Engine system

Abstract

To rapidly normalize a combustion state of an engine on the basis of an in-cylinder pressure and an exhaust gas temperature.SOLUTION: An engine system comprises an engine which has a plurality of cylinders and which can burn a mixture of gas fuel and liquid fuel, and a control part which adjusts a gas fuel injection quantity or a liquid fuel injection quantity. The control part executes first control for adjusting the gas fuel injection quantity or the liquid fuel injection quantity on the basis of in-cylinder pressures of the plurality of cylinders, and second control for adjusting the gas fuel injection quantity in timing different from timing of the first control on the basis of exhaust gas temperatures of the plurality of cylinders.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an engine system. [Background technology]

[0002] In engines capable of co-firing gas and liquid fuels, the combustion state of each cylinder tends to vary greatly when using gas fuel, which can lead to knocking in cylinders with high in-cylinder pressure and misfires in cylinders with low in-cylinder pressure. Furthermore, deterioration of the gas fuel injection valve over time can cause the gas fuel injection amount to exceed the specified value, potentially raising the exhaust gas temperature.

[0003] The following technologies are known to suppress the above-mentioned phenomenon. For example, Patent Document 1 discloses that in an engine that burns a mixture of gasoline and hydrogen, the amount of hydrogen added is corrected to a decreasing direction when the maximum in-cylinder pressure exceeds a first predetermined value. Patent Document 2 discloses that when using gas fuel, the amount of gas fuel injection is corrected to a decreasing direction when it is determined that the temperature in the exhaust passage has reached or exceeded a high-temperature determination value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-46075 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-134128 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if injection quantity control based on in-cylinder pressure and injection quantity control based on exhaust temperature are performed simultaneously, the injection quantity control based on in-cylinder pressure will also affect the exhaust temperature, and the injection quantity control based on exhaust temperature will also affect the in-cylinder pressure, which may complicate the control and raise concerns that it may take a long time for the in-cylinder pressure and exhaust temperature to return to normal.

[0006] SUMMARY OF THE INVENTION In consideration of the above circumstances, an object of the present invention is to quickly normalize the combustion state of an engine based on the in-cylinder pressure and exhaust temperature. [Means for solving the problem]

[0007] In order to solve the above problems, the engine system of the present invention comprises an engine having a plurality of cylinders and capable of mixing gas fuel and liquid fuel, and a control unit that adjusts the gas fuel injection amount and the liquid fuel injection amount, wherein the control unit executes a first control that adjusts the gas fuel injection amount or the liquid fuel injection amount based on the internal pressure of the plurality of cylinders, and a second control that adjusts the gas fuel injection amount at a timing different from the first control based on the exhaust temperature of the plurality of cylinders.

[0008] The control unit may perform the first control at a first time interval, and perform the second control at a second time interval that is longer than the first time interval.

[0009] In the first control, the control unit may reduce the gas fuel injection amount for the cylinder in which the in-cylinder pressure is equal to or higher than a first threshold, and regulate the gas fuel injection amount for the other cylinders by adjusting the gas fuel injection amount.

[0010] In the first control, the control unit may increase the liquid fuel injection amount for the cylinder in which the in-cylinder pressure is less than a second threshold value that is lower than the first threshold value, and may not change the liquid fuel injection amount for the other cylinders.

[0011] In the first control, the control unit may reduce the gas fuel injection amount for the cylinder whose in-cylinder pressure is greater than or equal to the first threshold at a first speed, and when the in-cylinder pressure becomes less than the first threshold, increase the gas fuel injection amount at a second speed slower than the first speed.

[0012] In the second control, the control unit may reduce the amount of gas fuel injection for the cylinder whose exhaust temperature is equal to or higher than a third threshold, and increase the amount of gas fuel injection for the cylinder whose exhaust temperature is the lowest.

