Controller, gas engine system and control method

Abstract

To provide a controller capable of more appropriately controlling an injection amount of fuel gas supplied to a gas engine than conventional arts, in a low-load operation where an output of a generator driven by a gas engine is less than a rated output.SOLUTION: A controller controls an injector for supplying fuel gas to a gas engine. The controller has a first mode in which the injector is controlled so that a fuel gas injection amount becomes a first injection amount for each cycle consisting of four strokes of the gas engine: intake, compression, expansion, and exhaust, and a second mode in which the injector is controlled so that the fuel gas injection amount becomes a second injection amount for every two or more cycles. During low-load operation in which an output of a generator driven by the gas engine is less than a rated output, the controller holds the fuel gas injection amount at a constant value different from the first injection amount and the second injection amount only for a predetermined period from the timing of switching from one of the first mode and the second mode to the other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a control device, a gas engine system, and a control method. [Background technology]

[0002] Patent Document 1 describes a fuel injection control method for an internal combustion engine, characterized in that in an electronic fuel injection control device for a multi-cylinder internal combustion engine having injection valves that intermittently inject fuel corresponding to each cylinder, when switching between injection methods such as simultaneous injection for all cylinders, independent injection for each cylinder, and group injection, a correction pulse different from the fuel injection pulse obtained by normal calculation is supplied so that the fuel required for one combustion cycle is not excessive or insufficient after switching in relation to the intake stroke. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-1349 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide, as an example, a control device, a gas engine system, and a control method that can more appropriately control the amount of fuel gas injected into a gas engine than conventional methods during low-load operation in which the output of a generator driven by a gas engine is less than the rated output. [Means for solving the problem]

[0005] A control device according to one aspect of the present disclosure is a control device that controls an injector for supplying fuel gas to a gas engine, and is equipped with a first mode in which the injector is controlled so that the fuel gas injection amount is a first injection amount for each cycle consisting of four strokes of the gas engine: intake, compression, expansion, and exhaust, and a second mode in which the injector is controlled so that the fuel gas injection amount is a second injection amount for each two or more of the cycles, and during low-load operation in which the output of a generator driven by the gas engine is less than the rated output, the control device maintains the fuel gas injection amount at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other.

[0006] A gas engine system according to one embodiment of the present disclosure includes a gas engine including a combustion chamber in which fuel gas is combusted and which drives a generator, and the above-described control device.

[0007] A control method of one embodiment of the present disclosure is a control method for controlling fuel gas injection into a gas engine, and includes a first mode in which the fuel gas injection amount is controlled to be a first injection amount for each cycle consisting of four strokes of intake, compression, expansion, and exhaust of the gas engine, and a second mode in which the fuel gas injection amount is controlled to be a second injection amount for each two or more of the cycles, and during low-load operation in which the output of a generator driven by the gas engine is less than rated output, the fuel gas injection amount is maintained at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other. Effect of the Invention

[0008] The control device, gas engine system, and control method of one embodiment of the present disclosure have the advantage of being able to control the amount of fuel gas injected into the gas engine more appropriately than conventional methods during low-load operation in which the output of the generator driven by the gas engine is less than the rated output. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a gas engine system according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a gas engine system according to an embodiment. [Diagram 3] FIG. 3 is a plan view showing an example of a gas engine system according to an embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of the operation of the control device in the gas engine system of the embodiment. [Diagram 5] FIG. 5 is a time chart showing an example of the operation of the control device in the gas engine system of the control example of the embodiment. [Figure 6A] FIG. 6A is a diagram showing an example of a temporary abnormal drop in the output of a generator driven by a gas engine when the first control example of fuel gas injection disclosed herein is not performed at the timing when the fuel gas injection mode switches from the normal injection mode to the thinning injection mode during low-load operation where the output of the generator is approximately 10% of the rated output. [Figure 6B] FIG. 6B is a diagram showing an example of improvement to an abnormal drop in generator output when the first control example of fuel gas injection of the present disclosure is performed at the timing when the fuel gas injection mode is switched from the normal injection mode to the thinning injection mode during low-load operation where the output of the generator driven by a gas engine is approximately 10% of the rated output. [Figure 7A] FIG. 7A is a diagram showing an example of a temporary abnormal increase in generator output when the second control example of fuel gas injection disclosed herein is not performed at the timing when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode during low-load operation where the output of the generator driven by a gas engine is approximately 10% of the rated output. [Figure 7B] FIG. 7B is a diagram showing an example of improvement of an abnormal increase in generator output when the second control example of fuel gas injection of the present disclosure is performed at the timing when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode during low-load operation where the output of the generator driven by a gas engine is approximately 10% of the rated output. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First, the circumstances by which the present inventors arrived at the above-mentioned aspects of the present disclosure will be described. In low-load operation where the output of a generator driven by a gas engine is less than the rated output, the amount of fuel gas injected by the injector of the gas engine system is smaller than the amount of fuel gas injected in high-load operation. On the other hand, since the spatial design of the combustion chamber of the gas engine is generally optimized for the high-load range, the amount of air in the combustion chamber remains the same as in the high-load operation. Then, combustion at an optimal air-fuel ratio in the combustion chamber cannot be maintained, and various problems are likely to occur. For example, the number of misfires in the gas engine may increase. In addition, the amount of unburned gas may increase. Furthermore, carbon may cause contamination of the exhaust system.

