> I don't know anything about a "power split" transmission, but isn't that the sort of thing a differential gear set does very well at?
A planetary gear set is often a component of a power split transmission, but there are other components. The key thing is that it is able to blend power from multiple sources [1]
> The thought occurs to me to make the rear wheels powered by the ICE and the front wheels electric.
> Then no wacky transmissions.
The problem is you then have a car that switches the basic drive characteristics (FWD to RWD) depending on what fuel you are using. Everything from the chassis to the suspension in a car is designed according to where the power is coming from.
Mitsubishi addressed this problem in their Outlander PHEV by using 2 electric motors, 1 on each axle, with the front axle being supplemented by the ICE engine (via a 1 way clutch) when more power is needed than the small battery can output, or when the battery is depleted [2]. This doesn't completely solve the problem but makes it less noticeable, and eliminates the need for a mechanical driveshaft between the front and rear.
Also, this approach only switches the vehicle from FWD to AWD, not from FWD to RWD. It's the same with dual motor EVs, they switch from 1 axle drive to 2 axle drive - they don't switch from one axle completely to the other. Imagine your car suddenly becoming RWD when the battery was depleted. That would be weird, and potentially even dangerous.
A planetary gear set is often a component of a power split transmission, but there are other components. The key thing is that it is able to blend power from multiple sources [1]
> The thought occurs to me to make the rear wheels powered by the ICE and the front wheels electric.
> Then no wacky transmissions.
The problem is you then have a car that switches the basic drive characteristics (FWD to RWD) depending on what fuel you are using. Everything from the chassis to the suspension in a car is designed according to where the power is coming from.
Mitsubishi addressed this problem in their Outlander PHEV by using 2 electric motors, 1 on each axle, with the front axle being supplemented by the ICE engine (via a 1 way clutch) when more power is needed than the small battery can output, or when the battery is depleted [2]. This doesn't completely solve the problem but makes it less noticeable, and eliminates the need for a mechanical driveshaft between the front and rear.
Also, this approach only switches the vehicle from FWD to AWD, not from FWD to RWD. It's the same with dual motor EVs, they switch from 1 axle drive to 2 axle drive - they don't switch from one axle completely to the other. Imagine your car suddenly becoming RWD when the battery was depleted. That would be weird, and potentially even dangerous.
1. https://www.sciencedirect.com/science/article/abs/pii/S00941....
2. https://www.youtube.com/watch?v=LZ__5-V6CTI