Abstract:
A breather system functions, during cold operation, as an open breather system, and functions as a closed breather system once the engine has sufficiently warmed. The breather system includes a first flow path between the engine crankcase and an air intake for the engine, and a three-way valve located within the flow path and responsive to ambient temperature and engine coolant temperature to close the conduit and to open a second flow path between the engine compartment and atmosphere.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to internal combustion engines, including but not limited to recirculation of crankcase gases into the intake system of an engine. 
       BACKGROUND 
       [0002]    The present invention relates to a closed loop breather system for a crankcase of an internal combustion engine of the type which recirculates piston blow-by gases in the crankcase to the intake air line of an engine to eliminate the discharge of oil mist into the environment and, more particularly, to a breather system which limits the pressure differential between the engine crankcase and atmosphere. 
         [0003]    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 of the internal combustion engine, and unless the gases are removed from the crankcase, they become trapped. These gases, commonly referred to in the art as “blow-by” gases, need to be released. Because of the “blow-by” gases, the crankcase pressure will inherently rise, promoting leakage of oil from the crankcase. Originally, crankcase pressure was vented to the atmosphere through a breather to solve this problem. 
         [0004]    Environmental considerations dictate that the blow-by gases in the crankcase be vented back to the combustion chamber rather than being released to the atmosphere. Accordingly, the crankcase was scavenged by being connected to the engine air intake thereby resulting in a vacuum in the crankcase with a depression valve being used to prevent the negative pressure in the engine cavity from exceeding a predetermined amount. 
         [0005]    Government regulations require the engine to be within defined levels of exhaust emissions, including crankcase vapors, under specific environmental conditions which include ambient temperature and altitude. Outside of the specified environmental conditions, the “emissions window” the engine is allowed to have different emission levels. 
         [0006]    The present inventors have recognized that during extreme cold weather operation, it is possible that water vapor in the combustion process captured in closed breather system can condense and can be detrimental to various engine components. 
       SUMMARY 
       [0007]    The exemplary embodiment of the invention provides a breather system that reduces the possibility of water vapor condensing on engine parts during cold weather operation while also meeting emissions requirements. 
         [0008]    The exemplary system would function, during cold operation, as an open breather system, and function as a closed breather system once the engine has sufficiently warmed. The exemplary system provides a flexible, two function crankcase breather system that responds to ambient conditions. 
         [0009]    An exemplary embodiment of the invention provides a breather system for an internal combustion engine that includes a first flow path between an engine compartment subject to blow-by gasses and an air intake for the engine, and a valve located within the flow path and responsive to at least one of an ambient temperature condition and a coolant temperature condition to close the conduit and to open a second flow path between the engine compartment and atmosphere. 
         [0010]    The system includes an ambient temperature sensor and a coolant temperature sensor. The valve is responsive to both the ambient temperature sensor and the coolant temperature sensor. 
         [0011]    The system can comprise a control unit and a valve actuator operatively connected to the valve to change flow paths through the valve upon command. The actuator is signal-connected to the control unit, and the ambient temperature sensor and the coolant temperature sensor are signal-connected to the control unit. The control unit determines a command to the actuator depending on ambient temperature and coolant temperature. 
         [0012]    An exemplary method of the invention for operating an internal combustion engine includes the steps of: 
         [0013]    sensing an engine temperature; 
         [0014]    providing the breather system can be operated as a closed breather system connecting an engine compartment subject to blow-by gasses and an air intake of the engine, or an open breather system connecting the engine compartment subject to blow-by gasses and atmosphere; and 
         [0015]    if engine temperature is below a predetermined low engine temperature threshold, operating the breather system as the open breather system, and when the engine temperature exceeds the predetermined low engine temperature threshold operating the breather system as the closed breather system. 
         [0016]    Alternately, the method of operating an internal combustion engine includes the steps of: 
         [0017]    sensing an engine temperature; 
         [0018]    sensing an ambient temperature; 
         [0019]    providing the breather system can be operated as a closed breather system connecting an engine compartment subject to blow-by gasses and an air intake of the engine, or an open breather system connecting the engine compartment subject to blow-by gasses and atmosphere; and 
         [0020]    if engine temperature is below a predetermined low engine temperature threshold, and if ambient temperature is below a predetermined low ambient temperature threshold, operating the breather system as the open breather system, and when the engine temperature exceeds the predetermined low engine temperature threshold or if the ambient temperature exceeds the low ambient temperature threshold, operating the breather system as the closed breather system. 
         [0021]    The step of sensing engine temperature can be accomplished by sensing engine coolant temperature. 
