Abstract:
The invention relates to a valve for controlling a gas flow, as it is used, for example, for controlling the gas flow between a crankcase and an intake tract of an internal combustion engine. The invention further relates to a liquid separator and to a ventilation system for the above-mentioned exemplary use for a crankcase and to an internal combustion engine.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a valve for the control of a gas stream, as it is for instance used for the control of a gas stream between a crank case and a suction tract of a combustion engine. The present valve further relates to a liquid separator as well as a ventilation system for the aforementioned exemplary application for a crank case as well as a combustion engine. 
     The present invention is for instance used in order to remove oil mist and/or oil droplets from blow-by gases of a combustion engine. To this end, the blow-by gases are conventionally guided from the crank case to the suction tract of the combustion engine via a ventilation line belonging to a ventilation system and this way are recirculated to the combustion process. It is however required to remove oil which has been carried over beforehand from these blow-by gases. The oil which has been carried over can be carried along as oil mist and/or oil droplets in the blow-by gases. 
     The oil separation is realized in so called oil separators, thus liquid separators for oil mist and/or oil droplets from a gas, here the blow-by gas. Such oil separators in the state of the art use different methods for the separation of the oil mist or the oil droplets, e.g. impaction separation, centrifugal separation or the like. 
     Depending on the operation conditions of the combustion engine, different gas streams (volumes per minute) have to be ventilated via the ventilation system. With different operation conditions, the pressure difference between the suction tract of the engine and the crank case varies, too. With a high underpressure in the suction tract, this can cause that the crank case is emptied by suction. On the other hand, too small a pressure in the suction tract or an excessive pressure loss in the ventilation line results in an overpressure in the crank case. An overpressure in the crank case relative to the atmospheric pressure is however not admissible. 
     As a consequence, in the state of the art, in almost every combustion engine, pressure control valves are arranged in the ventilation line, which control the pressure drop in the ventilation system and thus prevent the crank case from an inadmissibly high under- or overpressure. They close if the underpressure on the suction side becomes too high and this way cause an additional pressure drop in the ventilation line. 
     For the case that only a small underpressure is present in the suction tract or that an inadmissibly high pressure drop occurs in the ventilation line, e.g. by plugging of one of the oil separators arranged there, bypass lines are arranged in the ventilation line, which circumvent the corresponding areas, thus the oil separators. These are closed via bypass valves, which only react and open if the differential pressure of a separator becomes too large. 
     Such bypass valves can be preloaded, for instance using springs. They provide however no oil separation function. 
     While uncontrolled systems without bypass line at high volume streams of the blow-by gases cause a high pressure loss at the separator and at small volume streams result in poor separation rates, ventilation systems and oil separator valves with a bypass are very demanding in their construction and therefore also costly. It is especially always required to adapt such systems to the conditions of the respective combustion engine. 
     DE 103 62 162 B4 shows an oil separation device for a combustion engine, which comprises several constricted passages. Each of the passages shows a gap with variable width of the gap and a large passage cross section of the gap. The gap there is formed in such a way that it acts as an impactor separator for oil carried over in the blow-by gas. In order to control the passage resistance of the valve, the cross sectional area of the section through the gap varies with the pressure difference at the valve. 
     This state of the art has the disadvantage that such a valve can only be sealed off with difficulty and that an adaptation to various types of engines is very cumbersome. It does not provide for a simple scalability. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to provide a liquid separator or a valve, which does only require little space, has a small number of parts and realizes both a bypass function and a liquid separation function. It is further an object of the present invention to provide for a ventilation system and for a combustion engine using valves or liquid separators according to the invention. 
     This object is solved by the valve according to claim  1 , the liquid separator according to claim  35 , the ventilation system according to claim  36  as well as the combustion engine according to claim  37 . Advantageous embodiments of the valve according to the invention are given in dependent claims  2  to  34 . 
     The present invention is not limited to the separation of oil mist or oil droplets from blow-by gases, but is generally suited for the separation of liquids from gases. 
     The valve according to the invention comprises a valve seat with a valve opening, which can be closed by means of a valve closure, e.g. a valve disk. The valve opening in this context may be a single, connected opening or comprise several non-connected openings. The valve closure is seated on a valve bearing. According to the invention, the valve closure itself comprises one or several gas passage openings, which extend from the pressure side of the valve to the suction side of the valve. The gas passage openings themselves already function as liquid separator elements. 
     The gas passage openings, which are arranged in the valve closure, for example in a valve disk, can be designed in such a way that they are even open when the valve is closed, thus when the valve closure for instance rests on the valve seat. These openings cause that a gas stream can pass through the valve even with a closed valve and that in the passages or when passing through the passage openings, liquid, for instance oil, can be separated. These openings can further be provided with oil separator elements, in order to increase the effect of the liquid separation. 
