Fuel supply device and engine system

Abstract

The invention provides a fuel supply device and an engine system, which can more finely control the supply amount of gas fuel and finely control the output of an engine. A fuel supply device (3) for supplying at least gaseous fuel to a predetermined supply target such as an engine (2) is provided with: a gaseous fuel supply unit (16) as a gaseous fuel adjustment unit for adjusting the supply amount of gaseous fuel and supplying the gaseous fuel to the supply target; and a temperature adjustment unit (14) that adjusts the temperature of the gas fuel supplied to the gas fuel supply unit (16) in accordance with the operating state and / or operating environment of the object to be supplied.

Description

Technical Field

[0001] The present description relates to a fuel supply device that supplies at least gaseous fuel to a supply target such as an engine, and an engine system including the fuel supply device. Background Art

[0002] Conventionally, an engine system including a gas engine or a dual-fuel engine includes a gas fuel supply valve such as a GAV (Gas Admission Valve) in order to inject a gas fuel such as hydrogen into a combustion chamber within a cylinder.

[0003] The engine system disclosed in Patent Document 1 includes at least an engine that burns gas fuel to generate power, a gas fuel supply pipe that supplies gas fuel to the engine, and a fuel flow rate regulator that regulates the flow rate of gas fuel flowing into the gas fuel supply pipe.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-149336 Summary of the Invention

[0007] However, in order to precisely control engine output in an engine system, it is necessary to adjust the opening period of the gas fuel supply valve or the gas fuel injection amount by the fuel flow rate adjustment unit. However, in an engine system, the gas fuel supply valve is restricted to a minimum injection period, making it difficult to precisely control the gas fuel injection amount in the low-load range. Consequently, it is difficult to appropriately control a low engine output, such as one below the engine output during the minimum injection period.

[0008] An object of the present invention is to provide a fuel supply device and an engine system that can more finely control the supply amount of gas fuel and thereby finely control the output of an engine.

[0009] In order to solve the above-mentioned problems, the fuel supply device of the present invention supplies at least gas fuel to a specified supply object, and is characterized in that the fuel supply device comprises: a gas fuel adjustment unit, which adjusts the supply amount of the gas fuel and supplies it to the supply object; and a temperature adjustment unit, which adjusts the temperature of the gas fuel supplied to the gas fuel adjustment unit corresponding to the operating state and / or operating environment of the supply object.

[0010] Alternatively, the fuel supply device of the present invention supplies at least gas fuel to a specified supply object, and is characterized in that the fuel supply device comprises: a gas fuel adjustment unit, which adjusts the supply amount of the gas fuel and supplies it to the supply object; and a supply pressure adjustment unit, which adjusts the supply pressure of the gas fuel supplied to the gas fuel adjustment unit corresponding to the operating state and / or operating environment of the supply object.

[0011] In addition, the engine system of the present invention is equipped with the above-mentioned fuel supply device and the engine as the supply object, and is characterized in that the temperature adjustment unit has: a heat exchange unit, which allows the heat exchange medium to circulate and act on the gas fuel; and a flow adjustment unit, which adjusts the flow of the heat exchange medium, and also has: a control device for controlling the gas fuel adjustment unit and the flow adjustment unit, the control device calculates the target temperature of the gas fuel based on the target output of the engine, and when the monitored temperature of the gas fuel is lower than the target temperature, controls the flow adjustment unit in such a manner that the monitored temperature reaches the target temperature to increase the temperature of the gas fuel.

[0012] Alternatively, the engine system of the present invention comprises the above-mentioned fuel supply device and the engine as the supply object, and is characterized in that the temperature adjustment unit comprises: a heat exchange unit, which allows the heat exchange medium to circulate and act on the gas fuel; and a flow adjustment unit, which adjusts the flow of the heat exchange medium, and further comprises: a control device for controlling the gas fuel adjustment unit and the flow adjustment unit, and the control device controls the flow adjustment unit in such a manner that the circulation of the heat exchange medium is stopped when the target output of the engine is above a specified output threshold.

[0013] Alternatively, the engine system of the present invention comprises the above-mentioned fuel supply device and the engine as the supply object, and is characterized in that the temperature adjustment unit comprises: a heat exchange unit, which allows the heat exchange medium to circulate and act on the gas fuel; and a cooling device, which cools the heat exchange medium, and further comprises: a control device for controlling the gas fuel adjustment unit and the cooling device, and the control device controls the cooling device in a manner that causes the cooling device to operate when the target output of the engine is above a specified output threshold.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide a fuel supply device and an engine system that can more finely control the supply amount of gas fuel and thereby finely control the output of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram showing an example of an engine system including a fuel supply device according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram showing an example of an engine in an engine system including a fuel supply device according to an embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram showing an example of a temperature adjustment unit in the fuel supply device according to the embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram showing another example of the temperature adjustment unit in the fuel supply device according to the embodiment of the present invention.

[0020] Figure 5 This is a flowchart showing an example of the operation of the fuel supply device according to the embodiment of the present invention.

[0021] Figure 6 This is a timing chart showing an example of the operation of the fuel supply device according to the embodiment of the present invention when switching from the diesel mode to the gas mode.

[0022] Figure 7 This is a graph showing an example of a map of the relationship between the engine load and the target supply pressure of the gas fuel in the fuel supply device according to the modified example of the present invention.

[0023] Figure 8 This is a graph showing an example of a map of the relationship between the engine load and the target supply pressure of the gas fuel corresponding to the combustion ratio in the fuel supply device according to the modified example of the present invention.

[0024] Description of Reference Numerals

[0025] 1…engine system; 2…engine (supply object); 3…fuel supply device; 4…generator; 5…liquid fuel supply unit; 10…liquefied gas fuel tank (gas fuel storage unit); 11…gas fuel supply passage; 11a…common passage; 11b…branch passage; 12…carburetor; 13…pressure regulating device; 4…temperature regulating unit; 15…chamber; 16…gas fuel supply unit (gas fuel regulating unit); 17…control device; 21…cylinder; 25…combustion chamber; 36…first stop valve, 37…second stop valve; 38…open passage; 39…release valve; 40…first heat exchanger; 4…first flow regulating unit; 42…second heat exchanger; 43…second flow regulating unit; 44…cooling device. DETAILED DESCRIPTION

[0026] Referring to the accompanying drawings, an engine system 1 according to an embodiment of the present invention will be described. Figure 1 As shown, an engine system 1 includes an engine 2 that operates at least using gas fuel, and a fuel supply device 3 that supplies gas fuel to the engine 2 as a fuel supply target. While the engine 2 may be a propulsion engine (main engine) or a power generation engine (auxiliary engine) for a ship or the like, this embodiment will be described using the following example: the engine system 1 includes the engine 2 as a power generation engine (auxiliary engine), and the engine 2 is connected to a generator 4, where the generator 4 is driven by the output of the engine 2.

