Anti-rotation pin assembly for turbocharger shroud

Abstract

A pin member for a turbine having a shroud arranged to rotate within a turbine housing is disclosed. The pin member is configured to limit this rotation. It is a one-piece element comprising a cylindrical body and a limiting surface for opposing movement of the shroud.

Description

Technical Field

[0001] The present invention relates to a vane arrangement for positioning at a gas inlet of a turbine such as a turbocharger. Background Art

[0002] A turbocharger is a well-known device for supplying air to the intake of an internal combustion engine at a pressure above atmospheric pressure (boost). A conventional turbocharger primarily comprises an exhaust gas-driven turbine wheel mounted on a rotatable shaft within a turbine housing. The 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's intake manifold, thereby increasing engine power. The turbocharger shaft is typically supported by journal and thrust bearings, including a suitable lubrication system within a central bearing housing connected between the turbine and compressor wheel housings.

[0003] In known turbochargers, the turbine stage includes a turbine chamber in which a turbine wheel is mounted; an annular inlet passage defined between facing radial walls disposed about the turbine chamber; an inlet disposed about the inlet passage; and an outlet passage extending axially from the turbine chamber. The passage and chamber communicate so that pressurized exhaust gas admitted to the inlet chamber flows through the turbine, through the inlet passage, to the outlet passage, and rotates the turbine wheel.

[0004] It is known to improve turbine performance by providing vanes, known as nozzle vanes, in the inlet passage to deflect the gas flowing through the inlet passage toward the direction of rotation of the turbine wheel. Each vane is generally flaky and positioned so that a radially outer surface is arranged to impede the movement of exhaust gas within the inlet passage. In other words, the radially inward component of the movement of the exhaust gas within the inlet passage is directed against the outer surface of the vane and is then redirected into circumferential motion.

[0005] Turbines can be of fixed or variable geometry type. Variable geometry turbines differ from fixed geometry turbines in that the geometry of the inlet passage can be varied to optimize gas flow velocity within a range of mass flow rates, allowing the turbine's power output to be varied to accommodate changing engine demands.

[0006] In one form of variable geometry turbocharger, a nozzle ring carries a plurality of axially extending vanes that extend into the air inlet and pass through corresponding apertures ("slots") in a shroud forming a radially extending wall of the air inlet. The nozzle ring can be moved axially by an actuator to control the width of the air passage. Movement of the nozzle ring also controls the extent to which the vanes protrude through the corresponding slots. The shroud is annular and surrounds the axis of rotation.

[0007] An example of such a variable geometry turbocharger is shown in Figures 1(a) and 1(b), taken from US 8,172,516. The illustrated variable geometry turbine comprises a turbine housing 1 defining an inlet chamber 2 to which gas from an internal combustion engine (not shown) is delivered. Exhaust gas flows from the inlet chamber 2 to an outlet channel 3 via an annular inlet passage 4. The inlet passage 4 is defined on one side by the face of a movable annular wall member 5 constituting a nozzle ring and on the opposite side by an annular shroud 6 covering the opening of an annular recess 8 in the facing wall. The shroud 6 is an annular member (one-piece unit) defining a central bore and surrounding the axis of rotation. The facing wall is defined by a portion 28 of the turbine housing 1. The shroud 6 is connected to the portion 28 of the turbine housing 1 by a bracket 29 at the radially outer side of the shroud 6. In some arrangements, a retaining ring (not shown) is provided partially inserted into a radially outwardly facing recess in the bracket 29 , with the radially outer portion of the retaining ring being retained by the portion 28 of the turbine housing 1 .

[0008] The gas flowing from the inlet chamber 2 to the outlet channel 3 passes through the turbine wheel 9 and, as a result, torque is applied to the turbocharger shaft 10, which is supported by a bearing assembly 14 that drives the compressor wheel 11. The rotation of the compressor wheel 11 about the axis of rotation 100 pressurizes the ambient air present in the air inlet 12 and delivers the pressurized air to the air outlet 13, from which the pressurized air is fed to the internal combustion engine (not shown). The speed of the turbine wheel 9 depends on the speed of the gas passing through the annular inlet channel 4. For a fixed rate of mass of gas flowing into the inlet channel, the gas speed is a function of the width of the inlet channel 4, which is adjustable by controlling the axial position of the nozzle ring 5. As the width of the inlet channel 4 is reduced, the speed of the gas passing through it increases. Figure 1(a) shows the annular inlet channel 4 closed to its minimum width, while in Figure 1(b), the inlet channel 4 is shown as fully open.

[0009] The nozzle ring 5 supports a row of circumferential, equally spaced vanes 7, each of which extends through the inlet passage 4. The vanes 7 are oriented to deflect the gas flowing through the inlet passage 4 toward the direction of rotation of the turbine wheel 9. When the nozzle ring 5 approaches the annular shroud 6 and the facing wall, the vanes 7 protrude through appropriately configured slots in the shroud 6 and into recesses 8. Each vane has an "inner" major surface closer to the axis of rotation 100 and an "outer" major surface further away from the axis of rotation 100. The nozzle ring 5 and shroud 6 are both positioned at fixed angular positions about the axis 100. The vanes 7 are illustrated in Figures 1(a) and 1(b) as having chamfered end portions (towards the right in the figures), but in most modern arrangements, the vanes are longitudinally symmetrical along their entire length, or consist of two parts, each of which is longitudinally symmetrical but has a different profile from the other when viewed in the axial direction.

