Combustion monitoring device, combustion monitoring method and combustion monitoring program

Abstract

To provide a combustion monitoring device, a combustion monitoring method and a combustion monitoring program capable of accurately detecting a sign of backfire.SOLUTION: A combustion monitoring device is for monitoring the combustion of fuel, including hydrogen fuel, which is periodically repeated in a combustion chamber of an engine, the combustion monitoring device comprising a combustion prolongation determination unit that determines whether unburned residues have occurred, where combustion continues after end reference timing at which combustion should be ended during one combustion cycle has arrived, based on at least one of a pressure, a temperature, and brightness in the combustion chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a combustion monitoring device, a combustion monitoring method, and a combustion monitoring program for monitoring combustion in a combustion chamber of a hydrogen engine. [Background technology]

[0002] When the ECU that controls the hydrogen engine disclosed in Patent Document 1 detects pre-ignition, it determines that a sign of backfire has been detected and executes control to reduce the in-cylinder temperature. Pre-ignition is a phenomenon in which combustion begins in the combustion chamber after the intake valve closes but before the hydrogen fuel is ignited, causing excessive in-cylinder pressure. Backfire is a phenomenon in which flame flows backward from the combustion chamber into the intake passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-130473 Summary of the Invention [Problem to be solved by the invention]

[0004] In the hydrogen engine described above, backfire may have already occurred before pre-ignition is detected. Therefore, if the intake valve is open when the rise in in-cylinder pressure is detected, it is determined that backfire has occurred, and control is executed to increase the combustion speed in the combustion chamber (see S101 to S103 shown in Figure 2 of Patent Document 1).

[0005] When a backfire occurs, there is a risk of damaging components of the hydrogen engine, such as the intake passage, so it is preferable to more accurately detect the signs of backfire.

[0006] An object of the present disclosure is to provide a combustion monitoring device, a combustion monitoring method, and a combustion monitoring program that can accurately detect signs of backfire. [Means for solving the problem]

[0007] In accordance with at least one embodiment of the present disclosure, a combustion monitoring device includes: 1. A combustion monitoring device for monitoring cyclically repeated combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, comprising: The device is provided with a combustion prolongation determination unit for determining whether any unburned residue has occurred, in which the combustion continues even after the reference timing for the end of the combustion during one combustion cycle has arrived, based on at least one of the pressure, temperature, and brightness in the combustion chamber.

[0008] A combustion monitoring method according to one embodiment of the present disclosure includes: 1. A combustion monitoring method for monitoring cyclically repeated combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, comprising: Whether or not any unburned residue has occurred in which the combustion continues even after the reference timing for the end of the combustion during one combustion cycle has arrived is determined based on at least one of the pressure, temperature, and brightness in the combustion chamber.

[0009] A combustion monitoring program according to an embodiment of the present disclosure includes: 1. A combustion monitoring program for monitoring combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, the program comprising: To the computer Whether or not any unburned residue has occurred in which the combustion continues even after the reference timing for the end of the combustion during one combustion cycle has arrived is determined based on at least one of the pressure, temperature, and brightness in the combustion chamber. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a combustion monitoring device, a combustion monitoring method, and a combustion monitoring program that can accurately detect signs of backfire. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of an engine according to an embodiment; [Figure 2] FIG. 3 is a schematic diagram showing the change in pressure in the combustion chamber over time in correspondence with one combustion cycle. [Figure 3] 1 is a schematic diagram of an ember that can induce a backfire. [Figure 4] 1 is a schematic diagram of a combustion monitoring device according to a first embodiment. [Figure 5] FIG. 1 is a schematic diagram showing the change in heat release rate over time. [Figure 6] 3 is a flowchart of a combustion monitoring method according to the first embodiment. [Figure 7] FIG. 5 is a schematic diagram of a combustion monitoring device according to a second embodiment. [Figure 8] FIG. 10 is a schematic diagram showing the change over time in the integrated value of the heat release rate. [Figure 9] 6 is a flowchart of a combustion monitoring method according to a second embodiment. [Figure 10] FIG. 10 is a schematic diagram of a combustion monitoring device according to a third embodiment. [Figure 11] FIG. 4 is a schematic diagram showing changes in in-cylinder pressure over time. [Figure 12] 10 is a flowchart of a combustion monitoring method according to a third embodiment. [Figure 13] FIG. 10 is a schematic diagram of a combustion monitoring device according to a fourth embodiment. [Figure 14] 10 is a flowchart of a combustion monitoring method according to a fourth embodiment. [Figure 15] FIG. 10 is a schematic view of a combustion monitoring device according to a fifth embodiment. [Figure 16] 10 is a flowchart of a combustion monitoring method according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," or "have" one element are not exclusive expressions that exclude the presence of other elements. Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

[0013] <Engine 1 Overview> FIG. 1 is a schematic diagram of an engine 1 according to one embodiment of the present disclosure. The engine 1 is a four-stroke hydrogen engine configured to use a fuel (fuel gas) containing hydrogen fuel. In the combustion chamber C of the engine 1, either the hydrogen fuel alone or a mixture of hydrogen fuel and another fuel may be burned. For example, gasoline may be used as the other fuel.

[0014] The engine 1 includes a cylinder 6, a piston 7, and a cylinder head 5 that define a combustion chamber C, a crankshaft 8 that is connected to the piston 7 via a connecting rod 21, and a crank sensor 9 that detects the crank angle, which is the phase of the crankshaft 8. In addition, as an example, a pressure sensor 2 that measures the pressure in the combustion chamber C is provided in the cylinder 6. Hereinafter, the pressure in the combustion chamber C may be referred to as the "in-cylinder pressure."

[0015] The engine 1 also includes an intake valve 13 for opening and closing an intake port 11 provided in the cylinder head 5, an intake passage 17 connected to the intake port 11, a fuel injection device 15 for injecting fuel into the intake passage 17, an ignition device 19 provided in the cylinder head 5, an exhaust valve 14 for opening and closing an exhaust port 12 provided in the cylinder head 5, and an exhaust passage 18 connected to the exhaust port 12.

[0016] One combustion cycle E of the engine 1 will be described with reference to Figure 2. The graph in Figure 2 shows the relationship between the pressure in the combustion chamber C and the crank angle when normal combustion occurs in the combustion chamber C. The vertical axis of the graph indicates the in-cylinder pressure, which is a measurement value obtained by the pressure sensor 2. The horizontal axis of the graph indicates the after top dead center (ATDC) angle, which is a measurement value obtained by the crank sensor 9. The ATDC angle is a crank angle expressed with the crank angle when the piston 7 reaches top dead center as 0°.

[0017] While the engine 1 is operating, one combustion cycle E is continuously repeated. One combustion cycle E includes an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. During the intake stroke, the intake valve 13 opens the intake port 11, and fuel injected from the fuel injector 15 is drawn into the combustion chamber C together with air. After the intake end timing (θf) arrives, at which the intake valve 13 closes the intake port 11, the piston 7 rises from bottom dead center and the compression stroke begins. At this time, the pressure inside the cylinder rises.

[0018] Thereafter, the ignition device 19 is activated near the timing when the piston 7 reaches top dead center, and the combustion stroke begins. After the pressure inside the cylinder peaks, the combustion stroke ends. The exhaust valve 14 opens the exhaust port 12 at the exhaust start timing (θe). As a result, the combustion gas Bg (see FIG. 3) generated by combustion in the combustion chamber C is discharged into the exhaust passage 18.

