Abstract:
According to the present invention, a variable compression ratio machine having main bearings mounted in an eccentric carrier or support includes an oil seal located primarily in a main bearing cap for minimizing leakage of pressurized main bearing oil. The seal is located generally in a first main bearing fastener socket or fastener access cutout in order to minimize structurally compromising the bearing cap, and a portion of the fastener socket preferably is used as an oil passageway as well as for wrench access to the fastener. The oil seal and oil circuit of the present invention enable the size of the eccentric support to be minimized while also providing highly effective oil sealing. In more detail, a significant advantage of the present invention is that highly effective oil sealing is attained without compromising the size or structural integrity of the bearing cap. A second significant advantage of the present invention is that it can be manufactured and assembled at low cost. The oil sealing system of the present invention is robust and highly reliable.

Description:
[0001]    This application relates to Provisional Application No. 60/849,314 having a filing date of Oct. 3, 2006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Variable compression ratio can significantly increase the fuel efficiency of reciprocating piston engines used in passenger cars and trucks. The present invention relates to variable compression ratio mechanisms having a crankshaft mounted in eccentric supports, and more specifically to the oil supply circuit used to deliver oil to the main bearings of the crankshaft. 
         [0003]    Kurt Imren Yapici shows a variable compression ratio engine in U.S. Pat. No. 6,588,384 issued on Jul. 8, 2003 and assigned to FEV GmbH of Germany. An oil galley that circumnavigates an eccentric support can be seen in  FIG. 7  of the patent. A crankshaft main bearing for the engine is located in the eccentric support. An engine similar in design was shown in Issue  22  of the FEV publication Spectrum, dated February 2003. A similar oiling system is also shown in U.S. Pat. No. 6,247,430 issued on Jun. 19, 2001 to Yapici and also assigned to FEV.  FIG. 3  of the patent shows an oil feed passageway  20  in the engine housing that feeds a shallow channel  17  in the eccentric disk segment  3 . 2 . Oil then flows through drilling  18  to the crankshaft main bearings  2 . A stiff eccentric carrier is necessary for providing reliable and robust main bearing life. The oil flow passageway  18  weakens the bearing cap and compromises stiffness. Oil leakage from the oil circuit is believed to be a problem due to the large area through which oil can leak. However, any further enlargement of the oil flow passageway  18  to accommodate oil sealing means would further risk the structural integrity of the bearing cap. Alternatively, oil sealing means could be installed in the housing without compromising the structure of the bearing cap. Referring again to  FIG. 7  of U.S. Pat. No. 6,588,384, the leaking oil is used to lubricate the outer bearing surface of the eccentric support, with a groove around the outer circumference of the eccentric support being provided for distribution of the oil around the bearing surface. In general variable compression ratio engines offer the potential for significantly improving automobile fuel economy. Oil leakage with these variable compression ratio engines will increase oil pump power consumption, and increase aerodynamic drag and windage on the crankshaft webs and other cranktrain components. These losses have been accepted considering the larger gains that can be realized with variable compression ratio, and the secondary benefit of using the leakage oil for lubricating the eccentric support&#39;s outer bearings. 
         [0004]    Mendler (the current applicant) shows another variable compression ratio engine in U.S. Pat. No. 6,443,107 issued on Sep. 3, 2002.  FIG. 11  shows an oiling system similar to the FEV system. Mendler shows another variable compression ratio engine in U.S. Pat. No. 6,637,348 issued on Oct. 28, 2003.  FIGS. 1 and 2  show a fully enclosed oil circuit having no oil loss upstream of the main bearings. The United States Department of Energy and Argonne National Laboratory paid for construction of a prototype engine similar to the design shown in U.S. Pat. No. 6,637,348. A report on the engine by Charles Mendler and Roland Gravel was published by SAE International circa Jun. 5, 2002. The engine has proven to be highly robust, and is currently located at Oak Ridge National Laboratory where it continues to be used for research. While the enclosed sealing system is robust, the manufacturing and assembly cost of the enclosed oiling system is a significant disadvantage of the system. The eccentric carrier is also relatively large and heavy. 
