DIAGNOSTIC DEVICE FOR INTERNAL COMBUSTION ENGINE

Abstract

Diagnostic device for an internal combustion engine (1), wherein the internal combustion engine (1) comprises a blow-by gas passage (10) through which blow-by gas flows, and wherein the diagnostic device (100) comprises: a temperature sensor (20) that detects a temperature within the blow-by gas passage (10); an atmospheric temperature sensor (40) for detecting the atmospheric temperature; and an abnormality detection unit (30) comprising an atmospheric temperature map (M1) defining a relationship between the atmospheric temperature (TA) detected by the atmospheric temperature sensor (40) and a correction coefficient (KA), wherein the abnormality detection unit (30) detects an abnormality by comparing the detected value of the temperature sensor (20) with an abnormality threshold (TH) and corrects the abnormality threshold (TH) based on the atmospheric temperature (TA), and wherein the abnormality detection unit (30) repeatedly updates the corrected abnormality threshold value (TH) by multiplying a reference abnormality threshold value (TH0) by the correction coefficient (KA) corresponding to the atmospheric temperature (TA) defined by the atmospheric temperature map (M1) detected by the atmospheric temperature sensor (40).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a diagnostic device for an internal combustion engine. STATE OF THE ART

[0002] In the internal combustion engine, a blow-by gas processing device that releases blow-by gas that has escaped from a gap between a piston and a cylinder into a crankcase into the atmosphere or returns it to an intake port is known.

[0003] JP S61- 5 309 A describes a ventilation system for internal combustion engines.

[0004] DE 10 2006 013 188 A1 describes an engine with a chamber ventilation system and a sensor that can detect the operating state of the chamber ventilation system. In particular, the sensor can detect a gas temperature in the chamber ventilation system.

[0005] DE 10 2018 222 318 A1 describes a device for checking the functionality of a crankcase ventilation system of an internal combustion engine.

[0006] US 2018 / 0306074 A1 describes a device for detecting abnormalities in an engine system.

[0007] DE 10 2007 050 087 B3 describes a method for monitoring the ventilation of a crankcase of an internal combustion engine. SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0008] Furthermore, in an internal combustion engine, an abnormality such as an increase in blow-by gas may occur when a piston ring attached to the piston wears out. Such an abnormality increases the amount of oil contained in the blow-by gas and causes engine malfunctions, so the abnormality must be detected promptly.

[0009] The present disclosure provides a diagnostic device capable of detecting an abnormality in an internal combustion engine. SOLUTION TO THE PROBLEM

[0010] According to the invention, a diagnostic device having the features of claim 1 is provided.

[0011] According to one aspect of the present disclosure, there is provided a diagnostic device for an internal combustion engine, wherein the internal combustion engine includes a blow-by gas passage through which blow-by gas flows, and wherein the diagnostic device includes a temperature sensor that detects a temperature within the blow-by gas passage and an abnormality detection unit that detects an abnormality in the internal combustion engine based on a detected value of the temperature sensor.

[0012] The abnormality detection unit may detect an abnormality by comparing the detected value of the temperature sensor with a threshold value and correct the threshold value based on at least one of an atmospheric temperature, a temperature of engine oil, and a temperature of engine cooling water.

[0013] In addition, the abnormality detection unit may correct the threshold value to a higher value when at least one of the atmospheric temperature, the temperature of engine oil, and the temperature of engine cooling water is increased.

[0014] In addition, the internal combustion engine may further include an oil separator provided in the blow-by gas passage for separating oil from blow-by gas, and the temperature sensor may be located in the blow-by gas passage on a downstream side of the oil separator.

