Abstract:
The present invention relates to a cylinder head cover for covering a cylinder head of a combustion engine. Such cylinder head covers often comprise an oil separator for separating oil and/or oil spray from the blow-by gas of combustion engines. With the present invention the oil separator is formed as a flow-through tube ( 10 ) through which the gas with the oil and/or oil spray to be separated flows. The flow-through tube ( 10 ) with its longitudinal axis ( 14 ) in the flow-through direction lies essentially in the plane of extension of the cylinder head cover ( 1 ). A worm-like segment is arranged in the flow-through tube ( 10 ), and its thread surfaces ( 21 ) form a spiral flow path ( 2 ). At the same time the cross section of the flow path lies between 1 mm2 and 800 mm2.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a cylinder head cover with an integrated oil separator for separating oil and/or oil spray from the blow-by gases of a combustion engine. 
   BACKGROUND 
   Tubular separators are know from the state of the art, for separating solid particles from air, in particular for dedusting, which comprise a flow-through tube in which a spiral is arranged. This spiral sets the air flowing through into a rotational movement about the middle axis of the spiral and thus leads to a separation of the particles on account of the centrifugal forces. 
   A cylinder head cover (also called valve cover) is known from DE 101 27 620 A1, with which the blow-by gases (also called crank housing gases or blow-through gases) are introduced from the crank housing of a combustion engine into a cylinder head cover and here are purified of oil or oil spray. 
   For this, firstly for coarse separation a spiral is arranged perpendicular to the plane of extension of the cylinder head cover in this. The blow-by gas flows through this spiral with a diameter of approx. 5 cm so that here large oil droplets are separated. An adequate separation is not achieved so that a further fine separation device is arranged subsequently. 
   BRIEF SUMMARY 
   It is therefore the object of the present invention to provide a cylinder head cover with which, in a simple and efficient manner, oil and oil spray may be removed from crank housing gases or from blow-by gases. 
   This object is achieved by the cylinder head cover according to claim  1 . Advantageous further formations of the valve cover (=valve bonnet) according to the invention are specified in the dependent claims. 
   According to the invention, a flow-through tube as a tubular separator is arranged in the cylinder head cover in the horizontal or essentially in the horizontal position, at least not in the perpendicular position, through which the blow-by gases are led. A spiral or a worm-like segment is arranged in the flow-through tube, which sets the gases into a rotational movement about the middle axis of the worm-like segment. Oil and oil spray is separated by way of this. The spirals or worm-like segments at the same time are stationary and are not arranged in the flow-through tube in a rotatable manner. They therefore have no drive of their own, but act exclusively as passive, stationary deflection elements. It is therefore the case with the present tubular separators of purely passive separators in contrast to separators with rotatable impeller-like means for accelerating the fluid to be cleaned. 
   As is usual in the technical language, a worm is defined as a helical or also spiral thread led around a middle axis. 
   The purified gas as well as the separated oil is discharged through the same outlet of each flow-through tube. 
   At the same time however it is decisive that the flow-through tube comprises one or more flow paths (flights), wherein each of the flights has a cross section only of between 1 mm 2  and 800 mm 2 . Thus it becomes possible for the first time, by way of the almost horizontal installation and corresponding dimensioning of the flow-through tube, to provide an extremely flatly constructed valve cover which in particular with the restricted installation conditions may be used in the motor spaces of modern vehicles. The present cylinder head cover is to be particularly distinguished from the solution according to DE 101 27 820 A1 with which the constructional height of the cylinder head cover is more than 5 cm and at the same time achieves only a poor degree of separation. 
   Then at least one first, preferably a first and a second worm-like segment are located in the flow-through tube. With this, a worm as is usual in technical language is indicated as a thread which is guided about a middle axis in a helical or also spiral manner. The surfaces of the thread at the same time together with the inner wall of the flow-through tube limit flow paths for the gas. In a corresponding manner then the gases, by way of the stationary thread surfaces (=screw surfaces), are set into a rotational movement about the mentioned middle axis (axial direction) so that the oil or oil spray due to the centrifugal forces settles on the inner wall of the flow-through tube. 
   It has now been ascertained as being advantageous that with a worm-like element or with a serial arrangement of at least two of such worm-like segments, which advantageously only have a length between 0.5 times and 3 times, preferably 2.5 times their pitch, one may achieve a very efficient separation. The pitch of the spiral at the same time corresponds to that axial length of a worm-like segment which this would have if its thread surfaces were to revolve (orbit) once completely around the middle axis of the segment by 360°. 
   The separation may advantageously be carried out in an extremely efficient manner if the rotational direction of the two worm-like segments is in opposite directions to one another so that the gas needs to be deflected from the one rotational direction into the other rotational direction within the flow-through tube. 
