Turbocharger turbine with spring retainer

Abstract

A turbine arrangement comprises a turbine wheel, a nozzle ring and an annular spring retainer member. The turbine wheel (4) is located within a turbine chamber (30) defined at least in part by a turbine housing (5). The turbine wheel is mounted to a shaft, the shaft and mounted turbine wheel being supported for rotation about a turbine axis by a bearing arrangement. The bearing arrangement is located in a bearing housing (3), the bearing housing having an axially extending spigot feature (32), and the bearing housing being attached to the turbine housing. The nozzle ring (34) is received by the turbine housing. The nozzle ring includes one or more flow directing vanes (36) located in a flow path (F) between an inlet volute (9) and the turbine wheel, the inlet volute being defined by an inlet volute portion of the turbine housing. The annular spring retainer member (38) is compressed between the nozzle ring and the bearing housing, the spring retainer member defining a central aperture (40) which receives the spigot feature. An axial extent (E') of the spring retainer member, in an uncompressed state, is greater than an axial spacing (S) between a back face of the turbine wheel and the spigot feature.

Description

[0001] TURBOCHARGER TURBINE WITH SPRING RETAINER

[0002] The present invention relates to a turbine arrangement that includes an annular heat shield. The present invention also relates to a turbocharger that includes such a turbine arrangement. The present invention further relates to a corresponding method of assembling a turbine arrangement or turbocharger.

[0003] Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure (boost pressures). A conventional turbocharger comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to the intake manifold of the engine, thereby increasing engine power. The turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housings.

[0004] In known turbochargers, the turbine stage comprises a turbine chamber within which the turbine wheel is mounted; a circumferentially extending inlet passageway defined between opposing walls arranged around the turbine chamber; an inlet volute arranged around the inlet passageway; and an outlet passageway extending from the turbine chamber. The passageways and chambers communicate such that pressurised exhaust gas admitted to the inlet volute flows through the inlet passageway to the outlet passageway via the turbine and rotates the turbine wheel. It is also known to improve turbine performance by providing vanes, referred to as nozzle vanes, in the inlet passageway so as to deflect gas flowing through the inlet passageway towards the direction of rotation of the turbine wheel. The nozzle vanes may be located on a separate component known as a nozzle ring.

[0005] Turbines may be of a single-entry or multiple-entry type. Single-entry turbines comprise a single inlet volute that typically receives all of the exhaust gas from an internal combustion engine. Multiple-entry turbines comprise more than one volute which typically receive separate streams of exhaust gas from different cylinder banks of an internal combustion engine. One form of multiple-entry turbine is a “twin-entry” turbine in which two volutes extend circumferentially with one another around the turbine axis in angular alignment with one another. In such “twin-entry” turbines, a dividing wall is used to separate the volutes from one another.

[0006] Some turbines include an annular heat shield. The heat shield is located behind the turbine wheel, such that it is between the turbine wheel and the bearing housing. The heat shield helps to reduce heat that is transferred, from the hot exhaust gas passing through the turbine, to the bearing housing. Reducing heat which is transferred to the bearing housing may be beneficial as an increase in bearing housing temperature may result in a decrease in the performance of the bearing arrangement within the bearing housing - for example, the bearing arrangement may make use of a lubricant, the performance of which reduces with increasing temperature.

[0007] The manufacturing process for some turbines including a heat shield is a multi-step process. The turbine wheel is attached to a first end of the shaft. The heat shield is lowered on to the bearing housing so that it is mounted to the bearing housing. A second end of the shaft is lowered into the bearing housing such that it is inserted into the bearing housing, the shaft passing through the heat shield whilst it is mounted to the bearing housing. This arrangement constitutes a first sub-assembly. A second sub- assembly is formed by lowering the nozzle ring into the turbine housing. Final assembly of the turbine, or turbine arrangement, is achieved by inverting the first sub-assembly and lowering the first sub-assembly into the second sub-assembly such that the turbine wheel passes through the nozzle ring and is located in the turbine housing.

[0008] During this manufacturing process it is possible for components of the first and / or second sub-assemblies to become misaligned. Such misalignment may mean that it is no longer possible to assemble the first and second subassemblies together and / or it may mean that one or more components within the first and second subassemblies are damaged when assembling the first and second sub-assemblies together. In addition, or alternatively, if components of the first and / or second sub-assemblies become misaligned, then it may mean that, once the first and second sub-assemblies are assembled together, said components remain misaligned, which may have an adverse effect on the operating performance and / or reliability of the assembled turbine. The present invention seeks to provide an alternative turbine arrangement and assembly method. Such alternatives may obviate or mitigate one or more of the disadvantages associated with existing turbine arrangements and methods, whether discussed above or otherwise.

[0009] Whilst the examples discussed above relate to a turbine or turbine arrangement which forms part of a turbocharger, the invention applies equally to any turbine arrangement that forms part of any suitable turbine machine, such as, for example, a power turbine.

[0010] According to a first aspect of the invention there is provided a turbine arrangement comprising a turbine wheel located within a turbine chamber defined at least in part by a turbine housing, the turbine wheel being mounted to a shaft, the shaft and mounted turbine wheel being supported for rotation about a turbine axis by a bearing arrangement, wherein the bearing arrangement is located in a bearing housing, the bearing housing having an axially extending spigot feature, and the bearing housing being attached to the turbine housing; a nozzle ring, received by the turbine housing, the nozzle ring including one or more flow directing vanes located in a flow path between an inlet volute and the turbine wheel, the inlet volute being defined by an inlet volute portion of the turbine housing; an annular spring retainer member compressed between the nozzle ring and the bearing housing, the spring retainer member defining a central aperture which receives the spigot feature, wherein an axial extent of the spring retainer member in an uncompressed state, is greater than an axial spacing between a back face of the turbine wheel and the spigot feature.

[0011] Use of a spring retainer member which has an axial extent in an uncompressed state which is greater than an axial spacing between a back face of the turbine wheel and the spigot feature ensures that the spring retainer member does not dismount the spigot feature during the assembly process for the turbine arrangement. This may be beneficial as it facilitates easy assembly of the turbine arrangement and / or prevents misalignment of components of the turbine arrangement which may occur during assembly of the turbine arrangement.

