JP2022151044A - Abnormality determination device of internal combustion engine - Google Patents

Abstract

To avoid an unconditional notification of an abnormality when an internal combustion engine is in a misfired state due to the adhesion of ice to a valve at a part of cylinders.SOLUTION: In a step S24, a CPU performs first determination processing of determining whether or not an internal combustion engine is in a misfired state. When a first misfire generation rate R1 is equal to or higher than a first prescribed value L1 (S24: YES) in a step S26, the CPU performs stop processing of stopping the fuel supply of a misfired cylinder #id. When the CPU determines that a second prescribed period T2 has elapsed after the stop processing of the misfired cylinder #id (S27: YES) in a step S29, the CPU performs second determination processing of determining whether or not the internal combustion engine is abnormal. When a second misfire generation rate R2 is equal to or higher than a second prescribed value L2 (S29: YES), the CPU determines that the internal combustion engine is abnormal, and in a step S30, the CPU performs notification processing of notifying that the internal combustion engine is abnormal.SELECTED DRAWING: Figure 3

Description

The present invention relates to an abnormality determination device for an internal combustion engine.

The internal combustion engine described in Patent Literature 1 has a plurality of cylinders and an intake port and an exhaust port communicating with each cylinder. Also, the internal combustion engine has an intake valve and an exhaust valve corresponding to each cylinder. An intake valve is a valve that opens and closes between a cylinder and an intake port. An exhaust valve is a valve that opens and closes between a cylinder and an exhaust port.

JP 2006-009746 A

An internal combustion engine such as that described in Patent Document 1 may stop when the opening of at least one of the intake valve and the exhaust valve in one of the cylinders is very small. If the temperature of the internal combustion engine drops in such a state, ice may adhere to the surface of the valve whose degree of opening is small. A valve with ice will not open or close as designed between the cylinder and the port. As a result, the air-fuel mixture cannot be normally combusted in the cylinder corresponding to the ice-covered valve, and the internal combustion engine may be determined to be in a misfire state.

By the way, when many misfires are detected in some cylinders among a plurality of cylinders, it is possible to notify the user of a warning indicating an abnormality at the same time as stopping the fuel supply to the cylinders in which many misfires have been detected. be. In the case of this technology, even if it is determined that the internal combustion engine is in a misfire state due to many misfires detected in the cylinder corresponding to the valve due to the ice sticking to the valve, an abnormality is indicated to the user. A warning will be given.

However, even if many misfires are detected due to ice sticking to the valve, there is a high possibility that the temperature rise of the internal combustion engine will solve the problem. Therefore, it is unlikely that replacement of parts or the like will be required immediately. In spite of this, if the user is notified of a warning indicating an abnormality, there is a risk that the user will feel excessive anxiety.

In order to solve the above-described problems, the present invention provides an abnormality determination apparatus applied to an internal combustion engine having a plurality of cylinders, which detects that an air-fuel mixture does not burn in the cylinder when the cylinder reaches a combustion stroke. a misfire detection process for detecting whether or not the misfire has occurred in each of the plurality of cylinders each time the cylinder undergoes a predetermined number of combustion strokes in the event of a misfire; and a start request for the internal combustion engine. a first calculation process for calculating a first misfire occurrence rate indicating the frequency at which the misfire is detected with respect to the total number of times the misfire detection process is performed during a period of a predetermined first period after the occurrence of the first misfire; It is determined that the internal combustion engine is in a misfire state when the first misfire occurrence rate is equal to or greater than a predetermined first predetermined value, and the internal combustion engine is determined to be in a misfire state when the first misfire occurrence rate is less than the first predetermined value. a first determination process for determining that the engine is not in a misfired state; and the cylinder in which the misfire is detected most frequently among the plurality of cylinders when the first determination process determines that the internal combustion engine is in the misfired state. and a second misfire occurrence indicating the frequency at which the misfire is detected with respect to the total number of times the misfire detection process is performed by the elapse of a predetermined second predetermined period after the stop process. determining that the internal combustion engine is abnormal when the second misfire rate is equal to or greater than a second predetermined value larger than the first predetermined value; a second determination process for determining that the internal combustion engine is normal when the second misfire rate is less than the second predetermined value; and when it is determined by the second determination process that the internal combustion engine is abnormal, and a notification process for notifying that an abnormality has occurred.

