JP6565753B2 - Deposit prevention device for dual fuel internal combustion engine - Google Patents

Description

  The present invention relates to a deposit accumulation preventing apparatus for a dual fuel internal combustion engine.

  2. Description of the Related Art Conventionally, a dual fuel diesel engine using a gas fuel such as natural gas as a main fuel and a liquid fuel such as light oil as an ignition auxiliary fuel is known. The dual-fuel diesel engine supplies gaseous fuel and air into the combustion chamber in the compression process, and injects a small amount of liquid fuel into the combustion chamber from the fuel injection valve. It is an engine that burns a mixture of fuel and air.

  As a dual fuel diesel engine, for example, one described in Patent Document 1 is known. The technology described in Patent Document 1 is due to the combustion of liquid fuel by promoting the premixing of liquid fuel by sufficiently securing an ignition delay period from the end of injection of liquid fuel (light oil) to ignition. This is intended to reduce NOx generation.

Japanese Patent Laying-Open No. 2015-175311

  By the way, in the dual fuel diesel engine as described above, since the injection amount of the liquid fuel injected into the combustion chamber is small compared with a general diesel engine, it passes through the nozzle hole portion of the fuel injection valve. Since the penetration force of the fuel is small and the cooling effect of the fuel injection valve tip by the fuel is also small, there is a problem that deposits are likely to accumulate in the injection hole portion of the fuel injection valve. When a large amount of deposit accumulates in the nozzle hole part of the fuel injection valve, the opening area through which the fuel passes in the nozzle hole part becomes small, the amount of fuel injection from the fuel injection valve decreases, or the fuel injected from the fuel injection valve However, there is a possibility that the fuel spray shape changes due to interference with the deposit and the combustion state deteriorates. Therefore, it is necessary to prevent the deposit accumulation amount from being excessively increased in the nozzle hole portion of the fuel injection valve that injects liquid fuel.

  An object of the present invention is to suppress deposit accumulation in a nozzle hole portion of a fuel injection valve in a dual fuel internal combustion engine that supplies main fuel into the combustion chamber and injects ignition auxiliary fuel into the combustion chamber from the fuel injection valve. It is an object of the present invention to provide a deposit accumulation prevention device for a dual fuel internal combustion engine.

One aspect of the present invention is a deposit accumulation prevention apparatus for a dual-fuel internal combustion engine comprising a main fuel supply unit that supplies main fuel into a combustion chamber and a fuel injection valve that injects ignition auxiliary fuel into the combustion chamber. Injection information including an air amount detection unit for detecting the intake air amount into the combustion chamber, the main fuel supply amount by the main fuel supply unit, the injection amount of ignition auxiliary fuel from the preset fuel injection valve, and the injection timing Based on the amount of intake air into the combustion chamber, the amount of main fuel supplied by the main fuel supply unit, the amount of injection of ignition auxiliary fuel, and the injection timing of the injection auxiliary fuel from the fuel injection valve a cylinder temperature calculated unit for determining the temperature in the combustion chamber at the time of injection, and the in-cylinder pressure detection unit for detecting the pressure in the combustion chamber, the injection pressure detection for detecting the injection pressure of the ignition auxiliary fuel from fuel injection valves And the temperature of the combustion chamber at the time of injection of the ignition auxiliary fuel, the pressure in the combustion chamber at the time of injection of the ignition auxiliary fuel, the injection amount of the ignition auxiliary fuel, and the injection pressure of the ignition auxiliary fuel, When the reduction rate of the injection amount of the ignition auxiliary fuel estimated by the injection amount reduction rate estimation unit for estimating the reduction rate and the injection amount reduction rate estimation unit is equal to or greater than a threshold value, the deposit amount to the injection hole portion of the fuel injection valve is reduced. A control unit that performs control for suppressing accumulation, and the in-cylinder temperature obtaining unit is configured to determine a relationship between the intake air amount, the supply amount of the main fuel, the injection amount and the injection timing of the ignition auxiliary fuel, and the temperature in the combustion chamber. Injection of auxiliary combustion fuel from the fuel injection valve using the calculated map obtained from the map or thermodynamics and using the intake air amount, main fuel supply amount, injection amount of ignition auxiliary fuel, and injection timing as variables. In time The temperature of the combustion chamber is obtained, and the rate of decrease in the injection amount of the auxiliary combustion fuel is calculated by subtracting the injection amount of the new ignition auxiliary fuel from the injection amount of the new auxiliary combustion fuel and the current injection amount of the auxiliary combustion fuel. The injection amount reduction rate estimation unit is: A × (temperature in the combustion chamber at the time of injection of ignition auxiliary fuel × pressure in the combustion chamber at the time of injection of ignition auxiliary fuel) −B × (ignition auxiliary fuel in one cycle) The reduction rate of the injection amount of the ignition auxiliary fuel is calculated using a calculation formula (A, B, C is a coefficient) of the sum of the injection amounts of the fuel injection times x the injection pressure of the ignition auxiliary fuel) + C.