     In addition, further gas passage openings can be arranged in the valve closure, which are closed when the valve is closed by the valve seat and which are only opened when a particular pressure difference between the pressure side and the suction side of the valve is exceeded so that the valve closure lifts off from the valve seat. With this, these further gas passage openings in the valve closure are opened in order to allow for a passage of the gas. 
     Further valve passage openings can be arranged in the valve closure, too, which allow for a permanent passage of the gas stream independent of the condition of the valve itself. Further, further gas passage openings can be arranged in the valve seat, which are closed by the valve closure in the closed state of the valve, thus when the valve closure is seated on the valve seat, and which are opened when the valve closure lifts of from the valve seat. 
     These gas passage openings can for instance be cylindrical passages or conical passages which are constricted in the gas streaming direction, in the valve closure or in the valve seat, the diameter of which—with conical passages the maximum diameter of which is 0.5 to 5 mm, preferably 0.9 to 3 mm. The valve closure and/or the valve seat is preferably made from plastic material with thermoplastic material being preferred over thermoset material. In this case, the gas passage openings are integrally formed during moulding of the valve closure and/or the valve seat and the length/height of the gas passage opening essentially results from the height of the valve closure or the valve seat, which in general amounts to between 1 to 15 mm, preferably to between 2 and 15 mm. It is also possible to produce the valve closure and/or the valve seat from metal, in particular from metal sheet, especially from steel metal sheet. The gas passage opening in this case can only be formed by a passage in the metal sheet, which has for instance been stamped out. It is however also possible, especially with conical gas passage openings, to form the metal sheet in such a way that constricting protrusions results, the ends of which are torn open, thus comparable to the production of the protrusions of a tanged steel sheet. With metallic valve closures or valve seats, the height of the gas passage openings advantageously amount to between 0.2 and 10 mm, preferably to between 0.5 and 5 mm. 
     This way a bypass valve and a fluid separator are integrated into the same part according to the invention, which simultaneously causes a reduced number of parts and a small demand in space. The bypass function is realized together with the oil separator function. 
     Due to the small demand in space and the low number of parts, considerable cost savings result. The valve according to the invention here can be adapted to various functional and constructional demands as it is scaleable given the low number of parts and allows for a modular construction. Depending on the requirements with respect to the pressure differences to be tolerated between the pressure and suction side of the valve, valve closures and valve seats with a different number of gas passage openings can be used. The individual gas passage openings in addition can be designed with different dimensions and therefore allow different gas volume streams to pass. With this, the pressure difference dropping at these gas passage openings can be set, too. 
     According to the invention, the valve closure can be preloaded elastically, especially resiliently seated, especially preloaded in the direction closing the valve. In this case, the valve closure preloaded by a spring lifts off from the sealing seat at an increased pressure difference at the valve and then allows for a bypass of the gas stream around the gas passage openings. 
     The present invention allows for a regular compression of the valve closure on the valve seat and therefore for a plane rest on the sealing seat. This further enables a high tightness of the bypass valve. 
     The elastic seating for the valve closure can be realized using springs, bending beams, as a tongue valve, by means of meander-shaped springs, by means of spiral springs or by means of an elastic rubber disk, too. The choice of the type and dimension of the elastic means for preloading the valve closure in the direction of the valve seat, allows for an adaptation to the properties and characteristics of the respective situation, especially to the respective engine. If a progressive spring is used, the course of the pressure can be further improved. It is also possible to use a degressive spring element in order to achieve a desired pressure course. 
     Due to the low number of parts and the simple mechanical construction owed to the functional principle, an assembly of the individual parts, in particular of the spring, is possible without the need for any welding processes and the like, e.g. using a snap-fit engagement. As a consequence, the assembly process of the valve according to the invention is very simple and cost efficient. 
     A further possibility to elastically seat the valve closure on the valve seat results from the use of a valve disk as the valve closure, which valve disk is connected onto or to the valve seat outside of the valve opening. In the area between the connection, which can be concentric around the valve closure, and the valve opening, the valve closure can comprise openings, especially slits, which enable a lift off of the central part of the valve disk from the valve opening after excess of a preset differential pressure between the pressure side and the suction side of the valve. This seating of the valve disk comparable to a disk spring causes that openings, e.g. slits, open up, when the valve disk lifts off from the valve closure and as gas passage openings open a further gas passage path, e.g. a bypass. These slits advantageously are formed as circular arc segments, which encircle the valve opening concentrically. 
     In order to enable a multi-step lift off of the valve disk and a multi-step opening of additional bypass openings (e.g. slits) dependent on the differential pressure between the pressure and suction side, the valve disk can also comprise several areas with such openings, which areas are radially distanced to each other. Dependent on the design of the openings, the lift off of the most central part of the valve disk from the valve opening takes place first with simultaneous opening of a first perforated area given by the bypass openings. With a further increasing differential pressure between pressure and suction side of the valve, a larger area of the valve disk lifts off from the valve opening and opens further perforated areas situated more remote from the center of the valve disk. 
