Patent Publication Number: US-7594501-B2

Title: Cylinder head cover for an internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the priority of German Patent Application No. 10 2006 062 657.5, filed on Dec. 22, 2006, the subject matter of which is incorporated herein by reference. Each U.S. and foreign patent and patent application mentioned below is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The invention relates to a cylinder head cover for an internal combustion engine comprising an oil separator. 
   BACKGROUND OF THE INVENTION 
   Known cyclone separators, see documents DE 10 2004 033 677 A1, DE 203 00 596 U1, DE 10 2004 002 310 A1, DE 10 2004 019 154 A1, EP 1 614 871 A2, DE 10 2004 006 082 A1, JP 2005 155 423 A, comprise an essentially cylindrical vortex chamber with a tangential gas inlet. The helical gas vortex runs out in a cone wall and by means of an immersion tube provided in the region of the gas inlet, is extracted in the opposite direction through the interior of the gas vortex, such that a flow reversal of the gas occurs. Separated particles exit through an aperture for example in the tip of the cone wall. The manufacture of cyclone separators with closed chamber requires very elaborate injection moulds and is extremely difficult, which is why it was suggested with DE 10 2004 019 154 A1 to construct such cyclones from two parts to be manufactured with simple moulds. 
   Document DE 10 2004 016 742 B3 discloses an oil separator with a reed valve on the inlet side and a diffuser arranged downstream. Because of inertia owing to the sharp deflection of the gas, oil particles are separated on the wall surrounding the tip of the reed. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a cylinder head cover with an oil separator having a simple construction and significantly reduced manufacturing effort. 
   The above and other objects are accomplished by the invention, wherein there is provided, according to one embodiment, a cylinder head cover for an internal combustion engine, comprising an oil separator with a vortex chamber extending in a longitudinal direction from a proximal end to a distal end, said vortex chamber comprising: an essentially pipe-shaped wall extending in said longitudinal direction, a gas inlet arranged at said proximal end of said vortex chamber and oriented tangentially to said essentially pipe-shaped wall, for tangentially blowing blow-by gas into said vortex chamber, such that a gas vortex flow helically rotating along said essentially pipe-shaped wall in the longitudinal direction from said proximal end to said distal end of said vortex chamber is created, and a gas outlet opening, wherein said gas outlet opening is arranged in the region of said distal end of said vortex chamber. 
   According to another embodiment, there is provided a cylinder head cover for an internal combustion engine, comprising an oil separator with a vortex chamber extending in a longitudinal direction from a proximal end to a distal end, said vortex chamber comprising: a plurality of parallel sub-chambers each comprising an essentially pipe-shaped wall extending in said longitudinal direction, a gas inlet common to said sub-chambers arranged at said proximal end of said vortex chamber and oriented tangentially to each of said essentially pipe-shaped walls, for tangentially blowing blow-by gas into said sub-chambers, such that a gas vortex flow helically rotating along said essentially pipe-shaped wall in the longitudinal direction from said proximal end to said distal end of said vortex chamber is created in each of said sub-chambers, and at least one gas outlet opening, wherein said gas outlet opening is arranged in the region of said distal end of said vortex chamber. 
   Through the arrangement of the gas outlet opening in the region of the distal end of the vortex chamber the immersion tube provided in the prior art becomes dispensable which results in a simplified construction. In addition, during the manufacture of the oil separator preferably manufactured of a plastic, an injection mould can engage in the vortex chamber through the gas outlet opening, which substantially reduces the effort for the mould. It has shown that the arrangement of the gas outlet opening at the run-out end of the vortex chamber does not lead to a picking-up of separated oil droplets through the gas flow which would adversely affect the function of the separator. The distal end of the vortex chamber may be defined as an end of the vortex chamber where the vortex flow runs out and turns from the helical flow to an essentially non-helical flow after having passed through said vortex chamber. Therefore, the distal end of the vortex chamber may also be designated as a run-out end. 
   Owing to the tangential gas inlet a rotating, helical gas vortex is induced in the pipe-shaped vortex chamber which extends from the gas inlet to the distal end of the vortex chamber. For this purpose the vortex chamber is expediently shaped substantially cylindrically or pipe-shaped, wherein this term means a shape which is rounded in cross section, for example oval or round, and encompasses a cross section which changes over the length of the vortex chamber. The helical gas vortex is created without helical or coil-shaped facilities such as for example helical surfaces or helical channels. In other words, the vortex chamber is free of helical or coil-shaped guiding devices. This delimits the invention over helix-shaped oil separators. 
   Preferably the gas inlet is designed open, i.e. valve-free. Through this, the invention can for example be delimited over oil separators with a reed valve at the gas inlet. The open gas inlet allows an effective separating effect even with low flow rates at which a reed valve would not yet open. For the same reason it is further advantageous if the entire oil separator including gas inlet and gas outlet is designed valve-free. 
