Method for monitoring the ventilation of a crankcase of an internal combustion engine, and internal combustion engine

Abstract

The present invention relates to a method for monitoring the ventilation of a crankcase (120) of an internal combustion engine (100), and to an internal combustion engine (100). The internal combustion engine (100) has combustion chambers (110) and a nitrogen oxide sensor (140) which is arranged in the exhaust gas tract (130) of the internal combustion engine (100) and designed to detect the nitrogen oxide content in the exhaust gas of the internal combustion engine (100). The method according to the invention comprises determining a predefined operating mode of the internal combustion engine (100) during which essentially no combustion takes place inside the combustion chambers (110), determining a nitrogen oxide content in the exhaust gas of the internal combustion engine (100) during the predefined operating mode of the internal combustion engine (100) by means of the exhaust gas sensor (140), and determining an operational ventilation of the crankcase (120) if the nitrogen oxide value determined during the predefined operating mode of the internal combustion engine (100) exceeds a predetermined nitrogen oxide threshold value.

Description

[0001] The present invention relates to a method for monitoring the ventilation of a crankcase of an internal combustion engine and to an internal combustion engine, in particular to an internal combustion engine with crankcase ventilation.

[0002] In (piston) internal combustion engines with a closed crankcase, deviations from atmospheric pressure occur not only in the working chambers but also below the pistons. These are caused, on the one hand, by the volume changes caused by the rotating pistons and, on the other hand, by the gases accumulating in the crankcase from the working process.

[0003] In combustion engines, so-called blowby gases always occur in the crankcase. Since the crankcase is a closed space, the pressure would steadily increase without ventilation. To prevent this, the blowby gases, which contain combustion products and unburned hydrocarbons, can be selectively vented from the crankcase. The ideal relative crankcase pressure is in the slightly negative range, around -2 mbar, since under these conditions the engine is not prone to "sweating out" lubricating oil. If the negative pressure is significantly higher (the value is engine-specific and depends on the design of the sealing systems), there is a risk that air contaminated with dirt particles will be drawn in through the shaft seals and gaskets on the crankcase. This would lead to increased wear on internal components. During ventilation, oil droplets generated by rotating components are inevitably entrained from the crankcase.

[0004] During operation of the internal combustion engine, particularly during overrun cut-off phases of the internal combustion engine, high pressure in the intake manifold can cause the gases trapped in the crankcase to at least partially bypass the pistons into the combustion chambers and thus into the exhaust tract.

[0005] The ventilation line can become clogged, torn, or the connection to the intake tract may be missing. This restricts ventilation and allows pollutants from the crankcase to escape into the environment. Therefore, proper functioning of the crankcase ventilation system should be monitored.

[0006] DE 10 2014 218 971 A1 describes a method and systems for humidity and crankcase ventilation detection using an exhaust gas sensor. During selected conditions without fueling the internal combustion engine, the exhaust gas sensor (such as a linear lambda sensor, an HC or CO sensor, or a NOx sensor) can be used for humidity estimation and / or crankcase ventilation estimation (crankcase ventilation hydrocarbons (PCV hydrocarbons)).

[0007] Further prior art includes US 11 047 329 B2, JP 2009 / 174334 A, JP 2006 / 183641 A and US 9 127 578 B2.

[0008] The present invention is essentially based on the object of determining and checking the proper functionality of a crankcase ventilation system of an internal combustion engine in a simple and cost-effective manner.

[0009] This object is achieved by a method according to independent claim 1 and an internal combustion engine according to independent claim 7. Advantageous embodiments are specified in the subclaims.

