Engine misfire detection device and misfire detection method

Abstract

An engine misfire detection device comprises a misfire detection unit that detects a misfire state within at least one cylinder of the engine, an effective misfire determination unit that determines the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust flue, when the misfire detection unit detects the misfire state, and an engine stop processing control unit that performs engine stop processing based on the determination result of the effective misfire determination unit.

Description

Technology Field

[0001] The present disclosure relates to an engine misfire detection device and a misfire detection method.

[0002] The present application claims priority based on Japanese patent application No. 2022-018214 filed on February 8, 2022, and incorporates the contents thereof herein. Background Technology

[0003] In an engine, if a misfire (a state of non-combustion) occurs while fuel is supplied, unburned fuel leaks into the exhaust system, and in the worst case, the unburned fuel burns in the exhaust flue, leading to equipment damage or accidents. To prevent this, a control is used to detect engine misfires by various methods and to stop the engine as a protective action when the frequency or number of misfires exceeds a certain level (Patent Document 1).

[0004] Meanwhile, in transient conditions involving rapid load fluctuations or rotational speed changes, such as when the load is cut off, the fuel supply may be temporarily narrowed by governor control. Since misfires can occur due to the reduced fuel supply amount during this period, the engine may stop if the above control is applied. However, in this case, because the fuel supply amount itself during the misfire is small, the concentration of unburned gas in the exhaust is extremely low, and there are often cases where there is almost no risk of combustion within the exhaust pipe. As a result, the engine may stop even though there is actually no safety issue, causing disruption to operation.

[0005] For example, in the case of a self-generating engine, operations are sometimes performed to disconnect the engine from the grid in the event of a grid outage caused by lightning or similar factors, keep it running at no load or minimal load, and then resume power supply to the self-generation facility. However, if the above control is applied, the engine stops when the load changes rapidly after disconnection from the grid, causing delays in restoring power to the self-generation facility. In the worst-case scenario, there is a concern that power cannot be restored because the engine cannot be restarted due to the outage.

[0006] As a means to solve this, Patent Document 2 shows that intentional fire caused by control and fire caused by other failures are separated, and in the former, an alarm is not issued. Prior art literature

[0007] Japanese Patent Publication No. 6441291 Japanese Patent Publication No. 2009-121453 The problem to be solved

[0008] As described above, Patent Document 2 indicates that in the case of a misfire caused by control (intentional misfire), it is separated from a misfire caused by a failure other than control and does not trigger an alarm. However, even in the case of a misfire caused by a failure not controlled, there are cases where combustion does not occur within the exhaust pipe (e.g., temporary fuel supply failure or excessive air volume), and if an alarm is triggered for such cases, there is a possibility of over-detection. Furthermore, Patent Document 2 is strictly a determination of whether or not an alarm is triggered, and does not mention protective actions such as stopping the engine.

[0009] The present disclosure is made in consideration of the above-described problem and aims to provide an engine misfire detection device and a misfire detection method that allow operation to continue while ensuring safety by monitoring a misfire connected to combustion in the exhaust flue and stopping the engine. means of solving the problem

[0010] To achieve the above objective, the engine misfire detection device according to the present disclosure comprises a misfire detection unit that detects a misfire state in at least one cylinder of the engine, an effective misfire determination unit that determines the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter which is an indicator of the concentration of unburned fuel in the exhaust flue when the misfire detection unit detects the misfire state, and an engine stop processing control unit that performs engine stop processing based on the determination result of the effective misfire determination unit.

[0011] Additionally, the method for detecting a misfire in an engine according to the present disclosure comprises a misfire detection step for detecting a misfire state in at least one cylinder of an engine, an effective misfire determination step for determining the risk of combustion of unburned fuel in an exhaust flue based on an unburned parameter which is an indicator of the concentration of unburned fuel in an exhaust flue when the misfire state is detected in the misfire detection step, and an engine stop processing step for performing engine stop processing based on the determination result in the effective misfire determination step. Effects of the invention

[0012] According to the engine misfire detection device of the present disclosure, when a misfire state is detected by a misfire detection unit, an effective misfire determination unit determines whether the misfire is a misfire (effective misfire) that poses a risk of unburned fuel being combusted within the exhaust flue, based on an unburned fuel parameter which is an indicator of the concentration of unburned fuel within the flue. Therefore, in cases where unburned fuel does not reach combustion within the exhaust flue even in the event of a misfire caused by a failure not under control, the engine can be excluded from the protection operation of stopping the engine, thereby improving the continuity of operation. In other words, by monitoring only effective misfires that pose a risk of unburned fuel being combusted within the exhaust flue and stopping the engine, the continuity of operation can be improved while ensuring safety.