[0012] The spring retainer member may have a radially outer portion and a radially inner portion, wherein the radially outer portion contacts the nozzle ring and the radially inner portion receives the spigot feature. The axial extent may be measured between the radially outer portion of the spring retainer member and the radially inner portion of the spring retainer member.

[0013] A minimum axial spacing between the back face of the turbine wheel and the spring retainer member may be located between the back face of the turbine wheel and the radially outer portion of the spring retainer member.

[0014] The spring retainer member may be generally dish-shaped.

[0015] A radially extending outer rim of the spring retainer member may include the radially outer portion of the spring retainer member. A radially extending base of the spring retainer member may include the radially inner portion of the spring retainer member. The outer rim and base may be linked by an axially extending wall.

[0016] The axially extending wall may subtend an acute angle with the axis of between 20 and 75 degrees. The axially extending wall may subtend an acute angle with the axis of between 25 and 55 degrees.

[0017] A radial extent of the base may be at least twice a radial extent of the outer rim.

[0018] An outside radius of the turbine wheel may be greater than a radius of a radially innermost portion of the outer rim of the spring retainer member.

[0019] An outside radius of the turbine wheel may be between about 1.02 and about 1.6 times greater than a radius of a radially innermost portion of the outer rim of the spring retainer member. The outside radius of the turbine wheel may be: i) between about 1.02 and about 1 .4 times greater than a radius of a radially innermost portion of the outer rim of the spring retainer member; or ii) between about 1 .02 and about 1 .2 times greater than a radius of a radially innermost portion of the outer rim of the spring retainer member.

[0020] The bearing housing may include a raised feature, radially outboard of the spigot feature, wherein the raised feature has a maximum axial height, at a maximum axial height portion of the raised feature, which is less than a maximum axial height of the spigot feature, at a maximum axial height portion of the spigot feature, and greater than a maximum axial height of an outboard region of the bearing housing, at a maximum axial height portion of the outboard region, the outboard region being located radially outboard of the raised feature.

[0021] An axial separation between the maximum axial height portion of the raised feature and the maximum axial height portion of the spigot feature may be less than eight times an axial separation between the maximum axial height portion of the raised feature and the maximum axial height portion of the outboard region.

[0022] A maximum radius of the maximum axial height portion of the raised feature may be between about 1.03 and about 2.9 times greater than a maximum radius of the spigot feature. The maximum radius of the maximum axial height portion of the raised feature may be: i) between about 1.1 and about 2.9 times greater than a maximum radius of the spigot feature; ii) between about 1 .2 and about 2.9 times greater than a maximum radius of the spigot feature; ill) between about 1 .03 and about 1 .6 times greater than a maximum radius of the spigot feature; iv) between about 1.03 and about 1.4 times greater than a maximum radius of the spigot feature; or v) between about 1.03 and about 1.3 times greater than a maximum radius of the spigot feature.

[0023] A maximum radius of the maximum axial height portion of the raised feature may be between about 1.03 and about 2.9 times greater than a minimum radius of the central aperture. A maximum radius of the maximum axial height portion of the raised feature may be: i) between about 1.1 and about 2.9 times greater than a greater than a minimum radius of the central aperture; ii) between about 1 .2 and about 2.9 times greater than a than a minimum radius of the central aperture; ill) between about 1.03 and about 1.6 times greater than a minimum radius of the central aperture; iv) between about 1.03 and about 1.4 times greater than a minimum radius of the central aperture; or v) between about 1.03 and about 1.3 times greater than a greater than a minimum radius of the central aperture.

[0024] An outside radius of the turbine wheel is between about 2.9 and about 1 .2 times a radius of the maximum axial height portion of the raised feature. The outside radius of the turbine wheel may be i) between about 2.7 and about 1 .4 times a radius of the maximum axial height portion of the raised feature; ii) between about 2.5 and about 1.6 times a radius of the maximum axial height portion of the raised feature; or ill) between about 2.3 and about 1.8 times a radius of the maximum axial height portion of the raised feature. According to a second aspect of the invention there is provided a turbocharger including a turbine arrangement according to the first aspect of the invention, and a compressor comprising a compressor wheel mounted to said shaft.

[0025] According to a third aspect of the present invention there is provided a method of assembling a turbine arrangement, the turbine arrangement comprising: a turbine wheel having a back face, the turbine wheel being mounted to a shaft, a turbine housing comprising a volute housing portion defining an inlet volute, a bearing arrangement located in a bearing housing, the bearing housing having a spigot feature which extends along a turbine axis, a nozzle ring including one or more flow directing vanes, and an annular spring retainer member defining a central aperture. The method comprises: with the bearing housing in a first orientation in which the spigot feature extends upwards, mounting the spring retainer member, in an uncompressed state, on the bearing housing such that the spigot feature is received by the central aperture, inserting the shaft through the central aperture and spigot feature such that the shaft is received by the bearing arrangement, the bearing arrangement supporting the shaft and mounted turbine wheel for rotation about the turbine axis, whereby an axial extent of the spring retainer member in the uncompressed state is greater than an axial spacing between the back face of the turbine wheel and the spigot feature, inverting the bearing housing into a second orientation in which the spring retainer member contacts the back face of the turbine wheel and the spigot feature remains received by the central aperture, locating the nozzle ring within the turbine housing, and with the bearing housing in its second orientation, the spring retainer member mounted on the bearing housing and the shaft received by the bearing arrangement, locating the bearing housing, spring retainer member and turbine wheel into the turbine housing such that: i) the turbine wheel is located within a turbine chamber defined at least in part by the turbine housing; ii) the one or more flow directing vanes is located in a flow path between the inlet volute and the turbine wheel; and ill) the spring retainer member is compressed between the nozzle ring and the bearing housing, the spring retainer member thereby urging the nozzle ring away from the bearing housing and pushing the nozzle ring against the turbine housing.

[0026] According to a fourth aspect of the invention there is provided a method of assembling a turbocharger, the method including assembling a turbine arrangement in accordance with the third aspect of the invention, mounting a compressor wheel to the shaft and mounting a compressor housing to the bearing housing so that the compressor housing receives the compressor wheel.

