Abnormality diagnostic device

Abstract

To suppress deterioration of diagnosis accuracy.SOLUTION: A processing circuit 51 for an abnormality diagnostic device 50 derives a change corresponding value that is a value indicating transition of a PCV pressure sensor value during a monitoring period when the monitoring period is set in the situation where a suction air amount increases. The processing circuit 51 derives a determination parameter by integrating the derived change corresponding value when an increase amount of the suction air amount is a determination increase amount or larger. The processing circuit 51 makes a diagnosis to determine occurrence of a leakage abnormality in the case where the determination parameter when frequency of the integration of the change corresponding value reaches prescribed frequency is lower than a threshold value. The processing circuit 51 does not use the change corresponding value in the monitoring period in which both of the condition where the change corresponding value is lower than the determination value and the condition where an accelerator operation amount at the end of the monitoring period is smaller than that at start of the monitoring period are satisfied for the derivation of the determination parameter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an abnormality diagnosis device that is applied to an internal combustion engine having a function of returning blow-by gas that has leaked from a combustion chamber into a crankcase to an intake passage. [Background technology]

[0002] The internal combustion engine disclosed in Patent Document 1 includes an accumulation section where blow-by gas accumulates, a blow-by gas passage that connects the accumulation section to the intake passage, and a pressure sensor that detects the pressure in the blow-by gas passage. The detected value of the pressure sensor is called a PCV pressure sensor value. The blow-by gas passage is connected to a portion of the intake passage upstream of the turbocharger compressor. In such an internal combustion engine, if blow-by gas can be supplied to the intake passage via the blow-by gas passage, there is a correlation between changes in the intake air amount and changes in the PCV pressure sensor value. For example, when the intake air amount increases, the PCV pressure sensor value decreases.

[0003] Therefore, the control device for the internal combustion engine sets a monitoring period each time the intake air amount increases. When the control device sets the monitoring period, it sets the PCV pressure sensor value at the start of the monitoring period as a reference value. The control device derives a change response value by integrating the differences between multiple PCV pressure sensor values ​​detected during the monitoring period and the reference value. The control device derives a judgment parameter by integrating the derived change response value when the increase in the intake air amount is equal to or greater than a judgment increase amount. If the judgment parameter is less than a threshold value, the control device diagnoses that an abnormality has occurred in a downstream portion of the blow-by gas passage, which is closer to the intake passage than the PCV sensor connection point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-186702 Summary of the Invention [Problem to be solved by the invention]

[0005] When the supercharger is in a supercharging state, the intake air volume may continue to increase even after the driver reduces the accelerator pedal depression amount. For example, even if the accelerator pedal depression amount is reduced, the increase in the intake air volume may exceed the judgment increase amount. When the accelerator pedal depression amount is reduced, the internal combustion engine is not substantially under load. Because the change response value derived during such a period is relatively small, the judgment parameter, which is the integrated value of the change response value, also becomes small. As a result, the judgment parameter may become smaller than the threshold value even though no abnormality actually occurs in the downstream portion of the blow-by gas passage. In other words, the control device may erroneously diagnose an abnormality in the downstream portion even though no abnormality actually occurs in the downstream portion. [Means for solving the problem]

[0006] An abnormality diagnosis device for solving the above problems is applied to an internal combustion engine including a turbocharger, an accumulation unit that accumulates blow-by gas that leaks from a combustion chamber into a crankcase, a blow-by gas passage that connects a portion of an intake passage upstream of a compressor of the turbocharger with the accumulation unit, and a PCV pressure sensor that is connected to the blow-by gas passage and detects the pressure of the blow-by gas passage. The detected value of the PCV pressure sensor is a PCV pressure sensor value. The abnormality diagnosis device includes a processing circuit. When the intake air amount is increasing, the processing circuit sets a monitoring period each time, sets the PCV pressure sensor value at the start of the monitoring period as a reference value, and derives a change response value by integrating the differences between multiple PCV pressure sensor values ​​detected during the monitoring period and the reference value. The processing circuit is configured to derive a judgment parameter by integrating the derived change response value when the increase in the intake air amount is equal to or greater than a judgment increase amount, and when the judgment parameter is less than a threshold value when the number of times the change response value for deriving the judgment parameter has been integrated reaches a specified number of times, the processing circuit diagnoses that an abnormality has occurred in a portion of the blow-by gas passage closer to the intake passage than a connection point of the PCV pressure sensor.The processing circuit does not use the change response value for a monitoring period in which both the change response value is less than a judgment value and the accelerator depression amount at the end of the monitoring period is smaller than the start of the monitoring period, in deriving the judgment parameter. [Effects of the Invention]

