Bearing arrangement

Details Bearing arrangement Bearing arrangement

1997-06-06

1998-07-07

Hannon, Thomas R.

Bearings

Rotary bearing

Plain bearing

384905, F16C 1722

Patent

active

057758166

DESCRIPTION:

BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION

This is the national stage of International Application No. PCT/EP95/04832 filed Dec. 8, 1995.


BACKGROUND OF THE INVENTION

For functional reasons, it is often necessary to center a bearing bushing or sleeve on the associated shaft with as little play as possible. This may be problematic, in terms of the thermal expansion of the shaft, if the bushing consists of a material, such as ceramic, which is susceptible to tensile stress and has a smaller coefficient of thermal expansion than the shaft. In order to prevent the shaft from breaking the bushing near the top of the operating-temperature range, it may then be necessary to select the play in the bottom of the operating-temperature range to be greater than may be functionally permissible. A known way of countering this is to use resilient arrangements between the shaft and bushing (EP-B 345 214, DE-C 37 06 365), or resilient centering rings which enclose the bushing on the outside (U.S. Pat. No. 5,197,808), to ensure play-free centering over the entire operating-temperature range. In the latter case, the internal diameter of the bushing and the external diameter of the shaft may be coordinated with one another such that they are equal at the top end of the operating-temperature range and then interact in a play-free and force-transmitting manner. The resilient parts, however, are difficult and complex to produce.
JP-A 129 50 25 discloses an arrangement in which, in order to facilitate the operation of mounting the bushing on the shaft and to prevent the shaft from breaking the bushing, the bushing is seated on the shaft with play. The bushing is carried along in rotation by the shaft via two rings which are seated fixedly on the shaft on both sides of the bushing and are braced axially against the bushing. On the side facing the bushing, the rings have a protrusion which engages axially over a region of the bushing, it being possible for a radial clearance fit or snug fit to be provided between the protrusion and the bushing. However, depending on the dimensioning of the fit between the ring protrusion and the bushing, there may be a relatively large degree of play between the bushing and shaft over the operating-temperature range. Furthermore, the greater thermal expansion of the shaft with respect to the ceramic bushing may mean that the bushing is not braced or held axially between the ceramic rings, with result that it is no longer ensured that the ceramic bushing is carried along in rotation.


SUMMARY OF THE INVENTION

The object of the invention is thus to provide a bearing arrangement with low complexity, over the operating-temperature range, that has the smallest possible degree of centering play between the bushing and shaft and which ensures that the bushing is carried along in rotation.
The invention uses two centering rings, which act on the bushing from the outside, to counter the shaft-surface expansion characteristics, which act on the bushing from the inside. In the cold part of the operating-temperature range, in which there is a relatively large degree of play between the shaft surface and the bore of the bushing, centering is ensured by the play-free abutment of the centering rings, against the outside of the bushing. In the warm part of the operating-temperature range, the shaft surface assumes the centering task while there is play between the centering rings and the bushing. Whereas overdimensioning of the shaft with respect to the bushing bore has to be avoided in each case, it is quite possible, in this context, for the inner circumferential surface of the centering ring, which acts on an outer circumferential surface of the bushing from the outside, to have smaller dimensions than the bushing at the cold end of the operating-temperature range, because this merely results in compressive stresses in the bushing which can usually be safely absorbed by the latter. The centering function of the centering ring may thus be envisaged for a larger temperature range than that of the shaft. In this

REFERENCES:
patent: 4895462 (1990-01-01), Takata
patent: 4968158 (1990-11-01), Atkinson et al.
patent: 4997297 (1991-03-01), Blount
patent: 5040398 (1991-08-01), Nakagawa et al.
patent: 5197808 (1993-03-01), Takata

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