[0013] The engine is switchable between a gas mode in which the gas fuel and the liquid fuel are used simultaneously, a liquid mode in which only the liquid fuel is used, and a changeover mode in which the engine transitions bidirectionally between the gas mode and the liquid mode, and the control unit may not execute at least one of the first control and the second control in the changeover mode. [Effects of the Invention]

[0014] An object of the present invention is to quickly normalize the combustion state of an engine based on the in-cylinder pressure and the exhaust gas temperature. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a system diagram that schematically illustrates an engine system according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing the electrical configuration of an engine system according to an embodiment of the present invention. [Figure 3] 4 is a flowchart showing a first control according to one embodiment of the present invention. [Figure 4] 6 is a flowchart showing a second control according to one embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing an example of the in-cylinder pressure of each cylinder according to the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of changes in the cylinder pressure, exhaust temperature, gas fuel injection amount, and liquid fuel injection amount of the fifth cylinder according to one embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing changes in the governing output of liquid fuel and gas fuel when transitioning from the liquid mode to the gas mode according to a modified example of an embodiment of the present invention. [Figure 8]FIG. 10 is a diagram showing changes in the governing output of liquid fuel and gas fuel when transitioning from gas mode to liquid mode in a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] An engine system 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0017] First, a description will be given of the overall configuration of the engine system 100. Fig. 1 is a system diagram that schematically shows the engine system 100. Fig. 2 is a block diagram that shows the electrical configuration of the engine system 100.

[0018] The engine system 100 includes an engine 1, an air intake section 2, an exhaust section 3, a gas fuel supply section 4, a main fuel supply section 5, a pilot fuel supply section 6, a control section 7, and a turbocharger 8.

[0019] [engine] The engine 1 includes a cylinder block 11, a cylinder head 12, and a crankshaft 13. The cylinder block 11 includes a plurality of (six in this embodiment) cylinders 11C and a crankcase (not shown). The cylinder head 12 includes a combustion chamber 12C, an intake port 12N, and an exhaust port 12E for each cylinder 11C.

[0020] [Air supply section] The intake section 2 includes an intake pipe 21 and an intake manifold 22. The intake pipe 21 is connected via the intake manifold 22 to an intake port 12N for each cylinder 11C.

[0021] [Exhaust section] The exhaust section 3 includes an exhaust pipe 31 and an exhaust manifold 32. The exhaust pipe 31 is connected via the exhaust manifold 32 to the exhaust port 12E of each cylinder 11C.

[0022] [Gas fuel supply section] The gas fuel supply unit 4 includes a gas fuel tank 41, a gas valve unit 42, a gas fuel injection valve 43, and a gas fuel supply pipe 44. The gas fuel tank 41 stores a gas fuel that is gaseous at room temperature, such as hydrogen, methane, or ammonia. The gas fuel injection valve 43 is provided in the intake port 12N of each cylinder 11C. The gas fuel supply pipe 44 branches from the gas fuel tank 41 via the gas valve unit 42 to each cylinder 11C and is connected to the gas fuel injection valve 43 of each cylinder 11C.

[0023] The gas valve unit 42 includes, in order from upstream in the gas fuel supply direction G, a master valve 42M, an upstream shutoff valve 42U, a downstream shutoff valve 42D, and a regulator valve 42R, with the gas fuel tank 41 as the most upstream portion. A branch pipe 42T equipped with a bleed valve 42B is provided between the upstream shutoff valve 42U and the downstream shutoff valve 42D. At least the upstream shutoff valve 42U, the downstream shutoff valve 42D, and the bleed valve 42B are housed in an airtight housing 42H. An end of the branch pipe 42T is exposed to the outside of the housing 42H. A double pipe section 44D, in which an outer pipe 44E is placed over an inner pipe 44N, is provided in the section of the gas fuel supply pipe 44 from the housing 42H to the gas fuel injection valve 43.

