|The current Greenline BAS hybrid powertrain. Click to enlarge.|
GM will have its Saturn Aura Greenline Hybrid sedan on sale by the end of 2006, according to Jill Lajdziak, Saturn’s general manager. Saturn introduced the Aura hybrid during the New York International Auto Show. (Earlier post.)
The Aura uses the same hybrid powertrain as the Saturn VUE Greenline hybrid: a 2.4-liter Ecotec engine with a Belt-Alternator-Starter (BAS) system augmented with a 36-Volt NiMH battery pack.
|The hybrid accessory drive. The dual tensioner assembly that controls the motoring and generating loads is patent pending. Click to enlarge.|
Functionally, the VUE hybrid system offers start-stop and regenerative braking—features expected in a simple Belt Alternator Starter system. GM, however, developed a dual tensioner assembly for the hybrid accessory drive (the motor/generator package) that will transfer a small amount of torque to the drive system for very brief periods of time.
The assembly combines an hydraulic strut tensioner and a friction-damped rotary tensioner on a common pivoting arm to the control the bi-directional loads (motoring and generating).
This assistance takes three forms: electrically motored creep at startup, light power assist during acceleration, and light electric mode during deceleration.
The system consists of six elements:
The electric motor/generator unit that replaces the alternator, and is capable of 156 Nm of auto-start torque;
Engine-coolant cooled power electronics that control the motor/generator unit and provide 12-volt vehicle accessory power;
A Cobasys NiMHax 36-Volt NiMH hybrid battery pack capable of delivering and receiving more than 10 kW of peak power;
An engine control module;
An engine accessory drive with new, dual-tensioner assembly and cord belt that enables transfer of motoring and generating torque;
Hybrid-enabled Hydra-Matic 4T45-E electronically controlled four-speed automatic transaxle that includes an auxiliary oil pump and unique hybrid controls.
GM is using the BAS-based Greenline hybrid system to try to deliver a simple hybrid architecture flexible enough—and at a sufficiently low cost—to implement globally on a broad spectrum of both powertrains and vehicles.
The Saturn VUE hybrid offers an estimated 29 mpg US combined and is priced at less than $23,000, compared to the Ford Escape hybrid with 33 mpg US combined at a starting price of $27,500. The Toyota Highlander and Lexus Rx 400h both are rated at 30 mpg US combined, and priced at $33,000 and $48,500 respectively.
GM has yet to indicate performance specifications on the Aura Greenline or pricing.