[0015] In addition, an end portion of the downstream side of the blow-by gas passage may be open to the atmosphere and the temperature sensor may be located at the end portion of the downstream side of the blow-by gas passage. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0016] With the diagnostic device according to the present disclosure, an abnormality of the internal combustion engine can be detected based on the temperature in the blow-by gas passage. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic configuration diagram of an internal combustion engine. Fig. 2 is a diagram illustrating a temperature in a blow-by gas passage and a threshold value thereof. Fig. 3 is a map defining a relationship between the atmospheric temperature and a correction coefficient corresponding to the temperature. Fig. 4 is a map defining a relationship between a temperature of engine oil and a correction coefficient corresponding to the temperature. Fig. 5 is a diagram illustrating a control flow of an abnormality detection unit. Fig. 6 is a schematic configuration diagram of an internal combustion engine in a first modification example. Fig. 7 is a schematic configuration diagram of an internal combustion engine in a second modification example. Fig. 8 is a map defining a relationship between a temperature of engine cooling water in the second modification example and a correction coefficient corresponding to the temperature. Fig. 9 is a diagram illustrating a control flow of an abnormality detection unit in the second modification example. Fig. 10 is a diagram illustrating a control flow of an abnormality detection unit in a third modification example. DESCRIPTION OF THE EMBODIMENTS

[0017] Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to the following embodiments. In addition, each of the directions shown in the figure, top, bottom, left, and right, is defined only for convenience of explanation.

[0018] First, a schematic configuration of an internal combustion engine 1 will be described with reference to Fig. 1. In the figure, a white arrow A indicates a flow of intake air, and a shaded arrow B indicates a flow of blow-by gas. Furthermore, a black arrow O indicates a flow of oil separated from the blow-by gas.

[0019] The internal combustion engine 1 is a multi-cylinder compression-ignition internal combustion engine, that is, a diesel engine mounted on a vehicle (not shown). The vehicle is a large vehicle such as a truck. However, there are no particular restrictions on the type, shape, use, and the like of the vehicle and the internal combustion engine 1. For example, the vehicle may be a small vehicle such as a passenger car, or the internal combustion engine 1 may be a spark-ignition internal combustion engine, that is, a gasoline engine.

[0020] The internal combustion engine 1 includes an engine body 2, an intake manifold 3 connected to the engine body 2, and an intake pipe 4 connected to an upstream end of the intake manifold 3. The internal combustion engine 1 also includes exhaust system parts such as an exhaust pipe (not shown), but the description thereof is omitted here.

[0021] Furthermore, as described in detail below, the internal combustion engine 1 of the embodiment includes a blow-by gas passage 10 through which blow-by gas flows. Furthermore, the internal combustion engine 1 includes an oil separator 11 for separating oil from the blow-by gas.

[0022] The engine body 2 includes a cylinder block 5, a crankcase 6 integrally formed at a lower portion of the cylinder block 5, and an oil pan 7 connected to a lower portion of the crankcase 6. Furthermore, the engine body 2 includes a cylinder head 8 connected to an upper portion of the cylinder block 5, and a head cover 9 connected to an upper portion of the cylinder head 8.

[0023] A plurality of cylinders 5a are provided in the cylinder block 5, and a piston 5b is housed in each cylinder 5a. A crankshaft (not shown) is housed in the crankcase 6, and engine oil is stored in the oil pan 7. Further, a valve operating mechanism (not shown) is fixed to the cylinder head 8, and the valve operating mechanism is covered from above by the head cover 9. An oil passage G, in which engine oil is stored, is formed in the crankcase 6. Further, a water jacket J, through which engine cooling water is circulated, is formed in the cylinder block 5 and the cylinder head 8.

[0024] The intake manifold 3 is connected to the cylinder head 8 and distributes and supplies the air sent from the intake pipe 4 to an intake port of each cylinder 5a. The intake pipe 4 is provided with an air cleaner 4a, a turbocharger compressor 4b, and an intercooler 4c in this order from the upstream side.

[0025] The blow-by gas passage 10 includes an engine passage 10a extending through the interior of the engine body 2 and a blow-by gas pipe 10b exposed to the exterior of the engine body 2, in order from the downstream side in a blow-by gas flow direction. As is well known, blow-by gas is gas that escapes from a gap between the cylinder 5a and the piston 5b in the engine body 2 into the crankcase 6. Although not shown, an amount of blow-by gas in the crankcase 6 is minimized by a plurality of piston rings attached to the pistons 5b.

