Inlet regulating mechanism for turbocharger compressor having sealing device to prevent recirculation and / or oil transfer into the mechanism

Abstract

The turbocharger compressor includes an inlet adjustment mechanism operable to move between an open position and a closed position. The mechanism includes a plurality of movable vanes disposed around the compressor air inlet and between the upstream wall surface and the downstream wall surface of the annular space within the air inlet wall. When the vanes are in the closed position, the vanes move radially inward from the annular space into the air inlet to form an orifice of reduced diameter relative to the nominal diameter of the inlet. Recirculation of air upstream through the mechanism is prevented by downstream vane seals. When EGR is employed, upstream vane seals are included to prevent oil-laden air from being transferred into the mechanism. The vane seals may be of various types, including O-ring type seals or labyrinth seals.

Description

Technical Field

[0001] The present disclosure relates to centrifugal compressors, such as those used in turbochargers, and more particularly to centrifugal compressors whose effective inlet area or diameter can be adjusted for different operating conditions. Background Art

[0002] An exhaust-driven turbocharger is a device used in conjunction with an internal combustion engine that increases the power output of the engine by compressing air delivered to the air intake of the engine to mix with fuel and burn in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and another center housing is connected between the turbine housing and the compressor housing for accommodating the bearings of the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle leading from the chamber to the turbine wheel. Exhaust gas flows from the chamber to the turbine wheel through the nozzle and the turbine wheel is driven by the exhaust gas. Thus, the turbine extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through the inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

[0003] Turbochargers typically employ a centrifugal (also called "radial") type compressor wheel because centrifugal compressors can achieve relatively high pressure ratios in a compact arrangement. Intake air for the compressor is received at an inlet inducer portion of a centrifugal compressor wheel in a generally axial direction and is discharged at an outlet inducer portion of the wheel in a generally radial direction. Compressed air from the wheel is delivered to a volute, and from the volute the air is supplied to the intake of an internal combustion engine.

[0004] The operating range of the compressor is an important aspect of the overall performance of the turbocharger. The operating range is typically defined by a surge line and a choke line on an operating map of the compressor. A compressor map is typically represented as pressure ratio (discharge pressure Pout divided by inlet pressure Pin) on the vertical axis versus corrected mass flow rate on the horizontal axis. The choke line on the compressor map is located at high flow rates and represents the locus of maximum mass flow rate points over a range of pressure ratios; that is, for a given point on the choke line, it is not possible to increase the flow rate while maintaining the same pressure ratio because a choked flow condition occurs in the compressor.

[0005] The surge line is located at low flow rates and represents the locus of the minimum mass flow rate points over a range of pressure ratios at which surge does not occur; that is, for a given point on the surge line, either decreasing the flow rate without changing the pressure ratio or increasing the pressure ratio without changing the flow rate will cause surge to occur. Surge is a flow instability that typically occurs when the compressor blade incidence angle becomes so large that a large amount of flow separation occurs over the compressor blades. During surge, pressure fluctuations and reverse flow can occur.

[0006] In a turbocharger for an internal combustion engine, compressor surge may occur when the engine is operating at high load or torque and low engine speed or when the engine is operating at low speed and there is a high level of exhaust gas recirculation (EGR). Surge can also occur when the engine is suddenly decelerated from a high speed state. Extending the compressor's surge-free operating range to lower flow rates is often a goal pursued in compressor design.

[0007] Applicant's co-pending U.S. Patent Application No. 15 / 446,054, filed on March 1, 2017, which claims the benefit of the filing date of Provisional Application No. 62 / 324,488, filed on April 20, 2016, the entire disclosure of which is hereby incorporated by reference, describes a mechanism and method for a centrifugal compressor that can cause the surge line of the compressor to be selectively moved to the left (i.e., delaying surge to a lower flow rate at a given pressure ratio), and which claims the benefit of the filing date of Provisional Application No. 62 / 324,488, filed on April 20, 2016, the entire disclosure of which is hereby incorporated by reference. One embodiment described in said application includes a turbocharger having the following features:

[0008] a turbine housing, and a turbine wheel mounted in the turbine housing and connected to the rotatable shaft for rotation therewith, the turbine housing receiving the exhaust gas and supplying the exhaust gas to the turbine wheel;

