Turbocharger compressor with adjustable adjustment mechanism including vortex inducer

Abstract

The present invention relates to a turbocharger compressor having an adjustable adjustment mechanism including a vortex inducer. A centrifugal compressor for a turbocharger includes an inlet adjustment mechanism operable to move between an open position and a closed position. The inlet adjustment mechanism includes a plurality of blades disposed about the compressor air inlet and located within an annular space within the air inlet wall. The blades are pivotable about respective pivot points so that when the blades are in the closed position, the blades extend radially inwardly from the annular space into the air inlet so as to form an orifice with a reduced diameter relative to the nominal diameter of the inlet. An upstream surface of the blade includes a vortex inducer constructed and arranged to impart a pre-vortex or a reverse vortex to air entering the compressor wheel through the orifice.

Description

Technical Field

[0001] The present disclosure relates to centrifugal compressors such as used in turbochargers, and more particularly to centrifugal compressors in which the 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 to increase the power output of the engine by compressing the air intake delivered to the engine to mix with fuel and burn in the engine. A turbocharger includes a compressor wheel mounted in a compressor housing on one end of a shaft and a turbine wheel mounted in a turbine housing on the other end of the shaft. Typically, the turbine housing is formed separately from the compressor housing, and another center housing for containing bearings for the shaft is also connected between the turbine housing and the compressor housing. The turbine housing defines a generally annular chamber surrounding the turbine wheel and receiving 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 through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. The turbine thus 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 type (also known as a "radial flow") compressor wheel because centrifugal compressors can achieve relatively high pressure ratios in a compact arrangement. Intake air for the compressor is received in a generally axial direction at an inducer portion of a centrifugal compressor wheel and is discharged in a generally radial direction at an outlet inducer portion of the wheel. 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 generally defined by the surge line and the choke line on the operating map of the compressor. The compressor map is typically presented as the pressure ratio (discharge pressure Pout divided by inlet pressure Pin) on the vertical axis versus the corrected mass flow on the horizontal axis. The choke line on the compressor map is located at high flow rates and represents the locus of the maximum mass flow point over a range of pressure ratios; that is, for a given point on the choke line, the flow cannot be increased while maintaining the same pressure ratio due to the occurrence of a choked flow condition in the compressor.

[0005] The surge line is located at low flows and represents the locus of minimum mass flow points without surge over a range of pressure ratios; that is, for a given point on the surge line, decreasing the flow without changing the pressure ratio or increasing the pressure ratio without changing the flow will cause surge to occur. Surge is a flow instability that typically occurs when the compressor blade incidence angle becomes large enough to cause significant flow separation over the compressor blades. Pressure fluctuations and flow reversals can occur during surge.

[0006] In a turbocharger for an internal combustion engine, compressor surge can occur when the engine is operated at high load or torque and low engine speed or when the engine is operated 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 condition. Extending the surge-free operating range of the compressor to lower flows is a goal often sought 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 herein, describes a mechanism and method for a centrifugal compressor capable of selectively shifting the surge line of the compressor to the left (i.e., delaying surge to a lower flow at a given pressure ratio), the 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 herein. One embodiment described in the 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 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 about the air inlet and each pivotable about one end of the vane, the vanes pivoting radially inward through slots in the air inlet wall when the vanes are in the closed position to form an orifice having a reduced diameter relative to the nominal diameter of the inlet.

[0011] Applicant is also the owner of additional applications related to other inlet adjustment mechanisms employing movable vanes, including U.S. Application No. 15 / 446,090 filed on March 1, 2017, the entire disclosure of which is hereby 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 more particularly to variations or redesigns of such mechanisms directed to improving certain aspects of the mechanisms. Summary of the invention

[0013] One such aspect of the aforementioned inlet adjustment mechanism that is sought to be improved relates to the efficiency of the compressor at low engine speeds when the inlet adjustment mechanism is closed.

[0014] According to one embodiment disclosed herein, a turbocharger having the following features is described:

[0015] 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;

[0016] 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 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 annular space surrounding the air inlet and opening into the air inlet at a radially inner end of the annular space; and

[0017] 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 including a plurality of vanes disposed in the annular space, the vanes collectively defining a boundary of an orifice, each vane having an upstream surface relatively distal and facing away from the compressor wheel and a downstream surface relatively proximal and facing toward the compressor wheel, the vanes pivoting radially inwardly from the annular space into the air inlet about respective pivots 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;

[0018] Therein, the upstream surface of each of the blades includes a plurality of circumferentially spaced vortex inducers constructed and arranged to impart swirl to air entering the compressor wheel through the apertures.

[0019] In one embodiment, the vortex inducer comprises slots or grooves in the upstream surface of the blades.The slots can be oriented to impart a pre-vortex (vortex in the same direction as the compressor wheel rotation) or a reverse vortex.

