JP6134041B1 - Engine and engine control method - Google Patents

Abstract

An engine and an engine control method capable of stably operating an engine body are provided. An EGR system comprising: an engine main body; an engine control device that controls operation of the engine main body; and an EGR system that recirculates a part of the exhaust gas discharged from the engine main body to the engine main body as a recirculation gas. The engine control device controls the exhaust gas recirculation line that recirculates a part of the exhaust gas discharged from the engine body to the engine body as a recirculation gas, and the recirculation gas supplied to the engine through the exhaust gas recirculation line. And an EGR control device that transmits and receives information and a transition coefficient calculation device that outputs information on a transition coefficient that increases as time passes. The transition coefficient calculation device supplies exhaust gas from the exhaust gas recirculation line to the engine body. Start the increase of the transition coefficient and send the transition coefficient information to the EGR control device and the engine control device. . [Selection] Figure 2

Description

  The present invention relates to an engine having an EGR system for supplying an engine body and exhaust gas from the engine body to the engine body, and an engine control method.

  An exhaust gas recirculation (EGR) system is available for reducing NOx in exhaust gas discharged from the engine body. This EGR system returns a part of exhaust gas discharged from a combustion chamber of an internal combustion engine to a combustion chamber as a combustion gas (for example, Patent Document 1). Therefore, the combustion gas has a reduced oxygen concentration, and the combustion temperature is lowered by delaying the combustion speed, which is a reaction between the fuel and oxygen, and the amount of NOx generated can be reduced.

  Patent Document 2 describes a dual combustion engine that can switch between a diesel mode that operates only with oil and an operation mode that operates with oil and gas, and in which the control unit controls the fuel supply in the mode. Yes.

JP 2010-174661 A JP2015-165106A

  An engine including an engine body and an EGR system that supplies exhaust gas discharged from the engine body to the engine body is in a state in which the EGR system is operating (EGR mode) and a state in which the EGR system is stopped (normal mode) Need to drive in both. The engine has different control conditions between the normal mode and the EGR mode. For this reason, when the engine is switched from the normal mode to the EGR mode, the operation of the engine body may become unstable.

  The present invention solves the above-described problems, and an object thereof is to provide an engine and an engine control method capable of stably operating an engine body.

  The present invention for achieving the above object is an engine, comprising an engine body, an engine control device for controlling the operation of the engine body, and a part of exhaust gas discharged from the engine body as a recirculation gas. An EGR system that recirculates to the engine body, wherein the EGR system controls an exhaust gas recirculation line and a flow rate of the recirculation gas supplied to the engine body via the exhaust gas recirculation line And a transition coefficient calculation device that outputs information of a transition coefficient that increases with time, and the transition coefficient calculation device starts supplying the recirculation gas from the exhaust gas recirculation line to the engine body. If so, start to increase the transition coefficient and send the transition coefficient information to the EGR control device and the engine control device And wherein the Rukoto.

  Another aspect of the present invention for achieving the above object is an engine control method for controlling an operation of an engine body, and recirculating a part of exhaust gas discharged from the engine body. And an EGR control step of adjusting the flow rate of the recirculation gas and supplying the recirculated gas to the engine body in the EGR mode. A transition coefficient calculating step for outputting information, and when starting the EGR mode, an increase in the transition coefficient output by the transition coefficient calculating step is started, and based on the transition coefficient, the operation of the engine body and The flow rate of the recirculation gas is controlled.

  The engine outputs a transition coefficient that increases according to the time calculated by the transition coefficient calculation device to the engine control device and the EGR control device, thereby executing control linked with the engine control device and the EGR control device at the time of EGR activation. be able to. Thereby, the supply of the recirculation gas from the EGR system can be executed in accordance with the fluctuation of the control condition of the engine body, and the engine body can be operated stably.

  It is preferable that the transition coefficient calculating device increases the transition coefficient at a constant speed during a set time and sets a constant value after a predetermined time has elapsed. Thus, by setting the transition coefficient to a value that increases at a constant speed, it is possible to stably change the operating conditions when starting to supply the recirculated gas to the engine body.

  The engine control device can switch between an EGR mode in which the EGR system is operating and a normal mode in which the EGR system is stopped. When switching from the normal mode to the EGR mode, the engine control device Preferably, the control is executed with a control value in which the ratio of the EGR mode is increased based on the ratio and the ratio of the normal mode is decreased based on the transition coefficient. As a result, the operating conditions of the engine body can be gradually changed, and the conditions can be changed in accordance with an increase in the recirculation gas supplied from the EGR system. As described above, it is possible to prevent the operation of the engine body from becoming unstable.

  The EGR control device calculates a control value based on an operating condition of the engine body, and a control value obtained by reducing the calculated control value based on a ratio of the acquired transition coefficient to the maximum value of the transition coefficient It is preferable to execute the control. Thereby, the operating condition of the EGR system can be gradually changed based on the transition coefficient, and the condition can be changed in conjunction with the operating condition of the engine body. As mentioned above, it can suppress that the quantity of the recirculation gas supplied to an engine main body from an EGR system increases rapidly, and can suppress that the driving | operation of an engine main body becomes unstable.

  The EGR control device preferably increases the frequency of an EGR blower provided in the exhaust gas recirculation line based on the transition coefficient. Thereby, it can suppress that the increase amount of the amount of recirculation gas supplied to an engine main body increases rapidly, and can suppress that the driving | operation of an engine main body becomes unstable.

  The EGR control device stores a relationship of a target oxygen concentration of combustion gas supplied to the engine main body corresponding to a load of the engine main body, and the exhaust gas recirculation line based on the target oxygen concentration and the transfer coefficient It is preferable to control the EGR blower provided in the. Thereby, the target oxygen concentration can be gradually changed. By gradually changing the oxygen concentration, it is possible to suppress an increase in the amount of the recirculation gas supplied to the engine body from increasing rapidly, and to suppress the operation of the engine body from becoming unstable.

  It is preferable that the transition coefficient calculation device starts decreasing the transition coefficient when stopping the supply of the recirculation gas from the exhaust gas recirculation line to the engine body. The engine outputs a transition coefficient that decreases according to the time calculated by the transition coefficient calculation device to the engine control device and the EGR control device, thereby executing control linked with the engine control device and the EGR control device when the EGR is stopped. be able to. Thereby, the supply of the recirculation gas from the EGR system can be executed in accordance with the fluctuation of the control condition of the engine body, and the engine body can be operated stably.

