JP2006299831A - Internal combustion engine and control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a combustion state in a period from the start of reflux of reformed gas to the arrival of the reformed gas into a combustion chamber. <P>SOLUTION: An internal combustion engine 1 is equipped with a reformer 20 which reforms the reformation mixture Gmr of reformation fuel Fr and exhaust gas Ex discharged from the internal combustion engine by a reforming catalyst and generates the reformed gas Exr containing hydrogen. It is judged from combustion ion current in the combustion chambers whether or not the reformed gas Exr reaches the combustion chambers of cylinders 1S<SB>1</SB>-1S<SB>4</SB>. When the reformed gas Exr is judged to have reached the combustion chambers, the engine 1 is operated with ignition timing delayed than before the reformation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine that recirculates a reformed gas obtained by reforming an air-fuel mixture of exhaust gas and fuel, and an operation control device for the internal combustion engine.

  There is known a technique in which fuel is added to exhaust gas of an internal combustion engine, and a reformed gas obtained by reforming a mixture of the two with a reforming catalyst is supplied to an intake pipe of the internal combustion engine through a reflux pipe (for example, Patent Documents). 1).

JP 2004-92520 A

  However, since the reformed gas reaches the combustion chamber of the internal combustion engine through the recirculation passage and the intake pipe, the recirculation gas is not immediately supplied to the combustion chamber even when the recirculation of the reformed gas is started. Therefore, when the internal combustion engine is operated assuming that the reformed gas has reached the recirculation in the period from the start of the recirculation of the reformed gas until the reformed gas reaches the combustion chamber, the combustion state becomes unstable. The internal combustion engine may not operate properly. Patent Document 1 makes no mention of this point, and there is room for improving the combustion state during the period.

  Accordingly, the present invention has been made in view of the above, and is an internal combustion engine capable of stabilizing the combustion state in a period from when the reformed gas starts to recirculate until the reformed gas reaches the combustion chamber. And an operation control device for an internal combustion engine.

  In order to solve the above-mentioned problems and achieve the object, an internal combustion engine according to the present invention ignites an air-fuel mixture supplied from an intake passage by an ignition means and burns it in a combustion chamber. An internal combustion engine to be driven, wherein a reforming mixture of fuel and exhaust gas discharged from the internal combustion engine is reformed by a reforming catalyst to generate a reformed gas containing hydrogen, and the reformed gas Reforming means for recirculating gas to the combustion chamber, reformed gas arrival determining means for determining whether the reformed gas has reached the combustion chamber, and after the reformed gas has reached the combustion chamber Includes an operation parameter changing means for operating the internal combustion engine with the operation parameter having a value when the reformed gas is recirculated.

  This internal combustion engine determines whether or not the reformed gas has reached the combustion chamber, and operates with operating parameters when the reformed gas is recirculated after the reformed gas reaches the combustion chamber. Thus, after the reformed gas is reliably introduced into the combustion chamber, the operation can be performed with the operation parameters suitable for the reformed gas recirculation. As a result, stable combustion is obtained during the period in which the reformed gas reaches the combustion chamber from the start of the reformed gas recirculation.

  In the internal combustion engine according to the next aspect of the present invention, in the internal combustion engine, the operation parameter is an ignition timing of the ignition means, and the operation parameter change means changes the reforming gas when the reformed gas reaches the combustion chamber. When the quality gas arrival determination means determines, the ignition timing by the ignition means is delayed more than before the reformed gas reaches the combustion chamber.

  The internal combustion engine according to the present invention is characterized in that, in the internal combustion engine, the reformed gas arrival determination means determines the arrival of the reformed gas by determining a combustion state in the combustion chamber. .

  In the internal combustion engine according to the next invention, in the internal combustion engine, the combustion state in the combustion chamber of the internal combustion engine is at least one of a combustion ion current in the combustion chamber and a combustion pressure in the combustion chamber. It is determined by using as a combustion state determination parameter for determination.

  In the internal combustion engine according to the next aspect of the present invention, after the operating parameter changing means operates the reforming means and starts recirculation of the reformed gas, the combustion state in the combustion chamber once deteriorates. Then, the operating parameter is changed after the combustion state of the air-fuel mixture in the combustion chamber is improved than before the recirculation of the reformed gas is started.

  In the internal combustion engine according to the next aspect of the present invention, in the internal combustion engine, the operation parameter changing means is configured so that the reformed gas reaches the combustion chamber when the combustion state determination parameter becomes larger than a predetermined threshold value. It is characterized by determining that it has been.

  An internal combustion engine operation control apparatus according to the present invention is driven by igniting an air-fuel mixture of air and fuel supplied from an intake passage by an ignition means and combusting in a combustion chamber, and fuel, A reforming means for reforming a reforming gas mixture with exhaust gas discharged from an internal combustion engine by a reforming catalyst to generate a reformed gas containing hydrogen and recirculating the reformed gas to the combustion chamber; An internal combustion engine comprising: a gas arrival determination unit for determining whether or not the reformed gas has reached the combustion chamber; and reforming after the reformed gas has reached the combustion chamber And an operation parameter changing unit that changes the operation parameter so that the internal combustion engine can be operated with the operation parameter at the time of gas recirculation.

  This internal combustion engine operation control device determines whether or not the reformed gas has reached the combustion chamber, and after the reformed gas has reached the combustion chamber, operates the internal combustion engine with the operating parameters when the reformed gas recirculates. To do. Thus, after the reformed gas is reliably introduced into the combustion chamber, the internal combustion engine can be operated with operating parameters suitable for the reformed gas recirculation. As a result, stable combustion is obtained during the period in which the reformed gas reaches the combustion chamber from the start of the reformed gas recirculation.

  The internal combustion engine operation control apparatus according to the present invention is the internal combustion engine operation control apparatus, wherein the operation parameter is an ignition timing of the ignition means, and the operation parameter changing unit is configured such that the reformed gas contains the reformed gas. When the gas arrival determination unit determines that it has reached the combustion chamber, the ignition timing by the ignition means is retarded from before the reformed gas reaches the combustion chamber.

  In the internal combustion engine operation control apparatus according to the next aspect of the present invention, in the operation control apparatus for the internal combustion engine, the gas arrival determination unit determines arrival of the reformed gas by determining a combustion state in the combustion chamber. It is characterized by doing.

  The internal combustion engine operation control apparatus according to the present invention is characterized in that, in the internal combustion engine operation control apparatus, the gas arrival determination unit is configured such that a combustion ion current when the air-fuel mixture burns in the combustion chamber, or the combustion chamber The combustion state in the combustion chamber of the internal combustion engine is determined using at least one of the pressures as a combustion state determination parameter for determining the combustion state.

  The internal combustion engine operation control apparatus according to the next aspect of the present invention is the internal combustion engine operation control apparatus, wherein the operation parameter change unit operates the reforming unit and starts recirculation of the reformed gas, The operating parameter is changed after the combustion state in the combustion chamber is once deteriorated and after the combustion state in the combustion chamber is improved compared to before the recirculation of the reformed gas is started.