[0019] FIG. 3 is a schematic diagram showing residual combustion in combustion chamber C that may trigger a backfire. Residual combustion is a phenomenon in which combustion continues after the reference end timing for the end of fuel combustion during one combustion cycle E has arrived. Residual combustion refers to a prolonged period of combustion occurring in combustion chamber C, and does not occur in the normal combustion referred to herein. Also, by way of example only, the reference end timing may be greater than or equal to 20° ATDC and less than or equal to 90° ATDC, or more specifically, greater than or equal to 35° ATDC and less than or equal to 45° ATDC. The reference end timing may vary depending on the combustion conditions in combustion chamber C. For example, the reference end timing may vary depending on whether the combustion occurring in combustion chamber C is mono-fuel combustion or co-fuel combustion of hydrogen fuel and another fuel.

[0020] If unburned fuel remains in one of the continuously repeated combustion cycles E, high-temperature combustion gas Bg will remain in the combustion chamber C when the intake valve 13 opens the intake port 11 in the next combustion cycle E. When the hydrogen fuel that is allowed to pass through the intake port 11 by the intake valve 13 mixes with the high-temperature combustion gas Bg (arrow F in Figure 3), the hydrogen fuel may ignite before being ignited by the ignition device 19. This ignition may lead to a backfire, in which flame flows back into the intake passage 17.

[0021] The inventors of the present application have focused on the phenomenon that unburned fuel can induce backfire, and have devised a combustion monitoring device 30 shown in Fig. 1. The combustion monitoring device 30 is a device for monitoring the combustion of fuel containing hydrogen fuel that is periodically repeated in the combustion chamber C, and is equipped with a combustion prolongation determination unit 37 for determining whether unburned fuel has occurred.

[0022] The combustion prolongation determination unit 37 determines whether unburned fuel remains have occurred based on the pressure inside the cylinder, the temperature in the combustion chamber C, or the brightness in the combustion chamber C. When unburned fuel remains have occurred, all of these three specific values ​​become high, making it possible to determine whether unburned fuel remains have occurred. Therefore, with the above configuration, a combustion monitoring device 30 that can detect signs of backfire is realized. Details of determining whether unburned fuel remains have occurred using any of the three characteristic values ​​described above will be described later in the first, second, third, fourth, and fifth embodiments.

[0023] The occurrence of unburned residue does not necessarily mean that a backfire will occur in the next combustion cycle E. In this application, the terms "normal combustion" and "combustion that generates unburned residue" are used differently, but this is merely for convenience.

[0024] 1, the outline of the combustion monitoring device 30 will be continued. The combustion monitoring device 30 may further include a combustion control unit 39. When the combustion prolongation determination unit 37 determines that unburned fuel has been generated, the combustion control unit 39 executes control to lower the temperature in the combustion chamber C.

[0025] As a more specific example, the combustion control unit 39 controls the fuel injector 15 to retard the fuel injection timing or reduce the fuel injection amount. Retarding the fuel injection amount means delaying the fuel injection timing in the next combustion cycle E compared to the fuel injection timing in the combustion cycle E in which it is determined that unburned residue has occurred. The delayed timing promotes mixing of air and high-temperature combustion gas in the combustion chamber C, and the temperature of the combustion chamber C at the time the fuel flows into the combustion chamber C decreases. Reducing the fuel injection amount means reducing the fuel injection amount in the next combustion cycle E compared to the fuel injection amount in the combustion cycle E in which it is determined that unburned residue has occurred. The reduced fuel injection amount reduces the combustion heat generated in the combustion chamber C, and the temperature of the combustion chamber C decreases.

[0026] According to the above configuration, when the combustion prolongation determination unit 37 determines that unburned fuel has occurred, the combustion control unit 39 controls the fuel injector 15 to at least one of retarding the fuel injection timing and reducing the fuel injection amount. This reduces the temperature of the combustion chamber C in the next combustion cycle E, making it possible to suppress backfire in the next combustion cycle E.

[0027] When the combustion control unit 39 retards the fuel injection timing, it is preferable that the fuel injection amount be maintained between the two combustion cycles E. This makes it possible to suppress a decrease in the output of the engine 1 in the next combustion cycle E, and to stabilize the output of the engine 1.

[0028] The control by the combustion control unit 39 is not limited to the above. For example, the combustion control unit 39 may change the mixture ratio of hydrogen fuel and other fuel injected into the intake passage 17 in the next combustion cycle E. More specifically, the combustion control unit 39 may execute control to reduce the proportion of hydrogen fuel. Alternatively, the combustion control unit 39 may execute control to inject water into the intake port 11 in the next combustion cycle E. This control is achieved by the combustion control unit 39 controlling a water injector (not shown) provided in the intake port 11. As another example, the combustion control unit 39 may execute control to increase the amount of air taken into the combustion chamber C in the intake stroke of the next combustion cycle E.

[0029] As described above, the combustion prolongation determination unit 37 determines whether unburned residues have occurred by using at least one characteristic value of the in-cylinder pressure, the temperature in the combustion chamber C, or the brightness in the combustion chamber C. Below, the first to third embodiments that use the in-cylinder pressure, the fourth embodiment that uses the temperature, and the fifth embodiment that uses the brightness will be described in detail in this order. Furthermore, in the following description, combustion that causes unburned residues to occur during one combustion cycle E may be referred to as "peculiar combustion."

[0030] First Embodiment A combustion monitoring device 30A (30) according to the first embodiment will be described with reference to FIGS. 4 to 6. In the first embodiment, the presence or absence of unburned fuel is determined based on the heat release rate in the combustion chamber C, which is determined using the in-cylinder pressure. The heat release rate is the amount of change in heat generated by combustion in the combustion chamber C per unit crank angle, and is a parameter that correlates with the in-cylinder pressure, the volume of the combustion chamber C, and the like, as is well known. The principle of determining the presence or absence of unburned fuel based on the heat release rate is as follows.

[0031] 5 is a schematic graph showing the change over time in the heat release rate in combustion chamber C, divided into cases where normal combustion occurs and where peculiar combustion occurs. The horizontal axis of the graph represents the ATDC angle, θs represents the reference end timing, and θe represents the exhaust start timing when the exhaust valve 14 opens the exhaust port 12.

[0032] As can be seen from the graph, when normal combustion occurs during one combustion cycle E, the heat release rate peaks before the end reference timing (θs) and is equal to or less than 0 kJ between the end reference timing and the exhaust start timing (θe). The heat release rate falls below 0 kJ because a small amount of heat is released in the combustion chamber C between the end reference timing and the exhaust start timing. Note that the end reference timing in the graph is 40° ATDC, but as mentioned above, the end reference timing is not limited to this crank angle.

[0033] On the other hand, when peculiar combustion occurs, the heat release rate does not reach a significant peak, but remains greater than 0 as combustion continues from the reference end timing (θs) to the exhaust start timing (θe). Therefore, it is possible to determine whether unburned residues have occurred based on the heat release rate within the first specified period, which includes the period from the reference end timing to the exhaust start timing (dimension T in FIG. 5).

[0034] As a more specific first example, if the heat release rate at a single specified timing within a first specified period is a positive value, it can be determined that unburned fuel has been generated. The specified timing may be any timing within the first specified period, but is preferably a timing that is some time after the end reference timing. This is because even when normal combustion occurs, the actual timing at which combustion ends varies for each combustion cycle E, and therefore the heat release rate at the end reference timing can be a positive value.

[0035] Therefore, the single specified timing according to the first example is preferably after the intermediate timing (θm) that is after the end reference timing and before the exhaust start timing. In other words, the single specified timing is preferably after the intermediate timing and before the exhaust start timing.

