The present invention relates to a crankcase ventilation device for an internal combustion engine with the features of the precharacterizing clause of Claim 1. The invention furthermore relates to an internal combustion engine equipped with a crankcase ventilation device of this type. In addition, the invention relates to a method for ventilating a crankcase of an internal combustion engine.

During the operation of internal combustion engines which are configured as piston engines, exhaust gas, what is referred to as blow-by gas, passes out of the combustion chambers into the crankcase because of unavoidable leakages between cylinders and pistons. In order to avoid an impermissible positive pressure in the crankcase, it is customary to remove the blow-by gas, what is referred to as crankcase ventilation. An oil mist prevails in the crankcase, and therefore the blow-by gas removed from the crankcase contains oil in the form of small oil droplets. To reduce the oil consumption, it is customary to separate the oil entrained in the blow-by gas and to guide same back to the oil circuit. The separated-off oil is customarily supplied to an oil pan which adjoins the crankcase at the bottom.

A crankcase ventilation device of the type in question is known, for example, from DE 20 2005 003 462 Ul. It comprises a blow- by gas path for guiding blow-by gas, and also an oil-separating device which is arranged in the blow-by gas path and has an oil separator for separating off oil entrained in the blow-by gas.

In order to configure a crankcase ventilation device of this type to be as reasonably priced as possible, use may be made of passive inertial separators, such as, for example, cyclones or impacters. The efficiency in respect of the separating-off effect of passive inertial separators of this type depends, inter alia, on the flow rate at which the blow-by gas flows through the inertial separator. Inertial separators of this type operate with a pronounced deflection of the flow of blow-by gas laden with the oil. While the blow-by gas can easily follow said flow deflection, the impurities entrained therein, i.e. primarily the oil droplets, are deflected, and therefore they can impact, for example, against a stationary wall and can remain stuck thereto, and can accumulate and flow off.

Very high degrees of separation can be realized at high flow rates. A disadvantage of passive inertial separators of this type is the fact that the internal combustion engine can entirely also have operating states in which only comparatively little blow-by gas arises, and therefore ultimately the flow rate in the blow-by gas is comparatively small. In order to provide a remedy here, use may basically be made of active inertial separators, such as, for example, a plate separator, which, in contrast to passive inertial separators, are equipped with rotating walls. The crankcase ventilation can also be equipped with a dedicated conveying device for driving the blow-by gas. However, active systems of this type are comparatively expensive.

The present invention is concerned with the problem of specifying an improved embodiment for a crankcase ventilation device of the type mentioned at the beginning and for an internal combustion engine equipped therewith and for a crankcase ventilation method, which embodiment is distinguished in particular in that a high separating-off effect can be realized at low costs. According to the invention, this problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The invention is based on the general concept of cooling the blow-by gas upstream of the oil separator. The invention makes use here of the finding that the temperature of the blow-by gas correlates to the average droplet size of the oil entrained in the blow-by gas, specifically in such a manner that the average droplet size decreases as the temperature increases. Furthermore, the invention makes use of the finding that the separating-off effect of an inertial separator, besides depending on the flow rate, also depends significantly on the average droplet size of the oil to be separated off. Larger droplets can more easily be separated off than smaller droplets even at low flow rates. The invention therefore proposes to increase the average droplet size by lowering the temperature of the blow-by gas, which leads to the larger droplets being able to be separated off with great efficiency in the downstream oil separator even at low flow rates. As a result, the blow-by gas removed from the crankcase can be efficiently separated off in the respective oil separator without great additional costs. The improved separating-off effect is basically independent here of the type of the respective oil separator. For example, even in the case of an active inertial separator, an improved separating- off effect arises by the cooling of the blow-by gas. Even when an additional conveying device is used for driving the blow-by gas, an improved separating-off effect can be seen at the respective separator. However, the present invention is of particular advantage in a passive inertial separator since the high separating-off effect can be realized particularly simply there at low costs. The crankcase ventilation device according to the invention therefore comprises a cooling device for cooling the blow-by gas upstream of the oil separator. That is to say, the blow-by gas is cooled upstream of the oil separator, and / or the cooler is arranged in the flow of the blow-by gas upstream of the oil separator.

