SMM News: ZF is a world-renowned gearbox supplier, in the field of commercial vehicles and passenger vehicles, occupy a pivotal position. At present, the main product of passenger car AT is the 8th gear AT gearbox (8HP series), mainly supporting BMW, Audi, Chrysler and other international first-line brands.

To further improve combustion efficiency and performance, ZF has been continuously optimizing and upgrading the 8HP series longitudinal gearbox, and ZF 8HP has developed three generations (the third generation in 2018). And according to ZF, at least 70 per cent of new cars will still be equipped with internal combustion engines by 2030, not only in the form of traditional internal combustion engines, but also in electrified models such as the HEV or PHEV.

Recently, on Global Technology Day, ZF showed the media a new generation of 8AT gearbox, which is mainly developed in the face of electrified models, not only for plug-in hybrid models, but also for light hybrid and traditional fuel engines.

From the launch of the first generation 8HP series gearbox in 2009 to the latest generation of 8AT gearbox, the 8HP series has developed to the fourth generation, the fourth generation 8AT code named 8HP60, 8HP80, depending on the matching electrical system, with conv, MH, PH suffix. Compared with the previous three generations of 8HP series gearboxes, the fourth generation 8HP is an all-electrified modular innovative solution, carrying torque to cover the 600Nm-1000Nm.

The new generation of 8AT is still composed of four sets of planetary gears and five sets of shift elements, which can further improve the operation efficiency by fine-tuning the friction power. Of course, its main optimization is not only in the optimization of the internal gear shafting, after all, it has undergone three generations of innovation. This time, the main changes are focused on the integrated and modular design, the optimization of the accessory system and the redesign of the electrical system.

Traditional 8A (8HP60 conv) is suitable for 600Nm and 800Nm torque sections, including mechanical oil pump and electronic oil pump. Electrification is mainly realized by BSG motor (P0).

The light mixing 8AT (8HP60MH MHEV) adopts 48V electrical system, which can match the two torque segments of 600Nm and 800Nm, including P1 and P2 configurations according to the position of the motor. P1 configuration for the motor as for the hydraulic torque converter, the motor and the engine are connected by torque shock absorbers. The P2 configuration adds a K0 clutch between the motor and the torque converter, which is not available in the third generation.

The maximum power of the matched 48V auxiliary motor can reach 25kW, which can participate in the work under almost all working conditions of the vehicle. In addition to improving fuel economy through energy recovery, the matching 48V auxiliary motor can also provide power in the process of vehicle start-up and acceleration. Optimize the engine to work near the best working point, and greatly reduce the pollutant emission of the engine.

The plug-in hybrid 8AT (8HP80PH PHEV) adopts P2 configuration, the maximum peak power of the motor can reach 160kW, and the maximum torque is 450Nm.

The biggest bright spot of the new generation 8AT is the high integration and modularization of the gearbox, which can extend the product sequence of MHEV and PHEV under the condition of almost the same basic size, and the adaptive motor power has been improved from the third generation 15kw-100kw to 24kw-160kw.

The new generation of PHEV high voltage motor is independently developed for ZF, using welded copper rod instead of coiled copper wire, which greatly improves the filling level of copper and significantly improves the power density of the gearbox without increasing the volume of the gearbox. Compared with traditional technology, the same package size can match higher power engines.

At present, most of the hybrid gearboxes on the market basically install the electronic control unit of the motor independently and seal it in a small chassis. The new generation of ZF hybrid gearbox is to fully integrate the electronic control unit into the transmission housing, so as to reduce wiring, improve safety, save assembly time and reduce maintenance costs. The high density integration makes the ZF hybrid 8AT gearbox have more obvious advantages over its traditional hybrid gearbox.

An important technical support for the high integration of the new generation of 8AT is the adoption of a new small-volume hydraulic control system, which is mainly due to the use of direct shift valves to make room for the installation of electronic components. Compared with the hydraulic control unit of the third generation eight-speed automatic transmission, which requires 3.1L capacity, the new generation gearbox only needs 1.8L.

The new generation of 8AT gearbox is mainly aimed at hybrid models, so the hydraulic oil supply is also quite different from the traditional internal combustion engine 8AT gearbox in the past. In the past, two sets of fuel supply systems were used: one is a high efficiency mechanical vane pump, which is directly driven by the internal combustion engine; the other is an electronic pump or accumulator driven by electricity.

A single power shunt pump will be used in the new generation of 8AT gearbox. When the internal combustion engine is closed, the oil pump will be driven by a small, directly connected motor to meet the hydraulic requirements under various working conditions, and the operation efficiency of the system will be more efficient.

According to the official test data, taking a 2.0L test model as an example, the use of P2 MHEV 8AT can reduce the CO2 emissions of 15g/km.

According to ZF's production plan, the new generation of 8AT gearbox will begin production in the German city of Salbrucan in 2022, followed by the two major markets in China and the United States. At present, BMW and Fiat Chrysler Group have signed a new generation of eight-speed automatic transmission purchase order with ZF, which will be used in its hybrid models in the future.

"Click to enter the registration page

Scan QR code and apply to join SMM metal exchange group, please indicate company + name + main business