[0009] a centrifugal compressor assembly including a compressor housing, and a compressor wheel mounted in the compressor housing and connected to a rotatable shaft for rotation therewith, the compressor wheel having blades and defining an inlet inducer portion, the compressor housing having an air inlet wall defining an air inlet for directing air generally axially into the compressor wheel, the compressor housing further defining a volute for receiving compressed air discharged generally radially outwardly from the compressor wheel; and

[0010] A compressor inlet adjustment mechanism is disposed in the air inlet of the compressor housing and is pivotable radially inward and radially outward between an open position and a closed position, the inlet adjustment mechanism comprising a plurality of vanes disposed around the air inlet and each pivotable about one end of the vane, wherein when the vanes are in the closed position, the vanes are pivoted radially inward through slots in the air inlet wall to form an orifice of reduced diameter relative to a nominal diameter of the inlet.

[0011] Applicant is also the owner of additional applications related to other inlet adjustment mechanisms employing moving vanes, including U.S. Application No. 15 / 446,090 filed on March 1, 2017, the entire disclosure of which is incorporated herein by reference.

[0012] The present disclosure relates to inlet adjustment mechanisms generally of the type described in the aforementioned '054, '488 and '090 applications, and in particular to the modification or redesign of such mechanisms with the goal of improving certain aspects of the mechanisms. Summary of the invention

[0013] One such aspect of the aforementioned inlet regulating mechanisms that seeks improvement relates to the tendency of air to leak upstream through the mechanism and back into the air inlet when the vanes are moved to the closed position. This leakage or "flow recirculation" significantly reduces overall compressor efficiency.

[0014] Another such area where improvement is sought involves engine / turbocharger systems that employ exhaust gas recirculation (EGR) as a means of reducing nitrous oxide emissions. The exhaust gas recirculated back to the compressor inlet contains oil, which tends to transfer into the inlet conditioning mechanism, which can foul the mechanism and cause operating problems.

[0015] The present disclosure addresses the above-mentioned aspects of an inlet adjustment mechanism for a turbocharger.

[0016] According to one embodiment disclosed herein, a turbocharger having the following features is described:

[0017] a turbine housing, and a turbine wheel mounted in the turbine housing and connected to the rotatable shaft for rotation therewith, the turbine housing receiving the exhaust gas and supplying the exhaust gas to the turbine wheel;

[0018] a centrifugal compressor assembly including a compressor housing, and a compressor wheel mounted in the compressor housing and connected to a rotatable shaft for rotation therewith, the compressor wheel having blades and defining an inlet inducer portion, the compressor housing having an air inlet wall defining an air inlet for directing air generally axially into the compressor wheel, the compressor housing further defining a volute for receiving compressed air discharged generally radially outwardly from the compressor wheel, the air inlet wall defining an annulus surrounding the air inlet and opening into the air inlet at a radially inner end of the annulus; and

[0019] a compressor inlet adjustment mechanism disposed in an annular space of the air inlet wall and movable between an open position and a closed position, the inlet adjustment mechanism comprising a plurality of vanes disposed in the annular space between an upstream wall surface and a downstream wall surface, the vanes collectively surrounding the orifice, the upstream surface of each vane opposing the upstream wall surface and the downstream surface of each vane opposing the downstream wall surface, the vanes being movable inwardly from the annular space into the air inlet when the vanes are in the closed position so as to cause the orifice to have a reduced diameter relative to a nominal diameter of the inlet; and

[0020] at least one upstream vane seal formed between an upstream wall surface and an upstream sealing surface defined by each vane when the vanes move inwardly to a closed position, and a downstream vane seal formed between a downstream wall surface and a downstream sealing surface defined by each vane when the vanes move inwardly to a closed position.

[0021] In one embodiment, the upstream vane seal includes an upstream sealing ring supported by the upstream wall; the upstream sealing surface of each vane contacts and seals against the upstream sealing ring when the vanes move inwardly to the closed position.

[0022] In one embodiment, the downstream vane seal includes a downstream sealing ring supported by a downstream wall surface; the downstream sealing surface of each vane contacts and seals against the downstream sealing ring when the vanes move inwardly to the closed position.