[0007] The abnormality diagnosis device has the effect of suppressing a decrease in diagnostic accuracy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an internal combustion engine equipped with an abnormality diagnosis device according to an embodiment. [Figure 2] FIG. 2 is a time chart showing the relationship between the accelerator operation amount and the intake air amount. [Figure 3] FIG. 3 is a flowchart showing the first half of a series of processes executed by the abnormality diagnosis device of FIG. [Figure 4] FIG. 4 is a flowchart showing the latter half of a series of processes executed by the abnormality diagnosis device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the abnormality diagnostic device will be described below with reference to FIGS. <Configuration of an internal combustion engine> 1 shows an internal combustion engine 10 equipped with an abnormality diagnosis device 50. The internal combustion engine 10 is equipped with an exhaust-driven supercharger 11. A crankcase 13 is attached to the bottom of a cylinder block 12 of the internal combustion engine 10. A crankshaft 14 is housed within the crankcase 13. An oil pan 15 is attached to the bottom of the crankcase 13 to store oil circulating within the internal combustion engine 10.

[0010] A cylinder head 16 is attached to the top of the cylinder block 12. A plurality of cylinders 17 are defined by the cylinder block 12 and the cylinder head 16. A head cover 18 is attached to the top of the cylinder head 16.

[0011] A piston 19 is housed in each of the cylinders 17. Each of the pistons 19 is connected to the crankshaft 14 via a connecting rod 20. The reciprocating motion of each of the pistons 19 within the cylinder 17 causes the crankshaft 14 to rotate.

[0012] The internal combustion engine 10 is provided with a communication passage 21 that connects the space defined by the cylinder head 16 and the head cover 18 with the inside of the crankcase 13. The communication passage 21 spans the cylinder block 12 and the cylinder head 16. Therefore, blow-by gas that leaks into the crankcase 13 from a combustion chamber 22 defined in each cylinder 17 flows into the space through the communication passage 21. In other words, the space defined by the cylinder head 16 and the head cover 18 functions as an "accumulation section 23" where blow-by gas accumulates.

[0013] An intake passage 24 and an exhaust passage 25 are connected to the cylinder head 16. Intake air that flows through the intake passage 24 is introduced into the combustion chamber 22. In the combustion chamber 22, an air-fuel mixture containing the intake air and fuel is burned. Exhaust gas generated in the combustion chamber 22 by the combustion of the air-fuel mixture is discharged into the exhaust passage 25.

[0014] The supercharger 11 includes a turbine 111 and a compressor 112. The turbine 111 is provided in the exhaust passage 25. The compressor 112 is provided in the intake passage 24 at a position upstream of the throttle valve 26.

[0015] The internal combustion engine 10 is equipped with a blow-by gas treatment device 30 that returns blow-by gas accumulated in the accumulation section 23 to the intake passage 24. Hereinafter, the blow-by gas treatment device 30 will be referred to as the "PCV treatment device 30." A portion of the intake passage 24 upstream of the compressor 112 will be referred to as the "upstream intake passage 241." The PCV treatment device 30 is equipped with a blow-by gas passage 31 that connects the accumulation section 23 and the upstream intake passage 241, and a PCV pressure sensor 35 that detects the absolute pressure in the blow-by gas passage 31. The PCV pressure sensor 35 outputs a detection signal corresponding to the absolute pressure in the blow-by gas passage 31 to the abnormality diagnosis device 50.

[0016] The blow-by gas passage 31 has a joint 32 attached to the head cover 18 and a blow-by gas pipe 33. One end of the blow-by gas pipe 33 is connected to the joint 32, while the other end of the blow-by gas pipe 33 is connected to the upstream intake passage 241. A PCV pressure sensor 35 is connected to the joint 32.