[0010] A pneumatically or hydraulically operated actuator 16 is operable to control the axial position of the nozzle ring 5 within the annular cavity 19 defined by a portion 26 of the turbine housing via an actuator output shaft (not shown), which is connected to a stirrup member (not shown). The stirrup member, in turn, engages axially extending guide rods (not shown) that support the nozzle ring 5. Thus, through appropriate control of the actuator 16, the axial position of the guide rods, and thereby the axial position of the nozzle ring 5, can be controlled. It should be understood that an electrically operated actuator may be used in place of the pneumatically or hydraulically operated actuator 16.

[0011] The nozzle ring 5 has axially extending inner and outer annular flanges 17 and 18, respectively, extending into an annular cavity 19, with a wall 27 separating the annular cavity 19 from the chamber 15. Inner and outer sealing rings 20 and 21 are respectively provided to seal the nozzle ring 5 against the inner and outer annular surfaces of the annular cavity 19 while allowing the nozzle ring 5 to slide within the annular cavity 19. The inner sealing ring 20 is supported within an annular groove 22 formed in the inner surface of the cavity 19 and bears against the inner annular flange 17 of the nozzle ring 5, while the outer sealing ring 21 is supported within an annular groove 23 provided in the annular flange 18 of the nozzle ring 5 and bears against the radially outermost inner surface of the cavity 19. It will be appreciated that the inner sealing ring 20 may be mounted in an annular groove in the flange 17, rather than as shown, and / or the outer sealing ring 21 may be mounted in an annular groove provided in the outer surface of the cavity, rather than as shown. A first set of pressure balance holes 25 is provided in the nozzle ring 5 within the vane passages defined between adjacent holes, while a second set of pressure balance holes 24 is provided in the nozzle ring 5 outside the radius of the nozzle vane passages.

[0012] It should be noted that in other known turbines, the nozzle ring is axially fixed and the actuator is instead arranged to translate the shroud in a direction parallel to the axis of rotation. This is known as a "moving shroud" arrangement.

[0013] In known variable-geometry turbines that employ vanes protruding through slots in a shroud, a spacing is provided between the vanes and the edges of the slots to allow for thermal expansion of the vanes as the turbocharger heats up. Viewed in the axial direction, the vanes and slots have the same shape, but the vanes are smaller than the slots. In a typical arrangement, the vanes are positioned so that the axial centerline of each vane is at the center of its corresponding slot, such that in all directions away from the centerline transverse to the turbine axis, the distance from the centerline to the surface of the vane is the same as the distance from the centerline to the edge of the corresponding slot. The spacing between the vanes and slots is generally arranged to be at least approximately 0.5% of the distance from the center of the vane to the axis of rotation (the "nozzle radius") around the entire periphery of the vane (for example, for a 46.5 mm nozzle radius, the spacing may be 0.23 mm, or 0.5% of the nozzle radius) at room temperature (defined herein as 20 degrees Celsius). This means that if each of the vanes is thermally expanded gradually perpendicular to the axial direction, all points around the periphery of the vane will contact a corresponding point on the slot at the same time. At all lower temperatures, there is a spacing between the entire periphery of the vane and the edge of the corresponding slot. Summary of the Invention

[0014] The present invention aims to provide a new and useful blade assembly for a turbomachine, and a new and useful turbomachine (especially a turbocharger) incorporating the blade assembly.

[0015] In an earlier patent application, GB 1619347.6, the applicant proposed a turbine of a turbomachine in which, at the gas inlet between the nozzle ring and the shroud, the vanes project from the nozzle through slots in the shroud. A "conformal" portion of the transverse surface of each vane (i.e., the surface parallel to the axis of rotation) is substantially conformal to the shape of a corresponding "conformal" portion of the transverse surface of the corresponding slot at room temperature, so that the corresponding conformal portions of the surface can be positioned relative to each other with only a small spacing between them. This has the advantage of substantially reducing the flow of gas between the slot and the corresponding conformal portion of the vane's surface. This reduces leakage of gas into or out of the recess of the nozzle ring on the other side of the shroud. This leakage reduces the change in the circumferential direction of the gas caused by the vanes and has been found to result in a significant loss in efficiency.

[0016] In such an arrangement, at low temperatures (such as room temperature), the conformal portions of the blade surfaces and the slot surfaces can be positioned close to each other, or even in contact. At higher temperatures, this contact is maintained if the shroud and nozzle ring expand uniformly. However, in use, uneven thermal expansion of the components of the turbine may cause the blades and slots to press against each other, making it more difficult to move the blades axially relative to the slots. To some extent, this effect may be reduced by any free play in the mounting of the shroud and nozzle ring, which allows the blades to retract from the inwardly facing surfaces of the slots to prevent the corresponding surfaces from being pressed together by higher forces. Any such free play is not due to design, but is the result of tolerances in the formation of the components. It varies from one turbine unit to another, and it has been found experimentally that such free play allows the nozzle ring to rotate relative to the shroud by significantly less than 0.1 degrees, for example up to 0.05 degrees.