[0023] In another embodiment, the upstream vane seal comprises a labyrinth seal wherein one of the upstream wall surface and the upstream sealing surface of each vane defines a groove and the other of the upstream wall surface and the upstream sealing surface defines a tongue that fits into the groove when the vanes move inwardly to the closed position.

[0024] In one embodiment, the downstream vane seal comprises a labyrinth seal wherein one of the downstream wall surface and the downstream sealing surface of each vane defines a groove and the other of the downstream wall surface and the downstream sealing surface defines a tongue that fits into the groove when the vanes move inwardly to the closed position.

[0025] In one embodiment, there are only downstream vane seals that prevent or significantly reduce leakage flow in the upstream direction through the inlet conditioning mechanism (also referred to herein as "flow recirculation") back into the air inlet.

[0026] In another embodiment, only upstream vane seals are present, which prevent or significantly reduce the transfer of oil-laden air into the inlet regulating mechanism when the turbocharger is used in an engine system that includes exhaust gas recirculated to the compressor.

[0027] In further embodiments, the inlet adjustment mechanism includes both an upstream vane seal and a downstream vane seal.Thus, both flow recirculation and oil transfer are prevented or significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Having therefore generally described the invention, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0029] Figure 1 is an end view of a turbocharger according to the present invention excluding a vane seal, looking axially from the compressor end to the turbine end of the turbocharger;

[0030] Figure 2 yes Figure 1 A cross-sectional view of the turbocharger taken along line 2-2;

[0031] Figure 3 is a partial exploded view of a compressor portion of a turbocharger according to an embodiment of the present invention;

[0032] Figure 4 yes Figure 3 an enlarged view of the compressor portion of the compressor with the compressor cover (inlet duct member) exploded to make the inlet adjustment mechanism visible;

[0033] Figure 5 yes Figure 3 an axial cross-sectional view of a compressor portion of the embodiment of the present invention with the inlet adjustment mechanism in a closed position so as to cause the vanes to engage the sealing ring of the vane seal;

[0034] Figure 6 is with Figure 5 a similar axial view of a compressor section and an inlet regulating mechanism in a closed position, but wherein the inlet regulating mechanism lacks a vane seal;

[0035] Figure 7 yes Figure 5 , showing more clearly the structure and function of the blade seal; and

[0036] Figure 8 is with Figure 7 Similar views show another embodiment of the invention having a labyrinth seal rather than an O-ring type seal. DETAILED DESCRIPTION

[0037] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals represent like elements throughout.

[0038] In this disclosure, the term "orifice" refers to an "opening" regardless of the shape of the opening. Thus, an "orifice" may be circular or non-circular. In addition, when the vanes of an inlet adjustment mechanism are described as moving "radially" inwardly or outwardly, the term "radial" does not exclude some non-radial component of movement of the vanes (e.g., the vanes may occupy a plane that is slightly angled relative to the axis of rotation of the compressor, so that as the vanes pivot radially inwardly and outwardly, they also move with a small axial component of motion). When referring to vane seals, "upstream" and "downstream" refer to the predominant flow direction in the compressor inlet, whereby "downstream" refers to the axial direction in which air normally travels toward the compressor wheel, and "upstream" refers to the direction axially opposite to the "downstream" direction.

[0039] Figure 1 1 shows a turbocharger 10 of the type to which the invention is applicable but without a vane seal according to the invention in an axial end view, and Figure 2 15 / 806,267 filed on November 7, 2017, the entire disclosure of which is incorporated herein by reference. The turbocharger includes a compressor and a turbine. The compressor includes a compressor wheel or impeller 14 mounted on one end of a rotatable shaft 18 in a compressor housing 16. The compressor housing includes walls defining an air inlet 17 for directing air generally axially into the compressor wheel 14. The shaft is supported in bearings mounted in a center housing 20 of the turbocharger. The shaft is rotated by a turbine wheel 22 mounted on the other end of the shaft spaced from the compressor wheel, thereby rotatably driving the compressor wheel, which compresses air drawn through the compressor inlet and discharges the compressed air generally radially outward from the compressor wheel into a volute 21 for receiving the compressed air. The air is directed from the volute 21 to the intake of an internal combustion engine (not shown) for improving the performance of the engine.

