Engine device and control method for engine device

Abstract

To provide an engine device that can predict abnormal combustion before occurrence thereof by grasping a combustion state of an engine, and a control method for the engine device.SOLUTION: An engine device 1 driven by gas fuel detects a combustion period in a combustion chamber 12a of an engine 2, estimates abnormal combustion that occurs in the combustion chamber 12a on the basis of a correlation between the combustion period and the abnormal combustion (backfire), and when estimating the abnormal combustion, determines a suppression method for suppressing the abnormal combustion. As the suppression method, the engine device 1 performs control for shortening the combustion period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an engine device that is driven by injecting gaseous fuel into a combustion chamber, and a control method thereof. [Background technology]

[0002] Conventionally, engine devices include gas engines that are driven by feeding gaseous fuel such as hydrogen into a combustion chamber in a cylinder, and dual-fuel engines that are driven by feeding at least one of gaseous fuel such as hydrogen and liquid fuel such as light oil or heavy oil into a combustion chamber in a cylinder. For example, a dual-fuel engine operates in one of two operating modes: a gas mode in which gaseous fuel is fed into the combustion chamber and driven by feeding liquid fuel into the combustion chamber, and a mixed-fuel mode in which both gaseous fuel and liquid fuel are fed into the combustion chamber as another operating mode. In such engine devices, abnormal combustion such as pre-ignition (premature ignition) in which gaseous fuel self-ignites in the combustion chamber before ignition by a micro-pilot system that injects a small amount of liquid fuel or ignition by a spark ignition system ignition device using a spark plug may occur, so it is necessary to suppress abnormal combustion.

[0003] For example, according to Patent Document 1, an engine control device for controlling an engine that directly supplies hydrogen into a combustion chamber during the compression stroke includes a determination means for determining whether a torque down control condition is satisfied, an injection start timing correction means for correcting the hydrogen injection start timing by advancing it from the compression stroke to the intake stroke in order to reduce the engine drive torque, and an ignition timing correction means for correcting the ignition timing by retarding it in order to reduce the engine drive torque. When the determination means determines that the torque down control condition is satisfied, the engine control device corrects the hydrogen injection start timing by advancing it from the compression stroke to the intake stroke in an operating range in which backfire is likely to occur, using the injection start timing correction means, and corrects the ignition timing by retarding it in an operating range in which backfire is unlikely to occur, using the ignition timing correction means.

[0004] According to Patent Document 2, a control device for a hydrogen engine includes a hydrogen supplying means for supplying hydrogen, a control means for switching between and using an intake stroke supply to cause the hydrogen supplying means to supply hydrogen during an intake stroke and a compression stroke supply to cause the hydrogen supplying means to supply hydrogen during a compression stroke, and an exhaust gas recirculation means for recirculating exhaust gas to the intake system. In a first engine operating state in which the engine speed is less than a predetermined first rotation speed, the control means causes the hydrogen supplying means to perform the compression stroke supply and causes the exhaust gas recirculation means to recirculate exhaust gas to the intake system. In a second engine operating state in which the engine speed is equal to or greater than the first rotation speed and less than a predetermined second rotation speed that is faster than the first rotation speed, the control means causes the hydrogen supplying means to perform the intake stroke supply and compression stroke supply and causes the exhaust gas recirculation means to recirculate exhaust gas to the intake system. Furthermore, in a third engine operating state in which the engine rotation speed is equal to or higher than the second rotation speed, the control means causes the hydrogen supply means to perform hydrogen supply during the intake stroke and hydrogen supply during the compression stroke.

[0005] According to Patent Document 3, a control device for an internal combustion engine includes an occurrence frequency detection means for detecting the frequency of occurrence of pre-ignition per unit time, and a temperature range varying means for changing the range of the pre-ignition suppression temperature range when the occurrence frequency of pre-ignition exceeds an allowable limit in at least a portion of the pre-ignition suppression temperature range so that the occurrence frequency of pre-ignition is equal to or lower than the allowable limit in the portion of the pre-ignition suppression temperature range. Then, the cylinder wall temperature control means of this control device controls the wall temperature parameter to fall within the pre-ignition suppression temperature range changed by the temperature range varying means. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4406880 [Patent Document 2] Patent No. 4618150 [Patent Document 3] Patent No. 5939263 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional technology such as that described in Patent Document 1, the effectiveness of backfire suppression control is limited because the backfire suppression control is determined when the torque down control conditions are met without defining or detecting the combustion state of the engine.

[0008] In the conventional technology described in Patent Document 2, the engine combustion state is not defined or detected, and pre-ignition is suppressed and controlled by evaluating the engine speed and selectively using compression stroke supply, intake stroke supply, and exhaust gas recirculation, so the effect of the suppression control of pre-ignition is limited. Also, in this conventional technology, abnormal combustion is suppressed and controlled without changing combustion control items such as the engine ignition timing and ignition energy, so the effect of the suppression control of abnormal combustion is limited.

[0009] In conventional technology such as that described in Patent Document 3, the effectiveness of pre-ignition suppression control is limited because the pre-ignition suppression control is determined by evaluating only the frequency of occurrence of pre-ignition (early ignition) without defining or detecting the combustion state of the engine.

