Abnormality detection device, abnormality detection method and program

Abstract

To provide a method for detecting an abnormality in a combustion state in an engine combustion chamber without additionally providing a sensor in a cylinder.SOLUTION: An abnormality detection device comprises a determination unit that determines that a combustion state in a combustion chamber of an engine is abnormal when a temperature of exhaust gas discharged from the engine rises so as to exceed a predetermined rate within a predetermined first time period after an air-fuel ratio of the engine changes to a lean side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an anomaly detection device, an anomaly detection method, and a program. [Background technology]

[0002] When a solenoid valve installed in the system supplying fuel gas to a gas engine cylinder becomes clogged with debris, fuel gas can flow into the cylinder even when the solenoid valve is closed. The inflow of fuel gas affects the combustion state. Conventionally, a pressure sensor is installed in the cylinder and the combustion state is monitored by detecting changes in pressure inside the cylinder. However, installing a pressure sensor in each of the multiple cylinders in a gas engine increases costs. In addition, although a temperature sensor is installed in the exhaust system of a gas engine, detecting the inflow of fuel gas into the cylinder from the solenoid valve using this exhaust-side temperature sensor is delayed because it takes time for the exhaust temperature to reach a specified failure value. Therefore, in gas engines without a pressure sensor installed in the cylinder, the inflow of fuel gas causes the exhaust temperature to rise, and protection cannot be activated until knocking occurs, which may result in damage to the engine.

[0003] As a related technique, Patent Document 1 discloses a method for detecting abnormal combustion in a combustion chamber based on the air-fuel ratio of exhaust gas detected by an air-fuel ratio sensor and the temperature of the exhaust gas detected by a temperature sensor. However, even when the components of exhaust gas are monitored with an air-fuel ratio sensor instead of installing a pressure sensor in the cylinder, the installation of the air-fuel ratio sensor is costly. Patent Document 2 discloses a method for controlling the amount of fuel gas supplied to a gas engine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-291485 [Patent Document 2] Patent No. 7457663 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for a technology that can detect abnormalities in the combustion state in an engine combustion chamber without providing each cylinder with a pressure sensor, etc. Patent Documents 1 and 2 do not disclose a method for detecting abnormalities in the combustion state without providing each cylinder with a pressure sensor, etc.

[0006] The present disclosure provides an anomaly detection device, an anomaly detection method, and a program that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The abnormality detection device disclosed herein includes a determination unit that determines that the combustion state in the combustion chamber of the engine is abnormal if the temperature of the exhaust gas emitted from the engine increases at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side.

[0008] In the abnormality detection method disclosed herein, an abnormality detection device determines that the combustion state in the combustion chamber of the engine is abnormal when the temperature of the exhaust gas emitted from the engine rises at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side.

[0009] The program disclosed herein causes a computer to execute a process to determine that the combustion state in the combustion chamber of the engine is abnormal if the temperature of the exhaust gas emitted from the engine rises at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side. [Effects of the Invention]

