INCORPORATING THE SAME

BACKGROUND

[0001] Today's internal combustion engines must meet ever stricter emissions and efficiency standards demanded by consumers and government regulatory agencies. Accordingly, automotive manufacturers and suppliers expend great effort and capital in researching and developing technology to improve the operation of the internal combustion engine. Turbochargers are one area of engine development that is of particular interest in this case. [0002] A turbocharger uses exhaust gas energy, which would normally be wasted, to drive a turbine. The turbine is mounted to a shaft that in turn drives a compressor. The turbine converts the heat and kinetic energy of the exhaust into rotational power that drives the compressor. The objective of a turbocharger is to improve the engine's volumetric efficiency by increasing the density of the air entering the engine. The compressor draws in ambient air and compresses it into the intake manifold and ultimately the cylinders. Thus, a greater mass of air enters the cylinders on each intake stroke.

[0003] When a turbocharger is sized to provide maximum power output for a particular engine, the turbocharger' s low- load and transient response performance is generally less than optimal. A turbocharger's compressor performance is dependent on the compressor speed. In order for the compressor to rotate fast enough to provide significant compression, or boost, to the engine, there must be a corresponding increase in exhaust gas flow. However, there is a time delay while the exhaust gases build up and the inertia of the turbine and compressor wheel assembly is overcome. This time delay between the engine's demand for boost and the actual increase in manifold pressure is often referred to as turbo lag. [0004] In order to address turbo lag, the size of the turbocharger may be reduced thereby reducing the inertia of the rotating components which in turn improves the transient response of the turbocharger. However, such a reduction in size comes with a reduction in maximum mass flow that can be delivered to the engine at high speed. Thus, there is a tradeoff between transient response and peak engine output. Compound turbocharger systems have been devised that include a smaller high pressure stage to provide transient response coupled with a larger low pressure stage that provides the mass flow required at high engine speeds. [0005] A troublesome source of unwanted emissions is leakage of engine oil from the bearing housing of a turbocharger into either the compressor housing, where it is mixed with engine charge air and burned in the engine, or into the turbine housing, where it is introduced directly into the engine exhaust flow. To minimize leakage, turbochargers are typically equipped with a seal between the rotating shaft and the bearing housing to restrict the flow of oil out of the housing.

[0006] Various intermittent engine operating conditions can produce an unfavorable pressure gradient between the bearing housing and compressor, leading to oil migration. For example, in a compound turbocharger system, during periods of low engine output (idle, engine braking, or high EGR) the smaller high pressure turbo absorbs a significant amount of the available exhaust energy. In such a case, there is not enough exhaust energy to efficiently operate the larger low pressure turbo. As a result the low pressure turbocharger 's compressor wheel acts as an inlet restriction that in turn creates a vacuum in the low pressure turbocharger's compressor. Thus, an unfavorable pressure gradient from bearing housing to compressor is created.

[0007] While many turbocharger shaft seals exist, there is still a need for a robust shaft seal that is capable of sealing against unfavorable pressure gradients created under various engine operating conditions, such as the example described above with respect to a compound turbocharger system.

SUMMARY

[0008] Provided herein is a turbocharger sealing system comprising a thrust bearing disposed in a cavity formed in the turbocharger's housing adjacent the compressor wheel that is concentric with the turbocharger shaft. The sealing system includes an insert disposed in the cavity adjacent the thrust bearing. The thrust bearing and insert are configured to provide an oil drain cavity therebetween. An oil flinger is included that has a flinger flange and a sleeve portion extending therefrom. The flinger flange extends between the thrust bearing and insert and the sleeve extends axially into an insert bore formed through the center of the insert. The flinger sleeve includes at least one circumferential groove formed therearound for receiving corresponding piston rings that seal against the insert bore.

[0009] In certain aspects of the technology described herein, the thrust bearing includes an oil return groove for receiving oil from the flinger flange. A flinger groove is formed in the axial surface of the flinger flange facing the thrust bearing. The flinger groove includes a ramped surface that extends around the circumference of the groove's radially outer edge. The ramped surface is operative to impart an axial component to the trajectory of oil flung from the flinger flange such that oil is received in the thrust bearing's oil return groove. The oil drains downward and around the oil return groove, under the influence of gravity, and into an oil drain plenum. The insert includes a drain channel comprising an arcuate surface that captures oil that is flung past the oil return groove. Oil captured in the drain channel drains downward, under the influence of gravity, into the oil drain plenum.