[0036] For example, the ATDC angle of the intermediate timing may be 20° ATDC or more greater than the end reference timing. As a mere example, the illustrated intermediate timing (θm) is 90° ATDC. The specified timing may also coincide with the exhaust start timing. That is, it may be determined that unburned residue has occurred when the heat release rate at the exhaust start timing is a positive value.

[0037] As a more specific second example, the heat release rate may be obtained at each of a plurality of specified timings included in the first specified period, and if the average value of the plurality of heat release rates is a positive value, it may be determined that unburned residue has occurred.

[0038] 4 includes several components based on the above-described determination principle. Specifically, the combustion monitoring device 30A includes a pressure acquisition unit 31A (31) that acquires the in-cylinder pressure within a first specified period, and a heat release rate acquisition unit 32A (32) that acquires the heat release rate in the combustion chamber C within the first specified period based on the in-cylinder pressure acquired by the pressure acquisition unit 31A.

[0039] The pressure acquisition unit 31A acquires the in-cylinder pressure within a first specified period based on the measurement results of the crank sensor 9 and the pressure sensor 2. The pressure acquisition unit 31A may acquire the in-cylinder pressure continuously over the first specified period, or may acquire the in-cylinder pressure only when a specified timing within the first specified period arrives. In this example, the pressure acquisition unit 31A acquires the in-cylinder pressure at at least one specified timing after the intermediate timing (θm) and before the exhaust start timing (θe).

[0040] The heat release rate acquisition unit 32A calculates a specified heat release rate, which is the heat release rate at a specified timing, based on the in-cylinder pressure acquired by the pressure acquisition unit 31A and a known calculation formula. The heat release rate acquisition unit 32A may acquire the heat release rate over a first specified period, or may acquire the specified heat release rate only at a specified timing within the first specified period. In this example, the heat release rate acquisition unit 32A acquires the heat release rate at at least one specified timing that is after the intermediate timing (θm) and before the exhaust start timing (θe).

[0041] When the first example described above is adopted, the at least one specified timing is a single timing, and the heat release rate acquisition unit 32A acquires the specified heat release rate at the single specified timing. On the other hand, when the second example is adopted, the at least one specified timing is a plurality of timings, and the heat release rate acquisition unit 32A acquires the average value of the plurality of specified heat release rates corresponding to the plurality of specified timings.

[0042] The combustion prolongation determination unit 37A (37) according to the first embodiment determines whether unburned fuel has occurred based on the in-cylinder pressure acquired by the pressure acquisition unit 31A, and more specifically, determines whether unburned fuel has occurred based on the heat release rate acquired by the heat release rate acquisition unit 32A.

[0043] In the first example described above, if the single specified heat release rate acquired by the heat release rate acquisition unit 32A is a positive value, the combustion prolongation determination unit 37A determines that unburned residues have occurred. If the single specified heat release rate is 0 or less, the combustion prolongation determination unit 37A determines that unburned residues have occurred. In the second example described above, if the average value of the multiple specified heat release rates acquired by the heat release rate acquisition unit 32A is a positive value, the combustion prolongation determination unit 37A determines that unburned residues have occurred. If the average value of the specified heat release rates is 0 or less, the combustion prolongation determination unit 37A determines that unburned residues have occurred.

[0044] According to the above configuration, the combustion prolongation determination unit 37A determines whether unburned fuel remains have occurred based on the in-cylinder pressure acquired by the pressure acquisition unit 31A, and more specifically, the heat release rate acquired by the heat release rate acquisition unit 32A. The in-cylinder pressure used for the determination can be determined from the pressure sensor 2 for measuring in-cylinder pressure, which has been conventionally installed. Therefore, the cost of the configuration for determining whether unburned fuel remains have occurred can be reduced. Furthermore, the heat release rate, which correlates with the in-cylinder pressure, is a parameter that comprehensively indicates the combustion status in the combustion chamber C. Therefore, by using the heat release rate, the combustion prolongation determination unit 37A can accurately determine whether unburned fuel remains have occurred. Therefore, the combustion monitoring device 30A can accurately detect signs of backfire.

[0045] Furthermore, since the heat release rate acquisition unit 32A acquires at least one specified heat release rate after the intermediate timing and before the exhaust start timing, even if the actual end timing of normal combustion varies, the specified heat release rate during normal combustion is unlikely to be a positive value. Therefore, the combustion prolongation determination unit 37A can avoid erroneously determining that unburned residue has occurred when normal combustion is occurring.

[0046] Furthermore, when the first specific example described above is adopted, it is possible to determine whether unburned residue has occurred simply by determining whether the specified heat release rate at a single specified timing is a positive value, thereby simplifying the determination process executed by the combustion prolongation determination unit 37A.

[0047] Furthermore, when the second specific example described above is adopted, even if any of the multiple specified heat release rates accidentally becomes a negative value due to, for example, a measurement error of the pressure sensor 2, it can be determined that unburned fuel remains as long as the average value is a positive value. Therefore, the combustion prolongation determination unit 37A can accurately determine whether unburned fuel remains remain.

[0048] 6 is a flowchart showing a control process (combustion monitoring method) for determining unburned residue according to the first embodiment. This control process is executed by the processor of the combustion monitoring device 30A (30) reading out a combustion monitoring program stored in the memory of the combustion monitoring device 30A. Hereinafter, "step" may be abbreviated as "S."

[0049] First, the processor acquires the in-cylinder pressure within a first specified period based on the detection results of the pressure sensor 2 and the crank sensor 9 (S11). The processor that executes S11 is an example of the pressure acquisition unit 31A. Next, the processor acquires a specified heat release rate based on the in-cylinder pressure acquired in S11 (S13). The processor that executes S13 is an example of the heat release rate acquisition unit 32A.

[0050] Next, the processor determines whether unburned fuel remains have occurred based on the specified heat release rate acquired in S13. The processor that executes S15 is an example of the combustion prolongation determination unit 37A. If it is determined that unburned fuel remains have occurred (S15: NO), the processor ends this control process. If it is determined that unburned fuel remains have occurred (S15: YES), the processor executes control process to reduce the in-cylinder temperature (S20). The processor that executes S20 is an example of the combustion control unit 39. Then, the processor ends this control process.

[0051] Second Embodiment A combustion monitoring device 30B (30) according to the second embodiment will be described with reference to FIGS. 7 to 9. In these drawings, the same reference numerals are used for the components described in the first embodiment, and their description may be omitted or simplified below. In the second embodiment, the presence or absence of unburned fuel is determined based on the integrated value of the heat release rate in the combustion chamber C, which is determined using the in-cylinder pressure. The integrated value of the heat release rate is a cumulative value of the heat release rate as an instantaneous value continuously acquired over a predetermined period of time. The principle of determining the presence or absence of unburned fuel based on the integrated value of the heat release rate is as follows.

[0052] Figure 8 is a schematic graph showing the change over time in the integrated value of the heat release rate in combustion chamber C, divided into cases where normal combustion occurs and where peculiar combustion occurs. The horizontal axis of the graph represents the ATDC angle, θs represents the reference end timing, and θe represents the exhaust start timing. The dimension T in Figure 8 is the same as the dimension T in Figure 5.

[0053] As can be seen from the graph, when normal combustion occurs during one combustion cycle E, the integrated value of the heat release rate increases rapidly from 0° ATDC to the reference end timing (θs), and then remains constant or decreases slightly after approximately 90° ATDC. The decrease in the integrated value of the heat release rate is due to the slight heat release that occurs in combustion chamber C after normal combustion ends.

