Turbine with variable geometry and its assembly

Abstract

A turbine (1) with a variable geometry, comprising a turbine wheel (4) which is fixed for rotation about a turbine axis in a housing (5), a gas flow inlet passage (13) upstream of the turbine wheel (4), and a gas flow control mechanism which is located within the housing (5) upstream of the turbine wheel (4) and can be actuated to control the gas flow through the gas flow inlet passage (13), the gas flow control mechanism comprising a movable component (15, 18) for varying the size of the gas flow inlet passage (13), the movable component (15, 18) being movable in a direction substantially parallel to the turbine axis, and a transmission mechanism for connecting between an actuator and the gas flow control mechanism to convert the movement applied by the actuator into a movement of the movable component (15, 18),wherein the transmission mechanism comprises a bracket (22) with a shaft (23) which is rotatably mounted in at least one support provided in a wall of the housing (5) for rotation about a shaft rotation axis, the bracket (22) defining arms (26) which extend outwardly from the shaft (23) and which cooperate with the movable component (15, 18) such that rotation of the bracket (22) influences the movement of the movable component (15, 18), at least one recess (37) being defined in an inner surface of the housing (5), the at least one recess (37) extending away from the at least one support and from the shaft rotation axis, the at least one recess (37) being configured to allow passage along it of an end (23a, 23b) of the shaft (23) during insertion of the bracket (22) into the housing (5).

Description

[0001] The present invention relates to a variable geometry turbine and a method for assembling such a turbine.

[0002] Turbochargers are well-known devices for delivering air into the intake of an internal combustion engine at pressures above atmospheric (elevated pressures). A conventional turbocharger essentially comprises an exhaust-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 engine intake manifold. The turbocharger shaft is typically supported by journal and thrust bearings, including suitable lubrication systems, located within a central bearing housing connected between the turbine and the compressor wheel housing.

[0003] The turbine stage of a conventional turbocharger comprises: a turbine housing defining a turbine chamber within which the turbine wheel is mounted; an annular inlet passageway defined in the housing between facing, radially extending walls disposed around the turbine chamber; an inlet disposed around the inlet passageway; and an outlet passageway extending from the turbine chamber. The passageways and the chamber communicate such that pressurized exhaust gas permitted to the inlet flows through the inlet passageway into the outlet passageway via the turbine chamber and rotates the turbine wheel. It is known to improve the performance of the turbine by providing vanes in the inlet passageway, called nozzle vanes, to deflect gas flowing through the inlet passageway in the direction of rotation of the turbine wheel.

[0004] Turbines of this type can have either fixed or variable geometry. Variable geometry turbines differ from fixed geometry turbines in that the size of the inlet passageway can be varied to optimize gas flow velocities over a range of mass flow rates, allowing the turbine's power output to be varied in accordance with varying engine requirements.

[0005] Nozzle vane assemblies in variable geometry turbochargers can take various forms. In one type, known as a sliding "nozzle ring," the vanes are attached to an axially movable wall that slides over the inlet passageway. The axially movable wall moves toward a facing shroud plate to close off the inlet of the passageway, and thereby the vanes pass through openings in the shroud plate. The position of the nozzle ring relative to the shroud is adjustable to control the width of the inlet passageway. For example, as the gas flowing through the turbine decreases, the inlet passageway can also be reduced to maintain gas velocity and optimize turbine performance. In an alternative arrangement, the vanes extend from a rigid wall through slots provided in a movable shroud plate.

[0006] The movable nozzle ring or collar plate is generally supported by rods extending parallel to the rotational axis of the turbine wheel and is moved by an actuator operable to displace the rods in an axial direction. Various types of actuators can be used to move the nozzle ring or collar plate, including, for example, a pneumatic actuator, or a motor and gear transmission, which are generally mounted on the outside of the casing. The actuator is coupled to the nozzle ring by a bracket mounted on a separately formed shaft received in journal bearings in the wall of the turbine casing.The bracket rotates with the shaft and defines two spaced arms extending from the shaft on different sides of the turbine axis to engage portions of the support rods extending from the housing into the adjacent bearing housing.

[0007] Assembly of the device is accomplished by inserting the bracket into the interior of the bearing housing and sliding it into a cavity surrounding the bearing assembly. The shaft is then inserted through the bearing housing wall from the outside into the bearings and through a central hole defined in the bracket. A clamp integrally molded with the bracket is then tightened by turning a screw to secure the bracket to the shaft.

