BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of a fluid dynamic bearing according to the invention.
FIG. 2 shows a second embodiment of a fluid dynamic bearing according to the invention having a recirculation channel.
FIG. 3 shows a third embodiment of a fluid dynamic bearing according to the invention also having a recirculation channel.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1 shows a first embodiment of the bearing according to the invention. The bearing comprises a stationary bearing sleeve 10 that is held in an enclosing sleeve 20. The sleeve in turn may be held, for example, in a housing flange (not illustrated). The bearing bush 10 has a central bore in which a shaft 12 is rotatably supported. The bearing bush 10 is sealed at one end by a cover plate 16, whereas at the other end the shaft 12 projects beyond the bearing bush 10. The shaft is preferably supported radially by two radial bearings 28 and 30 that are disposed at a mutual distance. The radial bearings 28, 30 are defined in a conventional way by appropriate bearing patterns that are provided on the surface of the shaft 12 and/or of the bearing bush 10. On rotation of the shaft 12 in the bearing bush 10, the bearing patterns generate a pumping effect on the bearing fluid, thus giving the fluid bearing its load-carrying capacity. To support the shaft 12 axially, a thrust plate 14 is provided which is fixed in the shaft 12. The thrust plate is loosely accommodated in a recess in the bearing bush 10 and rotates together with the shaft 12. One of the end faces of the thrust plate 14 lies opposite a corresponding surface of the bearing bush 10 and the other opposite a corresponding surface of the cover plate 16. Bearing patterns are likewise provided on these bearing surfaces in a conventional way, the bearing patterns defining a first axial bearing 32 and preferably also a second axial bearing 34.
The bearing gap 18 that separates the stationary part of the bearing from the rotating part extends in its first section 18′ over the entire length of the shaft and in a second section 18″ around the thrust plate and is filled with a bearing fluid, preferably bearing oil.
The bearing gap is preferably sealed in the region of the free end of the shaft via a groove 26 that acts as a fluid brake and prevents bearing fluid from leaking from the bearing gap 18.
According to the invention, a recess is now provided at the outside circumference of the bearing bush 10, the recess being approximately triangular in cross-section and tapering to narrow in the direction of the cover plate 16. This recess is enclosed by the sleeve 20, so that a supply volume 22 is created between the bearing bush 10 and the sleeve 20, the supply volume being at least partly filled with bearing fluid. The supply volume 22 is connected at its narrow end to the second section 18″ of the bearing gap via a connecting channel 37. This means that an exchange of bearing fluid can take place between the bearing gap 18 and the supply volume 22. An opening 24 in the sleeve 20 that ends in an upper region of the supply volume 22 is used to equalize the pressure in the supply volume.
The first, upper radial bearing 28 comprises bearing patterns that are designed such that they generate a pumping effect on the bearing fluid in the direction of the thrust plate 14. In contrast, the second, lower radial bearing 30 generates a pumping effect in the direction of the first radial bearing 28. In this way, the pressure is equalized in the first section 18′ of the bearing gap. Via the connecting channel 37 in the lower region of the bearing, bearing fluid can be re-supplied from the supply volume when required.
FIG. 2 shows a second embodiment of a fluid bearing according to the invention. The construction of the bearing in FIG. 2 substantially corresponds to the construction of the bearing in FIG. 1, identical components being indicated by the same reference numbers. In contrast to FIG. 1, the groove 26′ is disposed in the sleeve 10 instead of in the shaft.
A substantial difference between the fluid bearing according to FIG. 2 and the bearing according to FIG. 1 lies in the fact that at least one recirculation channel 42 is provided in the bearing bush 10, the recirculation channel connecting the section of the supply volume 22 filled with bearing fluid to the first section 18′ of the bearing gap 18. The first radial bearing 38 still generates a pumping effect in the direction of the second radial bearing 40 or the thrust plate 14 respectively. In contrast to FIG. 1, here the second axial bearing 40 also generates a pumping effect in the direction of the thrust plate 14, so that bearing fluid is pumped via section 18″ of the bearing gap and the connecting channel 37 into the supply volume 22 and further via the recirculation channel 42 again into the first section 18′ of the bearing gap, thus creating a closed fluid circuit.
FIG. 3 shows a third embodiment of the bearing according to the invention whose essential construction also corresponds to the bearing described in FIG. 1. Here again, identical components are indicated by the same reference numbers.
In contrast to FIGS. 1 and 2 the bearing according to FIG. 3 comprises a recirculation channel that connects a section of the supply volume 22 filled with bearing fluid directly to a groove 26′ provided in the bearing bush 10. The groove 26′ is used to seal the bearing gap 18 and is supported by pumping patterns 50 provided at the end of the bearing gap 18, the pumping patterns pumping any bearing fluid escaping from the groove back into the region of the groove 26′.
The upper radial bearing 44 likewise generates a pumping effect mainly in the direction of the thrust plate 14, whereas the lower radial bearing 46 generates a pumping effect in the direction of the first upper radial bearing 44. Bearing fluid can flow from the groove 26′ back into the supply volume 22 via the recirculation channel 48.
In all three of the described embodiments according to FIGS. 1 to 3 a relatively large supply volume 22 is provided. By disposing the supply volume at the largest circumference of the bearing bush 10, a very large volume can be achieved with relative ease, the volume being preferably substantially larger than the quantity of bearing fluid found in the bearing gap. This makes possible a long useful life of the bearing according to the invention, even at high operating temperatures since evaporated bearing fluid can be replaced over a long period of time from the fluid supply found in the supply volume.
IDENTIFICATION REFERENCE LIST
10 Bearing bush
12 Shaft
14 Thrust plate
16 Cover plate
18 Bearing gap
18′ First section of the bearing gap
18″ Second section of the bearing gap
20 Sleeve
22 Supply volume
24 Opening (of the sleeve)
26 Groove (shaft)
26′ Groove (sleeve)
28 Radial bearing
30 Radial bearing
32 Axial bearing
34 Axial bearing
36 Rotational axis
37 Connecting channel
38 Radial bearing
40 Radial bearing
42 Recirculation channel
44 Radial bearing
46 Radial bearing
48 Recirculation channel
50 Pumping patterns (pumping seal)
Patent Application
20080089625
