Abnormality diagnosis apparatus for internal combustion engine

Abstract

To diagnose the presence or absence of abnormality in a recirculation passage for recirculating blow-by gas in an oil tank to an intake passage, including the occurrence of a hole in piping constituting the recirculation passage.SOLUTION: The internal combustion engine 10 includes a dry sump lubrication system that circulates lubricating oil between the internal combustion engine 10 and an external oil tank 30, and a ventilation system that recirculates blow-by gas in the oil tank 30 to the intake passage 17. The ECM40 determines whether the first recirculation path 34, which recirculates blow-by gas from the oil tank 30 to the intake path 17, has an abnormality based on whether the internal pressure of the oil tank 30 detected by the pressure sensor 43 exceeds a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an abnormality diagnosis device for an internal combustion engine equipped with a dry sump type lubrication system. [Background technology]

[0002] A known abnormality diagnosis device for a dry sump type internal combustion engine that stores lubricating oil in an external oil tank is described in Patent Document 1. This abnormality diagnosis device installs an electrical resistor in the pipe connecting the oil tank and the internal combustion engine, and detects disconnection or breakage of the pipe by monitoring the resistance value of the electrical resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-68452 Summary of the Invention [Problem to be solved by the invention]

[0004] A hole may develop in a pipe, causing a leak of gas or lubricating oil. The above-mentioned conventional abnormality diagnosis device cannot detect such a hole in the pipe. [Means for solving the problem]

[0005] The abnormality diagnosis device for an internal combustion engine that solves the above problem is a device that diagnoses the presence or absence of an abnormality in an internal combustion engine that has a dry sump type lubrication system that circulates lubricating oil between an external oil tank and the engine, and that returns blow-by gas in the oil tank to the intake passage.It is equipped with a pressure sensor that detects the tank internal pressure, which is the pressure inside the oil tank, and is configured to perform a diagnostic process that diagnoses the presence or absence of an abnormality in the return path of the blow-by gas based on whether the tank internal pressure exceeds a threshold value when the internal combustion engine is operating at low load. [Effects of the Invention]

[0006] The above-described internal combustion engine abnormality diagnosis device has the advantage of being able to diagnose the presence or absence of an abnormality in the recirculation path for recirculating blow-by gas in the oil tank to the intake passage, including the presence or absence of holes in the piping that constitutes the recirculation path. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram schematically illustrating the configuration of an abnormality diagnosis device for an internal combustion engine according to a first embodiment. [Figure 2] 2 is a flowchart of a diagnostic process performed by the abnormality diagnostic device of FIG. 1. [Figure 3] 6 is a flowchart of a diagnostic process performed by an internal combustion engine abnormality diagnostic device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) A first embodiment of an abnormality diagnosis device for an internal combustion engine will be described in detail below with reference to FIGS.

[0009] <Configuration of Internal Combustion Engine Abnormality Diagnosis Device> The configuration of the internal combustion engine abnormality diagnosis device of this embodiment will be described with reference to FIG. First, the configuration of an internal combustion engine 10 to which the abnormality diagnosis device of this embodiment is applied will be described. The internal combustion engine 10 includes a cylinder 12 in which a piston 11 is arranged so as to reciprocate. The piston 11 defines a combustion chamber 13 within the cylinder 12, where an air-fuel mixture is combusted. The piston 11 is connected to a crankshaft 15, which is the output shaft of the internal combustion engine 10, via a connecting rod 14. A crankcase 16 accommodating the crankshaft 15 is provided below the cylinder 12 in the drawing. The internal combustion engine 10 actually has multiple cylinders 12, but only one of them is shown in FIG. 1 . An intake passage 17, which is an intake passage for intake air, and an exhaust passage 18, which is an exhaust passage for exhaust gas, are connected to the combustion chamber 13. The intake passage 17 is provided with an air cleaner 19, a compressor 20, an intercooler 21, a throttle valve 22, and an intake manifold 23. A turbine 24, which rotates due to the exhaust flow, is provided in the exhaust passage 18. The air cleaner 19 is a filter device that filters out dust and other particles from the intake air. The compressor 20 rotates in conjunction with the turbine 24, compressing the intake air that has passed through the air cleaner 19. The intercooler 21 cools the intake air that has been heated by compression in the compressor 20. The throttle valve 22 is a valve for adjusting the flow rate of intake air in the intake passage 17, and is installed in a portion of the intake passage 17 downstream of the intercooler 21. The intake manifold 23 is a branch pipe that distributes the intake air that has passed through the throttle valve 22 to the combustion chambers 13 of each cylinder 12.

