Abstract:
In an aluminum turbocharger bearing housing, there is a potential for wear of the bearing housing at the interface with the turbine housing and/or the bearing system. One area of potential concern is the interface between the flange of the bearing housing and an abutment of the turbine housing. With a protective element at the interface, the potential for wear, and thus misalignment of the rotating assembly with the housings in which they operate can be mitigated. The protective element can be a cap for the bearing housing flange or a heat shield adapted to cover certain faces of the bearing housing flange. The protective element can be a sleeve provided within a bore in the bearing housing. The protective element can be made of a material with a higher heat resistance and/or a higher wear resistance than the aluminum bearing housing.

Description:
FIELD OF THE INVENTION 
       [0001]    Embodiments relate in general to turbochargers, and, more particularly, to turbochargers with bearing housings made of aluminum. 
       BACKGROUND OF THE INVENTION 
       [0002]    Turbochargers are a type of forced induction system. They deliver air, at greater density than would be possible in the normally aspirated configuration, to the engine intake, allowing more fuel to be combusted, thus boosting the engine&#39;s horsepower without significantly increasing engine weight. A smaller turbocharged engine, replacing a normally aspirated engine of a larger physical size, will reduce the mass and can reduce the aerodynamic frontal area of the vehicle. 
         [0003]    Referring generally to  FIGS. 1 and 2 , turbochargers ( 10 ) use the exhaust flow from the engine exhaust manifold to drive a turbine wheel ( 12 ), which is located within a turbine housing ( 14 ). The energy extracted by turbine wheel ( 12 ) is translated to a rotating motion, which then drives a compressor wheel ( 16 ), which is located within a compressor cover ( 18 ). The compressor wheel ( 16 ) draws air into the turbocharger ( 10 ), compresses this air, and delivers it to the intake side of the engine. The rotating assembly consists of the following major components: turbine wheel ( 12 ); compressor wheel ( 16 ); a shaft ( 20 ) upon which the turbine wheel ( 12 ) and compressor wheel ( 16 ) are mounted; journal bearings; flinger; and thrust components. The shaft ( 20 ) rotates on a bearing system which is fed oil, typically supplied by an engine oil pump. The bearing system is located within a bearing housing ( 22 ). Typically, there are two types of bearing systems—rolling element bearing (REB) systems and hydrodynamic journal bearing systems. 
         [0004]    A typical turbocharger ( 10 ) having a rolling element bearing (REB) system ( 21 ) is shown in  FIG. 1 . The bearings are presented in the form of a cartridge ( 30 ) in which the shaft ( 20 ) locates on the inner race ( 24 ) of the cartridge ( 30 ), and the outer race ( 26 ) of the cartridge ( 30 ) locates in a bore ( 36 ) in the bearing housing ( 22 ). Typically, the outer diameter of the outer race ( 24 ) is damped by an oil film between the outer diameter of the outer race ( 26 ) and the inner diameter of the bore ( 36 ) in the bearing housing ( 22 ). The axial constraint for the bearing cartridge ( 30 ) is an abutment in the bearing housing ( 22 ) on one end thereof and a clip ( 28 ) on the other end thereof. The clip ( 28 ) can also be used as an anti-rotation constraint. The shaft ( 20 ) is located in the bearing cartridge ( 30 ) by an abutment on the turbine-end of the shaft ( 20 ), itself abutting an abutment on the turbine-end of the inner race ( 24 ). 
         [0005]      FIG. 2  shows a typical turbocharger having a hydrodynamic journal bearing system ( 23 ). In such a configuration, the journal bearings ( 32 ) and thrust bearing ( 34 ) are individually assembled into the bearing housing ( 22 ). Both the outside diameter of the journal bearing ( 32 ) and the shaft ( 20 ) (which is located within the inside diameter of the journal bearing ( 32 )) are supported by oil films. Typically, the journal bearing bore ( 37 ) is finished to a very high degree of cylindricity and surface finish. The axial constraint in a typical journal bearing turbocharger ( 10 ) is provided by a thrust bearing ( 34 ), which axially locates against an abutment on the thrust bearing-end of the bearing housing ( 22 ). The shaft axial position is set by a thrust washer (axially controlled by the thrust bearing) abutting against an abutment on the compressor-end of the journal bearing diameter on the shaft ( 20 ). 
