GB2548393A - Turbine - Google Patents

Abstract

A turbine comprising a wastegate valve, for selectively opening and closing a wastegate passage. The valve member 21 is mounted to an actuation member 22, which passes through a bush 31 received by an actuator conduit 32 of the turbine housing. A sealing arrangement comprising a sleeve 36 is arranged to substantially prevent gas leakage through the actuator conduit to atmosphere. A surface at a first end 361 of the sleeve is sealed against a surface of a flange 34 mounted to the actuation member. A surface at a second end 362 of the sleeve is sealed against a surface of the bush. One of the surface of the first end of the sleeve and the surface of the flange is curved, and one of the surface of the second end of the sleeve and the surface of the bush is curved. The curved surfaces allow sealing contact to be maintained during axial misalignment of the actuation member.

Description

Turbine

The present invention relates to a turbine and in particular to a turbine having a wastegate and sealing arrangement. The turbine may form part of a turbomachine such as a turbocharger or power turbine.

Turbomachines are machines that transfer energy between a rotor and a fluid. For example, a turbomachine may transfer energy from a fluid to a rotor or may transfer energy from a rotor to a fluid. Two examples of turbomachines are a power turbine, which uses the rotational energy of the rotor to do useful work, for example, generating electrical power; and a turbocharger, which uses the rotational energy of the rotor to compress a fluid.

Turbochargers are well known devices for supplying air to an inlet of an internal combustion engine at pressures above atmospheric pressure (boost pressures). A conventional turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing connected downstream of an engine outlet manifold (or engine exhaust manifold). 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 an engine inlet manifold. 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.

The turbine of a conventional turbocharger comprises: a turbine chamber within which the turbine wheel is mounted; an annular inlet defined between facing radial walls arranged around the turbine chamber; an inlet volute passageway arranged around the annular inlet; and an outlet passageway extending from the turbine chamber. The passageways and chamber communicate such that pressurised exhaust gas admitted to the inlet volute flows through the inlet to the outlet passageway via the turbine chamber and rotates the turbine wheel.

It is also known to improve turbine performance by providing vanes, referred to as nozzle vanes, in the inlet so as to deflect gas flowing through the inlet. That is, gas flowing through the annular inlet flows through inlet passages (defined between adjacent vanes) which induce swiri in the gas fiow, turning the fiow direction towards the direction of rotation of the turbine wheei.

Turbines may be of a fixed or variabie geometry type. Variabie geometry turbines differ from fixed geometry turbines in that characteristics of the iniet (such as the iniet’s size) can be varied to optimise gas fiow veiocities over a range of mass fiow rates so that the power output of the turbine can be varied to suit varying engine demands. For instance, when the volume of exhaust gas being deiivered to the turbine is reiativeiy iow, the velocity of the gas reaching the turbine wheel is maintained at a level which ensures efficient turbine operation by reducing the size of the inlet using a variable geometry mechanism. Turbochargers provided with a variable geometry turbine are referred to as variable geometry turbochargers.

Nozzle vane arrangements in variable geometry turbochargers can take different forms. Two known types of variable geometry turbine are swing vane turbochargers and sliding nozzle turbochargers.

Generally, in swing vane turbochargers the inlet size (or flow size) of a turbocharger turbine is controlled by an array of movable vanes in the turbine inlet. Each vane can pivot about an axis extending across the inlet parallel to the turbocharger shaft and aligned with a point approximately half way along the vane length. A vane actuating mechanism is provided which is linked to each of the vanes and is displaceable in a manner which causes each of the vanes to move in unison, such a movement enabling the cross sectional area available for the incoming gas and the angle of approach of the gas to the turbine wheel to be controlled.

Generally, in sliding nozzle turbochargers the vanes are fixed to an axially movable wall that slides across the inlet. The axially movable wall moves towards a facing shroud plate in order to close down the inlet and in so doing the vanes pass through apertures in the shroud plate. Alternatively, the nozzle ring is fixed to a wall of the turbine and a shroud plate is moved over the vanes to vary the size of the inlet.

The compressor of a conventional turbocharger comprises a compressor housing defining a compressor chamber within which the compressor wheel is mounted such that it may rotate about an axis. The compressor also has a substantially axial inlet passageway defined by the compressor housing and a substantially annular outlet passageway defined by the compressor housing between facing radially extending walls arranged around the compressor chamber. A volute is arranged around the outlet passageway and an outlet is in flow communication with the volute. The passageways and compressor chamber communicate such that gas (for example, air) at a relatively low pressure is admitted to the inlet and is pumped, via the compressor chamber, outlet passageway and volute, to the outlet by rotation of the compressor wheel. The gas at the outlet is generally at a greater pressure (also referred to as boost pressure) than the relatively low pressure of the gas which is admitted to the inlet. The gas at the outlet may then be pumped downstream of the compressor outlet by the action of the compressor wheel.

It is known to provide a turbocharger turbine with a valve controlled bypass port referred to as a wastegate, to enable control of the turbocharger boost pressure and/or shaft speed. A wastegate valve (typically, but not always, a poppet type valve) is controlled to open the wastegate port (bypass port) when the boost pressure of the fluid in the compressor outlet increases towards a pre-determined level, thus allowing at least some of the exhaust gas to bypass the turbine wheel. Typically the wastegate port opens into a wastegate passage which diverts the bypass gas flow to the turbine outlet or vents it to atmosphere.