  As described above, in the deposit accumulation preventing apparatus for a dual fuel internal combustion engine according to the present invention, the temperature in the combustion chamber at the time of injection of the ignition auxiliary fuel, the pressure in the combustion chamber at the time of injection of the ignition auxiliary fuel, the injection amount of the ignition auxiliary fuel Based on the injection pressure of the ignition auxiliary fuel and the injection pressure of the ignition auxiliary fuel, the rate of decrease in the injection amount of the ignition auxiliary fuel is estimated. By performing control for suppressing deposit accumulation, deposit accumulation in the nozzle hole portion of the fuel injection valve can be suppressed.

Moreover , estimation of the rate of decrease in the injection amount of the ignition auxiliary fuel can be realized by a simple calculation process.

Further , the temperature in the combustion chamber at the time of injection of the ignition auxiliary fuel can be easily obtained using a map or a known calculation formula.

  The deposit accumulation preventing apparatus further includes an inert gas injection valve that injects an inert gas toward the injection hole of the fuel injection valve, and the control unit is configured to reduce the rate of decrease in the injection amount of the auxiliary ignition fuel when the injection rate is equal to or greater than a threshold value. The inert gas injection valve may be controlled to inject the inert gas. In this case, since the intrusion of the combustion gas into the nozzle hole part of the fuel injection valve is suppressed, the temperature rise in the nozzle hole part is suppressed. Thereby, the deposit of the deposit to the nozzle hole part of a fuel injection valve can be suppressed reliably.

  The deposit accumulation prevention device branches from the EGR path connecting the exhaust side of the combustion chamber and the intake side of the combustion chamber, and is connected to the EGR gas extraction path for extracting EGR gas flowing through the EGR path, and the EGR gas extraction path. An EGR gas injection valve that injects gas toward the injection hole of the fuel injection valve, and the control unit injects EGR gas when the rate of decrease in the injection amount of the ignition auxiliary fuel is equal to or greater than a threshold value. The EGR gas injection valve may be controlled. In this case, since the intrusion of the combustion gas into the nozzle hole part of the fuel injection valve is suppressed, the temperature rise in the nozzle hole part is suppressed. Thereby, the deposit of the deposit to the nozzle hole part of a fuel injection valve can be suppressed reliably.

  According to the present invention, in an internal combustion engine that supplies main fuel into the combustion chamber and injects ignition auxiliary fuel into the combustion chamber from the fuel injection valve, deposit accumulation in the injection hole portion of the fuel injection valve can be suppressed. A deposit accumulation prevention device for a dual fuel internal combustion engine is provided.

It is a schematic block diagram which shows the dual fuel diesel engine provided with the deposit prevention apparatus which concerns on one Embodiment of this invention. It is a block diagram of the control system of the dual fuel diesel engine containing the functional block of ECU shown by FIG. It is a graph which shows an example of a heat release rate waveform with a light oil injection pattern. FIG. 3 is a flowchart showing details of a deposit accumulation prevention control process executed by an ECU shown in FIG. 2. It is a graph which shows an example of the relationship between the temperature (in-cylinder temperature) in the combustion chamber at the time of light oil injection, and the fall rate of light oil injection amount. It is a schematic block diagram which shows a dual fuel diesel engine as a dual fuel internal combustion engine provided with the deposit accumulation prevention apparatus which concerns on other embodiment of this invention. It is a block diagram of the control system of the dual fuel diesel engine containing the functional block of ECU shown by FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram showing a dual fuel diesel engine equipped with a deposit accumulation preventing apparatus according to an embodiment of the present invention. In FIG. 1, a dual-fuel diesel engine 1 that is a dual-fuel internal combustion engine according to the present embodiment is a multi-cylinder (for example, four-cylinder) in-line diesel engine that uses natural gas and light oil as two types of fuel. In FIG. 1, only one cylinder is shown.

