Patent Publication Number: US-7913676-B2

Title: Internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Stage application which claims the benefit of International Application No. PCT/DE2006/002166 filed Dec. 6, 2006, which claims priority based on German Patent Application No. DE 10 2005 059 668.1, filed Dec. 12, 2005, both of which are hereby incorporated by reference in their entirety. 
     The present invention relates to an internal combustion engine, in particular in a motor vehicle. 
     An internal combustion engine usually comprises a fresh air system for supplying fresh air extracted from the environment of the internal combustion engine to combustion chambers of the internal combustion engine. During operation of the internal combustion engine, so-called blow-by gas can enter a crankcase of the internal combustion engine due to leakage of the pistons moving in the cylinders of the internal combustion engine. 
     Modern internal combustion engines are equipped with a degassing system, which serves to remove blow-by gas from the crankcase and to add the blow-by gas to the fresh air of the fresh air system. The blow-by gas removed from the crankcase may contain oil, for example, in the form of an oil mist, which is formed during operation in the crankcase. In order for this oil not to enter the fresh air and in order to reduce the oil consumption of the internal combustion engine, it is customary to provide an oil separator in the degassing system to remove oil from the blow-by gas. The separated oil is preferably recycled back to an oil sump of the crankcase. In the case of passive oil separators such as cyclones, the driving force for the separation of oil from the blow-by gas is the pressure difference made available between an inlet and an outlet of the oil separator; the greater this pressure difference, the better the oil separation functions. 
     In order for the vacuum prevailing in the fresh air system not to be able to spread into the crankcase, which would lead to damage to the internal combustion engine, it is fundamentally possible to equip the degassing system with a pressure-regulating valve which is arranged upstream or downstream from the oil separator in the blow-by gas path. Blow-by gas can then be removed from the crankcase only at a predetermined pressure. The disadvantage here is that such a pressure-regulating valve necessarily has a flow resistance which leads to a pressure drop in flow through the pressure-regulating valve. This pressure drop reduces the pressure difference that can be applied between the inlet and outlet of the oil separator and thereby reduces its cleaning effect. 
     This is where the present invention begins. The invention relates to the problem of providing an improved embodiment for an internal combustion engine of the type defined in the preamble, which is characterized in particular by an improved cleaning effect of the oil separator. 
     This problem is solved according to this invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims. 
     The present invention is based on the general idea of connecting a vacuum opening valve, which opens as a function of the vacuum prevailing in the crankcase, to the crankcase. The opened vacuum opening valve allows fresh air to flow in, e.g., from the environment into the crankcase and thereby prevents a further pressure drop in the crankcase. Accordingly, the vacuum opening valve prevents damage to the internal combustion engine due to an excessive vacuum in the crankcase. This advantageous effect of the vacuum opening valve results in the fact that a pressure-regulating valve in the blow-by gas path may be omitted. Subsequently, this also eliminates the pressure drop in flow through such a pressure-regulating valve, so that a greater pressure difference can be made available between the inlet and outlet of the oil separator, which improves the cleaning effect of the oil separator. In addition, during operation of the internal combustion engine a pressure difference may be continuously applied between the inlet and outlet of the oil separator, thereby permitting continuous operation of the oil separator and continuous removal of the blow-by gas. 
     In a preferred embodiment, an air filter may be provided in a flow path carrying fresh air through the vacuum opening valve into the crankcase. Due to this design, the fresh air intake from the environment into the crankcase is filtered, thereby preventing contamination of the oil lubricant in the crankcase. 
     Said air filter may expediently be integrated into the vacuum opening valve. With this design, the air filter and the vacuum-regulating valve are accommodated in a common housing, so that this is a compact module. 
     Essentially, the vacuum opening valve may be installed in any location. For example, a corresponding connecting line can connect the vacuum opening valve to an opening of the internal combustion engine which communicates with the crankcase. However, it is especially advantageous to insert the vacuum opening valve directly into said opening, so that this yields an extremely compact design. 
     In an especially advantageous embodiment, the vacuum opening valve may optionally be designed together with the air filter on an oil filling cover of the internal combustion engine or integrated into such an oil filling cover. The oil filling cover thereby has an additional functionality, whereby at the same time the require installation space for installing the vacuum opening valve is reduced. In addition, the invention can thereby be retrofitted especially easily. 
     Additional important features and advantages of the invention are derived from the subclaims, the drawings and the respective description of the figures on the basis of the drawings. 