[0010] The present invention is essentially based on the idea that, during predetermined operating modes during which no combustion of an air-fuel mixture occurs in the combustion chambers of the internal combustion engine, the crankcase ventilation is monitored by means of a nitrogen oxide sensor provided in the exhaust tract of the internal combustion engine. In particular, during the aforementioned predetermined operating modes, the exhaust gases trapped in the crankcase re-enter the combustion chambers and thus the exhaust tract via the ventilation line and / or as so-called blowby exhaust gases, and can thus be detected by the nitrogen oxide sensor arranged in the exhaust tract.If the nitrogen oxide sensor, which is already present and arranged in the exhaust tract, indicates a nitrogen oxide content above a predetermined threshold value during the predetermined operating modes of the internal combustion engine, it can be concluded that the crankcase ventilation system is functioning properly, since the ventilation path from the crankcase into the combustion chambers and thus into the exhaust tract is free and unblocked. However, if the exhaust gas sensor indicates an exhaust gas content below the predetermined threshold value during these predetermined operating modes of the internal combustion engine, it can be concluded that the crankcase ventilation system is not functioning properly. In particular, it can then be determined that the ventilation path from the crankcase into the exhaust tract is at least partially blocked or clogged.

[0011] Consequently, according to a first aspect of the present invention, a method for monitoring the ventilation of a crankcase of an internal combustion engine is disclosed, which has a nitrogen oxide sensor arranged in an exhaust tract of the internal combustion engine, which is designed to detect the nitrogen oxide content in the exhaust gas of the internal combustion engine.The method according to the invention comprises determining a predetermined operating mode of the internal combustion engine during which substantially no combustion of an air-fuel mixture takes place in a combustion chamber, determining a nitrogen oxide content in the exhaust gas of the internal combustion engine during the predetermined operating mode of the internal combustion engine by means of the nitrogen oxide sensor, determining a functional ventilation of the crankcase if the nitrogen oxide value determined during the predetermined operating mode of the internal combustion engine exceeds a predetermined nitrogen oxide threshold value, and determining a malfunctioning ventilation of the crankcase if the nitrogen oxide value determined during the predetermined operating mode of the internal combustion engine falls below the predetermined nitrogen oxide threshold value.

[0012] According to the invention, it is therefore provided that during the predetermined operating mode, such as an overrun fuel cut-off phase of the internal combustion engine, it can be concluded that the crankcase ventilation is functioning properly if a significant amount of nitrogen oxide continues to be detected at the position of the exhaust gas sensor. Furthermore, if the nitrogen oxide value determined during the predetermined operating mode of the internal combustion engine falls below the predetermined nitrogen oxide threshold value, it can be stated that the crankcase ventilation is at least partially or partially clogged or blocked, and consequently, crankcase ventilation can no longer function properly.

[0013] In a particularly preferred embodiment of the method according to the invention, the nitrogen oxide value is determined after a predetermined period of time has elapsed after the predetermined operating mode of the internal combustion engine has been determined. This can ensure, for example, that the exhaust gases generated during the combustion of the air-fuel mixture in the combustion chambers have been completely expelled from the combustion chambers and have already flowed past the nitrogen oxide sensor, so that during the predetermined operating mode, the exhaust gas measured by the nitrogen oxide sensor must originate from the crankcase. The predetermined period of time is preferably approximately 5 seconds, preferably approximately 3 seconds.

[0014] In an alternative embodiment, it may be preferable for the nitrogen oxide value to be determined only when an air mass integral in the exhaust tract exceeds a predetermined air mass integral threshold value. In particular, the time until the nitrogen oxide sensor can measure the exhaust gases originating from the crankcase depends on the mass flow rate and the volume of the exhaust tract. Consequently, in such an alternative embodiment, it is advantageous to determine the nitrogen oxide value only when the air mass integral in the exhaust tract exceeds the predetermined air mass integral threshold value. Furthermore, the nitrogen oxide sensor requires a certain amount of time to stabilize at the nitrogen oxide measured value.

