Patent Document

FIELD OF THE INVENTION 
     The present invention relates to air/oil separation in internal combustion engines. In particular, the present invention relates to air/oil separation in a positive crankcase ventilation system. 
     BACKGROUND OF THE INVENTION 
     Positive crankcase ventilation systems (PCV systems) provide a mechanism for transferring vapors from the engine crankcase, or another engine compartment containing oil, to the induction system of an engine. Many PCV systems provide some restriction to prevent engine oil from being drawn into the induction system and burned in the combustion process. As part of a PCV system, air/oil separation plays an important role in reducing the amount of engine oil that is carried into the induction system and later burned by the engine. Some air/oil separation systems include one or more chambers and baffles designed to cause oil particles entrained in the crankcase gasses to fall out of the gasses before those gasses are allowed to flow into the intake tract to be subsequently burned by the engine. 
     At least some PCV systems achieve air/oil separation by using a baffle plate with a series of holes. The baffle plates used in the prior art provide an effective means of separating air and oil. However, due to the relatively unrestricted path through certain baffle plates, oil that impacts the baffle plate may be able to become re-entrained in the mixture. As a result, oil is carried into the induction system and burned in the combustion process, resulting in oil consumption. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved positive crankcase ventilation system which affords advantages over the prior art. The current invention has the benefit of further limiting the amount of engine oil that is allowed to enter the induction system of an engine. This is possible through the use of protrusions extending from the face of a baffle plate. The protrusions circumscribe apertures in the baffle plate and extend in a direction generally opposing the direction of flow of an air/oil mixture. A barrier is created by the protrusion surrounding the aperture to prevent oil from flowing into the apertures after it impacts the plate. This results in less oil being drawn into the induction system, further resulting in lower oil consumption. 
     The result of lower oil consumption is both lower engine emissions and a greater sense of perceived quality from the customer, due to a reduced need to add engine oil to the system between scheduled oil changes. Another benefit of the reduced oil consumption is higher oil levels maintained in the oil pan or dry sump tank during vehicle operation towards the end of oil life. One desirable result of this is improved oil life. Because there is a greater volume of oil maintained in the engine throughout the engine oil life, the oil change interval may be longer. 
     A further benefit may be improved lubrication system performance. Lubrication system performance may be comprised if a pickup tube or other supply source to the oil pump is allowed to draw air instead of oil. When a vehicle is subject to high g-loads, oil inside of the oil pan or tank may slosh and move away from the oil pickup tube or other means of communication with the oil pump. Use of the baffle plate of the present invention may result in the ability of a vehicle to maintain higher g-load maneuvers toward the end of an oil life cycle, before the scheduled oil change. A remote dry sump oil tank is sometimes used to limit oil slosh. These tanks are generally taller and more narrow in design than conventional oil pans, allowing less opportunity for an oil pickup tube to become uncovered. However, these tanks are still susceptible to undesirable oil movement. The present invention provides the benefit of minimizing this effect when compared to the traditional hole-type baffle plates previously disclosed. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of a motor vehicle constructed in accordance with the teachings of the present invention; 
         FIG. 2  is a schematic illustration of an internal combustion engine including an exemplary baffle; 
         FIG. 3  is a fragmentary perspective view of an exemplary cylinder head cover containing the baffle for use in a positive crankcase ventilation system; 
         FIG. 4  is a schematic illustration of an internal combustion engine having a dry sump oil tank including an exemplary baffle; 
         FIG. 5  is a fragmentary cross-sectional side view of a dry sump oil tank containing the baffle of the present invention; 
         FIG. 6  is a perspective view of the baffle of the present invention in accordance with the teachings of the present invention; and 
         FIG. 7  is a view of a cross-section of an air/oil hole in the baffle of the present invention in accordance with the teachings of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to  FIG. 1 , an exemplary vehicle  10  includes an internal combustion engine and PCV system  11  constructed in accordance with the teachings of the present invention. The vehicle  10  includes an engine  12  and a transmission  14  for providing a driveline  16  with a torque input. The driveline  16  includes a drive shaft  20 , a rear axle  22 , and a plurality of wheels  24 . 