  The dual fuel diesel engine 1 includes a cylinder block 2, a cylinder head 3 fixed to the upper surface of the cylinder block 2, and a piston 4 disposed inside the cylinder block 2 so as to be able to reciprocate up and down. A space surrounded by the cylinder block 2, the cylinder head 3, and the piston 4 defines a combustion chamber 5.

  The cylinder head 3 is provided with an intake port 6 and an exhaust port 7 that communicate with the combustion chamber 5. An intake manifold 8 is connected to the intake port 6, and an exhaust manifold 9 is connected to the exhaust port 7.

  The dual fuel diesel engine 1 also includes a natural gas injector 10 that injects natural gas as main fuel into the intake manifold 8 and a light oil injector 11 that injects light oil as ignition auxiliary fuel into the combustion chamber 5. ing. The natural gas injector 10 is a main fuel supply unit that supplies main fuel into the combustion chamber 5. The light oil injector 11 is a fuel injection valve that injects ignition auxiliary fuel into the combustion chamber 5.

  The natural gas injected from the natural gas injector 10 is mixed with air and sent into the combustion chamber 5. The light oil injector 11 is attached to the cylinder head 3. The light oil injector 11 is connected to a common rail 12 that stores light oil in a high pressure state. In the compression stroke of the piston 4, the light oil injected from the light oil injector 11 is self-ignited, so that the mixture of natural gas and air is combusted. The output torque of the dual fuel diesel engine 1 is determined by the injection amount of natural gas.

  The dual fuel diesel engine 1 also includes an EGR path 13 that connects an exhaust manifold 9 on the exhaust side of the combustion chamber 5 and an intake manifold 8 on the intake side of the combustion chamber 5. The EGR path 13 is a path for returning a part of the exhaust gas generated in the combustion chamber 5 to the combustion chamber 5 as EGR (exhaust gas recirculation) gas.

  The dual fuel diesel engine 1 includes an inert gas injector 14 (inert gas injection valve) that injects an inert gas F toward the injection hole portion 11 a of the light oil injector 11. The inert gas injector 14 is attached to the cylinder head 3. The inert gas injector 14 is connected to a gas cylinder 15 that stores the inert gas F in a high pressure state. The inert gas F is a normal temperature gas for preventing the combustion gas from entering the nozzle hole portion 11 a of the light oil injector 11.

  Further, the dual fuel diesel engine 1 includes an engine speed sensor 16, an accelerator opening sensor 17, an air flow meter 18, an in-cylinder pressure sensor 19, an injection pressure sensor 20, and an ECU (Electronic Control Unit) 21. It has.

  The engine speed sensor 16 detects the speed (engine speed) of the dual fuel diesel engine 1. The accelerator opening sensor 17 detects the accelerator opening as a load (engine load) of the dual fuel diesel engine 1. The air flow meter 18 is an air amount detection unit that is attached to the intake manifold 8 and detects the amount of intake air into the combustion chamber 5. The in-cylinder pressure sensor 19 is an in-cylinder pressure detector that is attached to the cylinder head 3 and detects the pressure in the combustion chamber 5 (in-cylinder pressure). The injection pressure sensor 20 is an injection pressure detector that is attached to the common rail 12 and detects an injection pressure of light oil (hereinafter, light oil injection pressure) when light oil is injected from the light oil injector 11 (hereinafter, light oil injection).

  The ECU 21 includes a CPU, a RAM, a ROM, an input / output interface, and the like. The ECU 21 inputs detection values of the engine speed sensor 16, the accelerator opening sensor 17, the air flow meter 18, the in-cylinder pressure sensor 19, and the injection pressure sensor 20, performs predetermined processing, the natural gas injector 10, and the light oil injector 11. And the inert gas injector 14 is controlled.

  FIG. 2 is a configuration diagram of a control system of the dual fuel diesel engine 1 including the functional blocks of the ECU 21. In FIG. 2, the ECU 21 includes a natural gas injection control unit 22, a light oil injection control unit 23, an injection information acquisition unit 24, an in-cylinder temperature determination unit 25, an injection amount decrease rate estimation unit 26, and an inert gas injection And a control unit 27 (control unit).

  The natural gas injection control unit 22 determines an injection amount of natural gas (hereinafter referred to as a natural gas injection amount) based on detection values of the engine speed sensor 16 and the accelerator opening sensor 17, and according to the natural gas injection amount. The natural gas injector 10 is controlled to inject natural gas. At this time, the natural gas injection control unit 22 controls the natural gas injector 10 to start the injection of natural gas sufficiently before the time point when the piston 4 reaches the compression top dead center (TDC). The natural gas injection amount is a supply amount of natural gas into the combustion chamber 5.