[0010] According to the above-described abnormality detection device, abnormality detection method, and program, abnormalities in the combustion state in the combustion chamber of the engine can be detected early without the need for additional sensors. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an engine according to an embodiment. [Figure 2] FIG. 1 is a first diagram illustrating an example of an abnormality detection logic according to an embodiment. [Figure 3] FIG. 2 is a second diagram illustrating an example of an abnormality detection logic according to the embodiment. [Figure 4] 10 is a flowchart illustrating an example of an abnormality detection process according to the embodiment. [Figure 5] FIG. 1 is a schematic diagram illustrating an example of a hardware configuration of an anomaly detection device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Embodiment> Hereinafter, the method for detecting an abnormality in a combustion state according to this embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram of an engine 1 according to this embodiment. The engine 1 is a gas engine that uses fuel gas as fuel and outputs power by burning an air-fuel mixture produced by mixing the fuel gas with intake air (air). The engine 1 has multiple cylinders 10. FIG. 1 shows only one cylinder 10 as a representative example. The cylinder 10 includes a cylinder 3 and a piston 2 that reciprocates within the cylinder 3. The cylinder 3 is provided with an intake port 5 that is opened and closed by an intake valve 4 and an exhaust port 7 that is opened and closed by an exhaust valve 6. A combustion chamber 8 is formed between the cylinder 3 and the piston 2, and an ignition plug 9 is provided in the combustion chamber 8. An intake manifold 11 is connected to the intake port 5. An intake pipe 15 that supplies air and a fuel gas supply pipe 12 that supplies gas fuel are connected to the intake manifold 11. A gas supply solenoid valve 20 is attached to the fuel gas supply pipe 12. The amount of fuel gas supplied to the intake manifold 11 is controlled by opening and closing the gas supply solenoid valve 20. A throttle valve 14 is provided in the intake pipe 15, and the flow rate of air supplied to the intake port 5 is adjusted by controlling the opening degree of the throttle valve 14. A compressor 13c of the turbocharger 13 is connected to the upper end of the intake pipe 15. An air cleaner 17 is connected to the upstream end of an intake pipe 16 connected to the compressor 13c, and external air is drawn in through this. Air taken in from the outside is sent to the intake manifold 11 via the air cleaner 17, intake pipe 16, compressor 13c, and intake pipe 15, where it is mixed with fuel gas supplied from a fuel gas supply pipe 12 and the intake air taken in from the outside to generate an air-fuel mixture. The air-fuel mixture is supplied to the combustion chamber 8 via the intake port 5, where combustion takes place. An exhaust pipe 18 is connected to the exhaust port 7, and the exhaust gas after combustion is discharged into the exhaust pipe 18 via the exhaust port 7. A turbine 13t of the turbocharger 13 is connected to the downstream end of the exhaust pipe 18. The compressor 13c of the turbocharger 13 and the turbine 13t rotate integrally via a rotary shaft 13s. An exhaust pipe 19 is connected to the turbine 13t. A temperature sensor 21 that measures the temperature of the exhaust gas flowing through the exhaust pipe 18 is installed in the exhaust pipe 18.The detected value (exhaust temperature Tex) of the temperature sensor 21 is transmitted to a control device 22 that controls the engine 1 and an abnormality detection device 30 that detects abnormal combustion in the combustion chamber 8. The temperature sensor 21 is provided for each cylinder 10.

[0013] In addition to the exhaust temperature Tex detected by the temperature sensor 21, the control device 22 acquires a detected pressure value and a detected temperature value from a pressure sensor (not shown) that measures the pressure in the intake manifold 11 and a temperature sensor (not shown) that measures the temperature in the intake manifold 11, respectively. The control device 22 acquires the engine speed from a rotation speed sensor connected to a crankshaft (not shown) that is connected to the piston 2. The control device 22 calculates the mixture flow rate (Qmix) using the temperature and pressure in the intake manifold 11. A method for calculating the mixture flow rate (Qmix) is disclosed, for example, in Patent Document 2. The control device 22 performs feedback control (PID control) so that the engine speed detected by the rotation speed sensor becomes a target rotation speed. Specifically, the control device 22 calculates a command gas amount (Qgas), which is the amount of fuel gas supplied so that the engine speed becomes the target rotation speed, and controls the opening and closing of the gas supply solenoid valve 20 so that the calculated command gas amount (Qgas) can be supplied. Any known method can be used to calculate the command gas amount (Qgas). The control device 22 calculates the air-fuel ratio λ at a predetermined control cycle using the following equation (1), and adjusts the opening of the throttle valve 14 so that the air-fuel ratio λ becomes a target value. Lamba_st in equation (1) is a stoichiometric value, and is a parameter whose value is set in advance. Qmix and Qgas are the mixture flow rate and command gas amount (both calculated values) described above, respectively. The control device 22 also outputs the calculated air-fuel ratio λ to the abnormality detection device 30. Air-fuel ratio λ=(Qmix-Qgas) / (Qgas×Lamba_st)...(1)

[0014] The abnormality detection device 30 detects an abnormality in the combustion state of the combustion chamber 8 using the air-fuel ratio λ acquired from the control device 22 and the exhaust temperature Tex detected by the temperature sensor 21. As shown in the figure, the abnormality detection device 30 includes a signal acquisition unit 31, a determination unit 32, and an alarm output unit 33. Note that while FIG. 1 illustrates an example of a configuration in which the control device 22 and the abnormality detection device 30 are configured as separate entities, the abnormality detection device 30 may be incorporated into the control device 22.