[0011] Therefore, during low-load operation, instead of the normal injection in which fuel gas is injected for each cycle consisting of the four strokes of the gas engine - intake, compression, expansion and exhaust - a thinned injection is performed in which fuel gas is injected every two or more cycles.

[0012] For this reason, in low load operation, it is necessary to timely switch the fuel gas injection mode between the normal injection mode and the thinning injection mode. As a result of intensive research, the present inventors found that the output of the generator fluctuates when the fuel gas injection mode switches between the normal injection mode and the thinning injection mode, and came up with the above-mentioned aspects of the present disclosure. For example, it was found that the output of the generator temporarily abnormally increases due to a delay in PID control of the fuel gas injection amount when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode. Conversely, it was also found that the output of the generator temporarily abnormally decreases due to a delay in PID control of the fuel gas injection amount when the fuel gas injection mode switches from the normal injection mode to the thinning injection mode.

[0013] Hereinafter, specific examples of the above-mentioned aspects of the present disclosure will be described with reference to the accompanying drawings. The specific examples described below are all examples of the above-mentioned aspects of the present disclosure. Therefore, the shapes, numerical values, components, arrangement positions of the components, connection forms, and control contents of the control device shown below do not limit the scope of the claims unless otherwise stated in the claims.

[0014] In addition, among the components described below, components that are not described in the independent claims showing the highest concept of the present disclosure are described as optional components. In addition, in the drawings, the description of components with the same reference numerals may be omitted. The drawings are schematic illustrations of each component for ease of understanding, and may not accurately depict the shape and dimensional ratio. Furthermore, in the operation of the device, the order of steps may be changed or known steps may be added as necessary.

[0015] It should be noted that the functions of the elements disclosed herein can be performed using circuits or processing circuits including general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, or combinations thereof configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this specification, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed in this specification or other known hardware that is programmed or configured to perform the recited functions. In the case where the hardware is a processor that is considered a type of circuit, the circuit, unit, or means is a combination of hardware and software, and the software is used to configure the hardware or processor.

[0016] (Embodiment) [Device configuration] FIG. 1 is a schematic diagram showing an example of a gas engine system according to an embodiment. FIG. 2 is a cross-sectional view showing an example of a gas engine system according to an embodiment. FIG. 3 is a plan view showing an example of a gas engine system according to an embodiment. Here, a gas engine system 100 in which a plurality of cylinders are arranged in series is illustrated, but is not limited to this example. That is, the cylinder arrangement of the gas engine system 100 may be a series arrangement, a V-shaped arrangement, or a horizontally opposed arrangement. The number of cylinders in the gas engine system 100 may be one or many.

[0017] The gas engine system 100 includes a gas engine 10 and a control device 30. In FIG.

[0018] The gas engine 10 is a device that converts thermal energy into power by burning fuel gas. Examples of the fuel gas include, but are not limited to, natural gas and city gas.

[0019] The gas engine 10 is connected to an air intake passage 22 for supplying air to a combustion chamber in the gas engine 10. The air may be guided into the cylinder by negative pressure generated by the piston 12 in the cylinder descending as shown in FIG. 2, but the air intake passage 22 may also be connected to, for example, a compressor of a supercharger (not shown). By compressing the air in the air intake passage 22 with the compressor, it is possible to forcibly send high-density air into the combustion chamber compared to the case where the air is not compressed. This improves the efficiency of the gas engine 10. The piston 12 is connected to a crankshaft (not shown) via a connecting rod 13.

[0020] An exhaust passage 21 for discharging exhaust gas from a combustion chamber in the gas engine 10 is connected to the gas engine 10. The exhaust passage 21 may be connected to, for example, a turbine of a turbocharger (not shown).

[0021] As shown in FIG. 2, the gas engine 10 includes a combustion chamber in which a mixture of fuel gas and air is burned, and the combustion chamber includes a main chamber 11A and an auxiliary chamber 11B.

[0022] The gas engine system 100 is provided with a main fuel injector 23 and a secondary fuel injector 24 for supplying fuel gas to the gas engine 10 .