     It is self-evident that the features described above and those yet to be explained below may be used not only in the particular combination given but also in other combinations or alone without going beyond the scope of the present invention. 
    
    
     
       Preferred exemplary embodiments of the invention are depicted in the drawings and are described in greater detail in the following description, where the same reference numerals are used to refer to the same or similar or functionally identical components. 
       They each show schematically 
         FIG. 1  a schematic diagram like a wiring diagram of an internal combustion engine, 
         FIG. 2   a  a greatly simplified schematic longitudinal section through a vacuum opening valve in its closed position, 
         FIG. 2   b  a view like that in  FIG. 2   a  but with the vacuum opening valve in its open position, 
         FIG. 3  a greatly simplified schematic longitudinal section through a vacuum opening valve in another embodiment. 
     
    
    
     According to  FIG. 1 , an internal combustion engine  1 , preferably installed in a motor vehicle, comprises an engine block  2 , a fresh air system  3 , an exhaust system  4  and a degassing system  5 . The engine block  2  is designed in the usual manner and comprises a crankcase  6 , a cylinder head  7  and a rocker cover  8 . A crankshaft  9  is arranged in the crankcase  6  and drives connecting rods  11  via connectors  10  and by means of them drives pistons  12  in a variable stroke process in the respective cylinders  13 . In the simplified sectional view shown here, only one piston  12  can be seen in the respective cylinder  13 . Intake valves  14  and exhaust valves  15  are indicated symbolically. Lubrication of the crankcase  9  and the other movable components  10  through  12  is accomplished in the crankcase  6 . In doing so, an oil sump  16  develops in the crankcase  6 . The lower area of the crankcase  6  where the oil sump  16  develops is also referred to as the oil pan  17 . To be able to add fresh oil to the crankcase  6 , the engine block  2  is also equipped with an oil filling connection  18 , which is usually sealed with an oil filling cover  19 . 
     The fresh air system  3  serves to take in fresh air from the environment  20  of the internal combustion engine  1  to supply this fresh air to combustion chambers of the internal combustion engine  1 , i.e., to the cylinders  13 . To do so, the fresh air system  3  comprises a fresh air line  21  in which an air filter  22  is usually arranged. A hot film meter  23 , for example, may be arranged downstream from the air filter  22  to determine the amount of fresh air intake. 
     The preferred embodiment of the internal combustion engine  1  shown here, which is designed as a diesel engine or a gasoline engine or a natural gas engine, for example, is also equipped with a charger  24 , which serves to charge the fresh air intake. In this example, it is a turbocharger  24 , which comprises a turbine  25  and a compressor  27  connected thereto via a common drive shaft  26 . Said compressor  27  is situated in the fresh air line  21  and leads to the desired compression of the fresh air intake. Downstream from the compressor  27 , a charge air cooler  28  may be arranged in the fresh air line  21 . 
     The exhaust system  4  serves to remove exhaust gases from the internal combustion engine  1  from their cylinders and/or combustion chambers  13 . To do so, the exhaust system  4  comprises an exhaust line  29  in which the turbine  25  is arranged. Downstream from the turbine  25  the exhaust line  29  may contain the usual equipment for exhaust gas purification and noise abatement. 
     In the example shown here, the internal combustion engine  1  is also equipped with an exhaust gas recirculation system  30  which recycles exhaust gas from the exhaust gas line  29  through an exhaust gas cooler  32  into the fresh air line  21  with the help of an exhaust gas recirculation line  31 . 
     The degassing system  5  serves to remove blow-by gas from the crankcase  6  and add it to the fresh air of the fresh air system  3 . To do so, the degassing system  5  comprises a blow-by gas line  33  which is connected at one end to the crankcase  6  and at the other end to the fresh air line  21  at a connection point  34 . An oil separator  35  which may be designed in the manner of a cyclone, for example, is arranged in the blow-by gas line  33 . The oil separator  35  serves to remove oil entrained, e.g., in the form of droplets or mist, in the blow-by gas from the blow-by gas. The separated oil can be recycled back to the crankcase  6 , preferably to the oil sump  16  with the help of a return line  36 . 
