Bearing unit for an exhaust gas turbocharger or an exhaust gas turbine and bearing with such a bearing unit

Abstract

Bearing unit for an exhaust gas turbocharger or an exhaust gas turbine 1.1 with at least one inner bearing ring (1, 2); 1.2 with at least two outer bearing rings (3, 4); 1.3 with at least two rows of rolling elements (5, 6), comprising a first row of rolling elements (5) in the region of a first axial end of the bearing unit between a first of the two outer bearing rings (3) and the at least one inner bearing ring (1, 2) and a second row of rolling elements (6) in the region of a second axial end of the bearing unit opposite the first axial end between a second of the two outer bearing rings (4) and the at least one inner bearing ring (1, 2); 1.4 with an intermediate piece (8) which is positioned at least partially in the axial direction between the two outer bearing rings (3, 4); characterized in that 1.5 each bearing outer ring (3, 4) is elastically supported in the axial direction by at least one spring element (7) relative to the intermediate piece (8).

Description

[0001] The present invention relates to a bearing unit for an exhaust gas turbocharger or an exhaust gas turbine and a bearing of an exhaust gas turbocharger or an exhaust gas turbine.

[0002] The bearing support of the turbine shaft in an exhaust gas turbocharger or an exhaust gas turbine, which is located in the exhaust stream, particularly of a motor vehicle, represents a critical component. Due to the high speeds of the turbine shaft, often exceeding 100,000 revolutions per minute, and the high thermal stress caused by the high exhaust gas temperatures, the bearing unit is exposed to considerable vibration and thermal stress. Particularly disadvantageous are the significant speed spread and temperature variations within the bearing unit, which frequently require the passage of resonance speeds and the compensation of widely varying thermal damping.

[0003] In order to improve efficiency, rolling bearings are preferred for bearing units of this type, but are particularly combined with vibration damping in the form of crush oil dampers. If an oil film or oil ring is provided radially outside the bearing outer ring of such rolling bearings, the bearing outer ring no longer has a defined rotational position within the housing of the exhaust gas turbocharger or exhaust gas turbine, but can rotate more or less circumferentially relative to the housing and the turbine shaft. The co-rotation of the bearing outer ring can lead to wear on the outer surfaces of the bearing outer ring, which negatively affects the bearing function. Furthermore, the rolling behavior of the rolling elements on the raceway of the bearing outer ring is undefined and the oil supply to the bearing can be disrupted. This can also have a negative impact, particularly during long-term operation of the bearing unit.

[0004] Also, in the axial direction, undefined positions of the individual components of the bearing unit relative to one another, in particular the bearing outer rings relative to one another, due to their axial mobility in the axial direction can have an adverse effect on the service life of the bearing unit and can cause undesirable running noises and vibrations in the bearing unit.

[0005] To avoid the disadvantages mentioned, it has already been proposed to elastically support the outer bearing rings of a corresponding bearing unit against one another by means of a compression spring and to further lock them in the housing of an exhaust gas turbocharger by means of an anti-twist device. According to the published application DE 10 2010 054 996 A1, it is proposed to mount the bearing unit within a carrier ring, which can then be inserted into a corresponding bore in a turbocharger housing. The outer bearing rings within the carrier ring are elastically supported against one another by means of a compression spring that rests on the inside of the carrier ring and are secured against twisting by pins, journals, or bolts within the carrier ring. Pins or bolts that are inserted radially into the housing and thus also secure the carrier ring against twisting can also be considered as anti-twist devices.Thus, the outer bearing rings of both rows of rolling elements, which are provided at the axial ends of the bearing unit within the carrier ring, are rotationally and axially secured relative to the carrier ring.

[0006] The carrier ring is mounted in the housing via a vibration-damping oil film and completely and directly surrounds the bearing outer rings. Thus, the oil damping acts via the carrier ring onto the bearing outer ring.

[0007] By designing the carrier ring with a permanently connected bushing, a transport-secured bearing cartridge is achieved. Alternatively, the bearing inner ring can be designed as a single piece and serve as a transport lock itself.

[0008] A particular disadvantage of this design is the large number of different individual parts that must be manufactured separately and assembled during assembly. This makes the production and assembly of the bearing unit expensive. In particular, the nesting of the radially inner compression spring, the bearing outer rings that partially surround them, and the carrier ring that in turn surrounds them, increases the required installation space and the complexity of assembly.

[0009] A further disadvantage of this design is that, on the one hand, the manufacture of the carrier ring that holds the bearing outer rings, particularly in the form of a bushing extending over the entire axial length of the bearing unit, is complex and expensive. Since the bearing outer rings must be inserted precisely in the carrier rings in the radial direction to achieve the necessary centering, the inside of the carrier ring and the outside of the bearing outer rings must be precisely machined. The axial stop for the outer rings must also be precisely manufactured, as it limits the axial play of the rotor in the housing. Furthermore, the oil film damping takes place between the carrier ring and the housing, which complicates the installation of the bearing unit in the housing. In addition, the carrier ring reduces the maximum possible bearing diameter, which is why only bearings with lower load-bearing capacity can be used with a constant bore diameter in the housing.

[0010] EP 2 520 809 A2 discloses another bearing unit for a turbocharger, in which a spacer is positioned between the two outer bearing rings. The spacer has an oil bore for conveying oil to the axial end faces of the spacer. This allows a vibration-damping oil ring to be created between the outer bearing rings and the spacer. Optionally, an axial compression spring is also provided, which elastically supports the two outer bearing rings against each other in the axial direction. The rolling bearings themselves are supplied with oil via radial bores in the outer bearing rings.

[0011] The spacer can be locked in the turbocharger housing, ensuring a secure oil supply. However, since the bearing outer rings must rotate relative to the spacer to ensure axial oil damping, undefined conditions arise in the oil supply to the rolling bearings.

[0012] CN 102322336 A discloses an exhaust gas turbocharger with a bearing sleeve in which two rolling bearings, thrust sleeves, and compression springs are arranged. The two compression springs elastically support each other and push the thrust sleeves against the outer races of the rolling bearings.

