Meritor Developing Fuel-Saving Drive Axle
May 23, 2014
CAMERI, ITALY -- Meritor is developing a new drive axle intended to save fuel by reducing parasitic power losses resulting from oil churn. The company shared its plans for the new fuel-efficient drive axle at a press event for North American trade journalists, held at its axle plant in Cameri, Italy. Several prototype LogixDrive systems for the MS17X EVO drive axle are in prototype testing now with select European fleets.
The LogixDrive 17XEVO axle in European trim. It may come to North America in 2015, Meritor says.
The purpose of the system is reduce lube-related churning losses in the axle housing by temporarily reducing lube levels under certain driving conditions.
"We believe there's an opportunity to improve energy efficiency on the order of 0.1% to 0.2%," said Fabio Santinato, chief engineer for axles engineering for Europe. "It's a small but measurable improvement, and we are now doing evaluations for cost and life-cycle benefits."
The LogixDrive system uses an oil internal lubricant reservoir to store lube oil when it's not needed to cool the axle shafts, crown and pinion gears etc. During periods of high-stress operation, such as ascending or descending hills, the reservoir opens, releasing several liters of lube into the axle housing to provide the needed cooling.
"Segregating several liters of oil lowers the lube level in the axle, thus reducing the parasitic loses from churning," Santinato told reporters. "When the vehicle is operating at a steady state on an open flat highway, you don't need a lot of cooling. On a hill under a heavy load, the axle will get hotter and need more oil to cool the components. The tank opens and allows more oil into the axle to facilitate the cooling."
While the oil is not needed, the teeth of crown gear churns oil into an opening at the top of a reservoir built into the differential case. No pump is required to fill the tank. A normally open valve at the bottom of the tank is pneumatically closed to contain the oil. The system is failsafe, and will open in the event of a system failure. Draining the oil from the tank requires only gravity.
When full, the tank hold about 5 liters of oil, lowering the oil level in the axle to 7 liters from 12, and reducing the amount of oil that is churned up by the drive gears.
A cab-mounted electronic control unit monitors operating conditions for heat, torque, load, etc. to predict cooling needs of the axle. Santinato also noted the system can optimize oil change intervals by predicting the possible life expectancy of the lubricating oil.
Meritor says the 17X is currently the most popular drive axle in the European heavy-duty market, occupying positions at Volvo, DAF, Scania, and Iveco, among others as well as the motorcoach market. It was introduced to the market in 2007.
With the reservoir full, about 5 liters of lube oil are removed from the axle housing, lowering the fluid level and reducing churning losses.
In current applications, the 17X is rated for up to 88,000-pound gross combination weight with a 26,000-pound axle weight rating -- which are common European ratings. It's rated for up to 540 horsepower with 1,900 pounds-feet of torque and axle ratios of 2.64 to 6.17.
The high-efficiency 17XEVO was launched with Volvo in November 2013, allowing for faster ratios of 2.31 and 2.47, and a higher, 50-ton (100,000-pound) gross combination weight rating, as well as an upgraded torque rating of 2,065 pounds-feet.
The axle has not yet been introduced in North America, but company officials say North American fleet evaluations could begin sometime in 2015.
Additional lube oil can be drained from the reservoir by a cab-mounted ECM and a cable release-drain. The additional oil adds cooling and lubricating capacity under heavily loaded operating conditions.
The 17XEVO family are the first axles to use Meritor's patented laser welding process, which makes the differential case extremely rigid allowing for higher- torque capacity. Laser-welding eliminates 38 bolts in comparison with its predecessor, which yields a significant weight savings. Ring gear-to-case and case-to-case joints are laser-welded.
"Laser welding brings a very high energy level to a very localized area," said Santinato. "If you tried to use traditional welding methods to get those temperatures you would risk heat-related distortions to adjacent material."
Meritor says it is still early days for LogixDrive and the business case hasn't yet been solidified, but feedback from the first few fleets to uses the system has been positive.