  In the internal combustion engine operation control apparatus according to the next aspect of the present invention, in the operation control apparatus for the internal combustion engine, the operation parameter changing unit is configured such that when the combustion state determination parameter is equal to or greater than a predetermined threshold value. It is determined that the reformed gas has reached the combustion chamber.

  The internal combustion engine and the operation control device for the internal combustion engine according to the present invention can stabilize the combustion state in the period from the start of the recirculation of the reformed gas until the reformed gas reaches the combustion chamber.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. The present invention can be preferably applied particularly to an internal combustion engine mounted on a vehicle such as a passenger car, a bus, or a truck.

  In this embodiment, a reformed gas generated by reforming a reforming mixture of reforming fuel and exhaust gas discharged from an internal combustion engine with a reforming catalyst is recirculated to a combustion chamber of the internal combustion engine. It is. Then, it is characterized in that it is determined that the reformed gas has reached the combustion chamber, and then the internal combustion engine is operated with the operation parameters when the reformed gas is recirculated.

FIG. 1 is an overall configuration diagram of an internal combustion engine according to this embodiment. The configuration of the internal combustion engine according to this embodiment will be described with reference to FIG. The internal combustion engine 1 according to this embodiment guides a part of the exhaust gas Ex discharged from the internal combustion engine 1 to a reformer 20 as reforming means, and supplies fuel containing hydrocarbons (HC) to the exhaust gas Ex. This produces hydrogen (H ₂ ). Then, the reformer 20 causes the internal combustion engine 1 to recirculate a gas (hereinafter referred to as a reformed gas) Exr containing hydrogen obtained by the reforming reaction.

Although the internal combustion engine 1 according to this embodiment has four cylinders arranged in series, the number of cylinders and the cylinder arrangement are not limited to this. The internal combustion engine 1 may be a so-called rotary internal combustion engine. The fuel F supplied to the internal combustion engine 1 is supplied to the port injection valve 6 by a feed pump 71 in the fuel tank 70. Then, the fuel is injected from the port injection valve 6 into the intake passage 3 and forms a mixture for combustion with the air A passing through the intake passage 3. The combustion mixture is introduced through the intake manifold 7 _{1-7 4} constituting the intake passage into the combustion chamber of each cylinder 1S ₁ ~1S _4. The combustion air-fuel mixture is ignited and burned by spark plugs SP _{1 to} SP ₄ (subscripts are cylinder numbers, see FIG. 2-2) attached to the cylinders 1S _{1 to} 1S ₄ .

Incidentally, in this embodiment, supplying fuel F to each cylinder of the internal combustion engine 1 by the port injection valve 6 alone, the port injection valve 6 to prepare a few of cylinders, intake of each cylinder 1S ₁ ~1S ₄ The fuel F may be injected independently into the manifolds 7 _{1 to} 7 ₄ . Further, instead of the port injection valve 6, the fuel F may be supplied to the internal combustion engine 1 using a so-called direct injection valve that directly injects fuel into the cylinder. Further, both the port injection valve and the direct injection valve may be provided, and the fuel injection ratio of both may be changed according to the operating conditions of the internal combustion engine 1 to supply the fuel to the internal combustion engine 1.

  The air A supplied to the internal combustion engine 1 is sent to the internal combustion engine 1 after dust and the like are removed by an air cleaner 13 attached to the inlet of the intake passage 3. The flow rate of the air A supplied to the internal combustion engine 1 is adjusted by a throttle valve 4 provided in the intake passage 3. The opening degree of the throttle valve 4 is interlocked with the accelerator 17. In this embodiment, the opening of the accelerator 17 is detected by an accelerator opening sensor 47 and taken into an engine ECU (Electronic Control Unit) 50. Based on the accelerator opening information from the accelerator opening sensor 47, the engine ECU 50 adjusts the opening of the throttle valve 4.

  When the opening of the accelerator 17 is increased, the opening of the throttle valve 4 is increased, and when the opening of the accelerator 17 is decreased, the opening of the throttle valve 4 is decreased. The flow rate of the air A supplied to the internal combustion engine 1 is measured by an air flow sensor 42 provided in the intake passage 3 and upstream of the throttle valve 4. The measured value is taken into the engine ECU 50. The engine ECU 50 determines the fuel supply amount to the internal combustion engine 1 from the intake air amount Ga measured by the air flow sensor 42 and the engine rotational speed Ne of the internal combustion engine 1 measured by the rotational speed sensor 43.

The air-fuel mixture combusted in each of the cylinders 1S _{1 to} 1S ₄ of the internal combustion engine 1 becomes exhaust gas Ex and is discharged to the exhaust manifold 8. The exhaust gas Ex is introduced into the exhaust passage 22 of the reformer 20 through the exhaust passage 9, and gives heat for reforming the exhaust gas Ex. The exhaust gas Ex discharged from the reformer 20 is purified by the purification catalyst 16 and then released into the atmosphere. The purification catalyst 16 may be disposed between the reformer 20 and the internal combustion engine 1. An A / F (Air / Fuel) sensor 45 is attached to the exhaust passage 9 and measures the air-fuel ratio of the exhaust gas Ex. Then, the combustion state of the internal combustion engine 1 is determined from the air-fuel ratio of the exhaust gas Ex, and when it deviates from the predetermined air-fuel ratio, the fuel supply amount to the internal combustion engine 1 determined by the engine ECU 50 is corrected.

  A reforming conduit 11 branches from the exhaust passage 9, and the reforming conduit 11 is connected to the reforming chamber 21 of the reformer 20. The reforming conduit 11 is provided with a reforming fuel injection valve 24 which is a reforming fuel supply means, and the exhaust gas Ex led from the reforming fuel injection valve 24 to the reforming conduit 11. The reforming fuel Fr is injected. Fuel is supplied to the reforming fuel injection valve 24 from a feed pump 71 in the fuel tank 70. An evaporator may be provided at the outlet of the reforming fuel injection valve 24 to promote the evaporation of the reforming fuel.

  The reformer 20 includes a reforming chamber 21 and an exhaust passage 22. A reforming catalyst is supported on the inner wall surface of the reforming chamber 21, and the reforming catalyst is heated by the heat of the exhaust gas Ex flowing through the exhaust passage 22 and is maintained at the activation temperature θa or higher. The reformer 20 includes a plurality of reforming chambers 21, and the reforming chambers 21 communicate with each other, and a mixture (reforming mixture) Gmr of the exhaust gas Ex and the reforming fuel Fr is modified. It is reformed while passing through the quality chamber 21. Here, as the reforming catalyst, for example, a zirconia-based catalyst or a rhodium-based catalyst is used.

  A reforming catalyst bed temperature sensor 44 is attached to the reformer 20 in order to measure the temperature of the reforming catalyst. Since it is difficult to measure the temperature of the reforming catalyst itself, the temperature of the catalyst bed carrying the reforming catalyst is measured to obtain the reforming catalyst temperature. When the reforming catalyst temperature is low, the hydrogen concentration in the reformed gas Exr is low, and the hydrogen concentration in the reformed gas Exr increases as the reforming catalyst temperature increases. For this reason, the temperature of the reforming catalyst is monitored by the reforming catalyst bed temperature sensor 44 so that the reforming of the exhaust gas Ex is started after the reforming catalyst temperature becomes equal to or higher than the activation temperature θa. When a rhodium-based reforming catalyst is used, the activation temperature θa is about 600 ° C.

