Abstract:
Several embodiments of fittings or couplings for the crankcase ventilating gas return to the combustion chambers through the induction system. They each provide good insulation so as to avoid the likelihood that water condensation in the path can freeze and restrict the ventilating flow.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to an internal combustion engine and more particularly to a crankcase ventilating system for internal combustion engines.  
           [0002]    In order to reduce the emission of unwanted hydrocarbons and other combustible material to the atmosphere from internal combustion engines, it has been the practice to ventilate the crankcase of the engine by the blow-by gases that pass across the piston rings and into the crankcase chamber. These blow-by gases are then collected and returned by a crankcase ventilating system that normally utilizes a positive crankcase ventilating (PCV) valve to the induction system of the engine. Thus these gases are returned to the combustion chamber and further combustion of the undesirable constituents occurs.  
           [0003]    A problem with this type of positive crankcase ventilating system is that when the gases are returned to the induction system and under low ambient temperatures, not only is the induction system but the entire engine at a relatively low temperature, particularly when it is initially started. Since the ventilating gases also include a fair amount of water vapor, they can not only condense but also can solidify in the crankcase ventilating conduit and cause significant problems.  
           [0004]    This problem may be best understood by reference to FIG. 1, which is a partial cross sectional view showing the conventional type of crankcase ventilating system. The engine, indicated generally by the reference numeral  11 , is provided with an internal crankcase ventilating system which includes an arrangement for returning blow-by gases to an area such as the valve cover  12  which is provided with an oil separator, shown partially at  13 , for returning lubricant to the crankcase. The gases exist the cam chamber enclosed by the cam cover  12  through a first metallic fitting  14  onto which one end of a flexible hose  15  is positioned. The opposite end of the flexible hose  15  is connected to a further fitting  16 , which communicates with the interior of an air inlet device  17  that collects atmospheric air for delivery to the engine combustion chambers.  
           [0005]    Because of the aforenoted problems in connection with condensation and freezing, an insulating sleeve  18  frequently is employed encircling the flexible conduit  15  in the area between the metallic fittings  14  and  16 . In spite of this insulation, water vapor in the blow-by gases, which flow in the direction of the arrow shown in this figure, can condense particularly in the area where the fitting  16  joins the air inlet device  17 . Thus, ice particles indicated at  19  can form in this area and either restrict or in extreme cases totally cut off the re-circulating air flow. Various arrangements have been proposed for attempting to avoid this problem, but they have not been totally effective and in many instances can be expensive.  
           [0006]    It is, therefore, a principle object to this invention to provide an improved crankcase ventilating system for an internal combustion engine.  
           [0007]    It is a specific object to this invention to provide a simple and effective heat insulating arrangement for connecting the crankcase ventilating tube to the induction system of the engine that will provide adequate insulation to preclude the likelihood of freezing even under extremely low ambient temperatures.  
         SUMMARY OF INVENTION  
         [0008]    This invention is adapted to be embodied in an internal combustion engine and crankcase ventilating system therefore. The engine includes an induction system for collecting atmospheric air and delivering the collected air to at least one combustion chamber of the engine. A crankcase ventilating system collects and exhausts blow-by gases from the engine and returns them to the combustion chamber through the induction system for reducing undesirable emissions to the atmospheric. This crankcase ventilating system communicates with the induction system through a fitting having a double wall construction comprised of an inner tube received in an outer tube with the outer wall of the inner tube being circumferentially spaced from the inner wall of the outer tube for heat insulation of the blow gases and inner tube. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]    [0009]FIG. 1 is a cross sectional view in partially schematic form of a prior art type of crankcase ventilating system.  
         [0010]    [0010]FIG. 2 is a primarily schematic view showing a crankcase ventilating system constructed in accordance with the invention.  
         [0011]    [0011]FIG. 3 is an enlarged cross sectional view, in part similar to FIG. 1, but showing a first embodiment of the invention.  
