Engine device and method for controlling engine device

Abstract

The invention provides an engine device and a control method thereof, which can grasp the combustion state of an engine and predict abnormal combustion before the abnormal combustion occurs. An engine device (1) driven by gaseous fuel detects a combustion period in a combustion chamber (12a) of an engine (2), estimates abnormal combustion occurring in the combustion chamber (12a) on the basis of the correlation between the combustion period and abnormal combustion (backfire), and determines a suppression method for suppressing abnormal combustion when the abnormal combustion is estimated. As a suppression method, the engine device (1) performs control for shortening the combustion period.

Description

Technical Field

[0001] The present invention relates to an engine device which is driven by injecting gas fuel into a combustion chamber and a control method thereof. Background Art

[0002] In the past, there are gas engines that are driven by injecting gas fuel such as hydrogen into the combustion chamber in the cylinder, and dual-fuel engines that are driven by injecting gas fuel such as hydrogen and at least one of liquid fuels such as light oil and heavy oil into the combustion chamber in the cylinder. For example, the dual-fuel engine operates in any one of the gas mode in which gas fuel is injected into the combustion chamber to drive it, and the diesel mode in which liquid fuel is injected into the combustion chamber to drive it. In addition, as another operation mode, it operates in a mixed combustion mode in which both gas fuel and liquid fuel are injected into the combustion chamber to drive it. In such an engine device, before ignition by a micro-pilot method (Japanese: マイクロパイロット method) that injects a small amount of liquid fuel or ignition by an ignition device of a spark ignition method using a spark plug, abnormal combustion such as pre-ignition (premature ignition) in which gas fuel spontaneously ignites in the combustion chamber may occur, and therefore it is required to suppress abnormal combustion.

[0003] For example, according to Patent Document 1, an engine control device for controlling an engine that directly supplies hydrogen to a combustion chamber during a compression stroke comprises: a determination mechanism that determines whether a torque reduction control condition is established; an injection start timing correction mechanism that advances the injection start timing of hydrogen from the compression stroke to the intake stroke so as to reduce the engine's driving torque; and an ignition timing correction mechanism that delays and corrects the ignition timing so as to reduce the engine's driving torque. Furthermore, when the determination mechanism determines that the torque reduction control condition is established, the engine control device advances the injection start timing of hydrogen from the compression stroke to the intake stroke in an operating region where backfire is likely to occur through the injection start timing correction mechanism, and delays and corrects the ignition timing in an operating region where backfire is unlikely to occur through the ignition timing correction mechanism.

[0004] In addition, according to patent document 2, the control device of the hydrogen engine is provided with a hydrogen supply mechanism for supplying hydrogen, and a control mechanism for switching and using the hydrogen supply mechanism to supply hydrogen in the intake stroke and the hydrogen supply mechanism to supply hydrogen in the compression stroke to control the timing of hydrogen supply, and also provided with an exhaust gas reflow mechanism for reflowing the exhaust gas to the intake system. In addition, the control mechanism causes the hydrogen supply mechanism to supply the hydrogen in the compression stroke under the first engine operating state in which the engine rotation speed is less than the prescribed first rotation speed, and causes the exhaust gas reflow mechanism to reflow the exhaust gas to the intake system. In addition, the control mechanism causes the hydrogen supply mechanism to supply the hydrogen in the intake stroke and the compression process under the second engine operating state in which the engine rotation speed is greater than the first rotation speed and less than the prescribed second rotation speed faster than the first rotation speed, and causes the exhaust gas reflow mechanism to reflow the exhaust gas to the intake system. In addition, the control mechanism causes the hydrogen supply mechanism to supply the hydrogen in the intake stroke and the compression stroke under the third engine operating state in which the engine rotation speed is greater than the second rotation speed.

[0005] In addition, according to Patent Document 3, a control device for an internal combustion engine includes: an occurrence frequency detection mechanism that detects the occurrence frequency of pre-ignition per unit time; and a temperature range variable mechanism that changes the range of the pre-ignition suppression temperature range in such a manner that the occurrence frequency of pre-ignition in at least a part of the pre-ignition suppression temperature range is below the allowable limit when the occurrence frequency of pre-ignition in at least a part of the pre-ignition suppression temperature range exceeds the allowable limit. Furthermore, the cylinder wall temperature control mechanism of the control device controls the pre-ignition suppression temperature range changed by the temperature range variable mechanism in such a manner that the wall temperature parameter converges to the pre-ignition suppression temperature range.

[0006] Patent Document 1: Japanese Patent No. 4406880

[0007] Patent Document 2: Japanese Patent No. 4618150

[0008] Patent Document 3: Japanese Patent No. 5939263

[0009] In the prior art described in Patent Document 1, the combustion state of the engine is not defined and detected, and when the torque reduction control condition is satisfied, backfire suppression control is determined, so the effect of backfire suppression control is limited.