[0023] The main fuel injector 23 is a device for supplying fuel gas to the main chamber 11A of the combustion chamber. Specifically, the main fuel injector 23 is provided for each cylinder in a wall member forming the intake passage 22, and is configured to supply fuel gas to the intake passage 22 through a through hole in the wall member. As a result, a mixture of fuel gas and air is supplied to the intake port of the cylinder block of the gas engine 10. The mixture present in the intake port is supplied to the main chamber 11A of the gas engine 10 by the intake valve 14 provided for each cylinder opening at the appropriate time during the intake stroke of the gas engine 10.

[0024] The auxiliary fuel injector 24 is a device for supplying fuel gas to the auxiliary chamber 11B of the combustion chamber. Specifically, the auxiliary fuel injector 24 is provided in the cylinder head for each cylinder, and is configured to supply fuel gas to the auxiliary chamber 11B through a through hole in the cylinder head. In such an auxiliary chamber type gas engine 10, as shown in Figs. 2 and 3, an ignition plug 25 connected to an ignition coil 26 is provided in each auxiliary chamber 11B. Therefore, when the mixture supplied to the auxiliary chamber 11B is ignited by the ignition plug 25, the combustion gas generated in the auxiliary chamber 11B is blown out from a nozzle in a wall portion that separates the auxiliary chamber 11B from the main chamber 11A, and the flame propagates to the mixture present in the main chamber 11A, thereby burning the mixture. The combustion exhaust gas generated by the combustion of the mixture is exhausted outside the main chamber 11A of the gas engine 10 by opening the exhaust valve 15 provided for each cylinder at the appropriate time during the exhaust stroke of the gas engine 10.

[0025] The main fuel injector 23 and the secondary fuel injector 24 may be a main fuel injection valve and a secondary fuel injection valve, respectively. These main fuel injection valve and secondary fuel injection valve may be configured using, for example, an electromagnetic valve. Furthermore, the main fuel injector 23 and the secondary fuel injector 24 may be connected to a fuel gas supply source (not shown). The fuel gas supply source may be a fuel gas tank having a predetermined gas supply pressure.

[0026] The control device 30 controls the main fuel injector 23 for supplying fuel gas to the gas engine 10. In other words, the main fuel injector 23 corresponds to an example of an "injector" in the present disclosure.

[0027] That is, the control device 30 has a normal injection mode as a PID control mode of the fuel gas injection amount, in which the main fuel injector 23 is controlled so that the fuel gas injection amount becomes the normal injection amount for each cycle consisting of four strokes of intake, compression, expansion, and exhaust of the gas engine 10.

[0028] Here, in each cylinder, the piston 12 reciprocates twice along the piston sliding surface 16 of the cylinder, thereby repeatedly executing a cycle of the gas engine 10. The rotation angle of the crankshaft in each cylinder is detected by a crank angle detector (not shown). The crank angle detector may be, for example, a rotary encoder. Therefore, the control device 30 can control the fuel gas injection amount to be a normal injection amount, for example, by determining the opening time of the main fuel injection valve, which is an example of the main fuel injector 23, based on the rotation phase of the crankshaft for each cycle of the gas engine 10.

[0029] Furthermore, the control device 30 has, as a PID control mode for the fuel gas injection amount, a thinning injection mode in which the main fuel injector 23 is PID controlled so that the fuel gas injection amount becomes the thinning injection amount every two or more cycles.

[0030] An example of such a thinned-out injection mode is an injection mode in which the main fuel injector 23 is controlled so that a cycle in which fuel gas is injected during the intake stroke and a cycle in which fuel gas injection is stopped during the intake stroke are alternately repeated in each cylinder. Therefore, in this case, the control device 30 can control the fuel gas injection amount to be the thinned-out injection amount by determining the opening time of the main fuel injection valve, which is an example of the main fuel injector 23, based on the rotation phase of the crankshaft for every two consecutive cycles of the gas engine 10.

[0031] Furthermore, during low-load operation in which the output of the generator 50 driven by the gas engine 10 is less than the rated output, the control device 30 maintains the fuel gas injection amount at a constant value different from the normal injection amount and the thinned injection amount for a predetermined period from the timing of switching from one of the normal injection mode and the thinned injection mode to the other. The output of the generator 50 during such low-load operation may be less than 20% of the rated output, for example. Specific examples of the above control by the control device 30 will be described later in the control example.

[0032] Since the secondary fuel injector 24 is a device for creating a flame torch in the secondary fuel chamber 11B, the amount of fuel gas injected by the secondary fuel injector 24 is controlled to a constant amount in both the normal injection mode and the thinning injection mode.

