[crazyjncsu]

That’s what I thought too, but it’s not the case.

The transmission of a traditional ICE vehicle is a component commonly prone to failure due to reliance on clutches, friction couplings, gear engagements, etc.

Hybrids replace this transmission with one composed of two electric motors and planetary gear sets. One or both of the motors also act as generators. It’s complex, but the highly variable speed of the output shaft is managed almost purely by torque splitting of the planetary gear sets along with routing of electrical energy within the system— no clutches or gear disengaging/reengaging.

And the ICE engine itself has an easier time (often Atkinson cycle) because the electric motors can provide much of the responsiveness to immediate power demands, allowing the ICE to operate in a much less stressful power band.

[masklinn]

It reads like you’re describing a series hybrid where the ICE feeds into an electric generator which feeds into a battery or electric motors.

That is not how most hybrids work. That’s how almost none of them works in fact, although it is how diesel electric works on large vehicles (an electric transmission essentially).

[pbmonster]

No, he's right. If you're interested, read about the Prius e-CVT transmission. It's pretty amazing.

Essentially, it connects the ICE and two different electric motors to the same drive shaft. By spinning the electric motor forwards, backwards or using it as a generator, it can regulate torque going to the wheels for a wide band of RPM. At the same time, torque and RPM coming out of the ICE are kept in a much smaller band.

But yes, the ICE is still directly connected to the wheels.

[AYBABTME]

In a planetary gear setup, there's three different rotating planes you can hook onto. Traditionally one is free, two are rotating. But if instead, one is the output, another one the ICE engine (with electric boost) and the third one is another electric engine, the electric plane can change the influence of the output plane on the ICE plane, effectively intermediating the RPM and torque it sees.