Abstract:
An oil mist separator has a pressure regulator valve which is located in the blow-by line downstream of the oil mist separator element in the flow direction of the gas. The pressure regulator valve has a bias so that it opens above a specified pressure difference between the blow-by line and a neighboring chamber. Located around the oil mist separator element is a bypass line which has a bypass valve. The bypass valve has a bias that causes the bypass valve to close below a specified pressure difference between the suction side and the pressure side of the oil mist separation element. The pressure regulator valve and the bypass valve are connected with each other so that the pressure regulator valve, as it closes, increases the bias of the bypass valve.

Description:
RELATED APPLICATIONS 
   This application claims priority from German Patent Application No. DE 10 2006 051 143.3 filed on Oct. 30, 2006 which is incorporated by reference in its entirety. 
   FIELD OF THE INVENTION 
   This invention relates to an oil mist separator, a ventilation system and an internal combustion engine in which an oil mist or oil droplets are to be separated from a gas. 
   BACKGROUND OF THE INVENTION 
   Oil mist separators of this type are used in particular for the separation of oil mists and oil droplets from blow-by gases in an internal combustion engine. The blow-by gases are conventionally transported out of the crankcase by means of a ventilation line to the intake tract of the engine where they are recycled to the combustion process. However, it is necessary to first remove from the blow-by gases any oil that they may be carrying. 
   Depending on the operating conditions of the internal combustion engine, situations can thereby occur in which critical levels of operation are reached. On one hand, an excessive vacuum in the intake tract can cause the crankcase to be completely evacuated. An insufficient vacuum in the intake tract or an excessive pressure drop in the ventilation line can cause an overpressure to occur in the crankcase. However, an overpressure in the crankcase with respect to the atmospheric pressure cannot be allowed to occur. 
   Therefore, in the prior art, almost every internal combustion engine of the prior art includes pressure regulator valves in the blow-by path (ventilation line), which protect the crankcase from unallowably high vacuum. These valves close when the suction-side vacuum becomes too high and thereby cause an additional pressure drop in the blow-by line. 
   If only a low vacuum or an unallowably high pressure drop occurs in the intake line, for example on account of the clogging of one of the oil mist separators located in the intake line, bypass lines are provided in the ventilation line which bypass the corresponding locations, i.e. the oil mist separators. These bypass lines are closed by means of bypass valves which respond only when the pressure difference across a separator becomes too great. As a result of this bypassing, when the bypass valve is open, the vacuum of the intake tract of the engine is fully available in the crankcase for the ventilation of the crankcase. In this manner, an inflation of the crankcase is prevented. 
   DE 100 44 922 B4, for example, discloses a pressure regulator valve which is controlled by means of the pressure prevailing in the crankcase. The manipulated variable is thereby the pressure differential between the crankcase and the outside atmospheric pressure (constant pressure). 
   If the pressure in the crankcase increases, for example under operating conditions in which increased blow-by occurs, the pressure regulator valve opens again to effect an improved ventilation of the crankcase. 
   DE 20 2004 019 787 U1 describes an additional example of an oil mist separator in the blow-by ventilation line of an internal combustion engine. In this case a pressure regulator valve is located upstream of the oil mist separator. If the oil mist separator becomes clogged, there is a bypass line around the pressure regulator valve and the oil mist separator, which for its part is connected with a bypass valve. One problem with this example of the prior art is that the bypass valve is independent of the operating condition of the engine and the resulting intake vacuums. Therefore the bypass valve cannot react and adapt its response to different operating conditions. 
   SUMMARY OF THE INVENTION 
   The object of this invention is therefore to make available an oil mist separator, a ventilation system with an oil mist separator and an internal combustion engine and its use, in which there is an adaptive regulation of the oil mist separator. 
   The oil mist separator claimed by the invention has a line for the transport of a gas which can be, for example, the ventilation line of a ventilation system in the bypass system of an internal combustion engine. Located in the line is an oil mist separation element, such as a spiral-shaped helix, a cyclone, an impact separator or any other arbitrary type of separator that can be used for the separation of oil mist and oil droplets from a flowing gas. 
