JP6336818B2 - Fuel supply control system for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply control system for an internal combustion engine.

  Conventionally, a fuel supply control system for an internal combustion engine that supplies fuel based on a combustion state in a combustion chamber of the internal combustion engine is known. For example, in Patent Document 1, in a diesel engine, based on the rate of change in the pressure of the combustion chamber, the difference between the maximum pressure time in combustion of the main fuel and the maximum pressure timing in combustion of the auxiliary fuel that assists the combustion of the main fuel, etc. An injection control system for an internal combustion engine that performs injection control of main fuel and auxiliary fuel is described.

JP 2008-45471 A

  2. Description of the Related Art In recent years, an internal combustion engine that assists combustion of a main fuel having a low self-ignition property by combustion of a secondary fuel having a high self-ignition property is known. In the internal combustion engine, the sub fuel supply conditions are controlled so that the combustion state of the main fuel is optimized. However, since the auxiliary fuel with high self-ignitability has a relatively high combustion speed, it is difficult to detect only the combustion state of the auxiliary fuel from the combustion in the combustion chamber in which the combustion of the auxiliary fuel and the combustion of the main fuel are parallel. . For this reason, it is difficult to control the supply conditions of the auxiliary fuel in order to optimize the combustion state in the combustion chamber and improve the combustion efficiency of the internal combustion engine.

  The present invention has been made in view of the above points, and an object of the present invention is to control the fuel supply of an internal combustion engine that improves the combustion efficiency of the internal combustion engine to which the main fuel and the auxiliary fuel for assisting the combustion of the main fuel are supplied. Is to provide a system.

In the present invention, the main fuel supplied to the intake system (20) and the combustion chamber (11, 12, 13, 14) supplied to the combustion chamber (11, 12, 13, 14) of the internal combustion engine (10) have higher self-ignitability than the main fuel and combustion of the main fuel. A fuel supply control system for an internal combustion engine that controls the supply of the auxiliary fuel to the internal combustion engine to assist the crankshaft, comprising a crank angle detection means (73) , a control section (70) , a heat generation amount calculation means (70) , Combustion start timing calculation means (70) , heat generation amount determination means (70) , supply amount determination means (70) , and combustion start timing determination means (70) .
The crank angle detection means detects the crank angle of the crankshaft of the internal combustion engine and outputs a signal corresponding to the detected crank angle. The control unit controls the operation of the auxiliary fuel supply unit (16, 17, 18, 19) for supplying auxiliary fuel to the internal combustion engine. The calorific value calculation means calculates the calorific value in the combustion of the auxiliary fuel. The combustion start timing calculation means calculates the combustion start timing of the auxiliary fuel.
Whether the calorific value determining means calculates the calorific value calculated by the calorific value calculation means based on a map showing the relationship between the calorific value in the combustion of the auxiliary fuel and the total calorific value (Qall), or more than a predetermined calorific value (Qbpmin) Determine whether or not. The supply amount determination means is a sub fuel in one combustion cycle of the internal combustion engine based on a map showing a relationship between an injection amount per injection (Qi / N) and a cooling loss (CL0) in the combustion of the internal combustion engine. The supply amount per supply (Qip / Np) obtained by dividing the total supply amount (Qip) of the fuel by the number of times the auxiliary fuel is supplied in one combustion cycle is a predetermined supply amount (Qi0 / N) It is determined whether it is smaller. The combustion start timing determination means is a sub fuel combustion start timing (θ10) calculated by the combustion start timing calculation means based on a map showing a relationship between the combustion start timing of the auxiliary fuel and the maximum value (Pmax) of the pressure in the combustion chamber. ) Is on the retard side with respect to a predetermined crank angle (θL) .

  In the fuel supply control system for an internal combustion engine according to the present invention, when the heat generation amount determination means determines that the heat generation amount of the auxiliary fuel in one combustion cycle of the internal combustion engine is less than the predetermined heat generation amount, the heat generation amount is equal to or greater than the predetermined heat generation amount. When the supply amount determining means determines that the supply amount per supply is greater than or equal to the supply amount per predetermined supply, the supply amount per supply is the predetermined amount. Increase the number of times the auxiliary fuel is supplied in one combustion cycle of the internal combustion engine so that it is smaller than the supply amount per supply, and determine the combustion start timing if the combustion start timing of the auxiliary fuel is more advanced than the predetermined crank angle When the means determines, the sub fuel supply start timing is changed to the retard side so that the sub fuel combustion start timing is retarded from a predetermined crank angle.