[0040] The turbine wheel 22 is disposed within a turbine housing 24 which defines an annular chamber 26 for receiving exhaust gas from an internal combustion engine (not shown). The turbine housing further defines a nozzle 28 for directing the exhaust gas from the chamber 26 generally radially inwardly to the turbine wheel 22. The exhaust gas expands as it passes through the turbine wheel and rotatably drives the turbine wheel which in turn rotatably drives the compressor wheel 14, as already mentioned.

[0041] Reference Figure 1 and Figure 2 In the illustrated embodiment, the wall defining the air inlet 17 is formed in part by the compressor housing 16 and in part by a separate cover or inlet duct member 16d which is received in a cylindrical receiving portion defined by the compressor housing. The portion of the air inlet 17 proximate the compressor wheel 14 defines a generally cylindrical inner surface 17i having a diameter generally matching the diameter of the inlet inducer portion 14i of the compressor wheel.

[0042] The compressor housing 16 defines a shroud surface 16s that is immediately adjacent the radially outer tips of the compressor blades. The shroud surface defines a curved profile that is generally parallel to the profile of the compressor wheel.

[0043] The compressor of the turbocharger includes an inlet adjustment mechanism 100 disposed in the air inlet 17 of the compressor housing. The inlet adjustment mechanism includes an annular assembly and is disposed in an annular space defined between the compressor housing 16 and a separate inlet duct member 16d. The annular space is confined between an upstream wall surface 105 and a downstream wall surface 107 (see Figure 6 ). The inlet adjustment mechanism is operable to adjust the effective diameter of the air inlet into the compressor wheel. As such, the inlet adjustment mechanism is movable between an open position and a closed position, and may be configured to be adjusted to various points between the positions.

[0044] Reference Figure 1 , the inlet adjustment mechanism includes a plurality of vanes 102 disposed about a central axis of the air inlet and each pivotable about a pivot pin located at or near one end of the vane. In the illustrated embodiment, the pivot pin for the vane is secured in a downstream wall surface 107 of the compressor housing. The vanes are disposed between the upstream wall surface 105 and the downstream wall surface 107 with a small amount of axial clearance or play for the vanes between those wall surfaces so that the vanes can pivot freely without binding.

[0045] The inlet adjustment mechanism also includes a unison ring 106 for applying pivotal movement to the vanes. The unison ring surrounds the assembly of vanes 102 and is substantially coplanar with the vanes and is rotatable about an axis that coincides with the axis of rotation of the compressor wheel. The unison ring includes a plurality of recesses in its radially inner periphery, and each vane includes an end portion that is engaged in a respective one of the recesses. Thus, rotation of the unison ring in one direction causes the vanes 102 to pivot radially inwardly, and rotation of the unison ring in the other direction causes the vanes to pivot radially outwardly. The assembly of the vanes 102 and the unison ring 106 is captively held between the upstream wall surface 105 and the downstream wall surface 107.

[0046] The radially inner edges of the blades 102 include portions that are preferably generally arcuate in shape, and these edges collectively surround and define a generally circular opening or aperture (although the degree of roundness may vary depending on the location of the blade, as will be further described below).

[0047] The range of pivotal movement of the vanes is sufficient so that the vanes can be pivoted radially outwardly (by rotation of the unison ring in one direction) to an open position in which the vanes are completely within the inner surface 17i of the inlet ( Figure 2 ). Thus, in the open position of the vanes, the inlet adjustment mechanism does not modify the nominal inlet diameter defined by the inlet surface 17i.

[0048] The vanes may also be pivoted radially inwardly (by rotation of the unison ring in the opposite direction) to a closed position, e.g. Figure 2 and Figure 6 . In the closed position, the arcuate edges along the radially inner side of the blades together form an orifice that is substantially circular and has a diameter that is less than the diameter of the inlet surface 17i. (“Substantially circular” in this disclosure means that the arcuate edges are all located on the same circle and together occupy at least 80% of the circumference of the circle.) As a result, the effective diameter of the inlet is reduced relative to the nominal inlet diameter. Therefore, the inlet adjustment mechanism further reduces the effective diameter of the inlet relative to the closed position. In this way, the inlet adjustment mechanism can adjust the air inlet to approach the effective diameter of the compressor wheel.