     The separation effect at the bypass gap can be set by varying the ratio between the size of the valve closure and the width of the bypass gap. With a small gap and a large valve disk, even under bypass conditions, a separation of oil mist and oil droplets takes place at the bypass gap. With a small valve disk and a large bypass gap, the separation effect is smaller, although the total cross section of the bypass valve to be passed by the gas may be the same as in the aforementioned example. 
     According to the invention it is possible that liquid separators are inserted into the gas passage openings or formed as one-piece with them. These liquid separator elements then under normal conditions of the valve with a closed valve cause an improved separation of liquid, e.g. an improved separation of oil mist and oil droplets. The liquid separation elements there can be arranged in all or only in a part of the gas passage openings. It is however also possible to arrange separation elements immediately behind the respective gas passage opening, thus on the suction side. Impingement plates or fleece, at which liquids such as oil droplets and oil mist, can be separated after their passage through the gas passage opening are suited for this purpose. The gas passage openings, comparable to nozzles, here form an area in which the gases are accelerated to a higher velocity and thus conditioned for an efficient liquid separation. 
     It is also possible to arrange such liquid separation elements, for instance impingement plates or fleeces, behind the bypass opening—relative to the gas streaming direction—so that even under bypass conditions a certain liquid separation performance results. 
     The valve according to the invention can be used as such or as an element in further parts, e.g. as an oil separation valve inserted into a valve cover. Helical elements, which can be realized as described in DE 10 2004 037 157 A1 are suited as liquid separation elements, which can be inserted into the gas passage openings or be formed as one-piece with the gas passage openings. 
     The liquid separation elements used in the present invention can thus comprise at least one helical segment, the thread face of which together with the inner wall of the gas passage opening forms a helical streaming path for the gas, comparable to the liquid separator elements presented in DE 10 2004 037 157 A1. The helical segment can have a length smaller than or equal to half the pitch of the helical segments and in cases be formed as one piece with the wall element. 
     According to the invention, it is also possible that two such helical segments are arranged within one gas passage opening one behind the other with respect to the gas passage direction. It is then advantageous for the minimization of the streaming resistance that the consecutive segments show the same direction. It is advantageous for an improvement of the separation performance that they show opposite direction. 
     If two or more helical segments are arranged behind one another with respect to the gas passage direction in one of the gas passage openings, the outlet-sided edge of the thread face of the helical segment arranged frontwardly in the streaming path and the inlet-sided edge of the thread face of the immediately following helical segment can be rotated relative to each other, preferably by 0°, 45°, 90° or 135°. 
     In the following, some examples of valves and liquid separators according to the invention are described, especially such ones to be used in inventive ventilation systems and combustion engines. The same or similar reference numbers are used for the same or similar elements, so that their second and further use is not explained. 
     In the following examples and figures some individual enhancements of the invention are shown in a combination; nevertheless each individual one of these enhancements and each individual one of these elements as such represent an enhancement of the invention, also independent of the other elements of the respective example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It is shown in 
         FIGS. 1 to 6  various embodiments of the present invention; 
         FIG. 7  the pressure drop as a function of the volume stream at a valve according to the invention as shown in  FIG. 1 , at various spring rates or with fixed valve closure for seating of the valve disk; and 
         FIGS. 8 to 17  various further embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1 a    shows a valve  1 , which comprises a basic plate or a valve seat  7 . The valve seat  7  comprises a valve opening  6 , through which valve opening gas can pass from a first pressure side  2  of the valve to a second suction side  3  of the valve, if a pressure difference is given between the pressure side  2  and the suction side  3  of the valve  1 . If necessary, the valve opening  6  is closed by a valve disk  4 . This valve disk  4  rests on the valve seat  7 . In  FIG. 1 , the valve disk is supported via a resilient spiral spring  8  on the valve bearing  5 , which valve bearing comprises a gas passage opening  9 . By means of the spiral spring  8  as a pressure spring, the valve disk is preloaded in the direction opposite to the valve opening, so that the valve disk  4  only lifts off from the valve seat  7  after exceeding a particular pressure difference between the pressure side  2  and the suction side  3  and opens the valve opening  6 . It is of course also possible to mount the spring without preload, so that the height of the uncompressed spring under closed condition of the valve exactly corresponds to the distance between the valve disk  4  and the valve bearing  5 . An opening  9  is arranged in the bearing  5  of the valve disk, so that gas arriving along arrow A can stream via the valve opening  6  and the opening  9  in the valve bearing  5  in the direction of arrow B. The direction of the arrow at the same time indicates the longitudinal direction of a crankcase ventilation line, into which the valve  1  shown can be integrated in a laterally flush manner. 