[0010] In yet other aspects of the technology, the flinger flange has an axially-facing surface, opposite the flinger groove, that includes a plurality of labyrinth seal faces. The insert includes a plurality of corresponding labyrinth seal faces that together create a tortuous path through which oil must travel in order to reach the piston ring seal. The labyrinth seal faces are in closely confronting relationship in order to make it more difficult for oil to reach the piston rings.

[0011] These and other aspects of the sealing system will be apparent after consideration of the Detailed Description and Figures herein. It is to be understood, however, that the scope of the invention shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the background or includes any features or aspects recited in this summary.

DRAWINGS [0012] Non-limiting and non-exhaustive embodiments of the sealing system and turbocharger incorporating the same, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0013] FIG. 1 is a partial cross-section of a turbocharger incorporating a compressor-side sealing system according to a first exemplary embodiment;

[0014] FIG. 2 is an enlarged cross-sectional view of the sealing system shown in FIG. 1;

[0015] FIG. 3 is a perspective view of the thrust bearing shown in FIGS. 1 and 2;

[0016] FIG. 4 is an exploded view of the flinger and accompanying spacers shown in FIGS. 1 and 2; [0017] FIG. 5 is an enlarged cross-sectional view of the sealing system shown in FIGS. 1- 4; [0018] FIG. 5A is an enlarged cross-sectional view of the flinger according to an alternative construction; and

[0019] FIG. 6 is a cross-sectional view of a sealing system according to a second exemplary embodiment. DETAILED DESCRIPTION

[0020] Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

[0021] FIG. 1 illustrates a turbocharger 10 that incorporates a sealing system 28 according to a first exemplary embodiment. Turbocharger 10 includes a center housing 12 that supports shaft 18 in a pair of journal bearings 24 and 26. A compressor wheel 14 is mounted on one end of shaft 18 and a turbine wheel 16 is mounted on the opposite end of shaft 18. Oil is fed to the journal bearings 24 and 26 through oil inlet 20 and is collected and drained through oil plenum 22. Turbocharger 10 also includes a turbine housing and a compressor housing (not shown) installed over the turbine and compressor wheels, respectively. [0022] In this case, sealing system 28 is installed adjacent the compressor wheel 14 in order to help prevent oil migration into the compressor. While it is contemplated that the disclosed seal system technology is particularly useful in applications where an unfavorable pressure gradient is present near the compressor of a turbocharger, such as in compound turbocharger applications, the seal system may be used with turbines and in applications other than compound applications. Furthermore, the seal system may be used in other machines where liquid control is needed.

[0023] With further reference to FIG. 2, turbocharger housing 12 includes a cavity, or bore 30, formed in the compressor end of housing 12. In this case, bore 30 is concentric with the turbocharger shaft 18. A thrust bearing 80 is disposed in the bottom of bore 30, and an insert 40 is disposed in bore 30 adjacent thrust bearing 80. The thrust bearing 80 and insert 40 are configured to provide an oil drain cavity 21 therebetween. Seal system 28 also includes an oil flinger 60 that has a flinger flange 64 and a sleeve portion 62 extending therefrom. It should be noted that oil flinger 60 is attached to shaft 18 such that it rotates with the shaft, while thrust bearing 80 and insert 40 remain stationary with respect to housing 12. The flinger flange 64 extends radially between thrust bearing 80 and insert 40. Sleeve portion 62 extends axially into an insert bore 44 formed through the center of insert 40. In this case, a pair of piston rings 76 provide a seal between the sleeve portion 62 of flinger 60 and insert bore 44.

[0024] A spacer washer 74 abuts shoulder 19 formed on shaft 18. A spacer ring 72 abuts spacer washer 74 on one end and extends through thrust bearing 80 to abut flinger 60 on the other end, as shown. Accordingly, flinger 60 is located with respect to shoulder 19. Spacer washer 74 also abuts journal bearing 26. Accordingly, the flinger 60 as well as compressor wheel 14 are located with respect to the journal bearing 26. The spacer washer 74 and spacer ring 72 may be comprised of any suitable material, such as steel, or the like.

[0025] Insert 40 is retained in bore 30 by a retaining ring 34, such as a snap ring, that engages a ring groove 32 formed in housing 12. Insert 40 may include a groove 48 that facilitates the removal of the insert. Insert 40 is sealed to the interior of bore 30 by an O-ring 36 that is disposed in an O-ring groove that is formed circumferentially around the outer surface 42 of insert 40. Insert 40 may comprise any suitable material such as steel, aluminum, or the like. The bore 30 extends into housing 12 and intersects at 23 the oil drain plenum 22. Accordingly, oil captured by the sealing system flows from oil drain cavity 21 into oil drain plenum 22 via the intersection 23.