[0017] <Sensor> Detection signals are input to the abnormality diagnosis device 50 from multiple sensors. In addition to the PCV pressure sensor 35, the multiple sensors include an atmospheric pressure sensor 41, an air flow meter 42, and an accelerator sensor 43. The atmospheric pressure sensor 41 detects the atmospheric pressure, which is the pressure around the internal combustion engine 10. The air flow meter 42 detects the flow rate of intake air flowing through the intake passage 24. The accelerator sensor 43 detects the amount of accelerator pedal operation by the driver. Hereinafter, the absolute pressure based on the detection signal of the PCV pressure sensor 35 will be referred to as the "PCV pressure sensor value PCVS." The pressure based on the detection signal of the atmospheric pressure sensor 41 will be referred to as the "atmospheric pressure PHAC." The flow rate of intake air based on the detection signal of the air flow meter 42 will be referred to as the "intake air amount GA." The amount of accelerator pedal operation based on the detection signal of the accelerator sensor 43 will be referred to as the "accelerator operation amount ACC."

[0018] <Abnormality diagnosis device> The abnormality diagnosis device 50 diagnoses whether or not a leakage abnormality has occurred in the PCV treatment device 30. A leakage abnormality is an abnormality in which blow-by gas may leak to the outside from a portion of the blow-by gas passage 31 that is closer to the upstream intake passage 241 than the connection point of the PCV pressure sensor 35. A leakage abnormality may occur when any of the following occurs: the blow-by gas pipe 33 comes off the intake passage 24, the blow-by gas pipe 33 comes off the joint 32, or the blow-by gas pipe 33 is damaged.

[0019] The abnormality diagnosis device 50 includes a processing circuit 51. One example of the processing circuit 51 is an electronic control device. In this case, the processing circuit 51 includes a CPU 52, a first memory 53, and a second memory 54. The first memory 53 stores a control program executed by the CPU 52. The second memory 54 stores the results of calculations by the CPU 52, etc. The CPU 52 executes the control program in the first memory 53, causing the processing circuit 51 to diagnose whether a leakage abnormality has occurred.

[0020] <Relationship between intake air volume and PCV pressure sensor value> The relationship between the intake air amount GA and the PCV pressure sensor value PCVS when no leakage abnormality occurs will be explained. The blow-by gas passage 31 is connected to the upstream intake passage 241 of the intake passage 24. Therefore, when the intake air amount GA changes while the supercharger 11 is operating, the PCV pressure sensor value PCVS changes in conjunction with the change in the intake air amount GA. For example, when the intake air amount GA decreases, the PCV pressure sensor value PCVS increases. In other words, the PCV pressure sensor value PCVS increases toward 0 (zero). On the other hand, when the intake air amount GA increases, the PCV pressure sensor value PCVS decreases.

[0021] On the other hand, when a leakage abnormality occurs, the change in the PCV pressure sensor value PCVS when the intake air amount GA changes is smaller than when a leakage abnormality does not occur. In other words, even if the intake air amount GA increases, the PCV pressure sensor value PCVS does not decrease much.

[0022] Here, with reference to (A) and (B) in FIG. 2, the correlation between the accelerator operation amount ACC and the intake air amount GA will be described. Generally, when the accelerator operation amount ACC increases, the intake air amount GA also increases. When the accelerator operation amount ACC decreases, the intake air amount GA also decreases. However, the internal combustion engine 10 is equipped with a supercharger 11. Therefore, when the supercharger 11 is performing supercharging, even if the accelerator operation amount ACC decreases, the intake air amount GA may continue to increase because supercharging continues due to the inertial force of the compressor 112. In the example shown in FIG. 2, during the period from timing t1 to timing t2, the intake air amount GA increases despite the decrease in the accelerator operation amount ACC.

[0023] <Diagnosis processing> 3 and 4, a diagnostic process, which is a series of processes for diagnosing whether or not a leakage abnormality has occurred, will be described. The processing circuit 51 repeatedly executes the diagnostic process while the engine is running.

[0024] In step S11, the processing circuit 51 determines whether the intake air amount GA is equal to or greater than the intake air amount reference value GAth. The intake air amount reference value GAth is set to satisfy the following conditions (A1) and (A2). Therefore, even if the engine is running, if supercharging is not being performed by the supercharger 11, the intake air amount GA will not be equal to or greater than the intake air amount reference value GAth.

[0025] (A1) When supercharging is performed by the operation of the supercharger 11, the intake air amount GA becomes equal to or greater than the intake air amount reference value GAth. (A2) When the intake air amount GA is equal to or greater than the intake air amount reference value GAth, the PCV pressure sensor value PCVS becomes lower than the atmospheric pressure PHAC.