  In the fuel supply control system for an internal combustion engine of the present invention, the calorific value determining means determines whether or not the calorific value of the auxiliary fuel calculated by the calorific value calculating means is equal to or greater than a predetermined calorific value, and based on the determination result. Change the total supply of secondary fuel. Also, whether the supply amount per supply is less than or equal to the supply amount per predetermined supply based on the total supply amount of the auxiliary fuel and the number of times the auxiliary fuel is supplied in one combustion cycle. The determination means makes a determination, and changes the number of sub fuel supplies in one combustion cycle of the internal combustion engine based on the determination result. Further, it is determined by the combustion start timing determination means whether the combustion start timing of the auxiliary fuel calculated by the combustion start timing calculation means is behind the predetermined crank angle, and based on the determination result, the sub fuel combustion timing is determined. Change the supply start timing. As described above, in the fuel supply control system for an internal combustion engine of the present invention, the supply condition of the auxiliary fuel is corrected based on the calculated combustion start timing of the auxiliary fuel and the calorific value. Thereby, in an internal combustion engine in which it is difficult to detect the combustion state of the main fuel and the combustion state of the auxiliary fuel separately, it is possible to optimize the supply conditions of the auxiliary fuel and optimize the combustion state in the combustion chamber. . Therefore, the fuel supply control system for an internal combustion engine of the present invention can improve the combustion efficiency.

1 is a schematic configuration diagram of an engine system to which a fuel supply control system for an internal combustion engine according to an embodiment of the present invention is applied. It is a characteristic view showing the relationship between the calorific value of sub fuel and the total calorific value of main fuel and sub fuel. It is a flowchart of the fuel supply control process in the fuel supply control system of the internal combustion engine by one Embodiment of this invention. It is a characteristic view showing the relationship between the ignition delay of the auxiliary fuel and the calorific value of the auxiliary fuel in the fuel supply control system for the internal combustion engine according to the embodiment of the present invention. It is a characteristic view showing the relationship between the injection amount per injection of the auxiliary fuel and the cooling loss in the fuel supply control system of the internal combustion engine according to the embodiment of the present invention. It is a characteristic view showing the relationship between the combustion start timing of the auxiliary fuel and the maximum value of the pressure of the combustion chamber in the fuel supply control system of the internal combustion engine according to one embodiment of the present invention.

  Hereinafter, a fuel supply control system for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

(One embodiment)
A sub fuel injection control system 1 as a “fuel supply control system for an internal combustion engine” according to an embodiment of the present invention is applied to an engine system 5 mounted on a vehicle or the like. The auxiliary fuel injection control system 1 includes an air amount sensor 71 as “oxygen concentration detection means”, a temperature sensor 72 as “combustion chamber temperature detection means”, a crank angle sensor 73 as “crank angle detection means”, and “ As a "control section", "combustion start timing calculation means", "heat generation amount calculation means", "delay calculation means", "heat generation amount determination means", "supply amount determination means", and "combustion start timing determination means" The auxiliary fuel injection control unit 70 is provided.

  A schematic configuration of an engine system 5 to which the auxiliary fuel injection control system 1 is applied will be described with reference to FIG. The engine system 5 includes an engine 10 as an “internal combustion engine” using hydrogen as “main fuel” and light oil as “sub fuel”. The engine 10 has a plurality of combustion chambers 11, 12, 13, and 14. An intake passage 200 and an exhaust passage 300 through which air introduced from the atmosphere flows are communicated with the combustion chambers 11, 12, 13, and 14. A variable nozzle turbo 40 is provided between the intake pipe 20 having the intake passage 200 and the exhaust pipe 30 having the exhaust passage 300. In FIG. 1, the flow of air, recirculation exhaust, fuel, and the like in the engine system 5 is indicated by a solid arrow F.

The intake pipe 20 forms an intake passage 200 that communicates the intake ports 111, 121, 131, and 141 of the engine 10 with the atmosphere. The intake pipe 20 is provided with a compressor section 43, an intercooler 21, a flow control valve 22, and the like of the variable nozzle turbo 40 from the atmosphere side.
A low-pressure exhaust gas recirculation pipe 51 is connected to the atmosphere side from the position where the compressor section 43 of the intake pipe 20 is provided. Further, a high-pressure exhaust gas recirculation pipe 61 is connected to the engine 10 side from the position where the flow rate control valve 22 of the intake pipe 20 is provided. Further, the main fuel pipe 15 having the main fuel passage 150 communicating with the intake passage 200 is connected to the engine 10 side from the position where the high pressure exhaust gas recirculation pipe 61 of the intake pipe 20 is connected.

