WO2004079216A1

WO2004079216A1 - Anti-friction bearing assembly

Info

Publication number: WO2004079216A1
Application number: PCT/DE2004/000428
Authority: WO
Inventors: Achim Wiebelt; Achmed Schulz
Original assignee: Universität Karlsruhe
Priority date: 2003-03-05
Filing date: 2004-03-04
Publication date: 2004-09-16
Also published as: WO2004079216A8; DE10309828A1; DE112004000011D2

Abstract

The invention relates to a fluidic cage anti-friction bearing (1) comprising a large number of circulating anti-friction bearings (2a) and a lateral rim (3). The latter (3) has recesses (4) on the side of the anti-friction bearings.

Description

Title: - Rolling bearing arrangement

description

The present invention relates to what is claimed in the preamble and is therefore concerned with bearings.

Bearings are known. They serve to reduce the friction between a rotating shaft and a fixed housing or the like. For this purpose, between the shaft and the solid housing element or the like supporting it, such as balls (ball bearings) or cylinders are arranged, which are rotatable. Since the rotatable bodies rotate at least partially when the shaft rotates, the friction of the shaft when it rotates relative to the housing is reduced.

Different technical applications now require bearings that are optimized in different directions. A particular problem arises about then _y when the bearing shaft should rotate very fast. This is the case with exhaust gas turbochargers such as those used in internal combustion engines. Since the friction increases with increasing rotational speed, the friction between the individual components must be reduced. In principle, friction-reducing fluids such as lubricating oils and the like can be used for this.

Such a bearing is described for example in French patent 1,464,889.

DE 40 37 734 A1 also shows a machine part with a rolling or sliding bearing surface in which a plurality of tiny is formed arbitrarily recesses that have certain statistical properties.

DE OS 2162678 discloses a radial or axial roller bearing with rolling elements arranged between two bearing rings or disks, which are guided through fixed or loose ribs in one or both axial directions, with flat spiral grooves or in the contact surfaces of the ribs or the rolling elements the like is provided.

WO 94 / 2.4446 shows a self-pumping. Rolling bearings with an inner and an outer ring and a plurality of rolling elements. The inner surface of the outer ring and the outer surface of the inner ring have a channel in the circumferential direction of the bearing and a group of oblique grooves which are cut in the surface of the inner and / or outer ring, so that lubricant from one side of the Rolling bearing can be brought to the other side to lubricate the bearing surface and the rolling elements.

US 3 792 911 discloses a radially rotating bearing, in which one of the sections has a specific trough surface. For example, one of the trough rings is equipped with a rim, the front side of which lies in the plane perpendicular to the central axis of the bearing and on which there are spiral grooves.

The German utility model application 68 10 086 describes a front thrust washer for the journal of the cross member of a universal joint, which is arranged floating between the front side of the journal and the bottom of the associated bearing bush and has lubrication pockets in the end faces thereof. are seen, the face thrust washer made of a heat-stabilized, highly crystalline and heat-resistant plastic into which the lubrication pockets are pressed during manufacture.

German Offenlegungsschrift 1 575 500 describes a grease-lubricated thrust bearing consisting of a disk-shaped cage and a number of rolling elements accommodated in pockets of the cage, at least one of the two end faces of the cage being provided with groove-shaped depressions which extend over the whole or approximately the extend the entire radial height of the cage to its outer diameter and are inclined in the direction of rotation of the cage related to the adjacent running disk.

US 3 179 478 describes a roller bearing of the form in which a plurality of balls are forced by a cage ring to rotate on a circular path between the inner and the outer tread, the outer ball tread having a groove which corresponds to the shape of the Corresponds to balls and a web is provided on each side of this groove, on which the cage ring slides through hydrodynamic lubrication; the balls are held in spaced apart arrangement by a plurality of ball pockets along the circumference of the ring; it is proposed that the outermost part of the cage be changed by spiral grooves which are directed onto the ball path in the direction of rotation of the cage ring and are dimensioned to produce hydraulic forces which are sufficient to overcome the centrifugal displacement of oil in this bearing, the inner surface of the cage having the largest circumference in the plane of the spherical path and falls to a smaller extent at the end of the cage.

The aforementioned arrangements show rolling bearings that are lubricated with oil or the like.

However, there are a number of applications in which the use of friction-reducing fluids such as lubricating oils and the like is undesirable, impossible or insufficient. For example, the emission behavior of exhaust gas compressors deteriorates significantly when lubricants are used. In other cases, such as in high-temperature fuel cells, in which supplied air must also be compressed, a lubricant additive is e.g. B. not possible at all.

