The present invention relates to a two-part valve member assembly and an associated method of manufacturing the two-part valve assembly. In particular, the two-part valve member assembly may form part of a wastegate provided on a turbine. The turbine may form part of 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 comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing connected downstream of an engine outlet 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 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 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 swirl in the gas flow, turning the flow direction towards the direction of rotation of the turbine wheel. Turbines may be of a fixed or variable geometry type. Variable geometry turbines differ from fixed geometry turbines in that characteristics of the inlet (such as a size of the inlet) can be varied to optimise gas flow velocities over a range of mass flow rates so that the power output of the turbine can be varied to suit varying engine demands.

It Is known to provide a turbocharger turbine with a valve controlled bypass port, commonly referred to as a wastegate. The wastegate enables control of the turbocharger boost pressure and/or shaft speed. The wastegate includes a wastegate passage which extends between an inlet and an outlet of the turbine, bypassing the turbine wheel. The wastegate arrangement also includes a wastegate valve comprising a movable valve assembly and a valve seat. The wastegate 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 assembly typically comprises a valve member attached to support member, which may be of the form of a lever. The valve member can be moved between a closed position (wherein it cooperates with the valve seat to seal the wastegate passage) and an open position (wherein it is separated from the valve seat) by rotation of the lever. Typically, the valve member is not rigidly attached to the lever. Rather the valve member is typically connected to the lever such that it is free to rotate relative to the lever. The valve member and the lever may be considered to be a two-part wastegate valve member assembly.

It is an object of the present invention to provide two-part valve assembly which at least partially addresses one or more problems present In the prior art, whether identifed herein or otherwise.

According to a first aspect of the present invention there is provided a method for forming a two-part wastegate valve member assembly, the method comprising: casting a single manufacturing intermediate; processing the manufacturing intermediate so as to form a two-part assembly, the two-part assembly comprising a support member and a valve member, wherein the support member defines an aperture and wherein the valve member comprises a central portion extending through the aperture and two opposed end portions disposed on opposite sides of the aperture each of the two end

portions having dimensions such that the valve member is held captive by the support member.

The method according to the first aspect of the invention is advantageous over prior art arrangements, as now discussed.

The support member provides a connection between an actuation mechanism (optionally via a mechanical linkage) and the valve member. In particular, the support member can be used to transmit a force to the valve member such that the valve member contacts a valve seat. Since the valve member assembly is of two-part form, the valve member is free to move relative to the support member. In particular, the valve member can rotate about an axis that is generally aligned with the central portion of the valve member. This is beneficial since it allows each part of the valve member that, in use, contacts the valve seat to contact the valve seat in a range of different positions. This allows the valve member to wear more evenly during use, which can extend the time period over which the wastegate can form a good seal.

Although formed as a two part assembly (with the valve member held captive by the support member), each of the two parts of the two-part valve member assembly is formed from a single integral piece. In particular, the valve member is formed as a single piece with the central portion and two opposed end portions of the valve member being integrally formed. This is in contrast to prior art arrangements wherein, typically, the valve member would be formed from a plurality of assembled parts. For example, prior art valve members (which have an analogous role to the valve member of the first aspect of the invention) are typically formed from the following separate components: a part that contacts a valve seat (which is equivalent to a first end portion of the valve member); a valve pin (that extends through the aperture and is equivalent to the central portion of the valve member); one or more spacers; and a washer (which is equivalent to a second end portion of the valve member). Assembly of these parts is required followed by a joining process which may involve, for example, riveting or welding to form the valve member.

In contrast to such prior art arrangements, the valve member as formed by the method according to the first aspect of the invention is formed from a single unitary piece that is integrally formed. Advantageously, this removes the need for an assembly step. In addition, the process of casting the single manufacturing intermediate (which may, for example, use investment casting) can be more accurate than the assembly of

component parts such that the valve member can better meet desired tolerances. Furthermore, the single unitary valve member is more durable and less prone to mechanical failure in addition, the unitary valve member can be shaped such that mechanical stresses in the valve member can be decreased. Better durability is especially beneficial in light of the harsh conditions that the valve member assembly will typically experience during use (extreme operating temperatures and pressures that can vary extensively under a range of working and non-working conditions), when the two-part valve assembly forms part of a turbocharger.

