DE102014209669A1 - bearing arrangement - Google Patents

Abstract

The invention relates to a bearing assembly (1) comprising at least one rolling bearing (2), wherein the rolling bearing (2) at least one bearing inner ring (3) and at least one bearing outer ring (4), between which rolling elements (5) are arranged, wherein the bearing inner ring (3) is connected to a first machine part (6), wherein the bearing outer ring (4) with a second machine part (7) is connected and wherein the bearing inner ring (3) and the bearing outer ring (4) made of steel. To minimize the susceptibility of the bearing ring against cracking and to reduce the formation of tensile stresses, the invention provides that between the bearing inner ring (3) and the first machine part (6) and / or between the bearing outer ring (4) and the second machine part ( 7) a layer (8) of a material is arranged which has a lower rigidity than steel.

Description

The invention relates to a bearing assembly comprising at least one rolling bearing, wherein the rolling bearing has at least one bearing inner ring and at least one bearing outer ring, between which rolling elements are arranged, wherein the bearing inner ring is connected to a first machine part, wherein the bearing outer ring is connected to a second machine part and wherein the bearing inner ring and the bearing outer ring are made of steel.

Generic bearing arrangements have bearing rings which are arranged on or in a component. For example, a bearing inner ring can be arranged by means of a press fit on a shaft in order to fix it permanently during its service life on this component.

With appropriate load during the use of a rolling bearing, there are sometimes problems with crack formation in the raceway area. In this connection, it is known that cracks are formed on the raceway at high loads and in conjunction with slip occurring on the raceway surface in the axial direction. Therefore, it often comes to fretting corrosion on the bearing bore and the mounted shaft. In addition, a circulation bend is relevant, which acts during the rotation of the bearing ring. The effects mentioned limit the service life of the rolling bearing and sometimes lead to premature failure of storage.

The invention has for its object to provide a generic bearing assembly in which the tendency to cracking is at least greatly reduced. Also, the occurrence of fretting corrosion in the region of the cylindrical seat of the bearing is to be reduced by shaft deflection under load. Accordingly, the susceptibility of the bearing ring to crack formation is minimized and the formation of tensile stresses can be reduced.

The solution of this problem by the invention is characterized in that between the bearing inner ring and the first machine part and / or between the bearing outer ring and the second machine part a layer of a material is arranged, which has a lower rigidity than steel.

The material of the layer is preferably plastic, preferably polyamide, particularly preferably polyamide 6.6. The plastic may be fiber reinforced, with short fibers, long fiber or continuous fibers can be used. In general, any type of fiber reinforcement can be used here. This may be a fiber composite plastic (FRP), a carbon fiber reinforced plastic (CFRP), a glass fiber reinforced plastic (GRP), an aramide fiber reinforced plastic (AFK), a natural fiber reinforced plastic (NFK) and / or a fiber reinforced plastic. Ceramic composite (CMC) act. The fibers may optionally be embedded in a thermosetting or thermoplastic base material or such a matrix, which may be formed as a resin system.

The layer is preferably formed as a hollow cylindrical structure, d. H. it is in this case in particular a sleeve. The radial thickness of the layer is preferably between 0.5% and 5% of the diameter of the bearing ring at the location where the layer is in contact with the bearing ring.

The layer may be arranged according to a specific embodiment of the invention in a recess in the first machine part and / or in the second machine part. The layer can be flush with a cylindrical surface of the first machine part and / or the second machine part.

The axial extent of the layer and the axial extent of the bearing ring, which is in contact with the layer, may coincide; but it can also be provided that the axial extent of the layer projects slightly beyond the bearing ring.

Alternatively, it is also possible that the corresponding machine part is largely covered with said layer, d. H. In this case, the axial extent of the layer over the axial extent of the bearing ring, which is in contact with the layer out.

The layer can be produced, for example, by a winding method in which a (preferably hollow-cylindrical) base body is rotated about an axis and thereby wound with a winding-capable material. Also, a rolling bearing ring can be covered in this way with a layer.

The compound of said layer with the machine part or with the bearing ring can be made by gluing, microforming or traction. For this purpose, the surfaces of both elements (layer and machine part) may have a special profiling or roughness. For example, the bearing ring may have a roughness R _a = 5 to 20 microns.

