EP2491261A1

EP2491261A1 - Angular contact ball bearing, in particular a spindle bearing, having improved cage guidance

Info

Publication number: EP2491261A1
Application number: EP10763155A
Authority: EP
Inventors: Christoph Haizmann; Otmar Hartling; Volker Kestler; Norbert Kretzer; Manuel Lommel; Horst Masuch; Wolfgang May
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2009-10-21
Filing date: 2010-09-21
Publication date: 2012-08-29
Also published as: WO2011047925A1; US20120251025A1; DE102009050153A1; JP2013508633A; CN102597550A

Abstract

The invention relates to an angular contact ball bearing, comprising an outer ring, an inner ring, a plurality of balls, wherein the balls are arranged between the outer ring and the inner ring in a cage rotatably about a bearing axis, wherein the cage is guided via a cage guiding surface of the outer ring, and wherein the angular contact ball bearing has a nominal pressure angle of less than or equal to 30 degrees. The aim of the invention is to provide such an angular contact ball bearing which effects a reduction of the friction between the cage and the outer ring, wherein the balls continue to be securely guided, and which is simple and cost-effective to produce. To achieve said aim, according to the invention, in a sectional view, comprising the bearing axis, a circular arc running from a point of a track of the outer ring furthest away from the bearing axis along the track in the direction of a track end facing the cage guiding surface to an intersecting point of the circular arc and a straight line through the cage guiding surface has a central angle that is greater than or equal to 60 degrees.

Description

Name of the invention

Angular contact ball bearings, in particular spindle bearings, with improved cage guidance

The invention relates to an angular contact ball bearing comprising an outer ring, an inner ring, a plurality of balls, wherein the balls between the outer ring and the inner ring in a cage are arranged rotatably about a bearing axis, wherein the cage is guided over a cage guide surface of the outer ring and wherein the angular contact ball bearing has a nominal pressure angle less than or equal to 30 degrees.

Such angular contact ball bearings are used for example as spindle bearings in machine tools, these often for high speeds, z. B. over 15,000 revolutions / minute are designed. Especially with these high-speed roller bearings, it has been found to be advantageous that the cages are not guided rolling elements, but on the shoulders or rims of a bearing ring, generally cage guide surfaces, out. These are so-called on-board cages. In this way, problems with respect to the friction of the rolling elements are avoided in the pockets, since the game of rolling elements in the cage pockets can be chosen sufficiently large.

Such a generic angular contact ball bearing is shown in Figure 1. The angular contact ball bearing 1 comprises an inner ring 2 with an inner ring raceway 3, an outer ring 4 with an outer ring raceway 5 and balls 6 guided by a cage 10 which roll on a bearing axis 7 on the inner ring raceway 3 and the outer ring raceway 5. The outer ring 4 has a Board 8 with a cage guide surface 9, which faces a radially outwardly facing surface 1 1 of a ring member of the cage 10. The cage 10 is guided by its surface 11 and the cage guide surface 9 of the outer ring 4. The nominal pressure angle α (alpha) is 25 ° in this example. The nominal pressure angle refers to the angle that a pressure line with a radial plane at an unloaded bearing, that is at a bearing in which the balls contact the raceways stress-free includes. It has been found that during operation between the surface of the cage 1 1 and the cage guide surface 9 of the outer ring 8 friction occurs to a considerable extent. The friction gains in particular with increasing bearing speed in influence.

Object of the invention

The invention is based on the object to provide a generic angular contact ball bearing, which causes a reduction in the friction between the cage and outer ring, the balls continue to be guided safely and which is simple and inexpensive to manufacture.

Summary of the invention

This object is achieved by an angular contact ball bearing according to the independent claim. Accordingly, a generic angular contact ball bearing is characterized in that in a sectional view, comprising the bearing axis, a circular arc extending from one of the bearing axis point of a career of the outer ring along the track in the direction of a cage guide surface facing the track end to an intersection of the arc and a through the cage guide surface Just set a center angle greater than or equal to 60 degrees.