It has therefore already been proposed to design a bearing arrangement with an air cage, in which the friction of the individual components is reduced by the fact that air is pressed in between the bearing bodies.

Such bearings are known, for example, from DE 29 31 348 C2, which shows a radial cylindrical roller bearing, consisting of a race with radial rims provided at both ends, which with the end faces of cylindrical rollers, which with only a small mutual distance the circumference of the race almost completely fill cooperate in order to guide and extending radially at least bis- to the cylinder, the successive through the lines of contact the cylindrical rollers is, wherein the raceway on the circumferential distributed feed bores for a hydrostatic ^'medium are provided, wherein full between the The end faces of all cylindrical rollers and the adjacent ribs are only thin Liquid gaps are present and the feed bores, the number of which corresponds at least to the number of cylindrical rollers, are designed as throttle bores.

With such an arrangement, the proportion of sliding friction in bearings should be significantly reduced. Another aerostatic bearing is known from US-PS 48 87 914. Furthermore, from DE 32 23 007 C2 a multi-row cylindrical roller bearing, preferably a support roller, is known, consisting of two concentric races, which have radial, opposing ribs at both axial ends and roll between which cylindrical rollers, each of which has one flange On-board pair has a circumferential groove open to the other board, into which a sealing ring slotted at one circumferential point, which is supported under pretension on the other board, engages with slight play on all sides, one of the races providing a bore for the supply of oil mist in a manner known per se is, wherein at least one of the rims has a plurality of axially extending through openings, at least some of which are closed with removable plugs, the through openings being arranged in the radial region between the raceway of the associated race and the sealing ring.

Reference is also made to DE 198 35 261 AI and DE 39 33 689 C2 regarding further aerostatic bearings.

Although such improvements are achieved by the aerostatic cages in such cylindrical roller bearings or the like, increased demands make it desirable to further improve the usability of bearings. Such improvements are aimed at reducing the load gers with the same properties, the usability of cheaper material with otherwise the same parameters, the increase in the load capacity, the maximum non-destructive speeds, etc. In other words, it is worthwhile to enable advantageous changes in design.

The object of the present invention is to provide something new for commercial use.

The solution to this problem is claimed in an independent form. Preferred embodiments can be found in the subclaims.

The present invention thus proposes, in a first basic concept, a rolling bearing with a plurality of rotating rolling elements and a lateral flange for this purpose, in which it is provided that the rolling elements have recesses on the end face of the rolling element.

It is therefore initially proposed that the rims in a fluid cage roller bearing be structured in such a way that the end face of the rolling element does not rest on the entire surface. This can significantly reduce the friction between the ribs and the roller bearing body. The indentation already provides a further design parameter, which makes it possible to better adapt the rolling bearing design to the respective specific applications.

The rolling bearing will typically be an air cage. ^'' act in which air is pressed under the circumference under pressure into the rolling element area between the outer circumference and the shaft. On corresponding publications that the Describe the exact principle of such arrangements is pointed out. In particular the publication is made fully by reference to the part of this disclosure "Oil-free roller bearing with aerostatic Cage for Turbochar- ger Applications Part 2: An experimental Study" by A. Wiebelt, A. Schulz and S. Wittig, 9 ^th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, Honolulu, Hawaii, February 10-14-2002.

A fluid cage roller bearing is therefore a roller bearing with a fluid cage. It should be pointed out that an air cage bearing for the purposes of the present invention is also referred to as an air cage roller bearing or fluid cage roller bearing and is also referred to as an aerostatic roller bearing if not air but a different, compressible fluid such as helium or the like is used becomes. It should be mentioned that special applications in particular may require storage in which neither conventional liquid lubricants nor oxidizable or oxidizing gases are used for storage. The rolling bearing assembly of the present invention will be readily usable in such cases, as will be apparent to those skilled in the art from the entire description.

The rolling bearing is typically used for high-speed applications, in particular with rotational speeds of at least 12,000 rpm, preferably above 20,000 rpm. At such speeds of rotation, the friction between the rolling element face and the rims becomes significant and the indentations can contribute to an improvement to a greater extent. The high rotational speeds in connection with compressible fluids in the rolling element area allow this Floating the end faces of the rolling elements on fluid cushions, the cushion-forming fluid being pressed by the rolling element as it moves over the recess into the recess. The rolling element, which moves over the recess, thus initially pushes air or another fluid into the recess and then slides on the air compressed in this way. In this way, the friction is significantly reduced compared to even good tribological pairings between rolling elements and rims. With the same choice of material, this makes it possible to allow higher speeds before a bearing failure occurs. With a corresponding choice of material with regard to tribological and / or strength behavior, etc., a further increase in rotational speed can be achieved by the invention. It should be pointed out that the support or air cushion effect or the behavior of a rolling bearing arrangement according to the invention which is held for this will only occur with sufficiently rapid movement of the rolling bodies over the depressions. However, since the friction losses at low speeds, at which no significant effects due to fluid compression and / or displacement etc. into the recess or recess can be observed, are small, no damage or operational impairments are typically expected at low speeds , In this way, a turbine can be driven over the starting or stopping speed range like a turbocharger without negative effects being expected.

