GB2498760A - Turbine shaft with worm gear - Google Patents

Abstract

A turbine assembly comprises a turbine wheel 52 mounted on a turbine shaft 50 and the turbine shaft 50 comprises a worm gear 36 for engagement with a worm wheel 38. This allows a large speed reduction between the turbine 52 and the driven device 42. The turbine assembly may form part of a turbocharger, and the worm may be formed between the turbine and compressor (figure 2).

Description

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TURBINE ASSEMBLY

The present invention relates to a turbine assembly. The turbine assembly may be used in isolation, or form part of a fixed or variable geometry turbocharger.

Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric (boost) pressure.

A conventional turbocharger typically 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.

In accordance with the principles described in the preceding paragraph, energy in the exhaust gas that might otherwise be wasted is utilised. In the example given in the preceding paragraph, the energy, or at least a portion thereof, is used in the delivery of compressed air to an intake of the engine.

However, the energy can also be used in additional or alternative ways. For instance, it is known to provide a turbocharger assembly with an arrangement that is configured to interact with the shaft, in some way, to convert rotation of the shaft into another form of energy (e.g., electrical or the like), and/or configured to drive movement of another element using rotation of the shaft.

One example of an arrangement may comprise a bevel gear attached to the shaft, which is arranged to cause rotation of another, engaged, bevel gear that is attached to a secondary shaft. Rotation of the secondary shaft could be used to drive a generator to generate electricity, for example for use in a vehicle comprising the engine. Alternatively or additionally, the secondary shaft may be linked in some way (e.g., mechanically, hydraulically or electrically) to a crank shaft of the engine to urge (and therefore assist) rotation thereof A bevel gear arrangement is one example of how rotation of the shaft may be used to generate another form of energy, or to drive movement of another element. Another arrangement may be or comprise, for example, a freewheel or an overriding clutch.

A problem associated with the use of a bevel gear arrangement, or an arrangement being or comprising a freewheel or overriding clutch, may lie in the complexity, reliability or performance of such an arrangement. In one example, a turbocharger shaft may rotate at a speed in excess of 100,000 rpm, whereas an element to be driven by the shaft (e.g., a generator or alternator or crank shaft or the like) may need to be driven at a far lower speed. In order to achieve this lower speed with a bevel gear arrangement, the rotation of the shaft will have to be severely geared down to the required rate. This may require a large number of bevel (or other) gear components which can lead to unreliability and maintenance issues. A freewheel or overriding clutch arrangement may be inherently more complex than a bevel gear arrangement, and might also require such aforementioned gearing. A freewheel or overriding clutch arrangement might also therefore suffer from potential unreliability and maintenance issues.

It is an object of the present invention to provide a turbine assembly (which may form a part of a turbocharger) which at least partially obviates or mitigates a disadvantage of the prior art, whether identified herein or elsewhere, or which provides an alternative to an existing or proposed turbine assembly. For example, it is an object to provide a simpler means of utilising energy provided by a rotating shaft of a turbine assembly.

According to a first aspect of the invention, there is provided a turbine assembly comprising: a turbine wheel mounted on a turbine shaft; wherein the turbine shaft comprises a worm suitable for engagement with a worm wheel.

The turbine assembly may further comprise a worm wheel for engagement The worm wheel may be moveable into and out of engagement with the The turbine assembly may further comprise an arrangement configured to: convert rotation of the worm wheel into another form of energy; and/or configured to drive movement of another element using rotation of the worm wheel, and wherein the worm wheel forms part of, or is in connection with, the aria n gement.

The arrangement may be one or more of: an alternator for generating electrical power; and/or a generator for generating electrical power; and/or a linkage (e.g. a mechanical1 electrical, or hydraulic linkage) for engagement with a further shaft, for urging rotation of that further shaft. The further shaft may be, for example, a crankshaft or a drive shaft. The further shaft may be part of a drive train of an engine, or may be a shaft attached to a compressor wheel of a compressor.

The worm may be formed in the shaft (as opposed to, for example, being attached to the shaft).

The worm may serve as an axial spacer or as an axial stop for one or more shaft bearings located (axially) on one or both sides of the worm.

The turbine wheel may be mounted within a housing assembly for rotation about a turbine axis, the housing assembly defining a gas flow inlet passage (e.g. a substantially radial -with respect to the turbine wheel -inlet passage) upstream of the turbine wheel.

