Patent Publication Number: US-2023143633-A1

Title: Gear train joint

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to turbochargers and, more particularly, to turbochargers with a gear train joint. 
     BACKGROUND 
     Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines, employ turbochargers to deliver compressed air to combustion chambers within the engine. An increased supply of air enables increased fuel combustion within the combustion chambers of the engine, resulting in increased power output from the engine. 
     A typical turbocharger rotor includes a shaft extending between a compressor impeller (also referred to as a compressor wheel) and a turbine. Bearings typically support the shaft, and separate housings coupled together enclose the compressor impeller, the turbine, and the bearings. In operation, hot exhaust from the engine flows through the turbine housing and expands over the turbine, rotating the turbine and the shaft, which in turn rotates the compressor impeller. The compressor impeller receives cool air from ambient surroundings and forces compressed air into combustion chambers of the engine. A gear train may also be provided to drive the turbine during, for example, operation at lower speeds and loads, when the engine exhaust energy alone is insufficient to drive the turbine. 
     Turbocharger rotors driven by epicyclic gear trains require user of complex alignment mechanisms to ensure all mating surfaces run within specification, as any misalignment, for example, can cause damage to individual components and shorten service life. Spur gears, which are typically used to transmit motion and power between parallel shafts, may have offset centerlines, requiring the housings supporting the gears and associated bearings to include apertures in at least one side, which can make it difficult to align the housings via simple pilots. Some solutions require placing a structural bulkhead between drive and output gears, which adds even more to the complexity of aligning the various support structures. 
     One method of aligning multiple housings, involves locating the pieces relative to one another, machining out the bearing bores and then doweling the pieces together. Such an approach is disclosed in U.S. Pat. No. 10,526,954, in which a turbine housing includes dowels for attachment of an insert and to achieve a desired axial alignment with respect to the insert. While this general approach may achieve a desired alignment accuracy, it is done so at the expense of complex machining and the requirement for matched or paired assemblies. There is consequently a need for an improved gear train joint. 
     SUMMARY 
     In accordance with one aspect of the present disclosure, a bearing support for a turbocharger is disclosed. The bearing support may include a body, a bore, and a plurality of pilots. The bore may extend axially through the body and may be dimensioned to receive a bearing and a portion of a planet carrier. Each pilot may be formed on an external surface of the body, and each pilot may be machined for an interference fit with a different component of the turbocharger. 
     In accordance with another aspect of the present disclosure, a gear train assembly for a turbocharger is disclosed. The gear train assembly may include a drive shaft, a plurality of planetary gears, a planet carrier, a gear support and a bearing support. The drive shaft may be coupled to a turbine wheel and a sun gear. The planet carrier may extend from a center axis of the plurality of planetary gears through a primary bearing. The gear support may be coupled to a housing of the turbine wheel. In addition, the bearing support may include a body, a bore, and a plurality of pilots. The bore may extend axially through the body and may be dimensioned to receive the primary bearing and a portion of the planet carrier. Each pilot may be formed on an external surface of the body, and may be machined for interference fit with a different component of the turbocharger. 
     In accordance with yet another aspect of the present disclosure, a turbocharger is disclosed. The turbocharger may include a turbine wheel housed in a turbine housing having an end wall, a compressor impeller housed in a compressor housing, and a shaft extending between the turbine wheel and the compressor impeller. The turbine wheel and the compressor impeller may be mounted on the shaft for rotation together, and a gear train may be driven by an engine. The gear train may include a drive shaft couple to the turbine wheel, a plurality of planetary gears, a planet carrier configured to couple the plurality of planetary gears together; and a bearing support. The bearing support may include a body, a bore and four pilots. The bore may extend axially through the body and be dimensioned to receive the primary bearing and a portion of the planet carrier. Each pilot may be configured to form an interference fit between an external surface of the bearing support and a surface of a corresponding component of the turbocharger. 
     These and other aspects and features of the present disclosure will be better understood upon reading the following detailed description, when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration of an engine system including a turbocharger, in accordance with an embodiment of the present disclosure; 
         FIG.  2    is a perspective view of the turbocharger of  FIG.  1   , in accordance with an embodiment of the present disclosure; 
         FIG.  3    is a sectional view of the turbocharger of  FIG.  2   , in accordance with an embodiment of the present disclosure; 
         FIG.  4    is a perspective view of a portion of the turbocharger of  FIG.  2   , in accordance with an embodiment of the present disclosure; 
         FIG.  5    is a sectional view of a portion of the turbocharger of  FIG.  2   , in accordance with an embodiment of the present disclosure; and 
         FIG.  6    is a sectional view of a portion of the turbocharger of  FIG.  2   , in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. 