[0027] Within any of the aspects of the invention discussed above, the spring retainer member may take the form of a heat shield. As already mentioned, the spring retainer member will function so as to, via compression, exert a force on the nozzle ring to urge the nozzle ring into position against the turbine housing. The spring retainer member is also configured so as to prevent the spring retainer member from dismounting the spigot during assembly of the turbine arrangement. If the spring retainer member takes the form of heat shield it will also function so as to minimise the heat transferred from gas entering the turbine to the bearing housing. Within the present document, where a heat shield is discussed, it could be replaced by a spring retainer member - however, as mentioned, such a spring retainer member will no longer perform the function of a heat shield, but will still function to retain the nozzle ring and not dismount the spigot during assembly.

[0028] It will be appreciated that any of the optional features discussed in relation to the first aspect of the invention may, where appropriate, be applied to other aspects of the invention.

[0029] A detailed description of one or more exemplary embodiments of the invention is provided below with reference to the accompanying drawings, in which:

[0030] Figure 1 is a schematic cross-sectional view of a known turbocharger;

[0031] Figure 2 is a schematic cross-sectional view of a portion of a turbine arrangement in accordance with an embodiment of the invention;

[0032] Figures 3a to 3g are schematic cross-sectional views of a method of assembling a turbine arrangement in accordance with an embodiment of the invention;

[0033] Figures 4a and 4b are schematic cross-sectional views of portion of a turbine arrangement in accordance with an embodiment of the invention;

[0034] Figure 5 is a schematic cross-sectional view of a portion of a turbine arrangement in accordance with an embodiment of the invention; and Figure 6 a schematic cross-sectional view of a portion of a turbine arrangement in accordance with another embodiment of the invention.

[0035] Figure 1 shows a schematic cross-section through a known turbocharger. The turbocharger comprises a turbine 1 joined to a compressor 2 via a central bearing housing 3. The turbine 1 comprises a turbine wheel 4 for rotation within a turbine housing 5. Similarly, the compressor 2 comprises a compressor wheel 6, of the centrifugal type, which can rotate within a compressor housing 7. The compressor housing 7 defines a compressor chamber within which the compressor wheel 6 can rotate. The turbine wheel 4 and compressor wheel 6 are mounted on opposite ends of a common turbocharger shaft 8 which extends through the central bearing housing 3.

[0036] The turbine housing 5 has two inlet volutes 9 located annularly around the turbine wheel 4, and an axial exhaust gas outlet 10. The inlet volutes 9 are configured to receive exhaust gas from separate cylinder banks of the internal combustion engine. The compressor housing 7 has an axial air intake passage (compressor inlet) 11 and an outlet volute 12 arranged annularly around the compressor chamber. The outlet volute 12 is in gas flow communication with a compressor outlet 13 that delivers the compressed air onwards to an internal combustion engine (not shown).

[0037] The bearing housing 3 defines a bearing chamber through which the turbocharger shaft 8 passes. The shaft 8 is rotatably supported by a bearing assembly which comprises two journal bearings 14 and 15 housed towards the turbine end and compressor end respectively of the bearing housing 3. Oil is supplied to the bearing assembly from the oil system of the internal combustion engine via oil inlet 18 and is fed to the bearings 14, 15 by oil passageways 19. The oil fed to the bearings 14, 15 may be used to both lubricate the bearings and to remove heat from the bearings.

[0038] In use, the turbine wheel 4 is rotated about an axis 25 by the passage of exhaust gas from the exhaust gas inlet 9 to the exhaust gas outlet 10. Exhaust gas is provided to exhaust gas inlet 9 from an exhaust manifold (also referred to as an outlet manifold) of the engine. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet 11 and delivers boost air to an inlet manifold of the engine via the volute 12 and then the outlet 13. The compressor chamber is defined between a shroud portion 17 of the compressor housing 7 and a hub portion 20 of the bearing housing 3. The compressor housing 7 shown in Figure 1 may be formed as a one-piece (i.e. integral) unit including the shroud portion 17, although in alternative embodiments may comprise multiple components. The shroud portion 17 has an inwardly facing shroud surface 21.

[0039] Figure 2 shows a schematic cross section of a portion of a turbine arrangement in accordance with an embodiment of the present invention. The turbine arrangement may form part of a turbocharger of the type previously discussed. In order to aid understanding as to the location of the portion of the turbine arrangement shown within Figure 2, the dashed box indicated by the reference indication A in Figure 1 generally corresponds to where the turbine arrangement portion shown in Figure 2 would be located in a turbocharger of the type shown in Figure 1. Please note, as compared to the orientation of the turbocharger shown in Figure 1 , the portion of the turbine arrangement shown in Figure 2 has been rotated anti-clockwise by 90 degrees. Furthermore, in order for the correspondence between features shown in Figures 1 and 2 to be as easy as possible to discern, equivalent features have been numbered with the same reference numerals.

[0040] The turbine wheel 4 is located within a turbine chamber 30 defined in least in part by the turbine housing 5. The turbine wheel 4 is mounted to the shaft 8. The shaft 8 and mounted turbine wheel 4 are supported for rotation about the turbine axis 25 by a bearing arrangement (for example, but not limited to, including the journal bearings 14 and 15 discussed in relation to Figure 1 ). The bearing arrangement is located in a bearing housing 3. The bearing housing 3 has an axially extending spigot portion 32. The bearing housing 3 is attached to the turbine housing 4. Figure 1 shows the presence of a V-band 22 is used to clamp the bearing housing 3 and turbine housing 5 together. However, it will be appreciated that any appropriate method of attaching the bearing housing to the turbine housing may be used.

[0041] The turbine wheel 4 comprises a central hub 4a from which a plurality of circumferentially (or angularly) spaced blades 4b extend. The turbine wheel also includes a back face 4c. Back face 4c is a portion of the turbine wheel which faces the bearing housing. The back face 4c may be continuous (e.g. formed by a continuous surface of the turbine wheel) or may be discontinuous (e.g. formed by a portion of each of the turbine blades 4b). In general, the back face 4c of the turbine wheel 4 is the portion of the wheel 4 that, for any given angular and radial location on the wheel, is axially closest to the bearing housing. Furthermore, in general, the back face 4c of the turbine wheel 4 does not interact with the gas provided through the inlet volute to do work.

[0042] By way of difference to the turbocharger shown within Figure 1 , the turbine arrangement within Figure 2 includes a nozzle ring 34 that includes a plurality of flow directing vanes 36. The figure shows two vanes 36: the vane on the left being in cross section and the vane on the right showing an end on view of the vane. Whilst only two vanes are shown within the figure, it will be appreciated that there are many more vanes not shown in Figure 2 that are circumferentially spaced around the annular nozzle ring 34. The flow directing vanes 36, which may be referred to as nozzle vanes, deflect gas flowing from the inlet volutes 9 to the turbine wheel 4 towards the direction of rotation of the turbine wheel 4. As such, the nozzle ring 34 is received by the turbine housing 5 such that the flow directing vanes 36 are located in a flow path F between the inlet volute 9 and turbine wheel 4.

