Abstract:
The crankcase of an internal combustion engine includes a blow-by gas passage that is formed inside the crankcase and discharges blow-by gas inside the crankcase to the top of the crankcase. An oil drain passage is also formed inside the crankcase such that it discharges oil collected from the top of the crankcase into the crankcase, whereas the blow-by gas passage and the oil drain passage are interconnected with each other inside the crankcase.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of Korean Application No. 10-2003-0077685, filed Nov. 4, 2003, the disclosure of which is incorporated herein by reference. 
   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates to a crankcase for an engine of a motor vehicle. More specifically, the crankcase includes a blow-by gas passage and oil drain passage. 
   BACKGROUND OF THE INVENTION 
   Generally, blow-by gas is gas that leaks through a gap between a piston and a cylinder and flows into a crankcase. Blow-by gas contains non-combusted gas, combusted gas, and oil vapor. If blow-by gas remains inside a crankcase, pressure inside the crankcase increases. The increased pressure applies resistance to movement of the pistons and corrosion is likely to occur within the engine. 
   Therefore, to reduce blow-by gas from gathering within a crankcase, a technique for releasing blow-by gas is to recycle the blow-by gas and supply it to an intake device. A specific method of accomplishing this goal is to provide an oil drain hole and/or a blow-by hole on a crankcase to exhaust the blow-by gas to a cylinder head cover. 
   However, the blow-by gas recycle system does not smoothly pass the blow-by gas inside the crankcase to the cylinder head cover. Therefore, the pressure within the crankcase is maintained as a positive pressure. As a result, the reciprocating motion of the piston is interfered with so output is lowered. Furthermore, the force that pushes oil into the crankcase is exceeded by and oil leaks develop. Additionally, the oil contained in blow-by gas is supplied to a combustion chamber with the blow-by gas, thereby, increasing oil consumption and emitting harmful exhaust gas. Furthermore, carbon deposits increase within the engine and result in a lowering of the combustion efficiency. 
   SUMMARY OF THE INVENTION 
   According to a preferred embodiment the present invention provides a crankcase which effectively discharges blow-by gas that has accumulated within from a cylinder combustion chamber. Oil consumption is reduced by separating oil contained in blow-by gas and recycling it to the crankcase. Also, the generation of harmful exhaust gasses are reduced by improving the manner in which blow-by gasses are supplied to the combustion chamber. 
   Preferably, the crankcase of an internal combustion engine includes a blow-by gas passage that is formed inside the crankcase. The blow-by gas passage discharges blow-by gas inside the crankcase and to the top of the crankcase. An oil drain passage is formed inside the crankcase that discharges the oil collected from the top of a crankcase into the crankcase. The blow-by gas passage and the oil drain passage are interconnected with each other inside the crankcase. 
   Preferably, an expansion chamber is formed between the blow-by gas passage and the oil drain passage, the two passages being interconnection. The blow-by gas passage is formed so as to pass through a certain section of the expansion chamber. The oil drain passage is formed so as to pass by the end of the expansion chamber that is located in the flow direction of the blow-by gas. Preferably, the expansion chamber is formed so as to establish a downward slope in the flow direction of the blow-by gas. 
   According to a preferred embodiment, the internal combustion engine is a V-type engine that includes multiple cylinders and the blow-by gas passage and the oil drain passage are formed on one side of a cylinder bank of the V-type engine. 
   It is also preferable that the blow-by gas passage is formed further inside of a crankcase than the oil drain passage and the expansion chamber is extended almost perpendicularly to the cylinder axis of the cylinder bank. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For better understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is an perspective view of the crankcase according to an embodiment of this invention; and 
       FIG. 2  is a sectional view of the crankcase in  FIG. 1  taken along line I—I. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   According to  FIG. 1 , a crankcase  100  is illustrated showing generally oil drain passages  110  and a blow-by gas passage  120 . Like a typical V-type engine, intake and exhaust systems are combined at the top of the crankcase  100 , and an oil pan is combined at the bottom of the crankcase  100 . Shown are a plurality of oil drain passages  110  formed at the top face of the crankcase  100 . The oil drain passages  110  interconnect with the bottom face of a crankcase  100 . 
