2004 - 2009 Prius P112 Hybrid Transaxle (eCVT) Operation
Weber State University (WSU) - Automotive Technology Department - Transmission Lab. Toyota Prius Electronic Continuously Variable Transaxle (eCVT) model P112. How an eCVT Works. GM, Ford, and Nissan eCVTs are similar. The Honda Integrated Motor Assist System (IMA) is completely different.
eCVTs allow the engine to operate (when necessary) at the RPM for peak efficiency while increasing and decreasing the transmission drive ratio to change vehicle speed.
Questions:
1. List the four major components of an eCVT transmission
2. What is the purpose of the MG2?
3. To which piece of the planetary gear set is MG2 connected?
4. What is the purpose of the MG1?
5. To which piece of the planetary gear set is MG1 connected?
6. What is the purpose of the Internal Combustion Engine (ICE)?
7. To which piece of the planetary gear set is the ICE connected?
8. What are some advantages of an eCVT?
9. What are some disadvantages of an eCVT?
10. Tell me one thing you learned or found interesting in this video.
3rd Generation Toyota Hybrid (eCVT) Transaxles
A comparison and demonstration of the 2nd and 3rd generation Toyota hybrid transaxles
TIMELINE:
0:00 Introduction
0:51 Components from the 1st, 2nd, and 3rd generation Toyota Hybrid Transaxles
2:20 The torque limiting clutch from the 1st and 2nd generation transaxles
3:00 The torque limiting clutch from the 3rd generation transaxles
4:05 The torque limiting clutch and Internal Combustion Engine (ICE) drive the planet carrier
4:55 The oil pump driveshafts
5:55 The Motor/Generator 1 (MG1) drives the sun gear
7:45 The 1st and 2nd generation Motor/Generator 1 (MG2) drives the ring gear
9:21 The 3rd generation Motor/Generator 1 (MG2) drives the ring gear through a Motor Speed Reduction (MSR) planetary gearset.
13:40 The functional differences of MG2 on all three generations
18:00 Assembling the 3rd generation motor and gearsets
22:17 Review of components
24:28 Powerflow demonstration and modes of operation
24:48 Reverse
25:06 Forward at low speeds
26:38 Starting the ICE
29:18 Summary of video
For a more detailed overview of the Toyota Powersplit eCVT, see my 2021 video on the Toyota RAV4 Hybrid here • Understanding the Toyota RAV4 Hybrid
ABOUT US:
Weber State University (WSU) - Automotive Technology Department - Transmission Lab. A comparison and demonstration of the 3rd Generation Toyota Hybrid Transaxles used in the 2010-2015 Prius family (P410, P510), 2006 - 2017 Highlander HV family (P310, P313), and 2007-2017 Camry HV family (P311, P314). How an eCVT Works. eCVTs allow the engine to operate (when necessary) at the RPM for peak efficiency while increasing and decreasing the transmission drive ratio to change vehicle speed.
How a Hybrid e-CVT Works: Toyota 3rd Generation Hybrid Synergy Drive
Toyota's hybrid system is comprised of using a gasoline engine, two electric motors, a battery pack and a power inverter. These work together to propel the vehicle down the road, ultimately saving fuel and reducing emissions.
At the heart of the system is an electronic continuously variable transmission, or E-CVT. It is responsible for blending the power of the electric motors and gasoline engine to propel the vehicle, as well as recoup kinetic energy to charge the battery.
The E-CVT is unlike other CVT's that use a conventional cone and belt system. Instead a power split device, aka a planetary gearset, is used, with MG1, MG2 and the ICE connected to each part. MG2 always drives the wheels, while a combination of MG1 and the ICE rotating works to either charge the battery or add power from the ICE to the wheels for additional power.
In this video, the transmission from a third generation 2010 Toyota Prius Hybrid is torn down to see whats inside and how it works.
Hybrid Planetary Gearset Trainer
ConsuLab's EM-200-29 Hybrid Planetary Gearset Trainer is designed to help automotive instructors teach and students to understand the somewhat complex operation of a typical hybrid vehicle drivetrain.
Toyota Prius - Power Split Device (PSD)
The Toyota Prius is packed with some pretty high-tech stuff, but at the heart of the Hybrid Synergy Drive (HSD) is a simple little device called the Power Split Device, or PSD. The PSD is a planetary gear set that removes the need for a traditional stepped gearbox and transmission components, and also the familiar rev-lurch-rev-lurch of acceleration in an ordinary gas powered car. It acts as a continuously variable transmission (CVT) but with a fixed gear ratio.
If you have no mathematical or mechanical understanding of hybrid technology or even regular engine components, this will help you get a feel for how the PSD allows the car to use power from an internal combustion engine (ICE), as well as 2 electric Motor/Generators (MG1 and MG2), all spinning at different and variable speeds. The PSD even allows the smaller of the two Motor/Generators, MG1, to act as a starter for the ICE, thereby eliminating another component of a traditional gasoline engine.
The model below allows you vary the speed of both the ICE, and MG2. MG2 is the larger of the 2 electric motor/generators and is also referred to as the traction motor because its speed (RPM, or revolutions per minute) has a fixed relationship to the speed of the wheels. Dragging the MG2 slider, you'll see that the speedometer changes, while changing the speed of the ICE does not directly affect speed. Once you master that concept you'll start to see how the CVT function works. The ICE can spin faster or slower, depending on how much power is needed, and with either resistance or assistance from the electric motors the car can reach the desired speed while always keeping the ICE running at the most efficient rate possible.
Rotation speeds of MG1, MG2, and ICE are inter-dependent, and the speed of MG1 will always change when you vary the speed of either of the other 2. MG1 has a maximum rate of 10,000rpm in either direction (positive or negative) with a software limit of 6500 RPM if ICE is off. Using the model below, you can see for yourself why this software limit means the ICE will always spin if you're travelling above 42mph. And in case you were curious, yes MG1 can and often does change spin directions under normal driving conditions.
ICE rotation is limited to speeds between 1000rpm and 4500rpm. It can also stop completely, but anything between 0 and 1000 will force the slider up or down. That's because the internal combustion engine can't operate effectively below that speed. The hybrid computer knows, and will stop the ICE when it decides you don't need to use any gas, and start it again when you need more power, or higher speed from MG1.
