EP3286444A1

EP3286444A1 - Method for producing rolling bodies for anti-friction bearings

Info

Publication number: EP3286444A1
Application number: EP16722779.2A
Authority: EP
Inventors: Holger PÄTZOLD; Frank JOCHMANN
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2015-04-20
Filing date: 2016-04-18
Publication date: 2018-02-28
Also published as: KR20170138485A; JP2018513949A; CN107429736A; WO2016169564A1; US20180119741A1; DE102015207106A1

Abstract

The invention relates to a method for producing cylindrical rolling bodies (4) with crowned end surfaces (7) for anti-friction bearings, in particular bearing needles for high-speed axial needle bearings, having the following steps: a) providing of a spherical blank (5) with a diameter (D) which corresponds to the rolling body length (L) of the rolling body (4); b) grinding of the spherical blank (5) into a cylindrical shape of the rolling bodies (4) to their predefined diameter (d), wherein centreless cylindrical plunge grinding or centreless cylindrical throughfeed grinding is used. Moreover, the invention relates to rolling bodies which are produced according to said method, to anti-friction bearings having rolling bodies of this type, and to the use thereof.

Description

Method for producing rolling elements for rolling bearings

The invention relates to a method for producing rolling elements with spherical end faces for rolling bearings, in particular of bearing needles for high-speed axial needle bearings. The invention further relates to rolling elements produced by this method, rolling bearings with such rolling elements and their use.

In gearboxes sliding bearings are increasingly being replaced by axial needle bearings. One advantage is that the bearing friction is reduced, so that, for example, when used in motor vehicles, a fuel saving is achieved as a result.

In transmission applications high bearing speeds of up to 10,000 min ^"1 are achieved, which radially acts an up to 6000-fold acceleration due to gravity to the rolling elements of a the rolling elements enclosing roller retainer must be taken radially. The rollers are typically needle bearings with increased quality requirements for their End faces, wherein the bearing needles typically have a diameter of less than 2 mm and a length of less than 4 mm.

Bearing needles are currently being mass-produced for the industrial and automotive sectors with highly productive manufacturing methods. A conventional manufacturing method for bearing needles is such that first a metallic blank is produced by stretching a wire to a predetermined roughing diameter. Subsequently, pieces of suitable length are cut off from the wire by means of a cutting tool. The wire sections thus produced are then hardened, scrubbed, ground and finely worked. Hacking is done at very high speeds with a high speed cutting tool. This typically produces a technically resulting cutting contour on the needle end faces. The shape of the cutting contour is highly dependent on the guide ratios of the wire in the cutting area and the state of wear of the cutting tools and the wire diameter itself. Test bench tests have shown that rolling elements or bearing needles produced in this way are unsuitable for very high-speed axial needle bearings. The undefined end contour of the bearing needles leads to a strong mechanical load on the radial contact points of the rolling bearing pockets of the cage, resulting in a result only unsatisfactorily short service life of the Axialnadellagers result. Further optimization of the needle end faces will only be successful if the needle end faces are ground and smoothed and rounded by complex finishing processes.

In DE 10 2006 041 586 A1, this technical problem is discussed and solved in that in each pocket of the cage of a Axialnadellagers a bearing needle and a bearing ball in the radial direction are arranged one behind the other, wherein the bearing needle radially inward and the bearing ball are arranged radially outside. This ensures that bearing needles with an undefined face contour can not destroy the cage even at high rotational speeds. A disadvantage of this axial needle bearing, however, is that the additional necessary balls increase its manufacturing cost.

Against this background, the present invention seeks to provide a method for producing rolling elements with spherical end faces for rolling bearings, which is suitable for mass production and can be operated inexpensively. The invention is further based on the object to provide rolling elements produced by this method. The invention is finally based on the object to provide a roller bearing with such rolling elements and its use.