At least six, preferably at least eight, rolling elements are typically provided. These numbers allow a very smooth movement. In a practical embodiment, about ten to fourteen rolling elements are distributed around the circumference. When designing a roller bearing, the rolling element dimensions, etc., experience from other bearings with an aerostatic cage can be used.

The rolling elements will preferably have two flat end faces, which can in particular be parallel to one another. The term “even” also includes such configurations on which a chamfer and / or crowning is present. Barrel-shaped, frustoconical or conical rolling elements can be used with the invention, if this is desired and appropriate bearing training is provided. Particularly In a case in which the rolling elements have two generally flat end faces, the side rims will preferably be profiled with depressions on both rolling element end faces, the recesses preferably being designed such that this is the preferred behavior desired.

While it is possible per se to form a recess, for example as a circumferential groove, and optionally to make further depressions in this recess, it is preferred if the recesses are completely fluidly separated from one another, that is to say fluid from one recess into the next only via one can flow not deepened board area. In this case, the desired reduction in the friction behavior results in a special way.

The recess or recess is preferably dimensioned and / or shaped such that it can be covered completely by the individual rolling element or by its end face. The recess can also have an inclination to the shelf level. Is preferred when viewed in the case of asymmetrical depressions in the typical direction of rotation, the rolling element first passes over a further deepened area and then a less deep area of the deepening. Instead of an inclination, a gradation or the like can obviously also be provided. During production, however, there are manufacturing advantages due to a continuous inclination, since the recesses can be provided by spark erosion, for example.

The inclination or, in the case of gradation, imaginary inclination will typically be less than 10 ° ^' and in particular be in the range between above 0 ° and below 5 °. Inclinations that are too large result in a volume that is too large with reasonable indentation surfaces, which leads to a late onset of the effect, that is to say a reduction only at very high speeds. At too low inclinations in to sensitive ^■ royal air cushion results. For reasons of disclosure, it should be mentioned that a plateau without inclination can be provided in the depression area. Advantageous precise designs of the inclination, recess shape etc. can be obtained by the person skilled in the art from the description below, taking into account the desired bearing application, for example with regard to load, material, etc., by considering the hydrodynamic and hydrostatic or aerodynamic and aerostatic properties of the arrangement in addition to others, usual sizes. Attention is drawn to the possibility of modeling.

The recesses will preferably be arranged close to one another, the distance between two recesses in particular being smaller than the diameter of the rolling element end face. In other words, the rolling element covers recess on recess practically without interruption. special it is preferred if the distance between the recesses is less than the radius of the rolling element. It should be pointed out, however, that recesses that are too narrow can possibly result in the desired effect no longer being able to be achieved in the manner required for a significant improvement in behavior if the recesses are too close to one another. However, it is preferred in any case if the number of all depressions or recesses, which are in particular separated from one another, is greater than the number of rolling elements.

The invention is described below only by way of example with reference to the drawing. In this shows:

Fig. 1 is a developed sectional view through a

Rolling bearing of the present invention in the flange area, FIG. 2 shows a plan view of a section of a flange, FIG. 3 shows a plan view of a rolling bearing from above with the ribs partially broken away, FIG. 4 shows a perspective view of a rolling bearing of the invention.

According to FIG. 1, a rolling bearing 1, generally designated 1, comprises a plurality of rotating rolling elements 2a, two of which, namely rolling elements 2a and 2a2, are shown in FIG. 1, and a lateral flange 3 therefor, the recesses 4 towards the rolling element end face 2b having.

In the present case, the roller bearing 1 is formed as possible from 100 Cr6 roller bearing steel, which is already good Has tribological properties and is cheaper than the materials that can also be used for the purposes of the invention, such as ceramics, etc. The roller bearing 1 is formed as an aerostatic cage known per se, in which, as can be seen in particular in FIG. 3, air flows in from the circumferential side through inlet bores 1 a between roller elements 2 a 1, 2 a 2 lying close to one another, passes between them and near the mounted shaft 5 exits through the spaces 6 between the cylinder bodies and the shaft 5. Pressure chambers 7 are thus formed between the rolling elements in a manner known per se.

