Patent Publication Number: US-8985082-B2

Title: Engine assembly with pump cavity liner and method of assembling an engine

Description:
TECHNICAL FIELD 
     The present teachings generally include an engine assembly with an engine cover having a pump cavity and a method of assembling an engine. 
     BACKGROUND 
     Automotive engines are complex assemblies and must be made of materials having sufficient strength as well as the ability to withstand relatively high temperatures. Engines are typically cooled by a crankshaft-driven coolant pump mounted to the engine. Strategic use of composite components can meet engine durability requirements while decreasing overall weight. 
     SUMMARY 
     An engine assembly is provided that includes an engine cover having a pump cavity through which fluid is pumped. A liner is configured to line the pump cavity to protect the engine cover from erosion due to the pumped fluid. The liner is especially useful if the engine cover is a composite material. The liner may be a composite material as well, or in some embodiments, can be steel or another suitable material. 
     A method of assembling an engine includes securing a liner to an engine cover so that the liner lines a pump cavity of the engine cover to protect the engine cover from erosion at the pump cavity. 
     The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration in perspective exploded view of a portion of an engine assembly including an engine front cover, a pump cavity liner, and a pump assembly in accordance with a first aspect of the present teachings. 
         FIG. 2  is a schematic illustration in fragmentary cross-sectional view of an engine assembly including an engine front cover, a pump cavity liner co-molded with the front cover, and a pump assembly in accordance with a second aspect of the present teachings. 
         FIG. 3  is a schematic illustration in fragmentary cross-sectional view of an engine assembly including an engine front cover, a pump cavity liner vibration welded to the engine front cover, and a pump assembly in accordance with a third aspect of the present teachings. 
         FIG. 4  is a schematic illustration in fragmentary cross-sectional view of an engine assembly including an engine front cover, and a pump cavity liner integrated with a pump assembly in accordance with a fourth aspect of the present teachings. 
         FIG. 5  is a schematic illustration in fragmentary cross-sectional view of an engine assembly including an engine front cover, a pump cavity liner mechanically retained between a pump assembly and the engine front cover in accordance with a fifth aspect of the present teachings. 
         FIG. 6  is a flowchart of a method of assembling an engine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,  FIG. 1  shows an engine assembly  10  that includes a one-piece engine cover  12 . The engine cover  12  is configured to be secured with a plurality of bolts  14 , some of which are numbered in  FIG. 1 , to an engine block (not shown) on a side of the engine block. The engine cover  12  is secured to the engine block so that an engine crankshaft (not shown) can extend out of a crankshaft opening  16  formed in the engine cover  12 . The engine cover  12  can be referred to as a front cover. 
     The engine cover  12  can be an injection-molded, one-piece component of a first composite material. As used herein, a “composite” material is a material that is a composite of a polymer and another material. For example, a “composite” may be a glass-reinforced polyamide (i.e., nylon), a glass-reinforced Acrylonitrile Butadiene Styrene (ABS), a glass-filled thermoset, a glass-filled Polybutylene Terephthalate (PBT), a glass-filled Polyethylene terephthalate (PET), or other polymer composite. 
     The engine cover  12  is formed with a pump cavity  18 . The pump cavity  18  includes a central opening  20  through the engine cover  12  that functions as a coolant inlet. The engine cover  12  includes outlet openings  22  through which coolant is forced out by a pump assembly  24  that, when the engine assembly  10  is assembled, extends partially into the pump cavity  18 . One of the outlet openings  22  is visible in  FIG. 1 , and the other outlet opening  22  is indicated with hidden lines. 
     The engine assembly  10  includes a liner  26  configured to fit within the pump cavity  18  and line substantially the entire surface  28  of the pump cavity  18 . Because the pump cavity  18  is three-dimensional, the surface  28  includes both a bottom surface  29  and wall surface  31  surrounding the bottom surface  29 . That is, the liner  26  is configured to be in contact with the surface  26  of the engine cover  12  at the pump cavity  18  to prevent any coolant from contacting the surface  28 . The liner  26  has a central opening  30  substantially identical to the central opening  20  of the engine cover  12  to allow coolant to flow past the liner  26  to the pump assembly  24 . The liner  26  also is formed with outlet openings  32  that align with the outlet openings  22  in the pump cavity  18  to allow coolant to be pumped out through the aligned openings  22 ,  32 . The pump assembly  24  is secured to the engine cover  12  with bolts  34  that fit through openings  36  in a pump housing  37  aligned with openings  38  in the engine cover  12 , each containing a threaded nut  39 . 
