Bearings - 2010-09-14
NSK has developed a long-life cage and roller assembly with planetary shaft for the swing/travel reduction gear of construction machinery such as hydraulic shovels. This assembly offers twice the service life of conventional products - long life contributes to improved durability and reliability of the swing/travel reduction gear.
Planetary shafts, and cage and roller assemblies for swing/travel reduction gear are used in severe lubrication conditions where abrasion powder from gears and other foreign material can become mixed with the lubricant. In addition, since the swing and travel of construction machinery typically occurs at low speeds, an oil film does not readily form on the planetary shaft, and cage and roller assembly, creating further lubrication challenges.
In newly developing countries, the demand for new social infrastructure and resource development has increased rapidly in recent years. This has resulted in construction machinery being used under harsher conditions, being operated continuously for long periods of time, and being driven long distances over unpaved roads. Consequently, there is a growing need for planetary shafts, and cage and roller assemblies for swing/travel reduction gear that offer a longer service life in harsh environments.
By developing the planetary shaft, cage and roller assembly as a set, NSK has created a product with the following superior characteristics - all of which meet the need for longer service life.
1. Improved orbital plane offers greater reliability
The orbital plane of the planetary shaft and rollers is given a smooth mirror finish, enabling the formation of an even and sufficient oil film, thereby improving reliability.
2. Special heat treatment brings improved surface fatigue strength
Using a special heat treatment on the planetary shaft and rollers increases the fatigue strength of their surfaces making them resistant to abrasion powder from the gears and other foreign material in the lubricating oil. This increases service life in an environment where foreign matter is present.
Performance of the new product
With a service life more than twice that of conventional products, this product contributes to the following functional improvements in travel/swing reduction gears:
1. Increases durability and reliability under harsh conditions of use such as continuous operation for long periods of time
2. Reducing the frequency of maintenance improves work efficiency
3. The long-life cage and roller assembly with planetary shaft is itself more compact and lightweight, helping to minimise the size of travel/swing reduction gears
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