DE102008061112A1 - Exhaust gas turbocharger for supercharging internal-combustion engine of motor vehicle, has angular contact bearings subjected to axial pre-stress such that bearings are fixed at position relative to each other - Google Patents

Abstract

The turbocharger (1) has a rotor (2) rotatably supported in a stator (3) around a rotational axis (5) by a bearing arrangement (4). The bearing arrangement is provided with two angular contact bearings (6). The two angular contact bearings are axially arranged at a distance from each other with respect to the rotational axis. The two angular contact bearings are subjected to axial pre-stress (8) such that the two angular contact bearings are fixed at a position relative to each other, where axial pre-stress is produced at relative position. An independent claim is also included for a method for providing axial pre-stress to two angular contact bearings.

Description

The The present invention relates to an exhaust gas turbocharger for charging an internal combustion engine, in particular a motor vehicle.

Usually an exhaust gas turbocharger comprises a rotor, which by means of a bearing assembly is rotatably mounted in a stator about a rotation axis.

Provided for the realization of the bearing assembly two with respect to the axis of rotation axially spaced skew bearings are used, they must be subjected to an axial bias. Such Axial bias can be realized, for example, by that components that when assembling the turbocharger, the angular contact bearings axially clamped, manufactured with tight manufacturing tolerances. Furthermore you can Distance elements, eg. B. be used in the form of slices whose Thickness in dependence the preload to be set is selected. The required, very precise Manufacturing is associated with correspondingly high production costs. Alternatively, it is also possible Provide biasing springs, which in the installed state, the desired bias to initiate the angular contact bearings. The problem here is that the spring characteristics of such biasing springs temperature-dependent are so that with increasing operating temperature, the set Preload decreases. Order now at the expected, comparatively high operating temperatures realize the desired bias to be able to At low temperatures higher bias voltages are present especially at low speeds lead to increased friction losses. Increased friction especially at low speeds hampers the fast startup of the rotor and carries to the so-called "turbo lag" at.

The present invention employs dealing with the problem, for an exhaust gas turbocharger of the type mentioned or for an associated manufacturing process an improved embodiment which is characterized in particular by the fact that reduced costs a desired Bias is adjustable, which also be largely dependent on temperature should.

This Problem is caused by the objects of independent claims solved. Advantageous embodiments are the subject of the dependent Claims.

The Invention is based on the general idea, the angular contact bearings To fix in a relative position to each other that thereby the desired axial Bias is generated. For this purpose, the skew bearings are, for example, during assembly axially with the desired Bias externally loaded, creating a relative position for the two Schrägwälzlager yields. In this relative position, they are now fixed in position. If then the from the outside applied external biasing force is withdrawn, can the angular contact bearings do not follow this relaxation, since they are fixed in position relative to each other are. This has the consequence that introduced into the angular rolling bearings axial Preload is still included, the angular contact bearings are thus still with the desired axial preload applied.

The Positional fixation can, for example, by means of at least one welded joint, in particular laser welding connection, will be realized. Theoretically, at least one solder joint conceivable. By the proposed approach can, for example Vorspannfedern be waived. Accordingly, there is no Influence of a temperature-dependent Spring characteristic before. The position fixation and thus the internal preload remains at homogeneous temperature change the over get the position fixation coupled components. Furthermore have to during production no tight tolerances or manufacturing tolerances be noted, as the for the generation of the desired Preload needed Relative position between the angular contact bearings is found by applying the external bias and then secured by fixing the position. This only needs take care be worn that the entire bearing assembly axially compressible is. For example, you have to do this either outer rolling bearing surfaces of the two Angular bearings be axially positionable relative to each other. Alternatively, too inner rolling bearing surfaces of the two skew bearings be axially adjustable relative to each other. This adjustability is used to adjust the internal preload by applying an external preload used. By "freezing" or fixing the thus found relative position between the skew bearings The inner preload remains when the outer preload is taken away again. Overall, there is a considerable simplification in the making, as well inexpensive is feasible. Furthermore, eliminates the disadvantages of the temperature-dependent bias springs.