Assume that ice adheres to the valves of some of the cylinders. In this case, the frequency of misfires in cylinders corresponding to ice-covered valves is considerably high. Then, the first calculation process calculates the first misfire occurrence rate for all of the plurality of cylinders, and the first determination process determines that the internal combustion engine is in a misfire state. Further, fuel injection to the cylinder corresponding to the valve to which ice adheres is stopped. Due to the cessation of fuel injection, the cylinder corresponding to the iced valve will inevitably misfire. However, as described above, the frequency of misfires in cylinders corresponding to ice-covered valves is considerably higher before fuel injection is stopped. Therefore, the second misfire rate calculated in the second calculation process after the stop process does not rise much compared to the first misfire rate. Therefore, there is a high possibility that the second misfire rate will be less than the second predetermined value, and there is a high possibility that the internal combustion engine will not be determined to be abnormal in the second determination process. Therefore, when the internal combustion engine is in a misfire state due to ice adhering to the valves of some cylinders, it is possible to avoid unconditionally notifying the abnormality.

1 is a schematic diagram showing a schematic configuration of a vehicle; FIG. 4 is a flowchart showing the procedure of misfire detection processing; 4 is a flowchart showing a procedure of abnormality determination processing when starting an internal combustion engine;

<One Embodiment of Abnormality Determining Device for Internal Combustion Engine>
(About vehicle configuration)
As shown in FIG. 1 , the vehicle VC has an internal combustion engine 10 . The internal combustion engine 10 has four cylinders 11 . When distinguishing between the four cylinders 11, the cylinders 11 are referred to as cylinder #1, cylinder #2, cylinder #3, and cylinder #4.

The internal combustion engine 10 has an intake passage 12 for drawing outside air into the cylinders 11 . The intake passage 12 houses a throttle valve 14 . The throttle valve 14 adjusts the intake air amount Ga, which is the flow rate of the air flowing through the intake passage 12, by changing the opening degree of the valve.

A downstream portion of the intake passage 12 branches into four intake ports 12a. Each intake port 12 a is connected to each cylinder 11 .
The internal combustion engine 10 includes multiple port injection valves 16 . The port injection valve 16 injects fuel into the intake port 12a. A port injection valve 16 is provided for each intake port 12a. Therefore, four port injection valves 16 are provided corresponding to the number of cylinders 11 .

The internal combustion engine 10 has a plurality of intake valves 18 . In this embodiment, two intake valves 18 are provided for one cylinder 11 . The intake valve 18 opens and closes between the intake port 12 a and the cylinder 11 . When the intake valve 18 opens, the air flowing into the intake passage 12 and the fuel injected from the port injection valve 16 flow into the combustion chamber 20 inside the cylinder 11 . The combustion chamber 20 is a space defined by a wall defining the cylinder 11 and the piston in the cylinder 11, and is a space in which combustion takes place.

The internal combustion engine 10 includes a plurality of in-cylinder injection valves 22 . In-cylinder injection valve 22 injects fuel into combustion chamber 20 . The in-cylinder injection valve 22 is provided for each combustion chamber 20 . Therefore, four in-cylinder injection valves 22 are provided corresponding to the number of cylinders 11 .

The internal combustion engine 10 includes multiple spark plugs 24 . The spark plug 24 burns the mixture of air and fuel in the combustion chamber 20 by performing spark discharge. A spark plug 24 is provided for each combustion chamber 20 . Therefore, four spark plugs 24 are provided corresponding to the number of cylinders 11 .

The internal combustion engine 10 has a crankshaft 26 . The crankshaft 26 outputs combustion energy generated by combustion in each cylinder 11 as rotational energy. Although details are omitted, a piston in each cylinder 11 is connected to the crankshaft 26 via a connecting rod.

The internal combustion engine 10 includes an exhaust passage 28 that is an exhaust passage for exhaust gas produced by combustion in the combustion chamber 20 . An upstream portion of the exhaust passage 28 branches into four exhaust ports 28a. The exhaust port 28 a is connected to each cylinder 11 .

The internal combustion engine 10 has multiple exhaust valves 30 . In this embodiment, two exhaust valves 30 are provided for one cylinder 11 . The exhaust valve 30 opens and closes between the exhaust port 28 a and the cylinder 11 . When the exhaust valve 30 opens, the air-fuel mixture that has been burned in the cylinder 11 is discharged to the exhaust passage 28 as exhaust.

The internal combustion engine 10 includes a three-way catalyst 32 and a GPF 34. The three-way catalyst 32 is positioned in the middle of the exhaust passage 28 . The three-way catalyst 32 has an oxygen storage capacity. The GPF 34 is located downstream of the three-way catalyst 32 in the exhaust passage 28 . The GPF 34 is a PM-collecting filter carrying a three-way catalyst.