[0013] In addition, according to the engine misfire detection method of the present disclosure, when a misfire state is detected by the misfire detection step, the effective misfire determination step determines whether the misfire is a misfire (effective misfire) that poses a risk of unburned fuel being combusted within the exhaust flue, based on an unburned fuel parameter which is an indicator of the concentration of unburned fuel within the flue. Therefore, in cases where unburned fuel does not reach combustion within the exhaust flue even in the event of a misfire caused by a failure not under control, the engine can be excluded from the protection action of stopping the engine, thereby improving the continuity of operation. That is, by monitoring only effective misfires that pose a risk of unburned fuel being combusted within the exhaust flue and stopping the engine, the continuity of operation can be improved while ensuring safety. Brief explanation of the drawing

[0014] FIG. 1 is an overall schematic diagram of an engine misfire detection device and a misfire detection method according to a first embodiment of the present disclosure when applied to a gas engine, and a control block diagram of a misfire detection method. FIG. 2 is a schematic diagram and a control block diagram showing a modified example of the engine stop processing control unit (13) in the first embodiment of FIG. 1. FIG. 3 is an overall schematic diagram of the configuration when the engine misfire detection device and misfire detection method according to the second embodiment are applied to a gas engine, and a control block diagram of the misfire detection method. It is a drawing corresponding to FIG. 1. FIG. 4 is an overall schematic diagram of the configuration when the engine misfire detection device and misfire detection method according to the third embodiment are applied to a gas engine, and a control block diagram of the misfire detection method. It is a drawing corresponding to FIG. 1. FIG. 5a shows the behavior of the engine output when the engine load is cut off in the second embodiment of FIG. 3. Figure 5b shows the behavior of the engine speed when the engine load is cut off. Figure 5c shows the behavior of the governor opening degree (fuel amount) when the engine load is cut off. Figure 5d shows the behavior of the mixture (excess air ratio) when the engine load is cut off. Figure 5e shows the change in the presence or absence of misfire when the engine load is cut off. Figure 5f shows the change in the number of misfires and the effective number of misfires when the engine load is cut off. Figure 6 shows a comparative example and is a control block diagram of a conventional engine misfire detection device. Specific details for implementing the invention

[0015] Hereinafter, an engine misfire detection device and a misfire detection method according to an embodiment of the present disclosure will be described based on the configuration diagram and control block diagram. Such embodiments represent one aspect of the present disclosure and are not limited to this disclosure, but may be arbitrarily modified within the scope of the technical concept of the present disclosure.

[0016] <First Embodiment>

[0017] (composition)

[0018] FIG. 1 shows an engine misfire detection device (1) and a misfire detection method according to a first embodiment, an overall schematic diagram of the configuration when the misfire detection device (1) is applied to a gas engine (3), and a control block diagram of the control of the misfire detection method executed on the misfire detection device (1). In addition, the engine is not limited to a gas engine (3) and is shown as an example.

[0019] The gas engine (3) is a four-cycle reciprocating engine that uses fuel gas as fuel and has at least one cylinder. Additionally, it may be equipped with a fuel supply means not shown for supplying gas fuel into each cylinder of the gas engine (3) and an air supply means not shown for supplying combustion air into each cylinder, and at the same time, an operation control device (5) is provided to control the operating state of the gas engine (3) by controlling the amount of gas fuel and combustion air supplied into the cylinder from these supply means.

[0020] In addition, a cylinder pressure sensor (7) for detecting the pressure inside the cylinder of the combustion chamber is installed in each cylinder, and the detection signal from the cylinder pressure sensor (7) is input to the misfire detection device (1).

[0021] As shown in FIG. 1, the misfire detection device (1) is equipped with a misfire detection unit (9) that detects a misfire state in at least one cylinder of a gas engine (3), an effective misfire determination unit (11) that determines the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust flue, when a misfire state is detected by the misfire detection unit (9), and an engine stop processing control unit (13) that performs stop processing of the gas engine (3) based on the determination result from the effective misfire determination unit (11).

[0022] In the fire detection unit (9) of the fire detection device (1), for example, if the combustion pressure of each cylinder from the cylinder internal pressure sensor (7) is lower than the pressure range during normal combustion, it is determined that it is a fire.

[0023] In the effective misfire determination unit (11), when a misfire state is detected in the misfire detection unit (9), it is determined whether there is a risk of combustion of unburned fuel in the exhaust gas discharged from the cylinder within the exhaust flue through which exhaust gas from the gas engine (3) flows during the misfire, based on the unburned fuel parameter (P1), which is an indicator of the concentration of unburned fuel within the exhaust flue. This determination of an effective misfire is configured to be performed by comparing the value of the unburned fuel parameter (P1) acquired by the unburned fuel parameter acquisition unit (17) with the effective misfire determination threshold value of the unburned fuel parameter.

[0024] The unburned parameter (P1) is calculated or estimated based on the operating state signal from the gas engine (3) and the exhaust gas state signal from the exhaust gas by the unburned parameter acquisition unit (17) provided in the effective fire judgment unit (11).

[0025] In addition, the unburned parameter (P1) is, for example, an air-fuel ratio parameter (P2) which is an indicator of the air-fuel ratio in at least one cylinder, as in the second embodiment described later, and an exhaust gas characteristics parameter (P3) based on the characteristics of the exhaust gas flowing in the exhaust flue, as in the third embodiment described later. And, the effective misfire judgment threshold value is set based on a value in which there is a risk of combustion of unburned fuel occurring in the exhaust flue through prior testing or simulation, etc., after considering these parameters as well.

[0026] In the engine stop processing control unit (13), the number of times a valid misfire is determined from the valid misfire determination unit (11) in a past certain time or past certain cycle is counted to calculate an accumulated value, and the accumulated value is determined to be greater than or less than a predetermined accumulated threshold value, and if it is greater than, the engine stop processing is performed.

[0027] In this way, the engine stop processing control unit (13) calculates an accumulated value of the number of times an effective misfire is determined from the effective misfire determination unit (11) in a past certain time or past certain cycle, and when the accumulated value exceeds a predetermined accumulated threshold, the engine stop processing is performed, so that old misfires disappear over time. Accordingly, the risk of exhaust flue combustion can be determined in the latest misfire state, and the engine stop processing can be executed based on the determination result.