[0010] In the prior art described in Patent Document 2, the combustion state of the engine is not defined and detected, and the pre-ignition is suppressed and controlled by distinguishing between compression stroke supply, intake stroke supply, and exhaust gas recirculation by evaluating the engine rotation speed, so the effect of suppressing and controlling the pre-ignition is limited. In addition, in the prior art, the suppression control of abnormal combustion is performed without changing the combustion control items such as the ignition timing and ignition energy of the engine, so the effect of suppressing and controlling the abnormal combustion is limited.

[0011] In the prior art described in Patent Document 3, the combustion state of the engine is not defined and detected, and the pre-ignition suppression control is determined only by evaluating the occurrence frequency of pre-ignition (premature ignition), so the effect of the pre-ignition suppression control is limited.

[0012] As described above, in the prior art engine, it is impossible to accurately grasp the operating state (combustion state) of the engine where abnormal combustion occurs, so it is impossible to predict abnormal combustion before it occurs, and it can only be suppressed after abnormal combustion occurs in the engine. Therefore, the damage caused by abnormal combustion may accumulate in the engine and damage the engine. Summary of the invention

[0013] An object of the present invention is to provide an engine device and a control method thereof that can grasp the combustion state of an engine and predict abnormal combustion before it occurs.

[0014] In order to solve the above-mentioned problems, the engine device of the present invention is an engine device driven by gas fuel, characterized in that the combustion period in the combustion chamber is detected, the abnormal combustion occurring in the above-mentioned combustion chamber is inferred based on the correlation between the above-mentioned combustion period and the abnormal combustion, and when the above-mentioned abnormal combustion is inferred, a suppression method for suppressing the above-mentioned abnormal combustion is determined.

[0015] In addition, in order to solve the above-mentioned problems, the control method of the engine device of the present invention is a control method of an engine device driven by gas fuel, which is characterized in that the combustion period in the combustion chamber is detected, and the abnormal combustion generated in the above-mentioned combustion chamber is inferred based on the correlation between the above-mentioned combustion period and the abnormal combustion. When the above-mentioned abnormal combustion is inferred, a suppression method for suppressing the above-mentioned abnormal combustion is determined.

[0016] According to the present invention, it is possible to provide an engine device and a control method thereof which are capable of grasping the combustion state of the engine and predicting abnormal combustion before the abnormal combustion occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram showing an example of an engine device according to an embodiment of the present invention.

[0018] Figure 2This is a graph showing an example of an operable region in the relationship between the ignition timing and the excess air ratio in the engine device.

[0019] Figure 3 This is a graph showing an example of the distribution of the combustion period corresponding to the operable region in the relationship between the ignition timing and the excess air ratio in the engine device according to the embodiment of the present invention.

[0020] Figure 4 This is a graph showing an example of the relationship between the combustion period in the combustion chamber and the excess air ratio in the engine device according to the embodiment of the present invention.

[0021] Figure 5 This is a graph showing an example of the relationship between the combustion period in the combustion chamber and the excess air ratio in the engine device according to the embodiment of the present invention.

[0022] Figure 6 This is a graph showing an example of the relationship between the combustion period in the combustion chamber and the excess air ratio in the engine device according to the embodiment of the present invention.

[0023] Figure 7 This is a flowchart showing an example of an operation of suppressing abnormal combustion in the engine device according to the embodiment of the present invention.

[0024] Description of Reference Numerals

[0025] 1…engine device; 2…engine; 3…intake passage; 4…exhaust passage; 5…control unit; 6…gas fuel injection unit; 7…throttle valve; 8…ignition device; 11…cylinder body; 12…cylinder; 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. DETAILED DESCRIPTION

[0026] An engine device 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 As shown, the engine device 1 includes an engine 2 , an intake passage 3 , an exhaust passage 4 , and a control unit 5 .

[0027] In particular, in the present embodiment, the engine device 1 is a gas engine that is configured to be driven by injecting a gas fuel such as hydrogen into a combustion chamber 12a of the engine 2, and includes a gas fuel injection unit 6 for injecting the gas fuel, a throttle valve 7 for adjusting the amount of intake air, and an ignition device 8 for igniting the gas fuel in the combustion chamber 12a.

[0028] The engine 2 is configured by including a plurality of cylinders 12 in a cylinder block 11. Figure 1 Only one cylinder 12 is shown in the figure. Figure 1 As shown, each cylinder 12 is composed of a cylinder 13, a piston 14 and a cylinder head 15. Each cylinder 12 is provided with a gas fuel injection unit 6 and an ignition device 8.

[0029] The cylinder 13 is formed in a cylindrical shape, for example, in the cylinder body 11, and the piston 14 is slidably accommodated in 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 inside.

[0030] A crankshaft 17 is connected to the piston 14 below the cylinder 13 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 .

[0031] The cylinder 13 is provided with an angle sensor 18 for detecting the rotation angle of the crankshaft 17, that is, the rotation speed of the engine 2, and the angle sensor 18 sends the detection result to the control unit 5. The cylinder 13 is provided with a pressure sensor 19 for detecting the internal pressure of the combustion chamber 12a, that is, the cylinder pressure of the cylinder 13, and the pressure sensor 19 sends the detection result to the control unit 5. The cylinder 13 is provided with a torque sensor 20 for detecting the engine load (engine torque) of the engine 2 near the crankshaft 17, and the torque sensor 20 sends the detection result to the control unit 5.

