EP3870390A1

EP3870390A1 - Method for machining a bearing ring and for producing a rolling bearing

Info

Publication number: EP3870390A1
Application number: EP19748657.4A
Authority: EP
Inventors: André KUCKUK; Martin Buschka
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2018-10-22
Filing date: 2019-07-16
Publication date: 2021-09-01
Also published as: KR20210075066A; US20210339305A1; WO2020083422A1; JP2022505492A; JP7210719B2; CN112703080A; DE102018126181A1

Abstract

The invention relates to a method for machining a bearing ring (2, 3) of a rolling bearing (1), in particular a wheel bearing, comprising the following features: clamping a blank provided for the production of the bearing ring (2, 3) in a machining machine, structuring and simultaneously consolidating an annularly closed surface (10) of the bearing ring (2, 3) that forms a sealing face by means of the pulsating application of pressure by using a machining body (14).

Description

Process for processing and manufacturing a Laqerrinq

of a rolling bearing

The invention relates to a method for machining a rolling bearing ring. Furthermore, the invention relates to a method for producing a roller bearing and a roller bearing, in particular wheel bearing.

DE 29 20 889 C2 discloses a method for cold rolling components. A rolling force pulsates at a frequency of 30 to 300 Hz. The upper limit of the pulsating rolling force should not exceed 100% of a static rolling force. The result should be a workpiece surface of the desired quality with increased fatigue strength.

DE 10 2008 032 919 A1 discloses a method for the surface hardening of a component, which works with an oscillating rolling tool, which can be spherical. Alternatively, the rolling tool can be cylindrical. In both cases, the rolling tool swings when the surface to be solidified is deep-rolled in such a way that hammering is superimposed on the deep-rolling of the surface.

The surface of a component can also be solidified by surface blasting, which is also referred to as peening. In this connection, reference is made, for example, to documents EP 1 623 794 B1, DE 10 2011 117 401 A1, US 6,467,321 B2 and DE 10 2011 101 369 A1.

Document DE 10 2006 048 712 A1 relates to a method for ultrasonic shot peening of transmission shafts for vehicles. This method also provides for the inside of a hollow gear shaft to be machined by shot peening. The gear shaft to be machined is attached to a sonotrode body, whereby it itself forms part of the sonotrode. DE 10 2010 020 833 A1 discloses a method for surface hardening in a spring. This process also works with ultrasonic shot peening.

US 2010/0052262 A1 describes a sealing device provided for a wheel bearing, which comprises an elastic sealing element and a metallic stop element. The stop element here has a surface processed by shot peening.

The object of the invention is to make progress in rolling bearing technology with regard to the rational production of contact surfaces for seals.

This object is achieved according to the invention by a method for machining a rolling bearing ring according to claim 1 and by a method for producing a rolling bearing according to claim 8. Furthermore, the object is achieved by a rolling bearing with the features of claim 9 Refinements and advantages of the invention explained in connection with the roller bearing also apply mutatis mutandis to the machining and the production method and vice versa.

A bearing ring of the rolling bearing is processed in the following way:

A ring-shaped blank provided for the production of the bearing ring is clamped in a processing machine, for example a lathe, whereby, as an alternative to rotating the blank, a non-rotating arrangement of the blank is also possible,

- A structuring and at the same time solidification of an annularly closed, sealing surface forming the bearing ring by pulsating pressurization with a machining body. In the case of a rotating blank, the processing body is typically part of a non-rotating processing tool. In the case of a blank, for example fixed on a table, processing is possible in particular by means of a processing tool comprising the processing body, which is rotated as a whole about an axis, for example a multi-axis robot or a processing center.

If the structuring and hardening of the sealing surface takes place with a rotating workpiece, at least one rolling element raceway of the bearing ring is machined, that is to say by turning and / or grinding, in the same clamping, in the case of a rotating blank, that is to say the workpiece. There are several advantages to this process:

On the one hand, rational and precise machining is favored in that the structured surface of the bearing ring is produced in the same clamping in which the machining of the bearing ring is also carried out. On the other hand, no separate element, for example in the form of a stop disc to be connected to a bearing ring or a thrust ring, is required to produce a sealing contact. Rather, within the rolling bearing, the elastic sealing element attached to one of the bearing rings makes direct contact with the sealing surface of the other bearing ring processed by pulsating pressurization. Compared to conventional solutions, this not only minimizes the number of parts, but also tends to minimize the space requirement of the rolling bearing.