[0017] In an earlier patent application, GB 1807881.6 (unpublished at the priority date of the present application), the present inventors proposed that a turbine (e.g., a turbocharger) should allow the nozzle ring to move relative to the shroud in a circumferential direction by a relatively large angular amount (at least 0.1 degrees) to relieve pressure between the blades and the edges of the corresponding slots. The concept of arranging the nozzle ring to be rotatable relative to the shroud is referred to herein as "clocking." In one possibility, the nozzle ring is substantially rotationally fixed relative to the turbine housing, and the shroud is rotatable relative to the turbine housing about the turbine axis.

[0018] We refer to the connection between the turbine housing and the shroud as a coupling mechanism, which allows the shroud to rotate relative to the turbine housing by at least 0.1 degrees. In one possibility, the coupling mechanism may substantially fix the axial position of the shroud and / or maintain the center of the shroud substantially on the axis of the turbine wheel, but may allow the shroud to rotate relative to the turbine housing about the axis of the turbine wheel. The coupling mechanism may allow the shroud to rotate relative to the turbine housing through a fixed angular interval of at least 0.1 degrees, or to rotate freely (i.e., by an unlimited angular amount). In the latter case, rotation of the shroud / nozzle ring relative to the turbine housing may be limited only by the interaction between the vanes of the nozzle ring and the slots of the shroud. The turbine may include an actuator for rotating the shroud relative to the turbine housing about the axis. The actuator may typically be mounted on the turbine housing. In one possibility, the coupling mechanism couples the shroud to the turbine housing via the actuator.

[0019] Generally speaking, the present invention provides a pin member adapted to limit rotational movement of a shroud relative to a turbine casing. In use, at least one of the pin members is inserted into a hole in the turbine casing, which secures the pin member to the turbine casing at a specific angular position about the turbine's axis of rotation. The pin member is a one-piece element comprising a cylindrical body and a head portion having a limiting surface for opposing movement of the shroud.

[0020] The pin member includes a generally cylindrical body defining a pin axis and a head portion located at one end of the cylindrical body and formed integrally with the cylindrical body so that the head portion and the cylindrical body together form a one-piece unit. The head portion has two opposing surfaces: a limiting surface for bearing against a surface of the shield and limiting its rotational movement during use; and a locating surface for locating the pin member.

[0021] The head portion of the pin member has a head surface that is transverse to the pin axis and bounded on one side by the limiting surface and on the other side by the locating surface. In use, a first direction on the head surface that is transverse to the limiting surface and the locating surface and that extends from the limiting surface toward the locating surface is aligned with a circumferential direction of the turbine housing; and a second direction on the head surface that is transverse to the first direction and the pin axis is aligned with a radial direction.

[0022] The span H1 of the limiting surface along the second direction is smaller than the span H2 of the positioning surface. To facilitate this, a recess can be formed at one end of the head surface, extending along the first direction. This gives the head surface a generally L-shape. That is, the head surface can essentially consist of two generally rectangular portions, wherein the first rectangular portion extends further along the second direction than the second rectangular portion. The first rectangular portion can have a larger area than the second rectangular portion. Both the first rectangular portion and the second rectangular portion are bounded by the positioning surface. The opposite edges of the first rectangular portion constitute the limiting surface, and the opposite edges of the second rectangular portion face the recess.

[0023] The span of the locating surface may be designed to be as long as possible in the second direction, which makes it easier to locate the pin member in the turbine housing (as described below), for example by locating the locating surface along the surface of a locating tool used during assembly.

[0024] Conversely, if the limiting surface is too long in the second direction, it has the disadvantage that its end is more likely to impact the shield in use.

[0025] Furthermore, providing the recess reduces the amount of material required to produce the pin member.

[0026] The head portion of the pin member has a span W1 in the first direction that is greater than the span W2 of the second rectangular portion in the first direction. Optionally, the span W1 of the first rectangular portion in the first direction is less than 7 mm, less than 6 mm, less than 5 mm, less than 4 mm or even less than 3 mm.

[0027] The restraining surface may be substantially flat. Alternatively, it may be convex such that if the surface of the shroud that engages the restraining surface is flat (or convex, or concave, but with a radius of curvature greater than the restraining surface of the pin member), contact between the shroud and the restraining surface of the pin member is substantially at a point (e.g., if the restraining surface is a portion of a sphere or ellipsoid) or along a line.

[0028] In practice, it is preferred that the limiting surface has translational symmetry along a direction parallel to the pin axis (i.e. the limiting surface is a portion of a cylinder, but not necessarily a cylinder with a circular cross-section). The surface of the shield against which the head portion of the pin bears may be substantially flat, so that the contact therebetween is a line contact.

[0029] The radius of curvature R of the limiting surface is selected to be greater than (e.g., at least two times, or even at least three times, four times, or even at least five times) the span W1 of the head portion of the pin member in the first direction. For example, it may have a radius R = 22 mm, while W1 may be approximately 4 mm. It should be noted that a smaller R may lead to excessive concentration of forces in the portion of the limiting surface that contacts the shield, thereby causing undesirable wear.