         [0005]    Lawrence et al. show a variable compression ratio engine having eccentric main bearing supports in US Patent Application Publication No.: US 2006/0112911 A1, having a publication date of Jun. 1, 2006.  FIG. 3  show an oil feed passageway  46  in the engine housing that feeds a shallow channel  48  in the eccentric disk segment  26   a.  Oil then flows through drilling  42  to the crankshaft main bearings  34 . A report on the engine authored by Kevin Duffy was published by SAE International Sep. 25, 2006 titled  Update on Diesel HCCI Activities at Caterpillar.  The engine has been built and tested. While fuel economy is important, the primary objective for the Caterpillar engine is reduction of air pollutants using the variable compression ratio to change and control the combustion process. New federal regulations require engine manufacturers to reduce emissions of nitrous oxides NOx and particulate matter PM. The pictures of the engine in the report closely match  FIG. 3  of the patent. Channel  48  has an exceptionally long length, and it is expected that a significant amount of oil will leak from the system. Another problem with the oil circuit shown in  FIG. 3  is that it is not streamline. The sharp bends in the oil flow circuit will require use of a higher oil feed pressure, which will result both in increased oil leakage and need for a more power consuming oil pump. 
         [0006]    Accordingly, objectives of the present invention are to provide an oil supply circuit for variable compression ratio engines of the eccentric main bearing support type, that provides minimal oil loss and low manufacture and assembly cost. Another objective is to provide a streamline oil flow circuit in order to minimize the oil pump power requirements. Another objective is to provide an oil supply circuit and eccentric support design that is compact and light in design, while also providing rigid support and alignment of the crankshaft main bearings. 
       SUMMARY OF THE INVENTION 
       [0007]    According to the present invention, a variable compression ratio machine having main bearings mounted in an eccentric carrier or support includes an oil seal located primarily in a main bearing cap for minimizing leakage of pressurized main bearing oil. The seal is located generally in a first main bearing fastener socket or fastener access cutout in order to minimize structurally compromising the bearing cap, and a portion of the fastener socket preferably is used as an oil passageway as well as for wrench access to the fastener. The oil seal and oil circuit of the present invention enable the size of the eccentric support to be minimized while also providing highly effective oil sealing. In more detail, a significant advantage of the present invention is that highly effective oil sealing is attained without compromising the size or structural integrity of the bearing cap. A second significant advantage of the present invention is that it can be manufactured and assembled at low cost. The oil sealing system of the present invention is robust and highly reliable. 
         [0008]    In the preferred embodiment of the present invention the seal includes a boss that nests into the fastener socket, thereby providing a low cost means for retaining or holding the seal in position. 
         [0009]    Preferably the seal has a hole through the boss for permitting the oil to flow into the lower portion of the fastener socket. A short oil passageway or eccentric oil feed line is then used to direct oil from the fastener socket to the main bearings. The eccentric oil feed line is relatively short and results in an acceptably small reduction of bearing cap stiffness. 
         [0010]    The oil flow circuit is streamline and permits the oil feed pressure to be minimized. The low feed pressure and the effective sealing means according to the present invention enables oil pump power to be minimized and engine efficiency maximized. The oil seal is highly reliable and has a low manufacturing and assembly cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0011]      FIG. 1  is intended to illustrate a variable compression ratio engine or machine having an oil seal according to the present invention. 
           [0012]      FIG. 2  is a partial cutaway view of a portion of  FIG. 1 . 
           [0013]      FIG. 3  shows a detail view of the sealing element. 
           [0014]      FIG. 4  shows a second view of the sealing element. 
           [0015]      FIG. 5  is similar to  FIG. 2 , but shows an alternate location for the internal oil flow passageway. 
           [0016]      FIG. 6  is intended to illustrate a bearing cap having an alternate fastener cutout shape and an alternate seal shape. 
           [0017]      FIG. 7  is intended to illustrate the present invention with the oil sealing element located in the housing. 
           [0018]      FIG. 8  is intended to illustrate the present invention in an eccentric support having a vertical bearing cap. 
           [0019]      FIG. 9  is intended to illustrate a sealing element with an oil bleed groove. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]      FIGS. 1 and 2  are partial section views that are intended to schematically illustrate the preferred embodiment of the present invention.  FIGS. 1 and 2  show an oil circuit for a variable compression ratio mechanism  1  having an oil supply  2 , a housing  4  and at least one cylinder  6  mounted in the housing, a piston  8  mounted for reciprocating movement in the cylinder, a crankshaft  10  defining an axis about which the crankshaft rotates  12 , and a connecting rod  14  connecting the piston to the crankshaft. The variable compression ratio mechanism further has at least one eccentric support  16  for supporting the crankshaft about the rotational axis of the crankshaft  12 . The eccentric support is mounted in the housing for pivoting relative to the housing about a pivot axis  18 . The pivot axis is substantially parallel to and spaced from the rotational axis of the crankshaft. Main bearings  20  are mounted in the eccentric support for supporting the crankshaft. The variable compression ratio mechanism may be used in an engine or in other applications where a variable compression ratio is useful. The variable compression ratio mechanism has a range of compression ratio settings, the range including at least a maximum compression ratio setting and a minimum compression ratio setting. 