[0015] In a further advantageous embodiment of the method according to the invention, the predetermined operating mode of the internal combustion engine includes an overrun fuel cut-off phase of the internal combustion engine. This is preferably an overrun fuel cut-off phase that directly follows high-load operation of the internal combustion engine. In particular, the amount of nitrogen oxide, i.e., the amount of so-called blowby gas, in the crankcase increases with the higher the load of the internal combustion engine. Accordingly, it may be advantageous to diagnose the crankcase ventilation during an overrun fuel cut-off phase that directly follows high-load operation of the internal combustion engine.

[0016] In an advantageous embodiment, the method preferably further comprises issuing a warning to the operator of the internal combustion engine if a malfunctioning crankcase ventilation system has been detected. According to a particularly advantageous embodiment of the method according to the invention, the predetermined nitrogen oxide threshold value is between approximately 5 ppm [ppm = parts per million] and approximately 20 ppm. The predetermined nitrogen oxide threshold value can preferably be selected depending on the previous load of the internal combustion engine.

[0017] According to a further aspect of the present invention, an internal combustion engine is disclosed which has at least one combustion chamber which is formed by a piston (??) reciprocating back and forth within a cylinder, a crankcase in which the piston is at least partially arranged and which is at least partially fluidly connected to the combustion chamber via a gap between the piston and the cylinder, an exhaust tract which is fluidly connected to the at least one combustion chamber, a nitrogen oxide sensor arranged in the exhaust tract which is designed to detect the nitrogen oxide content in the exhaust gas of the internal combustion engine, and a control unit which is designed to carry out a method according to the invention for monitoring the ventilation of the crankcase.

[0018] Preferably, the internal combustion engine further comprises a catalyst arranged downstream of the nitrogen oxide sensor for aftertreating the exhaust gas.

[0019] In a further advantageous embodiment, the internal combustion engine further comprises an intake pipe which is fluidly connected to the at least one combustion chamber and is designed to supply air to the at least one combustion chamber for the combustion of an air-fuel mixture, and a vent line which fluidly connects the crankcase to the intake pipe.

[0020] Further features and objects of the invention will become apparent to those skilled in the art by practicing the present teachings and viewing the accompanying drawings in which: Fig. 1 shows a schematic view of an internal combustion engine of a vehicle, and Fig. 2 shows an exemplary flow diagram of a method according to the invention for monitoring the ventilation of the crankcase of the internal combustion engine of the Fig. 1 shows.

[0021] The Fig. 1 shows a schematic view of an internal combustion engine 100 of a vehicle. The internal combustion engine 100 has an intake manifold (or air intake line) 102 and combustion chambers 110 connected thereto (in the Fig. 1 only one of the four combustion chambers 110 is provided with a reference symbol). Intake air can enter the combustion chambers 110 via the intake pipe 102, where the intake air can be mixed with fuel and burned in a known manner. The direction of flow of the intake air is indicated by arrow 104.

[0022] The combustion chambers 110 are formed in particular by cylinders 112 and pistons 114 reciprocating therein, whereby the volume of the combustion chambers 110 varies over time. The pistons 114 are at least partially arranged in a crankcase 120 and mechanically coupled to a crankshaft 122 arranged therein, which is known from the prior art.

[0023] The combustion chambers 110 are fluidly connected to an exhaust tract 130, through which the exhaust gases generated by the combustion of the air-fuel mixture in the combustion chambers 110 can be discharged into the environment after post-treatment. The exhaust tract 130 merely describes the section of the internal combustion engine 100 that is designed exclusively for discharging the exhaust gases.

[0024] Arranged in the exhaust tract 130 is a nitrogen oxide sensor 140 and a catalyst 150 arranged downstream of the nitrogen oxide sensor 140, which is designed to aftertreat the exhaust gases. The nitrogen oxide sensor 140 is designed to determine the nitrogen oxide content in the exhaust gas at the position downstream of the combustion chambers 110. A control unit 160 is in communication with the nitrogen oxide sensor 140 and is designed to receive the nitrogen oxide values ​​detected by the nitrogen oxide sensor 140 and to at least partially control the operation of the internal combustion engine 100.

