Abstract:
A modular gear case assembly for an internal combustion engine is disclosed that includes a plate removably coupled to the block of the engine with a through hole in the plate through which an end of the crankshaft of the engine extends. The gear case is coupled to the plate and includes: a central gear that couples with the end of the crankshaft, a first interconnecting gear that meshes with the central gear, a second interconnecting gear that meshes with the central gear, a first side gear that meshes with the first interconnecting gear, a second side gear that meshes with the second interconnecting gear, a housing in which the gears are disposed, and a cover that sealingly couples with the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority benefit from U.S. provisional patent application 61/471,236 filed 4 Apr. 2011. 
     
    
     FIELD 
       [0002]    The present disclosure relates to an internal combustion engine and more particularly to driving accessories associated with the engine. 
       BACKGROUND 
       [0003]    Internal combustion engines are used to provide power to a vehicle and typically to other devices, such as pumps, generators, and/or compressors. Typically, the engine drives engine accessories and/or vehicle accessories as well via belts, chains, or gears. Front end accessory drive belts or chains are advantageous in that they provide greater flexibility in packaging. However, they are susceptible to breakage, particularly later in their operational life. Truck manufacturers often prefer a more robust solution than a belt or chain driven accessory drive for certain accessories, such as air brake compressors and power steering pumps. It is common to provide a gear case on the front of the engine to drive these accessories. The engine block casting is customized to accommodate such a gear case. This presents no problem for an engine that is designed specifically for a particular application. However, for an engine that is designed for multiple applications, either a conventional belt/chain driven front end accessory drive (FEAD) is tolerated or separate engine block castings are provided for each unique application. 
         [0004]    Prior art types of the engine blocks are illustrated by U.S. Pat. Nos. 3,047,085 to Kieffer et al., 6,415,758 to Pierro et al., 7,047,929 to Aketa, et al. The U.S. Pat. No. 6,415,758 to Pierro et al., for example, teaches an engine block having machined front and rear faces, in which each of the front and rear faces is capable of receiving and sealing against a housing enclosing a gear train for coupling the engine crankshaft to a camshaft of the engine. The front face is additionally capable of directly mating with and sealing against an engine front cover and the rear face is additionally capable of directly mating with and sealing against a flywheel housing. The same engine block may be selectively assembled into an engine having a front-mounted or a rear-mounted camshaft gear train. 
         [0005]    As the size and shape of the drive train housing will usually differ from the size and shape of the engine front cover, or the flywheel housing, the front and rear faces of an engine block will have machined sealing surfaces and holes for receiving fastening elements that are redundant in any selected camshaft gear train configuration. The gear case taught by the U.S. Pat. No. 6,415,758 to Pierro et al. requires customization of the engine block casting, which presents a problem for an engine that is to be used in a variety of applications. 
         [0006]    An opportunity exists for an improved system that both allows for both the ability to accommodate a variety of applications with a geared-drive for at least some of the accessories. 
       SUMMARY 
       [0007]    An internal combustion engine is disclosed which has an engine block having a crankshaft disposed inside the engine block and rotatable about a central axis and a gear case removably secured to the engine block. The gear case has a central gear coupled to an end of the crankshaft and first and second side gears that rotate in response to rotation of the central gear. A first ancillary device mechanically engages with the first side gear and a second ancillary device mechanically engages with the second side gear. The gear case also has a housing to receive the central gear and the side gears and a cover to enclose the housing. The housing and the cover each have an orifice adapted through which the crankshaft extends. A first interconnecting gear is disposed between and mechanically engages the first side gear with the central gear. A second interconnecting gear is disposed between and mechanically engages the second side gear with the central gear. 
         [0008]    The cover and the housing each have at least two blind holes to accommodate: a first shaft extending from a first blind hole in the cover through the first side gear and into a first blind hole in the housing and a second shaft extending from a second blind hole in the cover through the second side gear and into a second blind hole in the housing. The first gear engages with the first shaft such that the first shaft rotates with the first gear and the second gear engages with the second shaft such that the second shaft rotates with the second gear. A third shaft extends from a third blind hole in the cover through the first interconnecting gear and into a third blind hole in the housing and a fourth shaft extends from a fourth blind hole in the cover through the second side gear and into a fourth blind hole in the housing. A plate is coupled between the engine block and the gear box. In some embodiments, an additional plate is coupled to the gear box on a side of the gear box distal from the engine block. The first ancillary device is one of an air brake compressor, a power steering fluid pump, and a fuel pump, an auxiliary oil pump, a scavenge oil pump for a dry sump system, and a supercharger. 