[0010] As described above, in conventional engines, the operating state (combustion state) of the engine in which abnormal combustion occurs cannot be accurately grasped, so abnormal combustion cannot be predicted before it occurs, and abnormal combustion can only be suppressed after it has occurred in the engine. Therefore, damage caused by abnormal combustion accumulates in the engine, which may result in engine damage.

[0011] An object of the present invention is to provide an engine device and a control method thereof that are capable of grasping the combustion state of the engine and predicting abnormal combustion before it occurs. [Means for solving the problem]

[0012] In order to solve the above problems, the engine device of the present invention is an engine device driven by gaseous fuel, which detects the combustion period in a combustion chamber, estimates abnormal combustion occurring in the combustion chamber based on the correlation between the combustion period and abnormal combustion, and, when the abnormal combustion is estimated, determines a suppression method for suppressing the abnormal combustion.

[0013] In addition, in order to solve the above-mentioned problems, the control method for an engine device of the present invention is a control method for an engine device driven by gaseous fuel, which is characterized by detecting a combustion period in a combustion chamber, estimating abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion, and, when the abnormal combustion is estimated, determining a suppression method for suppressing the abnormal combustion. Effect of the Invention

[0014] According to the present invention, there is provided an engine device and a control method thereof that are capable of grasping the combustion state of the engine and predicting abnormal combustion before it occurs. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram illustrating an example of an engine device according to an embodiment of the present invention. [Diagram 2] 2 is a graph showing an example of an operable region in the relationship between ignition timing and an excess air ratio in an engine device. [Diagram 3] 4 is a graph showing an example of a distribution of a combustion period with respect to an operable region in terms of a relationship between an ignition timing and an excess air ratio in an engine device according to an embodiment of the present invention. [Figure 4] 4 is a graph showing an example of the relationship between a combustion period in a combustion chamber and an excess air ratio in the engine device according to the embodiment of the present invention. [Diagram 5] 4 is a graph showing an example of the relationship between a combustion period in a combustion chamber and an excess air ratio in the engine device according to the embodiment of the present invention. [Figure 6]4 is a graph showing an example of the relationship between a combustion period in a combustion chamber and an excess air ratio in the engine device according to the embodiment of the present invention. [Figure 7] 4 is a flowchart showing an example of an abnormal combustion suppression operation in the engine device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An engine device 1 according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG.

[0017] Particularly in this embodiment, the engine device 1 is a gas engine configured to be capable of being driven by injecting gaseous fuel such as hydrogen into the combustion chamber 12a of the engine 2, and is equipped with a gaseous fuel injection unit 6 for injecting the gaseous fuel, a throttle valve 7 for adjusting the amount of intake air, and an ignition device 8 for igniting the gaseous fuel in the combustion chamber 12a.

[0018] The engine 2 is configured with a cylinder block 11 and multiple cylinders 12, but Fig. 1 shows only one cylinder 12. As shown in Fig. 1, each cylinder 12 is configured with a cylinder 13, a piston 14, and a cylinder head 15. A gaseous fuel injection unit 6 and an ignition device 8 are provided for each cylinder 12.

[0019] The cylinder 13 is formed, for example, in a cylindrical shape within the cylinder block 11, and the piston 14 is slidably housed within the cylinder 13. The cylinder head 15 is attached to the upper side of the cylinder 13, and the cylinder 13 and the cylinder head 15 form a combustion chamber 12a therein.

[0020] Below the cylinder 13 , a crankshaft 17 is connected to the piston 14 via a connecting rod 16 , and the reciprocating motion of the piston 14 is converted into the rotational motion of the crankshaft 17 via the connecting rod 16 .

[0021] An angle sensor 18 is provided in the cylinder 13 to detect the rotation angle of the crankshaft 17, i.e., the rotation speed of the engine 2, and the angle sensor 18 transmits the detection result to the control unit 5. A pressure sensor 19 is provided in the cylinder 13 to detect the internal pressure of the combustion chamber 12a, i.e., the in-cylinder pressure of the cylinder 13, and the pressure sensor 19 transmits the detection result to the control unit 5. A torque sensor 20 is provided in the cylinder 13 near the crankshaft 17 to detect the engine load (engine torque) of the engine 2, and the torque sensor 20 transmits the detection result to the control unit 5.

[0022] The cylinder head 15 also has an intake port 22 and an exhaust port 23 that communicate with the combustion chamber 12a of the cylinder 13, and is equipped with an intake valve 24 and an exhaust valve 25 that respectively open and close the intake port 22 and the exhaust port 23 to the combustion chamber 12a.

[0023] The intake port 22 is connected to the intake passage 3 and introduces air supplied from the intake passage 3 into the combustion chamber 12a, while the exhaust port 23 is connected to the exhaust passage 4 and discharges exhaust gas generated in the combustion chamber 12a into the exhaust passage 4. By opening the intake valve 24, a mixture of fuel gas and air can be taken into the combustion chamber 12a via the intake port 22, while by opening the exhaust valve 25, exhaust gas generated in the combustion chamber 12a can be exhausted via the exhaust port 23.

