Patent Document

TECHNICAL FIELD 
   The present invention relates to reducing oil carry-over in internal combustion engines. In particular, but not exclusively, the invention relates to a barrier device provided in the cylinder block of an internal combustion engine to reduce the amount of oil being carried over from the crankcase to the crankcase breather system. 
   BACKGROUND 
   Internal combustion engines suffer from a process called blow-by where combustion gasses leak past the piston rings into the crankcase. To prevent seal damage these gasses will have to be vented, which can be done by a closed circuit breather system (CCB) or an open circuit breather system (OCB). When using an OCB, the gasses flow from the crankcase to the cylinder head and are from there vented to atmosphere. With a CCB, the gasses flow from the crankcase to the cylinder head and are from there re-introduced into the induction system, where they are burned off and subsequently depart the engine via the conventional exhaust system. 
   A major problem associated with both OCB and CCB systems is that the blow-by gasses usually carry a substantial amount of oil particles caused by reciprocating and rotating elements in the engine. This process is called oil carry-over and can pose several problems:
         in certain CCB systems the vented gas is fed through a filter to minimise the amount of carry-over oil in the blow-by gasses, before introduction of the gasses into the intake manifold for combustion. As the filter is an expensive service item, oil carry-over increases operating costs;   in CCB systems without a filter, the oil can cause fouling of components of the induction system such as turbocharger compressor vanes and engine poppet valves. Also, the liquid oil can form deposits on the valves which can be detrimental to the performance of the air intake system;   in OCB systems where the gasses are vented to air, oil carry-over can raise emission levels significantly;   oil carry-over can be a significant cause of oil loss and hence increases operating costs.       

   It is known to provide a PCV (Positive Crankcase Ventilation) valve to limit oil carry over. An example of such an apparatus is disclosed in U.S. Pat. No. 5,024,203. However, this design has several undesired characteristics in that it is fitted external to the engine thus enlarging the engine envelope, it requires a controlled heating process of the vapours, and several additional flow paths must be added to the engine to control the flow of the fluids involved. This combination of factors make the design complex, expensive, and introduces significant design constraints for both the engine manufacturer and the customers who wish to incorporate the engine into their products. 
   The present invention is directed to solving one or more of the problems set forth above. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention, there is provided an internal combustion engine with a cylinder block defining a first chamber, a second chamber and a passage connecting the first chamber and the second chamber. The passage allows gas flow between the first chamber and the second chamber. The internal combustion engine further has a barrier device positioned in the cylinder block with an impact surface located in the gas flow adjacent to a downstream end of the passage. The passage has a cross-sectional area and shape such that said gas flow has a velocity causing oil particles in the gas flow to impact on the impact surface. The impact surface extends over the cross-sectional area of the passage and substantially impedes oil particles in the gas flow whilst allowing gas to flow past the impact surface. 
   According to a second aspect of the present invention, an internal combustion engine has a first engine component with a passage therein, a second engine component and gasket sealing between the first and the second engine components The gasket has at least one perforation to allow gas flow from the passage in the first engine component to the second engine component. The gasket includes a barrier device positioned in the gas flow adjacent to a downstream end of the passage. The passage has a cross-sectional area and shape such that the gas flow has a velocity causing oil particles in the gas flow to impact on the impact surface. The impact surface extends over the cross-sectional area of the passage and substantially impedes oil particles in the gas flow whilst allowing gas to flow past the impact surface. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of an internal combustion engine indicating the flow path of the gasses that are to be vented from the crankcase. 
       FIG. 2  is a fragmentary cross-sectional view of a portion of an internal combustion engine illustrating a first embodiment of the present invention. 
       FIG. 3  is a perspective view of a barrier device as illustrated in  FIG. 2 . 
       FIG. 4  is a fragmentary cross-sectional view of a portion of an internal combustion engine illustrating a second embodiment of the present invention. 
       FIG. 5  is a plan view of a barrier device as illustrated in  FIG. 4 . 
       FIG. 6 . is a fragmentary cross sectional view of a portion of an internal combustion engine illustrating a third embodiment of the present invention. 
       FIG. 7  is a fragmentary cross-sectional view taken along line  7 — 7  of  FIG. 6 . 
       FIG. 8  is a fragmentary cross-sectional view similar to  FIG. 7 , but showing an alternative arrangement. 
       FIG. 9  is a fragmentary cross sectional view of a portion of an internal combustion engine illustrating a fourth embodiment of the present invention. 