   In order to counteract picking-up of separated oil droplets by the gas flow the vortex chamber preferably widens towards the gas outlet side in the manner of a diffuser through which the gas velocity is reduced in this region and the gas vortex separates from the chamber wall so that the draining liquid loses the gas contact and is not again dragged along by the gas flow. 
   In a further embodiment the vortex chamber has two sub-chambers arranged symmetrically to the gas inlet for the formation of two counter-rotating gas vortices. In comparison with a separator with only one gas vortex the flow rate of the separator can be substantially increased with moderately larger size in relative terms. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is explained by embodiments of the invention, making reference to the accompanying drawings. 
       FIG. 1  depicts a cross section through an oil separator. 
       FIG. 2   a  depicts a cross section through an oil separator in the region of the gas inlet. 
       FIG. 2   b  depicts a cross section through an oil separator in the region of the diffuser. 
       FIG. 3  depicts a cross section through an oil separator in the region of the gas inlet in a further embodiment. 
       FIGS. 4-7  depict longitudinal sections through an oil separator in further embodiments. 
       FIGS. 8   a ,  8   b  depict cross sections through an oil separator in the region of the gas inlet or the diffuser in a further embodiment. 
       FIG. 9  depicts a cross section through an oil separator in the region of the gas inlet in a further embodiment. 
       FIG. 10  depicts a cross section through an oil separator in a further embodiment. 
       FIG. 11  depicts a cross section through an internal combustion engine. 
   

   DETAILED DESCRIPTION 
   The internal combustion engine shown in  FIG. 11  comprises the cylinder head cover  10 , the cylinder head  35 , the crankcase  36  and the oil pan  37 . The cylinder head cover  10  comprises a gas inlet region  38  for oil-laden blow-by gas  17 , an oil separator  11  through which the introduced blow-by gas  17  flows with a vortex chamber  13 , an adjacent clean chamber  26  with oil drain  24 , a pressure control valve  34  and a gas outlet region  40 . The blow-by gas is directed from the crankcase  36  into the cylinder head cover  10  for example via channels provided in the engine housing which are not shown. The oil separator  11  has an inlet opening  12  through which the oil-laden blow-by gas  17  tangentially enters a pipe-shaped chamber  13 . 
   As is shown in  FIG. 1  the chamber  13  is formed by a pipe-shaped circumferential wall  14 . In the circumferential wall  14  a gas inlet opening  12  is provided at a proximal end of the vortex chamber  13 . Around the gas inlet opening  12  a pipe-shaped gas inlet  18  is provided which is arranged tangentially to the vortex chamber  13 . The pipe-shaped gas inlet  18  creates a tangentially directed flow of the blow-by gas entering the chamber  13  through the gas inlet opening  12 . The gas flow entering through the gas inlet opening  12  is directed along the chamber wall  14 . Because of the flow component in the longitudinal direction  21   a  helical gas vortex  20  rotating about the longitudinal axis is created in the chamber  13 , without additional guiding devices such as for example guide plates or the like being required. “Helical” means that the gas vortex in a mean load range of the engine performs at least one complete revolution, preferably at least two complete revolutions. The rotating gas vortex  20  spreads in a longitudinal direction  21  of the pipe-shaped chamber  13 . The longitudinal direction  21  runs along the centre axis of the chamber  13  and can therefore be joined together by segments, as is evident for example from  FIG. 1 . 
   The centrifugal forces acting on the oil particles in the gas vortex  20  bring about a separation of the oil particles through contact with the circumferential wall  14  and coalescence of the oil particles accumulating in the outer region of the chamber  13  into oil droplets. The separated oil drains along the circumferential wall  14  of the chamber  13  and is returned to the engine oil circuit by means of a return  24 . In order to ensure the gravity discharge of the oil without stagnant spaces the floor of the chamber  13  in the operating position preferably has a steady downward gradient as far as to the oil discharge  24 . Through a non-return valve  41  shown for example in  FIG. 11  the entry of blow-by gas into the clean chamber  26  through the oil drain line  24  in reverse direction is prevented. 
   The characteristic of the efficiency or the pressure loss of the vortex chamber separator  11  as a function of the flow rate corresponds approximately to the characteristic of a cyclone with immersion tube. 
   Having passed through the chamber  13  the helical gas vortex  20  runs out at the distal end  22  of the chamber  13 , i.e. it turns into a non-rotating flow and exits the chamber  13  through the gas outlet opening  25  arranged at the distal end  22  end of the vortex chamber  13 . The cleaned blow-by gas  23  is then directed through a clean chamber  26  for example to the pressure control valve  34  (see  FIG. 11 ). 
   Because the gas outlet is arranged at the distal end  22  of the vortex chamber  13 , an open design of the chamber  13  is obtained. In particular an injection mould used in the manufacture of the oil separator  11  can engage in the chamber  13  through the gas outlet opening  25 . For this purpose it is advantageous if, as in the examples of  FIGS. 1 ,  4  to  7  and  10 , the cross section of the chamber  13  has no constriction between the end near the inlet  19  and the opposing end  22  and that the area of the gas outlet opening  25  preferably is greater or equal to the maximum cross sectional area of the chamber  13 . 
