ZF 8-Speed Automatic Transmission. With the development of the new 8-speed automatic transmission by ZF, the focus is not on the number of speeds but rather. Weber State University (WSU) - Automotive Technology Department - Transmission Lab. This episode demonstrates the components and operation of the ZF 8HP 8-sp.

Plug-in Hybrid: New Electric Motor Equals Higher Power Density

ZF estimates that at least 70 percent of all new vehicles in 2030 will still have an internal combustion engine. Nevertheless, a plug-in hybrid drive could considerably lower the engine‘s CO2 emissions. This is contingent on electric range and electric power, both of which must allow for driving in everyday traffic with battery power only. ZF has laid the foundation for this with the plug-in model of the new generation 8-speed automatic transmission. The electric motor has a maximum power of 160 kilowatts and a continuous output of 80 kilowatts. The maximum torque, which can be attained without actuating the internal combustion engine, is 450 newton meters, thus allowing for swift passing, even in e-mode. This does not require a significant increase of the packaging size since ZF relies on a new generation of internally developed electric motors and uses welded copper rods instead of coiled copper wire. This technology, known as the “hairpin technique,“ allows the copper fill level to be significantly increased, which has a decisive impact on the power density.

Mild Hybrids: Variety Is Key

In addition to plug-in hybrids with high voltages of around 300 volts, mild hybrids will also play a big role in the coming decade. They have a voltage level of 48 volts and allow for considerable CO2 savings by generating power through regenerative braking recovery that can later be used as drive power. Furthermore, mild hybrids lower pollutant emissions by providing additional power during launch and acceleration processes – driving conditions in which conventional internal combustion engines emit a relatively high amount of pollutants in a short amount of time. Forty-eight-volt drives can be installed on several locations in the driveline. Installation on the crankshaft at the engine output (“Position 1“) and on the input shaft (“Position 2“) are particularly efficient. The new generation from ZF is suitable for both installation types. The electric motor can reach a maximum power of up to 25 kilowatts and thus optimally support the internal combustion engine in virtually all operating parameters.

Zf 8 Speed

Power Electronics: Active Involvement

Electric motors must be controlled via power electronics, which both convert the direct current from the battery into the required alternating current and control the power and speed of the electric motor. Until now, these power electronics were housed in a separate, shoebox-sized box for all series hybrid transmissions. However, with the fourth generation, ZF has integrated the complete power electronics into the transmission housing for the first time ever. This is a great advantage to automotive manufacturers since hybrid drive assembly is no longer considerably more complex than that of a conventional transmission. In addition, fewer high-voltage cables are needed in the vehicle, which enhances safety. The engineers at ZF were faced with the challenge of fully integrating the power electronics into the transmission without increasing the outer dimensions. They achieved this through an ingenious cooling concept, as well as through several other developments. The power semiconductors, especially the IGBTs for the high-volt model, produce a relatively high amount of waste heat. This is dissipated by connecting the power electronics to the refrigerant circuit of the vehicle‘s air conditioning system. However, the most important development was the considerable decrease in the size of the hydraulic control unit, which triggers mechanical shifts in the transmission. The hydraulic control unit in the current generation of the 8-speed automatic transmission requires a volume of 3.1 liters, but in the next generation, it will shrink to 1.8 liters. This is made possible primarily by using direct shifting valves. In contrast to the electric pressure actuators that were previously used, these electromagnetic actuators no longer require additional pistons and bushings.

Intelligent Adaptation to Hybrid Versions

Each additional component of the new 8-speed construction kit was also intelligently designed for hybrid operation. This is clearly evident when it comes to the oil circuit. Previously, two oil pumps were used: a very efficient vane cell pump driven directly by the internal combustion engine and a second electric pump and/or pulse memory for electric operation. In the future, a single power-split pump will be used. When the internal combustion engine is shut down, it is driven by a small, directly attached electric motor. The mechanics of the new transmission system also contribute to efficient hybrid operation. Although the body remains the same with four planetary gear sets and five shift elements, efficiency was further increased by fine-tuning the friction power. Thanks to this, CO2 emissions were lowered by one gram per kilometer during operation with the internal combustion engine. Drivers puma modems. During electric operation, the range has increased accordingly.

Comfort Is Crucial

The new generation 8-speed automatic transmission is designed for lengthwise installation of the engine and transmission – a drive configuration that will be successful especially in the premium segment because it satisfies the high demand for comfortable operation and noise reduction. Achieving this during hybrid operation is partly due to the solid mechanical foundation. Eight gears allow for transmission stepping of up to 8.6 with low gear steps, and thus low speed steps, over a wide speed range. In addition, the ZF-developed, centrifugal pendulum vibration absorber was optimized such that the driver barely feels the switch from electrical operation to operation with the internal combustion engine. In the future, the transmission control module will no longer be based on characteristic maps, but rather on mathematical models of all system components. This is an important prerequisite for satisfying the growing complexity of future drivelines.

Ready for the Drives of the Next Decade

ZF will begin manufacturing the new generation 8-speed automatic transmission in Saarbrücken, Germany, in 2022. The market launch in China and the United States will follow shortly thereafter. ZF can thus make significant strides toward ensuring that hybrid drives gain quick acceptance while reducing vehicle CO2 emissions in market segments where electrification cannot be fully implemented immediately.

For the 8-speed automatic transmission, ZF set out to design and develop an entirely new gear set concept. The result is a revolution in transmission design: a transmission concept with 4 gearsets which requires only 5 shift elements – of which only two are open in any given gear. The 8HP also requires no more than 3 multi-disk clutches and 2 brakes, which allows it to achieve a greater degree of efficiency than other concepts. As a result of the fact that only 2 shift elements are open per gear, drag losses in the transmission are sustainably reduced. This effect is supported by the use of a new parallel-axis vane-type oil pump. 4 A torque range from 300 to 1000 newton meter makes the 8HP the perfect partner for all rear-wheel-drive and all-wheel-drive designs. From the lower midsize segment to sporty luxury cars, and in every type of SUV and offroad vehicle – its revolutionary design is always an efficient and economical solution. Although the 8HP features 2 more speeds than the extremely successful 6HP, the dimensions have remained unchanged and the weight was even reduced by 3% to 87 kg (transmission modular system 8HP70) including oil. At the same time, the total transmission ratio spread of 7.0 ensures that the engine is always in its optimum operating range. This translates into improved acceleration and reduced fuel consumption.

Zf 8 Speed Transmission Maintenance

Based on a really successful product, it combines dynamics and comfort with improved efficiency – also with regard to the costs. And it is ideally equipped for even stricter fuel consumption and CO2 emission regulations. In the premium and mid-size car range, the optimized 8HP product family enables the average fuel consumption to be cut by another 3%. CO2 emissions decrease to the same extent. These potentials can also be completely transferred to hybrid drives. Incidentally, additional savings potential by a further optimized startstop function is not yet included here. To achieve these innovations, ZF engineers have optimized some details. Thus, the reduction of drag torques and engine speeds further reduced the already very low power losses. Essential success aspects are the higher transmission ratio spread and the reduction of system pressures in many areas. Another factor is the multidisk separation of the brakes. Furthermore, advanced torsional vibration dampers enable a faster bypassing of the hydrodynamic power transmission and therefore further reduction in speed. Thus, the new 8HP is perfectly prepared for use with the new engines (3-8 cylinders) which will determine the trend of the years-to-come.