The invention is based on the idea of achieving a reduction in the friction between cage and outer ring by reducing the cage mass. Thus, it was recognized that the cage mass on the centrifugal force, especially at very high speeds has a significant influence on the friction, since the contact force between the cage and outer ring increases sharply with the speed.

The solution according to the invention is now that the cage mass and thus the friction can be significantly reduced by the cage guide surface of the outer ring is further displaced in the direction of the bearing axis. It is exploited that the function of the cage can in principle already be met by a cage, which in comparison to the cages according to the prior art, for example, Figure 1, has a much smaller outer diameter. Thus, it is sufficient for the function of the cage, namely to effect a spacing of the balls, to have only a relatively slight radial extent on both sides of the pitch circle. According to the invention, the cage guide surface of the outer ring should now be displaced radially inwards to the bearing axis so far that the radial extent of the cage is determined exclusively by the requirements of its function, that is the spacing of the balls. The manner in which the cage guide surface of the outer ring is displaced radially in the direction of the bearing axis is not decisive for the realization of the core idea of the invention. As explained below, in particular an enlargement of the board including an extension of the track as well as on the board executed, separate Radialvor- jumps, comprising the cage guide surface, conceivable. Such radial projections may either be part of a one-piece Bordes or outer ring or be formed by separate ring elements, which on the Pushed on the outer ring.

According to the invention, the radial displacement of the cage guide surface is defined such that a circle segment which starts at a point of the raceway furthest away from the bearing axis runs along the raceway in the direction of a raceway end facing the cage guide surface and ends at an intersection of the circle segment with a straight line passing through the cage guide surface exceeds a certain midpoint angle. The midpoint angle defines, as usual in geometry, the angle between the two end points of a circle segment and the center point of the circle segment. The larger the center angle of the circle segment according to the invention, the further the cage guide surface shifts radially inwards, i.e., the cage guide surface moves radially inwards. towards the bearing axis. In particular, according to the invention, the center point angle should assume a value of 60 ° or more. From this value, on the one hand, a noticeable reduction of the friction sets in, on the other hand, the cage can continue to extend radially radially outward from the partial circle sufficiently radially outwards in order to guide the balls safely.

Although outer rings are already known with a board that radially moves so far inward that a correspondingly defined center angle occupies a value of about 60 degrees. However, such outer rings are intended for use in angular contact ball bearings with a nominal pressure angle of 40 degrees or more. For such bearings, which are not used, moreover, as a spindle bearing, but as a bearing for low speeds, such a board is necessary to form a corresponding to the high pressure angle career. In contrast, the outer ring according to the invention is an outer ring of an angular contact ball bearing with a nominal pressure angle of 30 degrees or less. Preferred embodiments of the invention are specified in the subclaims. According to one embodiment, the inner ring has two shoulders which are mirror-symmetrical with respect to a plane perpendicular to the bearing axis. The two shoulders of the inner ring are symmetrical at least bezüg- lent their basic shape. In particular, the two shoulders should have the same height, that is, both shoulders have a radially outwardly directed end surface whose distance from the bearing axis is the same. Such a design has the advantage that in the case of a sealed bearing, identical sealing disks can be used on both sides.

Due to the inventive design of the outer ring, i. Positioning of the cage guide surface, low-mass and also simple designs of the cage are made possible.

Thus, according to one embodiment, the cage has two ring elements and the ring elements connecting transverse webs, wherein the transverse webs terminate flush radially inwardly and / or radially outwardly with the ring elements. The ring elements run around the bearing axis and are arranged concentrically to one another. Preferably, the ring elements have the same inner and outer diameter, in particular, the cross section of the ring elements may be identical. While according to the prior art at least one ring element has been extended radially outwards in the direction of the cage guide surface in order to ensure a secure and precise guidance of the cage, such an extension can be dispensed with according to the invention. Instead, the two ring elements no longer have to extend beyond the radially maximum extension of the transverse webs. In particular, the cage may have an annular shape with a rectangular cross-sectional profile having cage pockets for receiving the balls. Preferably, the cage, starting from the pitch circle, ie a circle through the centers of the balls, a substantially equal extent in both radial directions. The inventive design of the cage allows not only a weight reduction but also a simplification of the cage production. Thus, according to a further embodiment of the cage with respect to a plane perpendicular to the bearing axis plane can be formed mirror-symmetrical. Such a symmetrical cage shape allows for easier production and easier assembly of the angular contact ball bearing and results from the fact that the cage design according to the invention is given essentially only by the function of the spacing of the balls.