  The intercooler 21 cools the air flowing through the intake passage 200 and the recirculated exhaust flowing through the low-pressure exhaust recirculation pipe 51.

  The flow rate control valve 22 adjusts the flow rates of the air flowing through the intake passage 200 and the recirculated exhaust gas. The flow control valve 22 is electrically connected to the auxiliary fuel injection control unit 70. The flow control valve 22 outputs a signal corresponding to the opening degree of the flow control valve 22 to the auxiliary fuel injection control unit 70.

The main fuel pipe 15 is provided with a reformer 151 and a flow rate control valve 152.
The reformer 151 reforms an organic compound, for example, methanol, supplied from a fuel tank (not shown) using the heat of the exhaust, and generates hydrogen as “main fuel”. The flow rate of the generated hydrogen is controlled by the flow rate control valve 152 and passes through the main fuel passage 150 and flows into the intake passage 200 and the recirculated exhaust gas. A mixture of air, recirculated exhaust gas, and hydrogen is sucked into the combustion chambers 11, 12, 13, 14 through intake ports 111, 121, 131, 141. The flow control valve 152 and the flow control valve 22 are electrically connected to the auxiliary fuel injection control unit 70.

The exhaust pipe 30 forms an exhaust passage 300 that connects the exhaust ports 112, 122, 132, and 142 of the engine 10 and the atmosphere. The exhaust pipe 30 is provided with a turbine section 42 of the variable nozzle turbo 40, a catalyst 31, a flow control valve 44 of the variable nozzle turbo 40, a reformer 151, and the like from the engine 10 side.
A high pressure exhaust gas recirculation pipe 61 is connected between the engine 10 of the exhaust pipe 30 and the turbine section 42. Further, a low pressure exhaust gas recirculation pipe 51 is connected between the catalyst 31 of the exhaust pipe 30 and the flow rate control valve 44.
The catalyst 31 decomposes chemical substances such as nitrogen oxides contained in the exhaust discharged from the combustion chambers 11, 12, 13, and 14.

The variable nozzle turbo 40 has a connection part 41, a turbine part 42, a compressor part 43, a flow control valve 44, and the like.
The connecting portion 41 rotatably accommodates a shaft (not shown) that connects a turbine (not shown) of the turbine portion 42 and a compressor (not shown) of the compressor portion 43. The shaft transmits the rotational torque of the turbine rotated by the exhaust flowing through the exhaust passage 300 to the compressor. The compressor is rotated by the rotational torque transmitted by the shaft, and pressurizes the air flowing through the intake passage 200 and the reflux exhaust.
The flow control valve 44 controls the rotational speed of the turbine by controlling the flow rate through the exhaust passage 300.

A low-pressure exhaust gas recirculation unit 50 that connects the atmosphere side from the compressor unit 43 of the intake pipe 20 and the atmospheric side from the turbine unit 42 of the exhaust pipe 30 without passing through the engine 10 includes a low-pressure exhaust recirculation pipe 51, a low-pressure recirculation exhaust cooler. 52, a flow control valve 53, and the like.
The low pressure exhaust recirculation pipe 51 forms a low pressure exhaust passage 510 that connects the intake passage 200 and the exhaust passage 300. The low pressure recirculation exhaust cooler 52 cools the relatively low pressure recirculation exhaust flowing through the low pressure exhaust passage 510. The flow rate control valve 53 controls the flow rate of the recirculated exhaust gas flowing through the low pressure exhaust passage 510. The flow control valve 53 is electrically connected to the auxiliary fuel injection control unit 70. The flow control valve 53 outputs a signal corresponding to the opening degree of the flow control valve 53 to the auxiliary fuel injection control unit 70.

A high-pressure exhaust gas recirculation unit 60 that connects the compressor 10 of the intake pipe 20 to the engine 10 side and the turbine unit 42 of the exhaust pipe 30 to the engine 10 side without passing through the engine 10 includes a high-pressure exhaust gas recirculation pipe 61 and a high-pressure recirculation pipe 61. An exhaust cooler 62, a flow control valve 63, and the like are included.
The high pressure exhaust recirculation pipe 61 forms a high pressure exhaust passage 610 that connects the intake passage 200 and the exhaust passage 300. The high-pressure recirculation exhaust cooler 62 cools the relatively high-pressure recirculation exhaust flowing through the high-pressure exhaust passage 610. The flow rate control valve 63 controls the flow rate of the recirculated exhaust gas flowing through the high pressure exhaust passage 610. The flow rate control valve 63 is electrically connected to the auxiliary fuel injection control unit 70. The flow control valve 63 outputs a signal corresponding to the opening degree of the flow control valve 63 to the auxiliary fuel injection control unit 70.

