Engine misfire detection device and misfire detection method

Abstract

To provide an accidental fire detection device for an engine capable of continuously operating while securing safety by monitoring accidental fire, which may lead to combustion in an exhaust flue, and stopping an engine, and an accidental fire detection method for an engine.SOLUTION: An accidental fire detection device for an engine comprises: an accidental fire detection unit that detects an accidental fire state in at least one cylinder of an engine; an effective accidental fire determination unit that when the accidental fire detection unit detects the accidental fire state, determines a risk of combustion of unburned fuel in an exhaust flue based on an unburned parameter, which is an indicator of an unburned fuel concentration in the exhaust flue; and an engine stop process control unit that performs a process to stop the engine based on the determination result of the effective accidental fire determination unit.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In an engine, when misfire (a state where combustion does not occur) occurs while fuel is being supplied, unburned fuel flows into the exhaust system. In the worst case, the unburned fuel may burn in the exhaust flue, leading to equipment damage or accidents. To prevent this, the engine misfire is detected by various methods, and when the frequency or number of misfires exceeds a certain level, control is used to stop the engine as a protection operation (Patent Document 1).

[0003] On the other hand, in a transient state accompanied by rapid load fluctuations or rotational speed fluctuations such as during load cut-off, fuel supply may be temporarily restricted by governor control. During this period, misfire may occur due to a decrease in the fuel supply amount. Therefore, when the above control is applied, the engine may stop. However, in this case, since the fuel supply amount during misfire is small, the concentration of unburned gas in the exhaust is extremely low, and in many cases, there is almost no risk of combustion in the exhaust flue. As a result, although there is actually no problem with safety, the engine may stop, causing an obstacle to operation.

[0004] For example, in a self-generation engine, when a power outage occurs due to lightning strike or the like, the engine may be disconnected from the power grid, and after surviving with no load or a minimum load, the power supply to the in-house equipment may be restarted. However, if the above control is incorporated, the engine will stop when the load suddenly changes after being disconnected from the power grid, and it will take time to restore the power supply to the in-house equipment. In the worst case, there is a risk that the engine cannot be restarted due to the power outage and the power supply cannot be restored.

[0005] As a means to solve this problem, Patent Document 2 shows that intentional misfire by control and misfire due to other failures or the like are separated, and no alarm is issued for the former.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, Patent Document 2 shows that in the case of controlled misfire (intentional misfire), an alarm is not issued by differentiating it from misfire due to a failure other than control. However, there are cases where misfire due to a failure not caused by control does not lead to combustion in the exhaust flue (for example, temporary fuel supply failure or excessive air volume, etc.), and if an alarm is issued in such cases, there is a possibility of over - detection. In addition, Patent Document 2 only determines whether to issue an alarm and does not mention protection operations such as engine stop.

[0008] The present disclosure has been made in view of the above - mentioned problems, and an object thereof is to provide an engine misfire detection device and a misfire detection method that can continue operation while ensuring safety by monitoring misfires that lead to combustion in the exhaust flue and stopping the engine.

Means for Solving the Problems

[0009] To achieve the above object, an engine misfire detection device according to the present disclosure includes a misfire detection unit that detects a misfire state in at least one cylinder of an engine, and when the misfire state is detected by the misfire detection unit, based on an unburned parameter that is an index of the unburned fuel concentration in the exhaust flue, an effective misfire determination unit that determines the risk of combustion of the unburned fuel in the exhaust flue, and an engine stop processing control unit that performs an engine stop process based on the determination result of the effective misfire determination unit.

[0010] In addition, the engine misfire detection method according to the present disclosure includes a misfire detection step of detecting a misfire state in at least one cylinder of the engine, and when the misfire state is detected in the misfire detection step, based on an unburned parameter that is an index of the unburned fuel concentration in the exhaust flue, an effective misfire determination step of determining the risk of combustion of the unburned fuel in the exhaust flue, and an engine stop processing step of performing stop processing of the engine based on the determination result in the effective misfire determination step.

Advantages of the Invention

[0011] According to the engine misfire detection device of the present disclosure, when a misfire state is detected by the misfire detection unit, the effective misfire determination unit determines whether the misfire is a misfire (effective misfire) that may lead to combustion of unburned fuel in the exhaust flue based on an unburned parameter that is an index of the unburned fuel concentration in the flue. Therefore, in the case where unburned fuel does not reach combustion in the exhaust flue even for a misfire caused by a failure not due to control, the continuity of operation can be improved by excluding it from the protection operation of engine stop. That is, by monitoring only effective misfires that may lead to combustion of unburned fuel in the exhaust flue and stopping the engine, the continuity of operation can be improved while ensuring safety.