[0008] The end of each arm of the bracket has a pin extending into a sliding block, which in turn is received in a slot defined in a corresponding support rod. Operation of the actuator causes the bracket and shaft to rotate about the shaft axis, so that the pins on the arms describe a circle and the blocks, in turn, move axially and slide vertically within the slots defined in the support rods. Axial movement of the nozzle ring or collar plate can thus be achieved by rotating the bracket about the shaft.

[0009] In applications where a smaller variable geometry turbocharger is required (e.g. for use in smaller engines or as a high pressure turbocharger in a two stage system), space constraints exist and there is a need to reduce the size of the spatial envelope required by the turbocharger by making it more compact without compromising its performance.

[0010] Prior art document GB 2 427 446 A describes a variable turbocharger device comprising a turbine housing, a turbine rotatably mounted within the turbine housing, an inlet for receiving exhaust gases from an engine, a chamber extending around the turbine and receiving the exhaust gases from the inlet before they are directed to the turbine, and a bearing arrangement enabling rotation of the turbine.

[0011] The prior art document DE 689 28 865 T2 describes a variable turbocharger with guide vanes which enter slots in the heat shield on a piston and protrude into a chamber in the assembled state of the turbocharger, wherein the chamber surrounds an end region of the bearing housing, and the guide vanes are designed such that they can always be inserted through the slots and into the chamber for ease of assembly of the variable turbocharger.

[0012] The prior art document DE 102 97 203 T5 describes a variable turbocharger comprising a housing, a compressor rotatably mounted in the housing, a turbine rotatably mounted in the housing, a first inlet for allowing air to be directed to the compressor, an outlet for allowing air from the compressor to be directed to an engine, a second inlet for allowing exhaust gases from the engine to be directed to the turbine to rotate the turbine, a chamber surrounding the turbine and receiving the exhaust gases from the second inlet before the exhaust gases are directed to the turbine, and a bearing arrangement to allow rotation of the turbine, wherein the variable turbocharger comprises fixed guide vanes mounted in the chamber and serving to direct exhaust gases precisely towards the turbine, a piston,which is slidable and which is positioned between the guide vanes and the turbine, and control means connected to the piston and which serve to control the sliding movement of the piston, the piston having one end closest to the bearing arrangement and which forms a gap, the size of the gap being variable depending on the sliding of the piston under the control of the control means, and the size of the gap acting to control the amount of exhaust gases acting on the turbine, and thereby precisely controlling the rotational speed of the turbine and thereby the amount of air passed through the compressor through the outlet to the engine.

[0013] It is, among other things, an object of the present invention to provide a compact turbocharger design. It is also an object to provide an alternative or improved variable geometry turbine.

[0014] According to a first aspect of the present invention, a variable geometry turbine is provided, comprising a turbine wheel mounted within a housing for rotation about a turbine axis, a gas flow inlet passageway upstream of the turbine wheel, and a gas flow control mechanism disposed within the housing upstream of the turbine wheel and operable to control the gas flow through the gas flow inlet passage, wherein the control mechanism comprises an operable member for varying the size of the gas flow inlet passage, the movable member being movable in a direction substantially parallel to the turbine axis, and a transmission mechanism for connecting an actuator and the control mechanism for transmitting a movement applied by the actuator into a movement of the movable member, the transmission mechanism comprising a yoke having a shaft,which is rotatably supported in at least one support provided in a wall of the housing for rotation about a shaft rotation axis, wherein the bracket defines arms extending outwardly from the shaft and which engage the movable component such that rotation of the bracket affects movement of the movable component, wherein at least one recess is provided which is defined in an inner surface of the housing, wherein at least one recess extends away from the at least one support and away from the shaft rotation axis, wherein the at least one recess is designed to allow passage of an end of the bracket shaft therealong during insertion of the bracket into the housing.

[0015] The recess in the inner surface facilitates insertion of the yoke into the housing from an open end, such as an exhaust end or an opposite end typically attached to a bearing housing. It can additionally accommodate rotation of the yoke about its shaft during actuation of the gas control mechanism by providing sufficient clearance for the passage of one of the arms. The invention provides a compact turbine housing with a small spatial envelope, enabling its use in circumstances where space constraints exist without compromising performance. The provision of the yoke within the turbine housing along the movable component enables a compact design.