[0026] The internal engine passage 10a extends through the interior of the cylinder block 5 and the cylinder head 8 from the interior of the crankcase 6 and communicates with the interior of the head cover 9.

[0027] For the blow-by gas pipe 10b, for example, a resin hose member is used. An upstream end of the blow-by gas pipe 10b is connected to an upper surface portion of the head cover 9. In contrast, a downstream end of the blow-by gas pipe 10b is opened to the atmosphere at a height near a lower end of the engine body 2.

[0028] The internal engine passage 10a and the blow-by gas pipe 10b communicate with each other via an oil separation chamber 10c provided in an upper part of the head cover 9. Although not shown, the oil separation chamber 10c has a plurality of baffles and is configured to allow the blow-by gas introduced from the internal engine passage 10a to collide with the baffles to separate the oil. Further, the oil separated by the blow-by gas is returned from the oil separation chamber 10c to the crankcase 6 through the internal engine passage 10a.

[0029] An oil separator 11 is provided outside the engine body 2 and in the center of the blow-by gas pipe 10b. The oil separator 11 includes a filter element 11a for separating oil from the blow-by gas. However, the type of oil separator 11 may be arbitrary and may, for example, be a centrifugal oil separator without a filter element.

[0030] Furthermore, a return pipe 11b for returning oil O separated from the blow-by gas to the crankcase 6 is connected to the oil separator 11 of the embodiment. Furthermore, although not shown, the oil separator 11 is provided with a bypass flow path for adjusting a flow rate bypassing the filter element 11a and a switching valve that opens and closes the bypass flow path.

[0031] According to the configuration described above, the blow-by gas flows in the crankcase 6 while the internal combustion engine 1 is running, as shown by the arrow B in Fig. 1, in this order, through the engine-internal passage 10a and the blow-by gas pipe 10b and is discharged into the atmosphere. In this case, the oil contained in the blow-by gas is separated from the blow-by gas by the oil separation chamber 10c and the oil separator 11.

[0032] Furthermore, the oil separated in the oil separation chamber 10c is discharged as indicated by the arrow O in Fig. 1, is returned to the crankcase 6 through the internal engine passage 10a. The oil separated by the oil separator 11 is returned to the crankcase 6 through the return pipe 11b.

[0033] Next, a diagnostic device 100 of the internal combustion engine 1 will be described in detail.

[0034] For example, in the internal combustion engine 1, an abnormality may occur in which the blow-by gas in the crankcase 6 increases due to wear or damage of the piston ring.

[0035] As the blow-by gas increases, the pressure inside the crankcase 6 increases. Therefore, it becomes difficult for the oil discharged from the oil separation chamber 10c to return to the inside of the crankcase 6 through the engine internal passage 10a. In addition, the oil may flow back into the oil separation chamber 10c and flow into the blow-by gas pipe 10b together with the blow-by gas. Therefore, the blow-by gas containing a large amount of oil flows through the oil separator 11, and the blow-by gas on the downstream side of the oil separator 11 also contains a large amount of oil. As a result, a larger amount of oil than in a normal state may be released into the atmosphere.

[0036] Furthermore, abnormalities such as the switching valve of the bypass flow path not closing and the connecting flow path with the return pipe 11b being blocked may occur in the oil separator 11. In this case, too, there is a risk of a larger amount of oil being released into the atmosphere than in the normal state.

[0037] Furthermore, as the blow-by gas increases, dilution of the engine oil in the crankcase 6 is likely to occur due to the blow-by gas. Dilution causes the internal combustion engine 1 to fail.

[0038] In this regard, the inventor of the present application has newly discovered that when the above-described abnormality of the internal combustion engine 1 occurs, the temperature (hereinafter, the temperature in the pipe) inside the blow-by gas pipe 10b tends to rise due to the heat of the oil contained in the blow-by gas. That is, the temperature of the oil contained in the blow-by gas pipe is higher than the temperature of the blow-by gas itself. Therefore, under normal conditions, blow-by gas containing almost no oil flows in the blow-by gas pipe 10b, so the temperature in the pipe becomes low. However, in the case of an abnormality, the blow-by gas containing a large amount of oil flows through the blow-by gas pipe 10b, so the temperature in the pipe rises.

