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Oerlikon Graziano launches 4-speed electric drive; up to 15% efficiency increase

Transmission specialist Oerlikon Graziano, part of Oerlikon’s Drive Systems Segment, is presenting its 4SED (4 Speed Electric Drive) (earlier post) to customers around Europe. This new compact, lightweight transmission offers increased efficiency, smooth shifting and a scalable design making it suitable for a wide range of vehicle types.

The 4SED, based on Graziano’s original eDCT (electric dual clutch transmission), uses two traction motors in a very compact package which provides four speeds to allow running closer to peak efficiency. The result is an overall efficiency improvement of up to 15%, which translates into increased range or improved performance for the vehicle. The mechanical design concept was developed by Oerlikon Graziano, while the shift control system was engineered by UK controls specialist Vocis Driveline.

Oerlikon Graziano developed the 4SED transmission in anticipation of market need for increasingly efficient transmissions for low and zero emission vehicles.

The four-speed transmission uses two input shafts, each driven by its own electric motor—i.e., the concept is similar to that of a DCT but uses two motors in place of the twin clutches. One motor drives a shaft that carries first and third gears, the other drives a shaft carrying second and fourth. This allows pre-selection of the next gear before the previous one has been disengaged, using the two motors to synchronize shaft speeds so that no synchronizers are needed.

The use of the traction motors also permits a reduced set of software algorithms compared to a normal automated gearbox, and since there are no hydraulics, there is no need for valve control.

Besides improving efficiency, a multi-speed transmission leads directly to faster acceleration and a higher top speed, noted Vocis. (Earlier post.) By improving hill climbing and pull-away performance, a multi-speed transmission can increase the load carrying capacity of an electric delivery vehicle. The higher ratios in the transmission can then be specified to provide more efficient high speed cruising, enabling EVs to mix more easily with other vehicles on highways.

Further, the improved powertrain efficiency of the multi-speed transmission can also help reduce the cost of the battery pack, Vocis said. A smaller battery pack, in combination with the multi-speed transmission, can provide the same vehicle range as a larger battery with only a single speed.

The technology is scalable to suit a wide range of different vehicle types, urban electric cars, high performance cars, hybrid 4WD applications, electric buses and trucks. It is also suitable for applications with 48V motors, allowing significant cost savings and reducing risks of high voltage, Oerlikon said.

A demonstrator has been fitted to an electric Mercedes Vito minibus and is currently touring European vehicle manufacturers to showcase its features.

The company will present more details on the 4SED at the CTI symposium in Berlin in December 2013.



I thought EV engines were 95% efficient.

How wrong I must have been.

Dave R

They are typically up to 95% efficient across a fairly wide load, but at low speeds, high speeds and low-torque outputs efficiency drops.

Here's the Nissan LEAF's plot from the Feb '11 SAE Newsletter:

Aside from efficiency boost, acceleration and top-speed would also improve.

A multi-speed transmission would let the Tesla Model S compete with it's gas-powered rivals at all speeds - instead of only speeds up to 90 mph where power starts falling off.


Future improved lighter twin e-motors power train will accomplish the equivalent efficiency gain at high and low speeds without the extra weight and cost?


@Dave R, thanks for the link.

Looks like a simple two speed transmission might be worth the economics to cover "low" 85% efficiency extremes.


..or just an overdrive to extend high speed range.


It seems a bit odd that the two motors cannot be integrated when required to provide the extra torque @ optimum rpm.
Given all the trouble to bring all the components together why not use it?
That might see less ratios possibly a third or some type of unconventional clutch
Not that gear selection be redundant, but possibly having both motors available could see them switching in or out so as to assist each other achieve optimal efficiency.a

Similar to parallel hybrid and the acceptance of dual input power delivery strategy, the second motor could be optimised for one end of load or rpm requirement.


Gentlemen! The motors are very (sometimes 96%) or more efficient if the design is right and ... the motor driver is right. As a power electronics designer I see NO need for multispeed transmission but I do see needs for motor driver. There are so many types of losses associated with ineffective motor driving that it is inevitable that it will be addressed rather sooner than later. BTW the solution exists.


I only see the need for this transmission in use with brushed DC motors. They have a much more limited RPM range (lower than ICE engines) and transmissions for DC powered conversions always leave the cars original transmission (preferably manual) because the approximately 0-3600 RPM range of a DC brushed motor is not wide enough to get a car to freeway speeds. For other more modern (DC motors date back to late 1800s) motors like brushless DC, AC inductive, switched reluctance (or others) have a wide enough RPM range to not require multi ratio transmissions.
Sure if you want a top speed over 90 MPH, but in reality, nobody needs a commuter car that goes that fast.

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