According to an advantageous embodiment, this cooling device can have a mixing chamber which has a blow-by gas inlet for supplying the blow- by gas to the mixing chamber, a cooling gas inlet for supplying a cooling gas to the mixing chamber and a blow-by gas outlet for removing cooled blow-by gas from the mixing chamber. The cooled blow-by gas is formed here by a mixture of blow-by gas and cooling gas. In other words, the blow-by gas is cooled by adding cooling gas to the blow-by gas. The cooling of the blow-by gas can therefore be realized at a particularly reasonable price. In addition, this adding of cooling gas to the blow- by gas has the advantage of diluting the blow-by gas to a certain extent, which can already lead to an improved separating-off effect in an inertial separator, for example by the associated increase in the volumetric flow.

As mentioned, the present invention can be realized at reasonable cost if the oil separator is formed by a passive inertial separator. An embodiment in which the oil separator is configured as an impacter which is arranged between an inflow chamber and an outflow chamber is particularly advantageous here.

An impacter of this type has a perforated wall with passage openings, and also an impact wall which, with regard to a flow of gas, in particular blow-by gas, through the impacter, is arranged downstream of the perforated wall. The impacter has the crude gas inlet for gas laden with impurities, in particular with oil, the clean gas outlet for gas freed from impurities, and the oil or dirt outlet for impurities separated off from the gas. When gas flows through the impacter, the gas first of all strikes against the perforated plate and, in the process, is forced to flow through the passage openings in the perforated plate. Since the total of the flow- through cross sections of all of the passage openings is smaller than the flow-through cross section in the impacter directly upstream of the perforated wall, the gas flow is accelerated here and the gas flow is divided up into individual jet-shaped partial flows passing through the passage openings. Said partial flows impact frontally, preferably perpendicularly, onto the impact wall, at which an abrupt flow deflection, generally by approximately 90°, takes place. The gas follows said flow deflection, while the entrained liquid and/or solid impurities are stopped at the impact wall, and therefore the impurities initially remain on the impact wall and are guided, for example, to a collecting chamber which is fluidically connected to the dirt outlet.

For example, the impact wall can be composed of a material which is permeable for the impurities, for example from an open-pore foam or from a nonwoven material. Impact wall and perforated wall are expediently arranged relative to each other in such a manner that there is a distance in the flow direction between the outlet ends of the passage openings and the impact wall. The passage openings can be extended on a side of the perforated wall facing the impact wall by means of pipes in order to improve the formation of the individual jet-shaped partial flows. These pipes also preferably end at a distance from the impact wall.

The inflow chamber is supplied with the oil-laden, i.e. uncleaned blow-by gas, which flows through the impacter and, in the process, is stripped of the oil, and therefore the blow-by gas stripped of the oil passes into the outflow chamber. As a result, the blow-by gas which is freed from oil, i.e. is cleaned, can be removed from the outflow chamber.

According to an advantageous development, the inflow chamber can form the mixing chamber, and therefore the impacter is arranged in the blow- by gas outlet of the mixing chamber. Alternatively thereto, the blow-by gas outlet can fluidically connect the mixing chamber to the inflow chamber. While the first variant is constructed particularly compactly, the second variant is distinguished by improved mixing and therefore by improved cooling of the blow-by gas. In addition, more time is available in the second variant so that the smaller droplets can grow into larger droplets by means of the cooling.

In a development, the blow-by gas outlet can be formed by a perforation in a partition which, in the oil-separating device, separates the mixing chamber from the inflow chamber. In this case, the mixing chamber is integrated in the oil-separating device, and therefore the cooling device is at least partially realized within the oil-separating device.

The internal combustion engine according to the invention has a crankcase in which blow-by gas arises during the operation of the internal combustion engine. Furthermore, the internal combustion engine is equipped with a crankcase ventilation device of the type described above. In addition, the internal combustion engine has a fresh air system for supplying fresh air to combustion chambers of the internal combustion engine. The blow-by gas path of the crankcase ventilation device is preferably connected to the fresh air system, and therefore the cooled and de-oiled blow-by gas can be supplied therein to the fresh air. In an advantageous embodiment, the internal combustion engine is configured as a supercharged internal combustion engine. In this case, the internal combustion engine has a charging device for supercharging the fresh air, i.e. for increasing the pressure in the fresh air, and also a charge air cooler for cooling the supercharged fresh air. The supercharged fresh air is also referred to as charge air. A charging device of this type can be, for example, an exhaust gas turbocharger or a compressor. In addition, the internal combustion engine can be equipped with a cooling gas line which connects the fresh air system downstream of the charge air cooler to the blow-by gas path upstream of the oil separator in such a manner that some of the supercharged and cooled fresh air can be supplied as cooling gas by said cooling gas line to the blow-by gas. In other words, the internal combustion engine which is presented uses some of the cooled charge air as cooling gas for cooling the blow-by gas. Since only comparatively little cooling gas is required, no significant drop in power for the supercharging of the internal combustion engine arises as a result. In addition, the removal of some of the charge air in the case of an exhaust gas turbocharger, the turbine of which is equipped with a variable turbine geometry or with a waste gate valve, can easily be compensated for by appropriate adaptation of the activation, for example by a suitable characteristic map shift.