The turbine wheel assembly may further comprise a displaceable member (e.g. an annular wall member that defines a wall of the inlet passage, or a sleeve moveable across the inlet that may be divided into multiple portions) that is displaceable to vary a geometry of the inlet passage, to control gas flow through that inlet passage. The displacement may be in a direction substantially parallel to the turbine axis -i.e. in an axial direction. The member may be one or more guides (e.g. vanes), and the displacement may involve a rotation of those guides, for example to change a swirl angle of gas passing through the inlet, and/or a throat area of the inlet.

In general, the turbine assembly might comprise, or be located within, a housing, in which one or more other elements of the assembly may be housed and/cr mounted.

According to a second aspect of the invention, there is provided a turbocharger assembly comprising the turbine assembly of the first aspect of the invention.

The turbine assembly of the first aspect of the invention may form part of a turbocharger of the turbocharger assembly.

The turbocharger may further comprise a compressor wheel mounted on an opposite end of the turbine shaft to the turbine wheel. The worm may be located mid-way between the compressor wheel and the turbine wheel.

The turbocharger assembly may comprise a turbocharger having a turbine, and the turbine assembly of the first aspect of the invention may be in addition to that turbine of that turbocharger. For example, the turbine assembly of the first aspect of the invention may be driven by exhaust gases leaving or bypassing the turbine of the turbocharger.

Other advantageous and preferred features of the invention will be apparent

from the following description.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying Figures, in which: Figure 1 schematically depicts an axial cross-section through a variable geometry turbocharger; Figure 2 schematically depicts a turbine shaft of a turbocharger, provided with a worm suitable for engagement with a worm wheel in accordance with an embodiment of the present invention; and Figure 3 schematically depicts a turbine assembly having turbine shaft provided with a worm, suitable for engagement with a worm wheel in accordance with another embodiment of the present invention.

Figure 1 illustrates a variable geometry turbocharger comprising a variable geometry turbine housing 1 and a compressor housing 2 interconnected by a central bearing housing 3. A turbocharger shaft 4 extends from the turbine housing 1 to the compressor housing 2 through the bearing housing 3. A turbine wheel 5 is mounted on one end of the shaft 4 for rotation within the turbine housing 1. and a compressor wheel 6 is mounted on the other end of the shaft 4 for rotation within the compressor housing 2. The shaft 4 rotates about turbocharger axis V-V on bearing assemblies located in the bearing housing 3.

The turbine housing 1 defines an inlet volute 7 to which gas from an internal combustion engine (not shown) is delivered, for example via one or more conduits (not shown). The exhaust gas flows from the inlet chamber 7 to an axial outlet passageway B via an annular inlet passageway 9 and turbine wheel 5. The inlet passageway 9 is defined on one side by the face 10 of a radial wall of a movable annular wall member 11, commonly referred to as a "nozzle ring", and on the opposite side by an annular shroud 12 which forms the wall of the inlet passageway 9 facing the nozzle ring 11. The shroud 12 covers the opening of an annular recess 13 in the turbine housing 1.

The nozzle ring 11 supports an array of circumferentially and equally spaced inlet vanes 14 each of which extends across the inlet passageway 9. The vanes 14 are orientated to deflect gas flowing through the inlet passageway 9 towards the direction of rotation of the turbine wheel 5. When the nozzle ring 11 is proximate to the annular shroud 12, the vanes 14 project through suitably configured slots in the shroud 12, into the recess 13. In another embodiment (not shown), the wall of the inlet passageway may be provided with the vanes, and the nozzle ring provided with the recess and shroud.

The position of the nozzle ring 11 is controlled by an actuator assembly, for example an actuator assembly of the type disclosed in US 5,868,552. An actuator (not shown) is operable to adjust the position of the nozzle ring 11 via an actuator output shaft (not shown), which is linked to a yoke 15. The yoke in turn engages axially extending moveable rods 16 that support the nozzle ring 11. Accordingly, by appropriate control of the actuator (which control may for instance be pneumatic, hydraulic, or electric), the axial position of the rods 16 and thus of the nozzle ring 11 can be controlled.

The nozzle ring 11 has axially extending radially inner and outer annular flanges 17 and 18 that extend into an annular cavity 19 provided in the turbine housing 1. Inner and outer sealing rings 20 and 21 are provided to seal the nozzle ring 11 with respect to inner and outer annular surfaces of the annular cavity 19 respectively, whilst allowing the nozzle ring 11 to slide within the annular cavity 19. The inner sealing ring 20 is supported within an annular groove formed in the radially inner annular surface of the cavity 19 and bears against the inner annular flange 17 of the nozzle ring 11. The outer sealing ring 20 is supported within an annular groove formed in the radially outer annular surface of the cavity 19 and bears against the outer annular flange 18 of the nozzle ring 11.