     According to this invention, the internal combustion engine  1  is also equipped with a vacuum opening valve  37 . The vacuum opening valve  37  is designed so that it opens depending on a vacuum prevailing in the crankcase  3 , and in the open position it allows fresh air to flow into the crankcase  6  from the environment  20 . To do so, the vacuum opening valve  37  is connected to the crankcase  6  via a connection site  38 . Due to the inventive design, the entire vacuum prevailing in the fresh air line  21  can be used more or less to generate a pressure difference between an inlet  39  and an outlet  40  of the oil separator  35 . Ultimately—apart from flow losses of the blow-by gas line  33 —the entire pressure difference between the pressure prevailing in the crankcase  6  and the pressure prevailing in the fresh air line  21  is available between the inlet  39  and the outlet  40  of the oil separator  35 . If the oil separator  35  operates passively and is driven by the pressure difference prevailing between the inlet  39  and outlet  40 , this yields an especially high efficiency and cleaning effect for the oil separator  35 . In addition, a pressure difference can be established continuously between the inlet  39  and outlet  40  during operation of the internal combustion engine  1 , so that the oil separator  35  constantly draws blow-by gas out of the crankcase  6  and sends it to the fresh air line  21 . An increase in pressure in the crankcase  6  and thus the risk of damage to the internal combustion engine  1  due to excess pressure can therefore be effectively prevented. 
     For the special case when the degassing system  5  is not functioning, e.g., when the blow-by gas line  33  is clogged, in particular due to ice in the area of the connection  34 , an excess pressure may build up in the crankcase  6 . In order for this excess pressure not to result in damage to the engine block  2 , in addition to the vacuum opening valve  37 , a pressurized opening valve  51  may also be provided. The pressurized opening valve  51  is connected directly or indirectly to the crankcase  6  and is designed so that it opens as a function of an excess pressure prevailing in the crankcase  6  and allows blow-by gas to flow out of the crankcase  6 , e.g., into the environment  20 . In the embodiment shown in  FIG. 1 , the pressurized opening valve  51  is integrated into the vacuum opening valve  37 . 
     The increased efficiency of the oil separator  35  is made possible by the vacuum opening valve  37  situated outside of and/or independently of the blow-by gas line  33 . Whereas the blow-by gas line  33  ensures that a critical excess pressure cannot build up in the crankcase  6 , the vacuum opening valve  37  ensures that no critical vacuum can build up in the crankcase  6 . Because the vacuum opening valve  37  allows the aeration of the crankcase  6  with fresh air from the environment  20  as a function of the vacuum prevailing in the crankcase  6 . A drop in the pressure in the crankcase  6  into critical vacuum ranges may thus be effectively prevented. 
     An air filter  42  is preferably arranged in a flow path  41  leading from the environment  20  through the vacuum opening valve  37  to the crankcase  6 . In comparison with the air filter  22  arranged in the fresh air line  21 , the air filter  42  arranged in said flow path  41  is small. The small air filter  42  cleans the fresh air intake from the environment  20  and reduces the risk of contamination of the crankcase  6  and/or the oil lubricant. The small air filter  42  is preferably arranged upstream from the vacuum opening valve  37  in the flow path  41  so that the vacuum opening valve  37  is protected from contamination. It is likewise basically possible for the small air filter  42  to be arranged downstream from the vacuum opening valve  37 . Furthermore, an integral design is possible in which the small air filter  42  is arranged in a housing of the vacuum opening valve  37 . 
     With the pressurized opening valve  51 , which is integrated into the vacuum opening valve  37 , the flow path  41  is at the same time utilized to remove the blow-by gas from the crankcase  6  when there is an excess pressure in the crankcase  6 . It may be expedient here to provide an activated carbon filter  52  in the flow path  41  to adsorb the contaminants entrained in the blow-by gas so that essentially only noncritical gas enters the environment  20 . It is especially advantageous here to integrate said activated carbon filter  52  into the small air filter  42 . In subsequent normal operation, i.e., when supplying fresh air from the environment  20  through the vacuum opening valve  37  into the crankcase  6 , the activated carbon filter  52  is regenerated by the fact that the fresh air resorbs the contaminants deposited there again. 
     In an alternative embodiment, it is possible to connect the flow path  41  to the fresh air line  21  of the fresh air system  3 , namely upstream from a throttle site and downstream from a filter site. The throttle site is usually formed by an intake throttle  50  situated in the fresh air line  21 , a so-called throttle valve. The filter site is usually formed by the air filter  22  and/or by the air filter element arranged in the air filter  22 . 
     The connection site  38  by which the vacuum opening valve  37  is connected to the crankcase  6  may be in general an opening formed on the engine block  2  which communicates with the crankcase  6  and is also labeled as  38  below. In the example shown here, said opening  38  is formed directly on the crankcase  6 . It is likewise possible to form said opening  38  on the cylinder head  7  or on the rocker cover  8 . In addition, it is conceivable for the vacuum opening valve  37  to be connected to said opening  38  via a connecting line (not shown). However, a design in which the vacuum opening valve  37  is mounted directly on the engine block  2  and is inserted directly into the respective opening  38  accordingly, in particular being screwed in place there, is preferred. 