The contact seal formed by the structured surface of the bearing ring and the elastic sealing element is characterized by low friction and low susceptibility to wear with a good sealing effect. The sealing effect relates here both to the retention of lubricants, i.e. grease or oil, in the rolling bearing and to the keeping dirt away from the inside of the rolling bearing. The process for manufacturing the rolling bearing comprises the following steps:

Provision of a bearing ring machined in the manner described and having a structured surface in the form of depressions, for example spherical depressions, and a further bearing ring,

Placing a number of rolling elements between the bearing rings,

- Assembly of a seal that is effective between the bearing rings in such a way that it is held on the further bearing ring and contacts the structured surface.

Balls as well as needles or rollers, for example cylindrical rollers or tapered rollers, can be provided as the rolling elements of the rolling bearing. The rolling bearing can be designed as a single or multi-row bearing and can comprise two bearing rings or a larger number of bearing rings, for example three bearing rings. For example, the roller bearing is a wheel bearing for a motor vehicle. In general, the rolling bearing has the following features:

A number of rolling elements and at least one seal are arranged between at least two bearing rings, which is held on one of the bearing rings and contacts a solidified surface of the other bearing ring which is structured in the form of depressions. The depressions can be spherical, conical, cylindrical or scale-shaped, for example.

In particular, the structured surface, that is to say the sealing surface with the depressions or dents produced, has a roughness depth Rt of at most 100 pm. This ensures that the sealing effect of the seal that runs against the structured surface or sealing surface is maintained, and at the same time brings about an optimization with regard to the friction that occurs between them. A roughness depth Rt of the structured surface of at most 10 pm is particularly preferably selected. A roughness depth Rt in the range from 3pm to 5pm has proven itself here. While one of the bearing rings of the rolling bearing is machined by pulsating pressure, no other machining is generally provided for the other bearing ring. The rolling bearing can be sealed either on one side or on both sides. Each of the bearing rings can either be a one-piece or a split bearing ring.

In typical configurations, the bearing ring of the rolling bearing machined by pulsating pressure is the inner ring. Either the inner ring or the outer ring can be provided as the rotating bearing ring.

The pulsating pressurization creates an irregular plastic deformation of the surface of the rolling bearing ring. The bearing ring to be machined, initially in the form of a blank, can be clamped in a lathe, for example, for machining and pulsating pressurization. The sequence of the machining steps and pulsating pressurization is not fixed in this case, and in all cases the workpiece, that is to say the bearing ring to be machined, preferably remains in the same setting during the two process steps.

While the bearing ring to be machined rotates, the machining tool which effects the pulsating pressurization can be shifted in the radial direction or axial direction of the bearing ring, depending on the position of the surface to be machined. This displacement of the machining tool, for example, describes a spiral line, a helical line or a frequently intersecting wavy line on the machined surface. In any case, at the end of the machining process, depressions which have been produced on the machined surface provided as a sealing surface are distributed approximately uniformly, expressed as the number of depressions per unit area. The tool, which contacts the surface of the bearing ring to be structured in a pulsating manner, can be designed, for example, as a ball or cylinder or barrel roller. In particular when a ball is used as a machining tool, this can be supported by a liquid cushion that transmits the pressure pulses. The pressure pulses can be generated piezoelectrically, pneumatically or mechanically. In cases where the processing tool is firmly connected to a tool holder, the pressure pulses are transmitted via the tool holder. If the processing tool, in particular in the form of a sphere, is supported by a liquid cushion, the pressure pulses are generated by pressure fluctuations in the liquid cushion.

