2011

[Major improvements to durability in severe environment such as on unpaved roads, in muddy water, and cold climates!]

NTN Corporation (hereafter, NTN) has developed the “Hub bearing for severe environment”, which provides highly reliable drivability and vehicle transportation, even in conditions such as on unpaved roads and in cold climates.

Hub bearings, which support the tires and wheels of vehicles, are subjected to a large amount of vibrations (load) and shocks, and often need to be used in muddy waters in emerging markets and similar areas where roads have not been fully developed. As a result, the raceway surface of bearings can become indented, causing muddy water to penetrate the hub bearing unit. This can wash away grease, cause deterioration and reduce the oil film layer (or lubrication) between the raceway surface and the rolling element (balls), which increases the wear in the bearing.

The use of long-distance railroad transportation for delivering completed cars to dealers has increased in recent years. In cold climates, the vibrations that are transferred due to shocks from gaps between rail tracks during transportation can cause fretting wear* in the raceway surface of hub bearings.

Development of the new “Hub bearing for severe environment” has focused on three main issues: load and shock, muddy water, fretting at low temperatures. To increase resistance against load and shock, the internal design of the hub bearing has been optimized, reducing the indentation depth of the raceway surface to 1/4 that of conventional products. The penetration of muddy water into the hub bearing has been reduced by optimizing the shape of the contact area between the hub bearing seal, which has more than doubled the operating life against muddy water resistance. The use of a special grease reduces low-temperature fretting by preventing contact between metallic components. This has improved resistance against fretting wear by 1/10, particularly when used in cold climates.

NTN will exhibit the new hub bearing at the “42^nd Tokyo Motor Show 2011”, held at Tokyo Big Sight between December 2 and 11, and aims to market it to customers globally, including those using bearings in severe environment.

* Fretting wear:
concentrated wear that occurs between two surfaces that are in contact due to vibrations with a small amplitude. The main cause is due to insufficient lubrication.

Features (compared to conventional NTN products)

(1) Internal designed for improved load resistance	reduces indentation depth of the raceway surface shoulder to 1/4 (increased raceway surface shoulder height, straight joins between the raceway surface grooves and shoulder)
(2) Use of a muddy water resistant, long-life seal	more than doubles the operating life against muddy water resistance (inner side: seal lip contact point reviewed, outer side: use of a ridged structure)
(3) Use of special grease	reduces the depth of fretting wear to 1/10 (at -50°C)

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