[0012] 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 may lead to combustion of unburned fuel in the exhaust flue based on an unburned parameter that is an index of the unburned fuel concentration in the flue. Therefore, in the case where unburned fuel does not reach combustion in the exhaust flue even for a misfire caused by a failure not due to control, the continuity of operation can be improved by excluding it from the protection operation of engine stop. That is, by monitoring only effective misfires that may lead to combustion of unburned fuel in the exhaust flue and stopping the engine, the continuity of operation can be improved while ensuring safety.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 5E

Figure 5F

Figure 6

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the engine misfire detection device and misfire detection method according to the embodiments of the present disclosure will be described based on the configuration diagram and control block diagram. Such embodiments show one aspect of the present disclosure and are not limited to this disclosure, and can be arbitrarily changed within the scope of the technical idea of the present disclosure.

[0015] <First Embodiment> (Configuration) FIG. 1 shows a misfire detection device 1 and a misfire detection method according to the first embodiment, and shows an overall schematic configuration diagram 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 in the misfire detection device 1. Note that the engine is not limited to the gas engine 3 and is shown as an example.

[0016] The gas engine 3 is a four-cycle reciprocating engine that uses fuel gas as fuel and has at least one cylinder. Further, fuel supply means (not shown) for supplying gas fuel into each cylinder of the gas engine 3 and air supply means (not shown) for supplying combustion air into each cylinder are provided, and a driving control device 5 for controlling the driving state of the gas engine 3 by controlling the supply amounts of the gas fuel and the combustion air from these supply means into the cylinder is provided.

[0017] In addition, a cylinder internal pressure sensor 7 for detecting the internal pressure of the combustion chamber is installed in each cylinder, and a detection signal from the cylinder internal pressure sensor 7 is input to the misfire detection device 1.

[0018] As shown in FIG. 1, the misfire detection device 1 includes a misfire detection unit 9 that detects a misfire state in at least one cylinder of the gas engine 3, and when the misfire state is detected by the misfire detection unit 9, based on an unburned parameter that is an index of the unburned fuel concentration in the exhaust flue, an effective misfire determination unit 11 that determines the risk of the unburned fuel in the exhaust flue burning, and an engine stop processing control unit 13 that performs a stop process of the gas engine 3 based on the determination result of the effective misfire determination unit 11.

[0019] In the misfire detection unit 9 of the misfire detection device 1, for example, when the combustion pressure of each cylinder from the cylinder internal pressure sensor 7 is smaller than the pressure range during normal combustion, it is determined as a misfire.

[0020] When the misfire detection unit 9 detects a misfire state, the effective misfire determination unit 11 determines whether it is an effective misfire having a risk of combustion of unburned fuel in the exhaust gas discharged from the cylinder in the exhaust flue through which the exhaust gas from the gas engine 3 flows during the misfire, based on the unburned parameter P1 which is an index of the unburned fuel concentration in the exhaust flue. This determination of effective misfire is configured to be performed by comparing the value of the unburned parameter P1 acquired by the unburned parameter acquisition unit 17 with the effective misfire determination threshold of the unburned parameter.

[0021] The unburned parameter P1 is calculated or estimated by the unburned parameter acquisition unit 17 provided in the effective misfire determination unit 11 based on the operation state signal from the gas engine 3 and the exhaust gas state signal from the exhaust gas.

[0022] Also, the unburned parameter P1 is, for example, the air-fuel ratio parameter P2 which is an index of the air-fuel ratio in at least one cylinder as in the second embodiment described later, and is the exhaust gas property parameter P3 based on the property of the exhaust gas flowing in the exhaust flue as in the third embodiment described later. And the effective misfire determination threshold is set based on a value at which there is a possibility of combustion of unburned fuel in the exhaust flue by test or simulation or the like in consideration of these parameters in advance.

[0023] The engine stop processing control unit 13 counts the number of determinations of effective misfire from the effective misfire determination unit 11 in the past fixed time or past fixed cycle to calculate an integrated value, determines whether the integrated value exceeds a predetermined integrated threshold, and performs the engine stop processing when it exceeds.

[0024] Thus, the engine stop processing control unit 13 calculates the integrated value of the number of determinations of effective misfire from the effective misfire determination unit 11 in the past fixed time or past fixed cycle, and performs the engine stop processing when the integrated value exceeds the predetermined integrated threshold, so that old misfires disappear over time. Therefore, it is possible to determine the risk of exhaust flue combustion in the latest misfire state, and the engine stop processing can be executed based on the determination result.

[0025] The engine stop process is performed by the engine stop process control unit 13 issuing a stop command to the operation control device 5, causing the operation control device 5 to stop the supply of gas fuel and the ignition to the gas engine 3, or to perform either the stop of the supply of gas fuel or the stop of ignition.

[0026] Note that the engine stop process in the engine stop process control unit 13 may be the case where a determination result that the integrated value of the number of times of valid misfire determination is equal to or greater than the integration threshold occurs in one control in the control cycle, or may be the case where it continues to occur continuously in a plurality of consecutive controls.

[0027] In some embodiments, the past fixed time or past fixed cycle, which is the calculation range of the integrated value, and the integration threshold in the engine stop process control unit 13 are set to larger values at low load than at high load from startup.