[0016] The gas flow control mechanism may comprise a nozzle ring having an array of vanes in the annular inlet passageway for directing gas flow to the turbine wheel. The movable member may be a movable collar for movement around a rigid nozzle ring, or it may be a nozzle ring movable relative to a rigid collar. The collar may comprise a collar plate having slots for receiving vanes of the nozzle ring. It may further comprise a sleeve from which the collar plate extends, the sleeve forming part of the movable member. The collar plate may be in the form of an annular flange extending radially outward from the sleeve. The sleeve may be supported for axial movement by a collar support, which may be in the form of a cylinder, and whose inner surface may define a gas outlet passageway of the turbine.The gas outlet passageway may extend from the turbine wheel, and the end of the support near the turbine wheel may have a profile complementary to that of the edges of the blades of the turbine wheel. The collar support may have a radially outwardly extending flange defining a cover for covering a radially outer portion of an outlet opening of the turbine housing. The cover may be attached to an edge of the turbine housing defining the outlet opening.

[0017] The arms may extend toward the inner surface of the housing.

[0018] The at least one recess preferably extends in a direction away from the shaft. It can be arranged between the edge portion in which the shaft is received and a gas outlet end of the housing.

[0019] The shaft may define an axis substantially perpendicular to and radially offset from the turbine axis so that it effectively describes a chord of a circle intersecting an imaginary circle described by a line passing around the turbine housing.

[0020] The at least one support may be provided with a first bore in which the shaft is rotatably supported directly or in a first bearing, such as a journal bearing. The at least one recess may extend from the first bore. There may be a second bore in the housing wall for supporting the shaft in rotation directly or in a second bearing. It may support the shaft near one end thereof. The first and second bores may be blind holes or extend through the wall of the housing.

[0021] The arms may each have an end distal from the shaft. When the bracket rotates, the ends describe a circular arc. The distal end is intended for connection to the movable member and may support a connection that accommodates limited relative displacement between the arms and the movable member. The connection may include a pin on which a sliding block is rotatably received. The sliding block may be captively received in sliding engagement with the movable member. The at least one recess may be provided proximate the arc described by the distal end of at least one of the arms.

[0022] The at least one recess may extend from the at least one support where the shaft is supported in the housing to a position near the arc defined by the distal end of the nearest arm. This recess may extend beyond the arc.

[0023] The at least one recess may be elongated. It may extend in a substantially circumferential direction around an imaginary line formed by the rotational axis of the turbine, although it may also have an axial component (extending in the direction of the turbine axis).

[0024] The bore may be defined by at least one boss for supporting the shaft in rotation. The at least one recess may extend from the interior of the at least one boss. The or each boss may be defined on an outer surface of the housing, with the bore defined by the boss extending outwardly from the inner surface of the housing. The at least one boss may accommodate a journal bearing in which the shaft is supported for rotation.

[0025] There may be a further recess in the inner surface of the housing on the opposite side of the bracket, in addition to the at least one recess referred to above. The further recess may be near the arc defined by one of the distal ends of the arms. The further recess may be located between the second bore and the outlet end of the housing.

[0026] The bracket can be arranged between the housing and the movable component. The movable component can be arranged between the bracket and the turbine axis.

[0027] The housing may define a turbine outlet end, with the bracket disposed at or near the outlet end. The opposite end may be provided for connection to a bearing housing for support bearings for a shaft of the turbine shaft.

[0028] The shaft and arms of the bracket are preferably formed in one piece.

[0029] According to a second aspect of the present invention, there is provided a method of assembling a variable geometry turbine, the turbine comprising a housing for receiving a turbine wheel, a gas flow control mechanism disposed within the housing for positioning upstream of the turbine wheel, and operable to control gas flow through a gas flow inlet passage, the control mechanism comprising a movable member for varying the size of the gas flow inlet passage by displacement in a direction substantially parallel to the turbine axis, and a transmission mechanism for connection between an actuator and the control mechanism, and comprising a bracket having a shaft supported for rotation in first and second bores defined in the housing wall for rotation about a shaft rotation axis, the bracket defining arms extending outwardly from the shaft,and at least one recess defined in the inner surface of the housing, the method comprising: inserting a first end of the shaft into a first bore from an outlet end of the turbine housing, moving a second end of the shaft into the turbine housing to occupy the at least one recess, moving the second end along the at least one recess in a direction toward the bore and the shaft rotation axis, moving the second end into the second bore, securing the shaft for rotation in the housing wall, and attaching the bracket to the control mechanism.