  The engine 10 is provided with auxiliary fuel injection valves 16, 17, 18, and 19 as “auxiliary fuel supply units” that can inject light oil directly into the combustion chambers 11, 12, 13, and 14. The auxiliary fuel injection valves 16, 17, 18, and 19 are electrically connected to the auxiliary fuel injection control unit 70.

The auxiliary fuel injection control unit 70 is configured by a microcomputer including a CPU, a ROM, a RAM, an input / output port, and the like.
The auxiliary fuel injection control unit 70 detects the amount of air flowing through the intake passage 200, and detects the temperature of the air-fuel mixture of the air flowing through the intake ports 111, 121, 131, 141, the recirculated exhaust gas, and hydrogen. The temperature sensor 72 and the crank angle sensor 73 for detecting the crank angle of the engine 10 are electrically connected. In the auxiliary fuel injection control unit 70, in addition to the signals output from the air amount sensor 71, the temperature sensor 72, the crank angle sensor 73, etc., based on the output command value to the engine 10 output from the host vehicle control unit (not shown), The auxiliary fuel injection valves 16, 17, 18, 19 control injection conditions as “supply conditions” of auxiliary fuel injected into the combustion chambers 11, 12, 13, 14.

Next, the combustion characteristics of the engine 10 that uses both hydrogen and light oil as fuel will be described.
In the engine system 5 using hydrogen, which is relatively low in self-ignitability, as a main fuel, it is difficult for the flame to be efficiently propagated in the combustion of hydrogen. For this reason, when only hydrogen is burned, there is a risk of misfire. Therefore, in the engine system 5, after supplying hydrogen to the combustion chambers 11, 12, 13, 14 using the main fuel pipe 15, the self-ignitability is relatively low using the auxiliary fuel injection valves 16, 17, 18, 19. High light oil is injected into the combustion chambers 11, 12, 13, 14. This makes it easier to burn than when only hydrogen is burned, but it does not burn even if light oil is supplied depending on the state of the mixture of the air in the combustion chambers 11, 12, 13, 14, the recirculated exhaust gas, and hydrogen. There is a fear.

In FIG. 2, the calorific value of light oil as the amount of heat generated when light oil is combusted in the engine 10, and the total calorific value that is the sum of the calorific value of hydrogen and the calorific value of light oil as the amount of heat generated when hydrogen is combusted, The characteristic view showing the relationship is shown. In FIG. 2, the horizontal axis represents the calorific value Qbp in light oil combustion, and the vertical axis represents the total calorific value Qall.
As shown in FIG. 2, when the calorific value Qbp of light oil is increased, the total calorific value Qall rapidly increases when the calorific value Qbp of light oil becomes equal to or greater than the calorific value Qbpmin as the “predetermined calorific value”. That is, when the calorific value Qbp of the light oil is lower than the calorific value Qbpmin, even if the light oil is supplied to the combustion chambers 11, 12, 13, and 14, hydrogen hardly burns. For this reason, there exists a possibility that the engine 10 cannot generate an output.
Therefore, in the auxiliary fuel injection control system 1 according to the embodiment, the auxiliary fuel injection control process is performed according to the flowchart shown in FIG.

First, in step (hereinafter referred to as “S”) 101, oxygen concentrations and temperatures of the combustion chambers 11, 12, 13, and 14 of the engine 10 are calculated. Specifically, the auxiliary fuel injection control unit 70 includes the oxygen concentration of the mixture of air, recirculated exhaust gas, and hydrogen sucked into the combustion chambers 11, 12, 13, 14, and the combustion chambers 11, 12, 13, 14 calculates the temperature of the air-fuel mixture sucked.
Of the mixture of air, recirculated exhaust gas, and hydrogen sucked into the combustion chambers 11, 12, 13, and 14, the amount of air is detected by an air amount sensor 71. Further, the amount of low-pressure recirculation exhaust is controlled by the opening degree of the flow control valve 53, and the amount of high-pressure recirculation exhaust is controlled by the opening degree of the flow control valve 63. Since the low-pressure recirculation exhaust and the high-pressure recirculation exhaust are part of exhaust exhausted by past combustion in the engine 10, the oxygen concentration contained in the exhaust can be estimated from the operating state of the engine 10 or the like. Therefore, the auxiliary fuel injection control unit 70 outputs a signal based on the opening of the flow control valve 53 output from the flow control valve 53, a signal based on the opening of the flow control valve 63 output from the flow control valve 63, and an air amount sensor 71. Is used to calculate the oxygen concentration of the combustion chambers 11, 12, 13, and 14.
Further, the auxiliary fuel injection control unit 70 calculates the temperature of the air-fuel mixture of the air, the recirculated exhaust gas, and the hydrogen sucked into the combustion chambers 11, 12, 13, 14 based on the signal output from the temperature sensor 72.

