EP1394363B1 - Variable guide vane system for a turbine unit - Google Patents

Description

Field of the invention

The present invention relates to a turbine unit - in particular for a turbocharger, but possibly also for other turbomachines, such as secondary air pumps - which is a rotor housing with at least one supply channel for a fluid - in the case of application of the invention to a turbocharger, this is the exhaust gas of an internal combustion engine - And has a turbine rotor which is mounted in a turbine chamber of the rotor housing and the periphery of which the fluid is supplied via a guide vanes of variable turbine geometry. The baffle has a vane bearing ring with a number of vane shafts mounted on this vane ring in the form of a ring and blades attached thereto on one side, which are each adjustable from an essentially tangential position relative to the rim to an approximately radial position, and at least one Adjustment element for adjusting the position of the blades. Furthermore, an actuating device for generating control movements to be transmitted to the guide vanes with variable turbine geometry is provided via an adjusting ring, which is arranged coaxially with the blade bearing ring and adjacent thereto and is movably connected to the at least one adjusting element, as well as a guiding and centering arrangement for the adjusting ring. which comprises at least one rolling bearing with running on a running surface of the adjusting rolling elements.

Background of the invention

A turbine unit of this type has become known from US-A-4,179,247 (see also US-A-4378960). This document emphasizes - undoubtedly rightly so - the precision of guidance and centering afforded by rolling bearings (ball bearings are provided there). Although this document is more than twenty years old, it has had no impact on practice. The reason is probably to seek that the turbine housing - to accommodate the rolling bearing - had such a complex shape that it could not be made in practice. Added to this were the necessary surface treatments in hard-to-reach areas, which additionally burdened production costs. The measures, which should allow access to the parts to be repaired at most, also weakened the housing and did not make its cohesion in operation very reliable. Overall, then This proposal - despite the undeniable advantages of rolling bearings - is immature and therefore unsuitable for practical use.

Although it was already known to attach the adjusting elements on the side facing away from the blades of the blade bearing ring on the blade shafts, being used approximately radially extending Verstellhebeln, each with a free end of the lever, it is already known from DE-C-964 551, the To provide adjusting ring with teeth, in which engages a pinion as adjusting. Other adjustment mechanisms with interlocking teeth have already been proposed. Furthermore, the use of slot cams for pivoting the blades around the stub axle is also known.

Summary of the invention

The invention is therefore an object of the invention to provide a simple and easy to assemble construction using (at least) a rolling bearing and while maintaining its advantages.

According to the invention, this object is achieved in that the rolling bearing between the adjusting ring and a releasably connectable to the rotor housing mounting ring is arranged so that adjusting ring, roller bearing and the releasably connectable ring are installed as a modular unit in the rotor housing.

In this way, not only the assembly is facilitated, but the rotor housing can also be simplified and thereby made more stable. The inherent in a rolling bearing precision is also guaranteed. Moreover, this makes it possible to prefabricate the modular unit with blades, spacers, etc., so that they then possibly represents their own marketable item.

As with US-A-4,179,247, the rolling bearing per se may well be a ball bearing, as will be apparent from the later description. However, it is preferred if the rolling bearing is designed as a roller bearing.

To form a cage or to hold the rollers of a roller bearing, it is advantageous if the rolling bearing is housed in an axially open space of one of the rings, preferably the adjusting ring, and this clearance by another ring, in particular axial extensions of the rollers Rolling bearing retaining ring, is completed. In the process, the friction of the rollers with each other and their number diminished when the rollers are held by this retaining ring at a distance from each other. The rolling bearing may therefore comprise rollers or balls which are either sufficient in number in the free space to substantially fill it, or a limited number of at least three rollers or balls may be passed through a retaining ring in the free space.

The cost is further reduced and the space required for installation of the modular unit reduced when the releasably connectable ring is the blade bearing ring.