[0013] The object of the present invention is to provide a bearing unit for an exhaust gas turbocharger or an exhaust gas turbine and a corresponding bearing which is improved over the prior art in that, on the one hand, vibrations and running noises due to axial displacements of the bearing outer rings are reduced and the bearing tolerances can be precisely adjusted, preferably by the bearing manufacturer, in such a way that the bearing unit can be inserted as a pre-assembled unit into the housing of an exhaust gas turbocharger or an exhaust gas turbine, but the manufacturing costs are reduced and assembly is made easier.

[0014] The object of the invention is achieved by a bearing unit having the features of claim 1, by a bearing unit having the features of claim 3, and by a bearing unit having the features of claim 12. Particularly advantageous embodiments and a bearing arrangement with a corresponding bearing unit are specified in the dependent claims.

[0015] A bearing unit according to the invention for an exhaust gas turbocharger or an exhaust gas turbine comprises at least one bearing inner ring. Advantageously, two separate bearing inner rings are provided, which are supported against one another, particularly in the axial direction, directly or via a spacer element. The two separate bearing rings can thus have the shape of a split hollow shaft. The at least one bearing inner ring can, in particular, be pressed or shrunk onto a turbine shaft with its inner surface, correspondingly with a torsion-proof press fit.

[0016] Furthermore, at least two bearing outer rings are provided, as well as at least two rows of rolling elements, for example in the form of ball bearing rows, comprising a first row of rolling elements in the region of a first axial end of the bearing unit between a first of the two bearing outer rings and the at least one bearing inner ring, and a second row of rolling elements in the region of a second axial end of the bearing unit opposite the first axial end, between a second of the two bearing outer rings and the at least one bearing inner ring. If two bearing inner rings are provided, in particular one row of rolling elements is provided between a bearing inner ring and a bearing outer ring at the first axial end and between a bearing inner ring and a bearing outer ring at the second axial end.

[0017] According to one embodiment, the bearing unit according to the invention comprises an intermediate piece that is positioned at least partially in the axial direction between the two bearing outer rings. "At least partially" means that the intermediate piece, according to one embodiment, can completely enclose the bearing outer rings on their outer circumference, but according to another embodiment, it is positioned completely between the two bearing outer rings in the axial direction or, particularly advantageously, only overlaps a portion of each bearing outer ring in the axial direction, radially inside or radially outside.

[0018] According to the invention, each of the two bearing outer rings is now elastically supported in the axial direction relative to the intermediate piece by at least one spring element. This eliminates the need for a central spring element, which directly supports the two bearing outer rings against each other, facilitating the manufacture and assembly of the bearing unit and optimizing the required installation space.

[0019] Particularly advantageously, at least one anti-rotation device is provided between the intermediate piece and each of the two bearing outer rings, so that the bearing outer rings cannot rotate freely, thus preventing the aforementioned co-rotation. To further reduce the number of parts, the at least one spring element, with which a bearing outer ring is elastically supported in the axial direction relative to the intermediate piece, can simultaneously form the anti-rotation device between the intermediate piece and the respective bearing outer ring.

[0020] The bearing unit according to the invention, according to a further embodiment, has at least two rows of rolling elements, namely at least one first row of rolling elements in the region of a first axial end of the bearing unit and at least one second row of rolling elements in the region of a second axial end of the bearing unit. The second axial end is opposite the first axial end.

[0021] Furthermore, at least one first bearing outer ring is provided, which encloses the first row of rolling elements, and at least one second bearing outer ring, which encloses the second row of rolling elements.

[0022] Furthermore, an intermediate piece is provided, which is positioned at least partially between the first and second bearing outer rings in the axial direction. This includes both an embodiment in which the intermediate piece is positioned entirely between the first and second bearing outer rings, as well as an embodiment in which the intermediate piece partially overlaps with the first and / or second bearing outer rings in the axial direction.

[0023] According to the invention, a stationary component is provided that encloses the intermediate piece and the bearing outer rings. Such a stationary component can, for example, be the housing of the exhaust gas turbocharger or the exhaust gas turbine, so that the intermediate piece and the bearing outer rings are directly enclosed radially on the outside by the housing. However, the stationary component can also be a separate component, for example, fixed in a housing of the exhaust gas turbocharger or the exhaust gas turbine, which then directly encloses the intermediate piece and the bearing outer rings on their radial outside. Stationary therefore means that the component does not rotate.

[0024] According to the invention, the intermediate piece is fixed in the stationary component, whereas the bearing outer rings are each mounted in the stationary component via an oil ring so as to be movable at least in the radial direction. The fixation of the intermediate piece in the stationary component ensures that the intermediate piece cannot move relative to the stationary component, in particular neither in the axial direction, nor in the radial direction, nor in the circumferential direction. By providing the oil ring radially outward between the bearing outer rings and the stationary component, at least a slight degree of mobility is achieved between the bearing outer rings and the stationary component in the radial direction, wherein the oil rings are designed in particular as a squeeze oil film or squeeze oil damper to dampen the bearings.

[0025] By directly supporting the spacer and the at least two bearing outer rings in a common stationary component, wherein the spacer does not extend completely beyond the bearing outer rings in the axial direction, so that the oil ring damping can be provided directly between the bearing outer rings and the stationary component, in combination with the fixation of the spacer in the stationary component, a bearing unit is created that is axially fixed in the center and in which all axial play is adjusted starting from this axial center during operation, which is advantageous in terms of minimal play addition. At the same time, by avoiding the carrier ring described above, which encloses the bearing outer rings and is itself mounted in the housing with an oil ring, the described problem of precisely adapting the bearing outer rings to the contour of the carrier ring is avoided.Rather, the arrangement of the oil rings between the outer surface of the bearing outer rings and the inner surface of the stationary component, in particular the housing, allows for tolerances in the manufacture of these surfaces.