[0020] In one embodiment of the invention, each vane comprises a radially inner edge having an arc shape, the vanes being configured such that the radially inner edges collectively form the orifice to be substantially circular in a selected position of the inlet adjustment mechanism.

[0021] The selected position where the radially inner edges of the vanes form the aperture into a generally circular shape may be a closed position in some embodiments of the invention.

[0022] In one embodiment, the inlet adjustment mechanism includes a pair of axially spaced (i.e., upstream and downstream) annular end plates, and the vanes are disposed between the end plates so that the inlet adjustment mechanism forms a "box" that can be installed in the compressor. The inlet adjustment mechanism or box is disposed in an annular space defined by the air inlet wall. The annular space can be defined between the main portion of the compressor housing and a separate inlet duct member that forms a majority of the air inlet to the compressor. The duct member is received into a socket defined in the main portion of the compressor housing.

[0023] The end plates can be spaced apart by a plurality of pins passing through holes in the blades, and about which the blades can pivot.

[0024] Alternatively, the pins can be fixed in the compressor housing so that a separate end plate is not required (i.e., the inlet adjustment mechanism is not a separate box). For example, the function of one end plate can be provided by an integral part of the compressor housing, and the function of the other end plate can be provided by an integral part of the inlet duct member.

[0025] According to one embodiment, the inlet adjustment mechanism further comprises a synchronizing ring surrounding the vanes, the synchronizing ring being rotatable about the rotation axis of the turbocharger, wherein each of the vanes is engaged with the synchronizing ring such that rotation of the synchronizing ring causes the vanes to pivot about the pin. Each vane comprises an end portion engaging a groove defined in an inner circumference of the synchronizing ring.

[0026] The inlet adjustment mechanism can also include a plurality of guides for guiding the rotation of the synchronizing ring.The guides can be fixed to at least one of the end plates (or to the compressor housing and / or inlet duct member in the case of a non-cassette version of the inlet adjustment mechanism). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Having thus generally described the invention, reference will now be made to the accompanying drawings which are not necessarily drawn to scale, and in which:

[0028] Figure 1is an end view of a turbocharger according to one embodiment of the present invention, looking axially from the compressor end of the turbocharger toward the turbine end;

[0029] Figure 2 It is along Figure 1 A cross-sectional view of the turbocharger taken along line 2-2;

[0030] Figure 3 yes Figure 1 A partial exploded view of a compressor portion of a turbocharger;

[0031] Figure 4 yes Figure 3 An isometric view of a compressor housing assembly with the compressor cover (inlet duct member) exploded so that the inlet adjustment mechanism is visible;

[0032] Figure 5 is an isometric view of a partial assembly of the inlet adjustment mechanism and thus the actuator as viewed from the upstream side of the mechanism, wherein the inlet adjustment mechanism is in an open position;

[0033] Figure 6 is with Figure 5 a similar view with the inlet adjustment mechanism in the closed position;

[0034] Figure 7 is an isometric view of a blade of an inlet adjustment mechanism showing an upstream surface of the blade with a vortex inducer;

[0035] Figure 8 is an axial view of the compressor wheel and vanes of the inlet adjustment mechanism in a closed position of the mechanism as viewed from upstream of the compressor toward the turbine of the turbocharger; and

[0036] Fig. 9 is through Figure 1 A cross-sectional view of the compressor housing assembly and inlet adjustment mechanism of a turbocharger. 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 satisfies applicable legal requirements. Like reference numerals refer to 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. Furthermore, when the vanes of the inlet adjustment mechanism are described as pivoting "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 inclined relative to the axis of rotation of the compressor, such that as the vanes pivot radially inwardly and outwardly, they also move with a small axial component of motion; alternatively, the vanes may pivot and translate, such as in a spiral-type motion).

[0039] exist Figure 1 A turbocharger 10 according to one embodiment of the present invention is illustrated in an axial end view in FIG. Figure 2 An axial cross-sectional view of a turbocharger is shown in FIG. A turbocharger includes a compressor and a turbine. The compressor includes a compressor wheel or impeller 14 mounted in a compressor housing 16 on one end of a rotatable shaft 18. The compressor housing includes a wall 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 away from the compressor wheel, thereby rotatably driving the compressor wheel, which compresses air drawn in 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. From the volute 21, the air is delivered 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 that defines an annular chamber 26 for receiving exhaust gases from an internal combustion engine (not shown). The turbine housing also defines a nozzle 28 for directing the exhaust gases from the chamber 26 generally radially inwardly to the turbine wheel 22. The exhaust gases expand as they pass through the turbine wheel and rotatably drive the turbine wheel, which in turn rotatably drives the compressor wheel 14 as already noted.