[0010] <Configuration of the lubrication system of the internal combustion engine 10> Next, the configuration of the lubrication system of the internal combustion engine 10 will be described. The internal combustion engine 10 has a dry sump type lubrication system. The dry sump type lubrication system includes an oil tank 30 installed outside the internal combustion engine 10. The lubrication system is configured to circulate lubricating oil between the oil tank 30 and the internal combustion engine 10 using a scavenge pump 31 and a supply pump 32. The scavenge pump 31 sends lubricating oil from the crankcase 16 to the oil tank 30. The supply pump 32 supplies lubricating oil stored in the oil tank 30 to the internal combustion engine 10. The oil tank 30 is equipped with a pressure sensor 43 that detects the pressure inside it. In the following description, the pressure inside the oil tank 30 will be referred to as the tank internal pressure.

[0011] <Ventilation system> The lubricating oil that the scavenge pump 31 delivers to the oil tank 30 is mixed with blow-by gas, which contains combustion gas that has leaked from the combustion chamber 13 into the crankcase 16. The internal combustion engine 10 is equipped with a ventilation system that recirculates the blow-by gas that has flowed into the oil tank 30 back into the intake air.

[0012] The ventilation system has two paths, a first recirculation path 34 and a second recirculation path 36, for recirculating blow-by gas from the oil tank 30 to the intake passage 17. The first recirculation path 34 and the second recirculation path 36 are configured with piping such as hoses and pipes and a PCV valve (described later). The end of the first recirculation path 34 on the intake passage 17 side is connected to the intake manifold 23. On the other hand, the end of the second recirculation path 36 on the intake passage 17 side is connected to a portion of the intake passage 17 downstream of the air cleaner 19 and upstream of the compressor 20. The first recirculation path 34 and the second recirculation path 36 are respectively provided with a first PCV valve 35 and a second PCV valve 37, which are one-way valves for preventing backflow of intake air from the intake passage 17 to the oil tank 30. The first PCV valve 35 is provided at a connection portion of the first recirculation path 34 to the intake manifold 23. On the other hand, the second PCV valve 37 is installed at a connection portion of the second return path 36 to the oil tank 30. An oil separator 33 that separates oil mist in the blow-by gas is installed in the oil tank 30. The oil tank 30 is configured to send the blow-by gas to the first return path 34 and the second return path 36 via the oil separator 33.

[0013] The ventilation system further includes an open valve 38 and an atmosphere introduction passage 39. When the open valve 38 is opened, it connects the oil tank 30 to a portion of the intake passage 17 downstream of the air cleaner 19 and upstream of the compressor 20. The open valve 38 is installed to open when the internal combustion engine 10 is stopped, thereby bringing the tank internal pressure close to atmospheric pressure. The atmosphere introduction passage 39 is a passage that connects the crankcase 16 to a portion of the intake passage 17 downstream of the air cleaner 19 and upstream of the compressor 20.

[0014] In the internal combustion engine 10 of FIG. 1, blow-by gas in the crankcase 16 is sent to the oil tank 30 together with lubricating oil by the scavenge pump 31. As the blow-by gas is sent out at this time, fresh air is replenished into the crankcase 16 through the atmospheric air introduction passage 39. When the internal combustion engine 10 is operating at a low load, the pressure inside the intake manifold 23 (hereinafter referred to as the intake manifold pressure) becomes negative. At this time, the blow-by gas in the oil tank 30 is sucked into the intake manifold 23 through the first recirculation passage 34 due to this negative pressure. When the load on the internal combustion engine 10 increases and the engine shifts to supercharging operation, the intake manifold pressure becomes positive, and the suction of blow-by gas through the first recirculation passage 34 stops. If the scavenge pump 31 continues to send blow-by gas from the crankcase 16 to the oil tank 30 under this condition, the pressure inside the tank increases. Even during supercharging operation, the pressure in the portion of the intake passage 17 upstream of the compressor 20 is maintained near atmospheric pressure. Therefore, when the tank internal pressure exceeds atmospheric pressure and becomes positive, the blow-by gas in the oil tank 30 is sent to the intake passage 17 through the second recirculation path 36. In this way, in the internal combustion engine 10 of FIG. 1, the blow-by gas in the crankcase 16 is recirculated into the intake air via the oil tank 30, thereby ventilating the crankcase 16.