[0033] The control device 30 may control the overall operation of the gas engine system 100. The control device 30 includes, for example, an arithmetic circuit and a memory circuit that stores a control program. Examples of the arithmetic circuit include an MPU and a CPU. Examples of the memory circuit include a memory. The control device 30 may be composed of a single controller that performs centralized control, or may be composed of multiple controllers that cooperate with each other to perform distributed control.

[0034] [Operation] 4 is a flowchart showing an example of the operation of the control device in the gas engine system of the embodiment. The following operation may be performed, for example, by the arithmetic circuit of the control device 30 reading a control program from the memory circuit of the control device 30. However, it is not essential that the following operation is performed by the control device 30. An operator may perform some of the operations. In the following example, a case where the operation is controlled by the control device 30 will be described.

[0035] In step S1, PID control of the fuel gas injection amount is performed during low load operation where the output of the generator 50 driven by the gas engine 10 is less than the rated output. This maintains the output of the generator 50 at a desired value.

[0036] During low load operation, in step S2, it is determined whether the fuel gas injection mode has been switched from one of the normal injection mode and the thinning injection mode to the other.

[0037] In step S2, if the fuel gas injection mode is switched from either the normal injection mode or the thinned injection mode to the other (if "Yes" in step S2), in step S3, the fuel gas injection amount is forcibly held at a constant value for a predetermined period from the timing of switching the fuel gas injection mode. In other words, during this predetermined period, PID control of the fuel gas injection is prohibited. Specific examples of the "predetermined period" and "constant value" in step S2 will be described later in the control example.

[0038] Next, when a predetermined period of time has elapsed since the timing of switching the fuel gas injection mode, the PID control of the fuel gas injection amount is resumed in step S4.

[0039] If the fuel gas injection mode has not been switched in step S2 (if "No" in step S2), the operations in steps S3 and S4 described above are not performed, and fuel gas injection continues as is.

[0040] Here, during low-load operation where the output of the generator 50 driven by the gas engine 10 is less than the rated output, the amount of fuel gas injected by the main fuel injector 23 of the gas engine system 100 is smaller than the amount of fuel gas injected during high-load operation. However, since the spatial design of the combustion chamber of the gas engine 10 is generally optimized to suit the high-load range, as described above, combustion at the optimal air-fuel ratio in the combustion chamber cannot be maintained, making it easy for various problems to occur.

[0041] Therefore, during low load operation, instead of normal injection in which fuel gas is injected for each cycle consisting of the four strokes of intake, compression, expansion, and exhaust of the gas engine 10, thinned injection is performed in which fuel gas is injected every two or more cycles.

[0042] For this reason, during low load operation, it is necessary to switch the fuel gas injection mode between the normal injection mode and the thinning injection mode at appropriate times. After careful consideration, the present inventors have found that output fluctuations in the generator 50 occur when the fuel gas injection mode switches between the normal injection mode and the thinning injection mode.

[0043] For example, it was found that a delay in the PID control of the fuel gas injection amount at the timing when the fuel gas injection mode is switched from the thinning injection mode to the normal injection mode causes a temporary abnormal increase in the output of the generator 50. Conversely, it was also found that a delay in the PID control of the fuel gas injection amount at the timing when the fuel gas injection mode is switched from the normal injection mode to the thinning injection mode causes a temporary abnormal decrease in the output of the generator 50.

[0044] However, the control device 30, gas engine system 100, and control method of this embodiment maintain the fuel gas injection amount at a constant value different from the normal injection amount and the thinned injection amount for a predetermined period of time from the time the fuel gas injection mode switches from one of the normal injection mode and the thinned injection mode to the other during low load operation, thereby making it less likely that output fluctuations will occur in the generator 50 compared to the case where such control of the fuel gas injection amount is not performed.

[0045] In addition, the control device 30, gas engine system 100, and control method of this embodiment execute a thinned injection mode in which fuel gas is injected every two or more cycles as a PID control mode of the fuel gas injection amount, thereby reducing the possibility of an increase in the number of misfires in the gas engine 10, an increase in the amount of unburned gas, and carbon contamination of the exhaust system during low load operation.

[0046] Furthermore, the control device 30, gas engine system 100, and control method of this embodiment execute a thinned injection mode in which fuel gas is injected every two or more cycles as a PID control mode of the fuel gas injection amount, thereby reducing the possibility of an increase in the number of misfires in the gas engine 10, an increase in the amount of unburned gas, and the possibility of carbon fouling the exhaust system, etc., during low-load operation, and enabling idling operation with the output of the generator 50 driven by the gas engine 10 at, for example, about 10% of the rated output. Then, the control device 30, gas engine system 100, and control method of this embodiment can shorten the time until the output of the generator 50 driven by the gas engine 10 reaches the rated output.

