Fire misfire diagnostic device and program

Abstract

It accurately diagnoses misfiring cylinders in multi-cylinder engines. [Solution] The misfire diagnosis device (20) diagnoses whether or not there is a misfire in an engine having multiple cylinders. The misfire diagnosis device is provided with a setting unit (22) which sets the calculation interval as the period during which at least all cylinders complete one ignition cycle; a recording unit (21) which records the crank angle acceleration for each cylinder from the ignition of that cylinder to the ignition of the next cylinder; a calculation unit (23) which calculates the difference between the maximum and minimum values ​​of the crank angle acceleration for each cylinder in the calculation interval; and a diagnosis unit (24) which diagnoses a cylinder as a misfired cylinder if the difference in crank angle acceleration for each cylinder is greater than or equal to a threshold.

Description

Technical Field

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[0001] The present invention relates to an engine misfire diagnosis device and a program.

Background Art

[0002] Conventionally, an abnormality diagnosis device for diagnosing abnormalities in each cylinder of an engine has been known (see, for example, Patent Document 1). In the abnormality diagnosis device described in Patent Document 1, the difference between the instantaneous minimum rotational speed and the instantaneous maximum rotational speed during the explosion stroke for each cylinder is calculated as the rotational fluctuation time difference. The rotational fluctuation time difference is calculated for each cylinder, and the rotational fluctuation deviation is calculated for each cylinder from the rotational fluctuation time difference for each cylinder and the average value of the rotational fluctuation time differences for all cylinders. Then, the rotational fluctuation deviation is compared with a preset threshold value, and in addition to the misfire state of insufficient combustion in each cylinder, abnormalities such as insufficient fuel injection or excessive fuel injection by the injector are diagnosed.

Prior Art Documents

Patent Documents

[0007] In one embodiment of the present invention, a misfire diagnostic device uses crank angular acceleration as an indicator of whether the rotational speed of the crankshaft is increasing or decreasing. As combustion energy decreases due to misfire, the crank angular acceleration tends to decrease, so when a cylinder misfires, the difference between the maximum and minimum values ​​of the crank angular acceleration becomes large. By monitoring the difference in crank angular acceleration for each cylinder, the misfired cylinder is diagnosed. Furthermore, since the crank angular acceleration from one cylinder ignition to the next is used, the misfired cylinder can be diagnosed accurately without being affected by the subsequent cylinder ignition. [Brief explanation of the drawing]

[0008] [Figure 1] This is a functional block diagram of the engine system of the first embodiment. [Figure 2] This is a functional block diagram of the misfire diagnosis device of the first embodiment. [Figure 3] This is a time chart for diagnosing misfiring cylinders in the first embodiment. [Figure 4] This is a flowchart of the recording process for misfiring cylinder diagnosis in the first embodiment. [Figure 5] This is a flowchart of the calculation process for misfiring cylinder diagnosis in the first embodiment. [Figure 6] This is a functional block diagram of the misfire diagnosis device of the second embodiment. [Figure 7] This is a time chart for misfire diagnosis in the second embodiment. [Figure 8]This is a flowchart of the recording process for misfire diagnosis in the second embodiment. [Figure 9] This is a flowchart of the calculation process for misfire diagnosis in the second embodiment. [Figure 10] This is a flowchart of the recording process for misfiring cylinder diagnosis in the second embodiment. [Figure 11] This is a flowchart of the calculation process for misfiring cylinder diagnosis in the second embodiment. [Modes for carrying out the invention]

[0009] A misfire diagnosis device according to one aspect of the present invention diagnoses the presence or absence of misfires in an engine having multiple cylinders. In the misfire diagnosis device, the setting unit sets a calculation interval for a period during which at least all cylinders have completed one ignition cycle, and the recording unit records the crank angular acceleration for each cylinder from the ignition of the current cylinder to the ignition of the next cylinder. The calculation unit calculates the difference between the maximum and minimum values ​​of the crank angular acceleration for each cylinder during the calculation interval, and the diagnosis unit diagnoses any cylinder in which the difference in crank angular acceleration for each cylinder is greater than or equal to a threshold as a misfired cylinder. Crank angular acceleration is an indicator that shows whether the rotational speed of the crankshaft is increasing or decreasing. As combustion energy decreases due to misfire, the crank angular acceleration tends to decrease, so when a cylinder misfires, the difference between the maximum and minimum values ​​of the crank angular acceleration becomes large. By monitoring the difference in crank angular acceleration for each cylinder, misfired cylinders are diagnosed. Furthermore, since the crank angle acceleration from one cylinder ignition to the next is used, misfiring cylinders can be accurately diagnosed without being affected by the subsequent cylinder ignition. [Examples]

[0010] <First Example> The misfire diagnosis device of the first embodiment will be described below with reference to the attached drawings. Figure 1 is a functional block diagram of the engine system of the first embodiment. Figure 2 is a functional block diagram of the misfire diagnosis device of the first embodiment. Figure 3 is a time chart of misfire cylinder diagnosis of the first embodiment.