[0043] The turbine arrangement further includes an annular heat shield 38 that defines a central aperture 40. The central aperture 40 receives the spigot feature 32.

[0044] The heat shield 38 is compressed between the nozzle ring 34 and bearing housing 3. In particular, the heat shield is compressed in the axial direction. Given that the heat shield is compressed, as compared to its uncompressed or equilibrium state, the heat shield 38 exerts a restoring force on the bearing housing 3 and nozzle ring 34. In this way the heat shield 38 urges the nozzle ring 34 away from the bearing housing 3 (in a generally axial direction) towards the turbine housing 5. As such, the heat shield 38 urges the nozzle ring 34 against the turbine housing 5. By urging the nozzle ring 34 against the turbine housing 5 this helps to not only ensure that the nozzle ring 34 is correctly located relative to the turbine housing (such that the flow directing vanes 36 of the nozzle ring 34 are correctly located in the flow path of the gas between the inlet volutes 9 and turbine wheel 4), but also helps to prevent the nozzle ring 34 from being rotated about the axis due to the force exerted on the flow directing vanes 36 by the gas incident on them. Preventing rotation of the nozzle ring not only reduces wear on the nozzle ring, but also maximises the effectiveness of the nozzle ring in directing gas flow, and hence the efficiency of the turbine arrangement. In other embodiments the turbine arrangement may include an anti-rotation arrangement to assist preventing relative rotation between the nozzle ring and turbine housing. For example, the anti-rotation arrangement may include a tab of the nozzle ring which is received in a corresponding recess of the turbine housing, or, alternatively, a tab of the turbine housing which is received in a corresponding recess of the nozzle ring. Alternatively, a pin may be used to secure the nozzle ring against rotation relative to the turbine housing.

[0045] For completeness, although not necessary for understanding the invention, two seals 42a and 42b are provided between the nozzle ring 34 and the turbine housing 5. The first seal 42a helps to prevent gas from one of the inlet volutes 9 leaking into the other inlet volute 9, upstream of the nozzle ring 34. Leakage between the separate inlet volutes 9 upstream of the nozzle ring 34 may reduce the efficiency of the turbine. The second seal 42b helps to reduce the occurrence of gas leaking from the inlet volute 9 to behind the turbine wheel 4. Again, gas leaking from the inlet volute 9 to behind the turbine wheel 4 may reduce the efficiency of the turbine.

[0046] In some embodiments of the invention, the compression of the heat shield between the nozzle ring and the bearing housing may result in the heat shield applying sufficient force on the nozzle ring and bearing housing that the heat shield acts to seal between the nozzle ring and bearing housing, thereby substantially preventing gas from leaking from the inlet volute to behind the turbine wheel. In such embodiments, this may mean that the second seal 42b is not needed.

[0047] Figure 3 shows a series of schematic images that illustrate a method of assembling a turbine arrangement in accordance with an embodiment of the present invention. In the embodiment of the method shown in Figure 3 the turbine arrangement which is assembled is the same as that shown in Figure 2. It follows that the same reference numerals are used for equivalent features. It will of course be appreciated that a method of assembling a turbine arrangement in accordance with the present invention need not be applied to the turbine arrangement shown in Figure 2, but may be equally applied to any appropriate turbine arrangement.

[0048] Figure 3a shows the bearing housing 3 in a first orientation in which the spigot feature 32 extends upwards. As will become clear in the description of further parts of the method, the term upwards is used to mean in a direction that is opposite to the direction of the force of gravity acting upon an object.

[0049] As shown in Figure 3b, the heat shield 38 is mounted in its uncompressed or equilibrium state onto the bearing housing such that the spigot feature 32 is received by the central aperture 40 of the heat shield 38. In other words, in order to mount the heat shield on the bearing housing, the heat shield 38 and hence central aperture 40 is lowered (or dropped) over the spigot feature 32 of the bearing housing 3.

[0050] In Figure 3c it can be seen that the shaft 8 to which the turbine wheel 4 is mounted is inserted through the central aperture 40 and spigot feature 32 such that the shaft 8 is received by the bearing arrangement (not shown within Figure 3). The bearing arrangement supports the shaft 8 and mounted turbine wheel 4 for rotation about the turbine axis 25. Again, when it is said that the shaft 8 is inserted through the central aperture 40 and spigot feature 32, it may also be said that the shaft 8 is lowered through the central aperture 40 and spigot feature 32 into the bearing arrangement of the bearing housing 3.

[0051] Figure 3d shows the turbine housing 5. The nozzle ring 34 is inserted into the turbine housing 5 as shown in Figure 3e. In the present example, locating the nozzle 34 within the turbine housing 5 involves lowering the nozzle ring 34 into the turbine housing 5.

[0052] Figure 3f shows a portion of the method in which a first sub assembly (as shown in Figure 3c - which includes the shaft 8, turbine wheel 4 mounted to the shaft 8, heat shield 38 and bearing housing 3) is inverted into a second orientation. In the second orientation the spigot feature 32 extends in a downward direction. In the second orientation the heat shield 38 contacts the back face 4c of the turbine wheel and the spigot feature 32 remains received by the central aperture 40 of the heat shield 38. Due to the fact that the spigot feature 32 remains received by the central aperture 40 when the first sub assembly is inverted, this means that it is not possible for the heat shield to become misaligned relative to the rest of the first sub assembly whilst assembly is carried out. Any such misalignment between the heat shield and the rest of the sub assembly may result in it no longer being possible to correctly assemble the turbine arrangement or it may result in the assembled turbine arrangement being assembled incorrectly and therefore operating improperly. It follows that the present invention provides an improved method of assembling a turbine arrangement.

[0053] The characteristics of the heat shield which enable it to remain located on the spigot feature 32 of the first sub assembly regardless of the orientation of the first sub assembly (for example, in the second orientation) are discussed in further detail later within this description.