[0024] 1 shows an example in which the intake passage 3 and the intake port 22 are directly connected, but in order to connect the intake passage 3 to each of the intake ports 22 of the multiple cylinders 12, an intake manifold having branch passages branching from the intake passage 3 to the multiple cylinders 12 may be provided between the intake passage 3 and the engine 2. Also, in FIG. 1 shows an example in which the exhaust passage 4 and the exhaust port 23 are directly connected, but in the case of connecting the exhaust passage 4 to each of the exhaust ports 23 of the multiple cylinders 12, an exhaust manifold having branch passages branching from the exhaust passage 4 to the multiple cylinders 12 may be provided between the exhaust passage 4 and the engine 2.

[0025] In each cylinder 12, the gaseous fuel injection unit 6 is provided in the intake port 22 and is controlled by the control unit 5 to inject gaseous fuel supplied from a gaseous fuel tank (not shown) into the intake port 22. A mixture of air supplied from the intake passage 3 and gaseous fuel supplied from the gaseous fuel tank (not shown) is supplied from the intake port 22 to the combustion chamber 12a. The gaseous fuel injection unit 6 is composed of, for example, a gas admission valve and a gas injector. The gaseous fuel injection unit 6 is controlled by the control unit 5 in terms of the injection amount, injection pressure, injection timing, etc., of the gaseous fuel, and can enrich the air-fuel ratio in the combustion chamber 12a by increasing the injection amount and injection pressure, for example.

[0026] In each cylinder 12, an ignition device 8 is provided in the cylinder head 15. The ignition device 8 is, for example, a micro-pilot type device that injects a small amount of liquid fuel, and is composed of an injector or the like that injects liquid fuel supplied from a liquid fuel tank (not shown) into the combustion chamber 12a below the cylinder head 15. The micro-pilot type ignition device 8 has the injection amount, injection pressure, injection timing, etc. of the liquid fuel controlled by the control unit 5, and can increase the ignition power by, for example, increasing the injection amount or injection pressure.

[0027] Alternatively, the ignition device 8 may be configured as a spark ignition type device using an ignition plug. The spark ignition type ignition device 8 has ignition energy (for example, power supplied to the ignition plug) and the like controlled by the control unit 5, and can increase ignition power by increasing the ignition energy, for example.

[0028] The intake passage 3 is connected to the intake ports 22 of the cylinders 12 of the engine 2, and supplies compressed and cooled air to each cylinder 12 via the intake ports 22. The intake passage 3 may be provided with a supercharger (not shown) that compresses the air flowing through the intake passage 3 and sends it downstream in the intake direction, or an intercooler (not shown) that cools the air flowing through the intake passage 3. An air filter (not shown) that purifies and introduces fresh air may be provided at the upstream end of the intake passage 3 in the intake direction.

[0029] The intake passage 3 is provided with a throttle valve 7 for adjusting the amount of intake air sent to the intake port 22. The throttle valve 7 is controlled by the control unit 5 to adjust its opening, and by adjusting the amount of intake air sent to the intake port 22 according to the opening of the throttle valve 7, it is possible to adjust the excess air ratio (the ratio of intake air in the mixture) of the mixture of gaseous fuel and air injected from the intake port 22 into the combustion chamber 12a, and for example, it is possible to enrich the air-fuel ratio of the combustion chamber 12a by reducing the amount of intake air. That is, by adjusting the opening of the throttle valve 7, it is possible to adjust the flow rate of air supplied from the intake passage 3 to the intake port 22.

[0030] The exhaust passage 4 is connected to an exhaust port 23 of each cylinder 12 of the engine 2, and exhaust gas generated in each cylinder 12 is discharged through the exhaust port 23. An air-fuel ratio sensor 21 that detects the air-fuel ratio of the exhaust gas is provided in the exhaust passage 4, and the air-fuel ratio sensor 21 transmits the detection result to the control unit 5.

[0031] The control unit 5 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 2, and includes a CPU, ROM, RAM, etc., and is configured to control each part of the engine 2. The control unit 5 may store various programs for controlling the engine 2, and control the engine 2 by reading and executing the programs.

[0032] In the engine device 1, the ignition device 8 is normally operated at the ignition timing set by the control unit 5, and for example, liquid fuel is injected into the combustion chamber 12a at a predetermined liquid fuel injection timing (injection timing), thereby igniting the gaseous fuel inside the combustion chamber 12a and starting combustion. However, if an abnormality occurs, such as the inside of the combustion chamber 12a becoming excessively high temperature or pressure, the gaseous fuel inside the combustion chamber 12a may self-ignite before the ignition timing (liquid fuel injection timing), causing abnormal combustion such as pre-ignition.

[0033] Furthermore, when operating the engine device 1, in terms of the relationship between the ignition timing (liquid fuel injection timing) of the combustion chamber 12a and the excess air ratio of the mixture (the proportion of intake air in the mixture) injected into the combustion chamber 12a, the engine device 1 can be operated within an operable region 30 as shown in FIG. 2, but outside the operable region 30, there is a high possibility that dangerous combustion will occur in the combustion chamber 12a, and the engine device 1 cannot be operated.