[0049] As previously described, the vanes 102 are actuated to pivot between their open and closed positions by a unison ring 106 rotatable about the central axis of the air inlet. Figure 1, a rotational motion is applied to the unison ring by an actuator 116 which is received in a receiving portion defined in the compressor housing. The actuator includes an actuating rod which extends through a space defined in the compressor housing and is attached at its distal end to a pin which engages a slot in the outer periphery of the unison ring 106. The actuator is operable to linearly extend and retract the rod along its length so as to rotate the unison ring 106 and thereby actuate the vanes 102. Extending the rod pivots the vanes toward the closed position, and retracting the rod pivots the vanes toward the open position.

[0050] As noted, the inlet adjustment mechanism 100 enables adjustment of the effective size or diameter of the inlet into the compressor wheel 14. Figure 2 As shown in , when the inlet adjustment mechanism is in the closed position, the effective diameter of the inlet into the compressor wheel is determined by the inside diameter defined by the vanes 102. To achieve this effect, the axial separation distance between the vanes and the compressor wheel must be as small as practical so that there is insufficient distance downstream of the vanes for the air to expand to the full diameter of the inlet inducer portion of the compressor wheel 14 when it encounters it. Thus, the inlet diameter is effectively reduced to a value that is dependent on the vanes.

[0051] At low flow rates (e.g., low engine speeds), the inlet adjustment mechanism 100 may be placed Figure 2 and Figure 6 The compressor wheel is then moved to a closed position in the compressor wheel. This may have the effect of reducing the effective inlet diameter and therefore increasing the flow velocity into the compressor wheel. The result will be a reduction in the compressor blade incidence angle, effectively stabilizing the flow (i.e., making blade stall and compressor surge less likely). In other words, the compressor surge line will be moved to a lower flow rate (to the left of the compressor pressure ratio versus flow rate graph).

[0052] At medium and high flow rates, the inlet adjustment mechanism 100 may be partially or fully opened. This may have the effect of increasing the effective inlet diameter so that the compressor regains its high flow performance and choke flow essentially as if the inlet adjustment mechanism was not present and as if the compressor had a conventional inlet matching the wheel diameter at the inlet inducer portion of the wheel.

[0053] As pointed out above, Figure 1 , Figure 2 and Figure 6 The figure shows a turbocharger which does not include a vane seal according to the invention. Figure 6 , a phenomenon that has been mentioned by the applicant is that, under operating conditions close to surge, when the inlet regulating mechanism such as Figure 6When closed to reduce or eliminate the possibility of surge, a portion of the air approaching the compressor wheel can be recirculated into the cavity of the inlet adjustment mechanism through the gap between the downstream surface of the blade 102 and the downstream wall surface 107, and then returned to the inlet 17 of the compressor via the gap between the upstream surface of the blade 102 and the upstream wall surface 105. Figure 6 This recirculation is generally indicated by the curved arrows 110 in FIG. Such flow recirculation can significantly reduce overall compressor efficiency.

[0054] Reference Figure 3 , Figure 4 , Figure 5 and Figure 7 , illustrates a first embodiment of the present invention having one or more vane seals for the vanes 102 of the inlet regulating mechanism. More specifically, with reference to Figure 7 , the illustrated embodiment includes an upstream vane seal 115 and a downstream vane seal 117, each of which includes an O-ring type seal. The upstream vane seal 115 includes an upstream sealing ring Su supported by the upstream wall surface 105, and an upstream sealing surface 103u defined by each vane 102. When the vanes move inwardly to the closed position, the upstream sealing surface 103u of each vane contacts the upstream sealing ring Su and seals against the upstream sealing ring Su, as shown in FIG. Figure 7 as shown in .