[0054] Figure 3f shows the first sub assembly being inserted into the second sub assembly (turbine housing 5 and nozzle ring 34). This occurs by lowering the first sub assembly into the second sub assembly. In this way, the bearing housing 3, heat shield 38 and turbine wheel 4 are located into the turbine housing 5 such that the turbine wheel 4 is located within a turbine chamber 30, defined at least in part by the turbine housing 5. In addition, the flow directing vanes 36 of the nozzle ring 34 are located in a flow path between the inlet volute of the turbine housing and the turbine wheel 4. In addition, as can be best seen in Figure 3g, the heat shield 38 is compressed between the nozzle ring 34 and the bearing housing 3, the heat shield thereby urging the nozzle ring 34 away from the bearing housing 3 and pushing the nozzle ring 34 against the turbine housing 5.

[0055] Given that the heat shield 38 is compressed between the nozzle ring 34 and the bearing housing 5, such that the nozzle ring (and in particular, the flow directing vanes 36) are pushed against the turbine housing 5, this correctly locates the flow directing vanes within the flow path of gas travelling from the turbine inlet to the turbine wheel 4 and substantially prevents rotation of the nozzle ring 34 relative to the turbine housing 5 (for example due to a circumferential component of the force of the received inlet gas - in particular the inlet gas incident on the flow directing vanes).

[0056] A turbocharger according to an embodiment of the present invention can be assembled by mounting a compressor wheel to the shaft (at the end of the shaft opposite to the end to which the turbine wheel is mounted) and mounting a compressor housing to the bearing housing. The compressor housing will define a compressor inlet, a compressor outlet and a compressor chamber, which contains the compressor wheel, located between the compressor inlet and compressor outlet. Such an arrangement is, common in the field of turbochargers and so, for the sake of brevity, not discussed any further here.

[0057] Mounting the compressor wheel to the shaft may occur after the shaft 8 to which the turbine wheel 4 is mounted is inserted through the central aperture 40 and spigot feature 32 such that the shaft 8 is received by the bearing arrangement (as shown in Figure 3c), such that the compressor wheel forms part of the first sub assembly, and before the first sub assembly is inserted into the second sub assembly (as shown in Figure 3f). Alternatively, the compressor wheel may be mounted to the shaft at any other appropriate point during the assembly process.

[0058] Mounting the compressor housing to the bearing housing may occur at any appropriate point during the assembly process. For example, it may occur at a point such that the compressor housing forms part of the first sub assembly before it is inverted and inserted into the second sub assembly. Alternatively, it may occur after the first sub assembly has been inverted and inserted into the second sub assembly.

[0059] Figure 4a is a schematic drawing showing an enlargement of a portion of the turbine arrangement as shown in Figures 2 and 3. In particular, Figure 4a shows the state of the heat shield in the portion of the method shown in Figure 3c.

[0060] Figure 4b shows the portion of the turbine arrangement of Figure 4a but during the portion of the assembly method shown in Figure 3f. Figure 4b also shows, in dashed lines, the portion of the turbine arrangement during the portion of the assembly method shown in Figure 3g, in which the heat shield 38 is compressed between the nozzle ring 34 and the bearing housing 3.

[0061] The figure shows that the axial extent of the heat shield 38 is reduced when the heat shield 38 is compressed. The axial extent of the heat shield indicated by E is the axial extent of the heat shield 38 when the heat shield is in its compressed state, whereas the axial extent of the heat shield indicated by E’ is the axial extent of the heat shield 38 in its uncompressed or relaxed state.

[0062] The axial extent E’ of the heat shield 38 in its uncompressed state is greater than the axial spacing S between the back face 4c of the turbine wheel 4 and the spigot feature 32. As previously discussed, this geometry of heat shield relative to the dimensions of the spigot feature and turbine wheel ensures that, once mounted to the spigot feature 32 of the bearing housing 3, with the turbine wheel 4 in situ, the heat shield 38 will not dismount the spigot feature of the bearing housing.

[0063] The heat shield 38 has a radially outer portion 38a and a radially inner portion 38b. The radially outer portion 38a contacts the nozzle ring 34 and the radially inner portion 38b receives the spigot feature 32. The axial extent of the heat shield 38 (E in the compressed state and the E’ in the uncompressed state) is measured between the radially outer portion 38a and the radially inner portion 38b.

[0064] A minimum axial spacing M between the back face 4c of the turbine wheel 4 and the heat shield 38 is located between the back face of 4c of the turbine wheel 4 and the radially outer portion 38a of the heat shield 38.

[0065] As may be best seen in Figure 3b, the heat shield 38 is generally dish-shaped. Given the dish-shaped nature of the heat shield 38, it may be said that the heat shield includes a radially extending outer rim 38c which includes the radially outer portion 38a of the heat shield 38. A radially extending base 38d of the heat shield 38 includes the radially inner portion 38b of the heat shield 38. The outer rim 38c and base 38d are linked by an axially extending wall 38e. By axially extending, what is meant is that the wall extends in a direction that has an axial component. However, additionally the wall may extend in a direction which has a radial component.

[0066] As can be best seen in Figure 2, the wall 38e subtends an acute angle AA with the axis of about 40 degrees. In order to make this angle easier to perceive in the figure the figure has been annotated with a line 25’ which is parallel to the turbine axis.

[0067] It will be appreciated that in other embodiments, the wall 38e of the heat shield 38 may subtend any appropriate acute angle with the axis. For example, the wall 38e of the heat shield may subtend an acute angle with the axis of between 25 degrees and 55 degrees.

[0068] A radial extent E1 of the base 38d of the heat shield 38 is at least twice the radial extent E2 of the outer rim 38c of the heat shield 38. Radial extent E1 of the base 38d is calculated by subtracting the radius (relative to the turbine axis) of the radially innermost portion of the base from the radius of the radially outermost portion of the base. Likewise, the radial extent E2 of the outer rim 38c is calculated by subtracting the radius (relative to the turbine axis) of the radially innermost portion of the outer rim from the radius of the radially outermost portion of the outer rim.

[0069] For completeness, it will be appreciated that the radially outermost portion of the base of the heat shield (also known as the radially inner portion of the heat shield) and the radially innermost portion of the outer rim 38c of the heat shield 38 (also known as the radially outer portion of the heat shield) may be connected by an axially extending wall 38e having any appropriate geometry.