[0047] Specifically, if idling operation is not performed in the gas engine system 100, the following time is required to start up the gas engine system 100 and the generator 50; however, in this embodiment, such time can be reduced by appropriately performing idling operation of the gas engine system 100. Fuel gas leak check and auxiliary engine start: Approx. 40 seconds - Increase the RPM of the gas engine 10 to the desired level: Approximately 40 seconds - Connecting to commercial power grid: Approx. 40 seconds

[0048] (Control example) FIG. 5 is a time chart showing an example of the operation of the control device in the gas engine system of the control example of the embodiment. In the example shown in FIG. 5, the operation when the number of cylinders of the gas engine 10 is four is shown, but the number of cylinders is not limited to this example. In addition, the following operation may be performed, for example, by the arithmetic circuit of the control device 30 reading out a control program from the memory circuit of the control device 30. However, it is not necessarily required that the following operation is performed by the control device 30. An operator may perform some of the operations. In the following example, a case where the operation is controlled by the control device 30 will be described.

[0049] As shown in the middle of FIG. 5, when the fuel gas injection mode of the gas engine system 100 is the normal injection mode, the main fuel injector 23 is PID controlled so that the fuel gas injection amount becomes the normal injection amount for each cycle consisting of four strokes of the gas engine 10, namely, intake, compression, expansion, and exhaust. Specifically, for each cylinder, fuel gas injection equivalent to the normal injection amount is performed in the intake stroke of all cycles of the gas engine 10 within a desired range of the rotation angle (crank angle) of the crankshaft. Since the operation cycle T of the gas engine 10 is constant, the desired range may be set using the main Dur (deg) as the rotation phase of the crankshaft. As an example, the main Dur (deg) corresponding to the normal injection amount of fuel gas may be about 50°, but is not limited thereto. The operation cycle T of the gas engine 10 may be, for example, about 0.16 seconds, but is not limited thereto.

[0050] In the example shown in FIG. 5, in cylinder 1, when the crankshaft rotation angle (crank angle) is 0° to 180°, fuel gas is injected in the intake stroke of every cycle. In cylinder 2, when the crankshaft rotation angle is 180° to 360°, fuel gas is injected in the intake stroke of every cycle. In cylinder 3, when the crankshaft rotation angle is 360° to 540°, fuel gas is injected in the intake stroke of every cycle. In cylinder 4, when the crankshaft rotation angle is 540° to 720° (0°), fuel gas is injected in the intake stroke of every cycle.

[0051] As shown in the lower part of FIG. 5, when the fuel gas injection mode of the gas engine system 100 is the thinned injection mode, the main fuel injector 23 is PID controlled so that the fuel gas injection amount becomes the thinned injection amount every two cycles. Specifically, for each cylinder, fuel gas injection equivalent to the thinned injection amount is performed only during the intake stroke of one of two consecutive cycles of the gas engine 10 within a desired range of the rotation angle of the crankshaft. Since the operating period T of the gas engine 10 is constant, the desired range may be set using the main Dur (deg) as the rotation phase of the crankshaft. As an example, the main Dur (deg) corresponding to the thinned injection amount of fuel gas may be about 70°, but is not limited thereto. The operating period T of the gas engine 10 may be, for example, about 0.16 seconds, but is not limited thereto.

[0052] In the example shown in FIG. 5, when the rotation angle of the crankshaft is 0° to 180°, in cylinder 1, cycle A in which fuel gas is injected in the intake stroke and cycle B in which fuel gas injection is stopped in the intake stroke are alternately repeated. That is, in the intake stroke of the former cycle A in which fuel gas is injected, a mixture of fuel gas and air is drawn into cylinder 1, while in the intake stroke of the latter cycle B in which fuel gas injection is stopped, only air is drawn into cylinder 1. In cylinder 2, when the rotation angle of the crankshaft is 180° to 360°, cycle A in which fuel gas injection is stopped in the intake stroke and cycle B in which fuel gas is injected in the intake stroke are alternately repeated. That is, in the intake stroke of the latter cycle B in which fuel gas is injected, a mixture of fuel gas and air is drawn into cylinder 2, while in the intake stroke of the former cycle A in which fuel gas injection is stopped, only air is drawn into cylinder 2. In cylinder 3, when the rotation angle of the crankshaft is 360° to 540°, cycle A in which fuel gas is injected in the intake stroke and cycle B in which fuel gas injection is stopped in the intake stroke are alternately repeated. That is, in the intake stroke of cycle A in which the former fuel gas is injected, a mixture of fuel gas and air is drawn into cylinder 3, while in the intake stroke of cycle B in which the latter fuel gas injection is stopped, only air is drawn into cylinder 3. In cylinder 4, when the rotation angle of the crankshaft is 540° to 720° (0°), cycle A in which fuel gas injection is stopped in the intake stroke and cycle B in which fuel gas is injected in the intake stroke are alternately repeated. That is, in the intake stroke of cycle B in which the latter fuel gas is injected, a mixture of fuel gas and air is drawn into cylinder 4, while in the intake stroke of cycle A in which the former fuel gas injection is stopped, only air is drawn into cylinder 4.

