Abstract:
In order to provide an oil separator for separating oil from a blowby gas of a cylinder head of an internal combustion engine, which oil separator is manufactured separately from a basic body of a cylinder head cover but may nevertheless be easily integrated into the cylinder head cover, it is proposed that the oil separator comprises an oil separator module, which is manufactured separately from a basic body of a cylinder head cover and comprises a cyclone plate having at least one cyclone as well as a base plate, wherein the cyclone plate is fastened to the base plate and the oil separator module is fastenable to the basic body of the cylinder head cover.

Description:
RELATED APPLICATION 
   The present disclosure relates to the subject matter disclosed in German Patent Application No. 10 2005 063 274.2 of Dec. 28, 2005, the entire specification of which is incorporated herein by reference. 
   FIELD OF THE DISCLOSURE 
   The present invention relates to an oil separator for separating oil from a blowby gas of a cylinder head of an internal combustion engine. 
   BACKGROUND 
   Such an oil separator is known for example from EP 1 559 876 A2. This known oil separator comprises a plurality of cyclones for separating the oil from the blowby gas, wherein each cyclone comprises a bowl, which is formed integrally with a bottom shell of a cylinder head cover, and an immersion tube, which is formed integrally with a top shell of the cylinder head cover. The cyclones in this case therefore form an integral component of a twin-shelled basic body of the cylinder head cover and are manufactured together with the basic body. 
   SUMMARY OF THE INVENTION 
   The underlying object of the present invention is to provide an oil separator of the initially described type that is manufactured separately from a basic body of a cylinder head cover but may nevertheless be easily integrated into the cylinder head cover. 
   In an oil separator having the features of the preamble of claim  1 , this object is achieved according to the invention in that the oil separator comprises an oil separator module, which is manufactured separately from a basic body of a cylinder head cover and comprises a cyclone plate having at least one cyclone and a base plate, wherein the cyclone plate is fastened to the base plate and the oil separator module is fastenable to the basic body of the cylinder head cover. 
   Because the oil separator module is manufactured separately from the basic body of the cylinder head cover, modifications to the oil separator module may be carried out without this affecting the manufacture of the basic body of the cylinder head cover. As a result, the oil separator module of the oil separator according to the invention may be designed in a particularly flexible manner and may be used together with cylinder head covers having different basic bodies. 
   In order to achieve a gastight permanent connection of the cyclone plate to the base plate of the oil separator module, it is advantageously provided that the cyclone plate is welded to the base plate. 
   In a preferred development of the invention, it is provided that the cyclone axis of the cyclone in the fitted state of the oil separator forms with the horizontal an angle of at most approximately +/−20°, preferably of at most +/−10°. The effect achieved by such a position of the cyclone, which differs only a little from a horizontal position, is that the overall height of the oil separator is smaller than in the case of a vertical position of the cyclone. Consequently, the overall height of the cylinder head cover, into which the oil separator module is integrated, may also be reduced. 
   In the case of the oil separator known from EP 1 559 876 A2, the cyclone axes of the cyclones form with the horizontal an angle of approximately 30°. 
   To reduce the necessary height, it is particularly advantageous when the cyclone axis of the cyclone in the fitted state of the oil separator is oriented substantially horizontally. 
   In principle, it may be provided that the cyclone plate comprises only one cyclone. 
   In a preferred development of the invention, it is however provided that the cyclone plate comprises at least two cyclones. 
   In order to prevent the gas streams, which pass out of the two cyclones, from obstructing one another, it is advantageous when the cyclone axes of at least two cyclones are mutually offset in a direction oriented horizontally in the fitted state of the oil separator. 
   When there is a plurality of cyclones on the cyclone plate, it may be provided that the at least two cyclones are swept successively by the blowby gas in order by means of a two-stage oil separation to achieve a particularly high oil separation effect. 
   As a rule, however, an adequate separation effect is already achieved by each volume fraction of the blowby gas flowing through only one cyclone. 
   In this case, it is advantageous when at least two cyclones are swept parallel to one another by the blowby gas in order to increase the flow rate of blowby gas through the oil separator. 