[0032] The cylinder head 15 has an intake port 22 and an exhaust port 23 communicating with the combustion chamber 12a of the cylinder 13, and includes an intake valve 24 and an exhaust valve 25 that respectively open and close the intake port 22 and the exhaust port 23 with respect to the combustion chamber 12a.

[0033] The intake port 22 is connected to the intake passage 3, and the air supplied from the intake passage 3 is introduced into the combustion chamber 12a. The exhaust port 23 is connected to the exhaust passage 4, and the exhaust gas generated in the combustion chamber 12a is discharged into the exhaust passage 4. By opening the intake valve 24, the mixed gas of fuel gas and air can be sucked into the combustion chamber 12a through the intake port 22, and on the other hand, by opening the exhaust valve 25, the exhaust gas generated in the combustion chamber 12a can be discharged through the exhaust port 23.

[0034] also, Figure 1 , the intake passage 3 and the intake port 22 are directly connected. However, in order to connect the intake passage 3 and the intake ports 22 of the plurality of cylinders 12, an intake manifold having a branch flow path branching from the intake passage 3 to the plurality of cylinders 12 may be provided between the intake passage 3 and the engine 2. Figure 1 The figure shows an example in which the exhaust passage 4 and the exhaust port 23 are directly connected, but when the exhaust passage 4 and the exhaust ports 23 of multiple cylinders 12 are connected, an exhaust manifold having a branch flow path branching from the exhaust passage 4 to the multiple cylinders 12 can be provided between the exhaust passage 4 and the engine 2.

[0035] In each cylinder 12, a gas fuel injection unit 6 is provided at an intake port 22, and is controlled by a control unit 5 to inject gas fuel supplied from a gas fuel tank (not shown) into the intake port 22. A mixed gas of air supplied from the intake passage 3 and gas fuel supplied from a gas fuel tank (not shown) is supplied from the intake port 22 to the combustion chamber 12a. The gas fuel injection unit 6 is composed of, for example, a gas intake valve, a gas injector, etc. The gas fuel injection unit 6 is controlled by the control unit 5 in terms of the injection amount, injection pressure, injection period, etc. of the gas fuel. For example, by increasing the injection amount and injection pressure, the air-fuel ratio of the combustion chamber 12a can be enriched.

[0036] 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 a combustion chamber 12a below the cylinder head 15. The micro-pilot type ignition device 8 is controlled by the control unit 5 in terms of the injection amount, injection pressure, injection timing, etc. of the liquid fuel, and, for example, the ignition capability (Japanese: ignition power) can be increased by increasing the injection amount and injection pressure.

[0037] Alternatively, the ignition device 8 may be a spark ignition device using a spark plug. The ignition energy (eg, power supplied to the spark plug) of the spark ignition device 8 is controlled by the control unit 5, and the ignition capacity can be increased by increasing the ignition energy.

[0038] The intake passage 3 is connected to the intake port 22 of the cylinder 12 of the engine 2, and compressed and cooled air is supplied to each cylinder 12 through the intake port 22. In addition, a supercharger (not shown) that compresses the air flowing through the intake passage 3 and sends it to the downstream side in the intake direction, and an intercooler (not shown) that cools the air flowing through the intake passage 3 can be provided in the intake passage 3. In addition, an air filter (not shown) that purifies and introduces fresh air can be provided at the upstream end of the intake passage 3 in the intake direction.

[0039] The intake passage 3 is provided with a throttle valve 7 for adjusting the amount of intake air delivered to the intake port 22. The throttle valve 7 is controlled by the control unit 5 and the opening is adjusted. The amount of intake air delivered to the intake port 22 is adjusted according to the opening of the throttle valve 7, so that the excess air ratio (the proportion of intake air in the mixture) of the gas fuel and air injected from the intake port 22 to the combustion chamber 12a can be adjusted. For example, by reducing the amount of intake air, the air-fuel ratio of the combustion chamber 12a can be enriched. That is, by adjusting the opening of the throttle valve 7, the flow rate of air supplied from the intake passage 3 to the intake port 22 can be adjusted.

[0040] The exhaust passage 4 is connected to the 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 is provided in the exhaust passage 4 to detect the air-fuel ratio of the exhaust gas. The air-fuel ratio sensor 21 sends the detection result to the control unit 5.

[0041] 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 various parts of the engine 2. The control unit 5 can store various programs for controlling the engine 2, and control the engine 2 by reading and executing the programs.

[0042] In the engine device 1, the ignition device 8 is usually operated at the ignition timing determined by the control unit 5, for example, by injecting liquid fuel into the combustion chamber 12a at a predetermined liquid fuel injection timing (injection timing), thereby igniting the gas fuel inside the combustion chamber 12a and starting combustion. However, when an abnormality such as excessively high temperature or excessively high pressure inside the combustion chamber 12a occurs, the gas fuel inside the combustion chamber 12a may spontaneously ignite before the ignition timing (liquid fuel injection timing), and abnormal combustion such as pre-ignition (premature ignition) may occur.