         [0006]    Most turbochargers mount to an engine via the turbine housing foot ( 38 ). In these cases, the forces exerted by the bearing housing ( 22 ), compressor cover ( 18 ), and the rotating assembly (including the rotating inertia) on the foot ( 38 ), and thus the engine, are transmitted through the joint attaching the turbine housing ( 14 ) to the bearing housing ( 22 ) so that particular jointing interface is susceptible to wear. The axial position of the turbine housing ( 14 ), relative to the bearing housing ( 22 ), is set by a turbine housing facing surface ( 40 ) on the locating flange ( 42 ) of the bearing housing ( 22 ), with the face of a complementary abutment ( 44 ) on the turbine housing ( 14 ). In some cases, a flange ( 42 ) on a turbine heat shield ( 46 ) is sandwiched between the turbine housing abutment ( 44 ) and the surface ( 40 ). 
         [0007]    The joint between turbine housing ( 14 ) and bearing housing ( 22 ) is typically one of two types. The first type of joint is a bolt and clamp-plate type of joint, as depicted in  FIGS. 1 ,  2  and  3 . In such an arrangement, a flange ( 42 ) is clamped on one part (of the turbine housing or bearing housing) to the body of the complementary part, with the clamp load supplied by a threaded fastener ( 50 ) through a clamp plate ( 52 ). 
         [0008]    The other type of joint for the turbine housing ( 12 ) to bearing housing ( 22 ) interface is a vee-band, as depicted in  FIG. 3 . In this type of joint, a flange ( 42 ) of the bearing housing ( 22 ) and a flange ( 64 ) of the turbine housing ( 14 ) are both axially and radially constrained by the complementary tapers on a vee-band retainer ( 56 ) and the flanges ( 42 ,  64 ) it pulls together. The vee-band ( 56 ) typically has a plurality of retainer segments ( 54 ), which are circumferentially compressed by a tee-bolt and trunnion. This compression in the tee-bolt exerts a tensile stress in a band the tee-bolt pulls the ends of the band ( 56 ) together. The force exerted by the band ( 56 ) on the retainer segments ( 54 ) is translated into a uniform closing force, with both a radially inwards component and an axially contracting component. The radial component pulls the vee-band flange retainer segments ( 54 ) down the tapers ( 58 ,  59 ), fabricated into flanges ( 42 ,  64 ), in the two components being clamped together (In this case, the turbine housing ( 14 ) and the bearing housing ( 22 )). 
         [0009]    In either type of joint between turbine housing ( 14 ) and bearing housing ( 22 ), the interface is subjected to a moment force as well as vibration and temperature differences. Any wear in the interface can cause a misalignment between the elements of the rotating assembly (i.e. the turbine and compressor wheels ( 12 ,  16 )) and the housings ( 14 ,  22 ) in which they reside. 
         [0010]    In modern auto applications, the mass of the vehicle is becoming a major issue when it comes to the efficiency of the vehicle. In an effort to reduce the mass of a turbocharger, an aluminum bearing housing was substituted for the former traditional gray iron bearing housing. With exhaust temperatures in the range of 700° C. to 1050° C., the turbine housing could not be cast in aluminum. This change in material produced a mass reduction in the range of 55% to 65% for the bearing housing and a potential reduction in moment about the interface of the turbine housing to the bearing housing of approximately 33%. However, in doing so, there can be increased wear at the interface between the hot turbine housing ( 14 ) and the relatively cool bearing housing ( 22 ) and also at the interface of the bearing housing ( 22 ) to any bearing system that may be implemented, as aluminum is relatively soft compared to gray iron. Thus, referring to the interface between the turbine housing ( 14 ) and the bearing housing ( 22 ) shown in  FIG. 3  as an example, the interaction of the inner surfaces of the retainer segments ( 54 ) on the tapers ( 58 ,  59 ) of the flanges ( 42 ,  64 ), particularly the aluminum bearing housing flange ( 42 ), can damage the surface of the flange ( 42 ) and be detrimental to a subsequent application of the vee-band ( 56 ) to the flange ( 42 ). 
         [0011]    Thus, there is a need for systems and methods that can permit the use of an aluminum bearing housing in a turbocharger while providing a suitable interface with the turbine housing and the bearings. 