[0026] According to this embodiment of the invention, at least one anti-rotation device is provided between the intermediate piece and each of the two bearing outer rings, so that the two bearing outer rings cannot rotate into an undefined position.

[0027] It is also advantageous in this embodiment if the bearing outer rings are elastically supported in the axial direction relative to the intermediate piece or elastically against each other by means of at least one spring element in order to avoid undefined positions of the bearing outer rings in the axial direction.

[0028] Advantageously, the respective spring element between a bearing outer ring and the intermediate piece also forms the anti-twist device.

[0029] Particularly advantageously, in all of the aforementioned embodiments of the invention, the spring element is designed as a spiral spring or as a wave spring with at least one radially inwardly or radially outwardly directed projection. Such a wave spring advantageously has individual contact surfaces arranged discretely distributed over the circumference, of which a first number or plurality bears against the intermediate piece and a second number or plurality bears against the respective bearing outer ring. The radially inwardly or radially outwardly directed projection can penetrate the intermediate piece in the radial direction and at least engage in the respective bearing outer ring in the radial direction or even pass through it.Alternatively, the radially inwardly or radially outwardly directed projection can penetrate the respective bearing outer ring in the radial direction and at least engage in the intermediate piece in the radial direction or pass through it in order to thus provide the anti-rotation device.

[0030] In a design with a wave spring, this can be discontinuous across its circumference, with two circumferential ends that overlap or are spaced apart. In the latter case, the wave spring does not extend over 360° of the circumference, but only over a smaller angular range.

[0031] According to an advantageous embodiment of the invention, each of the two bearing outer rings has a collar projecting inward in the axial direction with an outer diameter that is reduced compared to the axially outwardly adjoining region of the bearing outer rings, and the intermediate piece encloses only the respective collar of the bearing outer rings in the circumferential direction in the axial direction, wherein advantageously at least one anti-twist device is provided in the respective collar and the intermediate piece.

[0032] In one embodiment of the invention, the intermediate piece or the respective axially adjoining bearing outer ring has an open-edged circumferential groove in which the spring element is positioned. The spring element can thus be supported in the axial direction on one side against an end face of the intermediate piece or the bearing outer ring that delimits the open-edged groove, and on the other side, correspondingly, against an end face of the other component, if the open-edged circumferential groove is formed in the intermediate piece of the bearing outer ring or if the open-edged circumferential groove is formed in the bearing outer ring of the intermediate piece.

[0033] Particularly advantageously, the spring element is positioned radially inside the outer diameter of the intermediate piece in the circumferential groove.

[0034] According to one embodiment of the invention, the bearing unit has at least one spring element, which is provided in the axial direction between the two bearing outer rings and axially supports the two bearing outer rings against each other under elastic pressure. The support can be direct or indirect. With direct support, only the at least one spring element is positioned between the two bearing outer rings for their mutual support. With indirect support, further components are arranged between the two bearing outer rings and the at least one spring element in the force flow of the mutual support, as described above, for example, with reference to the possible design according to the invention.Thus, the two rows of rolling elements are advantageously preloaded in the axial direction via the bearing outer rings and, particularly due to the preload, are supported against a radially outwardly projecting shoulder of the bearing inner rings in every operating condition. Thus, the bearing outer rings and the bearing inner rings are in contact with each other in the axial direction and, in particular, in the radial direction via the rolling elements in every operating condition of the bearing unit, preventing indeterminate bearing conditions.

[0035] In the aforementioned inventive design, an intermediate piece is provided in the axial direction between the two bearing outer rings, as well as an anti-rotation device between the intermediate piece and each of the two bearing outer rings. This prevents rotation of the two bearing outer rings relative to each other and relative to the housing, particularly when the intermediate piece is held in a rotationally secure manner in a housing of the exhaust gas turbocharger or exhaust gas turbine, for example, via a press fit in a corresponding bore of the housing. This also contributes to defined rolling behavior in the bearing and to reduced vibrations and wear.

[0036] According to this embodiment of the invention, each of the two bearing outer rings now has a collar that projects inward in the axial direction and has a reduced outer diameter compared to the axially outwardly adjoining region of the bearing outer rings. The two collars of the two bearing outer rings are thus directed toward each other and positioned between the regions of the two bearing outer rings with a comparatively larger, in particular constant, outer diameter.

[0037] According to this design, the spacer now encloses the two bearing outer rings in the circumferential direction only over the axial section of the respective flange, thus not in the area of ​​the comparatively larger outer diameter at the respective axial end of the bearing unit. Thus, the spacer overlaps the respective flange of the bearing outer ring, but advantageously not the area of ​​the rolling element rows.

[0038] Typically, the two flanges are spaced apart in the axial direction, with this distance being bridged by the intermediate piece, which is preferably constructed as a single piece. The spring element can be provided at this distance. This spring element is advantageously designed as a wave spring. It rests against the bearing outer rings with individual, discrete contact surfaces distributed around the circumference, and thus axially against the bearing outer rings, forcing them apart in the axial direction of the bearing unit.

[0039] It is particularly advantageous if one or both of the at least two anti-rotation devices is / are designed as a snap ring interrupted around the circumference with at least one projection penetrating the intermediate piece in the radial direction, wherein the projection engages in the respective bearing outer ring in the radial direction or penetrates it. With such a snap ring, also called a retaining ring, a particularly simple anti-rotation and disassembly-proof bearing unit can be created, in which the clearances to be adjusted between the individual components are achieved in a pre-assembled state, so that the bearing unit can be installed as a pre-assembled module in a corresponding exhaust gas turbocharger or exhaust gas turbine for supporting the turbine shaft in a housing.Because pre-assembly can be performed at the bearing manufacturer, meaning the supplied exhaust gas turbocharger or power turbine manufacturer does not have to align the individual bearing components relative to each other, optimal assembly can be achieved, largely avoiding assembly errors while simultaneously achieving low bearing clearances and tolerances. This leads to an extended service life and improved performance of the bearing unit and thus of the entire exhaust gas turbocharger or power turbine.