[0028] The engine stop process is performed by the engine stop process control unit (13) issuing a stop command to the operation control device (5), so that the operation control device (5) performs either stopping the supply of gas fuel and stopping ignition, or stopping the supply of gas fuel and stopping ignition, for the gas engine (3).

[0029] In addition, the engine stop processing in the engine stop processing control unit (13) may be performed in cases where the judgment result in which the accumulated value of the number of judgments of effective misfires exceeds the accumulated threshold value occurs in a single control during the control cycle, or in cases where it continues to occur in successive multiple controls.

[0030] In some embodiments, the range of calculation for the accumulated value in the engine stop processing control unit (13), the past certain time or past certain cycle, and the accumulated threshold value are set such that the value at the low load from start is greater than the value at the high load.

[0031] This is because, during startup or in low-load areas, combustion becomes unstable and sporadic misfires are likely to occur, so the accumulated value tends to increase compared to high-load areas, and at the same threshold, it is easy to end up with engine shutdown. On the other hand, in this area, the absolute amount of fuel gas supplied is small, and even if combustion occurs in the exhaust pipe, the resulting damage is small.

[0032] As an example of a past fixed cycle, for instance, in the case of a 20-cylinder gas engine (3) (20 cylinders are burned in one cycle), the cycles are set to 5 to 20 cycles when starting at low load and 1 to 3 cycles when starting at high load. More preferably, the cycles are set to 10 cycles (200 cylinders) when starting at low load and 2 cycles (40 cylinders) when starting at high load.

[0033] And, within a set past fixed cycle, if the accumulated value of the number of cylinders with effective misfires among the number of monitored cylinders (N) (among the number of cylinders in the past fixed cycle monitored for each control cycle) is greater than or equal to the accumulated threshold number of cylinders (C), it is determined that there is a risk of combustion in the exhaust flue and the gas engine (3) is stopped. Specific examples are shown in Table 1.

[0034] Driving station threshold Number of monitoring cylinders (number of monitoring cycles) Total threshold number of cylinders N C Startup to low load 200 (10 cycles) 190 High load 40 (2 cycles) 38

[0035] In the example of Table 1, even though the ratio of the cumulative threshold number of cylinders to the number of monitoring cylinders is the same for low load and high load from the start, the number of monitoring cylinders is increased during low load from the start. By doing so, unnecessary engine stoppage due to temporary events is suppressed because combustion becomes unstable and sporadic misfires are likely to occur during the start or low load region. In addition, in several embodiments, a modified example of the engine stop processing control unit (13) as shown in FIG. 2 is shown, and the engine stop processing control unit (13) is provided with an effective misfire count correction unit (23). In this effective misfire count correction unit (23), a weight is applied to the cumulative value of the number of effective misfire judgments from the effective misfire judgment unit (11).

[0036] That is, the effective misfire determination unit (11) is configured to determine the risk of unburned fuel in the exhaust flue burning by comparing the unburned parameter (P1) with the effective misfire determination threshold value, and depending on the magnitude of this unburned parameter (P1), a weight is assigned to the accumulated value when calculating the accumulated value of the number of effective misfire determinations in the engine stop processing control unit (13).

[0037] For example, when a valid fire is determined in a state where the likelihood of combustion within the year is particularly high, such as when the pre-combustion parameter (P1) significantly exceeds the threshold value, or when damage during combustion increases, the number of valid fire determinations is not 1 time, but an accumulated value is calculated as a weighted number such as 1.5 times. In addition, correction is not made for each time, but when the number of valid fire determinations as an accumulated value is 10 times, the resulting accumulated value may be corrected as 15 times instead of 10 times.

[0038] In this way, the engine stop processing control unit (13) is equipped with an effective misfire count correction unit (23) that applies weights to the calculation of the effective misfire judgment count according to the magnitude of the unpredicted parameter (P1) in the calculation of the accumulated value, thereby improving the reliability of the engine stop processing and ensuring safety while improving the continuity of operation.

[0039] Next, the control flow of the fire detection method will be explained with reference to the control block diagram of the fire detection method shown in Fig. 1.

[0040] First, in step S1, a cylinder internal pressure signal is obtained from the cylinder internal pressure sensor (7). In the next step S2, it is determined whether the cylinder internal pressure is lower than the normal combustion pressure range, and if it is lower, it is determined to be a misfire.

[0041] In the next step S3, it is determined whether there is a risk of combustion of unburned fuel in the exhaust gas discharged from the cylinder within the exhaust flue through which exhaust gas from the gas engine (3) flows during the fire.

[0042] The determination of this step S3 is made by obtaining the value of the unpredictable parameter (P1) calculated or estimated by the unpredictable parameter acquisition unit (17) in step S4, and by comparing the value of this unpredictable parameter (P1) with the valid realization determination threshold, if the value of the unpredictable parameter (P1) is greater than the valid realization determination threshold, it is determined to be a valid realization.

[0043] If the judgment result of Step S3 is determined to be a valid fire, the value becomes Yes, and the process proceeds to Step S7. In Step S7, the number of times a valid fire is determined is counted. In other words, an accumulated value is calculated. Furthermore, the calculation of the accumulated value is based on the number of times a valid fire was determined over a past certain period of time or a past certain cycle.