[0039] Therefore, the diagnostic device 100 of the embodiment includes a temperature sensor 20 that detects the temperature in the pipe, and an abnormality detection unit 30 that detects an abnormality in the internal combustion engine 1 based on a detected value (hereinafter, a detected temperature in the pipe) of the temperature sensor 20.

[0040] Specifically, the temperature sensor 20 is attached to the blow-by gas pipe 10b. Although not shown, the abnormality detection unit 30 is composed of an electronic control unit (ECU) or a controller of the vehicle and includes a CPU, a ROM, a RAM, an input and output port, and the like. Further, the temperature sensor 20 is electrically connected to the abnormality detection unit 30.

[0041] As in Fig. 2, the abnormality detection unit 30 compares a detected temperature in the pipe T with a predetermined normality threshold value TL and detects that the internal combustion engine 1 is normal when the temperature in the pipe T is equal to or lower than the normality threshold T L Furthermore, the abnormality detection unit 30 compares the detected temperature in the pipe T with a predetermined abnormality threshold value T H and detects that the internal combustion engine 1 is abnormal when the detected temperature in the pipe T is equal to or higher than the abnormality threshold T H The abnormality threshold T H corresponds to a threshold value described in the claims and is set to a higher temperature than the normality threshold T L (T H >T L ). Then, when the abnormality detection unit 30 detects an abnormality in the internal combustion engine 1, a warning lamp (not shown) is turned on to notify a driver of the abnormality.

[0042] Therefore, the diagnostic device 100 according to the embodiment can detect an abnormality in the internal combustion engine 1 based on the temperature in the blow-by gas passage 10.

[0043] Further, the abnormality detection unit 30 of the embodiment maintains this state without detecting the normality or abnormality of the internal combustion engine 1 when the detected temperature in the pipe T is lower than the abnormality threshold T H and higher than the normality threshold T L This enables reliable detection taking into account the fluctuation of the measured temperature in the pipe T.

[0044] Furthermore, the temperature sensor 20 is located, as shown in Fig. 1, on the blow-by gas pipe 10b on the downstream side of the oil separator 11. Although not shown, when the temperature sensor 20 is located on the blow-by gas pipe 10b on the upstream side of the oil separator 11, the detected temperature in the pipe becomes high due to the blow-by gas before oil separation even under normal conditions. Further, for example, even when the oil separator 11 is not provided on the blow-by gas pipe 10b, the detected temperature in the pipe may be high for a similar reason. In these cases, a difference between the detected temperatures in the pipe T in the normal state and the abnormal state becomes small, and thus the detection accuracy may decrease.

[0045] In contrast, the temperature sensor 20 of the embodiment is located on the blow-by gas pipe 10b on the downstream side of the oil separator 11 and detects the temperature inside the pipe through which the blow-by gas flows after the oil is separated. Therefore, the detected temperature in the pipe T can be lowered in the normal state, and the detected temperature in the pipe T can be increased in the abnormal state. As a result, a temperature difference between the normal state and the abnormal state becomes clear, and thus the detection accuracy can be improved.

[0046] Furthermore, the temperature sensor 20 of the embodiment is located at an end portion of the downstream side of the blow-by gas pipe 10b, which is open to the atmosphere. Thus, the temperature sensor 20 is sensitive to the atmospheric temperature at the time of the normal state, and therefore the detected temperature in the pipe T tends to be lower. In contrast, the detected temperature in the pipe T becomes high at the time of the abnormal state due to the influence of the heat of the oil contained in the blow-by gas. As a result, the temperature difference between the normal state and the abnormal state becomes more noticeable, and thus the detection accuracy of the normal state and the abnormal state can be improved.

