Abstract:
An oil separator that removes oil from ventilation gases flowing between a crankcase and an intake manifold of an internal combustion engine. The oil separator includes a housing, a wall and a diaphragm. The housing has an inlet and an outlet. The wall is cooperative with the housing to define a path through which the gases flow between the inlet and the outlet. The wall is movably coupled to the housing to effect a change in the height of the path. The diaphragm has a movable portion coupled to the wall. The diaphragm defines a substantially closed volume. The volume is open with the intake manifold so that pressure changes in the intake manifold causes corresponding displacement of the movable portion and the wall relative to the housing.

Description:
FIELD OF THE INVENTION 
   The invention relates to an oil separator for an internal combustion engine. More particularly, the invention relates to an oil separator for removing oil from PCV gases of an internal combustion engine. 
   DESCRIPTION OF THE RELATED ART 
   An internal combustion engine typically includes a combustion chamber, where a fuel air mixture is burned to cause movement of a set of reciprocating pistons, and a crankcase, which contains the crankshaft driven by the pistons. During operation, it is normal for the engine to experience “blowby,” wherein combustion gases leak past the pistons from the combustion chamber and into the crankshaft. These combustion or blowby gases contain moisture, acids and other undesired by-products of the combustion process. 
   An engine typically includes a Positive Crankcase Ventilation (PCV) system for removing harmful gases from the engine and prevents those gases from being expelled into the atmosphere. The PCV system does this by using manifold vacuum to draw vapors from the crankcase into the intake manifold. Vapor is then carried with the fuel/air mixture into an intake manifold of the combustion chambers where it is burned. Generally, the flow or circulation within the system is controlled by the PCV valve, which acts as both a crankcase ventilation system and as a pollution control device. 
   It is normal for blowby gases to also include a very fine oil mist. The oil mist is carried by the PCV system to the manifold. The oil mist is then burned in the combustion chamber along with the fuel/air mixture. This results in an increase in oil consumption. A known method of removing oil from the blowby gases is to use a labyrinth or cyclone-type separator design. A path is provided through which small oil droplets pass. The small oil droplets impact the walls of the path and coalesce into larger droplets. The droplets are then re-introduced back to a sump, which generally holds excess oil in the system. Conventional cyclone separators, however, have a fixed radius and convergent nozzle and, as a result, require a high velocity to generate a sufficient centrifugal force to promote a formation of oil film from smaller droplets. Conventional cyclone separators are also known to generate a high pressure loss. Examples of cyclone separators are disclosed in U.S. Pat. Nos. 6,279,556 B1 and 6,626,163 B1 to Busen et al., both of which are assigned Walter Hengst GmbH &amp; Co. KG. 
   Thus, it remains desirable to provide a cyclone oil separator that provides improved oil separation performance, lower pressure loss and greater system flexibility over conventional cyclone designs. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, an oil separator for removing oil from ventilation gases flowing between a crankcase and an intake manifold of an internal combustion engine. The oil separator includes a housing, a wall and a diaphragm. The housing has an inlet and an outlet. The wall is cooperative with the housing to define a path through which the gases flow between the inlet and the outlet. The wall is movably coupled to the housing to effect a change in the height of the path. The diaphragm has a movable portion coupled to the wall. The diaphragm defines a substantially closed volume. The substantially closed volume is continuous with the intake manifold so that pressure changes in the intake manifold causes corresponding displacement of the movable portion and the wall relative to the housing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is an exploded view of an oil separator according to one embodiment of the invention; 
       FIG. 2  is a cross sectional view of the oil separator in an closed position; 
       FIG. 3  is a cross sectional view of the oil separator in an open position; 
       FIG. 4  is an exploded view of an oil separator according to a second embodiment of the invention; 
       FIG. 5  is a cross sectional view of the oil separator of  FIG. 4  shown in the closed position; and 
       FIG. 6  is a cross sectional view of the oil separator of  FIG. 4  shown in the open position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1–3 , an oil separator according to an embodiment of the invention is generally indicated at  10 . The separator  10  includes a housing  12  having first  14  and second  16  halves. Each half  14 ,  16  of the housing  12  is generally cylindrical and cup shaped with a closed end  18 ,  20  and an open end  22 ,  24 . The first half  14  of the housing  12  has a smaller diameter than the second half  16 , so that the first half  14  can be arranged concentrically inside of the second half  16 . The first  14  and second  16  halves are arranged with the open ends  22 ,  24  facing each other, such that a cavity  26  is defined between the closed ends  18 ,  20  of the first  14  and second  16  halves of the housing  12 . The cavity  26  is substantially enclosed. By this arrangement, the first  14  and second  16  halves of the housing  12  can be axially displaced relative to each other in a telescopic manner. Further, the volume of the cavity  26  varies as the first  14  and second  16  halves of the housing  12  are displaced relative to each other. The housing  12  includes an outlet  30  formed in the closed end  18  of the first half  14  of the housing  12 . 