Further important features and advantages of the invention will become apparent from the Dependent claims, from the drawings and from the associated description of the figures the drawings.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

preferred embodiments The invention are illustrated in the drawings and in the following description explains where like reference numerals refer to the same or similar or functionally identical components relate.

It show, in each case schematically,

1 to 7 in each case a greatly simplified longitudinal section through an exhaust gas turbocharger in the region of a bearing arrangement, in various embodiments.

According to the 1 - 7 includes an exhaust gas turbocharger 1 , with the aid of which an internal combustion engine, which can be arranged in particular in a motor vehicle, can be charged, a rotor 2 and a stator 3 , The rotor 2 is by means of a bearing assembly 4 around a rotation axis 5 at the stator 3 rotatably mounted. The bearing arrangement 4 includes at least two bearings. Shown are two skew bearings 6 which are arranged axially spaced from each other. The direction indicated by a double arrow axial direction 7 is doing through the axis of rotation 5 defined, which are parallel to the axial direction 7 extends. When mounted, the angular contact bearings are 6 subjected to an axial bias, indicated by two aligned arrows and with 8th is designated. This internal axial preload 8th ensures that the skew bearings 6 even at high speeds of the rotor 2 wear with low wear and low friction. This internal axial preload is generated 8th in that the two skew bearings 6 are fixed in position relative to each other in a relative position, the desired axial bias 8th generated. For example. can do this one of the angular contact bearings 6 during assembly towards the other angular contact bearing 6 with an outer preload force indicated by two arrows (actio = reactio) 9 be charged. The skew bearings 6 are on the rotor 2 or on the stator 3 so arranged by the outer bias 9 their relative position to each other can change, thereby simultaneously the internal bias 8th is produced. After the desired relative position has been found, it is fixed. Subsequently, the outer preload 9 be removed, while the inner bias 8th remains. The inner preload 8th remains, since the relative position of the angular contact bearings 6 is now fixed and no longer by a relative movement between the two angular contact bearings 6 can be reduced.

To the inner bias 8th by applying an external bias 9 in the angular roller bearings 6 to generate and to this inner bias 8th by fixing or freezing with the help of the outer preload 9 generated relative position of the angular contact bearings 6 to conserve each other, according to the embodiments of the 3 . 4 and 6 an outer bearing ring 10 at least one of the angular contact bearings 6 at the stator 3 be arranged axially adjustable and fixed. The axial fixation is symbolized in the figures by a solid circle and with 11 designated. In the embodiments of the 1 . 2 . 5 and 7 is an inner bearing ring 12 at least one of the angular contact bearings 6 on the rotor 2 axially fixed. This axial positional fixation is again with 11 designated. At the in 1 Shown embodiment, the positional fixation takes place 11 of the inner bearing ring 12 directly on the rotor 2 , In the example, the rotor comprises 2 a wave 13 which can, for example, carry a compressor wheel and a turbine wheel. This wave 13 can preferably according to 7 as a hollow shaft 13 be designed.

In the example of 2 is the inner bearing ring 12 on an inner bearing bush 14 Position fixated on the rotor 2 is arranged and the two angular contact bearings 6 assigned. This forms this inner bushing 14 the inner bearing ring 12 of the other angular contact bearing 6 or is the inner bearing ring 12 of the other angular contact bearing 6 integral to this inner bushing 14 formed. Here is one on the stator 3 with the bias 8th Pre-assembled storage cartridge created in which the shaft 13 of the rotor 2 can be used.

At the in 3 Shown embodiment, the outer bearing ring 10 of a skew roller bearing 6 directly on the stator 3 fixed in position.

At the in 4 shown embodiment is a common outer bearing bush 15 provided on which said outer bearing ring 10 is fixed in position. This outer bearing bush 15 is on the stator 3 arranged. She is both skew bearings 6 assigned. In particular, it forms the outer bearing ring 10 of the other angular contact bearing 6 , In other words, on this outer bushing 15 is the outer bearing ring 10 of the other angular contact bearing 6 integrally formed. This will make one on the rotor 2 with the bias 8th Pre-assembled storage cartridge created with the rotor 2 in the stator 3 can be used.