Gas flowing from the inlet chamber 7 to the outlet passageway 8 passes over the turbine wheel 5 and as a result torque is applied to the shaft 4 to drive the compressor wheel 6. Rotation of the compressor wheel 6 within the compressor housing 2 pressurises ambient air present in an air inlet 22 and delivers the pressurised air to an air outlet volute 23 from which it is fed to an internal combustion engine (not shown), for example via one or more conduits (not shown). The speed of the turbine wheel 5 is dependent upon the velocity of the gas passing through the annular inlet passageway 9. For a fixed rate of mass of gas flowing into the inlet passageway, the gas velocity is a function of the width of the inlet passageway 9, the width being adjustable by controlling the axial position of the nozzle ring 11. Figure 1 shows the annular inlet passageway 9 fully open. The inlet passageway 9 may be closed to a minimum by moving the face 10 of the nozzle ring 11 towards the shroud 12.

Figure 1 illustrates a variable geometry turbine in which a wall member (e.g. a nozzle ring) is moveable to define a width (i.e. control a geometry) of an inlet to the turbine wheel. In another embodiment (not shown), a variable geometry turbine may be provided with a substantially cylindrical sleeve that is moveable across the inlet to define a width of such an inlet. The inlet may be divided into axially offset inlet portions (e.g. by one or more baffles), and the sleeve moveable to selectively open or close -i.e. unblock or block -those inlet portions. In another embodiment, the geometry of the inlet may be changed by displacing one or more guides (e.g. vanes) located in the inlet, for example by rotating those guides to change a swirl angle of gas passing through the inlet, and/or a throat area of the inlet. In yet another embodiment (not shown), a turbine may have a fixed geometry.

The turbocharger of Figure 1 is1 in general, used to extract energy from exhaust gases that would otherwise be wasted. In Figure 1 this is generally

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achieved by using the energy in the exhaust gas to, in broad terms, deliver compressed air to the inlet of the engine that generated that exhaust gas.

Energy may be extracted or used in alternative or additional ways. For instance, an arrangement may be provided that is in connection with the shaft that links the compressor wheel and turbine wheel, rotation of that shaft being used to generate energy in another form (e.g., electrical or the like) or to drive motion of another element (for example, a crank shaft or the like). The arrangement in connection with shaft may comprise, for example, a bevel gear arrangement, or a freewheel or overriding clutch arrangement. However, such arrangements are not ideal for the reasons already described above. It is therefore desirable to seek an alternative to such arrangements, and preferably an alternative arrangement which obviates or mitigates problems associated with such arrangements. The present invention provides such an arrangement.

According to an embodiment of the present invention, there is provided a turbine assembly. The turbine assembly may form part of a turbocharger. In another embodiment the turbine assembly may not form part of a turbocharger, and might instead be used in isolation, or in connection with a turbocharger. The turbine assembly comprises a turbine wheel mounted on a turbine shaft. The turbine shaft comprises a worm suitable for engagement with a worm wheel. The use of a worm and a worm wheel is a far simpler way of providing the gearing down that might be required to make use of the rotation of the turbine shaft which, is often in excess of 100,000 rpm.

Furthermore, a worm and worm wheel is, in general, a far simpler arrangement than a multitude of bevel gears or the like, or a freewheel or overriding clutch arrangement. Thus, the use of a worm and worm wheel satisfies the requirements for extracting energy or some form of motion directly from the turbine shaft, yet in a simple and thus potentially more reliable manner.

Embodiments of the present invention will now be described, by way of example only, with reference to Figures 2 and 3. Like features appearing in both Figures have been given the same reference numerals for consistency and clarity. The Figures have not been drawn to any particular scale.

Figure 2 schematically depicts a shaft 30. The shaft 30 may for example be a shaft of the turbocharger shown in and described with reference to Figure 1.

The shaft 30 may thus be described as having an end 32 attached to and driven by a turbine wheel (not shown), and an opposite end 34 attached to a compressor wheel. The shaft 30 may be described as a turbine shaft, since in use it will be driven by rotation of the turbine wheel.

In contrast with known turbine assemblies, the shaft 30 comprises a worm 36 suitable for engagement with a worm wheel. Somewhat surprisingly, this simple arrangement has not been proposed previously, despite its simplicity and advantages. The worm 36 is formed in the shaft 30, as opposed to, for example, being attached to the shaft 30 in some way. This ensures that the structural integrity of the shaft 30 as a whole -and thus the connection between the compressor wheel and turbine wheel -is not comprised (or severely comprised) by the presence of the worm 36, The worm 36 may be formed in a casting process, or by appropriate machining of the shaft, or in any other appropriate manner.