The object is achieved by a method for producing cylindrical rolling elements with spherical end faces for rolling bearings, in particular bearing needles for high-speed axial needle bearing, with the following steps:

a) providing a spherical blank having a diameter D corresponding to the rolling element length L of the rolling element;

b) grinding the spherical blank into a cylindrical shape of the rolling elements to their predetermined diameter d, wherein a centerless outer circumferential Einstechschleifen or a centerless outer circumferential continuous grinding is used. The use of a centerless outside-round plunge grinding or a centerless external cylindrical through-hole grinding for the production of cylindrical rolling elements with crowned faces allows cost-effective mass production at very low cost.

The grinding methods for centerless outer circumferential plunge grinding and for centerless outer cylindrical throughfeed grinding are already known, see for example under http://www.hermle-schleiftechnik.de/pages/en_spitzenlos_durchlaufschleifen.php or http://www.hermle-schleiftechnik.de/ pages / de_spitzenlos_einstechschleifen.php

In this case, a spherical blank is used according to the invention, which is typically present as a commodity, such as Wälzkörperkugel, and is then brought by grinding to the cylindrical shape to a predetermined diameter d. The ball diameter D corresponds to the Wälzkörperlänge L. A material and a heat treatment of the blanks are to select wälzkörperauglich.

A use of Wälzkörperkugeln as blanks is advantageous because they already have an exact and elaborately smoothed surface. The radius of the ball corresponds to the radius of the spherical end faces of the rolling elements, which is determined centric centric and has a highest surface quality without reworking. No exactly grouped balls are needed since the length tolerance of the bearing needles is many times greater than the ball diameter typically grouped in the μηη range. Therefore, cheaper balls can be used than those used in rolling bearings.

The object is also achieved for cylindrical rolling elements with crowned faces by these are prepared by the process according to the invention.

The cylindrical rolling elements produced in the manner described above with spherical end faces for rolling bearings can be used wherever the presence of a defined, concentrically crowned frontal contour is required. This is especially the case with thrust bearings that are exposed to comparatively high bearing speeds with correspondingly high centrifugal forces. The cylindrical rolling element is designed in particular as a bearing needle with a diameter d of less than 2 mm and a length L of less than 4 mm. But also barrel-shaped rolling elements for toroidal bearings can be produced in the manner described.

A ratio of the length L to the diameter d is preferably not more than 3: 1 for economic reasons.

The object is furthermore achieved for the roller bearing, in particular axial needle bearing or toroidal bearing, in that it comprises a roller body ring which has a cage and furthermore the rolling elements according to the invention. Such a rolling bearing can be produced at very low cost and operable at high speeds.

A use of the rolling bearing according to the invention at storage speeds of up to 10,000 revolutions per minute has been proven.

The invention will be explained by way of example with reference to FIGS 1 to 4. So shows:

1 shows an axial plan view of a Wälzkörperkranz a thrust bearing with cage

with bearing needles housed in cage pockets,

2 shows a sectional view of a spherical blank and the resulting

manufactured rolling elements,

FIG. 3 shows a method using a centerless outer circumferential plunge grinding or a centerless outer circumferential through grinding in the side view; and FIG

4 shows a three-dimensional view of the method using the centerless outer-round grinding loop 1 shows an axial plan view of a Wälzkörperkranz 1 of a thrust bearing with a cage 2 and with pockets 3, in each of which a cylindrical rolling element 4 is received in the form of a bearing needle. The radial forces emanating from the rolling elements at very high rotational speeds must be absorbed by the radially outer boundary surface 6 of the pockets 3 nondestructively. For this purpose, the rolling elements 4 at their axial ends in each case a spherical end face 7, which have a high surface quality, so that the rolling elements 4 do not drill into these outer boundary surfaces 6 of the pockets 3. The diameter d of the bearing needles is typically less than 2 mm, while the length L is less than 4 mm. The ratio of length L to diameter d is not more than 3: 1 for economic reasons.