[0027] In this embodiment, the example in which the engine 2 is configured as a dual-fuel engine is described. This dual-fuel engine is driven by injecting at least one of a gas fuel such as hydrogen and a liquid fuel such as light oil or heavy oil into the combustion chamber 25 of the engine 2. When the engine 2 uses only gas fuel as fuel, it is in a gas mode; when it uses only liquid fuel, it is in a diesel mode; and when it uses both gas fuel and liquid fuel, it is in a mixed combustion mode. The engine system 1 operates in any of the gas mode, diesel mode, and mixed combustion mode.

[0028] The engine system 1 includes a liquid fuel supply unit 5 for supplying liquid fuel to the engine 2. The liquid fuel supply unit 5 is connected to a liquid fuel tank (not shown) via a liquid fuel supply passage (not shown) and injects (injects) the liquid fuel supplied through the liquid fuel supply passage into the combustion chamber 25 of the engine 2.

[0029] The fuel supply device 3 includes a liquefied gas fuel tank 10 (gas fuel storage unit), a gas fuel supply passage 11, a vaporizer 12, a pressure regulator 13, a temperature regulator 14, a chamber 15, a gas fuel supply unit 16 (gas fuel regulator), and a control device 17. The various components of the fuel supply device 3 will be described in detail later.

[0030] First, the engine 2 will be described.

[0031] The engine 2 is configured such that a cylinder block 20 is provided with a plurality of cylinders 21. Figure 2 As shown, each cylinder 21 is composed of, for example, a cylinder block 22, a piston 23, and a cylinder head 24, and forms a combustion chamber 25 therein. A gas fuel supply unit 16 and a liquid fuel supply unit 5 are provided for each cylinder 21.

[0032] The cylinder 22 is formed in a cylindrical shape, for example, within the cylinder block 20, and the piston 23 is slidably accommodated within the cylinder 22. The cylinder head 24 is mounted on the upper side of the cylinder 22, and a combustion chamber 25 is formed inside the cylinder 22 and the cylinder head 24.

[0033] The cylinder head 24 has an intake port 27 connected to an intake passage 26 for introducing air, and an exhaust port 29 connected to an exhaust passage 28 for discharging exhaust gas. The intake port 27 and the exhaust port 29 communicate with the combustion chamber 25, and the cylinder head 24 has an intake valve 30 and an exhaust valve 31 for opening and closing the intake port 27 and the exhaust port 29, respectively, with respect to the combustion chamber 25.

[0034] In addition, Figure 2 In the figure, an example is shown in which the intake passage 26 and the intake port 27 are directly connected. Alternatively, in another example, the intake passage 26 and the intake port 27 may be connected via an intake manifold provided between the intake passage 26 and the engine 2. Figure 2 , an example in which the exhaust passage 28 and the exhaust port 29 are directly connected is shown. Alternatively, in another example, the exhaust passage 28 and the exhaust port 29 may be connected via an exhaust manifold provided between the exhaust passage 28 and the engine 2.

[0035] The cylinder head 24 is provided with a gaseous fuel supply unit 16 for supplying gaseous fuel to the interior of an intake port 27, and a liquid fuel supply unit 5 for supplying liquid fuel to the combustion chamber 25. The intake port 27 is used to introduce a mixed gas of gaseous fuel supplied from the gaseous fuel supply unit 16 and air supplied from the intake passage 26 into the combustion chamber 25. The exhaust port 29 is used to discharge exhaust gas generated in the combustion chamber 25 to the exhaust passage 28.

[0036] In each cylinder 21, at an appropriate time when the air-fuel mixture introduced from the intake port 27 is compressed by the sliding movement of the piston 23, a small amount of pilot fuel (liquid fuel) is injected into the combustion chamber 25 via the liquid fuel supply unit 5, thereby igniting the gaseous fuel in the air-fuel mixture. The piston 23 reciprocates within the cylinder 21 using the propulsive force generated by the explosion in the combustion chamber 25.

[0037] Each cylinder block 22 of the plurality of cylinders 21 is connected to a crankcase 32, and a crankshaft 33 is rotatably supported by the crankcase 32. The piston 23 of each cylinder 21 is connected to the crankshaft 33 via a connecting rod 34, and the reciprocating motion of the piston 23 is converted into rotational motion of the crankshaft 33 via the connecting rod 34.

[0038] Next, each part of the fuel supply device 3 will be described.

[0039] The liquefied gas fuel tank 10 stores liquefied gas fuel, for example, hydrogen fuel in a liquid state, ie, liquid hydrogen fuel.

[0040] The gas fuel supply passage 11 connects the liquefied gas fuel tank 10 and the gas fuel supply unit 16, allowing the gas fuel to flow from the liquefied gas fuel tank 10 to the gas fuel supply unit 16. Disposed in this order on the gas fuel supply passage 11, between the liquefied gas fuel tank 10 and the gas fuel supply unit 16, are a vaporizer 12, a pressure regulator 13 (supply pressure regulator), a temperature regulator 14, and a chamber 15.

[0041] The fuel gas supply passage 11 is constructed of a multilayer tube (e.g., a double tube) between the chamber 15 and the fuel gas supply unit 16, and maintains the fuel gas pressure (supply pressure) adjusted by the pressure regulating device 13 or the fuel gas temperature adjusted by the temperature regulating unit 14. In the fuel gas supply passage 11 of the multilayer tube, fuel gas flows through the innermost tube, and air flows between the innermost tube and the outer tube covering the innermost tube.

[0042] The gas fuel supply passage 11 includes a common passage 11a, which is shared by the multiple gas fuel supply units 16 of the multiple cylinders 21 and through which the gas fuel flows, and multiple branch passages 11b, which branch from the common passage 11a and allow the gas fuel to flow through the multiple gas fuel supply units 16. The vaporizer 12, the pressure regulating device 13, the temperature regulating unit 14, and the chamber 15 are arranged in this order on the common passage 11a.