[0030] Preferably, W1, W2, H1, H2 and R satisfy the formula:

[0031]

[0032] The pin member can be formed without internal interfaces (e.g., due to abrupt changes in material composition), for example, by a molding process such as metal injection molding (MIM). Optionally, the limiting surfaces of the pin member can be subjected to a machining operation after molding to improve the accuracy of its shape.

[0033] The material of the pin member may be an alloy including cobalt.

[0034] In another aspect, the present invention provides a combination of a turbine housing for a turbine and defining a central axis that is the axis of rotation of the turbine in use, and at least one pin member as described above. For each pin, a surface of the turbine housing that faces parallel to the axis may be formed with a corresponding aperture that receives the cylindrical body of the pin member. Movement of the pin member into the aperture may be limited by interaction between the surface of the turbine housing and the head portion of the pin member. Preferably, the pin member is retained in the aperture by an interference fit between the outer surface of the cylindrical body and the inwardly facing surface of the aperture. This is sufficient to prevent rotation of the pin within the aperture about the pin axis.

[0035] The hole is preferably not a through hole and may form a chamber to contain gas trapped in the hole when the cylindrical body of the pin member is inserted, such that the pressure of the gas does not become high enough to overcome the force of the interference fit and expel the cylindrical body of the pin member from the hole even at operating temperatures of the turbine housing.

[0036] Preferably, the cylindrical body of the pin member has a circular cross-section to facilitate its manufacture. Similarly, the corresponding inwardly facing surface of the corresponding hole has a circular cross-section in the depth direction of the hole, and its cross-sectional area is only slightly smaller than the cross-sectional area of ​​the cylindrical body of the pin member. In this case, the hole can be conveniently formed by drilling. To form the cavity, the portion of the hole furthest in the depth direction of the hole can have a smaller cross-sectional area, specifically, smaller than the cross-sectional area of ​​the cylindrical body of the pin member.

[0037] In another aspect, the present invention provides a turbine assembly comprising a turbine housing defining a central axis (which in use is the axis of rotation of the turbine) and at least one pin member as described above. Each pin member is insertable into a respective bore of the turbine housing.

[0038] In another aspect, the present invention provides a turbine comprising a turbine housing in combination with one or more pin members as defined above, and a turbine wheel mounted within the turbine housing.

[0039] In another aspect, the invention provides a turbocharger comprising such a turbine.

[0040] In this document, describing two surfaces as being opposite means that they face in substantially opposite directions. That is, the directions of the corresponding normals to the exterior of the surfaces are substantially opposite. Describing a surface or body as "cylindrical" means that it has translational symmetry about an axis, but does not necessarily mean that a cross-section of the surface or body transverse to that axis is circular. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the present invention will now be described for purposes of example only with reference to the following drawings, in which:

[0042] FIG1 consists of FIG1( a ) and FIG1( b ), FIG1( a ) is an axial section of a known variable geometry turbine, and FIG1( b ) is a section of a portion of the turbine of FIG1 ;

[0043] Figure 2 is an axial view of a nozzle ring that may be used in the known arrangement of FIG. 1 ;

[0044] Figure 3 is an axial view of a shroud that may be used with the known arrangement of FIG. 1 ;

[0045] Figure 4 Shown in Figure 2 The nozzle ring and Figure 3 The relationship between the positions of the shields;

[0046] Figure 5 shows a first possible positional relationship between the blades and the shroud in an embodiment of the present invention;

[0047] Figure 6 shows a second possible positional relationship between the blades and the shroud in an embodiment of the present invention;

[0048] Figure 7 shows a third possible positional relationship between the blades and the shroud in an embodiment of the present invention;

[0049] Figure 8 A turbine housing including two pin members according to embodiments of the present invention is shown;

[0050] Figure 9 Depend on Figure 9 (a)- Figure 9 (c) composition, Figure 9 (a)- Figure 9 (c) Yes Figure 8 Perspective views of the pin member from different directions;

[0051] Figure 10 Depend on Figure 10 (a)-10(b), showing Figure 8 The pin member and the turbine housing are viewed from different directions when in use;

[0052] Figure 11 yes Figure 8 a cross-sectional view of the pin member in use; and

[0053] Figure 12 It illustrates how certain parameters of the pin member are defined. Specific embodiments

[0054] refer to Figure 2, a nozzle ring that can be used in the known turbocharger of Figure 1 is shown. The nozzle ring is viewed from the right in the axial direction in Figure 1 (a) (this direction is also referred to herein as "from the turbine end of the turbocharger"), and is viewed at a position between the nozzle ring 5 and the shroud 6.

[0055] Turbine impeller 9 (in Figure 2 1(a)) and the compressor impeller 11 (not shown in FIG. Figure 2 The axis of the axis about which the rotation is made (also not shown but visible in FIG. 1( a )) is indicated as 100 .

[0056] Viewed in this axial direction, the substantially planar annular nozzle ring 5 surrounds the axis 100. The blades 7 project in the axial direction from the nozzle ring 5. By defining a circle 70 centered on the axis 100 and passing through the centroid of the profile of the blades 7, we can define a nozzle radius 71 as the radius of the circle 70.

[0057] The gas moves radially inwardly between the nozzle ring 5 and the shroud 6. In some turbines, the radially outer surface of the blades 7 is the "high pressure" surface, while the radially inner surface of the blades 7 is the "low pressure" surface. In other turbines, these roles are reversed.