  In addition, the engine control device can switch between an EGR mode in which the EGR system is operating and a normal mode in which the EGR system is stopped. When switching from the EGR mode to the normal mode, the transition is performed. It is preferable that the control is executed with a control value that decreases the ratio of the EGR mode based on a coefficient and increases the ratio of the normal mode based on the transition coefficient. As a result, the operating conditions of the engine body can be gradually changed, and the conditions can be changed in accordance with a decrease in the recirculation gas supplied from the EGR system. As described above, it is possible to prevent the operation of the engine body from becoming unstable.

  Another aspect of the present invention for achieving the above object is an engine comprising an engine body, an engine control device for controlling the operation of the engine body, and a part of exhaust gas discharged from the engine body. An EGR system that recirculates to the engine body as a recirculation gas, and the EGR system supplies an exhaust gas recirculation line and a flow rate of the recirculation gas supplied to the engine body via the exhaust gas recirculation line. An EGR control device for controlling, and a transition coefficient calculation device that outputs information of a transition coefficient that decreases with time, the transition coefficient calculation device from the exhaust gas recirculation line to the engine body to the recirculation gas When the supply of the engine is stopped, the decrease of the transition coefficient is started, and the transition coefficient information is obtained from the EGR controller and the engine control. And transmits to the location.

  The engine outputs a transition coefficient that decreases according to the time calculated by the transition coefficient calculation device to the engine control device and the EGR control device, thereby executing control linked with the engine control device and the EGR control device when the EGR is stopped. be able to. Thereby, the supply of the recirculation gas from the EGR system can be executed in accordance with the fluctuation of the control condition of the engine body, and the engine body can be operated stably.

  According to the present invention, the transition coefficient that increases in accordance with the time calculated by the transition coefficient calculation device is output to the engine control device and the EGR control device, so that the engine control device and the EGR control device interlock with each other at the time of EGR activation. Can be executed. Thereby, the supply of the exhaust gas from the EGR system can be executed in accordance with the fluctuation of the control condition of the engine body, and the engine body can be operated stably.

FIG. 1 is a schematic diagram showing a diesel engine equipped with the EGR system of the present embodiment. FIG. 2 is a schematic configuration diagram showing each part of the diesel engine of the present embodiment. FIG. 3 is a block diagram showing a schematic configuration of each control device of the engine. FIG. 4 is a graph showing the transition coefficient. FIG. 5 is a graph showing the transition coefficient. FIG. 6 is a flowchart illustrating an example of control of the transition coefficient calculation apparatus. FIG. 7 is a flowchart showing an example of control of the engine control apparatus. FIG. 8 is an explanatory diagram for explaining control parameters calculated by the engine control apparatus. FIG. 9 is an explanatory diagram for explaining control parameters calculated by the EGR control device. FIG. 10 is a time chart showing the relationship between the transition coefficient and the operation of each unit. FIG. 11 is a flowchart illustrating an example of control of the transition coefficient calculation apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

  FIG. 1 is a schematic diagram showing a diesel engine equipped with an EGR system, and FIG. 2 is a schematic configuration diagram showing each part of the diesel engine. FIG. 3 is a block diagram showing a schematic configuration of each control device of the engine.

  As shown in FIG. 1, the marine diesel engine 10 of the present embodiment includes an engine body (engine) 11, a supercharger 12, and an EGR system 13.

  As shown in FIG. 2, the engine body 11 is a propulsion engine (main engine) that drives and rotates the propeller for propulsion via a propeller shaft, although not shown. This engine body 11 is a uniflow scavenging exhaust type diesel engine, which is a two-stroke diesel engine, in which the flow of intake and exhaust in the cylinder is unidirectional from the bottom to the top so as to eliminate the residual exhaust. It is. The engine body 11 includes a plurality of cylinders (combustion chambers) 21 in which pistons move up and down, a scavenging trunk 22 that communicates with each cylinder 21, and an exhaust manifold 23 that communicates with each cylinder 21. A scavenging port 24 is provided between each cylinder 21 and the scavenging trunk 22, and an exhaust passage 25 is provided between each cylinder 21 and the exhaust manifold 23. In the engine body 11, the air supply line G <b> 1 is connected to the scavenging trunk 22, and the exhaust line G <b> 2 is connected to the exhaust manifold 23.

  The engine body 11 is provided with a rotation speed detection unit 62 and a fuel input amount detection unit 64. The rotation speed detection unit 62 detects the rotation speed of the engine body 11 (the rotation speed of the rotation shaft connected to the propeller shaft). The rotation speed detection unit 62 may detect the rotation speed of the rotation shaft inserted into the engine body 11 or may detect the rotation speed of the propeller shaft. The fuel input amount detection unit 64 detects the fuel input amount of the engine body 11.

  The engine control device 26 controls the operation of the engine body 11. As shown in FIG. 3, the engine control device 26 includes an operation control unit 80, a normal mode table 82, an EGR mode table 84, and a parameter setting unit 86. The operation control unit 80 controls the operation of the engine body 11 based on the parameters (operating conditions) set by the parameter setting unit 86. The engine control device 26 controls the fuel injection amount and the rotation speed of the engine body 11 by controlling the fuel injection timing and the injection amount into the cylinder 21. The engine control device 26 controls the output of the engine body 11 by controlling the fuel input amount and the rotation speed. The normal mode table 82 stores parameters set for the state where the EGR system 13 is stopped (normal mode). The EGR mode table 84 stores parameters set for the state in which the EGR system 13 is operating (EGR mode). Here, the parameters are set corresponding to the control values of the respective units and the values detected by the sensors. The control value of each part and the value detected by the sensor include the load (output, calculated horsepower) of the engine body 11. The parameters are set as fuel injection timing and injection amount to the cylinder 21 and opening / closing timings of various valves of the engine body 11. The normal mode parameter and the EGR mode parameter may partially have the same value. The parameter setting unit 86 includes a transition coefficient calculated by a later-described transition coefficient calculation device 61, various input conditions such as a required load, and results detected by various sensors such as a rotation speed detection unit 62 and a fuel input amount detection unit 64. Based on the above, various parameters are set. The parameter setting unit 86 sends the set parameters to the operation control unit 80.