A crank rotor 40 is coupled to the crankshaft 26 . The crank rotor 40 has a plurality of teeth 42 . A toothed portion 42 indicates each of a plurality of rotation angles of the crankshaft 26 . The crank rotor 40 is basically provided with tooth portions 42 at intervals of 10° CA, but there is one missing tooth portion 44 where the interval between adjacent tooth portions 42 is 30° CA. is provided. This is for indicating the reference rotation angle of the crankshaft 26 .

The vehicle VC includes a torque converter 50 , a transmission 54 and drive wheels 60 . A crankshaft 26 of the internal combustion engine 10 can be connected to an input shaft 56 of a transmission 54 via a torque converter 50 . The torque converter 50 has a lockup clutch 52 . By engaging the lockup clutch 52, the crankshaft 26 and the input shaft 56 are connected. An output shaft 58 of transmission 54 is mechanically coupled to drive wheels 60 .

The vehicle VC has an airflow meter 80 . The air flow meter 80 detects the amount of intake air flowing through the intake passage 12, that is, the intake air amount Ga.
The vehicle VC has a crank angle sensor 82 . Crank angle sensor 82 detects an output signal Scr indicating the rotational position of crankshaft 26 .

The vehicle VC has an ignition switch 84 . When the ignition switch 84 is operated while the internal combustion engine 10 is stopped, it outputs a signal S1 requesting to start the internal combustion engine 10 . Further, when the ignition switch 84 is operated while the internal combustion engine 10 is running, it outputs a signal S2 requesting the stop of the internal combustion engine 10 .

The vehicle VC has a water temperature sensor 86 . A water temperature sensor 86 detects a water temperature THW, which is the temperature of the cooling water of the internal combustion engine 10 .
The vehicle VC has an outside air temperature sensor 88 . An outside air temperature sensor 88 detects an outside air temperature THA, which is the air temperature outside the vehicle VC.

Vehicle VC is provided with warning light 90 . The warning light 90 lights a mark on the instrument panel of the vehicle VC, for example, indicating that the internal combustion engine 10 is in an abnormal state.
The vehicle VC has a control device 70 . In this embodiment, the control device 70 is an abnormality determination device. The control device 70 acquires a signal indicating the intake air amount Ga from the airflow meter 80 . The control device 70 acquires an output signal Scr indicating the rotational position of the crankshaft 26 from the crank angle sensor 82 . The control device 70 acquires the start request signal S<b>1 and the stop request signal S<b>2 from the ignition switch 84 . Control device 70 acquires a signal indicating water temperature THW from water temperature sensor 86 . Controller 70 acquires a signal indicating outside air temperature THA from outside air temperature sensor 88 .

The control device 70 includes a CPU 71 , a peripheral circuit 72 , a ROM 73 , a storage device 74 and a bus 75 . A bus 75 connects the CPU 71, the peripheral circuit 72, the ROM 73, and the storage device 74 so that they can communicate with each other. The peripheral circuit 72 includes a circuit that generates a clock signal that defines internal operations, a power supply circuit, a reset circuit, and the like. The ROM 73 pre-stores various programs for the CPU 71 to execute various controls.

The CPU 71 controls the internal combustion engine 10 by executing various programs stored in the ROM 73 . For example, the CPU 71 controls the opening of the throttle valve 14, the injection amount of fuel injected from the port injection valve 16 and the in-cylinder injection valve 22, the ignition timing of the spark plug 24, etc. based on the values input from each sensor. .

(Misfire detection processing)
As shown in FIG. 2, the CPU 71 executes the misfire detection program stored in the ROM 73 to repeatedly execute the misfire detection process, for example, at predetermined intervals. Misfire means that the air-fuel mixture does not burn in each cylinder 11 when the cylinder 11 reaches the combustion stroke. In other words, a misfire also occurs when the cylinder 11 enters the combustion stroke without fuel being injected from the port injection valve 16 and the in-cylinder injection valve 22, and as a result, the air-fuel mixture does not burn. The misfire detection process is a process for detecting whether or not a misfire has occurred in each of the cylinders 11 each time each cylinder 11 undergoes a certain number of combustion strokes. In this embodiment, every time each cylinder 11 undergoes one combustion stroke, it is detected whether or not a misfire has occurred in that cylinder 11 .

Specifically, when the misfire detection program is started, the CPU 71 first executes the process of step S11. In step S11, the CPU 71 obtains a minute rotation time T30. The minute rotation time T30 is the time required for the crankshaft 26 to rotate 30° CA. Based on the output signal Scr of the crank angle sensor 82, the CPU 71 calculates the minute rotation time T30. Thereby, the CPU 71 obtains the minute rotation time T30. After that, the CPU 71 advances the process to step S12.