[0015] <Configuration of the abnormality diagnosis device> The internal combustion engine 10 is controlled by an ECM (engine control module) 40. The ECM 40 includes a storage device 41 that stores programs and data for engine control, and a processing device 42 that executes the programs. The ECM 40 controls the internal combustion engine 10 by having the processing device 42 execute the programs stored in the storage device 41. The ECM 40 receives detection results from various sensors that detect the operating conditions of the internal combustion engine 10. The sensors that receive detection results from the ECM 40 include the pressure sensor 43 described above.

[0016] <Diagnosis processing> As part of the control of the internal combustion engine 10, the ECM 40 performs a diagnostic process to diagnose whether or not there is an abnormality in the first recirculation path 34. Abnormalities in the first recirculation path 34 that are the subject of the diagnostic process include holes or disconnection in the pipes that make up the first recirculation path 34, the first PCV valve 35 being stuck closed, and the like.

[0017] A flowchart of the diagnostic process is shown in Fig. 2. The ECM 40 repeatedly executes the process of Fig. 2 at predetermined control intervals while the internal combustion engine 10 is in operation. When the processing of FIG. 2 starts, the ECM 40 first determines in step S100 whether or not the prerequisites for diagnosis are met. In the present embodiment, the prerequisites for abnormality diagnosis are that all of the requirements necessary for performing abnormality diagnosis are met. Examples of the requirements necessary for performing abnormality diagnosis include that the internal combustion engine 10 has finished warming up, that the atmospheric pressure is equal to or higher than a certain level, and that the relief valve 38 is closed. If the prerequisites are met (YES), the ECM 40 proceeds to step S105, and if they are not met (NO), the ECM 40 ends the abnormality diagnosis processing for the current control cycle.

[0018] In step S105, the ECM 40 determines whether the internal combustion engine 10 is operating at a low load. For example, the ECM 40 determines that the internal combustion engine 10 is operating at a low load when the rotation speed of the internal combustion engine 10 is equal to or lower than a predetermined value and the load factor is equal to or lower than a predetermined value. If the internal combustion engine 10 is operating at a low load (YES), the ECM 40 proceeds to step S110, and if the internal combustion engine 10 is not operating at a low load (NO), the ECM 40 ends the abnormality diagnosis process for the current control cycle. Here, low load operation refers to an operating state of the internal combustion engine 10 in which the intake manifold pressure is lower than a certain level.

[0019] In step S110, the ECM 40 acquires the tank pressure detected by the pressure sensor 43. Then, in step S115, the ECM 40 determines whether the tank pressure is equal to or lower than a predetermined threshold. The threshold is set to a value equal to or higher than the maximum intake manifold pressure during low-load operation and lower than atmospheric pressure. If the tank pressure is equal to or lower than the threshold (YES), the ECM 40 increments the value of the normal counter C1 in step S120 and clears the value of the abnormal counter C2 to 0, and then proceeds to step S130. If the tank pressure exceeds the threshold (NO), the ECM 40 clears the value of the normal counter C1 to 0 in step S125 and increments the value of the abnormal counter C2, and then proceeds to step S130. The value of the normal counter C1 thus manipulated represents the duration of the state in which the tank pressure is equal to or lower than the threshold, and the value of the abnormal counter C2 represents the duration of the state in which the tank pressure exceeds the threshold.

[0020] In step S130, the ECM 40 determines whether the value of the normality counter C1 is equal to or greater than a predetermined normality determination value. If the value of the normality counter C1 is equal to or greater than the normality determination value (YES), the ECM 40 determines in step S135 that there is no abnormality in the first recirculation path 34, i.e., makes a normality determination, and then ends the processing for the current control cycle. On the other hand, if the value of the normality counter C1 is less than the normality determination value (S130: NO), the ECM 40 determines in step S140 whether the abnormality counter C2 is equal to or greater than a predetermined abnormality determination value. If the value of the abnormality counter C2 is equal to or greater than the abnormality determination value (YES), the ECM 40 determines in step S145 that there is an abnormality in the first recirculation path 34, i.e., makes an abnormality determination, and then ends the processing for the current control cycle. Note that if the ECM 40 determines that there is an abnormality, it notifies the driver of the occurrence by turning on a warning light, for example.

[0021] <Operation of the First Embodiment> When the internal combustion engine 10 is operating at a low load, the blow-by gas is ventilated by sucking the blow-by gas from the oil tank 30 through the first recirculation path 34 using the negative pressure in the intake manifold 23. Therefore, the pressure inside the tank during low load operation becomes the same negative pressure as that inside the intake manifold 23.