The skew bearings 6 have rolling elements 16 which are in particular balls or rolls. The rolling elements 16 lie radially inward on an inner Wälzkörperlagerfläche 17 and radially outside each on an outer Wälzkörperlagerfläche 18 at. These storage areas 17 . 18 can also be called raceways 17 . 18 be designated. The respective inner rolling bearing surface 17 is usually on the respective inner bearing ring 12 educated. The respective outer rolling bearing surface 18 is usually on the respective outer bearing ring 10 educated.

The embodiments of the 5 - 7 show special constructions in which at least one of the rolling bearing surfaces 17 . 18 integral on the rotor 2 or at the stator 3 is trained.

5 shows an embodiment in which the inner rolling bearing surface 17 of a skew roller bearing 6 integral on the rotor 2 or integrally on the shaft 13 is formed. 6 shows an embodiment in which the inner Wälzkörperlagerflächen 17 both skew bearings 6 directly on the rotor 2 or on the shaft 13 are formed integrally.

At the in 6 The embodiment shown is also the outer Wälzkörperlagerfläche 18 of a skew roller bearing 6 integral on the stator 3 or on a housing 19 of the stator 3 formed.

In contrast, shows 7 a variant in which the two outer Wälzkörperlagerflächen 18 the two skew bearings 6 each integral to the stator 3 or integral to the housing 19 are formed. Further, in this embodiment, the inner Wälzkörperlagerfläche 17 of a skew roller bearing 5 integral with the shaft 13 or on the rotor 2 formed. It is clear that in principle also other combinations of the above-mentioned embodiments for the individual angular contact bearings 6 are conceivable.

In all embodiments, at least one bearing ring 10 or 12 at least one of the angular contact bearings 6 as part of the assembly of the warehouse order 4 axially adjustable to the desired axial preload 8th in the bearing arrangement 4 to contribute. In the embodiments shown here is only one of the bearing rings 10 . 12 as part of the assembly axially adjustable to the internal preload 8th to be able to adjust. The adjustable bearing ring for mounting 10 . 12 is characterized by an apostrophe. In 1 is the inner bearing ring 12 ' of the skew roller bearing shown on the right 6 axially adjustable during assembly. at 2 is also the inner bearing ring 12 ' of the skew roller bearing shown on the right 6 axially adjustable during assembly. In the embodiments of the 3 and 4 is in each case the outer bearing ring 10 ' of the skew roller bearing shown on the right 6 axially adjustable during assembly. Both 5 and 7 is again the inner bearing ring 12 ' of the skew roller bearing shown on the right 6 axially adjustable during assembly. Finally, at the in 6 embodiment shown again the outer bearing ring 10 ' of the skew roller bearing shown on the right 6 axially adjustable during assembly.

While in the embodiments of 1 . 2 and 4 to 7 the respective adjustable bearing ring 10 ' respectively. 11 ' directly via the position fixing 14 on the rotor 2 or on the stator 3 axially fixed, shows 3 an embodiment in which an adjustable stop 23 is used. At this stop 23 supports the respective angular contact bearings 6 or its adjustable bearing ring 10 ' axially. The stop 23 is about fixing the position 11 in the example on the stator 3 axially fixed. In the example, the stop works 23 with the outer bearing ring 10 ' together and is at the stator 3 fixed. In another embodiment, the stop 23 also with the respective adjustable inner bearing ring 12 ' interact. Then the stop 23 on the rotor 2 fixed in position. In the embodiments in which an inner bearing bush 14 (as in 2 ) or an outer bearing bush 15 (as in 4 ) can be used, the stop 23 also at said inner bush 14 or at said outer bushing 15 be fixed in position.