[0070] It is also possible to define the geometry of the heat shield 38 by reference to an outer radius OR of the turbine wheel 4. The outer radius OR of the turbine wheel 4 may be defined as the radius (relative to the axis) of the radially outermost portion of the turbine wheel 4. Put another way, it may be the greatest radius of the turbine wheel. As has previously been discussed, in some embodiments of the invention, in order to ensure the heat shield does not demount the spigot feature, the heat shield will contact the back face 4c when the bearing housing, heat shield, turbine wheel and shaft are inverted. For this reason it may be desirable that, as shown in Figure 5, the outer rim 38c of the heat shield 38 is located such that it is aligned, in a direction parallel to the axis, with a portion of the back face 4c. In light of this, radius R4 may be less than the outer radius OR of the turbine wheel 4. The radius R4 is the radius of the radially innermost portion of the outer rim 38c. The radially innermost portion of the outer rim 38c is the portion of the outer rim which adjoins the axially extending wall 38e.

[0071] It is preferable that there is a reasonable amount of overlap between the outer rim 38c and back face 4c of the turbine wheel 4. In the embodiment shown in Figure 5 this is achieved due to the outer radius OR of the turbine wheel being 1 .026 times greater than the radius R4. The outer radius OR of the turbine wheel can be any appropriate number of times greater than the radius R4. As previously discussed it is preferable for the outer radius OR of the turbine wheel to be greater than radius R4. The outer radius OR of the turbine wheel may between about 1 .02 and 1 .6 times greater than the radius R4.

[0072] As previously discussed, use of a heat shield which has an axial extent in an uncompressed state which is greater than an axial spacing between a back face of the turbine wheel and the spigot feature ensures that the heat shield does not dismount the spigot feature during the assembly process for the turbine arrangement. Alternative ways of defining the related geometries of the turbine arrangement so as to achieve the effect of the present invention are also possible. Two such alternative ways of defining the relevant geometries are discussed below:

[0073] First, as can be seen best in Figure 4a, when the heat shield is in an uncompressed state and when the heat shield is in contact with a portion of the bearing housing other than the spigot feature (in this example, the raised feature of the bearing housing, but not necessarily so in other examples), a minimum axial separation AX1 between the heat shield 38 and the back face 4c of the turbine wheel 4 is less than an axial spacing AX2 between a portion of the heat shield which defines the aperture of the heat shield and a maximum height portion 32a of the spigot feature 32.

[0074] The axial separation AX1 between the back face 4c of the turbine wheel 4 and the 38 may be defined as the axial separation between the back face of the turbine wheel and the heat shield at any given radial position on the heat shield 38.

[0075] As shown in Figure 4a, the configuration in which the heat shield 38 contacts a portion of the bearing housing 3 other than the spigot feature 32 is when the bearing housing 3 is in the first orientation, previously described, in which the spigot feature 32 extends upwards.

[0076] In the present example the minimum axial spacing AX1 between the heat shield 38 and the back face 4c of the turbine wheel occurs at the radially outer rim portion 38c of the heat shield 38. However, in other embodiments, this may not be the case. For example, the minimum axial spacing may occur at axially extending wall portion or at base portion of the heat shield.

[0077] A second alternative way of defining the relevant geometries of the turbine arrangement which facilitate the present invention is discussed with reference to Figure 4b. This shows that with the heat shield in the uncompressed state (as shown in this figure as feature 38 in solid line), when the heat shield 38 contacts the back face 4c of the turbine wheel 4, the portion of the heat shield 38 which defines the central aperture 40 axially overlaps with the spigot feature 32. The portion of the heat shield 38 which defines the opening 40 may be the radially innermost portion of the heat shield 38.

[0078] Figure 6 shows a schematic view of a portion of an alternative embodiment of turbine arrangement in accordance with the present invention. In this embodiment the turbine is inlet is of a segmented dual entry type - however, this is not of any importance for the present invention - it may be applied to a turbocharger having any type of inlet - single entry, axially divided dual entry, segmented dual entry or otherwise.

[0079] As for the previously discussed embodiment, an annular heat shield 38’ is compressed between the bearing housing 3 and the nozzle ring 34, such that the heat shield 38’ exerts an axial force on the nozzle ring 34 to urge the nozzle ring into the correct engagement against the turbine housing 5.

[0080] In this embodiment the heat shield 38’ has a radial cross-section which has a shape which generally corresponds to that of a “7” rotated clockwise by 90 degrees so that it is resting on its side. In this way the heat shield 38’ includes a radially extending outer rim 38c’ which includes a radially outer portion 38a’ of the heat shield 38’. The heat shield 38’ also includes an axially extending inner rim 38f’. The inner rim 38f’ defines the opening 40’, which receives the spigot portion 32 of the bearing housing 3.

[0081] The inner rim 38f’ includes the radially inner portion 38b’ of the heat shield 38’. The outer rim 38c’ and inner rim 38f’ are linked by an axially extending wall 38e’. By axially extending, what is meant is that the wall extends in a direction that has an axial component. However, additionally the wall may extend in a direction which has a radial component.

[0082] The inner rim 38f’ is not compressed when the heat shield 38’ is compressed between the nozzle ring 34 and bearing housing 3. As such, an axial extent of the heat shield, and, in particular, the axial extent of the radially inner portion 38b’ of the heat shield is substantially the same when the heat shield is in either its compressed or uncompressed state. The axial extent E of the heat shield 38’ in its uncompressed state is greater than an axial spacing S between the back face 4c of the turbine wheel 4 and the spigot feature 32. Furthermore, when the heat shield 38’ is in an uncompressed state, when the heat shield 38’ contacts the back face 4c of the turbine wheel 4, a portion of the inner rim 38f’ axially overlaps with the spigot feature 32. The portion of the inner rim 38f’ which axially overlaps the spigot feature may be the radially innermost portion of the heat shield 38.

[0083] Referring to Figure 5, the bearing housing 3 includes a raised feature 44, radially outboard of the spigot feature 32. The raised feature 44 has a maximum axial height H2, at a maximum axial height portion 44a of the raised feature 44, which is less than a maximum axial height H1 of the spigot feature 32 at a maximum axial height portion 32a of the spigot feature 32. The maximum axial height H2 of the raised feature 44 is greater than a maximum axial height H3 of an outboard region 3a of the bearing housing at a maximum axial height portion 3b of the outboard region 3a. The outboard region 3a is located radially outboard of the raised feature 44. The outboard region 3a has a surface which faces the turbine wheel, and, in particular the back face of the turbine wheel.