A problem in turbochargers is the high heat, which causes enormous thermal expansion. It has already been proposed in other guide devices to design these in such a way that rotary bodies run off either on an outer or inner web (cf US-A-4,659,295). The invention is, inter alia, based on the finding that yes in the relationship between the adjusting ring and blade bearing ring pre-centering can already be given by between approximately two radially extending adjusting levers. Therefore, it is preferred within the scope of the invention if a plurality of adjusting elements is formed in each case on the other side of the blade bearing ring facing away from the blades of adjusting levers which are fastened to the blade shafts and have approximately one free end each. The guiding and centering device must then actually secure this coaxial position only. Of course, such a pre-centering will be given to some extent as a rule even if the respective adjusting element is formed by a pinion engaging in a toothing.

Under these circumstances, it is not absolutely necessary that the rolling elements are in constant contact with at least one tread, but it is more advantageous if the cooperating with the rolling bearing diameter of the adjusting ring and the releasably connectable ring are dimensioned such that they substantially allow a radial clearance of the rolling elements at all operating temperatures. This game will then match the tolerance considered admissible. "Essentially" means that it may be in the range of the upper or lower limit temperature or in the context of tolerances that this game is repealed and then the rolling elements on one or the other ring just come to rest. This embodiment according to the invention, however, not only ensures perfect adjustment movement at all temperature ranges, but also increases the service life of the rolling bearing.

Undoubtedly, it is possible within the scope of the invention to fasten the modular unit in the housing by means of screws. However, it is preferred if the modular unit of adjusting ring, rolling bearing and releasably connectable ring (it is also generally included additional elements such as the or the spacers and fasteners) by interlocking projections and depressions is rotatably held, and preferably against this situation is loaded by a loading arrangement. This further simplifies assembly. Alternatively, instead of a loading device, a snap connection between said projections and recesses could be provided.

Of course, rolling bearings are delicate with regard to possible contamination. Therefore, it is favorable to provide an annular seal between rolling bearing and turbine chamber.

In itself, it would be quite possible within the scope of the invention, to provide the rolling elements between an outer surface of the adjusting ring and the inner surface of a surrounding him and releasably connectable to the housing ring. However, this of course increases the radial space requirement, which is why it is preferred if the running surface of the detachably connectable ring has a smaller diameter than the running surface of the adjusting ring.

Incidentally, the invention also relates to a guide vane of variable turbine geometry for such turbine units, which has the features discussed above.

Brief description of the drawings

Fig. 1

einen halben Axialschnitt durch ein Rotorgehäuse bis zur Rotationsachse, in das eine erfindungsgemäßes Leitgitter eingebaut ist;

Fig. 1a

eine Alternativlösung für ein Leitgitter, das ebenfalls in Kasettenform vorgefertigt werden kann;

Fig. 2

eine Schnittdarstellung des ganzen Leitgitters der Fig. 1;

Fig. 3

eine Variante der Ausführung nach Fig. 2 mit Dichtung, wobei nur der in Fig. 2 obere Teil in vergrößertem Maßstab dargestellt ist, der in

Fig. 4

in einer geschnittenen Perspektivdarstellung von der Seite des Verstellringes her zu sehen ist;

Fig. 5

eine perspektivische Teilansicht eines weiteren Ausführungsbeispiels; und

Fig. 6

einen Schnitt durch die Oberseite einer vierten Ausführungsform.

Further details of the invention will become apparent with reference to the following description of exemplary embodiments shown schematically in the drawing. Show it:

Fig. 1

a half axial section through a rotor housing to the axis of rotation, in which a guide grid according to the invention is installed;

Fig. 1a

an alternative solution for a baffle, which can also be prefabricated in cassette form;

Fig. 2

a sectional view of the entire Leitgitters of Fig. 1;

Fig. 3

a variant of the embodiment of FIG. 2 with seal, wherein only the upper part in Fig. 2 is shown in an enlarged scale, the in

Fig. 4

can be seen in a sectional perspective view of the side of the adjusting ring ago;

Fig. 5

a partial perspective view of another embodiment; and

Fig. 6

a section through the top of a fourth embodiment.

