The combination of tighter carbon dioxide targets and growing competitive and cost pressure, along with ever greater customer expectations calls for specific electric drive expertise: ZF offers this expertise with a modular approach that meets all the requirements in terms of functionality as well as vehicle manufacturers' commercial requirements. The ZF portfolio includes all components for the cost-effective electrified driveline including control units and power electronics, starting with individual hybrid modules, plug-in hybrid systems, through to all-electric concepts. These all-electric concepts include a drive module, which produces up to 150 kW, located centrally on the axle, as well as the eTB (Electric Twist Beam), which incorporates two electric motors close to the wheel in a semi-independent rear suspension.
Electric vehicles will need to be at least as affordable, cost-effective, powerful, comfortable, and also capable of covering long distances as their respective counterparts with combustion engines or hybrid technology if they are to gain widespread acceptance rapidly in the marketplace. In order to speed up this development, ZF is rolling out two groundbreaking concepts at the same time.
The first comprises a drive module positioned centrally on the axle; this module features an electric motor configured as a high-revving asynchronous motor. The electric motor, the single-speed transmission complete with differential, housing, and cooling unit, as well as the power electronics complete with control software form an integrated, extremely compact unit. Consequently, the complete drive module only weighs 113 kilograms. The high-revving concept – up to 13,000 revolutions per minute are possible – enables up to 150 kW of power to be generated. The drive's impressive axle torque of 3,500 Nm produces a maximum motor torque of 380 Nm from a standing start. ZF managed to address the resulting challenges placed on the noise characteristics associated with the high-revving concept by utilizing a single-speed transmission solution already proven in volume production, which, together with the effective integration of the electric motor, virtually eliminates all occurring vibrations.
The technology company is now further developing the drive system into a modular kit for various vehicle and performance classes ready for volume production. A downrated version demonstrates what is possible in practice: With 90 kW it accelerates a subcompact prototype from zero to 100 km/h in about nine seconds with zero emissions locally and virtually no noise.
The electric Twist Beam (eTB), which ZF is now presenting as an optimized version in the prototype stage, constitutes an equally attractive alternative for microcars and subcompact cars in particular. The innovation essentially comprises a semi-independent rear suspension with a compact drive unit on the left and right wheels – the drive unit in turn consists of an electric motor and a transmission in a lightweight aluminum housing. Each of the two motors currently supplies 40 kW. Further major benefits of this concept come courtesy of torque vectoring which allows the two motors to distribute the torque directly to individual wheels. The concept also saves valuable installation space. Compared with conventional systems, the subframe and various axle components, for instance, are eliminated, thus providing manufacturers with a great deal of additional design leeway in the center of the vehicle.
Uncompromising interim step: ZF plug-in hybrid transmission
The technology company has achieved the aim of all-electric, locally zero-emission motoring without limiting the overall range for volume production vehicles – thanks to its plug-in hybrid transmission. This unit is based on the advanced 8-speed automatic transmission (8HP) which replaces the torque converter in its housing with an electric motor generating up to 90 kW peak power and 45 kW continuous power – and virtually without taking up any additional installation space. Its additional power is sufficient to achieve all-electric speeds of up to 120 km/h – the combustion engine only kicks in at higher speeds. The ZF drive also provides plug-in hybrid vehicles with a much greater range of up to 50 kilometers in all-electric operation, depending on the installed battery system.
In the case of hybrids, the existing drive power can only be efficiently used to the full if precisely matched power electronics supplement the hardware. ZF is therefore also pursuing an end-to-end systemic approach in this respect and is developing the software in-house for the entire hybrid management – including control units and power electronics.
Full design leeway – the ZF modular hybrid kit
ZF also offers suitable solutions for automotive manufacturers looking for just modules or individual components rather than complete systems. Providing appropriate basic transmissions are used, virtually any individual solution can be realized thanks to the modular hybrid kit. The mild, full, and plug-in hybrid applications, whose core element is an electric motor, can thus be developed with a high percentage of identical parts and major synergies leveraged as a result. ZF hybrid technology is already a compelling proposition in numerous volume production vehicles.