[0026] Referring now to FIG. 3, it can be appreciated that thrust bearing 80 is comprised of a truncated disc, wherein the thrust bearing is circular in shape with a portion that is cut off to form a flat surface 90. Thrust bearing 80 may comprise any suitable material such as bronze (forged blank, bar, or sintered) or iron (sintered with copper), or the like. Thrust bearing 80 includes an aperture 86 sized to receive spacer ring 72. A bearing surface 94 extends around an edge margin of aperture 86 which confronts the flinger 60. A plurality of notches 88 are formed around the circumference of aperture 86, thereby creating a plurality of corresponding bearing lands 92. Extending from truncated surface 90 and around bearing surface 94 is an oil return groove 82 for receiving oil from flinger flange 64, as explained more fully below. Also shown in FIG. 3, is a pair of mounting apertures 84 for locating the thrust bearing with respect to housing 12. [0027] In FIG. 4, flinger 60 is shown in exploded relation to spacer ring 72 and spacer washer 74. Flinger 60 includes flinger flange 64 and sleeve portion 62 which extends axially therefrom. In this case, sleeve portion 62 includes a pair of grooves 66 that are configured to receive the piston rings 76. Flinger flange 64 includes an axially-facing surface 65 into which flinger groove 620 is formed. Flinger 60 may comprise any suitable material such as steel, or the like.

[0028] With further reference to FIG. 5, flinger groove 620 includes a ramped surface 622 extending around the circumference of the groove's radially outer edge. Ramped surface 622 is operative to impart an axial component to the trajectory of oil flung from the flinger flange 64 such that oil is received in the oil return groove 82. In this case, ramped surface 622 is oriented at an angle of approximately 45 degrees with respect to the axis of shaft 18. Preferably, the edge 623 between ramped surface 622 and axially facing surface 65 is a sharp corner, in order to help break up the oil film. Oil received in oil return groove 82 drains around the groove under the influence of gravity and into the oil drain plenum 22 via intersection 23. In this case, groove 620 includes an angled lead-in surface 624. Accordingly, as shown in FIG. 5, the cross-section of groove 620 is V-shaped. While lead-in surface 624 is angled in this case, the lead-in surface could be curved or flat, and may extend further toward the center of the flinger flange 64.

[0029] Oil that is flung from flinger flange 64 past groove 82 through the gap 56 and into oil drain cavity 21 may land in drain channel 50 directly or may impinge on drain channel surface 52 and thereafter run along channel surface 52 and into drain channel 50. Oil captured in drain channel 50 drains downward, under the influence of gravity, into the drain plenum 22.

[0030] Flinger flange 64 has an axially-facing surface, which is opposite flinger groove 620 that includes a plurality of labyrinth seal surfaces 601-605. Insert 40 includes a plurality of corresponding labyrinth seal surfaces 501-505. As shown, these surfaces create a tortuous path through which oil must travel in order to reach the piston rings 76. The labyrinth seal surfaces are in closely confronting relation to each other in order to make it more difficult for oil to reach the piston rings 76. FIG. 5 A illustrates an alternative construction of a flinger flange 64 that further includes a spiral auger groove 630 formed circumferentially around the outer surface 601 of flinger flange 64. The auger groove 630 may be formed in clock- wise or counter-clockwise fashion depending on which direction the compressor and turbine wheels are designed to operate. As flinger 60 rotates, auger groove 630 is operative to screw, or auger, oil out of the interface between outer surface 601 and corresponding surface 501. Auger groove 630 may be in the form of screw threads; however, other groove profiles may be used.

[0031] FIG. 6 illustrates a sealing system 128, according to a second exemplary embodiment, that is substantially the same as the embodiment shown in FIGS. 1-5. However, in this case, sealing system 128 includes an insert 150 having an additional groove 152 formed therein. Groove 152 is sized and configured to receive a face seal ring 154. Face seal ring 154 is comprised of an abradable, or sacrificial, material, such as graphite or carbon. Face seal ring 154 is operative to ride against axially-facing labyrinth seal surface 602 of flinger flange 64. Accordingly, the gap between labyrinth seal surface 602 and 154 is reduced to near zero. As mentioned above, and as one of ordinary skill in the art will appreciate, the smaller the gap between the labyrinth faces, the more difficult it is for oil to travel along the labyrinth seal.

[0032] Accordingly, the sealing system and turbocharger incorporating the same have been described with some degree of particularity directed to the exemplary embodiments. It should be appreciated, though, that modifications or changes may be made to the exemplary embodiments without departing from the inventive concepts contained herein.