[0015] The signal acquisition unit 31 acquires the air-fuel ratio λ from the control device 22 and the exhaust temperature Tex from the temperature sensor 21 . The determination unit 32 monitors the air-fuel ratio λ and the exhaust temperature Tex to determine whether or not there is an abnormality in the combustion state in the combustion chamber 8. A method for determining whether or not there is an abnormality in the combustion state will be described next with reference to FIGS.

[0016] The alarm output unit 33 outputs an alarm when the determination unit 32 determines that there is an abnormality in the combustion state. For example, the alarm output unit 33 outputs the alarm to the control device 22, a monitoring device, a display device (not shown), or the like. The alarm includes, for example, the result of the abnormality determination by the determination unit 32, the time when the abnormality was determined to exist, the level of the abnormality, and the like. For example, the alarm output unit 33 may output an alarm indicating that a level 1 abnormality has been detected when an abnormality that does not require engine 1 to be stopped is detected, or may output a level 2 alarm and stop the engine 1 when a combustion abnormality that requires engine 1 to be brought to an emergency stop is detected. An emergency stop refers to the immediate stopping of the engine 1 due to imminent danger.

[0017] (Abnormality judgment logic 1) FIG. 2 shows an example of an abnormality detection logic according to the embodiment. In a gas engine that uses a gas supply solenoid valve 20 to directly supply gas into the intake port 5, if debris or other foreign matter gets caught in the gas supply solenoid valve 20, fuel gas flows into the intake manifold 11 even when the gas supply solenoid valve 20 is closed, and excess fuel is supplied to the combustion chamber 8. This can result in abnormal combustion. During engine operation, the air-fuel ratio λ calculated in the control device 22 becomes richer as the command gas amount Qgas increases (as can be seen from equation (1), when the air-fuel ratio λ becomes richer, the value of the air-fuel ratio λ decreases). If debris or other foreign matter gets caught in the gas supply solenoid valve 20, the engine 1 rotation speed increases excessively by the amount of fuel gas flowing in, causing the exhaust temperature to rise. Then, the feedback control described above is activated, and the control device 22 reduces the command gas amount Qgas to reduce the engine 1 rotation speed. As a result, the air-fuel ratio λ becomes leaner (the value of the air-fuel ratio λ increases). Since the command gas amount Qgas is reduced, combustion in the combustion chamber 8 should be suppressed, and the exhaust gas temperature Tex should decrease. However, even if the command gas amount Qgas is reduced, if more fuel is supplied than the command gas amount Qgas due to the influence of foreign matter or the like, the exhaust gas temperature Tex will rise. The determination unit 32 monitors whether such a phenomenon occurs, and if the exhaust gas temperature Tex of the exhaust gas discharged from the cylinder 10 rises immediately (e.g., within 5 seconds) after the air-fuel ratio λ shifts to the lean side, the determination unit 32 determines that fuel is leaking from the gas supply solenoid valve 20 due to foreign matter or the like in that cylinder 10. Excessive fuel supply from the gas supply solenoid valve 20 leads to abnormal combustion. Therefore, when the determination unit 32 detects an excessive fuel supply state, it determines that the combustion state is abnormal. More specifically, the determination unit 32 calculates the exhaust temperature change amount = dTex / dt from the exhaust temperature Tex acquired from the signal acquisition unit 31 at each moment. The judgment unit 32 then monitors the air-fuel ratio λ acquired by the signal acquisition unit 31 and the calculated dTex / dt, and judges that an abnormality has occurred if the exhaust temperature change amount dTex / dt rises above a predetermined value within a predetermined time (for example, within 5 seconds) after the air-fuel ratio λ becomes lean (the value of the air-fuel ratio λ increases).