[0030] The bracket may be inserted into the housing through an open outlet end. The outlet end may be partially closed to provide an outlet passage for the gas that drives the turbine wheel.

[0031] The second end of the shaft can be moved along the at least one recess by rotating the bracket substantially about an axis that is oblique to the shaft rotation axis. The oblique axis can be substantially parallel to or coincide with the turbine axis.

[0032] The first and second holes can pass through the wall, and bearings can be inserted into the holes from the outside of the housing.

[0033] A second of the bearings may be partially inserted into the second hole before the yoke is inserted and may then be fully inserted over the second end of the shaft when the yoke is in position.

[0034] According to another aspect of the present invention, there is provided a turbo engine, such as a turbocharger having a variable geometry turbine as defined above.

[0035] According to a further aspect of the present invention, a turbine housing for a variable geometry turbine as defined above is provided. The turbine housing has at least one recess defined in the inner surface of the housing and extending from a wall portion in which a yoke of the control mechanism is supported during operation. The at least one recess extends from the wall portion and is dimensioned to allow the passage of one end of the yoke shaft therealong during insertion of the yoke into the housing.

[0036] A particular embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. Figure 1 is a longitudinal sectional view of a portion of a turbocharger in accordance with the present invention, with a collar plate and collar support removed for clarity; Fig. 1a shows the same view as Fig. 1, however the collar plate and collar support are shown schematically; Fig. 2 is a perspective view of the turbine housing of the turbocharger according to Fig. 1; Fig. 3 is a perspective view of the turbine housing of Fig. 2, looking into the outlet end, showing the insertion of the bracket of the variable geometry mechanism; Fig. Figure 4 is a perspective view of the turbine housing when looking towards the inlet end, showing the further insertion of the bracket; Fig. Figure 5 is a view looking into the exhaust end of the turbine, showing the further insertion of the bracket; Fig. 6 is a view similar to that of Fig. 5, but the turbine housing is shown in section; Fig. Figure 7 is a perspective view of one side of the turbine housing and the bracket in the position corresponding to the Fig. 5 and Fig. 6; Fig. Figure 8 is a sectional view looking into the inlet end of the turbine, showing the final step of inserting the bracket; Fig. Figure 9 is a view looking into the inlet end of the turbine with the bracket in the position of Fig. 8 is shown; Fig. 10 is a sectional view corresponding to the Fig. 8, and shows the insertion of a bracket bearing; Fig. 11 is a sectional view corresponding to the Fig. 10, and shows the bracket and bearings installed in the turbine housing; and Fig. 12 and Fig. 12a are perspective views of the turbine housing and show the assembly of a collar sleeve.

[0037] With reference to the Fig. 1 and Fig. 1a of the drawings, the variable geometry turbocharger shown comprises a turbine 1 connected to a compressor (not shown) via a central bearing housing 3. The turbine 1 comprises a turbine wheel 4 which rotates within a turbine housing 5. Likewise, the compressor comprises a compressor wheel which rotates within a compressor housing. The turbine wheel 4 and the compressor wheel are attached to opposite ends of a common turbocharger shaft 8 which extends through the central bearing housing 3. In Fig. 1, the compressor impeller would be mounted on the end of the shaft protruding from the left of the bearing housing 3.

[0038] As usual, the bearing housing 3 has a central section which houses plain bearing assemblies which are arranged towards the compressor and turbine ends of the bearing housing, respectively.

[0039] In operation, the turbine wheel 4 is rotated by the passage of exhaust gas passing over it from the internal combustion engine. This, in turn, rotates the compressor wheel, which draws intake air through a compressor inlet and delivers charge air to the intake air manifold of an internal combustion engine via an exhaust diffuser.

[0040] The turbine housing 5 defines an inlet chamber 11 (typically a diffuser) to which the exhaust gas from an internal combustion engine is conveyed, and an outlet end opening 10. The exhaust gas flows from the inlet chamber 11 to an axially extending outlet passageway 12 (only in Fig. 1) via an annular inlet passageway 13 and the turbine wheel 4. The inlet passageway 13 is defined on one side by the surface of a radial wall of a rigid annular wall component 14, which is commonly referred to as a "nozzle ring", and on the other side by an annular collar plate 15 facing the nozzle ring 14, which is movable in the axial direction. The collar plate 15 and the nozzle ring 14 are in Fig. 1a, but not in Fig. 1.

