Abnormality determination device for air flow meter

Abstract

To more appropriately determine an abnormality of an air flow meter due to water adhesion.SOLUTION: An abnormality determination device for an air flow meter that determines an abnormality of the hot film type air flow meter used in an internal combustion engine executes an abnormality determination for determining occurrence of an abnormality in the air flow meter due to water adhesion by comparing a detection value that is a suction air amount of the internal combustion engine detected by the air flow meter with a determination threshold value that is a maximum value or minimum value of the suction air amount based on of a throttle opening that is an opening of a throttle valve.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an abnormality determination device for an air flow meter. [Background technology]

[0002] Conventionally, as this type of air flow meter abnormality determination device, one that determines abnormalities in air flow meters used in internal combustion engines has been proposed (see, for example, Patent Document 1). This device determines abnormalities in the air flow meter due to disconnection, short circuit, deterioration over time, etc., by comparing the intake air volume indirectly measured by a throttle opening sensor and an intake pressure sensor with the intake air volume directly measured by the air flow meter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-261354 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned document does not disclose how to determine an abnormality caused by water droplets that have entered through the intake system of an internal combustion engine and adhere to the air flow meter. If water adheres to the air flow meter, it may be impossible to accurately measure the intake air volume, and the internal combustion engine may not be controlled properly. Therefore, it is recognized that it is an important issue to more accurately determine an abnormality caused by water adhesion in the air flow meter.

[0005] The main object of the air flow meter abnormality determination device of the present disclosure is to more accurately determine an abnormality caused by adhesion of water to the air flow meter. [Means for solving the problem]

[0006] The air flow meter abnormality determination device of the present disclosure employs the following means to achieve the above-mentioned main object.

[0007] The air flow meter abnormality determination device of the present disclosure is An air flow meter abnormality determination device for determining an abnormality in a hot film air flow meter used in an internal combustion engine, comprising: A detection value, which is an intake air amount of the internal combustion engine detected by the air flow meter, is compared with a determination threshold value, which is a maximum or minimum value of the intake air amount based on a throttle opening, which is an opening degree of a throttle valve, to perform an abnormality determination for determining whether or not an abnormality due to adhesion of water has occurred in the air flow meter. The gist of the present invention is as follows.

[0008] In the airflow meter abnormality determination device disclosed herein, a detection value, which is the intake air amount of the internal combustion engine detected by the airflow meter, is compared with a determination threshold value, which is the maximum or minimum value of the intake air amount based on the throttle opening, which is the opening degree of the throttle valve, to perform an abnormality determination to determine whether or not an abnormality due to water adhesion has occurred in the airflow meter. When water adheres to the airflow meter, the detection value becomes excessively large or excessively small depending on the location where the water adheres. Therefore, by performing an abnormality determination to determine whether or not an abnormality due to water adhesion has occurred in the airflow meter by comparing the detection value with a determination threshold value, which is the maximum or minimum value of the intake air amount based on the throttle opening, an abnormality determination can be performed to properly determine whether or not an abnormality due to water adhesion has occurred in the airflow meter.

[0009] In the air flow meter abnormality determination device of the present disclosure, the determination threshold may be the maximum value or a value obtained by adding a determination margin to the maximum value, and the abnormality determination may be performed by determining that an abnormality due to water adhesion has occurred in the air flow meter when the detection value exceeds the determination threshold. In this way, an abnormality due to water adhesion in the air flow meter can be more appropriately determined.

[0010] In the air flow meter abnormality determination device disclosed herein, the internal combustion engine may have a supercharger including a compressor installed upstream of the throttle valve in the intake pipe and a turbine installed in the exhaust pipe, and the abnormality determination may be performed when the internal combustion engine is operating autonomously. When the internal combustion engine is operating autonomously, the supercharging pressure is zero or close to zero, and the difference between the detected value and the intake air amount based on the throttle opening is small. Therefore, by performing the abnormality determination when the internal combustion engine is operating autonomously, the abnormality determination can be performed properly. This allows for more proper determination of an abnormality due to adhesion of water to the air flow meter.