[0018] Here, the determination unit 32 determines that a level 1 abnormality has been detected if the rate of increase in the amount of change in exhaust temperature immediately after the air-fuel ratio λ has changed to the lean side is such that it is not necessary to stop the engine 1, but is increasing at an abnormal rate, and determines that a level 2 abnormality has been detected if the rate of increase is such that it is necessary to urgently stop the engine 1, and outputs this determination result to the alarm output unit 33.

[0019] This allows early detection of a condition in which abnormal combustion may occur in the combustion chamber 8. Generally, a temperature sensor is provided on the exhaust side of an engine, and the air-fuel ratio is also calculated during control. The abnormality detection logic illustrated in FIG. 2 allows for detection of abnormalities in the combustion state or early detection of abnormalities and protection without the need for additional pressure sensors or the like for each cylinder 10. Furthermore, by using the exhaust temperature change dTex / dt, abnormalities can be detected earlier than with conventional abnormality detection methods that determine an abnormality when the exhaust temperature exceeds a threshold value. Furthermore, by dividing the abnormality level into two stages, operation can be continued as long as possible while ensuring safety when an abnormality occurs, and if operation must be stopped, operation of the engine 1 can be stopped promptly.

[0020] (Abnormality judgment logic 2) FIG. 3 shows a more detailed configuration example of the anomaly detection logic according to the embodiment. The logic in the section enclosed by 32b is logic for detecting an excessive supply of fuel gas when debris suddenly gets caught in the gas supply solenoid valve 20. The deviation between the current air-fuel ratio λ and the air-fuel ratio λ a certain time ago (for example, 4 to 6 seconds ago) is compared with a predetermined deviation judgment value to determine whether the air-fuel ratio λ has suddenly become leaner than the air-fuel ratio λ from the certain time ago. If the current air-fuel ratio λ has suddenly become leaner than the air-fuel ratio λ from the certain time ago, the logic 32b outputs an ON signal from the "ONE SHOT" circuit to the OR circuit 32f for a predetermined certain time, and otherwise outputs an OFF signal.

[0021] The logic in the portion enclosed by 32a is logic for detecting an excessive supply of fuel gas when fuel gas flows in slowly from the gas supply solenoid valve 20, rather than when dust is suddenly trapped as described above. The air-fuel ratio λ obtained from the control device 22 is passed through a low-pass filter to remove sudden fluctuations and noise, and the air-fuel ratio λ after passing through the low-pass filter is compared with a predetermined threshold. The predetermined threshold is a value obtained by adding a predetermined judgment value to the target value of the air-fuel ratio λ. While the air-fuel ratio λ after passing through the low-pass filter exceeds this threshold (while a lean state continues), the logic 32a outputs an ON signal to the OR circuit 32f; otherwise, it outputs an OFF signal. When an ON signal is output from either the logic 32a or the logic 32b, the OR circuit 32f outputs an ON signal to the AND circuit 32g. When an OFF signal is output from both the logic 32a and the logic 32b, the OR circuit 32f outputs an OFF signal to the AND circuit 32g.

[0022] The logic in the portion enclosed by 32c is logic for determining whether the rate of increase in the amount of change in the exhaust temperature of each cylinder 10 exceeds a threshold value. The determination unit 32 calculates the amount of change dTex / dt in the exhaust temperature Tex. The amount of change dTex / dt in the exhaust temperature is passed through a low-pass filter to remove sudden fluctuations and noise, and the amount of change dTex / dt in the exhaust temperature after passing through the low-pass filter is compared with a predetermined threshold value (first threshold value). The predetermined threshold value is a determination value set for each cylinder 10. Because there are individual differences between cylinders 10, a determination value is set for each cylinder 10. While the amount of change dTex / dt in the exhaust temperature after passing through the low-pass filter exceeds the threshold value, the logic 32c outputs an ON signal to the AND circuit 32g, and outputs an OFF signal otherwise.