Next, in step S12, the CPU 71 sets the latest micro-rotation time T30 acquired in the process of step S11 as the micro-rotation time T30[0]. Further, the CPU 71 sets the variable "m" of the minute rotation time T30 [m] to a larger value for the minute rotation time T30 obtained in the process of step S11 in the past. That is, "m=1, 2, 3, . . . " is set, and the micro-rotation time T30[m−1] immediately before the process of step S12 is performed is defined as the micro-rotation time T30[m]. As a result, for example, the micro-rotation time T30 acquired by the process of step S11 when the series of processes shown in FIG. 2 was executed last time becomes the micro-rotation time T30[1]. Of the minute rotation times T30[0], T30[1], T30[2], . Time is shown and the angular intervals do not overlap. After that, the CPU 71 advances the process to step S13.

Next, in step S13, the CPU 71 determines that the minute rotation time T30 acquired in step S10 is the rotation angle interval from 30° CA before compression top dead center of any one of cylinders #1 to #4 to compression top dead center. It is determined whether or not it is the time required for That is, in step S13, the CPU 71 determines whether or not cylinder #i, which is one of cylinders #1 to #4, is undergoing a combustion stroke.

When the CPU 71 determines that the minute rotation time T30 obtained in step S10 is not the time required for rotation of any of the cylinders #1 to #4 at an angle interval from 30° CA before compression top dead center to compression top dead center. (S13: NO), the series of processes is temporarily terminated.

On the other hand, when the CPU 71 determines that it is the time required for the rotation of the angle interval to the compression top dead center (S13: YES), the process proceeds to step S14.
In step S14, the CPU 71 sets the rotation fluctuation amount Δω(i) of the cylinder #i to be determined to "T30 [0]" in order to detect whether or not a misfire has occurred in the cylinder 11 at the compression top dead center. - Substitute "T30[6]". T30[0] is the time required to rotate the cylinder #i, which is subject to misfire determination, at an angular interval from 30° CA before compression top dead center to compression top dead center. Further, T30[6] is the rotation of the angle interval from 30° CA before the compression top dead center of the cylinder 11, which is the compression top dead center immediately before the cylinder #i for which misfire is to be determined, to the compression top dead center. is the time required for By subtracting T30[6] from T30[0] in this way, the rotational fluctuation amount Δω is quantified. After that, the CPU 71 advances the process to step S15.

Next, in step S15, the CPU 71 determines whether or not the rotation fluctuation amount Δω(i) is equal to or greater than a specified amount Δωth. This process is a process for determining whether or not a misfire has occurred in the cylinder #i that is subject to misfire determination. Here, the CPU 71 variably sets the specified amount Δωth based on the rotational speed NE and the charging efficiency η.

Specifically, the storage device 74 stores map data having the rotation speed NE and the charging efficiency η as input variables and the prescribed amount Δωth as an output variable. The CPU 71 performs map calculation of the specified amount Δωth based on the rotational speed NE, the charging efficiency η, and the map data.

Note that map data is set data of discrete values of input variables and values of output variables corresponding to the respective values of the input variables. In map calculation, for example, when the value of an input variable matches any of the values of input variables of map data, the value of the output variable of the corresponding map data is used as the calculation result. On the other hand, if they do not match, a process may be performed in which a value obtained by interpolating the values of a plurality of output variables included in the map data is used as the calculation result.

Incidentally, the CPU 71 calculates the rotational speed NE based on the output signal Scr of the crank angle sensor 82 . Here, the rotation speed NE is an average value of rotation speeds when the crankshaft 26 rotates by an angle interval larger than 180° CA, which is the interval between compression top dead centers. In this embodiment, the rotation speed NE is the average value of the rotation speeds when the crankshaft 26 rotates by one or more rotations of the crankshaft 26 . Further, the CPU 71 calculates the charging efficiency η based on the rotation speed NE and the intake air amount Ga.

When the CPU 71 determines that the rotation fluctuation amount Δω(i) is equal to or greater than the specified amount Δωth (S15: YES), it determines that a misfire has occurred in the cylinder #i. After that, the CPU 71 advances the process to step S16. In step S16, the CPU 71 increments the misfire counter CN(i) of cylinder #i. After that, the CPU 71 once terminates the series of processes.

On the other hand, when the CPU 71 determines that the rotation fluctuation amount Δω(i) is less than the specified amount Δωth (S15: NO), it determines that a misfire has not occurred in the cylinder #i. After that, the CPU 71 once terminates the series of processes.