[0028] This is because during startup and in the low load region, combustion becomes unstable and sporadic misfires are likely to occur. Therefore, the integrated value is more likely to increase compared to the high load region, and it is easier to reach the engine stop measure with the same threshold value. On the other hand, in this region, the absolute amount of fuel gas supplied is small, and even if combustion occurs in the exhaust flue, the damage caused by it is small.

[0029] As an example of the past fixed cycle, for example, in the case of the 20 - cylinder gas engine 3 (20 cylinders burn in one cycle), it is set to 5 - 20 cycles at low load from startup and 1 - 3 cycles at high load. More preferably, it is set to 10 cycles (200 cylinders) at low load from startup and 2 cycles (40 cylinders) at high load.

[0030] Then, within a set past fixed cycle, when the integrated 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 equal to or greater than the integrated 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. A specific example is shown in Table 1.

[0031]

Table 1

[0032] In the example of Table 1, even though the ratio of the integrated threshold number of cylinders to the number of monitored cylinders is the same at low load and high load from startup, the number of monitored cylinders is increased at low load from startup. Thereby, in the startup and low load regions, useless engine stops due to transient events where combustion becomes unstable and sporadic misfires are likely to occur are suppressed.

[0033] Also, in some embodiments, a modified example of the engine stop processing control unit 13 is shown as in FIG. 2, and the engine stop processing control unit 13 is provided with an effective misfire number correction unit 23. In this effective misfire number correction unit 23, weighting is performed on the integrated value in calculating the integrated value of the number of determination times of effective misfires from the effective misfire determination unit 11.

[0034] That is, the effective misfire determination unit 11 is configured to determine the risk of combustion of unburned fuel in the exhaust flue by comparing the unburned parameter P1 with the effective misfire determination threshold, and depending on the magnitude of this unburned parameter P1, weighting is performed on the integrated value in calculating the integrated value of the number of determination times of effective misfires in the engine stop processing control unit 13.

[0035] For example, when it is determined that an effective misfire has occurred in a state where the possibility of reaching combustion in the flue is particularly high, such as when the unburned parameter P1 greatly exceeds the threshold value, or in a state where the damage during combustion is large, the number of times of effective misfire determination is not 1 time, but an integrated value is calculated with a weighted number of times such as 1.5 times. Note that when the number of times of effective misfire determination is 10 times as an integrated value instead of correction for each time, the resulting integrated value may be corrected to 15 times instead of 10 times.

[0036] In this way, the engine stop processing control unit 13 has an effective misfire number correction unit 23 that performs weighting in the calculation of the integrated value of the number of times of effective misfire determination according to the magnitude of the unburned parameter P1 in the calculation of the integrated value. As a result, the reliability of the engine stop processing is improved, the safety is ensured, and the continuity of operation can be improved.

[0037] Next, with reference to the control block diagram of the misfire detection method shown in FIG. 1, the control flow of the misfire detection method will be described.

[0038] First, in step S1, a cylinder internal pressure signal is acquired from the cylinder internal pressure sensor 7. In the next step S2, it is determined whether the cylinder internal pressure is smaller than the pressure range during normal combustion, and if it is smaller, it is determined that a misfire has occurred.

[0039] In the next step S3, it is determined whether it is an effective misfire having a risk of combustion of unburned fuel in the exhaust gas discharged from the cylinder in the exhaust flue through which the exhaust gas from the gas engine 3 flows during misfire.

[0040] The determination in this step S3 takes in the value of the unburned parameter P1 calculated or estimated by the unburned parameter acquisition unit 17 in step S4, and by comparing the value of this unburned parameter P1 with the effective misfire determination threshold value, if the value of the unburned parameter P1 is greater than the effective misfire determination threshold value, it is determined that it is an effective misfire.

[0041] If the determination result in step S3 is determined to be a valid misfire, it becomes Yes and proceeds to step S7. In step S7, the number of determinations of valid misfires is counted. That is, an integrated value is calculated. Note that the calculation of the integrated value calculates the integrated value of the number of determinations of valid misfires over a certain past time or a certain past cycle.

[0042] Also, when having the valid misfire number correction unit 23 shown in FIG. 2, the integrated value of the determination times corrected by the valid misfire number correction unit 23 is calculated.

[0043] Then, in the next step S8, it is determined whether or not the integrated value of the valid misfire number calculated in step S7 is greater than or equal to the integrated threshold value. If so, it becomes Yes and proceeds to step S9. In step S9, engine trip (engine stop) is performed.

[0044] On the other hand, if the determination result in step S3 is No, the number of determinations of valid misfires is not counted in step S5, and in step S6, it moves to the next cylinder and repeats the processing from step S1.

[0045] Note that steps S1 and S2 constitute a misfire detection step, steps S3 and S4 constitute a valid misfire determination step, and steps S7 to S9 constitute an engine stop processing step.

