PATENT ABSTRACT
A breather system for a crankcase of an internal combustion engine includes a gas compressor configured to elevate the pressure of crankcase blow-by gas. At least one gas-oil separator receives gas with entrained oil from the compressor, separates oil from the gas and discharges cleaned gas. The oil is re-circulated back to the crankcase. The cleaned gas is either discharged through the engine exhaust system or re-circulated back into the engine combustion air intake. A bypass conduit allows cleaned gas to be re-circulated from the gas-oil separator outlet to the compressor inlet to balance the blow-by production with the capacity of the compressor.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
     This invention relates to internal combustion engines, including but not limited to recirculation of crankcase gases into the intake system of an engine. 
     BACKGROUND 
     The present invention relates to a breather system for a crankcase of an internal combustion engine of the type which separates oil drops or mist from blow-by gases. The blow-by gases are routed to the intake air line of an engine to eliminate the discharge of combustion gases into the environment. Separated oil is routed back to the oil pan. 
     Ideally, the pressure within an internal combustion engine crankcase should be maintained at a level equal to or slightly less than atmospheric pressure to prevent external oil leakage through the various gasketed joints, such as that between the valve cover and the cylinder head. Combustion gases are generated during the operation of an internal combustion engine. A small amount of these gases leaks past the piston seals, valve stems seals, and turbochargers of the internal combustion engine. Because of the “blow-by” gases, the crankcase pressure will inherently rise, promoting leakage of oil from the crankcase. These gases, commonly referred to in the art as “blow-by” gases, need to be released. 
     Environmental considerations suggest that the blow-by gases in the crankcase be vented back to the combustion chamber rather than being released to the atmosphere. Accordingly, it is known to scavenge the crankcase of blow-by gases by connecting the crankcase to the engine air intake. 
     Blow-by gases that are released from the crankcase carry combustion by-products and oil mist caused by splashing of the engine&#39;s moving components within the crankcase and the oil pan. It is known to substantially remove the oil mist from the blow-by gas prior to introduction into the intake air system. An apparatus that removes oil mist from blow-by gases is commonly referred to as a “breather.” Known breathers include breathers that include a stack of conical disks that spin at a high speed to fling heavier oil against a wall of the breather and allow gas to pass though the breather. Centrifuge type separators are disclosed for example in U.S. Pat. Nos. 7,235,177 and 6,139,595. Other types of breathers include filters such as described in U.S. Pat. Nos. 6,478,019, 6,354,283; 6,530,969; 5,113,836; swirl chambers or cyclone separators, such as described in U.S. Pat. Nos. 6,860,915; 5,239,972; or impactors, such as described in U.S. Pat. Nos. 7,258,111; 7,238,216 5,024,203. Each type of breather has advantages and limitations. 
     The present inventor has recognized that it would be desirable to provide a breather system that is more economical to produce and more effective in operation than existing breather systems. 
     SUMMARY 
     An exemplary embodiment of the invention provides a breather system for a crankcase of an internal combustion engine. The breather system includes a gas compressor having a compressor inlet and a compressor outlet. The gas compressor is configured to elevate the pressure of blow-by gas received into the inlet and to discharge elevated pressure gas from the compressor outlet. An inlet conduit is arranged to connect the crankcase to the compressor inlet. At least one gas-oil separator includes a gas inlet for receiving the elevated pressure gas from the compressor, an oil outlet for discharging oil separated from the elevated pressure gas, and a gas outlet for discharging a gas having a reduced oil content. The at least one outlet conduit connects the compressor outlet to the gas inlet. 
     The at least one gas-oil separator can comprise a swirl chamber separator in series with an impact separator. The swirl chamber separator and the impact separator can be cast as a unitary housing. The oil outlet can be flow-connected to return the separated oil to the crankcase. 
     According to an exemplary embodiment, the gas outlet is flow connected to an air intake for the engine to re-circulate the gas discharged from the at least one gas-oil separator. 
     According to another aspect of the disclosed embodiment, the at least one gas-oil separator includes a gas outlet and a bypass conduit flow connected between the gas outlet and the compressor inlet. 
     The compressor can be a piston pump type of compressor or other known type of compressor. 
     The disclosed embodiment provides a method for separating oil from crankcase gas from an internal combustion engine, including the steps of:
         receiving crankcase gas outside of the crankcase and into a compressor;   pressurizing the crankcase gas using the compressor;   channeling the pressurized crankcase gas into a gas-oil separator;   separating oil from the crankcase gas in the gas-oil separator; and   returning the separated oil from the gas-oil separator to the crankcase.       

     The method can also include the step of directing crankcase gas from the gas-oil separator to a combustion air intake of the engine. 
     The method can also include the step of: if the capacity of the compressor exceeds the crankcase gas production, directing gas flow from the gas-oil separator to the compressor. 
     Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, and from the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE is a schematic diagram of a breather system of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     The FIGURE is a schematic diagram that illustrates an embodiment of an engine breather system  10  according to the present invention. The system  10  is associated with an engine  20  which could be a diesel engine, such as a diesel engine for a long haul truck. The diesel engine can be normally aspirated or turbocharged. The engine  20  includes a crankcase  22  having an upper engine internal volume  23  partly defined by a valve cover  24 . The upper engine internal volume is generally in fluid communication with all the blow-by gases within the crankcase. 
