Patent Publication Number: US-7219642-B1

Title: Powertrain assembly and integral truss oil pan therefor

Description:
TECHNICAL FIELD 
     This invention relates to engine/transmission powertrain assemblies and, more particularly, to integral truss oil pans for stiffening such assemblies. 
     BACKGROUND OF THE INVENTION 
     In an automotive powertrain, a stiff junction between an engine block and a connected transmission bellhousing would benefit from a straight vertical wall, such as a “shear wall”, on the sides of the connecting engine oil pan. The need for tool access, however, tends to move the wall surrounding the oil pan bolts inward. To do this, while maximizing oil volume, requires moving the wall outward between the bolts. The result is an accordion shaped or corrugated sidewall that is easily bent, compromising the pan&#39;s contribution to powertrain bending stiffness. An improved oil pan is desired having increased structural stiffness in areas adjoining the transmission bellhousing and adjacent portions of the engine block oil pan flange 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved powertrain assembly wherein an engine to transmission connection is stiffened by incorporating integrally cast trusses in oil pan sidewalls at portions mounted between the engine crankcase and a lower portion of a transmission bellhousing. The trusses stiffen adjacent portions of the oil pan walls and receive extended oil pan bolts having heads engaging a lower truss portion accessible by power tools for securing and removing the bolts. 
     The integrally cast trusses each include a horizontal rail extending generally parallel to an oil pan upper flange and including bolt openings aligned with corresponding bolt openings in the upper flange. A plurality of bolt columns extend between the horizontal rail and the oil pan upper flange adjacent to the corresponding bolt openings of at least selected locations. A plurality of diagonal ribs extend from the oil pan flange generally toward a rear mounting flange connectible with a transmission bellhousing in the oil pan upper flange to adjacent portions of the rear mounting flange. 
     Some of the diagonal ribs extend directly from adjacent longitudinally spaced bolt openings in the oil pan upper flange to adjacent portions of the rear mounting flange. Additional diagonal ribs extend directly from adjacent upper flange bolt openings to openings for longitudinally spaced bolts in the horizontal rail. 
     The oil pan is die castable with the integral cast-in trusses with a minimal effect on manufacturing costs. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an automotive powertrain assembly formed according to the invention and including an engine and a transmission mounted to a crankcase and oil pan of the engine; 
         FIG. 2  is a right rear corner pictorial view of a first embodiment of oil pan according to the invention; 
         FIG. 3  is a fragmentary pictorial view from the left front corner showing the truss on the rear sump portion of the embodiment of  FIG. 2 ; and 
         FIG. 4  is a view similar to  FIG. 2  but showing the invention embodied in a forward sump oil pan. 
     
    
    
     DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
     Referring first to  FIG. 1  of the drawings in detail, numeral  10  generally indicates a powertrain assembly adapted for automotive application. Assembly  10  includes an engine  12  having a crankcase  14  and an oil pan  16  mounted together with an automatic transmission  18 . 
     The crankcase internally supports a power producing mechanism, not shown, such as a crankshaft, and includes a peripheral lower face  20  mounting the oil pan and a rear mounting face  22  mounting a bellhousing  24  of the transmission. The oil pan  16  includes a rear sump  25  and is mounted to the lower face  20  of the crankcase for containing engine oil for lubricating internal components, not shown, of the engine. The automatic transmission  18  is conventionally mounted to the engine  12  with a front flange  26  of the bellhousing  24  bolted to the rear mounting face  22  of the crankcase. 
     As shown best in  FIGS. 2 and 3 , the oil pan  16  is formed as an integral casting preferably a diecasting, although other casting or molding processes may be employed if desired or mandated by a choice of materials in appropriate applications. The pan structure includes left  28  and right  30  sidewalls and front  32  and rear  34  end walls and a bottom wall  36  defining a cavity  38  including the rear sump  25  for retention of engine oil. 
     A peripheral upper flange  40  defines upper edges of the pan walls and includes longitudinally spaced bolt openings  42  in the flange portions of the left and right sidewalls  28 ,  30 . A peripheral end flange  44  is also formed on the rear end wall  34  of the oil pan  16 . The end flange  44  is engaged in assembly by the front flange  26  of a lower portion  46  of the transmission bellhousing  24 , which is bolted to the end flange  44  to provide a stiff connection of the transmission lower portion  46  with the engine crankcase  14  through the oil pan sidewalls  28 ,  30 . 
     The left and right oil pan sidewalls  28 ,  30  each incorporate an integrally cast truss generally indicated by numerals  48 ,  50 , respectively. The trusses are essentially identical with only minor variations in specific integration due to necessary variations in the wall contours. 
     Each of the trusses extends between the end flange  44  of the oil pan and adjacent portions of the peripheral upper flange  40 . Each truss  48 ,  50  includes a horizontal rail  52  extending generally parallel to the upper flange  40  and including bolt openings  54  aligned with corresponding bolt openings  42  in the upper flange. A plurality of bolt columns  56  extend between the upper flange  40  adjacent the corresponding bolt openings of at least selected locations. 
     A plurality of diagonal ribs  58 ,  60 ,  62 ,  64  are also provided extending from the oil pan upper flange  40  generally toward the peripheral end flange  44 . Ribs  58  and  60  extend downward and rearward to the peripheral end flange  44  from the peripheral upper flange  40  adjacent the second and third bolt openings  42 , respectively, from the peripheral end flange  44 . 
     Ribs  58  on both sidewalls extend diagonally from a bolt column  56  adjacent the second upper flange bolt opening  42  (from the end flange  44 ) to the peripheral end flange  44 . Ribs  60  extend diagonally from a bolt column  56  adjacent the third upper flange bolt opening  42  (from the end flange  44 ) to the peripheral end flange  44 . The ribs  58 ,  60  also intersect intervening bolt columns along their lengths. 
     On the left sidewall ( FIG. 3 ), the ribs  58 ,  60  include enlarged portions  66  with bolt openings  68  aligned with the first pair of bolt openings  42 ,  54  adjacent the end flange  44 . Ribs  60  also include a second enlarged portion  70  with a bolt opening  72  aligned with the second pair of bolt openings  42 ,  54  from the end flange  44 . 
     On the right sidewall ( FIG. 2 ), the rib details differ slightly in that the first pair of bolt openings  42 ,  54  are moved outward so that the ribs  58 ,  60  pass behind the associated bolt location without requiring enlarged portions in the ribs. Also, the rib  60  is deeper at the location of the second pair of bolt openings from the end flange  44  so that a bolt opening  74  is formed in the rib  60  without needing an enlarged portion of the rib. These differences are only variants of the basic truss structures, which are adjusted to conform to variations in the sidewall configurations and bolt locations required by the particular engine design and packaging considerations. 
     Diagonal ribs  62  and  64  extend downward and rearward from adjacent the third and fourth bolt openings  42  in the upper flange  40  (from the end flange  44 ) to adjacent the second and third bolt openings  54  in the horizontal rail (from the end flange  44 ) to stiffen the truss structure and carry longitudinal loads from the end flange  44  to the pan upper flange  40 . Specifically, diagonal ribs  62  extend between a bolt column  56  adjacent the third pan flange bolt opening  42  location (from the end flange  44 ) to the horizontal rail  52  at the bolt column  56  location adjacent the second rail bolt opening location (from the end flange). Similarly, diagonal ribs  64  extend between the upper flange  40  adjacent the fourth bolt opening  42  (from the end flange  44 ) to the horizontal rail  52  at the bolt column  56  location adjacent the third pan rail bolt opening  54  location (from the end flange  44 ). 
     In assembly, the oil pan sidewalls  28 ,  30  are secured to the sides of the engine crankcase by fastening bolts including six long bolts  76  (three on each side) and five shorter bolts  78  (three on the left side and two on the right side). The number and location of fastening bolts may be varied to meet the requirements of the particular engine design. 
     The three long bolts  76  on each side extend through the first, second and third (from the end flange  44 ) pairs of bolt openings  54 ,  42 , from the truss longitudinal rail openings  54  through the corresponding upper flange  40  openings  42  to engage fastener openings, not shown, in the crankcase lower face  20 . Heads  80  of the bolts engage the horizontal rail  52  and place the bolt columns  56  in compression to hold the pan  16  in place. Similarly, the five shorter bolts  78  extend through other sidewall flange openings  42  to engage crankcase fastener openings, not shown, the bolt heads  80  also engaging the pan upper flange  40 . Additional oil pan securing bolts may also be used, such as long rear bolts  82  that extent through vertical openings in the pan end flange  44  to support the transmission-connected rear end of the pan. 16 . All these fasteners cooperate with the pan structure, including the integral trusses,  48 ,  50  to maintain a stiffened connection between the engine crankcase  14  and the lower portion of the transmission bellhousing  24  through the oil pan truss structures  48 ,  50  in accordance with the invention. 
     Referring now to  FIG. 4  of the drawings, an alternative embodiment of oil pan  116  according to the invention is shown. Oil pan  116  differs from the oil pan  16  in that the sump  125  is moved to a front end  184  of the pan. Thus, the rear end  186  is shallower and terminates in a smaller peripheral end flange  144  adjoining the peripheral upper flange  140  with its bolt openings  142 . Details of the bolt opening positions are similar since the pans are designed for use with the same or a similar engine crankcase, not shown. 
     As in the first embodiment, the now shallower rear end  186  of the oil pan connects with and supports the lower portion of a transmission, not shown, through the end flange  144 . The pan sidewalls  128 ,  130  are stiffened at the rear ends by trusses, only the right sidewall truss  150  being shown. The truss structure is smaller but similar to that previously described to accomplish the same purposes. 
     Referring to truss  150  as exemplary, it includes a horizontal rail  152  generally parallel to the pan upper flange  140  as before. However, the truss  150  is shorter by one bolt spacing, so the length of the rail  152  is shorter. Also, there are bolt columns  156  for only the long bolts, not shown, of the first and second bolt opening pairs (counting from the end flange  144 ). Further, the truss  150  includes only 3 diagonal ribs including one rib  158  extending from adjacent the second flange bolt opening  142  (from the end flange  144 ) to the end flange  144 . The two other diagonal ribs  162 ,  164  extend between the upper flange  140  and the horizontal rail  152 . Rib  162  connects a bolt column  156  adjacent the second (from the end flange  144 ) pan flange bolt opening  142  with the bolt column  156  adjacent the first (from the end flange  144 ) pan rail bolt opening  154 . Rib  164  connects the two next further bolt opening locations, that is the third (from the end flange) pan flange bolt opening  154  location is connected to the second (from the end flange) pan rail bolt opening  154  location. 
     As in the first embodiment, the smaller structure stiffens the pan walls at the rear end of the oil pan and provides a connection of increased stiffness through the oil pan between the engine crankcase and the lower portion of the associated transmission bellhousing. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.