[0053] The above is merely an example and is not limited to this example. If the number of cylinders in the gas engine 10 is more than four, a part of the intake stroke of one cylinder and a part of the intake stroke of another cylinder may be executed simultaneously at the same timing of the rotation of the crankshaft. As an example, if the number of cylinders in the gas engine 10 is eight, the latter half of the intake stroke of cylinder 1 and the first half of the intake stroke of cylinder 2 may be executed simultaneously when the rotation angle of the crankshaft is 90° to 180°.

[0054] <First control example of fuel gas injection according to the present disclosure> As shown in the middle of Fig. 5, during low-load operation in which the output of the generator 50 driven by the gas engine 10 is less than the rated output, the control device 30 holds the fuel gas injection amount at a constant value different from the normal injection amount and the thinned injection amount for a predetermined period from the timing when the fuel gas injection mode is switched from the normal injection mode to the thinned injection mode. For example, the control device 30 may hold the fuel gas injection amount at a value calculated from the normal injection amount for a first period from the same timing. Furthermore, the control device 30 may set the fuel gas injection amount per unit time to a value that is increased by a predetermined percentage relative to the normal injection amount per unit time at the same timing.

[0055] The first period may be, for example, about 0.1 seconds, and the predetermined ratio may be, for example, about 1.33 times the main Dur (deg) corresponding to the normal injection amount of fuel gas.

[0056] In other words, in the above case, for approximately 0.1 seconds from the timing when the fuel gas injection mode switches from the normal injection mode to the thinning injection mode, the main Dur (deg) in the fuel gas injection is set (fixed) to approximately 1.33 times the main Dur (deg) corresponding to the normal injection amount of fuel gas.

[0057] FIG. 6A shows an example of a temporary abnormal drop in the output of the generator 50 driven by the gas engine 10 when the generator 50 is operating at a low load where the output is approximately 10% of the rated output and the first control example of fuel gas injection of the present disclosure is not performed at the time when the fuel gas injection mode switches from the normal injection mode to the thinning injection mode.

[0058] FIG. 6B shows an example of improvement to the abnormal drop in output of the generator 50 when the first control example of fuel gas injection of the present disclosure is performed at the timing when the fuel gas injection mode switches from the normal injection mode to the thinning injection mode during low load operation where the output of the generator 50 driven by the gas engine 10 is approximately 10% of the rated output.

[0059] In other words, due to a delay in PID control of the fuel gas injection amount at the timing when the fuel gas injection mode is switched from the normal injection mode to the thinned injection mode, the output of the generator 50 temporarily drops abnormally, as shown in FIG. 6A. However, the control device 30 of this control example holds the fuel gas injection amount at a constant value that is approximately 1.33 times the main Dur (deg) corresponding to the normal injection amount of fuel gas for only approximately 0.1 second from that timing, thereby making it possible to improve this abnormal drop in the output of the generator 50, as shown in FIG. 6B.

[0060] <Second control example of fuel gas injection according to the present disclosure> As shown in the lower part of Fig. 5, during low-load operation in which the output of the generator 50 driven by the gas engine 10 is less than the rated output, the control device 30 holds the fuel gas injection amount at a constant value different from the normal injection amount and the thinned injection amount for a predetermined period from the timing when the fuel gas injection mode is switched from the thinned injection mode to the normal injection mode. For example, the control device 30 may hold the fuel gas injection amount at a value calculated from the thinned injection amount for a second period from the same timing. Furthermore, the control device 30 may set the fuel gas injection amount per unit time to a value obtained by reducing the thinned injection amount per unit time by a predetermined percentage at the same timing.

[0061] The second period may be, for example, about 1.0 second, and the predetermined ratio may be, for example, about 0.75 times the main Dur (deg) corresponding to the thinned-out injection amount of fuel gas.

[0062] In other words, in the above case, for approximately 1.0 second from the timing when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode, the main Dur (deg) in the fuel gas injection is set (fixed) to approximately 0.75 times the main Dur (deg) corresponding to the thinning injection amount of fuel gas.

[0063] FIG. 7A shows an example of a temporary abnormal increase in the output of the generator 50 driven by the gas engine 10 when the second control example of fuel gas injection disclosed herein is not performed at the time when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode during low load operation where the output of the generator 50 is approximately 10% of the rated output.