[0025] During operation of the internal combustion engine 100, deviations from atmospheric pressure occur not only in the combustion chambers 110, but also below the pistons 114. These are caused, on the one hand, by the volume changes caused by the rotating pistons 114 and, on the other hand, by the exhaust gases from the working process accumulating in the crankcase 120. In particular, exhaust gases from the combustion chambers 110 can enter the crankcase 120 through a gap between the cylinder 112 and the piston 114, which in the Fig. 1 indicated by an arrow 106.

[0026] In order to prevent these so-called blow-by gases from being expelled untreated into the atmosphere, a vent line 124 is provided, which fluidically connects the crankcase 120 to the intake manifold 102. A control valve 126 is provided in the vent line 124, with which the ventilation of the crankcase 120 into the intake manifold 102 can be controlled. The control valve 126 is preferably a pressure control valve, which can automatically control or regulate the pressure within the crankcase 120. Additionally or alternatively, the pressure in the crankcase 120 can be controlled by means of a mechanical control valve (in the Fig. 1 not shown) in the intake manifold 102. In particular, the exhaust gases collected in the crankcase 120 can be fed to the combustion chambers 110 and thus also to the exhaust tract 130 for later working cycles, where they can be aftertreated by the catalyst device 150.

[0027] According to the Fig. 1 In the embodiment shown, the blowby gases are introduced into the intake manifold 102 via the vent line 124. The negative pressure in the intake manifold 124 also creates a negative pressure in the crankcase 120 under most operating conditions of the internal combustion engine 100. In turbocharged internal combustion engines 100, the introduction can occur upstream of the turbocharger. The exhaust gases from the crankcase 120 are thus also drawn in.

[0028] With additional reference to the Fig. 2 In the following, an exemplary embodiment of a method according to the invention for monitoring the crankcase ventilation of the internal combustion engine 100 of the Fig. 1 described.

[0029] The procedure of Fig. 2 The method starts at step 200 and then proceeds to step 210, where it is determined whether the internal combustion engine 100 is in a predetermined operating mode during which no combustion of an air-fuel mixture takes place within the combustion chambers 110. For example, a predetermined operating mode may be in the form of an overrun fuel cut-off phase of the internal combustion engine 100. The method remains at step 210 until a predetermined operating mode is determined.

[0030] If a predetermined operating mode of the internal combustion engine 100 is determined in step 210, the method proceeds to step 220, where a nitrogen oxide value is determined using the nitrogen oxide sensor 140. In a subsequent step 230, it is determined whether the nitrogen oxide value determined in step 220 exceeds a predetermined nitrogen oxide threshold value, such as 50 ppm. Preferably, after the predetermined operating mode of the internal combustion engine 100 has been determined, a predetermined period of time of approximately 3 seconds, preferably approximately 1 second, can be waited before step 220 is carried out. This ensures that at the time of the nitrogen oxide measurement, the exhaust gases generated due to the combustion that previously took place in the combustion chambers 110 have already flowed past the nitrogen oxide sensor 140. Consequently, the exhaust gas measured in step 220 should be the exhaust gas vented from the crankcase 120.

[0031] If it is determined in step 230 that the nitrogen oxide value determined in step 220 exceeds the predetermined nitrogen oxide threshold, the method proceeds to step 240, where a properly functioning crankcase ventilation is diagnosed before the method ends in step 260. In particular, exceeding the predetermined nitrogen oxide threshold can be interpreted such that the exhaust gases trapped in the crankcase 120 are vented either via the ventilation line 124 or past the pistons 114 (ie along the arrow 108 in the Fig. 1 ) into the combustion chambers 110 and thus into the exhaust tract 130. Thus, these two vent paths are essentially unblocked and essentially free.

