Fire misfire diagnostic device and program

Abstract

It accurately diagnoses misfires in multi-cylinder engines. [Solution] The misfire diagnostic device (20) diagnoses whether or not there is a misfire in an engine having multiple cylinders. The misfire diagnostic device includes a recording unit (21) that records misfire index values ​​indicating the misfire state of several cylinders, a setting unit (22) that sets the calculation interval to the period during which at least all cylinders complete one ignition cycle, a calculation unit (23) that calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval, and a diagnostic unit (24) that diagnoses a misfire state if the difference in misfire index values ​​is greater than or equal to a threshold.

Description

Technical Field

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

Background Art

[0002] Conventionally, an abnormality diagnosis device for diagnosing an abnormality 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

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the abnormality diagnosis device described in Patent Document 1, index values such as rotational speed are calculated for each ignition, and in a multi-cylinder engine, since the ignition interval is short, the variation in the index values cannot be fully captured. Therefore, there is a risk that the presence or absence of misfire occurrence may be misdiagnosed.

[0005] In view of this point, the present invention has been made, and an object thereof is to provide a misfire diagnosis device and a program capable of accurately diagnosing the occurrence of misfire in a multi-cylinder engine.

Means for Solving the Problems

[0006] A misfire diagnosis device according to one aspect of the present invention is a misfire diagnosis device for diagnosing the presence or absence of misfires in an engine having multiple cylinders, and solves the above problem by comprising: a recording unit that records misfire index values ​​indicating the misfire state of several cylinders; a setting unit that sets the calculation interval to a period during which at least all cylinders complete one ignition cycle; a calculation unit that calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval; and a diagnosis unit that diagnoses a misfire state when the difference in misfire index values ​​is greater than or equal to a threshold. [Effects of the Invention]

[0007] According to one embodiment of the present invention, a calculation interval is set for each period during which at least all cylinders complete one ignition cycle, and the misfire state of all cylinders is comprehensively diagnosed. By ensuring a long calculation interval and comprehensively monitoring the ignition of all cylinders, fluctuations in the misfire index value can be sufficiently captured even in multi-cylinder engines with short ignition intervals, improving diagnostic accuracy. By setting a long calculation interval, the number of calculations is reduced compared to diagnosing misfires at each ignition interval, thereby reducing the computational load. [Brief explanation of the drawing]

[0008] [Figure 1] This is a functional block diagram of the engine system in this embodiment. [Figure 2] This is a functional block diagram of the misfire diagnosis device in this embodiment. [Figure 3] This is a time chart for misfire diagnosis in this embodiment. [Figure 4] This is a flowchart of the recording process for misfire diagnosis in this embodiment. [Figure 5] This is a flowchart of the calculation process for misfire diagnosis in this 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, a recording unit records misfire index values ​​indicating the misfire state of several cylinders, and a setting unit sets a calculation interval for a period during which at least all cylinders complete one ignition cycle. A calculation unit calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval, and a diagnosis unit diagnoses a misfire state if the difference in misfire index values ​​is greater than or equal to a threshold. As a result, a calculation interval is set for each period during which at least all cylinders complete one ignition cycle, and the misfire state of all cylinders is comprehensively diagnosed. By ensuring a long calculation interval and comprehensively monitoring the ignition of all cylinders, fluctuations in the misfire index value can be sufficiently captured even in multi-cylinder engines with short ignition intervals, improving diagnostic accuracy. By setting a long calculation interval, the number of calculations is reduced compared to diagnosing misfires at each ignition interval, thereby reducing the computational load. [Examples]

[0010] The misfire diagnosis device of this embodiment will be described below with reference to the attached drawings. Figure 1 is a functional block diagram of the engine system of this embodiment. Figure 2 is a functional block diagram of the misfire diagnosis device of this embodiment. Figure 3 is a time chart of the misfire diagnosis of this 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 addition, the ECU 5 calculates the engine speed Ne in response to the signal from the crank angle sensor 11, and from the engine speed Ne, the rotational speed of the crankshaft is determined and the ignition interval crank period (ignition period) Tx is calculated. The ignition interval 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°.

[0014] As shown in Figures 2 and 3, the engine 1 is connected to a misfire diagnostic device 20 that diagnoses whether or not there is a misfire in the engine 1 which has multiple cylinders. In this embodiment, the misfire diagnostic device 20 comprehensively monitors the ignition of all cylinders 2#1-2#6. The misfire diagnostic device 20 is provided with a recording unit 21 that records misfire index values ​​indicating the misfire state of several cylinders, a setting unit 22 that sets the calculation interval to the period during which at least all cylinders 2#1-2#6 complete one cycle of ignition, a calculation unit 23 that calculates the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval, and a diagnostic unit 24 that diagnoses a misfire state when the difference in misfire index values ​​is greater than or equal to a threshold.