In all cases, the amplitude of the vibration of the machining tool can either be at most as large as the maximum value of the depressions or greater than the maximum depth of the deformations in the surface of the workpiece, that is to say bearing rings. If the amplitude is limited to the maximum value of the depressions in the surface of the workpiece, permanent contact between the machining tool and the bearing ring remains during machining. If, on the other hand, amplitudes of the tool occur which are greater than the maximum value of the depressions, this means that the contact between the tool and the workpiece is interrupted regularly during machining.

Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show here:

Fig. 1 shows a schematic representation of the processing of a surface of a

Bearing rings due to pulsating pressurization,

2 shows the bearing ring processed with the method according to FIG. 1 in a perspective view, 3 shows a roller bearing designed as a deep groove ball bearing, including the bearing ring according to FIG. 2,

4 a section of a roller bearing designed as a wheel bearing with a bearing ring machined according to FIG. 1.

Unless otherwise stated, the following explanations relate to both exemplary embodiments. Parts or structures which correspond to one another or which in principle have the same effect are identified with the same reference symbols in all the figures.

A roller bearing, identified overall by the reference number 1, is designed as a ball bearing and comprises an inner ring 2 and an outer ring 3. The roller bearing 1 shown in FIG. 3 is a deep groove ball bearing, and the roller bearing 1 only partially shown in FIG. 4 is a double-row one Angular contact ball bearings, namely a wheel bearing for a motor vehicle. In this case, a flange of the inner ring 2 is designated 4.

Between the bearing rings 2, 3 balls roll as rolling elements 5 in both cases. The balls 5 can be guided in a cage, not shown. A raceway of the inner ring 2 contacting the rolling elements 5 is designated by 6, a raceway of the outer ring 3 by 7.

A seal 8, which has a sealing lip 9, is held on the outer ring 3. The sealing lip 9 contacts a surface 10 of the inner ring 2, which in the case of FIG. 3 describes a cylinder which is concentric with the central axis M of the rolling bearing 1. In contrast, in the case of FIG. 4, the surface 10 lies on a plane which is oriented normal to the central axis M. In both cases, the seal 8 is a contact seal. In a manner not shown, the seal 8 can have more than one sealing lip 9. The surface 10 which is contacted by the sealing lip 9 is structured by means of a method which is illustrated in FIG. 1 and which provides a surface structuring 11. This method is used in the production of the inner ring 2 of the rolling bearing 1 according to FIG. 3 as well as in the production of the inner ring 2 of the rolling bearing 1 according to FIG.

To produce the inner ring 2, a blank, the basic shape of which corresponds to the shape of the later inner ring 2, is clamped in a processing machine, not shown, in particular a lathe. During the subsequent processing, the blank, that is to say the later inner ring 2, rotates about its central axis M. The processing of the blank during clamping in the processing machine includes the machining of the rolling element raceway 6.

In the example outlined in FIGS. 1 to 3, the roller bearing 1 is only sealed on one side. Accordingly, the roller bearing 1 has only a single cylindrical surface 10, which functions as a sealing surface within the fully assembled roller bearing 1 (FIG. 3). The surface structuring 11 of the surface 10 indicated in FIG. 2 is likewise given in the exemplary embodiment according to FIG. 4. The surface structuring 11 has the shape of numerous depressions 12, which are quasi stochastically distributed on the surface 10. The roughness depth Rt of the structured surface 10 is in the range from 3 to 5 pm.

A tool 13, which is indicated in FIG. 1, is used to produce the depressions 12. The tool 13 is installed on the processing machine, in particular a lathe, and comprises a processing ball 14, which is generally referred to as a processing body. The machining ball 14 is rotatably arranged within the tool 13 and is supported here by a liquid cushion within the tool 13. By generating an oscillating pressure which acts within the liquid cushion, an oscillation of the machining ball 14 is caused, which is referred to as vertical oscillation V without any restriction of the generality. In the example according to FIG. 1, the vertical oscillation V is oriented in the radial direction with respect to the central axis M. In contrast, when machining the inner ring 2 of the rolling bearing 1 according to FIG. 4, a vertical oscillation V is to be generated. gene, which is aligned in the axial direction, based on the central axis M. The frequency of the vertical oscillation V is significantly higher than the speed of the inner ring 2 in both cases.

