Bearings – Rotary bearing – Antifriction bearing
Patent
1990-09-10
1992-09-29
Hannon, Thomas R.
Bearings
Rotary bearing
Antifriction bearing
384492, 384625, F16C 3310, F16C 3362
Patent
active
051509741
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
This invention relates to a grease-sealed bearing having grease sealed therein and particularly to one prevented from peculiar peeling which appears especially on the rolling surface of the bearing.
BACKGROUND ART
In recent years, as automobiles are getting more compact in size, lighter in weight and higher in efficiency, their electrical parts and accessories are required not only to be small in size and light in weight but also to have high performance and high power. In order to meet these requirements, with an alternator or a solenoid clutch for a compressor as shown in FIG. 4, it is necessary to compensate for a decrease in power owing to a reduction in size by increasing its rotating speed. In order to increase the speed, its pulley has to be as small as possible. Further, in order to prevent a reduction in the transmission efficiency, it is necessary to form the pulley 6 with a plurality of grooves 7 for receiving power transmission belts as shown in FIG. 4 and to keep the tension of the belts high. As a result, high-speed rotation and high load act on a bearing 1 supporting the pulley 6.
Such high-speed rotation and high load can cause peeling on the rolling surface of the bearing. Unlike an ordinary peeling occurring on the rolling surface or in its superficial area owing to metal fatigue, this type of peeling indicates a peculiar destructive phenomenon which has started from a deep area in the bearing. Owing to this peculiar peeling, the actual life of the bearing becomes shorter than its calculated life expectancy.
Generally speaking, with a grease-sealed bearing, the life of the grease is shorter than the rolling life of the bearing itself and thus the life of the bearing is determined by the life of the grease.
But, a decrease in the lubricity of the grease is not the only cause of the occurrence of the above-described peculiar peeling. Namely, from the fact that no influence of heat release such as coloring is seen on the rolling surface of the bearing even if the peculiar peeling appears thereon, it is apparent that the peeling is not caused by the metal-to-metal contact resulting from a decrease in lubricity. Also, the life resulting from the peculiar peeling is shorter than the durability resulting from the life of the grease.
Such peculiar peeling can be prevented by relaxing the conditions of use; e.g., by increasing the size and thus the load capacity of the bearing or by lowering the tension of the belts. However, increasing the size of the bearing leads to an increase in the size of the related parts. This will increase the cost and make it difficult to reduce the size of the machine and to improve the transmission efficiency.
In view of the aforementioned problems of the prior art, an object of the present invention is to provide a grease-sealed bearing which is free of the peculiar peelng and has a stable durability under the conditions of high-speed and high load.
SUMMARY OF THE INVENTION
The present invention encompasses a grease-sealed bearing 1, shown in FIG. 1, with an oxide coating 5 having a thickness of 0.1 to 2.5 microns on the rolling surfaces 4 of the rings.
With the bearing according to the present invention, the peculiar peeling which appears on the rolling surface can be prevented, and accordingly breakage owing to the peculiar peeling is also prevented. Thus the expected life of the bearing is assured. If the bearing according to this invention is used as a bearing in an alternator or the like which works under high-speed rotation and high load, its life will be less variable and stable bearing properties will be assured.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially cutaway perspective view showing the structure of this invention; FIG. 2 is a view schematically showing the internal structure of the rolling surface which has suffered the peculiar peeling; FIG. 3 is a graph showing the distribution of the shearing stress which develops under the metal surface as a result of rolling contact between metals; and FIG. 4 is a view sh
REFERENCES:
patent: 1661448 (1928-03-01), Taylor
patent: 3198735 (1965-08-01), Lamson et al.
patent: 3843962 (1974-10-01), Bogue
patent: 4871266 (1989-10-01), Oda
Mizutani Takahiro
Nakajima Hirokazu
Okayama Akio
Tamada Kenji
Hannon Thomas R.
NTN Corporation
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