     According to the invention, the valve disk  4  comprises gas passage openings  10   a ,  10   b  and  10   c , via which even in the closed state of the valve  1 , gas can pass from the pressure side  2  to the suction side  3  and then further through the opening  9  of the bearing  5  of the valve disk. These passage openings  10   a,    10   b  and  10   c  provide for a passage between the pressure side  2  and the suction side  3  with low pressure difference between the pressure side  2  and the suction side  3  and with small volume streams of the gas to be transferred via the valve. Given that the total cross section of the line reduces in these openings  10   a ,  10   b  and  10   c , these openings also act as nozzles, which provide for a liquid separation function on their own, especially an oil separation function. 
       FIG. 1 b    shows the same embodiment of the valve  1 , now however after the opening  10   b  has been blocked—for what reasons so ever—in the opened state. The arrows indicate that the gas passes through the openings  10   a ,  10   c  as well as through the bypass opening  12  of the valve. 
     This embodiment according to the invention can be enhanced by arranging separate liquid separator elements  11   a ,  11   b ,  11   c  into the gas passage openings  10   a ,  10   b  and  10   c . The above mentioned helical segments or sequences of such helical segments are suited as liquid separator elements  11   a ,  11   b , and  11   c . Of course, these separator elements can be formed as one piece with the valve disk  4 . With such an arrangement of additional liquid separator elements  11   a ,  11   b  and  11   c  in the passage openings  10   a ,  10   b  and  10   c , an improved separation performance of valve  1  in its closed state is achieved. 
     A simple modular adaptation of the valve according to the invention to the respective characteristics of the particular engine or of the particular gas stream can here be realized by arranging an adjusted number of gas passage openings, which comprise no separator elements and arranging an adjusted number of gas passage openings, into which additional separator elements have been arranged or which are specifically formed as separator elements in the valve disk  4 . 
       FIG. 2 b    shows an embodiment, in which the separator elements have not be arranged in the passage openings  10   a ,  10   b  and  10   c , but in the area of the bypass opening  12 . The plates  18  encircle the valve disk  4  in a self-contained manner, so that with an open valve the gases at least in part pass through the bypass and stream over the surface of the plates  18 . The plates  18  here are designed two-layered with a permeable fleece layer  18   b  on a non-permeable layer  18   a . The fleece layer  18   b  is circumferentially arranged on the wall of the plate layer  18   a  and along the gap-shaped bypass opening  12 . Here, the separation is achieved by the oil-carrying gases streaming along the surface of plate  18  and through the surface layer of fleece  18   b . Although it would be possible that for the guidance of the valve disk  4 , the plates adjoin to the valve disk  4  in a flush manner, the plates  18  in this embodiment keep a small distance from the fleece  18   b , so that even with a completely loaded fleece  18   b,  a passage is still possible. 
       FIG. 3 a    shows a further embodiment of a valve  1  according to the invention as shown in  FIG. 1 . Here, however, the bearing  5  of the valve disk is designed without opening  9 . The bearing  5  of the valve disk is now formed as a stable permeable fleece or as a mesh web, so that the bearing  5  itself acts as a liquid separator element. It is arranged behind the gas passage openings  10   a ,  10   b  and  10   c , so that the gas stream having passed the gas passage openings  10   a ,  10   b  and  10   c  and having been accelerated in these gas passage openings  10   a ,  10   b  and  10   c  impacts on the bearing  5  and that there, liquid is separated from this gas stream when passing through the bearing  5 . 
       FIG. 3 b    shows a variation of the previous embodiment, where the bearing  5  for the valve disk comprises a layer  5   a  which is impermeable for gas and liquid as well as a permeable layer  5   b , e.g. a fleece, which faces towards the gas stream. The oil-loaded gases stream to this permeable layer  5   b  and enter it. The particles are separated in the fleece  5   b , the gas re-enters the inner chamber  3  of the valve  1 . Other than in the former embodiments, the further transmission of the gas does not take place in continuation of the gas passage direction B through the passage openings  10   a ,  10   b  and  10   c , but in direction B′, thus transverse to direction B, as the bearing  5  of the valve disk is impermeable. 
     In  FIG. 4 a   , the embodiment of  FIG. 3 a    is varied in such a manner that a further liquid separator element  15  is arranged in the passage direction behind the gas passage openings  10   a ,  10   b  and  10   c , thus suction-sided to the gas passage openings  10   a ,  10   b  and  10   c . This further liquid separator element  15  is for instance an impactor plate or a fleece. Instead of a single further liquid separator element  15 , it is also possible that distinct liquid separator elements are provided for individual gas passage openings or single groups of gas passage openings or that no liquid separator elements are provided at all. 