  The supercharger 12 is configured by connecting a compressor 31 and a turbine 32 so as to rotate integrally with a rotary shaft 33. In the supercharger 12, the turbine 32 is rotated by the exhaust gas discharged from the exhaust line G2 of the engine body 11, the rotation of the turbine 32 is transmitted by the rotary shaft 33, and the compressor 31 is rotated. / Or the recirculated gas is compressed and supplied to the engine body 11 from the supply air line G1. The compressor 31 is connected to a suction line G6 that sucks air from the outside (atmosphere).

  The supercharger 12 is connected to an exhaust line G3 that discharges exhaust gas that has rotated the turbine 32. The exhaust line G3 is connected to a chimney (funnel) (not shown). An EGR system 13 is provided between the exhaust line G3 and the air supply line G1.

  The EGR system 13 includes exhaust gas recirculation lines G4, G5, and G7, a scrubber 42, a demister unit 14, an EGR blower (blower) 47, and an EGR control device 60. The EGR system 13 mixes recirculation gas, which is a part of exhaust gas discharged from the marine diesel engine 10, with air, and then compresses it by the supercharger 12 to recirculate it as a combustion gas to the marine diesel engine 10. This suppresses the generation of NOx due to combustion. Here, a part of the exhaust gas is extracted from the downstream side of the turbine 32, but a part of the exhaust gas may be extracted from the upstream side of the turbine 32.

  In the following description, the exhaust gas is exhausted from the engine body 11 to the exhaust line G2, and then exhausted to the outside from the exhaust line G3. The recirculated gas is separated from the exhaust line G3. A part of the exhaust gas is returned to the engine body 11 by the exhaust gas recirculation lines G4, G5, and G7.

  One end of the exhaust gas recirculation line G4 is connected to the middle part of the exhaust line G3. The exhaust gas recirculation line G4 is provided with an EGR inlet valve (open / close valve) 41A, and the other end is connected to the scrubber 42. The EGR inlet valve 41A opens and closes the exhaust gas recirculation line G4 to turn ON / OFF the inflow of exhaust gas that is diverted from the exhaust line G3 to the exhaust gas recirculation line G4. The flow rate of exhaust gas passing through the exhaust gas recirculation line G4 may be adjusted by using the EGR inlet valve 41A as a flow rate adjustment valve.

  The scrubber 42 is a venturi-type scrubber, and includes a throat portion 43 having a hollow shape, a venturi portion 44 into which recirculated gas is introduced, and an enlarged portion 45 that gradually returns to the original flow velocity. The scrubber 42 includes a water injection unit 46 that injects water to the recirculated gas introduced into the venturi unit 44. The scrubber 42 is connected to an exhaust gas recirculation line G5 that discharges recirculation gas from which harmful substances such as particulate matter (PM) such as SOx and dust are removed and waste water containing harmful substances. In addition, in this embodiment, although the venturi type is employ | adopted as a scrubber, it is not limited to this structure.

  The exhaust gas recirculation line G5 is provided with a demister unit 14 and an EGR blower 47.

  The demister unit 14 separates the recirculated gas from which harmful substances have been removed by water injection and mist (drainage). The demister unit 14 is provided with a drainage circulation line W <b> 1 that circulates drainage to the water injection unit 46 of the scrubber 42. The drainage circulation line W1 is provided with a hold tank 49 and a pump 50 for temporarily storing drainage.

  The EGR blower 47 guides the recirculation gas in the scrubber 42 from the exhaust gas recirculation line G5 to the demister unit 14. The EGR blower 47 sends the exhaust gas that has passed through the demister unit 47 to the compressor 31.

  The exhaust gas recirculation line G7 has one end connected to the EGR blower 47 and the other end connected to the compressor 31 via a mixer (not shown). The EGR blower 47 sends recirculation gas to the compressor 31. It is done. The exhaust gas recirculation line G7 is provided with an EGR outlet valve (open / close valve or flow rate adjusting valve) 41B. The air from the suction line G6 and the recirculation gas from the exhaust gas recirculation line G7 are mixed in a mixer to generate combustion gas. This mixer may be provided separately from the silencer, or the silencer may be configured to add a function of mixing the recirculated gas and air without providing a separate mixer. The supercharger 12 can supply the combustion gas compressed by the compressor 31 from the supply line G1 to the engine main body 11, and an air cooler (cooler) 48 is provided in the supply line G1. The air cooler 48 cools the combustion gas by exchanging heat between the combustion gas compressed by the compressor 31 and having a high temperature and the cooling water. In the EGR system 13, an oxygen concentration detection unit 66 is disposed in the supply line G1. The oxygen concentration detection unit 66 of this embodiment is disposed closer to the engine body 11 than the air cooler 48. The oxygen concentration detector 66 detects the oxygen concentration of the air supplied to the engine body 11, that is, the oxygen concentration of the combustion gas in which the recirculation gas and the air are mixed when the EGR system 13 is operating.

  The EGR control device 60 controls the operation of each part of the EGR system 13. Hereinafter, the EGR control device 60 will be described with reference to FIG. FIG. 3 is a block diagram showing a schematic configuration of the EGR control device.

  The EGR control device 60 includes a rotation speed acquisition unit 72, a fuel input amount acquisition unit 74, an oxygen concentration acquisition unit 76, and an EGR control unit 78. The rotational speed acquisition unit 72 acquires information on the rotational speed of the engine body 11 from the rotational speed detection unit 62. The fuel input amount acquisition unit 74 acquires information on the fuel input amount of the engine body 11 from the fuel input amount detection unit 64. The oxygen concentration acquisition unit 76 acquires information on the oxygen concentration of the combustion gas supplied from the oxygen concentration detection unit 66 to the engine body 11. The rotation speed acquisition unit 72, the fuel input amount acquisition unit 74, and the oxygen concentration acquisition unit 76 send the acquired information to the EGR control unit 78.

  The EGR control unit 78 is supplied to the engine main body 11 with the engine speed of the engine body 11 and the fuel input amount acquired by the engine speed acquisition unit 72, the fuel input amount acquisition unit 74, and the oxygen concentration acquisition unit 76. The amount of recirculated gas supplied from the EGR system 13 to the engine body 11 by controlling the operating state of the EGR blower 47, specifically, the frequency of the motor that rotates the compressor 31, based on the oxygen concentration of the combustion gas. To control.

  The EGR control unit 78 includes an operation control unit 90 and a parameter setting unit 92.

