Rolling bearing ring and method for machining a rolling bearing ring

Abstract

The present invention relates to a rolling bearing ring (2, 3), particularly a ball bearing outer ring, which is processed in the following steps: - deforming the rolling bearing ring (2, 3) in a path-controlled manner to cause plastic deformation, wherein its roundness is changed; - moving the point of application of the force causing plastic deformation on the circumference of the rolling bearing ring (2, 3); - restoring the rolling bearing ring (2, 3) to a circular shape.

Description

Technical Field

[0001] This invention relates to a method for machining rolling bearing rings, particularly outer rings of ball bearings. Furthermore, this invention relates to a rolling bearing ring for single-row rolling bearings. Background Technology

[0002] A method for manufacturing bearing rings, i.e., ball bearing rings, is described, for example, in DE 10 2014 216 313 A1. Herein lies a bearing ring designed for use in the transmission mechanism of an aircraft. Other rolling bearing components for use in aviation are disclosed in document DE 10 2012 205 242 A1. These rolling bearing components have nitrided edge regions where the nitrogen content decreases from the outside in, and where the residual compressive stress decreases from the outside in.

[0003] The installation of deep groove ball bearings is typically performed using an eccentric mounting method. In this method, the inner ring of the bearing is positioned eccentrically relative to the outer ring to allow for the insertion of rolling elements, in this case, balls. To increase the number of balls that can be inserted, one of the bearing rings can be deformed. The mounting method described in DE 10 2014 223 708 A1 even proposes deformation of both bearing rings.

[0004] Another eccentric mounting method is described in DE 2 137 979 A. In this case, balls are filled into the sickle-shaped space between bearing rings that are eccentrically positioned. During the subsequent centering of the bearing rings, small elastic deformation of the outer or inner ring can occur.

[0005] In principle, the feasibility of filling the rolling elements into the annular space between the two bearing rings through filling openings in the bearing rings has also been proposed. In the case of bearing devices known from EP 2 143 835 B1, the net width of the rolling element filling recess in the bearing ring is smaller than the diameter of the rolling element. Filling of the rolling elements is only feasible through the elastic deformation of the bearing ring. Summary of the Invention

[0006] The present invention aims to achieve an advancement in rolling bearing technology, enabling rolling bearings to be filled with particularly high filler density while also producing particularly small fluctuations in production quality under mass production conditions.

[0007] The objective according to the invention is achieved by a method for machining a rolling bearing ring. Similarly, the objective is achieved by a rolling bearing ring having the features of the invention. The design of the invention, described below in conjunction with the rolling bearing ring, is also meaningfully applicable to the machining method and vice versa.

[0008] The processing method includes the following steps:

[0009] - To deform the rolling bearing ring, particularly in a path-controlled manner, so that the rolling bearing ring undergoes plastic deformation while changing its roundness.

[0010] - This causes the point of application of the tool that induces plastic deformation to move along the circumference of the rolling bearing ring.

[0011] - To restore the rolling bearing ring to its original circular shape.

[0012] In principle, the alternative path-controlled deformation also considers the force-controlled deformation of the bearing ring, whereby the deformation involves a pre-defined deformation path and is performed independently of the applied force. The bearing ring recovers its circular shape through elastic deformation. Alternatively, the bearing ring is plastically deformed back to its circular shape at the end of the method.

[0013] The first two steps of the processing method can be configured as follows:

[0014] - Pressure is applied to the rolling bearing ring, with the force introduced at two points on the circumference of the rolling bearing ring that are 180° apart from each other, causing the rolling bearing ring to plastically deform, i.e., to be placed in an elliptical, non-circular shape.

[0015] - Move the point of application of the pressure diagonally opposite to the circumference of the rolling bearing ring.

[0016] The movement of the pressure application point can, in principle, be carried out in stages or continuously. Preferably, it is a continuous, sliding movement of all application points.

[0017] The roundness of a rolling bearing ring changes due to plastic deformation. Roundness describes the extent to which the circumferential line of the workpiece, that is, the annular line on the outer circumference of the bearing ring or in the bottom of the raceway, deviates from an ideal reference circle, which lies in the normal plane relative to the central axis of the bearing ring. Generally, the term "roundness" is referred to in standard DIN EN ISO 1101 "Geometric Product Specifications".