[0055] The downstream vane seal 117 includes a downstream seal ring Sd supported by the downstream wall surface 107, and a downstream sealing surface 103d defined by each vane 102. When the vanes move inwardly to the closed position, the downstream sealing surface 103d of each vane contacts the downstream seal ring Sd and seals against the downstream seal ring Sd, as shown in FIG. Figure 7 as shown in .

[0056] In the first embodiment, the upstream wall 105 defines a portion 105p extending in a direction having a downstream axial direction component, and the upstream sealing ring Su is supported on the radially outer side of the portion 105p, such as being retained in an annular groove formed in the portion, as shown. Correspondingly, each vane 102 defines a portion extending with the upstream axial direction component on its upstream side, and the upstream sealing surface 103u is defined by the portion, so that when each vane is in the closed position, the upstream sealing surface will engage the upstream sealing ring.

[0057] Similarly, in the illustrated embodiment, the downstream wall 107 defines a portion 107p extending in a direction having an upstream axial direction component, and the downstream sealing ring Sd is supported on the radially outer side of the portion 107p, such as being retained in an annular groove formed in the portion, as shown. Correspondingly, each vane 102 defines a portion extending with the downstream axial direction component on its downstream side, and the downstream sealing surface 103d is defined by the portion, so that when each vane is in the closed position, the downstream sealing surface will engage the downstream sealing ring.

[0058] Alternatively, one or both of the upstream wall 105 and the downstream wall 107 may be free of the axially extending portions 105p and 107p, and one or both of the sealing rings Su and Sd may be supported in an annular groove formed in the radially extending portion of the wall 105 and / or 107. The radially extending face of the blade 102 may engage the sealing ring supported in this manner to form a blade seal.

[0059] However, it will be appreciated that the blade seals 115 and 117 according to the present invention may have any of a variety of configurations. For example, Figure 8 A second embodiment of the invention is illustrated which does not have an O-ring type seal. Specifically, the vane seals 115 and 117 in this embodiment are labyrinth seals which function by creating a narrow and tortuous path for the leakage flow to prevent such leakage. Thus, each labyrinth seal 115, 117 comprises a groove and a corresponding tongue or rib which fits into the groove when the vane is in the closed position, such as Figure 8 In the illustrated embodiment, the groove of the upstream seal is formed in the portion 105P of the upstream wall surface, and the tongue of the upstream seal is formed on the portion of the blade 102 extending axially upstream. Similarly, the groove of the downstream seal is formed in the portion 107p of the downstream wall surface, and the tongue of the downstream seal is formed on the portion of the blade extending axially downstream. Alternatively, the portions 105p and 107p may define the tongue, and the blade may define the groove.

[0060] The downstream vane seal 117 effectively reduces or eliminates flow recirculation when the vanes 102 are closed (see Figure 6 110 ) and may be used alone (ie in the absence of upstream blade seals 115 ) for this purpose.

[0061] The upstream vane seal 115 has the advantage of targeting causes other than the flow recirculation phenomenon. When the turbocharger according to the present invention is applied to an engine-turbocharger system including exhaust gas recirculation (EGR) to reduce nitrogen oxide emissions under certain operating conditions (which tend to occur when it is desired to close the inlet adjustment mechanism 100), the oil-containing exhaust gas introduced into the compressor inlet can be transferred to the cavity of the inlet adjustment mechanism. Contamination of the mechanism with oil can then occur. The upstream vane seal according to the present invention can reduce or eliminate such transfer of oil into the inlet adjustment mechanism.

[0062] According to some embodiments of the present invention, the turbocharger may include only the downstream vane seal 117 without including the upstream vane seal 115. In other embodiments, the turbocharger may include only the upstream vane seal without including the downstream vane seal. In still other embodiments, such as specifically in Figure 7 As shown in , a turbocharger may include two types of vane seals.