     By lining the surface  28  of the pump cavity  18 , the liner  26  prevents the coolant from contacting the engine cover  12  at the pump cavity  18 . Because the pump assembly  24  causes relatively high speed flow of the coolant, including differential pressures within the coolant at the pump assembly  24  that create the potential for cavitation, certain materials in contact with the coolant flow could tend to erode due to the cavitation. Moreover, any particles carried in the coolant can contribute to erosion. If the coolant is an alcohol-based fluid, it can have an affinity toward certain polyamides, including certain composite materials, causing erosion. 
     The liner  26  can be of material with a high ability to withstand erosion from coolant flow. For example, depending on the method used to assemble the liner  26  to the engine cover  12 , the liner  26  can be a metallic component, such as steel. Alternatively, the liner  26  can be a second composite component that has a greater ability to withstand erosion than the composite from which the engine cover  12  is formed. Such a second composite is likely to be more expensive than the first composite. In one embodiment, the engine cover  12  can be polyamide 6 (PA6, also referred to as nylon 6) or polyamide 66 (PA66, also referred to as nylon 6,6) and the liner can be polyamide 46 (PA46, also referred to as nylon 4,6). Because the liner  26  is much smaller in size than the composite engine cover  12 , forming only the liner  26  of the more expensive second composite material can represent a cost savings compared to the alternative of forming the entire engine cover  12  from the second composite material. 
     The liner  26  can be secured to the engine cover  12  by use of a room temperature vulcanizing (RTV) sealant  40  inserted strategically between the engine cover  12  and the liner  26  by inserting a bead of RTV sealant  40  between the liner  26  and the engine cover  12 , such as by placing a bead of sealant  40  on the engine cover  12  at the pump cavity  18 , and then compressing the sealant  40  by pressing the liner  26  against the engine cover  12  until the sealant  40  is cured, thereby securing the liner  26  to the engine cover  12 . As shown in  FIG. 1 , the sealant  40  is placed both on the bottom surface  29  and the wall surface  31  of the cavity  18 . Alternatively, the sealant  40  can be placed on the outer surfaces of the liner  26  that face the surface  28  of the cavity  18 , and then the liner  26  can be pressed to the engine cover  12  until the sealant  40  cures. In another embodiment, an adhesive can be used in place of the sealant  40  to secure the liner  26  to the engine cover  12 . 
       FIG. 2  shows an alternative embodiment of an engine assembly  110  with a composite engine cover  112 , the pump assembly  24 , and a liner  126 . The pump assembly  24  is the same as that used in the engine assembly  10  of  FIG. 1 . The engine cover  112  and the liner  126  are alike in all aspects to the corresponding components engine cover  12  and liner  26  of the engine assembly  10  of  FIG. 1 , except that the liner  126  is co-molded with the engine cover  112 . To secure the liner  126  to the engine cover  112  by co-molding the liner  126  with the engine cover  112 , the liner  126  must be inserted into the injection molding die used to mold the front cover  112 , and held in a correct position within the die with dowels or the like. The liner  126  can be either steel or a composite material. 
     The cross-sectional view of  FIG. 2  illustrates the pump assembly  24  in greater detail. The pump assembly  24  includes the pump housing  37  and a drive shaft  41  extending through the pump housing  37 . An impeller  42  is mounted to and is driven by the drive shaft  41 . A shroud  44  is mounted to internal walls  46  of the impeller  44  to define pump passages  48  that direct fluid from the central opening  120  of the engine cover  112  and concentric central opening  130  of the co-molded liner  126  to outlet openings in the liner  126  like outlet openings  32  and aligned outlet opening in the engine cover  112  like outlet openings  22 . The pump assembly  24  is bolted to the engine cover  112  with bolts  34  extending into threaded nuts  39  seated in openings  38  in the engine cover  112 . The pump assembly  24  is configured so that a controlled clearance  45  exists between the shroud  44  and the liner  126 . The liner  126  is shown covering only a bottom surface  129  of the entire surface  128  of the pump cavity  118  of the engine cover  112 , protecting the bottom surface  129  from erosion due to current flow, but could be configured to also cover the wall surface  131  of the cavity  118 . 