[0024] The main fuel supply unit 5 is used in the liquid mode, which uses only liquid fuel. On the other hand, the pilot fuel supply unit 6 is used in the gas mode, which uses gas fuel, to supply a small amount of liquid fuel to promote ignition. The main fuel supply unit 5 and the pilot fuel supply unit 6 share a liquid fuel tank 51. The liquid fuel tank 51 stores a liquid fuel that is liquid at room temperature, such as light oil, heavy oil, biodiesel fuel, synthetic fuel, or gasoline.

[0025] The main fuel supply unit 5 includes a pump 52P, a main fuel injection valve 53, and a main fuel supply pipe 54. The main fuel injection valve 53 is a combined valve that integrates a governor and a solenoid valve, and is provided in the center of the combustion chamber 12C for each cylinder 11C. The main fuel supply pipe 54 branches from the liquid fuel tank 51 via the pump 52P to each cylinder 11C and is connected to the main fuel injection valve 53 for each cylinder 11C.

[0026] Pilot fuel supply unit 6 includes pump 62P, common rail 62C, pilot fuel injection valves 63, and pilot fuel supply pipes 64. Pilot fuel injection valves 63 are adjacent to main fuel injection valves 53 of each cylinder 11C. Pilot fuel supply pipes 64 are connected from liquid fuel tank 51 to common rail 62C via pump 62P. Common rail 62C is connected to pilot fuel injection valves 63 of each cylinder 11C.

[0027] [Control unit, various sensors] The control unit 7 is a computer such as an ECU (Engine Control Unit) and includes a calculation unit and a storage unit (not shown). The calculation unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The calculation unit performs various processes by reading and executing control programs stored in the storage unit. Note that the control unit 7 may also be realized by an integrated circuit that does not use software.

[0028] The control unit 7 is connected to an in-cylinder pressure sensor 71, an exhaust temperature sensor 72, and an engine speed sensor 73. The in-cylinder pressure sensor 71 is provided in each combustion chamber 12C and measures the in-cylinder pressure. The exhaust temperature sensor 72 is provided in the exhaust port 12E of each cylinder 11C and measures the exhaust temperature of each cylinder 11C. The engine speed sensor 73 is provided in the crankcase and measures the rotation speed of the crankshaft 13. The control unit 7 controls the engine system 100 based on the measurement values ​​obtained from the various sensors described above.

[0029] [Turbocharger] The supercharger 8 is, for example, a turbocharger, and includes a compressor 81 and a turbine 82. The compressor 81 is connected to the intake pipe 21. The turbine 82 is connected to the exhaust pipe 31. Note that the supercharger 8 does not necessarily have to be provided.

[0030] Next, the operation of the engine system 100 according to this embodiment will be described. When gas fuel and a small amount of liquid fuel for ignition are mixed and burned, generally, if the in-cylinder pressure indicates an abnormal value on the high-pressure side, there is a risk of knocking, so it is effective to reduce the amount of gas fuel. On the other hand, if the in-cylinder pressure indicates an abnormal value on the low-pressure side, there is a risk of misfire, so it is effective to increase the amount of liquid fuel. Also, if the exhaust temperature indicates an abnormal value on the high-pressure side, it is effective to reduce the amount of gas fuel, and if the exhaust temperature indicates an abnormal value on the low-pressure side, it is effective to increase the amount of gas fuel. In this embodiment, the control unit 7 executes the following control based on the in-cylinder pressure and the exhaust temperature.

[0031] The engine system 100 of this embodiment includes an engine 1 having multiple cylinders 11C and capable of mixing gas fuel and liquid fuel, and a control unit 7 that adjusts the gas fuel injection amount and liquid fuel injection amount, and the control unit 7 executes a first control that adjusts the gas fuel injection amount or the liquid fuel injection amount based on the internal pressure of the multiple cylinders 11C, and a second control that adjusts the gas fuel injection amount at a timing different from the first control based on the exhaust temperature of the multiple cylinders 11C.

[0032] Hereinafter, the in-cylinder pressure may be a measured value measured by the in-cylinder pressure sensor 71, or may be an estimated value estimated from other data that has a correlation with the in-cylinder pressure. The other data may be the exhaust temperature, the engine speed, the intake air temperature, the gas fuel injection amount, etc.