(Processing for judging abnormality of internal combustion engine)
As shown in FIG. 3 , the CPU 71 performs abnormality determination processing for the internal combustion engine 10 by executing an abnormality determination program stored in the ROM 73 when there is a request to start the internal combustion engine 10 . As described above, when the ignition switch 84 is operated while the internal combustion engine 10 is stopped, the start request signal S1 is output. Then, when the signal S1 is input to the control device 70, the CPU 71 determines that there is a request to start the internal combustion engine 10. FIG. That is, when the ignition switch 84 is operated while the internal combustion engine 10 is stopped, the CPU 71 executes abnormality determination processing for the internal combustion engine 10 .

When starting the abnormality determination process, the CPU 71 first executes the process of step S21. In step S21, the CPU 71 determines whether or not the internal combustion engine 10 will be started under low temperature conditions. Specifically, the CPU 71 determines whether or not the internal combustion engine 10 is started under low temperature conditions based on the water temperature THW obtained from the water temperature sensor 86 and the outside air temperature THA obtained from the outside air temperature sensor 88 . The CPU 71 determines that the internal combustion engine 10 is started under low temperature conditions when the water temperature THW is equal to or lower than a predetermined specified water temperature and the outside air temperature THA is equal to or lower than a predetermined specified outside air temperature.

In this embodiment, the prescribed water temperature is set at 0°C, and the prescribed outside air temperature is set at 0°C. The process of step S21 is for determining whether or not there is a possibility that ice adheres to the intake valve 18 and the exhaust valve 30 .

If it is determined that the internal combustion engine 10 will not be started under the low temperature condition (S21: NO), the CPU 71 terminates the current abnormality determination process for the internal combustion engine 10 . On the other hand, when determining that the internal combustion engine 10 will be started under the low temperature condition (S21: YES), the CPU 71 advances the process to step S22.

In step S22, the CPU 71 determines whether or not a predetermined first predetermined period T1 has elapsed since the internal combustion engine 10 was requested to start. In this embodiment, the first predetermined period T1 is set as a period during which the crankshaft 26 rotates 200 times. The CPU 71 counts the number of revolutions of the crankshaft 26 based on the output signal Scr of the crankshaft 26, for example.

When the CPU 71 determines that the first predetermined period T1 has not elapsed since the start request for the internal combustion engine 10 was issued (S22: NO), the process of step S22 is repeated. If the CPU 71 determines that the first predetermined period T1 has elapsed since the start request for the internal combustion engine 10 was issued (S22: YES), the process proceeds to step S23.

In step S23, the CPU 71 performs a first calculation process for calculating the first misfire rate R1 in the first predetermined period T1. The first misfire occurrence rate R1 is a value that indicates the frequency of misfire detection relative to the total number of misfire detection processes.

In the present embodiment, the misfire detection process is performed at intervals of 180° CA. Therefore, if a period in which the crankshaft 26 rotates 200 times is set as the first predetermined period T1, the misfire detection process is performed 400 times. Become.

The number of misfires detected is the total value of misfire counters CN(1) to CN(4) from when the start request for the internal combustion engine 10 is issued until the first predetermined period T1 elapses. Therefore, the CPU 71 divides the total value of the misfire counters CN(1) to CN(4) from the request for starting the internal combustion engine 10 to the elapse of the first predetermined period T1 by the total number of misfire detection processes. Thus, the first misfire rate R1 is calculated. After that, the CPU 71 advances the process to step S24.

In step S24, the CPU 71 performs first determination processing for determining whether or not the internal combustion engine 10 is in a misfire state. That the internal combustion engine 10 is in a misfire state means that misfires occur more frequently than a predetermined frequency in the plurality of cylinders 11 as a whole.

In the first determination process, when the first misfire occurrence rate R1 is less than the predetermined first predetermined value L1 (S24: NO), the CPU 71 determines that the internal combustion engine 10 is not in a misfire state, and the current series of processes is performed. exit. The first predetermined value L1 is set at 20%, for example, in this embodiment.

On the other hand, if the first misfire rate R1 is greater than or equal to the first predetermined value L1 (S24: YES), the CPU 71 determines that the internal combustion engine 10 is misfiring, and proceeds to step S25.
In step S25, the CPU 71 identifies the misfiring cylinder #id among the cylinders #1 to #4. The misfiring cylinder #id is the cylinder 11 in which misfiring has been detected most frequently from when the start request for the internal combustion engine 10 is issued to when the first predetermined period T1 elapses, among the plurality of cylinders 11 . Specifically, the CPU 71 compares the values of the misfire counters CN(1) to CN(4) from when the internal combustion engine 10 is requested to start until the first predetermined period T1 elapses. Then, the CPU 71 identifies the cylinder 11 corresponding to the misfire counter CN having the largest value among the values of the misfire counters CN(1) to CN(4) as the misfire cylinder #id. After that, the process proceeds to step S26.