       FIG. 10  is a fragmentary, top plan view looking in the direction of arrows  10 — 10  of  FIG. 9 . 
   

   DETAILED DESCRIPTION 
   For clarity the following description refers to a single cylinder engine only, but the principle can of course as easily be applied to multiple cylinder engines. 
   With reference to  FIG. 1 . an internal combustion engine  10  according to this invention has a first chamber such as a tappet or camshaft chamber  12 , a second chamber such as a vent chamber  14  and a passage  16  connecting the two chambers. Engine  10  further comprises a cylinder head  18 , a cylinder block  20 , a gasket  22  positioned between cylinder block  20  and cylinder head  18  and a crankcase  24 . Blow-by gasses to be vented from crankcase  24  flow from crankcase  24  through respectively tappet chamber  12 , passage  16 , vent chamber  14 , and gasket  22  to cylinder head  18 . The oil particles carried by the gasses are mainly introduced before the gasses enter passage  16 . 
   Four embodiments of this invention are described below in detail. Generally, each embodiment comprises an impact surface which is positioned adjacent to the downstream side of a passage connecting a first chamber and a second chamber. The impact surface extends over the passage in such a manner that substantially all gas flow is directed onto this impact surface. The passage has a both pre-determined cross-sectional area and shape such that the gas flow through the passage maintains or obtains a velocity within a pre-determined velocity range so it causes the oil particles carried by the gas flow to impact on the impact surface preferably with minimal atomisation of the particles on impact. The gas flow can continue, but the inertial impact of the oil particles on the impact surface cause the oil particles to coagulate and form oil droplets. As the droplets reach a certain size they depart from the impact surface and the droplets return to the first chamber. 
     FIGS. 2 and 3  illustrate a first embodiment of this invention. A barrier device, generally designated  26 , is positioned adjacent to passage  16  in cylinder block  20 . Barrier device  26  is preferably made from a plastic material, but other suitable materials such as metals or composites can also be used. Barrier device  26  comprises impact member  28  having impact surface  30  and at least one but preferably two or more locating portions or supporting members  31  having lower abutments  34  and upper abutments  36 . Supporting members  31  in combination with abutments  34  and  36  secure barrier device  26  by means of a snap-fit in passage  16 . 
   Barrier device  26  is fitted in chamber  14  via aperture  32 . After fitting barrier device  26  and carrying out any other desired operations, aperture  32  is closed off by for example press-fitting or threading plug  33  into aperture  32 . 
   The gas flow carrying the oil particles travels at a velocity within a desired velocity range after leaving passage  16 . The gas flow continues by flowing through apertures  35  between supporting members  31 . The inertia of the oil particles causes the oil particles to impact on impact surface  30 , and thus the oil particles coagulate to form oil droplets. As the droplets reach a certain size they depart from impact surface  30  and the droplets either fall back through passage  16  or run back via supporting members  31  into tappet chamber  12 . 
     FIGS. 4 and 5  show a second embodiment of the present invention, wherein a barrier device, generally designated  126 , is fitted adjacent to the downstream side of passage  116  in cylinder block  120 . Barrier device  126  is preferably made from a plastic material, but other suitable materials such as metals or composites can also be used. Barrier device  126  comprises a body  137  having a generally rectangular shape, but the body  137  could have any other suitable shape. Body  137  comprises a plurality of locating portions such as tabs  138 , an impact member  128  having impact surface  130 , cross-members  139 , and one or more perforations  140 . 
   Barrier device  126  is fitted in chamber  114  via aperture  132 . After fitting barrier device  118  and carrying out any other desired operations, aperture  132  is closed off by for example press-fitting or threading plug  133  into aperture  132 . 
   Barrier device  126  is secured by engaging locating portions  138  in receiving portions such as recesses (not shown) formed by the walls that define chamber  114 . 
   The gas flow carrying the oil particles travels at a velocity within a desired velocity range after leaving passage  116 . The gas flow continues by flowing through perforations  140 . The inertia of the oil particles causes the oil particles to impact on impact surface  130 , and thus the oil particles coagulate to form oil droplets. As the droplets reach a certain size they depart from impact surface  130  and the droplets fall back through passage  116 . 
     FIGS. 6 ,  7 , and  8  illustrate a third embodiment of the present invention, wherein a barrier device  226  projects from an inner wall surface  227  of cylinder block  220  adjacent to the downstream side of passage  116 . Impact member  226  is preferably made from metal, but other suitable materials such as plastics or composites can also be used. Barrier device  226  can be an integral cast part of cylinder block  220  or, alternatively it can be fitted after block  220  has been cast by methods well known to those skilled in the art, such as a press-fit or by using an adhesive. 