[0033] The exhaust temperature may be a measured value measured by the exhaust temperature sensor 72, or may be an estimated value estimated from other data that has a correlation with the exhaust temperature, such as the in-cylinder pressure, engine speed, intake air temperature, and gas fuel injection amount.

[0034] FIG. 3 is a flowchart showing the first control. FIG. 4 is a flowchart showing the second control. The first control and the second control are described as subroutines of a higher-level routine. During combustion in gas mode, the control unit 7 repeatedly executes the first control and the second control at different timings. The control unit 7 also executes the first control (see FIG. 3) at a first time interval (e.g., several milliseconds) and executes the second control (see FIG. 4) at a second time interval (e.g., several tens of seconds) longer than the first time interval. Here, executing the second control at a second time interval longer than the first time interval means that the frequency of executing the second control per unit time is less than the frequency of executing the first control per unit time.

[0035] First, the first control will be described. The control unit 7 acquires the in-cylinder pressures of all cylinders 11C (step S01), and determines whether the in-cylinder pressures of all cylinders 11C are equal to or greater than the second threshold and less than the first threshold (step S02). If it is determined that the in-cylinder pressures of all cylinders 11C are equal to or greater than the second threshold and less than the first threshold (step S02: YES), the control unit 7 returns to the upper routine.

[0036] On the other hand, if it is determined that there is a cylinder 11C whose in-cylinder pressure is equal to or greater than the second threshold and not less than the first threshold (step S02: NO), the control unit 7 determines whether there is a cylinder 11C whose in-cylinder pressure is equal to or greater than the first threshold (step S03). If it is determined that there is a cylinder 11C whose in-cylinder pressure is equal to or greater than the first threshold (step S03: YES), the control unit 7 reduces the gas fuel injection amount of the cylinder 11C whose in-cylinder pressure is equal to or greater than the first threshold by a predetermined percentage at a first speed (step S04), and proceeds to step S05. Here, the control unit 7 regulates the speed by adjusting the gas fuel injection amount of the cylinder 11C whose in-cylinder pressure is less than the first threshold. On the other hand, if it is determined that there is no cylinder 11C whose in-cylinder pressure is equal to or greater than the first threshold (step S03: NO), the control unit 7 proceeds to step S05.

[0037] In step S05, the control unit 7 determines whether there is a cylinder 11C whose internal cylinder pressure is less than the second threshold. If it is determined that there is a cylinder 11C whose internal cylinder pressure is less than the second threshold (step S05: YES), the control unit 7 increases the liquid fuel injection amount of the cylinder 11C whose internal cylinder pressure is less than the second threshold by a predetermined percentage (step S06), and proceeds to step S07. Note that the control unit 7 does not change the liquid fuel injection amount of any of the other cylinders 11C whose internal cylinder pressure is equal to or greater than the second threshold and less than the first threshold. On the other hand, if it is determined that there is no cylinder 11C whose internal cylinder pressure is less than the second threshold (step S05: NO), the control unit 7 proceeds to step S07.

[0038] In step S07, the control unit 7 determines whether the internal cylinder pressure of the cylinder 11C whose injection amount (gas fuel injection amount or liquid fuel injection amount) has been changed is equal to or greater than the second threshold and less than the first threshold. If it is determined that the internal cylinder pressure of the cylinder 11C whose injection amount has been changed is equal to or greater than the second threshold and less than the first threshold (step S07: YES), the control unit 7 restores the gas fuel injection amount instruction value of the cylinder 11C whose injection amount has been changed at a second speed (step S08). On the other hand, if it is determined that the internal cylinder pressure of the cylinder 11C whose injection amount has been changed is not equal to or greater than the second threshold and less than the first threshold (step S07: NO), the control unit 7 proceeds to step S03.