  The light oil injection control unit 23 controls the light oil injector 11 to inject a small amount of light oil set in advance. The light oil injection amount is smaller than the natural gas injection amount. At this time, as shown in FIG. 3, the light oil injection control unit 23, when performing one-stage injection, causes the light oil to be injected sufficiently before the time point when the piston 4 reaches the compression top dead center. The injector 11 is controlled. As shown in FIG. 3, the light oil injection control unit 23, when performing the two-stage injection, has the piston 4 at the compression top dead center sufficiently before the piston 4 reaches the compression top dead center. The light oil injector 11 is controlled so that the light oil is injected at the time of arrival. The light oil injection start time is later than the natural gas injection start time.

  By injecting the light oil in this manner, as shown in FIG. 3, the light oil ignites before and after the piston 4 reaches the compression top dead center, and the mixture of natural gas and air is combusted by the light energy of the light oil. To do. The combustion is controlled so that the peak of the heat generation rate appears after the piston 4 reaches the compression top dead center.

  The injection information acquisition unit 24 acquires injection information related to the injection of natural gas from the natural gas injector 10 and the injection of 11 light oil from the light oil injector. Specifically, the injection information acquisition unit 24 includes a natural gas injection amount determined by the natural gas injection control unit 22, a preset light oil injection amount (hereinafter referred to as light oil injection amount), and a light oil injection timing (hereinafter referred to as “light oil injection timing”). , Light oil injection timing).

  The in-cylinder temperature obtaining unit 25 is based on the intake air amount into the combustion chamber 5 detected by the air flow meter 18 and the natural gas injection amount, light oil injection amount, and light oil injection timing acquired by the injection information acquisition unit 24. Thus, the temperature (in-cylinder temperature) in the combustion chamber 5 at the time of light oil injection from the light oil injector 11 is obtained.

  The injection amount decrease rate estimation unit 26 calculates the temperature in the combustion chamber 5 at the time of light oil injection obtained by the in-cylinder temperature obtaining unit 25 and the pressure in the combustion chamber 5 at the time of light oil injection detected by the in-cylinder pressure sensor 19 ( In-cylinder pressure), the reduction rate of the light oil injection amount is estimated based on the light oil injection amount acquired by the injection information acquisition unit 24 and the light oil injection pressure detected by the injection pressure sensor 20. The method for estimating the reduction rate of the light oil injection amount will be described in detail later.

  The inert gas injection control unit 27 controls the inert gas injector 14 to inject the inert gas when the rate of decrease in the light oil injection amount estimated by the injection amount decrease rate estimation unit 26 is equal to or greater than a threshold value. Thus, control for suppressing deposit accumulation in the nozzle hole portion 11a of the light oil injector 11 is performed.

  The deposit accumulation preventing device 28 of the present embodiment is a device that prevents deposit accumulation on the injection hole portion 11 a of the light oil injector 11. The deposit accumulation prevention device 28 includes an inert gas injector 14, a gas cylinder 15, an air flow meter 18, an in-cylinder pressure sensor 19, an injection pressure sensor 20, an injection information acquisition unit 24, and an in-cylinder temperature determination unit 25. The injection amount reduction rate estimation unit 26 and the inert gas injection control unit 27 are provided.

  FIG. 4 is a flowchart showing details of the deposit accumulation prevention control process executed by the ECU 21. This process is executed for each cycle of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke.

  In FIG. 4, the ECU 21 first obtains the intake air amount into the combustion chamber 5 detected by the air flow meter 18, the natural gas injection amount from the natural gas injector 10, the light oil injection amount from the light oil injector 11, and the light oil injection timing. (Procedure S101).

  Then, the ECU 21 obtains the temperature (in-cylinder temperature) in the combustion chamber 5 at the time of light oil injection from the light oil injector 11 based on the intake air amount, the natural gas injection amount, the light oil injection amount, and the light oil injection timing (procedure S102). ). At this time, the ECU 21 prepares an in-cylinder temperature map that represents the relationship between the intake air amount, the natural gas injection amount, the light oil injection amount, the light oil injection timing, and the temperature in the combustion chamber 5 in advance. The temperature in the combustion chamber 5 at the time of light oil injection may be obtained from the map, or the temperature in the combustion chamber 5 at the time of light oil injection may be calculated using a known calculation formula obtained from thermodynamics, for example. Further, when performing the second-stage injection (see FIG. 3), the ECU 21 obtains the temperature in the combustion chamber 5 at the time of the second-stage light oil injection.