  The operation control unit 90 controls the operation of the EGR system 13 based on the parameters set by the parameter setting unit 92. For example, the operation control unit 90 stores the relationship between the load of the engine body 11 and the target value of oxygen concentration, and calculates the target value of oxygen concentration (target oxygen concentration) according to the load. The operation control unit 90 calculates the load (output) of the engine body 11 based on the rotation speed of the engine body 11 and the fuel input amount. The operation control unit 90 calculates the target oxygen concentration based on the relationship between the load of the engine body 11 and the target oxygen concentration, the relationship between the calculated target oxygen concentration and the acquired oxygen concentration, and the current frequency of the EGR blower 47. Based on the above, the frequency (operating frequency) of the EGR blower 47 is calculated. The operation control unit 90 rotates the EGR blower 47 at the calculated frequency of the EGR blower 47. When the calculated frequency of the EGR blower 47 exceeds the set limit value, the operation control unit 90 rotates the EGR blower 47 at the limit value frequency. The limit value may be a value that fluctuates based on at least one of the load (output) of the engine body 11, the rotational speed of the engine body 11, and the fuel input amount of the engine body 11, or may be a constant value. . Although the operation control unit 90 of this embodiment controls the frequency of the motor of the EGR blower 47, the operation control unit 90 may control the number of rotations of the compressor 31 by controlling the number of rotations of the motor. In the above embodiment, the case where the operation control unit 90 of the EGR control unit 78 controls the EGR blower 47 has been described. However, each part other than the EGR blower 47, for example, opening and closing of the EGR inlet valve 41A and the EGR outlet valve 41B, The operation of the scrubber 42 and the operation of the air cooler 48 are also controlled.

  The parameter setting unit 92 includes an engine operating state such as the rotational speed of the engine body 11 and the amount of fuel input, the oxygen concentration of the combustion gas supplied to the engine body 11, control values, and a transition coefficient calculation device 61 described later. Based on the calculated transition coefficient, control parameters for each part of the EGR system 13 are set. For example, the parameter setting unit 92 calculates a control parameter based on the engine operating state and the control value. When the transition coefficient is set, the parameter setting unit 92 calculates the engine operating state and the control calculated based on the control value. The control parameter calculated by multiplying the parameter by the transition coefficient is used as a control parameter, and is output to the operation control unit 90.

  Hereinafter, the operation of the EGR system of this embodiment will be described.

  As shown in FIG. 2, when combustion gas is supplied from the scavenging trunk 22 into the cylinder 21, the engine main body 11 compresses the combustion gas by a piston, and fuel is supplied to the high-temperature combustion gas. By firing, it ignites spontaneously and burns. The generated combustion gas is discharged as exhaust gas from the exhaust manifold 23 to the exhaust line G2. The exhaust gas discharged from the engine body 11 rotates the turbine 32 in the supercharger 12 and then is discharged to the exhaust line G3. When the EGR inlet valve 41A and the EGR outlet valve 41B are closed, the entire amount is exhausted. It is discharged from G3 to the outside.

  On the other hand, when the EGR inlet valve 41A and the EGR outlet valve 41B are open, part of the exhaust gas flows from the exhaust line G3 to the exhaust gas recirculation line G4 as recirculation gas. The scrubber 42 removes harmful substances from the recirculated gas that has flowed into the exhaust gas recirculation line G4. That is, the scrubber 42 injects water from the water injection unit 46 when exhaust gas passes through the venturi unit 44 at a high speed, thereby cooling the recirculated gas with this water and removing harmful substances by dropping with water. To do. Then, the waste water containing the harmful substance flows into the demister unit 14 together with the EGR gas.

  The recirculated gas from which harmful substances have been removed by the scrubber 42 is discharged to the exhaust gas recirculation line G5. After the mist (drainage) is separated by the demister unit 14, it is sent to the supercharger 12 by the exhaust gas recirculation line G7. . The recirculated gas is mixed with the air sucked from the suction line G6 to become a combustion gas, compressed by the compressor 31 of the supercharger 12, and then cooled by the air cooler 48, from the air supply line G1 to the engine. It is supplied to the main body 11.

  The marine diesel engine 10 further includes a transition coefficient calculation device 61. Here, in FIG. 2, the transition coefficient calculation device 61 is separated from the engine control device 26 and the EGR control device 60, but the transition coefficient calculation device 61 may be integrated with the engine control device 26 or the EGR control device 60. That is, the transition coefficient calculation device 61 may be included in the engine control device 26 or the EGR control device 60 as one function with the engine control device 26 or the EGR control device 60. As shown in FIG. 3, the transition coefficient calculation device 61 includes a time measuring unit 102, a condition table 104, and a coefficient calculation unit 106. The time measuring unit 102 is a device that measures time. The condition table 104 stores the relationship between the transition coefficient and time. 4 and 5 are graphs showing the transfer coefficient, respectively. The relationship shown in FIG. 4 stores information on a transition coefficient whose value increases in proportion to time. The relationship shown in FIG. 5 stores information on a transition coefficient whose value decreases in proportion to time. The transition coefficient according to the present embodiment has a maximum value of 1, a constant amount per unit time, that is, increases from 0 to 1 at a constant speed, and does not change after reaching 1. The transition coefficient increases from 0 to 1 at the set time. The set time is preferably several minutes, for example, 1 minute to 10 minutes. The coefficient calculation unit 106 calculates a transition coefficient at the time of calculation based on the relationship stored in the condition table 104 and the time calculated by the time measuring unit 102. The coefficient calculation unit 106 switches the relationship stored in the applied condition table 104 depending on whether the normal mode is switched to the EGR mode or the EGR mode is switched to the normal mode. Specifically, the coefficient calculator 106 uses the relationship shown in FIG. 4 when switching from the normal mode to the EGR mode. The coefficient calculation unit 106 uses the relationship shown in FIG. 5 when switching from the EGR mode to the normal mode. Note that the rate of change (slope) of the relationship in FIG. 4 and the relationship in FIG. 5 may be the same or different.

  Next, the transition coefficient calculation operation by the transition coefficient detection apparatus will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of control of the transition coefficient calculation apparatus. FIG. 6 shows a process when the EGR system 13 is started, that is, when the EGR system 13 is activated.

  When the transition coefficient calculation device 61 receives a signal for starting the operation of the EGR system (step S12), the transition coefficient calculation apparatus 61 starts measuring time by the time measuring unit 102, and calculates the transition coefficient based on the start time and the current time. (Step S14: Transition coefficient calculation step). That is, the current transition coefficient is calculated based on the relationship shown in FIG. After calculating the transfer coefficient, the transfer coefficient calculating device 61 outputs the calculated transfer coefficient (step S16). Specifically, the transition coefficient calculation device 61 outputs information on the calculated transition coefficient to the parameter setting units 86 and 92. After calculating the transfer coefficient, the transfer coefficient calculating device 61 determines whether the calculated transfer coefficient has reached 1 (step S18).