   By way of these spirals (worm-like segments) which are applied in the flow-through tube behind one another with opposite rotational directions, impingement surfaces arise at which the oil or oil spray is separated in an excellent manner. The thread surfaces of the worm-like segments may at the same time be arranged such that the thread surface of the subsequent segment projects into the flow path formed by a thread surface of the previous segment. Advantageously then at the beginning of the thread surface of the subsequent segment, an edge or flange directed counter to the gas flow is arranged on this segment so that separated oil flows away via the thread surface of the subsequent segment instead of being entrained again back into the gas flow over the free edge of the thread surface of the subsequent segment due to the flow of gas or any eddies. 
   If the flow-through tubes have diameters ≦30 mm, then these may advantageously be installed into flat valve covers. 
   Advantageously each flow-through tube not only contains one flow path (flight), but also is divided perpendicularly to the longitudinal axis in a manner such that two or more flights which are separate from one another arise. For this, thread surfaces which are interweaved within one another are required. 
   The flow may enter into the flow-through tube axially and/or tangentially, or exit from this axially and/or tangentially. An entry and exit at a limited angle with respect to the axial direction and/or tangential direction is likewise possible. 
   The tubes may furthermore be widened at the beginning and/or at their end in order to minimise the pressure loss in the flow-through tube. A widening at the end of a flow-through tube reduces further the gas speed so that no droplet shear and thus atomisation of the already separated oil is effected at possible edges of the thread surfaces at the end of the last segment. 
   The core (the heart) of the worm-like segment may further be removed in the inlet and/or in the outlet region. By way of this a further reduction of the flow pressure losses is effected. A cone-like removal of the core is particularly favourable so that a free flow region is present in the middle axis of the segment. 
   One or more spirals and/or the flow tube may be reduced with respect to their diameter in the flow direction. 
   In order to lead away the oil separated on the wall of the flow-through tube, the wall advantageously in the axial direction, may comprise grooves or channels. It is also possible in the axial direction to attach webs for leading the separated oil to the outlet of the flow-through tube. The thread sure may also comprise grooves and/or channels which lead away the separated oil. Advantageously these then run in the flow direction of the gas or in the direction of the greatest pitch of the thread surfaces. It is particularly advantageous if the grooves run in the outer edges of the thread surfaces. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A few examples of the present invention are described in the following. 
     There are shown in: 
       FIG. 1  a valve cover according to the invention (cylinder head cover); 
       FIG. 2  an oil separator to be inserted therein; and 
       FIGS. 3 to 6  worm-like segments for application in the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Here, as in the following, the same or similar reference numerals are given to the same or similar elements, so that their description to some extent is not repeated. 
     FIG. 1  shows a cylinder head cover  1  according to the invention which is attached onto a cylinder head  2  of a combustion engine. Such a combustion engine produces so-called blow-by gases which are led away from the crank housing (crank case) and are led back into the intake line of the combustion engine. These crank housing gases contain finely distributed oil or oil spray which must be separated from the gas before leading back into the intake line of the combustion engine. 
   The valve cover according to the invention which contains the tubular separator comprises a housing lower part  7  which extends over the cylinder head  2  of the combustion engine and defines a plane which extends in the longitudinal and transverse direction of the cylinder head cover  1 . The housing lower part  7  with a housing upper part  8  encloses a chamber which is subdivided by an intermediate wall  9 , into two parts, specifically an inlet chamber  5  and calming chamber  6  (oil tank). In the intermediate wall  9  two flow-through tubes  10   a ,  10   b  extend from one side to the other, which are installed inclined at an angle α to the previously mentioned plane. These flow-through tubes comprise inlets  12   a ,  12   b  and outlets  13   a ,  13   b  for the crank housing gases. Within the cylinder head cover the flow-through tubes  10   a ,  10   b  represent the only (single) passage between the inlet chamber  5  and the calming chamber  6 . 
   The housing of the cylinder head cover  1  comprises a gas inlet  3  for the crank housing gases which may flow into the inlet chamber  5 . In this, they are still charged with oil and oil spray. Furthermore the housing of the cylinder head cover  1  comprises an outlet  4  out of the calming chamber  6  via which the crank housing gases purified of oil or oil spray may be led to the intake line of the combustion engine. 
   Two worm-like segments  20   a ,  20   a ′ and  20   b ,  20   b ′ are located in the flow-through tubes  10   a ,  10   b  after one another and arranged at a certain distance to the inlet  12   a  and  12   b  respectively. At the same time the worm-like elements  20   a  and  20   a ′ or  20   b  and  20   b ′ have opposite revolving directions. Alternatively several segments revolving in each case in opposite directions to one another are possible. It must be noted that the worm-like segments do not rotate themselves, but are fixed within the flow-through tubes. 