[0054] On the other hand, when peculiar combustion occurs, the integrated value of the heat release rate continues to increase from 0° ATDC to the exhaust start timing (θe). This is because combustion in the combustion chamber C continues during the first specified period, and heat due to combustion continues to be generated. Therefore, if the integrated value of the heat release rate is positive during the first specified period, including the period indicated by the dimension T, from the first timing (θ1) after the end reference timing (θs) to the second timing (θ2) after the first timing but before the exhaust start timing, it can be assumed that unburned fuel has been generated. Note that, as a mere example, the first timing (θ1) is 90° ATDC, and the second timing (θ2) is the exhaust start timing (θe). However, the first timing and the second timing may be any timing within the first specified period.

[0055] Various methods can be used to determine whether the integrated value of the heat release rate from the first timing to the second timing is positive. For example, the heat release rate from the first timing to the second timing may be acquired, and it may be determined whether the integrated value of the heat release rate is positive.

[0056] Alternatively, a first integrated value, which is an integrated value of the heat release rate from the advance timing (θa) before the first timing to the first timing, may be compared with a second integrated value, which is an integrated value of the heat release rate from the advance timing to the second timing. Specifically, it may be determined that unburned residue has occurred when the following formula (1) is established: S1≦S2×A (1) In formula (1), S1 is the first integrated value, S2 is the second integrated value, and A is a positive value equal to or less than 1. The value of A is preferably a positive value less than 1, and is preferably, for example, equal to or greater than 0.9 and less than 1.

[0057] The above-mentioned advance timing is a timing after the intake end timing (θf in FIG. 2) when the intake valve 13 closes the intake port 11 and before the first timing in one combustion cycle E. Although this is merely an example, the advance timing (θa) may be 0° ATDC.

[0058] 7 includes several components based on the above-described determination principle. Specifically, the combustion monitoring device 30B includes a pressure acquisition unit 31B (31), a heat release rate acquisition unit 32B (32), and a combustion prolongation determination unit 37B (37).

[0059] The pressure acquiring unit 31B acquires the in-cylinder pressure within a first specified period based on the measurement results of the crank sensor 9 and the pressure sensor 2. More specifically, the pressure acquiring unit 31B continuously acquires the in-cylinder pressure based on the measurement results of the pressure sensor 2 from the advance timing to the second timing. The pressure acquiring unit 31B associates the acquired in-cylinder pressure with the crank angle acquired from the measurement results of the crank sensor 9.

[0060] The heat release rate acquisition unit 32B acquires a first integrated value and a second integrated value based on the in-cylinder pressure and crank angle acquired by the pressure acquisition unit 31B. The combustion prolongation determination unit 37B applies the first integrated value and the second integrated value acquired by the heat release rate acquisition unit 32B to the above-mentioned formula (1). The combustion prolongation determination unit 37B determines that unburned fuel remains have occurred if formula (1) is satisfied, and determines that unburned fuel remains have not occurred if formula (1) is not satisfied.

[0061] The pressure acquisition unit 31B may acquire the in-cylinder pressure only from the first timing to the second timing. In this case, the heat release rate acquisition unit 32B directly acquires the integrated value of the heat release rate from the first timing to the second timing. If the integrated value is a positive value, the combustion prolongation determination unit 37B determines that unburned fuel has occurred.

[0062] As described above, if no unburned residue is generated, the integrated value of the heat release rate decreases between the first timing and the second timing. Therefore, formula (1) does not hold. On the other hand, if unburned residue is generated, the integrated value of the heat release rate increases, and formula (1) holds. Therefore, with the above configuration, the combustion prolongation determination unit 37B can accurately determine whether unburned residue has been generated based on the integrated value of the heat release rate.

[0063] It is preferable that the value of A in equation (1) be a positive value less than 1. This is because even if the heat release rate temporarily decreases due to an accidental factor such as a measurement error in pressure sensor 2 despite the occurrence of unburned residue between the first and second timings, the magnitude relationship between S1 and S2×A remains unchanged. This makes it possible to accurately determine that unburned residue has occurred.

[0064] 9 is a flowchart showing a control process for determining the unburned residue according to the second embodiment. In the following, explanations of steps that overlap with the control process according to the first embodiment (see FIG. 6) may be omitted.

[0065] The processor continuously acquires the in-cylinder pressure from the advance timing to the second timing based on the measurement results of the pressure sensor 2 and the crank sensor 9 (S11A). The processor that executes S11A is an example of the pressure acquisition unit 31B.

[0066] Next, the processor acquires a first integrated value and a second integrated value as integrated values ​​of the heat release rate based on the in-cylinder pressure acquired in S11A (S13A). The processor that executes S13A is an example of the heat release rate acquisition unit 32B.

[0067] Next, the processor applies the first and second integrated values ​​acquired in S13A to formula (1) to determine whether any unburned material remains (S15A). If formula (1) is not satisfied, the processor determines that no unburned material remains (S15A: NO) and terminates the control process. On the other hand, if formula (1) is satisfied, the processor determines that any unburned material remains (S15A: YES), executes S20, and then terminates the control process.

[0068] <Third embodiment> A combustion monitoring device 30C (30) according to the third embodiment will be described with reference to FIGS. 10 to 12. In these drawings, the same components as those described in the first embodiment are given the same reference numerals, and their description may be omitted or simplified below. In the third embodiment, the presence or absence of unburned residue is determined based on the pressure inside the cylinder. The determination principle is as follows.

[0069] FIG. 11 is a schematic graph showing the change over time in the in-cylinder pressure determined from the measurement results of the pressure sensor 2, divided into cases where normal combustion occurs and cases where anomalous combustion occurs. The thick solid line indicates the change in the in-cylinder pressure (measured value) when normal combustion occurs, and the solid line of normal thickness indicates the change in the in-cylinder pressure (measured value) when anomalous combustion occurs. The horizontal axis of the graph is the ATDC angle. θ1 indicates the first timing, and θ2 indicates the second timing. These timings are as described in the second embodiment. In the following description, the in-cylinder pressure measured at the first timing may be referred to as the "first in-cylinder pressure," and the in-cylinder pressure measured at the second timing may be referred to as the "second in-cylinder pressure."

[0070] The dashed lines B1 and B2 in the graph indicate the ideal pressure in the combustion chamber C that is expected to be confirmed as a measured value at the second timing based on the pressure in the first cylinder. The thick dashed line B1 indicates the pressure in the first cylinder (P A ) is the ideal pressure expected based on the normal thickness dashed line B2. The normal thickness dashed line B2 is the pressure inside the first cylinder (P B ) is the ideal pressure expected based on

[0071] The ideal pressure can be calculated using the following formula (A). Pi = P1 × (V1 / V2) γ (A) In formula (A), Pi is the ideal pressure, which corresponds to the dashed lines B1 and B2 shown in the graph. P1 is the first cylinder pressure, which corresponds to the above P A ,P BV1 is the volume of the combustion chamber C at the first timing, and V2 is the volume of the combustion chamber C at the second timing. V1 is smaller than V2. γ is the specific heat ratio of the combustion gas Bg. Hereinafter, V1 and V2 may be referred to as the "first volume" and the "second volume", respectively.

[0072] P1 is measured by the pressure sensor 2, and V1 and V2 can be calculated by determining the vertical position of the piston 7 based on the crank angle. Note that, in the actual combustion stroke included in one combustion cycle E, ideal adiabatic expansion does not occur, so a correction that takes this into account may be added to formula (A) as appropriate.