According to a further embodiment, the cage has two concentric to the bearing axis extending ring elements and the ring elements connecting transverse webs, wherein the cage is guided over a radially outwardly facing surface of one of the ring elements through the cage guide surface of the outer ring. It thus forms an annular gap between the cage guide surface of the outer ring and the surface of the cage. It makes sense to extend both the cage guide surface and the surface of the cage along the bearing axis parallel to each other. In particular, according to one embodiment, the cage guide surface forms a cylinder arranged concentrically around the bearing axis. In a corresponding manner, the cage guide surface opposite surface of the cage also forms a concentrically arranged about the bearing axis cylinder. Between the cage guide surface and the surface of the cage thus forms a cylindrical annular gap. Of course, it would also be conceivable to have different courses of the surfaces, e.g. a cone-shaped course.

In one embodiment, the midpoint angle is between 60 and 70 degrees. Preferably, the midpoint angle is between 63 and 67 degrees. It was found that in these areas a good compromise between reducing friction by reducing the radial extent of the cage on the one hand and maintaining a safe and precise Guide the balls can be achieved by sufficient radial extent of the cage on the other hand, if transverse webs and ring elements of the cage to complete radially flush. According to one embodiment, the nominal pressure angle is between 15 and 25 degrees. Preferably, the nominal pressure angle is 15 or 25 degrees. These two values are typical values for spindle bearings, ie standardized inner rings can be used. According to one embodiment, in the sectional view, the track has an intersection with the cage guide surface. According to this embodiment, the board of the outer ring was thus increased radially to the bearing axis, ie the board is made higher than is known from the prior art, but in principle has the same basic shape as before. The intersection of raceway and cage guide surface can be rounded. Alternatively, however, it is also possible that according to an embodiment in the sectional view between the raceway and cage guide surface, a heel or a step is introduced. Instead of enlarging the board in the direction of the bearing axis with simultaneous extension of the track likewise in the direction of the bearing axis, according to this embodiment, a radially inwardly directed projection is formed on the previous board. The cage guide surface is located on a radially inwardly directed surface of the projection. The raceway can remain unchanged, so that a step is created between the projection and the raceway. The radial extension of the projection or the step represents the radial displacement of the cage guide surface. It is conceivable that this projection is an integral element of the rim or outer ring or is formed by a separate element. If the projection is an integral element of the rim or outer ring, according to one embodiment, the outer ring can be designed in particular in one piece. If the projection is formed by a separate element, this can for example consist of a ring element with a rectangular Cross-sectional profile exist, which is introduced into the outer ring. The separate element may consist of the same or a different material as the outer ring. The advantage of having a separate element is the possibility of being able to continue to use existing outer rings.

The reduction of the friction according to the invention does not require an increase in the installation space of the angular contact ball bearing - neither axial nor radial space. Thus, according to one embodiment, the inner ring and the outer ring on an equal axial extent. This corresponds to the value of corresponding standard angular contact ball bearings.

According to one embodiment, the angular contact ball bearing is sealed at one or at two axial ends. In this case, a sealing disc can be used in each case at the axial ends of the angular contact ball bearing between the inner ring and outer ring.

The angular contact ball bearing according to the invention is particularly suitable for this purpose as a spindle bearing, e.g. a machine tool to be used. Of course, other applications are conceivable, in particular as rolling bearings for high speeds.

Brief description of the drawings

Embodiments of the present invention will be described below with reference to the accompanying figures. Showing:

Fig. 1 is an angular contact ball bearing according to the prior art

Fig. 2 shows a first embodiment of an inventive

Angular contact ball bearing, 3 shows a second embodiment of an angular contact ball bearing according to the invention, and FIG. 4 shows a machine tool comprising an inventive

Angular contact ball bearings.