[0026] If the intake air amount GA is equal to or greater than the intake air amount reference value GAth (S11: YES), the processing circuit 51 proceeds to step S13. If the intake air amount GA is less than the intake air amount reference value GAth (S11: NO), the processing circuit 51 proceeds to step S37.

[0027] In step S13, the processing circuit 51 determines whether or not the reference operation amount ACCb has been set. The reference operation amount ACCb is the accelerator operation amount ACC at the start of the current monitoring period. The monitoring period is a period during which changes in the PCV pressure sensor value PCVS are monitored. If the reference operation amount ACCb for the current monitoring period has been set (S13: YES), the processing circuit 51 shifts the processing to step S17. If the reference operation amount ACCb for the current monitoring period has not yet been set (S13: NO), the processing circuit 51 shifts the processing to step S15. In other words, if the current time is the start of the monitoring period, the processing circuit 51 shifts the processing to step S15.

[0028] In step S15, the processing circuit 51 sets the latest value of the accelerator operation amount ACC to the reference operation amount ACCb, and then the processing circuit 51 proceeds to step S17. In step S17, the processing circuit 51 updates the measurement counter CNT so that the measurement counter CNT is incremented by 1. The measurement counter CNT corresponds to the elapsed time from the start of the current monitoring period.

[0029] In the following step S19, the processing circuit 51 derives a PCV pressure decrease amount ΔPCVS, which is the amount of decrease in the PCV pressure sensor value PCVS. Specifically, the processing circuit 51 sets the PCV pressure sensor value PCVS at the start of the current monitoring period to a reference value PCVSb. If the current PCV pressure sensor value PCVS is equal to or less than the reference value PCVSb, the processing circuit 51 derives the absolute value of the difference between the current PCV pressure sensor value PCVS and the reference value PCVSb as the PCV pressure decrease amount ΔPCVS. On the other hand, if the current PCV pressure sensor value PCVS is higher than the reference value PCVSb, the processing circuit 51 derives 0 (zero) as the PCV pressure decrease amount ΔPCVS.

[0030] In the next step S21, the processing circuit 51 derives the sum of the change response value X and the PCV pressure decrease amount ΔPCVS as the latest value of the change response value X. That is, the processing circuit 51 can derive the change response value X by integrating the PCV pressure decrease amount ΔPCVS.

[0031] In the following step S23, the processing circuit 51 determines whether the measurement counter CNT is equal to or greater than the determination counter CNTth. The determination criterion for determining whether the monitoring period has ended is set as the determination counter CNTth. In other words, the determination counter CNTth defines the length of the monitoring period. If the measurement counter CNT is equal to or greater than the determination counter CNTth (S23: YES), the processing circuit 51 proceeds to step S25. If the measurement counter CNT is less than the determination counter CNTth (S23: NO), the processing circuit 51 temporarily terminates the diagnostic processing.

[0032] In step S25, the processing circuit 51 determines whether the increase ΔGA in the intake air amount GA during the current monitoring period is equal to or greater than the judgment increase ΔGAth. The processing circuit 51 can derive the increase ΔGA by subtracting the intake air amount GA at the start of the monitoring period from the intake air amount GA at the end of the monitoring period. A criterion for determining whether the change in the intake air amount GA is large is set as the judgment increase ΔGAth. For example, the processing circuit 51 may set the judgment increase ΔGAth so that the higher the engine speed NE, the larger the value.

[0033] If the increase amount ΔGA is equal to or greater than the determined increase amount ΔGAth (S25: YES), the processing circuit 51 proceeds to step S27. If the increase amount ΔGA is less than the determined increase amount ΔGAth (S25: NO), the processing circuit 51 proceeds to step S37.

[0034] In step S27, the processing circuit 51 determines whether the change correspondence value X derived in step S21 is less than a judgment value Xth. A criterion for determining whether the change correspondence value X is small or not is set as the judgment value Xth. For example, a value obtained by dividing a parameter threshold value Zth (described later) by a specified number of times Nth (described later) is set as the judgment value Xth.

[0035] If the change correspondence value X is less than the judgment value Xth (S27: YES), the processing circuit 51 proceeds to step S29. If the change correspondence value X is equal to or greater than the judgment value Xth (S27: NO), the processing circuit 51 proceeds to step S31.