[0011] As shown in Figure 1, engine 1 is a four-stroke engine that repeats intake, compression, expansion, and exhaust strokes. Engine 1 has cylinders 2#1-2#6, and each cylinder 2#1-2#6 is equipped with an intake valve (not shown), an exhaust valve (not shown), fuel injectors 3#1-3#6, and spark plugs 4#1-4#6. The ECU (Electronic Control Unit) 5 controls the fuel injection from fuel injectors 3#1-3#6 and the ignition from spark plugs 4#1-4#6, so that cylinders 2#1-2#6 are ignited sequentially at crank angles with 120° intervals, and the ignition of all cylinders is repeated periodically.

[0012] ECU5 is connected to a group of sensors including a crank angle sensor 11, a cam angle sensor 12, a throttle position sensor 13, an airflow sensor 14, an intake air temperature sensor 15, and a water temperature sensor 16. The crank angle sensor 11 outputs a signal corresponding to the rotation angle of the crankshaft (not shown), and the cam angle sensor 12 outputs a signal corresponding to the rotation angle of the camshaft (not shown). The throttle position sensor 13 outputs a signal corresponding to the throttle opening, and the airflow sensor 14 outputs a signal corresponding to the intake air volume. The intake air temperature sensor 15 outputs a signal corresponding to the intake air temperature, and the water temperature sensor 16 outputs a signal corresponding to the coolant temperature of the engine 1.

[0013] Based on the output results of the crank angle sensor 11, cam angle sensor 12, throttle position sensor 13, airflow sensor 14, intake air temperature sensor 15, and water temperature sensor 16, the ECU 5 performs ignition timing and various other controls. In response to the signal from the crank angle sensor 11, the ECU 5 calculates the crank angular velocity for each cylinder by dividing the angular difference between the crank angle detected this time and the crank angle detected last time by the time interval of the detection times. Furthermore, the crank angular acceleration for each cylinder is calculated by dividing the angular velocity difference between the crank angular velocity calculated this time and the crank angular velocity calculated last time by the time interval of the detection times mentioned above. Note that the method for calculating the crank angular acceleration is not limited.

[0014] As shown in FIGS. 2 and 3, an engine 1 is connected to a misfire diagnosis device 20 that diagnoses the presence or absence of misfires in the engine 1 having a plurality of cylinders. In the misfire diagnosis device 20 of the first embodiment, ignition of all cylinders 2#1 - 2#6 is comprehensively monitored. The misfire diagnosis device 20 includes a setting unit 22 that sets a calculation section as a period during which ignition of at least all cylinders 2#1 - 2#6 makes one round, a recording unit 21 that records the crank angle acceleration from the ignition of each cylinder to the ignition of the next cylinder for each cylinder, a calculation unit 23 that calculates the difference between the maximum value and the minimum value of the crank angle acceleration in the calculation section for each cylinder, and a diagnosis unit 24 that diagnoses a cylinder in which the difference in crank angle acceleration is greater than or equal to a threshold value as a misfired state for each cylinder.

[0015] A pulse signal corresponding to the ignition timing of each cylinder 2#1 - 2#6 is input from an ECU 5 to the setting unit 22. The setting unit 22 is provided with an ignition counter 25, and the ignition counter 25 is counted each time each cylinder 2#1 - 2#6 is ignited based on the pulse signal. Counting starts after the open flag of the calculation window is set, and when the ignition counter 25 exceeds a predetermined value C1, it is reset to the first count. When the ignition counter 25 reaches one count, the open flag of the next set of calculation windows is set. The count period from when the open flag of the calculation window is set to the predetermined value C1 of the ignition counter 25 is set as the calculation section.