[0043] The vaporizer 12 vaporizes the liquid gas fuel supplied from the liquefied gas fuel tank 10 and supplies the vaporized gas fuel to the pressure regulating device 13 through the gas fuel supply passage 11 .

[0044] The pressure regulating device 13 regulates the supply pressure of the gas fuel supplied via the gas fuel supply unit 16 and supplies the gas fuel with the regulated supply pressure to the temperature regulating unit 14 via the gas fuel supply passage 11. The pressure regulating device 13 is constituted by, for example, a gas valve unit (GVU) having a plurality of valves.

[0045] For example, Figure 1As shown, the pressure regulating device 13 is configured to include a first stop valve 36 on the upstream side and a second stop valve 37 on the downstream side of the gas fuel supply passage 11 in the direction of gas fuel supply. A release valve 39 is provided in an open passage 38 branching from the gas fuel supply passage 11 between the first stop valve 36 and the second stop valve 37. The pressure regulating device 13 controls the supply pressure (flow rate per unit time) of the gas fuel flowing downstream of the pressure regulating device 13 by controlling the openings of the first stop valve 36 and the second stop valve 37 in response to a control signal from the control device 17. Furthermore, the pressure regulating device 13 normally closes the release valve 39. However, in response to a control signal from the control device 17, the pressure regulating device 13 closes the first stop valve 36, opens the release valve 39, and thereby controls the gas fuel purification function in the gas fuel supply passage 11.

[0046] The temperature regulating unit 14 is used to regulate the temperature of the gas fuel supplied via the gas fuel supply unit 16, and to supply the gas fuel having the regulated temperature to the chamber 15 via the gas fuel supply passage 11. The temperature regulating unit 14 is provided separately from the vaporizer 12 provided to convert the liquefied gas fuel stored in the liquefied gas fuel tank 10 into a gaseous state, and is used to regulate the temperature of the gaseous state gas fuel. Figure 3 As shown, the temperature adjustment unit 14 includes, for example, a first heat exchanger 40 (heat exchange unit) and a first flow rate adjustment unit 41 (flow rate adjustment unit), and further includes a second heat exchanger 42 and a second flow rate adjustment unit 43 .

[0047] The first heat exchanger 40 is used to circulate a heat exchange medium such as an aqueous ethylene glycol solution and a gas fuel, and regulates the temperature of the gas fuel by allowing the heat exchange medium to act on the gas fuel to exchange heat. The first flow rate regulator 41, which is composed of a pump or the like, regulates the flow rate of the heat exchange medium flowing through the first heat exchanger 40 in response to a control signal from the control device 17, thereby regulating the temperature of the gas fuel that is exchanging heat with the heat exchange medium.

[0048] The second heat exchanger 42 allows an auxiliary medium, such as engine cooling water or engine oil, to flow through, as well as gaseous fuel, and regulates the temperature of the heat exchange medium by causing the auxiliary medium to act on the heat exchange medium for heat exchange. The second flow rate regulator 43, comprised of a pump or the like, regulates the flow rate of the auxiliary medium flowing through the second heat exchanger 42 in response to a control signal from the control device 17, thereby regulating the temperature of the heat exchange medium that is exchanging heat with the auxiliary medium.

[0049] That is, the temperature of the gas fuel is finely adjusted by using the first heat exchanger 40 and the second heat exchanger 42. In addition, the first flow rate regulator 41 or the second flow rate regulator 43 can stop heat exchange by stopping the flow of the heat exchange medium or the auxiliary medium.

[0050] In addition, the temperature regulating unit 14 includes the first heat exchanger 40 and the first flow regulating unit 41, the second heat exchanger 42 and the second flow regulating unit 43, as shown in FIG. Figure 4 As shown, a cooling device 44 may be further provided. When the heat exchange medium that regulates the temperature of the gas fuel in the first heat exchanger 40 is temperature-regulated by the auxiliary medium in the second heat exchanger 42, the cooling device 44 is provided in the flow path of the heat exchange medium and is operated by electricity, thereby lowering the temperature of the heat exchange medium.

[0051] Chamber 15 is provided between temperature regulating unit 14 and gas fuel supply unit 16 in the direction of gas fuel supply in gas fuel supply passage 11. Chamber 15 stores a predetermined amount or more of gas fuel, the supply pressure of which has been regulated by pressure regulating device 13 and the temperature of which has been regulated by temperature regulating unit 14. Furthermore, chamber 15 pressurizes the interior of gas fuel supply passage 11 toward the downstream side of chamber 15. Consequently, regardless of the supply of gas fuel from gas fuel supply unit 16, the regulated supply pressure and temperature of gas fuel are maintained on the downstream side of chamber 15.

[0052] As described above, the gas fuel supply unit 16 is provided in the cylinder head 24 of each cylinder 21 of the engine 2. It supplies gas fuel to the interior of the intake port 27 in response to a control signal from the control unit 17. For example, the gas fuel supply unit 16 comprises a gas admission valve (GAV) that injects gas fuel. The gas fuel supply unit 16 adjusts the valve opening period in response to the control signal from the control unit 17, thereby adjusting the gas fuel supply amount.

[0053] The control device 17 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 2. It is configured with a CPU, ROM, RAM, and other components to control various parts of the engine 2. The control device 17 stores various programs for controlling the engine 2 and reads and executes these programs to control the engine 2. In particular, the control device 17 controls the pressure regulating device 13 and the temperature regulating unit 14 in accordance with the operating conditions of the engine 2, such as the engine output (engine speed), or the operating environment, such as the ambient temperature of the engine 2 or the fuel supply device 3. The control device 17 can be located on the engine 2 side or on the fuel supply device 3 side.

[0054] In engine system 1, when the target output of engine 2 is determined based on the operating state of generator 4 (generator load), the amount of gas fuel supplied to combustion chamber 25 of each cylinder 21 is determined based on the target output. Consequently, the valve opening period or supply pressure of the gas fuel supplied to combustion chamber 25 via gas fuel supply unit 16 is determined based on the target output. Therefore, control device 17 controls pressure regulating device 13 based on the target output to adjust the gas fuel supply pressure to a supply pressure (or supply pressure range) corresponding to the target output, i.e., a target supply pressure (or target supply pressure range). Alternatively, control device 17 may set the valve opening period of gas fuel supply unit 16 based on a previously set target supply pressure (or target supply pressure range), or may set the target supply pressure (or target supply pressure range) based on a previously set valve opening period of gas fuel supply unit 16.

