Abstract:
A PVC assembly includes a tubular fitting which significantly reduces the possibility of vapors freezing so as to block the PCV passage entry into a manifold. The fitting may be a material, such as nylon, with low heat conductivity as compared to a metal fitting and which is thermally isolated by an air gap from the PCV inlet opening of an aluminum metal manifold to minimize heat loss to the manifold walls. A mounting portion of the fitting includes a primary seal and a secondary seal/retainer that provides backup sealing and also acts as a snap-in retainer that releasably holds the fitting in the manifold PCV inlet opening without further retaining means. A simplified inlet fitting with both retaining and heat conserving features is thereby provided.

Description:
[0001]    This application claims priority from U.S. Provisional Application Serial No. 60/442,961 filed Jan. 27, 2003. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates to positive crankcase ventilation (PCV) systems for engines and, more particularly, to a PCV assembly and fitting for improving the assembly and operation of a PCV system.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is known in the art to provide positive crankcase ventilation (PCV) systems for internal combustion engines to draw crankcase vapors from the engine crankcase into an intake air passage, such as in an intake manifold, and conduct the crankcase vapors with the air into the engine cylinders for burning and disposal through the engine exhaust emission control system. Ventilation of engine crankcases is desirable to remove water and fuel vapors as well as combustion byproducts which may. accumulate in the crankcase during normal engine operation. Positive ventilation systems are desirable since they assure adequate crankcase ventilation while disposing of the crankcase vapors in the engine cylinders. There, substances such as hydrocarbons and combustion products are burned and treated with the engine exhaust gases prior to being released into the atmosphere.  
           [0004]    A typical PCV system may include a PCV control valve or orifice mounted in a rocker cover or other suitable portion of the engine which communicates with the engine crankcase. The PCV valve or outlet fitting is connected by a tube or hose with a tubular connector or other suitable fitting communicating with the interior of the engine intake manifold, or another portion of the engine air intake system in which a vacuum is developed by throttling the intake. During engine operation, the vacuum developed in the manifold or other component draws crankcase vapors through the PCV system and fitting into the manifold where it is mixed with the intake air and delivered to the engine cylinders for burning with the fuel supplied by the engine fuel system.  
           [0005]    When the engine is operated in very cold ambient temperatures, water that has accumulated in the engine oil and crankcase will vaporize and condense in the PCV system passages. The condensate may collect in the PCV passage where the delivery fitting enters the manifold due to loss of heat from the crankcase vapors to the fitting which is cooled by the walls of the manifold exposed to below freezing temperatures of the intake air. If the frost builds up in the passage it may become blocked, preventing the normal operation of the PCV system in disposing of crankcase vapors through the engine induction system and cylinders.  
           [0006]    Various devices have been utilized to avoid frost build up and blocking of the PCV system. These include heating sensitive portions of the PCV passages with engine coolant in a heat transfer device, using electrical heaters to heat the PCV fitting or valve or to raise the temperature of the vapor in the PCV system, and utilizing a heat conductive strap wrapped around the PCV tube to conduct heat from the cylinder head to the tube. These solutions, while effective, add complexity to the design and installation of the engine PCV system as well as adding to its cost.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides an improved PVC assembly and fitting which significantly reduces the possibility of vapors freezing so as to block the PCV passage. This is accomplished by using a plastic material, such as nylon, which has very low heat conductivity as compared to a metal fitting and which is also thermally isolated from the PCV inlet opening of the aluminum metal manifold to reduce heat loss from the fitting to the cold walls of the manifold.  
           [0008]    A further feature of the invention is the use of a double seal arrangement on the fitting. A first O-ring seal in a groove of the fitting slides into a smooth portion of an inlet opening in the manifold PCV passage to seal against leakage around the body of the fitting. A second O-ring seal is mounted on a slightly larger diameter portion of the fitting and expands into a groove provided in the inlet opening of the manifold PCV passage as well as being held in a groove of the fitting. This second seal acts as an additional back-up seal as well as providing a snap in attachment for the fitting within the PCV inlet opening of the manifold. The seal also acts to retain the fitting within the inlet opening subject to removal by pulling on the fitting with a sufficient force. This feature provides quick connection of the PCV fitting to the manifold as well as allowing removal for service or replacement without requiring a separate fastener for attaching the fitting to the manifold.  