[0022] If an abnormality occurs in the first recirculation path 34, such as a disconnected pipe, a hole, or the first PCV valve 35 being stuck closed, the blow-by gas in the oil tank 30 will not be drawn in by the negative pressure in the intake manifold 23. Therefore, when an abnormality occurs, the pressure inside the tank will not become negative even when the internal combustion engine 10 is operating at a low load.

[0023] In response to this, the ECM 40 checks whether the tank pressure during low-load operation exceeds a threshold value during diagnostic processing. If the tank pressure exceeds the threshold value, the ECM 40 determines that an abnormality exists, thereby diagnosing whether or not there is an abnormality in the first recirculation path 34. Therefore, when an abnormality such as that described above occurs in the first recirculation path 34, the ECM 40 diagnoses that there is an abnormality.

[0024] <Effects of the first embodiment> The abnormality diagnosis device of this embodiment can achieve the following effects. (1) The ECM 40 performs a diagnostic process to diagnose whether or not there is an abnormality in the first recirculation path 34 based on whether or not the tank internal pressure exceeds a threshold value when the internal combustion engine 10 is operating at a low load. Therefore, the ECM 40 can diagnose whether or not there is an abnormality in the first recirculation path 34, which recirculates blow-by gas in the oil tank 30 to the intake passage 17, including whether or not there is a hole in the piping.

[0025] (2) The internal combustion engine 10 to which the abnormality diagnosis device of this embodiment is applied includes a first PCV valve 35, which is a one-way valve for preventing backflow of intake air from the intake passage 17 to the oil tank 30 through the first recirculation path 34. The first PCV valve 35 is installed at a connection portion of the first recirculation path 34 to the intake passage 17. Consider a case where the first PCV valve 35 is installed at a connection portion of the first recirculation path 34 to the oil tank 30. In this case, if a pipe constituting the first recirculation path 34 becomes detached or develops a hole in the pipe, outside air will flow into the intake manifold 23. This inflow of outside air can be detected by a sensor already installed in the internal combustion engine, such as an air flow meter or an air-fuel ratio sensor. In contrast, if the first PCV valve 35 is installed at a connection portion of the first recirculation path 34 to the intake passage 17, outside air will not flow into the intake manifold 23 even if the pipe becomes detached or develops a hole. Therefore, an abnormality cannot be diagnosed using the above-mentioned existing sensor. The abnormality diagnostic device of this embodiment can diagnose whether or not there is an abnormality in the first recirculation path 34 even in an internal combustion engine 10 that is configured in such a way that an abnormality cannot be diagnosed using existing sensors.

[0026] (3) The ECM 40 determines whether the tank pressure is normal or abnormal if it exceeds the threshold for a specified period of time or longer. This reduces the impact of temporary fluctuations in the detected tank pressure value due to noise or disturbances on the diagnostic results, improving diagnostic accuracy.

[0027] (Second embodiment) In order to accurately perform the abnormality diagnosis based on the tank internal pressure during low-load operation performed by the abnormality diagnosis device of the first embodiment, it is desirable to perform the diagnosis when the difference between atmospheric pressure and intake manifold pressure is larger than a certain level. In the case of an internal combustion engine that performs intermittent operation control, such as a hybrid vehicle or a vehicle with idling stop control, the internal combustion engine is often stopped during low-load operation. Therefore, in an internal combustion engine that performs intermittent operation control, opportunities to perform abnormality diagnosis under favorable operating conditions that ensure diagnostic accuracy are limited. The abnormality diagnosis device of this embodiment is configured to perform intermittent operation control to ensure opportunities for abnormality diagnosis in the internal combustion engine. The hardware configuration of the abnormality diagnosis device of this embodiment is the same as that of FIG. 1. In the following description, components in this embodiment that are common to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0028] In this embodiment, the ECM 40 performs an abnormality diagnosis on the first recirculation path 34 through a preliminary diagnosis and a main diagnosis. Both the preliminary diagnosis and the main diagnosis are performed to determine whether or not there is an abnormality in the first recirculation path 34 based on the tank internal pressure. However, the execution conditions for the preliminary diagnosis are set to be met in a situation that is easier to meet than the execution conditions for the main diagnosis, but in which the diagnostic accuracy is lower. In this embodiment, the preliminary diagnosis is performed to determine whether or not there is a situation in which the occurrence of an abnormality in the first recirculation path 34 is suspected, and the main diagnosis is performed to determine whether or not there is an abnormality in the first recirculation path 34.