[0073] As can be seen from the graph, when normal combustion occurs, the second cylinder pressure (the cylinder pressure corresponding to point N1) determined by measurement roughly coincides with the ideal pressure (the cylinder pressure corresponding to dashed line B1) determined based on equation (A). On the other hand, when peculiar combustion occurs, the second cylinder pressure (the cylinder pressure corresponding to point N2) determined by measurement is greater than the ideal pressure (the cylinder pressure corresponding to dashed line B2). This is because heat generation associated with combustion continues after the first timing, and even if the volume of combustion chamber C increases, the heat generation prevents the cylinder pressure from decreasing.

[0074] Therefore, if the following formula (2) is established, it can be determined that unburned residue has occurred. Pr>Pi×B (2) In equation (2), Pr is the second cylinder pressure obtained by measurement by pressure sensor 2, Pi is as described above, and B is a value greater than or equal to 1. The value of B is preferably greater than 1, and may be, for example, greater than 1 and less than or equal to 1.05.

[0075] 10 illustrates a combustion monitoring device 30C (30) according to the third embodiment, which includes several components based on the above-described determination principle. Specifically, the combustion monitoring device 30C includes a pressure acquisition unit 31C (31), a volume acquisition unit 33, an ideal pressure acquisition unit 34, and a combustion prolongation determination unit 37C (37).

[0076] The pressure acquisition unit 31C acquires the first cylinder pressure and the second cylinder pressure based on the measurement results of the pressure sensor 2 and the crank sensor 9. The volume acquisition unit 33 acquires the first volume and the second volume by referring to fixed values ​​stored in a memory (not shown) of the combustion monitoring device 30C. The ideal pressure acquisition unit 34 acquires the ideal pressure (Pi) by applying the first volume and second volume determined by the volume acquisition unit 33 and the first cylinder pressure determined by the pressure acquisition unit 31C to equation (A).

[0077] The combustion prolongation determination unit 37C determines that unburned fuel has occurred when the formula (2) is satisfied for the second cylinder pressure (Pr) as a measured value acquired by the pressure acquisition unit 31C and the ideal pressure (Pi) acquired by the ideal pressure acquisition unit 34. When the formula (2) is not satisfied, the combustion prolongation determination unit 37C determines that unburned fuel has not occurred.

[0078] When normal combustion occurs, the combustion gas Bg undergoes a change close to adiabatic expansion between the first and second timings, so Pr is substantially equal to Pi. Therefore, equation (2) does not hold. On the other hand, when unburned residues are generated, heat is generated in the combustion chamber C between the first and second timings, so Pr is higher than Pi, and equation (2) holds. Therefore, with the above configuration, the combustion prolongation determination unit 37C can determine whether unburned residues have occurred. Note that in an embodiment in which the value of B is greater than 1, even if Pr becomes slightly larger than Pi due to a measurement error of the pressure sensor 2 or the like, even though no unburned residues have occurred, the magnitude relationship between Pr and Pi × B does not change. This makes it possible to avoid erroneously determining that unburned residues have occurred.

[0079] 12 is a flowchart showing a control process for determining the unburned residue according to the third embodiment. In the following, explanations of steps that overlap with the control process according to the first embodiment (see FIG. 6) may be omitted.

[0080] The processor acquires the first and second cylinder pressures based on the measurement results of the pressure sensor 2 and the crank sensor 9 (S11B). The processor executing S11B is an example of the pressure acquisition unit 31C. Next, the processor acquires the first and second volumes (S12). The processor executing S12 is an example of the volume acquisition unit 33. Next, the processor acquires the ideal pressure based on the first cylinder pressure acquired in S11B and the first and second volumes acquired in S12 (S14). The processor executing S14 is an example of the ideal pressure acquisition unit 34. Next, the processor determines whether or not unburned fuel remains have occurred based on the second cylinder pressure acquired in S11B and the ideal pressure acquired in S14 (S15B). If equation (2) is not established, the processor determines that unburned fuel remains have occurred (S15B: NO). On the other hand, if equation (2) is established, the processor determines that unburned fuel remains have occurred (S15B: YES). The processor that executes S15B is an example of the combustion prolongation determination unit 37C.

[0081] <Fourth embodiment> A combustion monitoring device 30D (30) according to a fourth embodiment will be described with reference to Figures 13 and 14. In these figures, the same reference numerals are used for the components described in the first embodiment, and their description may be omitted or simplified below. In the fourth embodiment, the presence or absence of unburned residue is determined based on the temperature of the combustion chamber C (hereinafter, sometimes referred to as "in-cylinder temperature"). When unburned residue is generated, the in-cylinder temperature after the end reference timing is higher than the in-cylinder temperature when normal combustion occurs, so the presence or absence of unburned residue can be determined.

[0082] As shown in FIG. 13, the combustion monitoring device 30D (30) includes a temperature acquisition unit 41 and a combustion prolongation determination unit 37D (37). The temperature acquisition unit 41 acquires the in-cylinder temperature within a second specified period, which includes the period from the end reference timing to the intake start timing when the intake valve 13 opens the intake port 11. If the end reference timing is included in one combustion cycle E in FIG. 2, the intake start timing occurs after the exhaust stroke shown in FIG. 2. The in-cylinder temperature is measured using a non-contact temperature sensor 3 provided in the engine 1. The temperature sensor 3 may be a thermographic camera configured to measure the temperature of the outer surface of the cylinder 6. In this case, the temperature of the outer surface is considered to be the same as the in-cylinder temperature. Alternatively, if a viewing window is provided on the side wall of the cylinder 6, the thermographic camera can more directly measure the in-cylinder temperature. The temperature acquisition unit 41 determines whether the temperature measurement timing has arrived based on the measurement result of the crank sensor 9.

[0083] The combustion prolongation determination unit 37D determines that unburned fuel has occurred when the temperature acquired by the temperature acquisition unit 41 exceeds the temperature threshold. The temperature threshold is a fixed value stored in the memory of the combustion monitoring device 30D. If the acquired temperature is equal to or lower than the temperature threshold, the combustion prolongation determination unit 37D determines that unburned fuel has not occurred. If unburned fuel has occurred, the temperature at a predetermined timing within the second specified period exceeds the temperature threshold. Therefore, the combustion prolongation determination unit 37D can determine whether unburned fuel has occurred.

[0084] 14 is a flowchart showing a control process for determining the unburned residue according to the fourth embodiment. In the following, explanations of steps that overlap with the control process according to the first embodiment (see FIG. 6) may be omitted.

[0085] The processor acquires the in-cylinder temperature at a predetermined timing within the second specified period (S9). The processor that executes S9 is an example of temperature acquisition unit 41. Next, the processor determines whether unburned fuel remains (S15C). The processor that executes S15C is an example of combustion prolongation determination unit 37D.

[0086] Fifth Embodiment A combustion monitoring device 30E (30) according to a fifth embodiment will be described with reference to Figures 15 and 16. In these drawings, the same reference numerals are used for the components described in the first embodiment, and their description may be omitted or simplified below. In the fifth embodiment, the presence or absence of unburned fuel is determined based on the brightness of the combustion chamber C (hereinafter, sometimes referred to as "brightness inside the cylinder"). When unburned fuel is generated, the brightness inside the cylinder after the end reference timing is higher than the brightness inside the cylinder when normal combustion occurs, so the presence or absence of unburned fuel can be determined.