[0058] The nozzle ring 5 is actuated by the actuator 16 (at Figure 2 1(a)) in an annular cavity defined by portion 60 of the turbine housing ( Figure 2 Each blade 7 is optionally longitudinally symmetrical (i.e., its profile, when viewed in the axial direction, may be the same in all axial positions), although in some embodiments only portions of the blade 7 are longitudinally symmetrical.

[0059] The actuator exerts a force on the nozzle ring 5 via two axially extending guide rods. Figure 2, portion 32 of the nozzle ring 5 is omitted so that the connection between the nozzle ring 5 and the first of the guide rods can be observed. The guide rod is not shown, but its center is located at the position marked 61. The guide rod is integrally formed with a bracket 33 (commonly called a "foot") that extends circumferentially from the guide rod to either side. The bracket 33 includes two circular holes 62, 63. The surface of the nozzle ring 5 facing away from the shroud 6 is formed with two bosses 34, 64, which protrude from the nozzle ring 6. Each of the bosses 34, 64 has a circular profile (as viewed in the axial direction). The bosses 34, 64 are inserted into the holes 62, 63 respectively, and the dimensions of the bosses 34, 64 are set so that the boss 34 substantially fills the hole 62, while the boss 64 is narrower than the hole 63. The connection between boss 34 and hole 62 fixes the circumferential position of nozzle ring 5 relative to bracket 33 (in a typical implementation, relative circumferential movement of nozzle ring 5 and shroud 6 about axis 100 does not exceed 0.05 degrees). However, if the guide rod moves radially apart due to thermal expansion, the spacing between boss 64 and hole 63 allows bracket 33 to rotate slightly about boss 34. For this reason, boss 34 is referred to as a "pivot."

[0060] The position of the second guide rod connected to the nozzle ring 5 when viewed in the axial direction is shown as 31. The connection between the nozzle ring 5 and the second guide rod is due to a second bracket (in the Figure 2 The second bracket is attached to the rear surface of the nozzle ring 5 in the same manner as bracket 33. The pivot of the second bracket is at position 35.

[0061] Holes 24, 25 are balancing holes provided in the nozzle ring for pressure equalization. They are provided to achieve the desired axial load (or force) on the nozzle ring.

[0062] The nozzle ring 5 is facing the Figure 3 The shield 6 is shown in the figure. Figure 3 This is a view from the nozzle ring 5 looking towards the shroud 6 (i.e., towards the right in FIG1 ). The shroud defines slots 30 (i.e., through-holes) for receiving corresponding ones of the vanes 7. The edge of each slot is an inwardly facing transverse (i.e., transverse to the axis 100) slot surface. It should be noted that in FIG1 , the slots 30 are formed by the nozzle ring 5 and the shroud 6 is ... Figure 7 , the slot 30 is not shown as having Figure 2 The blades 7 have the same profile, but generally the corresponding profiles do have substantially the same shape, although the slots are larger in size than the blades.

[0063] Figure 4Another view, viewed axially from the nozzle ring 5 toward the shroud 6 (i.e., toward the right in FIG. 1( a )), shows a representative blade 7 inserted into a corresponding representative slot 30. Blade 7 has a generally arcuate (crescent-shaped) profile, although in other forms the blade is substantially planar. Specifically, blade 7 has a blade inner surface 41 located closer to the impeller. Blade inner surface 41 is typically generally concave when viewed in the axial direction, but may alternatively be planar. Blade 7 also has a blade outer surface 42 located closer to the exhaust gas inlet of the turbine. Each of blade inner surface 41 and blade outer surface 42 is a major surface of the blade. Blade outer surface 42 is typically convex when viewed in the axial direction, but may also be planar. The major surfaces 41, 42 of blade 7 face in generally opposite directions and are connected by two axially extending end surfaces 43, 44, each of which has a smaller radius of curvature than either surface 41, 42 when viewed in the axial direction. The end surfaces 43 , 44 are referred to as the front edge surface 43 and the rear edge surface 44 , respectively.

[0064] In most arrangements, the blade outer surface 42 is arranged to impede the movement of the exhaust gas inlet passage, i.e., the movement of the exhaust gas in the inlet passage is such that the exhaust gas is directed against the blade outer surface. Consequently, the blade outer surface 42 is typically at a higher pressure than the blade inner surface 41 and is referred to as the "high pressure" (or simply "pressure") surface, while the blade inner surface 41 is referred to as the "low pressure" (or "suction") surface. These are opposed to corresponding portions of the inwardly facing surfaces defining the edges of the slot 30, and the corresponding portions are given the same respective names.

[0065] In some possible arrangements, it is the inner blade surface 41 that changes the direction of the gas flow. In this case, the inner blade surface 41 is generally at a higher pressure than the outer blade surface 42 and is referred to as the "high pressure" (or simply "pressure") surface, while the outer blade surface 42 is referred to as the "low pressure" (or "suction") surface. Again, they are opposite corresponding portions of the inwardly facing surfaces defining the edges of the slot 30, and the corresponding portions are given the same corresponding names.