[0046] (Operation and Effect) According to the engine misfire detection device 1 according to the first embodiment described above, when the misfire state is detected by the misfire detection unit 9, the valid misfire determination unit 11 determines whether or not it is a valid misfire in which unburned fuel in the exhaust flue is likely to lead to combustion, based on the unburned parameter P1 which is an index of the unburned fuel concentration in the flue. Therefore, even in the case of a misfire due to a failure not based on control, in the case where the unburned fuel in the exhaust flue does not reach combustion, the continuity of operation can be improved by excluding it from the protection operation for stopping the gas engine 3. That is, by monitoring only the valid misfires in which there is a risk that the unburned fuel in the exhaust flue leads to combustion and stopping the gas engine 3, the continuity of operation can be improved while ensuring safety.

[0047] Figure 6 is a control block diagram of a conventional engine misfire detection device that is a comparative example of the present embodiment. In this example, a cylinder internal pressure signal is acquired in step S101, it is determined in the next step S102 whether the cylinder internal pressure is less than the pressure range during normal combustion, the number of misfires less than the pressure range during normal combustion is counted in the next step S103, it is determined in the next step S104 whether the count number for a predetermined time is equal to or greater than a threshold value, if it is equal to or greater than the threshold value, the process proceeds to step S105 and engine trip (engine stop) processing is performed, if it is less than the threshold value, the process proceeds to step S106, moves to the next cylinder, and repeats from step S101.

[0048] In the comparative example shown in Figure 6, since misfire is determined only by whether the cylinder internal pressure is less than the pressure range during normal combustion, even a misfire where there is no risk of unburned fuel leading to combustion in the exhaust flue causes the engine to stop, which may interfere with operation.

[0049] In the present embodiment compared to the comparative example of Figure 6, by monitoring effective misfires where there is a risk of unburned fuel leading to combustion in the exhaust flue by the effective misfire determination unit 11 and stopping the gas engine 3, the safety can be ensured while improving the continuity of operation.

[0050] <Second Embodiment> The second embodiment will be described with reference to Figure 3. In the second embodiment, the effective misfire determination unit 27 is different from that of the first embodiment. In the second embodiment, the unburned parameter P1 of the first embodiment is the air-fuel ratio parameter P2 which is an index of the air-fuel ratio in at least one cylinder, and the effective misfire determination unit 27 determines effective misfires based on the air-fuel ratio parameter P2. In the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0051] (Configuration) As shown in FIG. 3, the effective misfire determination unit 27 includes an air-fuel ratio parameter acquisition unit 29 that calculates or estimates an air-fuel ratio parameter P2, which is an index of the air-fuel ratio in at least one cylinder, based on an operation state signal from the gas engine 3 and an exhaust gas state signal from the exhaust gas.

[0052] Then, when the misfire detection unit 9 detects a misfire state, the effective misfire determination unit 27 determines whether the misfire is an effective misfire having a risk of unburned fuel burning in the exhaust flue by comparing the value of the air-fuel ratio parameter P2 with the effective misfire determination threshold of the air-fuel ratio parameter P2.

[0053] As shown in the control flow of the misfire detection method in FIG. 3, the determination in step S3 takes in 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 this air-fuel ratio parameter P2 with the effective misfire determination threshold, if the value of the air-fuel ratio parameter P2 is greater than the effective misfire determination threshold, it is determined as an effective misfire.

[0054] Note that depending on the definition of the air-fuel ratio parameter P2, there may be cases where a case smaller than the effective misfire determination threshold or within a certain range is determined as an effective misfire. For example, when using the air excess ratio λ as the air-fuel ratio parameter P2, if it exceeds the effective misfire determination threshold (corresponding to the upper limit of the combustible range), it will be outside the combustible range and will not burn, so a case smaller than the effective misfire determination threshold is determined as an effective misfire.

[0055] As the air-fuel ratio parameter P2, which is an index of the air-fuel ratio in the cylinder, for example, it is calculated, estimated, and used by the following methods (A) to (E). Also, it may be calculated and estimated by combining each item of these (A) to (E).

[0056] (A) It is the air-fuel ratio calculated from the measured fuel supply amount and air amount. The air-fuel ratio calculated from this measured value is based on the measured result, so it may have problems with accuracy and responsiveness depending on the installation position of the measuring instrument and the operating accuracy of the measurement, but it is accurate because it is a measured value.

[0057] (B) It is the air-fuel ratio calculated and estimated from the measured exhaust gas composition and fuel properties. For example, the combustion state in the cylinder is estimated from the hydrocarbon (HC) concentration in the exhaust gas composition and the HC concentration in the fuel properties of the hydrocarbon-based fuel gas to estimate the air-fuel ratio. Although it is excellent in accuracy, a time delay is likely to occur until the detection result of the exhaust gas composition is obtained.

[0058] (C) It is the air-fuel ratio estimated from the operation data (the number of revolutions, intake air temperature, intake air pressure, fuel supply amount, etc. at each moment). It is estimated and calculated from these operation data how much fuel supply amount and air amount are currently supplied into the cylinder. Although it is excellent in responsiveness, since the amount of data processing increases, it may lead to an increase in the size and cost of the control device.