[0043] When the engine device 1 is operated, the relationship between the ignition timing (liquid fuel injection timing) of the combustion chamber 12a and the excess air ratio (ratio of intake air in the mixture) of the mixture injected into the combustion chamber 12a is as follows: Figure 2 As shown, the engine device 1 can be operated within the operable region 30 , but outside the operable region 30 , there is a high possibility that dangerous combustion will occur in the combustion chamber 12 a , and the engine device 1 cannot be operated.

[0044] In addition, near the edge of the operable region 30, there is a high possibility that abnormal combustion such as pre-ignition (premature ignition) will occur in the engine 2 even within the range of the operable region 30. For example, near the edge 31 of the operable region 30 on the side where the excess air ratio is relatively high and the ignition timing is relatively delayed, there is a high possibility that pre-ignition and backfire will occur as abnormal combustion.

[0045] in addition, Figure 33 shows the result obtained by monitoring the combustion period of the degree of combustion promotion in the combustion chamber 12a when the engine device 1 is operated within the range of the operable region 30. For example, the control unit 5 detects the rotation angle (deg) of the crankshaft 17 by the angle sensor 18 and detects the cylinder pressure of the cylinder 13 by the pressure sensor 19 during the operation of the engine device 1, and calculates the heat release rate in the combustion chamber 12a based on the change in the cylinder pressure of the cylinder 13 and the change in the volume of the combustion chamber 12a. Then, the control unit 5 calculates the difference (interval) between the crank angles of the crankshaft 17 at which the heat release amount is 10% and 90% of the total heat release amount in the combustion chamber 12a by accumulating the heat release rate in the crank angle throughout the combustion stroke as the combustion period.

[0046] According to the monitoring results, the distribution of the combustion period in the combustion chamber 12a is substantially parallel to the edge 31 of the operable region 30 and is uniform, and the larger the combustion period is, the distribution is near the edge 31 of the operable region 30, and the smaller the combustion period is, the farther the distribution is from the edge 31 of the operable region 30. In other words, the combustion period in the combustion chamber 12a and abnormal combustion have the following correlation: the larger the combustion period, the higher the possibility of abnormal combustion such as pre-ignition and backfire, and on the other hand, the smaller the combustion period, the lower the possibility of abnormal combustion. In addition, if the combustion period is too small, pre-ignition and knocking will occur, but it can be monitored by knocking detection that detects characteristic cylinder pressure vibration.

[0047] about Figure 3 The monitoring results of the combustion period shown in FIG. 1 show that the changes in the combustion period at the predetermined ignition times T1, T2, and T3 are as follows: Figure 4 , Figure 5 , Figure 6 As shown by the black dots in the figure, the linearity is good with respect to the change of the excess air rate (air-fuel ratio), so it is easy to detect the change of the combustion period corresponding to the abnormal combustion. 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 reaching the dangerous period P1 of abnormal combustion where backfire occurs. In addition, when evaluating the frequency of occurrence of slight abnormal combustion that also occurs at a low frequency in the operable area, the change of the frequency of occurrence at the specified ignition period T1, T2, and T3 is as shown in FIG. Figure 4 , Figure 5 , Figure 6 As shown by the white dots in the figure, the linearity with respect to the change of the excess air ratio (air-fuel ratio) is not very good, so it is difficult to detect the change of the combustion form toward abnormal combustion that cannot continue to operate. Therefore, before the occurrence frequency of abnormal combustion reaches the dangerous frequency P2 of abnormal combustion that causes backfire, it is difficult to detect that the occurrence frequency is approaching the dangerous frequency P2.

[0048] Therefore, in this embodiment, the control unit 5 detects the combustion period of the combustion promotion degree in the combustion chamber 12a, and based on the correlation between the combustion period and abnormal combustion, infers that abnormal combustion or its precursor occurs in the combustion chamber 12a. When abnormal combustion or its precursor is inferred, a suppression method for suppressing abnormal combustion is determined and executed.

[0049] Specifically, first, the control unit 5 calculates the difference (interval) between the crank angles of the crankshaft 17 at which the heat release amount obtained by accumulating the heat release rate throughout the combustion stroke crank angle in the combustion chamber 12a is 10% and 90% of the total as the combustion period. In addition, in the present embodiment, based on the correlation between the combustion period in the combustion chamber 12a and abnormal combustion, when viewed from the side with a smaller combustion period, it is closer to the edge 31 of the operable region 30, so the danger period is pre-set as a threshold value that can be inferred as a combustion period with a high possibility of abnormal combustion. In addition, the danger period is a (closer) combustion period that does not reach the edge 31 of the operable region 30, and is a combustion period that can predict a precursor of abnormal combustion that may occur in the future. The control unit 5 monitors the combustion period in the combustion chamber 12a, and in the case of exceeding the danger period, it is inferred that abnormal combustion with backfire occurs or there is a precursor of abnormal combustion, and in the case of being below the danger period, it is inferred that abnormal combustion with no backfire occurs or there is no precursor of abnormal combustion.