   If barrier device  226  is fitted after casting of cylinder block  220 , barrier device  226  is fitted in chamber  214  via aperture  132 . After fitting barrier device  226  and carrying out any other desired operations, aperture  232  is closed off by for example press-fitting or threading plug  233  into aperture  232 . 
   The gas flow carrying the oil particles travels at a velocity within a desired velocity range after leaving passage  216 . The gas flow continues by flowing around impact member  226 . The inertia of the oil particles causes the oil particles to impact on impact surface  230 , and thus the oil particles coagulate to form oil droplets. As the droplets reach a certain size they depart from impact surface  230  and the droplets fall back through passage  216 . 
   An alternative shaped barrier device is shown in  FIG. 8  wherein impact surface  230  is arcuate as opposed to the generally flat surface as shown in  FIGS. 6 and 7 . 
   In  FIGS. 9 and 10  an internal combustion engine  310  comprises a cylinder block  320 , a cylinder head (not shown) and a gasket  322  disposed between cylinder block  320  and the cylinder head. Gasket  322 , which can be conventional except as described herein, comprises a body  350 , at least one barrier device or impact portion  326  projecting from body  350  having impact surface  330 , and at least one perforation  356 . Gasket  322  can be considered part of cylinder block  320  for the purpose of this invention. Cylinder block  320  comprises vent chamber  314  having throat area  358 , passage  316  and tappet chamber  312 . 
   The embodiment shown in  FIGS. 9 and 10  uses the same general principle as described with regards to  FIGS. 2 to 8  with the main difference being the impact member has been repositioned. 
   Impact portion  326  is positioned in such a manner that the gas flow carrying the oil particles leaving throat area  358  of chamber  314  are obstructed by impact portion  326 . Throat area  358  has a both pre-determined cross-sectional area and shape such that the gas flow through the throat area maintains or obtains a velocity within a pre-determined velocity range so it causes the oil particles carried by the gas flow to impact on the impact surface  330  preferably with minimal atomisation of the particles on impact. Therefore throat area  358  functions similarly to passages  16 ,  116  and  216  as described above. Consequently, throat area  358  can be considered a passage for purposes of this invention. 
   The gas flow carrying the oil particles travels at a velocity within a desired velocity range after leaving throat area  358 . The gas flow continues by flowing around impact portion  326 . The inertia of the oil particles causes them to impact on impact surface  330 , and thus the oil particles coagulate to form oil droplets. As the droplets reach a certain size they depart from impact surface  330  and the droplets fall and run back through vent chamber  314  into passage  316  and then into tappet chamber  312 . 
   Industrial Applicability 
   In use, this invention provides a simple and robust solution to reduce the amount of liquid oil particles carried over to a crankcase ventilation oil filter or to the induction system of an engine. Gas flow from the crankcase  24  passes through a passage  16 ,  116 ,  216 ,  358  formed in the cylinder block  20 ,  120 ,  220 ,  320 . This ensures that oil particles carried by the gas flow have sufficient inertia that they impact against an impact surface  30 ,  130 ,  230 ,  330  positioned adjacent to the downstream end of the passage. However, the gas flow may continue past the impact surface  30 ,  130 ,  230 ,  330 . As a result, oil particles are removed from the gas flow, and the oil particles can coagulate to form droplets that then return to the crankcase and engine sump. 
   This invention can be readily fitted to existing engine designs without requiring substantial modification to the engine design. Moreover, because the invention is generally contained within the engine, the benefits of the invention can be obtained without increasing the space claim of the engine. In some cases, this invention may also be fitting to existing engines. 
   This invention is particularly useful in engine application that are likely to generate high levels of oil particles carried by the crankcase gases. One example of such an application is an engine for a hydraulic excavator. In a hydraulic excavator, the repeated slewing of the excavator during digging operations can cause increased splashing of oil within the engine, thereby increasing the likelihood that small oil particles will travel with the gas flow. For applications that present particularly high levels of oil particles in the gas flow, those skilled in the art will recognize that one of more of the embodiments of  FIGS. 2–8  can be combined with the embodiment of  FIGS. 9–10  to further reduce oil carry over. 
   Although the preferred embodiments of this invention have been described, improvements and modifications may be incorporated without departing from the scope of the following claims.

Technology Category: 2