Detailed description of the drawings

1, a turbine housing 2 is connected to a flange 16 of a bearing housing, protrudes from the cylinder piece 40 in the turbine housing 2 and the shaft 35 of a turbine rotor 4 superimposed. The turbine housing 2 comprises a supply channel 9 surrounding the turbine rotor 4 for a fluid driving the turbine rotor 4 (in the case of a turbocharger this is the exhaust gas of an internal combustion engine), a rotor space 23 and an axial connection 10 through which the fluid or the exhaust gas is discharged again ,

In order to supply fluid to the turbine rotor 4 in a controlled or controlled amount, a device is provided at the outlet of the feed channel 9 or in front of the rotor chamber 23, which device is known in the art as the "variable turbine nozzle guide grid". This guide grid essentially comprises a ring of movable guide vanes 7 which concentrically surrounds the turbine rotor 4 (cf., Fig. 4), which are mounted on adjustment shafts 8 fixedly connected to them in a blade bearing ring 6 which coaxially surrounds the turbine rotor 4.

The rotation or adjustment of Verstellwellen 8 can be done in per se, for example, from US-A-4,659,295, known manner by an actuator comprises a control housing 12 which controls the control movement of a attached to her, only dash-dotted lines indicated plunger member, the movement of which is converted via an actuating lever 13, an actuating shaft 14 connected thereto and, for example, via an eccentric 15 engaging in an opening of an adjusting ring 5 located behind the blade bearing ring 6 into a slight rotational movement of this ring 5 around the axis R. For in grooves or recesses 17 (see Fig. 4) of the adjusting ring 5, the free ends of the levers or heads 18 are mounted by adjusting levers 19 which are fixed to the adjusting shafts 8. At Position of radially extending recesses 17 but can also be provided in a conventional manner grooves on the radially inner side of the adjusting ring 5, in which the heads 18 are mounted so that then these heads 18 secure a certain pre-centering. As is apparent from the following description, but this is not necessary in an inventive design, so that the adjusting ring 5 can be made over the prior art even with a smaller diameter.

As a result of this rotational movement, the guide vanes 7 are adjusted relative to the turbine rotor 4 with respect to their rotational position via the shafts 8 in such a way that they can be adjusted from an approximately tangentially extending one extreme position into an approximately radially extending other extreme position. As a result, the exhaust gas supplied via the supply channel of an internal combustion engine is supplied more or less to the turbine rotor 4, before it exits again at the axial connection piece 10 extending along the axis of rotation R.

All of these arrangements are known in principle. But so far were used to guide and centering of adjusting 5 with respect to the fixedly connected to the rotor housing 2 blade bearing ring 6 means that were difficult to assemble and yet allowed only a low precision. As mentioned above, although the proposal for the use of rolling bearings has already been made, but this was not feasible in practice, because the bearings had to be mounted on precisely machined surfaces of the already subjected by the different thermal stress strong thermal expansion rotor housing. However, in order to achieve high precision with low structural complexity and low installation use, the rolling bearing with rolling elements 3 in the form of rollers between the adjusting ring 5 and one, possibly with the rotor housing releasably connectable bearing ring. Even this separation of serving as a tread releasably connectable ring from the actual rotor housing decouples this from a direct heat transfer from the housing 2 to him. For this purpose, however, it is possible to install the adjusting ring, roller bearing and the releasably connectable ring (with the above-mentioned additional parts) as a modular unit in the rotor housing, i. it even allows pre-assembly, which of course can be much easier and automated.

For, as can be seen from FIGS. 1 and 2, the adjusting ring 5 has a radially inwardly directed running surface 20, on which the rollers 3 can run off. However, this is preferably provided only for tolerance compensation, because in practice it is preferred if the rollers 3 in substantially all operating conditions both with respect to this Running surface 20 and an opposite outer, a shoulder-forming tread 21 on the vane bearing ring 6 a certain clearance p (Fig. 2).