[0050] When the control unit 5 infers abnormal combustion (or a precursor), as a suppression method for suppressing abnormal combustion, it determines and executes a suppression method for controlling each part of the engine device 1 in a manner of shortening the combustion period in the combustion chamber 12a. In addition, a safety period (e.g., 27 to 28 degrees) is pre-set as a combustion period in which the engine device 1 can be safely operated without abnormal combustion, and the control unit 5 preferably executes the suppression method until the combustion period in the combustion chamber 12a is less than the safety period.

[0051] For example, as a suppression method, the control unit 5 increases the ignition capacity in the combustion chamber 12a by means of the ignition device 8, thereby shortening the combustion period. When the ignition device 8 is in a micro-pilot mode, the control unit 5 increases the ignition capacity by increasing the injection amount and injection pressure of the liquid fuel. At this time, the control unit 5 preferably gradually increases the ignition capacity by gradually increasing the injection amount and injection pressure of the liquid fuel in each cycle. In addition, the control unit 5 can set an upper limit of the ignition capacity by setting an upper limit on the injection amount and injection pressure of the liquid fuel, and increase the ignition capacity to the upper limit of the ignition capacity.

[0052] Alternatively, the control unit 5 increases the ignition capacity by increasing the ignition energy of the spark plug when the ignition device 8 is in the spark ignition mode. In this case, the control unit 5 preferably gradually increases the ignition capacity by gradually increasing the ignition energy of the spark plug in each cycle. In addition, the control unit 5 may set an upper limit on the ignition capacity by setting an upper limit on the ignition energy of the spark plug, and increase the ignition capacity to the upper limit on the ignition capacity.

[0053] In addition, as a suppression method, the control unit 5 performs enrichment of the air-fuel ratio in the combustion chamber 12a, thereby shortening the combustion period. The control unit 5 reduces the intake air amount through the throttle valve 7, thereby enriching the air-fuel ratio in the combustion chamber 12a. At this time, the control unit 5 preferably gradually enriches the air-fuel ratio by gradually reducing the intake air amount. In addition, the control unit 5 may set a lower limit for the intake air amount to set an upper limit for enrichment, and enrich the air-fuel ratio to the upper limit for enrichment.

[0054] In addition, as a suppression method, the control unit 5 advances the ignition timing in the combustion chamber 12a by means of the ignition device 8, thereby shortening the combustion period. When the ignition device 8 is in a micro-pilot mode, the control unit 5 advances the ignition timing by advancing the injection timing of the liquid fuel, and when the ignition device 8 is in a spark ignition mode, the control unit 5 advances the ignition timing by advancing the ignition timing of the spark plug. At this time, the control unit 5 preferably gradually advances the ignition timing by gradually advancing the injection timing of the liquid fuel and the ignition timing of the spark plug in each cycle. In addition, 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 and the ignition timing of the spark plug, so that the ignition timing is advanced to the upper limit.

[0055] In addition, as a suppression method, the control unit 5 executes a reduction in the engine load (engine torque) of the engine 2, thereby avoiding abnormal combustion. At this time, the control unit 5 preferably gradually reduces the engine load in each cycle. In addition, the control unit 5 can set an engine load lower limit for the engine load and reduce the engine load to the engine load lower limit.

[0056] As the suppression method, the control unit 5 can increase the ignition capability 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, and it is preferable to set a priority for which suppression method to apply. For example, the control unit 5 preferably increases the ignition capability in the combustion chamber 12a in priority 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. In addition, the control unit 5 preferably enriches the air-fuel ratio in the combustion chamber 12a in priority to advancing the ignition timing in the combustion chamber 12a and reducing the engine load. In addition, the control unit 5 preferably advances the ignition timing in the combustion chamber 12a in priority to reducing the engine load.

[0057] Furthermore, the control unit 5 may stop the operation of the engine device 1 even if the control unit increases the ignition capacity in the combustion chamber 12a, enriches the air-fuel ratio in the combustion chamber 12a, advances the ignition timing in the combustion chamber 12a, and reduces the engine load, but is unable to shorten the combustion period and it is difficult to avoid abnormal combustion (for example, it is unable to fall below a prescribed safety period or other prescribed period).

[0058] Next, refer to Figure 7 The flowchart of FIG. 1 will explain the abnormal combustion suppression operation of the engine device 1 according to the present embodiment.

[0059] First, the control unit 5 determines whether abnormal combustion such as knocking has occurred in the engine 2 (step S1). If knocking has occurred (step S1: Yes), the control unit 5 performs knocking suppression control (step S2) and ends the suppression operation.

[0060] On the other hand, when knocking has not occurred (step S1: No), the control unit 5 determines whether abnormal combustion due to pre-ignition has occurred in the engine 2 (step S3).

[0061] When pre-ignition has not occurred (step S3 : No), the control unit 5 ends the suppression operation.