[0015] The recording unit 21 records the engine speed Ne and the ignition interval crank period Tx, calculated by the ECU 5, 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 ignition interval crank period Tx to lengthen. The misfire diagnostic device 20 uses these characteristics of engine speed Ne and ignition interval crank period Tx to diagnose whether or not engine 1 is misfiring. The recording unit 21 may also record either engine speed Ne or ignition interval crank period Tx as the misfire index value.

[0016] The setting unit 22 receives pulse signals from the ECU 5 corresponding to the ignition timing of each cylinder 2#1-2#6. The setting unit 22 is equipped with an ignition counter 25, which counts each time a 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 25 exceeds a predetermined value C1. When the ignition counter 25 reaches one 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 C1 of the ignition counter 25 is set is defined as the calculation interval.

[0017] In this embodiment, the setting unit 22 sets the calculation interval to a period during which all cylinders 2#1-2#6 have ignition cycles multiple times. Specifically, the ignition counter 25 is set to a predetermined value C1 of 24 counts, and the calculation interval is set to the period until all cylinders 2#1-2#6 have ignition cycles four times and 24 counts have been reached. This allows for the diagnosis of misfire conditions, including cases where a specific cylinder misfires only once every four cycles. Furthermore, when the ignition counter 25 reaches 24 counts, the setting unit 22 sets a calculation permission flag, indicating that the first set of calculation intervals has elapsed.

[0018] In the calculation unit 23, when the operation permission flag is set in the setting unit 22, the difference between the maximum value and the minimum value of the misfire index value in the operation interval is calculated. That is, the misfire index values in the operation interval until the operation permission flag is set are monitored, the maximum value and the minimum value are obtained from the misfire index values by the calculation unit 23, and further, the difference between the maximum value and the minimum value of the misfire index values is calculated by the calculation unit 23. The difference ΔNe between the maximum value Ne_MAX and the minimum value Ne_MIN of the engine speed in the operation interval is obtained, and the difference ΔTx between the maximum value Tx_MAX and the minimum value Tx_MIN of the ignition interval crank period in the operation interval is obtained.

[0019] In the diagnosis unit 24, the difference ΔNe of the engine speed is compared with the first threshold value TH1 for each operation interval, and the difference ΔTx of the ignition interval crank period is compared with the second threshold value TH2 for each operation interval. When the difference ΔNe of the engine speed is greater than or equal to the first threshold value TH1 and the difference ΔTx of the ignition interval crank period is greater than or equal to the second threshold value TH2, the diagnosis unit 24 diagnoses that it is in a misfire state. When the difference ΔNe of the engine speed is less than the first threshold value TH1 and / or the difference ΔTx of the ignition interval crank period is less than the second threshold value TH2, the diagnosis unit 24 diagnoses that it is not in a misfire state.

[0020] As described above, the engine speed Ne and the ignition interval crank period Tx can be recorded simultaneously, and the combustion state of the engine 1 is diagnosed with different index values simultaneously in the diagnosis unit 24, improving the diagnosis accuracy. Further, a misfire counter 26 is provided in the diagnosis unit 24, and the misfire counter 26 is counted each time the diagnosis unit 24 diagnoses that it is in a misfire state. Then, when the diagnosis period has elapsed, a final diagnosis is performed by the diagnosis unit 24, and when the count value of the misfire counter 26 (the number of diagnosis times diagnosed as a misfire state) is greater than or equal to a predetermined value (predetermined number of times) C2, the diagnosis unit 24 determines that there is a misfire in the engine 1 and notifies it.

[0021] Thus, when the diagnosis unit 24 repeatedly diagnoses that the engine is in a misfire state, it is determined that there is a misfire in the engine 1, so the diagnostic accuracy is enhanced. The first and second threshold values TH1 and TH2, and the predetermined values C1 and C2 are set to values obtained experimentally, empirically, or theoretically from past data or the like. Also, the number of rotations of the crankshaft is set as the diagnostic period. The misfire counter 26 is reset when the number of rotations of the crankshaft from the start of diagnosis reaches a predetermined number of rotations. Further, in the diagnosis unit 24, the misfire state may be diagnosed based on only one of the difference ΔNe in the engine speed and the difference ΔTx in the ignition interval crank period.

[0022] Note that each control block of the misfire diagnosis device 20 may be realized by software using a processor, or may be realized by a logic circuit (hardware) formed in an integrated circuit or the like. When using a processor, various processes are performed by the processor reading and executing a program stored in a memory. As the processor, for example, a CPU (Central Processing Unit) is used. Also, the memory is composed of one or more storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) according to the application.