     The further liquid separator element  15  represented in  FIG. 4 a    is also resiliently seated on the valve bearing  5 , by means of a spiral spring  16 . Dependent on the gas velocity and the magnitude of the gas stream through passage openings  10   a ,  10   b  and  10   c , the separator element  15  is pressed away from the gas passage openings  10   a ,  10   b  and  10   c  against the spring  16 . This results in a variable distance of the separator element  15  from the valve disk  4  and the gas passage openings  10   a ,  10   b  and  10   c . As a consequence, the degree of separation and the pressure loss caused by the separator element  15  can be controlled dependent on the gas volume stream. As in this embodiment, both springs  8 ,  16  as well as the magnitude of the plate  15  can be chosen independent of each other, it can be scaled particularly simple and in a versatile manner. 
       FIG. 4 b    shows a further variant comparable to the valve represented in  FIG. 4   a.    
     In this valve  1 , the separator element  15  is not separately seated via a spring. The separator element  15  is rather permanently fixed at the valve disk  4  via connecting rods  17 , so that the distance between these two elements  4  and  15  does not change. This allows this valve to be used together with a separator element designed as an impactor separator, where the acceleration in the gas passage opening  10   a ,  10   b  and  10   c  interacts with the impingement on the impactor plate  15 . As was the case for the plate  5  in the embodiments according to  FIGS. 3 a , 3 b    this plate  15  can be designed one- or multi-layered, permeable or impermeable, too. 
       FIG. 5  shows a further embodiment, in which the embodiment according to  FIG. 4 c    is complimented in such a way, that now further separator elements  11   a ,  11   b  and  11   c  are arranged in the gas passage openings  10   a ,  10   b  and  10   c  separately or one-piece with the gas passage openings  10   a ,  10   b  and  10   c . Due to this, a double liquid separation takes place in the gas passage openings  10   a,    10   b  and  10   c  and in the further separator element  15  arranged behind the former. 
       FIG. 6  shows a cross section of a further valve, which in principle corresponds to the construction of the valve  1  in  FIG. 1 . However, in  FIG. 5 , the valve disk  4  is not preloaded by a spiral spring, but by means of a resilient metallic tongue  8 ′, which itself is connected to the valve seat  7 . In this embodiment, the valve disk  4  can lift off from the valve  7 , too, but is preloaded in the direction of the valve seat  7 . Here, one has to keep in mind that the metallic tongue  8 ′ does not need to cover the valve disk completely and does not need to close the gas passage openings  10   a ,  10   b  and  10   c . Rather, it can only be one or several narrow metallic tongues  8 ′, which only in the cross sectional representation seem to also cover the gas passage openings  10   a,    10   b  and  10   c . The essential factor is the elasticity in the flank area. 
       FIG. 7  shows the course of the pressure drop at the valve  1  of  FIG. 1 , four different valves have been measured. On the one hand, a valve with fixed seating has been measured (graph “without spring”). With an increasing volume stream, here the pressure drop at the valve strongly increases. 
     The other three valves comprise a resilient, moveable seating as in  FIG. 1 , where different spring rate of spring  8  having been chosen. 
     As is obvious in  FIG. 7 , for the valves with a resilient seating, the pressure drop initially increases with increasing volume stream as for the valve with fixed valve disk, however a further increase of the pressure drop is limited. This limitation is achieved by a lift-off of the valve disk  4  from the valve seat  7  and the release of a gap between the valve opening  6  and the valve disk  4 , which results in a bypass of the valve disk  4 . One can see from  FIG. 7  that this lift-off of the valve disk already happens at a gas volume stream of about 60 l/min when the spring with the lowest spring rate of 0.2 N/ml is used, while with the use of a spring with a higher spring rate (0.5 N/mm or 1.0 N/mm), such a lift-off only happens at about 80 to 100 l/min. Thus, by choosing a suitable spring, the characteristics of the valve can be chosen. 
       FIG. 8  in three partial Figures A, B and C shows a further variant of a valve  1  according to the invention. The representation in  FIG. 8  shows a sectional view, but as a top-view with respect to spring  8 . This valve  1  possesses a valve seat, which comprises two partial elements  7   a  and  7   b . The valve seat comprises a central element  7   a , on which the valve closure rests when the valve is closed. The valve closure is preloaded by spring  8  in the direction of the valve seat element  7   a . The valve seat comprises a further element  7   b,  which comprises a wall  18 , inside of which the valve seat  4  is guided. The element  7   b  of the valve closure comprises gas passage openings  20   a  and  20   b,  which are permanently open and allow for a gas stream via the valve in the direction of arrow A and further in the direction of arrow B′. Already in these openings  20   a  and  20   b , which cause a reduction of the streaming cross section, a fluid carried along with the gas stream, e.g. oil, is separated. 
     The valve closure  4  itself comprises gas passage openings  10   a ′ and  10   b ′, which in the closed state of the valve  1  are however closed since the valve disk  4  rests on the element  7   a  of the valve seat. This state is shown in  FIG. 8A . 