[0084] The maximum axial height portion 3b of the outboard region 3a may be located at a radius which is less than an outer radius of the heat shield 38. The maximum axial height portion 3b of the outboard region 3a may be located at a radius which is less than a maximum radius of the base portion 38d of the heat shield 38.

[0085] In the present example the heights H1 , H2 and H3 have been measured parallel to the axis from an axial datum position / plane D along the axis. Any appropriate datum position / plane D along the axis may be utilised provided that all of the maximum height portions 32a, 44a and 3a are located in the same axial direction from the datum position and such that the axial height H1 of the maximum height portion 32a of the spigot 32 (measured relative to the datum position / plane) is greater than the other two heights H2 and H3 (measured relative to the datum position / plane).

[0086] The datum plane D is a plane that is perpendicular to the turbine axis 25.

[0087] An axial separation S1 between the maximum axial height portion 44a of the raised feature 44 and the maximum axial height portion 32a of the spigot feature is less than eight times an axial separation S2 between the maximum axial height portion 44a of the raised feature 44 and the maximum axial height portion 3b the outboard region 3a. In particular, in the present embodiment the axial separation S1 is approximately four times the axial separation S2. In other embodiments, any appropriate ratio between the axial separation S1 and axial separation S2 may be used.

[0088] Once the turbine arrangement has been assembled, the heat shield 38 may only contact the bearing housing at the raised feature or at the raised feature and the spigot portion.

[0089] A maximum radius R1 of the maximum radial height portion 44a of the raised feature 44 may be at least 1 .03 times greater than a maximum radius R2 of the spigot feature 32. In the present embodiment, the maximum radius R1 of the maximum axial height portion 44a of the raised feature 44 is 1.222 times greater than the maximum radius R2 of the spigot feature. Any appropriate ratio between the maximum radius of the maximum axial height portion of the raised feature and the maximum radius of the spigot feature is possible. For example, the maximum radial height portion of the raised feature may be between about 1 .03 and about 2.9 times greater than a maximum radius R2 of the spigot feature 32.

[0090] The radius R1 of the maximum axial height portion 44a of the raised feature 44 may be at least 1.03 times greater than a minimum radius R3 of the central aperture 40 of the heat shield 38. Any appropriate ratio between the maximum radius R1 of the maximum axial height portion 44a of the raised feature 44 and the minimum radius R3 of the central aperture 40 of the heat shield 38 is possible. For example, the maximum radial height portion of the raised feature may be between about 1.03 and about 2.9 times greater than the minimum radius R3 of the central aperture 40 of the heat shield 38.

[0091] It will be noted that the maximum radius R1 of the maximum radial height portion 44a of the raised feature 44 may be between about 1.03 and about 2.9 times greater than both i) the minimum radius R3 of the central aperture 40 of the heat shield 38 and ii) the maximum radius R2 of the spigot feature 32. The reason for this is that, generally the spacing between the minimum radius R3 of the central aperture 40 of the heat shield 38 and the maximum radius R2 of the spigot feature 32 is small. As such, the ratio between R1 and R3 is broadly equivalent to the ratio between R1 and R2. It follows that these ratios can be considered to be equivalent on a practical level. For example, in the present example, whilst R1 is 1 .222 times greater than R2, R1 is 1 .224 times greater than R3. In some embodiments, the maximum height portion 44a of the raised feature 44 will be located at a radius which is less than the maximum radius of the base portion 38d of the heat shield 38.

[0092] The raised feature 44 helps to control the axial load exerted on the nozzle ring 34 by the heat shield when the heat shield is compressed between the nozzle ring and the bearing housing 3. This may make it easier to arrive at a geometry of heat shield which not only remains mounted to the spigot feature during assembly, but also provides sufficient axial force on the nozzle ring (when compressed) so as to correctly secure the nozzle ring against the turbine housing.

[0093] In addition, the use of a raised feature 44 may desirably make the force applied by the heat shield to the nozzle ring relatively insensitive to the manufacturing tolerances in relation to the bearing housing and / or heat shield.

[0094] It is also possible to define the position of the radius R1 of the maximum axial height portion 44a of the raised feature 44 with reference to the outer radius OR of the turbine wheel. In the present example the outer radius OR of the turbine wheel is 2.1 times greater than the radius R1. The outer radius OR of the turbine wheel may be any appropriate multiple of the radius R1. It is preferable that the outer radius OR of the turbine is between about 2.9 and about 1 .2 times the radius R1 .

[0095] It will be appreciated that, with reference to figure 5 a raised feature of the bearing housing has been described which helps to control the axial load exerted on the nozzle ring 34 by the heat shield when the heat shield is compressed between the nozzle ring and the bearing housing 3. It is possible to achieve a similar effect with an equivalent lowered feature on the heat shield. A lowered feature on the heat shield can be used in combination with a raised feature on the bearing housing or as an alternative thereto. The lowered feature of the heat shield will protrude axially (i.e. have an axial component) from a portion of the heat shield, e.g. the base portion of the heat shield, toward the bearing housing. In this way, once the turbine arrangement has been assembled, the heat shield will contact the bearing housing at the lowered feature. The heat shield may only contact the bearing housing at the lowered feature. The lowered feature may be a generally annular feature which extends around the axis of the turbine arrangement or alternatively it may take the form of a plurality of discrete protruding features which are spaced angularly about the axis of the turbine arrangement.

[0096] It will be appreciated that, although the presently described embodiment of turbine arrangement includes a raised feature of the bearing housing, in other embodiments the raised feature of the bearing housing may be omitted.

[0097] Although the invention has been described in relation to a multiple-entry turbine, it will be appreciated that it could apply equally to a single-entry turbine.

[0098] Furthermore, whilst the invention has been described in relation to a turbine arrangement which forms part of a turbocharger, it may equally be applied to any turbine arrangement forming part of any suitable type of turbomachine, such as, for example, a power turbine.

[0099] Within the present document, a turbine arrangement (and associated assembly method) is discussed which includes a heat shield having certain characteristics which enable it to apply a force to the nozzle ring to urge it into position against the turbine housing, whilst, during the assembly process, preventing it from dismounting the spigot. It will be appreciated that the invention applies equally to a turbine arrangement (and associated assembly method) in which the heat shield is replaced by a spring retainer member (e.g. a disk spring) having the same functionality in terms of urging the nozzle ring into position and not dismounting the spigot during the assembly process, yet without having functionality as a heat shield - that is to say, it does not function to minimise the heat from the gas entering the turbine which is transferred to the bearing housing.