[0066] When viewed in the axial direction, each blade 7 has a center line 51 extending from one end of the blade to the other end (midway between the blade inner surface 41 and the blade outer surface 42 when viewed in the axial direction), and this center line 51 has a radial component and a circumferential component. We refer to the surface of the slot that the blade inner surface 41 faces as the slot inner surface 46, and the surface of the slot that the blade outer surface 42 faces as the slot outer surface 47. Figure 4As shown, there is a gap of substantially constant width between the periphery of the blade 7 and the surface of the slot 30. This gap comprises four portions: between the blade inner surface 41 and the slot inner surface 46; between the blade outer surface 42 and the slot outer surface 47; and between the leading edge surface 43 and trailing edge surface 44 of the blade and the corresponding leading portion 49 and trailing portion 59 of the edge of the slot. Surfaces 46, 47, 49 and 59 together constitute the inwardly facing slot surfaces that define the slot.

[0067] Steering Figure 5 , a first possible arrangement of positions is shown between the blades and the shroud slots in a turbine of an embodiment of the invention. The turbine has the form illustrated in Figures 1 and 2, with the difference that the blades and / or slots in the shroud are of different shapes and sizes. Figure 5 In Figures 1 to Figure 4 Elements corresponding to elements are given reference numerals 100 greater. Thus, a representative blade 107 is depicted within a representative slot 130. The blade outer surface 142 faces the slot outer surface 147, and the blade inner surface 141 faces the slot inner surface 146. Optionally, the blade 107 may be longitudinally symmetrical along its entire length (i.e., having the same profile when viewed in the axial direction in all axial positions). In another possibility, only a portion of the blade 107 may be axially symmetrical, for example comprising the portion that can be inserted into the slot 130 when the blade 107 is in its most advanced position. In this case, Figure 5 The portion of the blade shown in is part of this axially symmetrical portion of the blade. The blade 107 is formed integrally with the nozzle ring 5 as a one-piece unit, for example by casting and / or machining.

[0068] and Figure 4 Compared with the known leaves, Figure 5 The vanes 107 have a narrower spacing between the vane inner surface 141 and the opposing slot inner surface 146. By contrast, there is a wider gap between the vane outer surface 142 and the corresponding portion 147 of the slot outer surface 147. This means that exhaust gas entering the shroud recess 8 between the outer vane surface 142 and the slot outer surface 147 is largely prevented from exiting the shroud recess between the vane inner surface 141 and the slot inner surface 146.

[0069] To encourage this effect, the blade and slot surfaces are formed with conformal portions 145 that extend along at least about 15%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, or at least about 80%, or even at least about 85% or 90% of the length of the centerline 151. Figure 5 As shown in the figure, Figure 5Conformal portion 145 of the blade surface comprises substantially all of blade inner surface 141. The profile (i.e., shape when viewed in the axial direction) of blade inner surface 141 and the corresponding portion of slot inner surface 146 are sufficiently similar to one another that they can be positioned against one another along the entire length of conformal portion 145, with a very small (e.g., negligible) gap therebetween. Specifically, the profile of blade inner surface 141 and the corresponding portion of slot inner surface 146 at room temperature allow them to be positioned against one another, with the gap therebetween (e.g., transverse to centerline 151) not exceeding 0.35% of nozzle radius 71, and preferably not exceeding 0.2% or 0.1% of nozzle radius 71. Averaged over conformal portion 145 of the blade surface, the gap between blade inner surface 141 and slot inner surface 146 is no more than 20%, or no more than 10%, of the gap between blade outer surface 142 and slot outer surface 147. The leading edge surface 143 of the blade is spaced apart from the corresponding portion of the inner surface of slot 149.

[0070] Steering Figure 6 , a second possible position arrangement is shown between the blades 207 and the shroud 230 slots in a turbine of an embodiment of the present invention. Figure 5 Elements having the same meaning are given reference numerals 100 greater. The blade surface and the slot surface are formed with a conformal portion 245 extending along at least about 90% of the length of the centerline 251. Figure 6 The conformal portion 245 of the mid-blade surface includes substantially all of the blade inner surface 241 and also includes a majority of the blade front end surface 243 facing the slot front edge surface 249. At room temperature, the profiles of the blade inner surface 241 and the corresponding portion of the slot inner surface 246 are substantially identical within machining tolerances, allowing them to rest against each other with substantially no gap therebetween along the entire length of the conformal portion 245. There is a gap between the outer surface 242 of the blade 207 and the facing portion 247 of the slot 230.

[0071] Steering Figure 7A third possible positional arrangement is shown between blade 307 and shroud slot 330 in a turbine according to an embodiment of the present invention. In this arrangement, conformal portion 345 of blade 307 is at blade outer surface 342, and similarly, conformal portion 345 of slot 330 is at slot outer surface 347. Conformal portion 345 of blade 307 includes the majority of blade 307's outer surface 342, which rests on slot outer surface 347 for at least 90% of its length along centerline 351. It also includes aft surface 344, which rests on a corresponding portion 359 of the slot edge, to a point radially inward of the intersection of centerline 351 and aft surface 344. This positional arrangement hinders gas flow from outer surface 342 to inner surface 343 of blade 307 by substantially preventing gas leakage between blade outer surface 342 and slot outer surface 347.