   A spiral shaped guide  40  extends outwardly from the closed end  18  of the first half  14  of the housing  12  toward the second half  16 . A spiral shaped wall  42  extends outwardly from the closed end  20  of the second half  16  toward the first half  14 . The housing  12  includes an inlet  32  formed in the spiral shaped wall  42  of the second half  16 . The guide  40  and wall  42  have corresponding shapes so as to divide the cavity  26  and define a continuous spiral shaped path that guides a flow of gases between the inlet  32  and the outlet  30 . The guide  40  and wall  42  are slidably engaged along an axis  44 . Optionally, a seal or gasket is provided between the guide  40  and wall  42  to prevent gases from leaking therebetween. The path has a width that decreases in size between the inlet  32  and the outlet  30 . Preferably, the width of the path between the inlet  32  and the outlet  30  decreases at a constant rate. The function of the spiral path in the removal of oil from the crankshaft gases flowing between the inlet and the outlet of the housing is discussed in greater detail in co-pending U.S. patent application Ser. No. 10/961,557 filed on Oct. 8, 2004, which is incorporated herein by reference in it entirety. 
   The path has a height that varies within a predetermined range that corresponds with sliding movement of the wall  42  relative to the guide  40  along the axis  44 . More specifically, sliding the guide  40  and wall  42  apart increases the height and volume of the path, thereby increasing the amount of gases that can flow therethrough under a fixed pressure. Sliding the guide  40  and wall  42  toward each other decreases the height and volume of the path, thereby increasing flow speed under a fixed pressure drop condition. 
   The oil separator  10  also includes a cap  50  and a flexible diaphragm  52 . The cap  50  and diaphragm  52  are each cup shaped with frustoconical walls. The cap  50  and diaphragm  52  are arranged in an inverted or opposed manner relative to each other to define a substantially closed volume or cavity  54  therebetween. The cap  50  is fixedly secured to the housing  12  by a rigid L-shaped bracket  55 . The diaphragm  52  includes a movable portion or end  56  coupled to the wall  42 . The diaphragm  52  is made from an elastomeric material so as to be deformable between an closed position, as shown in  FIG. 2 , and an open position, as shown in  FIG. 3 . Deformation of the diaphragm  52  between the closed and open positions causes substantially linear displacement of the end  56  of the diaphragm  52  along the axis  44 . Optionally, the diaphragm is provided in the form a plurality of rigid shells arranged concentrically for telescopic movement between the open and closed position. Optionally, the diaphragm is provided in the form of a cylinder/plunger arrangement, wherein the plunger is slidably supported within the cylinder for movement between the closed and open positions. Optionally, the cap is integrally formed with the diaphragm, such that the diaphragm defines the substantially closed cavity. 
   A biasing member  60  is continuously energized between the cap  50  and the diaphragm  52  to bias the end  56  of the diaphragm  52  toward the closed position. Preferably, the biasing member  60  is a helical coil spring. Optionally, a washer  57  is disposed between the end  56  of the diaphragm  52  and the biasing member  60 . The washer  57  includes a boss to keep the biasing member  60  centered on the end  56  of the diaphragm  52 . 