[0011] Furthermore, in the air flow meter abnormality determination device disclosed herein, the abnormality determination may be performed every first hour, and after it is determined that an abnormality due to water adhesion has occurred in the air flow meter, if the detection value continues to be equal to or less than the determination threshold until a second time has elapsed during which it can be determined that the water adhesion has been reliably eliminated since the detection value became equal to or less than the determination threshold, it may be determined that the air flow meter has not experienced an abnormality due to water adhesion. In this way, it is possible to more reliably determine that an abnormality due to water adhesion has not occurred in the air flow meter. [Brief description of the drawings]

[0012] [Figure 1] 1 is a configuration diagram showing an outline of the configuration of an engine device 10. FIG. [Diagram 2] 2 is an explanatory diagram showing an example of input / output signals of an electronic control unit 70 provided in the engine device 10 and including an abnormality determination device for an air flow meter 23a of the present embodiment. FIG. [Diagram 3] 4 is an explanatory diagram for explaining the configuration and temperature distribution of an air flow meter 23a. FIG. [Figure 4] 4 is a flowchart showing an example of an abnormality determination process executed by an ECU 70. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of an engine device 10, and Fig. 2 is an explanatory diagram showing an example of input / output signals of an electronic control unit (hereinafter referred to as "ECU") 70 provided in the engine device 10 and including an abnormality determination device for an air flow meter 23a of this embodiment. The engine device 10 of this embodiment is mounted on a general vehicle that runs using power from an engine 12, or on various hybrid vehicles that are provided with a motor in addition to the engine 12, and includes the engine 12, a supercharger 40, a purification device 37, a PM filter 38, and an ECU 70, as shown in Figs. 1 and 2.

[0014] The engine 12 is configured as an internal combustion engine that outputs power using fuel such as gasoline or diesel fuel supplied from a fuel tank 11. The engine 12 has a fuel injection valve 28 that injects fuel into an intake port, and an ignition plug 32. The engine 12 draws air cleaned by an air cleaner 22 into an intake pipe 23, passes the air through an intercooler 25, a throttle valve 26, and a surge tank 27 in that order, and injects fuel from a fuel injection valve 28 downstream of the surge tank 27 of the intake pipe 23 to mix the air and fuel. The mixture is drawn into a combustion chamber 31 via an intake valve 30, and is explosively combusted by an electric spark generated by an ignition plug 32. The reciprocating motion of a piston 33, which is pushed down by the energy of the explosive combustion, is converted into the rotational motion of a crankshaft 14. The exhaust gas discharged from the combustion chamber 31 into an exhaust pipe 35 through an exhaust valve 34 is discharged into the outside air through a purification device 37 having a catalyst (three-way catalyst) that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), and a PM filter 38 that removes particulate matter (soot, etc.) in the exhaust gas. Although not shown, a starter that cranks the engine 12, an alternator that generates electricity using the power of the engine 12, and the like are attached to the crankshaft 14.

[0015] The supercharger 40 is configured as a turbocharger, and includes a compressor 41, a turbine 42, a rotating shaft 43, a wastegate valve 44, and a blow-off valve 45. The compressor 41 is disposed upstream of the intercooler 25 in the intake pipe 23. The turbine 42 is disposed upstream of the purification device 37 in the exhaust pipe 35. The rotating shaft 43 connects the compressor 41 and the turbine 42. The wastegate valve 44 is provided in a bypass pipe 36 that connects the upstream side and downstream side of the turbine 42 in the exhaust pipe 35, and is controlled by the ECU 70. The blow-off valve 45 is provided in a bypass pipe 24 that connects the upstream side and downstream side of the compressor 41 in the intake pipe 23, and is controlled by the ECU 70.

[0016] In this turbocharger 40, the opening degree of the wastegate valve 44 is adjusted to adjust the distribution ratio between the amount of exhaust gas flowing through the bypass pipe 36 and the amount of exhaust gas flowing through the turbine 42, thereby adjusting the rotational driving force of the turbine 42, adjusting the amount of air compressed by the compressor 41, and adjusting the supercharging pressure (intake pressure) of the engine 12. In detail, the distribution ratio is adjusted so that the smaller the opening degree of the wastegate valve 44, the smaller the amount of exhaust gas flowing through the bypass pipe 36 and the larger the amount of exhaust gas flowing through the turbine 42. When the wastegate valve 44 is fully open, the engine 12 can operate in the same manner as a naturally aspirated engine without the turbocharger 40.

