Automotive

Antonov's 3-speed transmission for electric vehicles boosts efficiency by 15 percent

Antonov has developed a 3-speed transmission for electric vehicles from the ground up
Antonov has developed a 3-speed transmission for electric vehicles from the ground up
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Antonov 3-speed test rig
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Antonov 3-speed test rig
Specifications of Antonov 3-speed transmission
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Specifications of Antonov 3-speed transmission
Antonov 3-speed transmission for electric vehicles
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Antonov 3-speed transmission for electric vehicles
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Antonov has developed a 3-speed transmission for electric vehicles from the ground up
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Antonov has developed a 3-speed transmission for electric vehicles from the ground up

Electric vehicles have been a reality for more than 100 years, but it's only in the last decade or so that the world has truly woken up to their potential as a viable, cleaner urban transport alternative to their combustion engined cousins. During this EV renaissance much of the focus has been on developing improved power sources like batteries and fuel cells in order to deliver the range and performance consumers have become accustomed to during the age of oil. Transmissions on the other hand, despite being so important in the ICE space, hardly rate a mention because the wide torque curve of electric motors makes them largely irrelevant. It could be time to rethink that approach according to U.K. based engineering firm Antonov. The company has produced a 3-speed transmission designed specifically for electric vehicles that promises to bring significant efficiency gains and a better driver experience. The company's Business Development Manager Dave Paul outlined these benefits in a presentation at the IDTechEX Electric vehicles conference this week in Stuttgart.

Why use a 3-speed transmission for electric vehicles?

Internal combustion engines typically reach maximum torque at between 3000 and 5000 rpm, so a gearbox is needed to keep the engine in this operating range as the speed of the vehicle increases. Electric motors on the other hand have full torque at 0 rpm and a much wider operating range. That's why most EVs have a single speed - or in some cases dual-speed - transmission. Despite this, the efficiency of electric motors still varies at different speeds - they operate at a peak efficiency of around 90 percent but this can fall to 60-70 percent, particularly at low speed. The question is whether or not it's worth adding a multi-speed transmission to the EV drive-train to optimize efficiency at all speeds. According to Antonov, the answer is definitely yes.

Benefits of the Antonov multi-speed transmission

The Antonov system grew out of the Jaguar Limo-Green project in 2009. Antonov was initially asked to provide a fixed ratio transmission for this range extended series hybrid, but it was decided to look at additional gears with the aim of improving off-the-line performance and top speed. It worked. In testing, the 3-speed transmission improved efficiency by 14.7 percent while delivering the same performance of the base line vehicle, which translates to greater range or alternatively, a smaller battery pack. On the flip-side, it can deliver better performance at the same level of efficiency. The unit was also compact enough to drop into the existing transmission tunnel.Almost 15 percent. That's a significant figure, but Paul says that it can also bring a raft of other benefits to EV architecture. The addition of a multi-speed transmission means a lower torque motor can be used which results in cost benefits and an overall reduction in the weight of the powertrain. It can offer better launch acceleration, lower noise and a higher cruising speed, while the hill climbing ability of utility vehicles can be improved.

Paul also argues that integrating the Antonov transmission can result in simpler, lighter and cheaper power electronics, and because the motor can be kept within its optimum speed range there's less wear. There are also gear overlap benefits compared to a 2-speed transmission, meaning that not as many gear changes are required at mid-range speeds.

One of the most interesting benefits is the potential to link the system to telematics so that the optimum gear can be selected when, for example you are approaching an uphill stretch of road.

Similarly, a "limp-home" facility could be incorporated to maximize efficiency over performance as the telematics system recognizes that you are likely to run out of juice before you reach your destination.

Another benefit to the overall efficiency of the vehicle is the ability to use first gear to maximize the regenerative braking.

The transmission has a "fairly conventional" twin shaft layout and uses two lubrication pumps - one mechanical, one electric - and a dual clutch for seamless gear changing. It could also be modified to become a 4-speed.

Antonov 3-speed transmission for electric vehicles
Antonov 3-speed transmission for electric vehicles

Antonov is currently involved in a project with Smith Electric Vehicles in which five prototype electric delivery vans are being developed for commercial applications.

This week the company also took out the IDTechEx Electric Vehicles Land Sea Air "Technology Award‟ for the most significant EV technical development over the past two years.

So why haven't we seen three (or more) speed transmissions in electric vehicles before? The idea goes against conventional thinking regarding electric drive systems and Paul believes that engineers engaged in EV development have thus far kept a narrow focus. Perhaps no-one realized the significant difference a multi-speed transmission can make ... we'd love to hear your thoughts in the comments section.

41 comments
robinyatesuk2003
if there is an idea, then quite often another point of view can see another opportunity within that idea., This 3 speed transmissionn seems to be something all the others missed so good luck to Antonov
Slowburn
The real question is what makes this transmission superior to other off the shelf transmissions for electric vehicles. There is no evidence that battery based electric cars are cleaner that IC, steam, pneumatic, or sterling cycle powered cars. The electricity must be generated somewhere and today that mostly means coal. And lets not forget the battery is energy intensive to manufacture, and will have to be replaced in 4-6 years. If you want to have practical electric cars, provide on the road electrical delivery for main roads. I prefer a non-physical contact induction system built into the road surface, but overhead electrical wires like most electrified railroads use, and for the life of me I don\'t understand why the NY city subway doesn\'t may be better, but it does not have the \'cool\' factor.
HerrDrPantagruel
Let\'s just not get carried away with multiple speeds. Electric motors do after all have insanely broad power band characteristics. And I would say that motor and power supply designers have not exhausted their bag of tricks to eliminate some of the efficiency losses that occur at the varying speed/power combination of single speed drives. . Until then, two speeds is probably enough to increase efficiency. Three probably doesn\'t get you that much more in the efficiency game, but I can see how it might enable you to shift gears less often in typical mid-speed traffic situations. Shifting gears smoothly is after all one of the greatest challenges in making an unobtrusive transmission and it\'s taken the auto industry 100 years to finally get that right for the most part. The quest for smooth shifts is what makes transmissions so fiendishly complicated. More gears mean more gear switching. So maybe it might be well to stop at 3, shall we? Unless you\'re traveling 200km/h or something on a regular basis, which is not really the thing to do on limited battery power at this point!
Dave Brumley
Sounds like win-win engineering at its best....
Todd Dunning
Kudos to this article for great technical coverage of the benefits and features of the system. Other off the shelf EV conversions I\'ve seen even integrate a manual transmission... this is a big positive step. It\'s great to read an EV article without use of the words \'Co2\', \'green\', \'eco-*\',\'climate\' or similar hogwash intended to dumb it down for teens. Good tech standing on its own without greenwashing... the way it should be.
Facebook User
one of the major benefits of electric vehicles...is their simplicity and few moving parts, reducing maintanance cost. transmissions sound like a no-brainer, but if you assume that battery power is going to increase and that motor designs will also increase, than the cost of mass producing an object that is only going to add further maintainance and lubrication costs to your car is not necessarlily an easy sell.
Kim Holder
Great to see an article with some depth on something other than EV basics.
Mark A
Prove the added efficiency and include it... I am still waiting for the VW 1L... who needs electric cars with this vehicle.
Mr Stiffy
People doing their maths, and finding ways to capitalise on obvious short comings. Very good.
katgod
What is the additional cost for this 15% savings, I doubt the 15% savings comes in any driving condition so what are the conditions that get this savings? This transmission will have to handle high torque if this is for a performance vehicle i.e more expensive. Is this transmission a good idea, I am sure in some situations it will be worth the added cost, weight and complexity.