   The crank housing gases which enter into the inlet chamber  5  via the opening  3 , now flow through the two flow-through tubes  10   a ,  10   b  into the calming chamber  6 . With this they are firstly set into one rotational direction by way of the worm-like segments  20   a ′,  20   b  and subsequently are set into an opposite rotational direction by way of the worm-like elements  20   a ,  20   b ′. By way of this the oil spray contained in the gas is separated on the wall of the flow-through tubes  10   a ,  10   b  and runs out along the wall via the openings  13   a ,  13   b . The separated oil then collects in the oil tank or the calming chamber  6 . From there it may be led away via a return valve, via a valve to be opened periodically or also via a siphon. This is not shown in this drawing. 
   The purified crank housing gases now leave the chamber  6  via the outlet  4 . 
   The plane which is defined by the cylinder head cover and which corresponds to the x-y plane represented in  FIG. 1   b  extends over the cylinder head  2  of the combustion engine. The middle axis of the flow-through tubes  10   a ,  10   b  runs inclined at the angle α with respect to this plane. This has the advantage that any separated water runs out by itself from these flow tubes  10   a ,  10   b , even if motor is at a standstill, and thus an icing-up of these flow tubes  10   a ,  10   b  is prevented. 
   The inclination must at the same time be selected such that also when the vehicle has been positioned obliquely, the running-away of water out of the flow tubes  10   a ,  10   b  is ensured. 
     FIG. 2  shows a flow-through tube according to the invention as an oil separator  10  with a wall  11 , with an inlet  12  and with an outlet  13 . 
     FIG. 2A  now shows the flow-through tube  10  which is cut open in the left part. One may recognise a fast worm-like segment  20  which has thread surfaces  21  twisted about the middle axis  14 . 
     FIG. 2B  shows a sequence of several worm-like segments  20   a  to  20   d , which have a different rotational direction. 
   The segment  20   a  rotates in the clockwise direction, whilst the segment  20   b  rotates in the anti-clockwise direction. The segment  20   c  which is represented partly interrupted is in turn clockwise rotating and the segment  20   d  anti-clockwise rotating. 
     FIG. 3  shows a further segment  21  as may be applied with the present invention. The segment  21  rotates clockwise and has two flow paths or two flights  22   a ,  22   a ′. These flow paths in the axial direction are offset to one another (mutually offset) by half a pitch, a complete pitch is indicated with the reference numeral  27 . 
     FIG. 3A  shows this worm-like segment which extends over in total three pitches, in cross section. Again the two flights  22   a  and  22   a ′ are to be recognised, wherein a core  24  is formed in the middle axis of the segment  20 . This core, as is to be recognised in  FIG. 3B , is removed at the beginning of the segment on the left side. At the same time this tore is removed from the segment in a conically converging shape. This has the effect that the pressure losses at the beginning of the segment are very greatly reduced. 
     FIG. 4  shows further worm-like segments in the part pictures A, B and C, which may be applied in the present invention. All of these segments rotate clockwise. 
   In  FIG. 4A , the diameter of the segment changes from the edge  23   a  to the edge  23   a ′ so that such a segment may be applied in a tapering flow-through tube. 
   The segment in  FIG. 4B  has a pitch which is uniform over its entire length, and an unchanged diameter. 
   The segment in  FIG. 4C  has a pitch which reduces in the course of the rotation from the edge  23   a  to  23   a ′. By way of this the total pressure loss in the segment is also reduced. 
     FIG. 5  in two different views in the  FIGS. 5A and 5B  shows the sequence of two worm-like segments  20   a  and  20   b . Both segments have two flights  22   a ,  22   a ′ and  22   b  and  22   b ′. The segment  20   a  at the same time rotates clockwise and the segment  20   b  anti-clockwise. The front edge  23   b  of the segment  20   b  at the same time is offset to the rearward edge  23   a ′ of the segment  20   a  by 90°. By way of this the thread surface  21   b  projects into the flow path which is formed by the flight  22   a . The same applies in a corresponding manner to the flight  22   a′.    
   The thread surface  21   b  now for the gas which flows through the flight  22   a  forms a impingement surface which further improves the separation of the oil. In order however to avoid an atomisation at the edge  23   b  of the oil spray separated on the surface  21   b , a flange  26   b  is attached along the edge  23   b  opposite to the flow direction of the gas, i.e. in the direction of the flight  22   a , said flange as a web or raised part preventing the overflow of the oil in the direction of the edge  23   b.    
     FIG. 6  in a corresponding manner shows two segments which are arranged after one another, wherein in  FIG. 5  as well as in  FIG. 6 , for the part figure A, the flow direction of the gas is to be observed from the top to the bottom, and for the part figure B the flow direction from the bottom right to the top left. 
   In  FIG. 6  again a clockwise rotating segment  20   a  is followed by an anti-clockwise rotating segment  20   b . This embodiment example corresponds completely to that in  FIG. 5 , however the web  26   b  is not present. In all further points, this embodiment corresponds to that in  FIG. 5 .