  Next, in S102, light oil injection conditions are determined based on the operating state of the engine 10 detected by the auxiliary fuel injection control unit 70. From the relationship between the output command value of the engine 10 and the rotational speed of the engine 10, the auxiliary fuel injection control unit 70 determines the injection start timing Ts as the “supply start timing” that is the light oil injection condition, and the “total supply amount” as It has a map that can read the total injection amount Qip in one combustion cycle and the number of injections Np of light oil in one combustion cycle as “number of times of supply”. In the auxiliary fuel injection control unit 70, based on the output command value of the engine 10 output by the host vehicle control unit, the crank angle of the engine 10 output by the crank angle sensor 73, and the map, the injection start timing Ts, The injection amount Qip and the number of injections Np are determined.

Next, in S103, the ignition delay τp of light oil and the calorific value Qbp of light oil are calculated.
Here, the ignition delay τp of light oil refers to the time difference from the injection start timing at which light oil injection starts to the combustion start timing at which light oil starts to burn. In the auxiliary fuel injection control system 1 according to the embodiment, the ignition delay τp of the light oil is, for example, the oxygen concentration in the combustion chambers 11, 12, 13, 14 calculated in S101, the combustion chambers 11, 12, 13, calculated in S101. 14 based on the temperature of 14 and the total injection amount Qip of light oil, using an equation obtained by integrating an Arrhenius speed equation with an energy model for light oil combustion.

Further, the calorific value Qbp of light oil is read based on a map representing the relationship between the total light fuel injection quantity Qip and the ignition delay τp. FIG. 4 shows the relationship between the ignition delay τp of light oil and the calorific value Qbp of light oil. In FIG. 4, the horizontal axis represents the ignition delay τp of light oil, and the vertical axis represents the calorific value of light oil. In FIG. 4, as a specific example, the relationship between the ignition delay τp and the heat generation amount Qbp at a relatively small total injection amount is shown by a broken line Qip1, and the relationship between the ignition delay τp and the heat generation amount Qbp at a relatively large total injection amount is shown. This is indicated by the solid line Qip2. Generally, when the total injection amount Qip is large, the heat generation amount increases, but even with the same total injection amount, the heat generation amount decreases as the ignition delay increases.
The auxiliary fuel injection control unit 70 has a map representing the relationship between the light oil total injection amount Qip and the ignition delay τp as shown in FIG. 4, and is calculated first with the total injection amount Qip determined in S102. The calorific value Qbp of light oil is read from the ignition delay τp of light oil.

Next, in S104, it is determined whether or not the calorific value Qbp of light oil is equal to or greater than a predetermined calorific value. The sub fuel injection control unit 70 determines whether or not the calorific value Qbp of the light oil is greater than or equal to a predetermined calorific value based on the map as shown in FIG.
FIG. 4 shows a calorific value Qbpmin indicating a boundary between a region where combustion of the combustion chambers 11, 12, 13 and 14, a mixture of air, recirculated exhaust gas, and hydrogen is sustainable for combustion and a region where misfiring occurs. When the calorific value Qbp read in S103 is smaller than the calorific value Qbpmin, the mixture in the combustion chambers 11, 12, 13, and 14 misfires. In S104, if the auxiliary fuel injection control unit 70 determines that the heat generation amount Qbp is equal to or greater than the heat generation amount Qbpmin, the process proceeds to S106. If the auxiliary fuel injection control unit 70 determines that the heat generation amount Qbp is smaller than the heat generation amount Qbpmin, the process proceeds to S105.

  In S105, the total injection amount Qip of light oil is increased. Accordingly, as shown in FIG. 4, when the total injection amount is increased from, for example, the total injection amount shown by the broken line Qip1 to the total injection amount shown by the solid line Qip2, the heat generation amount at the same ignition delay τp0 increases, and the heat generation amount Qbp becomes The calorific value is larger than Qbpmin. Thereby, in S105, misfire of the mixture of air, recirculated exhaust gas, and hydrogen is avoided even at the same ignition delay τp.