  If the transition coefficient calculation device 61 determines that the transition coefficient has not reached 1 (No in step S18), that is, the transition coefficient is less than 1, the process returns to step S14. The transition coefficient calculation device 61 repeats calculation and output of the transition coefficient until the transition coefficient reaches 1. If the transfer coefficient calculation device 61 determines that the transfer coefficient has reached 1 (Yes in step S18), it fixes the output of the transfer coefficient (step S20). That is, the transition coefficient calculation device 61 continues to output 1 as the transition coefficient based on the relationship of FIG.

  Next, an example of control (engine control method) by the engine control device 26 will be described with reference to FIG. FIG. 7 is a flowchart showing an example of control of the engine control apparatus. The process shown in FIG. 7 can be realized by executing an engine body control process in which the engine control device 26 controls the operation of each unit.

  The engine control unit 26 receives an EGR system operation start signal (step S32), that is, switches from the normal mode to the EGR mode, and controls the flow rate of the recirculated gas supplied to the engine body 11. Is executed, the transition coefficient is acquired (step S34). That is, the engine control device 26 acquires the current transition coefficient calculated and output by the transition coefficient calculation device 61 (transition coefficient calculation step S14). When the engine control device 26 acquires the transition coefficient, the engine control device 26 sets parameters based on the transition coefficient. (Step S36). Specifically, the engine control device 26 calculates a parameter in the normal mode (normal parameter) and a parameter in the EGR mode (EGR parameter) from various conditions. Next, the engine control device 26 calculates a parameter used for control by proportionally distributing the normal parameter and the EGR parameter using the transition coefficient. As an example, it is calculated by the parameter used for control = normal parameter × (1−transition coefficient) + EGR parameter × (transition coefficient). The engine control device 26 performs the same processing on various parameters, and calculates a parameter to be controlled based on the normal parameter, the EGR parameter, and the transition coefficient. The engine control device 26 controls the operation of each unit using the calculated parameters.

  After calculating the transition coefficient, the engine control device 26 determines whether the calculated transition coefficient has reached 1 (step S38). If the engine control device 26 determines that the transition coefficient has not reached 1 (No in step S38), that is, the transition coefficient is less than 1, the process returns to step S34. The engine control device 26 repeats calculation and output of the transition coefficient until the transition coefficient reaches 1. If it is determined that the transition coefficient has reached 1 (Yes in Step S38), the engine control device 26 operates in the EGR mode (Step S40).

  FIG. 8 is an explanatory diagram for explaining control parameters calculated by the engine control apparatus. FIG. 8 shows the relationship between the engine load of one of the parameters controlled by the engine control device 26 and the parameter value. As shown in FIG. 8, the engine control device 26 stores the relationship in the normal mode and the relationship in the EGR mode for one parameter. The engine control device 26 calculates a parameter value to which a value between the value of the normal mode and the value of the EGR mode is applied based on the transition coefficient. Since the value of the transition coefficient of the engine control device 26 gradually increases, the parameter value to be applied becomes closer to the value of the EGR mode as the time from the start of the start of the EGR system 13 becomes longer. Further, the parameters shown in FIG. 8 show the case where the parameter value changes in proportion to the engine load. However, the relationship between the engine load and the parameter is not limited to the proportional relationship, and may be various relationships. it can. Further, examples of the parameters include the rotation speed of the engine body 11, the fuel injection amount, the fuel injection timing, and the like. In addition, as a parameter, a control value of an actual control target such as opening / closing timing of various valves can be used.

  7 and 8, the operation of the engine control device 26 has been described. The EGR control device 60 similarly calculates a parameter value to be applied based on the transition coefficient. FIG. 9 is an explanatory diagram for explaining control parameters calculated by the EGR control device. The EGR control device 60 stores parameters corresponding to operating conditions for one parameter. Here, since the EGR control device 60 controls the operation of the EGR system 13, unlike the engine control device 26, parameters of the normal mode and the EGR mode are not stored. The relationship in the EGR mode is stored. The EGR control device 60 calculates a parameter value to which a value between 0 and the stored parameter value is applied based on the transition coefficient. Here, for the sake of explanation, in FIG. 9, the case where the parameter value is 0 is set as the normal mode, and the relationship between the stored parameter and the engine load is shown as the EGR mode. In the state where the EGR system 13 is not activated, that is, the state where the engine control device 26 is operating in the normal mode, the EGR control device 60 is not operated, so that the normal mode parameter is always set to 0. Perform the process. Specifically, the EGR control device 60 calculates the parameter used for the control = (parameter calculated based on the operating condition of the engine body 11, parameter value of the EGR mode shown in FIG. 9) × (transition coefficient). Good. The parameters based on the operating conditions of the engine main body 11 are parameters calculated under conditions other than the transition coefficient, and the marine diesel engine 10 is operated under the target conditions while the EGR system 13 is operated stably. A value that can be done. In addition, when the normal mode parameter is set to a value other than 0, the EGR control device 60 (parameter calculated based on the operating condition of the engine body 11) × (transition coefficient) + (normal mode parameter) You may calculate by x (1-transition coefficient). Examples of parameters controlled by the EGR control device 60 include target oxygen concentration, EGR inlet valve 41A and EGR outlet valve 41B opening / closing timing, scrubber 42 operating conditions, and EGR blower 47 operating conditions.

  The marine diesel engine 10 is controlled by the engine control device 26 and the EGR control device 60 based on the transition coefficient calculated by the transition coefficient calculation device 61, so that the marine diesel engine 10 is switched from the normal mode to the EGR mode. The operating conditions of each part can be controlled at a limited rate.

  FIG. 10 is a time chart showing the relationship between the transition coefficient and the operation of each unit. FIG. 10 shows the relationship between the transition coefficient when switching from the normal mode to the EGR mode, the frequency of the EGR blower 47, the opening degree of the EGR inlet valve 41A, the closing timing of the exhaust valve of the engine body 11, and the opening and closing timing of the EGR outlet valve 41B. Indicates. Here, the frequency of the EGR blower 47 and the opening / closing timing of the opening EGR outlet valve 41B of the EGR inlet valve 41A are controlled by the EGR control device 60, and the closing timing of the exhaust valve of the engine body 11 is controlled by the engine control device 26. To do.

