VARIABLE GEOMETRY TURBINE VANES FOR TURBOCHARGERS

Abstract: A variable geometry turbine vane (20) is provided, having at least one, and preferably two, side plates (34 and 36). These not only provide side sealing, by co-operating with the side plates of similar vanes, but also provide a mount for pivot bearings (44). This enables the vane to pivot about its trailing edge. This in turn assists in providing advantageous shaping of the gas flow.

Description: VARIABLE GEOMETRYTURBINEVANES FORTURBOCHARGERS Field of the Invention The present invention relates to variable geometry turbine vanes for turbochargers. Background to the Invention A turbocharger basically comprises a compressor and a turbine coupled together, generally with a common shaft. Engine exhaust gases are fed into the compressor and rotate the compressor and the common shaft. This drives the turbine which is used to force air into the engine to enhance its performance. It is desirable to control the flow of gases relative to the turbine vanes by changing their aspect relative to the gas flow to adjust the throat height between vanes. Turbines for this purpose are known and are referred to as "variable geometry turbines". Known variable geometry turbines have the disadvantage that leakage of gases occurs from the low pressure outer (relative to the axis for rotation) side of the vanes which is detrimental to their performance. Vanes on previous variable geometry turbines also suffer from the disadvantage that they are only able to pivot about a region roughly half-way along the length of the vane. This contributes to the need for a gap at the side of the vanes because of the deformation along the vanes side edge, over which leakage of gas, and hence loss of efficiency, can occur. Summary of the Invention According to a first aspect of the present invention there is provided a variable geometry turbine vane for a turbocharger, the vane comprising at least one side plate extending radially from the vane. The side plate can be used to restrict the flow of gas around the side of the vane or for mounting attachments to the vane. Normally, the side plates will extend radially outwardly from the vane in order that the gas flow around the side of the vane can be restricted as much as possible. Preferably there is a side plate on each side of the vane to restrict gas flow over both sides of the vane. The vane may comprise a leading edge and a trailing edge relative to the gases passing over it. Advantageously, the vane additionally comprises a pivot point in the region of the trailing edge of the vane, about which pivot point the vane can pivot in use. By providing a pivot point on a side plate in this way, pivoting can occur in the vicinity of the trailing edge which can be kept as thin is desired. In a second aspect, the present invention also provides a variable geometry turbine wheel for a turbocharger, the turbine wheel comprising a plurality of vanes as referred to above in relation to the first aspect of the present invention. Advantageously the vanes cooperate to provide a substantially contiguous side wall around the turbine wheel to restrict the flow of gas around the side of the vanes of the wheel. Usually there will be a substantially contiguous side wall on either side of the vanes of the wheel. Suitably the vanes comprise side plates extending radially inwardly, in which side plates are provided relief areas with which the pivot point of an adjacent vane cooperates. Preferably the vanes additionally comprise relief areas whereby the vanes are capable of nesting into one another. Advantageously, the vanes are so shaped that the flow of gases over the vanes results in a side pressure on the side plates whereby the side plates are compressed together to enhance the seal of the side plates against side ways leakage. Suitably the vanes additionally include an axial extension comprising an actuator lever which can be moved by an actuator ring to control the attitude of the vane relative to the gas flow. Conveniently, all of the vanes will be substantially similar. Suitably, an actuator ring is provided adjacent to the variable geometry turbine to control the aspect of the vanes. Brief Description of the Drawings The invention will now be described, by way of example only, with reference to the drawings that follow; in which: Figure 1 is a plan view of a turbocharger. Figure 2 is an enlarged view of a series of turbine vanes in accordance with the present invention, forming part of the turbine. Figure 3 is a side view of an actuator ring for use with the turbine wheel shown in Figure 2. Figure 4 is a further enlarged perspective view of one of the turbine vanes shown in Figure 2. Figure 5 is a side view of the turbine vane shown in Figure 4. Figures 6 and 7 are schematic side views of an adjacent pair of turbine vanes as shown in Figures 4 and 5, illustrating the operation of the present invention. Description of the Preferred Embodiment Referring to Figure 1 of the drawings, there is shown a turbocharger 2 comprising a turbocharger body 4 including a turbine inlet 6, a turbine outlet 8, a compressor inlet 10 and a compressor outlet 12 as is conventional in the art. Within the turbine body 4 is located a turbine wheel 14 shown in Figure 2. The turbine wheel 14 comprises a turbine axis 16 from which extend nine turbine wheel blades 18 each of which supports a turbine vane 20. The vanes 20, each of which are substantially similar, are described in more detail below in relation to Figures 4 to 7 to which reference is now made. Each vane 20 comprises a vane body 22 curved and tapered as is well known in the art. The vane body 22 comprises a leading edge 24 and a trailing edge 26 (relative to the gas flow over the vane 20 in use). Between the leading 24 and trailing 26 edges of the vane 20 are outer 28 and inner 30 faces, and side faces 32. The outer vane surface 28 is the low pressure side of the vane 20, and the inner vane surface 30 is the high pressure side of the vane 20 which is nearer to the turbine axis 16 than the outer surface 28. Extending from each side face 32 are side plates 34 and 36. Referring, in particular, to Figure 4 it can be seen that each side plate 34, 36 comprises a sealing element 38 extending outwardly (relative to the axis 16) from the outer face 28, a wing 40 extending inwardly from the inner face 30 and a relief area 42. A bearing 44 is provided in the relief area 42 adjacent to the trailing edge 26. On one side plate 34 only there is provided an actuator lever 46 on the sealing element 38. Within each of the wings 40 are gaps 48 the purpose of which is explained below. Figure 6 shows two vanes nested together in a "closed" configuration. The bearings 44 of one vane 20 fit into the gaps 48 of the adjacent vane 20, and the wings 40 of one vane 20 fit over the relief areas 42 of the adjacent vane 20. These nesting configurations are repeated all around the turbine wheel 14 as can be seen in Figure 2. Referring to Figure 6, the sealing elements 38 provide a contiguous side wall extending radially outwardly from the side faces 32 of the vane bodies 22. In fact, Figure 2 shows the turbine wheel 14 with the vanes 20 in their "closed" configuration. An actuator ring 50 shown in Figure 3 is mounted adjacent to the turbine wheel 14 on a common axis. The actuator ring 50 can be driven independently of the turbine wheel 14 as is well known in the art. The actuator ring 50 can be rotated relative to the turbine wheel 14 such that the actuator levers 46 move outwardly relative to the turbine axis 16 along slots 52 in the actuator ring 50. The nine slots 52 in the actuator ring 50 engage the nine actuator levers 46 of the turbine wheel 14. As the actuator levers 46 are moved outwardly, the vanes 20 pivot relatively freely about bearings 44. The vanes 20 can, in this way, be pivoted to the configuration shown in Figure 7. Figure 7 shows the "open" configuration of the vanes 20. It will be appreciated that in this "open" position the attitude of the vane and bodies 22 relative to the gas flow is different to that achieved in the "closed" position shown in Figure 6. In the "open" configuration shown in Figure 7, the sealing elements 38 still provide a contiguous side wall to restrict the flow of gases around the side edges of the vanes 20. The upper (radially outward) edges of the sealing elements 38 are, in this "open" configuration, proximate to the inside of the turbocharger body 4 restricting further the flow of gas around the turbine wheel 14. In Figure 2 the outer, dashed line indicated generally by reference numeral 54 shows the alignment of the sealing element 38 forming the contiguous sealing wall in the "open" configuration. Thus, in all configurations between and including the "closed" and "open" ones shown in Figures 6 and 7 respectively, the turbine wheel 14 provides a substantially contiguous side wall on each side of the vanes 20 restricting the flow of gases around the sides of the vanes 20. Furthermore, the relief areas 42, extending from the side 32 of the vane body 22, are used to provide convenient pivot points (comprising bearings 44) in the vicinity of the trailing edge 26 of d e vane body 22 to enhance the control and performance of the turbine wheel 14. In use, as gases flow over the turbine wheel 14, each turbine 20 experiences an outwards, sideways (relative to the vane body 22) force by virtue of the action of the gases against the sealing elements 38. This force induces the relief area 42 of each vane 20 to be urged towards the inside of the wing 40 of its adjacent trailing vane 20. In this way, the contiguous seal against flow of gases over the side of the vanes 20 is enhanced. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of die features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of die steps of any method or process so disclosed.