[0017] Furthermore, in the turbocharger 40, when the pressure downstream of the compressor 41 in the intake pipe 23 is somewhat higher than the pressure upstream of the intake pipe 23, the blow-off valve 45 is opened to release the excess pressure downstream of the compressor 41. Note that, instead of a valve controlled by the ECU 70, the blow-off valve 45 may be configured as a check valve that opens when the pressure downstream of the compressor 41 in the intake pipe 23 becomes somewhat higher than the pressure upstream of the intake pipe 23.

[0018] The ECU 70 is configured as a microprocessor centered on a CPU, and in addition to the CPU, it is equipped with a ROM for storing processing programs, a RAM for temporarily storing data, a non-volatile flash memory for storing and holding data, an input / output port, and a communication port. Signals from various sensors are input to the ECU 70 via the input ports.

[0019] Examples of signals input to the ECU 70 include a crank angle θcr from a crank position sensor 14a that detects the rotational position of the crankshaft 14 of the engine 12, a coolant temperature Tw from a water temperature sensor (not shown) that detects the temperature of the coolant for the engine 12, and a throttle opening TH from a throttle position sensor 26a that detects the opening of the throttle valve 26. Another example of signals input to the ECU 70 is a cam position θca from a cam position sensor (not shown) that detects the rotational positions of an intake camshaft that opens and closes the intake valve 30 and an exhaust camshaft that opens and closes the exhaust valve 34. Examples of the intake air quantity Qa from the air flow meter 23a attached upstream of the compressor 41 of the intake pipe 23, the intake air temperature Tin from the intake air temperature sensor 23t attached upstream of the compressor 41 of the intake pipe 23, the intake pressure (compressor pre-pressure) Pin from the intake pressure sensor 23b attached upstream of the compressor 41 of the intake pipe 23, and the boost pressure Pc from the boost pressure sensor 23c attached between the compressor 41 of the intake pipe 23 and the intercooler 25 can also be mentioned. FIG. 3 is an explanatory diagram for explaining the configuration and temperature distribution of the air flow meter 23a. The air flow meter 23a is configured as a hot film type (MEMS type) air flow meter. As shown in the figure, the air flow meter 23a includes a heater resistor 232 and temperature sensor resistors 234 and 236 arranged on both sides of the heater resistor 232 at a distance of several tens of μm on a diaphragm 230 formed by etching the back surface of a silicon substrate to a thickness of several μm. In the air flow meter 23a, a current is supplied to a heater resistor 232 to control it to a constant temperature, and the amount of heat transferred from the heater resistor 232 to the air is transferred to temperature sensor resistors 234, 236 depending on the air flow speed, and this is utilized to detect the intake air amount Qa based on the temperature difference ΔT between the temperature sensor resistors 234 and 236. Other examples include a surge pressure (post-throttle pressure) Ps from a surge pressure sensor 27a attached to the surge tank 27 and a surge temperature Ts from a temperature sensor 27b attached to the surge tank 27. Other examples include a fuel pressure Pfp from a fuel pressure sensor 28a that detects the pressure of the fuel supplied to the fuel injector 28.Other examples of such air-fuel ratios include the front air-fuel ratio AF1 from the front air-fuel ratio sensor 35a attached upstream of the purification device 37 in the exhaust pipe 35, the rear air-fuel ratio AF2 from the rear air-fuel ratio sensor 35b attached downstream of the purification device 37 in the exhaust pipe 35, the exhaust pressure Pex from the exhaust pressure sensor 35c attached to the exhaust pipe 35, and the filter differential pressure Ppm from the differential pressure sensor 39 attached upstream and downstream of the PM filter 38.

[0020] Various control signals are output from the ECU 70 via an output port. Examples of signals output from the ECU 70 include a control signal to the throttle valve 26, a control signal to the fuel injector 28, and a control signal to the spark plug 32. Other examples include a control signal to the wastegate valve 44, a control signal to the blow-off valve 45, and a control signal to the solenoid valve 18a.

[0021] The ECU 70 calculates the rotation speed Ne and the load factor KL (the ratio of the volume of air actually taken in one cycle to the stroke volume per cycle of the engine 12) of the engine 12. The rotation speed Ne is calculated based on the crank angle θcr from the crank position sensor 14a. The load factor KL is calculated based on the amount of intake air Qa from the air flow meter 23a and the rotation speed Ne.