The wastegate valve may be actuated by a variety of means, including electric actuators, but is more typically actuated by a pneumatic actuator operated by boost pressure delivered by the compressor wheel. The wastegate valve actuator is typically connected to the wastegate valve by a linkage, part of which passes through an actuator conduit in the turbine housing. Where the linkage passes through the actuator conduit it is possible that fluid from the wastegate passage or turbine outlet may leak into the actuator conduit and then leak to atmosphere. Leakage of fluid from the wastegate passage or turbine outlet to atmosphere may have an adverse effect on the performance of the turbine and/or turbocharger.

It is known to provide a sealing arrangement between the wastegate linkage and the actuator conduit of the turbine housing. In such an arrangement, leakage of fluid through the actuator conduit of the turbine housing may be prevented by the presence of a sealing ring. A rotatable actuator of the wastegate linkage, such as a rod, may pass through the actuator conduit and may be provided with a circumferentiai groove configured to iocate the seaiing ring. The seaiing ring may be radiaiiy urged against an inner face of the actuator conduit so as to substantiaiiy form a barrier between the actuator conduit and the rod and thus prevent ieakage through the actuator conduit. A disadvantage of such an arrangement is that the groove required by the seaiing ring creates iocaiised regions of high stress. As such, the diameter of the rod must be increased to counteract the effect of these stress concentrations.

During use the seaiing arrangement may be subject to vibration caused by the turbocharger or an internai combustion engine of which the turbocharger forms part. Depending on the ampiitude of the vibration, this may resuit in misaiignment of the actuator member within the actuator conduit, and may aiiow pressurised exhaust gas to ieak through the seaiing arrangement and actuator conduit to atmosphere.

It is an object of the present invention to provide a turbine which obviates or mitigates the above described disadvantage or other disadvantages present in the prior art. It is another object of the present invention to provide a turbine having an alternative wastegate actuator seaiing arrangement.

According to an aspect of the present invention, there is provided a turbine comprising: a turbine housing defining a turbine chamber within which a turbine wheel is mounted for rotation, a turbine iniet upstream of the turbine wheel, and a turbine outlet downstream of the turbine wheei; a wastegate passage connecting the turbine inlet and the turbine outiet; a wastegate vaive, for seiectiveiy opening and closing the wastegate passage, comprising a moveabie vaive member; wherein the valve member is mounted to an actuation member, the actuation member passing through a bush received by an actuator conduit of the turbine housing and being movabie so as to move the valve member; and a sealing arrangement comprising a sleeve arranged to substantially prevent gas leakage through the actuator conduit to atmosphere, wherein a first end of the sleeve is circumferentially received by a first feature mounted to the actuation member such that a surface of the first feature and a surface of the first end of the sleeve form a first seal therebetween, a second end of the sleeve is circumferentially received by the bush such that a surface of the bush and a surface of the second end of the sleeve form a second seal therebetween; and wherein one of the surface of the first end of the sleeve and the surface of the first feature is a first curved surface, and one of the surface of the second end of the sleeve and the surface of the bush is a second curved surface.

The first and second curved surfaces allow the sealing arrangement to accommodate axial and angular misalignment between the components of the sealing arrangement. For example, because the actuator rod is movable within the actuator conduit the actuator rod may move off-axis with respect to the longitudinal axis of the actuator conduit by a small amount. This may result in angular misalignment between the sleeve and the first or second curved surfaces. However, due to the curvature of the first and second curved surfaces, sealing contact between the components of the first seal and the components of the second seal is maintained. Furthermore, the first and second curved surfaces ensure that minimal contact is made between the valve member and the sleeve and between the sleeve and the bush respectively. As such, a sealing arrangement of the present invention ensures minimal friction and reduced wear between the valve member and the sleeve and between the sleeve and the bush, thus the sealing effectiveness of the sealing arrangement can be maintained over a long life span.

As previously discussed, the actuator member passes through a bush received by the actuator conduit. The actuator conduit is a conduit through which the actuation member can pass. The actuator conduit serves to permit the passage of the actuation member between the exterior of the turbine and the interior of the turbine. The actuator conduit opens at one end to a chamber within the turbine which includes the valve member. The actuator conduit opens at the other end to the exterior of the turbine. In some embodiments the bush may be omitted such that only the actuation member is received by the actuator conduit.

One of the purposes of the invention is to substantially prevent gas leakage from the interior of the turbine (and, in particular, from the chamber within the turbine which includes the valve member) through the actuator conduit to atmosphere. The way in which this is achieved is by sealing the valve member to the bush so that no gas can pass from the interior of the turbine into the bore in the bush through which the actuation member passes. If gas were to enter the bore in the bush it would subsequently be able to pass to atmosphere. Gas is substantially prevented from passing between the bush and the wall of the turbine housing defining the actuator conduit which receives the bush on account of the interference fit between the bush and the actuator conduit. It will be appreciated that the passage of gas through the bore in the bush (which is received by the actuator conduit) constitutes the passage of gas through the actuator conduit.

As previously discussed, the first end of the sleeve is circumferentially received by the first feature and the second end of the sleeve is circumferentially received by the bush. The term circumferentially received is intended to mean that the sleeve and the first feature or bush respectively axially overlap one another around a circumference. For example, if an end of a sleeve is circumferentially received by a flange of another article, the circumference of an internal or external surface of the sleeve may axially overlap the circumference of a corresponding external or internal surface of the flange respectively. In addition, when a first article is circumferentially received by a second article, the first article will surround a circumference of the second article or the second article will surround a circumference of the first article. As such, the situation where a first article is circumferentially received by a second article is quite different to the situation in which a first article is merely placed against a second article. For example, when a first article is placed against a second article, neither will the first article surround a circumference of the second article, nor will the second article surround a circumference of the first article.