   In order, prior to sweeping of the cyclones, to achieve a pressure equalization and a reduction of the speed of the blowby gas, it is advantageous when the oil separator module comprises a settling chamber, which is delimited by the base plate and by the cyclone plate and is connected by a cyclone approach flow channel to the interior of at least one cyclone. 
   In a preferred development of the invention, it is provided that the oil separator comprises at least two cyclones and that the settling chamber is connected to both cyclones by in each case at least one cyclone approach flow channel. The effect achieved in such a development by providing a common settling chamber for the at least two cyclones is that the blowby gas to be cleansed of oil is always distributed as uniformly as possible to the cyclones of the oil separator module independently of the operating state and the position of the internal combustion engine. 
   In order to generate a flow of the blowby gas that is directed towards the cyclone approach flow channel, it is advantageous when the base plate is provided with at least one baffle element that guides blowby gas in the direction of a cyclone approach flow channel. 
   Such a baffle element may in particular take the form of a baffle rib projecting from the base plate. 
   In a preferred development of the invention, it is further provided that the oil separator comprises at least one oil outflow valve that is disposed at the outlet of an oil collecting chamber. 
   Such an oil outflow valve may in particular comprise an elastically deformable cap provided with an oil through-opening. 
   The base plate is preferably manufactured separately from the cyclone plate. 
   The subject matter of the invention is further a cylinder head cover that comprises at least one oil separator according to the invention. 
   The oil separator module of the oil separator is in said case preferably fastened to a basic body of the cylinder head cover. 
   In order to achieve a gastight, permanent connection of the oil separator module to the basic body of the cylinder head cover, it is preferably provided that the oil separator module is welded to a basic body of the cylinder head cover. 
   The available installation space is utilized particularly well when the oil separator module is disposed in the interior of the cylinder head cover. 
   A further underlying object of the present invention is to indicate a method of manufacturing a cylinder head cover with an integrated oil separator whereby despite separate manufacture of an oil separator module, on the one hand, and of a basic body of the cylinder head cover, on the other hand, easy and efficient integration of the oil separator into the cylinder head cover is possible. 
   This object is achieved by a method that comprises the following method steps:
         fastening a cyclone plate having at least one cyclone to a base plate to form an oil separator module;   fastening the oil separator module to a basic body of the cylinder head cover.       

   In this case, the base plate is preferably manufactured separately from the cyclone plate and then connected to the cyclone plate. 
   The oil separator according to the invention comprises an oil separator module, in which a cyclone plate and a base plate (oil baffle) are combined into a unit that is easy to handle and simple to fasten to a basic body of the cylinder head cover. 
   The use of at least one cyclone in the oil separator according to the invention also allows large quantities of very finely distributed oil to be separated reliably from the blowby gas. 
   The cyclones of the oil separator module are fastened via a support of the base plate (oil baffle) to the basic body of the cylinder head cover, in particular by welding. 
   When cyclones are used in a horizontal position, the oil separator module of the oil separator according to the invention has a very low installation height of for example ca. 35 mm to ca. 40 mm, thereby saving a considerable amount of space compared to oil separator systems with vertically oriented cyclones. 
