A Class 8 commercial truck loaded with 159,080 lb (72,160 kg) of concrete and iron was at a standstill two-thirds of the way through a 15% incline, but the upward climb resumed without the tractor-trailer backsliding.
Simultaneously engaging the handbrake and the throttle is a typical way for a truck driver to prevent the tractor-trailer from rolling backward, "but the driveline, the transmission, the engine, and the clutch are really being abused in order to get that control," points out Michael Holahan, Program Manager for Eaton Corp.'s Global Transmission Business.
During a recent media event at Eaton's Marshall, MI, proving ground, journalists drove various on-highway and off-highway heavy-duty trucks equipped with Eaton's new UltraShift PLUS automated mechanical transmission featuring fully automated clutch controls technology, a hill-start aid feature, and intelligent shift selection software.
"Shifting is done automatically. The system monitors the speed of the vehicle, calculates the weight of the vehicle, assesses the grade being ascended or descended, and factors in the driver's throttle commands to decide if a gearshift is needed," said Samir Mazahem, Eaton Corp.'s Heavy-Duty Transmission Division Chief Engineer.
UltraShift PLUS shares its basic architecture with Eaton's previous-generation UltraShift transmissions for on-highway uses.
"The main box, meaning the mechanical piece, is pretty much identical, but the next-generation UltraShift PLUS modified the gears for faster shifting; upgraded the bearings, gaskets, sealants, and electrical harnesses; and added a sight glass for checking the oil fluid level. A low-capacity inertia brake—located inside the clutch area—replaces a high-inertia brake, which leaves room for the power take-off (PTO). In addition, the new automated mechanical transmission introduces wider overall gear ratio coverage combined with better low-speed clutch control to improve performance," said Mazahem.
Unlike UltraShift, UltraShift PLUS uses a self-adjusting clutch with an electric clutch actuator to open the clutch in about 200 milliseconds, according to Mazahem. "The clutch and the transmission were designed as one system, which means the clutch and the transmission were optimized all-in-one," Mazahem explained, adding that Eaton's electric clutch actuator is a carryover component from hybrid-electric medium-duty trucks.
The UltraShift PLUS clutch automatically closes to prevent freewheeling—a crucial safety feature, especially when the truck is moving from a standstill on an incline or launching in forward or reverse gears.
"We've designed a highly integrated system that uses various sensors, including a grade sensor, and with the increased logic in the new controllers and the tie-in to the antilock braking system, the UltraShift PLUS has been engineered to ensure that the transmission functions consistently and reliably," said Holahan.
Eaton engineers spent hundreds of hours at the proof-of-concept stage obtaining information from fleet owners and truck drivers in North and South America, Australia, Europe, the U.K., and Asia. The engineers rode in the cabs of Class 8 trucks as drivers navigated the terrain at mining sites, stacked and transported timber during logging operations, prepped construction fields, hauled cargo to and from loading docks, and performed other on- and off-highway driving tasks.
Engineers asked questions, shot videotape, and used data-acquisition systems to amass a comprehensive portfolio "to get a real-world perspective about how a particular vehicle is used day after day," said Shane Groner, Principal Engineer for the Electric Clutch Actuation on UltraShift PLUS.
Added Todd Simione, UltraShift PLUS Systems Engineer responsible for controls and performance integration, "Smooth clutch control and maneuverability in a reliable product were the primary wants from drivers and customers."
The transmission provides automatic, manual, and low mode selections as well as a creep function for maneuverability with continuous low-speed control. It also can be taken out of gear and put in neutral.
"In the past, it was sometimes difficult to get into neutral gear when the driveline and axle were locked up. As soon as you turn the key off, the system automatically pulls the transmission to neutral. We now have that mechanical efficiency in the gears where we can bring the transmission to neutral every time," said Mazaham.
UltraShift PLUS has six platform designations: Linehaul Active Shifting (available in overdrive and direct drive), Multipurpose High Performance (MHP), Multipurpose Extreme Performance (MXP), Vocational Construction Series (VCS), Vocational Multipurpose Series (VMS), and Vocational Extreme Performance (VXP).
The Linehaul series has a torque range from 1450 to 1850 lb·ft (1965 to 2510 N·m) with 10 forward and two reverse speeds. Torque range for the Performance series is 1450 to 2250 lb·ft (1965 to 3050 N·m), with the MHP having 13 forward and three reverse speeds and the MXP having 18 forward and four reserve speeds. The Vocational series torque range also is 1450 to 2250 lb·ft, with the VCS having 10 forward and three reverse speeds, the VMS having 11 forward and three reverse speeds, and the VXP having 18 forward and four reverse speeds.
"One size does not fit all, so that's why Eaton is offering six different platforms. The UltraShift PLUS provides the best behaviors of a manual transmission in the simplicity of an automatic," said Holahan.
More than 25 fleets in North America tested the UltraShift PLUS. Full production for the next-generation automated mechanical transmissions is slated to begin in early 2010.