Claims: C AJMS 1. A variable geometry turbine vane for a turbocharger, the vane comprising at least one side plate extending radially from the vane. 2. A vane as claimed in Claim 1 , having a side plate on each side of the vane. 3. A vane as claimed in Claim 1 or Claim 2, having a leading edge and a trailing edge relative to the gasses passing over it, the vane additionally having a pivot point in the region of the trailing edge of the vane, about which pivot point the vane can pivot in use. 4. A variable geometry turbine wheel for a turbocharger, the turbine wheel comprising a plurality of vanes as claimed in any one of the preceding claims. 5. A turbine wheel as claimed in Claim 4, in which the vanes co-operate to provide a substantially contiguous side wall around the turbine wheel to restrict the flow of gas around the side of the vanes of the wheel. 6. A turbine wheel as claimed in Claim 5, in which side plates on each side of each vane co-operates to provide a substantially contiguous side wall at each side of the wheel. 7. A turbine wheel as claimed in Claim 5 or Claim 6, in which the vanes additionally comprise relief areas whereby the vanes are capable of nesting into one another. 8. A turbine wheel as claim in any one of Claims 5 to 7 in which die vanes are so shaped that the flow of gases over the vanes results in a side pressure on the side plates whereby the side plates are compressed together to enhance the seal of the side plate against sideways leakage. 9. A turbine wheel as claimed in any one of Claims 5 to 8, in which each vane additionally includes an axial extension comprising an actuator lever which can be moved by an actuator ring to control the attitude of the vane relative to the gas flow. 10. A turbocharger having at least one variable geometry turbine vane as claimed in any one of Claims 1 to 4, and/or having a turbine wheel as claimed in any one of the Claims 5 to 9.

Inventors: O'HARA STEPHEN JOHN, O'HARA, STEPHEN, JOHN
Applicants: HARA STEPHEN JOHN O, SCHWITZER EUROP LTD, O'HARA, STEPHEN, JOHN, SCHWITZER (EUROPE) LIMITED
Application year: 1996
Main classification: F02B37
IPC codes: F01D17, F02B37, F02B39