Internal combustion engine

The invention relates to an internal combustion engine (1), in particular in a motor vehicle, having a fresh air system (3) for supplying fresh air, which is extracted from the environment (20) of the internal combustion engine (1), to combustion chambers (13) of the internal combustion engine (1), and having a degassing system (5) for discharging blowby gas from a crankcase (6) of the internal combustion engine (1) and for supplying the blowby gas to the fresh air of the fresh air system (3). Furthermore, the degassing system (5) has an oil separator (35) for removing oil from the blowby gas. In order to improve the performance of the oil separator (35), a vacuum opening valve (37) is connected to the crankcase (6). Said vacuum opening valve (37) opens as a function of a vacuum prevailing in the crankcase (6), and then permits an inflow of fresh air into the crankcase (6).

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.

According toFIG. 1, an internal combustion engine1, preferably installed in a motor vehicle, comprises an engine block2, a fresh air system3, an exhaust system4and a degassing system5. The engine block2is designed in the usual manner and comprises a crankcase6, a cylinder head7and a rocker cover8. A crankshaft9is arranged in the crankcase6and drives connecting rods11via connectors10and by means of them drives pistons12in a variable stroke process in the respective cylinders13. In the simplified sectional view shown here, only one piston12can be seen in the respective cylinder13. Intake valves14and exhaust valves15are indicated symbolically. Lubrication of the crankcase9and the other movable components10through12is accomplished in the crankcase6. In doing so, an oil sump16develops in the crankcase6. The lower area of the crankcase6where the oil sump16develops is also referred to as the oil pan17. To be able to add fresh oil to the crankcase6, the engine block2is also equipped with an oil filling connection18, which is usually sealed with an oil filling cover19.

The fresh air system3serves to take in fresh air from the environment20of the internal combustion engine1to supply this fresh air to combustion chambers of the internal combustion engine1, i.e., to the cylinders13. To do so, the fresh air system3comprises a fresh air line21in which an air filter22is usually arranged. A hot film meter23, for example, may be arranged downstream from the air filter22to determine the amount of fresh air intake.

The preferred embodiment of the internal combustion engine1shown here, which is designed as a diesel engine or a gasoline engine or a natural gas engine, for example, is also equipped with a charger24, which serves to charge the fresh air intake. In this example, it is a turbocharger24, which comprises a turbine25and a compressor27connected thereto via a common drive shaft26. Said compressor27is situated in the fresh air line21and leads to the desired compression of the fresh air intake. Downstream from the compressor27, a charge air cooler28may be arranged in the fresh air line21.

The exhaust system4serves to remove exhaust gases from the internal combustion engine1from their cylinders and/or combustion chambers13. To do so, the exhaust system4comprises an exhaust line29in which the turbine25is arranged. Downstream from the turbine25the exhaust line29may contain the usual equipment for exhaust gas purification and noise abatement.

In the example shown here, the internal combustion engine1is also equipped with an exhaust gas recirculation system30which recycles exhaust gas from the exhaust gas line29through an exhaust gas cooler32into the fresh air line21with the help of an exhaust gas recirculation line31.

The degassing system5serves to remove blow-by gas from the crankcase6and add it to the fresh air of the fresh air system3. To do so, the degassing system5comprises a blow-by gas line33which is connected at one end to the crankcase6and at the other end to the fresh air line21at a connection point34. An oil separator35which may be designed in the manner of a cyclone, for example, is arranged in the blow-by gas line33. The oil separator35serves 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 crankcase6, preferably to the oil sump16with the help of a return line36.

According to this invention, the internal combustion engine1is also equipped with a vacuum opening valve37. The vacuum opening valve37is designed so that it opens depending on a vacuum prevailing in the crankcase3, and in the open position it allows fresh air to flow into the crankcase6from the environment20. To do so, the vacuum opening valve37is connected to the crankcase6via a connection site38. Due to the inventive design, the entire vacuum prevailing in the fresh air line21can be used more or less to generate a pressure difference between an inlet39and an outlet40of the oil separator35. Ultimately—apart from flow losses of the blow-by gas line33—the entire pressure difference between the pressure prevailing in the crankcase6and the pressure prevailing in the fresh air line21is available between the inlet39and the outlet40of the oil separator35. If the oil separator35operates passively and is driven by the pressure difference prevailing between the inlet39and outlet40, this yields an especially high efficiency and cleaning effect for the oil separator35. In addition, a pressure difference can be established continuously between the inlet39and outlet40during operation of the internal combustion engine1, so that the oil separator35constantly draws blow-by gas out of the crankcase6and sends it to the fresh air line21. An increase in pressure in the crankcase6and thus the risk of damage to the internal combustion engine1due to excess pressure can therefore be effectively prevented.

For the special case when the degassing system5is not functioning, e.g., when the blow-by gas line33is clogged, in particular due to ice in the area of the connection34, an excess pressure may build up in the crankcase6. In order for this excess pressure not to result in damage to the engine block2, in addition to the vacuum opening valve37, a pressurized opening valve51may also be provided. The pressurized opening valve51is connected directly or indirectly to the crankcase6and is designed so that it opens as a function of an excess pressure prevailing in the crankcase6and allows blow-by gas to flow out of the crankcase6, e.g., into the environment20. In the embodiment shown inFIG. 1, the pressurized opening valve51is integrated into the vacuum opening valve37.