2 shows a sectional view of a spherical blank 5 and the rolling element 4 manufactured therefrom. The production of the rolling elements 4 from the spherical blank 5 takes place here from a roller bearing ball. The length L of the rolling elements 4 corresponds to the diameter D of the spherical blank 5, while the diameter d of the rolling elements 4 is freely definable. The rolling element 4 with its axis of rotation 8 is produced by grinding the area 9 shown hatched to the diameter d, wherein the spherical end faces 7 of the rolling element 4 have the radius of the spherical blank 5 and require no post-processing. 2 shows an enlargement of a spherical blank 5 with a diameter of 2.25 mm, from which a bearing needle 4 with a length L = 2.25 mm and a diameter d of 1 mm is produced. The grinding of the blank 5 is carried out by a centerless outside round-Einstechschleifen or a centerless outer-round through-grinding in order to use the method for mass production.

FIG. 3 shows a method according to the invention using a centerless outer circumferential plunge grinding or a centerless outer cylindrical throughfeed grinding on the spherical blanks 5 in a side view. Here, the blank 5 is not clamped, but guided between a rotating in the arrow direction about a rotation axis 10a grinding wheel 10 and in the arrow direction about the rotation axis 1 1 a regulating wheel 1 1 while held from below by means of a rail 12. One differentiates the Einstechschleifen, in which only one blank 5 between the Grinding wheel 10 and the regulating wheel 1 1 is guided and processed by continuous grinding, in which a plurality of blanks 5, which are arranged juxtaposed on the rail 12, are successively transported by the rail 12 between the grinding wheel 10 and the regulating wheel 1 1. In this case, a movement of the rail 12 in the direction of the z-axis in FIG 3, ie perpendicular to the plane spanned by the drawing sheet xy plane.

FIG. 4 shows a three-dimensional view of the method according to FIG. 3 using the centerless outer circumferential continuous grinding. The same reference numerals as in the preceding figures denote the same elements. The rail 12 transports a plurality of spherical blanks 5 between the grinding wheel 10 and the regulating wheel 1 1, where a grinding of the blanks 5 takes place in a cylindrical shape of the rolling elements 4. Very high throughputs can be achieved with this method. The spherical end faces 7 of the rolling elements 4 have after grinding the radius of the spherical blank 5 and require no further finishing.

All features mentioned in the preceding description of the figures, in the claims and in the introduction to the description can be used both individually and in any combination with each other and also includes the use of a profiled regulating wheel (transport screw) as used for example in the manufacture of tapered rollers. The invention is thus not limited to the described and claimed feature combinations, but all feature combinations are to be regarded as disclosed.

LIST OF REFERENCE NUMBERS

1 rolling element ring

2 cage

3 bag

4 rolling elements

5 Spherical blank

6 Radially outer boundary surface of a bag

7 Crowned face of the rolling element

8 axis of the rolling element

9 Area of the spherical blank to be ground

10 grinding wheel

10a rotation axis of the grinding wheel

1 1 regulating wheel

1 1 a Rotation axis of the regulating wheel

12 rail

D Diameter of the spherical blank

L Length of the rolling element

d diameter of the rolling element

Claims

claims

1 . Method for producing cylindrical rolling elements (4) with spherical end faces (7) for rolling bearings, in particular bearing needles for high-speed axial needle bearings, with the following steps:

a) providing a spherical blank (5) with one of the rolling element length (L) of the rolling body (4) corresponding diameter (D);

b) grinding the spherical blank (5) in a cylindrical shape of the rolling elements (4) to the predetermined diameter (d), wherein a centerless outside round Einstechschleifen or a centerless outer circumferential continuous grinding is used.

2. Cylindrical rolling elements (4) with spherical end faces (7), produced by a method according to claim 1.

3. Cylindrical rolling element (4) according to claim 2, which is designed as a bearing needle with a diameter (d) of less than 2 mm and a length (L) of less than 4 mm.

4. A cylindrical rolling element (4) according to claim 3, wherein a ratio of the length (L) to the diameter (d) is not more than 3: 1.

5. Rolling, in particular axial needle bearing or Toroidallager, comprising a Wälzkörperkranz (1), which has a cage (2) and further rolling elements (4) according to one of claims 2 to 4.

6. Use of a rolling bearing according to claim 5 at storage speeds of up to 10,000 revolutions per minute.