[0047] Furthermore, the detected temperature in the pipe T becomes higher because the atmospheric temperature and the engine oil temperature (hereinafter referred to as oil temperature) are higher. Therefore, if the normality threshold T described above L and the abnormality threshold T H remain constant, a possibility that normal or abnormal is falsely detected due to the atmospheric temperature and oil temperature.

[0048] Therefore, the abnormality detection unit 30 of the embodiment corrects the normality threshold T L and the abnormality threshold T H based on the atmospheric temperature and the oil temperature.

[0049] Specifically, the diagnostic device 100 of the embodiment further includes an atmospheric temperature sensor 40 for detecting the atmospheric temperature and an oil temperature sensor 50 for detecting the oil temperature.

[0050] An air flow meter capable of detecting the intake flow rate and atmospheric temperature is used for the atmospheric temperature sensor 40. The atmospheric temperature sensor 40 is attached to a part of the intake pipe 4, which is the part located on the upstream side of the compressor 4b and on the immediate downstream side of the air cleaner 4a in the intake flow direction. The oil temperature sensor 50 is attached to the oil line G of the crankcase 6. The atmospheric temperature sensor 40 and the oil temperature sensor 50 are electrically connected to the abnormality detection unit 30.

[0051] In addition, the abnormality detection unit 30 comprises, as shown in Fig. 3, an atmospheric temperature map M1 defining a relationship between a detected value (hereinafter, a detected atmospheric temperature) TA of the atmospheric temperature sensor 40 and a correction coefficient (hereinafter, an atmospheric temperature correction coefficient) KA corresponding to the detected atmospheric temperature TA.

[0052] In the atmospheric temperature map M1, the relationship between the detected atmospheric temperature TA and the atmospheric temperature correction coefficient KA is set such that the higher the detected atmospheric temperature TA, the larger the atmospheric temperature correction coefficient KA. Furthermore, the atmospheric temperature map M1 stores a reference atmospheric temperature correction coefficient KA0 (KA0 = 1) corresponding to a predetermined reference atmospheric temperature TA0 (for example, 25°C).

[0053] In the illustrated example, an atmospheric temperature correction coefficient KAa (KAa < KA0) smaller than the reference atmospheric temperature correction coefficient KA0 is obtained corresponding to a detected atmospheric temperature TAa (TAa < TA0) lower than the reference atmospheric temperature TA0. Furthermore, an atmospheric temperature correction coefficient KAb (KAb > KA0) larger than the reference atmospheric temperature correction coefficient KA0 is obtained corresponding to a detected atmospheric temperature TAb (TAb > TA0) higher than the reference atmospheric temperature TA0.

[0054] In addition, the abnormality detection unit 30 comprises, as shown in Fig. 4, an oil temperature map M2 defining a relationship between a detected value (hereinafter, detected oil temperature) TO of the oil temperature sensor 50 and a correction coefficient (hereinafter, an oil temperature correction coefficient) KO corresponding to the detected oil temperature TO.

[0055] In the oil temperature map M2, the relationship between the detected oil temperature TO and the oil temperature correction coefficient KO is defined such that the higher the detected oil temperature TO, the larger the oil temperature correction coefficient KO. Furthermore, the oil temperature map M2 stores a reference oil temperature correction coefficient KO0 (KO0 = 1) corresponding to a predetermined reference oil temperature TO0 (for example, 90°C).

[0056] In the illustrated example, an oil temperature correction coefficient KOa (KOa < KO0) smaller than the reference oil temperature correction coefficient KO0 is obtained corresponding to a detected oil temperature TOa (TOa < TO0) lower than the reference oil temperature TO0. Furthermore, an oil temperature correction coefficient KOb (KOb > KO0) larger than the reference oil temperature correction coefficient KO0 is obtained corresponding to a detected oil temperature TOb (TOb > TO0) higher than the reference oil temperature TO0.