[0016] In the first embodiment, the setting unit 22 sets a period during which ignition of all cylinders 2#1 - 2#6 makes multiple rounds as the calculation section. Specifically, 12 counts are set as the predetermined value C1 for the ignition counter 25, and the period until ignition of all cylinders 2#1 - 2#6 makes two rounds and is counted 12 times is set as the calculation section. It is possible to diagnose a misfired state including the case where a specific cylinder misfires only once in multiple times (twice). Also, when the ignition counter 25 is counted 12 times, the setting unit 22 sets the calculation permission flag, assuming that the first set of calculation sections has elapsed.

[0017] The recording unit 21 records the crank angle acceleration α calculated by the ECU 5 for each cylinder. When a misfire occurs in a cylinder, the combustion energy decreases due to the misfire, so the crank angle acceleration α of the misfired cylinder tends to decrease. The misfire diagnostic device 20 diagnoses the misfired cylinder by utilizing the characteristics of the crank angle acceleration α. ​​The crank angle acceleration α of a cylinder is recorded in the section from the ignition of that cylinder to the ignition of the next cylinder, so that the crank angle acceleration α of a given cylinder is not affected by the ignition of the next cylinder. For example, the crank angle acceleration α1 of cylinder 2#1 is recorded in the section from the ignition of cylinder 2#1 to the ignition of the next cylinder 2#6.

[0018] In the calculation unit 23, when the calculation permission flag is set in the setting unit 22, the difference between the maximum value α_MAX and the minimum value α_MIN of the crank angular acceleration α during the calculation interval is calculated for each cylinder. That is, the crank angular acceleration α during the calculation interval until the calculation permission flag is set is monitored for each cylinder, and the calculation unit 23 determines the maximum value α_MAX and the minimum value α_MIN from the crank angular acceleration α. ​​Furthermore, the calculation unit 23 calculates the difference Δα between the maximum value α_MAX and the minimum value α_MIN of the crank angular acceleration. For example, the maximum value α1_MAX and the minimum value α1_MIN of the crank angular acceleration α1 of cylinder 2#1 are determined during the calculation interval, and the difference Δα1 between the maximum value α1_MAX and the minimum value α1_MIN of the crank angular acceleration is calculated.

[0019] In the diagnostic unit 24, the difference Δα of the crank angle acceleration of each cylinder and the threshold TH are compared for each calculation interval. Cylinders whose difference Δα of crank angle acceleration is greater than or equal to the threshold TH are diagnosed as misfiring cylinders, and cylinders whose difference Δα of crank angle acceleration is less than the threshold TH are diagnosed as not misfiring cylinders. The diagnostic unit 24 is also equipped with a misfiring cylinder counter 26 for each cylinder, and the misfiring cylinder counter 26 is counted each time the diagnostic unit 24 diagnoses a cylinder as misfiring. When the diagnostic period has elapsed, the diagnostic unit 24 performs a final diagnosis, and if the count value of the misfiring cylinder counter 26 (the number of times a cylinder has been diagnosed as misfiring) is greater than or equal to a predetermined value (a predetermined number of times) C2, the diagnostic unit 24 confirms that the cylinder is misfiring and notifies the system.

[0020] In this way, the diagnostic accuracy is improved because the misfiring cylinder is confirmed only when it is repeatedly diagnosed as such by the diagnostic unit 24. The threshold TH and predetermined values ​​C1 and C2 are set to values ​​obtained experimentally, empirically, and theoretically from past data, etc. The crankshaft rotation speed is set as the diagnostic period. The misfiring cylinder counter 26 is reset when the crankshaft rotation speed reaches the predetermined rotation speed from the start of the diagnosis. In Figure 3, only the crank angular acceleration α1 and the difference in crank angular acceleration Δα1 of cylinder 2#1 are illustrated, but in reality, recording and calculation are also performed for cylinders 2#2-2#6.

[0021] Each control block of the misfire diagnosis device 20 may be implemented by software using a processor, or by logic circuits (hardware) formed on an integrated circuit or the like. When a processor is used, various processes are performed by the processor reading and executing a program stored in memory. For example, a CPU (Central Processing Unit) is used as the processor. The memory is composed of one or more storage media such as ROM (Read Only Memory) and RAM (Random Access Memory), depending on the application.

[0022] Here, we will explain an example of misfiring cylinder diagnosis. As shown in Figure 3, ignition is repeated in the order of cylinders 2#1, 2#6, 2#5, 2#4, 2#3, and 2#2. When the open flag of the calculation window is set, the ignition counter 25 counts the number of ignitions. When the ignition counter 25 of the setting unit 22 exceeds 12 counts, the ignition counter 25 is reset from the 12th count to the 1st count and the calculation permission flag is set. Also, the open flag of the calculation window for the next set is set, and the ignition counter 25 counts the number of ignitions again from the 1st count. In this way, one calculation interval is set in units of 12 counts.