[0034] Furthermore, near the edge of the operable range 30, there is a high possibility that abnormal combustion such as pre-ignition will occur in the engine 2, even within the range of the operable range 30. For example, near the edge 31 of the operable range 30 on the side where the air excess ratio is relatively high and the ignition timing is relatively retarded, there is a high possibility that pre-ignition and backfire will occur as abnormal combustion.

[0035] 3 shows the result of monitoring the combustion period of the degree of combustion promotion in the combustion chamber 12a when the engine device 1 is operated within the operable region 30. For example, during operation of the engine device 1, the control unit 5 detects the rotation angle (deg) of the crankshaft 17 by the angle sensor 18 and detects the internal pressure of the cylinder 13 by the pressure sensor 19, and calculates the heat release rate in the combustion chamber 12a based on the change in the internal pressure of the cylinder 13 and the change in the volume of the combustion chamber 12a. Then, the control unit 5 calculates, as the combustion period, the difference (interval) in the crank angle of the crankshaft 17 at which the amount of heat release obtained by integrating the heat release rate over the combustion stroke crank angle in the combustion chamber 12a is 10% and 90% of the total.

[0036] According to the monitoring results, the distribution of the combustion period in the combustion chamber 12a is uniform and approximately parallel to the edge 31 of the operable region 30, and combustion periods with relatively long combustion periods are distributed near the edge 31 of the operable region 30, while combustion periods with shorter combustion periods are distributed farther from the edge 31 of the operable region 30. In other words, there is a correlation between the combustion period and abnormal combustion in the combustion chamber 12a such that the longer the combustion period, the higher the possibility of abnormal combustion such as pre-ignition or backfire occurring, while the shorter the combustion period, the lower the possibility of such occurrence. Note that if the combustion period becomes too short, pre-ignition and knocking occur, but this can be monitored by knocking detection, which detects characteristic in-cylinder pressure vibrations.

[0037] Regarding the monitoring results of the combustion period as shown in FIG. 3, the change in each combustion period at the predetermined ignition timings T1, T2, and T3 has good linearity with respect to the change in the excess air ratio (air-fuel ratio) as shown by black circles in FIG. 4, FIG. 5, and FIG. 6, so that the change in the combustion period with respect to the abnormal combustion is easily detected. Therefore, when the combustion period increases during the operation of the engine device 1, it is easy to detect the approach of the combustion period to the dangerous period P1 before it reaches the dangerous period P1 at which abnormal combustion of backfire occurs. In addition, when evaluating the occurrence frequency of minor abnormal combustion that occurs at a low frequency even in the operable range, the change in the occurrence frequency at each predetermined ignition timing T1, T2, and T3 does not have good linearity with respect to the change in the excess air ratio (air-fuel ratio) as shown by white circles in FIG. 4, FIG. 5, and FIG. 6, so that the change in the combustion form toward abnormal combustion that cannot continue operation is difficult to detect. Therefore, it is difficult to detect the approach of the occurrence frequency to the dangerous frequency P2 before it reaches the dangerous frequency P2 at which abnormal combustion of backfire occurs.

[0038] Therefore, in this embodiment, the control unit 5 detects the combustion period of the degree of combustion promotion in the combustion chamber 12a, and estimates abnormal combustion or its precursor occurring in the combustion chamber 12a based on the correlation between the combustion period and abnormal combustion.If abnormal combustion or its precursor is estimated, then the control unit 5 determines and executes a suppression method for suppressing abnormal combustion.

[0039] Specifically, first, the control unit 5 calculates the difference (interval) between the crank angles of the crankshaft 17 at which the amount of heat generated, obtained by integrating the heat generation rate over the combustion stroke crank angle in the combustion chamber 12a, is 10% and 90% of the total, as the combustion period. In addition, in this embodiment, based on the correlation between the combustion period and abnormal combustion in the combustion chamber 12a described above, a danger period is set in advance as a threshold value of the combustion period that can be estimated to have a high possibility of abnormal combustion occurring because it is close to the edge 31 of the operable region 30 when viewed from the short combustion period side. Note that the danger period is a combustion period that has not yet reached the edge 31 of the operable region 30 (short), and is a combustion period in which a sign of abnormal combustion such as backfire that may occur in the future can be predicted. The control unit 5 monitors the combustion period in the combustion chamber 12a, and estimates that abnormal combustion such as backfire will occur or there is a sign of abnormal combustion when it exceeds the danger period, and estimates that abnormal combustion such as backfire will not occur or there is no sign of abnormal combustion when it is equal to or shorter than the danger period.

[0040] When the control unit 5 estimates abnormal combustion (or a precursor), it determines and executes a suppression method for suppressing abnormal combustion, which controls each part of the engine device 1 so as to shorten the combustion period in the combustion chamber 12a. It is preferable to set a safety period (e.g., 27 to 28 degrees) in advance as a combustion period during which the engine device 1 can be safely operated without causing abnormal combustion, and the control unit 5 executes the suppression method until the combustion period in the combustion chamber 12a becomes equal to or shorter than the safety period.