[0059] (D) It is a value based on the index value of the fuel supply amount (governor opening degree, etc.). Since it does not involve an increase in the data capacity, it is excellent in responsiveness and practical.

[0060] For example, it is determined whether there is a risk of effective misfire depending on whether the governor opening degree (index of fuel amount) exceeds a predetermined threshold value. That is, regardless of the amount of air, it is confirmed in advance by tests or the like that combustion will not occur in the exhaust flue when the fuel amount is less than a predetermined value. By using the governor opening degree, which is an index of the fuel amount, parameters related to the air-fuel ratio can be obtained with a simple configuration.

[0061] (E) It is the air-fuel ratio estimated from the operation set value. Although it is inferior in accuracy, it is effective when sufficient measured data cannot be detected. For example, the fuel amount and air amount are estimated from the engine output to calculate the air-fuel ratio.

[0062] Here, in the second embodiment, regarding the behavior of the gas engine 3 leading to the determination of effective misfire during load interruption due to control or a failure or the like, with the air excess ratio λ used as the air-fuel ratio parameter P2, FIGS. 5A to 5F will be referred to for explanation.

[0063] FIG. 5A shows the behavior of the engine output of the gas engine 3. The numbers on the horizontal axis indicate time (seconds) (the time axis of the horizontal axis is the same until FIG. 5F below), and the engine output is shown on the vertical axis. The time of load interruption is set to 0 (zero) seconds.

[0064] FIG. 5B shows the rotational speed after load interruption on the vertical axis. At the time of load interruption, since the load is removed, the rotational speed temporarily increases.

[0065] FIG. 5C shows the governor opening (a guide for the fuel amount) on the vertical axis. At the time of load interruption, fuel is temporarily cut to suppress an excessive increase in rotational speed.

[0066] FIG. 5D shows the air-fuel ratio λ of the air-fuel mixture on the vertical axis. Immediately after load interruption, due to fuel cut, the air-fuel mixture is temporarily thinned and goes out of the combustion range beyond the combustion limit A. In the range exceeding this combustion limit A, there is no concern about flue combustion.

[0067] FIG. 5E shows the presence or absence of misfires on the vertical axis. The presence or absence of this misfire is determined and shown by the misfire detection unit 9 based on whether the pressure of each cylinder from the in-cylinder pressure sensor 7 is smaller than the pressure range during normal combustion. During the fuel cut shown in FIG. 5C, misfires occur in all cylinders. As the fuel increases after recovering from the fuel cut, the number of cylinders in the ignition state increases, but in the low load range, since combustion is unstable, a state where misfiring cylinders are scattered is shown.

[0068] FIG. 5F shows the integrated values of the number of misfires (indicated by a dotted line) and the effective number of misfires (indicated by a solid line) on the vertical axis, showing the integrated value within a certain past time (within t seconds). If all misfires are counted, the integrated value exceeds the integrated threshold and the engine stops. On the other hand, as shown in FIG. 5D, when the air-fuel ratio λ exceeds the line of the combustion limit A due to fuel cut, the combustion range is outside the cylinder, and there is no risk of unburned fuel reaching combustion in the exhaust flue. By excluding misfires in this state from the count, the integrated value of effective misfires does not exceed the integrated threshold, and the operation of the engine continues.

[0069] (Operation and Effect) According to the second embodiment, the effective misfire determination unit 27 determines whether or not it is an effective misfire by using an air-fuel ratio parameter P2 which is an index of the air-fuel ratio in at least one cylinder. Since the operation control signal used for the engine operation control can be utilized, simplification of the system configuration of the misfire detection device 1 can be expected.

[0070] Further, when using, as the air-fuel ratio parameter P2, not the air-fuel ratio but an index value of the fuel supply amount (such as governor opening degree) as described in the above (D) as a parameter related to 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, by previously confirming through tests or the like that combustion will not occur in the exhaust gas passage when the fuel amount is less than a predetermined value, the determination of effective misfire by the effective misfire determination unit 27 can be made with a simpler configuration.

[0071] Also, the methods described in the above (A) to (E) may be combined, and by not necessarily performing all data measurement and calculation necessary for air-fuel ratio estimation, the load of control calculation can be reduced, leading to higher processing speed and prevention of control failures.

[0072] <Third Embodiment> The third embodiment will be described with reference to FIG. 4. In the third embodiment, the effective misfire determination unit 33 is different from that in the first embodiment. In the third embodiment, the unburned parameter P1 in the first embodiment is an exhaust gas property parameter P3 based on the property of the exhaust gas flowing in the exhaust gas passage. In particular, for the exhaust gas property parameter P3, the concentration of unburned fuel and / or oxygen concentration in the exhaust gas is used, and the effective misfire determination unit 33 determines effective misfire based on the exhaust gas property parameter P3. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0073] (Configuration) As shown in FIG. 4, the effective misfire determination unit 33 includes an exhaust gas property acquisition unit 35 that actually measures the exhaust gas property of the exhaust gas from the gas engine 3 and acquires the exhaust gas property parameter P3 used as the unburned parameter P1.

