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IAV 8-speed hybrid dual-clutch tranmission can reduce fuel consumption 18% over 6DCT

IAV has developed a high-power, high-torque eight-speed hybrid dual-clutch transmission (8H-DCT) that is capable of reducing fuel consumption by up to 18% in the NEDC over a conventional six-speed dual-clutch transmission (6DCT) due to its high number of speeds and integrated hybrid functionality. A further advantage of the IAV 8H-DCT450 lies in its extremely small package requirement.

IAV said that its design target was maximum efficiency at all operating points and in all driving situations; the high number of speeds plays a key part here. The unit makes optimum use of the map range when the combustion engine is the main source of propulsion, said 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. With continuous power output of 30 kW and maximum torque of 300 N·m, the efficiency-optimized 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 (14.57 inches), it takes up no more space than a comparable transmission without hybrid functionalities. Hybridization alone reduces fuel consumption in the NEDC by 13.8%.

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.

With its maximum torque of 450 N·m, 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 methods 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.

8H-DCT450 gear set. Intelligent multiple use of gear set components reduces the number of gearwheel planes and axial package. The number of gear set components is similar to that of conventional 6-speed dual-clutch transmissions. The IAV unit features 8 well-stepped forward speeds with variable ratio spread from 7.0 to 10.0. Click to enlarge.

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 small amount of space.

8H-DCT450 e-motor.


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