[0041] For example, as a suppression method, the control unit 5 increases the ignition power in the combustion chamber 12a by the ignition device 8, thereby shortening the combustion period. When the ignition device 8 is of a micro-pilot type, the control unit 5 increases the ignition power by increasing the injection amount and injection pressure of the liquid fuel. At this time, the control unit 5 may gradually increase the ignition power by gradually increasing the injection amount and injection pressure of the liquid fuel for each cycle. Also, the control unit 5 may set an upper limit of the ignition power by setting an upper limit of the injection amount and injection pressure of the liquid fuel, and increase the ignition power up to the upper limit of the ignition power.

[0042] Alternatively, when the ignition device 8 is a spark ignition type, the control unit 5 increases the ignition power by increasing the ignition energy of the spark plug. At this time, the control unit 5 may gradually increase the ignition power by gradually increasing the ignition energy of the spark plug for each cycle. Also, the control unit 5 may set an upper limit on the ignition power by setting an upper limit on the ignition energy of the spark plug, and increase the ignition power up to the ignition power upper limit.

[0043] Moreover, the control unit 5 executes the suppression method of enriching the air-fuel ratio in the combustion chamber 12a, thereby shortening the combustion period. The control unit 5 enriches the air-fuel ratio in the combustion chamber 12a by reducing the amount of intake air by the throttle valve 7. At this time, the control unit 5 may gradually enrich the air-fuel ratio by gradually reducing the amount of intake air. Moreover, the control unit 5 may enrich the air-fuel ratio up to the enrichment upper limit by setting a lower limit on the amount of intake air.

[0044] Moreover, as a suppression method, the control unit 5 executes the advancement of the ignition timing in the combustion chamber 12a by the ignition device 8, thereby shortening the combustion period. When the ignition device 8 is of a micro-pilot type, the control unit 5 advances the ignition timing by advancing the injection timing of the liquid fuel, and when the ignition device 8 is of a spark ignition type, the control unit 5 advances the ignition timing by advancing the ignition timing of the spark plug. At this time, the control unit 5 may gradually advance the ignition timing by gradually advancing the injection timing of the liquid fuel or the ignition timing of the spark plug for each cycle. Moreover, the control unit 5 may set an upper limit for the advancement of the ignition timing by setting an upper limit for the advancement of the injection timing of the liquid fuel or the ignition timing of the spark plug, and advance the ignition timing up to the advancement upper limit.

[0045] Furthermore, the control unit 5 executes a suppression method of reducing the engine load (engine torque) of the engine 2, thereby avoiding abnormal combustion. At this time, the control unit 5 may gradually reduce the engine load for each cycle. Furthermore, the control unit 5 may set an engine load lower limit and reduce the engine load to the engine load lower limit.

[0046] The control unit 5 may increase the ignition power in the combustion chamber 12a, enrich the air-fuel ratio in the combustion chamber 12a, advance the ignition timing in the combustion chamber 12a, and reduce the engine load as suppression methods, and may set a priority for which suppression method to apply. For example, the control unit 5 may give priority to increasing the ignition power in the combustion chamber 12a over enriching the air-fuel ratio in the combustion chamber 12a, advancing the ignition timing in the combustion chamber 12a, and reducing the engine load. Also, the control unit 5 may give priority to enriching the air-fuel ratio in the combustion chamber 12a over advancing the ignition timing in the combustion chamber 12a and reducing the engine load. Also, the control unit 5 may give priority to advancing the ignition timing in the combustion chamber 12a over reducing the engine load.

[0047] In addition, the control unit 5 may stop the operation of the engine device 1 when the combustion period cannot be shortened and it is difficult to avoid abnormal combustion (for example, when it cannot be shortened below a predetermined safety period or below another predetermined period) even if the ignition power in the combustion chamber 12a is increased, the air-fuel ratio in the combustion chamber 12a is enriched, the ignition timing in the combustion chamber 12a is advanced, and the engine load is reduced.

[0048] Next, the abnormal combustion suppression operation by the engine device 1 of this embodiment will be described with reference to the flowchart of FIG.

[0049] First, the control unit 5 determines (step S1) whether or not abnormal combustion such as knocking has occurred in the engine 2. If knocking has occurred (step S1: Yes), the control unit 5 performs knocking suppression control (step S2) and ends the suppression operation.

[0050] On the other hand, if knocking has not occurred (step S1: No), the control unit 5 determines whether or not abnormal combustion due to pre-ignition has occurred in the engine 2 (step S3).

[0051] If pre-ignition has not occurred (step S3: No), the control unit 5 ends the suppression operation.

[0052] On the other hand, if pre-ignition occurs (step S3: Yes), the control unit 5 calculates the combustion period as the difference (interval) between the crank angles of the crankshaft 17 at which the amount of heat generation, obtained by integrating the heat generation rate over the combustion stroke crank angle in the combustion chamber 12a, becomes 10% and 90% of the total, detects the combustion period corresponding to the rotation angle of the crankshaft 17 using the angle sensor 18, and determines whether the combustion period exceeds the dangerous period (step S4).

