Electronically controlled planetary CVT transmission

8 posts / 0 new
Last post
noobster
noobster's picture
Offline
Last seen: 12 years 6 months ago
Joined: Friday, May 16, 2008 - 20:11
Points: 45
Electronically controlled planetary CVT transmission

I have a weird idea and as with most I'm sure there is a fundamental flaw with it but here it is.
In this the sun gear is the primary motive motor, the planets are controlled by a brake motor and the ring is the final drive to the wheel.
While the primary is running full steam or in it's peak efficiency rpm(load dependent?) the wheel would not move unless the planets where slowed down. By varying the resistance to the planets the output could be varied so you could have a crazy cvt with no belts and weights. That's my thought.
I got this idea when I heard diesel electric trains use their motors as brakes and run the power through a large heat sink to dissipate the heat. I know with an alternator that by applying more power to the rotor more power will come from the stator and also make it harder to turn, though it couldn't stop if you wanted to use the power the stplanetarygears.gifator produces to feed back into the rotor. I want to know if there exists a motor that can be used as a brake that requires no out side power just a variable resister, also heat is wasted energy so I want to know if it would produce heat would it be negating the benefit of even having a cvt?
I know I'm on to something with the planetary cvt but have a feeling it's back to the drawing board with the motor brake reducing the speed of the planets.
Thanks- Ryan.

nerad136
Offline
Last seen: 10 years 6 months ago
Joined: Tuesday, March 24, 2009 - 13:28
Points: 1
Re: Electronically controlled planetary CVT transmission

Noobster, I like your way of thinking outside the box, to my knowledge the motor you are looking for does not exist. A thought I had would be some type of permanent magnet setup to control the planet gears, just a thought! The problem i see with a motor controlling the speed is that their would be a very quick cut out point for motor breaking as the speed of the planet gears slowed, you can feed current from a motor back into it, this is commonly reffered to as "plugging" and was once a very good way to slow down a motor, it has been replaced with "Regen Braking" on most newer control systems, regen braking feeds current back into the batteries, both of these methods create heat, but not to the extent that they cause problems. I would say that you idea would be a great hybrid drive using a constant rpm IC Engine and a motor/gen setup, as a matter of fact a car company with a hybrid little car uses a drive like this. (I do not know if i am allowed to mention who they are)

Mik
Mik's picture
Offline
Last seen: 5 years 1 month ago
Joined: Tuesday, December 11, 2007 - 15:27
Points: 3739
Re: Electronically controlled planetary CVT transmission

It seems impossible to make this setup of gears variable .

It's a fixed ratio no matter if you add motors for breaking to the planetary gears. If one cog turns in that setup, all turn.

It would also make more sense to use the motor driving the sun gear as the break making current for regen.

This is almost exactly the setup in the Vectrix hub, just different numbers of cogs.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

spinningmagnets
Offline
Last seen: 10 years 6 months ago
Joined: Wednesday, December 12, 2007 - 20:48
Points: 295
Re: Electronically controlled planetary CVT transmission

http://www.familycar.com/transmission.htm

scroll down and look at "Bands" and thats how the planetary carrier shaft is stopped and started

http://endless-sphere.com/forums/viewtopic.php?f=10&t=8420&hilit=alternator+motor+trailer&start=30

Heres a guy adapting a planetary gearset to try and get a couple gears. Trans shops give these away for scrap weight. Some really small cars might have a better sized planetary gear-set...

chas_stevenson
chas_stevenson's picture
Offline
Last seen: 9 years 8 months ago
Joined: Wednesday, December 6, 2006 - 17:14
Points: 1309
Re: Electronically controlled planetary CVT transmission

I thought you guys and gals might be interested in the NuVinci CVP.

Grandpa Chas S.

TheUnixGuy
Offline
Last seen: 9 years 2 months ago
Joined: Wednesday, February 18, 2009 - 19:35
Points: 5
Re: Electronically controlled planetary CVT transmission

You beat me to the Nuvinci. I saw it at the EV show in Anahiem California.

Mik
Mik's picture
Offline
Last seen: 5 years 1 month ago
Joined: Tuesday, December 11, 2007 - 15:27
Points: 3739
Re: Electronically controlled planetary CVT transmission

It seems impossible to make this setup of gears variable .

It's a fixed ratio no matter if you add motors for breaking to the planetary gears. If one cog turns in that setup, all turn.

It would also make more sense to use the motor driving the sun gear as the break making current for regen.

This is almost exactly the setup in the Vectrix hub, just different numbers of cogs.

HOGWASH!

Due to my extensive experience with exactly "1" planetary gear box I though I knew how they work....HAHAHA!

In a Vectrix the planet carrier is fixed - and I thought this is always the case!

Of course it ain't, and thanks to spinningmagnets links I know better now...

"all remaining in constant mesh" is the correct description of what I meant with "If one cog turns in that setup, all turn." But that is only correct if the planet carrier is fixed.

So, what noobster seems to be suggesting (if I am not totally off again...) is this:

The planet carrier is connected to a generator; this generator offers variable mechanical resistance to the turning of the planet carrier, and converts the absorbed energy into electrical current which is fed back into the battery that is powering the primary motor driving the sun gear (it could also drive the ring gear instead, I guess).

The big question is if the energy losses can be kept lower than those of other continuously variable transmission types. And how exactly to control this system.....

This information may be used entirely at your own risk.

There is always a way if there is no other way!

siai47
Offline
Last seen: 11 years 6 months ago
Joined: Monday, July 21, 2008 - 19:27
Points: 91
Re: Electronically controlled planetary CVT transmission

This is almost exactly how the Toyota Prius "power split device" works. There are two motor/generators in a Prius and a IC engine. One motor/generator is connected to the ring gear, the other motor generator is connected to the sun gear and the IC engine is connected to the planet carrier. The ring gear is connected directly to the output shaft going to the drive axle. When starting out (for example) the motor connected to the ring gear is energized causing the car to move. The IC engine is stopped and so is the planet carrier. The sun gear is free to turn. When IC power is needed, the motor/generator attached to the sun gear is energized as a generator and loaded to a point that it stalls the sun gear rotation causing the planet carrier to turn, thus starting the IC engine. The sun gear motor/generator is electronicly controlled to control the rpm and output of the IC. Thus you have an electroincally controlled CVT. The electronics contiune to control the outputs of the two motor/generators and the IC engine to achieve the desired output to the drive axle.

Log in or register to post comments


Who's online

There are currently 0 users online.

Who's new

  • freedomev
  • dpeilow
  • benthuis
  • Lenis Hvin
  • smith77

Support V is for Voltage