WO2015043629A1

WO2015043629A1 - Rolling bearing with pre-stressing member

Info

Publication number: WO2015043629A1
Application number: PCT/EP2013/069965
Authority: WO
Inventors: Laurent Varnoux
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2013-09-25
Filing date: 2013-09-25
Publication date: 2015-04-02
Anticipated expiration: 2016-03-25

Abstract

The rolling bearing comprising an inner ring (16), an outer ring (14), at least one row of rolling elements (18) disposed radially between the rings, and at least one seal (22) fixed to one o f the rings (14) and arranged radially between said rings. The rolling bearing further comprises at least an axially elastic member (26) fixed to said seal and mounted in axial contact with a lateral surface (14d) of said ring delimiting axially said ring.

Description

Rolling bearing with pre-stressing member

The present invention relates to rolling bearings, in particular rolling bearings having an inner ring and an outer ring with one or more rows of rolling elements, for example balls .

In particular, the present invention relates to rolling bearings used in industrial electric motors . An electric motor generally comprises a casing inside which is mounted a stator and a rotor, and two rolling bearings located at each end of the rotor' s shaft.

In such application, known ISO deep groove ball bearings are usually used. These bearings comprise inner and outer rings of the massive or solid type. A "so lid ring" is to be understood as a ring obtained by machining with removal o f material (by turning, grinding) from steel tube stock, bar stock, rough forgings and/or rolled blanks .

Document EP-B l - 1 037 05 1 disclo ses an instrumented rolling bearing mounted into the casing o f the electric motor and stacked conical washers axially interposed between said rolling bearing and the casing. Such a device uses a p lurality of pre-stressing washers that are independent of the rolling bearing. Accordingly, the motor manufacturer has to manage, handle and assemble a large number o f components.

One aim o f the present invention is to overcome these drawbacks.

It is a particular object of the present invention to provide a rolling bearing that is economical, having good sealing properties and easy to install in a machine for which it is intended, for example in an electric motor.

In one embodiment, the rolling bearing comprises an inner ring, an outer ring, at least one row of rolling elements disposed radially between the rings, and at least one seal fixed to one o f the rings and arranged radially between said rings . The rolling bearing further comprises at least an axially elastic member fixed to said seal and mounted in axial contact with a lateral surface o f said ring axially delimiting said ring.

The axial retention o f the elastic member on the seal of the rolling bearing makes it possible to reduce the number of components to be procured and to be fitted. Manufacturing errors resulting from forgetting the elastic member are thus avoided, for example for a motor manufacturer when the rolling bearing is intended to an electric motor.

Preferably, the elastic member is provided with a bearing surface axially spaced apart from the lateral surface of said ring and adapted to be in contact with an element outside said rolling bearing, and with an opposite abutment surface in axial contact with said lateral surface and axially located outside from a radial space existing between the inner and outer rings.

Said seal may comprise a fixing portion secured to said ring and a sealing portion cooperating with the other ring . In a preferred embodiment, the elastic member is secured to the fixing portion o f said seal.

Advantageously, the elastic member may comprise at least one axial retaining hook for fixing said member to said seal. The elastic member may comprise a plurality o f axial retaining hooks regularly spaced apart in the circumferential direction.

Preferably, the elastic member is made in one part. The elastic member may be a washer.

In one embodiment, the elastic member comprises radial portions mounted in axial contact with the lateral surface of said ring and elastic portions connected to said radial portions and axially spaced apart from said lateral surface. Preferably, the elastic portions are located axially on the side opposite to the retaining hook(s) with respect to the radial portions. The elastic portions may be regularly spaced apart in the circumferential direction.

The elastic portions may comprise corrugations. In another embodiment, the elastic portions may comprise tongues . Alternatively, the elastic member may be a conical washer. In one embodiment, said seal is fixed into a groove formed on said ring.

The present invention and its advantages will be better understood by studying the detailed description of a specific embodiment given by way o f non-limiting example and illustrated by the appended drawing showing an axial section of a ro lling bearing according to an example o f the invention.

As illustrated on the Figure, a rolling bearing 10, with an axis 12 , comprises an outer ring 14, an inner ring 16, a plurality o f ro lling elements 1 8 , which in this case are balls, interposed between the rings, and a cage 20 for maintaining said rolling elements circumferentially spaced apart. The ro lling bearing 10 further comprises on each side an annular seal 22, 24 to close the radial space that exists between the rings 14 and 1 6, and an axially elastic washer 26 mounted on the seal 22. As will be described later, the elastic washer 26 is adapted to exert an axial prelo ad.