[0053] If the combustion period is equal to or less than the danger period (step S4: No), the control unit 5 executes a reduction in the engine load (step S5), and returns to step S1 to repeat the suppression operation.

[0054] On the other hand, if the combustion period exceeds the danger period (step S4: Yes), the control unit 5 estimates a precursor to abnormal combustion such as backfire, and determines whether the ignition power is less than the ignition power upper limit in order to determine whether to increase the ignition power in the combustion chamber 12a by the ignition device 8 as a method of suppressing backfire (step S6).

[0055] If the ignition power is less than the ignition power upper limit (step S6: Yes), the control unit 5 increases the ignition power by increasing the injection amount, injection pressure, or ignition energy of the liquid fuel (step S7), and returns to step S1 to repeat the suppression operation.

[0056] On the other hand, if the ignition power is equal to or greater than the ignition power upper limit (step S6: No), the control unit 5 determines whether the air-fuel ratio is less than the enrichment upper limit (step S8) to determine whether to enrich the air-fuel ratio in the combustion chamber 12a as a method of suppressing backfire instead of increasing the ignition power.

[0057] If the air-fuel ratio is less than the enrichment upper limit (step S8: Yes), the control unit 5 enriches the air-fuel ratio in the combustion chamber 12a by reducing the amount of intake air using the throttle valve 7 (step S9), and returns to step S1 to repeat the suppression operation.

[0058] On the other hand, if the air-fuel ratio is equal to or greater than the enrichment upper limit (step S8: No), the control unit 5 determines whether the advance of the ignition timing is less than the advance upper limit (step S10) to determine whether to advance the ignition timing in the combustion chamber 12a instead of enriching the air-fuel ratio as a method of suppressing backfire.

[0059] If the advance of the ignition timing is less than the upper advance limit (step S10: Yes), the control unit 5 advances the ignition timing by advancing the injection timing of the liquid fuel and the ignition timing of the spark plug (step S11), and then returns to step S1 to repeat the suppression operation.

[0060] On the other hand, if the advance of the ignition timing is equal to or greater than the upper advance limit (step S10: No), the control unit 5 reduces the engine load instead of advancing the ignition timing as a method of suppressing backfire (step S5), and returns to step S1 to repeat the suppression operation.

[0061] As described above, according to this embodiment, the engine device 1, which drives the engine 2 by injecting gaseous fuel into the combustion chamber 12a, detects the combustion period in the combustion chamber 12a, for example, the combustion period of the degree of combustion promotion, estimates abnormal combustion occurring in the combustion chamber 12a based on the correlation between the combustion period and abnormal combustion (backfire), and when abnormal combustion is estimated, determines and executes a suppression method for suppressing the abnormal combustion.

[0062] In other words, the control method of the engine device 1 that drives the engine 2 by injecting gaseous fuel into the combustion chamber 12a detects the combustion period in the combustion chamber 12a, for example, the combustion period of the degree of combustion promotion, estimates abnormal combustion occurring in the combustion chamber 12a based on the correlation between the combustion period and abnormal combustion (backfire), and when abnormal combustion is estimated, determines and executes a suppression method for suppressing the abnormal combustion. Note that the control method may be executed by the control unit 5, and may be configured by, for example, a program.

[0063] As a result, the engine device 1 can improve the controllability of suppressing abnormal combustion by representing the degree of combustion promotion that causes abnormal combustion such as backfire by the combustion period calculated from the cylinder pressure (internal pressure of the combustion chamber 12a) of the cylinder 13. Since slow combustion promotion (incomplete combustion) in the combustion chamber 12a can cause pre-ignition in the next cycle and thereafter, which can progress further and cause backfire, by determining the combustion period as the combustion state of the engine 2, it is possible to predict (estimate) and suppress the most dangerous backfire in advance before it occurs. Therefore, it is also possible to suppress the accumulation of damage due to abnormal combustion in the engine 2, and damage to the engine 2 can be suppressed, so that the engine 2 can be operated more safely.

[0064] Moreover, according to this embodiment, the engine device 1 performs control to shorten the combustion period as a suppression method.

[0065] As a result, in the engine device 1, residual gaseous fuel caused by slow combustion promotion (incomplete combustion) is suppressed in order to shorten the combustion period, and abnormal combustion such as pre-ignition and backfire in the next cycle and thereafter can be suppressed before they occur. Note that the control to shorten the combustion period allows the combustion period to converge to a target value (for example, a safety period) more quickly, and is therefore particularly advantageous during transient operation when fast control is required.

[0066] Moreover, according to this embodiment, the engine device 1 increases the ignition power in the combustion chamber 12a as a suppression method.

[0067] For example, according to this embodiment, in the case of the engine 2 that uses a micro-pilot method of igniting gaseous fuel by injecting liquid fuel, the engine device 1 increases the ignition power by increasing the amount of liquid fuel injected and / or by increasing the injection pressure of the liquid fuel, while in the case of the engine 2 that uses a spark ignition method using an ignition plug, the engine device 1 increases the ignition power by increasing the ignition energy.