[0018] Plastic deformation can be performed using a rotating tool with the bearing ring not rotating, or using a non-rotating tool with the workpiece, i.e., the bearing ring, rotating. In both cases, the point of application that introduces pressure into the bearing ring preferably sweeps an angle of at least 180° across the circumference of the rolling bearing ring. This means that the entire circumference of the bearing ring can be machined as long as the two points of application are diagonally opposite each other.

[0019] Similarly, a variation of the method is possible in which each segment of the bearing ring's circumference is machined multiple times. Each point of pressure application here moves multiple revolutions around the circumference of the rolling bearing ring. During machining, the pressure acting on the bearing ring and causing its plastic deformation may increase.

[0020] By applying pressure to the bearing ring, the circumferential section of the inner circumferential surface of the bearing ring expands beyond the tensile limit in any case. As the bearing ring subsequently returns to its original circular shape, residual compressive stress is therefore necessarily generated in the corresponding circumferential section.

[0021] The recovery deformation of the bearing rings can be performed before bearing installation or during bearing installation, i.e., eccentric installation. In both cases, a particularly large number of rolling elements can be filled between the bearing rings due to the significantly stronger deformability compared to conventional eccentric installation methods.

[0022] After restoring the deformed bearing ring to its initial circular shape, a final machining process, particularly grinding, can be performed on the bearing ring. According to a possible variation of the cutting process, finishing involves machining the edges of the bearing ring. Here, only a small amount of material is removed from both edges, particularly by turning, grinding, and / or lapping, so that the volume in which residual compressive stress occurs is not significantly altered by the final machining. Therefore, in this case, particularly strong deformation of the bearing ring is possible during installation due to the residual compressive stress introduced into it. Similarly, the raceways of the bearing ring can also be machined.

[0023] The deformation of the bearing ring caused by applying pressure in the first method step is also called pre-deformation. This is especially true for pre-deformation of the entire circumference. Pre-deformation occurs after the heat treatment of the bearing ring.

[0024] Rolling bearing rings, particularly those configured as outer rings of ball bearings, which are pre-deformed, typically have two end sides, with raceways of a typical groove shape for the rolling elements spaced apart from the two end sides. According to the invention, the raceways are arranged between bearing ring regions adjacent to the end sides, in which residual compressive stresses arise from plastic pre-deformation, decreasing from the end sides towards the center of the raceways. In particular, the residual compressive stresses mechanically generated by plastic deformation exist only in the edges of the bearing ring adjacent to the raceways.

[0025] Radially outside the bearing ring region where residual compressive stress is generated, residual tensile stress exists within the bearing ring. According to a possible design, the bearing ring region with residual tensile stress extends from one end of the bearing ring to the opposite end. Measured radially in the bearing ring, the region with residual tensile stress preferably extends further than the cross-sectional region where mechanically generated residual compressive stress exists. Correspondingly, the average residual tensile stress is numerically smaller than the residual compressive stress. Attached Figure Description

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, which are shown in a rough schematic manner in this part:

[0027] Figure 1 This shows a circular, undeformed bearing ring, specifically the outer ring of a ball bearing used in deep groove ball bearings.

[0028] Figure 2 This illustrates the plastic deformation of the bearing ring during multiple processing stages.

[0029] Figure 3 Showing according to Figure 2 Deformed bearing rings and subsequently elastically recovering their deformation.

[0030] Figure 4 , 5 Showing the method for making according to Figure 1 Different equipment for bearing ring deformation.

[0031] Figure 6 , 7 Showing the basis Figure 1 A diagram showing the possible deformations of the bearing ring in a path-controlled manner.

[0032] Figure 8-10 Showing the use of according to Figure 3 Deep groove ball bearings with bearing ring assembly.

[0033] Figure 11 Showing according to Figure 3 A schematic diagram of the variation curve of bearing ring along with residual pressure stress.

[0034] Figure 12 A bearing ring with roundness that can be measured technically is shown. Detailed Implementation

[0035] Unless otherwise stated, the following description applies to all embodiments. Corresponding or functionally similar parts are indicated by the same reference numerals in the figures.