[0062] On the other hand, when pre-ignition occurs (step S3: yes), the control unit 5 calculates the cumulative heat release rate throughout the combustion stroke crank angle in the combustion chamber 12a and obtains the difference (interval) between the crank angle of the crankshaft 17 of 10% and 90% of the total heat release amount as the combustion period, and detects the combustion period corresponding to the rotation angle of the crankshaft 17 through the angle sensor 18 to determine whether the combustion period exceeds the dangerous period (step S4).

[0063] When the combustion period is equal to or shorter than the dangerous period (step S4: No), the control unit 5 reduces the engine load (step S5), returns to step S1, and repeats the suppression operation.

[0064] On the other hand, when the combustion period exceeds the dangerous period (step S4: yes), the control unit 5 infers the precursor of abnormal combustion of backfire, and determines whether the ignition capacity is less than the upper limit of the ignition capacity in order to determine whether to increase the ignition capacity in the combustion chamber 12a with the help of the ignition device 8 as a method of suppressing backfire (step S6).

[0065] When the ignition capability is less than the ignition capability upper limit (step S6: Yes), the control unit 5 increases the ignition capability by increasing the injection amount, injection pressure or ignition energy of the liquid fuel (step S7), returns to step S1 and repeats the suppression operation.

[0066] On the other hand, when the ignition capability is above the ignition capability upper limit (step S6: No), the control unit 5 determines whether the air-fuel ratio is less than the enrichment upper limit in order to determine whether to perform enrichment of the air-fuel ratio in the combustion chamber 12a as a backfire suppression method instead of increasing the ignition capability (step S8).

[0067] When the air-fuel ratio is less than the enrichment upper limit (step S8: Yes), the control unit 5 reduces the intake air amount via the throttle valve 7 to enrich the air-fuel ratio of the combustion chamber 12a (step S9), and returns to step S1 to repeat the suppression operation.

[0068] On the other hand, when the air-fuel ratio is above the enrichment upper limit (step S8: No), the control unit 5 determines whether the advancement of the ignition timing in the combustion chamber 12a is less than the advancement upper limit in order to determine whether to perform advancement of the ignition timing in the combustion chamber 12a as a backfire suppression method instead of enriching the air-fuel ratio (step S10).

[0069] When the advancement of the ignition timing is less than the advancement upper 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 returns to step S1 to repeat the suppression operation.

[0070] On the other hand, when the ignition timing is advanced by more than the advancement upper limit (step S10: No), the control unit 5 reduces the engine load (step S5) as a backfire suppression method instead of advancing the ignition timing, and returns to step S1 to repeat the suppression operation.

[0071] As described above, according to the present embodiment, the engine device 1 that drives the engine 2 by injecting gas 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, and infers the abnormal combustion occurring in the combustion chamber 12a based on the correlation between the combustion period and abnormal combustion (backfire). When abnormal combustion is inferred, a suppression method for suppressing the abnormal combustion is determined and executed.

[0072] In other words, the control method of the engine device 1 that is driven by injecting gas fuel into the combustion chamber 12a of the engine 2 is to detect the combustion period in the combustion chamber 12a, such as the combustion period of the degree of combustion promotion, and infer the abnormal combustion occurring in the combustion chamber 12a based on the correlation between the combustion period and the abnormal combustion (backfire). When the abnormal combustion is inferred, the suppression method for suppressing the abnormal combustion is determined and executed. In addition, the control method can be executed by the control unit 5, for example, it can be composed of a program.

[0073] Thus, the engine device 1 can improve the controllability of suppressing abnormal combustion by calculating the combustion period based on the cylinder pressure (internal pressure of the combustion chamber 12a) of the cylinder 13, which represents the degree of combustion promotion that causes abnormal combustion such as backfire. In addition, the slow combustion promotion (incomplete combustion) in the combustion chamber 12a sometimes causes pre-ignition in the next cycle and thereafter, and further progress may cause backfire. Therefore, the combustion period is judged as the combustion state of the engine 2, so that the most dangerous backfire can be predicted (inferred) in advance and suppression control can be performed before it occurs. Therefore, it is also possible to suppress the accumulation of damage caused by abnormal combustion in the engine 2, and the damage to the engine 2 can be suppressed, so that the engine 2 can be operated more safely.

[0074] Furthermore, according to the present embodiment, the engine device 1 performs control to shorten the combustion period as a suppression method.

[0075] Thus, the engine device 1 suppresses the combustion surplus of the gas fuel caused by the slow combustion promotion (incomplete combustion) in order to shorten the combustion period, and can perform suppression control before abnormal combustion such as pre-ignition and backfire occurs in the next cycle and thereafter. In addition, in the control of shortening the combustion period, the combustion period can be made to converge to the target value (such as the safety period) more quickly, which plays a particularly advantageous role in transient operation that requires rapid control.

[0076] Furthermore, according to the present embodiment, as a suppression method, the engine device 1 increases the ignition capability in the combustion chamber 12 a.

[0077] For example, according to the present embodiment, in the case of an engine 2 that ignites by a micro-pilot method in which gas fuel is ignited by injection of liquid fuel, the engine device 1 increases the ignition capability by increasing the injection amount of liquid fuel and / or increasing the injection pressure of liquid fuel. On the other hand, in the case of an engine 2 that ignites by a spark ignition method using a spark plug, the ignition capability is increased by increasing the ignition energy.