[0023] The logic in the portion enclosed by 32d is logic for halting abnormality detection because an abnormality cannot be correctly determined during transient operation in which the load changes suddenly, such as when a load is applied or removed, or when an abnormality occurs in the temperature sensor 21 used for abnormality determination or in the sensors that detect the pressure and temperature inside the intake manifold 11. An ON signal is output from logic 32d to AND circuit 32g only when there is no sensor abnormality and the engine 1 is not in a transient state, and an OFF signal is output in all other cases.

[0024] The logic in the portion enclosed by 32e is logic that does not perform abnormality detection when starting or stopping the engine 1. When the output of the engine 1 exceeds a predetermined threshold, the logic 32e outputs an ON signal to the AND circuit 32g, and in other cases, an OFF signal is output.

[0025] When logic 32c, logic 32d, logic 32e, and OR circuit 32f all output ON signals, AND circuit 32g outputs an ON signal; otherwise, it outputs an OFF signal. The determination unit 32 determines that an abnormality exists when AND circuit 32g outputs an ON signal, and determines that no abnormality exists when AND circuit 32g outputs an OFF signal. At this time, the determination unit 32 also determines whether the exhaust gas temperature change dTex / dt exceeds a predetermined threshold (second threshold) for determining whether operation should be stopped, and if so, determines that a level 2 abnormality requiring an emergency shutdown has occurred. If the change is equal to or less than the second threshold, it determines that a level 1 abnormality has occurred, allowing operation to continue.

[0026] 3, the determination unit 32 determines that there is an abnormality in the combustion state if the exhaust gas temperature change rate dTex / dt increases above a predetermined first threshold value within a certain period of time after the air-fuel ratio λ suddenly becomes lean, or while the air-fuel ratio λ continues to exceed the predetermined threshold value, except when a sensor abnormality occurs, when the engine 1 is in a transient state, or when the output of the engine 1 is equal to or lower than a threshold value. This prevents erroneous detection due to a sensor abnormality or a transient state, and enables early detection of abnormal combustion or its precursor (excessive fuel supply state). Furthermore, by setting threshold values ​​(first and second threshold values) for determining the rate of increase of the exhaust gas temperature change rate dTex / dt for each cylinder 10, it is possible to detect an abnormality in the combustion state with high accuracy.

[0027] (operation) Next, the flow of the abnormality detection process will be explained with reference to FIG. FIG. 4 is a flowchart illustrating an example of an abnormality detection process according to the embodiment. The abnormality detection device 30 repeats the following process at a predetermined control period. First, the signal acquisition unit 31 acquires the air-fuel ratio λ and the exhaust temperature Tex (step S1). The signal acquisition unit 31 outputs the acquired air-fuel ratio λ and exhaust temperature Tex to the determination unit 32. The determination unit 32 receives the air-fuel ratio λ and the exhaust temperature Tex and stores this information for a certain period of time. Next, the determination unit 32 determines whether or not there is an abnormality in the combustion state (step S2). The determination unit 32 determines whether or not there is an abnormality in the combustion state for each of the multiple cylinders 10 using the abnormality determination logic exemplified in FIG. 2 or FIG. 3. If there is an abnormality, the determination unit 32 compares the rate of increase of the exhaust temperature change amount dTex / dt with a second threshold value to determine the abnormality level. If the rate of increase exceeds the second threshold value, the determination unit 32 determines that there is a level 2 abnormality that requires an emergency stop, and if it is equal to or less than the second threshold value, the determination unit 32 determines that there is a level 1 abnormality. If there is no abnormality (step S3; No), the process proceeds to step S7. If an abnormality is detected (Step S3; Yes), the determination unit 32 outputs the determination result that an abnormality has been detected and the level of the abnormality to the alarm output unit 33. The alarm output unit 33, having received the determination result, etc., outputs an alarm according to the abnormality level. For example, if an emergency stop is required (Step S4; Yes), the alarm output unit 33 outputs an alarm to a display device or the like indicating that an abnormality requiring an emergency stop has been detected, and outputs a signal to the control device 22 instructing the control device 22 to stop the engine 1 (Step S6). Upon receiving this signal, the control device 22 stops the engine 1. If an emergency stop is not required (Step S4; No), the alarm output unit 33 outputs an alarm to a display device or the like indicating that an abnormality has been detected (Step S5). Next, the abnormality detection device 30 determines whether to end the abnormality detection process (Step S7). For example, when a command to stop the operation of the engine 1 is input by the user, the abnormality detection device 30 determines to end the abnormality detection process (Step S7; Yes) and ends the process of the flowchart of FIG. 4. If the abnormality detection process is not to be ended (step S7; No), the process from step S1 is repeatedly executed.