           [0009]    An isolated portion of the fitting extends into the manifold air passage so that the crankcase vapors entering the air stream are not cooled excessively by adjacent portions of the manifold wall. Accordingly, freezing of the vapors within the PCV fitting is avoided and the PCV passage remains free for the flow of crankcase vapors.  
           [0010]    These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a cross-sectional view through a portion of an engine intake manifold and an associated PCV fitting formed in accordance with the invention.  
         [0012]    [0012]FIG. 2 is a side view illustrating the external side configuration of a connecting portion of the fitting of FIG. 1.  
         [0013]    [0013]FIG. 3 is a side view of the fitting of FIG. 2 showing an end view of the connecting portion.  
         [0014]    [0014]FIG. 4 is a cross-sectional view from the line  4 - 4  of FIG. 3.  
         [0015]    [0015]FIG. 5 is a pictorial view of a PCV connecting harness shown connected with PCV fittings in accordance with the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring now to the drawings in detail, numeral  10  generally indicates a portion of a PCV assembly including an aluminum engine air intake manifold  12  having assembled therewith a PCV fitting  14 .  
         [0017]    In the illustrated embodiment, the PCV fitting  14  is mounted in a relatively long inlet opening  16  in a PCV mounting boss  18  of the manifold  12 . The use of the relatively long inlet opening is caused in part by the available space outside the manifold for connection to the PCV fitting. Thus, it should be understood that, in other applications, the fitting could be mounted in a thinner portion of the manifold wall so that a much shorter body of the fitting could be utilized.  
         [0018]    The inlet opening  16  originates at a machined face  20  and includes in series an enlarged mounting bore  22 , a slightly smaller sealing bore  24  and a still smaller isolation bore  26 , which extends to an inner end  28  of the PCV boss  18 . The boss  28  is cast integral with an exterior wall  30  of the manifold  12 , which internally defines an air intake passage  32  through which air is delivered to engine cylinder intake ports, not shown, leading to the engine cylinders, not shown.  
         [0019]    Referring now to FIGS.  1 - 4 , the PCV fitting  14  includes a tubular body  34  including an inlet end  36  and an outlet end  38  and defining an internal fluid passage  40  between the inlet and outlet ends. The body  34  is formed of a heat and oil resistant plastic suitable for use in a PCV system. Forms of nylon are examples of materials which may be suitable for particular applications of fittings according to the invention. However, any suitable plastic materials may be utilized.  
         [0020]    The body  34  of the PCV fitting  14  includes a mounting portion  42 , a connecting portion  44  and an isolating portion  46 .  
         [0021]    The mounting portion includes a flange  48  which, in assembly, engages the mounting face  20  of the manifold  12 . A relatively large mounting diameter  50  extends longitudinally from the mounting flange and, in assembly, extends in close fitting relation with the mounting bore  22  of the PCV inlet opening  16  of the manifold. A retaining groove  52  in the mounting diameter carries an O-ring seal and retainer member  54  which is received in an internal groove  56  of the mounting bore  22 . The seal  54  expands into the groove with a snap like motion upon assembly and acts to releasably retain the fitting  14  within the mounting bore  22  of the intake manifold  12 .  
         [0022]    Inwardly adjacent to mounting diameter  50 , fitting  14  includes a reduced diameter sealing portion  58  carrying an external groove  60  in which is carried a primary O-ring seal  62 . Seal  62  engages the smooth sealing bore  24  of the manifold to act as a primary seal preventing any transfer of gases between the interior of the manifold and the atmosphere external to the manifold.  
         [0023]    Inwardly adjacent the sealing portion  58 , is the isolating portion  46  of the fitting  14 . Portion  46  extends axially from the mounting portion  42  and has an outer diameter slightly less than the sealing portion  58 . The isolating portion  46  extends through the end  28  of the PCV inlet opening  16  and into the air intake passage  32  in which intake air flows during operation of the engine.  