[0055] On the other hand, in engine system 1, when determining the lower limit value (minimum valve open period) or upper limit value (maximum valve open period) of the valve open period of the gas fuel supplied by gas fuel supply unit 16, and the lower limit value (minimum supply pressure) or upper limit value (maximum supply pressure) of the gas fuel supply pressure of pressure regulating device 13, control unit 17 cannot set the valve open period or supply pressure outside the range of the lower limit and upper limit values. Therefore, even if the valve open period of the gas fuel supplied by gas fuel supply unit 16 calculated to correspond to the target output (generator load) is lower (in the low load range), and the valve open period of the gas fuel supplied by gas fuel supply unit 16 is less than the minimum valve open period, control unit 17 sets the valve open period of the gas fuel supplied by gas fuel supply unit 16 to be greater than the minimum valve open period, which may cause the actual output of engine 2 to exceed the target output.

[0056] However, according to this embodiment, the control device 17 adjusts the temperature of the gas fuel supplied to the gas fuel supply unit 16 based on the equation of state for the gas. This allows the energy density (supply pressure) of the gas fuel supplied to the gas fuel supply unit 16 to be adjusted to adjust the supply amount, regardless of the supply pressure set by the pressure regulating device 13. Furthermore, the temperature of the gas fuel supplied to the gas fuel supply unit 16 is not limited to a specific target temperature; as long as it is within a predetermined target temperature range, the gas fuel can be supplied at a target energy density, that is, at a target supply pressure (or within a target supply pressure range).

[0057] Specifically, to obtain the target temperature of the gas fuel corresponding to the target output of the engine 2, the control device 17 may predetermine and store a map or formula representing the relationship between the target output of the engine 2 and the target temperature (or target temperature range) of the gas fuel. The control device 17 calculates the target temperature of the gas fuel based on the target output and in accordance with the map or formula. Furthermore, while the parameter used to determine the target temperature may be solely the target output of the engine 2, in addition to or in lieu of the target output, a map or formula may be predetermine to determine the target temperature corresponding to the discharge pressure of the gasifier 12 or the reference injection period of the gas fuel supply unit 16. Furthermore, the control device 17 may store a map or formula representing the relationship between the target output of the engine 2 and the target temperature of the gas fuel for each operating environment (e.g., ambient temperature or humidity) so that the map or formula corresponding to the detected operating environment is used.

[0058] Furthermore, the control device 17 monitors the actual temperature (monitored temperature) of the gas fuel supplied to the gas fuel supply unit 16 and compares the monitored temperature with the target temperature (or target temperature range). If the monitored temperature is not the target temperature (or if the monitored temperature is outside the target temperature range), the temperature regulator 14 controls the gas fuel temperature so that the monitored temperature reaches the target temperature. Furthermore, in order to monitor the temperature of the gas fuel supplied to the gas fuel supply unit 16, the engine system 1 is provided with a temperature sensor (not shown) in any one of the temperature regulator 14, the chamber 15, the gas fuel supply passage 11, and the gas fuel supply unit 16.

[0059] In addition, when the gas fuel reaches the target temperature, the control device 17 causes the supply pressure of the gas fuel of the gas fuel supply unit 16 to change relative to the supply pressure of the gas fuel adjusted by the pressure regulating device 13 in accordance with the target temperature. Therefore, taking into account the supply pressure change, the control is performed in a manner that adjusts the supply pressure of the gas fuel using the pressure regulating device 13.

[0060] For example, when the target output of the engine 2 is low (in the low load range) and the monitored temperature is lower than the target temperature, the control device 17 controls the first flow rate regulating unit 41 of the temperature regulating unit 14 so that the monitored temperature reaches the target temperature, thereby raising the temperature of the gas fuel. Furthermore, when the target output of the engine 2 is equal to or higher than a predetermined output threshold (in the high load range), the control device 17 controls the temperature regulating unit 14 so that the temperature of the gas fuel does not rise, regardless of the target temperature corresponding to the target output. For example, the control device 17 controls the first flow rate regulating unit 41 so that the flow of the heat exchange medium by the temperature regulating unit 14 is stopped.

[0061] Therefore, the control device 17 not only controls the supply pressure of the gas fuel regulated by the pressure regulating device 13 but also controls the temperature of the gas fuel using the temperature regulating unit 14. This allows for more precise adjustment of the energy density (supply pressure) of the gas fuel supplied to the gas fuel supply unit 16, thereby enabling more precise adjustment of the supply amount. For example, even if the valve opening period of the gas fuel supply unit 16 calculated based on the target output of the engine 2 is less than the minimum valve opening period, the control device 17 can increase the temperature of the gas fuel using the temperature regulating unit 14 to reduce the energy density (supply pressure) of the gas fuel. This allows the actual output of the engine 2 to be maintained at the target output even if the valve opening period of the gas fuel supply unit 16 is set to be greater than the minimum valve opening period. In other words, if the valve opening period of the gas fuel supply unit 16 calculated based on the target output of the engine 2 (the target valve opening period) is less than the minimum valve opening period, the control device 17 increases the temperature of the gas fuel using the temperature regulating unit 14 so that the valve opening period of the gas fuel supply unit 16 actually controlled is greater than the minimum valve opening period.

[0062] Next, refer to Figure 5 An operation example of the fuel supply device 3 of the engine system 1 according to the present embodiment will be described with reference to the flowchart of FIG.

[0063] First, the control device 17 acquires various sensor values ​​and set values ​​related to the operating state of the engine 2 or the operating environment, such as the ambient temperature of the engine 2 or the fuel supply system 3, as control parameters for the fuel supply system 3 (step S1). For example, the control device 17 acquires the combustion mode, the mixture ratio (the ratio of gas to fuel), the monitored temperature of the gas fuel, and the target output of the engine 2 or the generator load of the generator 4 as control parameters related to the operating state. Furthermore, the control device 17 acquires the ambient temperature and humidity of the engine 2 or the fuel supply system 3 as control parameters related to the operating environment.