Detailed description of the drawings

The same or functionally identical components in the figures are provided with the same reference numerals.

FIG. 1 shows an angular contact ball bearing according to the prior art as described at the beginning in a sectional view, comprising the bearing axis 7, the upper half being illustrated. The pressure line 12 for the unloaded bearing is shown and forms with a plane perpendicular to the bearing axis 7 level 13, a radial plane, the nominal pressure angle α (alpha), which is 25 degrees in this example.

The outer ring raceway 5 has a point A which is farthest away from the bearing axis 7. Starting from point A along the outer ring raceway 5 in the direction of the cage guide surface 9 facing the end of the outer ring raceway 5 to an intersection B of the outer ring raceway 5 with a set by the cage guide surface 9 straight line 17 results in a circle segment whose center angle ß (beta) in this example about 50 degrees. That is, the nominal pressure angle α (alpha) is about half as large as the center point angle β (beta). The cage of the angular contact ball bearing according to Figure 1 consists of two ring elements 14, 15 which extend circumferentially and are connected by a plurality of axially extending transverse webs 16. The transverse webs 16 have guide ing surfaces for contacting the balls 6, wherein the balls may be made of metal or ceramic. For optimum guidance of the balls, it is necessary that these guide surfaces extend radially both outside and within a pitch circle through the ball center of the angular contact ball bearing 1.

In order to allow a guide of the cage 10 through the board 8 of the outer ring 4, the cage 10 extends radially correspondingly far outward. In particular, the cage 10, starting from the pitch circle, extends substantially farther radially outward than inwards.

FIG. 2 shows a first exemplary embodiment of an angular contact ball bearing according to the invention. In contrast to the angular contact ball bearing according to the prior art according to FIG. 1, in FIG. 2 the rim 8 of the outer ring 4 is clearly radially inwards, ie. radially towards the bearing axis 7, has been extended. By the same amount, the cage 10 could be shortened in its radial extent. On the board 8 axially opposite side of the outer ring 4, the outer ring 4 has only a slight radial projection in the direction of the bearing axis 7, to prevent falling out of the balls 6 between the cage guide surface 9 and the surface 1 1 , However, there is no cage guide surface on this side, i. the cage 10 is guided only by a single cage guide surface 9.

The cage guide surface 9 has been moved in the direction of the bearing axis 7 by the entire board 8 was enlarged to the bearing axis 7 out. In particular, while the outer ring raceway 5 was increased accordingly.

The midpoint angle β (beta) is 68 degrees. The nominal pressure angle α (alpha) was not changed, ie it is still 25 degrees. The new Construction of the board and the cage leads to no change in the rolling behavior of the balls 6 on the corresponding raceways 3, 5 with the exception that due to the reduced friction, a lower heat generation is achieved.

The cage 10 could be kept to a minimum in its radial extent. In a section comprising the bearing axis 7, it has a rectangular cross-section. Each of the two ring elements 14, 15 also has a rectangular cross-section and terminates radially flush with the transverse webs 16. With respect to a radial plane 13, the cage 10 is mirror-symmetrical.

The outer ring 4 and the inner ring 2 have the same axial extension and terminate axially flush. In particular, the outer dimensions of the angular contact ball bearing 1 correspond to those of a comparable standard bearing.

The inner ring 2 has two rims 18, 19 which extend radially outward by the same amount. In particular, both shelves 18, 19 are mirror-symmetrical with respect to a radial plane 13. None of the shelves 18, 19 has a cage guide surface, but instead there is a substantially larger annular gap 20 between the cage 10 and the ribs 18, 19 compared to the annular gap 18. This annular gap 20 allows the supply of lubricant during operation. The angular contact ball bearing 1 could be sealed by means of two sealing washers.