[0078] Thus, the engine device 1 can suppress the combustion surplus of the gas fuel and shorten the combustion period by increasing the ignition capacity in the combustion chamber 12a, and can perform suppression control before abnormal combustion such as backfire occurs.

[0079] Furthermore, according to the present embodiment, as a suppression method, the engine device 1 enriches the air-fuel ratio in the combustion chamber 12 a.

[0080] Thus, the engine device 1 can suppress the combustion surplus of the gas fuel and shorten the combustion period by enriching the air-fuel ratio in the combustion chamber 12a, and can perform suppression control before abnormal combustion such as backfire occurs. In addition, in the control of enriching the air-fuel ratio, the combustion period can be converged to the target value (such as the safety period) more quickly.

[0081] Furthermore, according to the present embodiment, as a suppression method, the engine device 1 advances the ignition timing in the combustion chamber 12a.

[0082] Thus, the engine device 1 can suppress the combustion surplus of the gas fuel and shorten the combustion period by advancing the ignition timing in the combustion chamber 12a, and can perform suppression control before abnormal combustion such as backfire occurs. In addition, since pre-ignition occurs due to spontaneous ignition in the combustion chamber 12a, pre-ignition can also be suppressed by setting the ignition timing before the spontaneous ignition occurs. In addition, in the control of advancing the ignition timing, a wider range of excess air ratios (air-fuel ratios) can be selected.

[0083] Furthermore, according to the present embodiment, the engine device 1 reduces the engine load as a suppression method.

[0084] Therefore, even if the combustion period is shorter than the pre-set danger period and the combustion period is shortened by changing the operating parameters (ignition ability, enrichment, ignition advance), if abnormal combustion such as pre-ignition occurs, hot spots may occur in the cylinder 13. Therefore, the engine device 1 can suppress abnormal combustion caused by hot spots by reducing the engine load, thereby suppressing damage to the engine 2.

[0085] In addition, according to the present embodiment, as a suppression method, the engine device 1 increases the ignition capacity in the combustion chamber 12a with priority 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, and / or enriches the air-fuel ratio in the combustion chamber 12a with priority over advancing the ignition timing in the combustion chamber 12a and reducing the engine load, and / or advances the ignition timing in the combustion chamber 12a with priority over reducing the engine load.

[0086] Thus, the engine device 1 prioritizes practical suppression methods such as increasing the ignition capacity, while deprioritizing suppression methods that are undesirable to the user of the engine device 1 such as reducing the engine load.

[0087] In addition, in the above-mentioned embodiment, the following example is described, that is, the engine device 1 is a gas engine configured to be driven by injecting a gas 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 can also be configured as a dual-fuel engine that is driven by injecting a gas fuel such as hydrogen and a liquid fuel such as light oil or heavy oil into the combustion chamber 12a of the engine 2. In this case, the engine device 1 injects gas fuel through the gas fuel injection unit 6 and injects liquid fuel through a liquid fuel injection unit such as a micro-pilot ignition device 8.

[0088] The engine device 1 of the dual-fuel engine operates in either a gas mode in which gas fuel is introduced into the combustion chamber 12a for driving, or a diesel mode in which liquid fuel is introduced into the combustion chamber 12a for driving. In addition, as another operating mode, it operates in a mixed combustion mode in which both gas fuel and liquid fuel are introduced into the combustion chamber 12a for driving.

[0089] The present invention can be modified appropriately within the scope of the gist or concept of the invention that can be read from the claims and the entire specification, and the engine device and control method thereof accompanying such modification are also included in the technical concept of the present invention.

[0090] [Notes on the invention]

[0091] The following is a summary of the invention extracted from the above-mentioned embodiment. In addition, each structure and each processing function described in the following notes can be selected and combined arbitrarily.

[0092] <Note 1>

[0093] An engine device is an engine device driven by gas fuel, characterized in that:

[0094] detecting a combustion period in a combustion chamber, and inferring abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion,

[0095] When the abnormal combustion is estimated, a suppression method for suppressing the abnormal combustion is determined.

[0096] <Note 2>

[0097] The engine device according to note 1, characterized in that:

[0098] As the suppression method, control is performed to shorten the combustion period.

[0099] <Note 3>

[0100] The engine device according to note 2 is characterized in that:

[0101] As the suppression method, the ignition capacity in the combustion chamber is increased.

[0102] <Note 4>

[0103] The engine device according to note 3, characterized in that:

[0104] In the case of an engine that ignites the above-mentioned gas fuel by a micro-pilot method through the injection of liquid fuel, the above-mentioned ignition capability is increased by increasing the injection amount of the above-mentioned liquid fuel and / or increasing the injection pressure of the above-mentioned liquid fuel. On the other hand, in the case of an engine that ignites by a spark ignition method using a spark plug, the above-mentioned ignition capability is increased by increasing the ignition energy.

[0105] <Note 5>

[0106] The engine device according to any one of appendixes 2 to 4, characterized in that:

[0107] As the suppression method, the air-fuel ratio in the combustion chamber is enriched.