Next, in S106, the injection amount per injection is calculated.
The total injection amount of light oil in one combustion cycle determined in S101 or the total injection amount of light oil in one combustion cycle increased in S105 is the number of injections Np of light oil in one combustion cycle determined in S101. The injection amount per injection (Qip / Np) as “supply amount per supply” is calculated.

  Next, in S107, it is determined whether or not the injection amount per injection is smaller than a predetermined injection amount. In S107, the injection amount per injection (Qip / Np) calculated in S106 is compared with a predetermined injection amount as a threshold value at which the cooling loss in combustion of the engine 10 increases.

FIG. 5 is a characteristic diagram showing the relationship between the injection amount per injection and the cooling loss in engine combustion. In FIG. 5, the horizontal axis indicates the injection amount (Qi / N) per injection, and the vertical axis indicates the cooling loss CL0 in engine combustion.
When the fuel is directly injected into the combustion chamber, if the injection amount is large, the injected fuel tends to collide with the inner wall of the cylinder forming the combustion chamber. Since the inner wall of the cylinder is kept at a relatively low temperature, the collided fuel is cooled and the cooling loss CL0 is increased. As shown in FIG. 5, when the injection amount per injection (Qi / N) is greater than the injection amount (Qi0 / N) as “a predetermined supply amount per supply”, the cooling loss CL0 increases. , Engine combustion efficiency decreases.

  Therefore, in the sub fuel injection control system 1 according to the embodiment, it is determined whether or not the injection amount (Qip / Np) per injection calculated in S106 is smaller than the injection amount (Qi0 / N). If the sub fuel injection control unit 70 determines in S107 that the injection amount per injection (Qip / Np) is smaller than the injection amount (Qi0 / N), the process proceeds to S109. If the auxiliary fuel injection control unit 70 determines that the injection amount per injection (Qip / Np) is equal to or greater than the injection amount (Qi0 / N), the process proceeds to S108.

  In S108, the auxiliary fuel injection control unit 70 increases the number of injections determined in S102 by one by increasing the number of injections in one combustion cycle. In S108, after increasing the number of injections once, the process returns to S106, and the injection amount per injection (Qip / Np) in one combustion cycle is calculated. Next, in S107, it is determined again whether or not the injection amount per injection is smaller than the injection amount (Qi0 / N). At this time, if it is determined that the injection amount (Qip / Np) per injection is smaller than the injection amount (Qi0 / N), the process proceeds to S109. If it is determined that the injection amount per injection is equal to or greater than the injection amount (Qi0 / N), the process proceeds to S108 again. That is, in S106 to S108, the number of injections is increased until the injection amount (Qip / Np) per injection becomes smaller than the injection amount (Qi0 / N), thereby reducing the cooling loss.

  Next, in S109, the injection pattern of the light oil injection amount determined in S102 or S105 and the number of light oil injections determined in S102 or S108 are set.

  Next, in S110, the light oil combustion start timing θ10 is calculated. Specifically, the auxiliary fuel injection control unit 70 calculates the oxygen concentration of the combustion chambers 11, 12, 13, and 14 calculated in S101, the temperatures of the combustion chambers 11, 12, 13, and 14 calculated in S101, and An ignition delay τp is newly calculated based on the light oil total injection amount Qip determined in S102 or S105. The auxiliary fuel injection control unit 70 calculates the light oil combustion start timing θ10 based on the light oil injection start timing Ts set in S109 and the newly calculated ignition delay τp.

Next, in S111, it is determined whether the combustion start timing of light oil is on the retard side with respect to a predetermined crank angle.
FIG. 6 shows the relationship between the start timing of light oil combustion and the maximum value of the pressure in the combustion chamber. In FIG. 6, the horizontal axis represents the combustion start timing θ10 of the light oil by the crank angle, and the vertical axis represents the maximum value Pmax of the pressure in the combustion chamber. Generally, the maximum value Pmax increases when the combustion start timing θ10 is close to the top dead center when the combustion start timing θ10 shifts from the compression stroke to the expansion stroke. However, if the combustion start timing θ10 is more advanced than the crank angle θL that is the “predetermined crank angle”, the maximum value Pmax becomes larger than the threshold pressure P0, and the cylinder may be damaged.

