Designed for Future CO2 Limit Values

IAV transmission is optimizing the efficiency of high-power, high-torque hybrid vehicles

The transmission has a major influence on how quickly the tank empties and on how much CO2 a car emits per kilometer. IAV has developed a high-power, high-torque eight-speed hybrid dual-clutch transmission that is capable of reducing fuel consumption by up to 18 percent over a conventional six-speed dual-clutch transmission on account of its high number of speeds and integrated hybrid function. A further advantage of the IAV 8H-DCT450 lies in its extremely small package requirement.

Maximum efficiency at all operating points and in all driving situations: that was the brief for developing the eight-speed hybrid dual-clutch transmission. The high number of speeds plays a key part here. “It makes optimum use of the map range when the combustion engine is the main source of propulsion”, says Dr. Jörg Müller, head of the Transmission, E-Motor and Hybrid Systems department at IAV. “This alone cuts fuel consumption in the New European Driving Cycle (NEDC) by 4.3 percent over a six-speed transmission.”

In addition, hybridization contributes to this effect: delivering a continuous power output of 30 kilowatts and maximum torque of 300 newton meters, the efficiency-optimized e-motor can provide all of the drive power necessary over some distance. It is also designed to minimize the overall transmission package needed – with a total installed length of 370 millimeters, it takes up no more space than a comparable transmission without hybrid functionalities. Hybridization reduces fuel consumption in the NEDC by 13.8 percent.

The two separate hydraulic circuits also help to provide the high level of efficiency of IAV’s in-house development. A circuit working at a low pressure of 5 bar cools the clutch and e-motor. A second circuit operating at a high pressure of up to 50 bar is responsible for actuating the clutches and shift elements.

Suitable for compact and upper standard class

“All told, this produces a potential fuel saving of 18.1 percent as compared with a conventional six-speed transmission”, Müller says. With its maximum torque of 450 newton meters, the eight-speed hybrid dual-clutch transmission is suitable for use in vehicles from the compact to upper standard class and even the SUV segment.

Various IAV development methodologies were used in the development process. The
transmission synthesis tool identified the transmission’s optimum structure from millions of possibilities under the given boundary conditions. It provides a high level of development certainty because all possible variants can be taken into consideration. IAV’s e-motor synthesis tool delivers electric drive systems that combine a high level of efficiency with minimum dimensions. Combining both tools made it possible to package the hybrid transmission’s functionalities in an extremely compact space.

The eight-speed hybrid dual-clutch transmission is a well-developed solution that can be tailored to specific customer demands and used straight away as the starting point for production-ready development.