FIG. 3 shows a second exemplary embodiment of an angular contact ball bearing according to the invention. In contrast to the embodiment of Figure 2, the cage guide surface 9 has been moved radially inwardly according to Figure 3 by the board 8 has a projection 21. The projection 21 extends radially from a radially inwardly facing surface 22 to the inside and has the cage guide surface 9. The outer ring raceway 5 remained unchanged. In this embodiment, the projection 21 is formed integrally with the board 8. Of course, a separate ring would also be conceivable, which is fitted into the outer ring 4 on the on-board surface 22. The center angle defined according to the invention is as in the first embodiment after 68 degrees.

Figure 4 shows a drive of a machine tool 23 comprising two angular contact ball bearings 1 according to the invention, which are designed as spindle bearings and used in O arrangement and serve as a fixed bearing.

LIST OF REFERENCE NUMBERS

1 angular contact ball bearing

2 inner ring

3 inner ring raceway

4 outer ring

5 outer ring raceway

6 balls

7 bearing axis

8 board

9 cage guide surface

10 cage

1 1 surface

12 printing line

13 level

14 ring element

15 ring element

16 crossbar

17 Straight

18 board

19 board

20 annular gap

21 lead

22 board surface

23 drive machine tool

Claims

claims

Angular contact ball bearing, comprising an outer ring (4), an inner ring (2), a plurality of balls (6), wherein the balls (6) between the outer ring (4) and the inner ring (2) in a cage (10) rotatable about a Bearing axis (7) are arranged, wherein the cage (10) via a cage guide surface (9) of the outer ring (4) is guided and wherein the angular contact ball bearing has a nominal pressure angle (a) is less than or equal to 30 degrees, characterized in that in a sectional view, comprising the bearing axis (7), a circular arc extending from one of the bearing axis (7) farthest point (A) of a raceway of the outer ring (4) along the track in the direction of one of the cage guide surface (9) facing the track end to an intersection (B) of the Circular arc and a line through the cage guide surface (17) has a center angle (ß) greater than or equal to 60 degrees.

Angular contact ball bearing according to claim 1, characterized in that the inner ring (2) has two shoulders (18, 19) which are mirror-symmetrical with respect to a plane (13) perpendicular to the bearing axis.

Angular contact ball bearing according to claim 1 or 2, characterized in that the cage guide surface (9) forms a cylinder arranged concentrically around the bearing axis (7).

Angular contact ball bearing according to one of the preceding claims, characterized in that the cage (10) with respect to a plane perpendicular to the bearing axis (7) plane (13) is mirror-symmetrical.

Angular contact ball bearing according to one of the preceding claims, characterized in that the cage (10) has two ring elements (14, 15) and transverse webs (16) connecting the ring elements, wherein the transverse webs (16) extend radially inwards and / or radially outwards with the Close ring elements (14, 15) flush.

Angular contact ball bearing according to one of the preceding claims, characterized in that the cage (10) has two ring elements (14, 15) and transverse webs (16) connecting the ring elements, wherein the cage has a radially outwardly facing surface (11) of a the ring elements (15) through the cage guide surface (9) of the outer ring (4) is guided.

Angular contact ball bearing according to one of the preceding claims, characterized in that the center point angle (β) is between 60 and 70 degrees.

Angular contact ball bearing according to 7, characterized in that the center point angle (β) is between 63 and 67 degrees.

Angular contact ball bearing according to one of the preceding claims, characterized in that the nominal pressure angle (a) is between 15 and 25 degrees.

Angular contact ball bearing according to one of claims 1 - 9, characterized in that in the sectional view of the raceway (5) has an intersection point (B) with the cage guide surface (9).

Angular contact ball bearing according to one of claims 1 - 9, characterized in that in the sectional view between the raceway (5) and cage guide surface (9) has a shoulder or a step is introduced.

Angular contact ball bearing according to one of the preceding claims, characterized in that the outer ring (4) is made in one piece.

Angular contact ball bearing according to one of the preceding claims, characterized in that the inner ring (2) and the outer ring (4) have an equal axial extent.

Angular contact ball bearing according to one of the preceding claims, characterized in that the angular contact ball bearing is sealed at one or at two axial ends.

15. Angular contact ball bearing according to one of the preceding claims,

characterized in that the angular contact ball bearing is a spindle bearing.