[0100] Within the embodiments described above the heat shield applies a force to a nozzle ring to urge it into position against the turbine housing. In the embodiments described above the nozzle ring has a single-piece construction. It will be appreciated that the invention applies equally to nozzle rings which are formed of more than one piece.

Claims

CLAIMS:1 . A turbine arrangement comprising: a turbine wheel (4) located within a turbine chamber (30) defined at least in part by a turbine housing (5), the turbine wheel being mounted to a shaft, the shaft and mounted turbine wheel being supported for rotation about a turbine axis by a bearing arrangement, wherein the bearing arrangement is located in a bearing housing (3), the bearing housing having an axially extending spigot feature (32), and the bearing housing being attached to the turbine housing; a nozzle ring (34), received by the turbine housing, the nozzle ring including one or more flow directing vanes (36) located in a flow path (F) between an inlet volute (9) and the turbine wheel, the inlet volute being defined by an inlet volute portion of the turbine housing; an annular spring retainer member (38) compressed between the nozzle ring and the bearing housing, the spring retainer member defining a central aperture (40) which receives the spigot feature, wherein an axial extent (E') of the spring retainer member in an uncompressed state, is greater than an axial spacing (S) between a back face of the turbine wheel and the spigot feature.

2. A turbine arrangement according to claim 1 , wherein the spring retainer member has a radially outer portion and a radially inner portion, wherein the radially outer portion contacts the nozzle ring and the radially inner portion receives the spigot feature, and wherein the axial extent is measured between the radially outer portion of the spring retainer member and the radially inner portion of the spring retainer member.

3. A turbine arrangement according to claim 2, wherein a minimum axial spacing between the back face of the turbine wheel and the spring retainer member is located between the back face of the turbine wheel and the radially outer portion of the spring retainer member.

4. A turbine arrangement according to claim 2 or claim 3, wherein the spring retainer member is generally dish-shaped and wherein a radially extending outer rim ofthe spring retainer member includes the radially outer portion of the spring retainer member and a radially extending base of the spring retainer member includes the radially inner portion of the spring retainer member, the outer rim and base being linked by an axially extending wall.

5. A turbine arrangement according to claim 4, wherein the axially extending wall subtends an acute angle with the axis of between 20 and 75 degrees.

6. A turbine arrangement according to claim 4 or claim 5, wherein a radial extent of the base is at least twice a radial extent of the outer rim.

7. A turbine arrangement according to any of claims 4 to 6, wherein an outside radius of the turbine wheel is greater than a radius of a radially innermost portion of the outer rim of the spring retainer member.

8. A turbine arrangement according to any of claims 4 to 7, wherein an outside radius of the turbine wheel is between about 1.02 and about 1.6 times greater than a radius of a radially innermost portion of the outer rim of the spring retainer member.

9. A turbine arrangement according to any preceding claim, wherein the bearing housing includes a raised feature, radially outboard of the spigot feature, wherein the raised feature has a maximum axial height, at a maximum axial height portion of the raised feature, which is less than a maximum axial height of the spigot feature, at a maximum axial height portion of the spigot feature, and greater than a maximum axial height of an outboard region of the bearing housing, at a maximum axial height portion of the outboard region, the outboard region being located radially outboard of the raised feature.

10. A turbine arrangement according to claim 9, wherein an axial separation between the maximum axial height portion of the raised feature and the maximum axial height portion of the spigot feature is less than eight times an axial separation between the maximum axial height portion of the raised feature and the maximum axial height portion of the outboard region.

11. A turbine arrangement according to claim 9 and claim 10, wherein a maximum radius of the maximum axial height portion of the raised feature is between about 1 .03 and about 2.9 times greater than a maximum radius of the spigot feature.

12. A turbine arrangement according to any of claims 9 to 11 , wherein a maximum radius of the maximum axial height portion of the raised feature is between about 1 .03 and about 2.9 times greater than a minimum radius of the central aperture.

13. A turbine arrangement according to any of claims 9 to 11 , wherein an outside radius of the turbine wheel is between about 2.9 and about 1 .2 times a radius of the maximum axial height portion of the raised feature.

14. A turbocharger including a turbine arrangement according to any preceding claim and a compressor comprising a compressor wheel mounted to said shaft.

15. A method of assembling a turbine arrangement, the turbine arrangement comprising: a turbine wheel having a back face, the turbine wheel being mounted to a shaft, a turbine housing comprising a volute housing portion defining an inlet volute, a bearing arrangement located in a bearing housing, the bearing housing having a spigot feature which extends along a turbine axis, a nozzle ring including one or more flow directing vanes, and an annular spring retainer member defining a central aperture; wherein the method comprises: with the bearing housing in a first orientation in which the spigot feature extends upwards, mounting the spring retainer member, in an uncompressed state, on the bearing housing such that the spigot feature is received by the central aperture, inserting the shaft through the central aperture and spigot feature such that the shaft is received by the bearing arrangement, the bearing arrangement supporting the shaft and mounted turbine wheel for rotation about the turbine axis, whereby an axial extent of the spring retainer member in the uncompressed state is greater than an axial spacing between the back face of the turbine wheel and the spigot feature,inverting the bearing housing into a second orientation in which the spring retainer member contacts the back face of the turbine wheel and the spigot feature remains received by the central aperture, locating the nozzle ring within the turbine housing, and with the bearing housing in its second orientation, the spring retainer member mounted on the bearing housing and the shaft received by the bearing arrangement, locating the bearing housing, spring retainer member and turbine wheel into the turbine housing such that: i) the turbine wheel is located within a turbine chamber defined at least in part by the turbine housing; ii) the one or more flow directing vanes is located in a flow path between the inlet volute and the turbine wheel; and ill) the spring retainer member is compressed between the nozzle ring and the bearing housing, the spring retainer member thereby urging the nozzle ring away from the bearing housing and pushing the nozzle ring against the turbine housing.

16. A method of assembling a turbocharger, the method including assembling a turbine arrangement in accordance with claim 15, mounting a compressor wheel to the shaft and mounting a compressor housing to the bearing housing so that the compressor housing receives the compressor wheel.

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