[0023] Here, an example of misfire diagnosis will be described. As shown in FIG. 3, ignition is repeated in the order of cylinders 2#1, 2#6, 2#5, 2#4, 2#3, 2#2. When the open flag of the calculation window is set, the number of ignition times is counted by the ignition counter 25. When the ignition counter 25 of the setting unit 22 exceeds 24 counts, the ignition counter 25 is returned from the 24th count to the 1st count and the calculation permission flag is set. Also, when the open flag of the next set of calculation windows is set, the number of ignition times is counted again from the 1st count by the ignition counter 25. Thus, one set of calculation intervals is set at 24 counts.

[0024] Furthermore, the recording unit 21 records the engine speed Ne and the ignition interval crank period Tx. When the calculation permission flag is set by the setting unit 22, the calculation unit 23 determines the maximum value Ne_MAX and minimum value Ne_MIN of the engine speed, and the maximum value Tx_MAX and minimum value Tx_MIN of the ignition interval crank period in the first set of calculation windows (calculation intervals). In addition, the calculation unit 23 determines the difference ΔNe of the engine speed and the difference ΔTx of the ignition interval crank period. The calculation process of the calculation unit 23 is repeated each time the calculation permission flag is set.

[0025] 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. Therefore, in the first set of calculation windows, the diagnostic unit 24 diagnoses a misfire condition and the misfire counter 26 is incremented by one. The calculation window is opened and the above process is repeated for each calculation interval, and the misfire counter 26 is incremented. The diagnostic period is set from the start of the diagnosis until the crankshaft has rotated 200 times. When the diagnostic period ends, the misfire counter 26 exceeds a predetermined value C2, so the diagnostic unit 24 confirms that there is a misfire in engine 1 and notifies the system.

[0026] The misfire diagnosis process will be explained with reference to Figures 4 and 5. Figure 4 is a flowchart of the misfire diagnosis recording process in this embodiment. Figure 5 is a flowchart of the misfire diagnosis calculation process in this embodiment.

[0027] As shown in Figure 4, when the Nth set of calculation windows N is opened (step S01), the ignition count is recorded in the ignition counter 25, and the engine speed Ne and the ignition interval crank period Tx are recorded (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.

[0028] 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 for the calculation window N is set (step S05). 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 S06). 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 S07), the count value of the misfire counter 26 is incremented (step S08). If the diagnosis period for misfire 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).

[0029] When the misfire diagnosis period ends (Yes in step S09), the count value of the misfire counter 26 is compared with a predetermined value C2 (step S11). If the count value of the misfire counter 26 is equal to or greater than the predetermined value C2 (Yes in step S11), it is confirmed that there is a misfire in engine 1 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, even before the end of the diagnosis period, notification may be given when the count value of the misfire counter 26 becomes equal to or greater than the predetermined value C2.

[0030] In steps S02, S06, and S07, 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 S03 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 S11, misfire diagnosis may also be performed based on the comparison result in step S07. In other words, steps S08-S11 may be omitted.

[0031] As described above, with the misfire diagnosis device 20 of this embodiment, the misfire state of all cylinders 2#1-2#6 is comprehensively diagnosed when ignition is instructed for all cylinders 2#1-2#6. By ensuring a long calculation interval and comprehensively monitoring the ignition of all cylinders 2#1-2#6, even in multi-cylinder engines with short ignition intervals, fluctuations in the engine speed Ne and ignition interval crank period Tx, which are misfire index values, are sufficiently captured, improving diagnostic accuracy. By setting a long calculation interval, the number of calculations is reduced and the computational load is alleviated compared to diagnosing misfires at each ignition interval.

[0032] In this embodiment, engine speed and ignition interval / crank period are used 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.

[0033] Furthermore, although a 6-cylinder engine is used as an example in this embodiment, the engine is not particularly limited as long as it has multiple cylinders.

[0034] Furthermore, the ECU may function as a misfire diagnostic device, or a separate misfire diagnostic device may be provided in addition to the ECU.

[0035] 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.

[0036] 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.

[0037] As described above, the first embodiment is a misfire diagnostic device (20) for diagnosing the presence or absence of misfires in an engine (1) having multiple cylinders (2#1-2#6), comprising: a recording unit (21) for recording misfire index values ​​indicating the misfire state of several cylinders; a setting unit (22) for which the calculation interval is set to a period during which at least all cylinders complete one ignition cycle; a calculation unit (23) for calculating the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval; and a diagnostic unit (24) for diagnosing a misfire state when the difference in misfire index values ​​is greater than or equal to a threshold. With this configuration, a calculation interval is set for each period during which at least all cylinders complete one ignition cycle, and the misfire state of all cylinders is comprehensively diagnosed. By ensuring a long calculation interval and comprehensively monitoring the ignition of all cylinders, fluctuations in the misfire index value can be sufficiently captured even in multi-cylinder engines with short ignition intervals, improving diagnostic accuracy. By setting a long calculation interval, the number of calculations is reduced and the computational load is reduced compared to diagnosing misfires at each ignition interval.