In step S26, the CPU 71 performs stop processing for stopping fuel supply to the misfiring cylinder #id. Specifically, the CPU 71 stops the fuel supply from the port injection valve 16 and the in-cylinder injection valve 22 corresponding to the misfiring cylinder #id. Further, the CPU 71 continues fuel supply from the port injection valve 16 and the in-cylinder injection valve 22 to the cylinders 11 other than the misfiring cylinder #id. After that, the CPU 71 advances the process to step S27.

In step S27, the CPU 71 determines whether or not a predetermined second predetermined period T2 has elapsed after the stop processing. In the present embodiment, the second predetermined period T2 is set as a period during which the crankshaft 26 rotates 400 times. For example, the CPU 71 initializes a counter that counts the number of rotations of the crankshaft 26 and starts counting the number of rotations of the crankshaft 26 by the stop processing.

If the CPU 71 determines that the second predetermined period T2 has not elapsed after the stop processing of the misfiring cylinder #id (S27: NO), it repeats the processing of step S27. On the other hand, when the CPU 71 determines that the second predetermined period T2 has elapsed after the misfiring cylinder #id is stopped (S27: YES), the process proceeds to step S28.

In step S28, the CPU 71 performs a second calculation process for calculating the second misfire rate R2 in the second predetermined period T2. The second misfire occurrence rate R2 is a value that indicates the frequency of misfire detection relative to the total number of misfire detection processes.

In the present embodiment, the misfire detection process is performed at intervals of 180° CA. Therefore, if a period in which the number of rotations of the crankshaft 26 is 400 is set as the second predetermined period T2, the misfire detection process is performed 800 times. Become.

The number of misfires detected is the total value of misfire counters CN(1) to CN(4) until the second predetermined period T2 elapses after the stop process. Therefore, the CPU 71 divides the total value of the misfire counters CN(1) to CN(4) by the total number of misfire detection processes until the second predetermined period T2 elapses after the stop process. A misfire rate R2 is calculated. After that, the CPU 71 advances the process to step S29.

In step S29, the CPU 71 performs second determination processing for determining whether the internal combustion engine 10 is abnormal or normal. The fact that the internal combustion engine 10 is abnormal means that parts need to be replaced or adjusted in order to eliminate the misfire state of the internal combustion engine 10 .

In the second determination process, when the second misfire occurrence rate R2 is less than the predetermined second predetermined value L2 (S29: NO), the CPU 71 determines that the internal combustion engine 10 is normal, and the current series of processes is performed. exit. The second predetermined value L2 is set at, for example, 30% in this embodiment.

On the other hand, if the second misfire rate R2 is equal to or greater than the second predetermined value L2 (S29: YES), the CPU 71 determines that the internal combustion engine 10 is abnormal, and proceeds to step S30.
In step S30, the CPU 71 performs notification processing for notifying that the internal combustion engine 10 is abnormal. Specifically, the CPU 71 notifies that the internal combustion engine 10 is abnormal by operating the warning light 90 . Then, the CPU 71 terminates the series of processes for determining the current abnormality of the internal combustion engine 10 .

(About the action of the embodiment)
Suppose that due to a defect in the throttle valve 14, the intake air amount Ga, which is the flow rate of air flowing through the intake passage 12, becomes larger than the target value that the controller 70 wants to control. In this case, there is a high possibility that misfires will be detected at approximately the same frequency in any of cylinders #1 to #4. Assume that the throttle valve 14 is defective and the first misfire occurrence rate R1 is 25%, as in this example. The breakdown of the first misfire occurrence rate R1 is assumed to be 7% for cylinder #1 and 6% for each of cylinders #2 to #4. In this case, in the first determination process, the first misfire occurrence rate R1 is greater than or equal to 20%, which is the first predetermined value L1, so it is determined that the internal combustion engine 10 is in a misfire state. Cylinder #1 has slightly more misfires detected than cylinders #2 to #4, and is identified as misfiring cylinder #id. After that, when the fuel supply to cylinder #1 is stopped by the stop processing, the air-fuel mixture is no longer burned in cylinder #1. Therefore, the misfire rate for cylinder #1 alone is 100%, and the breakdown of the first misfire occurrence rate R1 is 25% for cylinder #1 and 6% for each of cylinders #2 to #4. As a result, the second misfire rate R2 is 43%. In the second determination process, it is determined that the internal combustion engine 10 is abnormal because the second misfire rate R2 is equal to or greater than 30%, which is the second predetermined value L2.