An embodiment in which the internal combustion engine has a cylinder head and a cylinder head hood, wherein the oil-separating device is arranged in the cylinder head hood, is also advantageous. In particular, the oil-mist-separating device is at least partially integrally formed here on the cylinder head hood. This results in a particularly compact construction for the oil-separating device. The blow-by gas path can expediently now lead from the crankcase through the cylinder head to the cylinder head hood. The blow-by gas path therefore runs as far as the oil- separating device in the interior of the internal combustion engine.

Another embodiment proposes connecting the cooling gas line to the cylinder head hood. In this case, the cooling gas is added to the blow-by gas likewise within the cylinder head hood. In this respect, the cooling device is at least partially integrated in the cylinder head hood. In particular, the cooling device can at least partially form an integral part of the oil-separating device.

The blow-by gas path is expediently connected upstream of the charging device to the fresh air system. If the charging device is configured as an exhaust gas turbocharger, the blow-by gas path is connected to the fresh air system upstream of a compressor, which is connected into the fresh air system, of the exhaust gas turbocharger.

The use of some of the charge air as cooling gas also has the advantage that a significant increase in the pressure and / or the speed of the blow- by gas can be achieved upstream of the oil separator, which, firstly, likewise improves the separating- off effect in the oil separator. Secondly, the recycling of the cleaned blow-by gas to the fresh air system can also be improved as a result.

The method according to the invention for ventilating a crankcase of an internal combustion engine is based on the fact that the blow-by gas which arises in the crankcase is cooled upstream of an oil separator which serves for separating off the oil entrained in the blow-by gas.

An advantageous embodiment proposes that the blow-by gas is cooled upstream of the oil separator in order to increase an average droplet size of the oil entrained in the blow-by gas. In other words, the blow-by gas is cooled in a specific manner with the purpose of increasing the average droplet size of the oil or oil mist before the blow-by gas passes to the oil separator.

A development is particularly advantageous in which the blow-by gas is cooled upstream of the oil separator in such a manner that the average droplet size of the entrained oil increases by at least ten times. For example, an average droplet size of at maximum 1 μπι is present in the uncooled blow- by gas, while an average droplet size of at least 10 μπι arises in the cooled blow-by gas.

An embodiment in which the blow-by gas is cooled in that a cooling gas is supplied to the blow-by gas, and therefore the blow-by gas mixes with the cooling gas, is particularly advantageous. The mixing of the hot blow-by gas with the cold cooling gas results in efficient cooling of the blow-by gas. For example, the uncooled blow-by gas can have a temperature of 100°C ± 10°C. By the addition of a cooling gas, the temperature of which lies, for example, at 40°C ± 10°C, the temperature of the blow-by gas can be significantly reduced. For example, the temperature of the blow-by gas can be reduced by at least a quarter, preferably by at least a third, in each case with respect to °C, and therefore, starting from an initial temperature of, for example, 100°C, a reduction by ¼ corresponds to a reduction by 25°C, thus resulting in a final temperature of 75°C.

The method is preferably carried out in such a manner that a volumetric flow of the cooling gas which is supplied to the blow-by gas is smaller than a volumetric flow of the blow-by gas. Accordingly, only comparatively little cooling gas is required. A development is particularly expedient in which the volumetric flow of the cooling gas is at maximum 75%, but at least 25%, of the volumetric flow of the blow-by gas. Within this range for the volumetric flow of the cooling gas, efficient cooling can be realized by adding the cooling gas to the blow-by gas.

An embodiment in which cooled, supercharged fresh air, i.e. charge air, is used as the cooling gas, is also particularly advantageous for the method presented here. For this purpose, this cooled charge air can expediently be diverted downstream of a charge air cooler. Since most internal combustion engines have been equipped in the meantime with a charging device, charge air is sufficiently available.