In the case of FIG. 1, the vertical oscillation V is superimposed on an axial displacement AV of the tool 13. The axial displacement AV is also an oscillating movement. This oscillation describes a wavy line on the surface 10, along which the depressions 12 lie. In the course of the multiple rotations of the inner ring 2, there are multiple overlaps of this waveline, so that ultimately the desired quasi-statistical distribution of the depressions 12 on the surface 10 arises.

In a modified method, it is possible to move the machining body of the tool 13 only once in the axial direction over the surface 10, the axial displacement AV taking place in this case much more slowly than in the case of the wavy machining paths. The slow, unique movement of the tool 13 theoretically creates a helix on the surface 10. The pitch of this helical line is so small that in this case, too, there is ultimately a uniform distribution of the depressions 12 on the surface 10 with a very good approximation.

To produce the surface structuring of the inner ring 2 according to FIG. 4, the tool 13 is moved slowly and uniformly, for example, radially from the inside to the outside or from the outside to the inside. The depressions 12 produced in this way lie theoretically on a spiral line. If, on the other hand, the tool 13 is moved with a comparatively high frequency between a first extreme point, which is located radially on the inside, and a second extreme point, which represents the radially outer boundary of the surface 10, waveforms of the structuring 11, which in FIG a single plane, namely the plane of the surface 10. In the course of several revolutions of the inner ring 2, these waves overlap several times, in principle comparable to the exemplary embodiment according to FIG. 1, so that a high uniformity of the distribution of the depressions 12 within the surface 10 is also achieved in this case. Reference list

1 roller bearing

2 inner ring

3 outer ring

4 flange

5 rolling elements

6 raceway of the inner ring

7 Race of the outer ring

8 seal

9 sealing lip

10 surface

11 surface structuring

12 deepening

13 tools

14 machining ball

AV axial displacement

M central axis

V vertical oscillation

Claims

1 Method for machining a bearing ring (2, 3) in a roller bearing (1), with the following features:

- clamping a blank provided for the production of the bearing ring (2, 3) in a processing machine,

- Structuring and at the same time solidifying a ring-shaped, closed surface (10) of the bearing ring (2, 3) by pulsating pressurization with a processing body (14).

2. The method according to claim 1, characterized in that the pulsating pressure is applied with a spherical machining body (14).

3. The method according to claim 1 or 2, characterized in that in the same clamping, in which the sealing surface (10) of the bearing ring (2, 3) is structured by pulsating pressurization with a processing body (14) and at the same time is solidified, a raceway (6, 7) of the bearing ring (2, 3) is produced by machining, the blank rotating during the two processing steps mentioned.

4. The method according to any one of claims 1 to 3, characterized in that during the pulsating pressurization of the processing body (14) relative to the bearing ring (2,3) is displaced in its axial direction.

5. The method according to any one of claims 1 to 3, characterized in that during the pulsating pressurization of the processing body (14) relative to the bearing ring (2,3) is displaced in its radial direction.

6. The method according to claim 4 or 5, characterized in that in the course of the pulsating pressurization of the processing body (14) describes a helix or a spiral line on the surface to be structured (10).

7. The method according to claim 4 or 5, characterized in that in the course of the pulsating pressurization of the processing body (14) describes a frequently intersecting wavy line on the surface to be structured (10).

8. A method for producing a rolling bearing (1), comprising the following steps:

Provision of a bearing ring (2, 3) machined according to claim 1 and having a surface (10) structured in the form of depressions (12) and a further bearing ring (3, 2),

- Placing a number of rolling elements between the bearing rings (2, 3), - Mounting a seal (8) effective between the bearing rings (2, 3) in such a way that it is held on the further bearing ring (3, 2) and the structure - Contacted surface (10) contacted.

9. Rolling bearing (1), with at least two bearing rings (2, 3), between which a number of rolling elements (5) are arranged, and with at least one seal (8), which is held on one of the bearing rings (2, 3) and contacts a solidified surface (10) of the other bearing ring (3,2) structured in the form of depressions (12).

10. Rolling bearing according to claim 9, characterized in that it is designed as a wheel bearing.