[0063] The technical personnel of the field to which these inventions belong, who benefit from the teachings set forth in the foregoing description and the related drawings, will think of many modifications and other embodiments of the invention set forth herein. For example, although the illustrated embodiment employs three blades 102, the invention is not limited to any specific number of blades. The invention can be practiced with as few as two blades or as many as 12 or more blades. The more blades there are, the closer the opening surrounded by the blades can be to a circle (although, generally speaking, the opening can be circular in only one position of the blade). Therefore, the number of blades can be selected as desired, taking into account that the complexity will be greater when there are more blades, which may offset the advantages of increased roundness. In addition, in the illustrated embodiment, the blades are configured so that the opening surrounded by the blades is approximately circular when the blades are in the closed position. However, alternatively, the blades can be configured so that the opening is non-circular when the blades are in the closed position. Moreover, although blades with arc-shaped edges have been illustrated and described, the blades do not necessarily have arc-shaped edges. Blades with edges of different shapes (linear, elliptical, etc.) are also included in the scope of the invention. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims.Although specific terms are employed herein, these terms are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A turbocharger, comprising: a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing receiving exhaust gas and supplying the exhaust gas to the turbine wheel; a centrifugal compressor assembly including a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith, the compressor housing having an air inlet wall defining an air inlet for directing air generally axially into the compressor wheel, the air inlet wall defining an annulus surrounding the air inlet and opening into the air inlet at a radially inner end of the annulus; as well as a compressor inlet adjustment mechanism disposed in the annular space of the air inlet wall and movable between an open position and a closed position, the inlet adjustment mechanism comprising a plurality of vanes disposed within the annular space between an upstream wall surface and a downstream wall surface, the vanes collectively surrounding an orifice, the upstream surface of each vane opposing the upstream wall surface and the downstream surface of each vane opposing the downstream wall surface, the vanes being movable inwardly from the annular space into the air inlet when the vanes are in the closed position so as to cause the orifice to have a reduced diameter relative to a nominal diameter of the inlet; as well as at least one of an upstream vane seal formed between the upstream wall surface and an upstream sealing surface defined by each vane when the vanes move inwardly to the closed position and a downstream vane seal formed between the downstream wall surface and a downstream sealing surface defined by each vane when the vanes move inwardly to the closed position.

2. The turbocharger according to claim 1, wherein: The upstream vane seal is present and includes an upstream seal ring supported by the upstream wall surface and an upstream sealing surface defined by each vane that contacts and seals against the upstream seal ring when the vanes move inwardly to the closed position.

3. The turbocharger according to claim 1, wherein: The downstream vane seal is present and includes a downstream seal ring supported by the downstream wall surface and a downstream sealing surface defined by each vane that contacts and seals against the downstream seal ring when the vanes move inwardly to the closed position.

4. The turbocharger according to claim 1, wherein: The upstream vane seal is present and comprises a labyrinth seal wherein one of the upstream wall surface and the upstream sealing surface of each vane defines a groove and the other of the upstream wall surface and the upstream sealing surface defines a tongue that fits into the groove when the vanes move inwardly to the closed position.

5. The turbocharger according to claim 1, wherein: The downstream vane seal is present and comprises a labyrinth seal wherein one of the downstream wall surface and the downstream sealing surface of each vane defines a groove and the other of the downstream wall surface and the downstream sealing surface defines a tongue that fits into the groove when the vanes move inwardly to the closed position.

6. The turbocharger according to claim 1, wherein: The downstream vane seal is present, but the upstream vane seal is not present.

7. The turbocharger according to claim 6, wherein: The downstream wall surface defines a wall portion extending in a direction having an upstream axial direction component, and the downstream sealing ring is supported on the radially outer side of the wall portion, and each blade defines a blade portion extending together with the upstream axial direction component on its upstream side, and the upstream sealing surface is defined by the blade portion.

8. The turbocharger according to claim 1, wherein: The upstream vane seal is present, but the downstream vane seal is not present.

9. The turbocharger according to claim 8, wherein: The upstream wall surface defines a wall portion extending in a direction having a downstream axial direction component, and the upstream sealing ring is supported on the radially outer side of the wall portion, and each blade defines a blade portion on its downstream side extending together with the downstream axial direction component, and the downstream sealing surface is defined by the blade portion.

10. The turbocharger according to claim 1, wherein: There are both the upstream vane seal and the downstream vane seal.

11. The turbocharger according to claim 10, wherein: The upstream vane seal and the downstream vane seal each comprise an O-ring type seal.

12. The turbocharger according to claim 10, wherein: The upstream vane seal and the downstream vane seal each comprise a labyrinth type seal.

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