An advantageous embodiment proposes that an inertial separator, preferably a passive inertial separator, is used as the oil separator. A passive inertial separator of this type is, for example, an impacter or a cyclone. The separating- off effect of an inertial separator of this type greatly depends on the average droplet size of the oil to be separated off. The separating-off effect is greater, the larger the average droplet size is.

A further embodiment proposes lowering the temperature of the blow-by gas upstream of the oil separator by at least 30% by the cooling, again with reference to °C. This means that uncooled blow-by gas which has, for example, a temperature of 100°C is cooled by at least 30°C, and therefore the cooled blow-by gas then has a temperature of at maximum 70°C.

Further important features and advantages of the invention emerge from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings. It goes without saying that the features mentioned above and those which have yet to be explained below are usable not only in the respectively stated combination, but also in other combinations or by themselves without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the description below, wherein the same reference numbers refer to identical or similar or functionally identical components.

In the drawings, in each case schematically,

Figure 1 shows a greatly simplified schematic illustration in the manner of a circuit diagram of an internal combustion engine which is equipped with a crankcase ventilation device,

Figure 2 shows a greatly simplified schematic illustration in the manner of a circuit diagram of the crankcase ventilation device which is equipped with an oil separator,

Figure 3 shows a greatly simplified schematic illustration in the manner of a circuit diagram of the oil separator.

According to Figure 1, an internal combustion engine 1, which is preferably arranged in a motor vehicle, comprises an engine block 2 which contains at least one cylinder 3 which defines a combustion chamber 4 and in which a piston 5 is arranged so as to be adjustable by a stroke motion. It is clear that the internal combustion engine 1 customarily contains more than one, preferably also more than two cylinders 3 in the engine block 2. The engine block 2 is adjoined at the bottom in Figure 1 by a crankcase 6 while a cylinder head 7 adjoins the engine block 2 at the top. Furthermore, the cylinder head 7 is covered at the top with a cylinder head hood 8. The respective piston 5 is connected in terms of drive via a connecting rod 9 to a crankshaft 10 which is arranged in the crankcase 6. Gas exchange valves 11 for controlling gas exchange operations are customarily located in the cylinder head 7. An oil sump 12 is also contained in the crankcase 6. For example, the crankcase 6 is closed downwards, i.e. on the side facing away from the engine block 2, by an oil pan 13 which customarily accommodates the oil sump 12.

In the example of Figure 1, from the bottom upwards, the oil pan 13, the crankcase 6, the engine block 2, the cylinder head 7 and the cylinder head hood 8 together form a body 50 of the internal combustion engine 1.

The internal combustion engine 1 also has a fresh air system 14 for supplying fresh air to the respective combustion chamber 4, and also an exhaust gas system 15 for removing exhaust gas from the respective combustion chamber 4. In the example, the internal combustion engine 1 is supercharged, and therefore a charging device 16 which is configured here as a turbocharger 17 is provided. The turbocharger 17 has a compressor 18 arranged in the fresh air system 14, and a turbine 19 which is arranged in the exhaust gas system 15 and is connected in terms of drive to the compressor 18 in a suitable manner. The fresh air system 14 contains an air filter 20 for filtering the fresh air sucked up from an environment 25. Furthermore, a charge air cooler 21 is arranged downstream of the compressor 18 in the fresh air system 14 and serves for cooling the air which is compressed with the aid of the compressor 18 or with the aid of the charging device 16 and is also referred to as charge air. For this purpose, the charge air cooler 21 can be coupled to a cooling circuit 22. Furthermore, a throttle device 23 which, in the example, is arranged downstream of the charge air cooler 21 can be arranged in the fresh air system 14. The exhaust gas system 15 contains exhaust gas aftertreatment devices (not shown here), such as, for example, catalytic converters, particle filters and sound absorbers, in a customary manner downstream of the turbine 19.

The internal combustion engine 1 which is presented here is additionally equipped with a crankcase ventilation device 24, with the aid of which blow-by gas which arises in the crankcase 6 during the operation of the internal combustion engine 1 can be removed from the crankcase 6 and preferably supplied to the fresh air system 14. The blow-by gas can also be supplied to the environment 25 of the internal combustion engine 1. The crankcase ventilation device 24 has a blow-by gas path 26 which is indicated in Figure 1 by arrows. In addition, an oil-recycling path 27 is provided which is likewise indicated by means of arrows. The oil- separating device 24 furthermore comprises an oil-separating device 60 for separating off oil entrained in the blow-by gas. For this oil separation from the blow-by gas, the oil- separating device 60 comprises an oil separator 28. The oil-separating device 60 is arranged in the blow-by gas path 26, and therefore a flow of blow-by gas leads through the oil separator 28.