       FIG. 3  shows another embodiment of an engine assembly  210  that includes a composite engine cover  212  with a liner  226  vibration welded to the engine cover  212  at a pump cavity  218  of the engine cover  212 . The pump assembly  24  extends partially into the pump cavity  218 . The liner  226  is formed with tabs  246  near a center opening  230  of the liner  226  and with tabs  248  near an outer edge  250  of the liner  226 . To assemble the engine assembly  210  and secure the liner  226  to the engine cover  212 , the tabs  246  of the liner  226  are placed in recesses  252  of the engine cover  212 . Tabs  248  of the liner  226  are placed in recesses  254  of the engine cover  212 . Placing the tabs  246 ,  248  in the recesses  252 ,  254  attaches the liner  226  to the engine covers  212 . The liner  226  is then secured to the engine cover  212  by vibration welding, which causes the tabs  246 ,  248  to melt to the engine cover  212  at the recesses  252 ,  254 , and the liner  226  to be welded to the bottom surface  229  of the entire surface  228  of the cavity  218 , protecting the bottom surface  229  from erosion due to current flow. The liner  226  could alternatively be configured to also cover the wall surfaces  231  of the cavity  18 . The pump assembly  24  is then secured to the engine cover  212  with bolts  34  and nuts  39  as described with respect to engine assembly  10 . The controlled clearance  45  exists between the shroud  44  and the liner  226 . 
       FIG. 4  shows another embodiment of an engine assembly  310  that includes an engine cover  312  forming a pump cavity  318 . A liner  326  is integrated with a pump assembly  324  so that the liner  326  lines an entire surface  328  of the engine cover  312  at the pump cavity  318  when the pump assembly  324  is secured to the engine cover  312 . 
     The pump assembly  324  includes a pump housing  337  and a drive shaft  341  that extends at least partially into the pump cavity  318  when the pump assembly  324  is secured to the engine cover  312 . An impeller  342  is mounted to and is driven by the drive shaft  341 . A shroud  344  is mounted to internal walls  346  of the impeller  342  to define pump passages  348  that direct fluid from the central opening  320  of the engine cover  312  and concentric central opening  330  of the liner  326  to outlet openings  332  in the liner  326  like openings  32  and aligned outlet openings  322  in the engine cover  312  like openings  22 . The cross-sectional view in  FIG. 4  is taken rotated forty-five degrees from that of the engine assembly  10  of  FIGS. 2 and 3  so that the outlet openings  322  in the engine cover  312  and the outlet openings  332  in the liner  326  are visible. The liner  326  covers a bottom surface  329  of the pump cavity  318  of the engine cover  312 , protecting the bottom surface  329  from erosion due to current flow. The liner  326  also covers the wall surface  331  of the cavity  318 . 
     The liner  326  is integrated with the pump assembly  324  by attaching the liner  326  to the pump assembly  324  before the pump assembly  324  is secured to the engine cover  312 . The liner  326  may be attached to the pump assembly  324  by adhering the liner  326  to a surface  360  of the pump housing  337  with adhesive placed at the surface  360 , or by fastening the liner  326  to the pump housing  337  with fasteners (not shown) that extend through the housing  337  and liner  326  at openings at the surface  360 . The liner  326  is configured so that a controlled clearance  345  exists between the shroud  344  and the liner  326 . Once attached to the housing  337 , the liner  326  and housing  337  are together moved toward the engine cover  312  so that the liner  326  contacts the engine cover  312  at the surfaces  329 ,  331  and lines the surfaces  329 ,  331 . The pump housing  337  is then bolted to the engine cover  312  similarly to the way the pump housing  337  is bolted to engine cover  12  with bolts  34  and nuts  39  shown in  FIG. 1 , thus securing the liner  326  to the engine cover  312 . 
     A seal  362  can be inserted in a recess in the engine cover  312  prior to inserting the liner  326  into the cavity  318  so that the seal  362  will surround the liner  326  at the wall surface  331  of the cavity  318 . Another seal  364  can be inserted in a recess in the engine cover  312  prior to inserting the liner  326  into the cavity  318  so that the seal  364  surrounds the liner  326  at the bottom surface  329  of the cavity  318 . Alternately, the seals  362 ,  364  can be secured around the liner  326  before the liner  326  is inserted into the pump cavity  318 . 