[0028] (effect) As described above, according to this embodiment, it is possible to detect an abnormal combustion state (for example, a level 2 abnormality) in the combustion chamber 8 or a sign thereof (fuel gas unintentionally flowing into the cylinder 10 from the gas supply solenoid valve 20) without additionally installing an expensive pressure sensor in each cylinder 10. Since the abnormality is detected based on a change in the air-fuel ratio λ and the rate of increase in exhaust temperature, it is possible to detect the abnormality earlier than the conventional method of detecting abnormal combustion based on an increase in exhaust temperature.

[0029] FIG. 5 is a schematic block diagram showing the hardware configuration of the control device according to the embodiment. The computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94. The above-described control device 22 and anomaly detection device 30 are implemented in the computer 90. The operations of each of the above-described processing units are stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, loads it into the main memory 92, and executes the above-described processing in accordance with the program. The processor 91 also allocates storage areas in the main memory 92 corresponding to each of the above-described storage units in accordance with the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

[0030] The program may be for realizing some of the functions to be performed by the computer 90. For example, the program may be combined with other programs already stored in storage or implemented in other devices to perform the functions. In other embodiments, the computer 90 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor 91 may be realized by the integrated circuit. Such an integrated circuit is also an example of a processor.

[0031] Examples of storage 93 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. Furthermore, if this program is distributed to computer 90 via a communication line, computer 90 receiving the program may load the program into main memory 92 and execute the above-described processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium. Furthermore, the program may be for implementing some of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 93.

[0032] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0033] <Additional Notes> The anomaly detection device, the anomaly detection method, and the program described in each embodiment can be understood, for example, as follows.

[0034] (1) The abnormality detection device according to the first aspect includes a judgment unit that judges the combustion state in the combustion chamber of the engine to be abnormal when the temperature of the exhaust gas discharged from the engine rises at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side. This allows for early detection of abnormalities without the need for additional sensors.

[0035] (2) A second aspect of the abnormality detection device is the abnormality detection device of (1), wherein the judgment unit judges that an abnormality has occurred when the temperature of the exhaust gas rises at a rate exceeding the rate of rise while the air-fuel ratio remains greater than a predetermined value above the target air-fuel ratio value. This allows for early detection of abnormalities without the need for additional sensors.

[0036] (3) A third aspect of the abnormality detection device is the abnormality detection device of (1) to (2), wherein the judgment unit judges that an abnormality has occurred if the temperature of the exhaust gas rises faster than the rate of rise during the first time period from the first time period when the air-fuel ratio at a first time point is greater than a predetermined value compared to the air-fuel ratio at a predetermined time period before the first time point. This allows for early detection of abnormalities without the need for additional sensors.

[0037] (4) The abnormality detection device according to the fourth aspect is an abnormality detection device according to any one of (1) to (3), further comprising an alarm output unit that notifies the user that an abnormality in the combustion state has been detected when the judgment unit judges that an abnormality has occurred. This allows for prompt notification when an abnormality is detected.

[0038] (5) The fifth aspect of the abnormality detection device is the abnormality detection device of (4), wherein the judgment unit judges that an abnormality in the combustion state has occurred when the rate of rise in the temperature of the exhaust gas exceeds a predetermined first threshold, and judges that an abnormality requiring the engine to be stopped has occurred when the rate of rise in the temperature of the exhaust gas exceeds a second threshold that is greater than the first threshold, and when the judgment unit judges that an abnormality requiring the engine to be stopped has occurred, the alarm output unit outputs an instruction signal instructing the engine to be stopped. This allows the engine to be stopped if an abnormality in the combustion state that requires the engine to be stopped urgently is detected.