  As shown in FIG. 10, the marine diesel engine 10 starts switching to the EGR mode at time t1 from the state in which it is operating in the normal mode, and completes switching to the EGR mode at time t2. In the transition period between time t1 and time t2, the transition coefficient increases from 0 (0%) to 1 (100%). The marine diesel engine 10 adjusts the operating conditions of the frequency of the EGR blower 47, the opening degree of the EGR inlet valve 41A, and the closing timing of the exhaust valve of the engine body 11 based on the transition coefficient as described above. The operating conditions change in proportion to the transition coefficient during the transition period from to t2. Here, the control value of the frequency of the EGR blower 47 and the opening of the EGR inlet valve 41A increase as the transition coefficient increases. As for the closing timing of the exhaust valve of the engine body 11, the control value decreases as the transition coefficient increases.

  The opening / closing timing of the EGR outlet valve 41B is also controlled based on the transition coefficient, but it is only switching between opening and closing. If the transition coefficient is greater than 0, the condition is that it is open, so it switches from closing to opening at time t1. Instead, the open state is maintained thereafter. It should be noted that the control target only for switching between opening and closing and switching only between ON and OFF like the opening and closing timing of the EGR outlet valve 41B may be controlled without using the transition coefficient.

  In this way, the marine diesel engine 10 outputs a transition coefficient that increases according to the time calculated by the transition coefficient calculation device 61 to the engine control device 26 and the EGR control device 60 at the start of operation of the EGR system 13. Control that is interlocked between the engine control device 26 and the EGR control device 60 can be executed when the system 13 is activated. Thereby, the supply of the recirculation gas from the EGR system 13, which is a part of the combustion gas, can be executed in accordance with the fluctuation of the control condition of the engine body 11, and the engine body 11 can be operated stably. Can do. More specifically, the marine diesel engine 10 uses the transition coefficient to control various conditions at the start of operation of the EGR system 13, so that various control conditions change abruptly and engine performance changes. Can be suppressed.

  The marine diesel engine 10 controls the frequency of the EGR blower 47, the opening degree of the EGR inlet valve 41A, and the closing timing of the exhaust valve of the engine body 11 based on the transition coefficient calculated by the transition coefficient calculating device 61. The operating conditions of the diesel engine 10 can be changed stably, and the operation of the marine diesel engine 10 can be prevented from becoming unstable when the transition from the normal mode to the EGR mode, and the load can be prevented from being concentrated on some equipment. .

  The marine diesel engine 10 is not limited to the parameters for controlling the operation based on the transition coefficient as described above. For example, the closing timing of the exhaust valve of the engine body 11, the timing of fuel injection, the operating oil pressure, the fuel injection pattern, etc. can be gradually shifted from the normal mode setting to the EGR mode setting based on the transition coefficient. .

  The marine diesel engine 10 preferably controls at least the frequency of the EGR blower 47 and various control parameters of the engine control device 26 based on the transition coefficient. The engine control device 26 stores parameters for achieving an optimal combustion state in each of the normal mode and the EGR mode. Further, the EGR blower 47 has an appropriate frequency of the EGR blower 47 (that is, the supply amount of the recirculated gas) for the operation of the parameters set by the engine control device 26. The marine diesel engine 10 controls at least the frequency of the EGR blower 47 and various control parameters of the engine control device 26 based on the transition coefficient, thereby changing the frequency of the EGR blower 47 (change in the amount of recirculated gas supplied). At the same time, various control parameters of the engine body 11 can be changed, and the normal mode can be switched to the EGR mode or the EGR mode to the normal mode while maintaining the combustion state of the engine body 11. Thereby, generation | occurrence | production of the trouble by combustion, such as abnormal combustion and misfire, can be prevented more reliably.

  The marine diesel engine 10 preferably controls at least the frequency of the EGR blower 47, various control parameters of the engine control device 26, and the control of the EGR inlet valve 41A of the EGR system 13 based on the transition coefficient. When the EGR inlet valve 41A is operated from closed to open without using the transfer coefficient, exhaust gas (recirculation gas) flows into the exhaust gas recirculation line G4 from the EGR inlet valve 41A, and the EGR blower 47 is driven by the force of the recirculation gas. May cause control failure of the EGR blower 47. On the other hand, at least the frequency of the EGR blower 47, various control parameters of the engine control device 26, and the control of the EGR inlet valve 41A of the EGR system 13 are controlled based on the transition coefficient, and the EGR inlet is used using the transition coefficient. By operating the valve 41A from closed to open, it is possible to suppress exhaust gas (recirculation gas) from flowing into the exhaust gas recirculation line G4 from the EGR inlet valve 41A at an unintended timing, resulting in poor control of the EGR blower 47. Can be prevented.

  It is preferable that the transition coefficient calculating device 61 increases the transition coefficient at a constant speed during a set time and sets a constant value after the predetermined time has elapsed. In this way, by changing the transition coefficient to a value that increases at a constant speed, fluctuations in operating conditions when starting to supply the recirculation gas, which is part of the combustion gas, to the engine body 11 are stably performed. Can do. Thereby, the EGR control device 60 can be operated in a state where the EGR system 13 is in operation, that is, in an EGR mode condition, after the set time has elapsed. Thereby, the oxygen concentration of the combustion gas supplied to the engine body 11 can be set to an appropriate concentration, and the generation of nitrogen oxides can be suppressed. Also, by controlling the frequency of the EGR blower 47 based on the target oxygen concentration in the EGR mode after the set time has elapsed, the difference between the current oxygen concentration and the target oxygen concentration can be reduced. It can suppress that the quantity of the recirculation gas to supply becomes excess.

  The engine control unit 26 can switch between the EGR mode and the normal mode. When switching from the normal mode to the EGR mode, the engine control device 26 increases the ratio of the EGR mode based on the transition coefficient, and the normal mode based on the transition coefficient. The control is executed with the control value in which the ratio is reduced. Thereby, the operating conditions of the engine body 11 can be gradually changed, and the conditions can be changed in accordance with an increase in the recirculation gas supplied from the EGR system 13 which is a part of the combustion gas. it can. As described above, it is possible to suppress the operation of the engine body 11 from becoming unstable.

  Next, the transition coefficient calculation operation by the transition coefficient detection apparatus will be described with reference to FIG. FIG. 11 is a flowchart illustrating an example of control of the transition coefficient calculation apparatus. In FIG. 11, the process is performed when the EGR system 13 is stopped, that is, when the EGR system 13 is switched from the operating state to the stopped state.

