The Schaeffler eDifferential. It has two motors, one for driving the vehicle and another for vectoring the torque between the two wheels.
Jeff Hemphill is vp and chief technical officer for Schaeffler Group North America (schaeffler.us). Schaeffler is a Germany-based supplier to industries including automotive (about 60% of its business is with the auto industry, with aerospace and industrial taking up the rest); its brands include LuK, for clutch systems, dual mass flywheels, CVT components, and torque converters; INA, for bearings, linear guides, and engine elements; and FAG, for bearings. The company has some 70,000 employees throughout the world in 50 countries. The company has a keen focus on product development with some 4,800 of its employees focused on product development. Hemphill is based at the company’s operations in Wooster, OH. The company’s North American Automotive Center is located in Troy, MI.
According to Hemphill, there are two areas that the company is focusing on: to improve the efficiency of what he calls the “conventional powertrain,” as in the
internal combustion engine and trans-mission, and the electrification of the vehicle. One of the most notable developments in the first category is what’s said to be the world’s first fully variable hydraulic vale control system, a cam-actuated, electro-hydraulic valve train system that Schaeffler Group worked on with Fiat. While Schaeffler calls the system “UniAir,” it may be more familiar with the Fiat name, “MultiAir,” the system that is available in Fiat vehicles including the Fiat 500. Essentially, the system allows throttle-free, continuously variable, software-based load control across the gasoline engine operating gap, thereby facilitating improved engine performance and reduced emissions.
They’re working on torque converters, developing things like a centrifugal pendulum type absorber that, compared to other types of absorbers, helps reduce fluctuations between compression and combustion events, thereby improving fuel efficiency, reducing emissions, and reducing engine noise, which, Hemphill points out, is important particularly when there are downsized, high-compression engines.
And the third thing that they’ve developed to improve the conventional powertrain is the dry double clutch for transmissions, which Hemphill says is “the most efficient transmission that can theoretically be made.” Unlike the wet double clutches that are available, there is no hydraulic pump, and the drag torque is greatly reduced. Because it facilitates faster gearshifts, it helps save fuel. He acknowledges, however, that because the dry clutches are air- not oil-cooled, there are some thermal limits associated with them, which means that there are engine torque limitations. And he notes that control system software and compute power have been essential for the smooth drivability of the dual dry clutch transmission.
In the electrification arena they’ve developed a hybrid module and an electric axle system. The former is essentially a combination of a disconnect clutch and an electric motor. It can be installed in a conventional powertrain between the engine and transmission, with the crankshaft on one side and the torque converter on the other. Add in a battery and power electronics, and, he says, it allows making “a hybrid out of a conventional vehicle.” He adds, “It’s a very good way to take advantage of invested capital for producing today’s engines and transmissions, not tool up a new transmission, especially for what is still a comparatively low volume.”
Then there is the active electric differential (eDifferential) that can be mounted on the front and rear axle. It is available in various types, with the highest level providing torque vectoring by driving power to the necessary wheels. The system consists of two different-sized water-cooled permanent magnet synchronous motors, a planetary gear, a transmission for active torque distribution, and a lightweight differential. One of the electric motors provides the drive for the wheels; it can be up to 105-kW. The other regulates the distribution of torque between the wheels; it is much smaller, supplying 5 kW. Hemphill says that the system could be used, say in a conventional front-drive car, placed in the rear axle, thereby providing all-wheel-drive and hybridiza-tion for a single cost. Or it can be used to develop a completely electric car.
They are also pursuing other developments, such as wheel motors that Hemphill says are applicable for urban mobility applications.