In the embodiments shown, all other bearing rings 10 . 12 - if available - each on an axial stop 20 respectively. 21 supported. In 1 is the other inner bearing ring 12 on a rotor-side axial stop 20 at. Further, in 1 the two outer bearing rings 10 in each case on a stator-side axial stop 21 at. In the assembled state results in the realization and preservation of the internal bias 8th a closed power path. This begins at the position fixing 11 , go through the rotor 2 , via the rotor-side axial stop 20 on the other inner bearing ring 12 , about the rolling elements 16 and the associated outer bearing ring 10 and the rolling element 16 and the associated outer bearing ring 10 and the stator-side axial stop 21 in the stator 3 and from this via the other stator-side axial stop 21 in the other outer bearing ring 10 and over the rolling elements 16 in the position-fixed inner bearing ring 12 ' back to the situation fixation 11 ,

At the in 2 As shown embodiment, the common inner bearing bush is supported 14 on the rotor-side axial stop 20 from, with the inner bearing bush 14 For example, with the help of a sleeve 22 can be fixed or positioned. The closed force path does not run through the shaft here 13 but through the inner bushing 14 , The same then applies to the closed power paths in the embodiments of 3 and 4 ,

In the embodiments of the 5 - 7 omitted those bearing rings 10 . 12 , whose Wälzkörperlagerflächen 17 . 18 integral on the rotor 2 or on the stator 3 are formed. Accordingly, then no axial stops 20 . 21 for axially supporting the respective bearing rings 10 . 12 required. However, the power transmission simplifies to realize the internal Vorspan voltage 8th , The omission of the inner bearing ring 12 at least one of the angular contact bearings 6 causes the corresponding skew roller bearing 6 allows higher speeds or easier and thus can be dimensioned cheaper. For example, it has been shown that the product of the average bearing diameter and the maximum permissible rotational speed is constant, thereby forming a design limit. By omission of the inner ring 12 Reduced at the same rolling elements and the same shaft diameter thus the average bearing diameter, which increases the maximum speed.

For producing the preloaded bearing assembly 4 is during the assembly of the exhaust gas turbocharger 1 before attaching the position fixing 11 the external preload 9 applied at a predetermined height. This allows the skew bearings 6 or their components 10 . 12 . 16 position relative to each other. It turns a relative position between the angular contact bearings 6 one. At the same time, the inner preload force builds up via the aforementioned force path 8th on. For example. must do this at the in 1 shown embodiment of the rotor 2 or the wave 13 be held so that on the reaction forces the internal bias 8th in the angular contact bearings 6 can be introduced. At the in 2 shown embodiment, this also has the rotor 2 or the inner bearing bush 14 be held to the internal bias 8th to build up. At the in 3 and 4 shown embodiment, however, the stator 3 be fixed in order to build the desired internal bias can. Optionally available at 4 also the outer bearing bush 15 be fixed to build the internal bias. In the embodiments of the 5 and 7 is the rotor again 2 to fix, while at the in 6 embodiment shown again the stator 3 is to fix.

The relative position thus found between the angular rolling bearings 6 is now frozen using the fixation 11 , This situation fixation 11 can be realized by a welded joint or by a solder joint or by an adhesive bond. For example. extend a plurality of circumferentially spaced welding points or solder joints from around the respective inner bearing ring 12 ' on the rotor 2 or the respective outer bearing ring 10 ' at the stator 3 to fix. After fixing the position, the external or external preload force can 9 be relieved or taken away. About the position fixation 11 is the internal preload force 8th conserved so they are in the bearing assembly 4 remains.

Claims (15)