  A gas recirculation passage 10 that connects the reforming chamber 21 and the intake passage 3 is attached to the outlet 21 o of the reforming chamber 21. The gas recirculation passage 10 has a function of recirculating the exhaust gas Ex or the reformed gas Exr to the intake side of the internal combustion engine 1, that is, the intake passage 3. The gas recirculation passage 10 is provided with a cooler 12 for cooling the exhaust gas (reformed gas Exr) reformed in the reforming chamber 21. A recirculation flow rate adjusting valve 5 that is a recirculation flow rate adjusting means is provided between the cooler 12 and the outlet 10 o of the gas recirculation passage 10. The flow rate of the quality gas Exr is adjusted.

The exhaust gas Ex led from the exhaust passage 9 to the reforming conduit 11 is injected with reforming fuel Fr from the reforming fuel injection valve 24. The reforming fuel Fr is a part of the fuel F supplied to the cylinders 1S ₁ to 1S _{4 of} the internal combustion engine 1, and the supply amount of the reforming fuel Fr is determined according to the operating conditions of the internal combustion engine 1. The The reforming mixture Gmr of the reforming fuel Fr and the exhaust gas Ex is introduced into the reforming chamber 21 from the reforming conduit 11 and is expressed by the formula ( The reformed gas Exr is reformed by the reforming reaction shown in 1).
_{1.56 (7.6CO 2 + 6.8H 2 O} + 40.8N 2) + 3C 7.6 H 13.6 + 4122kJ → 31H 2 + 34.7CO + 63.6N 2 ··· (1)

  Here, the first term on the left side represents the exhaust gas Ex, the second term on the left side represents fuel (hydrocarbon CH, gasoline in this embodiment), and the right side represents the reformed gas Exr. Hydrogen contained in the reformed gas Exr on the right side is 24 vol% with respect to the total reformed gas volume. Further, this reforming reaction is an endothermic reaction, whereby the thermal energy of the exhaust gas Ex is recovered. Thus, since the exhaust gas Ex is reformed by the endothermic reaction, even if the amount of fuel supplied to the internal combustion engine 1 is the same, the amount of heat generated in the combustion in the internal combustion engine 1 by the amount absorbed by the heat of the exhaust gas Ex. Will increase.

The calorific value of hydrogen (H ₂ ) is 241.7 kJ / mol, and the calorific value of gasoline (CH _1.869 ) is 596.5 kJ / mol. However, the reforming reaction of the formula (1) generates 31 moles of hydrogen from 3 moles of gasoline (fuel). Therefore, when the calorific value is multiplied by the change in the number of moles due to the reforming of the formula (1), the calorific value of the reformed gas Exr is significantly increased as compared with the case where gasoline alone is combusted. As a result, the output torque of the internal combustion engine 1 is increased and the fuel consumption is reduced.

  The reformed gas Exr generated in the reforming chamber 21 is introduced into the intake passage 3 through the gas recirculation passage 10. Since the reformed gas Exr becomes a high temperature around 700 ° C., it is cooled by the cooler 12 provided in the middle of the gas recirculation passage 10 and then introduced into the intake passage 3. The flow rate (recirculation flow rate) of the reformed gas Exr introduced into the intake passage 3 is controlled by the recirculation flow rate adjustment valve 5. The flow rate of the reformed gas Exr introduced into the intake passage 3 is determined based on the operating conditions of the internal combustion engine 1 so that the maximum reformed gas under the operating conditions can be introduced into the internal combustion engine 1. In this case, in consideration of the amounts of hydrogen and carbon monoxide (CO) contained in the reformed gas Exr, the fuel injection amount of the port injection valve 6 is reduced to optimize the air-fuel ratio A / F.

Hydrogen (H ₂ ) contained in the reformed gas Exr has a maximum ignition energy of about 1/10 as compared with gasoline, and a maximum combustion rate of slightly less than 10 times. For this reason, hydrogen burns faster than gasoline. When the reformed gas Exr containing hydrogen obtained by the reforming reaction is supplied to the internal combustion engine 1, the combustion improvement effect is obtained by the hydrogen in the reformed gas Exr.

  In the operation of the internal combustion engine 1, so-called EGR (Exhaust Gas Recirculation), in which the exhaust gas Ex is recirculated to the intake side, may be executed. If EGR is executed when the internal combustion engine 1 is operated at a light load, the pump loss is reduced and fuel consumption can be reduced. However, if the exhaust gas Ex has an excessive flow rate (EGR amount), the combustion speed becomes slow and combustion occurs. Gets worse. As a result, the output torque of the internal combustion engine 1 is lowered and drivability is deteriorated. Since the internal combustion engine 1 according to this embodiment recirculates the reformed gas Exr containing hydrogen to the internal combustion engine 1, even when the recirculation amount of the reformed gas Exr is increased, the rapid combustion of hydrogen causes deterioration of combustion. Is suppressed. As a result, it is possible to suppress a decrease in output torque due to deterioration in combustion and suppress deterioration in drivability.

  Further, when the EGR is executed when the internal combustion engine 1 is under a high load (for example, an operation in the WOT region or an operation in which the load factor exceeds about 80%), the temperature of the combustion chamber can be lowered. = 1) The range that can be operated is expanded. However, combustion may deteriorate due to EGR, output torque may decrease, and drivability may deteriorate. Since the internal combustion engine 1 according to this embodiment recirculates not only the exhaust gas Ex but also the reformed gas Exr containing hydrogen to the internal combustion engine 1, the deterioration of combustion is suppressed by rapid combustion of hydrogen in the reformed gas Exr. The Further, since knocking can be improved by rapid combustion of hydrogen, the ignition timing can be advanced and the output torque of the internal combustion engine 1 can be improved. As a result, it is possible to suppress a decrease in output torque due to deterioration in combustion and suppress deterioration in drivability.

The internal combustion engine 1 has a function of determining whether or not the reformed gas Exr has reached the combustion chamber in each of the cylinders 1S _{1 to} 1S ₄ . In the internal combustion engine 1 according to this embodiment, it is determined whether the reformed gas Exr has reached the combustion chamber by determining the combustion state in the combustion chamber in each of the cylinders 1S _{1 to} 1S ₄ . That is, even if the reforming is started, it takes time until the reformed gas Exr reaches the combustion chamber. For this reason, even if reforming is started, the combustion state is not improved until the reformed gas Exr reaches the combustion chamber. When the reformed gas Exr reaches the combustion chamber, the combustion state is improved. By utilizing the change in the combustion state, it can be determined whether the reformed gas Exr has reached the combustion chamber.