[0068] As a result, the engine device 1 can increase the ignition power in the combustion chamber 12a, thereby suppressing unburned gaseous fuel and shortening the combustion period, and can suppress and control abnormal combustion such as backfire before it occurs.

[0069] Moreover, according to this embodiment, the engine device 1 enriches the air-fuel ratio in the combustion chamber 12a as a suppression method.

[0070] As a result, the engine device 1 can suppress unburned gaseous fuel and shorten the combustion period by enriching the air-fuel ratio in the combustion chamber 12a, and can suppress abnormal combustion such as backfire before it occurs. Note that control to enrich the air-fuel ratio can make the combustion period converge to a target value (for example, a safe period) more quickly.

[0071] Moreover, according to this embodiment, the engine device 1 advances the ignition timing in the combustion chamber 12a as a suppression method.

[0072] As a result, the engine device 1 can suppress unburned gaseous fuel and shorten the combustion period by advancing the ignition timing in the combustion chamber 12a, and can suppress and control abnormal combustion such as backfire before it occurs. Note that since pre-ignition occurs due to self-ignition in the combustion chamber 12a, it is also possible to suppress pre-ignition by setting the ignition timing before the occurrence of self-ignition. Furthermore, in the control of advancing the ignition timing, a wider range of air excess ratios (air-fuel ratios) can be selected.

[0073] Moreover, according to this embodiment, the engine device 1 reduces the engine load as a suppression method.

[0074] As a result, if the combustion period of the engine device 1 is shorter than a preset danger period or abnormal combustion such as pre-ignition occurs even though the combustion period has been shortened by changing the operating parameters (ignition power, enrichment, ignition advance), there is a possibility that a heat spot or the like has occurred in the cylinder 13. Therefore, by reducing the engine load, abnormal combustion caused by heat spots or the like can be suppressed, thereby suppressing damage to the engine 2.

[0075] Furthermore, according to this embodiment, the engine device 1 uses, as a suppression method, increasing the ignition power in the combustion chamber 12a in preference to enriching the air-fuel ratio in the combustion chamber 12a, advancing the ignition timing in the combustion chamber 12a, and reducing the engine load, and / or enriching the air-fuel ratio in the combustion chamber 12a in preference to advancing the ignition timing in the combustion chamber 12a and reducing the engine load, and / or advancing the ignition timing in the combustion chamber 12a in preference to reducing the engine load.

[0076] This enables the engine device 1 to prioritize practical suppression methods such as increasing ignition power, while deprioritizing undesirable suppression methods that may be exposed to the user of the engine device 1, such as reducing engine load.

[0077] In the above embodiment, the engine device 1 is a gas engine configured to be driven by supplying gaseous fuel such as hydrogen into the combustion chamber 12a of the engine 2, but the present invention is not limited to this example. In another example, the engine device 1 may be configured as a dual-fuel engine that is driven by supplying at least one of gaseous fuel such as hydrogen and liquid fuel such as diesel or heavy oil into the combustion chamber 12a of the engine 2. In this case, the engine device 1 supplies gaseous fuel by the gaseous fuel injection unit 6 and supplies liquid fuel by a liquid fuel injection unit such as a micro-pilot type ignition device 8.

[0078] The dual-fuel engine unit 1 operates in either a gas mode in which gas fuel is fed into the combustion chamber 12a to drive the engine, or a diesel mode in which liquid fuel is fed into the combustion chamber 12a to drive the engine, and also operates in a multi-combustion mode in which both gas fuel and liquid fuel are fed into the combustion chamber 12a to drive the engine.

[0079] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or concept of the invention that can be read from the claims and the entire specification, and the engine device and its control method involving such modifications are also included in the technical concept of the present invention.

[0080] [Appendix to the invention] The following will provide an overview of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0081] <Appendix 1> An engine device driven by gaseous fuel, Detecting a combustion period in a combustion chamber, and estimating abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion; The engine device further comprises a suppression method for suppressing the abnormal combustion when the abnormal combustion is estimated.

[0082] <Appendix 2> 2. The engine device according to claim 1, wherein the suppression method comprises performing control to shorten the combustion period.

[0083] <Appendix 3> 3. The engine device according to claim 2, wherein the suppression technique is to increase an ignition power in the combustion chamber.

[0084] <Appendix 4> The engine device according to appendix 3, characterized in that in the case of an engine that performs ignition by a micro-pilot method in which the gaseous fuel is ignited by injecting liquid fuel, the ignition power is increased by increasing the injection amount of the liquid fuel and / or increasing the injection pressure of the liquid fuel, while in the case of an engine that performs ignition by a spark ignition method using an ignition plug, the ignition power is increased by increasing ignition energy.

[0085] <Appendix 5> 5. The engine device according to claim 2, wherein the suppression method comprises enriching the air-fuel ratio in the combustion chamber.

[0086] <Appendix 6> 6. The engine device according to claim 2, wherein the suppression method comprises advancing an ignition timing in the combustion chamber.