The internal combustion engine 1 which is presented here or the crankcase ventilation device 24 of which is also equipped with a cooling device 29, with the aid of which the blow-by gas can be cooled upstream of the oil separator 28. According to Figure 2, said cooling device 29 can be at least partially integrated in the crankcase ventilation device 24 or in the oil-separating device 60. For this purpose, the cooling device 29 can have, for example, a mixing chamber 30 which has a blow-by gas inlet 31 for supplying the blow-by gas to the mixing chamber 30, a cooling gas inlet 32 for supplying a cooling gas to the mixing chamber 30 and a blow-by gas outlet 33 for removing cooled blow-by gas from the mixing chamber 30. The cooled blow-by gas is formed here by a mixture of blow-by gas and cooling gas. The blow-by gas is therefore cooled by the addition of the cooling gas to the blow-by gas.

The oil separator 28 is preferably configured as an inertial separator. An embodiment in which the oil separator 28 is configured as an impacter 34 is particularly advantageous. The basic construction of an impacter 34 of this type is illustrated in Figure 3. According to Figure 3, the oil separator 28 or the impacter 34 has a crude gas inlet 35 for the purified blow-by gas, a clean gas outlet 36 for cleaned blow-by gas and a dirt outlet 37 for the separated-off oil. The impacter 34 is equipped with a perforated wall or plate 38 which extends completely over the cross section through which the gas flow within the impacter 34 can flow. The perforated plate 38 has a plurality of passage openings 39 which run here perpendicularly to the plane of the perforated plate 38 and pass through the perforated plate 38. Since all of the passage openings 39 together have a common flow-through cross section which is significantly smaller than the flow-through cross section directly upstream of the perforated plate 38, the gas flow flows through the passage openings 39 at an increased speed. In this respect, the passage openings 39 may also be referred to as nozzle openings. Accordingly, the perforated plate 38 may also be referred to as a nozzle plate. In the example, for each passage opening 39, the perforated plate 38 has a pipe segment 40 which extends the respective passage opening 39, i.e. perpendicularly to the plane of the plate. In the example, the pipe segments 40 are arranged on the downstream side. It is also conceivable to form pipe segments 40 of this type on the inflow side of the perforated plate 38.

The impacter 34 has an impact plate or wall 41 spaced apart axially from the perforated plate 38, said impact wall being positioned in such a manner that the gas flows emerging from the individual passage openings 39 impact substantially perpendicularly against the impact wall 41. The gas is greatly deflected in the process while the impurities entrained therein remain stuck to the impact wall 41. The impact wall 41 is expediently also arranged axially spaced apart from the optionally provided pipe segments 40. The impact wall 41 is expediently produced from a material which is permeable for the contaminants. For example, the impact wall 41 is formed by a nonwoven material. The impact wall 41 can likewise be formed by an open-pore foam body. In the example, the impact wall 41 rests on a grid 42. The dynamic pressure arising on the inflow side of the impact wall 41 causes the contaminants which have been separated off on said impact wall to be pressed into the material of the impact wall 41 and to be pressed out of the latter again on the outflow side. By this means, the contaminants pass into a collecting chamber 43 from which they are removed from the impacter 34 via the dirt outlet 37. The dirt outlet 37 can be controlled with a control valve 44, only indicated symbolically here .

Instead of such a grid 42 also an impermeable plate can be used. Said impermeable plate can guide the separated dirt or oil to the collecting chamber 43. In such a case the blow-by gas cannot flow through the impermeable plate but is deviated. In another embodiment the impact wall 41 can be made of an impermeable or porous material. Preferably, the impact wall 41 is formed by a plain plate in particular provided with protrusions. Optionally, on this impact wall 41 a fleece layer can be arranged. In this case, a permeable impact plate 41 is arranged on an impermeable plate supporting the permeable impact wall 41.

In the example of Figure 3, the impacter 34 is configured to be flat, and therefore the perforated plate 38 and the impact plate 41 are in each case flat and are arranged parallel to each other and also next to each other. It is clear that basically also a cylindrical impacter 34 can be realized, in which the perforated wall 38 and the impact wall 41 are cylindrical and are arranged concentrically one in the other.

