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Schaeffler showcases eDifferential and eWheel Drive for electric Mobility

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Schaeffler’s eDifferential provides drive power for the vehicle as well as allowing power distribution between the wheels on an axle. Click to enlarge.

The Schaeffler Group, a leading global supplier to the automotive industry, used the North American International Auto Show (NAIAS) in Detroit to highlight a number of hybrid solutions and electric mobility products as well as products for optimizing conventional drivetrains based on the internal combustion engine.

The Schaeffler eSolutions concept model at NAIAS showcased technologies such as the eWheel Drive electric wheel hub drive and the eDifferential—an electric axle that allows both the specific distribution of the drive torque to individual wheels and torque vectoring to provide enhanced driving dynamics in electric and hybrid vehicles. Schaeffler has applied these and other eMobility technologies in a trio of on-the-road concept vehicles: ACTIVeDRIVE, the Schaeffler Hybrid (earlier post), and the combustion-engine oriented CO2ncept-10%.

eDifferential. The active electric Differential, mounted on the front and rear axle, is the main innovation in Schaeffler’s ACTIVeDRIVE concept, which is based on a Skoda Octavia Scout.

The eDifferential integrates two water-cooled permanent magnet synchronous motors (PMSM) of different dimensions, a planetary gear, a transmission for active torque distribution and, as a key element, a Schaeffler lightweight differential. The electric drives are manufactured by Schaeffler brand IDAM. The larger PMSM (up to 105 kW and 170 N·m ) provides the drive. The second PMSM, which regulates the distribution of torque, must only supply 5 kW of power in order to generate a difference in torque on the axle of up to 2000 N·m.

The other innovations incorporated in the ACTIVeDRIVE are an integrated electromechanical parking lock, a new force-feed lubrication system without an oil pump for the transmission, planet carriers of sheet metal and various high-speed bearing solutions with optimized friction characteristics. The electronic control system is manufactured by AFT and is therefore also a Schaeffler product.

Due to the use of two active electric differentials, the concept vehicle has an overall output of up to 210 kW (281 hp) and features four-wheel drive. Li-ion batteries located in the propshaft tunnel and in front of the rear axle with a capacity of 18 kWh function as energy stores. Thanks to its performance and traction capacity, the test platform, which weighs 1,900 kilograms, accelerates from 0 to 100 km/h in 8.5 seconds. The vehicle features electronic top speed regulation at 150 km/h (93 mph). The vehicle’s range in this configuration is up to 100 kilometers (62 miles).

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Schaeffler eWheel Drive. Click to enlarge.

eWheel Drive. The eWheel Drive features in the Schaeffler Hybrid, which combines a volume-produced combustion engine from a basic vehicle, and a central electric motor along with two wheel hub motors.

The various elements can each be switched on and off and incorporate a wide range of various driving conditions. These options range from classic operation using a combustion engine, operation as a parallel hybrid or serial hybrid to operation using the electric motor only. The combustion engine can power the vehicle and be coupled for use as a range extender. An automated manual transmission increases the options available.

The energy store, a 16 kWh lithium-ion battery (400 V, 400 A), is charged by means of energy recovery; the range extender; and by an external power supply (plug-in hybrid).

The central electric motor unit is flange-located to the automated manual transmission by means of a toothed chain and drives the front wheels. The unit comprises a liquid-cooled 50 kW, 95 N·m electric motor designed and manufactured by Schaeffler subsidiary IDAM.

The second-generation motors in the two eWheel Drive units have an output of around 70 kW each and torque of around 700 N·m. Schaeffler profits from its expertise in the field of wheel bearings and direct drive technology during the design and manufacture of these high-performance components. The wheel hub motors form a compact unit that integrates wheel bearing, drive and brake.

Schaeffler is also contributing to increasing the efficiency of vehicles with conventional drivetrains.

After all, the majority of all automobiles in the future will still have internal combustion engines serving either as the single or primary drive source, or as a range extender. These internal combustion engine drivetrains still have a great deal of room for improvement in terms of fuel consumption and CO2 emissions—up to 30% in practice.

—Prof. Peter Gutzmer, member of the executive board and chief technology officer

This potential can be achieved by optimizing the thermodynamics, minimizing pump losses and frictional resistance, using ancillary equipment controlled according to requirements, improving targeted thermal management, downspeeding, downsizing and optimizing the start-stop function. Schaeffler also showcased innovations in torque converter technology, a thermal management module and components for variable valvetrains at NAIAS.

Comments

SJC

I would put the motors inboard in place of the mechanical differential for less unsprung mass and better suspension response.

Independent drive to all four wheels is a good idea. I saw a demonstration of a Volvo that had a motor for each wheel and it drove around a frozen lake without breaking traction...very impressive.

ChrisL

I agree that less unsprung weight is better, and my personal preference is that simpler is also better (less total weight, less maintenance). Schaeffler's products seem to add a lot of complexity, which are perhaps inherent in hybrid solutions.

Getting back to unsprung weight, a lot of car design now seems driven by fashion more than better handling. Huge and heavy SUVs with huge and heavy wheels and tires (e.g. 20"). You can see this by how people drive cars on the road--in straight lines. Driving quickly through an S-curve pulling some significant lateral Gs is becoming a rare art.

The article says the test vehicle weighs 1,900 kg, then brags about its 0-100 kph acceleration. I'm not sure less unsprung weight is going to make much difference in how these things are driven.

SJC

It depends on the vehicle, an SUV does not handle like a sport sedan. If you want to get range, lighter is better so that sort of rules out an SUV.

Herm

Aluminum brake rotors could save a lot of unsprung weight, aluminum suspension components would help also. Why are we all so fascinated by hub motors?

That electric differential is brilliant, could be very popular up in snow country.. either in an AWD or FWD configuration.

SJC

You can create an electronic differential with two inboard mounted motors in place of the mechanical differential. The motors each drive a wheel through half shafts and CV joints.

Lucas

Several years ago, in response to my suggestion that we put an electric motor in each wheel, the matter of unsprung weight was throughly discussed here. I rather like to explore such diversities by examining the extremes.

One of the concepts was much like SJC's suggestion. Wherever possible I used carbon fiber and even Titanium. I used two external rotor motors, one driving the rear wheels and one the front. At the time of examination, AWD had not yet reached todays level of usage. (Today I wouldn't even look at a new vehicle that didn't have AWD.)

I strongly suspect that the primary reason for lack of acceptance of all electric vehicles is the obvious fear of your wife running out of electricity on a remote, dark road, late at night.

(BTW - I'm Gen "A".) 80 years old Jan 28th.

Jay Kalend

This system sounds complex but looks thrifty in a pure front wheel drive. Your dumb rear wheels need no differential or even ABS ... they just roll along.

3PeaceSweet

There should be a good overlap in an e-CVT and eDifferential should make a simple 4WD plug in hybrid with small atkinson cycle ICE eCVT driving the front wheels with a rear axle electric motor.

SJC

When you use two motors connected to half shafts connected to each wheel the computer/controller receives inputs from sensors that tells it how to act as a differential. No gears, clutches, bearing nor other parts, just direct control by computer of each wheel. Now that you can do that you can put all of that on the front, back or both ends and have TRUE all wheel drive with complete control of all four wheels sampled dozens of times per second.

John Annen

Anybody see the electric parking brake sprag, pawl, pall in the eDifferential drawing?

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