[0023] Furthermore, the recording unit 21 records the crank angular acceleration α for each cylinder. When the calculation permission flag is set by the setting unit 22, the calculation unit 23 determines the maximum value α1_MAX and minimum value α1_MIN of the crank angular acceleration of cylinder 2#1 in the first set of calculation windows (calculation intervals). In addition, the calculation unit 23 determines the difference Δα1 of the crank angular acceleration of cylinder 2#1. Although not shown in the diagram, the same calculation process is performed for cylinders 2#2-22#6 in parallel with the calculation process for cylinder 2#1. The calculation process of the calculation unit 23 is repeated each time the calculation permission flag is set.

[0024] The difference Δα1 in the crank angular acceleration of cylinder 2#1 is greater than or equal to the threshold TH. Therefore, in the first calculation window, the diagnostic unit 24 diagnoses cylinder 2#1 as a misfired cylinder, and the misfired cylinder counter 26#1 for cylinder 2#1 is incremented by one. The above process is repeated for each calculation interval as the calculation window is opened, and the misfired cylinder counter 26#1 for cylinder 2#1 is incremented. The diagnostic period is set from the start of the diagnosis until the crankshaft has rotated 200 times. At the end of the diagnostic period, since the misfired cylinder counter 26#1 exceeds a predetermined value C2, the diagnostic unit 24 confirms that cylinder 2#1 is a misfired cylinder and notifies the system.

[0025] The flow of misfire cylinder diagnosis will be explained with reference to Figures 4 and 5. Figure 4 is a flowchart of the recording process for misfire cylinder diagnosis in the first embodiment. Figure 5 is a flowchart of the calculation process for misfire cylinder diagnosis in the first embodiment.

[0026] As shown in Figure 4, when the Nth set of calculation windows N is opened (step S01), the number of ignitions is counted in the ignition counter 25 and the crank angle acceleration α is recorded for each cylinder (step S02). The process in step S02 is repeated until the count value of the ignition counter 25 exceeds a predetermined value C1 (step S03 is No). When the count value of the ignition counter 25 exceeds the predetermined value C1 (step S03 is Yes), the N+1th set of calculation windows N+1 is opened and processing starts again from step S01 (step S04). The calculation process for calculation window N proceeds in parallel with the recording process for calculation window N+1. Note that the recording process may be stopped at the end of the diagnostic period.

[0027] As shown in Figure 5, when the count value of the ignition counter 25 exceeds a predetermined value C1 (Yes in step S03), the calculation permission flag in the calculation window N is set (step S05). In the calculation window N (calculation interval N), the difference Δα between the maximum value α_MAX and the minimum value α_MIN of the crank angular acceleration is calculated for each cylinder (step S06). If the difference Δα of the crank angular acceleration for each cylinder is greater than or equal to the threshold TH (Yes in step S07), the count value of the misfire cylinder counter 26 for each cylinder is incremented (step S08). If the diagnosis period for misfire cylinder diagnosis has not ended (No in step S09), the process returns to step S06 and calculation processing for calculation window N+1 is performed (step S10).

[0028] When the diagnostic period for misfire cylinder diagnosis ends (Yes in step S09), the count value of the misfire cylinder counter 26 for each cylinder is compared with a predetermined value C2 (step S11). If there is a cylinder whose misfire cylinder counter 26 count value is equal to or greater than the predetermined value C2 (Yes in step S11), this cylinder is confirmed to be a misfire cylinder and the user is notified (step S12). The notification method is not particularly limited, but may be an error message, a machine voice, a warning sound, or a warning lamp. Alternatively, notification may be given even before the end of the diagnostic period, as soon as the count value of the misfire cylinder counter 26 becomes equal to or greater than the predetermined value C2.

[0029] In addition, the predetermined value C1 in step S03 may be set to a value that allows all cylinders to complete one ignition cycle (for example, 6 counts), or to a value that allows all cylinders to complete multiple ignition cycles (for example, 12 counts). Although the misfiring cylinder is diagnosed by the comparison result in step S11, the misfiring cylinder may also be diagnosed by the comparison result in step S07. In other words, steps S08-S11 may be omitted.