   Downstream of the oil mist separation element, i.e. downstream in the direction of the gas flow, there is a pressure regulator valve which has a bias that opens the pressure regulator valve above a specified pressure in the line, in particular the pressure in the line between the oil mist separation element and the pressure regulator valve. In this manner, there is a biased valve which is fully open under normal operating conditions. A bias of this type can be achieved, for example, by realizing the valve in the form of a membrane-regulated valve. The membrane can then be located between the line and a constant pressure such as atmospheric pressure, for example. If the pressure difference between the line and this pressure decreases, the membrane exerts increased pressure on a valve body which increasingly closes the valve. By means of this pressure regulator valve it is possible to protect the inlet side of the line, such as a crankcase for example, against an excessive vacuum from an intake tract of an engine located on an outlet side of the line. 
   On the oil mist separator claimed by the invention, there is further a bypass line which bypasses the oil mist separator located in the line. This bypass line has a bypass valve which is closed under normal operating conditions. For this purpose a bias is provided which closes the valve below a specified pressure difference between the suction side and the pressure side of the oil mist separation element. Only when there is a high pressure difference between the suction side and the pressure side of the oil mist separator element does the bypass valve open and release an additional flow path for the gas from the inlet side to the outlet side. A condition of this type can occur, for example, if the oil mist separator is frozen. That would otherwise result in an unacceptable inflation of the crankcase. 
   For its part, one or more additional oil mist separation elements can be located in the bypass line. It is also possible, however, to provide only one bypass line to realize a bypassing of the oil separation element in the ventilation line with the smallest possible pressure drop. 
   A decisive factor in this invention is that the pressure regulator valve and the bypass valve are functionally coupled or connected to each other. When the pressure regulator valve closes, it thereby increases the bias of the bypass valve. Therefore if the pressure regulator valve is closed, which normally occurs at a very high intake vacuum of the intake tract, the bias of the bypass valve is simultaneously increased. Under operating conditions of this type, the high vacuum of the intake tract is sufficient to empty the crankcase of the blow-by via the oil mist separation elements in the ventilation line, even if the blow-by flow is very large or the oil mist separation element, because of partial clogging, produces a large pressure drop. Therefore a bypass valve is provided that opens later at a high suction pressure to effectively clean the blow-by flow under these conditions, too, before uncleaned gas is transported through the bypass valve and the bypass line into the intake tract. 
   One particularly advantageous embodiment of this invention uses a membrane-regulated valve as the pressure regulator valve, in which the membrane is pulled toward the valve seat, and a valve body is thereby moved toward the valve seat to make the flow gap in the valve smaller if the suction vacuum is too high. Thus the resistance in the valve, i.e. the pressure drop, is increased and it becomes possible to reliably prevent the crankcase from being totally evacuated. At low suction vacuums, the membrane is in contact against the cap of the pressure regulator valve and opens the valve all the way. 
   The membrane is supported on a spring that biases the membrane toward the cap of the pressure regulator valve. 
   Also provided is a bypass valve in which a valve body is pressed by a spring onto the aperture of the bypass valve. The bias of the spring consequently determines the force and thus the pressure difference necessary to lift the valve body of the bypass valve out of its seat and thus to open the bypass valve. In one particularly advantageous variant, the bypass valve can be located immediately next to the pressure regulator valve. In this manner, when there is a high pressure difference in the intake tract, the pressure regulator valve is increasingly closed and simultaneously the bias of the bypass valve is increased. When the vacuum in the intake tract is high, the ventilation of the crankcase is guaranteed even in the event of a high blow-by flow or a partial clogging of the oil mist separator element. 
   The switch point of the two valves is thereby determined on the basis of the coordination of the surface areas of the intakes, the valve bodies, the membrane characteristics (active surface area, thickness, material, shape, stiffness) and the strength(s) of the spring or springs used. 
   In an additional advantageous variant, at least one separation element is also integrated into the bypass. In this manner, an oil mist separation also occurs in the blow-by gases transported through the bypass. In this manner, completely uncleaned blow-by gas is prevented from getting into the intake tract. An arrangement of this type could also be called an adaptive oil mist separator, because different oil mist separation paths are opened as a function of the blow-by amount and the pressure conditions in the intake tract. 
   The oil mist separator claimed by the invention has a better control characteristic and a higher degree of separation than unregulated oil mist separators. The protection of the oil separator against failure is also improved. Because the valves (pressure regulator valve and bypass valve) are next to each other, the number of replacement parts required in the oil mist separator claimed by the invention is reduced, which results in easier installation and cost advantages. 
   One example of an oil mist separator of the type claimed by the invention is described below. Identical and similar components are identified by identical and similar reference numbers in all of the figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which: 
       FIG. 1  shows one embodiment of an oil mist separator; and 
       FIGS. 2A to 2E  illustrate different operating conditions of the oil mist separator illustrated in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise. 