The term circumferentially received is not intended to define whether a first article circumferentially received by a second article is in contact with the second article. For example, a first article circumferentially received by a second article may not be in direct contact with the second article. The space between the first article and the second article may be narrow. As such, any fluid flow between the first article and the second article in the region where the first article is said to be circumferentially received by the second article may be small or negligible. Alternatively, a first article which is circumferentially received by a second article may contact the second article such that the circumference of the first article is in contact with the circumference of the second article. Contact between a first article circumferentially received by a second article may be defined between either a part of the circumferences of the first and second articles or by the whole of the circumferences of the first and second articles. As such, any fluid flow between the first article and the second article in the region where the first article is said to be circumferentially received by the second article may be substantially prevented by contact between the first and second articles. In light of the above, it may be said that, because the first article is said to be circumferentially received by the second article, any leakage flow between the first article and the second article in the region where the first article is said to be circumferentially received by the second article is controlled or minimised.

The term received is not intended to define whether a first article circumferentially received by a second article is located inside the second article. A first article circumferentially received by a second article may be located inside the second article or outside the second article.

The surfaces which are curved are said to be curved because they have a profile, in a direction parallel to the axis about which the circumferential receipt of the first end of sleeve by the first feature occurs or the circumferential receipt of the second end of sleeve by the bush occurs, which is curved. The axis may be a longitudinal axis of the actuation member.

The first feature may be the valve member. Alternatively the first feature may be a ring secured to the actuation member. Alternatively the first feature may be integral with the actuation member - for example, the first feature may be a portion of the actuation member which has an enlarged diameter as compared to other portions of the actuation member.

The valve member may be moveable between an open state in which gas may pass between the turbine inlet and the turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage.

The first curved surface may be an outer surface arranged for receipt by a corresponding inner surface of one of the valve member or the first end of the sleeve to form the first seal, and the second curved surface may be an outer surface arranged for receipt by a corresponding inner surface of one of the bush or the second end of the sleeve to form the second seal. The benefit of such an arrangement is that the curved surface will always be convex, and as such the first and second seals can be maintained regardless of axial or angular misalignment.

The terms inner surface and outer surface are intended to denote radially inner and outer surfaces respectively. In some examples, a portion of an inner surface faces another portion of the inner surface, whereas a portion of an outer surface does not face any other portions of the outer surface. The radially inner and outer surface may be defined relative to an axis, for example, the longitudinal axis of the actuator rod. The inner surface generally faces the axis, whereas the outer surface generally faces away from the axis.

The inner surface of the first seal may be a cylindrical surface configured to receive the first curved surface, and the inner surface of the second seal may be a cylindrical surface configured to receive the second curved surface.

The surface of the valve member which forms the first seal may be the first curved surface, and the surface of the bush which forms the second seal may be the second curved surface.

The surface of the first end of the sleeve which forms the first seal may be the first curved surface, and the surface of the second end of the sleeve which forms the second seal may be the second curved surface.

The surface of the valve member which forms the first seal may be the first curved surface, and the surface of the second end of the sleeve which forms the second seal may be the second curved surface.

The surface of the first end of the sleeve which forms the first seal may be the first curved surface, and the surface of the bush which forms the second seal may be the second curved surface.

The first curved surface may define an outer radius and the second curved surface may define an outer radius such that the outer radius of the first curved surface may be substantially equal to the outer radius of the second curved surface.

The outer radius of an article is the radius of the outermost portion of that article. The radius may be measured relative to an axis, for example the longitudinal axis of the actuator rod or the longitudinal axis passing through the centre of the sleeve. As will be appreciated by those skilled in the art, in some situations, the outer radius of an article is equivalent to half the outer diameter of an article. The outer diameter may be the distance between diametrically opposed outermost portions of the article. The diameter may pass through an axis, for example the longitudinal axis of the actuator rod or the longitudinal axis passing through the centre of the sleeve.

The sleeve may be generally cylindrical or tubular. In other words the sleeve may be formed of a hollow cylinder. A cylinder differs from a ring in that it has length along the central axis of the cylinder.

The first curved surface may define an outer radius and the second curved surface may define an outer radius such that the outer radius of the first curved surface may be less than the outer radius of the second curved surface.

The first curved surface may define an outer radius and the second curved surface may define an outer radius such that the outer radius of the first curved surface may be greater than the outer radius of the second curved surface.

The first and second curved surfaces may each be a surface of a generally spherical segment. The benefit of a sealing arrangement in which the first and second curved surfaces are spherical is that the corresponding surface which forms the first seal and the corresponding surface which forms the second seal shall mate with the first and second curved surfaces respectively such that corresponding surface of the first seal and the corresponding surface of the second seal are always tangential to the first and second curved surfaces. That is to say, regardless of angular or axial misalignment between the components of the first or second seals, the physical form of each seal shall remain the same, i.e. each seal shall be formed around the circumference of a sphere.

The valve member may be pivotally movable between the open and closed states by rotation of the actuation member.

The valve member may be linearly movable between the open and closed states by linear movement of the actuation member.

The surface of the valve member and the surface of the first end of the sleeve which form the first seal may be movable relative to one another, and may substantially prevent gas from passing to atmosphere via the first seal during relative movement between the valve member and the sleeve.

The surface of the second end of the sleeve and the surface of the bush which form the second seal may be moveable relative to one another, and may substantially prevent gas from passing to atmosphere via the second seal during relative movement between the sleeve and the bush.

The sealing arrangement may be located within the interior of the turbine housing. In use, pressurised exhaust gas may be substantially prevented from passing from the interior of the turbine to the actuator conduit by the sealing arrangement.