The outer and inner rings 14, 16 are concentric and o f the solid type . One o f the rings rotates while the other is fixed or also rotates . The outer ring 14 comprises a toroidal circular raceway 14a for the rolling elements 1 8 which is formed onto its bore and directed radially inwards, and two annular recesses or grooves 14b, 14c formed radially towards the outside from the bore and arranged laterally to the raceway 14a. The grooves 14b, 14c are symmetrical relative to a radial plane passing through the centre of the rolling bearing 10. The outer ring 14 also comprises opposite radial lateral surfaces 14d, 14e which axially delimit the bore and the outer surface of said ring.

The inner ring 16 comprises a toroidal circular raceway 16a for the rolling elements 1 8 which is formed onto its outer surface and directed radially outwards, and two opposite radial lateral surfaces 16b , 1 6c which axially delimit the bore and the outer surface of said ring. The lateral surfaces 16b, 16c are respectively coplanar with the lateral frontal surfaces 14d, 14e of the outer ring.

Each seal 22, 24 is arranged radially between the outer and inner rings 14 and 1 6, fixed to said outer ring and arranged laterally to the rolling elements 1 8. Each seal 22, 24 is entirely housed into the radial space delimiting between the outer and inner rings 14, 1 6. Each seal 22, 24 is axially offset towards the inside with regard to associated lateral surface 14d, 14e of the outer ring.

In this example, each seal 22, 24 is made in one part and has a form o f a shield which is advantageously made o f metal, for example by cutting and stamping a metal sheet. The seals 22, 24 are identical to one another and symmetrical relative to the transverse radial plane passing through the centre of the rolling bearing 10. Since the seals 22, 24 are identical in this example, only one o f them will be described here.

The seal 22 comprises an annular fixing portion 22a mounted into the groove 14b o f the outer ring in order to fix the seal to the said ring, an annular radial portion 22b extending radially inwards said fixing portion, and an annular axial portion 22c extending axially inwards the small-diameter edge of the radial portion 22b. The axial portion 22c extends axially in the direction of the ro lling elements 1 8 and forms an annular narrow passageway with the outer surface of the inner ring 1 6. The fixing portion 22a and the axial portion 22c form two radially opposed peripheral sealing portions applying respectively a static sealing with the outer ring 14 and a dynamic sealing with the inner ring 16. "Static sealing" means the sealing made between two parts that do not move relative to one another. "Dynamic sealing" means the sealing made between two parts that move relative to one another. The fixing portion 22a of the seal is press-fitted in the groove 14b o f the outer ring in order to attach the seal 22 to said ring.

The elastic washer 26 is made in one part and may be advantageously manufactured in an economic way by cutting, stamping and fo lding a metal sheet. Alternatively, the washer 26 may be made from synthetic material like po lyamide.

In this example, the elastic washer 26 is a corrugated washer. The washer 26 bears axially against the lateral surface 14d of the outer ring. The washer 26 has an outer diameter equal or smaller to the outer diameter of the outer ring 14. The washer 26 comprises a plurality o f radial portions 26a coming into axial contact with the lateral surface 14d of the outer ring and a plurality of corrugated portions 26b connected to said radial portions . Each corrugated portion 26b is connected to two successive radial portions 26a. The corrugated portions 26b are regularly spaced apart in the circumferential direction. The washer 26 comprises here four corrugated portions 26b . The corrugated portions 26b extend axially outwards, i. e. axially on the side opposite to the outer and inner rings 14, 16. The corrugated portions 26b are axially spaced apart from the lateral surface 14d o f the outer ring 14 and more generally from said ring. The radial portions 26a and the corrugated portions 26b of the washer are located outside from the radial space that exists between the outer and inner rings 14, 16. Each radial portion 26a delimits a radial abutment surface 28 of the washer against the lateral surface 14d of the outer ring and each corrugated portion 26b delimits a bearing surface 30 lo cated axially on the opposite side to said abutment surface 28 and axially spaced apart from said lateral surface 14d.

The washer 26 further comprises a plurality o f lugs 26 c proj ecting axially from the bore of the radial portions 26a. Each lug 26c extends axially inwards the associated radial portion 26a in the direction of the seal 22. Each lug 26c comprises at its free end a retaining hook 26d extending radially outwards to secure the washer 26 to the fixing portion 22a of the seal. The hooks 26d are regularly spaced apart in the circumferential direction. The lugs 26c and the hooks 26d are located axially on the side opposite to the corrugated portions 26b with regard to the radial portions 26a. The hooks 26d are identical to one another and have a complementary shape with the fixing portion 22a o f the seal in order to secure the elastic washer 26 on the seal 22. The hooks 26d are adapted to engage with the fixing portion 22a o f the seal. The elastic washer 26 is secured on the outer ring 14 by virtue of the seal 22. The hooks 26d form retaining or anchorage means cooperating directly with the seal 22 to fix or attach the washer 26 to said seal. The mounting of the washer 26 on the seal 22 can be easily achieved for example with a simple axial pushing movement without angular indexation.