         [0009]    A gear case assembly for an internal combustion engine is disclosed which includes: a plate removably coupled to the block of the engine with a through hole in the plate through which an end of the crankshaft of the engine extends and a gear case coupled to the plate. The gear case includes a central gear that couples with the end of the crankshaft via a key or other coupler, a first interconnecting gear that meshes with the central gear, a second interconnecting gear that meshes with the central gear, a first side gear that meshes with the first interconnecting gear, a second side gear that meshes with the second interconnecting gear, a housing in which the gears are disposed, and a cover that sealingly couples with the housing. In one embodiment, either the cover or the housing of the gear box is integrally formed with the plate. In another embodiment, the housing of the gear box is coupled to the plate coupled to the engine block with the assembly further including a plate coupled to the cover of the gear box. Alternatively, the cover of the gear box is coupled to the plate coupled to the engine block and the assembly includes a plate coupled to the housing of the gear box. 
         [0010]    A first ancillary is mechanically coupled to the first side gear via a first shaft and a second ancillary is coupled to the second side gear via a shaft. The first ancillary is one of: an air brake compressor, a power steering fluid pump, a fuel pump, an auxiliary oil pump, a scavenge oil pump for a dry sump system, and a supercharger. 
         [0011]    The gear case may further include an oil fill orifice defined in an upper surface of the gear case and an oil level orifice a side surface of the gear case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates an isometric view of an engine system wherein a crankshaft extending from the engine is connected with a plurality of accessories by a single belt; 
           [0013]      FIG. 2  illustrates a perspective view of the gear case of the present disclosure; 
           [0014]      FIG. 3  illustrates an exploded view of the gear case shown in  FIG. 2  also showing a portion of a crankshaft of the engine; and 
           [0015]      FIG. 4  illustrates a schematic of an opposed-piston, opposed-cylinder engine having a gear case mounted thereon to drive accessories. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated. 
         [0017]    By the way of background, truck manufacturers drive certain accessories, such as, an air brake compressor and a power steering pump, by gears so as to avoid front end accessory drive belt breakage that could cause loss of air brakes and/or power steering. Therefore, it is common to provide a gear case on the front of the engine to drive the aforementioned accessories. The U.S. Pat. No. 6,415,758 to Pierro et al., for example, discloses such gear case rigidly connected to the front of the engine. However, for an engine designed for multiple applications in which some accessories are to be gear driven, a modular gear case approach is desired. 
         [0018]      FIG. 1  illustrates an engine system, generally shown at  20 , with a crankshaft  22  extending from an engine block  12 . Crankshaft  22  is coupled to a pulley  36  to drive via a belt  32  a plurality of pulleys  26  and  28 , as examples. Pulleys  26  and  28  are coupled to accessories or ancillary devices, such as a water pump, a power steering pump, an air brake compressor, an alternator, an auxiliary engine oil pump, a supercharger, etc. Many of the accessories are, at best, partially visible in  FIG. 1 . However, an alternator  27  can be seen in  FIG. 1 . Belt  32  is typically called a serpentine belt as it takes on a complicated shape to engage multiple pulleys as well as a belt tensioner. Torque from the engine is transmitted through the crankshaft to drive the various ancillary devices that are used in the particular application. 
         [0019]    Referring now to  FIGS. 2 and 3 , a modular gear case  40  is shown in assembled view,  FIG. 2 , and an exploded view in  FIG. 3 . Modular gear case  40  has plates  46  and  48  on either side. Orifices  49  to accommodate bolts for mounting to an engine block are shown in  FIG. 2 . Orifices  49  can be placed in whatever location on plate  46  desired to allow secure mounting on the engine block. In one alternative, modular gear case is coupled to plate  46 . In another alternative, plate  46  is formed integrally with cover  44  of gear case  40 . Another plate  48  is provided on the front side of gear case  40  so that a conventional chain or belt-driven FEAD may be installed onto plate  48 . That is, certain accessories may be gear driven, while other accessories may continue to be belt driven. Although a crankshaft is not shown in  FIG. 2 , the crankshaft can be extended out of plate  48  and coupled to a pulley to drive one or more belt-driven accessories. 