[0072] exist Figure 5 、 Figure 6 and Figure 7 In the relationship between the positions of the blades 107, 207, 307 and the shroud, if there is a different thermal expansion between the blades 107, 207, 307 and the shroud (for example, because they are formed of different materials and / or experience different temperatures), the conformal portion of the blades 107, 207, 307 can be forced against the slot inner surface 146, 246 or the slot outer surface 347. The friction between them can then prevent axial movement of the blades relative to the shroud. However, even if the nozzle ring and shroud are mounted in a "fixed" angular position as in the system of FIG. 1, there will still be some degree of freedom in the system (for example, due to the nozzle ring 5 to Figure 2 , the nozzle ring may have a certain inherent freedom to rotate about the axis 100), and through experimentation we have found that this can be up to 0.05°. This will allow the blades 107, 207, 307 to be retracted from the conformal portion of the surface of the slot by a certain span. However, the span of this retraction will be limited and, as it depends on the tolerances of the components, may not be consistent from one turbine unit to another. To this end, the shroud 6 is rotatable about the axis of rotation at least through a certain axial interval greater than 0.05° and typically greater than at least 0.1°. However, it is not desirable for the shroud to rotate completely freely relative to the turbine housing, for example because it may cause wear between the shroud and the turbine housing.

[0073] A pin member according to an embodiment of the present invention will now be described, and is used in a turbine in which a shroud is arranged to rotate relative to a turbine casing about the turbine's axis of rotation. At least one pin member of this type is provided in the turbine to limit the rotational range of the shroud.

[0074] refer to Figure 8, a turbine housing 51 is shown coupled to two pin members 52. As described below, each pin member 52 comprises a cylindrical body that is inserted into a correspondingly shaped hole in the surface of the turbine, the hole facing in a direction parallel to the turbine's axis of rotation.

[0075] Figure 9 (a)-(c) illustrate the pin member 52 from three different perspectives. The pin member 52 comprises a cylindrical body 53 and a head portion 54. The cylindrical body has a central "pin" axis 60 that, in use, is substantially parallel to the turbine's axis of rotation. The head portion 54 has a head surface 55 that is transverse to the pin axis 60. The head surface 55 is generally L-shaped and includes, or may consist essentially of, a first generally rectangular portion 56 and a second generally rectangular portion 57. The area of ​​the first rectangular portion 56 is greater than the area of ​​the second rectangular portion 57. The second rectangular portion 57 extends further than the first rectangular portion 55 in a second direction y. The second direction is transverse to the pin axis 60 and, in use, is arranged to extend radially from the turbine's axis of rotation. It should be noted that, from another point of view, the head portion 54 can be viewed as a cuboid minus the generally cuboid recess 75. Any or all edges and corners of the pin member 52 are beveled, rounded, or otherwise smoothed to avoid sharp corners; references herein to surfaces ignore this effect and treat the surfaces as if they extended to the sharp corners.

[0076] The pin member 52 may be formed by molding, preferably by a process that does not create transitions (interfaces) within the pin member 52. The molding material may be a cobalt alloy.

[0077] The diameter of the cylindrical body can be selected based on the distance from the axis of rotation to the pin axis 60 (i.e., half the pitch circle diameter (PCD)). Through experimentation, it has been found that the diameter d of the cylindrical body that provides sufficient strength for the pin without requiring unnecessary material is given by d = A × PCD to within 10% accuracy, where A = 0.035. For example, in the case of a PCD of 115 mm, the cylindrical body can have a diameter of substantially 4 mm, for example, 4 mm to within 0.4 mm accuracy.

[0078] The rectangular portions 56, 57 are each delimited by a substantially flat positioning surface 58. The surface of the head portion opposite the positioning surface 57 is a limiting surface 59, which forms one side of the first rectangular portion 55. The limiting surface may be translationally symmetrical parallel to the pin axis 60.

[0079] The positioning surface 58 and the limiting surface 59 are along Figure 9 The first direction shown as x in (c) is spaced apart. The first direction is transverse to the locating surface 58, the pin axis 60 and the second direction y.

[0080] Steering Figure 10 (a) In use, the cylindrical body 53 of the pin member 52 is inserted into the generally cylindrical bore 71 of the axially facing surface 61 of the turbine housing, leaving only the head portion 54 of the pin member 52 exposed. In this configuration, the pin axis 60 coincides with the turbine's axis of rotation, so both directions are referred to as "axial." The second direction y may extend in a radial direction away from the turbine's axis of rotation, while the first direction x may extend circumferentially around the axis of rotation. Thus, the locating surface 58, like the limiting surface 59, faces generally circumferentially, at least at its point 73 furthest from the locating surface 58.

[0081] Figure 10 (b) is a view viewed in the axial direction at the pin member 52 inserted into the hole 71. This view shows the two shroud edge portions 62, 72 of the shroud 70. The shroud 70 is rotatable about the turbine axis and has a limiting surface 63 for impacting the limiting surface 59 of the pin member 52. It should be noted that the rotation of the shroud 70 is additionally limited by its collision with the blades, so that the shroud 70 does not impact the positioning surface 58 of the head portion 54 of the pin member 52.