[0022] In the engine device 10 of the embodiment thus configured, the ECU 70 performs intake air amount control for controlling the opening of the throttle valve 26, fuel injection from the fuel injector 28, ignition control for controlling the ignition timing Tp of the spark plug 32, supercharging control for controlling the opening of the wastegate valve 44, and the like, based on the required load rate KL* of the engine 12 set using the accelerator opening Acc. In the supercharging control, a required air amount Ga* (the amount of intake air flowing into the intercooler 25 when the engine 12 is operated at the required load rate KL*) is set based on the required load rate KL* and the rotation speed Ne of the engine 12, and a target supercharging pressure Ptb*, which is a target value of the supercharging pressure Pc, is set based on the required air amount Ga*. Then, the wastegate valve 44 is controlled so that the supercharging pressure Pc becomes the target supercharging pressure Ptb*.

[0023] Next, the operation of the engine system 10 equipped with the abnormality determination device for the air flow meter 23a of this embodiment will be described, in particular the operation when determining whether an abnormality due to adhesion of water to the heater resistor 232 or the temperature sensor resistors 234, 236 of the air flow meter 23a occurs. Fig. 4 is a flowchart showing an example of an abnormality determination process executed by the ECU 70. This routine is repeatedly executed by the CPU of the ECU 70 at time (first time) t1 (for example, every few msec).

[0024] When this routine is executed, the CPU of the ECU 70 determines whether the engine 12 is operating autonomously (idling) or not (S100). When the engine 12 is not operating autonomously, for example, when the engine 12 is operating under load, this routine is terminated. When the engine 12 is operating autonomously, the abnormality determination of S110 to S200 is executed. The reason for executing the abnormality determination when the engine 12 is operating autonomously will be described later.

[0025] When the engine 12 is operating independently in S100, the intake air amount Qa and the throttle opening TH are input (S110). The intake air amount Qa is a value detected by the air flow meter 23a. The throttle opening TH is a value detected by the throttle position sensor 26a.

[0026] Next, the maximum intake amount Qmax, which is the maximum amount of air (intake air amount) passing through the throttle valve 26, is set based on the input throttle opening TH (S120). Then, the maximum intake amount Qmax plus a measurement margin M is set as a judgment threshold Qth (S130). Furthermore, it is determined whether the intake air amount Qa input in S110 is larger than the judgment threshold Qth (S140). The setting of S120 uses a map that is determined by experiment, analysis, machine learning, etc., to determine the relationship between the throttle opening TH and the maximum amount of air passing through the throttle valve 26, and the maximum value corresponding to the throttle opening TH input in S110 in the map is set to the maximum intake amount Qmax. When the intake air amount Qa exceeds the judgment threshold Qth in S140, it is determined that an abnormality due to water adhesion has occurred in the air flow meter 23a (S150). Then, the abnormality judgment flag F is set to a value of 1 (S160), and this routine ends. The abnormality determination flag F is initially set to a value of 0, and is set to a value of 1 if it is determined in S150 that an abnormality due to adhesion of water has occurred in the air flow meter 23a.

[0027] Here, the reasons for performing the abnormality determination when the engine 12 is operating independently and for determining that an abnormality due to water adhesion has occurred in the air flow meter 23a when the intake air amount Qa exceeds the determination threshold value Qth will be described. When the air flow meter 23a is normal, the intake air amount Qa detected by the air flow meter 23a is equal to or less than the maximum intake air amount Qmax plus the change in the air flow rate due to supercharging control, ΔQa. If water droplets adhere only to the temperature sensor resistor on the upstream side of the air flow among the temperature sensor resistors 234, 236 of the air flow meter 23a, the temperature of the upstream temperature sensor resistor to which the water droplets adhere will excessively drop, and the temperature difference ΔT between the temperature sensor resistors 234 and 236 will become large, causing the air flow meter 23a to output an abnormal value, exceeding the value obtained by adding the change ΔQa to the maximum intake air amount Qmax. Therefore, by comparing the intake air amount Qa detected by the air flow meter 23a with the value obtained by adding the change amount ΔQa to the maximum intake air amount Qmax, it is possible to check whether or not an abnormality due to water adhesion has occurred in the air flow meter 23a. However, when the engine 12 is operating under load and the boost pressure changes, the change amount ΔQa in the air flow rate due to the boost control cannot be calculated with high accuracy due to the effect of a delayed response of the boost pressure sensor 23c. In this embodiment, since the abnormality determination is performed when the engine 12 is operating independently (idling), the change amount ΔQa in the air flow rate due to the boost control can be ignored. Then, by comparing the intake air amount Qa detected by the air flow meter 23a with the determination threshold value Qth obtained by adding a measurement margin M to the maximum intake air amount Qmax, it is possible to more appropriately determine whether or not the air flow meter 23a has an abnormality due to water adhesion.