[0087] As shown in FIG. 15, the combustion monitoring device 30E (30) includes a light acquisition unit 42 and a combustion prolongation determination unit 37E. The light acquisition unit 42 acquires the brightness inside the cylinder during the second specified period described above. The brightness inside the cylinder is measured using an optical sensor 4 provided in the engine 1. For example, the optical sensor 4 is a camera, and captures an image of the combustion chamber C through a viewing window disposed in the side wall of the cylinder 6. This allows the brightness (e.g., luminance) of the combustion chamber C to be measured. The optical sensor 4 determines whether the timing for measuring the brightness inside the cylinder has arrived based on the detection result of the crank sensor 9.

[0088] The combustion prolongation determination unit 37E determines that unburned fuel has occurred when the brightness inside the cylinder acquired by the light acquisition unit 42 exceeds the light threshold. The light threshold is a fixed value stored in the memory of the combustion monitoring device 30E. If the acquired brightness inside the cylinder is equal to or less than the light threshold, the combustion prolongation determination unit 37E determines that unburned fuel has not occurred. If unburned fuel has occurred, the brightness inside the cylinder at a predetermined timing within the second specified period exceeds the light threshold. Therefore, the combustion prolongation determination unit 37E can determine whether unburned fuel has occurred.

[0089] 16 is a flowchart showing a control process for determining unburned residue according to the fifth embodiment. In the following, explanations of steps that overlap with the control process according to the first embodiment (see FIG. 6) may be omitted.

[0090] The processor acquires the brightness inside the cylinder at a predetermined timing within the second specified period (S7). The processor that executes S7 is an example of the light acquisition unit 42. Next, the processor determines whether unburned remains have occurred based on the brightness inside the cylinder acquired in S7 (S15D). The processor that executes S15D is an example of the combustion prolongation determination unit 37E.

[0091] <Other> The combustion monitoring devices 30A, 30B, 30C, 30D, and 30E (30) described above are configured by a computer and include a processor, a memory (storage medium), and an external communication interface. The processor may be a CPU, a GPU, an MPU, a DSP, or a combination thereof. In other embodiments, the processor may be implemented by an integrated circuit such as a PLD, an ASIC, an FPGA, or an MCU. The memory is configured to temporarily or non-temporarily store various data and is implemented by at least one of a RAM, a ROM, and a flash memory, for example. The processor executes various control processes according to instructions of a program loaded into the memory.

[0092] In the first to fifth embodiments described above, the presence of unburned fuel is determined based on one specific value of the in-cylinder pressure, the in-cylinder temperature, or the brightness inside the cylinder. In other embodiments, the presence of unburned fuel may be determined by combining these characteristic values. For example, the presence of unburned fuel may be determined when the specified heat release rate at the specified timing is a positive value and the in-cylinder temperature within the second specified period exceeds the temperature threshold.

[0093] <Summary> The contents of the above-described embodiments can be understood, for example, as follows.

[0094] 1) A combustion monitoring device (30) according to at least one embodiment of the present disclosure includes: A combustion monitoring device for monitoring combustion of fuel including hydrogen fuel that is periodically repeated in a combustion chamber (C) of an engine (1), comprising: The device is provided with a combustion prolongation determination unit (37) for determining whether any unburned residue has occurred, in which the combustion continues even after the reference end timing (θs) at which the combustion should end during one combustion cycle, based on at least one of the pressure, temperature, and brightness in the combustion chamber.

[0095] The inventors discovered that if unburned fuel remains during one combustion cycle (E), hydrogen fuel flowing into the combustion chamber during the intake stroke of the next combustion cycle may begin to burn before the engine's ignition operation. Backfire may occur when hydrogen fuel begins to burn during the intake stroke. In other words, the inventors identified unburned fuel as a phenomenon that can trigger backfire. When unburned fuel remains are generated, the pressure, temperature, and brightness in the combustion chamber all take high values, so it is possible to determine whether unburned fuel remains have occurred based on at least one of these characteristic values. Therefore, according to the configuration of 1) above, the combustion prolongation determination unit determines whether unburned fuel remains have occurred, thereby realizing a combustion monitoring device that can accurately detect signs of backfire.

[0096] 2) In some embodiments, the combustion monitoring device described in 1) above, The engine is a cylinder (6), a piston (7), and a cylinder head (5) that define the combustion chamber; an intake valve (13) for opening and closing an intake port (11) provided in the cylinder head, the intake valve (13) being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve (14) for opening and closing an exhaust port (12) provided in the cylinder head, the exhaust valve (14) being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a pressure acquisition unit (31) for acquiring the pressure within a first specified period including a period (dimension T) from the end reference timing to an exhaust start timing (θe) at which the exhaust valve opens the exhaust port, The combustion prolongation determination unit is configured to determine whether the unburned residue has occurred based on the acquired pressure.

[0097] According to the configuration of 2) above, it is possible to determine whether unburned residue has occurred based on the measurement results of a pressure sensor that has been conventionally installed to measure the pressure in the combustion chamber, thereby reducing the cost of the configuration for determining whether unburned residue has occurred.

[0098] 3) In some embodiments, the combustion monitoring device described in 2) above is a heat release rate acquisition unit (32) for acquiring a heat release rate in the combustion chamber within the first specified period based on the acquired pressure, The combustion prolongation determination unit is configured to determine whether the unburned residue has been generated based on the acquired heat release rate.

[0099] According to the configuration of 3) above, the heat release rate, which correlates with the pressure in the combustion chamber, is a parameter that comprehensively indicates the combustion status in the combustion chamber, so the combustion prolongation determination unit can accurately determine whether unburned fuel remains, and therefore the combustion monitoring device can accurately detect signs of backfire.

[0100] 4) In some embodiments, the combustion monitoring device described in 3) above, the first specified period includes an intermediate timing (θm) that is after the end reference timing and before the exhaust start timing, The heat release rate acquisition unit is configured to acquire a specified heat release rate, which is the heat release rate at at least one specified timing after the intermediate timing and before the exhaust start timing.

[0101] According to the configuration of 4) above, the specified heat release rate is the heat release rate after the intermediate timing, so even if the actual timing at which normal combustion ends varies, the specified heat release rate is unlikely to take a positive value. Therefore, the combustion prolongation determination unit can avoid erroneously determining that unburned residue has occurred when normal combustion is occurring.

[0102] 5) In some embodiments, the combustion monitoring device described in 4) above, the at least one specified timing is a single specified timing, The combustion prolongation determination unit is configured to determine that the unburned residue is present when the specified heat release rate is a positive value.

[0103] According to the configuration of 5) above, it is possible to determine whether unburned residue has occurred simply by determining whether the specified heat release rate at a single specified timing is a positive value, thereby simplifying the determination process executed by the combustion prolongation determination unit.

[0104] 6) In some embodiments, the combustion monitoring device described in 4) above, the at least one specified timing is a plurality of the specified timings, the heat release rate acquisition unit is configured to acquire a plurality of specified heat release rates corresponding to the plurality of specified timings, The combustion prolongation determination unit is configured to determine that the unburned residue is present when an average value of the plurality of specified heat release rates is a positive value.

[0105] According to the configuration of 6) above, even if one of the specified heat release rates accidentally becomes a negative value when unburned fuel remains, it can be determined that unburned fuel remains have occurred as long as the average value of the specified heat release rates is a positive value. Therefore, the combustion prolongation determination unit can accurately determine whether unburned fuel remains have occurred.

[0106] 7) In some embodiments, the combustion monitoring device described in 3) above, The first specified period is: a first timing after the end reference timing; a second timing that is later than the first timing and before the exhaust start timing, the heat release rate acquisition unit is configured to continuously acquire the heat release rate between the first timing and the second timing; The combustion prolongation determination unit is configured to determine that the unburned residue is present when an integrated value of the heat release rate from the first timing to the second timing is a positive value.