[0044] In addition, if the effective number of real numbers correction unit (23) shown in FIG. 2 is provided, the accumulated value of the number of judgments corrected by the effective number of real numbers correction unit (23) is calculated.

[0045] Then, in the next step S8, it is determined whether the accumulated value of the effective fire rate calculated in step S7 is greater than or equal to the accumulated threshold value; if it is greater than or equal to, the result is Yes, and the process proceeds to step S9, where an engine trip (engine stop) is performed.

[0046] Meanwhile, if the judgment result of Step S3 is No, it is not counted in the number of valid fire judgments in Step S5, and in Step S6, the process moves to the next cylinder and repeats the processing from Step S1.

[0047] In addition, steps S1 and S2 constitute a misfire detection step, steps S3 and S4 constitute an effective misfire determination step, and steps S7 to S9 constitute an engine stop processing step.

[0048] (Actions / Effects)

[0049] According to the engine misfire detection device (1) of the first embodiment described above, when a misfire state is detected by the misfire detection unit (9), the effective misfire determination unit (11) determines whether there is a risk of unburned fuel being connected to combustion within the exhaust flue based on the unburned parameter (P1), which is an indicator of the concentration of unburned fuel within the flue. Therefore, even in cases of misfire caused by a failure not controlled, if there is a case where unburned fuel is not connected to combustion within the exhaust flue, the gas engine (3) is excluded from the protection operation of stopping, thereby improving the continuity of operation. That is, by monitoring only the effective misfires that are at risk of unburned fuel being connected to combustion within the exhaust flue and stopping the gas engine (3), safety can be ensured while improving the continuity of operation.

[0050] FIG. 6 is a control block diagram of a conventional engine misfire detection device that serves as a comparative example of the present embodiment. In this example, a cylinder internal pressure signal is acquired in step S101, and in the next step S102, it is determined whether the cylinder internal pressure is smaller than the pressure range during normal combustion, and in the next step S103, the number of misfires that are smaller than the pressure range during normal combustion is counted, and in the next step S104, it is determined whether the count of a predetermined time is greater than or equal to a threshold value. If it is greater than or equal to the threshold value, the process proceeds to step S105 to perform engine trip (engine stop) processing, and if it is less than the threshold value, the process proceeds to step S106 to move to the next cylinder, and the process from step S101 is repeated.

[0051] In the comparative example shown in Fig. 6, since the internal cylinder pressure is determined to be a misfire based solely on whether it is lower than the normal combustion pressure range, there is a risk that the engine will stop even if there is no risk of unburned fuel being combusted in the exhaust pipe, which could cause difficulties in operation.

[0052] In this embodiment, regarding the comparative example of Fig. 6, the gas engine (3) can be stopped by monitoring the effective misfire, which is at risk of unburned fuel being connected to combustion within the exhaust flue, using the effective misfire determination unit (11), thereby ensuring safety and improving the continuity of operation.

[0053] <Second Embodiment>

[0054] A second embodiment is described with reference to FIG. 3. The second embodiment differs from the first embodiment in that the effective misfire determination unit (27) is different. In the second embodiment, the unburned parameter (P1) of the first embodiment is the air-fuel ratio parameter (P2), which is an indicator of the air-fuel ratio within at least one cylinder, and the effective misfire determination unit (27) determines the effective misfire based on the air-fuel ratio parameter (P2). In the second embodiment, the same reference numerals are assigned to components identical to those of the first embodiment, and their detailed description is omitted.

[0055] (composition)

[0056] As illustrated in FIG. 3, the effective fire detection unit (27) is equipped with an air-fuel ratio parameter acquisition unit (29) that calculates or estimates an air-fuel ratio parameter (P2), which is an indicator of the air-fuel ratio in at least one cylinder, based on an operating state signal from the gas engine (3) and an exhaust gas state signal from the exhaust gas.

[0057] And, in the effective misfire determination unit (27), when a misfire state is detected for the misfire detection unit (9), whether the misfire is an effective misfire that has a risk of unburned fuel burning in the exhaust flue is determined by comparing the value of the air-fuel ratio parameter (P2) with the effective misfire determination threshold value of the air-fuel ratio parameter (P2).

[0058] As illustrated in the control flow of the fire detection method of FIG. 3, the determination of step S3 is made by obtaining the value of the air-fuel ratio parameter (P2) calculated or estimated by the air-fuel ratio parameter acquisition unit (29) in step S11, and by comparing the value of the air-fuel ratio parameter (P2) with the effective fire detection threshold, if the value of the air-fuel ratio parameter (P2) is greater than the effective fire detection threshold, it is determined to be an effective fire.

[0059] In addition, depending on the definition of the air-fuel ratio parameter (P2), a case that is smaller than the effective fire judgment threshold or a case that is within a certain range may be judged as an effective fire. For example, when the air excess ratio (λ) is used as the air-fuel ratio parameter (P2), if it exceeds the effective fire judgment threshold (equivalent to the upper limit of the combustible range), it becomes outside the combustible range and does not combust, so a case that is smaller than the effective fire judgment threshold is judged as an effective fire.

[0060] As for the air-fuel ratio parameter (P2), which is an indicator of the air-fuel ratio within the cylinder, it is calculated and estimated and used, for example, according to the methods (A) to (E) below. Alternatively, it may be calculated and estimated by a combination of each of these items (A) to (E).