[0030] As described above, according to the misfire diagnosis device 20 of the first embodiment, the crank angle acceleration α tends to decrease as combustion energy decreases due to misfire. Therefore, when a cylinder misfires, the difference Δα between the maximum value α_MAX and the minimum value α_MIN of the crank angle acceleration becomes large. By monitoring the difference in crank angle acceleration for each cylinder, the misfired cylinder is diagnosed. Furthermore, since the crank angle acceleration α from one cylinder ignition to the next cylinder ignition is used, the misfired cylinder can be diagnosed accurately without being affected by the next cylinder ignition.

[0031] <Second Example> Next, the misfire diagnosis device of the second embodiment will be described. Figure 6 is a functional block diagram of the misfire diagnosis device of the second embodiment. Figure 7 is a time chart of the misfire diagnosis of the second embodiment. Note that the second embodiment differs from the first embodiment in that the engine misfire diagnosis is performed in parallel with the misfire cylinder diagnosis, and the misfire cylinder is determined when the engine is diagnosed as being in a misfire state and a misfire cylinder is identified. Therefore, explanations of the configuration corresponding to the first embodiment will be omitted as much as possible.

[0032] As shown in Figures 6 and 7, the misfire diagnosis device 30 includes a setting unit 32 that sets the calculation interval to the period during which at least all cylinders 2#1-2#6 complete one ignition cycle, a recording unit 31A that records misfire index values ​​indicating the misfire state of several cylinders, a calculation unit 33A that calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval, and a diagnosis unit 34A that diagnoses a misfire state when the difference in misfire index values ​​is greater than or equal to a threshold. In addition, although a detailed explanation is omitted, the misfire diagnosis device 30 also includes a recording unit 31B, a calculation unit 33B, and a diagnosis unit 34B, which correspond to the recording unit 21, calculation unit 23, and diagnosis unit 24 of the first embodiment.

[0033] The setting unit 32 receives pulse signals from the ECU 5 corresponding to the ignition timing of each cylinder 2#1-2#6. The setting unit 32 is equipped with an ignition counter 35A, which counts each time each cylinder 2#1-2#6 ignites based on the pulse signals. Counting begins after the calculation window's open flag is set, and resets to the first count when the ignition counter 35A exceeds a predetermined value C3. When the ignition counter 35A reaches 1 count, the open flag for the next set of calculation windows is set. The counting period from when the calculation window's open flag is set until the predetermined value C3 of the ignition counter 35 is set is defined as the calculation interval.

[0034] When the ignition counter 35A counts to a predetermined value C3, the setting unit 32 sets a calculation permission flag, indicating that the first calculation interval has elapsed. The setting unit 32 sets not only the calculation interval for misfire diagnosis of engine 1, but also the calculation interval for misfire cylinder diagnosis as described above (see Figure 3). For this reason, the setting unit 32 is provided with an ignition counter 35B for misfire cylinder diagnosis that returns to the first count when it exceeds a predetermined value C1. Note that the same length of calculation interval may be set for misfire diagnosis and misfire cylinder diagnosis, or different length calculation intervals may be set for misfire diagnosis and misfire cylinder diagnosis.

[0035] The recording unit 31A records the engine speed Ne and the crank period Tx, calculated by the ECU 5 (see Figure 1), as misfire index values. If a misfire occurs in any of cylinders 2#1-2#6, the combustion energy decreases due to the misfire, causing the engine speed Ne to decrease while the crank period Tx increases. The misfire diagnostic device 30 uses these characteristics of engine speed Ne and crank period Tx to diagnose whether or not there is a misfire in engine 1. The recording unit 31A may also record either the engine speed Ne or the crank period Tx as the misfire index value. The crank period Tx is the rotation time of the crankshaft from the ignition of one cylinder to the ignition of the next cylinder, and in this embodiment, it represents the time required for the crankshaft to rotate 120°.

[0036] In the calculation unit 33A, when the calculation permission flag is set in the setting unit 32, the difference between the maximum and minimum values ​​of the misfire index value in the calculation interval is calculated. That is, the misfire index value in the calculation interval is monitored until the calculation permission flag is set, the calculation unit 33A determines the maximum and minimum values ​​from the misfire index value, and further calculates the difference between the maximum and minimum values ​​of the misfire index value. The difference ΔNe between the maximum value Ne_MAX and the minimum value Ne_MIN of the engine speed in the calculation interval is determined, and the difference ΔTx between the maximum value Tx_MAX and the minimum value Tx_MIN of the ignition interval crank period in the calculation interval is determined.

