2k1Toaster said:
kubel said:
asimba2 said:
Again, it says "may include a nonelectrical source of power designed to charge batteries." That's how a Volt works, but not a Prius.
If the PIP does not qualify for this reason, the Volt doesn't qualify either, since it can, under certain circumstances, use the ICE to help power the front wheels directly. At that point, the Volt is merely a more electrically dominant version of the Prius.
No that means that the Prius
ALWAYS qualifies where the Volt does not.
The Prius never drives the wheels directly with the engine. I don't know where asimba2 is getting that from. The volt does clutch in the engine at higher speeds (which is advantageous is some regards). The Prius has no clutch, no way to change gears, it is a static planetary gearset.
Notice how the outer ring gear driven by MG2 is the only source powering the wheels. The best the engine can do is spin the planetary carriers and use MG1 in the inner circle to generate power to be spent by MG2 going forwards and backwards.
So the Prius is an electric vehicle with a gasoline engine that powers it. Even the non plug in versions.
Ah, no, not quite.
Anyone who has driven a Prius knows that the engine speed can vary independent of the speed of the car. That's why the Prius transmission is called an eCVT or electrically controlled continuously variable transmission. It effectively changes gears....
The Prius and Volt have similar although not identical planetary gear transmissions. The Prius has no clutch so the engine is, as you say,
ALWAYS connected to the wheels via the planetary gears. The planetary gears are all mechanically connected at different fixed ratios to each other and to the drive axles that move the front wheels. That clutch in the Volt allows the engine to be disconnected from the planetary gears. Neither the Prius or the Volt would go anywhere if the gas engine were running by itself without an electric motor active.
There are three gears in a planetary arrangement. The engine is attached to one. The wheels are attached to another. One of the two electric motors is attached to the third. By default, the gear connected to the running engine would spin and the gear with the motor would spin freely leaving the gear attached to the wheels going nowhere. This is similar to the planetary gear in a conventional differential of a car stuck on the side of a road -- the engine is spinning one gear, another gear is connected to a wheel that is stuck in some mud and the third gear is connected to the other wheel that is hanging free and not contacting the road and is therefore doing all of the spinning.
The Prius engine spins the gear it is attached to and generates electricity with its smaller generator motor attached to a second gear which causes that motor to resist spinning and that forces some of the mechanical power to spin the gear attached to the wheels. Some of the power being generated by the motor is used by the big motor to help spin the gear attached to the wheels.
In other words, the engine spins the Prius planetary carriers, MG1 attached to the Sun gear generates electricity, some mechanical force also spins the ring gear and power from MG1 is used to spin MG2 which is attached to the ring gear along with the wheels.
So, the Prius normally has both electrical and mechanical power flowing to the wheels. In the Prius, when the engine is actively running there is always a mechanical flow of power to the wheels unless the brakes prevent the wheels (and therefore the ring gear) from spinning.
The Prius can continuously vary the load or effective gearing on the gas engine by varying how much electricity is generated by MG1 and therefore how much power flows electrically from MG1 to MG2 versus how much flows mechanically from the planetary carriers to the ring. These effective combined variable ratios keep the gas engine operating at its most efficient rpm and torque while most of the power flows efficiently through the mechanical path and avoids the conversion from mechanical to electrical back to mechanical. This is what makes the Prius highly efficient. The electrical flow of power from MG1 to MG2 effectively
bypasses the mechanical path that would have otherwise gone through the fixed gearing ratios so varying the electrical flow varies the overall effective gearing on the engine.
The Volt transmission operates similarly to a Prius transmission at a conceptual level but there are differences in the way the engine and motors are arranged and hooked up to the planetary gears. Unlike the Prius, the Volt can unclutch the engine and the smaller generator motor from the planetary gears and operate entirely as a series mode hybrid while stopped or all the way up to high vehicle speeds.
When clutched to a planetary gear, the main motor on the Volt's second planetary gear actively resists spinning using electricity generated by the smaller generator motor attached to the engine and this forces the mechanical power to spin the third gear which is attached to the wheels.
Neither the Prius or Volt connects the gas engine "directly" to the wheels. In both cars the engine is connected to a planetary gear member and drives the car through an indirect mechanical path that is modulated by the spinning or resistance of the other two planetary gears members.