     When the pressure difference between the pressure side  2  and the suction side  3  of the valve now exceeds a predetermined limit, the valve closure  4  lifts off from element  7   a  against the preload of the spring  8  and this way opens the openings  10   a ′ and  10   b ′ as further gas streaming paths. These further gas streaming paths are indicated with arrows A′ and shown in  FIG. 8B . 
     If the pressure difference between the pressure side  2  and the suction side  3  of the valve  1  further increases and limits a predetermined limit, the valve disk  4  is pressed out of the valve seat  7   b  against the preload of the spring to such an extent, that a further bypass opening  12  results between the valve disk  4  and the wall  18  of the valve seat element  7   b , through which further gas can stream. This is shown in  FIG. 8   c.    
     With such an arrangement and design of the valve  1 , it is possible to achieve a multi-step switching behaviour of the valve  1 . 
     In  FIG. 9  a fundamentally similar valve  1  as in  FIG. 8  is shown, in which here however the openings  10   a ′ and  10   b ′ for a further increase of the liquid separation effect, separator elements  11   a ′ and  11   b ′, as shown above, are inserted. In the openings  20   a  and  20   b , liquid separator elements  21   a  and  21   b  are inserted too, in order to increase the liquid separation efficiency and rate of separation. The representations in  FIGS. 9A and 9B  relate on the one hand to a condition, in which the valve  1  is closed ( FIG. 9A  corresponding to  FIG. 8A ) and in which the valve is completely open ( FIG. 9B  corresponding to  FIG. 8C ), respectively. 
       FIG. 10  shows a further valve  1  according to the invention, in which the valve seat  7  is designed as one piece and which comprises a wall  18 . In this wall  18 , a valve closure  4  is guided. In the area, in which the valve closure rests on the valve seat  7  when the valve is closed, openings  10   a ′ and  10   b ′ are arranged in the valve disk  4 , which are provided as gas passage openings. In the closed state of the valve  1 , as it is shown in  FIG. 10A , these openings are closed by the valve seat  7 . In addition, openings  10   a  and  10   b  are arranged in the valve closure  4 . They are positioned inside of the valve opening  6 , so that they are permanently open for gas passage even with a closed valve  1 . They thus enable the gas passage along the arrows A and B′ in case of a low pressure difference between the pressure side  2  and the suction side  3  with a closed valve  1 . 
       FIG. 10B  shows the same valve  1 , now however with an increased pressure difference between the pressure side  2  and the suction side  3 , where the valve disk  4  already lifts off from the valve seat  7 , but is still guided within the wall  18  of the valve seat  7 . Here, the openings  10   a ′ and  10   b ′ are additionally open for the gas passage in the direction of the arrows A′, so that the pressure drop at the valve disk is reduced overall and the volume stream is increased. 
       FIG. 10C  shows the state of the valve  1  with completely open valve disk  4 . This has now lifted off from the valve seat  7  against the force of the spring  8  to such an extent that a further annular opening  12  results as a bypass opening with gas passages A′ between the circumferential edge of the valve disk  4  and the wall  18 . 
       FIG. 11  shows a further example of a valve according to the invention, which generally shows a comparable construction to the valve in  FIG. 10 . However, now the openings  10   a  and  10   b  of the valve closure are generally arranged outside of the valve opening  6 . However, the valve seat  7  itself, in the area of the openings  10   a  and  10   b , comprises openings  20   a  and  20   b , which together with the openings  10   a  and  10   b  enable a gas path from the pressure side  2  to the suction side  3  of the valve  1  even at closed valve  1 , thus when the valve closure  4  rests on the valve seat  7 . In order to increase the separation effect, an oil separation element  21   a  and  21   b , respectively, is arranged in each of the openings  20   a  and  20   b , respectively. 
       FIG. 11A  now shows the condition of the valve  1 , when it is closed to the highest extent possible. Then, only the passage openings  20   a ,  10   a  and  20   b,    10   b , respectively, are open for a gas passage. Nevertheless, an efficient liquid separation already takes place here. 
     In  FIG. 11B , the state is shown in which the valve disk  4  has lifted off from the valve seat  7  to the highest extent possible. Then, it is not only the openings  10   a ′ and  10   b ′, which are open as gas streaming paths along arrows A′ (in the way it was shown in  FIG. 10B ), but also a further annular bypass-opening  12  between the wall  18  and the valve disk  4  for the gas passage along arrows A′. The representation in  FIG. 11B  corresponds to the one for the valve in  FIG. 10C . 