  In the internal combustion engine 1 according to this embodiment, the combustion state in the combustion chamber is determined based on the combustion ion current in the combustion chamber. FIG. 2-1 is an explanatory diagram showing a device configuration for detecting a combustion ion current. FIG. 2-2 is an explanatory diagram showing a device configuration for detecting a combustion ion current in an internal combustion engine having a plurality of cylinders. The combustion ion current detection device 63 is incorporated in the direct ignition 60, and uses the ignition plug SP as a combustion ion current detection sensor (combustion state detection means), so that the combustion ion current in the combustion chamber 1b in the cylinder 1S. Is detected. In this embodiment, the ignition plug SP and the combustion ion current detection device 63 constitute a combustion state detection means. Note that a combustion ion current detection probe may be provided in the vicinity of the ignition plug SP separately from the ignition plug SP, thereby determining the combustion state in the combustion chamber 1b. The combustion ion current detection device 63 may be prepared separately from the direct ignition 60.

  The direct ignition 60 includes an igniter unit 62 and an ignition coil unit 61. The engine ECU 50 determines the ignition timing for the internal combustion engine 1 from the operating conditions and operating state of the internal combustion engine 1. The direct ignition 60 receives an ignition command from the engine ECU 50, generates a spark from the spark plug SP, and ignites the air-fuel mixture in the combustion chamber 1b.

  The combustion ion current detection device 63 includes a detection circuit 64, an inversion circuit 66, and a VI conversion circuit 65. The detection circuit 64 is connected to the secondary coil 61 s constituting the ignition coil unit 61. When the air-fuel mixture in the combustion chamber 1b burns, combustion ions are generated in the combustion chamber 1b. Due to the combustion ions, a combustion ion current I flows between the center electrode SPc and the side electrode SPs of the spark plug SP. The detection circuit 64 detects this combustion ion current I. The detected electric signal of the combustion ion current I is taken into the engine ECU 50 through the inversion circuit 66 and the V-I conversion circuit 65.

When the internal combustion engine 1 comprises a plurality of cylinders 1S ₁ ~1S _4, direct ignition 60 ₁ to 60 ₄ with respect to the spark plugs SP ₁ to SP ₂ of each cylinder 1S ₁ ~1S _4, combustion ion current detecting device 63 ₁ 63 ₄ are provided. Thus, the combustion state is determined for each of the cylinders 1S _{1 to} 1S ₄ .

  FIG. 3 is an explanatory diagram showing an example of the waveform of the combustion ion current. FIG. 3 shows an example of the waveform of the combustion ion current detected by the combustion ion current detection device 63 and before being taken into the engine ECU 50. As shown in FIG. 3, when the engine ECU 50 gives an ignition signal to the igniter 62, a spark is generated between the center electrode SPc and the side electrode SPs of the spark plug SP in response to the ignition signal. This spark ignites the air-fuel mixture in the combustion chamber 1b and burns it.

The actual combustion ion current generated in the combustion chamber 1b by the combustion of the air-fuel mixture becomes as shown by the broken line in FIG. However, in the ignition device using the ignition coil, LC resonance noise is generated by the stray capacitance Cf (see FIG. 2-1) and the ignition coil unit 61. Due to the influence of the LC resonance noise, the combustion ion current I detected by the combustion ion current detection device 63 is as shown by the solid line in FIG. The maximum value of the combustion ion current I is Imax. When the combustion state is improved, the value of the combustion ion current I increases and the maximum combustion ion current Imax also increases. In this embodiment, the combustion state in the combustion chamber 1b is determined from the time change of the maximum combustion ion current Imax. In order to avoid LC resonance noise, the combustion ion current I is acquired after the delay time _Td from the ignition timing _TF .

  Next, an internal combustion engine operation control apparatus according to this embodiment will be described. FIG. 4 is an explanatory view showing an operation control apparatus for an internal combustion engine according to this embodiment. The operation control of the internal combustion engine according to this embodiment can be realized by the operation control device 30 for the internal combustion engine according to this embodiment. As shown in FIG. 2, the operation control device 30 for the internal combustion engine is configured to be incorporated in an engine ECU 50. The engine ECU 50 includes a CPU (Central Processing Unit) 50p, a storage unit 50m, input and output ports 55 and 56, and input and output interfaces 57 and 58.

  Separately from the engine ECU 50, an operation control device 30 for an internal combustion engine according to this embodiment may be prepared and connected to the engine ECU 50. In realizing the operation control of the internal combustion engine according to this embodiment, the control function of the internal combustion engine 1 provided in the engine ECU 50 may be configured so that the operation control device 30 of the internal combustion engine can be used.

  The operation control device 30 for the internal combustion engine includes a gas arrival determination unit 31, an operation parameter change unit 32, and a reforming control unit 33. These are the parts that execute the operation control method for the internal combustion engine according to this embodiment. The gas arrival determination unit 31 corresponds to a gas arrival determination unit included in the internal combustion engine according to this embodiment, and the operation parameter change unit 32 corresponds to an operation parameter change unit included in the internal combustion engine 1 according to this embodiment. .

In this embodiment, the operation control device 30 for the internal combustion engine is configured as a part of a CPU (Central Processing Unit) 50p constituting the engine ECU 50. In addition, the CPU 50 p includes a control unit 53 that controls the operation of the internal combustion engine 1. The CPU 50p and the storage unit 50m are connected via an input port 55 and an output port 56 via buses 54 _{1 to} 54 ₃ .

  As a result, the gas arrival determination unit 31, the operation parameter change unit 32, and the reforming control unit 33 constituting the operation control device 30 of the internal combustion engine can exchange control data with each other or issue a command to one side. Configured. The operation control device 30 of the internal combustion engine acquires the load factor KL of the internal combustion engine 1 and the engine rotational speed Ne and other operation control data of the internal combustion engine that the engine ECU 50 has, and controls the operation control device 30 of the internal combustion engine. It is possible to interrupt the operation control routine of the internal combustion engine of the engine ECU 50.

An input interface 57 is connected to the input port 55. The input interface 57 includes an air flow sensor 42, a rotation speed sensor 43, a reforming catalyst bed temperature sensor 44, an A / F sensor 45, a cooling water temperature sensor 46, an accelerator opening sensor 47, and combustion ion current detection devices 63 _{1 to} 63 _4. (Subscript is combustion chamber number), Combustion chamber combustion chamber pressure sensors 48 _{1 to} 48 ₄ (Subscript is combustion chamber number), and other sensors for acquiring information necessary for operation control of the internal combustion engine 1 are connected. Yes. Signals output from these sensors are converted into signals that can be used by the CPU 50 p by the A / D converter 57 a and the digital buffer 57 d in the input interface 57 and sent to the input port 55. Thus, the CPU 50p can acquire information necessary for fuel supply control and operation control of the internal combustion engine 1.

An output interface 58 is connected to the output port 56. Connected to the output interface 58 are control objects necessary for operation control of the internal combustion engine 1, such as the recirculation flow rate adjustment valve 5, the single port injection valve 6, the reforming fuel injection valve 24, the igniter unit 62, and the like. The output interface 58 includes control circuits 58 ₁ , 58 _{2 and the} like, and operates the control target based on a control signal calculated by the CPU 50p. With such a configuration, the CPU 50p of the engine ECU 50 can control the operation of the internal combustion engine 1 based on the output signals from the sensors.

  The storage unit 50m stores a computer program and a control map including a processing procedure for operation control of the internal combustion engine according to this embodiment, a data map of a fuel injection amount used for operation control of the internal combustion engine 1, and the like. Here, the storage unit 50m can be configured by a volatile memory such as a RAM (Random Access Memory), a nonvolatile memory such as a flash memory, or a combination thereof.