The casting of the single manufacturing intermediate may be achieved using investment casting.

The casting the single manufacturing intermediate may involve: forming first and second temporary patterns, each of the first and second temporary patterns corresponding to a different portion of the manufacturing intermediate, wherein the first temporary pattern comprises a portion that corresponds to a portion of the manufacturing intermediate from which part of the valve member will be formed and the second temporary pattern comprises a portion that corresponds to a portion of the manufacturing intermediate from which a second part of the valve member will be formed; joining the temporary patterns together to form an assembled pattern cluster; applying investment materials to the assembled pattern cluster to form an investment mould; and casting the single manufacturing intermediate in the investment mould.

Processing the manufacturing intermediate so as to form a two-part assembly may comprise using a cutting mechanism for removing material from the manufacturing intermediate while moving the manufacturing intermediate relative to the cutting mechanism. The cutting mechanism may be referred to as a cutter.

It will be appreciated that the cutting mechanism can use any suitable form of subtractive manufacturing process. The cutting mechanism may cut generally linearly into the manufacturing intermediate. For example, the cutting mechanism may comprise a cutting tool that can be moved in a cutting direction into the manufacturing intermediate or, alternatively, the cutting mechanism may comprise a laser beam or water jet. Alternatively, the cutting mechanism may comprise a rotary cutter comprising, for example, a rotary cutting tool.

It will be appreciated that moving the manufacturing intermediate relative to the cutting mechanism may be achieved by either: moving the manufacturing intermediate while

the cutting mechanism is stationary; moving the cutting mechanism while the manufacturing intermediate is stationary; or moving both the manufacturing intermediate and the cutting mechanism.

Using a cutting mechanism for removing material from the manufacturing intermediate while moving the manufacturing intermediate relative to the cutting mechanism may comprise rotating the single manufacturing intermediate about an axis while the cutting mechanism cuts generally linearly into the manufacturing intermediate.

The cutter may cut into the manufacturing intermediate in a direction that is generally perpendicular to the axis. Alternatively, the cutter may cut into the manufacturing intermediate in a direction that is inclined at an oblique angle relative to the axis.

After the manufacturing intermediate has been processed to form the two-part wastegate valve member assembly, the valve member may be deformed so as to reduce the extent of the movement of the valve member that is possible relative to the support member.

The deformation may be achieved, for example, using a hydraulic press.

During the casting and/or processing of the single manufacturing intermediate, the valve member may be provided with one or more features to aid the deformation of the valve member. Such features may include one or more features provided on a surface of the valve member, for example a depression, to aid the deformation of the valve member. Additionally or alternatively, such features may include one or more voids or absences of the material from which the valve member is formed.

The method may further comprise vibration of the two-part valve assembly to deburr the two-part wastegate valve member assembly.

Such vibration may be used to improve the surface finish of an interface between a first end portion of the valve member and the support member.

Complementary curved surfaces may be formed: on a first end portion of the valve member; and a portion of the support member surrounding the aperture which is arranged to contact the first end portion.

For example, the first end portion of the valve member may be provided with a generally convex surface (which may, for example, be generally spherical) in addition, a portion of the support member surrounding the aperture which is arranged to contact the first end portion may be provided with a generally concave surface (which may, for example, be generally spherical). These two complementary surfaces provide a centring effect for the valve member. Advantageously, this can increase the sealing ability of the wastegafe valve.