According to Figures 2 and 3, the impacter 34 separates an inflow chamber 45, to which the unpurified blow-by gas is supplied, from an outflow chamber 46 from which the cleaned blow-by gas can be removed. Since the blow-by gas path 26 leads through the impacter 34, the unpurified blow-by gas is forced to flow through the impacter 34. In the process, the oil entrained in said blow-by gas is separated off.

According to Figure 2, the mixing chamber 30 is connected to the inflow chamber 45 via the blow-by gas outlet 33. In the example shown, the blow-by gas outlet 33 is formed by a perforation 47 in a partition 48 which, within the oil- separating device 60, separates the mixing chamber 30 from the inflow chamber 45. In the example, this perforation 47 is formed by a multiplicity of separate passage openings which penetrate the partition 48. By this means, the mixture of blow-by gas and cooling gas is homogenized in order to optimize the cooling of the blow- by gas. At the same time, the blow-by gas outlet 33 defines a cross-sectional constriction which, in the flow of the blow-by gas, forces the oil droplets entrained therein to be concentrated. This results in an increased droplet density which assists an increase in the droplet size, in particular in conjunction with the reduced temperature.

If, in the example of Figure 2, the partition 48 is left out, the mixing chamber 30 is virtually integrated into the inflow chamber 45, and vice versa. In this case, the oil separator 28 is then arranged in the blow-by gas outlet 33 of the mixing chamber 30.

According to Figures 1 to 3, the blow-by gas path 26 upstream of the oil- separating device 60 leads through a crude gas line 49 which, in the example of Figure 1, runs in the interior of the body 50 of the internal combustion engine 1. The blow-by gas therefore passes along the blow- by gas path 26 from the crankcase 6 through the engine block 2 and through the cylinder head 7 into the cylinder head hood 8.

The blow-by gas path 26 removes the blow-by gas from the oil-separating device 60 through a clean gas line 51 which is connected to the fresh air system 14. According to Figure 1, the clean gas line 21 is preferably connected upstream of the compressor 18 or upstream of the charging device 16 to the fresh air system 14.

The oil-recycling path 27 returns the oil which has been separated off by the oil-separating device 60 through a recycling line 52 to the oil sump 12. In the example of Figure 1, the recycling line 52 runs within the body 50 of the internal combustion engine 1.

A cooling gas path 53 which is indicated by arrows is provided for supplying the cooling gas to the mixing chamber 30. In the example of Figure 1, said cooling gas path 53 leads through a cooling gas line 54. The cooling gas line 54 is connected on the input side to the fresh air system 14 and on the output side to the oil-separating device 60, specifically upstream of the oil separator 28. The configuration which is selected here and in which the cooling gas line 54 is connected downstream of the charge air cooler 21 to the fresh air system 14 is particularly advantageous here. Accordingly, supercharged and cooled fresh air can be supplied as the cooling gas to the blow-by gas.

The oil- separating device 16 is expediently integrated in the cylinder head hood 8. The cooling gas line 54 is then expediently connected to the cylinder head hood 8.

The internal combustion engine 1 presented here and the crankcase ventilation device 24 presented here may be improved with further optional measures which can be realized cumulatively or alternatively or in any desired combination. Measures of this type are, for example, a throttle device 55 which, according to Figure 1, can be arranged in the cooling gas line 54. It is also conceivable to arrange a throttle device 55 of this type in the cooling gas inlet 32 of the mixing chamber 30. The quantity of the supplied cooling gas can be limited to a predetermined limit value with the aid of the throttle device 55.

According to Figure 2, a temperature sensor 56 can be provided in order to determine the temperature of the cooled blow-by gas upstream of the oil separator 28. This temperature sensor 56 is connected here to the inflow chamber 45. By this means, for example, an open-loop control or a closed-loop control can be realized in order to be able to set a target temperature for the cooled blow- by gas. For example, the quantity of the supplied cooling gas can be controlled via a corresponding control device. Additionally or alternatively, the temperature of the uncooled blow-by gas can be determined, for example, via a temperature sensor 57, which is connected to the crude gas line 49, in order to ascertain the requirement for cooling gas from said temperature.

The blow-by gas penetrating into the crankcase 6 from the respective combustion chamber 4 during the operation of the internal combustion engine 1 is indicated by an arrow 58. The removal of the blow-by gas from the crankcase 6 with the aid of the crankcase ventilation device 24 via the blow-by gas path 26 is indicated by an arrow 59 in Figure 1.