[0057] The abnormality detection unit 30 calculates the corrected normality threshold T L by multiplying a reference normality threshold T L0 before correction with the atmospheric temperature correction coefficient KA and the oil temperature correction coefficient KO (T L = T L0× KA × KO). Further, the abnormality detection unit 30 calculates the corrected abnormality threshold value T H by multiplying a reference abnormality threshold T H0 before correction with the atmospheric temperature correction coefficient KA and the oil temperature correction coefficient KO (T H = T H0 × KA × KO).

[0058] Therefore, the normality threshold T L and the abnormality threshold T H They are corrected to higher values when the detected atmospheric temperature TA and the detected oil temperature TO are higher, and are corrected to lower values when the detected atmospheric temperature TA and the detected oil temperature TO are lower. As a result, erroneous detection due to the atmospheric temperature and oil temperature can be suppressed.

[0059] Next, a control routine of the abnormality detection unit 30 with respect to Fig. 5 described.

[0060] The abnormality detection unit 30 repeatedly performs a control flow of Fig. 5 at predetermined calculation cycles (e.g., 10 ms) while the internal combustion engine 1 is in a predetermined operating state (e.g., idle operating state). As a result, the temperature in the pipe and the oil temperature, which fluctuate depending on the operating state and the internal combustion engine 1, can be detected under certain conditions.

[0061] In step S101, the detected pipe temperature T, the detected atmospheric temperature TA, and the detected oil temperature TO are obtained. In step S102, the reference normality threshold value T L0 and the reference abnormality threshold T H0 obtained.

[0062] In step S103, the atmospheric temperature correction coefficient KA corresponding to the detected atmospheric temperature TA is obtained by referring to the atmospheric temperature map M1.

[0063] In step S104, the oil temperature correction coefficient KO corresponding to the detected oil temperature TO is obtained by referring to the oil temperature map M2.

[0064] In step S105, the corrected normality threshold T L by multiplying the reference normality threshold T L0 with the atmospheric temperature correction coefficient KA and the oil temperature correction coefficient KO (T L = T L0 × KA × KO).

[0065] In step S106, the corrected abnormality threshold value T H by multiplying the reference abnormality threshold T H0 with the atmospheric temperature correction coefficient KA and the oil temperature correction coefficient KO (TH = T H0 × KA × KO).

[0066] In step S107, it is determined whether the temperature in the pipe T detected in step S101 is equal to or greater than the abnormality threshold value T H (T ≥ T H ). If it is determined in step S107 that the detected temperature in the pipe T is equal to or greater than the abnormality threshold T H (T ≥ T H ) (YES), the process proceeds to step S108, and it is detected that the engine 1 is abnormal. Then, the process proceeds to step S109, and a warning lamp is turned on, and then the process returns.

[0067] On the other hand, if it is determined in step S107 that the detected temperature in the pipe T is not equal to or greater than the abnormality threshold T H (T ≥ T H) is (NO), proceed to step S110 and it is detected whether the detected temperature in the pipe T is equal to or lower than the normality threshold value T L (T ≤ T L ) is.

[0068] If it is determined in step S110 that the detected temperature in the pipe T is equal to or lower than the normality threshold T L (T ≤ T L ) (YES), the process proceeds to step S111 and it is detected that the engine 1 is normal, and then the process returns.

[0069] On the other hand, if it is determined in step S 110 that the detected temperature in the pipe T is not equal to or lower than the normality threshold T L (T ≤ T L ) is (NO), into a pending state in which neither abnormality nor normality is detected.

[0070] The above-described embodiment may be modified in the following examples or in combination. In the following description, the same numerals and letters are used for the same components as those in the above-described embodiment, and a detailed description thereof is omitted. (First modification example)

[0071] The blow-by gas can be returned to the intake pipe 4 without being released into the atmosphere from the blow-by gas pipe 10b. Specifically, a downstream end of the blow-by gas pipe 10b of a first modification example, as shown in Fig. 6, is connected to a part of the intake pipe 4, which is the part located between the atmospheric temperature sensor 40 and the compressor 4b. (Second modification example)

[0072] Parameters other than atmospheric temperature and oil temperature can be used to determine the normality threshold T L and the abnormality threshold T H to correct.