As particularly Fig. 4 illustrates, only a relatively small number of rollers 3 are required when a cage or retaining ring 22 is assigned to them. Although the rollers 3 could also run in recesses of this retaining ring 22, the rollers 3 advantageously have axial extensions 24 of smaller diameter, which engage in holes 25 of the retaining ring 22 so that this one hand ensures their distance in the circumferential direction and on the other hand, the rollers and axially fixed on their track opposite the treads 20 and 21 holds. As will be explained later with reference to FIG. 6, such a retaining ring, more in the sense of a cage ring, even with balls 3 'are used as rolling elements, which balls 3' he then can also hold in distributed over the circumference of the treads intervals by having the balls corresponding indentations in these distances. For spheres 3 '(Figure 6), such spacing is less critical because, even with close alignment, they will only point contact, whereas with closely packed rollers 3 they would have a linear contact and would therefore be subject to greater frictional wear. Therefore, the retaining ring 22 is particularly advantageous when using rollers as rolling elements, especially as this friction can play a not insignificant role in the high numbers of revolutions occurring in turbochargers.

As FIG. 1 also shows, it would also be conceivable to also provide the modular unit or cassette formed by adjusting ring 5 and blade bearing ring 6 with all the parts fastened thereto, which are either screwed to a wall 2 'of the turbine housing 2 or, as shown, by means of bolts 30 via spacers 30a bolted to the blade bearing ring 6. It may also be a load device, such as a plate spring 32 which engages an inner flange 6 'of the blade bearing ring 6, suffice to hold it in the axial direction and to press against the wall 2'. The other radial end of the plate spring 32 is located on the cylinder piece 40 of the bearing housing. In this case, it is favorable to the mounting ring by means of pins 24a against rotation, but axially movable to store in the turbine housing.

If a Belleville spring 32 is used as the load means for frictional seating of the unit 26 (see Fig. 2) in the housing 2, it must be clear for the preferred application of the turbocharger design discussed herein that such a Belleville spring 32 is subject to enormous thermal stress which can range from minus degrees at winter standstill to about 1000 ° C. Of course, this affects the metallic structure of the disc spring 32, which is why other loading devices and arrangements will generally be preferred. For example, it would be possible to provide gas springs around the perimeter of the modular unit 26, i. in sliding with air over a check valve cylinders sliding piston whose piston rods press on the blade bearing ring 6. The air could be taken from the compressor room (not shown here, located on the axis of rotation R compressor). Although a pressure loading device is preferred, a tensile loading device would also be conceivable.

FIG. 1a shows an alternative solution for a guide grid which can also be prefabricated in the form of a cassette, likewise as shown in FIG. Here, the rolling elements 3 'are not mounted between adjusting ring 5' and blade bearing ring 6 ', but between adjusting ring 5 and another, possibly with a housing part releasably connectable ring 38, and are located on the' from the blade bearing ring 6 'side facing the adjusting ring 5'. , The cassette can be made by simple (not shown) solidarization of the ring 38 with the blade bearing ring 6 ', such as by screwing or welding radially inwardly and practically adjacent parts 6 "and 38" of these two rings 6' and 38th

The embodiment shown in Fig. 5 uses this alternative solution.

The illustrated in Fig. 2 modular unit 26 (of FIG. 1), the retaining ring 22 preferably between a radial flange 6 'of the blade bearing ring 6 and an inwardly extending radial flange 5' of the adjusting ring 5, which defines an axially open space 5 " It is understood that this interaction of adjusting ring 5 and - in this embodiment, the blade bearing ring 6 as another ring - in reverse Arrangement can be formed in that the adjusting ring 5 has a flange corresponding to the radial flange 6 'and the blade bearing ring 6 has an axially open free space corresponding to the axially open free space 5. In fact, its running surface 21 together with the radial flange 6' forms such an axially open space 2, that the adjusting shafts 8 can optionally have a reduced diameter at their end facing the blades 7, which can be used, for example, with an interference fit in bores of the blades 7.