[0064] FIG. 7B shows an example of improvement to an abnormal increase in the output of the generator 50 when the second control example of fuel gas injection of the present disclosure is performed at the timing when the fuel gas injection mode switches from the thinning injection mode to the normal injection mode during low load operation where the output of the generator 50 driven by the gas engine 10 is approximately 10% of the rated output.

[0065] In other words, due to a delay in PID control of the fuel gas injection amount at the timing when the fuel gas injection mode switches from the thinned injection mode to the normal injection mode, the output of the generator temporarily rises abnormally, as shown in FIG. 7A. However, the control device 30 of this control example holds the fuel gas injection amount at a constant value that is approximately 0.75 times the main Dur (deg) corresponding to the thinned injection amount of fuel gas for only approximately 1.0 second from that timing, thereby making it possible to improve this abnormal rise in the output of the generator 50, as shown in FIG. 7B.

[0066] In addition, the embodiment, the first control example, and the second control example of the embodiment may be combined with each other as long as they do not exclude each other. From the above description, many improvements and other embodiments of the present disclosure will be apparent to those skilled in the art. Therefore, the above description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art how to carry out the present disclosure. The structure and function of the present disclosure may be substantially changed without departing from the spirit of the present disclosure.

[0067] (Regarding each aspect of the present disclosure) From the above description, the following aspects of the present disclosure are conceived.

[0068] A first aspect of the present disclosure is a control device that controls an injector for supplying fuel gas to a gas engine, and includes a first mode in which the injector is controlled so that the fuel gas injection amount is a first injection amount for each cycle consisting of four strokes of the gas engine: intake, compression, expansion, and exhaust, and a second mode in which the injector is controlled so that the fuel gas injection amount is a second injection amount for each two or more cycles, and during low-load operation in which the output of a generator driven by the gas engine is less than the rated output, the fuel gas injection amount is maintained at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other.

[0069] According to the above configuration, the control device of this embodiment can control the injection amount of fuel gas supplied to the gas engine more appropriately than in the past during low-load operation when the output of the generator driven by the gas engine is less than the rated output. Specifically, the control device of this embodiment can make the output fluctuation of the generator less likely to occur compared to the case where such control of the fuel gas injection amount is not performed by maintaining the fuel gas injection amount at a constant value different from the first injection amount and the second injection amount for a predetermined period from the timing when the fuel gas injection mode is switched from one of the first mode and the second mode to the other during low-load operation.

[0070] In addition, the control device of this embodiment executes a second mode, in which fuel gas is injected every two or more cycles, as a PID control mode for the fuel gas injection amount, thereby reducing the possibility of an increase in the number of misfires in the gas engine, an increase in the amount of unburned gas, and carbon contamination of the exhaust system during low-load operation.

[0071] Furthermore, the control device of this embodiment executes a second mode in which fuel gas is injected every two or more cycles as a PID control mode of the fuel gas injection amount, thereby reducing the possibility of an increase in the number of misfires in the gas engine, an increase in the amount of unburned gas, and the possibility of carbon fouling the exhaust system, etc., during low-load operation, and enabling the output of the generator driven by the gas engine to idle at, for example, about 10% of the rated output. As a result, the control device of this embodiment can shorten the time it takes for the output of the generator driven by the gas engine to reach the rated output.

[0072] A control device of a second aspect of the present disclosure may be configured to hold the fuel gas injection amount at a value calculated from the first injection amount for a first period from the timing of switching from the first mode to the second mode in the control device of the first aspect. Also, a control device of a third aspect of the present disclosure may be configured to set the fuel gas injection amount per unit time to a value obtained by increasing the first injection amount per unit time by a predetermined percentage in the control device of the first aspect at the timing of switching from the first mode to the second mode.

[0073] According to the above configuration, the control device of each of these aspects can improve, more than ever before, the temporary abnormal drop in the generator output caused by a delay in PID control of the fuel gas injection amount when the fuel gas injection mode switches from the first mode to the second mode.

[0074] A control device of a fourth aspect of the present disclosure may be configured to hold the fuel gas injection amount at a value calculated from the second injection amount for a second period from the timing of switching from the second mode to the first mode in the control device of the first aspect. Also, a control device of a fifth aspect of the present disclosure may be configured to set the fuel gas injection amount per unit time to a value obtained by reducing the second injection amount per unit time by a predetermined percentage in the control device of the first aspect at the timing of switching from the second mode to the first mode.

[0075] According to the above configuration, the control device of each of these aspects can improve, more than ever before, the temporary abnormal increase in the generator output caused by a delay in PID control of the fuel gas injection amount when the fuel gas injection mode switches from the second mode to the first mode.