[0087] <Appendix 7> 7. The engine device according to any one of claims 2 to 6, wherein the suppression method comprises reducing an engine load.

[0088] <Appendix 8> The engine device according to appendix 2, characterized in that, as the suppression method, increasing the ignition power in the combustion chamber is prioritized over enriching the air-fuel ratio in the combustion chamber, advancing the ignition timing in the combustion chamber, and reducing the engine load, and / or enriching the air-fuel ratio in the combustion chamber is prioritized over advancing the ignition timing in the combustion chamber and reducing the engine load, and / or advancing the ignition timing in the combustion chamber is prioritized over reducing the engine load.

[0089] <Appendix 9> A method for controlling a gaseous fuel-driven engine device, comprising: Detecting a combustion period in the combustion chamber, and estimating abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion; A control method for an engine device, comprising: determining a suppression technique for suppressing the abnormal combustion when the abnormal combustion is estimated.

[0090] <Appendix 10> 10. The control method for an engine device according to claim 9, wherein the suppression method comprises performing control to shorten the combustion period.

[0091] <Appendix 11> 11. The control method for an engine device according to claim 10, wherein the suppression technique is to increase ignition power in the combustion chamber.

[0092] <Appendix 12> 12. The control method for an engine device according to claim 11, characterized in that, in the case of an engine that performs ignition by a micro-pilot method in which the gaseous fuel is ignited by injecting liquid fuel, the ignition power is increased by increasing the injection amount of the liquid fuel and / or increasing the injection pressure of the liquid fuel, while, in the case of an engine that performs ignition by a spark ignition method using an ignition plug, the ignition power is increased by increasing ignition energy.

[0093] <Appendix 13> 13. The control method for an engine device according to any one of claims 10 to 12, wherein the suppression method comprises enriching an air-fuel ratio in the combustion chamber.

[0094] <Appendix 14> 14. The control method for an engine device according to any one of claims 10 to 13, wherein the suppression method comprises advancing an ignition timing in the combustion chamber.

[0095] <Appendix 15> 15. The control method for an engine device according to any one of claims 10 to 14, wherein the suppression method comprises reducing an engine load.

[0096] <Appendix 16> The control method for an engine device according to claim 10, characterized in that, as the suppression technique, increasing the ignition power in the combustion chamber is given priority over enriching the air-fuel ratio in the combustion chamber, advancing the ignition timing in the combustion chamber, and reducing the engine load, and / or enriching the air-fuel ratio in the combustion chamber is given priority over advancing the ignition timing in the combustion chamber and reducing the engine load, and / or advancing the ignition timing in the combustion chamber is given priority over reducing the engine load. [Explanation of symbols]

[0097] 1 Engine unit 2 Engine 3 Intake passage 4 Exhaust passage 5. Control Unit 6 Gas fuel injection section 7 Throttle valve 8 Igniter 11 Cylinder block 12 cylinders 12a Combustion chamber 13 Cylinder 14 Piston 15 Cylinder head 16 Connecting rod 17 Crankshaft 18 Angle Sensor 19 Pressure Sensor 20 Torque Sensor 21 Air-fuel ratio sensor 22 Intake port 23 Exhaust port 24 Intake valve 25 Exhaust valve

Claims

1. An engine device driven by gaseous fuel, Detecting a combustion period in a combustion chamber, and estimating abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion; The engine device further comprises a suppression method for suppressing the abnormal combustion when the abnormal combustion is estimated.

2. 2. The engine apparatus according to claim 1, wherein the suppression method comprises performing control to shorten the combustion period.

3. 3. The engine apparatus according to claim 2, wherein the suppression method is to increase an ignition force in the combustion chamber.

4. 4. The engine device according to claim 3, wherein in the case of an engine that performs ignition by a micro-pilot method in which the gaseous fuel is ignited by injecting liquid fuel, the ignition power is increased by increasing the injection amount of the liquid fuel and / or by increasing the injection pressure of the liquid fuel, while in the case of an engine that performs ignition by a spark ignition method using an ignition plug, the ignition power is increased by increasing ignition energy.

5. 3. The engine apparatus according to claim 2, wherein the suppression method comprises enriching the air-fuel ratio in the combustion chamber.

6. 3. The engine apparatus according to claim 2, wherein the suppression method comprises advancing an ignition timing in the combustion chamber.

7. 3. The engine device according to claim 2, wherein the suppression method comprises reducing an engine load.

8. 3. The engine device according to claim 2, characterized in that, as the suppression method, increasing the ignition power in the combustion chamber is given priority over enriching the air-fuel ratio in the combustion chamber, advancing the ignition timing in the combustion chamber, and reducing the engine load, and / or enriching the air-fuel ratio in the combustion chamber is given priority over advancing the ignition timing in the combustion chamber and reducing the engine load, and / or advancing the ignition timing in the combustion chamber is given priority over reducing the engine load.

9. A method for controlling a gaseous fuel-driven engine device, comprising: Detecting a combustion period in a combustion chamber, and estimating abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion; A control method for an engine device, comprising: determining a suppression method for suppressing the abnormal combustion when the abnormal combustion is estimated.

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