  Subsequently, the ECU 21 detects the pressure (in-cylinder pressure) in the combustion chamber 5 during light oil injection detected by the in-cylinder pressure sensor 19, the light oil injection amount from the light oil injector 11, and the light oil injection detected by the injection pressure sensor 20. A pressure is acquired (procedure S103). At this time, when performing the second-stage injection (see FIG. 3), the ECU 21 acquires the pressure in the combustion chamber 5 at the time of the second-stage light oil injection, and the first-stage light oil injection amount and the second-stage light oil injection amount. Get the total value with the light oil injection amount. Note that the light oil injection pressure at the time of the first-stage light oil injection is equal to the light oil injection pressure at the time of the second-stage light oil injection.

  Then, the ECU 21 is based on the temperature in the combustion chamber 5 at the time of light oil injection obtained in step S102 and the pressure, the light oil injection amount, and the light oil injection pressure in the combustion chamber 5 at the time of light oil injection obtained in step S103. Thus, the reduction rate of the light oil injection amount is estimated (step S104). The decrease rate of the light oil injection amount represents a ratio of a subtracted value between the light oil injection amount at the new time and the current light oil injection amount with respect to the light oil injection amount at the new time. The ECU 21 calculates the reduction rate of the light oil injection amount by the following equation (1).

Reduction rate of light oil injection amount = A × (temperature in the combustion chamber during light oil injection × pressure in the combustion chamber during light oil injection) −B × (total value of light oil injection amount in one cycle × light oil injection pressure) + C (1) )
A, B, and C are coefficients calculated from the results of multiple regression analysis

  The above equation (1) is obtained by performing multiple regression analysis from data such as the engine speed, engine output torque, and the number of light oil injections, and finding a parameter that is significant for the rate of decrease in the light oil injection amount. It is a regression equation. The term of the coefficient A in the above equation (1) is a deposit generation term representing energy for generating deposit in the injection hole portion 11a of the light oil injector 11. The term of the coefficient B in the above equation (1) is a deposit peeling term representing energy for peeling the deposit from the nozzle hole portion 11a of the light oil injector 11. Further, as shown in FIG. 5, when the temperature (in-cylinder temperature) in the combustion chamber 5 at the time of light oil injection increases, the rate of decrease in the light oil injection amount increases.

  Subsequently, the ECU 21 determines whether or not the reduction rate of the light oil injection amount estimated in step S104 is equal to or greater than a threshold value (for example, 1%) (step S105). When the ECU 21 determines that the rate of decrease in the light oil injection amount is lower than the threshold value, the present process is terminated. Note that the threshold value is appropriately set depending on hardware differences such as the engine and the injector, or target performance.

  When the ECU 21 determines that the reduction rate of the light oil injection amount is equal to or greater than the threshold value, the ECU 21 causes the inert gas injector 14 to inject the inert gas toward the injection hole portion 11a of the light oil injector 11 for a predetermined period. Control (procedure S106), and this process is terminated.

  At this time, when performing the first stage injection (see FIG. 3), the ECU 21 causes the inert gas injector 14 to inject the inert gas before the combustion gas enters the injection hole portion 11 a of the light oil injector 11. Control. The time before the combustion gas enters the nozzle hole portion 11a of the light oil injector 11 is, for example, when the heat generation rate (see FIG. 3) reaches 10%. When performing the second-stage injection (see FIG. 3), the ECU 21 controls the inert gas injector 14 so that the inert gas is injected immediately after the second-stage light oil injection is completed. When performing the two-stage injection, the ECU 21 controls the inert gas injector 14 so that the inert gas is injected before the combustion gas enters the injection hole portion 11a of the light oil injector 11 in the next cycle. May be.

  In the above, the injection information acquisition part 24 performs said procedure S101, S103. The in-cylinder temperature obtaining unit 25 executes the above steps S101 and S102. The injection amount decrease rate estimation unit 26 executes the above steps S103 and S104. The inert gas injection control unit 27 executes the above steps S105 and S106.