   The open design of the vortex chamber  13  allows to drain the separated oil  27  from the vortex chamber  13  through the gas outlet opening  25  having a large cross section (see exemplary embodiments according to  FIGS. 1 ,  4  to  6  and  10 ). In this way, the oil discharge with low cross section present in the prior art which shows unfavourable freezing characteristic can be avoided. In other words the oil discharge  24  preferably leads into the clean chamber  26  and not into the vortex chamber  13  as in the prior art. 
   As is evident from  FIG. 1  no flow reversal of the gas in the opposite direction takes place at the distal end of the vortex chamber  13  in pronounced distinction from a conventional cyclone with immersion tube. 
   As shown in  FIG. 1 , the chamber  13  in particular in the gas inlet region preferably comprises a substantially cylindrical section  15  so that a stable gas vortex  20  is able to form, with a preferred axial length of at least 0.5 times the diameter, more preferably in the range of 0.5 to 5-times and more preferably 1 to 3 times the diameter. “substantially cylindrical” encompasses a conicity of some degrees, i.e. up to 10°, owing to an extraction draft due to the manufacture. 
   As is shown in  FIGS. 1 and 2   b  the chamber  13  in particular in the distal end region preferably comprises a section  16  widening in longitudinal direction  21  for the formation of a diffuser in which the rotating velocity of the gas is reduced and as a result the probability that the draining liquid is again picked up by the gas vortex is reduced. At the same time, the pressure loss is reduced via the separator  11 . With a view to the desired effect the conicity of the diffuser  16  preferably amounts to at least 10°, further preferably at least 20°, yet further preferably at least 30°. 
   With the formation of the diffuser  16  oval in cross section as shown in the  FIGS. 1 ,  2   b  and  8   b , the gas vortex  20  initially separates from the lower rim of the chamber  13  so that the draining liquid  27  no longer has any gas contact there and thus cannot be picked up by the gas flow again. For this purpose it is advantageous if the chamber  13  in the lower region widens more intensively than in the upper region, in particular if the chamber  13  widens merely downwards, but not in the upper region, as is the case for example in  FIG. 1 . 
   In the preferred embodiment according to  FIGS. 2   a ,  2   b  the vortex chamber  13  has two sub-chambers  13   a ,  13   b  which are preferably arranged in parallel and contact each other tangentially with a jointly utilized gas inlet  18  for the formation of two gas vortices  20   a ,  20   b  rotating in opposite directions and arranged in parallel; this is thus a dual chamber. The gas inlet  18  is preferably tangentially directed in the region of the tangential contact of the two sub-chambers  13   a ,  13   b  and further preferably to the centre of a land  33  which serves as flow divider. The sub-chambers  13   a ,  13   b  are preferably located (mirror) symmetrically to the gas inlet  18 . The circumferential wall  14  of the chamber  13  is therefore preferably designed omega shaped or ω-shaped, as shown in  FIG. 2   a . Compared with a separator with only one gas vortex the flow rate of the separator can be substantially doubled with a relatively slightly larger size. However, the invention is not restricted to a defined number of gas vortices. It encompasses in particular embodiments with one gas vortex, as with the chamber  13  shown in  FIGS. 8   a ,  8   b . Embodiments with more than two parallel gas vortices are also conceivable. 
   In order to stop the gas contact with the draining oil  27  at as early a stage as possible, a drain slot  28  or, in the case of several sub-chambers  13   a ,  13   b , one or several drain slots  28   a ,  28   b  can be provided in the circumferential wall  14  in an embodiment according to  FIG. 3  or  9  in the lower part of the chamber  13  or the diffuser  16 , which are arranged below the circumference defined by the circumferential wall  14 . 
   The embodiments shown in the  FIGS. 4 to 6  make clear that the formation of the vortex chamber  13  in longitudinal direction is variable in a variety of manners. In the example of  FIG. 4  a more or less intensively widening region  29  follows the diffuser  16 . In the example of  FIG. 5  the entire vortex chamber  13  widens uniformly. In the example of  FIG. 6  the vortex chamber  13  widens with steadily increasing downward gradient in the gas outlet direction. 
   In the exemplary embodiment shown in  FIG. 7  an oil drain opening  30  to an oil drain channel  31  is present in the floor of the chamber  13 . Through the separation of gas vortex  20  and draining oil  27  by means of the separating wall  32  re-absorption of separated oil  27  by the gas vortex  20  is effectively stopped. 
   The embodiment according to  FIG. 10  relates to a vertically arranged vortex chamber  13  in contrast with the—preferred with regard to a reduced height—substantially horizontal installation position in the examples of  FIGS. 1 and 4  to  7 . Since emulsion incurred in the vertical arrangement according to  FIG. 10  is able to drain off better this is preferred with regard to the freezing characteristics. 
   Depending on the application separators with inclined installation position of the vortex chamber  13  are also possible.