In addition, as a result of this centring effect, a radial clearance between the central portion of the valve member and the aperture in the support member can be increased relative to prior art arrangements. Advantageously, this provides a larger radial gap in which investment materials can be received. In addition, this increased radial clearance provides an increased volume for a cutting tool to break through into. For these reasons the combination of the provision of the pair of generally complementary curved surfaces (on the first end portion and a portion of the support member which is arranged to contact the first end portion) may be considered to have a synergistic effect in combination with the method according to the first aspect of the invention.

According to a second aspect of the present invention there is provided a two-part wastegate valve member assembly comprising: a support member which defines an aperture; and a valve member, wherein the valve member comprises a central portion extending through the aperture and two opposed end portions disposed on opposite sides of the aperture each of the two end portions having dimensions such that the valve member is held captive by the support member; wherein the central portion and two opposed end portions of the valve member are integrally formed.

It will be appreciated that integrally formed is intended to mean formed from a single piece. For example a piece that was formed from a single casting process (whether or not subsequently machined). Equivalently, that an object is integrally formed is intended to mean that the object is not formed from component parts that are first formed and then subsequently assembled.

The two-part wastegate valve member assembly according to the second aspect of the invention may, for example, be formed using the method according to the first aspect of the invention. Where appropriate, the two-part wastegate valve member assembly according to the second aspect of the invention may comprise features which correspond to any of the features of the method according to the first aspect of the invention.

The two-part wastegate valve member assembly is beneficial, as discussed above, since it allows the valve member to rotate relative to the support member, allowing the valve member to wear more evenly during use. However, although formed as a two part assembly (with the valve member held captive by the support member), each of the two parts of the two-part valve member assembly is formed from a single integral piece. In particular, the valve member is formed as a single piece with the central portion and two opposed end portions of the valve member being integrally formed.

This is in contrast to prior art arrangements wherein, typically, the valve member is formed from a plurality of assembled parts. For example, prior art valve members (which have an analogous role to valve member) are typically formed from the following separate components: a part that contacts a valve seat (which is equivalent to a first end portion of the valve member); a valve pin (that extends through aperture and is equivalent to the central portion of the valve member); one or more spacers; and a washer (which is equivalent to a second end portion of the valve member). Assembly of these parts is required followed by a joining process which may involve, for example, riveting or welding to form the valve member.

In contrast to such prior art arrangements, the valve member is formed from a single unitary piece that is integrally formed. Advantageously, this removes the need for an assembly step. In addition, the investment casting process can be more accurate than the assembly of component parts such that the valve member can better meet desired tolerances. Furthermore, the single unitary valve member is more durable and less prone to mechanical failure. In addition, the unitary valve member can be shaped such that mechanical stresses in the valve member can be decreased. Better durability is especially beneficial in light of the harsh conditions that the valve member assembly will typically experience during use (extreme operating temperatures and pressures that can vary extensively under a range of working and non-working conditions), when the two-part valve assembly forms part of a turbocharger.

A first end portion of the valve member and a portion of the support member surrounding the aperture which is arranged to contact the first end portion may be provided with complementary curved surfaces.

For example, the first end portion of the valve member may be provided with a generally convex surface (which may, for example, be generally spherical). In addition, a portion of the support member surrounding the aperture which is arranged to contact the first end portion may be provided with a generally concave surface (which may, for example, be generally spherical). These two complementary surfaces provide a centring effect for the valve member. Advantageously, this can increase the sealing ability of the wastegafe valve.

A second end portion of the valve member may be provided with one or more voids or absences of the material from which the valve member is formed. For example, the second end portion of the valve member may be generally of the form of a disc and the one or more voids or absences of the material from which the valve member is formed may be generally of the form of recesses that extend from a perimeter of the disc towards a centre of the disc. The recesses that extend from the perimeter of the disc towards the centre of the disc may be generally triangular recesses.

