Theory of Operation

John's site is very good John's Stuff - Toyota Prius and more Look in Prius info.

Hobbit's articles seem just over my head, perhaps they will be what you want Hobbit's techie-rants

 

I think the earlier references are excellent if somewhat sparse sources. I would recommend these SAE papers to address architecture:

• Prius die de wereld "The Prius That Shook The World" - translated by Albert Yamada and Masako Ishikawa
• 2000-01-C042 - Shinichi Abe - covers development of the NHW11
• "Development of Electric Motors for the TOYOTA Hybrid Vehicle "PRIUS" - Kazuaki Shingo, Kaoru Kubo, Toshiaki Katsu, Yuji Hata - another article comparing and contrasting the NHW10 and NHW11 motors.
• 2004-01-0064 - Koichiro Muta, Makoto Yamazaki and Junji Tokieda - covers development of the NHW20
• ORNL/TM-2004/247 - C.W. Ayers, J.S. Hsu, L.D. Marlino, C.W. Miller, G.W Ott, Jr., C.B. Oland - Evaluation of 2004 Toyota Prius Hybrid Electric Drive System Interim Report

These articles will give you a foundation, an ubber view, to how the Prius works. But I would also recommend:

• "Hybrid Electric Vehicles: Control, Design, and Applications" Prof. Chris Mi, Depart.ment of Electrical and Computer Engineering, University of Michigan

Now it may take a little while to assemble all of these paper so I'll offer my view:

The engine uses a delayed, intake valve closing so part of the fuel-air charge is pushed back into the intake manifold. On average, the compression stroke is 8 to 1 but after ignition, the power stroke is 14 to 1. What this means is the Prius engine approaches the thermodynamic efficiency of a diesel because of the high expansion ratio and lower intake overhead compared to an ordinary gas engine. It keeps the low emissions characteristics of a gas engine without the NOx problems of a diesel.

The transmission is a computer controlled, "continously variable transmission," that optimizes the torque load on the engine. The transmission to the maximum extent possible, keeps the engine in the maximum, fuel efficiency, power band. Each successive Prius has done a better job of keeping the engine in the 'sweet spot.'

The traction battery and MG2 in the transmission are powerful enough that at many speeds under 42-46 mph, the Prius can sustain speed on electric only power. This means the engine can only run as needed in very efficienct power bands to sustain speed and recharge the traction battery.

When the brake is applied, MG2 generates as much charging current as possible to recharge the battery. This converts part of the kinetic energy into traction battery energy.
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I hope this helps.

Bob Wilson

 

My most favorite is Graham Davies site.
Graham's Toyota Prius
Go to "Understanding the Prius" from the side menu.

Ken@Japan

 

techinfo.toyota.com contains repair manual, training docs and other technical info. In particular, the New Car Features Manual contains substantial theory of ops not found in the repair manual. If you subscribe to that website I suggest that you at minimum download NCF for the 2001, 2004, and 2010 model years so that you can track the evolution of the HSD over three Prius generations.

 

Here's how I picture things happening:

1. Driver sets pedal position
2. ECU looks up wheel power value by using pedal position and vehicle speed in a table (tables are different for each mode, eco, normal, power)
3. ECU takes battery SOC and looks up battery power target (supply power if over target SOC, charge if below target SOC)
4. ECU finds ICE power = wheel power - battery power target (positive if supplying or negative if charging)
5. ECU looks up ICE speed/load from a table describing the operating line on the engine map. For every ICE power, there is a best (target) speed/load point.
6. ECU sets MG1 to hold engine speed at target and receives power P1 from MG1
7. ECU sets throttle/EGR to achieve target load
8. ECU sets MG2 power out = P1+battery power target
9. Energy balance goes to / comes from battery

It's more complicated than that with the engine shutdown at low loads, fuel cut/run on MG2, max MG1 speed, and the engine stop/start hysteresis. But, that's the way I view the control logic when the ICE does run.