[0064] Based on the acquired control parameters, the control device 17 calculates a target temperature (or target temperature range) for the gas fuel supplied to the gas fuel supply unit 16. For example, the target temperature is acquired based on a map representing the relationship between the target output of the engine 2 and the target temperature of the gas fuel. The control device 17 then compares the monitored gas fuel temperature with the target temperature (step S2).

[0065] When the monitored temperature of the gas fuel is the target temperature (or within the target temperature range) (step S2: Yes), the control device 17 maintains the current control state of the temperature adjustment unit 14 (step S3) and switches to control of the pressure regulating device 13 (step S4).

[0066] On the other hand, if the monitored temperature of the gas fuel is not the target temperature (or is outside the target temperature range) (step S2: No), the control device 17 calculates the control variable for the temperature regulator 14 (step S5) and controls the temperature regulation of the gas fuel by the temperature regulator 14 based on the control variable (step S6). For example, the control device 17 calculates the flow rate of the heat exchange medium in the first flow regulator 41 or the flow rate of the auxiliary medium in the second flow regulator 43 based on the difference between the monitored temperature and the target temperature as the control variable, and controls the first flow regulator 41 or the second flow regulator 43.

[0067] In parallel with the temperature adjustment of the temperature adjustment unit 14, the control device 17 re-monitors the monitored temperature of the gas fuel and compares the monitored temperature of the gas fuel with the target temperature (step S7). If the re-monitored monitored temperature of the gas fuel is not the target temperature (step S7: No), the control device 17 continues to adjust the temperature of the temperature adjustment unit 14 (step S6).

[0068] On the other hand, if the monitored gas fuel temperature is the target temperature (step S7: Yes), the control device 17 controls the temperature regulator 14 to maintain the current gas fuel temperature and switches to control of the pressure regulator 13 (step S4).

[0069] During the control of the pressure regulating device 13 (step S4), the control device 17 adjusts the supply pressure of the gas fuel so that it reaches the target supply pressure corresponding to the target output. Furthermore, when the temperature regulating unit 14 is adjusting the temperature of the gas fuel, the control device 17 controls the pressure regulating device 13 to adjust the supply pressure of the gas fuel so that the supply pressure of the gas fuel supplied to the gas fuel supply unit 16 reaches the target supply pressure corresponding to the target output, taking into account the fluctuation of the supply pressure of the gas fuel due to the temperature adjustment by the temperature regulating unit 14.

[0070] In addition, the control device 17 calculates the control quantities such as the valve opening period or injection pressure of the gas fuel supply unit 16 or the liquid fuel supply unit 5 based on the required supply amount of gas fuel in the combustion chamber 25 based on the target output of the engine 2 and the supply pressure of the gas fuel of the gas fuel supply unit 16 (step S8).

[0071] Then, the control device 17 controls the gas fuel supply unit 16 or the liquid fuel supply unit 5 based on the calculated control amount, thereby supplying a necessary amount of gas fuel or liquid fuel to the combustion chamber 25 to drive the engine 2 (step S9).

[0072] Furthermore, in the above-described operational example, the temperature of the gas fuel is re-monitored and compared with the target temperature in step S7, which represents the transition condition for transitioning to control of the pressure regulating device 13 after temperature adjustment by the temperature adjusting unit 14. However, the present invention is not limited to this example. As another example, the control device 17 may replace the above-described transition condition with a determination that the transition condition is satisfied when a timer detects the passage of a predetermined time.

[0073] Alternatively, the control device 17 may omit the transition condition determination step and directly transition to gas fuel supply pressure control (steps S8 and S9) after activating the temperature adjustment unit 14. Furthermore, if gas fuel temperature adjustment is necessary during operation in gas mode, for example, if an instruction is received to change the engine 2 from medium output to low output, the responsiveness of the engine output change may decrease when transitioning to the next step while waiting for the target temperature to be reached. Therefore, the control device 17 may omit the transition condition determination step described above, prioritizing responsiveness to engine output changes.

[0074] In addition, refer to Figure 6 The timing chart of FIG. 1 illustrates an example of the operation of the fuel supply device 3 when the engine system 1 of the present embodiment changes from the diesel mode to the gas mode (or the co-firing mode).

[0075] exist Figure 6 In it, the target output of the engine 2, the set value of the mixing ratio of the fuel fed into the combustion chamber 25, the proportion of the liquid fuel, the temperature of the gas fuel supplied to the gas fuel supply unit 16, the valve opening period of the gas fuel supply unit 16, the flow rate of the gas fuel supplied from the gas fuel supply unit 16, and the change in the actual output of the engine 2 with respect to the passage of time are shown.

[0076] In this operation example, while the combustion mode is the diesel mode, the actual output of the engine 2 is the target output. At time t1, the combustion mode is changed from the diesel mode to the gas mode (or the co-firing mode).

[0077] The control device 17 sets the valve opening period of the gas fuel supply unit 16 to the minimum valve opening period corresponding to the change in the combustion mode, and sets the flow rate of the gas fuel in the gas fuel supply unit 16 to a specified flow rate. Thus, when the actual output of the engine 2 is higher than the target output, the temperature adjustment unit 14 is controlled in such a way that the gas fuel supplied to the gas fuel supply unit 16 is heated.

[0078] By raising the temperature of the gas fuel as described above, the control device 17 can reduce the flow rate of the gas fuel supplied by the gas fuel supply unit 16 during the minimum valve opening period, compared to the case where the gas fuel is not raised in temperature. As a result, the actual output of the engine 2 can be reduced, and more specifically, can be suppressed to the target output, compared to the case where the gas fuel is not raised in temperature. Figure 6 In the diagram, the temperature and flow rate of the gas fuel, and thus the actual output of the engine 2, are shown by a solid line when the gas fuel temperature is regulated, and by a dashed line when the gas fuel temperature is not regulated. When the gas fuel temperature is not regulated, the actual output of the engine 2 rises until the liquid fuel is exhausted, thus exceeding the target output as shown by the dashed line. However, in this embodiment, by regulating the temperature of the gas fuel, it is possible to prevent the target output from being exceeded.

[0079] Alternatively, the control device 17 may control the gas fuel so that the temperature gradually increases. In this case, the control device 17 may control the gas fuel flow rate of the gas fuel supply unit 16 so that it gradually decreases from a predetermined flow rate, thereby gradually reducing the actual output of the engine 2. Alternatively, the control device 17 may control the liquid fuel supply unit 5 and the gas fuel supply unit 16 so that the proportion of liquid fuel gradually decreases as the gas fuel temperature increases. Furthermore, when the gas fuel temperature reaches the target temperature, the control device 17 stops temperature regulation by the temperature regulator 14. As a result, the actual output of the engine 2 is reduced to a certain output, such as the target output, and then maintained there.