[0029] 3 shows a flowchart of a diagnostic control routine executed by the ECM 40 in the abnormality diagnostic device of this embodiment. The ECM 40 repeatedly executes the process of FIG. 3 at predetermined control intervals while the internal combustion engine 10 is in operation.

[0030] When starting this routine, the ECM 40 first determines in step S200 whether the execution conditions for the preliminary diagnosis are met. The execution conditions for the preliminary diagnosis include a condition under which a diagnosis based on the tank internal pressure can be performed but under which the execution conditions for the main diagnosis are not met. Specifically, the execution conditions for the preliminary diagnosis include a condition under which the vehicle is operating at a low load, causing the intake manifold pressure to become negative, and the vehicle is not idling while stopped. If the execution conditions for the preliminary diagnosis are met (YES), the ECM 40 proceeds to step S205. If the execution conditions for the preliminary diagnosis are not met (NO), the ECM 40 proceeds to step S220.

[0031] In step S205, the ECM 40 performs a preliminary diagnosis. The preliminary diagnosis is performed through the processing from step S110 onwards in FIG. 2. Next, in step S210, the ECM 40 determines whether or not an abnormality has been determined in the preliminary diagnosis. If it has been determined that an abnormality has been present (YES), the ECM 40 stops the intermittent operation control of the internal combustion engine 10 in step S215 and then proceeds to step S220. On the other hand, if it has not been determined that an abnormality has been present (NO), the ECM 40 skips step S215 and proceeds to step S220.

[0032] In step S220, the ECM 40 determines whether the execution conditions for this diagnosis are met. In this embodiment, the execution condition for this diagnosis is that the vehicle is idling. If the execution conditions for this diagnosis are met (YES), the ECM 40 proceeds to step S225. If the execution conditions for this diagnosis are not met (NO), the ECM 40 ends the processing of this routine for the current control cycle.

[0033] In step S225, the ECM 40 performs a main diagnosis. Like the preliminary diagnosis, the main diagnosis is performed through the processing from step S110 onwards in FIG. 2. However, in the main diagnosis, a lower pressure is set as the threshold value used for the determination in step S115 in FIG. 2 than in the preliminary diagnosis. Next, in step S230, the ECM 40 determines whether or not an abnormality has been determined in the main diagnosis. If an abnormality has been determined (YES), the ECM 40 confirms the diagnosis result that an abnormality has been determined in the first return path 34 in step S235, and then ends the processing of this routine for the current control cycle. On the other hand, if an abnormality has not been determined in the main diagnosis (S230: NO), the ECM 40 skips step S235 and ends the processing of this routine for the current control cycle.

[0034] <Operation of the Second Embodiment> In an internal combustion engine 10 that performs intermittent operation control, the operation of the internal combustion engine 10 is often stopped during low-load operation. This limits opportunities for accurately performing an abnormality diagnosis of the first recirculation path 34 based on the tank internal pressure. In contrast, in this embodiment, the ECM 40 performs a preliminary diagnosis when conditions enabling a diagnosis based on the tank internal pressure are met, even if diagnostic accuracy cannot be ensured. If such a preliminary diagnosis determines that an abnormality exists, it is not necessarily determined that an abnormality has occurred, but it is considered highly likely that an abnormality has occurred. If the preliminary diagnosis determines that an abnormality exists, the ECM 40 stops the intermittent operation control of the internal combustion engine 10. When the intermittent operation control is stopped, the internal combustion engine 10 continues to operate even in a low-load operation range where operation is normally stopped. The ECM 40 then performs a main diagnosis when the intake manifold pressure drops to a level where a highly accurate diagnosis is possible, specifically, when the vehicle is idling. Note that the ECM 40 also performs a main diagnosis when execution conditions are met during intermittent operation control.

[0035] <Effects of the second embodiment> In addition to the above-mentioned effects (1) to (3), the abnormality diagnosis device of this embodiment can further achieve the following effects.

[0036] (4) If a preliminary diagnosis indicates an abnormality while the intermittent operation control of the internal combustion engine 10 is being performed, the ECM 40 stops the intermittent operation control and performs a main diagnosis while the intermittent operation control is stopped, thereby diagnosing whether or not there is an abnormality in the first recirculation path 34. Therefore, even in an internal combustion engine 10 that performs intermittent operation control, an opportunity to diagnose an abnormality in the first recirculation path 34 can be ensured.