     In an especially advantageous embodiment (not shown here), the vacuum opening valve  37  may be formed on the oil filling cover  19  and/or may be integrated into the oil filling cover  19 . For example, said opening  38  may be situated in the oil filling cover  19 . If a small air filter  42  is provided, this is then in or on the oil filling cover  19 . 
     According to  FIGS. 2 and 3 , the vacuum opening valve  37  comprises a housing  43  with an inlet opening  44  and an outlet opening  45 . In the example shown here, the small filter  42  is situated in the housing  43 . The small filter  42  is in a flow path connecting the inlet opening  44  to the outlet opening  45 . For example, the small air filter  42  is designed as a ring filter element. The housing  43  may be sealed with a cover  46  which makes it possible to replace the small air filter  42 . As  FIGS. 2   a  and  2   b  indicate, the vacuum opening valve  37  may be screwed into the opening  38 . 
     The vacuum opening valve  37  contains a valve member  47  in the form of a plate, for example. In the embodiment according to  FIGS. 2   a  and  2   b , the valve member  47  controls the outlet opening  45 . In contrast with that, the valve member  47  in the embodiment according to  FIG. 3  controls the inlet opening  44 . To prestress the valve member  47  into a closed position in which it seals off the respective opening  44  or  45 , a closing pressure spring  48  may be provided. In the embodiment shown in  FIG. 3 , a final control element  49  is also shown, which may be present additionally or as an alternative to the closure pressure spring  48 . The control element  49  may be designed as a snap switch, for example, may be operable electrically or pneumatically and may allow an electronic state query in particular. In this way, the vacuum opening valve  37  may be connected to a vehicle electric system, for example, which performs an on-board diagnosis of the degassing system  5 . The prevailing switch setting and/or valve setting of the vacuum opening valve  37  can be determined via the state of the control element  49  and this setting in turn provides information about the fresh air stream currently being supplied to the crankcase  6 . 
     According to  FIG. 2   a  and  FIG. 3 , the valve member  47  and thus the vacuum opening valve  37  have a closed position in which no fresh air flows through the respective opening  44  or  45 . If a predetermined vacuum develops in the crankcase  6 , this leads to an opening movement of the valve member  47  against the closing force of the closing pressure spring  48 . According to  FIG. 2   b , the valve member  47  and/or the vacuum opening valve  37  has an open position in which the respective opening  44  and/or  45  is opened and allows aeration of the crankcase  6  with fresh air. 
     In a simple embodiment, the vacuum opening valve  37  is designed so that it opens at a predetermined vacuum prevailing in the crankcase  6  and closes at any pressure higher than that. It is clear here that the vacuum opening valve  37  opens more strongly, the further the pressure in the crankcase  6  drops below the predetermined vacuum, depending on the design. By opening the vacuum opening valve  37 , fresh air flows into the crankcase  6 , which leads to an equalization of pressure, so that the pressure in the crankcase  6  again rises above the predetermined vacuum. 
     In another more complex embodiment (not shown here), the vacuum opening valve  37  may also be designed in such a way that it opens with a first opening cross section at a predetermined first vacuum in the crankcase  6  and opens with a second opening cross section, which is larger than the first opening cross section, at a predetermined second vacuum which is greater in amount than the first vacuum. The vacuum opening valve  37  closes only in the case of pressures which are above the first vacuum. In this design, only the first opening cross section is needed for aeration of the crankcase  6  for especially frequent operating states of the internal combustion engine  1  with a low or moderate load. In extraordinary operating states, preferably at full load, it may be necessary to increase the aeration of the crankcase  6 , to which end the second larger opening cross section is released. 
     In an alternative embodiment, the vacuum opening valve  37  may also be designed so that it is open constantly with a first opening cross section at all pressures in the crankcase  6  which are above a predetermined vacuum, and at said predetermined vacuum in the crankcase it opens with a second opening cross section, which is greater than the first opening cross section. Thus in this embodiment the first opening cross section is permanently active, regardless of the pressure prevailing in the crankcase  6 . Only when the pressure in the crankcase  6  drops below the predetermined vacuum is the required greater aeration, e.g., at full load of the internal combustion engine  1 , ensured through activation of the larger second opening cross section.