[0061] (A) This is the air-fuel ratio calculated from the actual measured fuel supply and air volumes. Since the air-fuel ratio calculated from these actual values ​​is based on actual measurement results, it may have issues with precision or responsiveness depending on the installation location of the measuring instrument or the operational precision of the measurement; however, because it is an actual measurement value, it is excellent in terms of accuracy.

[0062] (B) This is an air-fuel ratio estimated by calculating from the measured exhaust gas composition and fuel characteristics. For example, the air-fuel ratio is estimated by estimating the combustion state within the cylinder from the hydrocarbon (HC) concentration in the exhaust gas composition and the HC concentration in the fuel characteristics of the hydrocarbon fuel gas. Although it offers excellent accuracy, there is a tendency for a time delay to occur until the results of the exhaust gas composition detection are obtained.

[0063] (C) This is the air-fuel ratio estimated from operating data (hourly rotational speed, supply air temperature, supply air pressure, fuel supply amount, etc.). It is calculated by estimating the current fuel and air supply amounts within the cylinder from this operating data. While it offers excellent responsiveness, the high data processing volume can lead to larger control units or higher costs.

[0064] (D) It is a value based on the indicator value of the fuel supply amount (e.g., governor opening degree). It is practical because it offers excellent responsiveness without entailing large data capacity.

[0065] For example, the risk of effective misfire is determined by whether the governor opening degree (an indicator of fuel quantity) exceeds a predetermined threshold. In other words, by confirming in advance through testing, etc., that combustion does not occur within the exhaust flue when the fuel quantity is less than a predetermined value, regardless of the amount of air, parameters regarding the air-fuel ratio can be obtained with a simple configuration by utilizing the governor opening degree, which is an indicator of fuel quantity.

[0066] (E) This is the air-fuel ratio estimated from the driving setpoint. Although it is less accurate, it is effective when sufficient actual measurement data cannot be obtained. For example, the air-fuel ratio is calculated by estimating the fuel and air quantities from the engine output.

[0067] Here, in the second embodiment, the behavior of the gas engine (3) leading to the determination of an effective fire when the load is cut off, by using the excess air ratio (λ) as the air-fuel ratio parameter (P2), will be explained with reference to FIGS. 5a to 5f.

[0068] FIG. 5a shows the behavior of the engine output of the gas engine (3). The numbers on the horizontal axis represent time (seconds) (the time axis on the horizontal axis is the same up to FIG. 5f), and the vertical axis represents the engine output. The time when the load is cut off is set to 0 (zero) seconds.

[0069] Figure 5b shows the rotational speed after the load is cut off on the vertical axis, and when the load is cut off, the rotational speed temporarily increases because the load is removed.

[0070] FIG. 5c shows the governor opening degree (based on fuel amount) on the longitudinal axis, and temporarily cuts the fuel to suppress excessive increase in rotational speed when the load is cut off.

[0071] FIG. 5d shows the air excess ratio (λ) of the mixture on the vertical axis, and immediately after the load cut-off, the mixture is temporarily leaned by the fuel cut and exceeds the combustion limit (A) and goes outside the combustion range. In the range exceeding this combustion limit (A), there is no concern about flue combustion.

[0072] FIG. 5e indicates the presence or absence of a fire on the longitudinal axis. The presence or absence of a fire is determined by the fire detection unit (9) based on whether the pressure of each cylinder from the cylinder internal pressure sensor (7) is lower than the normal combustion pressure range. During the fuel cut shown in FIG. 5c, a fire occurs in either cylinder, and as fuel increases after recovering from the fuel cut, the number of cylinders in a burning state increases, but because combustion is unstable in the low load region, a state in which cylinders with fire are scattered appears.

[0073] FIG. 5f shows the cumulative values ​​of the number of misfires (indicated by the dotted line) and the effective number of misfires (indicated by the solid line) on the vertical axis, and the cumulative values ​​within a certain time period in the past (within t seconds). When the number of misfires is fully counted, it exceeds the cumulative threshold value, causing the engine to stop. On the other hand, as shown in FIG. 5d, when the excess air ratio (λ) exceeds the line of the combustion limit (A) due to fuel cut, it becomes outside the combustion range within the cylinder, and there is no risk of unburned fuel burning in the exhaust pipe. By excluding misfires in this state from the count, the cumulative value of the effective number of misfires does not exceed the cumulative threshold value, and the engine continues to operate.

[0074] (Actions / Effects)

[0075] According to the second embodiment, the effective misfire determination unit (27) determines whether or not there is an effective misfire by means of an air-fuel ratio parameter (P2), which is an indicator of the air-fuel ratio in at least one cylinder. Since the operation control signal used for engine operation control can be utilized, simplification of the system configuration of the misfire detection device (1) can be expected.

[0076] In addition, as the air-fuel ratio parameter (P2), if an indicator value of the fuel supply amount (governor opening degree, etc.) as described in (D) above is used as a parameter related to the air-fuel ratio, rather than the air-fuel ratio, the system configuration of the misfire detection device (1) can be further simplified. That is, regardless of the amount of air, if the amount of fuel is less than a predetermined value, it is confirmed in advance through testing, etc. that combustion does not occur within the exhaust flue, so the determination of an effective misfire by the effective misfire determination unit (27) can be determined with a simpler configuration.