       FIG. 2  depicts the internal combustion engine and PCV system  11  in greater detail. The internal combustion engine and PCV system  11  includes the engine  12  having a head  26 , a valve cover  28 , a block  30 , an oil pan  32 , and an oil pump  34 . The internal combustion engine and PCV system  11  further comprises an air intake system  36 , and a conduit  38  connecting the valve cover  28  to the air intake system  36 . The air intake system  36  is in communication with air external to the engine  12 . The head  26  contains a baffle plate  40  shown in greater detail in  FIG. 3 . 
     The baffle plate  40  separates oil from crankcase gases before the mixture combines with fresh air in the intake system  36 . During engine operation gas located within the combustion chamber air escapes into the crankcase past the piston rings. This process is known as blow-by. The gas travels into the crankcase and back up into the head  26  through passages typically cast into the block  30  and head  26 . These blow-by gases are typically drawn from the crankcase through a passage in the valve cover  28 . A conduit  38  extending from the valve cover  28  to the intake system  36  allows the blow-by gases to combine with the fresh air of the intake system  36 . 
     When the blow-by gas enters the crankcase, oil often becomes entrained with the gases to form a mixture. In order to separate the air from the oil, the present invention provides a baffle plate  40  in the valve cover  28 . The mixture of blow-by gases and oil is forced through apertures  42  in the baffle plate  40  as a result of a pressure differential across the baffle plate  40 . The pressure within the engine crankcase is greater than that in the intake system  36 , causing the mixture to flow from the crankcase to the intake system  36 . The mixture either passes through the apertures  42  in the baffle  40  or impacts the remaining portion of the baffle  40 . Upon impact, oil in the mixture runs down the baffle  40  and returns to the oil pan  32 . 
     The valve cover  28  includes a top  44 , a first sidewall  46 , a second sidewall  48  and an intermediate wall  50  interconnecting the first and second sidewalls. A series of baffle plates  40  are positioned within a cavity  52  formed between the top  44  and the intermediate wall  50 . An outlet  54  extends through the first sidewall  46  to place cavity  52  in communication with the intake system  36 . A series of cylindrical walls  56  extend from the top  44  to the intermediate wall  50  in the center of the valve cover  28 . Apertures  58  defined by the cylindrical wall  56  provide access for valve cover mounting fasteners (not shown). 
     The baffle plates  40  are formed from substantially planar sheets. In the embodiment shown, two baffle plates  40   a  and  40   b  are integrally formed with one another. Baffle plates  40   a  and  40   b  are arranged generally parallel to and spaced apart from one another. An end portion  60  interconnects baffle plates  40   a  and  40   b . End portion  60  extends from top  44  to intermediate wall  50  to force the majority of the crankcase gases through the apertures  42 . Tabs  62  extend from the baffle plates to provide mounting provisions for coupling the baffle plates  40  to the valve cover  28 . Additional baffle plates  40   c  and  40   d  are integrally formed with one another and coupled to valve cover  28 . A first volume  64  is defined between baffle plate  40   a  and valve cover  28 . A second volume  66  exists between baffle plate  40   b  and  40   c . A third volume  68  is positioned between baffle plate  40   d  and valve cover  28 . 
     Each baffle plate  40   a – 40   d  includes the plurality of apertures  42 . Because each of the baffle plates are substantially similar to one another, baffle plate  40   a  will be described in further detail. Baffle plate  40   a  includes a plurality of projections  70  circumscribing each aperture  42 . Projections  70  extend perpendicularly from a surface  72  of baffle plate  40 .  FIG. 7  depicts an exemplary projection  70  having a conical portion  130  and a substantially cylindrically shaped portion  132 . An inlet  74  extends through the valve cover  28  to allow a crankcase gas mixture to pass into the valve cover  28 . The inlet  74  is an aperture located in the intermediate wall  50  of the cover  28 . 
     During engine operation, the air/oil mixture enters the first volume  64  of the valve cover  28  through the inlet  74  in the intermediate wall  50  of the valve cover  28 . In order to exit the first volume  64 , the mixture must pass through baffle plates  40   a  and  40   b  or through the relatively small clearances surrounding the baffle plates  40 . 