[0082] The shield 70 defines a gap 65 between the shield edge portions 62, 72. The head portion 54 of the pin member 52 is located in the gap. Therefore, the pin member 52 prevents the shield 70 from moving along the Figure 10 (b) is rotated counterclockwise over a certain angular amount. It should be noted that this is achieved without requiring high tolerances in the shape of the shroud rim portions 62, 72. This is because the exact circumferential span of the gap 65 is irrelevant. Assuming that the gap 65 is significantly larger than the circumferential span of the head portion 54 of the pin member 54 (e.g., at least 50% larger), the pin member 52 can be easily inserted into the hole 71 when the shroud 70 is attached to the turbine housing 1; or conversely, the shroud 70 can be easily assembled to the turbine housing when the pin member(s) 52 are already inserted into the hole(s) 71. Only the surface 63 of the shroud rim portion 62 impacts the limiting surface 59 of the pin member 52.

[0083] Figure 11 FIG2 is a cross-sectional view of the turbine housing when the turbine housing supports the shroud 70. The bearing housing and nozzle ring are omitted. The radially inner portion of the shroud 70 defines a frame having an inner annular wall 66 and an outer annular wall 67. A retaining ring 68 is positioned between the annular walls 66, 67. The retaining ring 68 extends radially inwardly beyond the gap between the annular walls 66, 67, and its inner portion is retained by an annular lip 69 of the turbine housing. It has been found that providing the retaining ring 68 on the radially inner portion of the shroud 70 provides excellent resistance to gas leakage at the radially inner edge of the shroud 70.

[0084] The cylindrical body 53 of the pin member is inserted into a corresponding bore 71 defined by the turbine housing. A chamber 72 is provided in the interior of the bore 71 to prevent the pressure of any trapped gas from becoming too high during operation of the turbine and thereby forcing the pin 52 out of the bore 71.

[0085] Steering Figure 12 , defining parameters H1, H2, W1, W2, and R, where R is the radius of curvature of the limiting surface 59. Distance W1 is measured from the substantially flat locating surface 58, along a transverse first direction x, to a point 73 on the limiting surface 59 that is furthest from the locating surface 58. The radius of curvature of the cylindrical limiting surface 59 at point 73 is R. R is greater than the span W1 of the head portion of the pin member along the first direction x. W1 is greater than the span W2 of the head portion 57, the smaller rectangular portion of the pin member 52, along the first direction x.

[0086] Ideally,

[0087]

Claims

1. A pin member adapted to limit rotational movement of a shroud relative to a turbine casing, the pin member comprising a generally cylindrical body defining a pin axis and a head portion at one end of the cylindrical body, the head portion being integrally formed with the cylindrical body such that the head portion and the cylindrical body together form a one-piece unit, the head portion having a limiting surface and an opposing locating surface, the limiting surface being adapted to bear against a surface of the shield in use and limit rotational movement thereof, the locating surface being adapted to locate the pin member, the limiting surface and the locating surface being spaced apart from each other in a first direction; the head portion of the pin member having a head surface transverse to the pin axis, the head surface being bounded on one side by the limiting surface and on the other side by the locating surface, The span H1 of the limiting surface along the second direction transverse to the first direction and the pin axis is smaller than the span H2 of the positioning surface along the second direction. The limiting surface is convex.

2. The pin member according to claim 1, wherein The head surface is substantially composed of a first and a second rectangular portion, wherein the first rectangular portion is further along the second direction than the second rectangular portion, the first rectangular portion has a larger area than the second rectangular portion, and the first and second rectangular portions are both defined by a positioning surface.

3. The pin member according to claim 2, wherein The head portion of the pin member has a span W1 in a first direction that is larger than a span W2 in the second rectangular portion in the first direction.

4. The pin member according to claim 2, wherein The limiting surface has translational symmetry parallel to the pin axis, and the limiting surface has a radius of curvature R.

5. The pin member according to claim 4, wherein A curvature radius R of the limiting surface is greater than a span W1 of the head portion of the pin member in the first direction.

6. The pin member according to claim 4 or claim 5, wherein the head portion of the pin member has a span W1 in a first direction that is larger than a span W2 in the second rectangular portion in the first direction, W1, W2, H1, H2 and R satisfy the formula: 。 7. The pin member according to claim 1, wherein The pin member has no internal jumps. 8 . The pin member according to claim 1 , wherein the pin member is composed of an alloy containing cobalt.

9. The pin member according to claim 1, wherein The cylindrical body has a diameter of substantially 4 mm.

10. A combination of a turbine housing for a turbine and defining a central axis which, in use, is the axis of rotation of the turbine, and at least one pin member according to any one of claims 1 to 5.

11. The combination according to claim 10, wherein Each pin member is located in a corresponding bore of the turbine housing.

12. The combination according to claim 10, wherein The pin member has a circular cross-section with a diameter d given to within 10% by d = A x PCD, where A = 0.035 and PCD is twice the distance from the pin axis to the central axis.

13. The combination according to claim 11, wherein The pin member does not fill the cavity of the bore, whereby the pressure of any gas trapped within the bore is reduced when the cylindrical body of the pin member is located in the bore.

14. A turbine comprising the combination according to claim 10 and a turbine wheel mounted in the turbine housing.

15. A turbocharger comprising the turbine according to claim 14 and a compressor driven by the turbine.

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