       SUMMARY OF THE INVENTION 
       [0012]    Embodiments described herein facilitate the use of an aluminum bearing housing by providing systems and methods for protecting the interface between the bearing housing and the turbine housing and/or between the bearing housing and the bearing system, thereby avoiding wear and other issues that may arise from the use of an aluminum bearing housing while allowing the advantages of such a bearing housing to be realized. Systems and methods provide a protective surface of steel or other suitable materials in the interface to protect the aluminum surfaces that would otherwise form the interface. Suitable materials have a higher heat resistance and/or a higher wear resistance than the base aluminum material of the bearing housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention is illustrated by way of example and not limitation in the accompanying drawings in which like reference numbers indicate similar parts, and in which: 
           [0014]      FIG. 1  is a cross-sectional view of a typical turbocharger assembly with rolling element bearings; 
           [0015]      FIG. 2  is a cross-sectional view of a typical turbocharger assembly with a hydrodynamic bearing; 
           [0016]      FIG. 3  shows a typical vee-band type of clamping system for the turbine housing and the bearing housing; 
           [0017]      FIG. 4  shows a first embodiment of a protective system for an interface between an aluminum bearing and a turbine housing and/or a bearing system; 
           [0018]      FIG. 5  shows a second embodiment of a protective system for an interface between an aluminum bearing and a turbine housing; and 
           [0019]      FIG. 6  shows a third embodiment of a protective system for an interface between an aluminum bearing and a turbine housing and/or a bearing system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Arrangements described herein relate to device turbocharger with an aluminum bearing housing configured for improved interface with the turbine housing and/or bearing system. Detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are intended only as exemplary. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the aspects herein in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of possible implementations. Arrangements are shown in  FIGS. 4-6 , but the embodiments are not limited to the illustrated structure or application. 
         [0021]    Referring to  FIG. 4 , examples of protective systems for an interface between an aluminum bearing housing ( 22 ) and a turbine housing ( 14 ) and/or a bearing system (not shown) are shown. The bearing housing ( 22 ) can be made of any suitable type of aluminum. 
         [0022]    A protective element ( 70 ) can be operatively positioned between at least a portion the aluminum bearing housing, such as the flange ( 42 ), that contacts the turbine housing ( 14 ). The protective element ( 70 ) can be made of any suitable material. For instance the protective element ( 70 ) can be made of a material that has a higher heat resistance and/or a higher wear resistance than the aluminum of the bearing housing ( 22 ). For instance, the protective element ( 70 ) can be made of cast iron, titanium, or any suitable type of steel. The protective element ( 70 ) can be made of a material that it harder than the aluminum bearing housing ( 22 ). The protective element ( 70 ) can provide resistance to potential wear problems between the turbine housing ( 14 ) and the relatively soft aluminum bearing housing ( 22 ). The protective element ( 70 ) may also provide protection to the aluminum bearing housing ( 22 ) from the heat of the turbine housing ( 14 ). 
         [0023]    The protective element ( 70 ) can have any suitable conformation. In one embodiment, the protective element ( 70 ) can be configured like a cap having a generally U-shaped cross-section, as is shown in  FIG. 4 . In such case, the protective element ( 70 ) can cover at least a portion of the bearing housing ( 22 ), such as flange ( 42 ). In such case, the protective element ( 70 ) can include a generally cylindrical radially protecting surface ( 72 ), and one or more axially protecting surfaces ( 74 , 76 ). In the arrangement shown in  FIG. 4 , two axially protecting surfaces ( 74 ,  76 ) are provided, but embodiments are not limited to there being two axially protecting surfaces. The pair of axially protecting surfaces ( 74 , 76 ) can be generally transverse to the generally cylindrical radially protecting surface ( 72 ). In one embodiment, the pair of axially protecting surfaces ( 74 , 76 ) can at substantially  90  degrees to the generally cylindrical radially protecting surface ( 72 ). Naturally, the surfaces ( 72 ,  74 ,  76 ) can extend at any suitable any relative to each other, depending on the configuration of the bearing housing ( 22 ) and/or other components at the interface. 
         [0024]    The surfaces ( 72 ,  74 ,  76 ) can be formed together as a unitary structure, or at least one of the surfaces ( 72 ,  74 ,  76 ) can be defined by a separate piece and joined to the other surface defining piece(s). The protective element ( 70 ) can be a ring-like structure. The protective element ( 70 ) can be made as a single piece or a plurality of circumferential ring segments, that is, in a direction about the axis ( 98 ) of the bore ( 100 ) in the aluminum bearing housing ( 22 ). Again, it will be understood that the above-description of the protective element ( 70 ) is provided merely as an example, and embodiments are not limited to this configuration. In some instances, the protective element ( 70 ) can be formed by applying (e.g. spraying) a suitable metal over at least a portion of the aluminum flange ( 42 ), which could have reduced dimensions to accommodate the thickness of the protective element ( 70 ). Alternatively, the protective element ( 70 ) can be cast in place over at least a portion of the flange ( 42 ) of the bearing housing ( 22 ). In at least some instances, the protective element ( 70 ) can be attached to the bearing housing ( 22 ) in any suitable manner, including, for example, by fasteners, adhesives, and/or mechanical engagement, just to name a few possibilities. 