   A conduit  58  is coupled between the cap  50  and the intake manifold (not shown) so that the cavity  54  of the diaphragm  52  is open with an atmosphere defined by the intake manifold. The diaphragm  52  stays in the closed position while the pressure of the cavity  54  remains above a threshold amount. The threshold amount is related to the predetermined spring rate of the biasing member  60 . That is, it is possible for the pressure to be below ambient pressure, while the biasing member  60  maintains the end  56  of the diaphragm  52  in the closed position. 
   Typically, a vacuum is created in the intake manifold and cavity  54  due to decreased engine speed. The diaphragm  52  begins to deform and collapse toward the open position when the pressure in the cavity  54  falls below the threshold amount. The extent of the deformation of the diaphragm  52  and resulting displacement of the end  56  of the diaphragm  52  is proportional to the amount of change in the pressure below the threshold amount. Thus, low engine speeds will result in the formation of a large vacuum or pressure drop in the intake manifold and cavity  26 . In turn, the large pressure drop below the threshold amount causes a large displacement of the end  56  and wall  42  along the axis  44  away from the guide  40 . Displacement of the wall  42  away from the guide  40  increases the height of the path, thereby allowing decreased gas flow velocity between the inlet  32  and outlet  30  of the housing  12 . The increased capacity of the path between the inlet  32  and outlet  30 , therefore, accommodates the decreased demand from the PCV valve. 
   Increased engine speeds results in a pressure drop decrease between manifold and cavity  26 , which tends to expand the cavity  54  and displace the end  56  of the diaphragm  52  toward the closed position. It should be appreciated that pressure increase means positive change in the pressure, although the resulting pressure may still be below ambient, i.e. a vacuum may still exist in the cavity  54 . Displacement of the diaphragm  52  toward the closed position shortens the path between the inlet  32  and outlet  30 , as the wall  42  is moved toward the guide  40 . The shortened path allows increased gas flow velocity between the inlet  32  and outlet  30  of the housing  12  for improving oil droplet capturing function. The capacity of the path between the inlet  32  and outlet  30 , therefore, increases device efficiency in response to the decreased functionality of PCV valve. 
   Referring to  FIGS. 4–6 , a second embodiment of the oil separator is generally indicated at  110 , wherein like components are referenced by numerals offset by  100 . The oil separator  110  includes an impact plate  70 , a guide plate  72  and a wall  74 . The impact plate  70 , guide plate  72  and wall  74  are each planar and substantially parallel to each other. The guide plate  72  is disposed between the impact plate  70  and the wall  74 . The guide plate  72  includes a plurality of holes  76  allowing gases to flow between the inlet  132  and outlet  130  of the housing  112 . Each of the plurality of holes  76  has a predetermined diameter, preferably ranging between 2 and 4 mm. The wall  74  is slidably coupled to the housing  112  and coupled to the end  156  of the diaphragm  152  for movement along a linear path between the closed position, as shown in  FIG. 5 , and the open position, as shown in  FIG. 6 . 
   In the closed position, the wall  74  prevents the flow of gases through all except at least one of the plurality of holes  76 , therefore to increase gas flow velocity to improve oil droplet capturing efficiency. Sliding the wall  74  to the open position reveals all of the plurality of holes  76  allowing increased gas flow through the guide plate  72  when enough flow rate is achieved to main consistent oil droplet capturing efficiency at different engine operating conditions. The plurality of holes  76  are arranged in rows normal to the linear path of the wall  74 , such that movement of the wall  74  toward the open position reveals successive rows of holes  76 . In either position, gases flow through the guide plate  72  and toward the impact plate  70 . A high velocity impact region is formed at the impact plate  70  as gases are redirected around the impact plate  70  and toward the outlet  130 . The high velocity impact region promotes coalescence due to impact and removal of oil from the gas flow. 
   The invention has been described in an illustrative manner. It is, therefore, to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Thus, within the scope of the appended claims, the invention may be practiced other than as specifically described.