[0028] When the intake air amount Qa is equal to or less than the judgment threshold value Qth in S140, it is determined that the intake air amount Qa detected by the air flow meter 23a is within a normal range, and it is determined whether the abnormality judgment flag F (previous F) from the previous time this routine was executed was equal to 1 (S170). When the previous F was equal to 0, it is determined that the air flow meter 23a is normal (S190). Then, the abnormality judgment flag F is set to 0 (S200), and this routine is terminated.

[0029] When the abnormality determination flag F is set to 1 in S170, that is, when it was determined that an abnormality due to water adhesion occurred in the air flow meter 23a the previous time this routine was executed, it is determined whether the time (continuation time) tc during which it has been determined that the intake air amount Qa is continuously equal to or less than the determination threshold value Qth has elapsed a time (second time) t2 (S180). The time t2 is set in advance based on experiments, analysis, machine learning, etc., as the time during which water adhesion is reliably eliminated. Note that the duration time tc is reset to 0 when the intake air amount Qa exceeds the determination threshold value Qth and it is determined in S150 that an abnormality has occurred.

[0030] If the duration tc has not reached time t2 in S180, the water adhering to the heater resistor 232 and temperature sensor resistors 234, 236 of the air flow meter 23a has moved, temporarily causing the intake air amount Qa detected by the air flow meter 23a to become normal, but it is determined that there is a possibility that further movement of the water will cause water to adhere to the heater resistor 232 and temperature sensor resistors 234, 236 again in a short time, causing the intake air amount Qa to become abnormal, so the abnormality determination flag F is maintained at value 1 (S160) and the routine is terminated. If the duration tc has reached time t2, the air flow meter 23a is determined to be normal (S190), the abnormality determination flag F is set to value 0 (S200), and the routine is terminated. In this way, even when the intake air volume Qa is equal to or less than the judgment threshold value Qth, the air flow meter 23a is not determined to be normal until the duration tc has elapsed to time t2, so that it can be more reliably determined that the air flow meter 23a is normal (that no abnormality has occurred in the air flow meter 23a).

[0031] According to the engine device 10 equipped with the air flow meter abnormality judgment device of the present embodiment described above, the intake air volume Qa (detection value) of the internal combustion engine detected by the air flow meter 23a is compared with the judgment threshold value Qth, which is the maximum intake air volume based on the throttle opening TH, which is the opening of the throttle valve 26, to perform abnormality judgment to determine whether or not an abnormality due to water adhesion has occurred in the air flow meter 23a, thereby making it possible to properly judge whether or not an abnormality due to water adhesion has occurred in the air flow meter 23a.

[0032] Furthermore, in the engine device 10 equipped with the air flow meter abnormality determination device of this embodiment, the determination threshold Qth is a value obtained by adding a determination margin to the maximum intake air volume based on the throttle opening TH, and the abnormality determination is performed by determining that an abnormality due to water adhesion has occurred in the air flow meter 23a when the intake air volume Qa exceeds the determination threshold Qth, thereby making it possible to more appropriately determine an abnormality due to water adhesion in the air flow meter 23a.

[0033] Furthermore, in the air flow meter abnormality determination device of the present disclosure, the engine 12 has a turbocharger 40 including a compressor 41 attached upstream of the throttle valve 26 in the intake pipe 23 and a turbine 42 attached in the exhaust pipe 35, and by performing abnormality determination when the engine 12 is operating autonomously, an abnormality due to water adhesion in the air flow meter 23a can be more accurately determined.