The sealing arrangement may be located external to the turbine housing. In use, pressurised exhaust gas may be substantially prevented from passing from the actuator conduit to atmosphere by the sealing arrangement. The sealing arrangement may be located such that, in use, pressurised exhaust gas may enter the actuator conduit.

The turbine may form part of a turbomachine, such as, but not limited to a turbocharger or a power turbine. In other words, according to a further aspect of the invention, there is provided a turbomachine comprising a turbine according to the previously discussed aspect of the invention.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying Figures, of which:

Figure 1 shows a schematic cross-section through a known turbocharger;

Figure 2 shows a schematic perspective view of a portion of a known turbocharger;

Figure 3 shows a schematic end-on perspective view of a portion of the turbocharger shown in Figure 2;

Figure 4 shows a schematic cross-section view of a first embodiment of a wastegate sealing arrangement according to the present invention;

Figure 5 shows a schematic cross-section view of a wastegate sealing arrangement according to the first embodiment of the present invention, in which the components of the wastegate sealing arrangement are misaligned;

Figure 6 shows a schematic cross-section view of a second embodiment of a wastegate sealing arrangement according to the present invention;

Figure 7 shows a schematic cross-section view of a portion of a third embodiment of a wastegate sealing arrangement according to the present invention; and

Figure 8 shows a schematic cross-section view of a portion of a fourth embodiment of a wastegate sealing arrangement according to the present invention.

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 which can rotate within a compressor housing 7. The turbine wheel 4 and compressor wheel 6 are mounted at either ends of a shaft 8. 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.

The turbine housing 5 has an exhaust gas inlet volute 9 located annularly around the turbine wheel 4, and an axial exhaust gas outlet 10. The compressor housing 7 has an axial air intake passage 11 and a volute 12 arranged annularly around the compressor chamber. The volute 12 is in gas flow communication with a compressor outlet 18. The turbocharger shaft 8 rotates on journal bearings 13 and 14 housed towards the turbine end and compressor end respectively of the bearing housing 3. The compressor end bearing 14 further includes a thrust bearing 15 which interacts with an oil seal assembly including an oil slinger 16. Oil is supplied to the bearing housing from the oil system of the internal combustion engine via oil inlet 17. The oil fed to the bearing assemblies may be used to both lubricate the bearing assemblies and to remove heat from the bearing assemblies.

In use, the turbine wheel 4 is rotated 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 (not shown) to which the turbocharger is attached. 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 25.

The exhaust gas inlet 9 is defined by a portion of the turbine housing 5 which includes a turbocharger mounting flange 19 at the end of the exhaust gas inlet 9 remote from the turbine wheel 4.

In addition to the features of the turbine shown in Figure 1, an embodiment of a known turbine of a turbocharger is shown in Figures 2 and 3 that also includes a wastegate assembly. The wastegate assembly 20 is configured to selectively allow exhaust gas to bypass the turbine wheel 4 via a wastegate passage (not shown) which connects the turbine inlet 9 and the turbine outlet 10. The wastegate assembly 20 includes a valve member 21 having an open state in which gas may pass between the turbine inlet 9 and the turbine outlet 10 via the wastegate passage, and a closed state in which gas is substantially prevented from passing between the turbine inlet 9 and the turbine outlet 10 via the wastegate passage. The valve member 21 is mounted to an actuator rod 22 which passes through a conduit 32 of the turbine housing 5. The conduit 32 through the turbine housing 5 through which the actuator rod 22 passes, between a chamber in which the valve member 21 is located and the exterior of the turbine may be referred to as the actuator conduit. An end 220 of the actuator rod 22 protrudes from the turbine housing 5 and is attached to one end of a linkage member 23 such that pivotal movement of the linkage member 23 causes rotation of the actuator rod 22 within the actuator conduit 32 (and hence rotation of the attached valve member). A second end of the linkage member 23 is pivotally connected to a push rod 24 that is mounted to an actuator 25. During use, the actuator 25 linearly moves the push rod 24 to cause rotation of the linkage member 23 about an axis defined by the actuator conduit 32.

The actuator rod 22, fixedly attached to the linkage member 23, rotates within the actuator conduit 32 to move the valve member 21 between the open and closed states, and hence to permit or substantially prevent gas flow through the wastegate passage. The actuator rod 22 has a longitudinal axis 37 about which the rod 22 rotates to move the valve member 21 between the open and closed states.

In addition to the features shown in Figures 1-3, a schematic cross-section view of a first embodiment of a wastegate sealing arrangement according to the present invention is shown in Figure 4. A sealing arrangement 30 is configured to substantially prevent gas leakage from the turbine outlet 10 to the atmosphere. The sealing arrangement 30 comprises a bush 31 which passes through an actuator conduit 32 of the turbine housing 5 and is held in place within the actuator conduit 32 by mechanical interference. The actuator conduit 32 passes between a chamber within the turbine in which the valve member 21 is located and the exterior of the turbine. The mechanical interference between the bush 31 and the turbine housing 5 is sufficient to ensure that in use substantially no gas can pass between the bush 31 and the turbine housing 5. The bush 31 defines a bore 33 within which the actuator rod 22 is moveable. In order to allow rotation of the actuator rod 22 within the bore 33, the diameter of the rod 22 is less than the diameter of the bore 33. With no sealing arrangement according to the present invention in place, it is possible that pressurised exhaust gas will leak from the chamber in which the valve member 21 is located to atmosphere through the actuator conduit 32, and in particular through the gap between the wall of bore 33 and the rod 22.