[0080] As described above, according to this embodiment, the fuel supply device 3 that supplies at least gas fuel to a specified supply object such as an engine 2 includes: a gas fuel supply unit 16 as a gas fuel adjustment unit, which adjusts the supply amount of the gas fuel and supplies it to the supply object; and a temperature adjustment unit 14, which adjusts the temperature of the gas fuel supplied to the gas fuel supply unit 16 corresponding to the operating state and / or operating environment of the supply object.

[0081] Thus, by adjusting the temperature of the gas fuel supplied to the gas fuel supply unit 16, the fuel supply device 3 can more precisely control the amount of gas fuel supplied from the gas fuel supply unit 16, thereby enabling precise operation control of the supply target, such as the output control of the engine 2. Furthermore, when adjusting the temperature of gas fuel in a gas phase, the required heat transfer area is larger than when adjusting the temperature of gas fuel in a liquid phase. By arranging the temperature adjustment unit 14 upstream of the gas fuel supply unit 16, the required heat transfer area can be easily ensured.

[0082] According to the present embodiment, the fuel supply device 3 includes a pressure regulator 13 for regulating the supply pressure of the gas fuel, and the temperature regulator 14 is provided between the pressure regulator 13 and the gas fuel supply unit 16 in the supply direction of the gas fuel.

[0083] Thus, in the fuel supply device 3, the temperature adjustment unit 14 performs heat exchange on the gas fuel that has increased its flow rate after passing through the pressure reducing valve of the pressure regulating device 13, etc., thereby achieving higher heat exchange efficiency and enabling more appropriate temperature adjustment. This allows for more precise control of the amount of gas fuel supplied from the gas fuel supply unit 16, thereby enabling precise operation control of the supply target, such as the output control of the engine 2.

[0084] In addition, according to this embodiment, the fuel supply device 3 includes: a liquefied gas fuel tank 10 serving as a gas fuel storage unit that stores gas fuel, a gas fuel supply passage 11 that is connected to a gas fuel supply unit 16 and allows the gas fuel to circulate, and a pressure regulating device 13 and a temperature regulating unit 14 are arranged in the gas fuel supply passage 11.

[0085] With this, the fuel supply device 3 can appropriately adjust the supply pressure or the temperature of the gas fuel supplied to the gas fuel supply unit 16 .

[0086] Furthermore, according to the present embodiment, the fuel supply device 3 includes the chamber 15 which is provided between the temperature regulating unit 14 and the gas fuel supply unit 16 and which stores the gas fuel whose temperature has been regulated.

[0087] Thus, by providing the chamber 15 after the temperature regulating unit 14, the fuel supply device 3 can stably supply the temperature-regulated gas fuel to the engine 2 regardless of the supply of gas fuel in the gas fuel supply unit 16. Furthermore, by providing the chamber 15, various valves such as the first stop valve 36 and the second stop valve 37 included in the pressure regulating device 13 can be simplified.

[0088] In addition, according to this embodiment, the fuel supply device 3 is constructed as follows: the supply object is an engine 2 having multiple cylinders 21, the gas fuel supply part 16 is a gas fuel supply valve respectively possessed by the multiple cylinders 21, and the gas fuel supply passage 11 has: a common passage 11a shared by the multiple cylinders 21 and allowing the gas fuel to circulate, and the temperature adjustment part 14 is arranged in the common passage 11a.

[0089] According to this, the fuel supply device 3 can be simplified compared to a case where a mechanism for adjusting the temperature of the gas fuel is provided for each gas fuel supply valve.

[0090] In addition, according to the present embodiment, in the engine system 1 having the above-mentioned fuel supply device 3 and the engine 2, the temperature adjustment unit 14 has: a first heat exchanger 40 as a heat exchange unit, which allows the heat exchange medium to circulate and act on the gas fuel; and a first flow adjustment unit 41, which adjusts the flow of the heat exchange medium, and also has: a control device 17 that controls the gas fuel supply unit 16 and the first flow adjustment unit 41. The control device 17 calculates the target temperature of the gas fuel based on the target output of the engine 2. When the monitored temperature of the gas fuel is lower than the target temperature, the first flow adjustment unit 41 is controlled so that the monitored temperature reaches the target temperature to increase the temperature of the gas fuel.

[0091] In engine system 1, even when the required valve opening period of gas fuel supply unit 16 calculated based on the target output of engine 2 is less than the minimum valve opening period, in order to operate gas fuel supply unit 16 and supply gas fuel during the minimum valve opening period, gas fuel may be supplied in excess of the predetermined amount, causing the actual output of engine 2 to exceed the target output. In this embodiment, the gas fuel temperature is raised to a target temperature based on the target output of engine 2, thereby reducing the energy density of the gas fuel supplied from gas fuel supply unit 16. This allows control to be performed so that the actual output of engine 2 reaches the target output, even when gas fuel supply unit 16 is operated for a valve opening period exceeding the minimum valve opening period, even when the required valve opening period is less than the minimum valve opening period.

[0092] In addition, according to the present embodiment, in the engine system 1 having the above-mentioned fuel supply device 3 and the engine 2, the temperature adjustment unit 14 has: a first heat exchanger 40 as a heat exchange unit, which allows the heat exchange medium to circulate and act on the gas fuel; and a first flow adjustment unit 41, which adjusts the flow of the heat exchange medium, and also has: a control device 17 that controls the gas fuel supply unit 16 and the first flow adjustment unit 41. When the target output of the engine 2 is above a specified output threshold, the control device 17 controls the first flow adjustment unit 41 in such a manner that the circulation of the heat exchange medium is stopped.

[0093] Alternatively, in the engine system 1, the temperature adjustment unit 14 includes: a first heat exchanger 40 as a heat exchange unit, which allows a heat exchange medium to circulate and act on the gas fuel; and a cooling device 44, which cools the heat exchange medium, and further includes: a control device 17 that controls the gas fuel supply unit 16 and the cooling device 44. The control device 17 controls the cooling device 44 in a manner that causes the cooling device 44 to operate when the target output of the engine 2 is above a specified output threshold.