       FIG. 12  shows a further valve according to the invention. Similar as for the valve shown in  FIG. 8 , the valve seat is constructed with two-parts in the form of a center element  7   a  and an edge element  7   b . The valve opening  6  here comprises the shape of a concentric opening  20   a , which encircles the center element  7   a . The edge element  7   b  comprises a wall  18 , which serves for the guidance of the valve closure  4 . The valve closure  4  here comprises several openings  10   a  and  10   b , which are arranged in the area of the valve opening  6 ,  20   a  and which are therefore open for the gas passage along arrow A (see  FIG. 12A ) in every condition of the valve. The openings  10   a ,  10   b  may have the shape of separate, elongated annular sections on a line concentric to the opening  20   a.    
       FIG. 12A  shows the valve  1  in the maximum closed condition, thus when only openings  10   a  and  10   b  are in the open state.  FIG. 12B  shows the valve  1  when the pressure difference between the pressure side  2  and the suction side  3  exceeds a first predefined pressure, so that the valve closure  4  lifts off from the valve seat  7   a ,  7   b  against the preload of the spring  8 . 
     In the area of the central valve seat element  7   a , the valve closure  4  shows further openings  10   a ′ and  10   b ′, which rest on element  7   a  and therefore are closed by this element  7   a , if the valve is closed to the highest degree, as shown in  FIG. 12A . These openings are opened for a gas stream in the direction of the arrows A′ when the valve closure  4  lifts off from the valve seat  7   a ,  7   b , as shown in  FIG. 12B . In  FIG. 12B , the valve closure is additionally guided by the wall  18  of the valve seat element  7   b.    
     If the pressure difference between the pressure side  2  and the suction side  3  of the valve exceeds a second predefined value, the valve closure  4  lifts off from the valve seat  7   a ,  7   b  against the preload of the spring  8  to such an extent that between the circumferential edge of the valve closure  4  and the wall  18 , a further annularly shaped bypass opening  12  is opened, through which gas can stream from the pressure side  2  to the suction side  3  in the direction of arrows A′. In this condition, the valve is opened to the maximum extent, as is shown in  FIG. 12C . By the choice of the load-deflection line of the spring  8  as well as the length of the wall  18  in the gas passage direction, it is possible for this valve (in the same way as with valves  1  depicted in  FIGS. 8 to 11 ) to regulate at which pressure difference between the pressure side  2  and the suction side  3  of the valve, gas passage openings, here the openings  10   a ′ and  10   b ′, are opened and at which further pressure difference the openings  12  are opened, too. 
       FIG. 13  in partial Figure A in a top view and in partial Figure B in a cross section shows a further valve  1  according to the invention.  FIG. 13A  here shows the valve closure  4  in a top view, while  FIG. 13B  shows the valve closure in a section along line C-C in  FIG. 13A . 
     The valve seat  7  comprises a central valve opening  6 , which is covered by the valve closure  4 . The valve closure  4  shows fastening areas  19  which are situated radially peripherally, by means of which it is mounted to or on the valve seat  7 . In the center area, which is preloaded via a step  14  in the area  14  with respect to the fastening area  19 , the valve closure  4  comprises openings  10   a,    10   b , and  10   c , which are permanently open for the passage of the gas from the pressure side  2  to the suction side  3 . They ascertain a basic gas stream via the valve and with the constriction of the streaming cross sections in the openings  10   a ,  10   b  and  10   c  already provide for a basic liquid separation. This central area within the step  14  is seated on a flange  24 , which is arranged in such a way that it protrudes from the valve seat  7  in the gas streaming direction and encircles the valve opening. With a closed valve  1 , the valve closure  4  rests on the flange  24 , so that only the openings  10   a ,  10   b  and  10   c  are open for the passage through the valve  1 . 
     In the stepped area  14  of the valve closure  4 , here slits are arranged as segments of circular arcs which are arranged concentrically around the center of the opening  10   b  or the center of the valve opening  6 . These slits have been produced by punching or cutting out, e.g. by laser cutting, in the valve closure  4  and therefore permanently show an opening. When a predefined pressure difference between the pressure side  2  and the suction side  3  is exceeded, the central area of the valve closure  4  lifts off from the flange  24 , which causes that the slits are opened as bypass openings  12 . These slits thus cause that the valve closure  4  with its central area is seated comparable to a disk spring on the valve seat  7  and at the same time that due to the opening of the slits  12  at the lift off a bypass function with simultaneous liquid separation is guaranteed. 
       FIG. 14  shows a further example of such a valve closure  4 . It is obvious, that here the slits  12 , which provide for the spring effect of the bridges between them as well as for the bypass function by themselves, are given in a smaller quantity but with a longer length than the slits  12  in the valve closure  4  of  FIG. 13 . 
       FIG. 15  in partial  FIGS. 15A and 15B  in a top-view and in a cross section, respectively, shows a further comparable valve  1  in  FIG. 15B  and its valve closure  4  in  FIG. 15A . 