[0074] And when the misfire detection unit 9 detects a misfire state in the effective misfire determination unit 33, it is determined whether 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 misfire, based on the comparison between the concentration of the exhaust gas property parameter P3 based on the measured exhaust gas properties and the effective misfire determination threshold of the exhaust gas property parameter P3.

[0075] As shown in the control flow of the misfire detection method in FIG. 4, the determination in step S3 takes in the value of the exhaust gas property parameter P3 calculated or estimated by the exhaust gas property acquisition unit 35 in step S12, and by comparing this exhaust gas property value with the effective misfire determination threshold, when the value of the exhaust gas property parameter P3 is greater than the effective misfire determination threshold, it is determined as an effective misfire.

[0076] As the exhaust gas property parameter P3, in particular, the unburned component concentration is used. As the unburned gas, the hydrocarbon (THC) concentration and the carbon monoxide (CO) concentration are used. In the case of an engine using hydrogen gas as the fuel gas, the hydrogen (H2) concentration is used.

[0077] When using a hydrocarbon-based fuel gas, a large amount of unburned hydrocarbon (THC) that has not been completely burned is discharged due to incomplete combustion in the cylinder, and a large amount of carbon monoxide (CO) is also discharged due to incomplete combustion in the cylinder. Also, in the case of a hydrogen engine, when incomplete combustion occurs in the cylinder, hydrogen (H2) is directly discharged.

[0078] As the exhaust gas property parameter P3, in addition to using the measured exhaust gas properties as they are, an index value (such as the air-fuel ratio of the exhaust gas) calculated based on the exhaust gas properties and other data may also be used.

[0079] The effective misfire determination threshold for whether the concentration of unburned fuel in the exhaust gas has a risk of combustion in the exhaust flue may be set for each unburned component concentration, or may also be set according to the ratio of each unburned component.

[0080] Further, the effective misfire determination threshold value may be corrected based on other components (such as oxygen concentration and carbon dioxide concentration). For example, when the oxygen concentration is high, it becomes easier to burn, so the concentration of the effective misfire determination threshold value for each unburned gas component is corrected to the lower side, and the unburned gas is corrected to be determined as an effective misfire even at a low concentration. Also, when the carbon dioxide concentration is high, it becomes difficult to burn, so the concentration of the effective misfire determination threshold value for each unburned gas component is corrected to the higher side, and the unburned gas is corrected so as not to be determined as an effective misfire even at a high concentration. By correcting in this way, the reliability of the determination of effective misfire by the exhaust gas property parameter P3 can be improved.

[0081] (Function and Effect) According to the third embodiment, since the effective misfire determination unit 33 determines whether or not it is an effective misfire using the exhaust gas property parameter P3 in the exhaust flue as an index, based on the actually measured data of the exhaust gas, the determination of effective misfire becomes accurate, and it is possible to surely achieve both ensuring safety and improving the continuity of operation.

[0082] The content described in each of the above embodiments is understood as follows, for example.

[0083] [1] The misfire detection device (1) of the engine (3) according to the present disclosure includes a misfire detection unit (9) that detects a misfire state in at least one cylinder of the engine, and when the misfire state is detected by the misfire detection unit, based on an unburned parameter (P1) that is an index of the unburned fuel concentration in the exhaust flue, an effective misfire determination unit (11, 27, 33) that determines the risk of combustion of the unburned fuel in the exhaust flue, and an engine stop processing control unit (13) that performs stop processing of the engine based on the determination result of the effective misfire determination unit.

[0084] 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 units (11, 27, 33) determine an effective misfire in which unburned fuel in the exhaust flue has a risk of leading to combustion based on the unburned parameter (P1) which is an index of the unburned fuel concentration in the flue. Therefore, in cases where unburned fuel does not reach combustion in the exhaust flue even due to misfires caused by malfunctions not related to control, the continuity of operation can be improved by excluding them from the protection operation for engine stop. That is, by monitoring only effective misfires in which unburned fuel in the exhaust flue has a risk of leading to combustion and stopping the engine, the continuity of operation can be improved while ensuring safety.

[0085] [2] In some embodiments, in the configuration described in [1] above, the unburned parameter is an air-fuel ratio parameter which is an index of the air-fuel ratio in at least one cylinder, and the effective misfire determination unit (27) determines an effective misfire based on the air-fuel ratio parameter.

[0086] According to the configuration described in [2] above, since the effective misfire determination unit (27) determines whether it is an effective misfire by using the air-fuel ratio parameter (P2) which is an index of the air-fuel ratio in at least one cylinder, the system configuration of the misfire detection device (1) can be simplified because the operation control signal used for the engine operation control can be utilized.

[0087] [3] In some embodiments, in the configuration described in [2] above, the air-fuel ratio parameter (P2) is an index value of the fuel supply amount to at least one cylinder, and the effective misfire determination unit (27) determines an effective misfire based on whether the index value of the fuel supply amount exceeds a predetermined threshold value.