[0073] For example, as in Fig. 7 to 9, in a second modification example, a temperature (hereinafter referred to as the water temperature) of the engine cooling water instead of the oil temperature in the correction of the normality threshold value T L and the abnormality threshold T H used. Since the engine cooling water only correlates with the oil temperature at a certain temperature lower (for example, 10°C) than the oil temperature, it can be a parameter for correcting the threshold values T L and T H similar to the oil temperature.

[0074] Specifically, as in Fig. 7, in the second modification example, the oil temperature sensor 50 is omitted, and instead, a water temperature sensor 60 attached to the water jacket J to detect the water temperature is used. Furthermore, the abnormality detection unit 30 of the second modification example includes a water temperature map M3 instead of the oil temperature map M2. As shown in Fig. 8, replaces the water temperature map M3 with respect to the Fig. 4, the detected oil temperature TO is replaced by a detected value (hereinafter, detected water temperature) TW of the water temperature sensor 60, and the oil temperature correction coefficient KO is replaced by a correction coefficient (hereinafter, water temperature correction coefficient) KW corresponding to the detected water temperature TW.

[0075] Furthermore, as in Fig. 9, in a control flow of the second modification example, the Fig. 5 are replaced by steps S101A and 104A to 106A. In step S101A, the detected pipe temperature T, the detected atmospheric temperature TA, and the detected water temperature TW are obtained, and in step S104A, the water temperature correction coefficient KW is obtained. Then, in steps S105A and S106A, the normality threshold value T L and the abnormality threshold T H calculated based on the atmospheric temperature correction coefficient KA and the water temperature correction coefficient KW. (Third modification example)

[0076] In addition to the atmospheric temperature and the oil temperature, other parameters can be used to determine the normality threshold T L and the abnormality threshold T H to correct.

[0077] Specifically, as in Fig. 10, in a control flow of a third modification example, the water temperature is used as a parameter and the Fig. 5 are replaced by steps S101B, S105B, and S106B. Furthermore, step S104B is provided between step S104 and step S105B. In step S101B, the detected pipe temperature T, the detected atmospheric temperature TA, the detected oil temperature TO, and the detected water temperature TW are obtained, and in step S104B, the water temperature correction coefficient KW is obtained. Then, in steps S105B and S106B, the normality threshold value T L and the abnormality threshold T H calculated based on the atmospheric temperature correction coefficient KA, the oil temperature correction coefficient KO and the water temperature correction coefficient KW. (Fourth modification example)

[0078] The normality threshold T Land the abnormality threshold T H can be corrected based on only one parameter (for example, atmospheric temperature). (Fifth modification example)

[0079] Although not shown, the normality threshold T L and the abnormality threshold T H cannot be corrected. Specifically, the abnormality detection unit 30 of a fifth modification example compares the detected temperature in the pipe T with the reference normality threshold value T L0 and the reference abnormality threshold T H0 to detect the normality and abnormality of the internal combustion engine. (Sixth modification example)

[0080] Instead of the normality threshold T L and the abnormality threshold T HTo correct the abnormality, the detected temperature in the pipe T can be corrected. Specifically, the abnormality detection unit 30 of a sixth modification example calculates a corrected detected temperature in the pipe T' by dividing the detected temperature in the pipe T by the atmospheric temperature correction coefficient KA and the oil temperature correction coefficient KO (T' = T / (KA × KO)). Then, the corrected detected temperature in the pipe T' is compared with the reference normality threshold value T L0 and the reference abnormality threshold T H0 compared to detect the normality and abnormality of the internal combustion engine. (Seventh modification example)

[0081] From the normality threshold T L and the abnormality threshold T H the normality threshold T Lbe omitted. In a seventh modification example, it is only determined whether the detected temperature in the pipe T is equal to or greater than the abnormality threshold T H is. (Eighth modification example)

[0082] When the temperature difference between the detected temperatures in the pipe T during normal and abnormal conditions is clear, the oil separator 11 can be omitted from the blow-by gas pipe 10b. (Ninth modification example)

[0083] If the temperature difference between the detected temperatures in the pipe T during normal and abnormal conditions is clear, the temperature sensor 20 does not need to be located at the downstream end portion of the blow-by gas pipe 10b. For example, the temperature sensor 20 of the ninth modification example is attached to the blow-by gas pipe 10b, located immediately downstream of the oil separator 11.

