Development of ¡°High function cradle bearing¡± for Disc Brakes of Large Commercial Vehicles

Development of ¡°High function cradle bearing¡± for Disc Brakes of Large Commercial Vehicles NTN Corporation (hereafter NTN) developed a ¡°High function cradle bearing¡± that enables a life of more than twice that of conventional-type cradle bearings, and improves the assembling efficiency by the new non-separable structure. In Japan, drum brakes are primarily used for large commercial vehicles such as trucks and buses because they are superior in wear performance. On the other hand, in the North America and Europe, disc brakes are mainstream for the reasons of high stability and anti-fade characteristics*1 under high speed driving conditions. Components for disc brakes are maintenance free. Accordingly, a long service life to last for the entire life of vehicle and a high reliability are required for those components. With this ¡°High function cradle bearing¡±, the configuration of the cage pocket stake has been improved so that the quantity of rollers and roller diameter is nearly the same as a full complement type bearing. Additionally, a special heat treatment is applied to the outer ring and rollers. By these improvements, the bearing service life is more than doubled, and fretting wear*2 is reduced by up to 50% when compared with a conventional bearing. This product will contribute greatly to improving the reliability of disk brakes. Also, the unique design of the outer ring retains the cage component, leading to a non-separable structure of the outer ring, cage and roller assembly. This will make initial assembly work at the customer easier and allow for improvements in productivity. To start with, NTN will market this new product to disk brake manufacturers in the North America and Europe where the market demand is high. *1 anti-fade characteristics: Phenomenon that the friction material temperature increases and the brake effectiveness decreases due to braking during high speed driving or continuously repeated braking during down hill driving. *2 fretting wear: Defect due to micro relative oscillating slide movement. Phenomenon that wear generates locally when contact portions in a bearing at stationary condition receive micro vibrations, is called a fretting wear.