[0108] <Note 6>

[0109] The engine device according to any one of appendixes 2 to 5, characterized in that:

[0110] As the suppression method, the ignition timing in the combustion chamber is advanced.

[0111] <Note 7>

[0112] The engine device according to any one of appendixes 2 to 6, characterized in that:

[0113] As the above-mentioned suppression method, the engine load is reduced.

[0114] <Note 8>

[0115] The engine device according to note 2 is characterized in that:

[0116] As the above-mentioned suppression method, the ignition capacity in the above-mentioned combustion chamber is increased with priority over the enrichment of the air-fuel ratio in the above-mentioned combustion chamber, the advancement of the ignition timing in the above-mentioned combustion chamber and the reduction of the engine load, and / or the air-fuel ratio in the above-mentioned combustion chamber is enriched with priority over the advancement of the ignition timing in the above-mentioned combustion chamber and the reduction of the engine load, and / or the ignition timing in the above-mentioned combustion chamber is advanced with priority over the reduction of the engine load.

[0117] <Note 9>

[0118] A control method for an engine device is a control method for an engine device driven by gas fuel, characterized in that:

[0119] detecting a combustion period in the combustion chamber, and inferring abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion,

[0120] When the abnormal combustion is estimated, a suppression method for suppressing the abnormal combustion is determined.

[0121] <Note 10>

[0122] The control method of the engine device according to Appendix 9 is characterized in that:

[0123] As the suppression method, control is performed to shorten the combustion period.

[0124] <Note 11>

[0125] The control method of the engine device according to Appendix 10 is characterized in that:

[0126] As the suppression method, the ignition capacity in the combustion chamber is increased.

[0127] <Note 12>

[0128] The control method of the engine device according to Appendix 11 is characterized in that:

[0129] In the case of an engine that ignites the above-mentioned gas fuel by a micro-pilot method through the injection of liquid fuel, the above-mentioned ignition capability is increased by increasing the injection amount of the above-mentioned liquid fuel and / or increasing the injection pressure of the above-mentioned liquid fuel. On the other hand, in the case of an engine that ignites by a spark ignition method using a spark plug, the above-mentioned ignition capability is increased by increasing the ignition energy.

[0130] <Note 13>

[0131] The control method of an engine device according to any one of appendixes 10 to 12, characterized in that:

[0132] As the suppression method, the air-fuel ratio in the combustion chamber is enriched.

[0133] <Note 14>

[0134] The control method of an engine device according to any one of appendixes 10 to 13, characterized in that:

[0135] As the suppression method, the ignition timing in the combustion chamber is advanced.

[0136] <Note 15>

[0137] The control method of an engine device according to any one of appendixes 10 to 14, characterized in that:

[0138] As the above-mentioned suppression method, the engine load is reduced.

[0139] <Note 16>

[0140] The control method of the engine device according to Appendix 10 is characterized in that:

[0141] As the above-mentioned suppression method, the ignition capacity in the above-mentioned combustion chamber is increased with priority over the enrichment of the air-fuel ratio in the above-mentioned combustion chamber, the advancement of the ignition timing in the above-mentioned combustion chamber and the reduction of the engine load, and / or the air-fuel ratio in the above-mentioned combustion chamber is enriched with priority over the advancement of the ignition timing in the above-mentioned combustion chamber and the reduction of the engine load, and / or the ignition timing in the above-mentioned combustion chamber is advanced with priority over the reduction of the engine load.

Claims

1. An engine device is an engine device driven by gas fuel, characterized in that: detecting a combustion period in a combustion chamber, and inferring abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion, When the abnormal combustion is estimated, a suppression method for suppressing the abnormal combustion is determined.

2. The engine device according to claim 1, characterized in that: As the suppression method, control is performed to shorten the combustion period.

3. The engine device according to claim 2, characterized in that: As the suppression method, the ignition capacity in the combustion chamber is increased.

4. The engine device according to claim 3, characterized in that: In the case of an engine that ignites the gas fuel by a micro-pilot method through the injection of liquid fuel, the ignition capability is increased by increasing the injection amount of the liquid fuel and / or increasing the injection pressure of the liquid fuel. On the other hand, in the case of an engine that ignites by a spark ignition method using a spark plug, the ignition capability is increased by increasing the ignition energy.

5. The engine device according to claim 2, characterized in that: As the suppression method, the air-fuel ratio in the combustion chamber is enriched.

6. The engine device according to claim 2, characterized in that: As the suppression method, the ignition timing in the combustion chamber is advanced.

7. The engine device according to claim 2, characterized in that: As the suppression method, the engine load is reduced.

8. The engine device according to claim 2, characterized in that: As the suppression method, increasing the ignition capacity 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.

9. A method for controlling an engine device driven by gas fuel, characterized in that: detecting a combustion period in a combustion chamber, and inferring abnormal combustion occurring in the combustion chamber based on a correlation between the combustion period and abnormal combustion, When the abnormal combustion is estimated, a suppression method for suppressing the abnormal combustion is determined.

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