Hey,
The title explains it all. Say its in the "EV" mode and then I push the acceleration pedal down harder and the gas engine engages...
How come you don't hear the "cranking" noise regular gas engine cars go through? The gas engine in the hybrid just sputters on without hearing that "cranking noise"
Thanks

 

The TCH doesn't have a starter!

Actually, it uses one of the electric motors to turn the engine and when required, the CPU enables fuel and spark.

 

Essentially a regular car and a hybrid are both started by an electric motor. The difference is in the capabilities of the motor. A regular car's starter uses a 12V motor powered from a comparitively small 12V battery. That starter motor has to give all it can just to crank the engine at about 300 to 400rpm; and hopefully the car starts within a few seconds because if you ran a starter motor continuously for more than a minute or two it would burn itself out. Compare that to the relatively large hybrid traction battery powering a high voltage motor capable not only of rapidly spinning the engine up to 1000rpm for start but also capable propelling the entire vehicle indefinitely (as long as it has electricity), and it's easy to understand why one is noisy and the other quiet.

 

It's MG1 (Motor Generator 1). It can act as a generator (powering MG2 or charging the Traction Battery). It can also act as a motor (starting the ICE).

 

The generator can not actually move the car. It's a fairly small motor, when compared to the traction motor, yet still MUCH larger than a starter motor. IIRC it tops out at 10,000 RPM, and has enough torque to not only start the ICE with ease, but it is able to counter the power generated by the ICE while the car is stopped and in reverse.

 

A typical 4-cylinder engine has a 3/4 HP starter motor driven by a 12V battery. It cranks the engine up to about 400 RPM where the fuel will ignite and take over roughly getting the engine up to at least idle around 1000 RPM. As it cranks the engine, it is also turning all the accessories attached to the engine (alternator, water pump, power steering pump, and more).

In the TCH, the MG1 motor (along with MG2) can pull up to 40 HP from the 280V (?) traction battery and use a small part of that power (a couple HP) to rapidly spin up the engine to 1000 RPM. Fuel and spark are withheld from the engine until it is already up to idle speed (and valve timing is adjusted to also help the engine start easily). And, unlike the conventional engine, there are next to no accessories being driven directly by the engine that also need cranking during the startup (electric AC, electric power steering, starter solenoid, etc.).

So, even though there is more than twice the power applied to a much less loaded down engine with advanced computer coordination of everything, only a small part of the available power (less than 5%) is used to start the car, with the rest of the power used to continue smoothly accelerating the vehicle.

And thus, we have another wonderful aspect of the automagical marvel of the HSD.

-- Alan

 

Note that the Traction Motor (The big one) CAN NOT start the motor without the first being in motion. The traction Motor is linked the to final drive, and therefore only rotates with the wheels. (even when the car is in neutral...)

 

MG2 is tied to the wheels, and MG1 starts the engine. It makes no difference whether the car is moving forwards, backwards, or standing still. MG1 starts the engine, while MG2 provides enough counter torque to the engine drag while starting to maintain the car's motion or acceleration.

MG1 and MG2 are both 55 HP motors. I'm not certain, but I believe the Prius motors are slightly different sizes, but the TCH motors are about, if not exactly the same size/power. Most normal driving conditions will have one motor (generator) powering the other, which is why the motors can generate or use more power than the battery is capable of supplying. At low speeds, MG1 taps power from the engine and feeds it to MG2 ("low gear"). At high speeds, MG2 taps power from the engine/wheels and feeds it to MG1 ("high gear" or "overdrive"). The difference between the MG1 power in (or out) and the MG2 power out (or in), is the amount of power the charging or coming out of the battery.

-- Alan

 

Hrmm. I'll have to find it, but I'm pretty sure the Toyota FRM states that the ICE will be started by the momentum of the car, once it's above a certain speed. I'll also have to check on the size of MG1 and MG2 in the TCH. I don't think they are the same size.

 

Via the CVT, which is actually a planetary gearset, one of the motor-generators, MG1(?) can "crank" the ICE while the other motor-generator MG2(?) turns in a direction and rate so as to neutralize any rotation of the output, final, drive shaft.