ZF’s 8-speed automatic has cut a good figure in numerous car models for years. The new generation integrates a wide variety of hybrid drives. First information and technical details.
Automatic transmissions are on the rise. The installation rates have been increasing for almost all manufacturers for years. Sooner or later they will have to sort the aisles in a majority of the vehicles. Why? To achieve the CO2 targets, manufacturers increasingly have to electrify the drives, and in hybrids the interaction between the electric motor and the combustion engine works best with an automatic system.
Supplier ZF estimates that in 2030 at least 70 percent of all new cars will still be powered by a combustion engine – many of them with a hybrid drive. Depending on the vehicle class and area of application, different shapes are possible, from simple mild hybrids based on 48 volts to plug-in hybrids that can drive up to 100 kilometers purely electrically. That is why ZF makes its widely used eight-speed automatic transmission (8HP) fit for it. And thanks to the modular system with relatively little effort when implementing in the vehicle.
All components in the gearbox
The secret behind the concept: ZF integrates all the necessary components into the gearbox. In this way, the various drive types can be implemented in the vehicles in a space-neutral manner. This means that in the case of a hybrid, an electric motor replaces the torque converter and the power electronics now also find space within the housing. So far, it has been sitting in a separate box the size of a shoe box. The advantages of the new arrangement are not only the simpler assembly, but also greater safety, since it means that fewer high-voltage cables have to be installed in the vehicle.
The integration of the power electronics is made possible by a new cooling concept in which it is connected to the conventional refrigerant circuit of the vehicle air conditioning system. In addition, the engineers were able to significantly reduce the hydraulic control for the mechanical gear changes, thus creating space in the gearbox. In addition, only one power-split oil pump will be used in the future, instead of two, and the efficiency of the mechanical transmission part could be increased slightly.
From 25 to 160 kW electrical support
Depending on the manufacturer’s wishes, ZF can map different performance levels with the fourth generation 8HP. In the 48-volt mild hybrid, the electric machine delivers up to 25 kilowatts and thus supports the combustion engine when starting and accelerating and generates electricity as an electric brake. With the plug-in hybrid, on the other hand, which works with voltages of around 300 volts, the asynchronous machine delivers up to 160 kW (80 kW continuous output) and achieves a maximum torque of 450 Newton meters. With the new eight-speed automatic transmission, ZF can cover a total of system outputs from 430 to 550 kW and three torque classes (up to 600 to 800 to 1000 Nm).