[0032] However, if it is determined in step 230 that the nitrogen oxide value determined in step 220 does not exceed, i.e., falls below, the predetermined nitrogen oxide threshold value, the method proceeds to step 250, where an improperly functioning or malfunctioning crankcase ventilation is diagnosed before the method again ends in step 260. In particular, falling below the predetermined nitrogen oxide threshold value can be interpreted to mean that the exhaust gases trapped in the crankcase 120 cannot be discharged as desired via the ventilation line 124 or past the pistons 114 (i.e., along the arrow 108 in the Fig. 1 ) into the combustion chambers 110 and thus into the exhaust tract 130. Thus, at least one of these two venting paths is at least partially blocked or clogged, for example by soot particles, a defective oil separator, a crushed line, or a clogged intake air filter.

[0033] The method according to the invention can therefore be used to monitor whether one of the above-mentioned ventilation paths leading from the crankcase 120 into the exhaust tract 130 is substantially clear or at least partially blocked. This monitoring can be carried out in a simple manner according to the invention using the nitrogen oxide sensor 140, which is already arranged in the exhaust tract 130.

Claims

1. Method for monitoring the ventilation of a crankcase (120) of an internal combustion engine (100) which has combustion chambers (110) and a nitrogen oxide sensor (140) which is arranged in an exhaust gas system (130) of the internal combustion engine (100) and is designed to detect the nitrogen oxide content in the exhaust gas of the internal combustion engine (100), wherein the method comprises: - determining a predefined mode of operation of the internal combustion engine (100), during which substantially no combustion of an air-fuel mixture takes place within the combustion chambers (110), - determining the nitrogen oxide content in the exhaust gas of the internal combustion engine (100) during the predefined mode of operation of the internal combustion engine (100) by means of the exhaust gas sensor (140), - determining functional ventilation of the crankcase (120) if the nitrogen oxide value obtained during the predefined mode of operation of the internal combustion engine (100) exceeds a predefined nitrogen oxide threshold, and - detecting faulty ventilation of the crankcase (120) if the nitrogen oxide value obtained during the predefined mode of operation of the internal combustion engine (100) falls below the predefined nitrogen oxide threshold.

2. Method according to Claim 1, wherein determining the nitrogen oxide value takes place after the expiration of a predefined time period, after the predefined mode of operation of the internal combustion engine has been determined.

3. Method according to Claim 2, wherein the predefined time duration is approximately 5 seconds, preferably approximately 3 seconds.

4. Method according to one of the preceding claims, wherein the predefined mode of operation of the internal combustion engine (100) has an overrun cut-off phase of the internal combustion engine (100).

5. Method according to one of the preceding claims, further comprising: - outputting a warning to the operator of the internal combustion engine (100) if malfunctioning ventilation of the crankcase (120) has been detected.

6. Method according to one of the preceding claims, wherein the predefined nitrogen oxide threshold value is between approximately 5 ppm and approximately 20 ppm.

7. Internal combustion engine (100), comprising: - at least one combustion chamber (110) formed by a piston (114) moving reciprocally to and fro within a cylinder (112), - a crankcase (120), in which the piston (114) is at least partially arranged and which is at least partially fluidically connected to the combustion chamber (110) via a gap between the piston (114) and the cylinder (112), - an exhaust gas system (130) which is fluidically connected to the at least one combustion chamber (110), - a nitrogen oxide sensor (140) which is located in the exhaust gas system (130) and is designed to detect the nitrogen oxide content in the exhaust gas of the internal combustion engine (100), and - a control unit (160) which is designed to carry out a method according to one of the preceding claims for monitoring the ventilation of the crankcase (120).

8. Internal combustion engine according to Claim 7, further comprising: - a catalytic converter (150) located downstream of the nitrogen oxide sensor (140).

9. Internal combustion engine (100) according to either of Claims 7 or 8, further comprising: - an intake manifold (102) which is fluidically connected to the at least one combustion chamber (110) and is designed to supply air to the at least one combustion chamber (110) for the combustion of an air-fuel mixture, and - a ventilation pipe (124) which fluidically connects the crankcase (120) to the intake manifold (102).

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