Fig. 3 shows a slightly modified unit 26a in a similar section to Fig. 2. The changes compared to Fig. 2 relate on the one hand the arrangement of a sealing ring 27 in a sealing groove 28 of the blade bearing ring 6. As a comparison with Fig. 1 shows the blade bearing ring 6 in the region of a housing wall 2a. Now various sealing arrangements are conceivable: Either the sealing ring 27 is formed as a flexible sealing lip, which lays against the wall 2a from below. This is not a problem in itself, because these two parts do not move relative to each other during operation. But it can also (possibly additionally) the (or a) sealing ring 27 protrude into a groove of the wall 2a and form a kind of labyrinth seal, and combinations of both possibilities are also possible, as can be found in the field of seals known solutions application. In any case, with this seal, contaminants from the region of the feed channel are kept away from the rolling bearing 3, 20, 21.

A further modification of the unit 26a with respect to the unit 26 is that it is here provided with a fastening ring 29 protecting the blades 7 at a defined distance (see also Fig. 1), which is attached to the rotor housing on the wall 2 '. Conversely, it is, as can be seen, fastened by means of bolts 30 on the blade bearing ring 6, wherein in a known manner spacers 31 provide for a slightly greater distance than the width of the blades 7 corresponds, so as not to hinder them in their movement in all temperature ranges.

Although reference has already been made above to Fig. 4, because it does not differ in the structure of the rolling bearing of the embodiment of FIG. 2, it will now be understood in comparison with Fig. 3 that Fig. 4 shows a different view of the embodiment represents according to FIG. 3. Because it is both the mounting ring 29 and the seal 27 can be seen.

By contrast, the exemplary embodiment according to FIG. 5 deviates from the previously discussed variants insofar as the sequence of the parts in the axial direction was reversed. While this possibility will be explained by way of example only, it should be understood that combinations with the above-described modifications and variations are readily possible.

In the embodiment of FIG. 5, the adjusting lever 19 are not arranged on the side facing away from the blade bearing ring 6 of the adjusting ring 5, but are, as can be seen, between these two rings 5, 6. The adjusting ring 5 may be formed as shown in FIG. 4, but it may also have pins 36 which engage in slots 37. While the adjusting ring 5 in turn has a, radially inwardly swept running surface 20 for the rolling elements 3, the other, opposite running surface 21 'is formed by a separate ring 38 which is housed inside the adjusting ring and its tread 20. In the axial direction then follows again the retaining ring 22. To set the movable retaining ring 22 in the axial direction, a closure ring 39 may be fixedly connected to the race 38, for example, by the retaining ring 22 by cross-bolts and spacers. In essence, this end ring plays a similar role to that shown in Figures 3 and 4 on the other side by securing the integrity of the modular unit and connecting it to the housing 2 in one of the manners described.

Reference has already been made above to FIG. 6. Here, therefore, it should only be said in addition that the arrangement here is similar to the case of the embodiments of Figures 1 to 4. This means that the rolling bearing 3 ', 20', 21 'is formed between the adjusting ring 5 and the blade bearing ring 6, as is preferred. It should be noted, however, that in this case the arrangement of FIG. 5 could be selected, in which the rolling elements roll on a separate race 38. It can also be seen that here the running surfaces 20 ', 21' recesses for receiving the balls 3 ', so that a separate cage ring (corresponding to the retaining ring 22) can be omitted, although there may be room for it. If, on the other hand, one wishes to use cylindrical surfaces instead of recessed surfaces 20 ', 21', then one will either resort to rollers 3 (cf the previous examples) or else to accommodate a cage ring of the embodiment discussed above in the gap 22 '. Furthermore, it can be seen from FIG. 6 that a sealing groove 28 can be provided, in which either a sealing ring 27 (FIGS. 3, 4) is inserted or a housing-side sealing ring, which may also be designed as a piston ring engages to form a labyrinth seal.