[0039] Next, the second control will be described. The control unit 7 acquires the exhaust gas temperatures of all the cylinders 11C (step S11), and determines whether the exhaust gas temperatures of all the cylinders 11C are equal to or greater than the fourth threshold value and less than the third threshold value (step S12). If it is determined that the exhaust gas temperatures of all the cylinders 11C are equal to or greater than the fourth threshold value and less than the third threshold value (step S12: YES), the control unit 7 returns to the upper routine.

[0040] On the other hand, if it is determined that there is a cylinder 11C whose exhaust temperature is equal to or greater than the fourth threshold and not less than the third threshold (step S12: NO), the control unit 7 determines whether there is a cylinder 11C whose exhaust temperature is equal to or greater than the third threshold (step S13). If it is determined that there is a cylinder 11C whose exhaust temperature is equal to or greater than the third threshold (step S13: YES), the control unit 7 reduces the gas fuel injection amount of the cylinder 11C whose exhaust temperature is equal to or greater than the third threshold by a predetermined percentage (step S14), and proceeds to step S15. On the other hand, if it is determined that there is no cylinder 11C whose internal cylinder pressure is equal to or greater than the third threshold (step S13: NO), the control unit 7 proceeds to step S15.

[0041] In step S15, the control unit 7 determines whether or not there is a cylinder 11C whose exhaust temperature is less than the fourth threshold. If it is determined that there is a cylinder 11C whose exhaust temperature is less than the fourth threshold (step S15: YES), the control unit 7 increases the gas fuel injection amount of the cylinder 11C whose exhaust temperature is less than the fourth threshold by a predetermined percentage (step S16), and proceeds to step S17. On the other hand, if it is determined that there is no cylinder 11C whose exhaust temperature is less than the fourth threshold (step S15: NO), the control unit 7 proceeds to step S17.

[0042] In step S17, the control unit 7 determines whether the exhaust temperature of the cylinder 11C in which the gas fuel injection amount has been changed is equal to or greater than the fourth threshold and less than the third threshold. If it is determined that the exhaust temperature of the cylinder 11C in which the gas fuel injection amount has been changed is equal to or greater than the fourth threshold and less than the third threshold (step S17: YES), the control unit 7 returns to the upper routine. On the other hand, if it is determined that the exhaust temperature of the cylinder 11C in which the gas fuel injection amount has been changed is not equal to or greater than the fourth threshold and less than the third threshold (step S17: NO), the control unit 7 proceeds to step S13.

[0043] FIG. 5 is a diagram showing an example of the in-cylinder pressure of each cylinder 11C. FIG. 6 is a diagram showing an example of changes in the in-cylinder pressure, exhaust temperature, gas fuel injection amount, and liquid fuel injection amount of the fifth cylinder. In the example of FIG. 5, among the first to sixth cylinders, the in-cylinder pressure of the fifth cylinder is equal to or greater than the first threshold, and the in-cylinder pressures of the other five cylinders 11C are less than the first threshold. In this case, the first control returns a NO determination in step S02 and a YES determination in step S03, so the gas fuel injection amount of the fifth cylinder is reduced by a predetermined percentage at a first speed (step S04, period P1 in FIG. 6). Since there is no cylinder 11C whose in-cylinder pressure is less than the second threshold, the first control returns a NO determination in step S5. Thereafter, the in-cylinder pressure decreases to equal to or greater than the second threshold and less than the first threshold, so the first control returns a YES determination in step S07, and the gas fuel injection amount is restored at the second speed (step S08, period P2 in FIG. 6).

[0044] However, the internal pressure of the fifth cylinder increases again, and the determination in step S03 is YES, so the gas fuel injection amount of the fifth cylinder is reduced by a predetermined percentage at the first speed (step S04, period P3 in FIG. 6). Thereafter, the internal pressure decreases to be equal to or greater than the second threshold value and less than the first threshold value, and the determination in step S07 is YES, so the gas fuel injection amount is restored at the second speed (step S08, period P4 in FIG. 6).