[0077] In addition, the methods described in (A) to (E) of the tactics may be combined, and by not necessarily performing all data measurements or calculations required for estimating the performance ratio, the load of control calculations can be reduced, which leads to faster processing and prevention of control failures.

[0078] <Third Embodiment>

[0079] A third embodiment is described with reference to FIG. 4. The third embodiment differs from the first embodiment in that the effective misfire determination unit (33) is different. In the third embodiment, the unburned parameter (P1) of the first embodiment is an exhaust gas characteristic parameter (P3) based on the characteristics of the exhaust gas flowing through the exhaust flue, and in particular, the exhaust gas characteristic parameter (P3) uses the concentration of unburned fuel and / or oxygen concentration in the exhaust gas, and the effective misfire determination unit (33) determines an effective misfire based on the exhaust gas characteristic parameter (P3). In the third embodiment, components identical to those of the first embodiment are given the same reference numerals, and their detailed description is omitted.

[0080] (composition)

[0081] As illustrated in FIG. 4, the effective fire detection unit (33) is equipped with an exhaust gas characteristic acquisition unit (35) that measures the exhaust gas characteristics of the exhaust gas from the gas engine (3) and acquires an exhaust gas characteristic parameter (P3) used as an unburned parameter (P1).

[0082] And, in the effective misfire determination unit (33), when a misfire state is detected in the misfire detection unit (9), whether or not the concentration of unburned fuel in the exhaust gas discharged from the cylinder has a risk of combustion in the exhaust flue through which the exhaust gas from the gas engine (3) flows during the misfire is determined by comparing the concentration of the exhaust gas characteristic parameter (P3), based on the actual characteristics of the exhaust gas, with the effective misfire determination threshold value of the exhaust gas characteristic parameter (P3).

[0083] As illustrated in the control flow of the fire detection method of FIG. 4, the determination of step S3 is made by obtaining the value of the exhaust gas characteristic parameter (P3) calculated or estimated by the exhaust gas characteristic acquisition unit (35) in step S12, and by comparing this value of the exhaust gas characteristic with the effective fire detection threshold, if the value of the exhaust gas characteristic parameter (P3) is greater than the effective fire detection threshold, it is determined to be an effective fire.

[0084] As for the exhaust gas characteristic parameter (P3), the concentration of unburned gas is used in particular. As for the unburned gas, the concentration of hydrocarbons (THC) and carbon monoxide (CO) is used. In addition, in the case of an engine where the fuel gas is hydrogen gas, the concentration of hydrogen (H2) is used.

[0085] When hydrocarbon-based fuel gas is used, a large amount of unburned hydrocarbons (THC) are emitted due to incomplete combustion within the cylinder, and a large amount of carbon monoxide (CO) is also emitted due to incomplete combustion within the cylinder. Furthermore, in the case of a hydrogen engine, if incomplete combustion occurs within the cylinder, hydrogen (H2) is emitted directly.

[0086] As for the exhaust gas characteristic parameter (P3), in addition to using the measured exhaust gas characteristics as they are, an indicator value (such as the air-fuel ratio of the exhaust gas) calculated based on the exhaust gas characteristics or other data may also be used.

[0087] In the exhaust flue, the effective misfire judgment threshold for determining whether there is a risk of combustion due to the concentration of unburned fuel in the exhaust gas may be set for each concentration of unburned fuel, or it may be set based on the ratio of each unburned fuel.

[0088] In addition, the effective misfire judgment threshold may be adjusted based on other components (such as oxygen concentration or carbon dioxide concentration). For example, when the oxygen concentration is high, combustion becomes easier; therefore, the concentration of the effective misfire judgment threshold for each unburned gas is adjusted to the lower side, so that the unburned gas is judged as an effective misfire even at a low concentration. Also, when the carbon dioxide concentration is high, combustion becomes difficult; therefore, the concentration of the effective misfire judgment threshold for each unburned gas is adjusted to the higher side, so that the unburned gas is not judged as an effective misfire even at a high concentration. By making such adjustments, the reliability of the effective misfire judgment based on the exhaust gas characteristics parameter (P3) can be improved.

[0089] (Actions / Effects)

[0090] According to the third embodiment, the effective fire determination unit (33) determines whether or not there is an effective fire using the exhaust gas characteristic parameter (P3) in the exhaust flue as an indicator. Since it is based on actual measurement data of the exhaust gas, the determination of an effective fire is accurate, making it possible to ensure safety and improve the continuity of operation.

[0091] The contents described in each of the above embodiments are understood, for example, as follows.

[0092] [1] The misfire detection device (1) of an engine (3) according to the present disclosure comprises a misfire detection unit (9) that detects a misfire state in at least one cylinder of the engine, an effective misfire determination unit (11, 27, 33) that determines the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter (P1) which is an indicator of the concentration of unburned fuel in the exhaust flue when the misfire detection unit detects the misfire state, and an engine stop processing control unit (13) that performs engine stop processing based on the determination result of the effective misfire determination unit.

[0093] According to the configuration described in [1] above, when the misfire detection device (1) of the engine (3) detects a misfire state by the misfire detection unit (9), the effective misfire determination unit (11, 27, 33) determines an effective misfire that has a risk of unburned fuel being connected to combustion in the exhaust flue based on the unburned parameter (P1), which is an indicator of the concentration of unburned fuel in the flue. Therefore, in cases where unburned fuel is not connected to combustion in the exhaust flue even in the event of a misfire caused by a failure not controlled, the engine can be excluded from the protection operation of stopping the engine, thereby improving the continuity of operation. That is, by monitoring only the effective misfire that has a risk of unburned fuel being connected to combustion in the exhaust flue and stopping the engine, safety can be ensured while improving the continuity of operation.

