Abstract:
An assembly for cleaning blowby gases has an electric heater and a downstream catalyst positioned in series relationship in a blowby conduit leading from an engine&#39;s crankcase to the atmosphere. The heater is controlled by a controller to maintain a selected temperature at the inlet to the catalyst as determined by a temperature sensor. The heating of the blowby gases increases the blowby gas temperature to a level where the catalyst is active to oxidize the constituents of the blowby gas stream.

Description:
FIELD OF THE INVENTION 
     The present invention relates to internal combustion engines and more particularly to the treatment of blowby gases from such engines. 
     BACKGROUND OF THE INVENTION 
     Reciprocating internal combustion engines have a series of pistons reciprocating in appropriate cylinders. These pistons are connected to a crankshaft to translate the reciprocating movement to a rotary output. All reciprocating internal combustion engines have some degree of gases that pass by the pistons from the combustion chamber to an interior chamber for the engine, usually called the crankcase. 
     Internal combustion engines of the heavy duty diesel type, where the heat of intake air compression is used to ignite fuel that is injected by a fuel injection system at, or near the end of the compression stroke to provide combustion and a power output have greater issues with blowby gases. Such engines are typically turbocharged so that the charge at the beginning of the compression stroke can be above atmospheric pressure. This and other factors such as the normal high compression of the diesel engine cause blowby gases to pass from the cylinder past the piston into a crankcase that houses the crankshaft and other working mechanisms for the engine. 
     In the past, blowby gases have been vented directly to the atmosphere. The reason for this is that it is not possible to contain the gases in the crankcase because pressure would eventually build up and cause leakage through various seals and other gaskets. 
     Recent proposals in the emissions laws have mandated that blowby gas (also called crankcase ventilation gases) must be included as part of the regulated emissions. This means that any product of the fluids coming from the crankcase must be either treated or somehow dealt with. One approach has been to direct the blowby gas into the inlet of a turbocharger compressor so that the blowby gas is mixed with the fresh air and consumed by the combustion process of the engine. However, since the blowby gases have oil particles as well as unburned hydrocarbons, the entry of these gases into the compressor inlet can cause a deposit on the compressor. In cases where a high pressure ratio compressor is used for the turbocharger, the discharge temperature of the compressor may be high enough to cause coking. 
     Other manufacturers have used elaborate liquid separation and filtration devices to remove the emissions. Using filtration devices, requires periodic replacement which in turn increases the complexity and cost to maintain the engine. Even when the bypass flow is filtered, it does not completely eliminate the emissions of components of the bypass flow that are subject to regulation. 
     Thus, a need exists in the art to provide a cleaning of the fluids passing through the bypass flow passageway. 
     SUMMARY OF THE INVENTION 
     In one form, the invention includes a blowby assembly for an internal combustion engine having a combustion chamber and an internal chamber exterior to the combustion chamber. The assembly includes a passageway for fluid leading from the internal chamber to the atmosphere and a catalyst is positioned in the passageway. A heater is positioned in the passageway between the catalyst and the internal chamber. 
     In another form, the invention includes an internal combustion engine having a housing and a plurality of pistons reciprocable within the housing in associated combustion chambers. The pistons are connected to a crankshaft journaled within the housing to provide a rotary output. The housing has an internal chamber exterior to the combustion chamber and the engine has a passage for fluids from the internal chamber to the atmosphere. A catalyst is positioned in the passage so that fluid passing from the internal chamber to the atmosphere passes over the catalyst. A heater is positioned in the passage between the catalyst and the housing for heating the fluid passing to the catalyst. 
     In yet another form the invention includes a method for cleaning blowby gas from an internal combustion engine which has a passage leading the blowby gas to the atmosphere. The method has the steps of heating the blowby gas in the passage and then passing the heated blowby gases over a catalyst before passing to the atmosphere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows an external perspective view of an internal combustion engine and a blowby gas cleaning assembly embodying the present invention along with schematic representation of associated components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The sole  FIG. 1  shows an internal combustion engine generally indicated by reference character  10 . Internal combustion engine  10  has an engine crankcase  12  in which a series of cylinder liners (not shown) receive pistons (also not shown) that reciprocate and are connected to a crankshaft which provides a rotary output through flywheel  14 . As herein shown, engine  10  is of the compression engine, or diesel type, in which the heat of compression is used to ignite fuel that is injected into combustion chambers from a fuel injection system  16 . Fuel injection system  16  may be one of a number of types including hydromechanical, high pressure common rail, or unit injectors. These fuel systems all have, as their object, the metering of the correct quantity at the correct time to provide demanded power from engine  10  while still maintaining emissions output within limits established by local and national regulatory bodies, as appropriate for the engine application. 
