Two new Jatco continuously variable transmissions will offer OEMs significant fuel economy benefits when they enter production later this year. The two units—CVT7, designed for input torque below 180 N·m (133 lb·ft), and the CVT8, capable of handling up to 380 N·m (280 lb·ft)—feature high ratio spreads, reduced internal friction, and lighter-weight, more compact packages.
Jatco will have cutaways of both CVTs on display at the 2012 SAE World Congress, booth 1024. The design execution of the CVT7 impressed the AEI editors to a high degree, making it one of the magazine’s 2012 Tech Award recipients for supplier innovation.
The CVT7 (which is known internally as the APO) replaces Jatco’s CVT-1 and will be used in the next Nissan Versa, among other compact vehicles. It adds a planetary gearset engineered into the CVT, which provides a 7.3 ratio spread for improved efficiency. It also features a slimmer drive belt, and its new pulleys with a smaller internal diameter provide a tighter “wrap” at launch, according to engineers.
The high gear ratio spread provided by the planetary gearbox reduces the ratio coverage of the belt-pulley to 4.0, which in turn reduces the size and corresponding weight of the pulley system (normally a significant component of the CVT unit), according to Jatco engineers.
The smaller-diameter pulleys allowed the engineering team to relocate the primary pulley to a more elevated position inside the CVT housing. This repositioning allows both the pulley and belt to rotate without touching transmission fluid, thereby reducing fluid friction.
The addition of the auxiliary gearbox allows the CVT to function more frequently in its most efficient 1:1 pulley ratio configuration. Traditional CVTs utilize only 1:1 pulley ratios for a brief period. In high gear the CVT7 is capable of maintaining this efficient condition during most normal driving conditions, the company claims.
CVT8 for higher input torque
Jatco’s new CVT8 (coded ARO), which appears first in Nissan's 2013 Altima, is key to that car achieving a 38-mpg highway fuel economy rating. Branded “Xtronic” by Nissan, it is considered to be that automaker’s “global strategic” CVT for higher input torque capacity. In that role it uses two different internal drive systems, depending on engine application. A belt drive is used on all four-cylinder models (shown). CVTs designed for use with V6 engines feature a chain drive. The two applications differ in the size of their torque converters and number of clutch plates, engineers say.
The CVT8 will replace Jatco’s CVT2 and CVT3. In the new Altima it will be used with the 2.5-L I4 and 3.5-L V6 for North America. See related story http://www.sae.org/mags/aei/10886.