[0040] The intermediate piece advantageously has at least one, in particular two, circumferential grooves, so that a snap ring can be mounted in a circumferential groove as an anti-twist device. The snap ring can be positioned radially within the outer diameter of the intermediate piece in the circumferential groove, i.e., it does not protrude beyond the outer diameter of the intermediate piece, which facilitates the installation of the intermediate piece in the housing and simultaneously further secures the snap ring, which is particularly elastically designed. Except for the at least one, advantageously two, circumferential grooves, the intermediate piece can have an at least substantially constant outer diameter.

[0041] It is advantageous if the spacer has two axially outer end faces, each of which faces an axially inward-facing shoulder of the bearing outer rings with an axial clearance. The spacer extends only from one outer end face to the other outer end face, to which the two bearing outer rings then adjoin in the axial direction.

[0042] The anti-rotation devices can be advantageously manufactured as a cost-effective stamped part and simply clipped onto the spacer and into the two bearing outer rings.

[0043] It is advantageous if the spacer extends axially only between the rows of rolling elements, thus not extending beyond the rows of rolling elements. According to a preferred embodiment, the spacer has two axially outer end faces, each of which faces an axially inwardly directed shoulder of the bearing outer rings with an axial clearance. These end faces can, for example, be positioned at the axially outer end of the circumferential groove if an open-edged circumferential groove is formed in the spacer.

[0044] The outer diameter of the intermediate piece advantageously corresponds substantially to the outer diameter of the bearing outer rings. According to one embodiment, however, the outer diameter of the intermediate piece is slightly larger than the outer diameter of the bearing outer rings so that the intermediate piece can be mounted in the housing with a press fit, while a clearance remains between the bearing outer rings and the housing, in particular for forming an oil film or oil gap, in particular for producing a squeeze oil damper.

[0045] In particular, the maximum outer diameter of the intermediate piece is less than 10%, advantageously less than 5%, in particular less than 1% larger than the maximum outer diameter of the two bearing outer rings.

[0046] According to one embodiment, the two bearing outer rings have identical outer diameters and in particular identical inner diameters.

[0047] The spacer is advantageously positioned with a radial clearance on the protruding collars of the bearing outer rings.

[0048] The intermediate piece can be made of a different, particularly cheaper, material than the bearing outer rings.

[0049] The anti-rotation devices advantageously have a play in the axial direction and / or circumferential direction compared to the intermediate piece and / or the bearing outer rings.

[0050] According to one embodiment of the invention, the rolling elements in the rolling element rows are held in cages. The cages can be externally guided, i.e., in radial contact with the bearing outer ring. However, other designs are possible.

[0051] Depending on the installation conditions, it is advantageous to provide oil holes in the bearing outer rings for supplying lubricating oil to the rolling element rows, but not in the spacer. The oil holes are advantageously arranged axially between the raceways of the rolling element rows and the spacer.

[0052] In a further embodiment, the oil supply can be provided via the bores penetrated by the spring element projections. These bores are located radially in the intermediate piece and in the collar of the bearing outer rings. After the spring elements are installed, they are aligned with each other via the respective spring element projection, allowing the oil to be directed into the bearing interior.

[0053] The two rows of rolling elements, together with the bearing outer rings and the at least one bearing inner ring, in particular the two bearing inner rings, can form a rolling bearing arrangement with a so-called O-arrangement. In such an O-arrangement in a bearing, the adjustment is such that the force flow lines through the bearings have a pressure center axially outside the rows of rolling elements, at least outside their axial center.

[0054] The inventive design allows the bearing outer rings to be comparatively solid with a large outer diameter, thus improving the load-bearing capacity of the bearing unit. Furthermore, radial mobility is reduced, which has a positive effect on service life.

[0055] In a bearing arrangement according to the invention for an exhaust gas turbocharger or an exhaust gas turbine, the two bearing outer rings and the intermediate piece can be directly enclosed by the housing, i.e., without the need for additional components. According to one embodiment, only an oil film or oil ring is provided between the bearing outer rings and the housing to achieve oil damping. The intermediate piece is advantageously inserted into the housing with a snug fit or even a press fit.

[0056] A turbine wheel or a compressor wheel as well as an electric generator can also be mounted on the turbocharger bearing according to the invention by means of the turbine shaft.

[0057] Advantageously, an axial locking between the bearing unit and the housing is only produced in the area of ​​the intermediate piece, in particular by the aforementioned pressing of the intermediate piece into the housing.

[0058] Particularly when clearance remains between the bearing outer rings and the housing, costly, precise remachining of the outer surface of the bearing outer rings and the bearing housing bore can be eliminated, at least in the area of ​​the bearing outer rings. According to one embodiment of the invention, only the radially outer surface of the spacer, and in particular the end faces facing the bearing outer rings, need to be ground or precision-turned after production.

[0059] In the aforementioned configuration, according to which each of the two bearing outer rings has a collar projecting inward in the axial direction, the two collars of the two bearing outer rings are directed toward each other and positioned between the areas of the two bearing outer rings with a comparatively larger, in particular constant, outer diameter. In this configuration, the spacer does not enclose the two bearing outer rings in the area of ​​the comparatively larger outer diameter at the respective axial end of the bearing unit and overlaps the respective collar of the bearing outer ring, but advantageously not the area of ​​the rolling element rows.

[0060] The two collars can be spaced apart axially, with the distance being a multiple of the axial collar length. However, this is not mandatory.

[0061] The collars on the bearing outer rings that protrude inwards and have a comparatively reduced diameter can have a constant diameter.

[0062] According to one embodiment of the invention, the intermediate piece has a constant inner diameter.

[0063] The flanges of the bearing outer rings, which project inward in the axial direction, can be designed to be continuous around the circumference. However, according to an alternative embodiment, they are interrupted around the circumference.