According to a third aspect of the invention there is provided a turbine comprising: a turbine housing defining a turbine inlet upstream of a turbine wheel and a turbine outlet downstream of the turbine wheel; a wastegate passage connecting the turbine inlet and the turbine outlet; and a wastegate valve comprising the two-part wastegate valve member assembly according to the second aspect of the invention, the wastegate valve having an open state in which gas may pass between the turbine inlet and 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.

According to a fourth aspect of the present invention there is provided a turbocharger or powerturbine including a turbine according to the third aspect of the present invention.

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic cross-section through a portion of a first turbocharger that may incorporate a two-part valve member assembly according to an embodiment of the invention;

Figure 2 shows a schematic perspective view of a second turbocharger that incorporates a two-part valve member assembly according to an embodiment of the invention;

Figure 3 shows a schematic end-on perspective view of a portion of the turbocharger shown in Figure 1 ;

Figure 4 shows a schematic cross-section through a portion of the turbocharger shown in Figures 1 and 2; and

Figure 5A shows a schematic exploded perspective view of a valve member assembly and an actuation assembly which form part of the turbocharger shown in Figures 2 to 4;

Figure 5B shows a lever arm and a stub, which together form part of the actuation assembly shown in Figure 5A;

Figure 6A shows a schematic cross sectional view of a two-part wastegate valve member assembly according to an embodiment of the invention disposed in a closed state;

Figure 6B shows a schematic cross sectional view of the two-part wastegate valve member assembly shown in Figure 6A disposed in an open state;

Figure 7 is a schematic representation of the steps involved in an investment casting process according to an embodiment of the present invention for a manufacturing intermediate from which the two-part wastegate valve member assembly shown in Figures 6A and 6B is formed;

Figure 8A is a cross sectional view of a first temporary pattern formed as an intermediate in the manufacture of the two-part wastegate valve member assembly as shown in Figures 8A and 6B;

Figure 8B is a cross sectional view of a second temporary pattern formed as an intermediate in the manufacture of the two-part wastegate valve member assembly as shown in Figures 6A and 6B;

Figure 8C shows a cross section of an assembled pattern duster that is formed from the two temporary patterns shown in Figures 8A and 8B;

Figure 9A shows a one-piece manufacturing intermediate and a cutting tool before the cutting tool has contacted the one-piece manufacturing intermediate;

Figure 9B shows the one-piece manufacturing intermediate and cutting tool shown in Figure 9A, with the cutting tool having contacted and partially cut into, the one-piece manufacturing intermediate;

Figure 9C shows a two-part valve member assembly formed from the one-piece manufacturing intermediate and cutting tool shown in Figures 9A and 9B;

Figure 10 shows a schematic cross sectional view of a first variant of the two-part wastegate valve member assembly shown in Figures 6A and 6B;

Figure 11 shows a schematic cross sectional view of a second variant of the two-part wastegate valve member assembly shown in Figures 6A and 6B;

Figure 12A shows a schematic cross sectional view of a third variant of the two-part wastegate valve member assembly shown in Figures 6A and 6B in a first configuration;

Figure 12B shows a valve member that forms part of the two-part wastegate valve member assembly shown in Figure 12A;

Figure 12C shows a schematic cross sectional view of the two-part wastegate valve member assembly as shown in Figure 12A disposed in a second configuration, the valve member having been deformed so as to reduce a clearance between the valve member and the support member; and

Figure 12D is a perspective view of the third variant of the two-part wastegate valve member assembly as shown in Figures 12A-12C disposed in the second configuration.

Figure 1 shows a schematic cross-section of a 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 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 arranged 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 around the compressor chamber. The volute 12 is in gas flow communication with a compressor outlet 25. 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 infernal combustion engine via oil inlet 17 and is fed to the bearing assemblies by oil passageways 18. 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 27 at the end of the exhaust gas inlet 9 remote from the turbine wheel 4.