  By the way, when the high-temperature combustion gas enters the injection hole portion of the light oil injector, the carbon compound contained in the combustion gas is easily deposited as a deposit on the injection hole portion of the light oil injector. In particular, as in this embodiment, in a dual fuel diesel engine that uses natural gas and light oil as fuel, the injection amount of light oil injected into the combustion chamber as compared to a normal diesel engine that uses only light oil as fuel Because the amount of gas is small, the penetration force of light oil passing through the nozzle hole part of the light oil injector is small and the cooling effect of the light oil injector tip by the light oil is also small, so the combustion gas easily enters the nozzle hole part of the light oil injector. . When the combustion gas enters the nozzle hole part of the light oil injector, the amount of deposits deposited in the nozzle hole part increases. Then, the light oil injection amount from the light oil injector is reduced.

  In contrast, in the present embodiment, the rate of decrease in the light oil injection amount is estimated based on the temperature in the combustion chamber 5 during light oil injection, the pressure in the combustion chamber 5 during light oil injection, the light oil injection amount, and the light oil injection pressure. When the rate of decrease in the light oil injection amount is equal to or greater than the threshold value, control for suppressing deposit accumulation on the injection hole portion 11a of the light oil injector 11 is performed, whereby the injection to the injection hole portion 11a of the light oil injector 11 is performed. In order to prevent deposit accumulation, the light oil injector 11 need not be provided with a cooling structure for cooling the nozzle hole portion 11a of the light oil injector 11. Thereby, the deposit of the deposit to the nozzle hole part 11a of the light oil injector 11 can be suppressed without complicating the structure of the light oil injector 11. As a result, it is possible to prevent problems such as a decrease in the amount of light oil injection from the light oil injector 11 and an increase in the light oil injection time from the light oil injector 11. Moreover, it becomes possible to suppress the change in the spray shape of light oil and to prevent deterioration of the combustion state.

  Further, in the present embodiment, A × (temperature in the combustion chamber during light oil injection × pressure in the combustion chamber during light oil injection) −B × (total value of light oil injection amount in one cycle × light oil injection pressure) + C By calculating the reduction rate of the light oil injection amount using (A, B, and C are coefficients), the reduction rate of the light oil injection amount can be estimated by a simple calculation process.

  Further, in the present embodiment, using the map or a known calculation formula, the inside of the combustion chamber 5 at the time of light oil injection based on the intake air amount, the natural gas injection amount, the light oil injection amount, and the light oil injection timing into the combustion chamber 5. The temperature can be easily obtained.

  Further, in the present embodiment, by controlling the inert gas injector 14 to inject the inert gas toward the injection hole portion 11a of the light oil injector 11 when the rate of decrease in the light oil injection amount is equal to or greater than the threshold value, Since the intrusion of the combustion gas into the injection hole portion 11a of the light oil injector 11 is suppressed, the temperature rise in the injection hole portion 11a is suppressed. Thereby, the deposit of the deposit to the nozzle hole part 11a of the light oil injector 11 can be suppressed reliably.

  FIG. 6 is a schematic configuration diagram showing a dual fuel diesel engine as a dual fuel internal combustion engine provided with a deposit accumulation preventing apparatus according to another embodiment of the present invention, and corresponds to FIG. In FIG. 6, the dual fuel diesel engine 1 according to the present embodiment is branched from the EGR path 13 and connected to the EGR gas extraction path 30 for extracting the EGR gas flowing through the EGR path 13 and the tip of the EGR gas extraction path 30. And an EGR gas injector 31 (EGR gas injection valve) that injects the EGR gas S toward the injection hole portion 11a of the light oil injector 11. The dual fuel diesel engine 1 according to this embodiment does not include the inert gas injector 14 in the above embodiment.

  In the EGR gas extraction path 30, a compressor 32 and a cooler 33 are sequentially arranged from the upstream side (EGR path 13 side) to the downstream side (EGR gas injector 31 side). The compressor 32 pressurizes the EGR gas taken out from the EGR path 13. The cooler 33 cools the EGR gas pressurized by the compressor 32. Accordingly, the EGR gas injector 31 injects the EGR gas S cooled by the cooler 33 toward the injection hole portion 11 a of the light oil injector 11. The cooled EGR gas S is a gas for preventing the combustion gas from entering the injection hole portion 11 a of the light oil injector 11. The EGR gas injector 31 is controlled by the ECU 21 described above.