[0064] Particularly when designed with the spring element as a spiral spring or as a wave spring with at least one radially inwardly or radially outwardly directed projection, a particularly simple, torsion- and disassembly-proof bearing unit can be created in which the required clearances between the individual components are achieved in a pre-assembled state, so that the bearing unit can be installed as a pre-assembled module in a corresponding exhaust gas turbocharger or an exhaust gas turbine for supporting the turbine shaft in a housing. Because the pre-assembly can be carried out by the bearing manufacturer and thus the supplied exhaust gas turbocharger manufacturer or power turbine manufacturer does not have to carry out the alignment of the individual bearing components relative to one another, optimal assembly can be achieved in which assembly errors can be largely avoided and, at the same time, low bearing clearances and bearing clearance tolerances can be realized.This leads to an extended service life and better performance of the bearing unit and thus of the entire exhaust gas turbocharger or the exhaust gas turbine.

[0065] The wave spring design of the spring element provides improved vibration damping. The spring constant, which is less linear during compression compared to a cylindrical compression spring, can be neglected due to the short stroke that occurs during operation.

[0066] If the intermediate piece is locked axially in the housing of the exhaust gas turbocharger or the exhaust gas turbine and the two bearing outer rings are at least limitedly movable in the axial direction relative to the housing, an optimized temperature behavior during operation can be achieved.

[0067] An exhaust gas turbocharger according to the invention or an exhaust gas turbine according to an advantageous embodiment of the invention comprises a housing and a turbine shaft mounted in the housing. The turbine shaft is mounted in the housing by means of a bearing unit according to the invention. The stationary component of the bearing unit can be fixed in the housing, advantageously in the axial direction, radial direction, and circumferential direction. However, the stationary component is particularly preferably formed by the housing itself, so that the intermediate piece is fixed directly in the housing and the two outer bearing rings face the housing only with the interposition of the oil ring.

[0068] The bearing outer rings form outer rolling element raceways for the rolling element rows. Inner rolling element raceways for the rolling element rows can be formed either by the turbine shaft itself, which is then also referred to as an integral shaft, or by separate bearing inner rings that accommodate the turbine shaft.

[0069] In this embodiment, the intermediate piece is advantageously pressed into the housing of the exhaust gas turbocharger or the exhaust gas turbine.

[0070] Here, too, the intermediate piece can be made of a different, particularly cheaper material than the bearing outer rings.

[0071] A turbine wheel and a compressor wheel and / or an electric generator can be mounted on the turbine shaft. In a turbocompound system, a turbine wheel combined with a pinion can also be mounted on the turbine shaft.

[0072] According to one embodiment of the invention, only the radially outer surface of the intermediate piece needs to be ground or precision-turned after production, and in particular the end faces of the intermediate piece facing the bearing outer rings. Remachining of the outer surface of the bearing outer rings and in particular the bearing housing bore, at least in the area of ​​the bearing outer rings, can be omitted.

[0073] The invention will be described below using an exemplary embodiment and the figures.

[0074] They show: Fig. 1 a three-dimensional exploded view of a bearing unit according to the invention; Fig. 2 a frontal plan view of a bearing unit according to the invention; Fig. 3 an axial section along the line A - A in the Fig. 2; Fig. 3a a detailed view of a Fig. 3 modified anti-twist device; Fig. 4 a three-dimensional exploded view of another bearing unit according to the invention; Fig. 5 a frontal plan view of the further bearing unit according to the invention; Fig. 6 an axial section along the line A - A in the Fig. 5.

[0075] In the Fig. 1 shows a bearing unit according to the invention, with two bearing inner rings 1, 2 and two bearing outer rings 3, 4, which form two rolling bearings, here ball bearings, with corresponding rows of rolling elements 5, 6.

[0076] In the embodiment shown, the rolling elements of the rolling element rows 5, 6 are held in cages 21 which are positioned between the bearing inner rings 1, 2 and the bearing outer rings 3, 4.

[0077] The bearing outer rings 3, 4 have a collar 10 with a reduced outer diameter that projects in the axial direction. In the assembled state, the collars 10 of the bearing outer rings 3, 4, wherein the collars 10 are in particular designed as one piece with the respective bearing outer ring 3, 4, engage in an intermediate piece 8 positioned in the axial direction between the two bearing outer rings 3, 4. The intermediate piece 8 encloses or overlaps only that axial section of the two bearing outer rings 3, 4 that is formed by the respective collar 10, but not the adjoining regions in which the rolling element rows 5, 6 are located and which have a comparatively larger diameter. Rather, the regions with a comparatively larger diameter of the two bearing outer rings 3, 4 and the intermediate piece 8 have essentially the same, in particular cylindrical, outer diameter.

[0078] The bearing outer rings 3, 4 and the intermediate piece 8 have a bore at their mutually facing axial ends, which in the illustrated embodiment serves as an oil bore 16 through which the rolling bearings are supplied with lubricating oil. These oil bores 16 are arranged axially between the raceways of the rolling element rows 5, 6.

[0079] At the same time, these holes serve to accommodate anti-twist devices 9, which are designed as spring elements 7 interrupted over the circumference, each spring element 7 being designed here as a wave spring, which is supported on the one hand on a shoulder 15 of a bearing outer ring 3, 4 and on the other hand on a shoulder 26 of the intermediate piece 8, see also the Fig. 3. The shoulder 26 defines an open-edged circumferential groove 13 at each axial end of the intermediate piece 8, with each circumferential groove 13 extending to the end face 14 of the intermediate piece 8, and this end face 14 faces the shoulder 15 of the respective bearing outer ring 3, 4 with a greater or lesser axial clearance 22. Depending on the operating condition, the axial clearance 22 can also be completely bridged.

[0080] Due to the design shown, the two bearing outer rings 3, 4 are elastically supported against each other in the axial direction via the spring elements 7 and the intermediate piece 8.

[0081] The assembly of the spring elements 7 is simple; they can be elastically expanded and simply inserted into the circumferential grooves 13 from the radial outside, so that they snap into the circumferential grooves 13 and the oil bores 16. The spring elements 7 can therefore also be referred to as snap rings 11.

