ZF Gets Big Orders for Innovative Transmission
ZF announced this past April that it had received what its CEO Wolf-Henning Scheider said was “the largest single order in the history of ZF,” providing BMW with a new eight-speed automatic transmission. While a specific number for the order hasn’t been announced, it is a “two-digit billion Euro value,” which is sizeable in any currency. The transmission can be installed in an array of vehicle sizes and types that feature a front-longitudinal configuration. What makes this transmission notable from other eight speeds that ZF offers (and has been doing so since 2019) is that it has a modular design such that an electric motor can be integrated. According to Michael Hankel, member of the ZF Board of Management whose portfolio includes transmissions, “The order was based on the fact that the customer sees our technology as a sustainable drive solution for its vehicles which supports them in achieving CO2 targets. In addition, the possibility to easily change from one transmission variant to another allows our customer the flexibility to react to market requirements.
"Alongside the significant CO2 savings potential, this high degree of flexibility is resulting in strong interest in our transmission. We are in very promising discussions with other customers.”
Inside the new ZF eight-speed that is specifically designed and engineered for hybrid drives. (Image: ZF)
And now one of the “other customers” has been announced and it represents what is the second-biggest order for the “8HP,” Fiat Chrysler Automobiles. FCA will use the transmission in rear-wheel and all-wheel drive vehicles.
Production for the 8HP will start in Saarbrücken, Germany, in 2022, then roll out to ZF plants in Gray Court, South Carolina, and Shanghai, China.
As regards the tech of the new transmission, it can be used for mild, full and plug-in hybrid configurations.
The electric motor used has a maximum power of 160 kW and a continuous output of 80 kW. It has a maximum torque of 450 Nm that can be achieved without starting the engine
One of the things that was considered from the start of developing the 8HP was packaging: they didn’t want to make it substantially larger even though there would integration of things like the motor. So in the case of the electric motors, ZF developed its own suite of motors for the application that, for example, use welded copper rods instead of coiled copper wire, which allows an increase in the amount of copper used (which results in higher power density) without having a proportionate increase in size.
ZF will be producing the 8HP transmission in three facilities on three continents: in Germany, the U.S. and China. (Image: ZF)
In addition, the compete power electronics are integrated into the 8HP. A big consideration is that power semiconductors (notably the IGBTs that are used for the high-voltage setup) have plenty of waste heat. So to handle it, the power electronics are cooled via connection to the refrigerant circuit of the vehicle’s air conditioning system.
Another way that the overall size of the transmission was managed is through the redesign of the hydraulic control unit. In the new approach direct shifting valves, electromagnetic actuators, are used in place of electric pressure actuators. Whereas the electric pressure actuators require additional pistons and bushings, the electromagnetic actuators don’t. And the difference between the two hydraulic control unit dimensions is notable: 3.1 liters for the previous generation and just 1.8 liters for the new one.
While some hybrids have a slight-but-noticeable shift when going from electric to internal combustion operation (and vice versa), ZF has developed a centrifugal pendulum vibration absorber that is tuned to smooth out any discontinuous moments.
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