The first machine part is preferably a shaft.

mit:

h_c:

radialer Differenzbetrag zwischen maximalem und minimalem Wert des Radius über dem Umfang der zylindrischen Sitzfläche in mm;

D:

Durchmesser der zylindrischen Sitzfläche des Lagerrings in mm;

E:

Elastizitätsmodul des Materials des Lagerrings in N/mm² (MPa);

σ_c:

kritische Umfangsspannung im Lagerring vor dem Aufbringen einer äußeren Belastung, gegebenenfalls nach der Herstellung eines Presssitzes, in N/mm² (MPa);

σ_nom:

nominale Umfangsspannung im Lagerring nach seiner Montage, gegebenenfalls hervorgerufen durch einen Presssitz, in N/mm² (MPa).

The proposed solution allows only a limited effort to be made for the production of the seat of the bearing ring. It has proven particularly useful if the geometry of the seat is only processed to a defined extent. Therefore, a preferred development provides that the bearing inner ring for the layer forms a cylindrical seat surface and / or that the bearing outer ring for the layer forms a cylindrical seat surface, wherein the cylindrical seat surface is designed such that the radial difference between maximum and minimum value above the The circumference of the cylindrical seat is at least equal to the following value:

With:

h _c:

radial difference between the maximum and minimum values of the radius over the circumference of the cylindrical seat in mm;

D:

Diameter of the cylindrical seat of the bearing ring in mm;

e:

Modulus of elasticity of the bearing ring material in N / mm ² (MPa);

σ _c:

critical hoop stress in the bearing ring before application of an external load, possibly after the production of an interference fit, in N / mm ² (MPa);

σ _nom :

nominal hoop stress in the bearing ring after its installation, possibly caused by an interference fit, in N / mm ² (MPa).

In this case, it is preferably provided that the critical hoop stress (σ _c ) in the bearing ring before the application of an external load is based on a value between 180 MPa and 220 MPa, preferably of 200 MPa.

The raceway of the bearing rings can be hard turned; it can also be hard-rolled. The raceway and / or the cylindrical seat of the bearing rings may also be burnished.

The rolling bearing is preferably designed as a tapered roller bearing or as a cylindrical roller bearing.

It has been found that the tendency to crack on the raceway of the bearing ring and the tendency to fretting corrosion can be significantly reduced when the proposed design of the bearing assembly is used.

In the drawings, embodiments of the invention are shown. Show it:

1 in radial section, a bearing arrangement in which a shaft is mounted in a housing, according to a first embodiment of the invention,

2 in the illustration according to 1 a bearing arrangement according to a second embodiment of the invention,

3 in the illustration according to 1 a bearing assembly according to a third embodiment of the invention,

4 for the cylindrical seat of the bearing inner ring the course of the radius of the seat over the circumference and

5 the preferably provided minimum radial difference between the maximum and minimum values of the radius over the circumference of the cylindrical seat as a function of the diameter of the cylindrical seat for different nominal hoop stresses in the bearing race.

In 1 is the radial section of a bearing assembly 1 to see. With the bearing arrangement 1 becomes a first machine part 6 in the form of a shaft in a second machine part 7 stored in the form of a housing. This purpose is a rolling bearing 2 with a bearing inner ring 3 and a bearing outer ring 4 , where between the bearing rings rolling elements 5 are arranged. The rolling bearing 2 is formed according to the embodiment as a cylindrical roller bearing.

On the cylindrical surface 10 the wave 6 - The contact surface to the bearing inner ring 3 forms - is usually a certain waviness before. To the emergence of tensile stresses due to this waviness in the rolling bearing 2 To avoid and further complicate the transmission of vibrations, it is envisaged that between the bearing inner race and the shaft 6 a layer 8th is made of a material that, in comparison with the rigidity of the bearing rings 3 . 4 (usually bearing steel 100 Cr 6) has a lower rigidity. Specifically, a sleeve-shaped layer 8th made of plastic, with polyamide being preferred.

Shown is the situation where the sleeve-shaped layer 8th between the wave 6 and the bearing inner ring 2 is provided. Accordingly, however, alternatively or additively, a layer between the bearing outer ring 4 and the housing 7 be provided.