[0041] refer to Figure 1-Figure 4 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 received in a cylindrical socket 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 that generally matches the diameter of the inducer portion 14i of the compressor wheel.

[0042] The compressor casing 16 defines a shroud surface 16s 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] According to the present invention, 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 defined between an upstream wall surface 105 and a downstream wall surface 107. The inlet adjustment mechanism is operable to adjust the effective diameter of the air inlet into the compressor wheel. Therefore, the inlet adjustment mechanism can be moved between an open position and a closed position, and can be configured to be adjusted to various intermediate points between the positions.

[0044] Reference now Figure 3-Figure 8 , the inlet adjustment mechanism includes a plurality of vanes 102 arranged about a central axis of the air inlet and each pivotable about a pivot pin 102p located at or near one end of the vane. In the illustrated embodiment, the pivot pin for the vane is journaled in a hole in a downstream wall surface 107 of the compressor housing so that the pivot pin can rotate in the hole. In this embodiment, the pivot pin is integrally and rigidly attached to the vane. The vane is arranged between an upstream wall surface 105 and a downstream wall surface 107, wherein there is a small amount of axial clearance or play for the vane between those wall surfaces so that the vane can freely pivot without restraint.

[0045] The inlet adjustment mechanism also includes a synchronizing ring 106 for imparting pivotal movement to the vanes. The synchronizing ring surrounds the assembly of vanes 102, is substantially coplanar with the vanes, and is rotatable about an axis that coincides with the axis of rotation of the compressor wheel. The synchronizing ring includes a plurality of recesses 108 in its radial periphery, and each vane includes an end 102e that engages in a corresponding one of the recesses 108. Thus, rotation of the synchronizing ring in one direction pivots the vanes 102 radially inwardly, and rotation of the synchronizing ring in the other direction pivots the vanes radially outwardly. The assembly of the vanes 102 and the synchronizing 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 varies depending on the position of the blade, as further described below).

[0047] The range of the blade pivot movement is sufficient for the blade to (by rotation of the synchronizing ring in one direction, Figure 5 (clockwise rotation) radially outwardly to Figure 5 , in which the vanes are completely within the inner surface 17i ( Figure 2). Thus, in the open position of the vanes, the inlet adjustment mechanism does not change the nominal inlet diameter as defined by the inlet surface 17i.

[0048] The blades can also (by rotating the synchronizing ring in the opposite direction, Figure 5 counterclockwise) radially inwardly to the Figure 6 The closed position is shown. In the closed position, the arcuate edges along the radially inner side of the blades collectively form an orifice. In the illustrated embodiment, the orifice is generally circular in the closed position so as to have a diameter that is smaller than the diameter of the inlet surface 17i. ("Generally circular" in this disclosure means that the arcuate edges are all located on the same circle and collectively 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. In addition, in an embodiment not shown, the blades can pivot an additional amount to an over-closed position in which there is a certain degree of overlap of adjacent blades, which is achieved by forming the corresponding overlapping edge portions of the adjacent blades into complementary or concave-convex shapes. When the blades are in the over-closed position, the arcuate edges of the blades collectively define an opening or orifice that is not completely circular, but is smaller than for Figure 6 The opening of the closed position is effectively smaller. Thus, 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 effective diameter of the air inlet close to the compressor wheel.

[0049] However, it should be noted that it is not essential that the orifice defined by the inlet adjustment mechanism is circular in the closed position. Alternatively, the orifice may be non-circular. The present invention is not limited to any particular shape of orifice.

[0050] As previously mentioned, the vanes 102 are actuated by a synchronizing ring 106 rotatable about the central axis of the air inlet to pivot between their open and closed (and optionally over-closed) positions. Figure 4-Figure 6 , by being received into a socket 116a ( Figure 3 ) imparts rotational motion to the synchronizing ring. The actuator includes an actuator rod 117 extending through a space defined in the compressor housing and fixed at its distal end to a stop extending from the synchronizing ring 106 ( Figure 3 ) has a protrusion 109 protruding radially outwardly from the periphery of the cam 106. The actuator is operable to linearly extend and retract the rod 117 along its length so as to rotate the synchronizing 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.

[0051] As noted, the inlet adjustment mechanism 100 enables adjustment of the effective size or diameter of the inlet into the compressor wheel 14. Figure 2As illustrated 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 inner diameter defined by the blades 102. To achieve this effect, the axial separation distance between the blades and the compressor wheel must be as small as possible so that the distance downstream of the blades is insufficient for the flow to expand to the full diameter of the inducer portion of the compressor wheel 14 by the time the air encounters the compressor wheel. The inlet diameter is thereby effectively reduced to the value determined by the blades.