The increased efficiency of the oil separator35is made possible by the vacuum opening valve37situated outside of and/or independently of the blow-by gas line33. Whereas the blow-by gas line33ensures that a critical excess pressure cannot build up in the crankcase6, the vacuum opening valve37ensures that no critical vacuum can build up in the crankcase6. Because the vacuum opening valve37allows the aeration of the crankcase6with fresh air from the environment20as a function of the vacuum prevailing in the crankcase6. A drop in the pressure in the crankcase6into critical vacuum ranges may thus be effectively prevented.

An air filter42is preferably arranged in a flow path41leading from the environment20through the vacuum opening valve37to the crankcase6. In comparison with the air filter22arranged in the fresh air line21, the air filter42arranged in said flow path41is small. The small air filter42cleans the fresh air intake from the environment20and reduces the risk of contamination of the crankcase6and/or the oil lubricant. The small air filter42is preferably arranged upstream from the vacuum opening valve37in the flow path41so that the vacuum opening valve37is protected from contamination. It is likewise basically possible for the small air filter42to be arranged downstream from the vacuum opening valve37. Furthermore, an integral design is possible in which the small air filter42is arranged in a housing of the vacuum opening valve37.

With the pressurized opening valve51, which is integrated into the vacuum opening valve37, the flow path41is at the same time utilized to remove the blow-by gas from the crankcase6when there is an excess pressure in the crankcase6. It may be expedient here to provide an activated carbon filter52in the flow path41to adsorb the contaminants entrained in the blow-by gas so that essentially only noncritical gas enters the environment20. It is especially advantageous here to integrate said activated carbon filter52into the small air filter42. In subsequent normal operation, i.e., when supplying fresh air from the environment20through the vacuum opening valve37into the crankcase6, the activated carbon filter52is 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 path41to the fresh air line21of the fresh air system3, namely upstream from a throttle site and downstream from a filter site. The throttle site is usually formed by an intake throttle50situated in the fresh air line21, a so-called throttle valve. The filter site is usually formed by the air filter22and/or by the air filter element arranged in the air filter22.

The connection site38by which the vacuum opening valve37is connected to the crankcase6may be in general an opening formed on the engine block2which communicates with the crankcase6and is also labeled as38below. In the example shown here, said opening38is formed directly on the crankcase6. It is likewise possible to form said opening38on the cylinder head7or on the rocker cover8. In addition, it is conceivable for the vacuum opening valve37to be connected to said opening38via a connecting line (not shown). However, a design in which the vacuum opening valve37is mounted directly on the engine block2and is inserted directly into the respective opening38accordingly, in particular being screwed in place there, is preferred.

In an especially advantageous embodiment (not shown here), the vacuum opening valve37may be formed on the oil filling cover19and/or may be integrated into the oil filling cover19. For example, said opening38may be situated in the oil filling cover19. If a small air filter42is provided, this is then in or on the oil filling cover19.

According toFIGS. 2 and 3, the vacuum opening valve37comprises a housing43with an inlet opening44and an outlet opening45. In the example shown here, the small filter42is situated in the housing43. The small filter42is in a flow path connecting the inlet opening44to the outlet opening45. For example, the small air filter42is designed as a ring filter element. The housing43may be sealed with a cover46which makes it possible to replace the small air filter42. AsFIGS. 2aand2bindicate, the vacuum opening valve37may be screwed into the opening38.

The vacuum opening valve37contains a valve member47in the form of a plate, for example. In the embodiment according toFIGS. 2aand2b, the valve member47controls the outlet opening45. In contrast with that, the valve member47in the embodiment according toFIG. 3controls the inlet opening44. To prestress the valve member47into a closed position in which it seals off the respective opening44or45, a closing pressure spring48may be provided. In the embodiment shown inFIG. 3, a final control element49is also shown, which may be present additionally or as an alternative to the closure pressure spring48. The control element49may 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 valve37may be connected to a vehicle electric system, for example, which performs an on-board diagnosis of the degassing system5. The prevailing switch setting and/or valve setting of the vacuum opening valve37can be determined via the state of the control element49and this setting in turn provides information about the fresh air stream currently being supplied to the crankcase6.

According toFIG. 2aandFIG. 3, the valve member47and thus the vacuum opening valve37have a closed position in which no fresh air flows through the respective opening44or45. If a predetermined vacuum develops in the crankcase6, this leads to an opening movement of the valve member47against the closing force of the closing pressure spring48. According toFIG. 2b, the valve member47and/or the vacuum opening valve37has an open position in which the respective opening44and/or45is opened and allows aeration of the crankcase6with fresh air.

In a simple embodiment, the vacuum opening valve37is designed so that it opens at a predetermined vacuum prevailing in the crankcase6and closes at any pressure higher than that. It is clear here that the vacuum opening valve37opens more strongly, the further the pressure in the crankcase6drops below the predetermined vacuum, depending on the design. By opening the vacuum opening valve37, fresh air flows into the crankcase6, which leads to an equalization of pressure, so that the pressure in the crankcase6again rises above the predetermined vacuum.

In another more complex embodiment (not shown here), the vacuum opening valve37may also be designed in such a way that it opens with a first opening cross section at a predetermined first vacuum in the crankcase6and 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 valve37closes 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 crankcase6for especially frequent operating states of the internal combustion engine1with a low or moderate load. In extraordinary operating states, preferably at full load, it may be necessary to increase the aeration of the crankcase6, to which end the second larger opening cross section is released.

In an alternative embodiment, the vacuum opening valve37may also be designed so that it is open constantly with a first opening cross section at all pressures in the crankcase6which 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 crankcase6. Only when the pressure in the crankcase6drops below the predetermined vacuum is the required greater aeration, e.g., at full load of the internal combustion engine1, ensured through activation of the larger second opening cross section.