[0041] The nozzle ring 14 supports an array of circumferentially spaced and evenly spaced inlet vanes 17, each of which extends axially across the inlet passageway 13 and projects through a corresponding slot in the collar plate 14. The vanes 17 are oriented to deflect gas flowing through the inlet passageway 13 in the direction of rotation of the turbine wheel 4.

[0042] The rotational speed of the turbine wheel 4 is independent of the velocity of the gas passing through the annular inlet passage 13. For a fixed mass rate of gas flowing into the inlet passage, the gas velocity is a function of the gap between the radial wall of the nozzle ring 14 and the collar plate 15. It is this gap that effectively defines the size of the passage 13 and is adjustable by controlling the axial position of the collar plate 15. As the gap is reduced, the velocity of the gas passing through it increases.

[0043] The collar plate 15 is in the form of a radial flange extending outwardly from a sleeve 18 with which it is integrally molded, and is penetrated by the slots for receiving the blades. The sleeve 18 is supported for movement in the axial direction by a collar support cylinder 19 concentric with the rotational axis of the turbine wheel 4. The outer surface of the support cylinder supports the sleeve for axial movement on a pair of axially spaced seals 20, the inner surface defining the outlet passageway 12 extending from the turbine wheel to the outlet end opening 10 of the casing 5 in a direction substantially parallel to the turbine axis.The support cylinder 19 has a radially outwardly extending flange 19a at the outlet end, and its periphery is secured to an edge of the turbine casing 5, which serves to define the outlet end opening 10. At the turbine wheel end, the support cylinder 19 has an edge profiled complementarily to the profile of the edge of the blades of the turbine wheel 5.

[0044] The axial position of the collar plate 15 and the sleeve 18 is controlled by an actuator (not shown) in response to signals from a controller, such as the engine management system. The actuator may be of any suitable type, such as a pneumatic device or an electric rotary actuator mounted on the exterior of the turbine casing 5. A transmission link connects an output shaft of the actuator and the sleeve 18, so that the stroke of the actuator's output shaft is translated into an axial movement of the collar plate 15.

[0045] The transmission connection comprises a bracket 22 which is arranged inside the turbine housing 5 towards the outlet end in a radial recess between a wall of the turbine housing 5 and the collar support cylinder 19, as shown in the Fig. 1 and Fig. 1a. The bracket 22 has a shaft 23 which is mounted for rotation at each end 23a, 23b in bearings 24, 25 (see Fig. 11) which are arranged in a wall of the turbine housing 5, and a pair of spaced arms 26 which extend outwardly from the shaft 23 in different directions for connection to the collar sleeve 18. A first end 23a of the shaft 23 extends out of the housing 5 and past the bearing 24 for connection to the actuator, and in operation, the actuator rotates the shaft 23 so that the arms 26 describe an arc about the shaft rotation axis. Each of the arms terminates in an end 26a which extends in a direction substantially along a radial line from the shaft, the ends 26a being substantially parallel rather than continuous along the different directions of the remainder of the arms 26. The bracket arms 26 are rotatably connected to the collar sleeve 18 by pins 27 which extend inwardly from each arm 26 into corresponding sliding blocks 28 which only in the Fig. 12 and Fig. 12a. The blocks 28 are received between pairs of arcuate ribs 29 defined on the outer wall of the sleeve 18, the ribs 29 extending in a circumferential direction and defining a slot 30 therebetween. The pins 27 are fixed within the arm ends 26a and are rotatably received within the sliding blocks, which are restricted from movement relative to the sleeve by the ribs 29, except in the direction along the corresponding slots 30. The sliding movement of the blocks 28 in the slots 30 allows eccentric movement of the pins 27. Movement of the collar sleeve 18 and the plate 15 along the axis of the turbine is thus controlled by rotation of the bracket 22.

[0046] The turbine housing 5 has an inner surface with a substantially circular cross-section at the outlet end, and the wall of the housing is relatively thick in this region. To support the yoke bearings 24, 25, the wall includes a pair of integrally molded inserts 32 extending outwardly from the outer surface on opposite sides of the turbine axis at the end adjacent the outlet port 10. The inserts 32 are penetrated by openings 33 to define cylindrical bores in which the bearings 24, 25 are received with an interference fit.After assembly, each end of the bracket shaft 23 is supported for rotation in a corresponding bearing 24, 25 such that the axis of rotation of the shaft 23 extends substantially perpendicular to the axis of rotation of the turbine wheel 4, the shaft axis being radially offset from the turbine axis so that it effectively describes a chord intersecting an imaginary circle described by a line passing around the turbine housing 4 and intersecting the centers of the inserts 32.