The valve member 21 is mounted to the actuator rod 22 such that the actuator road is received by a socket 26 of the valve member 21. The valve member 21 comprises a circumferential flange 34, which extends in a direction along the rod 22, and which has a first substantially spherical surface 340. Likewise, the bush 31 comprises a circumferential flange 35 which extends along the rod 22 towards the flange 34 of the valve member 21 and has a second substantially spherical surface 350. In the current embodiment, the diameter of the first spherical surface 340 is substantially equal to the diameter of the second spherical surface 350. That is to say, the outer diameter (relative to axis 37) of the first spherical surface 340 is substantially equal to the outer diameter (relative to axis 37) of the second spherical surface 350. A hollow tubular sleeve 36 (which In this case Is generally cylindrical) Is arranged to circumferentially receive the flange 34 of the valve member 21 at a first end 361, and the flange 35 of the bush 31 at a second end 362. A first seal Is formed between the generally spherical surface 340 of the valve member 21 and an Inner face 360 of the sleeve 36 at the first end 361. In this case, the Inner face 360 of the sleeve 36 at the first end 361 is generally cylindrical. Likewise, a second seal is formed between the generally spherical surface 350 of the bush 31 and the inner face 360 of the sleeve 36 at the second end 362. In this case, the inner face 360 of the sleeve 36 at the second end 362 is generally cylindrical. In use, the first and second seals substantially prevent ingress of pressurised exhaust gas from the turbine outlet or the wastegate passage into the bore 33 and hence substantially prevent exhaust gas from passing from the chamber in which the wastegate valve is located to atmosphere via the actuator conduit 32.

The first and second generally spherical surfaces 340, 350 ensure a small area of contact between the sleeve 36 and the flanges 34, 35 during use. As such friction between the first spherical surface 340 and the sleeve 36, and friction between the second spherical surface 350 and the sleeve 36, is minimised. This enables the spherical surfaces 340, 350 to be produced such that their outer diameters are very close to the diameter of the inner face of the sleeve 360 which is contacted by the generally spherical surfaces. In addition, the manufacturing tolerances of the spherical surfaces and the sleeve required in order to produce an effective seal are much easier and cheaper to achieve as compared to the manufacturing tolerances of the bore 33 of the bush 31 and the rod 22 if attempting to achieve a similar seal between the bush 31 and the rod 22.

During use, the actuator rod 22 is pivotally moved about axis 37 within the actuator conduit 32 due to a force supplied by the actuator 25 and transmitted via the push rod 24 and the linkage member 23, in order to pivotally move the valve member 21 between the open and closed states. In operation, when the actuator rod 22 and the valve member 21 are rotated, the components of the sealing arrangement 30 which form the first seal, namely the spherical surface 340 of the valve member 21 and the inner cylindrical face 360 of the sleeve 36, may rotate relative to one another whilst maintaining a seal. Likewise, in use the components of the sealing arrangement 30 which form the second seal, namely the inner cylindrical face 360 of the sleeve 36 and the spherical face 350 of the bush 31, may rotate relative to one another whilst maintaining a seal. Relative rotation may occur either: solely between the components of the first seal, solely between the components of the second seal, or between the components of the first seal and the components of the second seal simultaneously. The exact nature of the relative rotation is dependent on the frictional force between the components of the first seal and the frictional force between the components of the second seal.

Figure 5 shows a schematic cross-section view of a wastegate sealing arrangement according to the first embodiment of the present invention, in which the components of the wastegate sealing arrangement are misaligned. As previously discussed, the actuator rod 22 is rotatable about a longitudinal axis 37 running through its centre. Likewise, the bush 31 defines a longitudinal axis 38 that under normal operating conditions is collinear with the axis 37.

Under some operating conditions a portion of the actuator rod 22 may be urged into contact with the bush 31 (for example, due to gravity acting on the actuator rod 22 and attached valve member, actuation forces transmitted by the actuator 25 acting on the actuator rod 22, or by external vibration transmitted to the actuator rod 22). In this situation the longitudinal axis 37 of the actuator rod 22 and the axis 38 of the bush 31 are misaligned. In the example shown in Figure 5 the longitudinal axis 37 of the actuator rod 22 and the axis 38 of the bush 31 are misaligned by a distance M. The axial misalignment M has caused the sleeve 36 to become inclined relative to the axis 38 of the bush 31 by an angle A. The spherical surfaces 340, 350 are able to accommodate angular misalignment of the sleeve 36 relative to the flange 34 of the valve member 22 and the flange 35 of the bush 31. This is because, despite the misalignment, the inner cylindrical face 360 of the sleeve 36 is substantially tangential to the point of contact of the respective spherical surface 340, 350 and, as such, the first and second seals will be maintained regardless of the axial misalignment M. It follows that another advantage of the sealing arrangement according to the present invention is that it can accommodate axial misalignment between the actuator rod 22 and the bush 31 and/or actuator conduit 32.

Figure 6 shows a schematic cross-section view of a second embodiment of a wastegate sealing arrangement according to the present invention. Equivalent features of the previous embodiment that appear in the embodiment shown in Figure 6 retain the same reference signs. The wastegate seaiing arrangement 40 is arranged to substantiaiiy prevent ieakage of pressurised exhaust gas through the actuator conduit 32 to atmosphere. The vaive member 21 comprises a generally annular flange 41 extending in a direction aiong the actuation rod towards a corresponding annular flange 42 of the bush 31 extending in a direction aiong the actuation rod towards flange 41. A sleeve 43 comprises a first end 44 having a first substantially spherical surface 440 and a second end 45 having a second substantially spherical surface 450. The first end 44 of the sleeve 43 is received by an inner cylindrical face 410 of the annular flange 41 to form a first seal therebetween. Likewise a second seal is formed between the second end 45 of the sleeve 43 and an inner cylindrical face 420 of the annular flange 42 received by the second end 45 of the sleeve 43. In use, the first and second seals substantially prevent ingress of pressurised exhaust gas from the turbine outlet or the wastegate passage into the bore 33 and hence substantially prevent exhaust gas from passing from the chamber in which the wastegate valve is located to atmosphere via the actuator conduit 32.