[0082] Since at the same time radial projections 12 of the spring elements 7 penetrate the intermediate piece 8 in the radial direction and engage in one of the two bearing outer rings 3, 4 or penetrate its wall thickness, a rotation of the bearing outer rings 3, 4 relative to the intermediate piece 8 is prevented. This is in the Fig. 3, the Fig. 3a as well as in the Fig. 6 can be seen.

[0083] Because the bores in the intermediate piece 8 or in the bearing outer rings 3, 4 are larger in the axial direction than the radial projections 12, a sufficient free cross-section remains so that the bores can be used, as explained, as oil bores 16. In particular, if the projections 12 have a geometrically different cross-section than the bores, for example, if they are designed as flat wire, a remaining free cross-section is reliably achieved in the mostly circular bores.

[0084] The radial projections 12 do not have to be provided at a circumferential end of the spring elements 7, but could also be provided at another position, for example in the region of the circumferential center.

[0085] The design of the storage unit from the Fig. 1 is also in the Fig. 2 and Fig. 3 in a frontal plan view and an axial section. Corresponding components are marked with corresponding reference numerals. Fig. 2 it can be seen that the bearing outer rings, here visible on the bearing outer ring 3, can be designed with a relatively large thickness in the radial direction, which contributes to the rigidity of the bearing.

[0086] From the Fig. 3 shows that the two bearing inner rings 1, 2 abut one another at the end face. The bearing rings 1, 2 can thus be designed in the form of a two-part hollow shaft 24, 25. The hollow shaft 24, 25, consisting of the bearing inner rings 1, 2, can, for example, be shrunk onto a turbine shaft 17, which is only schematically indicated here by dashed lines. However, this is not mandatory. Such a turbine shaft 17 can be connected to an exhaust gas turbine wheel and a compressor wheel, or also to an exhaust gas turbine wheel and a pinion, the latter for use in a turbocompound system. It is also possible to connect the turbine shaft 17 to an electric generator or its rotor. The bearing inner rings 1, 2 are preferably integrally integrated into the respective hollow shaft 24, 25.

[0087] The intermediate piece 8 can be pressed into a housing 18 of an exhaust gas turbocharger or an exhaust gas turbine, whereas the bearing outer rings 3, 4 advantageously have a radial play with respect to an inner surface of the housing 18, so that, for example, an oil film or oil ring 20 can be provided between the housing 18 and the bearing outer rings 3, 4 for vibration damping.

[0088] The bearing unit is mounted in particular in a bore 19 of the housing 18.

[0089] In the embodiment shown, the intermediate piece 8 further has a bore for forming an oil drain 23.

[0090] Although in the embodiment shown the spring element 7 is arranged in a circumferential groove 13 at each axial end of the intermediate piece 8, a corresponding spring element 7 could also be positioned in a corresponding circumferential groove 13 of the respective bearing outer ring 3, 4 and with its projection 12 initially pass through the bearing outer ring 3, 4. This is shown schematically in detail a of the Fig. 3. It is also possible in principle for the spring element 7 to be provided in a radially inwardly directed circumferential groove 13 and to have a correspondingly radially outwardly directed projection 12 which penetrates the respective bearing outer ring 3, 4 and the intermediate piece 8 or at least partially penetrates into the latter.

[0091] In the Fig. 4 shows a further bearing unit according to the invention, with two bearing inner rings 1, 2 and two bearing outer rings 3, 4, which form two rolling bearings, here ball bearings, with corresponding rows of rolling elements 5, 6.

[0092] In the embodiment shown, the rolling elements of the rolling element rows 5, 6 are held in cages 21 which are positioned between the bearing inner rings 1, 2 and the bearing outer rings 3, 4.

[0093] The bearing outer rings 3, 4 are elastically supported against each other in the axial direction by a spring element 7, here in the form of a wave spring. The bearing outer rings each have at least one, in particular exactly one, oil bore 16 through which the rolling bearings are supplied with lubricating oil. This oil bore 16 is arranged axially between the raceways of the rolling element rows 5, 6 and the spacer 8.

[0094] The bearing outer rings 3, 4 have a collar 10 with a reduced outer diameter that projects in the axial direction. In the assembled state, the collars 10 of the bearing outer rings 3, 4, wherein the collars 10 are in particular designed as one piece with the respective bearing outer ring 3, 4, engage in an intermediate piece 8 positioned in the axial direction between the two bearing outer rings 3, 4. The intermediate piece 8 encloses or overlaps only that axial section of the two bearing outer rings 3, 4 that is formed by the respective collar 10, but not the adjoining regions in which the rolling element rows 5, 6 are located and which have a comparatively larger diameter. Rather, the regions with a comparatively larger diameter of the two bearing outer rings 3, 4 and the intermediate piece 8 have essentially the same, in particular cylindrical, outer diameter.

[0095] Two circumferential grooves 13 are provided in the intermediate piece 8, more precisely on its outer circumference. Each of the circumferential grooves 13 accommodates an anti-rotation device 9, with which the two bearing outer rings 3, 4 are mounted on the intermediate piece 8 in a rotationally secure manner.

[0096] The two anti-rotation devices 9 are designed here as snap rings 11 interrupted around the circumference. Each snap ring 11 has at least one projection 12, here exactly one, which penetrates the intermediate piece 8 in the radial direction and engages in one of the two bearing outer rings 3, 4 or penetrates its wall thickness.

[0097] The design of the storage unit from the Fig. 4 is also again in the Fig. 5 and Fig. 6 in a frontal plan view and an axial section. Corresponding components are marked with corresponding reference numerals. Fig. 5 it can be seen that the bearing outer rings, here visible on the bearing outer ring 3, can be designed with a relatively large thickness in the radial direction, which contributes to the rigidity of the bearing.