   Further features and advantages of the invention are the subject matter of the following description and graphic representation of an embodiment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1 : a diagrammatic plan view of a portion of a cylinder head cover with an integrated oil separator module; 
       FIG. 2 : a diagrammatic longitudinal section through the cylinder head cover with the integrated oil separator module of  FIG. 1  along the line  2 - 2  in  FIG. 1 ; 
       FIG. 3 : a diagrammatic section though the cylinder head cover with the integrated oil separator module of  FIG. 1  along the line  3 - 3  in  FIG. 1 ; 
       FIG. 4 : a diagrammatic inverted plan view of a portion of a basic body of the cylinder head cover of  FIG. 1 , without the oil separator module; 
       FIG. 5 : a diagrammatic longitudinal section through the basic body of the cylinder head cover of  FIG. 4  along the line  5 - 5  in  FIG. 4 ; 
       FIG. 6 : a diagrammatic side view of the oil separator module; 
       FIG. 7 : a diagrammatic plan view of the oil separator module of  FIG. 6 ; 
       FIG. 8 : a diagrammatic section through the oil separator module of  FIG. 7  along the line  8 - 8  in  FIG. 7 ; 
       FIG. 9 : a diagrammatic longitudinal section through the oil separator module of  FIG. 7  along the line  9 - 9  in  FIG. 7 ; 
       FIG. 10 : a diagrammatic side view of a cyclone plate of the oil separator module of  FIG. 6 ; 
       FIG. 11 : a diagrammatic plan view of the cyclone plate of  FIG. 10 ; 
       FIG. 12 : a diagrammatic longitudinal section through the cyclone plate of  FIG. 11  along the line  12 - 12  in  FIG. 11 ; 
       FIG. 13 : a diagrammatic longitudinal section through a cyclone of the cyclone plate of  FIG. 11  along the line  13 - 13  in  FIG. 11 ; 
       FIG. 14 : a diagrammatic side view of an immersion tube element of a cyclone of the oil separator module; 
       FIG. 15 : a diagrammatic longitudinal section through the immersion tube element of  FIG. 14  along the line  15 - 15  in  FIG. 14 ; 
       FIG. 16 : a diagrammatic plan view of a base plate of the oil separator module of  FIG. 7 ; 
       FIG. 17 : a diagrammatic side view of the base plate of  FIG. 16 , viewed in the direction of the arrow  17  in  FIG. 16 ; and 
       FIG. 18 : a diagrammatical longitudinal section through the base plate of  FIG. 16  along the line  18 - 18  in  FIG. 16 . 
   

   Identical or functionally equivalent elements are denoted by the same reference characters in all of the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   A cylinder head cover denoted as a whole by  100  and having an integrated oil separator  102  is represented in  FIGS. 1 to 5  and comprises a basic body  104 , which surrounds an interior  106 , and a pressure control valve  107 , which is disposed on the outside of the basic body  104  and has an interior-side inlet and an outlet  108 . 
   The basic body  104  is manufactured for example as an injection moulded part from a plastics material having the required chemical and heat resistance. 
   Formed on the inside of the basic body  104  is a substantially rectangular welding edge  110  (see  FIG. 4 ), along which the basic body  104  is welded to a complementary welding edge  112  of a base plate  114  of an oil separator module denoted as a whole by  116  (see  FIGS. 3 and 4 ). 
   As is evident from  FIGS. 16 to 18 , the base plate  114  is of a substantially rectangular design and comprises at a left end a first inflow channel  118  and at a right end a second inflow channel  120 . 
   The first inflow channel  118  leads from an inflow opening  124 , which is oriented substantially vertically and at right angles to a longitudinal direction  122  of the base plate  114 , at an underside of the base plate  114  to a substantially horizontally oriented outflow opening  126  at the upper side of the base plate  114 . 
   The second inflow channel  120  leads from an inflow opening  128 , which is oriented substantially vertically and parallel to the longitudinal direction  122  of the base plate  114 , at the underside of the base plate  114  to a substantially horizontally oriented outflow opening  113  at the upper side of the base plate  114 . 
   The base plate  114  further comprises a first oil outlet opening  132 , which is adjacent to the first inflow channel  118 , and a second oil outlet opening  134 , which is adjacent to the second inflow channel  120 . 
   The base plate  114  is moreover provided with two angular baffle ribs  136  projecting upwards from its upper side, which serve as baffle elements  138  to guide blowby gas, which flows in through the inflow channels  118 ,  120 , in each case in the direction of an approach flow opening of a cyclone approach flow channel  165 , which will be described in greater detail below. 
   The portion of the upper side of the base plate  114  that has the outflow openings  126 ,  130  and the baffle ribs  136  is surrounded by a upwardly projecting, annularly closed welding edge  140  and forms a base  142  of a settling chamber  144  of the oil separator module  116 . 
   The base plate  114  is of an integral construction and is manufactured for example as an injection moulded part from a plastics material having the necessary chemical and thermal resistance. 
   Along the welding edge  140  the base plate  114  is welded to a cyclone plate  148 , which is separately represented in  FIGS. 10 to 13 . 