     As discussed before, diesel engines have a bypass flow of gases from the combustion chamber of the engine. The blowby gases are a normal part of the engine operating cycle and are caused by piston ring reversals and passage of gases across the end gaps of piston rings. The blowby gases travel from the combustion chamber past the piston to an internal chamber (not shown) in engine  10 . Part of the chamber includes the lower portion of crankcase  12  which houses the connecting rod, crankshaft, and sump for the engine  10 . As is typical practice, the chamber within the block  12  extends to a head  18  which has a set of rocker levers or other camshaft mechanism for actuating poppet valves within the engine to admit intake air and permit the discharge of exhaust air from the combustion chamber. Head  18  is covered by a rocker cover  20  and the space bounded by rocker cover  20  and head  18  is connected to the chamber within engine block  12  by appropriate passages. Usually these passages include passages for pushrods going down to a lower mounted camshaft, in addition to defined paths for oil from the rocker cover  20  to the sump in the lower portion of crankcase  12 . The interior of housing of rocker cover  20 , and therefore the internal chamber of the engine  10 , is vented to atmosphere by a passage  22  within a conduit  24  connected to an opening  26  on rocker cover  20 . Conduit  24  extends to a lower portion of the engine and has an opening  28  that vents the internal chamber to the atmosphere. A component  27  is positioned in the rocker cover  20  to block the flow of large droplets of oil from entering the passage  22 . This may be in the form of a circuitous path through a series of baffles or a wire mesh. It should be apparent to those skilled in the art that other methods may be used to prevent large droplets from entering the passage  22 . 
     A housing  30  is interposed in conduit  24  so that all the fluid flow in passage passes through the housing  30 . A heater  34  is positioned at the upstream end  32  of chamber  30 . A catalyst  36  is positioned downstream of heater  34  and a temperature sensor  38  is between the two, but closely adjacent catalyst  36 . Heater  34  can be a typical resistance heater that receives power via line  40  from a controller  42 . Controller  42  receives power from an appropriate power source  44  via line  46 . Power source  44  typically would be the engine/vehicle electrical system. Typically, the power source would be DC voltage at the level appropriate for the vehicle&#39;s electrical system. The controller  42  directs current to heater  34  via the line  40  to heat fluids passing through conduit  24  to a temperature at which the catalyst  36  is active. In order to provide a closed loop to the control system, the signal from the temperature sensor  38  is fed to the controller  42  via line  48 . The details of such a control scheme are not discussed in order to simplify the understanding of the present invention. It should be apparent, however, that the control may be implemented in analog or digital form to provide the appropriate control of the temperature of the fluid passing in and over the catalyst  36 . 
     The catalyst material may be selected from the precious metals consisting of platinum, palladium, and a combination of both. It should be apparent to those skilled in the art that other catalyst materials may be selected with equal applicability. 
     The impact of heater  34  is that it heats the fluids in passage  22  from a temperature of around 100° C. to at least 200° C. and preferably 250° C. so that the catalyst  36  is able to act on the blowby gases to oxidize the constituents in the bypass conduit prior to discharge to the atmosphere through opening  28 . The blowby is in an aerosol form consisting mainly of small oil droplets with some carbon and traces of wear debris and fugitive dust. Particle sizes range from 0.1 to 3 micrometers with most of the mass distribution falling between 0.5 to 2 micrometers. The particle distribution is such that the aerosol is highly likely to be inhaled by humans. By heating the gases to the temperatures indicated, the catalyst  36  oxidizes the hydrocarbons and the lube oil to minimize, if not eliminate, the aerosol from those components being discharged to the atmosphere. 
     The capacity of the heater is dependent on engine conditions and especially engine displacement. The capacity of the heater can vary up to about 500 watts on a 9 liter engine. It should be apparent to those skilled in the art, however, that the engine may be provided in other forms and would require heaters of different capacity. Such a system eliminates the need for a complex filtration system and subsequent cleaning and/or replacement of such a filter. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.