[0088] According to the configuration described in [3], the system configuration of the fire detection device (1) can be further simplified. That is, regardless of the amount of air, it is confirmed in advance by tests or the like that when the fuel amount is less than a predetermined value, combustion will not occur in the exhaust flue. Thus, the determination of valid misfire by the valid misfire determination unit (27) can be made with a simpler configuration.

[0089] [4] In some embodiments, in the configuration described in [1], the unburned parameter (P1) is an exhaust gas property parameter (P3) based on the properties of the exhaust gas flowing in the exhaust flue, and the valid misfire determination unit (33) determines valid misfire based on the exhaust gas property parameter.

[0090] According to the configuration described in [4], since the valid misfire determination unit (33) determines whether it is a valid misfire using the exhaust gas property parameter (P3) based on the measured data of the exhaust gas in the exhaust flue as an index, the determination accuracy of valid misfire can be improved.

[0091] [5] In some embodiments, in the configuration described in [4], the exhaust gas property parameter (P3) includes the unburned fuel concentration and the oxygen concentration in the exhaust gas, and the valid misfire determination unit (33) determines valid misfire based on the unburned fuel concentration and the oxygen concentration.

[0092] According to the configuration described in [5], since valid misfire is determined using the unburned component concentration and the oxygen concentration that greatly affect the combustion by the unburned fuel in the exhaust flue, the determination accuracy is further improved.

[0093] [6] In some embodiments, in the configuration described in [1] to [5], the engine stop processing control unit (13) calculates the integrated value of the number of determinations of valid misfire from the valid misfire determination units (11, 27, 33) in a past fixed time or a past fixed cycle, and performs the engine stop processing when the integrated value exceeds a predetermined integrated threshold value.

[0094] According to the configuration described in [6] above, the engine stop processing control unit (13) calculates the integrated value of the number of valid misfire determinations from the valid misfire determination units (11, 27, 33) in a past fixed time or a past fixed cycle, and when the integrated value exceeds a predetermined integrated threshold value, it performs an engine stop process. Therefore, old misfires disappear over time. Accordingly, it is possible to determine the risk of exhaust flue combustion in the latest misfire state, and based on the determination result, it is possible to execute an engine stop process.

[0095] [7] In some embodiments, in the configuration described in [6] above, the valid misfire determination units (11, 27, 33) are configured to determine the risk of unburned fuel in the exhaust flue burning by comparing the unburned parameter with a valid misfire determination threshold value, and the engine stop processing control unit (13) further includes a valid misfire number correction unit (23) that weights the integrated value of the number of valid misfire determinations according to the magnitude of the unburned parameter in the calculation of the integrated value.

[0096] According to the configuration described in [7] above, the engine stop processing control unit (13) further includes a valid misfire number correction unit (23) that weights the integrated value of the number of valid misfire determinations according to the magnitude of the unburned parameter in the calculation of the integrated value. Therefore, the reliability of the engine stop process is improved, and while ensuring safety, the continuity of operation can be improved.

[0097] [8] In some embodiments, in the configuration described in [6 or 7] above, the past fixed time or the past fixed cycle and the integrated threshold value are set to larger values at low load than at high load from startup.

[0098] According to the configuration described in [8] above, by setting the past fixed time or the past fixed cycle and the integrated threshold value to larger values at low load than at high load from startup, it is possible to suppress unnecessary engine stops due to transient events where combustion becomes unstable and sporadic misfires are likely to occur at startup or in the low load region.

[0099] [9] The engine misfire detection method according to the present disclosure includes a misfire detection step (steps S1 to S2 in the first embodiment) for detecting a misfire state in at least one cylinder of the engine, and when the misfire state is detected in the misfire detection step, based on an unburned parameter which is an index of the unburned fuel concentration in the exhaust flue, an effective misfire determination step (steps S3 to S4 in the first embodiment) for determining the risk of combustion of the unburned fuel in the exhaust flue, and an engine stop processing step (S7 to S9 in the first embodiment) for performing stop processing of the engine based on the determination result in the effective misfire determination step.

[0100] According to the configuration described in [9] above, in the engine misfire detection method, when a misfire state is detected by the misfire detection step, an effective misfire which has a risk of leading to combustion of unburned fuel in the exhaust flue is determined based on an unburned parameter which is an index of the unburned fuel concentration in the flue by the effective misfire determination step. Therefore, even for misfires not caused by control due to failures or the like, in cases where the unburned fuel in the exhaust flue does not reach combustion, the continuity of operation can be improved by excluding it from the target of the engine stop protection operation. That is, by monitoring only effective misfires that have a risk of leading to combustion of unburned fuel in the exhaust flue and stopping the engine, the continuity of operation can be improved while ensuring safety.