[0036] In step S29, the processing circuit 51 determines whether the accelerator operation amount ACC at the end of the current monitoring period is less than the reference operation amount ACCb. If the accelerator operation amount ACC at the end of the current monitoring period is less than the reference operation amount ACCb, this means that the accelerator operation amount ACC has decreased during the current monitoring period. If the accelerator operation amount ACC at the end of the current monitoring period is less than the reference operation amount ACCb (S29: YES), the processing circuit 51 temporarily ends the diagnosis process. If the accelerator operation amount ACC at the end of the current monitoring period is equal to or greater than the reference operation amount ACCb (S29: NO), the processing circuit 51 proceeds to step S31.

[0037] In step S31, the processing circuit 51 updates the number of accumulations N so that the number of accumulations N increases by 1. In the following step S33, the processing circuit 51 derives the sum of the decision parameter Z and the change correspondence value X as the latest value of the decision parameter Z. That is, the processing circuit 51 can derive the decision parameter Z by accumulating the derived change correspondence value X when the increase amount ΔGA is equal to or greater than the decision increase amount ΔGAth.

[0038] In the next step S35, the processing circuit 51 determines whether the cumulative number N is equal to or greater than a specified number Nth. For example, the specified number Nth is set to a positive number equal to or greater than 2. If the cumulative number N is equal to or greater than the specified number Nth (S35: YES), the processing circuit 51 proceeds to step S39. If the cumulative number N is less than the specified number Nth (S35: NO), the processing circuit 51 proceeds to step S37.

[0039] In step S37, the processing circuit 51 resets both the measurement counter CNT and the change correspondence value X to 0 (zero). After that, the processing circuit 51 temporarily ends the diagnostic processing. In step S39, the processing circuit 51 determines whether the judgment parameter Z is equal to or greater than the parameter threshold value Zth. The judgment criterion for diagnosing whether a leakage abnormality has occurred using the judgment parameter Z is set as the parameter threshold value Zth. If the judgment parameter Z is equal to or greater than the parameter threshold value Zth (S39: YES), the processing circuit 51 proceeds to step S41. If the judgment parameter Z is less than the parameter threshold value Zth (S39: NO), the processing circuit 51 proceeds to step S43.

[0040] In step S41, the processing circuit 51 determines that no leakage abnormality has occurred, that is, that no abnormality has occurred in the portion of the blow-by gas passage 31 closer to the intake passage 24 than the connection portion of the PCV pressure sensor 35. Then, the processing circuit 51 temporarily ends the diagnostic process.

[0041] In step S43, the processing circuit 51 diagnoses that a leakage abnormality has occurred, that is, that an abnormality has occurred in a portion of the blow-by gas passage 31 closer to the intake passage 24 than the connection portion of the PCV pressure sensor 35. Then, the processing circuit 51 temporarily ends the diagnostic process.

[0042] <Actions and Effects of This Embodiment> When the accelerator pedal depression amount ACC increases due to the driver's operation of the accelerator pedal, the intake air amount GA increases. Under this condition, if the intake air amount GA is equal to or greater than the intake air amount reference value GAth, it can be considered that the supercharger 11 is operating.

[0043] When the internal combustion engine 10 is operating, the processing circuit 51 sets a monitoring period each time. When the processing circuit 51 sets the monitoring period, the processing circuit 51 derives the change response value X by integrating the differences between a plurality of PCV pressure sensor values ​​PCVS detected during the monitoring period and a reference value PCVSb.

[0044] Furthermore, the processing circuit 51 derives a judgment parameter Z by integrating the derived change response value X when the increase amount ΔGA of the intake air amount is equal to or greater than the judgment increase amount ΔGAth. The processing circuit 51 diagnoses whether or not a leakage abnormality has occurred using the judgment parameter Z when the number of times N of integrating the change response value X has reached a specified number Nth. Specifically, the processing circuit 51 diagnoses that a leakage abnormality has occurred when the judgment parameter Z is less than a parameter threshold value Zth. The processing circuit 51 diagnoses that a leakage abnormality has not occurred when the judgment parameter Z is equal to or greater than the parameter threshold value Zth.

[0045] As described above, when the supercharger 11 is operating, the intake air amount GA may increase for a while even after the accelerator depression amount ACC starts to decrease. When the accelerator depression amount ACC is decreasing, even if the intake air amount GA increases, no load is actually applied to the internal combustion engine 10. The change response value X derived during such a period is relatively small. Therefore, the determination parameter Z, which is the integrated value of the change response value X, also becomes small. As a result, there is a risk that the determination parameter Z will become less than the parameter threshold value Zth even though a leakage abnormality has not actually occurred.