  The computer program may be capable of realizing the processing procedure of the operation control of the internal combustion engine according to this embodiment, in combination with the computer program already recorded in the CPU 50p. The internal combustion engine operation control device 30 implements the functions of the gas arrival determination unit 31, the operation parameter change unit 32, and the reforming control unit 33 using dedicated hardware instead of the computer program. There may be. Next, operation control of the internal combustion engine according to this embodiment will be described. In this description, please refer to FIGS.

  FIG. 5 is an explanatory diagram showing the change over time of the combustion ion current when the operation control of the internal combustion engine according to this embodiment is being executed. FIG. 5 shows the time change of the maximum combustion ion current (hereinafter simply referred to as combustion ion current) during one cycle of the internal combustion engine 1. FIG. 6 is a flowchart for explaining the operation control procedure of the internal combustion engine according to this embodiment. In the operation control of the internal combustion engine according to this embodiment, the combustion ion current is used as a combustion state determination parameter for determining the combustion state. In executing the operation control of the internal combustion engine according to this embodiment, the reforming control unit 33 included in the operation control device (hereinafter referred to as the operation control device) 30 of the internal combustion engine determines whether to start the recirculation of the reformed gas. (Step S101).

  Whether or not to start the recirculation of the reformed gas is determined based on information from an air flow sensor 42, a rotation speed sensor 43, a cooling water temperature sensor 46, a reforming catalyst bed temperature sensor 44, and other various sensors attached to the internal combustion engine 1. The reforming control unit 33 determines. If the recirculation of the reformed gas is not started (step S101: No), the process returns to START, and the operation control device 30 continues to monitor the internal combustion engine 1.

When the recirculation of the reformed gas is started (step S101: Yes), the reforming control unit 33 determines the amount of the reformed gas Exr to be recirculated from the engine speed Ne and the intake air amount Ga of the internal combustion engine 1 and the reforming fuel injection. The supply amount of the reforming fuel Fr supplied from the valve 24 to the reformer 20 is determined. Based on the determined value, the reforming control unit 33 injects the reforming fuel Fr from the reforming fuel injection valve 24 and opens the recirculation flow rate adjustment valve 5 (time t _{1 in} FIG. 5).

The gas arrival determination unit 31 of the operation control device 30 determines the combustion state from the combustion ion current detection devices 63 _{1 to} 63 ₄ (FIGS. 2-2 and 4), and the combustion ion current I in the combustion chamber of the internal combustion engine 1. Is acquired (step S102). When the combustion chambers are respectively provided in the plurality of cylinders 1S _{1 to} 1S _{4 as} in the internal combustion engine 1 according to this embodiment, the combustion ion current detection devices 63 _{1 to} 63 ₄ (see FIG. 2-2, FIG. 4), the combustion ion current I for the combustion chamber for determining the combustion state is acquired.

Prior to the start of reforming (before t _{1 in} FIG. 5), the internal combustion engine 1 is operated at a certain air-fuel ratio A / F (for example, stoichiometric). At this time, even if the reformed gas Exr is not recirculated, a gas having a component close to the exhaust gas Ex of the internal combustion engine 1 is present in the exhaust passage 22 of the reformer 20 or in the gas recirculation passage 10 (see FIG. 1). Exists. When the reforming is started and the recirculation flow rate adjustment valve 5 is opened, a gas having a component close to the exhaust gas Ex existing in the gas recirculation passage 10 or the like first recirculates to the combustion chamber of the internal combustion engine 1 (t in FIG. 5). ₁ ~t _2). Thereafter, the reformed gas Exr gradually begins to recirculate to the combustion chamber of the internal combustion engine 1 (after t _{2 in} FIG. 5).

When a gas having a component close to the exhaust gas Ex is recirculated into the combustion chamber of the internal combustion engine 1, the combustion ion current I is decreased as compared with that (t _{1 in} FIG. 5). That is, combustion worsens. When the reformed gas Exr begins to recirculate to the combustion chamber of the internal combustion engine 1, the combustion ion current I becomes the minimum value Imin, and then starts to increase (t _{2 in} FIG. 5). That is, combustion is improved by hydrogen in the reformed gas Exr. At t ₄ , only the reformed gas Exr is returned to the combustion chamber of the internal combustion engine 1.

  When the exhaust gas Ex or a gas having a component close to the exhaust gas Ex returns to the combustion chamber, the combustion becomes slow. Therefore, unless the ignition timing, which is an operation parameter, is set to a more advanced side, the combustion becomes unstable and drivability is reduced. On the other hand, since the reformed gas Exr contains hydrogen, the combustion speed becomes faster than during normal operation, that is, when EGR is not executed (when the exhaust gas Ex is not recirculated). In this case, the output torque of the internal combustion engine 1 decreases unless the ignition timing is retarded. For this reason, the ignition timing differs between when the reformed gas Exr is recirculated and when the exhaust gas Ex or a gas having a component close to the exhaust gas Ex is recirculated.

  Therefore, when the reformed gas starts to be recirculated, and the gas of the component close to the exhaust gas Ex is first recirculated to the combustion chamber, the ignition timing when the reformed gas Exr is recirculated is delayed more than before. If changed to the side, combustion becomes unstable. As a result, drivability is reduced. Therefore, in this embodiment, it is determined whether or not the reformed gas Exr is recirculated to the combustion chamber from the combustion state, and the reformed gas Exr is recirculated after the reformed gas Exr reaches the combustion chamber. The ignition timing is changed to a suitable timing, that is, a retarded side. That is, the combustion state in the combustion chamber is determined from the combustion ion current I, and when the combustion ion current I becomes larger than the predetermined threshold Is, it is determined that the reformed gas Exr has sufficiently returned to the combustion chamber, The ignition timing is changed to the ignition timing when the reformed gas recirculates, that is, to the retard side. Note that “the reformed gas Exr reaches the combustion chamber” means a state in which combustion is sufficiently promoted. For example, all the gas at the outlet 10o of the gas recirculation passage 10 is reformed by the reformer 20. In this state, the ratio of the reformed gas Exr is about 50% or more. In such a state, normally, after starting the recirculation of the reformed gas Exr, the combustion is improved more than before starting the recirculation of the reformed gas Exr.

The gas arrival determination unit 31 compares the combustion ion current I in the combustion chamber of the internal combustion engine 1 acquired in step S102 with a predetermined threshold Is (step S103). The predetermined threshold Is is used to determine whether or not the reformed gas Exr reaches the combustion chamber and the ignition timing, which is an operation parameter, may be changed to the value at the time of reformed gas recirculation. As described above, when the reformed gas Exr is refluxed to the combustion chamber, combustion is improved as compared with a state in which the reformed gas Exr is not refluxed. That is, when the reformed gas Exr is recirculated to the combustion chamber, the combustion is improved more than before the recirculation of the reformed gas Exr is started (before t _{1 in} FIG. 5). Accordingly, when the combustion ion current I becomes larger than before the start of the recirculation of the reformed gas Exr, it is determined that the reformed gas Exr is recirculating to the combustion chamber, and the operation parameter (in this example, ignition is performed). (Time) can be changed.