         [0012]    [0012]FIG. 4 is a cross sectional view taken through the outer tube of the fitting illustrated in FIG. 3 and illustrated in assembled form in FIG. 6.  
         [0013]    [0013]FIG. 5 is a cross sectional view of the inner tube of the fitting.  
         [0014]    [0014]FIG. 6 is an assembled view of the fitting with the tubes of FIGS. 4 and 5 interfitted with each other.  
         [0015]    [0015]FIG. 7 is a cross sectional view of another embodiment of the invention.  
         [0016]    [0016]FIG. 8 is a cross sectional view of a still further embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Referring first to FIG. 2, this shows schematically an internal combustion engine, indicated generally by the reference numeral  21  that shows the general structure with which the invention is practiced. The engine  21  includes a cylinder block  22  to which a cylinder head  23  is affixed in any suitable manner including being integrally formed therewith. The cylinder block  22  has one or more cylinder bores in which pistons reciprocate and which cooperate with the cylinder head  23  to form the combustion chambers of the engine. Since the internal construction of the engine forms no particular part of the invention and the invention can be utilized with a wide variety of engine types, the internal details are not illustrated.  
         [0018]    The pistons are connected to a crankshaft, which is not shown, but which is journalled in a crankcase assembly formed by the skirt of the cylinder block  22  and a crankcase member  24  affixed thereto.  
         [0019]    A suitable valve arrangement is incorporated in the cylinder head assembly  23  and this is covered by a cam cover  25 .  
         [0020]    Camshafts are journalled in the cylinder head  23  in a suitable manner and are driven by a timing drive that is contained within a timing case  26  affixed to the forward portion of the cylinder head  23 , cylinder block  22 , crankcase member  24  and cam cover  25 .  
         [0021]    An induction system is provided for delivering at least an air charge to the combustion chambers of the engine. This induction system is indicated generally by the reference numeral  27  and includes an atmospheric air inlet device  28 , which draws air from the atmosphere and passes it through a filter element (not shown).  
         [0022]    This filtered air is then delivered to a throttle body  29  in which a butterfly type throttle valve  31  is rotatably positioned.  
         [0023]    The throttle body  29  communicates with a plenum chamber  32 , which, in turn, communicates with a plurality of manifold runners  33  (only one of which is shown in the drawings) that supply the air charge to the combustion chambers of the engine.  
         [0024]    The engine  21  is provided with a crankcase ventilation system, which relies primarily upon the blow-by gases passing around the piston rings of the engine into the crankcase chamber  24  for ventilation purposes. These blow-by gases are indicated by the solid line arrows in FIG. 2 and are primarily delivered back to the induction system  27  through one of two paths. The primary path is from the crankcase  24  through suitable passages therein and/or in the cylinder block  22  to the timing case  26 . The gases then pass through the cylinder head and specifically the valve chamber thereof for collection in the cam cover  25 . A separator  34  is formed therein for separating the lubricating oil from the crankcase gases and returning the lubricating oil back to the lubricating system of the engine.  
         [0025]    A PCV valve  35  cooperates with the oil separator  34  and communicates with the induction system  27  downstream of the throttle valve  31  through a flexible conduit  36 , which may be suitably insulated, as will be described later, and a coupling or fitting  37  that is constructed in accordance with a first embodiment of the invention and which will be described in more detail very shortly by reference to FIGS. 3 through 6.  
         [0026]    In addition, the air inlet device  28  has a fitting  38 , which communicates with the crankcase chamber  24  through a further flexible conduit  39 . Normally, flow will occur through this conduit  39  only when the engine is running under certain conditions and these crankcase gases will be returned back to the combustion chambers through the throttle body  29  and plenum chamber  32 . This flow is, for the most part, minimal.  