     FIG. 1  shows an oil mist separator  1  claimed by the invention, which can be located in the ventilation line of an internal combustion engine between the crankcase and intake tract (blow-by line). 
   The oil mist separator  1  has a line  2 , which can be part of the ventilation line of the internal combustion engine. This line  2  has an inlet  3  and an outlet  4 . In the vicinity of the inlet  3  the line is realized in the form of a cylinder which has a center discharge in the vicinity of a pressure regulator valve  10 . 
   Concentric to the line  2  there is a bypass line  6  which is in communication with the inlet of the line  2  on the inlet side and is closed with a bypass valve  20  on the outlet side. If the bypass valve  20  is opened, the gases that are flowing in the line  2  also flow via the bypass line  6  from the inlet side  3  via the bypass line  6  and the valve  20  and then, because the pressure regulator valve  10  is open, continue through the line  2  to the outlet  4 . 
   Located at the inlet  3  of the line  2  are oil mist separation elements  5   a ,  5   b ,  5   c  and  5   d  in which the oil mist or oil droplets are removed from the gas flowing in the line  2 . The bypass line  6  is used to bypass these oil separator elements  5   a ,  5   b ,  5   c  and  5   d.    
   The line  2  has walls  8  which simultaneously form the housing for the pressure regulator valve  10 . The boundaries of the bypass line  6  are defined by the walls  9 . A portion of these walls forms the valve seat  16  of the pressure regulator valve  10 . 
   The pressure regulator valve  10  has a regulating membrane  11  which presses on a valve body  12 . The regulating membrane  12  is biased by means of a spring  15  toward the opening of the flow path through the valve. The spring  15  is supported on one hand on the membrane  11  and on the other hand on a valve body  22  of the bypass valve  20 . Often a small plastic platelet is held between the spring  15  and the membrane  11 , whereby the collar on the platelet prevents direct contact between the spring  15  and membrane  11 , thereby counteracting the destruction of the membrane. The spring  15  therefore exerts a bias on one hand on the membrane  11  to open the pressure regulator valve  10  and simultaneously a bias on the valve body  22  of the bypass valve  20  to close the bypass valve  20 . 
   The housing cover  28  and the membrane  11  form an additional chamber  13  which in the illustrated example is in communication via an opening  14  in the housing cover with the outside pressure (atmospheric pressure), which can be considered approximately constant. In this manner, the chamber  13  is continuously pressurized at an approximately constant pressure. Instead of atmospheric pressure, the chamber  13  can optionally also be pressurized at another pressure, for example at the pressure of another compartment of the internal combustion engine or of the vehicle. If the pressure in the line  2  increases, a smaller pressure difference between the pressure in the chamber  13  and the pressure in the line  2  is exerted on the membrane. The spring  15  thus moves the membrane  11  and also the valve body  12  upward and opens the pressure regulator valve  10 . However, if a high vacuum is present in the line  2 , for example on account of a high vacuum in the intake tract of the internal combustion engine, the pressure difference across the membrane  11  counteracts the force of the spring  15  and the valve body is moved downward so that the pressure regulator valve reduces the gas path from the inlet side  3  to the outlet side  4  of the line  2 . Simultaneously, however, the bias on the valve body  22  of the bypass valve  20  increases, which means that the bypass valve is closed more firmly. In that case, a greater pressure drop across the oil mist separator elements  5   a  to  5   d  is necessary to open the bypass valve. Thus the higher vacuum that is present is utilized for an effective oil mist separation. 
   In the example of an oil mist separator claimed by the invention illustrated in  FIG. 1 , the spring  15  which creates the bias of the pressure regulator valve  10  is simultaneously used as the spring  25  to apply a bias to the bypass valve  20 . The spring  15 ,  25  is therefore supported on one hand in bearings  17   a  and  17   b  on the bypass valve  20  and on the pressure regulator valve  10 . These bearings therefore represent simultaneously the bearings for the bias springs of the bypass valve  20 , which are provided with their own reference numbers  27   a ,  27   b.    
   Embodiments are also conceivable in which the springs  15  and  25  are separate springs which are mounted in separate bearings  17   a ,  17   b  and  27   a ,  27   b  respectively. In that case, a transmission element is necessary to transmit the closing force of the pressure regulator valve to the bypass valve  20  in the form of a bias. In the illustrated example, the spring  15  or  25  simultaneously performs this transmission function. Progressive springs can also be used as an alternative. 