On the other hand, it is assumed that ice adheres to at least one of the intake valve 18 and the exhaust valve 30 corresponding to cylinder #1 among the four cylinders 11 . Also, in this case, it is assumed that in cylinder #1, the combustion chamber 20 cannot be sufficiently compressed, and misfire always occurs. It is assumed that normal combustion occurs in cylinders #2 to #4. In this case, the first misfire rate R1 is 25%. Then, in the first determination process, since the first misfire occurrence rate R1 is equal to or greater than 20%, which is the first predetermined value L1, it is determined that the internal combustion engine 10 is in a misfire state. Then, cylinder #1 is specified as the misfiring cylinder #id. After that, even if the fuel supply to cylinder #1 is stopped by the stop processing, since cylinder #1 is already in a misfire state before the stop processing, the second misfire incidence rate R2 is lower than the first misfire incidence rate R1. It remains unchanged at 25%. Therefore, in the second determination process, it is determined that the internal combustion engine 10 is normal because the second misfire rate R2 is less than 30%, which is the second predetermined value L2. Note that when the internal combustion engine 10 is warmed up, the ice attached to the intake valve 18 or the exhaust valve 30 corresponding to cylinder #1 melts. Therefore, the misfire in cylinder #1 is also eliminated.

(About effect of embodiment)
(1) In the above embodiment, it is assumed that ice adheres to at least one of the intake valves 18 and exhaust valves 30 corresponding to some of the plurality of cylinders 11 . In this case, the frequency of misfires in cylinders 11 corresponding to valves with ice on them is considerably high. Then, the first calculation process calculates the first misfire occurrence rate R1 for the entire plurality of cylinders 11, and the first determination process determines that the internal combustion engine 10 is in a misfire state. Also, the fuel injection to the cylinder 11 corresponding to the valve to which ice adheres is stopped. Due to the suspension of fuel injection, the cylinder 11 corresponding to the ice-covered valve always misfires. However, as described above, the frequency of misfires in cylinders 11 corresponding to ice-covered valves is considerably higher before fuel injection is stopped. Therefore, the second misfire rate R2 calculated in the second calculation process after the stop process does not rise much compared to the first misfire rate R1. Therefore, there is a high possibility that the second misfire rate R2 will be less than the second predetermined value L2, and there is a high possibility that the internal combustion engine 10 will not be determined to be abnormal in the second determination process. Therefore, when ice adheres to the valves of some cylinders 11 and the internal combustion engine 10 is in a misfire state, it is possible to avoid an unconditional notification of abnormality.

(2) In the above embodiment, the fuel supply to the misfiring cylinder #id is stopped by performing the stop processing. Therefore, it is possible to prevent unburned fuel from reaching the three-way catalyst 32 in the exhaust passage 28 until the second determination process is completed after determining that the internal combustion engine 10 is in a misfire state. Accordingly, it is possible to prevent the three-way catalyst 32 from being eroded due to combustion of the fuel reaching the three-way catalyst 32 . Therefore, the second predetermined value L2 can be set considerably large.

(3) According to the above embodiment, in step S21, it is determined whether or not the internal combustion engine 10 will be started under low temperature conditions. Then, when the internal combustion engine 10 is started under low temperature conditions, the first determination process and the second determination process are performed. That is, the first determination process and the second determination process are performed only when there is a possibility that ice adheres to the intake valve 18 and the exhaust valve 30 corresponding to any cylinder 11 . In other words, the first determination process and the second determination process are not performed under the condition that ice does not adhere to each valve. Therefore, it is possible to avoid performing a series of processes such as the first determination process and the second determination process unnecessarily.

<Other embodiments>
The above embodiment can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other within a technically consistent range.

- The misfire detection process is not limited to the example of the above embodiment. The misfire detection process may detect whether or not a misfire has occurred in each cylinder 11 every time each cylinder 11 undergoes a certain number of combustion strokes. For example, it may be determined whether or not a misfire has occurred in each cylinder 11 based on the amount of torque fluctuation of the crankshaft 26 . Further, the misfire detection process may be performed once each time each cylinder 11 undergoes one combustion stroke, for example, each time each cylinder 11 undergoes a plurality of combustion strokes.

- The process of step S21 is not restricted to the example of the said embodiment. The intake air temperature may be used instead of the outside air temperature THA, and the temperature of the oil for lubricating the internal combustion engine 10 or the exhaust temperature may be used instead of the water temperature THW. Also, the outside air temperature THA or the water temperature THW may be used. In any case, it suffices if the temperature of the internal combustion engine 10 is such that the possibility of ice adhering to each valve is low to some extent. Also, the process of step S21 may be omitted. That is, when there is a request to start the internal combustion engine 10, the abnormality determination process may always be performed.