[0037] In the diagnostic unit 34A, the difference in engine speed ΔNe is compared with a first threshold TH1 for each calculation interval, and the difference in ignition interval crank period ΔTx is compared with a second threshold TH2 for each calculation interval. If the difference in engine speed ΔNe is greater than or equal to the first threshold TH1 and the difference in ignition interval crank period ΔTx is greater than or equal to the second threshold TH2, the diagnostic unit 34A diagnoses that there is a misfire. If the difference in engine speed ΔNe is less than the first threshold TH1 and / or the difference in ignition interval crank period ΔTx is less than the second threshold TH2, the diagnostic unit 34A diagnoses that there is no misfire.

[0038] As described above, the engine speed Ne and the ignition interval crank period Tx can be recorded simultaneously, and the diagnostic unit 34A diagnoses the combustion state of engine 1 using different indicator values ​​at the same time, thereby improving diagnostic accuracy. The diagnostic unit 34A is also equipped with a misfire counter 36, and the misfire counter 36 is counted each time the diagnostic unit 34A diagnoses a misfire condition. When the diagnostic period has elapsed, the diagnostic unit 34A performs a final diagnosis, and if the count value of the misfire counter 36 (the number of diagnoses in which a misfire condition was diagnosed) is equal to or greater than a predetermined value (a predetermined number of times) C4, the diagnostic unit 34A confirms that there is a misfire in engine 1 and notifies the diagnostic unit 34B of the diagnosis result.

[0039] Then, if the diagnostic unit 34B diagnoses that a cylinder is a misfiring cylinder, it is confirmed that the cylinder is a misfiring cylinder and this is reported. The first and second thresholds TH1 and TH2, and the predetermined values ​​C3 and C4 are set to values ​​obtained experimentally, empirically, and theoretically from past data, etc. The diagnostic period is set to the rotational speed of the crankshaft (200 rpm in this embodiment). The misfire counter 36 is reset when the crankshaft rotational speed reaches the predetermined rotational speed from the start of the diagnosis. In addition, the diagnostic unit 34A may diagnose the misfire state using only one of the differences in engine rotational speed ΔNe and the difference in ignition interval crank period ΔTx.

[0040] Each control block of the misfire diagnosis device 30 may be implemented by software using a processor, or by logic circuits (hardware) formed on an integrated circuit or the like. When a processor is used, various processes are performed by the processor reading and executing a program stored in memory. For example, a CPU (Central Processing Unit) is used as the processor. The memory is composed of one or more storage media such as ROM (Read Only Memory) and RAM (Random Access Memory), depending on the application.

[0041] The misfire diagnosis process will be explained with reference to Figures 8 to 11. Figure 8 is a flowchart of the misfire diagnosis recording process in the second embodiment. Figure 9 is a flowchart of the misfire diagnosis calculation process in the second embodiment. Figure 10 is a flowchart of the misfire cylinder diagnosis recording process in the second embodiment. Figure 11 is a flowchart of the misfire cylinder diagnosis calculation process in the second embodiment. Note that the misfire cylinder diagnosis is performed in parallel with the misfire diagnosis in the second embodiment. However, the misfire cylinder diagnosis in the second embodiment differs from the first embodiment in that it refers to the misfire diagnosis results.

[0042] As shown in Figure 8, when the Nth set of calculation windows N is opened (step S21), the ignition count is recorded in the ignition counter 35A, and the engine speed Ne and the ignition interval crank period Tx are recorded (step S22). The process in step S22 is repeated until the count value of the ignition counter 35A exceeds a predetermined value C3 (No in step S23). When the count value of the ignition counter 35A exceeds the predetermined value C3 (Yes in step S23), the N+1th set of calculation windows N+1 is opened, and processing starts again from step S21 (step S24). The calculation process for calculation window N proceeds in parallel with the recording process for calculation window N+1. Note that the recording process may be stopped at the end of the diagnostic period.

[0043] As shown in Figure 9, when the count value of the ignition counter 35A exceeds a predetermined value C3 (Yes in step S23), the calculation permission flag for the calculation window N is set (step S25). The difference ΔNe between the maximum value Ne_MAX and the minimum value Ne_MIN of the engine speed, and the difference ΔTx between the maximum value Tx_MAX and the minimum value Tx_MIN of the ignition interval crank period are calculated in the calculation window N (calculation interval N) (step S26). If the difference in engine speed ΔNe is greater than or equal to the first threshold TH1 and the difference in ignition interval crank period ΔTx is greater than or equal to the second threshold TH2 (Yes in step S27), the count value of the misfire counter 36 is incremented (step S28). If the diagnosis period for misfire diagnosis has not ended (No in step S29), the process returns to step S26 and calculation processing for calculation window N+1 is performed (step S30).