As mentioned, in the context of the invention, all features described here with reference to individual embodiments can be combined both with each other and with features of the prior art. Although it has been emphasized that the inventive design is preferably used for turbocharger, for their particular load conditions, it is also optimally designed. However, it would also be conceivable to use them for operation with other fluids. Furthermore, it is understood that the rotor housing 2 can also have a plurality of turbine rotors 4 and / or a plurality of supply channels 9, as has already been proposed in the prior art. Accordingly, in the case of a plurality of rotors 4, a plurality of such guide grid units 26, 26a may be provided, which may be identical or different, so that, for example, one guide grid corresponds to one of the embodiments described, the other guide grid corresponds to another embodiment.

LIST OF REFERENCE NUMBERS

2

rotor housing

2 '

Wall v. 2

2a

Wall of 2

3

Rolling elements (rollers), 3 '= balls

4

turbine rotor

5

Adjusting ring with radial flange 5 '

6

Blade bearing ring with flange 6 '

7

vane

8th

adjusting

9

supply channel

10

Axialstutzen

11

actuator

12

control housing

13

actuating lever

14

actuating shaft

15

eccentric

16

flange

17

recess

18

Head or lever end v. 19

19

adjusting

20

Tread v. 5

21

Tread v. 6; 21 'tread v.

22

Cage or retaining ring (in 22 ')

23

rotor chamber

24

axial extension

25

Holes of 22

26

modular unit

27

Dichtungsrin

28

seal groove

29

fixing ring

30

Bolze

31

spacer

32

Belleville spring

33

gearing

34

35

rotor shaft

36

pen

37

Long hole

38

race

39

final ring

40

cylinder part

Claims (10)

1. Turbine unit, in particular for a turbocharger, which comprises the following:

   a rotor housing (2) having at least one feed channel (9) for a fluid;

   a turbine rotor (4) which is mounted in a turbine space (23) of the rotor housing (2) and the periphery of which is supplied with the fluid via

   a guide vane system (5-8) of variable turbine geometry, which has

   a annular guide conduit (6) having a multiplicity of blade shafts (8) mounted on this annular guide conduit (6) in the form of a ring and blades (7) fastened thereto on one side, which blades are adjustable in each case from a substantially tangential position relative to the ring to an approximately radial position, and at least one adjusting element (19) for adjusting the position of the blades (7);

   an actuating means (11) for producing controlled movements to be transmitted to the guide vane system (5-8) having variable turbine geometry, via

   an adjusting ring (5) which is arranged coaxially with the annular guide conduit (6) and adjacent thereto and is displaceably connected to the at least one adjusting element (19), and

   a guide and centring arrangement for the adjusting ring (5), which arrangement comprises at least one roller bearing (3, 20, 21) having roll bodies (3) running on a running surface (20) of the adjusting

   ring (5);

   
   characterized in that the roller bearing (3, 20, 21) is arranged between the adjusting ring (5) and a ring (6; 38) which may be capable of being detachably connected to the roller housing (2), such as, for example, the annular guide conduit (6) or a bearing ring (38), so that adjusting ring (5), roller bearing (3, 20, 21) and the ring (6; 38) which may be capable of being detachably connected can be installed as a modular unit (26) in the rotor housing (2).
2. Turbine unit according to Claim 1, characterized in that at least one of the following features is provided:

   a) the roller bearing (3, 20, 21) is in the form of a rolling contact bearing;

   b) the ring which may be capable of being detachably connected is the annular guide conduit (6);