[0039] (6) The sixth aspect of the abnormality detection device is an abnormality detection device according to any one of (1) to (5), wherein the judgment unit does not judge the combustion state as abnormal if there is an abnormality in the sensor that detects the temperature of the exhaust gas, if there is an abnormality in a sensor required for calculating the air-fuel ratio, if the engine operating state is in a transient state, or if the engine output is less than a predetermined value. This makes it possible to prevent erroneous detection.

[0040] (7) In the seventh aspect of the abnormality detection method, an abnormality detection device determines that the combustion state in the combustion chamber of the engine is abnormal when the temperature of the exhaust gas discharged from the engine rises at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side.

[0041] (8) A program according to an eighth aspect causes a computer to execute a process of determining that the combustion state in the combustion chamber of the engine is abnormal when the temperature of the exhaust gas discharged from the engine rises at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine changes to the lean side. [Explanation of symbols]

[0042] 1. Engine 2. Piston 3. Cylinder 4. Intake valve 5. Intake port 6. Exhaust valve 7. Exhaust port 8. Combustion chamber 9. Spark plug 10 cylinders 11. Intake manifold 12 Fuel gas supply pipe 13. Turbocharger 13t turbine 13s···Rotation axis 13c···Compressor 14. Throttle valve 15. Intake pipe 16. Intake pipe 17. Air cleaner 18···Exhaust pipe 19. Exhaust pipe 20 Gas supply solenoid valve 21 Temperature sensor 30. Anomaly detection device 31 Signal acquisition unit 32... Judgment section 33 Alarm output unit 90. Computer 91 Processor 92 Main Memory 93 Storage 94···Interface

Claims

1. a determination unit that determines that a combustion state in a combustion chamber of the engine is abnormal when a temperature of exhaust gas discharged from the engine increases at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine has changed to the lean side; An anomaly detection device comprising:

2. the determination unit determines that an abnormality has occurred when the temperature of the exhaust gas increases at a rate exceeding the rate of increase while the air-fuel ratio continues to be greater than a target air-fuel ratio by a predetermined value. The anomaly detection device according to claim 1 .

3. the determination unit determines that an abnormality has occurred if the air-fuel ratio at a first time point is greater by a predetermined value than the air-fuel ratio at a predetermined time before the first time point and the temperature of the exhaust gas increases at a rate exceeding the rate of increase during the first time point until the first time point has elapsed. The anomaly detection device according to claim 1 or 2.

4. an alarm output unit that notifies the user that an abnormality in the combustion state has been detected when the determination unit determines that an abnormality has occurred; The anomaly detection device according to claim 1 or 2, further comprising:

5. the determination unit determines that an abnormality in the combustion state has occurred when the rate of increase in the temperature of the exhaust gas exceeds a predetermined first threshold, and determines that an abnormality requiring a stop of the engine has occurred when the rate of increase in the temperature of the exhaust gas exceeds a second threshold that is greater than the first threshold, When the determination unit determines that an abnormality requiring the engine to be stopped has occurred, the warning output unit outputs an instruction signal to instruct the engine to be stopped. The anomaly detection device according to claim 4.

6. the determination unit does not perform an abnormality determination of the combustion state when an abnormality exists in a sensor that detects the temperature of the exhaust gas, when an abnormality exists in a sensor required for calculating the air-fuel ratio, when the operating state of the engine is in a transient state, or when the output of the engine is less than a predetermined value. The abnormality detection device according to claim 1 or 2.

7. The anomaly detection device If the temperature of exhaust gas discharged from the engine increases at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine has changed to the lean side, the combustion state in the combustion chamber of the engine is determined to be abnormal. Anomaly detection methods.

8. On the computer, a process of determining that a combustion state in a combustion chamber of the engine is abnormal when a temperature of exhaust gas discharged from the engine increases at a rate exceeding a predetermined rate of increase within a predetermined first time period after the air-fuel ratio of the engine has changed to a lean side; A program that executes the following.

Images