[0037] (5) The ECM 40 stops the intermittent operation control to operate the internal combustion engine 10 at low intake manifold pressure. The ECM 40 then performs this diagnosis when the internal combustion engine 10 is operating at low intake manifold pressure. Therefore, by performing intermittent operation control, it is possible to diagnose an abnormality in the first recirculation path 34 with high accuracy even in an internal combustion engine 10 that is not frequently operated at low intake manifold pressure, at which a diagnosis can be performed with high accuracy.

[0038] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0039] <About the diagnostic control routine in Figure 3> In the second embodiment, different values ​​may be used for the normality determination value used in the determination at step S130 in FIG. 2 and the abnormality determination value used in the determination at step S140 in FIG. 2 in the case of preliminary diagnosis and the case of main diagnosis.

[0040] In the second embodiment, a condition other than idling while the vehicle is stopped may be set as the execution condition for the main diagnosis, as long as the condition enables the diagnosis to be performed with higher accuracy than when the execution condition for the preliminary diagnosis is met.

[0041] <About the diagnostic process in Figure 2> In the diagnostic process in Figure 2, the tank pressure is determined to be normal / abnormal if it remains below or above the threshold for a predetermined period of time. However, it is also possible to determine whether the tank pressure is normal / abnormal simply by whether it remains below or above the threshold, without requiring it to remain above the threshold for a predetermined period of time.

[0042] The diagnostic process may be configured to perform only an abnormality determination without performing a normality determination. In this case, the diagnostic process may be modified from the procedure shown in Figure 2 by, for example, omitting steps S120, S130, and S135 and proceeding to step S140 after step S125.

[0043] Processing other than notifying the driver may be performed when it is determined that an abnormality exists. For example, when it is determined that an abnormality exists, the output of the internal combustion engine 10 may be limited in order to reduce blow-by gas. Furthermore, the operation of the internal combustion engine 10 may be limited until a normality determination is made, and the limit may be lifted when a normality determination is made.

[0044] <Ventilation system configuration> The end of the first recirculation path 34 on the intake passage 17 side may be connected to a portion of the intake passage 17 downstream of the throttle valve 22 other than the intake manifold 23 .

[0045] The first PCV valve 35 may be installed at a location other than the connection portion of the first recirculation path 34 to the intake passage 17 . When the ventilation system is applied to a non-supercharged internal combustion engine, the second recirculation path 36 and the second PCV valve 37 may be omitted from the ventilation system shown in Fig. 1. Also, the release valve 38 may be omitted.

[0046] <Other> The abnormality diagnosis devices of the above-described embodiment and modified examples can also be applied to internal combustion engines having a configuration different from that of the internal combustion engine 10 shown in FIG. [Explanation of symbols]

[0047] 10...internal combustion engine, 16...crankcase, 17...intake passage, 23...intake manifold, 30...oil tank, 34...first return passage, 35...first PCV valve (one-way valve), 40...ECM (abnormality diagnosis device), 41...processing device, 42...storage device, 43...pressure sensor

Claims

1. A device for diagnosing the presence or absence of an abnormality in an internal combustion engine that has a dry sump type lubrication system that circulates lubricating oil between the oil tank and an external oil tank and that recirculates blow-by gas in the oil tank to an intake passage, A pressure sensor is provided to detect the internal tank pressure, which is the pressure inside the oil tank, and a diagnostic process is performed to diagnose whether or not there is an abnormality in the recirculation path of the blow-by gas depending on whether or not the internal tank pressure exceeds a threshold value during low load operation of the internal combustion engine. An abnormality diagnosis device for internal combustion engines.

2. 2. The internal combustion engine abnormality diagnosis device according to claim 1, further comprising a one-way valve installed at a connection portion of the return path with the intake passage to prevent backflow of intake air from the intake passage to the oil tank.

3. 2. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the diagnosis process is carried out while intermittent operation control of the internal combustion engine is stopped.

4. 2. An abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the diagnostic process is carried out while intermittent operation control of the internal combustion engine is being carried out, and when the diagnostic process diagnoses that there is an abnormality in the return path, the diagnostic process is carried out again with the intermittent operation control stopped.

5. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the diagnosis process is performed by diagnosing that there is an abnormality in the reflux path when the state in which the tank internal pressure exceeds the threshold value continues for a predetermined time or longer.

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