   c) the unit (26a) also comprises a fixing ring (29) which is opposite the blades (7), is to be fastened to the rotor housing (2) and is connected to the annular guide conduit (6).
3. Turbine bearing unit according to Claim 1 or 2, characterized in that the roller bearing (3, 20, 21) is housed in a free space (5 ' ') of one of the rings which is open in the axial direction, preferably of the adjusting ring (5), and in that this free space (5 ") is closed by a further ring, in particular by a ring (22) holding axial extensions (24) of the rollers (3) of the roller bearing, the rollers (3) optionally being held a distance apart by this retaining ring (22) (Fig. 2, 4).
4. Turbine unit according to any of the preceding Claims, characterized in that a majority of the adjusting elements (19), in each case on the other side of the annular guide conduit (6) which faces away from the blades (7), is formed by approximately radially extending adjusting levers (19) fixed to the blade shafts (8) and having in each case a free lever end (18).
5. Turbine unit according to any of the preceding Claims, characterized in that diameters of the adjusting ring (5) and of the ring (6) which can be detachably connected, which diameters cooperate with the roller bearing (3, 20, 21) are dimensioned so that they permit a radial play (p) of the roll bodies (3) substantially at all operating temperatures (Fig. 2).
6. Turbine unit according to any of the preceding Claims, characterized in that the modular unit (26, 26a) comprising an adjusting ring (5), roller bearing (3, 20, 21) and ring (6; 38) which can be detachably connected is held nonrotatably by intermeshing projections and indentations (33), and preferably loaded towards this position by a loading arrangement.
7. Turbine unit according to any of the preceding Claims, characterized in that at least one annular seal (27, 28) is provided between roller bearing (3, 20, 21) and a fluid-carrying space (9, 23).
8. Turbine unit according to any of the preceding Claims, characterized in that the running surface (21) of the ring (6; 38) which can be detachably connected has a smaller diameter than the running surface (20) of the adjusting ring (5).
9. Guide vane system (5-8) of variable turbine geometry for a turbine unit according to any of the preceding Claims, comprising
   a annular guide conduit (6) on which adjusting shafts (8) for one variable guide blade (7) each fastened to one end of the respective adjusting shaft (8) are mounted, at the other end of which adjusting elements (19) for adjusting the position of the guide vanes (7) are provided,
   an adjusting ring (5) for adjusting the adjusting elements (19), and
   a guide and centring arrangement for the adjusting ring (5), which arrangement comprises at least one roller bearing (3, 20, 21) having roll bodies (3) running on a running surface (20) of the adjusting ring (5);
   characterized in that the roller bearing (3, 20, 21) is arranged between the adjusting ring (5) and a ring (6; 38) which can be detachably connected to the rotor housing (2), so that adjusting ring (5), roller bearing (3, 20, 21) and the ring (6; 38) which can be detachably connected form a modular unit (26).
10. Guide vane system (7) according to Claim 9, characterized in that at least one of the following features is provided:

    a) the roller bearing (3, 20, 21) is in the form of a rolling contact bearing;

    b) the roller bearing (3', 20, 21) is in the form of a ball bearing;

    c) the roller bearing (3, 20, 21) is housed in a free space (5'') of one of the rings, preferably of the adjusting ring (5), which free space is open in the axial direction, this free space (5") being closed by a further ring, in particular a ring (22) holding axial extensions (24) of the rollers (3) of the roller bearing (3, 20, 21);

    d) the ring which can be detachably connected is the annular guide conduit (6);

    e) the diameters of the adjusting ring (5) and of the ring (6; 38) which can be detachably connected and which diameters cooperate with the roller bearing (3, 20, 21), are dimensioned so that they permit a radial play (p) of the roll bodies (3) substantially at all operating temperatures;

    f) the modular unit (26; 26a) comprising adjusting ring (5), roller bearing (3, 20, 21) and ring (6; 38) which can be detachably connected is held nonrotatably by intermeshing projections and indentations (33), and preferably loaded towards this position by a loading arrangement (32);

    g) an annular seal (27, 28) is provided between roller bearing (3, 20, 21) and a space (9, 23) carrying fluid in the state when in use;

    h) the running surface (21) of the ring (6; 38) which can be detachably connected has a smaller diameter than the running surface (20) of the adjusting ring (5);

    i) the roller bearing is formed from a number of rollers or balls which substantially fills the free space (5'');

    j) the roller bearing is formed from at least three rollers or balls which are guided in the free space (5'') by a freely rotatable retaining ring (22).

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