Description of Reference Numerals

[0101] 1 Misfire detection device 3 Gas engine (engine) 5 Operation control device 7 In-cylinder pressure sensor 9 Misfire detection unit 11, 27, 33 Effective misfire determination unit 13 Engine stop processing control unit 17 Unburned parameter acquisition unit 23 Effective misfire number correction unit 29 Air-fuel ratio parameter acquisition unit 35 Exhaust gas property acquisition unit P1 Unburned parameter P2 Air-fuel ratio parameter P3 Exhaust gas property parameter

Claims

1. An engine misfire detection device, comprising: a misfire detection unit configured to detect a misfire state in at least one cylinder of the engine; a valid misfire determination unit configured to determine a risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter that is an index of the unburned fuel concentration in the exhaust flue when the misfire state is detected by the misfire detection unit; an engine stop processing control unit configured to perform an engine stop process based on a determination result of the valid misfire determination unit; wherein the engine stop processing control unit calculates an integrated value of the number of determinations of valid misfires from the valid misfire determination unit in a past fixed time or a past fixed cycle, and performs an engine stop process when the integrated value exceeds a predetermined integrated threshold value; wherein the valid misfire determination unit is configured to determine a risk of combustion of unburned fuel in the exhaust flue by comparing the unburned parameter with a valid misfire determination threshold value; wherein the engine stop processing control unit further includes a valid misfire number correction unit configured to weight the integrated value of the number of determinations of valid misfires according to the magnitude of the unburned parameter in the calculation of the integrated value; An engine misfire detection device.

2. An engine misfire detection device, comprising: a misfire detection unit configured to detect a misfire state in at least one cylinder of the engine; a valid misfire determination unit configured to determine a risk of combustion of unburned fuel in the exhaust flue based on an unburned parameter that is an index of the unburned fuel concentration in the exhaust flue when the misfire state is detected by the misfire detection unit; an engine stop processing control unit configured to perform an engine stop process based on a determination result of the valid misfire determination unit; wherein the engine stop processing control unit calculates an integrated value of the number of determinations of valid misfires from the valid misfire determination unit in a past fixed time or a past fixed cycle, and performs an engine stop process when the integrated value exceeds a predetermined integrated threshold value; wherein the past fixed time or the past fixed cycle and the integrated threshold value are set to larger values at low load than at high load from startup; An engine misfire detection device.

3. The unburned parameter is an air-fuel ratio parameter that is an index of the air-fuel ratio in the at least one cylinder; the valid misfire determination unit determines valid misfires based on the air-fuel ratio parameter; The engine misfire detection device according to claim 1 or 2.

4. The air-fuel ratio parameter is an indicator of the fuel supply amount into the at least one cylinder, The effective misfire determination unit determines effective misfire based on whether or not the fuel supply amount exceeds a predetermined threshold value, The misfire detection device for an engine according to claim 3.

5. The unburned parameter is an exhaust gas property parameter based on the property of the exhaust gas flowing in the exhaust passage, The effective misfire determination unit determines effective misfire based on the exhaust gas property parameter, The misfire detection device for an engine according to claim 1 or 2.

6. The exhaust gas property parameter includes the unburned fuel concentration and the oxygen concentration in the exhaust gas, The effective misfire determination unit determines effective misfire based on the unburned fuel concentration and the oxygen concentration, The misfire detection device for an engine according to claim 5.

7. An engine misfire detection method, comprising: A misfire detection step of detecting a misfire state in at least one cylinder of the engine; When the misfire state is detected in the misfire detection step, an effective misfire determination step of determining the risk of combustion of the unburned fuel in the exhaust passage based on an unburned parameter that is an indicator of the unburned fuel concentration in the exhaust passage; An engine stop processing step of performing stop processing of the engine based on the determination result in the effective misfire determination step, The engine stop processing step calculates an integrated value of the number of determinations of effective misfire in the effective misfire determination step in a past fixed time or a past fixed cycle, and when the integrated value exceeds a predetermined integrated threshold value, performs stop processing of the engine, and The effective misfire determination step determines the risk of combustion of the unburned fuel in the exhaust passage by comparing the unburned parameter with an effective misfire determination threshold value, The engine stop processing step further includes an effective misfire number correction step of weighting the integrated value of the number of determinations of effective misfire according to the magnitude of the unburned parameter in the calculation of the integrated value, An engine misfire detection method.

8. An engine misfire detection method, comprising: A misfire detection step of detecting a misfire state in at least one cylinder of the engine; When the misfire state is detected in the misfire detection step, an effective misfire determination step of determining the risk of combustion of the unburned fuel in the exhaust passage based on an unburned parameter that is an indicator of the unburned fuel concentration in the exhaust passage; An engine stop processing step for performing stop processing of the engine based on the determination result in the effective misfire determination step, and the engine stop processing step calculates an integrated value of the number of determinations of effective misfires in the effective misfire determination step in a past fixed time or a past fixed cycle, and when the integrated value exceeds a predetermined integrated threshold value, performs stop processing of the engine, and the past fixed time or the past fixed cycle and the integrated threshold value are set to larger values during low load than during high load from startup, An engine misfire detection method.

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