[0047] A first of the bearings 24 has a through-bore 34 such that the first end 23a of the yoke shaft protrudes from the bearing 24 and the turbine housing 5 for connection to the actuator. The other of the bearings has a blind bore 35 for receiving the opposite end 23b of the yoke shaft 23.

[0048] The wall of the turbine housing 5 at the outlet end has a pair of recesses 36, 37 defined in its inner surface on opposite sides of the turbine axis. A first of these recesses 36 is located below the first bearing 24 and is centered around a location substantially at the same level as the turbine axis and is designed to allow passage of one of the ends 26a of one of the bracket arms 22. Thus, a clearance is provided for the end of the bracket arm 22. This can best be seen in the Fig. 2, 3, 5, 6 and 8 to 11. The other recess 37, which is best seen in the Fig. 7 to 11, has a different elongated profile, extending from the insert 32, which houses the bearing 25, around the inside of the turbine housing 5 to a location below the other bracket arm end 26a, just below the level of the turbine axis. This recess 37 is designed to facilitate insertion of the bracket into the turbine housing 5. In the embodiment shown, it extends in a substantially circumferential direction around the turbine axis.

[0049] The insertion of the bracket 22 into the turbine 1 is now carried out with respect to the Fig. 2 to 11.

[0050] First, the bearing 25 with the blind hole 35 is partially inserted into its insert 32 so that its blind hole end extends out of the insert 32, as shown in Fig. 2. The bracket 22 is then inserted through the turbine housing 5 at the outlet end with the first end 32a of the shaft 23, which is inserted into the opposite open insert 32 with the shaft axis inclined to an axis extending between the centers of the inserts 32, as shown in Fig. 3. The bracket shaft 32 can then be rotated about its axis so that the arms 26 extend outwardly from the open outlet passageway 12, as shown in Fig. 4. When the first end 23a extends into and beyond the insert 32, the opposite second end 23b of the stem 23 is then lowered beyond the edge of the outlet passageway 12 and into the recess 37, as shown in the Fig. 6 and Fig. 7. The bracket 22 is then rotated approximately about the turbine axis so that the shaft axis is aligned with the inserts 32. During this movement, the second end of the shaft 23b extends along the length of the recess 37. The Fig. 8 and Fig. 9 show the bracket just before it reaches its final position.

[0051] Once the axis of the bracket shaft 23 is aligned with the axis passing between the centers of the inserts 32, the bearing 24 is inserted into its shoulder 32 over the first end 23a of the bracket shaft ( Fig. 10) until it is completely absorbed ( Fig. 11), and the other bearing 24 is pushed fully back into the insert to support the shaft. In this position, the bracket 22 is free to rotate about its axis while the arm ends 26a sweep through the recess 36.

[0052] To connect the bracket 22 to the sliding collar sleeve 18, the shaft is rotated so that the arm ends 26a protrude from the outlet passageway 12. The sliding blocks 28 are then connected to the pins 27, and the sleeve 18 is inserted into the turbine housing 5 so that it is concentric with the turbine axis. The sleeve 18 is positioned so that the slots 30 between the ribs 29 are axially aligned with the sliding blocks 28, but are angularly spaced therefrom, as shown in Fig. 12. The sleeve 18 is then rotated so that the ribs 29 extend over the sliding blocks 28, which are then received in the slots 30, as in Fig. 12a shown.

[0053] The collar support cylinder 19 is inserted into the collar sleeve 18 from the outlet port 10, and the turbine wheel 4 is inserted from the other end before the bearing housing 3 is connected to complete the main components of the turbine assembly, the completed assembly being placed in the Fig. 1 and Fig. 1a is shown.

[0054] The actuator is then attached to a bracket (not shown) which is connected to the outside of the turbine housing 5 and is connected to the bracket shaft 23, for example by a lever arm.