- The 1st predetermined value L1 and the 2nd predetermined value L2 are not restricted to the example of the said embodiment. The second predetermined value L2 may be changed as appropriate as long as it is greater than the first predetermined value L1.
For example, the first predetermined value L1 may be variably set according to the rotation speed NE of the crankshaft 26 and the charging efficiency η. For example, the first predetermined value L1 may be predetermined by a map having the rotation speed NE of the crankshaft 26 and the charging efficiency η as input variables and the first predetermined value L1 as an output variable.

Specifically, the first predetermined value L1 may be set smaller as the rotation speed NE of the crankshaft 26 increases. Further, specifically, the first predetermined value L1 may be set smaller as the charging efficiency η increases. As the rotation speed NE of the crankshaft 26 increases and the charging efficiency η increases, the amount of exhaust gas flowing through the exhaust passage 28 of the internal combustion engine 10 per unit time increases. Therefore, the degree of temperature rise of the three-way catalyst 32 increases. Therefore, in such a case, in order to prevent overheating of the three-way catalyst 32, it is preferable to set the first predetermined value L1 to a small value so that it is easier to determine that the internal combustion engine 10 is in a misfire state. In this regard, the same applies to the second predetermined value L2.

- Although notification processing turned on warning light 90 was illustrated, it is not restricted to this. For example, you may notify by sounding. Further, if the vehicle VC has a communication function with an external device, the abnormality may be notified by transmitting information to the effect that the abnormality is indicated to the external device. Examples of the external device include a smartphone owned by the user, a server collectively managing information on a plurality of vehicles VC, and the like.

- Although the internal combustion engine 10 having four cylinders 11 is illustrated in the above embodiment, the internal combustion engine 10 may have a plurality of cylinders 11 . That is, it may have two or three cylinders 11 or may have five or more cylinders 11 .

In the above embodiment, the internal combustion engine 10 has four valves for one cylinder 11, but one intake valve 18 and one exhaust valve 30 for one cylinder 11. You may have

- The control device 70 is not limited to one that includes the CPU 71 and the ROM 73 and executes software processing. For example, a dedicated hardware circuit (for example, an ASIC, etc.) that performs hardware processing at least part of what is software-processed in the above embodiments may be provided. That is, the execution device may have any one of the following configurations (a) to (c). (a) A processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) A processing device and a program storage device for executing part of the above processing according to a program, and a dedicated hardware circuit for executing the remaining processing. (c) provide dedicated hardware circuitry to perform all of the above processing; Here, there may be a plurality of software execution devices provided with a processing device and a program storage device, or a plurality of dedicated hardware circuits.

- In the above embodiment, an example in which the control device 70 functions as an abnormality determination device was shown, but an abnormality determination device that performs misfire detection processing and abnormality determination processing may be provided separately from the control device 70. .

DESCRIPTION OF SYMBOLS 10... Internal combustion engine 11... Cylinder 18... Intake valve 30... Exhaust valve 70... Control device 71... CPU
72... Peripheral circuit 73... ROM
74 storage device

Claims (1)

An abnormality determination device applied to an internal combustion engine having a plurality of cylinders,
When misfiring means that the air-fuel mixture does not burn in the cylinder when the cylinder reaches the combustion stroke,
a misfire detection process for detecting whether or not the misfire has occurred in each of the plurality of cylinders each time the cylinder undergoes a predetermined number of combustion strokes;
calculating a first misfire rate indicating the frequency of misfires detected with respect to the total number of times the misfire detection process is performed within a first predetermined period of time after the start request for the internal combustion engine is issued; a calculation process;
If the first misfire occurrence rate is equal to or greater than a predetermined first predetermined value, it is determined that the internal combustion engine is in a misfire state, and if the first misfire occurrence rate is less than the first predetermined value, the internal combustion engine is determined to be in a misfire state. a first determination process for determining that the engine is not in a misfire state;
a stop process of stopping fuel supply to the cylinder in which the most misfires are detected among the plurality of cylinders when the first determination process determines that the internal combustion engine is in a misfired state;
a second calculation process for calculating a second misfire occurrence rate indicating the frequency at which the misfire is detected with respect to the total number of times the misfire detection process is performed before a second predetermined period elapses after the stop process;
When the second misfire rate is equal to or greater than a second predetermined value larger than the first predetermined value, it is determined that the internal combustion engine is abnormal, and the second misfire rate is equal to or greater than the second predetermined value. a second determination process for determining that the internal combustion engine is normal when the value is less than the value;
An abnormality determination device for an internal combustion engine, which performs a notification process of notifying that an abnormality has occurred when the second determination process determines that the internal combustion engine is abnormal.

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