GKN Driveline Says Countertrack Constant Velocity Joint Technology Saves Fuel

17 July 2009

GKN Driveline countertrack technology for fixed joints. Top: sideshaft SX CVJ. Bottom: propshaft PX CVJ. Click to enlarge.

GKN Driveline’s new constant velocity joint (CVJ) technology “countertrack” offers potential for fuel savings, according to the company. CVJs allow the transmission of power through a variable angle  at constant rotational speed; they are used on both ends of front-wheel drive (FWD) axle shafts and also in other vehicle applications as well. Most vehicles today have two CVJ driveshafts per vehicle and some SUVs have up to seven.

GKN cited independent engineering analysis showing the countertrack technology improves fuel economy by an average of 0.2 mpg US on a typical FWD mid-size vehicle, resulting in a CO₂ emission reduction of 1g/km. For special vehicle segments such as SUVs, GKN said that case studies have shown that countertrack technology can lead to CO₂ emission reductions of 3g/km and more.

Besides the highlighted impact on vehicle efficiency and fuel economy, significant weight saving can be achieved by applying GKN’s countertrack. A weight reduction of up to 29% is possible, which translates to a 9 lb (4.0kg) saving for a typical FWD mid size car in production today.

Today’s CVJ driveshafts are based on designs developed by Alfred Rzeppa in the mid-1930s. Originally referred to as “ball-type universal joints,” they first appeared on the front-wheel-drive Cord 810/812 in 1936.  Although modified and improved, the basic design for these components has remained unchanged for 70 years.

A Rzeppa joint consists of a grooved spherical inner, and an enveloping outer shell. Each groove guides one ball. The design breakthrough for the countertrack technology is to use sets of opposed ball tracks with a unique track shape profile.

By combining sets of opposed tracks with a specific track shape profile for operating angles, new levels of performance can be achieved for driveshaft products.

Opposed set of tracks and S-shaped tracks in a sideshaft CVJ. Click to enlarge.

For sideshafts, the opposed tracks are used with an S-curve track shape to achieve high steering angles up to 50 degrees. An option exists of 52 degrees for improved low speed vehicle steerability. For propshafts, the opposed tracks are used with a flat radial offset track shape to achieve high endurance at a wide operating angle range.

Countertrack technology results in finely tuned driveshafts for each vehicle platform and powertrain combination.

The first production vehicles with countertrack technology will appear in the market during 2009. Overall, 38 applications are now in the customer vehicle validation phase and three million countertrack CVJs are expected to be manufactured in 2010.

Resources

• GKN countertrack