     FIGS. 2A to 2E  illustrate the same oil mist separator as in  FIG. 1 , but in a side view offset by 90°. 
     FIG. 2A  shows an operating condition in which the vacuum is low at the outlet  4  of the intake pipe vacuum, i.e. in the internal combustion engine. In this case, the pressure regulator valve  10  is opened to the maximum, because the pressure in the line  2  is approximately equal to the atmospheric outside pressure. 
   In the operating condition illustrated in  FIG. 2A , the blow-by flow is also low, so that the pressure drop across the oil mist separator elements  5   a  to  5   d , which are not shown here in any further detail, is also small. The bias of the spring  15  or  25  is in this case sufficient to both open the pressure regulator valve  10  to the maximum and to completely close the bypass valve  20 . 
     FIG. 2B  shows an operating condition in which the intake pipe vacuum is low, but there is a very large blow-by flow. In this case, the pressure drop across the oil separator elements  5   a  to  5   d  is very large, so that a complete ventilation of the crankcase via the oil mist separator elements  5   a  to  5   d  would no longer be guaranteed. In this case, the pressure regulator valve  10  is also fully open, and the bypass valve  20  is also opened so that the crankcase gases (blow-by gases) can flow from the inlet side  3  to the outlet side  4  of the line  2  with a small pressure drop. 
     FIG. 2C  illustrates an operating condition in which the intake pipe vacuum, i.e. the vacuum at the outlet  4 , is very high, while the blow-by gas flow is low. To avoid the complete evacuation of the crankcase, in this operating condition the pressure regulator valve  10  is closed as far as possible, so that a large pressure drop occurs across the opening  16  of the pressure regulator valve  10 . The intake pipe vacuum is therefore not transmitted in full to the crankcase, as a result of which there is a limited ventilation of the crankcase via the oil mist separator elements  5   a  to  5   d . As a result of the closing of the pressure regulator valve  10 , the spring  15 ,  25  is compressed so that the bias on the bypass valve  20  increases. The bypass valve  20  therefore remains securely closed. 
     FIG. 2D  shows an operating condition in which both the intake pipe vacuum and the blow-by gas flow are high. In this case, on account of the high intake pipe vacuum, the pressure regulator valve is closed (although not completely sealed), so that a reduced vacuum is present at the crankcase. On account of the high blow-by gas flow, however, there is a large pressure drop across the oil mist separator elements  5   a  to  5   d , so that the bypass valve  20  is still slightly open. In this manner, by means of the valve opening  26  of the bypass valve  20 , a connection is created between the uncleaned gas in the crankcase and the clean gas at the outlet  4  of the line  2 . 
   If an additional oil mist separator element is located in the bypass line, there is also at least a partial or preliminary separation of oil droplets or oil mist in the bypass line  6 . 
     FIG. 2E  illustrates the case in which the intake pipe vacuum is high and the blow-by gas flow also reaches unallowably high values. In this case, the pressure regulator valve is closed and the bypass valve  20  is simultaneously open. As a result of the opening of the bypass valve  20 , on the other hand, the pressure regulator valve is held in a somewhat opened position, because the force of the bypass valve  20 , via the spring  15 ,  25 , is transmitted in the form of an opening force to the pressure regulator valve  10 . Consequently, on one hand the blow-by flow is securely sucked out and on the other hand the pressure regulator valve is held sufficiently open to utilize the high intake pipe vacuum for at least partial ventilation of the crankcase. 
   This invention therefore makes available an oil mist separator in which both a total evacuation of the crankcase at a high vacuum and an inflation of the crankcase when there is a high blow-by gas flow are reliably prevented. Different tensions are applied to the spring of the pressure regulator valve as a result of the different membrane positions of the pressure regulator valve. This bias varies precisely in the direction in which the bias of a bypass valve is to be varied to achieve the advantages described above. In the above example, the bypass valve is installed directly next to—given an installation situation with the illustrated inclination—and underneath the spring for the bias of the membrane position of the pressure regulator valve, and for its part is biased in the closing direction by the same spring. Thus the advantages of the pressure regulator valve and of the bypass valve are realized in a single arrangement with a minimum number of components. The switch point of the two valves can therefore be influenced and/or determined by the coordination of the surface areas of the intake pipe, the bypass valve, the membrane characteristics (active surface area, thickness, material, shape, stiffness) and the strength of the spring. 
   In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.