The layer 8th So here is designed as a plastic sleeve, which in the assembly of the illustrated Arrangement between the bearing inner ring 3 and the wave 6 is placed.

In 1 is further to realize that the extension of the layer 8th and the bearing inner ring 3 in the axial direction a is substantially equal.

However, the sleeve-shaped layer is 8th relatively thin. This is indicated by the radial thickness d of the layer 8th and the diameter D of the bearing ring 3 at the point where sleeve is 8th and bearing ring 3 contacted. It is envisaged that the thickness d of the layer 8th is approximately in the range between 0.5% and 5% of the diameter D.

According to the embodiment 2 a slightly different configuration is provided. Here is in the wave 6 a groove-shaped recess incorporated (eg., Screwed), ie a recess 9 having an outer cylindrical surface. In this recess 9 is the layer 8th placed.

This can for example be done so that the plastic material after manufacturing the recess 9 injected into the same. But it is also possible (this depends on the elasticity of a prefabricated sleeve-shaped layer 8th in relation to the geometry), that the sleeve-shaped layer 8th radially expanded and into the recess 9 is inserted axially.

As in 2 can be seen results in flushing between the cylindrical surface 10 the wave 6 and the radially outer surface of the layer 8th , In this area is the bearing inner ring 3 mounted by axial sliding.

In 3 another embodiment of the invention is shown. Here is the wave 6 over its entire axial extent with a plastic layer 8th Mistake; the wave 6 In that sense, it is virtually encased in plastic material. On this layer 8th then becomes the rolling bearing 2 pushed and fixed in the corresponding axial position.

The axial fixation of both the bearing inner ring 3 on the wave 6 as well as the bearing outer ring 4 in the case 7 is not shown for reasons of clarity in all three outlined cases.

For the shift 8th has the bearing inner ring 3 a cylindrical seat 11 onto. 1 ). It is envisaged that this will have a defined out-of-roundness across the circumference of the layer 8th is equalized.

In 4 is shown as extending over the circumference of the bearing inner ring 3 The cylindrical bore with its nominal diameter D (in mm) changed in radius, although the course of the bore is shown greatly exaggerated. As a result, due to the unevenness or waviness, there is a radial difference between the maximum and minimum values of the radius; this difference is denoted by h _c .

The cylindrical seat 11 can be brought into its final form by hard turning; However, even more mechanical machining operations of the cylindrical seat 11 done, z. B. by honing.

A very advantageous result, taking into account technical requirements and economic efficiency, results when the radial difference h _c exceeds the following value:

As the course of h _c looks like, is different for different values of the nominal circumferential stress σ _nom to the diameter D and steel as the ring material (E = 210.000 N / mm ²⁾ in 5 shown. Here a critical hoop stress σ _c of 200 MPa is used. The value h _c represents the value of the unevenness of the bore which is still permissible in any case. The formula given above gives the value for h _c in mm, even if the diameter D in mm is used.

Accordingly, in the implementation of the idea according to the invention, the procedure is such that, based on the intended design and the planned use of the rolling bearing, it is first determined with which hoop stress σ _nom, for example, the bearing inner ring will sit on its shaft. This results in particular from the intended fit between the cylindrical seat of the bearing ring and the shaft. For this purpose, appropriate computer programs can be used with which the nominal hoop stress in the bearing ring can be determined, which results from the intended interference fit.

Then, the critical hoop stress σ _{c is determined} in the bearing ring, as it exists after the production of the press fit and before the application of an external load in the bearing ring. This value is material-dependent; an example of said voltage has been given above.

It can then be determined from the mathematical relationship mentioned above, when the mechanical machining of the cylindrical seat can be canceled (determined, for example, by interactive measurement), ie when the limit for the radial difference h _{c is} given, which can be tolerated in any case ,

The effort for the mechanical processing of the bearing seat surface can be minimized.