[0076] A control device according to a sixth aspect of the present disclosure is the control device according to any one of the first to fifth aspects, wherein an output of the generator during low load operation may be less than 20% of a rated output.

[0077] A gas engine system according to a seventh aspect of the present disclosure includes a gas engine including a combustion chamber in which fuel gas is combusted and which drives a generator, and a control device according to any one of the first to fifth aspects.

[0078] According to the above configuration, the gas engine system of this embodiment can control the injection amount of fuel gas supplied to the gas engine more appropriately than in the past during low-load operation in which the output of the generator driven by the gas engine is less than the rated output. The details of the effects of the gas engine system of this embodiment are similar to those of the control device of the first embodiment, so a description thereof will be omitted.

[0079] A gas engine system according to an eighth aspect of the present disclosure is the gas engine system according to the seventh aspect, wherein the combustion chamber includes a main chamber and an auxiliary chamber, and the injector supplies fuel gas to the main chamber.

[0080] According to the above configuration, the gas engine system of this embodiment can reduce the possibility of an increase in the number of misfires, an increase in the amount of unburned gas, and carbon contamination of the exhaust system in a pre-chamber type gas engine during low load operation by controlling the amount of fuel gas injection from the injector for supplying fuel gas to the main chamber to an appropriate amount in the second mode.

[0081] A control method of a ninth aspect of the present disclosure is a control method for controlling fuel gas injection into a gas engine, and includes a first mode in which the fuel gas injection amount is controlled to be a first injection amount for each cycle consisting of four strokes of the gas engine: intake, compression, expansion, and exhaust, and a second mode in which the fuel gas injection amount is controlled to be a second injection amount for each two or more cycles, and during low-load operation in which the output of the generator driven by the gas engine is less than the rated output, the fuel gas injection amount is maintained at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other.

[0082] As described above, the control method of this embodiment can control the injection amount of fuel gas supplied to the gas engine more appropriately than in the past during low-load operation in which the output of the generator driven by the gas engine is less than the rated output. The details of the effects of the control method of this embodiment are similar to those of the control device of the first embodiment, so a description thereof will be omitted. [Explanation of symbols]

[0083] 10: Gas engine 11A: Main room 11B: Antechamber 12: Piston 13: Connecting rod 14: Air supply valve 15: Exhaust valve 16: Piston sliding surface 21: Exhaust duct 22:Air supply path 23: Main fuel injector 24 :Auxiliary fuel injector 25: Spark plug 26: Ignition coil 30: Control device 50: Generator 100: Gas engine system

Claims

1. A control device for controlling an injector for supplying fuel gas to a gas engine, a first mode in which the injector is controlled so that the fuel gas injection amount becomes a first injection amount for each cycle consisting of four strokes of intake, compression, expansion and exhaust of the gas engine, and a second mode in which the injector is controlled so that the fuel gas injection amount becomes a second injection amount for each two or more of the cycles, A control device that maintains the fuel gas injection amount at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other during low-load operation in which the output of the generator driven by the gas engine is less than rated output.

2. 2 . The control device according to claim 1 , wherein the fuel gas injection amount is held at a value calculated from the first injection amount for a first period from a timing when the first mode is switched to the second mode.

3. 2. The control device according to claim 1, wherein, at a timing when the first mode is switched to the second mode, the fuel gas injection amount per unit time is increased by a predetermined percentage relative to the first injection amount per unit time.

4. 2 . The control device according to claim 1 , wherein the fuel gas injection amount is held at a value calculated from the second injection amount for a second period from a timing when the second mode is switched to the first mode.

5. 2. The control device according to claim 1, wherein, at a timing when the second mode is switched to the first mode, the fuel gas injection amount per unit time is set to a value obtained by reducing the second injection amount per unit time by a predetermined percentage.

6. 6. The control device according to claim 1, wherein the output of the generator during the low load operation is less than 20% of a rated output.

7. A gas engine system comprising: a gas engine including a combustion chamber in which fuel gas is combusted and which drives a generator; and the control device according to any one of claims 1 to 5.

8. The gas engine system according to claim 7 , wherein the combustion chamber includes a main chamber and an auxiliary chamber, and the injector supplies the fuel gas to the main chamber.

9. A method for controlling fuel gas injection into a gas engine, comprising: a first mode in which the fuel gas injection amount is controlled to a first injection amount for each cycle consisting of four strokes of intake, compression, expansion, and exhaust of the gas engine, and a second mode in which the fuel gas injection amount is controlled to a second injection amount for each of two or more of the cycles, A control method in which, during low-load operation in which the output of a generator driven by the gas engine is less than rated output, the fuel gas injection amount is maintained at a constant value different from the first injection amount and the second injection amount for a predetermined period of time from the timing of switching from one of the first mode and the second mode to the other.

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