In the current embodiment, the outside diameter of the first spherical surface 440 is substantially equal to the outside diameter of the second spherical surface 450. Likewise, the inside diameter of the first cylindrical face 410 is substantially equal to the inside diameter of the second cylindrical face 420.

As discussed in relation to the first embodiment, the first and second spherical surfaces 440, 450 ensure a small area of contact between the sleeve 43 and the annular flanges 41, 42. As such, friction between the inner cylindrical face 410 of the valve member 21 and the first spherical surface 440, and friction between the inner cylindrical face 420 of the bush 31 and the second spherical face 450 is minimised. The benefits of a small area of contact between the sleeve 43 and the annular flanges 41, 42 have already been discussed above in relation to the first embodiment.

In a similar manner to that previously discussed above, the components of the sealing arrangement 40 which form the first seal, namely the inner cylindrical surface 410 of the valve member 21 and the spherical surface 440 of the first end of the sleeve 43, may rotate relative to one another whilst maintaining a seal. Likewise the components of the sealing arrangement 40 which form the second seal, namely the spherical face 450 of the second end of the sleeve 43 and the inner cylindrical face 420 of the bush 31, may rotate relative to one another whilst maintaining a seal.

As is the case with the previously discussed embodiment, due to the spherical surfaces 440, 450 of the sleeve 43, the sealing arrangement 40 shown in Figure 6 can accommodate axial misalignment between the actuator rod and the bush and/or actuator conduit.

Figure 7 shows a schematic cross-section view of a third embodiment of a wastegate sealing arrangement according to the present invention. Equivalent features of the previously discussed embodiments that appear in Figure 7 retain the same reference signs. The wastegate sealing arrangement 50 is arranged to substantially prevent leakage of pressurised exhaust gas through the actuator conduit 32 to atmosphere. The valve member 21 comprises a circumferential flange 51 which extends in a direction along the actuator rod 22 having a first substantially spherical surface 510. A sleeve 52 comprises a first end 53 arranged to circumferentially receive the first spherical surface 510 of the valve member 21 via an inner generally cylindrical face 530 to form a first seal. A second end 54 of the sleeve 53 comprises a second substantially spherical surface 540 having a substantially equal outer diameter to that of the first spherical surface 510. The bush 31 comprises an annular protrusion 55 which extends towards the valve member 21 and which is arranged to circumferentially receive the second spherical surface 540 of the sleeve 52 via an inner cylindrical face 550, to form a second seal. The internal diameter of the inner cylindrical face 550 of the bush 31 is substantially equal to outer diameter of the cylindrical face 530 of the sleeve 52. As is the case with the other embodiments of the invention discussed above, the first and second seals substantially prevent ingress of pressurised exhaust gas from the turbine outlet or the wastegate passage into the bore 33 and hence substantially prevent exhaust gas from passing from the chamber in which the wastegate valve is located to atmosphere via the actuator conduit 32.

As discussed in relation to the previous embodiments, the first and second spherical surfaces 510, 540 ensure a small area of contact between the sleeve 52 and the annular flanges 53, 55. As such, friction between the spherical surface 510 of the valve member 21 and the inner cylindrical surface 530 of the sleeve 52, and friction between the inner cylindrical face 550 of the bush 31 and the spherical face 540 of the sleeve 52 is minimised. The benefits of a smaii area of contact between the sieeve 52 and the fianges 51,55 have already been discussed above in relation to the first embodiment.

As discussed in relation to previous embodiments, the components of the sealing arrangement 50 which form the first seal, namely the inner cylindrical surface 530 of the sleeve 52 and the spherical surface 510 of the flange 51, may rotate relative to one another whilst maintaining a seal. Likewise the components of the sealing arrangement 50 which form the second seal, namely the spherical face 540 of the sleeve 52 and the inner cylindrical face 550 of the bush 31, may rotate relative to one another whilst maintaining a seal.

As is the case with the previously discussed embodiments, due to the spherical surfaces 510, 540 of the valve member 21 and sleeve 52, the sealing arrangement 50 shown in Figure 7 can accommodate axial misalignment between the actuator rod 22 and the bush 31 and/or actuator conduit 32.

Figure 8 shows a schematic cross-section view of a fourth embodiment of a wastegate sealing arrangement according to the present invention. Equivalent features of the previously discussed embodiments that appear in the embodiment shown in Figure 8 retain the same reference signs. The wastegate sealing arrangement 60 is arranged to substantially prevent leakage of pressurised exhaust gas through the actuator conduit 32 to atmosphere. A sleeve 63 comprises a first end 62 defining a first substantially spherical surface 620, and a second end 64 defining an inner substantially cylindrical face 640. The valve member 21 comprises an annular protrusion (or flange) 61 which extends in a direction along the actuator rod 22 and which has an inner cylindrical face 610 arranged to receive the first spherical surface 620 in order to form a first seal. The bush 31 comprises a circumferential flange 65 which extends in a direction along the actuator rod 22 towards the valve member 21 and which defines a second substantially spherical surface 650, which is received by the inner cylindrical surface 640 of the sleeve 63 in order to form a second seal. In use, the first and second seals substantially prevent ingress of pressurised exhaust gas from the turbine outlet or the wastegate passage into the actuator conduit bore 33 and hence substantially prevent exhaust gas from passing from the chamber in which the wastegate valve is located to atmosphere via the actuator conduit 32.