         [0021]    The eccentric support includes a bearing cap  22  and a plurality of fasteners  24  for retaining the crankshaft in the eccentric support. 
         [0022]    According to the present invention, the eccentric support further includes a first fastener access cutout  26 . According to the preferred embodiment of the present invention, eccentric support  16  also includes an oil seal  28  located primarily in the region of the first access cutout  26 . 
         [0023]    Bearing cap  22  further including a bearing socket  30  for retaining one or more of the main bearings  20  in eccentric support  16 . 
         [0024]    Housing  4  includes at least one housing oil feed line  32 . Housing oil feed line  32  has an upstream end  34 , the upstream end being in fluid communication with oil supply  2 , and a down stream end  36 , the down stream end being in fluid communication with first fastener access cutout  26 . 
         [0025]    Referring now to  FIGS. 1 ,  2  and  3 , eccentric support  16  includes an eccentric oil feed line  38 . Eccentric oil feed line  38  has an upstream end  40 , the upstream end being connected to the first fastener access cutout  26 , and a down stream end  42 , the down stream end being in fluid communication with main bearings  20 . 
         [0026]    Arrow  44 , including upper and lower arrow segments, is intended to illustrate the primary oil flow pathway of the bearing oil. Primary oil flow pathway  44  extends from oil supply  2  to main bearings  20 . Primary oil flow pathway  44  including a first pathway section  45  extending from oil supply  2  to first fastener access cutout  26 , and a second pathway section  47  extending from first fastener access cutout  26  to main bearings  20 . According to the preferred embodiment of the present invention, the oil primarily flows directly out of the first pathway section  45  into the second pathway section  47 , with the junction of the two pathways being located within the first fastener access cutout. 
         [0027]    Eccentric support  16  has an outer bearing surface  46  having an outer circumference  48  for pivotably supporting eccentric support  16  in housing  4 . A small clearance gap  49  separates bearing surface  46  from housing  4 . 
         [0028]    According to the present invention, the oil circuit further has a sealing curtain area  43  around first fastener access cutout  26 . The preferred embodiment of the present invention includes sealing means for providing a small sealing curtain area  43  through which oil can leak from the oil flow pathway  44 . In more detail, the present invention includes sealing means for minimizing oil leakage between the housing oil feed line  32  and eccentric oil feed line  38 . The sealing curtain area  43  is generally the product of the average or approximate radial clearance gap  49  between the eccentric outer bearing surface including the sealing means and the housing  4  around curtain  43 , and the minimum perimeter length around oil flow pathway  44  at the interface of the outer bearing surface  46  and housing  4 . In more detail sealing curtain area  43  is generally the smallest imaginary surface that if it was impermeable, would seal the clearance gap between the housing oil feed line  32  and the eccentric oil feed line  38  and stop oil leakage. In the preferred embodiment of the present invention, oil seal  28  forms a seal with housing  4  for minimizing the oil sealing curtain area  43 , and thereby minimizing oil leakage. With respect to location of oil seal  28 , the sealing function is preferably primarily located in or generally in the first fastener access cutout in order to minimize the length of the sealed perimeter and in turn minimize curtain area. Preferably oil seal  28  is located in first fastener access cutout  26 , although the sealing means may extend outside of first fastener cutout  26  in some embodiments of the present invention. 
         [0029]    According to the present invention, oil supply  2  is in fluid communication with first fastener access cutout  26  through housing oil feed line  32 , and first fastener access cutout  26  is in fluid communication with main bearings  20  through eccentric oil feed line  38 , thereby providing an oil supply circuit for delivering oil from oil supply  2  to the main bearings  20  with minimal oil leakage. 
         [0030]    Preferably, according to the present invention, the downstream end of the housing oil feed line  36  is directly or almost directly aligned with first fastener access cutout  26  at all compression ratio settings, to provide streamlined flow of oil from the first pathway section  45  into the second pathway section  47 , for reducing the required oil pressure of the lubrication system. 