[0084] The embodiment of the present disclosure is described in detail above. However, embodiments of the present disclosure are not limited to the above-described embodiment, and all modification examples, applications, and equivalents included in the ideas of the present disclosure defined by the claims are included in the present disclosure. Therefore, this disclosure should not be construed as limiting and can be applied to any other technology that falls within the scope of the ideas of this disclosure.

[0085] This application is based on a Japanese patent application filed on March 15, 2019 (Japanese Patent Application No. 2019-048605), the contents of which are incorporated herein by reference. INDUSTRIAL APPLICABILITY

[0086] With the diagnostic device according to the present disclosure, the abnormality of the internal combustion engine can be detected based on the temperature in the blow-by gas passage. REFERENCE SYMBOL LIST 1 combustion engine 2 engine bodies 3 intake manifold 4 intake pipe 5 cylinder block 6 Crankcase 7 Oil pan 8 cylinder head 9 Head cover 10 Blow-by gas passage 10a internal engine passage 10b Blow-by gas pipe 10c Oil separation chamber 11 oil separators 20 Temperature sensor 30 Abnormality Detection Unit 40 Atmospheric temperature sensor 50 Oil temperature sensor 100 diagnostic devices A intake air B Blow-by gas O oil separated from blow-by gas T L Normality threshold T HAbnormality threshold (threshold)

Claims

[1] Diagnostic device for an internal combustion engine (1), wherein the internal combustion engine (1) comprises a blow-by gas passage (10) through which blow-by gas flows, and wherein the diagnostic device (100) comprises: a temperature sensor (20) that detects a temperature within the blow-by gas passage (10); an atmospheric temperature sensor (40) for detecting the atmospheric temperature; and an abnormality detection unit (30) comprising an atmospheric temperature map (M1) defining a relationship between the atmospheric temperature (TA) detected by the atmospheric temperature sensor (40) and a correction coefficient (KA), wherein the abnormality detection unit (30) detects an abnormality by comparing the detected value of the temperature sensor (20) with an abnormality threshold (TH) and corrects the abnormality threshold (TH) based on the atmospheric temperature (TA), and wherein the abnormality detection unit (30) repeatedly updates the corrected abnormality threshold value (TH) by multiplying a reference abnormality threshold value (TH0) by the correction coefficient (KA) corresponding to the atmospheric temperature (TA) defined by the atmospheric temperature map (M1) detected by the atmospheric temperature sensor (40). [2] The diagnostic device for the internal combustion engine (1) according to claim 1, wherein the abnormality detection unit (30) detects an abnormality by comparing the detected value of the temperature sensor (20) with the reference threshold value and corrects the reference abnormality threshold value (TH0) based on at least one of the atmospheric temperature (TA), a temperature of engine oil, and a temperature of engine cooling water. [3] Diagnostic device for the internal combustion engine (1) according to claim 2, wherein the abnormality detection unit (30) corrects the abnormality threshold value (TH) to a higher value when at least one of the atmospheric temperature, the temperature of engine oil and the temperature of engine cooling water is increased. [4] The diagnostic device for the internal combustion engine (1) according to any one of claims 1 to 3, wherein the temperature sensor (20) is configured to be located in the blow-by gas passage (10) on a downstream side of one of the oil separators (11) in the blow-by gas passage (10). [5] The diagnostic device for the internal combustion engine (1) according to any one of claims 1 to 4, wherein the temperature sensor (20) is configured to be located at an end portion of a downstream side of the blow-by gas passage (10), the downstream side end portion being open to the atmosphere.

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