Drive System Design Develops Range-Increasing 3-Speed Transmission For EVs

FEB 26 2014 BY MARK KANE 17

MSYS transmission

MSYS transmission

Drive System Design, an engineering consultancy specialising from UK, recently unveiled at the CTI Symposium in Berlin technical details of its novel transmission for hybrid and electric vehicles called MSYS.

It has 3 speeds and, according to Drive System Design, will makes EVs and HEVs better.

“By making fundamental changes to synchroniser layout that allow smoother shifts with higher efficiency, DSD has been able to provide a multi-speed transmission with a 40 percent weight saving and 10-15 percent lower vehicle energy consumption compared to a single-speed EV or HEV transmission.”

10-15% higher efficiency is of course welcome but the cost and weight will be higher as well compared to single-speed, so we are still waiting to see if some automakers will use a multi-speed gearbox in its plug-in vehicles.

By the summer, DSD plans to build a demonstration vehicle and would like to be ready with series production by Q4 2016.

Seamless shifting is possible thanks to use multi-cone clutch and is described as follows:

The powershift elements in the MSYS transmission separate the two basic synchroniser functions of friction and latching and use the enhanced friction capacity of multi-cone clutch assemblies to provide an uninterrupted flow of torque to the wheels while using no energy to hold the transmission in gear. The increased friction capacity allows the powershift cone clutch to temporarily drive the vehicle during shift events while latching in gear is achieved by dog clutches with self-locking teeth, similar to a conventional synchroniser.”

“By using proven technologies in a unique arrangement, i.e. synchroniser-derived cone clutches and dog clutches, DSD has been able to seek patent protection for the system while minimising the technical risks during development and enabling system suppliers to make use of their existing expertise. Enhanced friction levels have been achieved in the multi-cone clutches by using forced lubrication with variable flow through the clutch packs. Flow variation permits good thermal management at times of high slip with maximum efficiency at times of lower demand.”

DSD technical director, Alex Tylee-Birdsall stated:

“The main consumer concern holding back sales of electric vehicles is range anxiety. By using an MSYS multi-speed transmission, energy consumption can be improved by up to 15 percent which translates directly into increased range. It permits downsizing of the motor and, by being in the optimum gear ratio more often, extends the time the motor spends operating at high efficiency.”

100 kW drivetrain consisting of a YASA motor and MSYS has 91% overall efficiency – about 98% for transmission and 93% for the motor. Its weight is 67 kg (148 lbs) from which 55 kg is MSYS, which sadly is a significant value.

 

Prototype specification of MSYS with YASA motor:

MSYS Transmission

MSYS is a next generation powertrain for electric vehicles. The heart of the system is an alternate approach to powershifting (no torque interrupt) achieved by separating the existing functions of a synchroniser

The system supplies 55 kW of continuous power and over 2000 Nm of torque at the wheels in an extremely compact package with over 90% total electric powertrain efficiency. A low cost, high efficiency unit, weighing just 55kg including motor, MSYS offers a powerful and efficient powertrain solution to the electric vehicle market. The integrated design of an axial flux YASA® motor with the multi-speed transmission has led to simplification of the motor cooling system, electrical architecture and powertrain control system.

The full specification is:

  • Rating: 55kW continuous, 100kW peak (for 60 seconds)
  • Motor torque: 200Nm
  • Output torque: 2000Nm
  • Efficiency: 91% overall, 98% transmission only
  • Mass: 55kg wet, including motor (12kg)
  • Gearing: 3-speed with Powershifting
  • Ratios: 1st 10.01:1, 2nd 7.15:1, 3rd 5.42:1
  • Cooling: integrated pump and radiator
  • Park lock: integrated plunger type with electric actuation

The low cost is due to the use of:

  • Minimised rare earth material content
  • Simple actuation system
  • Novel motor construction
  • Integrated cooling system

The high efficiency is due to the use of:

  • Low inductance motor
  • Minimised power electronics demand
  • Dry sump lubrication
  • High efficiency bearings

The low weight is achieved by using:

  • Low motor weight (12kg)
  • Light weight materials
  • Compact and integrated design (approx. 300x300x400mm)

MSYS also features rapid ratio shifting using DSD Overlap Shift Technology to minimise torque interruption.

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17 Comments on "Drive System Design Develops Range-Increasing 3-Speed Transmission For EVs"

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James

Let the testing begin! 150 more pounds is like having your wife in the car
( and the dog – and maybe some groceries )… Don’t want to put the wife
on the spot here 🙂 .