[0034] Furthermore, in the air flow meter abnormality determination device disclosed herein, the abnormality determination is performed every time t1, and if it is not determined that an abnormality due to water adhesion has occurred in the air flow meter 23a after the abnormality determination has determined that an abnormality due to water adhesion has occurred until the time t2, which is the time for confirming that the abnormality in the air flow meter 23a has been resolved, it is determined that no abnormality due to water adhesion has occurred in the air flow meter 23a, thereby preventing hunting between abnormal and normal determinations in a short period of time.

[0035] In the above-described embodiment, the engine device 10 includes the turbocharger 40. However, the engine device 10 does not necessarily need to include the turbocharger 40. In this case, in the abnormality determination process of Fig. 4, S100 may not be executed, and the abnormality determinations of S110 to S200 may be executed regardless of whether the engine 12 is operating autonomously or under load.

[0036] In the above-described embodiment, the maximum intake air amount Qmax, which is the maximum amount of air passing through the throttle valve 26, is set based on the throttle opening TH in S120, and the maximum intake air amount Qmax plus a measurement margin M is set as the judgment threshold value Qth in S130. However, the maximum intake air amount Qmax may be set as the judgment threshold value Qth in S130. Alternatively, the minimum air amount Qmin, which is the minimum amount of air passing through the throttle valve 26, is set based on the throttle opening TH in S120, and the minimum air amount Qmin plus a measurement margin M is set as the judgment threshold value Qth in S130. In this case, it is sufficient to determine in S140 whether the intake air amount Qa is less than the judgment threshold value Qth.

[0037] The relationship between the main elements of the embodiment and the main elements of the invention described in the section on Means for Solving the Problems will be described below. In the embodiment, the engine 12 corresponds to the "internal combustion engine", the air flow meter 23a corresponds to the "air flow meter", and the ECU 70 corresponds to the "abnormality determination device".

[0038] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

[0039] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure. [Industrial Applicability]

[0040] The present disclosure can be used in the manufacturing industry of air flow meter abnormality determination devices. [Explanation of symbols]

[0041] 10 engine device, 12 engine, 14 crankshaft, 14a crank position sensor, 22 air cleaner, 23 intake pipe, 23a air flow meter, 23b intake pressure sensor, 23c boost pressure sensor, 24 bypass pipe, 25 intercooler, 26 throttle valve, 27 surge tank, 27a surge pressure sensor, 27b temperature sensor, 28 fuel injector, 28a fuel pressure sensor, 29 intake valve, 30 combustion chamber, 31 spark plug, 32 piston, 34 exhaust valve, 35 exhaust pipe, 35c exhaust pressure sensor, 36 bypass pipe, 37 purification device, 38 PM filter, 39 differential pressure sensor, 40 turbocharger, 41 compressor, 42 turbine, 43 rotating shaft, 44 wastegate valve, 45 blow-off valve, 70 electronic control unit.

Claims

1. An air flow meter abnormality determination device for determining an abnormality in a hot film air flow meter used in an internal combustion engine, comprising: A detection value, which is an intake air amount of the internal combustion engine detected by the air flow meter, is compared with a determination threshold value, which is a maximum or minimum value of the intake air amount based on a throttle opening, which is an opening degree of a throttle valve, to perform an abnormality determination for determining whether or not an abnormality due to adhesion of water has occurred in the air flow meter. An abnormality detection device for an air flow meter.

2. 2. The air flow meter abnormality determination device according to claim 1, the determination threshold is the maximum value or a value obtained by adding a determination margin to the maximum value, The abnormality determination determines that an abnormality due to adhesion of water has occurred in the air flow meter when the detection value exceeds the determination threshold value. An abnormality detection device for an air flow meter.

3. 3. The air flow meter abnormality determination device according to claim 1, the internal combustion engine has a supercharger including a compressor installed upstream of the throttle valve in an intake pipe and a turbine installed in an exhaust pipe; The abnormality determination is executed when the internal combustion engine is operating autonomously. An abnormality detection device for an air flow meter.

4. 3. The air flow meter abnormality determination device according to claim 2, The abnormality determination is performed every first hour, and after it is determined that an abnormality due to water adhesion has occurred in the air flow meter, if the state in which the detection value is equal to or less than the determination threshold continues until a second time has elapsed during which it can be determined that the water adhesion has been reliably eliminated after the detection value becomes equal to or less than the determination threshold, it is determined that an abnormality due to water adhesion has not occurred in the air flow meter. An abnormality detection device for an air flow meter.

Images