[0036] The rolling bearing, specifically the deep groove ball bearing, generally indicated by reference numeral 1 in the attached drawing, comprises an inner ring 2 and an outer ring 3 as bearing rings 2 and 3, with balls 4 rolling between them as rolling elements. The balls 4 are positioned in a predetermined location between the bearing rings 2 and 3 in an eccentric mounting method. The inner ring 2, like the outer ring 3, is also configured as a one-piece bearing ring without a filling opening. Within the mounted rolling bearing 1, the balls 4 roll in the grooved raceways 14 of the bearing rings 2 and 3 in a manner known per se, such that radial force and—secondarily—axial force can be transmitted between the bearing rings 2 and 3. Edges 12 and 13 are located on either side of the raceway 14 of each bearing ring 2 and 3.

[0037] As the starting point for the installation of rolling bearing 1, it provides... Figure 1 The outer ring 3, indicated by a symbol, has a perfectly circular shape in practice at this stage. (In the subsequent...) Figure 2 In the processing stage illustrated in the diagram, the outer ring 3 is pressed into a non-circular, elliptical shape, wherein the outer ring 3—in Figure 2 The deformation path of bearing ring 3 is exaggeratedly shown as plastic deformation. D1 This indicates that the deformation of bearing ring 3 is performed using a path-controlled method.

[0038] In this embodiment, the outer ring 3 is held in a constant angular position during plastic deformation. A machining tool (not shown) rotating around the outer ring 3 generates a deformation path S. D1 Numerically, the deformation path S D1 They are equal throughout all deformation stages, Figure 2 Five of the entire deformation stages are illustrated exemplarily. The following angles vary, and the deformation path inducing plastic deformation acts on the outer ring 3 at said angles. Overall, by applying the deformation path, the outer ring 3 is machined over its entire circumference. The mechanically applied deformation path and the variation in angle are arranged such that the bearing ring 3 returns to its original, approximately circular shape after the deformation path is no longer applied.

[0039] During each stage of plastic deformation, i.e., pre-deformation, two diagonally opposite tensile zones 7 appear on the inner circumferential surface of the outer ring 3 (denoted by 6). These tensile zones are located in circumferential regions where pressure is introduced from the outer circumferential surface (denoted by 5). During processing, the tensile zones 7 move around the entire circumference of the outer ring 3. Between the two tensile zones 7, i.e., offset by 90°, two compression zones 8 are formed during each deformation process. The compression of the material of the outer ring 3 in the zones 8 is less significant than the tension in the zones 7 in terms of the resulting residual stress. This is partly because the tensile yield strength is less than the compressive yield strength. Furthermore, the tensile load in the tensile zones 7 of the outer ring 3 is greater than the compressive load in the compression zones 8.

[0040] Finally, residual compressive stress appears on the entire circumference of the outer ring 3 through plastic deformation. Before further processing of the outer ring 3, the outer ring is restored to its circular shape, as shown in... Figure 3 As shown in the diagram. The recovery deformation can be performed using specialized machinery or in the same environment as the preceding plastic deformation, which also forces movement of the deformation region. In the latter case, deformations with varying magnitudes are particularly considered, as described below. Figures 4 to 7 As explained.

[0041] Figure 4 and 5 The diagram illustrates two different devices that enable the bearing ring 3 to be plastically deformed in a "pinch-through" manner, wherein the deformed area moves along the circumference of the bearing ring 3. Not only according to... Figure 4 In its variant forms, and also according to Figure 5 In the variant, the bearing ring 3 is supported on exactly three parts at any given moment when it is "squeezed through". According to... Figure 4 Two inner support rollers 15 support the inner bearing ring 3, while the outer support roller 16 applies pressure to the outer ring 3 from the outside. In contrast, according to... Figure 5 In the arrangement, the three external support rollers 16 that jointly deform the bearing ring 3 describe an isosceles, non-equilateral triangle. In both cases, the support rollers 15, 16, or support roller 16, are configured such that the desired deformation path S is obtained. D1 .