     The mixture flows in a direction generally perpendicular to the baffle plates  40 . As the mixture attempts to flow through the baffle plates  40 , a portion passes through the apertures  42 . The remainder will impact the surface  72  of the baffle plate  40  or a portion of the protrusion  70 . When the mixture impacts a baffle surface, oil entrained in the mixture may be released. The oil content will then flow down the plate  40 . The protrusions  70  extending from the plate  40  prevent oil from running down surface  72  and through the apertures  42 . Oil preferably runs down surface  72  and into contact with intermediate wall  50 . Oil then eventually returns to the oil pan  32  to be reused by the engine  12 . 
     The mixture then flows into the second volume  66  bounded by baffle plate  40   b  and a baffle plate  40   c . The exit path comprises apertures  42  through baffle plates  40   c  and  40   d . The mixture not passing through the apertures  42  impacts surface  72  of the baffle plate  40  and flows down the plate  40 . The remainder of the mixture enters a third volume  68 . The mixture in the third volume  68  then exits to the intake system  36  through the outlet  54  on the first sidewall  46 . 
     The additional oil that has been released from the mixture may return to the oil pan  32 . The oil is able to return by draining back to the head  26  through the inlet  74  or another passage (not shown) in the valve cover  28 . Once the oil returns to the head  26 , it may follow a typical oil drainback path through passages in the head  26  in communication with the block  30 . The oil is able to flow past the baffle plates  40  in the valve cover  28  due to clearances formed between the baffle plate  40  and the intermediate wall  50 . 
     An alternate embodiment internal combustion engine and PCV system  76  is depicted in  FIGS. 4 and 5 . Internal combustion engine and PCV system  76  is substantially similar to internal combustion engine and PCV system  11 . As such, like elements will retain their previously introduced reference numerals. The engine and PCV system  76  includes a dry sump oil tank  78  and a conduit  80  for communication of air between the air intake system  36  and the tank  78 . Lines  82  and  84  interconnect oil pump  86  and oil tank  78 . The dry sump oil tank  78  includes a baffle plate  88  depicted in  FIGS. 6 and 7 . 
     The flow path for the blow-by gas and oil mixture is similar to that previously explained referencing  FIG. 2 . However, in the present embodiment, a baffle plate  88  is not positioned in a valve cover  90 . Instead, the mixture flows from the valve cover  90  to the remote dry sump oil tank  78 . 
     The mixture exits the valve cover  90  through a conduit  92  that connects the valve cover  90  to the dry sump oil tank  78 . It then combines with an air and oil mixture in the tank  78  and the new resulting mixture is drawn through the baffle plate  88  contained in the tank  78 . The mixture is drawn through the baffle plate  88  as a result of a pressure differential across the plate  88 . The pressure in the intake system  36  is less than the pressure in the dry sump tank  78 , causing the mixture to flow from the tank  78  to the intake system  36 . 
     The dry sump oil tank  78  includes an oil fill tube  96 , a baffle plate  88  and has four main volumes  98 ,  100 ,  102 ,  104 . The first volume  98  is defined by a wall  106  generally running down the middle of the tank  78  and an outer wall  108  surrounding the tank  78 . The first volume  98  also includes the oil fill tube  96 . A cap  110  for the oil fill tube  96  is located on the top of the tank  78 . The first volume  98  also includes an inlet  112  for the conduit  92  connecting the first volume  98  to the valve cover  28 . The inlet  112  allows for a mixture of blow-by gases and oil to enter the tank  78  from the valve cover  28 . As a result of the mixture impacting the wall  106 , some of the oil within the mixture flows down the wall  106  and is removed from the mixture. The remaining mixture flows into the second volume  100  where it combines with a mixture of air and oil from the dry sump tank  78 . 
     The second volume  100  generally includes the lower portion of the tank  78 . The second volume  100  has a volume of air  114  and a volume of oil  115 . The volume of air  114  exists to provide a communication path between the first volume  98  and the third volume  102 . The oil volume  115  is generally great enough to keep the oil lines  82 ,  84  covered with oil. Lines  82  and  84  provide communication between the tank  78  and the oil pump  86 . Line  84  contains oil flowing to the pump and line  82  contains oil flowing to the tank  78 . The air and oil mixture present in the tank  78  combines with the mixture from the valve cover  28  and travels to the third volume  102 . 