  Therefore, in the auxiliary fuel injection control system 1 according to the embodiment, a map that represents the relationship between the light oil combustion start timing θ10 and the maximum value Pmax of the combustion chamber that the auxiliary fuel injection control unit 70 has, and the crank angle sensor 73. Based on the crank angle of the engine 10 detected by the engine, it is determined whether or not the combustion start timing θ10 of light oil is retarded from the crank angle θL. In S111, when it is determined that the combustion start timing of the light oil is retarded from the predetermined crank angle θL, the auxiliary fuel injection control process is terminated. In S111, if it is determined that the combustion start timing of the light oil is on the advance side from the predetermined crank angle θL, the process proceeds to S112.

In S112, the auxiliary fuel injection control unit 70 shifts the light oil injection start timing Ts to the retard side. As calculated in S110, the light oil combustion start timing θ10 is calculated based on the light oil injection start timing Ts and the ignition delay τp. Therefore, in S112, the light oil combustion start timing θ10 is changed to the retard side by changing the light oil injection start timing Ts to the retard side.
The horizontal axis of FIG. 6 shows the injection start timing Ts together with the combustion start timing θ10. In S112, as shown in FIG. 6, the light oil injection start timing Ts1 is set to the retarded-side injection start timing Ts2 so that the maximum value of the pressure in the combustion chamber becomes smaller than the threshold pressure P0. Thereafter, the auxiliary fuel injection control process is terminated.

  In the auxiliary fuel injection control system 1 according to the embodiment, the auxiliary fuel injection control unit 70 calculates the ignition delay τp of light oil and the calorific value Qbp of light oil. The auxiliary fuel injection control unit 70, based on these two values indicating the operating state of the engine 10, the injection start timing Ts that is the injection condition of light oil, the total injection amount Qip in one combustion cycle, The number Np of light oil injections in the combustion cycle is determined. At this time, the auxiliary fuel injection control unit 70 does not misfire the air-fuel mixture of the combustion chambers 11, 12, 13, 14 in accordance with the flow from S103 to S112 shown in FIG. Correct injection conditions to reduce losses. Thereby, in the engine 10 which uses hydrogen and light oil together as fuel, the injection condition of light oil can be optimized, and the combustion state of hydrogen in the combustion chambers 11, 12, 13, and 14 can be optimized. Therefore, the auxiliary fuel injection control system 1 according to the embodiment can improve the combustion efficiency of the engine 10.

  In the auxiliary fuel injection control system 1 according to the embodiment, the amount of air taken into the combustion chambers 11, 12, 13, and 14 detected by the air amount sensor 71, the combustion chambers 11, 12, 13, and The ignition delay τp of light oil and the calorific value Qbp of light oil are calculated based on the temperature of the mixture of air, recirculated exhaust gas, and hydrogen immediately before being sucked into 14. Thereby, the combustion state of the auxiliary fuel in the combustion chamber can be accurately grasped as compared with the case where the combustion state of the auxiliary fuel in the combustion chamber is grasped based on the pressure change in the combustion chamber. Therefore, the combustion efficiency of the engine 10 can be further improved.

(Other embodiments)
(A) In the above-described embodiment, the ignition delay of the light oil is determined based on the amount of air detected by the air amount sensor, and the temperature of the mixture of air, recirculated exhaust gas, and hydrogen sucked into the combustion chamber detected by the temperature sensor. The calorific value of light oil was calculated. However, the calculation method of the ignition delay and the calorific value is not limited to this.

  (A) In the above-described embodiment, the heat generation amount of light oil is read from the map based on the ignition delay of light oil and the total injection amount of light oil. However, the calorific value calculation method is not limited to this. The calorific value of the light oil may be calculated from an equation that can calculate the calorific value of the light oil based on the ignition delay of the light oil and the total injection amount of the light oil.

  (C) In the above-described embodiment, the engine system uses hydrogen and light oil as fuels. However, the engine system to which the auxiliary fuel injection control system is applied is not limited to this. Any engine system that is supplied with main fuel and auxiliary fuel that assists combustion of the main fuel may be used.

  (D) In the above-described embodiment, hydrogen having a relatively low self-ignitability is used as the main fuel, and light oil having a relatively high self-ignitability is used as the auxiliary fuel. However, the type of fuel is not limited to this.

  (E) In the above-described embodiment, the light oil is supplied to the combustion chamber by the auxiliary fuel injection valve that injects fuel directly into the combustion chamber. However, the method of supplying light oil is not limited to this.

  (F) In the above-described embodiment, the auxiliary fuel injection control unit includes the “control unit”, “combustion start timing calculation unit”, “heat generation amount calculation unit”, “delay calculation unit”, “heat generation amount determination unit”, “ It is assumed that they are provided as “supply amount determination means” and “combustion start timing determination means”. However, these components may be provided separately.

