system means that not only can the electrical system handle a maximum of 12kW — four times that of the familiar 12V system — but also the system’s cabling can be 75% smaller, saving weight, reducing costs and improving the maker’s ability to package the wiring harness into the car.

The P2 can also be used to recuperate energy under braking, saving it as electrical energy to a 48V battery.

The P2 unit is designed to be retro-fitted to existing vehicle structures with minimal engineering changes. Around half of all global car sales are of cars with a manual gearbox.

Changes are not needed to existing gearbox designs and the unit doesn’t need water cooling like some hybrid setups. It could help reduce fuel consumption by as much as 20%, according to Schaeffler.

The P2 module is intended to be used with Schaeffler’s new E-clutch set-up, which, it claims, can help cut fuel consumption by as much as 8%. There are two versions of the E-clutch — one that uses a pedal and hydraulic or cable connection with the electronic ‘intelligent actuator’ and the other that dispenses with the clutch pedal altogether.

Future versions of the P2 unit, one developing a continuous 33bhp and 74 lb ft and the other 64bhp and 118lb ft, are also under development.

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