   The oil drain passage  110  is the passage through which lubricating oil that has completed lubricating actions is returned to an oil pan combined with the bottom of the crankcase  100 . The returned oil flows into the top face of the crankcase  100  and then flows out of the bottom face. In addition, a blow-by gas passage  120  is formed on the top face of the crankcase  100  and interconnects with the bottom face of the crankcase  100 . 
   The blow-by gas passage  120  is the passage used to recycle blow-by gas generated inside the crankcase  100  during engine operation. The blow-by gas is represented to an intake system that is mounted on the top face of the crankcase  100 . The blow-by gas is allowed to flow, first, into the bottom face of the crankcase  100  and then be discharged to the top face. 
   Shown in  FIG. 2 , are the oil drain passage  110  and the blow-by gas passage  120  that, respectively, pass through the top face and bottom face of the crankcase  100 . An expansion chamber  220  is formed between the oil drain passage  110  and the blow-by gas passage  120  for interconnection. The oil  250 , recycled from the top face of the crankcase  100  is discharged to the bottom face of the crankcase  100  through the oil drain passage  110 . The blow-by gas  230  flown from a combustion chamber into an internal space  210  of the crankcase  100  is allowed to go from the bottom face of the crankcase  100 , pass through an expansion chamber  220 , and be discharged into the top face of the crankcase  100  via a blow-by gas passage  120 . A downward directed lip may be formed at the entrance to expansion chamber  220 . 
   In a V-type engine as illustrated in the Figures, the oil drain passage  110  and blow-by gas passage  120 , and the expansion chamber  220  are formed at one side of the cylinder bank of the crankcase  100 . The expansion chamber  220  is a space formed inside the crankcase  100  and formed so that its sectional area may be larger than inlet and outlet of the oil drain passage  110  and blow-by gas passage  120 . 
   Preferably, the blow-by gas passage  120  is formed further inside of the crankcase  100  than the oil drain passage  110 , and the expansion chamber ( 220 ) is extended approximately perpendicular to the cylinder axis of the cylinder bank. The oil drain passage  110  is formed to pass by the left end of the expansion chamber  220 , and the blow-by gas  230  is allowed to flow into the left end of the expansion chamber  220 . The blow-by gas  230  then flows through a certain section in the direction of left end before it is discharged into the top face of the crankcase  100 . 
   The blow-by gas  230  flowing from the bottom face of the crankcase  100  contains non-combusted gas, combusted gas, and oil vapor  240  that has been vaporized by the high heat of the engine. The oil vapor  240 , of the blow-by gas, that has been liquefied from flowing through a section of the expansion chamber  220  is allowed to flow into the outer end of the expansion chamber  220  along the inclined surface and flow in from the top surface of the crankcase  100  through an oil drain passage  110  before it is combined with the oil  250  passing through the outer end of the expansion chamber  220  and discharged into the bottom surface of the crankcase  100 . 
   Therefore, the blow-by gas  230  may be recovered into the top surface of the crankcase  100  after the oil vapor  240  has been removed. As a result, the pressure inside the crankcase  100  may be lowered, and oil consumption may also be reduced at the same time. 
   By ventilating the engine crankcase as described above, the blow-by gas that flows from a combustion chamber into the internal space of the crankcase may be effectively discharged to prevent elevation of the internal pressure of the crankcase while improving efficiencies of an engine. Additionally, since the blow-by gas passage and the oil drain passage are interconnected, oil that has flown into the blow-by gas passage may be discharged into the oil drain passage. In addition, by forming an expansion chamber inside the crankcase that interconnects the blow-by gas passage with the oil drain passage, the oil contained in the blow-by gas may be separated and combined with the oil recovered, thereby, reducing oil consumption. Furthermore, by separating oil from the blow-by gas, generation of hazardous exhaust gas may be suppressed when blow-by gas is allowed to re-pass through an intake system and be supplied to a combustion chamber.