     Referring now to  FIG.  1   , an exemplary power system  10  is illustrated schematically. The power system  10  includes an internal combustion engine  12 , an integrated turbocharger  14 , an air induction system  16 , and an exhaust system  18 . For the purposes of this disclosure, the engine  12  may be a two-stroke diesel engine, although one skilled in the art will recognize that the engine may be any other type of internal combustion engine such as, for example, a four-stroke diesel engine or a two- or four-stroke gasoline or gaseous fuel-powered engine. Further, the engine  12  may find applications in mobile machines (not shown) such as, but not limited to, locomotives, vehicles, heavy mechanical equipment, large tractors, on-road vehicles, off-road vehicles, marine vessels and the like, as well as in stationary machines (not shown) such as generator sets and pumps. 
     The engine  12  may include an engine block  20  that at least partially defines a plurality of cylinders  22 . A piston (not shown) may be slidably disposed within each cylinder  22  to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head (not shown) may be associated with each cylinder. Each cylinder  22 , piston, and cylinder head may, together, at least partially define a combustion chamber. In the embodiment illustrated in  FIG.  1   , the engine  12  includes six cylinders  22  arranged in an inline configuration. However, it is contemplated that the engine  12  may include a greater or lesser number of cylinders  22 , and that the cylinders may be arranged in a V-configuration (i.e., a configuration having first and second banks or rows of cylinders), an opposing-piston configuration, or another configuration as will be apparent to those skilled in the art. Combustion of a fuel and air mixture in each cylinder  22  generates motive power that rotates an engine output shaft  24 , and a resultant exhaust gas is produced, as is known in the art. 
     The engine  12  may further include an air intake manifold  26  and an exhaust manifold  28  that are selectively in fluid communication with each compression cylinder  22 . The air intake manifold  26  may provide compressed intake air to the compression cylinders  22  from the air induction system  16 , which draws air from the ambient atmosphere surrounding the engine  12  and any machine in which the engine is installed. Compressed air from the air intake manifold  26 , along with fuel from a fuel tank (not shown), forms a combustible mixture that ignites when compressed, such as in each cylinder  22 , or in the presence of a spark, for example. Combustion byproducts are evacuated from each cylinder  22  through the exhaust manifold  28 , to one of the exhaust system  18  and the turbocharger  14 . At least a portion of the exhaust gases may be transmitted to the exhaust system  18  for after-treatment prior to being released back into the atmosphere. 
     Another portion of the exhaust gases may be transmitted to the turbocharger  14 , and, more specifically, to a turbine wheel  30  via a high pressure exhaust gas line  32 , for example. A turbocharger housing  34  may be configured to direct the pressurized exhaust gas toward the turbine wheel  30 , which may be mounted opposite a compressor impeller  36  on a shaft  38  within the turbocharger housing. The compressor impeller  36  may be mounted on the shaft  38 , and configured for rotation with the shaft and turbine wheel  30 . When the temperature and pressure of the exhaust gas from the engine  12  are sufficient, exhaust torque generated by the exhaust gas drives the turbine wheel  30 , which causes rotation of the shaft  38  and, ultimately, the compressor impeller  36 . The rotating compressor impeller  36  thereby compresses air received from the air induction system  16 , and outputs compressed air to the air intake manifold  26 , where the compressed air is mixed with air provided by the air induction system. After powering the turbine wheel  30 , spent exhaust gas is discharged to the exhaust system  18  via, for example, a low pressure exhaust gas return line  40 . 
     During some operating conditions of the engine  12 , it may be desirable to drive the turbine wheel  30  of the turbocharger  14  even though a temperature and pressure of the exhaust gas may be insufficient to rotate the turbine wheel at a desired speed. For example, at low engine speeds, such as when the engine  12  is idling, emissions of pollutants such as nitrous oxides (NOx) can increase and low exhaust temperatures can make exhaust after treatment systems in the exhaust system  18  ineffective. In one exemplary embodiment, to selectively provide direct drive to the turbocharger  14  by the engine  12  when the operating conditions dictate, the engine output shaft  24  may drive the shaft  38  when the exhaust gas will not drive the turbine wheel  30 , and may be disengaged when the exhaust gas will create sufficient torque and rotate the turbine wheel and the compressor impeller  36  at sufficient speeds so that direct drive by the engine is unnecessary. 