         [0031]    Bearing cap  22  has a first fastener  50 , and first fastener  50  has a first fastener line of action  52 . First fastener  50  has a first fastener head  54  having an approximate first fastener head circumference  56 . Those skilled in the art will appreciate that various types of fastener heads may be used according to the present invention. First fastener head circumference  56  and line of action  52  define an imaginary cylinder  58 . According to the preferred embodiment of the present invention, first fastener access cutout  26  includes at least the region inside imaginary cylinder  58  and inside outer circumference  48  that can be occupied with oil that is freely in fluid communication with main bearings  20 . In embodiments of the present invention including a seal such as oil seal  28 , first fastener access cutout  26  also refers to the region inside seal  28 . In the preferred embodiment of the present invention, first fastener access cutout  26  extends slightly outside  27  of imaginary cylinder  58 . According to the preferred embodiment of the present invention, the oil circuit passes through first fastener access cutout  26 , and in more detail eccentric oil feed line  38  and second pathway  47  do not bypass first fastener access cutout  26 . 
         [0032]    Referring now to  FIGS. 2 and 5 , preferably according to the present invention the fastener access cutout  26  includes retaining means for retaining the oil seal in location. Eccentric support  16  may optionally include a first fastener socket  60  or  60 B. Optionally the access cutout may be the first fastener socket.  FIG. 7  shows a first fastener access cutout that is simply the first fastener socket. Preferably first fastener socket  60  is slightly larger in diameter than imaginary cylinder  58  to provide access for assembly and wrench access. First fastener  50  may be a hex head bolt, a 12 point bolt (shown), a socket head bolt, or another functional type of fastener. In the preferred embodiment of the present invention, oil seal  28  or  28 B further includes a boss  62  or  62 B. Preferably boss  62  or  62 B is positioned in first fastener socket  60  or  60 B for retaining oil seal  28  or  28 B in position for oil sealing. 
         [0033]    Referring now to  FIG. 2 , preferably eccentric oil feed line  38  is connected to first fastener socket  60  downstream of said first fastener access cutout  26 . 
         [0034]    Oil seal  28  is intended to substantively minimizing leakage of oil between housing oil feed line  32  and eccentric oil feed line  38 . Those skilled in the art will appreciate that various types and shapes of sealing means can be used according to the present invention.  FIGS. 1 through 4  show oil seal  28 . Referring now to  FIG. 5 , eccentric oil feed line  38 B bypasses first fastener socket  60 B. Oil seal  28 B is similar to oil seal  28 , but accommodates eccentric oil feed line  38 B. Referring now to  FIG. 6 , oil seal  28 C has an alternate shape. Referring now to  FIG. 7 , an optional housing oil seal  29  is located in housing  4 . Sealing means may be provided in some embodiments of the present invention by minimizing perimeter length around oil flow pathway  44  at the interface of the outer bearing surface  46  and housing  4 , and by employing small assembly tolerances to minimizing the radial clearance gap between the eccentric outer bearing surface  46  and the housing  4  and thereby provide an acceptably small sealing curtain area. Preferably a removable oil seal is used such as oil seal  28 , however, some embodiments of the present invention may be practiced without a removable sealing element, and in more detail where the sealing means includes small mechanical tolerances to provide a small radial clearance gap, and a short perimeter length to provide a small oil sealing curtain area. 
         [0035]    Referring now to  FIGS. 2-4 , preferably the upstream end of said eccentric oil feed line  38  is in fluid communication with first fastener socket  60 , and boss  62  has a cutaway section or hole  64  to permit flow of oil from the housing oil feed line  32  to the eccentric oil feed line  38 . The upstream end of housing oil feed line  34  is in fluid communication with oil supply  2 , and the down stream end of housing oil feed line  36  is in fluid communication with first fastener socket  60 . The upstream end of eccentric oil feed line  38  is in fluid communication with first fastener socket  60 , and the down stream end of eccentric oil feed line  42  is in fluid communication with main bearings  20 . Accordingly, oil supply  2  is in fluid communication with first fastener socket  60  through housing oil feed line  32 , and first fastener socket  60  is in fluid communication with main bearings  20  through eccentric oil feed line  38 , thereby providing an oil supply circuit for delivering oil from the oil supply  2  to the main bearings  20 . 
