Does this patent app describe the Volt transmission?
I found the following patent application from GM titled "Output Split Electrically-Variable Transmission with Electric Propulsion Using One or Two Motors": http://www.freepatentsonline.com/20090082171.pdf. (The file is a pdf so you'll need the free Adobe reader to view it.)
I believe that it describes the Volt's transmission (what GM has elsewhere called the Power Electronics Module or PEM).
Back in June I proposed in post #8 of the following thread http://gm-volt.com/forum/showthread.php?t=4745 that the Volt transmission consists of a planetary gearset and three clutches connecting the input from the ICE with Motors A and B to the output to the final drive. Here is the drawing I made for that posting: .
If you compare figure 1 of the GM patent application to my drawing you'll see that they are functionally the same. What I called Motor A and B are called M/G A and B. The clutches I called CBRing, CAOut, and CAIn are called C1, C2, and C3. The only significant difference is that GM's figure shows an alternate optional configuration where C3 is eliminated in favor of a full time connection between the Engine and M/G A.
Of course, there is no proof that the Volt's transmission is what this patent application describes, but the timing (filed September 10, 2007) is right and it fits the statement by GM public relations guy Rob Peterson that the Volt has a planetary gearset and a number of clutches. It also fits the statements Volt powertrain engineer Alex Cattelan made in her interviews with Lyle last November. In addition, several people who've ordered Volts have posted the following description from the myvolt.com order tracking site:
If the patent application does describe the Volt's transmission it means that the Volt is NOT a single speed only transmission. It is an Electrically Variable Transmission (EVT). In addition, if the clutches C2 and C3 are engaged simultaneously there is a mechanical power path from the engine to the wheels. It may be that GM has chosen to never engage C2 and C3 simultaneously, but they could if they wanted to. (I don't know if that would be an infringement of Toyota's Hybrid Synergy Drive patents; I'm an engineer, not a patent lawyer.)
Last edited by Cab Driver; 09-22-2010 at 08:39 PM.