[0094] [2] In some embodiments, in the configuration described in [1], the pre-combustion parameter is an air-fuel ratio parameter that is an indicator of the air-fuel ratio in the at least one cylinder, and the effective fire judgment unit (27) determines the effective fire based on the air-fuel ratio parameter.

[0095] According to the configuration described in [2] above, the effective misfire determination unit (27) determines whether or not there is an effective misfire by means of an air-fuel ratio parameter (P2), which is an indicator of the air-fuel ratio in at least one cylinder, and thus can use an operation control signal used for engine operation control, thereby simplifying the system configuration of the misfire detection device (1).

[0096] [3] In some embodiments, in the configuration described in [2], the air-fuel ratio parameter (P2) is an indicator value of the fuel supply amount within the at least one cylinder, and the effective misfire determination unit (27) determines the effective misfire by whether the indicator value of the fuel supply amount exceeds a predetermined threshold value.

[0097] According to the configuration described in [3] above, the system configuration of the fire detection device (1) can be further simplified. That is, regardless of the amount of air, if the amount of fuel is less than a predetermined value, it is confirmed in advance through testing, etc. that combustion does not occur within the exhaust flue, so the determination of an effective fire by the effective fire determination unit (27) can be determined with a simpler configuration.

[0098] [4] In some embodiments, in the configuration described in [1], the pre-combustion parameter (P1) is an exhaust gas characteristic parameter (P3) based on the characteristics of the exhaust gas flowing through the exhaust flue, and the effective misfire determination unit (33) determines the effective misfire based on the exhaust gas characteristic parameter.

[0099] According to the configuration described in [4] above, the effective fire judgment unit (33) determines whether or not there is an effective fire by using the exhaust gas characteristic parameter (P3), which is based on actual measurement data of the exhaust gas in the exhaust pipe, as an indicator, thereby improving the accuracy of the determination of an effective fire.

[0100] [5] In some embodiments, in the configuration described in [4], the exhaust gas characteristics parameter (P3) includes the concentration of unburned fuel and oxygen in the exhaust gas, and the effective misfire determination unit (33) determines the effective misfire based on the concentration of unburned fuel and oxygen.

[0101] According to the configuration described in [5] above, the effective fire is determined by using the concentration of unburned fuel and the oxygen concentration, which greatly affect the combustion of unburned fuel in the exhaust flue, so the accuracy of the determination is further improved.

[0102] [6] In some embodiments, in the configuration described in [1] to [5] above, the engine stop processing control unit (13) calculates an accumulated value of the number of times an effective misfire is determined from the effective misfire determination unit (11, 27, 33) in a past certain time or past certain cycle, and performs engine stop processing when the accumulated value exceeds a predetermined accumulated threshold.

[0103] According to the configuration described in [6] above, the engine stop processing control unit (13) calculates an accumulated value of the number of times an effective misfire is determined from the effective misfire determination unit (11, 27, 33) in a past certain time or past certain cycle, and when the accumulated value exceeds a predetermined accumulated threshold, the engine stop processing is performed, so that old misfires disappear over time. Therefore, the risk of exhaust flue combustion can be determined in the latest misfire state, and the engine stop processing can be performed based on the determination result.

[0104] [7] In some embodiments, in the configuration described in [6], the effective misfire determination unit (11, 27, 33) is configured to determine the risk of unburned fuel in the exhaust flue burning by comparing the unburned parameter with the effective misfire determination threshold, and the engine stop processing control unit (13) additionally has an effective misfire count correction unit (23) that gives weight to the accumulated value of the effective misfire determination count according to the magnitude of the unburned parameter in calculating the accumulated value.

[0105] According to the configuration described in [7] above, the engine stop processing control unit (13) additionally includes an effective misfire count correction unit (23) that gives weight to the accumulated value of the number of effective misfire judgments according to the magnitude of the unacquired parameter in calculating the accumulated value, thereby improving the reliability of the engine stop processing and ensuring safety while improving the continuity of operation.

[0106] [8] In some embodiments, in the configuration described in [6] or [7], the past fixed time or past fixed cycle and the accumulated threshold are set to a value greater than the low load value from the start than the high load value.

[0107] According to the configuration described in [8] above, the past certain time or past certain cycle and the accumulated threshold value are set such that the low load value from the start is greater than the high load value. Since combustion becomes unstable during the start or low load region, sporadic misfires are likely to occur, so unnecessary engine stoppage due to temporary events can be suppressed.

[0108] [9] The method for detecting a misfire in an engine according to the present disclosure includes a misfire detection step (steps S1 to S2 of the first embodiment) for detecting a misfire state in at least one cylinder of the engine, an effective misfire determination step (steps S3 to S4 of the first embodiment) for determining the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter which is an indicator of the concentration of unburned fuel in the exhaust flue when the misfire state is detected in the misfire detection step, and an engine stop processing step (S7 to S9 of the first embodiment) for performing engine stop processing based on the determination result in the effective misfire determination step.