When such a rolling bearing 10 is mounted in a motor, the bore of the inner ring 16 is fitted tightly on the shaft supporting the rotor and the outer surface of the outer ring 14 is fitted with a sliding fit in the motor casing. During the mounting of the rolling bearing 10 into the casing, the bearing surface 30 of washer axially comes into contact with a radial shoulder of said casing. An axial compression o f the elastic washer 26 between the outer ring 14 and the shoulder of the housing is achieved. In return, by reaction from the shoulder of the housing, the axial washer 26 exerts a permanent axial force on the outer ring 14. The axial pre-stress exerted by the axial washer 26 is transmitted from the outer ring 14 to the inner ring 16 by way o f the rolling elements 1 8.

The use of the elastic washer 26 allows the rolling bearing 10 to be axially preloaded while accommodating different expansions o f the rotor' s shaft, generally made of steel, and of casing, generally based on aluminium, said rolling bearing being able to slide axially with respect to the casing.

The ro lling bearing is compact and may be transported and handled with complete safety without any risk o f loss of the elastic washer. Besides, the motor manufacturer has one less component to procure, manage and fit. The roller bearing may be fitted in the electric motor, particularly easily without requiring any special precaution.

In the illustrated example, a corrugated washer is used for axially pre-stressing or preloading the rolling bearing. Alternatively, it is also possible to provide another type of elastic member, such as conical washer of the Belleville type or a washer provided with a plurality o f elastic tongues, having retaining means cooperating with the seal fixed on the associated ring.

The invention has been illustrated on the basis of a rolling bearing comprising a washer mounted on a seal which is made in one part, mounted on the outer ring and applying a dynamic sealing without contact with the inner ring. Alternatively, the seal may be provided with a rigid insert and with an elastic sealing member which partially covers the insert and having at least a friction sealing lip bearing against the inner ring and/or at least a labyrinth sealing lip , the elastic washer being secured to said rigid insert or sealing member. In the disclo sed embo diment, the elastic washer is fixed on a seal mounted on the outer ring. Alternatively, it might be possible to fix the elastic washer on a seal mounted on the inner ring.

Claims

1 . Ro lling bearing comprising an inner ring ( 16), an outer ring ( 14), at least one row of rolling elements ( 1 8) disposed radially between the rings, and at least one seal (22) fixed to one o f the rings ( 14) and arranged radially between said rings, characterized in that it further comprises at least an axially elastic member (26) fixed to said seal and mounted in axial contact with a lateral surface ( 14d) of said ring delimiting axially said ring.

2. Ro lling bearing according to claim 1 , wherein the elastic member (26) is provided with a bearing surface (30) axially spaced apart from the lateral surface ( 14d) of said ring and adapted to be in contact with an element outside said rolling bearing, and with an opposite abutment surface (28) in axial contact with said lateral surface ( 14d) and axially located outside from a radial space existing between the inner and outer rings.

3. Ro lling bearing according to claim 1 or 2, wherein said seal (22) comprises a fixing portion (22a) secured to said ring and a sealing portion (22c) cooperating with the other ring ( 16) .

4. Ro lling bearing according to claim 3 , wherein the elastic member (26) is secured to the fixing portion (22a) of said seal.

5. Ro lling bearing according to any o f the preceding claims, wherein the elastic member (26) comprises at least one axial retaining hook (26d) for fixing said member to said seal.

6. Ro lling bearing according to claim 5 , wherein the elastic member (26) comprises a plurality o f axial retaining hooks regularly spaced apart in the circumferential direction.

7. Ro lling bearing according to any o f the preceding claims, wherein the elastic member (26) is made in one part.

8. Ro lling bearing according to any o f the preceding claims, wherein the elastic member (26) is a washer.

9. Ro lling bearing according to any o f the preceding claims, wherein the elastic member (26) comprises radial portions (26a) mounted in axial contact with the lateral surface ( 14d) of said ring and elastic portions (26b) connected to said radial portions and axially spaced apart from said lateral surface.

10. Rolling bearing according to claim 9 dependent to claim 5 or 6, wherein the elastic portions (26b) are located axially on the side opposite to the retaining hook(s) (26d) with respect to the radial portions (26a).

11. Rolling bearing according to claim 9 or 10, wherein the elastic portions (26b) are regularly spaced apart in the circumferential direction.

12. Rolling bearing according to any of the preceding claims 9 to 11, wherein the elastic portions comprise corrugations.

13. Rolling bearing according to any of the preceding claims 9 to 11, wherein the elastic portions comprise tongues.

14. Rolling bearing according to any of the preceding claims 1 to 8, wherein the elastic member is a conical washer.

15. Rolling bearing according to any of the preceding claims, wherein said seal (22) is fixed into a groove (14b) formed on said ring (14).