     For example, in one embodiment, a carrier shaft  44  may be operatively coupled to the turbine wheel  30  and may have a carrier drive gear  46  mounted thereon and rotatable therewith. An operative connection between the engine  12  may be provided by a turbocharger drive gear  48  connected to a gear train or transmission  52  that is driven by the engine output shaft  24 . The turbocharger drive gear  48  may be operatively connected to the carrier drive gear  46  by one or more idler gears  50  so that the carrier shaft  44  will spin at a desired speed and direction relative to the engine output shaft  24 . In other embodiments, other appropriate drive mechanisms and arrangements may be utilized to drive the turbine wheel  30  and compressor impeller  36 . 
     Referring now to  FIGS.  2 - 3   , with continued reference to  FIG.  1   , an exemplary embodiment of the turbocharger  14  is illustrated. The turbocharger housing  34  includes both a compressor housing  54  and a turbine housing  56 . In operation, air may enter the compressor housing  54  from the air induction system  16  via a compressor inlet  58 , and may exit the compressor housing toward the air intake manifold  26  via a compressor outlet  60 . Similarly, exhaust gases may enter the turbine housing  56  from the exhaust manifold  28  via a turbine inlet  64 , and may exit the turbine housing toward the exhaust system  18  via a turbine exhaust duct  62 . 
     Further, the turbocharger  14  may include at least a compressor stage  66  and a turbine stage  68  disposed within the turbocharger housing  34 . The compressor stage  66  may include the compressor impeller assembly including the compressor impeller  36 , a stud  72 , an insert  74 , an impeller cap  76 , a thrust washer  78 , and the shaft  38 , all of which may be disposed around a rotational axis  80 . As air moves through the compressor stage  66 , the compressor impeller  36  may increase the pressure of the air, which may be directed toward the engine  12 . The turbine stage  68  may include the turbine housing  56  and the turbine wheel  30 , which may be attached to the shaft  38 . As hot exhaust gases move through the turbine housing  56  and expand against blades  70  of the turbine wheel  30 , the turbine wheel may rotate, causing the compressor impeller  36  to rotate via the shaft  38  and the stud  72 . 
     The turbocharger  14  may further include a compressor side bearing housing (not shown) and a turbine side bearing housing  82  that may connect the compressor impeller  36  and the turbine wheel  30  to their respective support housings  54 ,  56 . More specifically, the turbine side bearing housing  82  may be a generally cylindrical, multi-stepped component configured to internally support the shaft  38  via bearings  84 , and to engage an exterior surface  86  of an end wall  88  at an outer periphery. The turbine side bearing housing  82  may also at least partially house and support a gear train  90 . The gear train  90  may facilitate selective operation of the turbocharger  14  in a turbocharging mode of operation (i.e., where the turbine wheel  30  drives the compressor impeller  36  in a conventional manner) where the engine  12  drives the compressor impeller via the turbine wheel. The gear train  90  may be a planetary or epicyclic gear train. A planetary gear train is generally made up of at least three different elements, including a sun gear, a planet carrier having at least one set of planet gears, and a ring gear. The planet gears of the planet carrier mesh with the sun gear and the ring gear. The sun gear, planet carrier and ring gear are driven as an input, while another of the sun gear, planet carrier, and ring gear rotates as an output. 
     In the illustrated embodiment, as shown in  FIGS.  4 - 6    with continued reference to  FIGS.  1 - 3   , the gear train  90  may include a drive shaft  92  coupled, at a first end  94 , to the turbine wheel  30 . A sun gear  96  may be formed by or at a second end  98  of the drive shaft  92 . A plurality of planet gears  100  may orbit, and mesh with, the sun gear  96 . A planet carrier  102  may extend from center axes of the planet gears  100  and have formed thereon a spur gear  104 . The spur gear  104  may, for example, drive one or more adjacent input gears  106 . A gear support  108  may connect to the end wall  88  of the turbine housing  56 , and may provide a means of supporting and providing oil to the planet carrier  102  and its associated rotating components. 
     The planet carrier  102  may be supported at one end by a primary bearing  110  that may be housed within a bore  112  of a bearing support  114 , and at an opposing end by a secondary bearing  116  that may be pressed into a stepped bore  118  of the gear support  108 . The secondary bearing  116  may include an inner race  120  and an outer race  122 . Inner race  120  may engage the spur gear  104  on one end and a cap  124  on an opposite end. The cap  124  may engage an interior shoulder of the stepped bore  118  and support a lateral end of the planet carrier  102 . The outer race  122  may be free on one end and the engage stepped bore  118  on an opposite end. A conduit  126  may extend through the cap  124  and direct oil toward bearings (not shown) associated with the planet gears  100 . 