[0044] When the misfire diagnosis period ends (Yes in step S29), the count value of the misfire counter 36 is compared with a predetermined value C4 (step S31). If the count value of the misfire counter 36 is greater than or equal to the predetermined value C4 (Yes in step S31), the misfire state of engine 1 is determined and the diagnosis result is notified to the diagnosis unit 34B (step S32). In the misfire cylinder diagnosis shown in Figures 10 and 11, the processes in steps S41-S51 (same as the processes in steps S01-S11) are performed, and if there is a cylinder in step S51 where the count value of the misfire cylinder counter 37 is greater than or equal to the predetermined value C2 (Yes in step S51), it is determined whether or not a notification has been received from the diagnosis unit 34A (step S52). If a notification has been received from the diagnosis unit 34A (Yes in step S52), the misfire cylinder is determined and notified to the user (step S53).

[0045] In steps S22, S26, and S27, engine speed Ne and crank period Tx are used as misfire indicator values, but either engine speed Ne or crank period Tx may be used as the misfire indicator value. The predetermined value C1 in step S23 may be set to a value that allows all cylinders to complete one ignition cycle (e.g., 6 counts), or to a value that allows all cylinders to complete multiple ignition cycles (e.g., 24 counts). Although misfire diagnosis is performed based on the comparison result in step S31, misfire diagnosis may also be performed based on the comparison result in step S27. In other words, steps S28-S31 may be omitted.

[0046] As described above, with the misfire diagnosis device 30 of the second embodiment, the misfire state of the engine 1 is diagnosed, and when a misfired cylinder is diagnosed, the misfired cylinder is identified, thus improving the diagnostic accuracy.

[0047] In the second embodiment, engine speed and ignition interval / crank period are given as examples of misfire indicator values, but the misfire indicator values ​​are not particularly limited as long as they are indicator values ​​that indicate a misfire state.

[0048] Furthermore, while the first and second embodiments illustrate a 6-cylinder engine as an example, the engine is not particularly limited as long as it has multiple cylinders.

[0049] Furthermore, the ECU may function as a misfire diagnostic device, or a separate misfire diagnostic device may be provided in addition to the ECU.

[0050] Furthermore, a misfire diagnosis function may be added by installing a program in the ECU. This program may be stored on a storage medium. The storage medium is not particularly limited, but may be a non-transient storage medium such as an optical disc, magneto-optical disc, or flash memory.

[0051] Furthermore, the misfire diagnostic device of this embodiment is not limited to outboard motor engines, but may also be applied to engines of other vehicles.

[0052] As described above, the first embodiment is a misfire diagnostic device (20, 30) for diagnosing the presence or absence of misfires in an engine (1) having multiple cylinders (2#1-2#6), comprising: a setting unit (22, 32) that sets the calculation interval to the period during which at least all cylinders complete one ignition cycle; a recording unit (21, 31B) that records the crank angular acceleration for each cylinder from the ignition of that cylinder to the ignition of the next cylinder; a calculation unit (23, 33B) that calculates the difference between the maximum and minimum values ​​of the crank angular acceleration for each cylinder in the calculation interval; and a diagnostic unit (24, 34B) that diagnoses a cylinder as a misfired cylinder if the difference in crank angular acceleration for each cylinder is greater than or equal to a threshold. Crank angular acceleration is an indicator that shows whether the rotational speed of the crankshaft is increasing or decreasing. As combustion energy decreases due to misfire, the crank angular acceleration tends to decrease, so when a cylinder misfires, the difference between the maximum and minimum values ​​of the crank angular acceleration becomes large. The misfiring cylinder is diagnosed by monitoring the difference in crank angle acceleration for each cylinder. Furthermore, since the crank angle acceleration from one cylinder ignition to the next is used, the misfiring cylinder can be diagnosed accurately without being affected by the subsequent cylinder ignition.

[0053] In the second embodiment, the setting unit uses the period during which all cylinders ignite multiple times as the calculation interval. With this configuration, it is possible to diagnose the misfiring cylinder, including cases where a specific cylinder misfires only once every multiple times.

[0054] In the third embodiment, in the first or second embodiment, the diagnostic unit identifies cylinders that have been diagnosed as misfiring a predetermined number of times or more after the diagnostic period has elapsed as misfiring cylinders. With this configuration, misfiring cylinders are identified only when they have been repeatedly diagnosed as misfiring cylinders, thus improving diagnostic accuracy.