   The cyclone plate  148  comprises two cyclones  150   a ,  150   b , which in the fitted state of the oil separator  102  have substantially horizontally oriented cyclone axes (longitudinal centre lines)  152   a  and  152   b  respectively. The cyclone axes  152   a ,  152   b  extend substantially parallel to the upper side of the base plate  114  and substantially parallel to one another but are offset at right angles to one another in a horizontal direction by an amount d that corresponds approximately to the outside diameter of a cyclone  150   a ,  150   b  (see in particular  FIG. 7 ). 
   Furthermore, the cyclone axes  152   a ,  152   b  form with the longitudinal direction  122  of the base plate  114  an acute angle α of for example approximately 10°. 
   This rotation relative to the longitudinal direction of the base plate  114  and the lateral offset d prevent the air streams, which exit from the mutually opposing outlet openings of the two cyclones  150   a ,  150   b , from colliding directly with one another, which would lead to adverse flow conditions through the oil separator  102 . 
   As is evident for example from  FIG. 8 , each of the horizontally disposed cyclones  150   a ,  150   b  comprises in each case a substantially hollow-cylindrical front portion  154  adjoined along the cyclone axis  152   a ,  152   b  by a tapering rear portion  156 . 
   Opening into the front portion  154  of the cyclone  150   a ,  150   b  there is in each case a cyclone approach flow channel  165 , which extends tangentially to the inner wall of the cyclone  150   a ,  150   b  and leads from an approach flow opening lying opposite a baffle rib  136  of the base plate  114  into the interior  160  of the cyclone  150   a ,  150   b.    
   The rear end of the rear portion  156  remote from the front portion  154  is closed, apart from an oil through-opening  158 . 
   By means of this oil through-opening  158  the interior  160  of each cyclone  150   a ,  150   b  is connected to an oil collecting chamber  162 , which is disposed under the rear portion  156  of the cyclone  150   a ,  150   b  and formed by a closed chamber that is delimited in an upward direction by the rear portion  156  of the relevant cyclone  150   a ,  150   b , laterally by substantially vertical side walls  164  formed integrally with the cyclone plate  148 , and in a downward direction by a portion of the base plate  114  that contains a respective one of the oil outlet openings  132  and  134 . 
   The cyclone plate  148  and the base plate  114  moreover jointly surround the settling chamber  144 , into which the blowby gas flows through the inflow channels  118 ,  120  and out of which the blowby gas flows through the cyclone approach flow channels  165  and which is otherwise closed in a gastight manner. 
   At its front end remote from the rear portion  156 , the front portion  154  of each cyclone  150   a ,  150   b  is closed by means of an immersion tube element  166 , one of which is represented separately in  FIGS. 14 and 15 . 
   Each immersion tube element  166  comprises an immersion tube  168  having a substantially hollow-cylindrical rear portion  170  and a flared front portion  172  emanating from the rear portion  170  as well as an annular collar  174 , which in the region of the transition from the rear portion  170  to the front portion  172  of the immersion tube  168  projects radially outwards from the immersion tube  168 . 
   The annular collar  174  is welded at its outer edge along a welding edge  176  to the end face of the front portion  154  of the respective associated cyclone  150   a ,  150   b  (see for example  FIG. 8 ). 
   Each of the immersion tube elements  166  is designed integrally and for example in the form of an injection moulded part from a plastics material having the necessary chemical and thermal resistance. 
   The cyclone plate  148  is also designed integrally and for example in the form of an injection moulded part from a suitable plastics material having the necessary chemical and thermal resistance. 
   As may best be seen from  FIG. 3 , the oil separator module  116  formed by base plate  114 , cyclone plate  148  and immersion tube elements  166  is disposed in such a way on the inside of the basic body  104  of the cylinder head cover  100  that the oil separator module  116  and a portion  178  of the basic body  104  jointly surround a clean gas chamber  180 , which is separated in a gastight manner from the remaining interior  106  of the cylinder head cover  100  and into which the immersion tubes  168  of the cyclones  150   a ,  150   b  and the inlet of the pressure control valve  107  open. 
   The remaining interior of the cylinder head cover  100  forms a crank chamber  182 . 