[0055] In operation, the actuator is controlled so that the yoke 22 rotates about its shaft axis. The arms 26 of the yoke sweep through a circular sector with the ends 26a each describing an arc. This movement is translated into movement of the collar sleeve 18 and the plate 14 in the direction of the turbine axis through cooperation with the pins 27, the sliding blocks 28, and the ribs 29 on the sleeve 18. The blocks 28 press against the ribs 29 to move the sleeve with an eccentric movement, which is absorbed by the blades 28, which rotate on the pins 27 and slide within the slots 30 between the ribs 29. As the yoke 22 rotates about the shaft axis, the sliding collar sleeve 18 and the plate 14 move axially to vary the size of the inlet passageway 13.

[0056] The arrangement described above provides a compact turbine housing with a relatively small spatial envelope. The recesses 36, 37 allow for easy and quick insertion of the bracket 22 and serve its subsequent rotation due to its location at or near the arc described by the ends 26a of the arms. The provision of a bracket in which the shaft and arms are integrally molded to provide a unitary (i.e., one-piece) bracket structure simplifies the manufacturing process and reduces associated costs. It eliminates angular misalignment between the bracket arms and the shaft according to prior art devices and provides a more compact design that eliminates the need for a clamping feature to clamp the brackets to the shaft.

[0057] Numerous modifications and variations can be made to the exemplary design described above without departing from the scope of the invention as defined in the claims. For example, the arrangement described above can be used to move a nozzle ring axially relative to a fixed collar plate. Furthermore, at least one of the openings defined by the lugs may not extend through the housing, but may be in the form of a blind bore. Finally, the exact shape of each of the recesses 36 and 37 may vary from that described and shown while still performing the same function.

[0058] While the invention has been shown and described in detail in the drawings and the foregoing description, it is considered to be illustrative and not restrictive in its nature; it is understood that only the preferred embodiments have been shown and described, and that all changes and modifications which come within the scope of the inventions as defined in the claims are contemplated. It should be understood that while the use of words such as preferably, preferentially, preferably, or more preferably used in the above description indicates that the feature so described may be more desirable, it may nevertheless not be necessary, and embodiments not having the same are considered to be within the scope of the invention, which scope is defined by the following claims.In reading the claims, it is desired that when words such as "a", "an", "at least one" or "at least one section" are used therein, there is no intention to limit the claim to only one component, unless the contrary is emphasized in the claim. When the words "at least one section" and / or "a section" are used, the component may include a section and / or the entire component, unless the contrary is specifically emphasized. List of reference symbols 1 turbine 3 bearing housings 4 Turbine wheel 5 Turbine housing 10 Outlet end opening 11 Inlet chamber 12 Outlet passageway 13 Gas flow inlet passage 14 Nozzle ring 15 Movable component 17 Inlet vane 18 Movable component 19 collar support cylinders 19a flange 20 Seal 22 brackets 23 shaft 23a Shaft end 23b Shaft end 24 warehouses 25 warehouses 26 Arm 26a Arm end 27 pen 28 sliding block 29 rib 30 slots 32 deployment 33 Opening 34 Hole 35 bore 36 recess 37 recess