         [0036]    In the embodiment of the present invention shown in  FIG. 2 , the primary oil flow pathway  44  from oil supply  2  to main bearings  20  is open at all of said compression ratio settings. In more detail, primary oil flow pathway  44  including a first pathway section  45  from oil supply  2  to imaginary cylinder  58  into first fastener socket  60  and a second pathway section from first fastener socket  60  through eccentric oil feed line  38  to main bearings  20  that is streamline and open at all compression ratio settings, thereby providing a streamline flow passageway with minimal pressure loss. 
         [0037]    Referring now to  FIGS. 1 and 2 , variable compression ratio mechanism  1  has a plurality of compression ratio settings including a first compression ratio setting  66 . Flow pathway  44  also includes a first flow segment  68  at first compression ratio setting  66 . According to an embodiment of the present invention, first flow stream segment  68  and first fastener line of action  52  are generally aligned at first compression ratio setting  66 , thereby providing a streamlined flow path. Preferably first flow segment  68  passes through oil seal  28 . 
         [0038]      FIG. 5  shows a blocked first fastener socket  60 B. In the embodiment of the present invention illustrated in  FIG. 5 , first fastener socket  60 B is not considered part of first fastener access cutout  26  because oil cannot flow freely to main bearings  20  through first fastener socket  60 B. According to the present invention, the upstream end of eccentric oil feed line  38 B may optionally bypasses first fastener socket  60 B. As mentioned previously, in the preferred embodiment of the present invention, first fastener access cutout  26  extends slightly outside  27  of imaginary cylinder  58 , as depicted in  FIGS. 2  and  5 . According to the preferred embodiment of the present invention, the oil circuit passes through first fastener access cutout  26 , and in more detail eccentric oil feed line  38  or  38 B does not bypass first fastener access cutout  26 . As shown in  FIG. 5 , eccentric oil feed line  38 B may optionally bypass first fastener socket  60 B, while being in fluid communication with first fastener cutout  26  according to the present invention. 
         [0039]    Referring now to  FIGS. 1 through 4 , preferably, according to the present invention oil seal  28  is made out of an elastic or compressive material to provide sealing contact between the oil seal and housing  4 . Oil seal  28  may be formed out of PTFE or another functional material. Oil seal  28  may additionally be made out of a composition of materials, such as a metal backed seal having a PTFE sliding surface. 
         [0040]    Referring now to  FIG. 5 , a spring  70  may be used to bias oil seal  28 B into contact with housing  4  for providing a sealing contact. If used, preferably spring  70  is located in first fastener socket  60 B. 
         [0041]    Referring now to  FIGS. 1 ,  2 ,  5  and  6 , preferably first fastener access cutout  26  is located in bearing cap  22 . Referring now to  FIG. 8 , optionally first fastener access cutout  26 D is located in the primary support structure  76  of the eccentric support  16 B. 
         [0042]    Referring now to  FIGS. 2 and 9 , eccentric support  16  has one or more eccentric support outer bearings  46  that ride on a suitably formed mating surface in housing  4 . Referring now to  FIG. 9 , oil seal  28 E may include bleed holes or grooves  74  for release of oil from the oil supply circuit for lubricating the eccentric support outer bearings  46 . 
         [0043]    Referring again to  FIG. 1 , bearing cap  22  has a parting surface  78  and a normal imaginary plane  80 . The normal imaginary plane is normal to parting surface  78 , and the rotational axis of the crankshaft  12  lies entirely within imaginary plane  80 . Bearing cap  22  has a minor half  82  located on one side of said normal imaginary plane, and a major half  84  located on the other side of said normal imaginary plane, where the major half of the bearing cap is generally larger than the minor half of the bearing cap. Preferably, according to the present invention, first fastener access cutout  26  is located in the major half  84  of bearing cap  22 , for providing a small diameter eccentric  16  having a first fastener access cutout  26  long enough for an open oil circuit at all compression ratio settings. 
         [0044]    Preferably according to the present invention, connecting rod  14  advances from the region adjacent to minor half  82  of bearing cap  22  to the region adjacent to major half  84  of said bearing cap  22 , thereby providing a crankshaft rotational direction yielding an eccentric support that is stiff and compact while also having a first fastener access cutout and an eccentric oil feed line drilled hole that can weaken the part due to removed metal. According to the preferred embodiment of the present invention, the downstream end  42  of flow pathway  47  introduces oil to the crankshaft main bearings  20  slightly after piston  8  reaches its highest location in cylinder  6 , thereby providing optimum lubrication of main bearings  20  and crankshaft  10 .