[0055] The fourth embodiment includes, in any one embodiment of the first to third embodiments, another recording unit (31A) that records misfire index values ​​indicating the misfire state of several cylinders, another calculation unit (33A) that calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval, and another diagnostic unit (34A) that diagnoses a misfire state when the difference in misfire index values ​​is greater than or equal to a threshold, and the misfire cylinder is confirmed when the other diagnostic unit diagnoses the engine as being in a misfire state and the diagnostic unit diagnoses a misfire cylinder. With this configuration, the misfire state of the engine is diagnosed and the misfire cylinder is confirmed when a misfire cylinder is diagnosed, so the diagnostic accuracy is improved.

[0056] The fifth aspect is a program for a misfire diagnostic device that diagnoses the presence or absence of misfires in an engine having multiple cylinders, wherein the program causes the misfire diagnostic device to perform the following steps: setting the calculation interval to a period during which at least all cylinders have completed one ignition cycle; recording the crank angular acceleration for each cylinder from the ignition of that cylinder to the ignition of the next cylinder; calculating the difference between the maximum and minimum values ​​of the crank angular acceleration for each cylinder during the calculation interval; and diagnosing a cylinder for which the difference in crank angular acceleration for each cylinder is greater than or equal to a threshold as a misfired cylinder. With this configuration, by installing the program in the engine control device, etc., the control device, etc. can be used as a misfired cylinder diagnostic device.

[0057] Although this embodiment has been described, other embodiments may include combinations of the above embodiment and its modifications, either entirely or partially.

[0058] Furthermore, the technology of the present invention is not limited to the embodiments described above, and may be modified, substituted, or transformed in various ways without departing from the spirit of the technical idea. Moreover, if the technical idea can be realized in a different way by advances in the technology or by other derived technologies, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea. [Explanation of symbols]

[0059] 1: Engine 2: Cylinder 20, 30: Misfire diagnostic device 21, 31B: Record Section 22, 32: Settings section 23, 33B: Calculation part 24, 34B: Diagnostic Department 31A: Records Department (Other Records Departments) 33A: Calculation unit (other calculation unit) 34A: Diagnostic Department (Other Diagnostic Departments)

Claims

1. A misfire diagnostic device for diagnosing the presence or absence of misfires in an engine having multiple cylinders, A setting unit that defines the calculation interval as the period during which at least all cylinders complete one ignition cycle, A recording unit that records the crank angle acceleration for each cylinder from the ignition of the current cylinder to the ignition of the next cylinder, A calculation unit that calculates the difference between the maximum and minimum values ​​of the crank angular acceleration in the calculation interval for each cylinder, A misfire diagnosis device characterized by comprising a diagnostic unit that diagnoses a cylinder as a misfired cylinder if the difference in crank angle acceleration for each cylinder is greater than or equal to a threshold.

2. The misfire diagnosis device according to claim 1, characterized in that the setting unit uses a calculation interval that is the period during which ignition of all cylinders occurs multiple times.

3. The misfire diagnosis device according to claim 1 or 2, characterized in that, after the diagnostic period has elapsed, the diagnostic unit determines that any cylinder that has been diagnosed as misfiring for a predetermined number of times or more is a misfiring cylinder.

4. Other recording units record misfire index values ​​indicating the misfire state of several cylinders, Other calculation units that calculate the difference between the maximum and minimum values ​​of the misfire index value in the calculation interval, It includes another diagnostic unit that diagnoses a misfire condition when the difference in misfire index values ​​is greater than or equal to a threshold, The misfire diagnosis device according to claim 1 or 2, characterized in that the other diagnostic unit diagnoses the engine as being in a misfire state, and the misfire cylinder is identified when the diagnostic unit diagnoses a misfire cylinder.

5. A program for a misfire diagnostic device that diagnoses the presence or absence of misfires in an engine having multiple cylinders, The calculation interval is defined as the period during which at least all cylinders complete one ignition cycle, A step of recording the crank angle acceleration for each cylinder from the ignition of the current cylinder to the ignition of the next cylinder, The steps include: calculating the difference between the maximum and minimum values ​​of the crank angular acceleration for each cylinder during the calculation interval; A program characterized by causing the misfire diagnostic device to perform the steps of: diagnosing a cylinder as a misfired cylinder if the difference in crank angle acceleration for each cylinder is greater than or equal to a threshold.

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