VACUUM PUMP

Abstract

Vacuum pump comprising a housing, a rotor shaft disposed in the housing, at least one bearing rotatably supporting the rotor shaft against the housing including an inner race in contact with the rotor shaft and an outer race in contact with the housing, and an axial spring applying an axial force onto the outer race, wherein a bearing ring is disposed between the axial spring and the outer race, the bearing ring applying a clamping force to the housing.

Claims

1. A vacuum pump comprising a housing; a rotor shaft disposed in the housing; at least one bearing rotatably supporting the rotor shaft against the housing including an inner race in contact with the rotor shaft and an outer race in contact with the housing; and an axial spring applying an axial force onto the outer race, wherein a bearing ring is disposed between the axial spring and the outer race, the bearing ring applying a clamping force to the housing.

2. The vacuum pump according to claim 1, wherein the bearing and bearing ring are axially movable.

3. The vacuum pump according to claim 1, wherein the bearing ring is in direct contact with the outer race applying a friction force to the outer race.

4. The vacuum pump according to claim 1, wherein the bearing ring comprises textured surface.

5. The vacuum pump according to claim 1, wherein the bearing ring comprises a non-constant cross-section along its perimeter to provide an even clamping force along the bearing ring.

6. The vacuum pump according to claim 1, wherein the bearing ring comprises a slanted surface being oriented towards the bearing and in direct contact with the outer race creating a radial force component of the axial force of the axial spring applied to the outer race.

7. The vacuum pump according to claim 1, wherein a contact surface of the outer race being in contact with the bearing ring is rounded.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the following, the present invention is described in more detail with reference to the accompanied drawings.

[0019] The Figures show:

[0020] FIG. 1, is a sectional side view of a portion of a vacuum pump in accordance with a first embodiment,

[0021] FIG. 2A, is a top view of a bearing ring of a first embodiment,

[0022] FIG. 2B, is a top view of a bearing ring of a second embodiment, and

[0023] FIG. 3, is a sectional side view of a portion of a vacuum pump in accordance with a further embodiment.

DETAILED DESCRIPTION

[0024] Referring to FIG. 1 showing a rotor shaft 12 rotated by an electro motor and supported against a housing 14 of the vacuum pump by a roller bearing 16, exemplified in FIG. 1 as ball bearing. The bearing is arranged in a bearing seat bore of the housing 14. The roller bearing 16 comprises an inner race 18 directly connected to the rotor shaft 12 and rotated together with the shaft 12 and an outer race 20 in direct connection with the housing 14. Between the inner race 18 and the outer race 20, a roller element 22, exemplified as ball element, is disposed in order to allow rotation of the rotor shaft 12 in the housing 14. Therein, the roller bearing 16 is built as floating bearing, i.e. at least the outer race 20 is not clampingly fixed in its axial direction to the housing 14, i.e. an inner surface of the bearing seat bore.

[0025] An axial spring 26 is provided applying an axial force to the outer race 20. Thus, upon thermal expansion of the rotor shaft 12, the roller bearing 16 is moved in an axial direction against the axial force of the axial spring 26. If the thermal expansion of the rotor shaft 12 is reduced again, the roller bearing 16 is reverted to its initial position by the axial force of the axial spring 26. Thereby, the axial spring 26 cannot provide a radial stiffness and radial movement of the outer race or the roller bearing 16 is possible in conventional vacuum pumps. Thus, according to the present invention, a bearing ring 24 is disposed between the axial spring 26 and the outer race 20. The bearing ring 24 is clampingly fixed to the housing 14 by its outer perimeter. However, the bearing ring 24 can still be moved in axial direction in connection with the roller bearing 16 either by the thermal expansion of the rotor shaft 12 or by the axial force of the axial spring 26. Therein, the bearing ring 24 directly abuts a surface of the outer race 20 creating a friction force in a radial direction upon radial movement of the roller bearing 16. Due to the friction between the bearing ring 24 and the outer race 20 of the roller bearing 16, radial movement of the roller bearing 16 is hampered, thereby effectively reducing noise of the vacuum pump. Therein, the contact surface of the bearing ring 24 contacting the outer race 20 of the roller bearing 16 might be textured in order to increase the friction force or at least tailor the applied friction force to the required values.

[0026] Thus, by the bearing ring 24, acceleration of the roller bearing 16 in axial direction by the axial force of the axial spring 26 is reduced due to the radial force provided by the bearing ring 24. However, movement of the roller bearing 16 is still possible and at the same time radial movement of the roller bearing 16 is hampered due to the applied radial friction force towards the center access of the rotor shaft 12.

[0027] Referring to FIG. 2A showing a first embodiment of the bearing ring 24A built as clamping ring having a gap. By compressing the ends of the clamping ring 24A together, the perimeter of the bearing ring 24A is reduced. In this condition, the bearing ring 24A can be introduced into the bearing seat bore of the housing 14 accommodating the bearing of the vacuum pump.

[0028] In another embodiment shown in FIG. 2B, the bearing ring 24B shows a non-constant cross-section, thereby evenly distributing the clamping force applied by the bearing ring 24B to the housing 14 along the perimeter of the bearing ring 24B.

[0029] Referring to FIG. 3 showing another embodiment of the present invention. Therein, same or similar elements are provided with the identical reference signs.

[0030] In the embodiment of FIG. 3, the bearing ring 24 has a slanted surface 30 which is angled towards the roller bearing 16. The slanted surface 30 is in contact with a rounded or chamfered edge of the outer race 20 of the roller bearing 16. By interaction of the slanted surface 30 and the chamfered or rounded surface 32 of the roller bearing 16, a radial force component towards the center axis of the rotor shaft is created from the axial force of the axial spring 26. By this radial force component, radial movement of the roller bearing 16 is hampered, thereby reducing noise of the vacuum pump but still allowing the bearing 16 to move under thermal expansion.

[0031] In particular, the vacuum pump is a dry vacuum pump, wherein in those vacuum pumps noise is most critical due to absence of any friction and a less gas load. Thus, by the present invention, noise produced by vacuum pumps and in particular dry vacuum pumps can be further reduced enhancing the usability and versatility of these vacuum pumps.

[0032] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0033] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.