  When the transition coefficient calculation device 61 receives a stop signal of the EGR system 13 (step S52), the transition coefficient calculation device 61 starts measuring time by the time measuring unit 102, and calculates the transition coefficient based on the start time and the current time. (Step S54). That is, the current transition coefficient is calculated based on the relationship shown in FIG. In this case, the transition coefficient decreases with time. After calculating the transfer coefficient, the transfer coefficient calculating device 61 outputs the calculated transfer coefficient (step S56). Specifically, the transition coefficient calculation device 61 outputs information on the calculated transition coefficient to the parameter setting units 86 and 92. After calculating the transfer coefficient, the transfer coefficient calculating device 61 determines whether the calculated transfer coefficient has reached 0 (step S58).

  If the transition coefficient has not reached 0 (No in step S58), that is, if it is determined that the transition coefficient is greater than 0, the transition coefficient calculation device 61 returns to step S54. The transition coefficient calculation device 61 repeats calculation and output of the transition coefficient until the transition coefficient reaches zero. If the transition coefficient calculation device 61 determines that the transition coefficient has reached 0 (Yes in step S58), the transition coefficient calculation device 61 fixes the output of the transition coefficient (step S60). That is, the transition coefficient calculation device 61 continues to output 0 as the transition coefficient based on the relationship of FIG.

  When the EGR system 13 is stopped, that is, when the EGR system 13 is switched from the operating state to the stopping state, the engine control device 26 and the EGR control device 60 are based on the transition coefficient calculated in FIG. The same processing as that shown in FIG. 6 is executed, and when the transition coefficient becomes 0, the operation is performed in the normal mode.

  As described above, the marine diesel engine 10 outputs the transition coefficient that decreases according to the time calculated by the transition coefficient calculation device 61 to the engine control device 26 and the EGR control device 60 when the EGR system 13 is stopped. When the engine 13 is stopped, the engine controller 26 and the EGR controller 60 can perform linked control. Thereby, the supply of the recirculation gas from the EGR system 13 can be executed in accordance with the fluctuation of the control conditions of the engine body 11, and the engine body 11 can be operated stably. More specifically, the marine diesel engine 10 can suppress various control conditions from changing suddenly by controlling various conditions when the EGR system 13 is stopped using the transition coefficient.

  Further, when switching from the EGR mode to the normal mode, the engine control device 26 reduces the ratio of the EGR mode based on the transition coefficient and controls the control value by increasing the ratio of the normal mode based on the transition coefficient. Run. As a result, the operating conditions of the engine body 11 can be gradually changed, and the conditions can be changed in accordance with a decrease in the recirculation gas supplied from the EGR system 13. As described above, it is possible to suppress the operation of the engine body 11 from becoming unstable.

  Further, the EGR control device 60 calculates a control value based on the operating condition of the engine body 11, and uses the control value obtained by reducing the calculated control value based on the ratio of the acquired transition coefficient to the maximum value of the transition coefficient. When the control is executed, that is, when the maximum value of the transfer coefficient is 1, it is preferable to calculate by the calculated parameter × (transfer coefficient). Accordingly, the operating condition of the EGR system 13 can be gradually changed based on the transition coefficient, and the condition can be changed in conjunction with the operating condition of the engine body 11. As mentioned above, it can suppress that the quantity of the recirculation gas supplied to the engine main body 11 from the EGR system 13 which is a part of combustion gas increases rapidly, and suppresses the driving | operation of the engine main body 11 becoming unstable. can do.

  Moreover, the EGR control apparatus 60 can use the rotation speed of the EGR blower 47 as a parameter, for example. The EGR control device 60 raises the frequency of the EGR blower 47 based on the transition coefficient, so that the amount of increase in the amount of recirculation gas supplied to the engine body 11 that is a part of the combustion gas suddenly increases. The increase can be suppressed, and the operation of the engine body 11 can be suppressed from becoming unstable.

  For example, the EGR control device 60 can use the oxygen concentration as a parameter. The EGR control device 60 stores the relationship with the target oxygen concentration of the combustion gas supplied to the engine main body 11 corresponding to the load of the engine main body 11, and based on the value obtained by multiplying the target oxygen concentration by the transfer coefficient. 47 is controlled. Thereby, the target oxygen concentration can be gradually changed. By gradually changing the oxygen concentration, it is possible to suppress an increase in the amount of the recirculation gas supplied to the engine body 11 that is a part of the combustion gas from increasing rapidly, and the operation of the engine body 11 can be prevented. It can suppress becoming unstable.

  As described above, the marine diesel engine 10 adjusts the oxygen concentration or the rotation speed of the EGR blower 47 based on the transition coefficient, thereby limiting the rising speed of the EGR blower 47 at the time of start-up, and the oxygen concentration rapidly changes. It is possible to suppress the oxygen concentration from becoming lower than the target oxygen concentration. The difference between the target oxygen concentration and the current oxygen concentration is increased, and the oxygen concentration can be prevented from overshooting and the oxygen concentration being lowered. That is, it is possible to suppress the supply of recirculation gas, which is part of the combustion gas, from becoming excessive and the combustion state in the engine body 11 from deteriorating. Further, it is possible to suppress the occurrence of hunting in which the oxygen concentration oscillates after the oxygen concentration overshoot occurs and the fluctuation in the rotational speed of the EGR blower 47 becomes large. In addition, by setting the time for the transition coefficient to change as the set time, it is possible to suppress an increase in the time taken for the oxygen concentration to reach the target oxygen concentration, and the time to reach the operating condition that can reduce nitrogen oxides. Can be prevented from becoming longer. As described above, the EGR control device 60 limits the rate of increase in the frequency of the EGR blower at the start-up by the transition coefficient, so that the recirculation gas that is part of the combustion gas is supplied to the engine body 11 at the start-up excessively. Can be suppressed. Thereby, the engine main body 11 can be operated stably. The marine diesel engine 10 adjusts the oxygen concentration or the number of revolutions of the EGR blower 47 based on the transition coefficient, thereby limiting the descending speed of the EGR blower 47 even when the EGR system 13 is stopped. The oxygen concentration can be suppressed from becoming lower than the target oxygen concentration.

  In the above embodiment, when the transition coefficient reaches 1 or reaches 0, the control is performed so that the operation is performed in each mode as the switching end. However, the transition coefficient is determined based on the information of 1 or 0. You may make it control by considering a coefficient.