[0098] From the Fig. 6 shows that the two bearing inner rings 1, 2 abut one another at the end face. The bearing rings 1, 2 can thus be designed in the form of a two-part hollow shaft 24, 25. The hollow shaft 24, 25, consisting of the bearing inner rings 1, 2, can, for example, be shrunk onto a turbine shaft 17, which is only schematically indicated here by dashed lines. However, this is not mandatory. Such a turbine shaft 17 can be connected to an exhaust gas turbine wheel and a compressor wheel, or also to an exhaust gas turbine wheel and a pinion, the latter for use in a turbocompound system. It is also possible to connect the turbine shaft 17 to an electric generator or its rotor. The bearing inner rings 1, 2 are preferably integrally integrated into the respective hollow shaft 24, 25.

[0099] The intermediate piece 8 can be pressed into a housing 18 of an exhaust gas turbocharger or an exhaust gas turbine, whereas the bearing outer rings 3, 4 advantageously have a radial play with respect to an inner surface of the housing 18, so that, for example, an oil film or oil ring 20 can be provided between the housing 18 and the bearing outer rings 3, 4 for vibration damping.

[0100] The bearing unit is mounted in particular in a bore 19 of the housing 18.

[0101] From the Fig. 6 also shows that the intermediate piece 8 has two end faces 14, each of which faces an axially inwardly directed shoulder 15 with a more or less large axial play 22. Depending on the operating condition, the axial play 22 can also be completely bridged.

[0102] In the embodiment shown, the intermediate piece 8 further has a bore for forming an oil drain 23. List of reference symbols 1 bearing inner ring 2 bearing inner ring 3 Bearing outer ring 4 Bearing outer ring 5 rows of rolling elements 6 rows of rolling elements 7 Spring element 8 Intermediate piece 9 Anti-twist device 10 frets 11 Snap ring 12 lead 13 circumferential grooves 14 end faces 15 Shoulder 16 oil drilling 17 Turbine shaft 18 housings 19 Hole 20 oil ring 21 cages 22 Axial play 23 Oil drain 24 hollow shaft 25 hollow shaft 26 Shoulder