In the current embodiment, the outer diameter of the first spherical surface 620 is substantially equal to that of the second spherical surface 650. Likewise, the inner diameter of the inner cylindrical surface 610 of the valve member 21 is substantially equal to that of the inner cylindrical surface 640 of the second end of the sleeve 63.

Again, as discussed in relation to the previous embodiments, the first and second spherical surfaces 620, 650 ensure a small area of contact between the sleeve 63 and the annular flanges 61, 65. As such, friction between the spherical surface 620 of the sleeve 63 and the inner cylindrical surface 610 of the valve member 21, and friction between the spherical surface 650 of the bush 31 and the inner cylindrical surface 640 of the sleeve 63 is minimised. The benefits of a small area of contact between the sleeve 63 and the flanges 61,65 have already been discussed above in relation to the first embodiment.

Again, as discussed in relation to previous embodiments, the components of the sealing arrangement 60 which form the first seal, namely the inner cylindrical surface 610 of the flange 61 of the valve member 21 and the spherical surface 620 of the sleeve, may rotate relative to one another whilst maintaining a seal. Likewise the components of the sealing arrangement 60 which form the second seal, namely the spherical face 650 of the bush 31 and the inner cylindrical face 640 of the sleeve 63, may rotate relative to one another whilst maintaining a seal.

Again, as is the case with the previously discussed embodiments, due to the spherical surfaces 620, 650 of the sleeve 63 and bush 31, the sealing arrangement 60 shown in Figure 8 can accommodate axial misalignment between the actuator rod 22 and the bush 31 and/or actuator conduit 32.

For all embodiments of the present invention described herein, it will be appreciated that because friction between the components of each seal is minimised, wear between the components forming the first and second seals is also minimised. As such, a sealing arrangement according to the present invention provides a durable sealing arrangement resistant to degradation. It will further be appreciated that because the first and second seals are circumferentially arranged, the effectiveness of each seal is maintained regardless of rotational movement between the components which form the seal.

Although the description above focuses on the fact the co-operating substantially curved and substantially cylindrical surfaces permit the sealing arrangement to maintain a seal whilst there is relative rotation between the sleeve and the valve member and/or bush. It will also be appreciated that the nature of the surfaces also permits a degree of relative translational movement (i.e. along the axis 37 of the actuation rod) between the sleeve and the valve member and/or bush whilst maintaining a seal. This may be advantageous in arrangements in which there is some translational play - for example If the valve member can translate relative to the actuator rod, If the actuator rod can translate relative to the turbine housing through the actuator conduit, and/or If the bush can translate relative to the turbine housing.

Within the above described embodiments, each seal which forms part of the sealing arrangement can be said to Include a male portion and a female portion when a first article is circumferentially received by a second article, one of the first article and second article Is located Inside the other of the first article and second article. The article which Is located Inside the other article may be referred to as the male portion of the seal and the other article may be referred to as the female portion of the seal. The embodiments described above each have seals which are formed as the interface between a generally cylindrical surface and a generally spherical surface. The generally spherical surface may be either the male or the female portion of the seal, but it is preferably the male portion of the seal. In some embodiments both the first and second seals may be formed by a curved surface which is the male portion of the seal.

Numerous modifications may be made to the above described embodiments without departing from the scope of the invention as claimed.

In the above described embodiments, each seal is formed between a spherical surface and an inner cylindrical surface. However, it will be appreciated that alternative embodiments of the present invention may include a generally curved surface rather than a spherical surface. For example, the curved surface may take the form of the surface of a segment of an ellipsoid.

In the above described embodiments, the first spherical surface has an outer diameter which is substantially equal to that of the second spherical surface. However it will be appreciated that alternative embodiments of the present invention may include a first spherical surface having a larger or smaller outer diameter as compared to that of the second spherical surface. In such an embodiment, the corresponding inner cylindrical surface which forms the first seal will have, respectively, a corresponding larger or smaller inner diameter as compared to that of the inner cylindrical surface which forms the second seal.

In the above described embodiments, the actuator conduit 32 contains a bush 31 received by the turbine housing 5. However, it will be appreciated that alternative embodiments of the present invention may not include a bush. In such an embodiment, the features of the bush in the above described embodiments which form the second seal may form part of the turbine housing.

In the above described embodiments, the actuator rod 22 is rotationally moveable within the actuator conduit 32 so as to pivotally move the valve member 21 between the open and closed states. However, it will be appreciated that alternative embodiments of the present invention may include an actuator rod which is linearly movable within the actuator conduit 32 in order to linearly move the valve member 21 between the open and closed states.

In the above described embodiments, the sealing arrangement is positioned within the turbine housing such that, in use, pressurised exhaust gas located in the chamber of the turbine which contains the wastegate valve member 21 is substantially prevented from entering the actuator conduit 32. However, it will be appreciated that alternative embodiments of the present invention may include a sealing arrangement positioned externally to the turbine housing. In such embodiments the pressurised exhaust gas may be permitted to enter the actuator conduit but is substantially prevented from escaping to atmosphere by the sealing arrangement. In embodiments in which the sealing arrangement is positioned externally to the turbine housing, instead of sealing the valve member to the bush, the sleeve may seal the bush to another component external to the turbine, such as an enlarged portion of the actuator rod or to a ring feature fixed to the actuator rod.