  FIG. 7 is a configuration diagram of a control system of the dual fuel diesel engine 1 including the functional blocks of the ECU 21, and corresponds to FIG. In FIG. 7, the ECU 21 has an EGR gas injection control unit 34 (control unit) instead of the inert gas injection control unit 27 in the above embodiment. The EGR gas injection control unit 34 causes the EGR gas to be injected toward the injection hole portion 11a of the light oil injector 11 when the decrease rate of the light oil injection amount estimated by the injection amount decrease rate estimation unit 26 is equal to or greater than a threshold value. By controlling the EGR gas injector 31, control for suppressing deposit accumulation in the injection hole portion 11 a of the light oil injector 11 is performed.

  The deposit accumulation preventing apparatus 35 of the present embodiment includes an EGR gas extraction path 30, an EGR gas injector 31, a compressor 32, a cooler 33, an air flow meter 18, an in-cylinder pressure sensor 19, an injection pressure sensor 20, An injection information acquisition unit 24, an in-cylinder temperature determination unit 25, an injection amount decrease rate estimation unit 26, and an EGR gas injection control unit 34 are provided.

  In this embodiment as well, when the rate of decrease in the light oil injection amount is equal to or greater than the threshold value, control is performed to suppress deposit accumulation in the nozzle hole portion 11a of the light oil injector 11, so that it is the same as in the above embodiment. In addition, deposits on the injection hole 11a of the light oil injector 11 can be suppressed without complicating the structure of the light oil injector 11.

  Further, in the present embodiment, the light oil injector 31 is controlled by controlling the EGR gas injector 31 so as to inject the EGR gas toward the injection hole portion 11a of the light oil injector 11 when the reduction rate of the light oil injection amount is equal to or greater than the threshold value. Since the intrusion of the combustion gas into the nozzle hole portion 11a is suppressed, the temperature rise in the nozzle hole portion 11a is suppressed. Thereby, the deposit of the deposit to the nozzle hole part 11a of the light oil injector 11 can be suppressed reliably.

  Further, in the present embodiment, the EGR gas is taken out from the middle of the EGR path 13, and the EGR gas is injected from the EGR gas injector 31 toward the injection hole portion 11a of the light oil injector 11, so that a gas cylinder is unnecessary. Therefore, it is not necessary to perform operations such as replacing the gas cylinder or filling the gas cylinder with gas.

  In the present embodiment, since the EGR gas taken out from the EGR path 13 is pressurized, the EGR gas can be injected into the combustion chamber 5 even under a high pressure in the combustion chamber 5.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the inert gas injector 14 is controlled to inject the inert gas toward the nozzle hole portion 11a of the light oil injector 11 when the rate of decrease in the light oil injection amount is equal to or greater than the threshold value, or By controlling the EGR gas injector 31 so as to inject EGR gas toward the injection hole portion 11a of the light oil injector 11, control for suppressing deposit accumulation in the injection hole portion 11a of the light oil injector 11 is performed. However, the form is not particularly limited. For example, when the rate of decrease in the light oil injection amount is equal to or greater than the threshold value, the light oil injector 11 may be controlled to increase the light oil injection amount or increase the light oil injection pressure in the next cycle. In this case, as is apparent from the deposit peeling term of the above formula (1), the deposit deposited on the injection hole portion 11a of the light oil injector 11 is easily peeled off. Therefore, it is possible to suppress deposit accumulation on the injection hole portion 11a of the light oil injector 11.

  Further, in the above embodiment, A × (temperature in the combustion chamber during light oil injection × pressure in the combustion chamber during light oil injection) −B × (total value of light oil injection amount in one cycle × light oil injection pressure) + C (A, B, and C are coefficients) are used to calculate the reduction rate of the light oil injection amount. However, the present invention is not particularly limited to this mode. For example, the temperature in the combustion chamber during light oil injection, the combustion chamber during light oil injection The correction coefficient may be individually multiplied to the total pressure of the light oil injection amount in one cycle and the light oil injection pressure.

  Furthermore, in the above embodiment, the temperature in the combustion chamber 5 at the time of light oil injection is obtained based on the amount of intake air into the combustion chamber 5, the amount of natural gas injection, the light oil injection amount, and the light oil injection timing. The form is not limited, and the engine speed or the like may be used in addition to the information.

