CVT and e-CVT FWD Hybrid Transmission
C
VTs and FWD hybrids cur- rently represent a small per- centage of vehicles coming
into the shops today. But it seems as though new designs are emerging every year; it may not be long before these transmissions represent a good portion of the cars we work on. This is where seminars, online train- ing and continuing education will be worth their weight in gold. There are two commonly-used variations: The Variator and Electronic.
Variator-Type CVT The Continuously Variable
Transmission, better known as the CVT, is fitted with two diameter- changing pulleys, also known as variators. A linked push-belt or pull- chain connects the pulleys. The diam- eter of the pulleys determines the input to output ratio. The ratio range can go from 2.61.1 reduction to 0.5 overdriven. This type of CVT uses one plan-
etary gearset for forward or reverse direction only. Most CVTs use a torque converter
with a lockup clutch. The Honda Civic, BMW MINI and Audi CVTs use a dampener drive plate; they have no converter. This style of CVT modulates clutch slip to manage slip/coupling dur- ing engagement. CVTs with or without a converter can be found in non-hybrid and hybrid applications. Some Honda and Nissan hybrids
use an IMA/integrated motor assist machine sandwiched between CVT transmission and the engine.
26
by Mark Puccinelli
members.atra.com www.atra.com
Application Guide, ID, and Fluid Requirements
The 2nd generation Prius has two drain plugs near one another, one for coolant and one for the transmission.
Electronic CVTs 101 Electronic Continuously Variable
Transmissions are for hybrid vehicles only. The e-CVT transmission, some- times referred to as a power-sharing transmission, uses the combination of the ICE (internal combustion engine) along with the internal electric motor- generators through a unique planet arrangement to drive the vehicle. This type of CVT drive is accomplished without the use of variator pulleys or push-belt/chain. Note: Some e-CVT transmissions
are fitted with a fixed-ratio drive chain. This drive chain connects the output
power of the motor generator to the final drive. Don’t confuse this chain with the push-belt/chain in a CVT transaxle. Listed on page 36 are the most
common front wheel drive CVTs and Hybrid e-CVTs on the road today. The manufacturers’ specified fluid is pro- vided for servicing data. Some of these units have a level
gauge (dipstick) for checking fluid level. Others have a fill-level check port. We’ll cover more on these and other innovative units in future articles. Stay tuned.
(Continued Page 36) GEARS August 2012
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