[0042] according to Figure 4 The same equipment is as in Figure 5 The device schematically drawn in the diagram is suitable for performing according to Figure 6 The deformation method or according to Figure 7 The deformation method. In both cases, the bearing ring 3 rotates multiple times, where the deformation, represented by S, first increases and then decreases back to zero at the end of the deformation process. According to... Figure 6 In the variant form, a complete circle of bearing ring 3 is reached before the deformation S increases to half of its maximum value, corresponding to an angle α of 360°. According to... Figure 7 In the variant form, the deformation S first increases until it reaches a first plateau. In this state, the bearing ring 3 continues to rotate, thus being "shaped" through plastic deformation of its various circumferential segments, until it reaches an angle α1 overall, which corresponds to a complete multi-turn of the bearing ring 3. Subsequently, the deformation S increases to a second plateau and remains on this plateau again during multiple turns until a second angle α2 is reached regarding the rotation of the bearing ring 3. The deformation S increases to a third level, which is again maintained during multiple turns of the bearing ring 3, until the deformation S finally and continuously returns to zero.

[0043] When bearing ring 3 recovers its deformation, according to Figure 6 The variant forms and in accordance with Figure 7 In the variant form, towards the end of the deformation method, an elastic shape change occurs, which leads to at least an approximately ideal circular shape, such as in Figure 3 Simplified Chinese drawing. This also applies to drawings already based on... Figure 2 The deformation method is described. In this deformation method, according to Figure 6 Or according to Figure 7 The magnitude of the deformation S can be changed over multiple turns of the bearing ring 3.

[0044] For details regarding the geometric features of bearing ring 3 involving plastic deformation, please refer to... Figure 12 Here, the shape of the outer ring 3 after pre-deformation is compared with the geometrically ideal shape. An outer circle K is provided around the outer circumferential surface 5 of the bearing ring 3. a The inner circumferential surface 6 of bearing ring 3 is similarly connected to the inner circle K. i Tangent. On the outer circle K a and inner circle K i There exists a standard circle K n The standard circle represents a geometrically ideal circle that is equidistant from the outer ring circumferential surface 5 and the inner ring circumferential surface 6 in the initial, undeformed state of the bearing ring 3.

[0045] Standard circle K n radius and inner circle K i The difference between the radii is called the inner radius difference d. i Similarly, in the standard circle K... n radius and outer circle k a The difference between the radii is called the outer radius difference d. a Use d ges Indicates that on the outer circle K a and inner circle K i The total radius difference between them. By restoring the deformation, the radius difference d ges Approximately zero, such that according to Figure 3 The shape of bearing ring 3 is according to Figure 1 The shapes are actually not different.

[0046] exist Figure 3 In the simplified depiction of a state of multiple plastic deformation, a bearing ring region (denoted by 9) exists at the inner circumferential surface 6 of the bearing ring 3, in which residual compressive stress ES is generated. The bearing ring region 9 is surrounded by a bearing ring region 10 extending to the outer circumferential surface 5, in which residual tensile stress exists.

[0047] The residual compressive stress ES is ideally distributed across the width of bearing ring 3 from... Figure 11This is derived from the results. Accordingly, the maximum residual compressive stress ESm is generated only in the region of edges 12 and 13, that is, in the region adjacent to the end sides of bearing ring 3 indicated by S1 and S2. In contrast, there is a very small residual compressive stress ES generated by plastic deformation in the region of the curved raceway 14 located between edges 12 and 13, and there is approximately no residual compressive stress ES.

[0048] The assembly of bearing rings 2 and 3 and rolling element 4 is as follows: Figures 8 to 10 The diagram illustrates this. Bearing rings 2 and 3 are initially positioned eccentrically to allow for the insertion of rolling element 4. Subsequently, as shown in the diagram... Figure 9 As illustrated in the diagram, the bearing ring 3 undergoes elastic deformation, where the deformation path is represented by S in this case. D2 This is indicated. For example, the elastic deformation region within the bearing ring 3, which has an elliptical, non-circular shape, is... Figure 9 The value is represented by 11. Other elastic deformation regions are directly located along the deformation path S. D2 Below. Due to the residual compressive stress in bearing ring region 9, particularly strong elastic deformation of bearing ring 3 is possible during eccentric mounting.