From this point of view, the threshold Is when determining whether or not the reformed gas Exr is recirculated to the combustion chamber using the combustion ion current I is at least before the recirculation of the reformed gas Exr is started (in FIG. 5). the value of the combustion ion current I ₁ above) than t _1. And it is preferable to make it a value somewhat larger than the combustion ion current I ₁ before starting the recirculation of the reformed gas Exr. In this way, even when a variation in the detection of the combustion ion current I or a variation in the reforming occurs, the ignition timing is set to the same as that at the time of the reforming gas recirculation while the reformed gas Exr reliably recirculates to the combustion chamber. It can be changed to the ignition timing. Here, since the value of the combustion ion current I also changes depending on the operating conditions of the internal combustion engine 1, the combustion state before starting the recirculation of the reformed gas Exr, that is, before starting the recirculation of the reformed gas Exr. It is preferable to set a predetermined threshold Is based on the value of the combustion ion current.

The threshold Is may be set, for example, by adding a predetermined threshold correction value ΔI to the combustion ion current (I = I ₁ ) before starting the recirculation of the reformed gas Exr. At this time, the threshold correction value ΔI may be changed according to the operating conditions, reforming conditions, and the like of the internal combustion engine 1. For example, depending on the reforming conditions, the degree of improvement in the combustion state may be low. In such a case, if the threshold correction value ΔI is too large, the reformed gas Exr is recirculated to the combustion chamber. Further, it may be determined that the reformed gas Exr is not recirculated to the combustion chamber. If the threshold correction value is changed according to the operating conditions, reforming conditions, and the like of the internal combustion engine 1, such problems can be solved and the recirculation of the reformed gas Exr can be detected more reliably.

As a result of comparing the combustion ion current I with the predetermined threshold Is, if I ≦ Is (step S103: No, the period from t ₁ to t _{4 in} FIG. 5), the reformed gas Exr is returned to the combustion chamber. Judge that it is not. In this case, the process waits until the reformed gas Exr returns to the combustion chamber. In the case of I> Is (step S103: Yes, t = t ₄ later in FIG. 5) determines that the reformed gas Exr is refluxed into the combustion chamber. In this case, the operation parameter changing unit 32 of the operation control device 30 changes the ignition timing (operation parameter) to the ignition timing at the time of reforming gas recirculation, that is, to the more retarded side (step S104, t = t in FIG. 5). ₅ ). Then, the operation parameter changing unit 32 gives the changed ignition timing to the control unit 53, and causes the control unit 53 to operate the internal combustion engine 1 at the changed ignition timing (step S105).

  The internal combustion engine 1 may be operated at an ignition timing (operation parameter) that is changed after the reformed gas Exr reaches the combustion chamber, that is, suitable for the reformed gas recirculation. Therefore, the ignition timing (operation parameter) may be changed before the reformed gas Exr reaches the combustion chamber (the same applies hereinafter).

  In addition, when providing a some combustion chamber like the internal combustion engine 1 which concerns on this Example, ignition timing is changed in the order of the combustion chamber exceeding the said threshold value. That is, after the start of recirculation of the reformed gas Exr, if the combustion state is improved after the deterioration of the combustion state once compared to before the recirculation of the reformed gas Exr is started, the reformed gas Exr returns to the combustion chamber. The ignition timing is retarded.

In the state where the reformed gas Exr is recirculated to the combustion chamber (after t _{4 in} FIG. 5), if it is ignited at the ignition timing before the reforming is started, it becomes an over-advanced state. In the over-advance state, combustion is improved and the combustion ion current I increases (t = t _{4 to} t 5 in FIG. ₅ ), but the output torque of the internal combustion engine 1 decreases. Therefore, at the time point t = t ₅ , the ignition timing is changed to the retard side with respect to the optimal ignition timing in the state where the reformed gas Exr is recirculated, that is, the ignition timing before the reforming is started. When the ignition timing is changed to the ignition timing at the reformed gas recirculation at t = t ₅ in FIG. 5, the combustion is optimized, the output torque of the internal combustion engine 1 is improved, and the combustion ion current I is slightly reduced (t = t _6).

Since the reformed gas Exr is recirculated to the combustion chamber at the time t = t ₄ in FIG. 5, if t = t ₄ or later, the ignition timing is changed to the ignition timing at the reformed gas recirculation. Good. As in this embodiment, when the ignition timing is changed after a certain period of time has elapsed since the reformed gas Exr recirculated to the combustion chamber (t = t ₄ ), the reformed gas Exr is more reliably recirculated. In this state, the ignition timing can be changed, and the risk of unstable combustion can be more reliably reduced.

  Here, for example, when the reforming catalyst included in the reformer 20 is S (sulfur) poisoned or coking occurs in the reforming catalyst, the reforming is stopped and reforming is performed from the S poisoning or the like. Recover the catalyst. Further, depending on the operating conditions of the internal combustion engine 1, the reformed gas Exr may not be recirculated. Thus, the operation control of the internal combustion engine 1 when the recirculation of the reformed gas is stopped will be described. FIG. 7 is an explanatory diagram showing a change over time in the combustion ion current when the operation control is executed when the recirculation of the reformed gas is stopped. FIG. 8 is a flowchart showing a procedure of operation control when the recirculation of the reformed gas is stopped.

First, the reforming control unit 33 included in the operation control device 30 determines whether to stop the recirculation of the reformed gas (step S201). When the recirculation of the reformed gas is not stopped (step S201: No), the process returns to START, and the operation control device 30 continues to monitor the internal combustion engine 1. When the recirculation of the reformed gas is stopped (step S201: Yes), the reforming control unit 33 stops the injection of the reforming fuel Fr from the reforming fuel injection valve 24 and closes the recirculation flow rate adjustment valve 5. (Time t _{1 in} FIG. 7).

Next, in order to determine the combustion state, the gas arrival determination unit 31 of the operation control device 30 performs combustion in the combustion chamber of the internal combustion engine 1 from the combustion ion current detection devices 63 _{1 to} 63 ₄ (FIGS. 2-2 and 4). The ion current I is acquired (step S202). Then, the gas arrival determination unit 31 compares the combustion ion current I in the combustion chamber of the internal combustion engine 1 acquired in step S202 with a predetermined lower limit value Isl (step S203). When the recirculation of the reformed gas Exr is stopped, a mixture of the air A introduced from the intake passage 3 and the fuel Fe for the internal combustion engine is introduced into the combustion chamber of the internal combustion engine 1, and this mixture (combustion mixture) is generated. The internal combustion engine 1 is driven by the combustion.

  Since the combustion mixture has a combustion speed slower than that of the reformed gas Exr containing hydrogen, the combustion state becomes unstable unless the ignition timing is changed to the advance side as compared with the case where the reformed gas Exr is recirculated. Affects drivability. The predetermined lower limit value Isl is determined from such a viewpoint, and is set to a minimum value within a range in which deterioration of the combustion state is allowable. Since the value of the combustion ion current I also changes depending on the operating conditions of the internal combustion engine 1, the combustion state before stopping the recirculation of the reformed gas Exr, that is, the combustion before stopping the recirculation of the reformed gas Exr. It is preferable to set a predetermined lower limit Isl based on the value of the ionic current I.