[0045] After that, the in-cylinder pressure becomes less than the second threshold (period P5 in FIG. 6), the determination is YES in step S05, and the liquid fuel injection amount is increased by a predetermined percentage (step S06, period P5 in FIG. 6). After that, the in-cylinder pressure becomes equal to or greater than the second threshold, and the determination is NO in step S05, but after period P6 in FIG. 6, the exhaust temperature becomes equal to or greater than the third threshold, so the determination is YES in step S13, and the gas fuel injection amount is decreased by a predetermined percentage (step S14).

[0046] The engine system 100 according to the present embodiment described above includes an engine 1 having multiple cylinders 11C and capable of co-firing gas fuel and liquid fuel, and a control unit 7 that adjusts the gas fuel injection amount and the liquid fuel injection amount. The control unit 7 executes two control operations: a first control that adjusts the gas fuel injection amount or the liquid fuel injection amount based on the internal pressure of the multiple cylinders 11C, and a second control that adjusts the gas fuel injection amount at a timing different from the first control based on the exhaust temperature of the multiple cylinders 11C. If injection amount control based on internal pressure and injection amount control based on exhaust temperature are simultaneously performed, the injection amount control based on internal pressure also affects the exhaust temperature, and the injection amount control based on exhaust temperature also affects the internal pressure. This may complicate the control process, potentially resulting in a long time required for the internal pressure and exhaust temperature to normalize. According to the present embodiment, the interaction between the first control and the second control is suppressed, thereby enabling the combustion state of the engine 1 to be quickly normalized when the combustion state deteriorates.

[0047] Furthermore, in the engine system 100 according to this embodiment, the control unit 7 executes the first control at a first time interval and executes the second control at a second time interval that is longer than the first time interval. Because the in-cylinder pressure fluctuates with each combustion cycle and can cause knocking or misfire, the first control must be executed quickly and frequently. On the other hand, because the exhaust gas temperature fluctuates more slowly over time than the in-cylinder pressure, executing the second control at the same frequency as the first control would be wasteful. According to this embodiment, the first control can quickly normalize the in-cylinder pressure, while eliminating the wastefulness of the second control.

[0048] Furthermore, in the engine system 100 according to this embodiment, in the first control, the control unit 7 reduces the gas fuel injection amount for the cylinder 11C whose internal cylinder pressure is equal to or greater than the first threshold, and regulates the gas fuel injection amount for the other cylinders 11C. If the internal cylinder pressure indicates an abnormal value on the high-pressure side, excessive gas fuel injection is suspected, and it is necessary to reduce the gas fuel injection amount for the cylinder 11C that indicates the abnormal value. Here, reducing the gas fuel injection amount may result in a decrease in engine speed. Normally, regulation is performed using the gas combustion injection valves of all cylinders 11C. However, if the gas fuel injection amount is increased for regulation of the cylinder 11C whose internal cylinder pressure has been reduced, the internal cylinder pressure may again indicate an abnormal value. According to this embodiment, it is possible to prevent the internal cylinder pressure of the cylinder 11C whose internal cylinder pressure has been reduced from increasing due to regulation.

[0049] Furthermore, in the engine system 100 according to this embodiment, the control unit 7 increases the liquid fuel injection amount for the cylinder 11C whose in-cylinder pressure is less than a second threshold value that is lower than the first threshold value, and does not change the liquid fuel injection amounts for the other cylinders 11C. This embodiment makes it possible to prevent misfire in the cylinder 11C whose in-cylinder pressure indicates an abnormal value on the low-pressure side.

[0050] Furthermore, according to the engine system 100 of this embodiment, in the first control, the control unit 7 reduces the gas fuel injection amount for the cylinder 11C whose internal cylinder pressure is equal to or greater than a first threshold value at a first speed, and when the internal cylinder pressure becomes less than the first threshold value, increases the gas fuel injection amount at a second speed slower than the first speed. If the gas fuel injection amount is increased too rapidly, the internal cylinder pressure may again indicate an abnormal value. According to this embodiment, it is possible to suppress an increase in the internal cylinder pressure due to an increase in the gas fuel injection amount. Furthermore, because the increase in the internal cylinder pressure is suppressed, even if the internal cylinder pressure again indicates an abnormal value, the internal cylinder pressure can be quickly reduced by the first control.

