Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1999-12-02
2001-08-14
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S447000, C384S569000, C418S055100
Reexamination Certificate
active
06273616
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns an arrangement for mounting a shaft comprising a shaft journal arranged eccentric to a central longitudinal axis of the shaft on an end portion of the shaft, said end portion being supported by a first needle roller bearing in a housing, and said eccentric shaft journal being connected by a second needle roller bearing to a movable part of a connecting structure.
BACKGROUND OF THE INVENTION
An arrangement of the pre-cited type for mounting a shaft is known from SAE TECHNICAL PAPER SERIES No. 970113 “Improvement of Scroll Compressor for Vehicle Air Conditioning Systems”.
FIG. 6
of this prior art publication shows a schematic representation of a so-called scroll compressor. The guidance and support of is achieved by a fixed bearing arranged in the figure on the left and configured as a groove ball bearing which guides the shaft in axial direction, while an enlarged-diameter end portion of the shaft spaced from the ball bearing is held in a second bearing. This second bearing is configured as a needle roller bearing. This enlarged-diameter end portion continues into a shaft journal arranged eccentric to the central longitudinal axis of the shaft, said shaft journal being connected by a further needle roller bearing to an orbiting scroll of a scroll compressor.
A drawback of this construction, however, is that with an improperly functioning fixed bearing, the shaft can be displaced in axial direction. Either the eccentric shaft journal comes to abut against the orbiting scroll of the scroll compressor in one axial direction, or, in the other axial direction, the enlarged-diameter end portion of the shaft abuts against a surrounding housing part. In both cases, an undesired high wear occurs in this prior art mounting arrangement.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide an improved arrangement for mounting a shaft with which wear within the mounting arrangement is avoided even when the fixed bearing is impaired in its function.
This and other objects and advantages of the invention will become obvious from the following detailed description.
SUMMARY OF THE INVENTION
The invention achieves the above objects by the fact that the outer ring of each needle roller bearing is made as a deep-drawn bushing which is shaped without chip removal and comprises an inner and an outer rim, the diameter d of the inner edge of the outer rims facing away from each other being smaller than the diameter D of the associated inner raceway.
Due to this mirror-image arrangement of the two needle roller bearings with their inwardly extending outer rims, the mounting arrangement of the shaft is fixed as a whole in axial direction, i.e. on failure of the fixed bearing, the eccentric shaft journal comes to bear against the inwardly extending rim of the second bearing, while the end face of the end portion of the shaft comes to bear against the inwardly extending rim of the first needle roller bearing. By virtue of this mirror-image arrangement of the two needle roller bearings configured according to the invention, a mounting arrangement having the function of a fixed bearing is created. The positive result of this is that if the actual fixed bearing fails, neither the housing nor the connecting structure can be damaged by an axial displacement of the shaft. This is an elegant solution for assuring an excellent protection of the mounting arrangement from wear.
According to an advantageous feature of the invention, the outer rims of the needle roller bearings facing away from each other and the shoulders of the end portion of the shaft and of the shaft journal are hardened. Thus, upon failure of the fixed bearing, the hardened end faces of the eccentric shaft journal and of the end portion of the shaft run against the likewise hardened rims of the needle roller bearings so that a reliable wear protection is realized.
According to another feature of the invention, the movable part of the connecting structure is a scroll of a scroll compressor and is pressed with its reception bore onto the bushing of the second needle roller bearing.
In a second embodiment, the invention achieves its objects by the fact that the outer ring of each needle roller bearing is made as a deep-drawn bushing which is shaped without chip removal and comprises an inner and an outer rim, and a stop disc or a stop ring is arranged between the needle crown ring and outer rims facing away from each other.
In this case, the axial positioning of the shaft is not realized by the rims but by the stop disc or stop ring. With this configuration, the radial dimension of the two opposing rims of the needle roller bearing does not have to extend inwards beyond the inner raceway diameter, but has only to be large enough so as to reliably retain the stop disc or the stop ring within the bearing arrangement.
According to a further feature of this embodiment of the invention, the stop disc or stop ring has a goffered structure oriented toward the eccentric shaft journal or the end portion. This goffered structure with its elevations and depressions has a better retention capacity for lubricant than a smooth surface.
According to still another feature of the second embodiment of the invention comprising a stop disc or a stop ring, the movable part of the connecting structure is again a scroll of a scroll compressor and is pressed with its reception bore onto the bushing of the second needle roller bearing.
Finally, according to a third embodiment, the invention achieves its objects by the fact that the outer ring of each needle roller bearing is made as a deep-drawn bushing which is shaped without chip removal and comprises an inner and an outer rim, a stop ring and a stop disc being arranged between the outer rims facing away from each other and the housing and the connecting structure respectively.
The invention will now be described more closely with the help of the following examples of embodiment.
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Bierman, Muserlian and Lucas
Hannon Thomas R.
Ina Walzlager Schaeffler OHG
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