         [0024]    At the inlet end  36  of the fitting  14  is the connecting portion  44  which extends axially outward from the flange  48  and turns at a right angle to an external cylindrical portion  64 , terminating adjacent the end  36  with a pair of spaced raised mounting rings  66 . The cylindrical portion  64  and mounting rings  66  are adapted to be press fitted into tubular arms  68  of a PCV harness  70  illustrated in FIG. 5. Harness  70  is shown as only one of many examples of harnesses and conducting tubes which could be connected between one or more PCV fittings  14  and an associated engine crankcase.  
         [0025]    The tubular arms  68  of harness  70  form conduits that are joined by a T-connector  72  which in turn connects with an inlet pipe  74  and elbow  76 . The components of the harness  70  are preferably formed of temperature and oil resistant plastic material such as nylon. The elbow  76  is adapted to be fitted onto a PCV valve or orifice adapter, not shown, which is connected in the PCV system with the engine crankcase, not shown.  
         [0026]    The extended cylindrical isolating portion  46  of the PCV fitting  14  is sized to define an air gap  78  between the isolation bore  26  of the manifold and the outer diameter of the isolating portion  46  of the PCV fitting. The air gap provides isolation of the terminal portion of the fitting from the manifold inlet opening  16  through which the fitting extends and thus increases the resistance to heat transfer from the fitting to the manifold.  
         [0027]    In use of the disclosed embodiments of the invention in association with a particular model of engine, two PCV fittings are provided for assembly into separate inlet openings provided on opposite sides of the manifold which connect with separate air passages  32  within the intake manifold  12 . The O-rings  54  and  62  of each fitting  14  are installed in their respective grooves by sliding them onto the body  34  from the outlet end of the isolating portion  46 .  
         [0028]    The fittings  14  may then be slid into their respective inlet openings of the intake manifold as shown in FIG. 1. The O-ring seal/retainers  54  are snapped into the retaining grooves  52  of the manifold mounting bores  22  and the primary O-ring seals  62  are positioned in engagement with the sealing bores  24  of the manifold while the isolating portions  46  of the fittings extend in spaced relation from the isolation bores  26 , being separated by the air gap  78 .  
         [0029]    The PCV harness  70  is then installed with the tubular arms  68  being pushed onto the connecting portions  44  of the two fittings  14 . The mounting rings  66  provide means by which the expanded plastic tubes of the arms  68  are retained on the connecting portions  44  of the fittings  14 . Elbow  76  may then be connected with an associated PCV valve or other fitting in order to complete the PCV system for the engine.  
         [0030]    If desired, alternative assembly steps could be utilized wherein the PCV harness  70  is assembled in individual sections or wherein the PCV fittings  14  are installed on the harness  70  before assembly into the intake manifold.  
         [0031]    In operation of the engine, not shown, intake air is drawn into air intake passages  32  of the manifold and may be throttled to form a vacuum. The vacuum draws crankcase gases from the engine crankcase through the harness  70  into fittings  14 . The gases then pass through the passages  40  in the connecting, mounting and isolating portions of the fittings to enter the air stream at the outlet ends  38  of the fittings which extend beyond the ends  28  of the manifold bosses  18 .  
         [0032]    In extremely cold weather, the aluminum intake manifold walls reach below freezing temperatures. However heat transfer from the warmer crankcase vapors passing thorough the fittings  14  is resisted by the low thermal conductivity of the plastic fittings  14  as well as by the air gaps  16  which isolate the outlet ends of the fittings from the adjacent manifold walls. Thus, the crankcase vapors passing into the intake air stream are not sufficiently cooled to form ice crystals or frost from the water vapor in the crankcase vapors. Plugging of the fluid passages  40  in the fittings  14  is therefore avoided and free flow of crankcase ventilation fluids is assured.  
         [0033]    In addition, installation of the fittings with snap in motion and ease of removal by pulling outward with an adequate force provides a simplified mounting arrangement which significantly improves both the ease and the cost of assembly of the PCV harness between the engine crankcase and the intake manifold bosses. The use of the secondary seal and retainer not only provides the snap in connection of the fittings  14 , but also a back-up seal against leakage of additional air into the manifold.  
         [0034]    The illustrated embodiment shows the low conductivity fittings  14  used with an aluminum alloy intake manifold. However, the fittings may also be used with other metal manifolds as well as those made with plastic materials to reduce the possibility of icing in the PCV system and to improve assembly and servicing of the PCV systems used in engines.  
         [0035]    While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.