     Referring now to  FIGS.  5  and  6   , and with continued reference to  FIGS.  1 - 4   , the bearing support  114  may be utilized as a primary structural bulkhead and piloting device to align the numerous components of the gear train  90  and turbocharger  14 . Specifically, bore  112  of the bearing support  114  may extending axially through a body  170  of the bearing support and may be dimensioned to house the primary bearing  110  of the epicyclic gear train  90 . Similar to the secondary bearing  116 , the primary bearing  110  may also include an inner race  128  and an outer race  130 . The inner race  128  may engage the planet carrier  102  on one end, and a spacer  132 , disposed around the planet carrier, on an opposite end. The outer race  130  may engage a shoulder  134  of the bearing support  114  on one end, and a snap ring  136  disposed within snap-ring groove  138  of the bearing support, on an opposite end. 
     The bearing support  114  may be fixedly installed to the end wall  88  using a bolt  140 , for example, inserted from the compressor impeller  36  side of the turbocharger  14  through an aperture  142  in the bearing support. To ensure proper alignment of the bearing support  114  during installation, the bearing support may be machined directionally from the compressor impeller  36  side toward the turbine wheel  30  side (or, as typically called in the art, “from right to left”), and may also be constructed to form a plurality of pilots with surrounding components. For example, the bearing support  114  may include the bore  112  that may include a grooved portion  152  and a bearing portion  154 . The grooved portion  152 , for example, may include the snap-ring groove  138 . A first pilot  144 , therefore, may be formed between a radially exterior surface  156  of part of the bearing portion  154  of the bearing support  114  and a radially internal surface  158  of the end wall  88  of the turbine housing  56 . A second pilot  146  may be formed between a radially exterior surface  160  of the grooved portion  152  of the bearing support  114  and a radially internal surface  162  of the gear support  108 . The bearing portion  154  of the bearing support  114  may be dimensioned to accommodate the outer race  130  of the primary bearing  110 , such that a third pilot  148  is formed between a radially internal surface  164  of the bearing portion of the bearing support and a radially external surface  166  of the outer race  130  of the primary bearing. Finally, a fourth pilot  150  may be formed between a radially external surface  168  of the bearing support  114  and a radially internal surface of the turbine housing  56 . The plurality of pilots  144 ,  146 ,  148 ,  150  are configured to align the bearing support  114 , the turbine housing  56 , the end wall  88 , the gear support  108 , the primary bearing  110  and its associated inner  128  and outer  130  races, by way of interference fit at the locations of each of the pilots. In an alternative embodiment, however, one or more of the plurality of pilots  144 ,  146 ,  148 ,  150  may be configured to align the bearing support  114 , the turbine housing  56 , the end wall  88 , the gear support  108 , the primary bearing  110  and its associated inner  128  and outer  130  races, by way of a standard pilot fit or a transitional fit at the locations of each of the pilots 
     INDUSTRIAL APPLICABILITY 
     In practice, the teachings of the present disclosure may find applicability in many industries including, but not limited to, the railroad, marine, power generation, mining, construction, and farming industries, as well as other industries known in the art. More specifically, the present disclosure may be beneficial to locomotives, other vehicles, and any other machine utilizing a turbocharger. 
     Traditionally, doweling assemblies have been used to align complex housings and components of turbochargers utilizing drive trains. In that arrangement, the centers of the each component must first be aligned, holes then would be drilled through the components corresponding to locations of dowels, which were subsequently inserted. With the dowels installed, the components could be disassembled and then properly realigned during installation. The doweling method requires special tooling of each component, and accuracy is still incredibly difficult to achieve. 
     In contrast, the present bearing support  114  is a fully piloted assembly, relying on four critical pilots  144 ,  146 ,  148  and  150 , which ultimately align each of the components in at least the turbine stage  68  of the turbocharger  14 . More specifically, the bearing support  114 , once interference fit within the turbocharger  14 , aligns not only the primary bearing  110  and the secondary bearing  116 , but all components of the epicyclic gear train  90  as well. The bearing support  114  is also machined for easy removal and replacement. For example, the turbocharger  14  may endure various stresses over its life span due to aerodynamic, thermal and mechanical loads. Occasionally, failures or problems may occur in the gear train  90  components. With traditional doweling arrangements, failures or damage within the turbocharger  14 , or more specifically within the gear train  90 , typically result in damage to the component at issue, but also all components surrounding the damaged component. As such, trying to repair damage to a doweled assembly of components is generally not feasible. In contrast, the fully piloted bearing support  114  relies on the pilots  144 ,  146 ,  148 ,  150  to align the bearing support within the turbocharger  14 , as well as all the surrounding components, simply by inserting the bearing support into position. 
     While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and assemblies without departing from the scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof. 
     It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.