Can the mechanical advantage outweigh the weight penalty and complexity
issue? I for one enjoy the thought of not having a transmission which equals
maintenance and cost. If the AER advantage were that significant though,
those concerns might be outdone by the added efficiencies.

Martin Tesar

interesting mechanical solution,
however I would much prefer to see a multiple electric motor “in one” solution if one
could be developed.

Dr. Kenneth Noisewater

Axiflux is sort of like that, with electronically-controlled and -reconfigurable stator coils.

Haven’t heard much from them lately though, hope it’s not snake oil.

David Murray

So this might add 10 miles at most to a Leaf. I’d be surprised if it were that much. I’m not sure it is worth the added cost and complexity.

Here’s a thought. I’m not sure how this would work out in the cost of production. But the way I understand it, this would likely not increase the car’s torque any or make it accelerate any faster than it does already. So perhaps the motor could be split into two parts. One would be on a different gear ratio than the other. One could be for highway cruising and the other for acceleration power and low speed driving. The highway part would not need to be very large as it would only need to provide enough power for cruising, and the less efficient one could help when more power is needed. This would unfortunately require a separate motor controller as well. But at least it would keep everything solid state.

Spec9

I skeptical as to whether a transmission added to an EV is worth the added cost & complexity. It adds something mechanical that can break. Meh.

DanCar

Transmission makes more sense for high performance vehicles like a Tesla. The 10-15% number might be optimistic for a Leaf. If the motor doesn’t have to spin at super high speeds it might save money on controller and motor. Transmission isn’t cheap, especially for low volumes.

scottf200

Bet it is hard for any transmission to handle the torque of the high output motors tho.

Anon

Yeah…

Nix

I’d rather have 150 pounds more of batteries.

Giza

It’s a lie. A single gear borg warner egeardrive is nearly 98% efficient and the typical AC induction motor might be up to 95% efficient. It’s just not possible to be 10% more efficient with that gearbox. Indeed it will likely be less efficient.

Their product is a big mistake and will fade away like the misguided vaporware it is.
What they should have done is make a single speed gearbox like the egeardrive but at the very low price it could be instead of borgwarner’s punishment price.
Make a 300, 200 and 100Nm version. Egeardrive is 300 and weighs something like 28kg iirc.

ModernMarvelFan

EDN recently had an article on the so called EV motor efficiency rating.

They are NO where near the 95% that some claims. Most of them are based on the industrial motor application where the load is constant. In the case of EV driven driven, the load, speed and operation point are shifting all over the place….

If a motor is really 95% efficient, then an ICE based EV conversion would be about 4x-5x more efficient in efficiency. But they are barely 3x more efficient than its ICE version. So, we can can safely assume that most EV motors aren’t nearly 95% efficient like you claimed.

Giza

You can see efficiency maps for for instance AC propulsion AC150. Varies from 88 to 91% combined over most of the surface. Very difficult for the gearbox to find 10-15% there.
Particularly when the efficiency is largely rpm independent at moderate power.
So all you gain is weight.

Mikael

Don’t want transmissions. It ruins a part of the concept of the electric car and it’s durability and simpleness.

There must be better ways (or not doing anything at all). I’d rather have that weight and extra cost in batteries as well.

Aaron

Agreed! I don’t want a transmission. It’s another moving part that can break.

Bill Howland

I would actually like it if they made the drive motor slower (I’ll take the Larger and Heavier penalty), to keep the pinion speed more reasonable at high mph, thereby gaining a percentage point increased efficiency at higher car speeds, if they only have so called ‘1-speed’ gearboxes..

Djoni

Bad idea as I can see.
Put that weight in batterie is going to add more range.
Otherwise, it’s feasible to gear down or up a single electric motor for specific usage and gain some amount of range for that purpose.
The customer just choose the end ration that suit is need.
Other than that, electric motor/inverter could be design whith even geater efficiency for the full spectrum of speed down the road without the weight/complexity/breaking/maintenance aspect of this idea
Non shifting is part of the electric drive I’ll stick with.

Phr3d

I’m not getting 3 speed as much as 2 speed has intuitively appealed to me from the start, i.e., a smaller less KW hungry motor offset by weight of a transmission that transmitted 100% up to 30mph, then ‘cruised’, like my camaro’s chevy-glide from way back.
It -seems- like a good balance could be realized here -even with re-gen issues- to increase BEV miles, but I’m pretty sure that E-engineers have proven this ‘intuition’ false by now, else we would already Have E-transmissions.
verdict=fail.