[0107] If no unburned residue is generated, the integrated value of the heat release rate decreases between the first timing and the second timing. On the other hand, if unburned residue is generated, the integrated value of the heat release rate increases. Therefore, according to the configuration of 7) above, the combustion prolongation determination unit can accurately determine whether unburned residue has been generated based on the integrated value of the heat release rate.

[0108] 8) In some embodiments, the combustion monitoring device according to 7) above, the first specified period further includes an advance timing (θa) that is after an intake end timing (θf) at which the intake valve closes the intake port and that is before the first timing, the heat release rate acquisition unit is configured to continuously acquire the heat release rate from the advance timing to the second timing; A first integrated value, which is the integrated value from the advance timing to the first timing, is defined as S1, a second integrated value, which is the integrated value from the advance timing to the second timing, is defined as S2, and a positive value equal to or less than 1 is defined as A, The combustion prolongation determination unit is configured to determine that the unburned residue is present when the following formula (1) is satisfied: S1≦S2×A (1)

[0109] If the heat release rate increases between the first and second timings, equation (1) holds. Therefore, the combustion prolongation determination unit can accurately determine whether unburned fuel has occurred based on the first and second integrated values. Note that if the value of A is a positive value less than 1, the magnitude relationship between S1 and S2 × A will not change even if the heat release rate temporarily decreases due to an accidental factor despite the occurrence of unburned fuel between the first and second timings. Therefore, it can be accurately determined that unburned fuel has occurred.

[0110] 9) In some embodiments, the combustion monitoring device described in 2) above, The engine further includes a crankshaft (8) connected to the piston; The first specified period is: a first timing after the end reference timing; a second timing that is later than the first timing and before the exhaust start timing, The pressure acquisition unit acquires a first pressure (first cylinder pressure; P A ,P B ) and a second pressure (second cylinder pressure), The combustion monitoring device an ideal pressure acquisition unit (31) for acquiring an ideal pressure, which is the pressure at the second timing in a case where no unburned residue has been generated between the first timing and the second timing, based on a first volume (V1) and a second volume (V2), which are volumes of the combustion chamber at the first timing and the second timing, and the first pressure; Furthermore, The second pressure is defined as Pr, the ideal pressure as Pi, and a value equal to or greater than 1 as B, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the following formula (2) is satisfied: Pr>Pi×B (2)

[0111] When normal combustion occurs, the combustion gas undergoes a change close to adiabatic expansion between the first timing and the second timing, so Pr is substantially equal to Pi. Therefore, formula (2) does not hold. On the other hand, when unburned residues are generated, heat is generated in the combustion chamber between the two timings, so Pr is higher than Pi, and formula (2) holds. Therefore, according to the configuration of 9) above, the combustion prolongation determination unit can determine whether unburned residues have occurred. Note that in an embodiment in which the value of B is greater than 1, even if Pr becomes slightly larger than Pi due to measurement error or the like, even though no unburned residues have occurred, formula (2) does not hold. This makes it possible to avoid erroneously determining that unburned residues have occurred.

[0112] 10) In some embodiments, the combustion monitoring device described in 1) above, The engine is a cylinder (6), a piston (7), and a cylinder head (5) that define the combustion chamber; an intake valve (13) for opening and closing an intake port (11) provided in the cylinder head, the intake valve (13) being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve (14) for opening and closing an exhaust port (12) provided in the cylinder head, the exhaust valve (14) being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a temperature acquisition unit (41) for acquiring the temperature within a second specified period including a period from the end reference timing to an intake start timing at which the intake valve opens the intake port, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the acquired temperature exceeds a temperature threshold value.

[0113] According to the configuration of 10) above, when unburned fuel remains, the temperature at a predetermined timing within the second specified period exceeds the temperature threshold value, so that the combustion prolongation determination unit can determine whether unburned fuel remains.

[0114] 11) In some embodiments, the combustion monitoring device according to 10) above, The engine is a cylinder (6), a piston (7), and a cylinder head (5) that define the combustion chamber; an intake valve (13) for opening and closing an intake port (11) provided in the cylinder head, the intake valve (13) being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve (14) for opening and closing an exhaust port (12) provided in the cylinder head, the exhaust valve (14) being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a light acquisition unit (42) for acquiring the brightness within a second specified period including a period from the end reference timing to an intake start timing at which the intake valve opens the intake port, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the acquired brightness exceeds a light threshold value.

[0115] According to the configuration of 11) above, when unburned fuel is generated, the brightness exceeds the light threshold at a predetermined timing within the second specified period. This phenomenon can be confirmed as soon as unburned fuel is generated, so it is possible to determine whether unburned fuel has been generated at an early stage. This also makes it possible to ensure sufficient time to make control changes, such as changing the fuel injection method, in the next combustion cycle.

[0116] 12) In some embodiments, the combustion monitoring device according to any one of 1) to 11) above, The combustion control unit (39) is further provided, which is configured to execute control for lowering the temperature in the combustion chamber when it is determined that the unburned residue has been generated.

[0117] According to the configuration of 12) above, when the combustion prolongation determination unit determines that unburned fuel has occurred, the temperature of the combustion chamber in the next combustion cycle decreases, thereby preventing backfire from occurring in the next combustion cycle.

[0118] 13) In some embodiments, the combustion monitoring device described in 12) above, The engine further comprises a fuel injector (15) for injecting the fuel for delivery to the combustion chamber; The combustion control unit is configured to control the fuel injection device so that at least one of a fuel injection timing in the next combustion cycle is retarded or a fuel injection amount is reduced in the next combustion cycle.

[0119] According to the configuration of 13) above, the fuel injection timing is retarded or the fuel injection amount is reduced in the next combustion cycle, so that backfire in the next combustion cycle can be suppressed.

[0120] 14) In some embodiments, the combustion monitoring device described in 13) above, When it is determined that the unburned residue has occurred, the combustion control unit is configured to control the fuel injection device so that in the next combustion cycle, the fuel injection timing is retarded while maintaining the fuel injection amount compared to the combustion cycle in which the unburned residue has occurred.

[0121] According to the configuration of 14) above, the occurrence of backfire can be suppressed by retarding the fuel injection timing. In addition, since the fuel injection amount is maintained, it is also possible to suppress a decrease in engine output in the next combustion cycle. Therefore, it is possible to stabilize the engine output.

[0122] 15) A combustion monitoring method according to at least one embodiment of the present disclosure comprises: A combustion monitoring method for monitoring combustion of a fuel containing hydrogen fuel that is periodically repeated in a combustion chamber (C) of an engine (1), comprising: Whether or not any unburned residue has occurred, in which the combustion continues even after the reference end timing (θs) at which the combustion should end during one combustion cycle, is determined based on at least one of the pressure, temperature, and brightness in the combustion chamber.

[0123] The configuration 15) above provides the same technical advantages as the configuration 1).

[0124] 16) In some embodiments, the combustion monitoring program according to 15) above, A combustion monitoring program for monitoring combustion of fuel including hydrogen fuel in a combustion chamber (C) of an engine (1) periodically, the program comprising: To the computer Whether or not any unburned residue has occurred, in which the combustion continues even after the reference end timing (θs) at which the combustion should end during one combustion cycle has arrived, is determined based on at least one of the pressure, temperature, and brightness in the combustion chamber.