[0051] Furthermore, in the engine system 100 according to this embodiment, the control unit 7, in the second control, reduces the amount of gas fuel injected into the cylinder 11C whose exhaust temperature is equal to or higher than the third threshold, and increases the amount of gas fuel injected into the cylinder 11C whose exhaust temperature is the lowest. This embodiment makes it possible to quickly reduce the exhaust temperature of the cylinder 11C that exhibits an abnormal value on the high temperature side. It also makes it possible to suppress a decrease in the rotation speed.

[0052] The above embodiment may be modified as follows.

[0053] FIG. 7 shows changes in the speed-governed output of liquid fuel and gas fuel when transitioning from liquid mode to gas mode. FIG. 8 shows changes in the speed-governed output of liquid fuel and gas fuel when transitioning from gas mode to liquid mode. In this modification, the engine 1 can be switched between a gas mode in which both gas fuel and liquid fuel are used simultaneously, a liquid mode in which only liquid fuel is used, and a changeover mode in which transition is made from the liquid mode to the gas mode. In the changeover mode, the control unit 7 does not execute at least one of the first control and the second control. In the changeover mode, load fluctuations become large, so even if the transition from the liquid mode to the gas mode is progressing normally, the in-cylinder pressure and the exhaust temperature may indicate abnormal values. This modification prevents the in-cylinder pressure and the exhaust temperature from indicating abnormal values ​​even if the transition from the liquid mode to the gas mode is progressing normally. [Explanation of symbols]

[0054] 1 engine 7 Control Unit 11C cylinder

Claims

1. an engine having a plurality of cylinders and capable of burning a mixture of gas fuel and liquid fuel; a control unit that adjusts the gas fuel injection amount and the liquid fuel injection amount, The control unit a first control that adjusts the gas fuel injection amount or the liquid fuel injection amount based on the in-cylinder pressures of the plurality of cylinders; and a second control that adjusts the gas fuel injection amount at a timing different from that of the first control based on the exhaust temperatures of the plurality of cylinders.

2. The control unit Executing the first control at a first time interval; 2. The engine system according to claim 1, wherein the second control is executed at a second time interval that is longer than the first time interval.

3. The engine system according to claim 1 or 2, characterized in that, in the first control, the control unit reduces the amount of gas fuel injection for the cylinder whose internal cylinder pressure is equal to or higher than a first threshold, and regulates the amount of gas fuel injection for the other cylinders by adjusting the amount of gas fuel injection.

4. 4. The engine system according to claim 3, wherein, in the first control, the control unit increases the liquid fuel injection amount for the cylinder in which the in-cylinder pressure is less than a second threshold value that is lower than the first threshold value, and does not change the liquid fuel injection amount for the other cylinders in which the in-cylinder pressure is equal to or greater than the second threshold value and less than the first threshold value.

5. The engine system described in claim 3, characterized in that, in the first control, the control unit reduces the gas fuel injection amount for the cylinder whose in-cylinder pressure is equal to or greater than the first threshold at a first speed, and when the in-cylinder pressure becomes less than the first threshold, increases the gas fuel injection amount at a second speed slower than the first speed.

6. The engine system described in claim 1 or 2, characterized in that, in the second control, the control unit reduces the gas fuel injection amount for the cylinder whose exhaust temperature is equal to or higher than a third threshold, and increases the gas fuel injection amount for the cylinder whose exhaust temperature is the lowest.

7. the engine is switchable between a gas mode in which the gas fuel and the liquid fuel are used simultaneously, a liquid mode in which only the liquid fuel is used, and a changeover mode in which the engine transitions bidirectionally between the gas mode and the liquid mode; 3. The engine system according to claim 1, wherein the control unit does not execute at least one of the first control and the second control in the changeover mode.

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