Compact 48V electric drive module for hybrid electric vehicles

Paul Boughton

The core element of this range is a compact 48V electric drive module that includes a clutch and planetary transmission, which can be placed either on the front or the rear axle of the vehicle.

The drive module paves the way for the economical hybridisation of vehicles. The low-voltage design reduces costs compared to high-voltage solutions with their associated requirements. This economical hybridisation allows significant advances to be made in terms of increased drive efficiency, as the use of a 48V electric system opens up operational possibilities that were previously the exclusive domain of vehicles equipped with high-voltage hybrid components, including 'crawling' in traffic jams – electrically powered driving in dense inner-city traffic, i.e. moving off, driving at low speeds, and parking using electric power. In addition to electric ‘boosting’ during starting and electric ‘sailing’ – a driving mode in which the electric motor ensures constant speed while the internal combustion engine is switched off – the system also enables recovery and storage of energy during deceleration, which is key in terms of reducing fuel consumption.

The electric drive, which has an output of up to 12kW, acts as the hybrid vehicle‘s sole source of power when 'crawling' in stop-and-go traffic. The electrically generated propulsion of Schaeffler‘s 48V drive module is also sufficient for driving in residential areas, parking in garages and for other low speed driving situations. This is also true of the comfortable driving mode known as 'sailing', in which the electric motor ensures virtually constant speed across a wide operating range while the internal combustion engine is switched off. The electric drive assists the internal combustion engine by providing additional torque, or 'boosting', for example, when moving off from traffic lights.

The high performance of the 48V system also means that the drive element opens up new potential for energy recovery. Due to the higher recuperation capability, the kinetic energy released during deceleration is now no longer converted into heat that subsequently dissipates – as was previously the norm – but is instead fed back into the onboard electric system in the form of electrical energy. Therefore a hybrid solution with combustion engine and 48V system proves to be advantageous when generating electricity from braking energy.

“Using a 48V solution today makes it possible to achieve outputs of up to 12 kilowatts,” summarises Prof. Peter Gutzmer, CTO at Schaeffler. “This entry-level form of hybridisation therefore already offers the essential advantages of a hybrid vehicle while simultaneously providing an economically attractive, low-cost option that allows CO2 emissions to be reduced by up to 15%.”

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