     The third volume  102  is located below the baffle plate  88 . The fourth volume  104  is positioned above the baffle plate  88 . The third volume  102  is generally defined by the wall  106  running down the center of the tank  78 , the surrounding tank wall  108  and the baffle plate  88 . The wall  106  forces the air/oil mixture from the valve cover  28  to flow through the baffle plate  88  if it leaves the tank  78 . The baffle plate  88  performs a similar function to the baffle plate  40  depicted in  FIG. 3 . However, in one embodiment, baffle plate  88  is positioned substantially parallel to the ground. An edge  116  of the baffle plate  88  abuts the surrounding walls  108  of the tank  78  and the wall  106  running down the center of the tank  78 . The mixture is drawn through the apertures  118  in the baffle plate  88  and into the fourth volume  104  as a result of a pressure differential across the plate  88 . The portion of the mixture that does not pass through the apertures  118  impacts a first surface  120  of the baffle plate  88  or a portion of protrusions  122 . The oil that impacts the first surface  120  falls back to the second volume  100  and mixes with the oil volume  115  contained therein. The protrusions  122  extending from the baffle  88  and surrounding the apertures  118  prevent the oil from passing over the apertures  118  and being drawn into the intake system  36 . 
     The fourth volume  104  is generally defined by the wall  106  extending down the middle of the tank  78 , the surrounding walls  108  of the tank  78  and the baffle plate  88 . The fourth volume  104  is in communication with the intake system  36  through an outlet port  124 . The outlet port  124  is in communication with the intake system  36  through the conduit  80 . Communication between the fourth volume  104  and the intake system  36  causes the pressure differential providing for the flow across the baffle plate  88  and into the intake system  36 . 
     The flow path for the mixture in the dry sump oil tank  78  is generally shown by the arrows in the figure. A mixture enters from the valve cover  28  through the conduit  92  and the inlet port  112 . The mixture then enters the first volume  98  of the tank  78 , then proceeds to the second volume  100 . Next the mixture enters the third volume  102  and flows across the baffle plate  88  and into the fourth volume  104  where it may then exit the tank  78  through an outlet port  124  in communication with a conduit  80 . 
       FIGS. 6 and 7  further depict the baffle plate  88 . Baffle plate  88  is shaped as a substantially planar thin sheet having the first surface  120  and an opposite second surface  128 . Baffle plate  88  includes the plurality of apertures  118  surrounded by the protrusions  122 . Each protrusion  122  consists generally of the first wall portion  130  and the second wall portion  132  surrounding the aperture  118 . The first wall portion  130  extends from the first surface  120  of the baffle plate  88 , generally opposing the direction of airflow, and has a conical shape. The second wall portion  132  is substantially cylindrical and extends substantially perpendicular to the first surface  120 . The shape of protrusion  122  is merely exemplary and may take many other forms without departing from the scope of the present invention. 
     During operation, an air and oil mixture impacts the baffle plate  88  on the first surface  120  having protrusions  122  extending therefrom. A portion of the air and oil mixture passes through the apertures  118 , but the remainder impacts the first surface  120  of the baffle plate  88  or protrusions  122 . The protrusions  122  surrounding the apertures  118  prevent the oil that has impacted the first surface  120  of the baffle plate  88  from passing over the apertures  118  and being drawn into the fourth volume  104 . Instead, the oil that has impacted the baffle plate  88  falls from the first surface  120  into oil volume  115 . The edge surface  116  has a tab  134  extending therefrom for attachment with wall  106 . 
     A further embodiment of the present invention could include the features found in  FIGS. 2 and 4 . The embodiment of  FIG. 4  could include one or more baffle plates  40  depicted in  FIG. 2 . In this embodiment the mixture of oil and blow-by gases would first flow past the baffle plate  40  shown in  FIG. 2 , providing for an initial reduction in oil content of the mixture. The mixture would then proceed as previously explained with reference to  FIG. 4 . The mixture would combine with the air and oil mixture in the dry sump tank  78 . This new mixture would then have its oil content further reduced as a result of being drawn through a baffle plate  88  in the tank  78 . 
     Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.

Technology Category: 2