         [0020]    An exploded view of gear set  40  is shown in  FIG. 3 . A plurality of blind holes  45  are defined in cover  44  to support shafts  60  and  61 . Similar blind holes are provided in housing  42  to support shafts  61 . Shafts  60  extend through cover  42  to engage with accessories, i.e., extending out of mounting bosses  62  (accessories not shown in  FIG. 3 ). Large through holes  75  are defined in plate  46  (not shown), cover  44 , housing  42  (not shown) and plate  48 . Through holes  45  are provided to accommodate the end of crankshaft  22  to extend through gear case  40 . A keyway  23  is provided on crankshaft  22  with a key  24  inserted in keyway  23 . Key  24  engages with a keyway  51  provided on a central gear  50  ( FIG. 3 ). Crankshaft  22  may extend out of plate  48 . A pulley (not shown) can be coupled to the end of crankshaft  22  to drive additional accessories via a conventional belt or chain system. 
         [0021]    Inside gear case  40  are central gear  50 , which rotates with the crankshaft via a key coupling or other alternative coupling system. Central gear  50  meshes with interconnecting gears  56  and  58  that rotate on shafts  61 . Shafts  61  may rotate with gears  56  and  58  or alternatively may be stationary with gears  56  and  58  rotating with respect to shafts  61 . Side gears  52  and  54  mesh with gears  58  and  56 , respectively, with shafts  60  coupling with side gears  52  and  54  so that shafts  60  rotate with gears  52  and  54 . In one example, shafts  60  are splined in the region where they couple with side gears  52  and  54 , which are complementarily splined. Furthermore, shafts  60  are splined where they couple with accessories (not shown). On the outside of housing  42 , a pair of mounting bosses  62  and  64  is provided for mounting accessories. Accessories, such as a power steering pump and an air brake compressor, can be coupled each to one of the mounting bosses. The pump and the compressor each engage with one of shafts  60 . When crankshaft  22  rotates, the pump and the compressor are caused to rotate due to the rotation of gears  52 ,  54 ,  56  and  58  and shafts  60 . Shafts  60  may be splined or have an alternative coupling system. In yet another alternative, a shaft may be provided on the accessory with that shaft coupling with the side gears. 
         [0022]    In one alternative, there are no interconnecting gears  56  and  58  and no shafts  61 . That is, side gears  52  and  54  mesh directly with central gear  50 . It is a cheaper, simpler, and lighter design. However, gears  52  and  54  rotate in the opposite direction from what they would rotate when interconnecting gears  56  and  58  are provided. Furthermore, in some situations, it may be desirable to have mounting bosses  61  and  64  spread farther apart, which the interconnecting gears  56  and  58  allow. 
         [0023]    Referring to  FIG. 3 , an oil fill orifice  80  is provided in housing  42  with a plug  81 . Housing  42  is also provided with an oil level orifice  82  with a plug  83 . The housing may also have an oil drain orifice with a plug. Such oil drain orifice is not visible in  FIG. 3 . Gear oil may be provided in gear case  40  to provide lubrication. 
         [0024]    Cover  44  mates with housing  42  to hold gear case  40  together. In one embodiment, the two are welded together. Alternatively, a series of bolts and bolt holes are used to couple the two. In such embodiment, a gasket may be employed to aid in holding gear oil inside the housing. 
         [0025]    Gear case  40  in  FIGS. 2 and 3  accommodates two ancillary devices to be gear driven. However, this is one example. Additional gears may be driven by a pulley (not shown) coupled to crankshaft  22  to drive additional accessories. 
         [0026]    Referring to  FIG. 4 , an opposed-piston, opposed-cylinder engine  100  having a modular gear case  140  is represented schematically. One example of such an engine is disclosed in U.S. Pat. No. 6,170,443. Engine  100  has a crankshaft  122  that extends through gear case  140 . A central gear  150  is coupled to crankshaft  122  in such a manner that the two rotate together. Central gear  150  engages with an interconnecting gear  158 , which in turn engages with a side gear  152 . Side gear  152  rotates in response to rotation of crankshaft  122 . Side gear  152  rotates with shaft  160 . Shaft  160  and side gear  152  may be splined, keyed, or coupled in any known manner so that they rotate together. Gear case  140  includes an accessory mounting boss  164 , shown in  FIG. 4  as extending outwardly from gear case  140 , but could alternatively be flush with the surface of gear case  140 . Accessory  180  is mounted to accessory mounting boss  164  and driven via shaft  160 . Alternatively, accessory  180  could include a shaft that engages with side gear  152 . 
         [0027]      FIG. 4  shows gear case  140  driving two accessories  180  and  182 . Alternatively, gear case  140  could drive more accessories. Selected accessories, e.g., air conditioning compressor, could be driven by a conventional pulley and belt or chain system. To accommodate such accessories for which it is desirable to use the pulley/belt system, a pulley  170  is shown also coupled to crankshaft  122 . 
         [0028]    While the best mode has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.