[0094] Thus, when the engine 2 is in a high load range, the engine system 1 can supply more gas fuel to the engine 2 by lowering the temperature of the gas fuel supplied to the gas fuel supply unit 16 , thereby achieving high output.

[0095] As another example, in order to improve the real-time performance of the temperature adjustment of the gas fuel by the temperature adjustment unit 14, a separate passage may be provided to connect the temperature adjustment unit 14 to the gas fuel supply unit 16 without passing through the chamber 15. Furthermore, in order to improve the real-time performance of the temperature of the gas fuel waiting from the chamber 15 to the gas fuel supply unit 16, the gas fuel whose temperature has been adjusted by the temperature adjustment unit 14 may be circulated.

[0096] In the above-mentioned embodiment, although the following example is used for explanation, namely, the engine system 1 (control device 17) uses the pressure regulating device 13 to adjust the supply pressure of the gas fuel in such a manner as to become a target supply pressure (or a target supply pressure range) corresponding to the target output of the engine 2, and further, the temperature of the gas fuel is controlled by the temperature regulating unit 14 in such a manner that the monitored temperature of the gas fuel supplied to the gas fuel supply unit 16 becomes a target temperature corresponding to the operating state of the engine 2 (for example, the target output) or the operating environment of the engine 2 or the fuel supply device 3, thereby adjusting the supply amount of the gas fuel, but the present invention is not limited to this example.

[0097] For example, in a modified example of the present invention, the engine system 1 (control device 17) may not control the temperature of the gas fuel, but may use the pressure regulating device 13 to adjust the supply pressure of the gas fuel in accordance with the operating state of the engine 2 and / or the operating environment of the engine 2 or the fuel supply device 3, and use the gas fuel supply unit 16 to adjust the valve opening period, thereby adjusting the supply amount of the gas fuel.

[0098] In this modification, specifically, Figure 7 As shown, when the engine 2 is normally operated, the control device 17 regulates the supply pressure of the gas fuel supplied from the fuel supply device 3 to the gas fuel supply unit 16 via the pressure regulating device 13 to a constant value regardless of the operating state and / or operating environment.

[0099] On the other hand, when operating the engine 2 in the low load range, the control device 17 adjusts the supply of gas fuel to a supply pressure appropriate to the operating state and / or operating environment via the pressure regulating device 13. In this case, the control device 17 detects the actual load applied to the engine 2 and determines that the engine is in the low load range if the actual load is below a predetermined load threshold (e.g., 20%).

[0100] The control device 17 may also predetermine and store a map or formula representing the relationship between the load on the engine 2 and the target gas fuel supply pressure (or target supply pressure range). Alternatively, the control device 17 may store a map or formula representing the relationship between the load on the engine 2 and the target gas fuel supply pressure for each operating environment (e.g., ambient temperature or humidity), thereby using the map or formula corresponding to the detected operating environment. Based on this map or formula, the control device 17 determines the target supply pressure corresponding to the detected actual load on the engine 2 and adjusts the gas fuel supply pressure to the target supply pressure via the pressure regulating device 13.

[0101] At this time, the control device 17 controls the pressure regulating device 13 to change the gas fuel supply pressure using the pressure change rate corresponding to the operating mode of the engine 2. Specifically, the control device 17 adjusts the gas fuel supply pressure to reduce the gas fuel supply pressure if the detected gas fuel supply pressure is higher than the target supply pressure corresponding to the actual load of the engine 2. Alternatively, the control device 17 adjusts the gas fuel supply pressure to increase the gas fuel supply pressure if the detected gas fuel supply pressure is lower than the target supply pressure corresponding to the actual load of the engine 2.

[0102] In downshift mode or emergency mode, the control device 17 sets a larger pressure change rate than when the engine 2 is operating in standard mode. For example, in standard mode, the pressure change rate is set to ±1 MPa / min, and in downshift mode or emergency mode, the pressure change rate is set to ±15 MPa / sec. Furthermore, since the target supply pressure is an upper or lower limit, the control device 17 does not adjust the supply pressure beyond the target supply pressure.

[0103] in addition, Figure 7 : shows a map showing the relationship between the load of the engine 2 and the target supply pressure of the gas fuel when the combustion mode of the engine 2 is the gas mode. Figure 8 : A map showing the relationship between the load of the engine 2 and the target feed pressure of the gas fuel corresponding to the co-firing ratio in the case of the co-firing mode is shown.

[0104] In the mixed combustion mode, when the mixed combustion rate is low, in order to reduce the supply amount of gas fuel, it is necessary to use the gas fuel supply unit 16 to make a small injection of gas fuel. However, due to the response speed of the gas fuel supply unit 16 for the small injection control, the supply amount of gas fuel may not be fully used. Figure 8As shown, the control device 17 may prepare in advance a map or an equation that represents the relationship between the load of the engine 2 and the target supply pressure of the gas fuel so that the load threshold value increases as the co-firing ratio decreases.

[0105] The present invention may be modified as appropriate within the scope of the gist and concept of the invention as reflected in the claims and the entire specification, and the fuel supply device and engine system accompanying such modifications are also included in the technical concept of the present invention.

[0106] [Invention Notes]

[0107] The following is a supplementary note on the outline of the invention extracted from the above embodiments. In addition, the various structures and processing functions described in the following supplementary notes can be selected and combined arbitrarily.

[0108] Note 1

[0109] A fuel supply device that supplies at least gas fuel to a specified supply object, characterized in that the fuel supply device comprises: a gas fuel adjustment unit that adjusts the supply amount of the gas fuel and supplies it to the supply object; and a temperature adjustment unit that adjusts the temperature of the gas fuel supplied to the gas fuel adjustment unit corresponding to the operating state and / or operating environment of the supply object.

[0110] Note 2

[0111] A fuel supply device that supplies at least gas fuel to a specified supply object, characterized in that the fuel supply device comprises: a gas fuel adjustment unit that adjusts the supply amount of the gas fuel to supply it to the supply object; and a supply pressure adjustment unit that adjusts the supply pressure of the gas fuel supplied to the gas fuel adjustment unit corresponding to the operating state and / or operating environment of the supply object.