The worm 36 is preferentially located midway between the compressor wheel and the turbine wheel, so as to not adversely affect balance of the compressor wheel-shaft-turbine wheel arrangement as a whole, which could otherwise lead to undesirable and potentially damaging vibrations or oscillations. The worm 36 might thus be located within a bearing housing of a turbocharger. Although not shown in the Figures, the worm may also serve as an axial spacer or as an axial stop for one or more shaft bearings located on one or both sides of the worm 36.

The shaft 30, together with the turbine wheel, and in this example the compressor wheel, form part of a turbocharger assembly. The assembly further comprises a worm wheel 38 for engagement with the worm 36 of the shaft 30. The worm wheel 38 is mounted within a housing of the turbine assembly. The worm wheel 38 may be movable into and out of engagement with the worm 36. This may be advantageous. For example, when there is no desire to rotate the worm wheel 38, the worm wheel 38 may be moved out of engagement with the worm 36, which may advantageously reduce a load on the worm 36, and/or shaft 30, and/or the turbine wheel attached thereto.

This may improve turbine/turbocharger efficiency. However, it may not be straightforward to move the worm wheel 38 into and out of engagement with the worm 36. It is thus likely that in most practical implementations of the invention the worm wheel 38 will always be engaged with the worm 36, to avoid any complications that might otherwise arise with engagement and disengagement of the worm wheel 38 with the worm 36.

The purpose of the worm 36 and worm wheel 38 is to directly derive energy from rotation of the shaft 30. In this regard, the assembly may further comprise an arrangement configured to convert rotation of the worm wheel 38 into another form of energy (e.g., electrical, potential or the like), andlor configured to drive movement of another element using rotation of that worm wheel 38. The worm wheel 38 may form part of, or be in connection with, the arrangement, for example, forming a rotor of a generator or the like, or being attached to such a rotor in some way. The arrangement may for instance be one or more of an alternator for generating electrical power, and/or a generator for generating electrical power, and/or a linkage (e.g., a mechanical, electrical or hydraulic linkage) for engagement with a further shaft, for urging rotation of that further shaft. For instance, the further shaft may be a crankshaft or the like, the worm 36 and worm gear 38 being used to urge rotation of that further shaft and improve engine efficiency. In another example, the arrangement might be a shaft forming part of a (further) :ii compressor or the like. It is most likely that in a practical implementation the arrangement will be an alternator or a generator, since these are best suited to the gearing-down provided by the worm and worm wheel arrangement.

In Figure 2, the arrangement that is configured to convert rotation of the worm wheel 35 into another form of energy, and/or configured to drive movement of another element using rotation of that worm wheel, is generically denoted by a square bracket 40. An element or component utilising the converted energy, or driven by the arrangement, is generically denoted by the box 42. The box 42 may denote, in practice, a crankshaft or driveshaft as described above, or may be one or more electrical components of: the turbocharger; an engine in which a turbocharger is used; or a vehicle or other apparatus in which the turbocharger is used.

Figure 2 shows the provision of a worm in a shaft of a turbocharger, the shaft connecting a turbine wheel to a compressor wheel. However, the invention is not limited solely to this application. For instance, the invention may be more generally described as the provision of a worm, suitable for engagement with a worm wheel, on a shaft that is connected to a turbine -i.e. a turbine shaft.

Figure 3 shows such an example, in which the worm 36 is provided (in this example) at the end of a turbine shaft 50, on which is mounted a turbine wheel 42. All other elements are as shown in and described with reference to Figure 2.

The turbine assembly of Figure 3 may be used in a turbocharger assembly.

In one instance, the turbine assembly may form part of a turbocharger of that assembly, for example as shown in and described with reference to Figure 2.

Alternatively and/or additionally, a turbine assembly as shown in Figure 3 may be used in addition to that turbocharger, for example wherein the turbine of the turbine assembly is driven by exhaust gases that pass through or bypass a turbine of an upstream turbocharger. However, and to reiterate, it will be appreciated that the turbine assembly of Figure 3 can be used in isolation and in applications completely separate from the field of turbochargers.

Modifications to the structure of the illustrated embodiments of the invention will or may be readily apparent to the appropriately skilled person after assessment of the provided description, claims and Figures, especially in the context of the field of the invention as a whole Thus, it should be understood that various modifications may be made to the embodiments of the invention described above, without departing from the present invention as defined by the claims that follow.