     The system  10  includes a gas compressor or pump  26  that includes a piston or a rotary impeller (not shown) or other fluid actuating device that can be belt driven, gear driven or otherwise driven by the engine  20 . Alternately the compressor could be driven by another power source. A number of compressor or pump types can be used, in addition to the standard piston pump, such as a gear pump, a gear-rotor pump, a vane pump, a rotary screw pump, or a diaphragm pump. According to one embodiment, the compressor would be rated at less than 50 PSI and to maintain a relatively small size, would be capable of being driven at speeds up to 10,000 RPM. A typical maximum bow-by gas flow rate for the compressor is 700 CFH (ft 3 /hour). 
     The gas compressor  26  includes an inlet  26   a  that is in fluid communication via a conduit  28  with the internal volume  23  by a connection to the valve cover  24 . An outlet  26   b  of the compressor is in fluid communication with an inlet  50   a  of a swirl chamber separator or cyclone separator  50 . Such a cyclone separator is described for example in U.S. Pat. Nos. 6,860,915 and 5,239,972, herein incorporated by reference. An outlet  50   b  of the swirl chamber is in fluid communication with in inlet  60   a  of an impactor or impact separator  60 . such an impact separator is described for example in U.S. Pat. Nos. 7,258,111; 7,238,216 and 5,024,203. An outlet  60   b  of the impactor  60  is in fluid communication with a pressure regulator  70 . The pressure regulator maintains a desired gas pressure within the impact separator and swirl chamber separator by varying the gas flow restriction through the regulator. 
     Oil that is separated from the gas in the swirl chamber  50  drains through an oil outlet  50   c  at a bottom of the swirl chamber  50 . Oil that is separated from the gas in the impactor  60  drains through an oil outlet  60   c  at a bottom of the impactor  60 . The outlets  50   c ,  60   c  can be small drain orifices. The combined oil from the outlets  50   c ,  60   c  is collected in a conduit or conduits  80  and returned to the crankcase  22 . 
     The compressor  26  sucks blow-by gases from the crankcase  22  and compresses the blow-by gases to a pre-selected pressure, which may be below  50  PSIG. The blow-by gases are delivered into the swirl chamber  50  and then into the impactor  60  at elevated pressure. Each of the swirl chamber  50  and then into the impactor  60  separate some oil from the oil entrained blow-by gases. The pressure regulator  70  can be set to a desired working pressure to maintain elevated pressures within the components  50 ,  60  and allow cleaned gas to pass into a discharge conduit  90  that can either be directed to atmosphere or can be redirected to the engine intake manifold for a normally aspirated engine or to the turbocharger compressor for a turbocharged engine. Alternately, with a sufficient arrangement of valves, the discharge conduit could be directed into the exhaust system. 
     Pressure pulses from the compressor, in the form of a piston pump compressor, aid in the separation of oil and gas from the blow-by gases, because of the instantaneous high velocity of blow-by gases that enter the impactor. 
     According to one embodiment of the invention, the size of the compressor should be large enough to outpace the amount of blow-by gases that are drawn into the compressor, which may be as high as 700 CFH (ft 3 /hour). If the compressor is of the piston type with one-way valve or valves, the piston should be orientated in a manner where the outlet valve is at the lowest point, below the piston so that any condensed oil can drain through the drain orifice and back into the engine to prevent oil from pooling and overwhelming the system when it leaves the compressor. 
     The swirl chamber  50  and impactor  60  typically have no moving components and the swirl chamber  50  and impactor  60  can be cast as part of a common or unitary housing. 
     Additionally, impactors of current design typically require high gas velocity to function. Therefore, small orifices are typically required but are restrictive such as to require a significant pressure drop. However, according to the disclosed embodiment, the compressor elevates the pressure of the blow-by gases to push the air through smaller orifices at higher velocity, i.e., more pressure drop is available. Furthermore, the high velocity of the cleaned blow-by gases from the impactor may reduce condensation and possible ice buildup in the discharge conduit  90 . 
     A screen (not shown) can be used at each of the oil outlets  50   c ,  60   c  to protect the outlets from clogging with debris. The oil drain diameters for the outlets  50   c,    60   c  can be sized in a manner that allows the system  10  to keep up with the amount of oil that is being separated from gas but not allow excessive loss of pressure by venting gas. During high engine speed and low power operation, the outlets  50   c ,  60   c  will normally be clear of oil and gas pressure may vent through the outlets  50   c ,  60   c  to the crankcase, which will then vent back to the compressor. This is not detrimental to the system  10  or to engine operation during these engine operating conditions. 
     A bypass conduit  110  can be provided to direct gas from the low pressure output of the regulator  70  at the discharge conduit  90  to a low pressure compressor intake at the conduit  28 . When engine speed is high and the load is low, the compressor will be oversized for the amount of blow-by gas generated, which would result in formation of a vacuum within the engine. To avoid this condition, the bypass conduit  110  can be used to re-circulate cleaned blow-by gas from the discharge conduit  90  back into the compressor  26  where it is re-introduced to the separators  50 ,  60 , re-cleaned and proper crankcase pressure can be maintained. 
     If under unusual circumstances blow-by volume from the engine exceeds compressor capacity, the excess blow-by gas will bypass the compressor through the bypass conduit  110  and discharge through the discharge conduit  90 . 
     Parts List 
       10  engine breather system 
       20  engine 
       22  crankcase 
       23  upper engine internal volume 
       24  valve cover 
       26  pump or compressor 
       28  conduit 
       50  swirl chamber or cyclone separator 
       50   a  swirl chamber gas inlet 
       50   b  swirl chamber gas outlet 
       50   c  swirl chamber oil outlet 
       60  impact separator or impactor 
       60   a  impactor gas inlet 
       60   b  impactor gas outlet 
       60   c  impactor oil outlet 
       70  pressure regulator 
       80  conduits 
       90  discharge conduit 
       110  bypass conduit 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.