[0109] According to the configuration described in [9] above, the engine misfire detection method detects a misfire state by the misfire detection step, and by the effective misfire determination step, determines an effective misfire that has a risk of unburned fuel being combusted in the exhaust flue based on the unburned fuel parameter, which is an indicator of the concentration of unburned fuel in the flue. Therefore, even in cases of misfires that are not controlled by a malfunction, etc., if the unburned fuel in the exhaust flue does not reach combustion, the engine can be excluded from the protection action of stopping the engine, thereby improving the continuity of operation. In other words, by monitoring only the effective misfires that have a risk of unburned fuel being combusted in the exhaust flue and stopping the engine, safety can be ensured while improving the continuity of operation. Explanation of the symbols

[0110] 1: Fire detection device 3: Gas engine (engine) 5: Driving control unit 7: Cylinder internal pressure sensor 9: Fire detection unit 11, 27, 33: Valid Real Fire Determination Unit 13: Engine Stop Processing Control Unit 17: Undetermined Parameter Acquisition Unit 23: Effective Real Number Correction Unit 29: Performance Cost Parameter Acquisition Section 35: Exhaust Gas Characteristics Acquisition Section P1: Undefined parameter P2: Performance cost parameter P3: Exhaust gas characteristics parameter

Claims

Claim 1 A misfire detection device for an engine comprises: a misfire detection unit that detects a misfire state within at least one cylinder of the engine; an effective misfire determination unit that determines the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust flue, when the misfire detection unit detects the misfire state; and an engine stop processing control unit that performs engine stop processing based on the determination result of the effective misfire determination unit. The engine stop processing control unit calculates an accumulated value of the number of effective misfire determinations from the effective misfire determination unit during a past certain time or past certain cycle, and performs engine stop processing when the accumulated value exceeds a predetermined accumulated threshold value. The effective misfire determination unit is configured to determine the risk of combustion of unburned fuel in the exhaust flue by comparing the unburned parameter and the effective misfire determination threshold value. In calculating the accumulated value, the engine stop processing control unit assigns a weight to the accumulated value of the number of effective misfire determinations according to the magnitude of the unburned parameter. An engine misfire detection device further equipped with a correction unit. Claim 2 A misfire detection device for an engine, comprising: a misfire detection unit for detecting a misfire state within at least one cylinder of the engine; an effective misfire determination unit for determining the risk of combustion of unburned fuel in the exhaust pipe based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust pipe, when the misfire detection unit detects the misfire state; and an engine stop processing control unit for performing engine stop processing based on the determination result of the effective misfire determination unit, wherein the engine stop processing control unit calculates an accumulated value of the number of effective misfire determinations from the effective misfire determination unit during a past certain time or past certain cycle, and performs engine stop processing when the accumulated value exceeds a predetermined accumulated threshold value, wherein the past certain time or past certain cycle and the accumulated threshold value are set such that the value for the low load period from startup is greater than the value for the high load period. Claim 3 In claim 1 or 2, the aforementioned pre-ignition parameter is an air-fuel ratio parameter which is an indicator of the air-fuel ratio within the at least one cylinder, and the effective misfire determination unit determines an effective misfire based on the air-fuel ratio parameter. Claim 4 In claim 3, the air-fuel ratio parameter is an indicator of the amount of fuel supplied into the at least one cylinder, and the effective misfire determination unit determines an effective misfire by whether the amount of fuel supplied exceeds a predetermined threshold value or not. Claim 5 In claim 1 or 2, the pre-combustion parameter is an exhaust gas characteristic parameter based on the characteristics of the exhaust gas flowing within the exhaust flue, and the effective misfire determination unit determines an effective misfire based on the exhaust gas characteristic parameter. Claim 6 In claim 5, the exhaust gas characteristic parameters include unburned fuel concentration and oxygen concentration in the exhaust gas, and the effective misfire determination unit determines an effective misfire based on the unburned fuel concentration and the oxygen concentration. Claim 7 A method for detecting misfires in an engine comprises: a misfire detection step for detecting a misfire state within at least one cylinder of the engine; an effective misfire determination step for determining the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust flue, when the misfire state is detected in the misfire detection step; and an engine stop processing step for performing engine stop processing based on the determination result in the effective misfire determination step. The engine stop processing step calculates an accumulated value of the number of effective misfire determinations in the effective misfire determination step during a past certain time or past certain cycle, and performs engine stop processing when the accumulated value exceeds a predetermined accumulated threshold. The effective misfire determination step determines the risk of combustion of unburned fuel in the exhaust flue by comparing the unburned parameter and the effective misfire determination threshold. The engine stop processing step assigns a weight to the accumulated value of the number of effective misfire determinations according to the magnitude of the unburned parameter in calculating the accumulated value. A method for detecting misfires in an engine, further comprising a misfire correction step. Claim 8 A method for detecting misfire in an engine, comprising: a misfire detection step for detecting a misfire state in at least one cylinder of the engine; an effective misfire determination step for determining the risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter, which is an indicator of the concentration of unburned fuel in the exhaust flue, when the misfire state is detected in the misfire detection step; and an engine stop processing step for performing engine stop processing based on the determination result in the effective misfire determination step, wherein the engine stop processing step calculates an accumulated value of the number of effective misfire determinations in the effective misfire determination step in the past certain time or past certain cycle, and performs engine stop processing when the accumulated value exceeds a predetermined accumulated threshold value, wherein the past certain time or past certain cycle and the accumulated threshold value are set such that the value for the low load from start is greater than the value for the high load. Claim 9 delete

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