         [0022]    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, from the claims and from the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a plan view of a turbocharged engine and shows schematically a crankcase breather system of the present invention engaged to and between a valve housing of the engine and the compressor air inlet line of a turbocharger; and 
           [0024]      FIG. 2  is a schematic diagram of a dual function crankcase breather system of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    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. 
         [0026]    Referring now to the drawings in greater detail, there is illustrated therein a dual function engine crankcase breather system of the present invention generally identified by the reference numeral  10  mounted on an internal combustion engine  18 , preferably a diesel engine. 
         [0027]    The breather system  10  comprises a breather tube assembly  12  having an inlet end  14  in fluid communication with the interior of a valve housing or rocker arm cover  16  of engine  18  and an outlet end  20  ( FIG. 2 ) in fluid communication with a pitot tube fitting  13  mounted on an intake air line  22  of the engine  18  and extending therewithin. When the engine  18  is turbocharged as shown, pitot tube fitting  13  is located in the compressor air inlet line to the turbocharger  24 . In a naturally aspirated engine, the pitot tube would be located in the intake air passage from the air cleaner. 
         [0028]    In a V-8 engine, such as shown in  FIG. 1 , a crossover tube  25  interconnects the valve housing  16  with the rocker arm cover  17  of the other bank of the engine to equalize the pressure throughout the engine. It will be understood that the rocker arm cover  16  defines a portion of a closed interior cavity of the engine and that there is a continuous internal air path existing within and between the crankcase and the rocker arm cover  16 . Thus, venting of the valve housing  16  will necessarily vent the interior of the crankcase as well as valve housing  17 . 
         [0029]    The pitot tube  13  includes an opening  40 . A complete description of the arrangement and structure of the pitot tube  13  can be found in U.S. Pat. No. 5,140,968, herein incorporated by reference. 
         [0030]    The breather tube assembly  12  includes an oil mist separator  44  connected to the inlet end  14 , and a dual function selection valve  46  connected to the separator  44 . The dual function selection valve  46  is connected to an outlet tube  50  which is connected to the pitot tube  13  via a fitting  54 . 
         [0031]    The separator  44  can be configured as described in U.S. Pat. No. 7,185,643, herein incorporated by reference. 
         [0032]    The dual function selection valve  46  can be a three-way valve that is acted on by an electrically controlled solenoid actuator  60 . Alternately, the actuator can be an electrically controlled and vacuum operated valve. 
         [0033]    The state or position of the valve  46  either allows engine gas to pass into the intake air line  22  of the engine  18  according to a path marked “A” or pass directly to atmosphere through an outlet tube  62  according to a path marked “B”. Depending on a signal from the engine control module or unit (ECU)  66 , the actuator  60  changes the state of the valve to either pass engine gases through the path “A” while closing the path “B” or pass engine gases through the path “B” while closing the path “A”. The path “A” corresponds to a closed breather system, and the path “B” corresponds to an open breather system. 
         [0034]    In order for the ECU  66  to automatically select the path “A” or “B”, the ECU  66  receives and evaluates two temperature signals. A first temperature signal is received from an ambient temperature sensor  72  that measures ambient temperature T 1 . A second temperature signal is received from a coolant temperature sensor  74  that measures coolant temperature T 2  within the engine block or just after the coolant exits the engine block cooling jackets. 
         [0035]    When the temperature of the coolant T 2  sensed by the sensor  74  exceeds a predetermined coolant cold temperature limit Tc 2 , for example Tc 2  being about 50 degrees F., the path “A” is automatically selected by the ECU  66  and the actuator  60  changes the position of the valve  46  to the position corresponding to the path “A” or if the path “A” is already selected, the ECU  66  maintains that configuration. This configuration corresponds to a closed breather system. 
         [0036]    During cold ambient conditions, when the temperature sensor T 1  senses an ambient temperature T 1  below a predetermined ambient cold temperature limit Tc 1 , for example Tc 1  being about 20 degrees F., and the temperature of the coolant T 2  is below the predetermined coolant cold temperature limit Tc 2 , the ECU  66  selects the path “B” and the configuration is set to be an open breather system. Once the engine warms up to where the coolant temperature T 1  is above Tc 2 , the ECU  66  commands the actuator  60  to change the position of the valve  46  to the path “A” regardless of the ambient temperature. 
         [0037]    If the ambient temperature T 1  is above the cold temperature limit Tc 1  the ECU  66  commands the actuator  60  to change the position of the valve  46  according to the “A” path, or maintains the valve  46  according to the “A” path, regardless of the coolant temperature T 1 . 
         [0038]    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.