In the above described embodiments the sealing arrangement substantially prevents gas from leaking through the actuator conduit to atmosphere by sealing the bush to the valve member so that gas is substantially prevented from passing into the bore of the bush. In other embodiments the first end of the sleeve may be circumferentially received by a feature other than the valve member. The feature may be any appropriate feature mounted to the actuation member. For example, the feature may be a ring mounted co-axially to the actuation member. The ring may be mounted to the actuation member in a manner such that substantially no gas can pass between the ring and the actuation member. Alternatively, the feature may be portion of the actuation member which has an enlarged diameter as compared other portions of the actuation member.

Although in embodiments described above the bush extends into the turbine such that the bush extends out of the actuator conduit and such that the second seal is located outside of the actuator conduit. In other embodiments the at least the portion of the bush which circumferentially receives the second end of the sleeve may be located inside actuator conduit such that the second seal is located inside the actuator conduit.

In the above described embodiments, the sealing arrangement is described for use within a turbine of a turbocharger. However, it will be appreciated that alternative embodiments of the present invention may be for use within a turbine which forms part of any appropriate turbomachine, for exampie a power turbine.

Claims (21)

CLAIMS:

1. A turbine comprising: a turbine housing defining a turbine chamber within which a turbine wheel is mounted for rotation, a turbine inlet upstream of the turbine wheel, and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; a wastegate valve, for selectively opening and closing the wastegate passage, comprising a moveable valve member; wherein the valve member is mounted to an actuation member, the actuation member passing through a bush received by an actuator conduit of the turbine housing and being movable so as to move the valve member; and a sealing arrangement comprising a sleeve arranged to substantially prevent gas leakage through the actuator conduit to atmosphere, wherein a first end of the sleeve is circumferentially received by a first feature mounted to the actuation member such that a surface of the first feature and a surface of the first end of the sleeve form a first seal therebetween, a second end of the sleeve is circumferentially received by the bush such that a surface of the bush and a surface of the second end of the sleeve form a second seal therebetween; and wherein one of the surface of the first end of the sleeve and the surface of the first feature is a first curved surface, and one of the surface of the second end of the sleeve and the surface of the bush is a second curved surface.

2. A turbine according to claim 1, wherein the first feature is the valve member.

3. A turbine according to claim 1 or claim 2 wherein the valve member is moveable between an open state in which gas may pass between the turbine inlet and the turbine outlet via the wastegate passage and a closed state in which the valve member substantially prevents gas from passing between the turbine inlet and the turbine outlet via the wastegate passage

4. A turbine according to any preceding claim, wherein the first curved surface is an outer surface arranged for receipt by a corresponding inner surface of one of the first feature or the first end of the sieeve to form the first seai, and wherein the second curved surface is an outer surface arranged for receipt by a corresponding inner surface of one of the bush or the second end of the sieeve to form the second seai.

5. A turbine according to ciaim 4, wherein the corresponding inner surface of the first seai is a cyiindricai surface configured to receive the first curved surface, and wherein the corresponding inner surface of the second seai is a cyiindricai surface configured to receive the second curved surface.

6. A turbine according to any preceding ciaim, wherein the surface of the first feature which forms the first seai is the first curved surface, and wherein the surface of the bush which forms the second seai is the second curved surface.

7. A turbine according to any of ciaims 1 to 5, wherein the surface of the first end of the sieeve which forms the first seai is the first curved surface, and wherein the surface of the second end of the sieeve which forms the second seai is the second curved surface.

8. A turbine according to any of ciaims 1 to 5, wherein the surface of the first feature which forms the first seal is the first curved surface, and wherein the surface of the second end of the sleeve which forms the second seal is the second curved surface.

9. A turbine according to any of claims 1 to 5, wherein the surface of the first end of the sleeve which forms the first seal is the first curved surface, and wherein the surface of the bush which forms the second seal is the second curved surface.

10. A turbine according to any of claims 4 to 9, wherein the first curved surface defines an outer radius and the second curved surface defines an outer radius such that the outer radius of the first curved surface is substantially equal to the outer radius of the second curved surface.

11. A turbine according to claim 10, wherein the sleeve is generally cylindrical.

12. A turbine according to any of claims 4 to 9, wherein the first curved surface defines an outer radius and the second curved surface defines an outer radius such that the outer radius of the first curved surface is less than the outer radius of the second curved surface.

13. A turbine according to any of claims 4 to 9, wherein the first curved surface defines an outer radius and the second curved surface defines an outer radius such that the outer radius of the first curved surface is greater than the outer radius of the second curved surface.

14. A turbine according to any preceding claim, wherein the first and second curved surfaces are each a surface of a generally spherical segment.

15. A turbine according to any of claims 3 to 14, wherein the valve member is pivotally movable between the open and closed states by rotation of the actuation member.

16. A turbine according to any of claims 3 to 14, wherein the valve member is linearly movable between the open and closed states by linear movement of the actuation member.

17. A turbine according to any preceding claim, wherein the surface of the first feature and the surface of the first end of the sleeve which form the first seal are movable relative to one another, and wherein gas is substantially prevented from passing to atmosphere via the first seal during relative movement between the first feature and the sleeve.

18. A turbine according to any preceding claim, wherein the surface of the second end of the sleeve and the surface of the bush which form the second seal are moveable relative to one another, and wherein gas is substantially prevented from passing to atmosphere via the second seal during relative movement between the sleeve and the bush.

19. A turbine according to any preceding claim, wherein the sealing arrangement is iocated within the interior of the turbine housing such that, in use, pressurised exhaust gas is substantially prevented from passing from the interior of the turbine to the actuator conduit.

20. A turbine according to any preceding claim, wherein the sealing arrangement is located external to the turbine housing such that, in use, pressurised exhaust gas is substantially prevented from passing from the actuator conduit to atmosphere.

21. A turbine according to any preceding claim, wherein the turbine forms part of a turbocharger or a power turbine.