[0125] According to the configuration 16) above, the same technical advantages as those of the configuration 1) above can be obtained. [Explanation of symbols]

[0126] 1: Engine 2: Pressure sensor 3: Temperature sensor 4: Optical sensor 5: Cylinder head 6: Cylinder 7: Piston 8: Crankshaft 9: Crank sensor 11: Intake port 12: Exhaust port 13: Intake valve 14: Exhaust valve 15:Fuel injection device 17: Intake passage 18: Exhaust duct 19:Ignition device 21: Connecting rod 30A~30E(30): Combustion monitoring device 31A to 31C (31): Pressure acquisition unit 32A, 32B(32): Heat release rate acquisition section 33: Volume acquisition unit 34: Ideal pressure acquisition section 37A to 37E (37): Combustion prolongation determination section 39: Combustion control unit 41:Temperature acquisition section 42:Light acquisition section B1, B2: Dashed line Bg: Combustion gas C: Combustion chamber E:1 combustion cycle F: Arrow P A ,P B : First cylinder pressure T:Dimensions V1: First volume V2: Second volume θa: Advance timing θe: Exhaust start timing θf: Intake end timing θm: Intermediate timing θs: End reference timing

Claims

1. 1. A combustion monitoring device for monitoring cyclically repeated combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, comprising: and a combustion prolongation determination unit for determining whether or not a residual combustion has occurred, in which the combustion continues even after the reference timing for the end of the combustion has arrived during one combustion cycle, based on at least one of the pressure, temperature, and brightness in the combustion chamber. Combustion monitoring device.

2. The engine is a cylinder, a piston, and a cylinder head defining the combustion chamber; an intake valve for opening and closing an intake port provided in the cylinder head, the intake valve being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve for opening and closing an exhaust port provided in the cylinder head, the exhaust valve being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a pressure acquisition unit that acquires the pressure within a first specified period that includes a period from the end reference timing to an exhaust start timing at which the exhaust valve opens the exhaust port, The combustion prolongation determination unit is configured to determine whether the unburned residue has occurred based on the acquired pressure. The combustion monitoring device of claim 1.

3. a heat release rate acquisition unit for acquiring a heat release rate in the combustion chamber within the first specified period based on the acquired pressure; The combustion prolongation determination unit is configured to determine whether the unburned residue has occurred based on the acquired heat release rate.

3. The combustion monitoring device of claim 2.

4. the first specified period includes an intermediate timing that is after the end reference timing and before the exhaust start timing, The heat release rate acquisition unit is configured to acquire a specified heat release rate, which is the heat release rate at at least one specified timing after the intermediate timing and before the exhaust start timing.

4. The combustion monitoring device according to claim 3.

5. the at least one specified timing is a single specified timing, The combustion prolongation determination unit is configured to determine that the unburned residue is generated when the specified heat release rate is a positive value.

5. The combustion monitoring device according to claim 4.

6. the at least one specified timing is a plurality of specified timings, the heat release rate acquisition unit is configured to acquire a plurality of specified heat release rates corresponding to the plurality of specified timings, The combustion prolongation determination unit is configured to determine that the unburned residue is generated when an average value of the plurality of specified heat release rates is a positive value.

5. The combustion monitoring device according to claim 4.

7. The first specified period is: a first timing subsequent to the end reference timing; a second timing that is later than the first timing and before the exhaust start timing, the heat release rate acquisition unit is configured to continuously acquire the heat release rate between the first timing and the second timing; The combustion prolongation determination unit is configured to determine that the unburned residue is generated when an integrated value of the heat generation rate from the first timing to the second timing is a positive value.

4. The combustion monitoring device according to claim 3.

8. the first specified period further includes an advance timing that is after an intake end timing at which the intake valve closes the intake port and before the first timing, the heat release rate acquisition unit is configured to continuously acquire the heat release rate from the advance timing to the second timing, A first integrated value, which is the integrated value from the advance timing to the first timing, is defined as S1, a second integrated value, which is the integrated value from the advance timing to the second timing, is defined as S2, and a positive value equal to or less than 1 is defined as A, The combustion prolongation determination unit is configured to determine that the unburned residue is generated when the following formula (1) is satisfied:

8. The combustion monitoring device of claim 7. S1≦S2×A (1)

9. The engine further includes a crankshaft coupled to the piston. The first specified period is: a first timing subsequent to the end reference timing; a second timing that is later than the first timing and before the exhaust start timing, the pressure acquisition unit is configured to acquire a first pressure and a second pressure, which are the pressures at the first timing and the second timing; The combustion monitoring device an ideal pressure acquisition unit that acquires an ideal pressure, which is the pressure at the second timing when no unburned residue has been generated between the first timing and the second timing, based on a first volume and a second volume, which are volumes of the combustion chamber at the first timing and the second timing, and the first pressure; Furthermore, The second pressure is defined as Pr, the ideal pressure is defined as Pi, and a value equal to or greater than 1 is defined as B, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the following formula (2) is satisfied:

3. The combustion monitoring device of claim 2. Pr>Pi×B...(2)

10. The engine is a cylinder, a piston, and a cylinder head defining the combustion chamber; an intake valve for opening and closing an intake port provided in the cylinder head, the intake valve being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve for opening and closing an exhaust port provided in the cylinder head, the exhaust valve being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a temperature acquisition unit configured to acquire the temperature within a second specified period including a period from the end reference timing to an intake start timing at which the intake valve opens the intake port, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the acquired temperature exceeds a temperature threshold. The combustion monitoring device of claim 1.

11. The engine is a cylinder, a piston, and a cylinder head defining the combustion chamber; an intake valve for opening and closing an intake port provided in the cylinder head, the intake valve being configured to allow the fuel to be drawn into the combustion chamber by opening the intake port; an exhaust valve for opening and closing an exhaust port provided in the cylinder head, the exhaust valve being configured to allow combustion gas generated by the combustion to be discharged from the combustion chamber by opening the exhaust port; Including, the combustion monitoring device further includes a light acquiring unit configured to acquire the brightness within a second specified period including a period from the end reference timing to an intake start timing at which the intake valve opens the intake port, The combustion prolongation determination unit is configured to determine that the unburned residue has occurred when the acquired brightness exceeds a light threshold. The combustion monitoring device of claim 1.

12. a combustion control unit configured to execute control to reduce the temperature in the combustion chamber when it is determined that the unburned residue has occurred.

3. The combustion monitoring device according to claim 1 or 2.

13. the engine further comprising a fuel injector for injecting the fuel for delivery to the combustion chamber; The combustion control unit is configured to control the fuel injection device so that at least one of a fuel injection timing in the next combustion cycle is retarded or a fuel injection amount is reduced in the next combustion cycle.

13. The combustion monitoring device of claim 12.

14. When it is determined that the unburned residue has occurred, the combustion control unit is configured to control the fuel injection device so that, in the next combustion cycle, the fuel injection timing is retarded while maintaining the fuel injection amount, compared to the combustion cycle in which the unburned residue has occurred.

14. The combustion monitoring device of claim 13.

15. 1. A combustion monitoring method for monitoring cyclically repeated combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, comprising: A combustion monitoring method that determines whether any unburned fuel remains in the combustion chamber after the reference end timing for the combustion to end during one combustion cycle, based on at least one of the pressure, temperature, or brightness in the combustion chamber.

16. 1. A combustion monitoring program for monitoring combustion of a fuel including hydrogen fuel in a combustion chamber of an engine, the program comprising: To the computer A combustion monitoring program that determines whether any unburned residue has occurred, where the combustion continues after the reference timing for the end of the combustion during one combustion cycle, based on at least one of the pressure, temperature, or brightness in the combustion chamber.

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