[0049] According to an alternative method, before eccentric mounting begins, the bearing ring 3 is not fully or completely returned to its circular shape. In this case, the bearing ring 3 deforms not only elastically but also plastically during eccentric mounting, with the final circular shape of the bearing ring 3 appearing only after this final deformation process. Alternatively, the circular shape is achieved by remachining the raceways 14, edges 12, 13, and / or the outer ring circumferential surface 5 before the final mounting step.

[0050] In any case, the eccentric installation is terminated by centering bearing rings 2 and 3 together and distributing the rolling elements on the circumference of bearing rings 2 and 3, thereby achieving the desired effect for rolling bearing 1. Figure 10 The state is shown in the diagram. Subsequently, a rolling bearing cage, such as a riveted cage made of a plate, can be installed in a manner known per se. Similarly, a seal that functions between bearing rings 2 and 3 can be installed in a manner known in principle.

[0051] List of reference numerals in the attached diagram:

[0052] 1 Rolling bearing

[0053] 2 Inner Ring

[0054] 3 Outer Ring

[0055] 4 Rolling elements

[0056] 5. Outer ring circumference

[0057] 6. Inner ring circumference

[0058] 7. Tension Zone

[0059] 8. Compression Area

[0060] 9. Bearing ring region with residual compressive stress

[0061] 10 Bearing ring region with residual tensile stress

[0062] 11 Elastic Deformation Region

[0063] 12 Edges

[0064] 13 Edge

[0065] 14 Rolling Track

[0066] 15 Internal support rollers

[0067] 16 External support rollers

[0068] α angle

[0069] α1 Angle

[0070] α2 angle

[0071] d a outer radius difference

[0072] d i Internal radius difference

[0073] d ges Total radius difference

[0074] ES residual stress

[0075] Maximum residual stress ESm

[0076] K a outer circle

[0077] K i Inner circle

[0078] K n Standard circle

[0079] S-shape

[0080] S D1 Deformation path

[0081] S D2 Deformation path

[0082] S1 end side

[0083] S2 end side

Claims

1. A method for machining rolling bearing rings (2, 3), comprising the following steps: - The circular rolling bearing rings (2, 3) are deformed in a path-controlled manner, causing plastic deformation of the rolling bearing rings, wherein the roundness of the rolling bearing rings is changed to a non-circular shape. - The point of application of the force causing the plastic deformation is moved along the circumference of the rolling bearing rings (2, 3). - The rolling bearing rings (2, 3) are restored to their circular shape; the restoration deformation is performed before or during bearing installation.

2. The method according to claim 1, Its features are, The point of application of the force that causes plastic deformation of the rolling bearing ring (2, 3) sweeps through an angle of at least 180° on the circumference of the rolling bearing ring (2, 3).

3. The method according to claim 2, Its features are, The point of application of the force that causes plastic deformation of the rolling bearing ring (2, 3) moves multiple revolutions around the circumference of the rolling bearing ring (2, 3).

4. The method according to claim 2 or 3, Its features are, The plastic deformation occurs when the rolling bearing rings (2, 3) are stationary.

5. The method according to claim 2 or 3, Its features are, The plastic deformation occurs as the rolling bearing rings (2, 3) rotate.

6. The method according to claim 1, Its features are, The rolling bearing rings (2, 3) are finished after the plastic deformation.

7. The method according to claim 6, Its features are, The finishing process includes cutting the edges (12, 13) of the rolling bearing rings (2, 3).

8. A rolling bearing ring (2, 3) obtained by any one of claims 1 to 7, having two end sides (S1, S2) and a raceway (14) for rolling elements located therebetween and spaced apart from the two end sides (S1, S2). Its features are, The raceway (14) is disposed between the bearing ring regions (9) adjacent to the end sides (S1, S2), where residual compressive stress exists, wherein the residual compressive stress decreases from the end sides (S1, S2) toward the middle of the raceway (14).

9. The rolling bearing ring (2, 3) according to claim 8. Its features are, The rolling bearing ring is configured as a ball bearing outer ring, wherein the bearing ring region (9) with residual compressive stress is surrounded by the bearing ring region (10) with residual tensile stress.

Images