         [0025]    Alternatively or in addition to the protective element ( 70 ), the system can be configured to minimize wear of a bore ( 100 ) in the aluminum bearing housing ( 22 ) by providing a protective sleeve ( 78 ) therein. Thus, the sleeve ( 78 ) can be operatively positioned between the bore ( 100 ) and any bearing system (not shown). The sleeve ( 78 ) can be made of any suitable material. For instance, the sleeve ( 78 ) can be made of a material that has a higher heat resistance and/or a higher wear resistance than the aluminum of the bearing housing ( 22 ). For instance, the sleeve ( 78 ) can be made of cast iron, titanium, or any suitable type of steel. The sleeve ( 78 ) can be made of a material that has a hardness greater than the base aluminum metal of the bearing housing ( 22 ). The sleeve ( 78 ) can have a turbine end ( 80 ) and a compressor end ( 82 ). The sleeve ( 78 ) can be hollow and have any suitable cross-sectional size and/or shape. The sleeve ( 78 ) can have a wall of any suitable thickness. 
         [0026]    The sleeve ( 78 ) can be provided in the bore ( 100 ) in any suitable manner. For instance, the sleeve ( 78 ) can be cast in place within the bore ( 100 ). Alternatively, the sleeve ( 78 ) can be inserted into the bore ( 100 ) and attached by, for example, press fit, interference fit, fasteners, adhesives, and/or mechanical engagement, just to name a few possibilities. The sleeve ( 78 ) can be formed by applying (e.g., spraying), a suitable metal over at least a portion of the bore ( 100 ), which can have increased dimensions. 
         [0027]    The sleeve ( 78 ) can be formed as a single component, or it can be formed by a plurality of sleeve segments that are joined together in any suitable manner. The sleeve ( 78 ) can include accommodations for other components. For instance, the sleeve ( 78 ) can include passages ( 84 ) for fluid connection of the journal bearing oil delivery ports ( 86 ) to the oil delivery galleries ( 87 ). Further, the sleeve ( 78 ) can be configured to allow spent oil out of the bearing system, such as by slots ( 88 ) formed in the sleeve ( 78 ). In a similar fashion, the turbine-end ( 80 ) of the sleeve ( 78 ) must have accommodation for a step bore ( 90 ) and accommodation for the exit of oil flung off the turbine-end flinger of the shaft ( 20 )(see  FIG. 2 ). The turbine-end ( 80 ) of the sleeve ( 78 ) would be part of the main sleeve, but it could be a separate component. 
         [0028]    Referring to  FIG. 5 , another example of a protective system for an interface between the aluminum bearing housing ( 22 ) and the turbine housing ( 14 ) for a vee-band type of clamping is shown. Such an arrangement can resist damage caused by the inner surface of the retainer segment ( 54 ) on the outer tapered surface ( 92 ) of the aluminum flange ( 42 ). A protective element ( 94 ) can be provided to form a protective surface over at least a portion of the aluminum flange ( 42 ). The outer tapered surface ( 96 ) provided by the protective element ( 94 ) in this configuration can be in direct contact with the inner surface of the retainer ( 54 ), thus minimizing wear and damage to the aluminum flange ( 42 ), thereby avoiding hindrances to the correct sliding mechanism required of the vee-band configuration. The protective element ( 94 ) can be made of any suitable material. For instance the protective element ( 94 ) can be made of a material that has a higher heat resistance and/or a higher wear resistance than the aluminum of the bearing housing ( 22 ). For instance, the protective element ( 94 ) can be made of cast iron, titanium, or, any suitable type of steel. The protective element ( 94 ) can be made of a material that it harder than the aluminum bearing housing ( 22 ). 
