6-Speed Automatic Idea: Electromagnetic Clutches

[Nisky]

Does anyone have any observations about building an automatic transmission (e.g., 6-speed automatic) that uses electromagnetic clutches instead of traditional friction-disc packs to do all the internal clutching? This idea includes eliminating the torque converter. In other words, hydraulic fluid would not be required, and this "dry" transmission would not suffer from ATF leakage, contamination (and the damage that ensues), and pumping losses. Seems like if this idea was so great somebody would already be building it.

 

[EdDanzer]

The cost of electromagnetic clutching a transmission is too expensive and you still have to have lubrication of the gears and bearings.

 

[stingc]

Interesting idea, but I think the currents and coil sizes required would be prohibitive. It would require either massive currents and/or a lot of lever arm or hydraulic mechanisms.

And it would still need lubrication as EdDanzer stated above (same as manual transmission).

 

[aorangi]

The French Cotal transmission of the 50s and the British Smith Easidrive of the 60s worked with electromagnetic clutches.

Cheers,
Aorangi

 

[Chumley]

Electromagnetic clutches with ample apply pressures would
also require major current flow which would probably be
most economically done by some type of brush/slip ring
assembly to transfer the current to the rotating clutch
packs. In high current DC motors and alternators, the
brush assemblies are usually one of the more chronic
maintenance/wear/contamination items.

For reference, an induction type electromagnetic clutch
in a common automotive air conditioning compressor uses
about 10-20 amps at 12 volts. The compressor usually
requires about 10 HP or less. A multi clutch automatic
transmission would have say, 2 to 3 clutches engaged at
any one time and would need to transfer over 100 hp with
compounded torque. The numbers aren't looking too good.

The electrical system in the vehicle of choice would almost
certainly require higher voltage and current capacity than
what is normally used. Electricity in vehicles isn't free.
It takes power to generate and costs money to distribute.

As Aorangi mentioned, if the electromagnetic clutches used
by the British and French in the 50's and 60's were more
successful, we would probably see a lot more of them today.

We don't. Hydraulically applied clutches with electronic
solenoid valves as controls seems to be the preferred
method of the day. (that is changing)

Chumley

 

[crysta1c1ear]

They are called electromechanical automatic transmissions or EMAT for short. You could do your own internet search.

EMAT electro-mechanical automatic transmission
Dodge ESX3 Powertrain Keeps the Fun in Driving a Fuel-Efficient Vehicle

http://www.autointell.com/news-2000/February-2000/February-28-00-p2.htm

http://www.daimlerchrysler.com/index_e.htm?/news/top/2000/t00222_e.htm

Volkswagen used one in its 285 miles per gallon 'cigar car'.
DC have been playing with them too, as you can see from the references above. The basic advantage is like electromechanical steering in that it only uses electricity when a change occurs, turning the steering wheel, or in this case a gearchange. There is no point bringing these to market until the change to 42 Volts has occurred.

The Audi A8 has an electromechanical parking brake.

http://www.audiworld.com/news/02/a8launch/content4.shtml

Electromechanical parking brake

 

[automatic2]

You would likely look at a fluid submerged drive for cooling purposes. Eddy current?.