The rolling elements 2 are cylindrical in the present case, the rollers being slightly spherical and having a small chamfer in order to avoid the occurrence of critical edge stresses in the generally cylindrical rolling element. The chamfer is selected so small that the leakage gap that arises between a rolling element and the outer raceway is at most small, that is to say the aerostatic cage effect is not significantly impaired. As can be seen in FIGS. 3 and 4, a large number of rolling elements, approximately 10 (FIG. 3) and 14 (FIG. 4) respectively, are provided.

The rims 3 do not extend exactly to the shaft 5, but leave a free area 8 open to it. However, the width of the shelves is selected so that more than half of the rolling element end is covered by the shelves 3, as can be seen in particular from FIG. 3.

The depressions 4 are, as shown in Fig. 2, arranged close to each other. In the preferred direction of rotation of the bearing shown by arrow 9, each indentation 4 is things formed inclined with changing height in the running direction. The selected shape is only shown as an example as a semicircle, since such a design can be produced particularly easily. Obviously, other training courses would be feasible without any problems. It can be seen that - as possible, but not absolutely necessary - the indentations in the radial-radial direction extend over more than half of a rolling element end face, as can be seen from the rolling element end face shown in broken lines. In the running direction, each indentation is smaller than the rolling element diameter at the widest point.

The recess 4 is inclined, namely at an angle to the general plane of the shelves 3 in a preferred embodiment 5 °. (Fig. 1 is drawn exaggerated.)

The arrangement is used as follows:

First, the bearing is fastened in a suitable manner with the shaft to be supported on a fixed part, such as a machine housing, relative to which the bearing is to be carried out. Then the pressure lines for supplying the aerostatic cage are connected.

Now the pressure source is put into operation and the rotational movement of the shaft in the direction of rotation is initiated. The board-roller contact results in normal-oriented loads due to an axial thrust, which results from angular errors between the shaft and the bearing, the angular errors occurring either due to installation tolerances and / or during operation due to rotor dynamically excited rotor vibrations can result. Due to the contact, frictional losses now occur per se in the usual way. As soon as the rotational speed of the shaft and thus also the rotational speed of the rolling elements has exceeded a certain critical limit, the rotating rolling cylinders drive air in front of them to a large extent into the depressions 4. During this driving-in process, the air is compressed and at the same time the rolling cylinder continues to move beyond the recess until the recess is finally completely covered. The air compressed and compressed into the recess leads to the end face of the rolling cylinder no longer rubbing on the shelves but sliding on an air cushion. Since this process is practically continuous due to the close arrangement of the depressions, there is no wobbling or the like and wear and friction are significantly reduced. In comparison to an otherwise identical, but not deepened roller bearing, 10 to 15% higher speeds are achieved before component failure.

Claims

claims

1. Fluid cage roller bearing with a plurality of rotating rolling elements and a lateral ribs therefor, characterized in that the ribs are provided with recesses on the end face of the rolling element.

2. Fluid cage rolling bearing according to one of the preceding claims, characterized in that it is the fluid

Air acts.

3. Fluid cage roller bearing according to one of the preceding claims, characterized in that it is designed for speeds of at least 12,000 rpm, in particular over 20,000 rpm.

4. Fluid cage rolling bearing according to one of the preceding claims, characterized in that at least six, preferably at least eight, particularly preferably at least ten rolling elements are provided.

5. Fluid cage roller bearing according to one of the preceding claims, characterized in that the rolling bodies have two flat end faces, in particular have two flat end faces of the same size and in particular are cylindrical.

6. Fluid cage roller bearing according to the preceding claim, characterized in that a lateral rim with recesses is provided on both sides of the rolling elements.

7. fluid cage roller bearing according to one of the preceding claims, characterized in that the recesses are formed by fluidically separated recesses, in particular such that a non-recessed on-board area of fluid must be overflowed for fluid communication from recess to recess.

8. Fluid cage roller bearing according to one of the preceding claims, characterized in that recesses which can be covered completely are provided by the rolling element.

9. Fluid cage roller bearing according to one of the preceding claims, characterized in that the recesses have an inclination to the general shelf level.

10. Fluid cage roller bearing according to one of the preceding claims, characterized in that the inclination is less than 10 and in particular in the range above 0 and below 5.

11. Fluid cage roller bearing according to one of the preceding claims, characterized in that closely spaced depressions are provided, in particular with a distance from edge to edge smaller than a Wälzkör- ^" perstirndurc knife, preferably less than a Wälzkör- perstirnseitenradius.

12. Fluid cage roller bearing according to one of the preceding claims, characterized in that the number of recesses is greater than the number of rolling elements.