LIST OF REFERENCE NUMBERS

1

 bearing arrangement

2

 roller bearing

3

 Bearing inner ring

4

 Bearing outer ring

5

 rolling elements

6

 first machine part (shaft)

7

 second machine part (housing)

8th

 Layer (sleeve)

9

 recess

10

 cylindrical surface

11

 cylindrical seat

d

 radial thickness of the layer

D

 Diameter of the bearing ring

a

 axial direction

h _c

 Radial difference between the maximum and minimum value of the radius over the circumference of the cylindrical seat

D

Diameter of the cylindrical seat

e

 Young's modulus of the material of the bearing ring

σ _c

 critical hoop stress in the bearing ring before the application of an external load and possibly after the production of a press fit

σ _nom

 nominal hoop stress in the bearing ring, possibly caused by a press fit

Claims (12)

Bearing arrangement ( 1 ) comprising at least one rolling bearing ( 2 ), the rolling bearing ( 2 ) at least one bearing inner ring ( 3 ) and at least one bearing outer ring ( 4 ), between which rolling elements ( 5 ) are arranged, wherein the bearing inner ring ( 3 ) with a first machine part ( 6 ), the bearing outer ring ( 4 ) with a second machine part ( 7 ) and wherein the bearing inner ring ( 3 ) and the bearing outer ring ( 4 ) consist of steel, characterized in that between the bearing inner ring ( 3 ) and the first machine part ( 6 ) and / or between the bearing outer ring ( 4 ) and the second machine part ( 7 ) a layer ( 8th ) is disposed of a material having a lower rigidity than steel. Bearing arrangement according to claim 1, characterized in that the material of the layer ( 8th ) Is plastic, preferably polyamide, more preferably polyamide 6.6. Bearing arrangement according to claim 2, characterized in that the plastic is fiber-reinforced. Bearing arrangement according to one of claims 1 to 3, characterized in that the layer ( 8th ) is designed as a hollow cylindrical structure. Bearing assembly according to claim 4, characterized in that the radial thickness (d) of the layer ( 8th ) between 0.5% and 5% of the diameter (D) of the bearing ring ( 3 . 4 ) at the point where the layer ( 8th ) with the bearing ring ( 3 . 4 ) is in contact. Bearing arrangement according to one of claims 1 to 5, characterized in that the layer ( 8th ) in a recess ( 9 ) in the first machine part ( 6 ) and / or in the second machine part ( 7 ) is arranged. Bearing arrangement according to claim 6, characterized in that the layer ( 8th ) with a cylindrical surface ( 10 ) of the first machine part ( 6 ) and / or the second machine part ( 7 ) flush. Bearing arrangement according to one of claims 1 to 7, characterized in that the axial (a) extension of the layer ( 8th ) and the axial extent of the bearing ring ( 3 . 4 ), with the layer ( 8th ) is in contact, or the axial extent of the layer ( 8th ) of the bearing ring ( 3 . 4 ) only slightly surmounted. Bearing arrangement according to one of claims 1 to 7, characterized in that the axial (a) extension of the layer ( 8th ) over the axial extent of the bearing ring ( 3 . 4 ), with the layer ( 8th ) is in contact. Bearing arrangement according to one of claims 1 to 9, characterized in that the first machine part ( 6 ) is a wave. Bearing arrangement according to one of claims 1 to 10, characterized in that the bearing inner ring ( 3 ) for the layer ( 8th ) forms a cylindrical seat and / or that the bearing outer ring ( 4 ) for the layer ( 8th ) forms a cylindrical seat surface, wherein the cylindrical seat surface is designed such that the radial difference amount (h _c ) between maximum and minimum value over the circumference of the cylindrical seat surface is at least equal to the following value:

With: h _c : radial difference between the maximum and minimum values of the radius over the circumference of the cylindrical seat in mm; D: diameter of the cylindrical seat of the bearing ring ( 3 . 4 in mm; E: modulus of elasticity of the material of the bearing ring ( 3 . 4 ) in N / mm ² (MPa); σ _c : critical hoop stress in the bearing ring ( 3 . 4 ) before applying an external load, optionally after the production of an interference fit, in N / mm ² (MPa); σ _nom : nominal hoop stress in the bearing ring ( 3 . 4 ) after its assembly, possibly caused by a press fit, in N / mm ² (MPa). Method according to Claim 11, characterized in that the critical hoop stress (σ _c ) in the bearing ring ( 3 . 4 ) is applied before the application of an external load a value between 180 MPa and 220 MPa, preferably of 200 MPa.

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