Coating processes – With post-treatment of coating or coating material – Solid treating member or material contacts coating
Reexamination Certificate
1999-12-15
2001-05-29
Beck, Shrive (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Solid treating member or material contacts coating
C427S181000, C427S203000, C427S236000, C427S388100, C427S409000, C427S419700, C427S421100, C384S463000, C384S625000, C384S913000
Reexamination Certificate
active
06238744
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to vehicle noises, and, more particularly, to a method for reducing an objectionable whining noise sometimes present at vehicle startup referred to as hoot.
BACKGROUND OF THE INVENTION
In vehicle front end accessory drive systems, idler pulleys with ball bearings are used to route a drive belt for improved wrap on accessory pulleys and to reduce drive belt span lengths. Similar pulleys with ball bearings are also used in tensioners for maintaining the proper belt tension. Both are subject to the same problem. During cold starts at temperatures below about 20° F., the pulleys sometimes produce an objectionable whining noise called hoot that lasts for about five to thirty seconds. Noises coming from the engine area can be very alarming to vehicle owners, particularly those who are mechanically challenged or uninformed about various sounds associated with engine and vehicle operation. The hoot only occurs during cold startup and is attributed to a lack of lubrication at the bearing contacting surfaces; namely, the interaction between the rolling balls, the inner raceway and the outer raceway. Accordingly, it will be appreciated that it would be highly desirable to have a method for lubricating the idler bearings so that the bearings remain lubricated at cold startup to eliminate the hoot noise.
Bearing assemblies have conventionally had contact surfaces coated to prevent rust, reduce friction or increase wear resistance. The rust preventive coating process is a complicated process requiring a phosphatized film. The process for increasing wear resistance uses plasma spray coating which requires special plasma equipment. One friction reducing process coats roller bearings with a lubricating paint that is insoluble in oil, but the paint requires time to dry and erodes quickly. Another friction reducing process uses bronze or molybdenum applied by thermal spraying. Unfortunately, the coating erodes during use; so, multiple layers in different colors must be used to gauge wear. Bearing assemblies have conventionally used coatings and coating processes that increase manufacturing time or are complicated requiring multiple coatings or numerous manufacturing steps to accomplish. It is desirable to permanently coat bearing surfaces to reduce friction and eliminate hoot using a relatively simple, inexpensive process.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a method for eliminating hoot noise in a bearing assembly of an idler or tensioner pulley having ball bearings riding on inner and outer raceways, comprises the steps of: applying a dry lubricating compound to surfaces of the inner and outer raceways on which the ball bearing rides and curing the dry lubricant. This in turn allows the following actions judged favorable to eliminate hoot. Oil is attracted to the contact surfaces which itself is a desirable outcome. The particles of the lubricating compound are rolled into the surfaces of the raceways through normal operation effectively changing the surfaces to an alloy containing the metal, dry lubricant particles and oil. These in turn fill voids in the surfaces thereby smoothing the surfaces for reduced friction and elimination of the hoot noise.
Using a three component dry lubricating compound instead of grease or in combination with grease ensures better performance than grease alone, especially at low operating temperatures where grease is too viscous and at high operating temperatures where grease is too thin. The dry lubricant is as easily applied as paint and does not require the use of expensive or complicated equipment. It is more cost effective than polishing the raceways to a high polish finish to achieve low friction. It allows the use of less costly and more durable bearing materials with less need for precise machined tolerances.
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Magoulick Thomas
Rao Vemulapalli Durga Nageswar
Barr Michael
Beck Shrive
Ford Motor Company
May Roger L.
Porcari Damian
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