Another Truck New Guy

The Prius uses quite a lot of CPUs to control the car. Both the throttle and brakes are drive by wire, mere suggestions to the CPUs of what you hope to acheive. The 'transmission' never shifts or engages different gears. (the only mechanical change is a parking pawl that keeps the car stationary in Park) The ICE never drives the wheels in reverse, the electronics rotate the motor (MG2) backwards so the car goes backwards.

The two drive motors and the ICE are connected to a planetary gearset, MG1 is the sun gear and is most often used as a generator, although it is also the starter motor and sometimes a motor for propulsion. MG2 is 5 times as strong and is directly geared to the wheels on the ring gear, it is most often a propulsion motor, unless you press the brake pedal, then it does regenerative braking, charging the traction battery. (The 12v battery helps start the computers, and powers the accesories when the car is off)

The Internal Combustion Engine is on the planetary gear, and sends 28% of its energy to MG1 on the sun gear and 72% to the ring gear with MG2. If the traction battery does not need all 28%, then MG1 sends power to MG2 as well.

I find this simulation informative:
A simulation of Prius's Planetary Gear

You can apply power to the Motor MG2, and the engine, and the Generator (MG1) will adjust. If you click where it says THS, (2001 -2003) it will switch to THSII, the system used on 2004 to 2009 Prius.

For completeness I should mention N, where both motors are off, so the ICE has nothing to push againist, no battery charging can happen in N. B is a mode to use the ICE as a Jake Brake. If you go down an incline of over 600 feet, you will have recharged the Traction Battery, so the motors have no way to bleed off energy and you will have to rely on the Disc/Drum brakes. B mode can use the ICE as an air pump to help bleed of energy going down long hills (like compression braking)

 

Prius is a car that defies many conventional wisdoms that many gear-heads love to hate.

To understand Prius, you need to have an open mind to see the shortcomings of the current cars/trucks. Prius is highly efficient because it use more energy from the gasoline that would otherwise wasted.

It starts from the "more efficient" ICE with Atkinson cycle. It recovers braking energy, exhaust heat and sun light to get the most MPG.

Bill Gates referred to Prius as a "software car" because the majority of the complexity is in the software.

 

If you thinks thats mind boggling, go to you Toy dealer and take one for a test drive. Don't freak when the engine turns off at the stop signs!

 

Mechanically, the transmission is quite simple and compact. The biggest problem is that it is so different from what we are accustomed to in non-hybrids.