  The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

1 ... Sub fuel injection control system (fuel supply control system for internal combustion engine),
10 ... Engine (internal combustion engine),
16, 17, 18, 19 ... sub fuel injection valve (sub fuel supply part),
70 ... Sub fuel injection control unit 70 (control unit, combustion start timing calculation means, heat generation amount calculation means, delay calculation means, heat generation amount determination means, supply amount determination means, combustion start timing determination means)
71 ... Oxygen concentration sensor (oxygen concentration detection means),
72 ... Temperature sensor (combustion chamber temperature detection means),
73 ... Crank angle sensor (crank angle detecting means).

Claims (4)

The main fuel supplied to the intake system (20) and the auxiliary fuel that is supplied to the combustion chambers (11, 12, 13, 14) of the internal combustion engine (10) and has higher self-ignitability than the main fuel and assists the combustion of the main fuel. an internal combustion engine fuel supply control system for controlling the supply of secondary fuel to the internal combustion institution to which the fuel is supplied (1),
Crank angle detecting means (73) for detecting a crank angle of the crankshaft of the internal combustion engine and outputting a signal corresponding to the detected crank angle;
A control unit (70) for controlling the operation of a sub fuel supply unit (16, 17, 18, 19) for supplying sub fuel to the internal combustion engine;
A calorific value calculation means (70) for calculating a calorific value (Qbp) in the combustion of the auxiliary fuel;
Combustion start timing calculating means (70) for calculating the combustion start timing of the auxiliary fuel;
It is determined whether or not the calorific value calculated by the calorific value calculation means is greater than or equal to a predetermined calorific value (Qbpmin) based on a map showing the relationship between the calorific value and the total calorific value (Qall) in the combustion of the auxiliary fuel. Calorific value determination means (70);
Based on the map showing the relationship between the injection amount per injection (Qi / N) and the cooling loss (CL0) in the combustion of the internal combustion engine, the total supply amount of sub fuel in one combustion cycle of the internal combustion engine ( Qip) divided by the number of sub fuel supplies in one combustion cycle, whether or not the supply amount per supply (Qip / Np) is smaller than a predetermined supply amount (Qi0 / N) Supply amount determination means (70) for determining
The combustion start timing (θ10) of the auxiliary fuel calculated by the combustion start timing calculation means based on a map showing the relationship between the combustion start timing of the auxiliary fuel and the maximum value (Pmax) of the pressure in the combustion chamber is a predetermined crank angle. Combustion start timing determination means (70) for determining whether or not the angle is on the retard side with respect to (θL);
With
The controller is
When the calorific value determination means determines that the calorific value of the auxiliary fuel in one combustion cycle of the internal combustion engine is less than the predetermined calorific value, the calorific value of the auxiliary fuel in one combustion cycle of the internal combustion engine is Increase the total supply amount of secondary fuel so that it exceeds the predetermined heat generation amount,
When the supply amount determination means determines that the supply amount per supply is equal to or greater than the supply amount per predetermined supply, the supply amount per supply is more than the supply amount per predetermined supply. Increasing the number of times the auxiliary fuel is supplied in one combustion cycle of the internal combustion engine so as to be reduced,
When the combustion start timing determination means determines that the combustion start timing of the auxiliary fuel is an advance side from the predetermined crank angle, the auxiliary fuel is set so that the combustion start timing of the auxiliary fuel is retarded from the predetermined crank angle. The fuel supply control system for an internal combustion engine is characterized in that the supply start timing (Ts) is changed to the retard side. Detecting the oxygen concentration before Ki燃 combustion chamber, the oxygen concentration detection means for outputting a signal corresponding to the detected oxygen concentration (71),
Combustion chamber temperature detection means (72) for detecting the temperature of the combustion chamber and outputting a signal corresponding to the detected temperature;
With
The combustion start timing calculating means calculates the combustion start timing of the auxiliary fuel based on the oxygen concentration in the combustion chamber, the temperature of the combustion chamber, and the total supply amount of the auxiliary fuel. A fuel supply control system for an internal combustion engine as described. A delay calculating means (70) for calculating an ignition delay that is a time difference between the supply start timing of the auxiliary fuel and the combustion start timing of the auxiliary fuel;
The fuel supply control system for an internal combustion engine according to claim 1 or 2, wherein the heat generation amount calculation means calculates a heat generation amount of the auxiliary fuel based on the ignition delay calculated by the delay calculation means.   The fuel supply control system for an internal combustion engine according to any one of claims 1 to 3, wherein the main fuel is hydrogen and the auxiliary fuel is light oil.

Images