   The crank chamber  182  is connected to the oil separator module  116  by the inflow channels  118 ,  120 , through which oil-containing blowby gas may be sucked out of the crank chamber  182 , as well as by two oil discharge valves  184 , which are inserted each into one of the oil outlet openings  132  and  134  in the base plate  114  and through which oil separated from the blowby gas by means of the cyclones  150   a ,  150   b  is returned to the crank chamber  182 . 
   Each of the oil discharge valves  184  may comprise for example an elastically deformable cap having a narrow, slot-shaped oil through-opening. 
   The procedure for manufacturing the previously described cylinder head cover  100  with integrated oil separator  102  is as follows: 
   The cylinder head cover  100 , the base plate  114 , the cyclone plate  148  and the immersion tube elements  166  are manufactured separately from one another as injection moulded parts from a suitable plastics material. 
   The cyclone plate  148  is placed onto the base plate  114  and welded along the welding edges  146 ,  140  to the base plate  114 . 
   This welding operation may be effected in particular by means of a friction welding technique. 
   The immersion tube elements  166  are inserted into the respective associated cyclone  150   a ,  150   b  of the cyclone plate  148  and welded along the welding edge  176  to the respective cyclone  150   a ,  150   b.    
   This welding operation may be effected for example by means of an ultrasonic welding technique. 
   The welding of the immersion tube elements  166  to the cyclone plate  148  may alternatively be effected before the cyclone plate  148  is welded to the base plate  114 . 
   Finally, the oil separator module  116  formed by base plate  114 , cyclone plate  148  and immersion tube elements  166  is inserted into the cylinder head cover  100  and welded along the welding edges  110 ,  112  to the basic body  104  of the cylinder head cover  100 . 
   This welding operation may be effected for example by means of an ultrasonic welding technique. 
   Compared to friction welding, ultrasonic welding offers the advantage that the weld seam takes up less space. 
   On the other hand, compared to ultrasonic welding, the friction welding technique offers the advantage that, with it, three-dimensional weld seams, i.e. weld seams that do not extend exclusively within one plane, may be produced. 
   The oil separator  102  integrated in the previously described manner into the cylinder head cover  100  operates as follows: 
   During operation of the oil separator  102  the outlet  108  of the pressure control valve  107  is connected by a suction line (not shown) to an air intake arrangement of the internal combustion engine, on which the cylinder head cover  100  is disposed. 
   Between this suction line and the crank chamber  182  there occurs a pressure difference that causes a gas flow of oil-containing blowby gas from the crank chamber  182  through the oil separator module  116  into the clean gas chamber  180  and from there through the pressure control valve  107  into the suction line. 
   The oil-containing blowby gas passes first through the inflow channels  118 ,  120  of the base plate  114  into the settling chamber  144 , which is surrounded by the base plate  114  on the one hand and by the cyclone plate  148  on the other hand and separated in a gastight manner from the clean gas chamber  180 . 
   In the settling chamber  144  a pressure equalization and a reduction of the speed of the blowby gas occurs. 
   By means of the baffle ribs  136  disposed in the settling chamber  144 , the blowby gas is directed into the cyclone approach flow channels  165  of the two cyclones  150   a ,  150   b , through which the blowby gas passes substantially tangentially into the front portion  154  of the respective cyclone  150   a ,  150   b.    
   In the interior  160  of each of the cyclones  150   a ,  150   b  a turbulent flow of the blowby gas is therefore generated, as a result of which the oil particles entrained by the blowby gas are deposited on the inner wall of the respective cyclone  150   a ,  150   b  and pass in the cyclone  150   a  and/or  150   b  rearwards to the oil through-opening  158  and through it into the respective oil collecting chamber  162 , whereas the blowby gas cleansed of the oil passes through the immersion tubes  168  of the cyclones  150   a ,  150   b  into the clean gas chamber  180  and from there through the pressure control valve  107  into the suction line. 
   The cyclones  150   a ,  150   b  also allow large oil quantities in the form of very fine oil particles (for example with a diameter of less than a micrometer) to be separated from the blowby gas. 
   The oil collected in the oil collecting chambers  162  of the oil separator module  116  passes through oil discharge valves  184  at the oil outlet openings  132  and  134  back into the crank chamber  182  or, through oil removal lines connected to the oil discharge valves  184 , into the oil sump of the internal combustion engine.