As a result of comparing the combustion ion current I with the predetermined lower limit value Isl, if I> Isl (step S203: No, the period from t ₁ to t _{2 in} FIG. 7), the combustion state is within the allowable range. judge. In this case, the internal combustion engine 1 is operated without changing the ignition timing. In the case of I ≦ Isl (step S203: Yes, t = t ₂ later in FIG. 7), it is determined that the combustion state is not acceptable. In this case, the operation parameter changing unit 32 of the operation control device 30 changes the ignition timing (operation parameter) to the advance side with respect to the ignition timing at the reformed gas recirculation (step S204, t = t _{2 in} FIG. 7). ). Then, the control unit 53 operates the internal combustion engine 1 at the changed ignition timing (operation parameter) (step S205). As a result, a combustion state suitable for the combustion air-fuel mixture is obtained, and therefore it is possible to suppress a decrease in drivability compared to before the reformed gas Exr is stopped to recirculate.

(Modification)
This modification has substantially the same configuration as that of the above embodiment, but differs in that a change in combustion pressure in the combustion chamber (hereinafter referred to as “combustion chamber pressure”) is used to determine the combustion state. That is, the difference is that the pressure in the combustion chamber is used as a combustion state determination parameter for determining the combustion state. Other configurations are the same as in the above embodiment. In a so-called hybrid (hereinafter referred to as HV) drive device that combines an internal combustion engine and an electric motor, the torque of the internal combustion engine can be absorbed by an electric system including an electric motor and a storage battery while the throttle valve opening is kept constant. Thus, if the opening degree of the throttle valve is kept constant, the combustion state improves as the recirculation amount of the reformed gas Exr increases, and as a result, the maximum pressure in the combustion chamber increases. In this modification, this is used to determine whether the reformed gas has reached the combustion chamber.

  FIG. 9 is an explanatory diagram showing the change over time in the pressure in the combustion chamber when the operation control of the internal combustion engine according to the modification of this embodiment is being executed. FIG. 9 shows the time change of the maximum combustion chamber pressure (hereinafter simply referred to as the combustion chamber pressure) during one cycle of the internal combustion engine 1. FIG. 10 is a flowchart for explaining the procedure of operation control of the internal combustion engine according to a modification of this embodiment.

In the operation control of the internal combustion engine according to this modification, the combustion chamber each cylinder 1S ₁ ～1S ₄ of the internal combustion engine 1 is provided, provided the combustion chamber pressure sensor 48 _{1-48 4} is a combustion state detection means (see FIG. 1 ), Thereby detecting the pressure in the combustion chamber. In executing the operation control of the internal combustion engine according to this modification, the reforming control unit 33 provided in the operation control device 30 determines whether or not to start the recirculation of the reformed gas (step S301). When the recirculation of the reformed gas is not started (step S301: No), the process returns to START, and the operation control device 30 continues to monitor the internal combustion engine 1.

When the recirculation of the reformed gas is started (step S301: Yes), the reforming control unit 33 determines the amount of the reformed gas Exr to be recirculated from the engine speed Ne and the intake air amount Ga of the internal combustion engine 1 and the reforming fuel injection. The supply amount of the reforming fuel Fr supplied from the valve 24 to the reformer 20 is determined. Based on the determined value, the reforming control unit 33 injects the reforming fuel Fr from the reforming fuel injection valve 24 and opens the recirculation flow rate adjustment valve 5 (time t _{1 in} FIG. 9).

The gas arrival determination unit 31 of the operation control device 30 acquires the combustion chamber pressure P in the combustion chamber of the internal combustion engine 1 from the combustion chamber pressure sensors 48 _{1 to} 48 ₄ (FIG. 1) in order to determine the combustion state (step S302). ). When the combustion chambers are respectively provided in the plurality of cylinders 1S _{1 to} 1S _{4 as} in the internal combustion engine 1 according to this embodiment, the combustion chamber pressure sensors 48 _{1 to} 48 ₄ (FIG. 1) corresponding to the respective combustion chambers. ) To obtain the combustion chamber pressure P for the combustion chamber for determining the combustion state.

The gas arrival determination unit 31 compares the combustion chamber pressure P acquired in step S302 with a predetermined threshold value Psl (step S303). The predetermined threshold value Psl is used to determine whether or not the reformed gas Exr reaches the combustion chamber and the ignition timing, which is an operation parameter, may be changed to a value when the reformed gas recirculates. As described above, when the reformed gas Exr is refluxed to the combustion chamber, combustion is improved as compared with a state in which the reformed gas Exr is not refluxed. That is, when the reformed gas Exr is recirculated to the combustion chamber, the combustion is improved more than before the recirculation of the reformed gas Exr is started (before t _{1 in} FIG. 5). Therefore, when the pressure P in the combustion chamber becomes larger than before the start of the recirculation of the reformed gas Exr, it can be determined that the reformed gas Exr is recirculating to the combustion chamber.

From this point of view, the threshold value Psl for determining whether or not the reformed gas Exr is recirculated to the combustion chamber using the combustion chamber pressure P is at least before starting the recirculation of the reformed gas Exr (FIG. 9). the value of the combustion chamber pressure P ₁ before) than t _1. And it is preferable to make it a value somewhat larger than the combustion chamber pressure P ₁ before starting the recirculation of the reformed gas Exr. In this way, even when a variation in the detection of the pressure P in the combustion chamber or a variation in the reforming occurs, the ignition timing is set to the same as that at the time of the reforming gas recirculation while the reformed gas Exr is reliably recirculated to the combustion chamber. It can be changed to the ignition timing. Here, since the value of the pressure P in the combustion chamber also changes depending on the operating conditions of the internal combustion engine 1, the combustion state before starting the recirculation of the reformed gas Exr, that is, before starting the recirculation of the reformed gas Exr. Based on the value of the pressure P in the combustion chamber, it is preferable to set a predetermined threshold value Psl.

As a result of comparing the pressure P in the combustion chamber with the predetermined threshold value Psl, if P ≦ Psl (step S303: No, the period from t ₁ to t _{4 in} FIG. 9), the reformed gas Exr returns to the combustion chamber. Judge that it is not. In this case, the process waits until the reformed gas Exr returns to the combustion chamber. In the case of P> Psl (step S303: Yes, t = t ₄ later in FIG. 9), it determines that the reformed gas Exr is refluxed into the combustion chamber. In this case, the operation parameter changing unit 32 of the operation control device 30 changes the ignition timing (operation parameter) to the ignition timing at the time of reforming gas recirculation, that is, to the more retarded side (step S304, t = t in FIG. 9). ₅ ). Then, the operation parameter changing unit 32 gives the changed ignition timing to the control unit 53, and causes the control unit 53 to operate the internal combustion engine 1 at the changed ignition timing (step S305).