     The valve closure now in the central area comprises openings  10   a  and  10   b  which are permanently open for the gas passage. They are encircled by a first cohort of slits  12   a  in an area  14   a  with a step  13 . Upon excess of a first differential pressure between the pressure side  2  and the suction side  3  of the valve  1 , this central area with the openings  10   a  and  10   b  lifts off from the valve seat  7  and the flange  24 , so that the slits  12   a  are released, open up and release bypass openings for the gas stream. 
     The cohort of slits  12   a  outside of the valve opening  6  is enclosed by the gas passage openings  10   a ′,  10   b ′ etc. mentioned. In the most closed state possible of the valve  1 , they rest on the valve seat  7  and are not open for the gas stream because the valve closure  4  rests on the flange  24 . Radially further peripherally, outside of the gas passage openings  10   a ′,  10   b ′, a further cohort of slits  12   b  is situated, which opens upon excess of a further, higher pressure difference between the pressure side  2  and the suction side  3  and which lifts off the central area including the openings  10   a ′,  10   b ′ from the valve seat  7  and at the same time releases further bypass openings  12   b  for the gas stream. 
       FIG. 16  shows a further valve  1  comparable to the one in  FIG. 15 , in which permanently open gas passage openings  10   a ,  10   b  and  10   c  are arranged in the central area within a first cohort of slits in the area  14   a  and in which further, non-permanently open gas passage openings  10   a ′ and  10   b ′ are arranged between this first cohort of slits in an area  14   a  and a second cohort of slits in an area  14   b . In  FIG. 16 , the valve  1  is depicted in a condition in which due to a sufficiently high pressure difference between the pressure side  2  and the suction  3 , the area between the slit areas  14   a  and  14   b  has already lifted off from the valve seat  7 , so that the openings  10   a ′ and  10   b ′ have been released. By means of the steps  13   a  and  13   b  in the areas  14   a  and  14   b , a stepwise opening behaviour of valve  1  is achieved, too. 
       FIG. 17  shows in partial figures A, B, C, and D four further valves according to the invention. 
     In  FIG. 17A , a valve is represented which is constructed comparable to the valve in  FIG. 1 a   . In contrast to the valve shown in  FIG. 1 a   , here the valve seat  7  shows further gas passage openings  10   c ,  10   d , which are permanently open independent of the opening condition of the valve or the valve opening  6 . These openings  10   c  and  10   d  together with the openings  10   a  and  10   b  provide that even in the case of a closed valve, thus when the valve closure  4  rests on the valve seat  7 , a minimum passage through the valve  1  is always guaranteed for. 
       FIG. 17B  shows a valve  1 , which is constructed comparable to the valve in  FIG. 15  or in  FIG. 16 . The valve seat again shows a flange  24 , which here in  FIG. 17B  is however angled. The upper surface of the angled area pointing towards the valve closure  4  in the closed state of valve  1  serves as a seating area for the valve closure  4 . If the valve closure  4  completely rests on this seating surface of the flange  24 , only the openings  10   a ,  10   b  and  10   c  are open for the gas passage. 
     In contrast to  FIGS. 15 and 16 , but comparable to  FIG. 17A , the valve closure  4  now is not seated on the valve seat  7 , but on a valve bearing  5  which is separate from the latter. This valve bearing comprises a passage opening  9 , through which the gases can pass towards the suction side. 
     The valve bearing  5  itself comprises a flange  27  projecting rectangularly, which is seated on the valve closure  4  at its outer edge. The further design of the valve closure  4  corresponds to the one in  FIGS. 15 and 16 , especially with respect to the slit areas  14   a  and  14   b.    
     If the valve closure  4  now lifts off from the surface of the flange  24 , the further gas passage openings  10   a ′ and  10   b ′ are opened for the gas passage. Further, a gas stream can form between the flange  24  and the valve closure  4 , which circumvents the valve bearing  5  in the direction of the suction side  3 . In both cases, bypass paths open for the gas stream. 
     In  FIG. 17C , a similar valve  1  is shown as in  FIG. 17B . This valve in  FIG. 17 c    in contrast to  FIG. 17B  is however not shown in the open state but in the closed state, in which the valve closure  4  rests on the surface of the angled area of the flange  24  so that both the openings  10   a ′ and  10   b ′ are closed and the gas path for the bypass of the valve bearing  5  is no longer available. 
       FIG. 17D  shows a further valve  1 , which to a large extent corresponds to the one in  FIGS. 17B and 17C . In contrast to the valve in  FIGS. 17B and 17C , the flange  24  shows no angled area. Rather, the valve closure rests on the end of flange  24 . Further, the valve closure does not comprise passage openings outside of the area of the valve opening  6 , which are open or close as a function of the opening condition of the valve  1 . The openings  10   a ,  10   b  and  10   c  arranged in valve closure  4  are permanently open and guarantee a minimum gas passage through valve opening  6 , the passage openings  10   a,    10   b  and  10   c  and the opening  9  from the pressure side  2  to the suction side  3  of the valve  1 .