Claims

[1] A turbine (1) with a variable geometry, comprising a turbine wheel (4) mounted for rotation about a turbine axis in a housing (5), a gas flow inlet passage (13) upstream of the turbine wheel (4), and a gas flow control mechanism located within the housing (5) upstream of the turbine wheel (4) and operable to control the gas flow through the gas flow inlet passage (13), wherein the gas flow control mechanism comprises a movable member (15, 18) for varying the size of the gas flow inlet passage (13), the movable member (15, 18) being movable in a direction substantially parallel to the turbine axis, and a transmission mechanism for connecting an actuator and the gas flow control mechanism for converting the movement applied by the actuator into a movement of the movable member (15, 18),wherein the transmission mechanism comprises a bracket (22) with a shaft (23) rotatably mounted in at least one support provided in a wall of the housing (5) for rotation about a shaft rotation axis, wherein the bracket (22) defines arms (26) extending outwardly from the shaft (23) and which cooperate with the movable component (15, 18) such that rotation of the bracket (22) influences the movement of the movable component (15, 18), wherein at least one recess (37) is defined in an inner surface of the housing (5), wherein the at least one recess (37) extends away from the at least one support and away from the shaft rotation axis, wherein the at least one recess (37) is designed to allow passage of an end (23a, 23b) of the shaft (23) therealong during insertion of the bracket (22) into the housing (5). [2] Turbine (1) with variable geometry according to claim 1, wherein the at least one recess (37) is elongated. [3] A variable geometry turbine (1) according to claim 1 or 2, wherein the at least one support comprises a first bore (35) or a recess (37) defined in the wall. [4] A variable geometry turbine (1) according to claim 3, wherein the at least one support further comprises a first bearing (25) in the first bore (35) or the recess (37). [5] Variable geometry turbine (1) according to claim 3 or 4, wherein the at least one recess (37) extends from the first bore (35). [6] A variable geometry turbine (1) according to claim 3, 4 or 5, wherein the at least one support further comprises a second bore (34) or recess (37) in the housing wall. [7] A variable geometry turbine (1) according to claim 6, wherein the at least one further support further comprises a second bearing (24) in the second bore (34) or the recess (37). [8] A variable geometry turbine (1) according to claim 7, wherein a first bearing (25) is provided in the first bore (35) and a second bearing (24) is provided in the second bore (34), the first bearing (25) defining a blind bore (35) for receiving one end (23b) of the shaft (23), and the second bearing (24) defining a through bore (34) for receiving an opposite end (23a) of the shaft (23). [9] A variable geometry turbine (1) according to any one of claims 3 to 8, wherein the first bore (35) is defined by a boss (32) for receiving the shaft (23) in rotation. [10] A variable geometry turbine (1) according to claim 9, wherein the at least one recess (37) extends from the interior of the at least one projection (32). [11] A variable geometry turbine (1) according to any one of the preceding claims, wherein the arms (26) each have an end (23a, 23b) distal from the shaft (23), and rotation of the bracket (22) about its shaft (23) causes the ends (23a, 23b) to describe a circular arc, at least one further recess (37) being defined in the inner surface of the casing (5) near one of the arcs. [12] Variable geometry turbine (1) according to claim 11, wherein at least one of the distal ends (23a, 23b) is connected to the movable member (15, 18). [13] A variable geometry turbine (1) according to any one of the preceding claims, wherein the at least one recess (37) extends in a substantially circumferential direction defined around an imaginary line formed by the axis of rotation of the turbine (1). [14] Variable geometry turbine (1) according to any one of the preceding claims, wherein the bracket (22) is arranged between the housing (5) and the movable member (15, 18). [15] A variable geometry turbine (1) according to any one of the preceding claims, wherein the shaft (23) and the arms (26) of the bracket (22) are integrally formed. [16] A variable geometry turbine (1) according to any one of the preceding claims, wherein the casing (5) defines a turbine outlet end, the bracket (22) being arranged at or near the outlet end. [17] A method of assembling a variable geometry turbine (1), the turbine (1) comprising a housing (5) for receiving a turbine wheel (4), a gas flow control mechanism located within the housing (5) for positioning upstream of the turbine wheel (4) and operable to control the gas flow through a gas flow inlet passage (13), the gas flow control mechanism comprising a movable member (15, 18) for varying the size of the gas flow inlet passage (13) by translating in a direction substantially parallel to the turbine axis, and a transmission mechanism for connecting an actuator to the gas flow control mechanism, the transmission mechanism comprising a bracket (22) having a shaft (23) supported for rotation about first and second bores (34, 35) defined in the housing wall for rotation about a shaft rotation axis, the bracket (22) defining arms (26),extending outwardly from the shaft (23), and at least one recess (37) defined in the inner surface of the housing (5), the method comprising: inserting a first end (23b) of the shaft (23) into a first bore (35) from an outlet end of the housing (5), moving a second end (23a) of the shaft (23) into the housing (5) so that it occupies the at least one recess (37), moving the second end (23a) along the at least one recess (37) in a direction toward the bore (35) and the shaft rotation axis, moving the second end (23a) in the second bore (34), securing the shaft (23) for rotation in the housing wall, and attaching the bracket (22) to the gas flow control mechanism. [18] A method according to claim 17, wherein the first and second bores (34, 35) extend through the wall, and bearings (24, 25) are inserted into the bore (34, 35) from outside the housing (5). [19] The method of claim 18, wherein a second (24) of the bearings is partially inserted into the second bore (34) before the bracket (22) is inserted and then fully inserted over the second end (23a) of the shaft (23) when the bracket (22) is in position. [20] The method according to claim 17, wherein the second end (23a) of the shaft (23) is moved along the at least one recess (37) by rotation of the bracket (22) substantially about an axis which is oblique to the axis of rotation.

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