[0038] 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 misfire condition, including cases where a specific cylinder misfires only once every multiple times.

[0039] In the third embodiment, the recording unit records the engine speed (Ne) or ignition period (ignition interval crank period Tx) as a misfire index value, as in the first or second embodiment. With this configuration, the presence or absence of a misfire is diagnosed by utilizing the fact that a misfire reduces combustion energy, lowers the engine speed, and lengthens the ignition period.

[0040] The fourth embodiment is one of the first to third embodiments, in which the recording unit records engine speed and ignition cycle as misfire index values, the calculation unit calculates the difference between the maximum and minimum values ​​of engine speed and the difference between the maximum and minimum values ​​of ignition cycle within the calculation interval, and the diagnostic unit diagnoses a misfire state if the difference in engine speed is greater than or equal to a first threshold (TH1) and the difference in ignition cycle is greater than or equal to a second threshold (TH2). With this configuration, the presence or absence of a misfire is diagnosed by utilizing the fact that combustion energy decreases due to a misfire, causing the engine speed to decrease and the ignition cycle to lengthen. In addition, engine speed and ignition interval can be recorded simultaneously, and the combustion state of the engine is diagnosed at the same time using different index values, improving the diagnostic accuracy.

[0041] The fifth embodiment is one of the embodiments from the first to the fourth, in which the diagnostic unit determines that a misfire is present if, after the diagnostic period has elapsed, the number of diagnoses in which a misfire condition has been diagnosed is greater than or equal to a predetermined number (predetermined value C2). With this configuration, the diagnostic accuracy is improved because the presence of a misfire in the engine is determined when a misfire condition is repeatedly diagnosed.

[0042] The sixth aspect is a program for a misfire diagnostic device that diagnoses the presence or absence of misfires in an engine having multiple cylinders, and causes the misfire diagnostic device to perform the following steps: recording misfire index values ​​indicating the misfire state of several cylinders; setting a calculation interval to a period during which at least all cylinders complete one ignition cycle; calculating the difference between the maximum and minimum values ​​of the misfire index values ​​in the calculation interval; and diagnosing a misfire state if the difference in misfire index values ​​is greater than or equal to a threshold. With this configuration, by installing the program in the engine control device, etc., the control device, etc., can be used as a misfire diagnostic device.

[0043] Although this embodiment has been described, other embodiments may include combinations of the above embodiment and its modifications, either entirely or partially.

[0044] 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]

[0045] 1: Engine 2: Cylinder 20: Misfire Diagnosis Device 21: Records Department 22: Settings Section 23: Calculation Section 24: Diagnostic Department

Claims

1. A misfire diagnostic device for diagnosing the presence or absence of misfires in an engine having multiple cylinders, A recording unit that records misfire index values ​​indicating the misfire state of several cylinders, A setting unit that defines the calculation interval as the period during which at least all cylinders complete one ignition cycle, A calculation unit that calculates the difference between the maximum and minimum values ​​of the misfire index value in the calculation interval, A misfire diagnosis device characterized by comprising a diagnostic unit that diagnoses a misfire condition when the difference in misfire index values ​​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 the recording unit records engine speed or ignition cycle as a misfire index value.

4. The recording unit records engine speed and ignition cycle as misfire index values. The calculation unit calculates the difference between the maximum and minimum values ​​of the engine speed and the difference between the maximum and minimum values ​​of the ignition cycle within the calculation interval. The misfire diagnosis device according to claim 1 or 2, characterized in that the diagnostic unit diagnoses a misfire condition when the difference in engine speed is greater than or equal to a first threshold and the difference in ignition cycle is greater than or equal to a second threshold.

5. The fire misfire diagnostic device according to claim 1 or 2, characterized in that the diagnostic unit determines that a fire misfire exists if the number of diagnoses in which a fire misfire condition has been determined exceeds a predetermined number after the diagnostic period has elapsed.

6. A program for a misfire diagnostic device that diagnoses the presence or absence of misfires in an engine having multiple cylinders, A step of recording misfire index values ​​that indicate the misfire state of several cylinders, The calculation interval is defined as the period during which at least all cylinders complete one ignition cycle, The steps include: calculating the difference between the maximum and minimum values ​​of the misfire index value in the calculation interval; A program characterized by causing the misfire diagnostic device to perform the steps of: diagnosing a misfire condition when the difference in misfire index values ​​is greater than or equal to a threshold.

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