         [0029]    The protective element ( 94 ) can have any suitable conformation. In one embodiment, the protective element ( 94 ) can be configured like a cap for the flange ( 42 ) in a vee-band configuration. The protective element ( 94 ) can have a generally v-shaped cross-section, as is shown in  FIG. 5 . The protective element ( 94 ) can include first and second inner surfaces ( 102 ,  104 ). The first and second inner surfaces ( 102 ,  104 ) can be angled relative to each other. In the embodiment shown in  FIG. 5 , an acute angle is formed between the first and second inner surfaces ( 102 ,  104 ). The first and second inner surfaces ( 102 ,  104 ) can be connected by a third inner surface ( 106 ). The protective element ( 94 ) can be configured to cover at least a portion of the flange ( 42 ). The protective element ( 94 ) can have any suitable thickness. 
         [0030]    The protective element ( 94 ) can be formed in any suitable manner. For instance, the protective element ( 94 ) can be formed as separate component that is placed over the aluminum flange ( 42 ). The protective surfaces provided by the protective element ( 94 ) can be a single piece construction or it can be made of a plurality of pieces. The protective element ( 94 ) can be a ring-like structure. It can be made as a single piece or a plurality of circumferential ring segments, that is, in a direction about the axis ( 98 ) of the bore ( 100 ) in the aluminum bearing housing ( 22 ). Again, it will be understood that the above-description of the protective element ( 94 ) is provided merely as an example, and embodiments are not limited to this configuration. In some instances, the protective element ( 94 ) can be formed by applying (e.g. spraying) a suitable metal over at least a portion of the aluminum flange ( 42 ), which could have reduced dimensions to accommodate the thickness of the protective element ( 94 ). Alternatively, the protective element ( 94 ) can be cast in place over at least a portion of the flange ( 42 ) of the bearing housing ( 22 ). In at least some instances, the protective element ( 94 ) can be attached to the bearing housing ( 22 ) in any suitable manner, including, for example, by fasteners, adhesives, and/or mechanical engagement, just to name a few possibilities. 
         [0031]    Referring to  FIG. 6 , additional examples of protective systems for an interface between an aluminum bearing housing ( 22 ) and a turbine housing ( 14 ) and/or a bearing system (not shown) are shown. Here, the turbine heat shield ( 46 ′) can be modified from the typical design so as to provide a protective buffer, both axially, in the direction of the compressor cover, and radially, for the aluminum bearing housing ( 22 ) interface with the turbine housing ( 14 ). In this arrangement, there may be no fixed protective cover on the bearing housing ( 22 ), but the turbine-end facing axial mating face ( 112 ) of the bearing housing flange ( 42 ) (with the complementary abutment ( 44 ) in the turbine housing ( 14 )) can be protected by an extended axially facing surface ( 114 ) of the turbine heat shield ( 46 ′). 
         [0032]    The surface of radial mating face ( 116 ) of the bearing housing flange  42 ) (with the complementary pilot diameter in the turbine housing ( 14 )) can be protected by the extension portion ( 110 ) by a further extended radially facing flange ( 118 ) of the turbine heat shield ( 46 ′) continuing from the extended axially facing surface ( 114 ) of the turbine heat shield ( 46 ′). The heat shield ( 46 ′) can be formed in any suitable manner. 
         [0033]    Further, the compressor facing side ( 120 ) of the flange ( 42 ) can be protected by either clamp plates ( 52 ), which can have a large surface area, or by parts of a segmented ring to spread the clamp load from the nut ( 54 ) and clamp plate ( 52 ) to minimize wear on the aluminum flange surface. 
         [0034]    Alternatively on in addition to the heat shield ( 46 ′), the protective system can include a sleeve ( 78 ). The above discussion of the sleeve ( 78 ) made in connection with  FIG. 6  is equally applicable here. 
         [0035]    The heat shield ( 46 ′) can be made of any suitable material. For instance the heat shield ( 46 ′) can be made of a material that has a higher heat resistance and/or a higher wear resistance than the aluminum of the bearing housing ( 22 ). For instance, the heat shield ( 46 ′) can be made of cast iron, titanium, or any suitable type of steel. 
         [0036]    It will be appreciated that embodiments herein can provide numerous benefits. For instance, by providing the protective interfaces described herein, various areas of an aluminum bearing housing ( 22 ) can be protected from wear. Thus, an aluminum bearing housing ( 22 ) can be used in a turbocharger, thereby allowing for mass reduction and the associated reduction in the moment carried on the turbine housing to bearing housing interface. 
         [0037]    The terms “a” and “an,” as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). 
         [0038]    Aspects described herein can be embodied in other forms and combinations without departing from the spirit or essential attributes thereof. Thus, it will of course be understood that embodiments are not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the following claims.