       FIG. 5  shows another embodiment of an engine assembly  410  that includes an engine cover  412  forming a pump cavity  418 . A pump assembly  424  includes a pump housing  437  and a drive shaft  441  that extends at least partially into the pump cavity  418  when the pump assembly  424  is secured to the engine cover  412 . An impeller  442  is mounted to and is driven by the drive shaft  441 . A shroud  444  is mounted to internal walls  446  of the impeller  442  to define pump passages  448  that direct fluid from the central opening  420  of the engine cover  412  and concentric central opening  430  of the liner  426  to outlet openings in the liner  426  like openings  32  and aligned outlet openings in the engine cover  412  like openings  22 . The liner  426  covers an entire surface  428  of the engine cover  412  at the cavity  418 , including a bottom surface  429  of the pump cavity  418  of the engine cover  412 , and a wall surface  431  of the cavity  418 , thereby protecting the entire surface  428  from erosion due to current flow. 
     The liner  426  is mechanically retained between the pump assembly  424  and the engine cover  412  so that the liner  426  lines the entire surface  428  of the engine cover  412  at the pump cavity  418  when the pump assembly  424  is secured to the engine cover  412 . As used herein, “mechanically retained” means retained with fasteners, such as the bolts  34  and nuts  39  as described with respect to the engine assembly  10  of  FIG. 1 . The liner  426  is configured so that a controlled clearance  445  exists between the shroud  444  and the liner  426 . In the engine assembly  410 , the liner  426  also has openings  470  that align with the openings  472  in the pump housing  437  and the threaded nuts  39  held in the openings  438  of the engine cover  412 . In an alternative embodiment, fasteners can be used to fasten the liner to the engine cover  412  that are separate from fasteners used to fasten the pump housing  424  to the engine cover  412 . 
     Assembly of the engine assemblies  10 ,  110 ,  210 ,  310 ,  410  of  FIGS. 1-5  thus involves various methods of securing a liner to an engine cover to line a pump cavity of the engine cover. Referring to  FIG. 6 , a flowchart shows a method  500  of assembling an engine. The method  500  is described with respect to each of the embodiments of  FIGS. 1-5 , and includes step  502 , securing a liner to an engine cover so that the liner lines a pump cavity of the engine cover to protect the engine cover from erosion at the pump cavity. 
     In the embodiment of  FIG. 1 , the securing step  502  includes sub step  504 , inserting a room temperature vulcanizing (RTV) sealant  40  between the liner  26  and the engine cover  12 , such as on the surface  28  of the engine cover  12  at the pump cavity  18 . The securing step  502  then includes sub step  506 , compressing the sealant  40  by pressing the liner  26  against the engine cover  12  until the sealant  40  is cured, thereby securing the liner  26  to the engine cover  12 . Alternatively, in the embodiment of  FIG. 1 , the securing step  502  can be by sub step  508 , adhering the liner  26  to the engine cover  12 . 
     In the embodiment of  FIG. 2 , the securing step  502  includes sub step  510 , co-molding the liner  126  with the engine cover  112 . As discussed with respect to  FIG. 2 , the liner  126  may be either a composite material, steel, or other material, and must be positioned within the injection mold used to form the engine cover  112 . 
     In the embodiment of  FIG. 3 , the securing step  502  includes sub step  512 , attaching the liner  226  to the engine cover  212  at the pump cavity  218  by inserting tabs  246 ,  248  of the liner  212  into recesses  252 ,  254  formed in the engine cover  212 . Step  502  then includes sub step  514 , vibration welding the liner  226  to the engine cover  212  sufficiently to melt the tabs  252 ,  254  to the engine cover  212 , securing the liner  226  to the engine cover  212 . 
     In the embodiment of  FIG. 4 , the liner  326  is integrated with the pump assembly  324 . Accordingly, the securing step  502  includes sub step  516 , connecting the liner  326  to a pump assembly  324 , followed by sub step  518 , inserting the pump assembly  324  into the cavity  318  so that the liner  326  lines the cavity  318 . The securing step  502  may also include sub step  520 , surrounding the liner  326  with a sealing component  362  and/or  364  to prevent any fluid from contacting the engine cover  312  at the cavity  318 . 
     In the embodiment of  FIG. 5 , the liner  426  is mechanically retained between the engine cover  412  and the pump housing  437 . Accordingly, the securing step  502  includes sub step  522 , fastening the liner  426  to the engine cover  412  and to a pump housing  437  of a pump assembly  424  placed in the pump cavity  418  so that the liner  426  is between the engine cover  412  and the pump assembly  424  and lines the surface  428  of the engine cover  412  at the cavity  418 . 
     While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.