         [0027]    Referring now in detail to FIGS. 3 through 6, the construction of the fitting  37  will be described in detail. This figure also shows more detail of the way in which the flexible conduit  36  is connected to this fitting  37  as well as the insulating material afore referred to for the flexible conduit  36  and which is indicated by the reference numeral  41 .  
         [0028]    The fitting  37  is comprised of an inner tube  42  (see FIGS. 5 and 6) that is formed of a thin wall structure from a highly heat conductive material such as aluminum. A flange  43  is formed at one end of this inner tube  42 . Received around the area contiguous to the opposite ends of the inner tube  42  are a pair of insulating rings  44  and  45 , with the ring  45  being juxtaposed and engaged with the flange end  43  while the ring  44  is disposed adjacent the plain end thereof.  
         [0029]    These insulating rings  44  and  45  may be formed from an elastromeric type of material such as rubber or the like and are adhesively bonded to the exterior surface of the inner tube  42  by vulcanization or any other suitable manner.  
         [0030]    Supported around the inner tube  42  in spaced relationship thereto is an outer tube  46 . This outer tube  46  is formed from a less highly heat conductive material than the inner tube  42  and preferably has a greater wall thickness. Cast iron may be a suitable material used for this purpose. A pair of ridge like projections  47  are formed on the outer tube  46 . As seen in FIG. 6, the outer tube  46  is telescopically received over the inner tube  43  and held in spaced relationship thereto by the elastic insulating rings  44  and  45 .  
         [0031]    This also forms an insulating air gap  48  around the periphery of the inner tube  42  which will be heated by the heat transmission through the inner tube  42  caused by the flow of the heated ventilating gases and blow-by gas. Thus, the open communication between the flange end  43  and the plenum chamber  32  will insure that even if there are low ambient temperatures, any water vapor in the ventilating gases will not freeze and obstruct their flow.  
         [0032]    In this embodiment, the surge tank  32  is preferably formed also from a highly heat conductive material such as aluminum. But since it is engaged with the cast iron or less heat conductive outer sleeve  46 , the heat transfer will be substantially minimized.  
         [0033]    A coupling formed in accordance with another embodiment of the invention is shown in FIG. 7 and is identified generally by the reference numeral  51 . In this embodiment, the outer sleeve  52  is formed integrally with the plenum chamber, shown partially and indicated by the reference numeral  53 . The surge tank  53  is formed from a fairly thick walled plastic material that has relatively low thermal conductivity.  
         [0034]    An inner tube  54  again formed from aluminum of thin walled construction is held in spaced relationship to the inner surface of the outer tube  52  by means of a pair of insulating rings  55  and  56  which may be formed in the same manner and attached thereto as the rings  44  and  45  of the previously described embodiment.  
         [0035]    This inner tube  54  and insulating rings  55  and  56  are then pressed fit into the outer tube  52  to provide an insulating air gap  57  there between. Hence, this device operates substantially in the manner as that previously described.  
         [0036]    A still further coupling embodiment is shown in FIG. 8 and is indicated generally by the reference numeral  61 . In this embodiment, there are provided inner and outer tubes  62  and  63 , respectively. These tubes  62  and  63  may be formed from materials previously mentioned wherein the inner tube  62  has a lesser wall thickness than the outer tube  63  and is more highly heat conductive.  
         [0037]    In accordance with this embodiment, rather than an air gap there is provided an insulating sleeve  64  between the two tubes  62  and  63  to hold them in spaced relationship. This heat insulating material  64  may, for example, be a highly insulating expanded urethane rubber that is expanded into the space between the two tubes  62  and  63  to hold them in their spaced relationship.  
         [0038]    Therefore, from the foregoing description, it should be readily apparent that the described embodiments of the invention all provide very effective insulating couplings between the crankcase gas return tube and the induction system and which will provide good heat transfer from the blow-by gases to the unions so as to avoid the likelihood of water vapor freezing therein and clogging the flow under low ambient conditions. Of course, the foregoing description is that of several preferred embodiments of the invention and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.