  As described above, the combustion state can be determined using the combustion ion current and the pressure in the combustion chamber described above. In addition, for example, the combustion state may be determined by using the fluctuation of the engine speed of the internal combustion engine 1 detected by the rotation speed sensor 43 (FIG. 1) as a combustion state determination parameter. Further, the ignition timing may be changed based on the amount of hydrogen supplied to the internal combustion engine 1 by recirculating the reformed gas. For example, the hydrogen concentration sensor 49 (FIG. 1) provided in the intake passage 3 is used to determine the hydrogen concentration supplied to the combustion chamber of the internal combustion engine 1, and the ignition timing is changed based on this. The ignition timing is determined in advance according to the ratio of hydrogen to the total amount of gas introduced into the combustion chamber of the internal combustion engine 1. Note that the combustion ion current reacts sensitively to the air-fuel ratio A / F and the ratio of exhaust gas and reformed gas recirculated to the combustion chamber, so that the determination of the combustion state is facilitated and the determination accuracy is improved.

  As described above, in this embodiment and the modification thereof, it is determined that the reformed gas has reached the combustion chamber, and thereafter, the internal combustion engine is operated with the operation parameters when the reformed gas is recirculated. Thus, after the reformed gas is reliably introduced into the combustion chamber, the internal combustion engine can be operated with an operation parameter (ignition timing) suitable for the reformed gas recirculation. As a result, stable combustion is obtained in the period in which the recirculated gas reaches the combustion chamber from the start of recirculation of the reformed gas, and a decrease in drivability can be suppressed.

  As described above, the internal combustion engine and the operation control device for the internal combustion engine according to the present invention are useful for an internal combustion engine that supplies fuel to exhaust gas and generates reformed gas containing hydrogen. It is suitable for stabilizing the combustion state in the period from the start of the reflux until the reformed gas reaches the combustion chamber.

1 is an overall configuration diagram of an internal combustion engine according to an embodiment. FIG. It is explanatory drawing which shows the apparatus structure which detects a combustion ion current. It is explanatory drawing which shows the apparatus structure which detects a combustion ion current in an internal combustion engine provided with a some cylinder. It is explanatory drawing which shows an example of the waveform of a combustion ion current. It is explanatory drawing which shows the operation control apparatus of the internal combustion engine which concerns on this Example. It is explanatory drawing which shows the time change of a combustion ion electric current in the case of performing the operational control of the internal combustion engine which concerns on this Example. It is a flowchart explaining the procedure of the operation control of the internal combustion engine which concerns on this Example. It is explanatory drawing which shows the time change of the combustion ion current in the case of performing the operational control when the recirculation of the reformed gas is stopped. It is a flowchart which shows the procedure of the operation control when the recirculation | reflux of reformed gas is stopped. It is explanatory drawing which shows the time change of the pressure in a combustion chamber in the case of performing the operational control of the internal combustion engine which concerns on the modification of this Example. It is a flowchart explaining the procedure of the operation control of the internal combustion engine which concerns on the modification of this Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 1b Combustion chamber 3 Intake passage 4 Throttle valve 5 Recirculation flow rate adjustment valve 10 Gas recirculation passage 11 Reformation conduit 20 Reformer 24 Reformation fuel injection valve 30 Operation control device 31 of internal combustion engine 31 Gas arrival judgment unit 32 Operation parameter changing unit 33 Reforming control unit 48 _{1 to} 48 ₄ Combustion chamber pressure sensor 50 Engine ECU
63 Combustion ion current detector

Claims (12)

An internal combustion engine that is driven by igniting an air-fuel mixture supplied from an intake passage with ignition means and burning the mixture in a combustion chamber,
A reforming mixture of fuel and exhaust gas discharged from the internal combustion engine is reformed by a reforming catalyst to produce reformed gas containing hydrogen, and the reformed gas is recirculated to the combustion chamber. Quality means,
Reformed gas arrival determining means for determining whether or not the reformed gas has reached the combustion chamber;
After the reformed gas reaches the combustion chamber, an operating parameter changing means for operating the internal combustion engine with an operating parameter having a value when the reformed gas is recirculated;
The internal combustion engine characterized by including. The operating parameter is an ignition timing of the ignition means,
When the reformed gas arrival determining means determines that the reformed gas has arrived at the combustion chamber, the operating parameter changing means determines the ignition timing by the ignition means, and the reformed gas reaches the combustion chamber. The internal combustion engine according to claim 1, wherein the internal combustion engine is retarded more than before. The reformed gas arrival judging means is
The internal combustion engine according to claim 1, wherein arrival of the reformed gas is determined by determining a combustion state in the combustion chamber.   The combustion state in the combustion chamber of the internal combustion engine is determined using at least one of the combustion ion current in the combustion chamber or the combustion pressure in the combustion chamber as a combustion state determination parameter for determining the combustion state. The internal combustion engine according to claim 3. The operation parameter changing means is
After the reforming means is operated and the reformed gas starts to be recirculated, the mixing in the combustion chamber is performed more than before the reformed gas is recirculated after the combustion state in the combustion chamber is once deteriorated. The internal combustion engine according to claim 3 or 4, wherein the operating parameter is changed after the combustion state of the gas is improved. The operation parameter changing means is
6. The internal combustion engine according to claim 4, wherein when the combustion state determination parameter becomes larger than a predetermined threshold, it is determined that the reformed gas has reached the combustion chamber. An air-fuel mixture of air and fuel supplied from the intake passage is ignited by ignition means and burned in the combustion chamber. The air-fuel mixture for reforming the fuel and exhaust gas discharged from the internal combustion engine Is reformed by a reforming catalyst to generate a reformed gas containing hydrogen, and reforming means for recirculating the reformed gas to the combustion chamber, to control an internal combustion engine,
A gas arrival determination unit for determining whether or not the reformed gas has reached the combustion chamber;
After the reformed gas reaches the combustion chamber, an operating parameter changing unit that changes the operating parameter so that the internal combustion engine can be operated with the operating parameter at the time of reformed gas recirculation;
An operation control device for an internal combustion engine, comprising: The operating parameter is an ignition timing of the ignition means,
The operating parameter changing unit is configured to determine an ignition timing by the ignition means before the reformed gas reaches the combustion chamber when the gas arrival determination unit determines that the reformed gas has reached the combustion chamber. The operation control device for an internal combustion engine according to claim 7, wherein the operation angle is retarded more than that. The gas arrival determination unit
The operation control device for an internal combustion engine according to claim 7 or 8, wherein arrival of the reformed gas is determined by determining a combustion state in the combustion chamber. The gas arrival determination unit
The combustion state in the combustion chamber of the internal combustion engine, using at least one of the combustion ion current when the air-fuel mixture burns in the combustion chamber or the pressure in the combustion chamber as a combustion state determination parameter for determining the combustion state The operation control device for an internal combustion engine according to claim 9, wherein: The operation parameter changing unit
After the reforming means is operated to start the recirculation of the reformed gas, after the combustion state in the combustion chamber is once deteriorated, the combustion state in the combustion chamber is more than before the recirculation of the reformed gas is started. The operation control device for an internal combustion engine according to claim 10, wherein the operation parameter is changed after improvement. The operation parameter changing unit
The internal combustion engine according to claim 10 or 11, wherein when the combustion state determination parameter is equal to or greater than a predetermined threshold value, it is determined that the reformed gas has reached the combustion chamber. Operation control device.

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