[0112] Note 3

[0113] The fuel supply device according to Supplementary Note 1 is characterized in that the fuel supply device includes: a pressure regulating device that regulates the supply pressure of the gas fuel, and the temperature regulating unit is provided between the pressure regulating device and the gas fuel regulating unit in the supply direction of the gas fuel.

[0114] Note 4

[0115] The fuel supply device according to Note 3 is characterized in that the fuel supply device comprises: a gas fuel storage portion, which stores the gas fuel; and a gas fuel supply passage, which connects the gas fuel storage portion with the gas fuel adjustment portion and allows the gas fuel to circulate, and the pressure regulating device and the temperature adjustment portion are arranged in the gas fuel supply passage.

[0116] Note 5

[0117] The fuel supply device according to any one of Supplementary Notes 1 to 4, further comprising a chamber provided between the temperature adjustment unit and the gas fuel adjustment unit and storing the gas fuel having its temperature adjusted.

[0118] <Note 6>

[0119] The fuel supply device according to Note 4 or 5 is characterized in that the supply object is an engine having multiple cylinders, the gas fuel adjustment unit is a gas fuel supply valve respectively provided with the multiple cylinders, the gas fuel supply passage includes: a common passage shared by the multiple cylinders and allowing the gas fuel to circulate, and the temperature adjustment unit is arranged in the common passage.

[0120] <Note 7>

[0121] An engine system comprising the fuel supply device described in Appendix 6 and the engine, characterized in that the temperature regulating unit comprises: a heat exchange unit that allows a heat exchange medium to circulate and act on the gas fuel; and a flow regulating unit that regulates the flow of the heat exchange medium, and further comprising: a control device that controls the gas fuel regulating unit and the flow regulating unit, the control device calculating a target temperature of the gas fuel based on a target output of the engine, and controlling the flow regulating unit so that the monitored temperature reaches the target temperature when the monitored temperature of the gas fuel is lower than the target temperature, thereby raising the temperature of the gas fuel.

[0122] <Note 8>

[0123] An engine system comprising the fuel supply device described in Note 6 and the engine, characterized in that the temperature adjustment unit comprises: a heat exchange unit that allows a heat exchange medium to circulate and act on the gas fuel; and a flow adjustment unit that adjusts the flow of the heat exchange medium, and further comprising: a control device that controls the gas fuel adjustment unit and the flow adjustment unit, wherein the control device controls the flow adjustment unit in such a manner that the circulation of the heat exchange medium is stopped when the target output of the engine is above a specified output threshold.

[0124] <Note 9>

[0125] An engine system comprises the fuel supply device described in Note 6 and the engine, characterized in that the temperature adjustment unit has: a heat exchange unit, which allows a heat exchange medium to circulate and act on the gas fuel; and a cooling device, which cools the heat exchange medium, and further comprises: a control device for controlling the gas fuel adjustment unit and the cooling device, wherein the control device controls the cooling device in a manner that causes the cooling device to operate when the target output of the engine is above a specified output threshold.

Claims

1. A fuel supply device that supplies at least gaseous fuel to a predetermined supply target. It is characterized in that The fuel supply device includes: a gas fuel adjustment unit that adjusts the supply amount of the gas fuel and supplies it to the supply target; and a temperature adjustment unit that adjusts the temperature of the gas fuel supplied to the gas fuel adjustment unit according to the operating state and / or operating environment of the supply target.

2. A fuel supply device that supplies at least gaseous fuel to a predetermined supply target. It is characterized in that The fuel supply device includes: a gas fuel adjustment unit that adjusts the supply amount of the gas fuel and supplies it to the supply target; and a supply pressure adjustment unit that adjusts the supply pressure of the gas fuel supplied to the gas fuel adjustment unit according to the operating state and / or operating environment of the supply target.

3. The fuel supply device according to claim 1, characterized in that The fuel supply device includes: a pressure regulating device for regulating the supply pressure of the gas fuel; The temperature adjustment unit is provided between the pressure regulating device and the gas fuel adjustment unit in the supply direction of the gas fuel.

4. The fuel supply device according to claim 3, characterized in that The fuel supply device includes: a gas fuel storage portion that stores the gas fuel; and a gas fuel supply passage that connects the gas fuel storage portion and the gas fuel adjustment portion and allows the gas fuel to flow. The pressure regulating device and the temperature regulating unit are provided in the gas fuel supply passage.

5. The fuel supply device according to claim 1, characterized in that The fuel supply device includes a chamber provided between the temperature adjustment unit and the gas fuel adjustment unit and configured to store the gas fuel having its temperature adjusted.

6. The fuel supply device according to claim 4, characterized in that The supply object is an engine with multiple cylinders, The gas fuel regulating unit is a gas fuel supply valve provided in each of the plurality of cylinders. The gas fuel supply passage includes a common passage shared by the plurality of cylinders and through which the gas fuel flows. The temperature adjustment unit is provided in the common passage.

7. An engine system comprising the fuel supply device according to claim 6 and the engine, It is characterized in that The temperature adjustment unit includes: a heat exchange unit that allows a heat exchange medium to flow and act on the gas fuel; and a flow adjustment unit that adjusts the flow rate of the heat exchange medium. The engine system further includes a control device for controlling the gas fuel adjustment unit and the flow rate adjustment unit. The control device calculates a target temperature of the gas fuel based on a target output of the engine, When the monitored temperature of the gas fuel is lower than the target temperature, the flow rate adjustment unit is controlled to increase the temperature of the gas fuel so that the monitored temperature reaches the target temperature.

8. An engine system comprising the fuel supply device according to claim 6 and the engine, It is characterized in that The temperature adjustment unit includes: a heat exchange unit that allows a heat exchange medium to flow and act on the gas fuel; and a flow adjustment unit that adjusts the flow rate of the heat exchange medium. The engine system further includes a control device for controlling the gas fuel adjustment unit and the flow rate adjustment unit. The control device controls the flow rate adjustment unit so as to stop the flow of the heat exchange medium when the target output of the engine is equal to or greater than a predetermined output threshold.

9. An engine system comprising the fuel supply device according to claim 6 and the engine, It is characterized in that The temperature adjustment unit includes: a heat exchange unit that allows a heat exchange medium to flow and act on the gas fuel; and a cooling device that cools the heat exchange medium. The engine system further includes a control device for controlling the gas fuel adjustment unit and the cooling device. The control device controls the cooling device so as to operate when the target output of the engine is equal to or greater than a predetermined output threshold.

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