  Further, the transition coefficient calculating device 61 may change the rising speed or the falling speed of the transition coefficient based on the control state of each part acquired from at least one of the engine control device 26 and the EGR control device 60. The transition coefficient calculation device 61 may temporarily stop the increase of the transition coefficient when acquiring information that is not controlled to follow the transition coefficient from at least one of the engine control device 26 and the EGR control device 60. The rate of increase of the transition coefficient may be reduced. The transition coefficient calculation device 61 outputs an instruction to stop the EGR system 13 to each unit when acquiring information indicating that control following the transition coefficient is not possible from at least one of the engine control device 26 and the EGR control device 60. May be.

  Further, the engine control device 26 and the EGR control device 60 may end the control based on the transition coefficient before the transition coefficient reaches the maximum value or 0. In addition, when the transition coefficient calculation device 61 determines that an abnormality has occurred and the EGR system 13 is to be stopped while the EGR system 13 is in operation, the transition coefficient calculation device 61 makes the transition coefficient decrease rate faster than the normal stop control. It is preferable to do. In addition, when the EGR system 13 stops suddenly or cannot transmit or receive a control signal, the engine control device 26 does not use the transition coefficient and controls the engine control device 26 to shift from the EGR mode to the normal mode. Good.

  Moreover, in embodiment mentioned above, although demonstrated using the main engine as a marine diesel engine, it is applicable also to the diesel engine used as a generator.

DESCRIPTION OF SYMBOLS 10 Marine diesel engine 11 Engine main body 12 Supercharger 13 EGR system 14 Demister unit 26 Engine control apparatus 41A EGR inlet valve 41B EGR outlet valve 42 Scrubber 47 EGR blower 48 Air cooler (cooler)
60 EGR Control Device 61 Transition Coefficient Calculation Device 62 Rotational Speed Detection Unit 64 Fuel Input Amount Detection Unit 66 Oxygen Concentration Detection Unit 72 Rotation Number Acquisition Unit 74 Fuel Input Amount Acquisition Unit 76 Oxygen Concentration Acquisition Unit 78 EGR Control Unit 80 Operation Control Unit 82 Normal mode table 84 EGR mode table 86 Parameter setting unit 90 Operation control unit 92 Parameter setting unit 102 Timing unit 104 Condition table 106 Coefficient calculation unit G4, G5, G7 Exhaust gas recirculation line G6 Suction line W1 Drainage circulation line

Claims (10)

The engine body,
An engine control device for controlling the operation of the engine body;
An EGR system that recirculates a part of the exhaust gas discharged from the engine body as a recirculation gas to the engine body,
The EGR system
An exhaust gas recirculation line;
An EGR control device for controlling a flow rate of the recirculation gas supplied to the engine body through the exhaust gas recirculation line;
A transition coefficient calculation device that outputs information of a transition coefficient that increases with time, and
The transfer coefficient calculating device starts increasing the transfer coefficient when starting to supply the recirculated gas from the exhaust gas recirculation line to the engine body, and obtains information on the transfer coefficient from the EGR control device and Transmitted to the engine control device ,
The engine control device controls operation based on the transition coefficient;
The engine , wherein the EGR control device controls a flow rate of the recirculation gas based on the transition coefficient .   2. The engine according to claim 1, wherein the transition coefficient calculation device increases the transition coefficient at a constant speed during a set time and sets a constant value after a predetermined time has elapsed.   The engine control device can switch between an EGR mode in which the EGR system is operating and a normal mode in which the EGR system is stopped. When switching from the normal mode to the EGR mode, the engine control device 3. The engine according to claim 1, wherein the control is executed with a control value in which the ratio of the EGR mode is increased based on and the ratio of the normal mode is decreased based on the transition coefficient.   The EGR control device calculates a control value based on an operating condition of the engine body, and a control value obtained by reducing the calculated control value based on a ratio of the acquired transition coefficient to a maximum value of the transition coefficient The engine according to any one of claims 1 to 3, wherein the control is executed by the engine.   The engine according to claim 4, wherein the EGR control device increases a frequency of an EGR blower provided in the exhaust gas recirculation line based on the transition coefficient. The EGR control device stores a relationship of a target oxygen concentration of a combustion gas supplied to the engine body corresponding to a load of the engine body,
The engine according to claim 4, wherein an EGR blower provided in the exhaust gas recirculation line is controlled based on the target oxygen concentration and the transfer coefficient.   The said transfer coefficient calculation apparatus starts the reduction | decrease of the said transfer coefficient, when stopping supply of the said recirculation gas to the said engine main body from the said exhaust gas recirculation line. The engine according to one item.   The engine control device can switch between an EGR mode in a state in which the EGR system is operated and a normal mode in a state in which the EGR system is stopped. When switching from the EGR mode to the normal mode, the transition coefficient is set to The engine according to claim 7, wherein the control is executed with a control value in which the ratio of the EGR mode is decreased based on the ratio and the ratio of the normal mode is increased based on the transition coefficient. The engine body,
An engine control device for controlling the operation of the engine body;
An EGR system that recirculates a part of the exhaust gas discharged from the engine body as a recirculation gas to the engine body,
The EGR system
An exhaust gas recirculation line;
An EGR control device for controlling a flow rate of the recirculation gas supplied to the engine body through the exhaust gas recirculation line;
A transition coefficient calculating device that outputs information of a transition coefficient that decreases with time, and
When the supply of the recirculation gas from the exhaust gas recirculation line to the engine main body is stopped, the transfer coefficient calculation device starts to decrease the transfer coefficient, and information on the transfer coefficient is provided to the EGR control device and Transmitted to the engine control device ,
The engine control device controls operation based on the transition coefficient;
The engine , wherein the EGR control device controls a flow rate of the recirculation gas based on the transition coefficient . An engine body control process for controlling the operation of the engine body;
An EGR control step in which a part of the exhaust gas discharged from the engine main body can be switched to an EGR mode in which recirculation gas is used, and in the EGR mode, the flow rate of the recirculation gas is adjusted and supplied to the engine main body. When,
An engine control method comprising:
A transition coefficient calculation step for outputting information of a transition coefficient that increases as time passes;
When starting the EGR mode, start increasing the transition coefficient output by the transition coefficient calculating step, and control the operation of the engine body and the flow rate of the recirculation gas based on the transition coefficient. An engine control method characterized by the above.

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