IAV says new version of modular electric drive can boost range 5-10% vs system with fixed transmission ratio
IAV presented a new version of its modular electric drive concept at the Vienna Motor Symposium. Combining a 50 kW (continuous) / 80 kW (maximum) e-motor and transmission, the modular drive unit can support electrification solutions in vehicle classes A to D. The unit represents a further development of a solution IAV presented in 2010. IAV’s aim is to deliver a high level of ride comfort, efficiency and compact packaging at a competitive cost.
Many of today’s electric drives use a combination of an e-motor and transmission with fixed gear ratio. Although solutions of this type are relatively simple in terms of structure, they can be challenged to meet the full range of use cases, IAV says. For example, high hill-climbing performance and maximum efficiency demand very different transmission ratios. To address this, IAV chose a modular concept based on an e-motor and a transmission with one to three speeds.
Our modular electric drive unit meets the demands on torque with more speeds than comparable solutions. Instead of a multiple-speed transmission, these use a larger motor with means they need more package and encounter problems because of the higher motor speeds involved, such as with NVH.—Jens Liebold, Technical Consultant for Electromechanical Drive Systems at IAV
Solutions with a fixed transmission ratio also come with efficiency drawbacks; IAV says that its solution increases traveling range by five to ten percent.
The e-motor developed by IAV generates constant torque of 150 N·m which can be increased to 300 N·m for short periods of time. IAV designed the motor using IAV’s e-motor synthesis tool which finds the optimum solution for the given application from an almost unlimited number of potential variants.
Providing a maximum of three speeds, the planetary transmission is installed at the side of the e-motor and is capable of generating output torque levels of up to 3,000 N·m. At the same time, this makes it possible to limit the motor’s maximum speed to 8,000 revolutions per minute.
|Modular transmission system with up to three speeds. Click to enlarge.|
The differential is accommodated in the e-motor, making optimum use of limited package. The overall transmission ratio is adjusted by the spurgear stages that are mounted downstream of the differential and are easy to adapt to the specific application case.
Compared to a pure coaxial solution, this produces package benefits as the output axis can be spun in relation to the unit’s actual centerline, making it much easier to observe the ground clearance limit or meet other package restrictions, IAV says. On demand, the hydraulic module with an integrated electric oil pump provides the pressure and volumetric flow required for the circuits that split off downstream of the main control valve for lubrication and cooling as well as actuation.
The system supports hill-climbing ability to a maximum 30% grade, supports a top speed of 160 km/h (99 mph) (continuous) / 185 km/h (115 mph) (maximum), with acceleration from 0 – 60 km/h in 4 seconds and 0 – 100 km/h in 10 seconds.
We can match the electric drive unit to different vehicle platforms and demands. Our solution delivers a high level of torque across a wide vehicle speed range.—Mathias Krause, head of the Cylinder Head/Crankcase department in IAV’s Powertrain System Development division
IAV partnered with Nemak, a global manufacturer of aluminum castings for the automotive industry, on the development of the housing. The housing design was optimized for functional integration, cooling, structural stiffness and NVH as well as cost-effective, large-scale and robust manufacturability. Growing complexity puts more emphasis on low-pressure die casting and core-package sand casting process (CPS).
Developing the casing also presented a particular challenge. Compact design, a high level of functional integration and temperature management have been combined to provide additional benefits.
With IAV’s solution, for example, the power electronics are accommodated in the casing to reduce costs from copper wiring, ensure good EMC shielding as well as include the power electronics in the electric motor’s cooling circuit.
In our case, we use the stator’s circuit to control the temperature of the power electronics because we can bring it into contact with a large area of the casing’s cooled sections. The transmission lubrication system, in turn, also cools the e-machine’s rotor.—Mathias Krause
|Cooling duct geometry in the housing. Click to enlarge.|