[0046] In this regard, in this embodiment, the processing circuit 51 does not use the change response value X for a monitoring period in which both of the following conditions are met: the change response value X is less than the judgment value Xth, and the accelerator operation amount ACC at the end of the monitoring period is smaller than the start of the monitoring period, in deriving the judgment parameter Z. In the diagnosis processing shown in Figures 3 and 4, if both of the following conditions are met: the change response value X is less than the judgment value Xth, and the accelerator operation amount ACC at the end of the monitoring period is smaller than the start of the monitoring period, the processing from step S31 onwards is not executed.

[0047] As a result, the change response value X during the period when the accelerator operation amount ACC is decreasing is not reflected in the derivation of the determination parameter Z. As a result, when no leakage abnormality actually occurs, the determination parameter Z is less likely to become less than the parameter threshold value Zth. Therefore, the abnormality diagnosis device 50 can suppress a decrease in diagnosis accuracy.

[0048] In this embodiment, the following effects can be further obtained. The determination value Xth is a value obtained by dividing the parameter threshold value Zth by the specified number of times Nth, thereby enabling the abnormality detection device 50 to determine whether the change response value X is small due to a decrease in the accelerator operation amount ACC.

[0049] <Example of change> 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.

[0050] The judgment value Xth may be a value other than the value obtained by dividing the parameter threshold Zth by the specified number of times Nth, as long as it is smaller than the parameter threshold Zth. For example, the judgment value Xth may be set to a value equal to or smaller than the value obtained by dividing the parameter threshold Zth by 2.

[0051] The determination increase amount ΔGAth may be fixed at a predetermined value. The processing circuit 51 is not limited to a circuit having a CPU and ROM and executing software processing. In other words, the processing circuit 51 may have any one of the following configurations (a), (b), and (c):

[0052] (a) The processing circuit 51 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0053] (b) The processing circuit 51 includes one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits (ASICs) or FPGAs. ASIC stands for "Application Specific Integrated Circuit," and FPGA stands for "Field Programmable Gate Array."

[0054] (c) The processing circuitry 51 includes one or more processors that execute some of the various processes in accordance with a computer program, and one or more dedicated hardware circuits that execute the remaining processes among the various processes. [Explanation of symbols]

[0055] 10...internal combustion engine, 11...supercharger, 112...compressor, 13...crankcase, 22...combustion chamber, 23...accumulator, 24...intake passage, 241...upstream intake passage, 31...blow-by gas passage, 35...PCV pressure sensor, 50...abnormality diagnosis device, 51...processing circuit

Claims

1. The present invention is applied to an internal combustion engine including: a turbocharger; an accumulation portion that accumulates blow-by gas leaked from a combustion chamber into a crankcase; a blow-by gas passage that communicates a portion of an intake passage upstream of a compressor of the turbocharger with the accumulation portion; and a PCV pressure sensor that is connected to the blow-by gas passage and detects the pressure of the blow-by gas passage, the detected value of the PCV pressure sensor is a PCV pressure sensor value, a processing circuit; The processing circuit is configured to execute the following when the intake air amount is increasing: setting a monitoring period each time; setting the PCV pressure sensor value at the start of the monitoring period as a reference value; and deriving a change response value by integrating the differences between a plurality of the PCV pressure sensor values ​​detected during the monitoring period and the reference value; the processing circuit derives a judgment parameter by integrating the derived change correspondence value when the increase amount of the intake air amount is equal to or greater than a judgment increase amount, and when the judgment parameter is less than a threshold value when the number of times the change correspondence value is integrated for deriving the judgment parameter reaches a specified number, diagnoses that an abnormality has occurred in a portion of the blow-by gas passage that is closer to the intake passage than a connection portion of the PCV pressure sensor, The processing circuit does not use the change response value for a monitoring period in which both of the following conditions are met: the change response value is less than the judgment value; and the accelerator operation amount at the end of the monitoring period is smaller than that at the start of the monitoring period. Abnormality diagnosis device.

2. The judgment value is a value obtained by dividing the threshold value by the specified number of times. The abnormality diagnosis device according to claim 1 .

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