Figures 2 to 4 show various schematic views of portions of a turbocharger 30 which includes a two-part wastegate valve member assembly 37 in accordance with an embodiment of the present invention. The turbocharger 30 includes all of the features of the turbocharger described above in relation to Figure 1. The same numbering is used within Figures 2 to 5B for features of the turbocharger 30 shown in Figures 2 to 5B which are equivalent to features shown in the turbocharger of Figure 1.

CLAIMS:

1. A method for forming a two-part wastegate valve member assembly, the method comprising:

casting a single manufacturing intermediate;

processing the manufacturing intermediate so as to form a two-part assembly, the two-part assembly comprising a support member and a valve member, wherein the support member defines an aperture and wherein the valve member comprises a central portion extending through the aperture and two opposed end portions disposed on opposite sides of the aperture each of the two end portions having dimensions such that the valve member is held captive by the support member.

2. The method of claim 1 wherein the casting of the single manufacturing intermediate is achieved using investment casting.

3. The method of claim 1 or claim 2 wherein casting the single manufacturing intermediate involves:

forming first and second temporary patterns, each of the first and second temporary patterns corresponding to a different portion of the manufacturing intermediate, wherein the first temporary pattern comprises a portion that corresponds to a portion of the manufacturing intermediate from which part of the valve member will be formed and the second temporary pattern comprises a portion that corresponds to a portion of the manufacturing intermediate from which a second part of the valve member will be formed;

joining the temporary patterns together to form an assembled pattern cluster;

applying investment materials to the assembled pattern cluster to form an investment mould; and

casting the single manufacturing intermediate in the investment mould.

4. The method of any preceding claim wherein processing the manufacturing intermediate so as to form a two-part assembly comprises:

using a cutting mechanism for removing material from the manufacturing intermediate while moving the manufacturing intermediate relative to the cutting mechanism.

5. The method of claim 4 wherein using a cutting mechanism for removing material from the manufacturing intermediate while moving the manufacturing intermediate relative to the cutting mechanism comprises rotating the single manufacturing intermediate about an axis while the cutting mechanism cuts generally linearly into the manufacturing intermediate.

6. The method of any preceeding claim wherein after the manufacturing intermediate has been processed to form the two-part wastegate valve member assembly, the valve member is deformed so as to reduce the extent of the movement of the valve member that is possible relative to the support member.

7. The method of claim 6 wherein during the casting and/or processing of the single manufacturing intermediate, the valve member is provided with one or more features to aid the deformation of the valve member.

8. The method of any preceeding claim further comprising vibration of the two-part valve assembly to deburr the two-part wastegate valve member assembly.

9. The method of any preceeding claim wherein complementary curved surfaces are formed on: a first end portion of the valve member; and a portion of the support member surrounding the aperture which is arranged to contact the first end portion.

10. A two-part wastegate valve member assembly comprising:

a support member which defines an aperture; and

a valve member, wherein the valve member comprises a central portion extending through the aperture and two opposed end portions disposed on opposite sides of the aperture each of the two end portions having dimensions such that the valve member is held captive by the support member;

wherein the centra! portion and two opposed end portions of the valve member are integrally formed.

11 The two-part wastegate valve member assembly of claim 10 wherein: a first end portion of the valve member; and a portion of the support member surrounding the aperture which is arranged to contact the first end portion, are provided with complementary curved surfaces.

12. The two-part wastegate valve member assembly of claim 10 or claim 11 wherein: a second end portion of the valve member is provided with one or more voids or absences of the material from which the valve member is formed.

13. The two-part wastegate valve member assembly of claim 12 wherein the second end portion of the valve member is generally of the form of a disc and wherein the one or more voids or absences of the material from which the valve member is formed are generally of the form of recesses that extend from a perimeter of the disc towards a centre of the disc.

14. A turbine comprising:

a turbine housing defining a turbine inlet upstream of a 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 comprising the two-part wastegate valve member assembly of any one of claims 10 to 13, the wastegate valve having an open state in which gas may pass between the turbine inlet and 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.

15. A turbocharger or powerturbine including a turbine according to claim 14.