Exhaust gas turbocharger for charging an internal combustion engine, in particular a motor vehicle, - with a rotor ( 2 ), which by means of a bearing assembly ( 4 ) in a stator ( 3 ) about a rotation axis ( 5 ) is rotatably mounted, - wherein the bearing assembly ( 4 ) at least two with respect to the axis of rotation ( 5 ) axially spaced skew bearings ( 6 ) having an axial preload ( 8th ) are applied, - wherein the axial preload ( 8th ) is produced by the fact that the angular contact bearings ( 6 ) are fixed in position relative to one another in a relative position producing this axial prestress. Exhaust gas turbocharger according to claim 1, characterized in that at least one of the angular contact bearings ( 6 ) an outer bearing ring ( 10 ) on the stator ( 3 ) is axially fixed in position. Exhaust gas turbocharger according to claim 1, characterized in that in one of the angular contact bearings ( 6 ) an outer bearing ring ( 10 ) on one of the stator ( 3 ), common outer bearing bush ( 15 ) is axially fixed, on which an outer bearing ring ( 10 ) of the other angular contact bearing ( 6 ) is integrally formed. Exhaust gas turbocharger according to one of claims 1 to 3, characterized in that at least one of the angular contact bearings ( 6 ) an inner bearing ring ( 12 ) on the rotor ( 2 ) is axially fixed. Exhaust gas turbocharger according to one of claims 1 to 3, characterized in that in one of the angular contact bearings ( 4 ) an inner bearing ring ( 12 ) on one of the rotors ( 2 ), common inner bearing bush ( 14 ) is axially fixed, on which an inner bearing ring ( 12 ) of the other angular contact bearing ( 6 ) is integrally formed. Exhaust gas turbocharger according to one of claims 2 to 5, characterized in that all other inner and / or outer bearing rings ( 10 . 12 ) each at one on the stator ( 3 ) or on the rotor ( 2 ) formed axial stop ( 20 . 21 ) under the axial preload ( 8th ) issue. Exhaust gas turbocharger according to one of claims 1 to 6, characterized in that at least one of the angular contact bearings ( 6 ) an inner rolling bearing surface ( 17 ) integral to the rotor ( 2 ) is formed. Exhaust gas turbocharger according to claim 7, characterized in that the inner Wälzkörperlagerfläche ( 17 ) integral with a shaft ( 13 ) of the rotor ( 2 ) is formed. Exhaust gas turbocharger according to one of claims 1 to 8, characterized in that at least one of the angular contact bearings ( 6 ) an outer rolling bearing surface ( 18 ) integral to the stator ( 3 ) is formed. Exhaust gas turbocharger according to claim 9, characterized in that the outer rolling bearing surface ( 18 ) integral with a housing ( 19 ) of the stator ( 3 ) is formed. Exhaust gas turbocharger according to one of claims 1 to 10, characterized in that the respective fixation ( 11 ) is formed by at least one solder joint or at least one welded joint. Exhaust gas turbocharger according to one of claims 1 to 11, characterized in that the position fixing ( 11 ) by means of a stop ( 23 ) is realized at which at least one of the angular contact bearings ( 6 ) is supported axially with the bias voltage on the rotor ( 2 ) or on the stator ( 3 ) or at a two angular rolling bearings ( 6 ) associated inner or outer bearing bush ( 14 . 15 ) is fixed in position in a bias position generating the relative position. Method for producing an axial preload ( 8th ) in two axially spaced oblique roller bearings ( 6 ) for supporting a rotor ( 2 ) in a stator ( 3 ) of an exhaust gas turbocharger ( 1 ), - in which the angular contact bearings ( 6 ) with an external predetermined biasing force ( 9 ) are axially loaded, resulting in a relative position between the angular contact bearings ( 6 ), - in which the angular contact bearings ( 6 ) with applied external bias ( 9 ) are fixed in position in the set relative position relative to each other, - in which the angular contact bearings ( 4 ) from the external prestressing force ( 9 ) be relieved. A method according to claim 13, characterized in that in at least one of the angular contact bearings ( 6 ) an inner bearing ring ( 12 ' ) relative to the rotor ( 3 ) is axially adjustable, by the load with the external biasing force ( 9 ) axially along the rotor ( 2 ) and in which in the external prestressing force ( 8th ) set relative position on the rotor ( 3 ) is fixed. Method according to claim 13 or 14, characterized in that at least one of the angular contact bearings ( 6 ) an outer bearing ring ( 10 ' ) relative to the stator ( 3 ) is axially adjustable, by the load with the external biasing force ( 9 ) axially along the stator ( 3 ) and in which with the external prestressing force ( 9 ) adjusted relative position on the stator ( 3 ) is fixed.