[0052] At low flow rates (e.g., low engine speeds), the inlet adjustment mechanism 100 may be in Figure 2 and Figure 6 The compressor wheel is moved to a closed position. This can have the effect of reducing the effective inlet diameter and thereby increasing the flow velocity into the compressor wheel. The result is a reduction in the compressor blade incidence angle to effectively stabilize the flow (i.e., make blade stall and compressor surge less likely). In other words, the compressor surge line is moved to lower flows (to the left on a plot of compressor pressure ratio versus flow).

[0053] At medium and high flow rates, the inlet adjustment mechanism 100 may be partially opened or Figure 5 This can have the effect of increasing the effective inlet diameter so that the compressor regains its high flow performance and surge flow essentially as if the inlet adjustment mechanism did not exist and the compressor had a conventional inlet at the inducer portion of the wheel that matched the wheel diameter.

[0054] According to one aspect of the invention disclosed herein, the inlet adjustment mechanism 100 includes features for improving the low-end performance of the compressor when the inlet adjustment mechanism is closed. More specifically, as Figure 7 As best seen in FIG. 1 , each of the blades 102 of the mechanism includes a vortex inducer SW on the upstream surface 102u of the blade. The vortex inducer may include a slot or groove in the upstream surface. Figure 8 The groove or trench extends at an angle α with respect to the radial direction of the compressor (indicated by line R). The angle α can be positive or negative, where a positive angle indicates a pre-vortex (e.g. Figure 8 As shown, vortex in the same direction as the rotation of the compressor wheel 14), and negative angles indicate reverse vortex. The vortex inducer turns the air passing through the apertures of the mechanism from a flow direction without a circumferential component to a flow direction with some circumferential component.

[0055] The walls or ribs between adjacent vortex guide wheel grooves are as follows: Figure 8 Shown is a rib having a thickness t. The number of slots SW, the thickness t of the rib and the angle a of the slots are design variables that can be selected when designing the vanes of the inlet adjustment mechanism.

[0056] When the inlet adjustment mechanism is closed, the vortex inducer SW can be effectively used to improve the low-end performance of the compressor. For example, when the vortex inducer is tilted to induce a pre-vortex in the flow, the angle of incidence of the compressor blades can be reduced; this is particularly beneficial when the compressor is operated close to the surge line of the compressor diagram, where the angle of incidence is high so that flow separation can begin to occur on the compressor blades, resulting in less efficient compressor operation. The pre-vortex reduces the angle of incidence and can thereby improve efficiency.

[0057] With the benefit of the teachings presented in the foregoing description and the accompanying drawings, a person skilled in the art to which the inventions set forth herein belong will recognize many variations and other embodiments of these inventions. For example, although the illustrated embodiment employs three blades 102, the invention is not limited to any particular number of blades. The invention can be practiced with as few as two blades or as many as 12 or more blades. The number of blades can be selected as required. In addition, although blades with arc edges have been illustrated and described, the blades do not necessarily have arc edges. Also included within the scope of the invention are blades with edges of different shapes (linear, elliptical, etc.). Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed, and variations and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used only in a general and descriptive sense and are not used for limiting purposes.

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 the 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 wheel having blades and defining an 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 annular space surrounding the air inlet and opening into the air inlet at a radially inner end of the annular space; and 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 in the annular space, the vanes collectively defining a boundary of an orifice, each vane having an upstream surface relatively distal and facing away from the compressor wheel and a downstream surface relatively proximal and facing toward the compressor wheel, the vanes pivoting radially inwardly from the annular space into the air inlet about respective pivots 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 air inlet; wherein the upstream surface of each of the blades includes a plurality of circumferentially spaced vortex inducers constructed and arranged to impart swirl to air entering the compressor wheel through the apertures.

2. The turbocharger according to claim 1, wherein: The vortex inducer includes a slot in the upstream surface of each blade.

3. The turbocharger according to claim 2, wherein: The slots are oriented to impart a pre-swirl to the air.

4. The turbocharger according to claim 2, wherein: The slots are oriented to impart a reverse swirl to the air.

5. The turbocharger according to claim 1, wherein: The radially inner edge of each vane has an arc shape, the vanes being configured such that the radially inner edges collectively form the orifice to be generally circular in a selected position of the inlet adjustment mechanism.

6. The turbocharger according to claim 1, wherein: The number of blades of the inlet adjustment mechanism is three.

7. The turbocharger according to claim 1, wherein: The inlet adjustment mechanism also includes a synchronizing ring rotatable about an axis of rotation of the turbocharger, wherein each of the vanes is engaged with the synchronizing ring such that rotation of the synchronizing ring pivots the vanes.

8. The turbocharger according to claim 7, wherein: Each vane includes an end portion that engages an outer circumference of the synchronizing ring.

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