Claims

[1] Bearing unit for an exhaust gas turbocharger or an exhaust gas turbine 1.1 with at least one bearing inner ring (1, 2); 1.2 with at least two bearing outer rings (3, 4); 1.3 with at least two rows of rolling elements (5, 6), comprising a first row of rolling elements (5) in the region of a first axial end of the bearing unit between a first of the two bearing outer rings (3) and the at least one bearing inner ring (1, 2) and a second row of rolling elements (6) in the region of a second axial end of the bearing unit opposite the first axial end between a second of the two bearing outer rings (4) and the at least one bearing inner ring (1, 2); 1.4 with an intermediate piece (8) which is positioned at least partially in the axial direction between the two bearing outer rings (3, 4); characterized by , that 1.5 each bearing outer ring (3, 4) is elastically supported in the axial direction relative to the intermediate piece (8) by at least one spring element (7). [2] Storage unit according to claim 1, characterized by that at least one anti-twist device (9) is provided between the intermediate piece (8) and each of the two bearing outer rings (3, 4). [3] Bearing unit for an exhaust gas turbocharger or an exhaust gas turbine 3.1 with at least two rows of rolling elements (5, 6), comprising a first row of rolling elements (5) in the region of a first axial end of the bearing unit and a second row of rolling elements (6) in the region of a second axial end of the bearing unit opposite the first axial end; 3.2 with at least one first bearing outer ring (3) surrounding the first row of rolling elements (5) and at least one second bearing outer ring (4) surrounding the second row of rolling elements (6); 3.3 with an intermediate piece (8) which is positioned at least partially in the axial direction between the first and the second bearing outer ring (3, 4); 3.4 with a stationary component enclosing the intermediate piece (8) and the bearing outer rings (3, 4); wherein 3.5 the intermediate piece (8) is fixed in the stationary component, whereas the bearing outer rings (3, 4) are each mounted in the stationary component via an oil ring (20) so as to be movable at least in the radial direction; characterized by , that 3.6 at least one anti-rotation device (9) is provided between the intermediate piece (8) and each of the two bearing outer rings (3, 4). [4] Storage unit according to claim 3, characterized by that the stationary component is a housing (18) for the exhaust gas turbocharger or the exhaust gas turbine. [5] Storage unit according to one of claims 3 or 4, characterized bythat the bearing outer rings (3, 4) are elastically supported in the axial direction relative to the intermediate piece (8) or relative to one another by means of at least one spring element (7). [6] Storage unit according to claim 1 and claim 2 or according to claim 5, characterized by that the at least one spring element (7) simultaneously forms the anti-twist device (9) between the intermediate piece (8) and the respective bearing outer ring (3, 4). [7] Storage unit according to claim 6, characterized by that the spring element (7) is designed as a spiral spring or as a corrugated spring with at least one radially inwardly or radially outwardly directed projection (12) which penetrates the intermediate piece (8) in the radial direction and at least engages in the respective bearing outer ring (3, 4) in the radial direction or which penetrates the respective bearing outer ring (3, 4) in the radial direction and at least engages in the intermediate piece (8) in the radial direction. [8] Storage unit according to claim 7, characterized by that the spring element (7) is designed as a corrugated spring and the corrugated spring is interrupted over its circumference, with two circumferential ends which overlap one another or which are arranged at a distance from one another. [9] Storage unit according to one of claims 1 to 8, characterized by that each of the two bearing outer rings (3, 4) has a collar (10) projecting inwards in the axial direction and having an outer diameter which is reduced compared to the axially outwardly adjoining region of the bearing outer rings (3, 4), and the intermediate piece (8) only encloses the respective collar (10) of the bearing outer rings (3, 4) in the circumferential direction in the axial direction, wherein at least one anti-twist device (9) is provided between the respective collar (10) and the intermediate piece (8). [10] Storage unit according to one of claims 7 to 9, characterized bythat the intermediate piece (8) or the respective bearing outer ring (3, 4) adjoining it in the axial direction has an open-edged circumferential groove (13) in which the spring element (7) is positioned. [11] Storage unit according to claim 10, characterized by that the spring element (7) is positioned radially inside the outer diameter of the intermediate piece (8) in the circumferential groove (13). [12] Bearing unit for an exhaust gas turbocharger or an exhaust gas turbine 12.1 with at least one bearing inner ring (1, 2); 12.2 with at least two bearing outer rings (3, 4); 12.3 with at least two rows of rolling elements (5, 6), comprising a first row of rolling elements (5) in the region of a first axial end of the bearing unit between a first of the two bearing outer rings (3) and the at least one bearing inner ring (1, 2) and a second row of rolling elements (6) in the region of a second axial end of the bearing unit opposite the first axial end between a second of the two bearing outer rings (4) and the at least one bearing inner ring (1, 2); 12.4 with at least one spring element (7) in the axial direction between the two bearing outer rings (3, 4), which supports the two bearing outer rings (3, 4) directly or indirectly axially against each other under pressure; 12.5 with an intermediate piece (8) in the axial direction between the two bearing outer rings (3, 4); 12.6 with at least one anti-rotation device (9) between the intermediate piece (8) and each of the two bearing outer rings (3, 4); characterized by , that 12.7 each of the two bearing outer rings (3, 4) has a collar (10) projecting inwards in the axial direction and having an outer diameter which is reduced compared to the axially outwardly adjoining region of the bearing outer rings (3, 4), and the intermediate piece (8) in the axial direction only encloses the respective collar (10) of the bearing outer rings (3, 4) in the circumferential direction, wherein at least one anti-twist device (9) is provided between the respective collar (10) and the intermediate piece (8). [13] Storage unit according to claim 12, characterized by that one or both of the at least two anti-rotation devices (9) is / are designed as a snap ring (11) interrupted over the circumference with at least one projection (12) penetrating the intermediate piece (8) in the radial direction, which projection engages in the respective bearing outer ring (3, 4) in the radial direction or penetrates this. [14] Storage unit according to claim 13, characterized bythat the intermediate piece (8) has at least one circumferential groove (13) in which the snap ring (11) is positioned. [15] Storage unit according to claim 14, characterized by that the snap ring (11) is positioned radially inside the outer diameter of the intermediate piece (8) in the circumferential groove (13). [16] Storage unit according to one of claims 12 to 15, characterized by that the spring element (7) is designed as a wave spring which bears axially against the respective collar (10) of the bearing outer rings (3, 4) with individual, discrete contact surfaces distributed over the circumference. [17] Storage unit according to one of claims 1 to 16, characterized by that the intermediate piece (8) extends in the axial direction only between the rows of rolling elements (5, 6). [18] Storage unit according to one of claims 1 to 17, characterized bythat the intermediate piece (8) has two axially outer end faces (14), each of which faces an axially inwardly directed shoulder (15) of the bearing outer rings (3, 4) with an axial play (22). [19] Storage unit according to one of claims 1 to 18, characterized by that the outer diameter of the intermediate piece (8) corresponds to the outer diameter of the bearing outer rings (3, 4). [20] Storage unit according to one of claims 1 to 19, characterized by that the bearing outer rings (3, 4) have oil holes (16) for supplying lubricating oil to the rows of rolling elements (5, 6) and that the intermediate piece (8) is free of such oil holes. [21] Storage unit according to claim 20, characterized by that the oil holes (16) are arranged in the axial direction between the raceways of the rows of rolling elements (5, 6) and the intermediate piece (8). [22] Storage unit according to one of claims 1 to 21, characterized bythat two bearing inner rings (1, 2) are provided which are in axial contact with one another. [23] Storage unit according to one of claims 1 to 22, characterized by that the two rows of rolling elements (5, 6) together with the bearing outer rings (3, 4) and the at least one bearing inner ring (1, 2) form a rolling bearing arrangement with an O arrangement. [24] Bearing of an exhaust gas turbocharger or an exhaust gas turbine 24.1 with a storage unit according to one of claims 1 to 23; 24.2 with a turbine shaft (17) mounted in the at least one bearing inner ring (1, 2); 24.3 with a housing (18) enclosing the two bearing outer rings (3, 4) and the intermediate piece (8). [25] Storage according to claim 24, characterized by that the bearing inner rings (1, 2) are designed in the form of a two-part hollow shaft (24, 25) and the hollow shaft (24, 25) accommodates the turbine shaft (17). [26] Storage according to claim 24 or 25, characterized bythat the two bearing outer rings (3, 4) are accommodated in a bore (19) in the housing (18) free of a bush enclosing them. [27] Storage according to one of claims 24 to 26, characterized by that the intermediate piece (8) is pressed into the housing (18), in particular into the bore (19) in the housing (18). [28] Storage according to one of claims 24 to 27, characterized by that the bearing outer rings (3, 4) are mounted directly in the housing (18) via an oil film or oil ring (20). [29] Storage according to one of claims 24 to 28, characterized by that an axial locking between the bearing unit and the housing (18) is only established in the area of ​​the intermediate piece (8). [30] Exhaust gas turbocharger with a bearing according to one of claims 24 to 29, characterized by that an exhaust gas turbine wheel and a compressor wheel and / or the rotor of an electric generator are mounted on the turbine shaft (17). [31] Exhaust gas turbocharger or exhaust gas turbine 31.1 with a housing (18); 31.2 with a turbine shaft (17); characterized by , that 31.3 the turbine shaft (17) is mounted in the housing (18) by means of a bearing unit according to one of claims 3 to 11, wherein the stationary component is fixed in the housing (18) or is formed by the latter and the turbine shaft (17) is received in at least one bearing inner ring (1, 2) provided in the bearing unit, which bearing inner ring (1, 2) together with the bearing outer rings (3, 4) encloses the rows of rolling elements (5, 6) to form rolling element raceways, or the turbine shaft (17) with the bearing outer rings (3, 4) encloses the rows of rolling elements (5, 6) to form rolling element raceways.

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