  DESCRIPTION OF SYMBOLS 1 ... Dual fuel diesel engine (dual fuel internal combustion engine), 5 ... Combustion chamber, 10 ... Natural gas injector (main fuel supply unit), 11 ... Light oil injector (fuel injection valve), 13 ... EGR path, 14 ... Non Active gas injector (inert gas injection valve), 19 ... In-cylinder pressure sensor (in-cylinder pressure detection unit), 20 ... Injection pressure sensor (injection pressure detection unit), 24 ... Injection information acquisition unit, 25 ... In-cylinder temperature determination , 26 ... injection amount decrease rate estimation part, 27 ... inert gas injection control part (control part), 28 ... deposit accumulation prevention device, 30 ... EGR gas extraction path, 31 ... EGR gas injector (EGR gas injection valve), 34 ... EGR gas injection control unit (control unit), 35 ... Deposit accumulation prevention device, F ... Inert gas, S ... EGR gas.

Claims (3)

A deposit accumulation preventing apparatus for a dual fuel internal combustion engine, comprising: a main fuel supply unit that supplies main fuel into a combustion chamber; and a fuel injection valve that injects ignition auxiliary fuel into the combustion chamber.
An air amount detector for detecting the amount of intake air into the combustion chamber;
An injection information acquisition unit for acquiring injection information including the supply amount of the main fuel by the main fuel supply unit, the injection amount of the ignition auxiliary fuel from the fuel injection valve set in advance, and the injection timing;
Based on the intake air amount into the combustion chamber, the supply amount of the main fuel by the main fuel supply unit, the injection amount of the ignition auxiliary fuel, and the injection timing, at the time of injection of the ignition auxiliary fuel from the fuel injection valve An in-cylinder temperature obtaining unit for obtaining the temperature in the combustion chamber;
An in-cylinder pressure detector for detecting the pressure in the combustion chamber ;
An injection pressure detection unit for detecting the injection pressure of the ignition auxiliary fuel from the fuel injection valve,
The ignition assistance is based on the temperature in the combustion chamber at the time of injection of the ignition auxiliary fuel, the pressure in the combustion chamber at the time of injection of the ignition auxiliary fuel, the injection amount of the ignition auxiliary fuel, and the injection pressure of the ignition auxiliary fuel. An injection amount reduction rate estimation unit for estimating a reduction rate of the fuel injection amount;
Control for performing control to suppress deposit accumulation in the nozzle hole portion of the fuel injection valve when the rate of decrease in the injection amount of the ignition auxiliary fuel estimated by the injection amount decrease rate estimation unit is equal to or greater than a threshold value and a part,
The in-cylinder temperature obtaining unit is obtained from a map representing the relationship between the intake air amount, the main fuel supply amount, the ignition auxiliary fuel injection amount and injection timing, and the temperature in the combustion chamber, or thermodynamics. And the combustion chamber at the time of injection of the ignition auxiliary fuel from the fuel injection valve using a calculation formula with the intake air amount, the main fuel supply amount, the ignition auxiliary fuel injection amount, and the injection timing as variables. Find the temperature of
The rate of decrease in the injection amount of the ignition auxiliary fuel is a ratio of a subtracted value between the injection amount of the ignition auxiliary fuel when new and the injection amount of the current ignition auxiliary fuel with respect to the injection amount of the ignition auxiliary fuel when new.
The injection amount reduction rate estimation unit is A × (temperature in the combustion chamber at the time of injection of ignition auxiliary fuel × pressure in the combustion chamber at the time of injection of ignition auxiliary fuel) −B × (injection amount of the ignition auxiliary fuel in one cycle). A dual fuel internal combustion engine characterized in that the reduction rate of the injection amount of the ignition auxiliary fuel is calculated using a calculation formula (A, B, C is a coefficient) of total value x ignition auxiliary fuel injection pressure) + C Deposit prevention device. An inert gas injection valve that injects an inert gas toward the injection hole of the fuel injection valve;
Wherein, when the rate of decrease in the injection amount of the ignition auxiliary fuel is not less than the threshold value, according to claim 1 Symbol, wherein the controller controls the inert gas injection valve so as to inject the inert gas The deposit accumulation prevention apparatus of the dual fuel internal combustion engine described. An EGR gas extraction path that branches out from an EGR path connecting the exhaust side of the combustion chamber and the intake side of the combustion chamber and extracts EGR gas flowing through the EGR path;
An EGR gas injection valve connected to the EGR gas extraction path and injecting the EGR gas toward the injection hole of the fuel injection valve;
Wherein, when the rate of decrease in the injection amount of the ignition auxiliary fuel is not less than the threshold value, No placement claim 1 Symbol and controls the EGR gas injection valve so as to inject the EGR gas Deposit accumulation prevention device for dual fuel internal combustion engine.

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